2.17.1-1

Add new NVLS algorithm for allreduce using NVLink SHARP (intra-node only).
Add new config options: cgaClusterSize, minCTAs, maxCTAs, netName.
Enable LL128 when we use PXN to close rings.
NVTX3 includes update.
Fix crash when one CollNet (SHARP) rail fails to initialize.

makefiles/version.mk

@@ -1,6 +1,6 @@
 ##### version
 NCCL_MAJOR   := 2
-NCCL_MINOR   := 16
+NCCL_MINOR   := 17
-NCCL_PATCH   := 5
+NCCL_PATCH   := 1
 NCCL_SUFFIX  :=
 PKG_REVISION := 1

src/Makefile

@@ -12,7 +12,8 @@ INCEXPORTS  := nccl.h nccl_net.h
 LIBSRCFILES := init.cc init_nvtx.cc channel.cc bootstrap.cc transport.cc enqueue.cc group.cc debug.cc proxy.cc net.cc \
 		misc/cudawrap.cc misc/nvmlwrap.cc misc/ibvwrap.cc misc/gdrwrap.cc \
 		misc/utils.cc misc/argcheck.cc misc/socket.cc misc/shmutils.cc misc/profiler.cc misc/param.cc misc/strongstream.cc \
-		transport/p2p.cc transport/shm.cc transport/net.cc transport/net_socket.cc transport/net_ib.cc transport/coll_net.cc \
+		misc/ipcsocket.cc \
+		transport/p2p.cc transport/shm.cc transport/net.cc transport/net_socket.cc transport/net_ib.cc transport/coll_net.cc transport/nvls.cc \
                 collectives/sendrecv.cc collectives/all_reduce.cc collectives/all_gather.cc collectives/broadcast.cc collectives/reduce.cc collectives/reduce_scatter.cc \
                 graph/topo.cc graph/paths.cc graph/search.cc graph/connect.cc graph/rings.cc graph/trees.cc graph/tuning.cc graph/xml.cc
 
@@ -62,7 +63,7 @@ ALWAYS_REBUILD:
 -include $(DEPFILES)
 $(LIBDIR)/$(LIBTARGET) $(LIBDIR)/$(STATICLIBTARGET) : $(LIBOBJ)
 
-$(INCDIR)/nccl.h : nccl.h.in
+$(INCDIR)/nccl.h : nccl.h.in ../makefiles/version.mk
 # NCCL_VERSION(X,Y,Z) ((X) * 10000 + (Y) * 100 + (Z))
 	@$(eval NCCL_VERSION := $(shell printf "%d%02d%02d" $(NCCL_MAJOR) $(NCCL_MINOR) $(NCCL_PATCH)))
 	mkdir -p $(INCDIR)

src/bootstrap.cc

@@ -386,6 +386,24 @@ ncclResult_t bootstrapIntraNodeAllGather(void* commState, int *ranks, int rank,
   return ncclSuccess;
 }
 
+// IntraNode in-place Broadcast
+ncclResult_t bootstrapIntraNodeBroadcast(void* commState, int *ranks, int rank, int nranks, int root, void* bcastData, int size) {
+  if (nranks == 1) return ncclSuccess;
+  TRACE(NCCL_INIT, "rank %d nranks %d root %d size %d - ENTER", rank, nranks, root, size);
+
+  if (rank == root) {
+    for (int i=0; i<nranks; i++) {
+      if (i != root) NCCLCHECK(bootstrapSend(commState, ranks[i], /*tag=*/ranks[i], bcastData, size));
+    }
+  }
+  else {
+    NCCLCHECK(bootstrapRecv(commState, ranks[root], /*tag=*/rank, bcastData, size));
+  }
+
+  TRACE(NCCL_INIT, "rank %d nranks %d root %d size %d - DONE", rank, nranks, root, size);
+  return ncclSuccess;
+}
+
 ncclResult_t unexpectedEnqueue(struct bootstrapState* state, int peer, int tag, struct ncclSocket* sock) {
   // New unex
   struct unexConn* unex;

src/channel.cc

@@ -13,14 +13,15 @@ ncclResult_t initChannel(struct ncclComm* comm, int channelId) {
   if (channel->id != -1) return ncclSuccess;
 
   int nRanks = comm->nRanks;
+  int nPeers = nRanks + 1 /* Collnet */ + comm->localRanks /* NVLS */;
   channel->id = channelId;
   channel->workFifoSent = 0;
 
   NCCLCHECK(ncclStrongStreamAcquireUncaptured(&comm->deviceStream));
 
   // The extra on nRanks+1 is for collnet root (i.e. network)
-  channel->peers = ncclMemoryStackAlloc<struct ncclChannelPeer>(&comm->memPermanent, nRanks+1);
+  channel->peers = ncclMemoryStackAlloc<struct ncclChannelPeer>(&comm->memPermanent, nPeers);
-  NCCLCHECK(ncclCudaCallocAsync(&channel->devPeers, nRanks+1, comm->deviceStream.cudaStream));
+  NCCLCHECK(ncclCudaCallocAsync(&channel->devPeers, nPeers, comm->deviceStream.cudaStream));
   ncclCommPushCudaFree(comm, channel->devPeers);
 
   channel->ring.userRanks = ncclMemoryStackAlloc<int>(&comm->memPermanent, nRanks);
@@ -29,7 +30,7 @@ ncclResult_t initChannel(struct ncclComm* comm, int channelId) {
 
   NCCLCHECK(ncclStrongStreamRelease(ncclCudaGraphNone(), &comm->deviceStream));
 
-  for (int r=0; r < nRanks+1; ++r) {
+  for (int r=0; r < nPeers; ++r) {
     for (int b=0; b < NCCL_MAX_CONNS; b++) {
       channel->peers[r].send[b].comm = comm;
       channel->peers[r].recv[b].comm = comm;

src/collectives/device/all_gather.h

@@ -97,3 +97,45 @@ struct RunWorkElement<ncclFuncAllGather, T, RedOp, NCCL_ALGO_RING, NCCL_PROTO_LL
     runRing<T, RedOp, ProtoLL128>(args);
   }
 };
+
+template<typename T, typename RedOp>
+struct RunWorkElement<ncclFuncAllGather, T, RedOp, NCCL_ALGO_NVLS, NCCL_PROTO_SIMPLE> {
+  __device__ __forceinline__ void run(ncclWorkElem *args) {
+    const int tid = threadIdx.x;
+    const int bid = args->bid;
+    const int nChannels = args->nChannels;
+    struct ncclNvls* nvls = &ncclShmem.channel.nvls;
+    const ssize_t chunkSize = int(args->lastChunkSize);
+    const ssize_t size = args->count;
+    const ssize_t loopSize = nChannels*chunkSize;
+
+    const int nThreadsGather = 128;
+    const int nThreadsBcast = 384 + WARP_SIZE;
+    const int tidEndGather = nThreadsGather;
+    const int tidEndBcast = tidEndGather + nThreadsBcast;
+
+    using Proto = ProtoSimple<1, 1>;
+
+    if (tid < tidEndGather) {
+      // Gather
+      int group = (0*Proto::MaxGroupWidth) | (0<<16);
+      Primitives<T, RedOp, FanAsymmetric<NCCL_MAX_NVLS_ARITY, 0>, /*Direct=*/0, Proto, 0>
+        prims(tid, nThreadsGather, nvls->up, NULL, NULL, args->recvbuff, args->redOpArg, group, args);
+      for (ssize_t gridOffset = 0; gridOffset < size; gridOffset += loopSize) {
+        ssize_t offset = gridOffset + bid*chunkSize;
+        int nelem = min(chunkSize, size-offset);
+        prims.gather(offset, nvls->nHeads*size, nelem, size, -1, 0);
+      }
+    } else if (tid < tidEndBcast) {
+      int group = (3*Proto::MaxGroupWidth) | (1<<16);
+      // Bcast through MC
+      Primitives<T, RedOp, FanAsymmetric<0, 1>, /*Direct=*/0, Proto, 0>
+        prims(tid-tidEndGather, nThreadsBcast, NULL, &nvls->down, args->sendbuff, NULL, args->redOpArg, group, args);
+      for (ssize_t gridOffset = 0; gridOffset < size; gridOffset += loopSize) {
+        ssize_t offset = gridOffset + bid*chunkSize;
+        int nelem = min(chunkSize, size-offset);
+        prims.send(offset, nelem);
+      }
+    }
+  }
+};

src/collectives/device/all_reduce.h

@@ -306,9 +306,9 @@ struct RunWorkElement<ncclFuncAllReduce, T, RedOp, NCCL_ALGO_COLLNET_DIRECT, NCC
         ssize_t offset = gridOffset + bid*direct->nHeads*chunkSize;
         int nelem = min(direct->nHeads*chunkSize, size-offset);
         if (args->regUsed) {
-          prims.directScatter(offset, nelem, chunkSize, direct->headRank, direct->shift);
+          prims.directScatter(offset, nelem, chunkSize, chunkSize, direct->headRank, direct->shift);
         } else {
-          prims.scatter(offset, nelem, chunkSize, direct->headRank, direct->shift);
+          prims.scatter(offset, nelem, chunkSize, chunkSize, direct->headRank, direct->shift);
         }
       }
     } else if (tid >= tidStartReduce && direct->out != -1) {
@@ -344,7 +344,7 @@ struct RunWorkElement<ncclFuncAllReduce, T, RedOp, NCCL_ALGO_COLLNET_DIRECT, NCC
       for (ssize_t gridOffset = 0; gridOffset < size; gridOffset += loopSize) {
         ssize_t offset = gridOffset + bid*direct->nHeads*chunkSize;
         int nelem = min(direct->nHeads*chunkSize, size-offset);
-        prims.directGather(offset, nelem, chunkSize, direct->headRank, direct->shift);
+        prims.directGather(offset, nelem, chunkSize, chunkSize, direct->headRank, direct->shift);
       }
     } else if (tid >= tidStartBcast && tid < tidStartScatter && direct->out != -1) {
       int group = (1*Proto::MaxGroupWidth) | (0<<16);
@@ -371,6 +371,65 @@ struct RunWorkElement<ncclFuncAllReduce, T, RedOp, NCCL_ALGO_COLLNET_DIRECT, NCC
   }
 };
 
+template<typename T, typename RedOp>
+struct RunWorkElement<ncclFuncAllReduce, T, RedOp, NCCL_ALGO_NVLS, NCCL_PROTO_SIMPLE> {
+  __device__ __forceinline__ void run(ncclWorkElem *args) {
+  #if NCCL_NVLS_ENABLED
+    const int tid = threadIdx.x;
+    const int bid = args->bid;
+    const int nChannels = args->nChannels;
+    struct ncclNvls* nvls = &ncclShmem.channel.nvls;
+    const ssize_t chunkSize = int(args->lastChunkSize);
+    const ssize_t size = args->count;
+    const ssize_t loopSize = nChannels*nvls->nHeads*chunkSize;
+    const int nranks = ncclShmem.comm.nRanks;
+    const int reduceWarps = nranks <= 6 ? 6 : 4;
+    const int copyWarps = ((NCCL_MAX_NTHREADS/WARP_SIZE) - reduceWarps)/2;
+
+    const int nThreadsScatter = copyWarps*WARP_SIZE;
+    const int nThreadsGather  = (copyWarps-1)*WARP_SIZE;
+    const int nThreadsReduce = (reduceWarps+1)*WARP_SIZE;
+    const int tidEndScatter = nThreadsScatter;
+    const int tidEndGather = tidEndScatter + nThreadsGather;
+    const int tidEndReduce = tidEndGather + nThreadsReduce;
+
+    using Proto = ProtoSimple<1, 1, COLL_UNROLL, /*NVLS=*/true>;
+
+    if (tid < tidEndScatter) {
+      // Scatter
+      int group = (0*Proto::MaxGroupWidth) | (0<<16);
+      Primitives<T, RedOp, FanAsymmetric<0, NCCL_MAX_NVLS_ARITY>, /*Direct=*/0, Proto, 0>
+        prims(tid, nThreadsScatter, NULL, nvls->up, args->sendbuff, args->recvbuff, args->redOpArg, group, args);
+      for (ssize_t gridOffset = 0; gridOffset < size; gridOffset += loopSize) {
+        ssize_t offset = gridOffset + bid*nvls->nHeads*chunkSize;
+        int nelem = min(nvls->nHeads*chunkSize, size-offset);
+        prims.scatter(offset, nelem, chunkSize, chunkSize, -1, 0);
+      }
+    } else if (tid < tidEndGather) {
+      // Gather
+      int group = (2*Proto::MaxGroupWidth) | (0<<16);
+      Primitives<T, RedOp, FanAsymmetric<NCCL_MAX_NVLS_ARITY, 0>, /*Direct=*/0, Proto, 0>
+        prims(tid-tidEndScatter, nThreadsGather, nvls->up, NULL, args->sendbuff, args->recvbuff, args->redOpArg, group, args);
+      for (ssize_t gridOffset = 0; gridOffset < size; gridOffset += loopSize) {
+        ssize_t offset = gridOffset + bid*nvls->nHeads*chunkSize;
+        int nelem = min(nvls->nHeads*chunkSize, size-offset);
+        prims.gather(offset, nelem, chunkSize, chunkSize, -1, 0);
+      }
+    } else if (tid < tidEndReduce) {
+      int group = (3*Proto::MaxGroupWidth) | (1<<16);
+      // Reduce, broadcast through NVLS
+      Primitives<T, RedOp, FanSymmetric<1>, /*Direct=*/0, Proto, 0>
+        prims(tid-tidEndGather, nThreadsReduce, &nvls->down, &nvls->down, args->sendbuff, args->recvbuff, args->redOpArg, group, args);
+      for (ssize_t gridOffset = 0; gridOffset < size; gridOffset += loopSize) {
+        ssize_t offset = gridOffset + (bid*nvls->nHeads+nvls->headRank)*chunkSize;
+        int nelem = min(chunkSize, size-offset);
+        prims.recvSend(nelem);
+      }
+    }
+  #endif // NCCL_NVLS_ENABLED
+  }
+};
+
 template<typename T, typename RedOp>
 struct RunWorkElement<ncclFuncAllReduce, T, RedOp, NCCL_ALGO_COLLNET_CHAIN, NCCL_PROTO_SIMPLE> {
   __device__ __forceinline__ void run(ncclWorkElem *args) {

src/collectives/device/common.h

@@ -11,31 +11,23 @@
 #include "devcomm.h"
 #include "op128.h"
 
-#if __CUDA_ARCH__ >= 800
+#define COLL_UNROLL (ncclCollUnroll())
-#define COLL_UNROLL 8
-#else
-#define COLL_UNROLL 4
-#endif
-
 #define NCCL_MAX_DEV_ARITY (NCCL_MAX_TREE_ARITY-1)  // Using balanced tree instead of split tree
 
 typedef void(*ncclKern_t)();
 extern __device__ ncclKern_t ncclFuncs[];
 
 struct ncclShmemGroup {
-  ncclConnInfo *recvConns[NCCL_MAX_DIRECT_ARITY];
+  ncclConnInfo *recvConns[NCCL_MAX_NVLS_ARITY];
-  ncclConnInfo *sendConns[NCCL_MAX_DIRECT_ARITY];
+  ncclConnInfo *sendConns[NCCL_MAX_NVLS_ARITY];
-  void* srcs[NCCL_MAX_DIRECT_ARITY+1];
+  void* srcs[NCCL_MAX_NVLS_ARITY+1];
-  void* dsts[NCCL_MAX_DIRECT_ARITY+1];
+  void* dsts[NCCL_MAX_NVLS_ARITY+1];
-  int totalSendSize[NCCL_MAX_SLICE_PER_CHUNK];
+  int nvlsRecv;
 };
 
 struct ncclShmemData {
-  union {
-    uint64_t ll128warp[NCCL_LL128_MAX_NTHREADS/WARP_SIZE][NCCL_LL128_SHMEM_ELEMS_PER_THREAD*WARP_SIZE];
   struct ncclShmemGroup groups[NCCL_MAX_GROUPS];
-  };
+  uint64_t redOpArgs[NCCL_MAX_NVLS_ARITY+1];
-  uint64_t redOpArgs[NCCL_MAX_DIRECT_ARITY+1];
   int channelId;
   int aborted;
   alignas(16) struct ncclDevComm comm;
@@ -45,6 +37,15 @@ struct ncclShmemData {
 static_assert(offsetof(struct ncclShmemData, work)%16 == 0, "shmem.work needs to be 16B aligned");
 
 extern __shared__ ncclShmemData ncclShmem;
+#if __CUDA_ARCH__ >= 700
+  extern __shared__ ulong2 ncclShmemPerWarp[/*ncclShmemDynamicSize()/sizeof(ulong2)*/];
+#else
+  extern __shared__ ulong2 ncclShmemPerWarp[ncclShmemScratchWarpSize()*(NCCL_MAX_NTHREADS/WARP_SIZE)/sizeof(ulong2)];
+#endif
+
+__device__ inline void* ncclScratchForWarp(int warp) {
+  return (char*)ncclShmemPerWarp + warp*ncclShmemScratchWarpSize();
+}
 
 __device__ inline bool barrierReduceAny(int bit) {
   uint32_t popc;
@@ -235,7 +236,8 @@ __device__ void NCCL_FUNC_NAME(func, algo, proto, devredop, type)() { \
   IMPL_COLL4(func, TREE,    devredop, type, ncclType) \
   IMPL_COLL4(func, RING,    devredop, type, ncclType) \
   IMPL_COLL4(func, COLLNET_DIRECT, devredop, type, ncclType) \
-  IMPL_COLL4(func, COLLNET_CHAIN, devredop, type, ncclType)
+  IMPL_COLL4(func, COLLNET_CHAIN, devredop, type, ncclType) \
+  IMPL_COLL4(func, NVLS, devredop, type, ncclType)
 
 #if NCCL_TYPE == 0
 #define IMPL_COLL2(func, devredop) IMPL_COLL3(func, devredop, int8_t,   ncclInt8)
@@ -291,4 +293,6 @@ __device__ void NCCL_FUNC_NAME(func, algo, proto, devredop, type)() { \
 #define IMPL_COLL_P(func)
 #endif
 
+#define NCCL_NVLS_ENABLED (__CUDA_ARCH__ >= 900 && NCCL_NVLS_SUPPORTS(NCCL_TYPE, NCCL_OP))
+
 #endif

src/collectives/device/functions.cu

@@ -9,6 +9,9 @@
 #include "common.h"
 
 __shared__ ncclShmemData ncclShmem;
+#if __CUDA_ARCH__ < 700
+  __shared__ ulong2 ncclShmemPerWarp[ncclShmemScratchWarpSize()*(NCCL_MAX_NTHREADS/WARP_SIZE)/sizeof(ulong2)];
+#endif
 
 #define NCCL_FUNC5(func, algo, devredop, type, nullify) \
   MACRO_IF(nullify, nullptr, NCCL_FUNC_NAME(func, algo, LL,     devredop, type)), \
@@ -19,7 +22,8 @@ __shared__ ncclShmemData ncclShmem;
   NCCL_FUNC5(func, TREE,    devredop, type, nullify), \
   NCCL_FUNC5(func, RING,    devredop, type, nullify), \
   NCCL_FUNC5(func, COLLNET_DIRECT, devredop, type, nullify), \
-  NCCL_FUNC5(func, COLLNET_CHAIN, devredop, type, nullify)
+  NCCL_FUNC5(func, COLLNET_CHAIN,  devredop, type, nullify), \
+  NCCL_FUNC5(func, NVLS,           devredop, type, nullify)
 
 #if defined(__CUDA_BF16_TYPES_EXIST__)
 // Must be consistent with ncclDataType_t

src/collectives/device/onerank_reduce.cu

@@ -6,7 +6,7 @@
 
 #include "devcomm.h"
 #include "collectives.h"
-#include "reduce_kernel.h"
+#include "common_kernel.h"
 #include "common.h"
 
 namespace {
@@ -35,8 +35,10 @@ namespace {
       i1 = i1 < eltN ? i1 : eltN;
       src += i0;
       dst += i0;
-      ReduceOrCopyMulti<COLL_UNROLL, RedOp, T, 1, 1, 1, 1, 1>
+      void *vsrc = (void*)src;
-        (tid, tn, &(we->redOpArg), true, 1, &src, 1, &dst, i1-i0);
+      void *vdst = (void*)dst;
+      ReduceOrCopyMulti<COLL_UNROLL, RedOp, T, 1, 1, 1, 1, /*PreOpSrcs=*/1>
+        (tid, tn, we->redOpArg, &(we->redOpArg), true, 1, &vsrc, 1, &vdst, i1-i0);
     }
   }
 }

src/collectives/device/op128.h

@@ -65,4 +65,290 @@ inline __device__ void loadShmemMisaligned128(T *ptr, uint64_t &v0, uint64_t &v1
   v1 = tmp8[1];
 }
 
+
+template<typename T>
+__device__ __forceinline__ uint32_t cvta_to_shared(T* ptr) {
+  return (uint32_t)__cvta_generic_to_shared(ptr);
+}
+template<typename T>
+__device__ __forceinline__ uintptr_t cvta_to_global(T* ptr) {
+  return (uintptr_t)__cvta_generic_to_global(ptr);
+}
+
+template<typename T>
+__device__ __forceinline__ T* cvta_from_shared(uint32_t shptr) {
+  T* ans;
+  asm("cvta.shared.u64 %0, %1;" : "=l"(ans) : "l"(uint64_t(shptr)));
+  return ans;
+}
+template<typename T>
+__device__ __forceinline__ T* cvta_from_global(uintptr_t gptr) {
+  T* ans;
+  asm("cvta.global.u64 %0, %1;" : "=l"(ans) : "l"(gptr));
+  return ans;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// BytePack<Size>: struct of bytes.
+
+template<int Size>
+union BytePack;
+template<>
+union BytePack<1> {
+  uint8_t u8, native;
+};
+template<>
+union BytePack<2> {
+  BytePack<1> half[2];
+  uint8_t u8[2];
+  uint16_t u16, native;
+};
+template<>
+union BytePack<4> {
+  BytePack<2> half[2];
+  uint8_t u8[4];
+  uint16_t u16[2];
+  uint32_t u32, native;
+};
+template<>
+union BytePack<8> {
+  BytePack<4> half[2];
+  uint8_t u8[8];
+  uint16_t u16[4];
+  uint32_t u32[2];
+  uint64_t u64, native;
+};
+template<>
+union alignas(16) BytePack<16> {
+  BytePack<8> half[2];
+  uint8_t u8[16];
+  uint16_t u16[8];
+  uint32_t u32[4];
+  uint64_t u64[2];
+  ulong2 ul2, native;
+};
+
+template<typename T>
+__device__ __forceinline__ BytePack<sizeof(T)> toPack(T value)  {
+  union { BytePack<sizeof(T)> p; T v; };
+  v = value;
+  return p;
+}
+template<typename T>
+__device__ __forceinline__ T fromPack(BytePack<sizeof(T)> pack)  {
+  union { BytePack<sizeof(T)> p; T v; };
+  p = pack;
+  return v;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// Load/store of BytePack<?> using integral addresses.
+
+template<int Size> __device__ BytePack<Size> ld_global(uintptr_t addr);
+template<int Size> __device__ BytePack<Size> ld_volatile_global(uintptr_t addr);
+template<int Size> __device__ BytePack<Size> ld_shared(uint32_t addr);
+template<int Size> __device__ BytePack<Size> ld_volatile_shared(uint32_t addr);
+template<int Size> __device__ void st_global(uintptr_t addr, BytePack<Size> value);
+template<int Size> __device__ void st_shared(uint32_t addr, BytePack<Size> value);
+
+// Used to define implementations for above prototypes.
+#define DEFINE_ld_st(bytes, data_cxx_ty, data_ptx_ty, data_reg_ty, space, addr_cxx_ty, addr_reg_ty) \
+  template<> \
+  __device__ __forceinline__ BytePack<bytes> ld_##space<bytes>(addr_cxx_ty addr) { \
+    data_cxx_ty tmp; \
+    asm("ld." #space "." #data_ptx_ty " %0, [%1];" : "="#data_reg_ty(tmp) : #addr_reg_ty(addr)); \
+    BytePack<bytes> ans; \
+    ans.native = tmp; \
+    return ans; \
+  } \
+  template<> \
+  __device__ __forceinline__ BytePack<bytes> ld_volatile_##space<bytes>(addr_cxx_ty addr) { \
+    data_cxx_ty tmp; \
+    asm("ld.volatile." #space "." #data_ptx_ty " %0, [%1];" : "="#data_reg_ty(tmp) : #addr_reg_ty(addr)); \
+    BytePack<bytes> ans; \
+    ans.native = tmp; \
+    return ans; \
+  } \
+  template<> \
+  __device__ __forceinline__ void st_##space<bytes>(addr_cxx_ty addr, BytePack<bytes> value) { \
+    data_cxx_ty tmp = value.native; \
+    asm volatile("st." #space "." #data_ptx_ty " [%0], %1;" :: #addr_reg_ty(addr), #data_reg_ty(tmp) : "memory"); \
+  }
+// Single-byte types use 4-byte registers since there is no 1-byte register
+// character for asm blocks. See https://docs.nvidia.com/cuda/inline-ptx-assembly/index.html#constraints
+DEFINE_ld_st(1, uint32_t, b8, r, global, uintptr_t, l)
+DEFINE_ld_st(1, uint32_t, b8, r, shared, uint32_t, r)
+DEFINE_ld_st(2, uint16_t, b16, h, global, uintptr_t, l)
+DEFINE_ld_st(2, uint16_t, b16, h, shared, uint32_t, r)
+DEFINE_ld_st(4, uint32_t, b32, r, global, uintptr_t, l)
+DEFINE_ld_st(4, uint32_t, b32, r, shared, uint32_t, r)
+DEFINE_ld_st(8, uint64_t, b64, l, global, uintptr_t, l)
+DEFINE_ld_st(8, uint64_t, b64, l, shared, uint32_t, r)
+#undef DEFINE_ld_st
+
+#define DEFINE_ld_st_16(space, addr_cxx_ty, addr_reg_ty) \
+  template<> \
+  __device__ __forceinline__ BytePack<16> ld_##space<16>(addr_cxx_ty addr) { \
+    BytePack<16> ans; \
+    asm("ld." #space ".v2.b64 {%0,%1}, [%2];" : "=l"(ans.u64[0]), "=l"(ans.u64[1]) : #addr_reg_ty(addr)); \
+    return ans; \
+  } \
+  template<> \
+  __device__ __forceinline__ BytePack<16> ld_volatile_##space<16>(addr_cxx_ty addr) { \
+    BytePack<16> ans; \
+    asm("ld.volatile." #space ".v2.b64 {%0,%1}, [%2];" : "=l"(ans.u64[0]), "=l"(ans.u64[1]) : #addr_reg_ty(addr)); \
+    return ans; \
+  } \
+  template<> \
+  __device__ __forceinline__ void st_##space<16>(addr_cxx_ty addr, BytePack<16> value) { \
+    asm("st." #space ".v2.b64 [%0], {%1,%2};" :: #addr_reg_ty(addr), "l"(value.u64[0]), "l"(value.u64[1]) : "memory"); \
+  }
+DEFINE_ld_st_16(global, uintptr_t, l)
+DEFINE_ld_st_16(shared, uint32_t, r)
+#undef DEFINE_ld_st_16
+
+////////////////////////////////////////////////////////////////////////////////
+// Atomic load/store using c++ pointers.
+
+__device__ __forceinline__ uint64_t ld_volatile_global(uint64_t *ptr) {
+  uint64_t ans;
+  asm("ld.volatile.global.u64 %0, [%1];" : "=l"(ans) : "l"(cvta_to_global(ptr)));
+  return ans;
+}
+__device__ __forceinline__ uint64_t ld_relaxed_sys_global(uint64_t *ptr) {
+  uint64_t ans;
+  #if __CUDA_ARCH__ >= 700
+    asm("ld.relaxed.sys.global.u64 %0, [%1];" : "=l"(ans) : "l"(cvta_to_global(ptr)));
+  #else
+    asm("ld.volatile.global.u64 %0, [%1];" : "=l"(ans) : "l"(cvta_to_global(ptr)));
+  #endif
+  return ans;
+}
+__device__ __forceinline__ uint64_t ld_acquire_sys_global(uint64_t *ptr) {
+  uint64_t ans;
+  #if __CUDA_ARCH__ >= 700
+    asm("ld.acquire.sys.global.u64 %0, [%1];" : "=l"(ans) : "l"(cvta_to_global(ptr)));
+  #else
+    asm("ld.volatile.sys.global.u64 %0, [%1]; membar.gl;" : "=l"(ans) : "l"(cvta_to_global(ptr)));
+  #endif
+  return ans;
+}
+
+__device__ __forceinline__ void st_volatile_global(uint64_t *ptr, uint64_t val) {
+  asm volatile("st.volatile.global.u64 [%0], %1;" :: "l"(cvta_to_global(ptr)), "l"(val) : "memory");
+}
+__device__ __forceinline__ void st_relaxed_sys_global(uint64_t *ptr, uint64_t val) {
+  #if __CUDA_ARCH__ >= 700
+    asm volatile("st.relaxed.sys.global.u64 [%0], %1;" :: "l"(cvta_to_global(ptr)), "l"(val) : "memory");
+  #else
+    asm volatile("st.volatile.global.u64 [%0], %1;" :: "l"(cvta_to_global(ptr)), "l"(val) : "memory");
+  #endif
+}
+__device__ __forceinline__ void st_release_sys_global(uint64_t *ptr, uint64_t val) {
+  #if __CUDA_ARCH__ >= 700
+    asm volatile("st.release.sys.global.u64 [%0], %1;" :: "l"(cvta_to_global(ptr)), "l"(val) : "memory");
+  #else
+    asm volatile("membar.sys; st.volatile.global.u64 [%0], %1;" :: "l"(cvta_to_global(ptr)), "l"(val) : "memory");
+  #endif
+}
+
+__device__ __forceinline__ void fence_acq_rel_sys() {
+  #if __CUDA_ARCH__ >= 700
+    asm volatile("fence.acq_rel.sys;" ::: "memory");
+  #else
+    asm volatile("membar.sys;" ::: "memory");
+  #endif
+}
+__device__ __forceinline__ void fence_acq_rel_gpu() {
+  #if __CUDA_ARCH__ >= 700
+    asm volatile("fence.acq_rel.gpu;" ::: "memory");
+  #else
+    asm volatile("membar.gl;" ::: "memory");
+  #endif
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// Multimem stores of BytePack<?>.
+
+template<int Size>
+__device__ __forceinline__ void multimem_st_global(uintptr_t addr, BytePack<Size> val);
+
+#if __CUDA_ARCH__ >= 900 && CUDART_VERSION >= 12010
+template<>
+__device__ __forceinline__ void multimem_st_global<4>(uintptr_t addr, BytePack<4> val) {
+  asm volatile("multimem.st.global.b32 [%0], %1;" :: "l"(addr), "r"(val.u32) : "memory");
+}
+template<>
+__device__ __forceinline__ void multimem_st_global<8>(uintptr_t addr, BytePack<8> val) {
+  asm volatile("multimem.st.global.b64 [%0], %1;" :: "l"(addr), "l"(val.u64) : "memory");
+}
+template<>
+__device__ __forceinline__ void multimem_st_global<16>(uintptr_t addr, BytePack<16> val) {
+  asm volatile("multimem.st.global.v4.f32 [%0], {%1,%2,%3,%4};"
+    :: "l"(addr), "r"(val.u32[0]), "r"(val.u32[1]), "r"(val.u32[2]), "r"(val.u32[3])
+    : "memory");
+}
+#else
+template<int Size>
+__device__ __forceinline__ void multimem_st_global(uintptr_t addr, BytePack<Size> val) {
+  // nop
+}
+#endif
+
+// Warp-uniform memory copy from shared address (not generic) to global memory.
+// The number of bytes copied is `min(MaxBytes, nBytesAhead)`, a negative value
+// is interpeted as zero. EltSize is the guaranteed alignment of the addresses and sizes.
+template<int EltSize, int MaxBytes, bool Multimem, typename IntBytes>
+__device__ __forceinline__ void copyGlobalShared_WarpUnrolled(
+    int lane, uintptr_t dstAddr, uint32_t srcAddr, IntBytes nBytesAhead
+  ) {
+  static_assert(std::is_signed<IntBytes>::value, "`IntBytes` must be a signed integral type.");
+  int nBytes = min(nBytesAhead, (IntBytes)MaxBytes);
+  int nFrontBytes = min(nBytes, (16 - int(dstAddr%16))%16);
+  int nMiddleBytes = (nBytes-nFrontBytes) & -16;
+  int nBackBytes = (nBytes-nFrontBytes) % 16;
+
+  { int backLane = WARP_SIZE-1 - lane;
+    bool hasFront = lane*EltSize < nFrontBytes;
+    bool hasBack = backLane*EltSize < nBackBytes;
+    int offset = hasFront ? lane*EltSize : (nBytes - (backLane+1)*EltSize);
+    if (hasFront | hasBack) {
+      BytePack<EltSize> tmp = ld_shared<EltSize>(srcAddr+offset);
+      // Can't use multimem_st since it doesn't support EltSize==2
+      st_global<EltSize>(dstAddr+offset, tmp);
+    }
+  }
+
+  srcAddr += nFrontBytes;
+  int srcMisalign = EltSize < 4 ? (srcAddr%4) : 0;
+  srcAddr += -srcMisalign + lane*16;
+  dstAddr += nFrontBytes + lane*16;
+  nMiddleBytes -= lane*16;
+  #pragma unroll
+  for (int u=0; u < divUp(MaxBytes, WARP_SIZE*16); u++) {
+    if (nMiddleBytes <= 0) break;
+    union {
+      BytePack<4> b4[4];
+      BytePack<16> b16;
+    };
+    b4[0] = ld_shared<4>(srcAddr + 0*4);
+    b4[1] = ld_shared<4>(srcAddr + 1*4);
+    b4[2] = ld_shared<4>(srcAddr + 2*4);
+    b4[3] = ld_shared<4>(srcAddr + 3*4);
+    if (srcMisalign != 0) {
+      BytePack<4> b4_4 = ld_shared<4>(srcAddr + 4*4);
+      b4[0].u32 = __funnelshift_r(b4[0].u32, b4[1].u32, srcMisalign*8);
+      b4[1].u32 = __funnelshift_r(b4[1].u32, b4[2].u32, srcMisalign*8);
+      b4[2].u32 = __funnelshift_r(b4[2].u32, b4[3].u32, srcMisalign*8);
+      b4[3].u32 = __funnelshift_r(b4[3].u32, b4_4.u32, srcMisalign*8);
+    }
+    if (Multimem) multimem_st_global<16>(dstAddr, b16);
+    else          st_global<16>(dstAddr, b16);
+
+    srcAddr += WARP_SIZE*16;
+    dstAddr += WARP_SIZE*16;
+    nMiddleBytes -= WARP_SIZE*16;
+  }
+}
+
 #endif

src/collectives/device/primitives.h

@@ -9,6 +9,7 @@
 
 #include <type_traits>
 #include "reduce_kernel.h" // for reduction funcs
+#include "common_kernel.h"
 #include "common.h"
 
 #define NCCL_SPINS_BEFORE_CHECK_ABORT 1000000
@@ -20,12 +21,13 @@
  * to how that protocol operates with a consistent interface so that our
  * algorithm code can operate protocol parametrically.
  */
-template<int SlicePerChunk_1, int StepPerSlice_1, int Unroll_1 = COLL_UNROLL>
+template<int SlicePerChunk_1, int StepPerSlice_1, int Unroll_1 = COLL_UNROLL, bool NVLS_1 = false>
 struct ProtoSimple {
   static constexpr int Id = NCCL_PROTO_SIMPLE;
   static constexpr int SlicePerChunk = SlicePerChunk_1;
   static constexpr int StepPerSlice = StepPerSlice_1;
   static constexpr int Unroll = Unroll_1;
+  static constexpr bool NVLS = NVLS_1;
 
   // Data bytes (no flags etc) in one step of the fifo queue.
   __device__ static int calcBytePerStep() {

src/collectives/device/prims_ll.h

@@ -255,18 +255,18 @@ class Primitives<T, RedOp, Fan, Direct, ProtoLL, P2p>:
       }
       if (SRC) {
         data = dl.loadFinish();
-        if (SrcBuf == Input) data = MULTI<RedOp, T>().preOp(redOp, data);
+        if (SrcBuf == Input) data = applyPreOp(redOp, data);
       }
       if (RECV) {
-        data = !SRC ? peerData : MULTI<RedOp,T>()(redOp, peerData, data);
+        data = !SRC ? peerData : applyReduce(redOp, peerData, data);
         #pragma unroll MaxRecv
         for (int i=1; i < MaxRecv && i < fan.nrecv(); i++) {
           peerData = readLLFinish(offset, line, i);
-          data = MULTI<RedOp,T>()(redOp, peerData, data);
+          data = applyReduce(redOp, peerData, data);
         }
       }
 
-      if (postOp) data = MULTI<RedOp, T>().postOp(redOp, data);
+      if (postOp) data = applyPostOp(redOp, data);
 
       // Send : inter-node, then intra-node, then local
       if (SEND) {

src/collectives/device/prims_ll128.h

@@ -82,7 +82,14 @@ class Primitives<T, RedOp, Fan, Direct, ProtoLL128, P2p>:
     if (recvConnHeadPtr) *recvConnHeadPtr = recvConnHead += 1;
   }
   inline __device__ void postSend() {
-    if (sendConnTailPtr) { __threadfence(); *sendConnTailPtr = sendConnTail += 1; }
+    if (sendConnTailPtr) {
+#if __CUDA_ARCH__ >= 900
+      __threadfence_system();
+#else
+      __threadfence();
+#endif
+      *sendConnTailPtr = sendConnTail += 1;
+    }
   }
 
   template<int WordPerThread>
@@ -109,7 +116,7 @@ class Primitives<T, RedOp, Fan, Direct, ProtoLL128, P2p>:
       // buffer into shmem.
       int misalignment = reinterpret_cast<uintptr_t>(src) % 16;
       uint64_t *src8 = reinterpret_cast<uint64_t*>(reinterpret_cast<uintptr_t>(src) & -uintptr_t(16));
-      uint64_t *shm8 = shmemCvtPtr(ncclShmem.ll128warp[warpInBlock]);
+      uint64_t *shm8 = shmemCvtPtr((uint64_t*)ncclScratchForWarp(warpInBlock));
       #pragma unroll
       for(int g=0; g < WordPerThread/2; g++)
         if((g*WARP_SIZE + wid)*16 < misalignment + eltN*sizeof(T))
@@ -153,7 +160,7 @@ class Primitives<T, RedOp, Fan, Direct, ProtoLL128, P2p>:
     }
     // Write to dst if 16-byte aligned, shmem otherwise.
     int misalignment = reinterpret_cast<uintptr_t>(dst)%16;
-    uint64_t *shm8 = shmemCvtPtr(ncclShmem.ll128warp[warpInBlock]);
+    uint64_t *shm8 = shmemCvtPtr((uint64_t*)ncclScratchForWarp(warpInBlock));
     #pragma unroll
     for(int g=0; g < WordPerThread/2; g++) {
       int ix = g*WARP_SIZE - 4*(g/2) + wid - (g%2)*(wid/8);
@@ -167,7 +174,7 @@ class Primitives<T, RedOp, Fan, Direct, ProtoLL128, P2p>:
     __syncwarp();
     // Write rest from shmem to dst. No need to coalesce stores to 16-bytes,
     // the hardware keeps up fine.
-    T *shm = (T*)ncclShmem.ll128warp[warpInBlock];
+    T *shm = (T*)ncclScratchForWarp(warpInBlock);
     int skip = misalignment == 0 ? eltN & -EltPer16B : 0;
     for(int i=skip+wid; i < eltN; i += WARP_SIZE)
       dst[i] = shm[i];
@@ -196,6 +203,10 @@ class Primitives<T, RedOp, Fan, Direct, ProtoLL128, P2p>:
         }
         needReload &= (0 == checkAbort(spins, 0, 0));
       } while (__any_sync(WARP_MASK, needReload));
+
+      #pragma unroll
+      for (int u=0; u<ELEMS_PER_THREAD; u+=2)
+        load128(ptr+u*WARP_SIZE, vr[u], vr[u+1]);
     }
 
     /************* Finish register load **************/
@@ -206,9 +217,9 @@ class Primitives<T, RedOp, Fan, Direct, ProtoLL128, P2p>:
       if (SrcBuf == Input) {
         #pragma unroll
         for (int u=0; u<ELEMS_PER_THREAD; u+=2) {
-          v[u] = MULTI<RedOp, T>().preOp(redOp, v[u]);
+          v[u] = applyPreOp(redOp, v[u]);
           if (!flagThread)
-            v[u+1] = MULTI<RedOp, T>().preOp(redOp, v[u+1]);
+            v[u+1] = applyPreOp(redOp, v[u+1]);
         }
       }
     }
@@ -218,8 +229,8 @@ class Primitives<T, RedOp, Fan, Direct, ProtoLL128, P2p>:
       { // Consume data from first recv
         #pragma unroll
         for (int u=0; u<ELEMS_PER_THREAD; u+=2) {
-          v[u] = SRC ? MULTI<RedOp, T>()(redOp, vr[u], v[u]) : vr[u];
+          v[u]   = SRC ? applyReduce(redOp, vr[u], v[u]) : vr[u];
-          v[u+1] = SRC ? MULTI<RedOp, T>()(redOp, vr[u+1], v[u+1]) : vr[u+1];
+          v[u+1] = SRC ? applyReduce(redOp, vr[u+1], v[u+1]) : vr[u+1];
         }
       }
 
@@ -238,20 +249,24 @@ class Primitives<T, RedOp, Fan, Direct, ProtoLL128, P2p>:
           needReload &= (0 == checkAbort(spins, i, 0));
         } while (__any_sync(WARP_MASK, needReload));
 
+        #pragma unroll
+        for (int u=0; u<ELEMS_PER_THREAD; u+=2)
+          load128(ptr+u*WARP_SIZE, vr[u], vr[u+1]);
+
         #pragma unroll
         for (int u=0; u<ELEMS_PER_THREAD; u+=2) {
-          v[u] = MULTI<RedOp, T>()(redOp, vr[u], v[u]);
+          v[u]   = applyReduce(redOp, vr[u], v[u]);
-          v[u+1] = MULTI<RedOp, T>()(redOp, vr[u+1], v[u+1]);
+          v[u+1] = applyReduce(redOp, vr[u+1], v[u+1]);
         }
       }
     }
     /********************** End Recv ************************/
 
-    if (postOp && !FuncTraits<RedOp>::IsPostOpIdentity) {
+    if (postOp) {
       #pragma unroll
       for (int u=0; u<ELEMS_PER_THREAD; u+=2) {
-        v[u]   = MULTI<RedOp, T>().postOp(redOp, v[u]);
+        v[u]   = applyPostOp(redOp, v[u]);
-        v[u+1] = MULTI<RedOp, T>().postOp(redOp, v[u+1]);
+        v[u+1] = applyPostOp(redOp, v[u+1]);
       }
     }
 
@@ -282,14 +297,6 @@ class Primitives<T, RedOp, Fan, Direct, ProtoLL128, P2p>:
   __device__ __forceinline__ void GenericOp(intptr_t srcIx, intptr_t dstIx, int nelem, bool postOp) {
     constexpr int SRC = SrcBuf != -1 ? 1 : 0;
     constexpr int DST = DstBuf != -1 ? 1 : 0;
-    static_assert(-1<=SrcBuf && SrcBuf < 2, "Uhoh");
-    static_assert(-1<=DstBuf && DstBuf < 2, "Uhoh");
-    static_assert(DstBuf!=Input, "Mistake?");
-    #if 0
-    assert((SrcBuf==-1) == (srcIx==-1));
-    assert((DstBuf==-1) == (dstIx==-1));
-    #endif
-
     T const *srcPtr = SrcBuf == -1 ? nullptr : userBufs[SrcBuf] + srcIx;
     T       *dstPtr = DstBuf == -1 ? nullptr : userBufs[DstBuf] + dstIx;
     int wireOffset = WireWordPerSlice*warp + 2*wid;

src/collectives/device/prims_simple.h

@@ -5,9 +5,9 @@
  ************************************************************************/
 
 template<typename T, typename RedOp, typename Fan, int Direct,
-         int SlicePerChunk, int StepPerSlice, int Unroll, int P2p>
+         int SlicePerChunk, int StepPerSlice, int Unroll, int P2p, bool NVLS>
 class Primitives<
-    T, RedOp, Fan, Direct, ProtoSimple<SlicePerChunk, StepPerSlice, Unroll>, P2p
+    T, RedOp, Fan, Direct, ProtoSimple<SlicePerChunk, StepPerSlice, Unroll, NVLS>, P2p
   > {
   static constexpr int MaxRecv = Fan::MaxRecv, MaxSend = Fan::MaxSend;
   static constexpr int Input=0, Output=1;
@@ -22,8 +22,10 @@ class Primitives<
                        SizesFifoEnabled = 0x100,
                        DirectWrite = 0x200,
                        DirectRead = 0x400,
-                       ThreadsSynced = 0x800;
+                       ThreadsSynced = 0x800,
-  const int tid;
+                       NvlsMinPolling = 0x1000,
+                       NvlsRecv = 0x2000;
+  const int tid, tidInBlock;
   int nthreads;
   int nworkers;
   const int stepSize;
@@ -41,22 +43,54 @@ class Primitives<
     int volatile *connSizesFifoPtr; //  (flags & SizesFifoEnabled)
     T *directBuff;                  // !(flags & SizesFifoEnabled)
   };
-  uint64_t volatile *connStepPtr;
+  uint64_t *connStepPtr;
   uint64_t connStepCache; // Cache last seen value of (*connStepPtr)
 
   // Don't use barrier 0 as it's used by the final sync
-  inline __device__ void barrier() {
+  __device__ void barrier() {
-    if (nthreads == WARP_SIZE)
-      __syncwarp();
-    else
-      asm volatile("bar.sync %0, %1;" :: "r"(15-group), "r"(nthreads));
     flags |= ThreadsSynced;
+    if (nthreads == WARP_SIZE) __syncwarp();
+    else {
+      int bar = 15-group;
+      asm volatile("bar.sync %0, %1;" :: "r"(bar), "r"(nthreads) : "memory");
+    }
+  }
+  __device__ void subBarrier() {
+    if (nworkers == WARP_SIZE) __syncwarp();
+    else {
+      int bar = (nworkers==nthreads ? 15 : 8) - group;
+      asm volatile("bar.sync %0, %1;" :: "r"(bar), "r"(nworkers) : "memory");
+    }
+  }
+
+  __device__ bool barrierAny(int vote) {
+    flags |= ThreadsSynced;
+    if (nthreads == WARP_SIZE) {
+      return __any_sync(~0u, vote);
+    } else {
+      int ans, bar = 15-group;
+      asm volatile(
+        "{ .reg .pred p;"
+        "  setp.ne.s32 p, %1, 0;"
+        "  bar.red.or.pred p, %2, %3, p; "
+        "  selp.s32 %0, 1, 0, p; }"
+        : "=r"(ans) : "r"(vote), "r"(bar), "r"(nthreads) : "memory");
+      return ans != 0;
+    }
+  }
+  __device__ bool subBarrierAny(int vote) {
+    if (nworkers == WARP_SIZE) {
+      return __any_sync(~0u, vote);
+    } else {
+      int ans, bar = (nworkers==nthreads ? 15 : 8) - group;
+      asm volatile(
+        "{ .reg .pred p;"
+        "  setp.ne.s32 p, %1, 0;"
+        "  bar.red.or.pred p, %2, %3, p; "
+        "  selp.s32 %0, 1, 0, p; }"
+        : "=r"(ans) : "r"(vote), "r"(bar), "r"(nworkers) : "memory");
+      return ans != 0;
     }
-  inline __device__ void subBarrier() {
-    if (nworkers == nthreads)
-      barrier();
-    else
-      asm volatile("bar.sync %0, %1;" :: "r"(8-group), "r"(nworkers));
   }
 
   inline __device__ bool checkAbort(int &spins) {
@@ -71,6 +105,19 @@ class Primitives<
     return flags & Aborted;
   }
 
+  inline __device__ uint64_t loadStepValue(uint64_t* ptr) {
+    #if __CUDA_ARCH__ >= 900 && CUDART_VERSION >= 12010
+    if (NVLS && (flags & NvlsMinPolling)) {
+      uint64_t ans;
+      asm("multimem.ld_reduce.acquire.sys.global.min.u64 %0, [%1];" : "=l"(ans) : "l"(cvta_to_global(ptr)));
+      return ans;
+    }
+    #endif
+    // volatile is faster than acquire but not as correct. Make sure ReduceOrCopyMulti
+    // loads data using volatile so it doesn't see stale data in L1.
+    return ld_volatile_global(ptr);
+  }
+
   template <int DirectRecv, int DirectSend, int Recv, int Send, int Src, int Dst>
   __device__ __forceinline__ void waitPeer(intptr_t dstIx, intptr_t remoteIx, int offset, int nelts) {
     const bool isSendNotRecv = (Send && Recv) ? (flags & RoleWaitSend) : Send;
@@ -80,7 +127,7 @@ class Primitives<
         ((flags & (Send*RoleWaitSend)) && !noSendWait)) {
       int spins = 0;
       while (connStepCache + (isSendNotRecv ? NCCL_STEPS : 0) < step + StepPerSlice) {
-        connStepCache = *connStepPtr;
+        connStepCache = loadStepValue(connStepPtr);
         if (checkAbort(spins)) break;
         //if (spins == 0) printf("r=%d b=%d t=%d SPUN OUT got=%d want=%d\n", ncclShmem.comm.rank, blockIdx.x, threadIdx.x, int(connStepCache + (isSendNotRecv ? NCCL_STEPS : 0)), int(step+StepPerSlice));
       }
@@ -119,10 +166,11 @@ class Primitives<
   }
 
   template<int Recv, int Send>
-  inline __device__ void postPeer() {
+  inline __device__ void postPeer(bool dataStored) {
     if (flags & (Recv*RolePostRecv | Send*RolePostSend)) {
       step += StepPerSlice;
-      *connStepPtr = step;
+      if (Send && (flags & RolePostSend) && dataStored) fence_acq_rel_sys();
+      st_relaxed_sys_global(connStepPtr, step);
     }
   }
 
@@ -166,7 +214,7 @@ class Primitives<
       //     post();
       //   } // Since we no longer unroll, new branch added here
       #if __CUDA_ARCH__ < 700
-        // Yeah, so all that above don't matter a lick on older hardware.
+        // Above doesn't matter on older hardware.
         #pragma unroll SlicePerChunk
       #else
         #pragma unroll 1
@@ -181,37 +229,39 @@ class Primitives<
         subBarrier();
         /* if user abort the kernel, we don't need to actually perform copy/reduce; just set size
          * to 0 to avoid unnecessary workload. */
-        size_t workSize = ncclShmem.aborted ? 0 : sliceSize;
+        int workSize = ncclShmem.aborted ? 0 : sliceSize;
-        if (DirectRecv && ncclShmem.groups[group].srcs[0] == ncclShmem.groups[group].dsts[0]) {
+        if (NVLS && ncclShmem.groups[group].nvlsRecv) {
+          void* src = ncclShmem.groups[group].srcs[0];
+          void* dst = ncclShmem.groups[group].dsts[0];
+          copyMultimemMultimem<RedOp>(tid, nworkers, ncclShmem.redOpArgs[0], postOp, src, dst, workSize,
+          cvta_to_shared(ncclScratchForWarp(tidInBlock/WARP_SIZE)));
+        } else if (DirectRecv && ncclShmem.groups[group].srcs[0] == ncclShmem.groups[group].dsts[0]) {
           // We can only have one direct receive. Since srcs[0] == dstPtr+offset, skip one copy
           if (Send) {
-            // (1-Send) is only there to avoid compilation errors in case MaxSend=0 (and Send=0).
+            ReduceOrCopyMulti<Unroll, RedOp, T, 1, 1, 1, MaxSend, /*PreOpSrcs*/0>
-            ReduceOrCopyMulti<Unroll, RedOp, T, 1, 1, 1, (1-Send)+MaxSend, 0>
+              (tid, nworkers, /*redArg*/0, /*preOpArgs*/nullptr, /*postOp*/false,
-              (tid, nworkers, nullptr, false,
+               1, ncclShmem.groups[group].srcs,
-               1, (T const**)ncclShmem.groups[group].srcs,
+               fan.nsend(), ncclShmem.groups[group].dsts+1,
-               fan.nsend(), (T**)ncclShmem.groups[group].dsts+1,
                workSize);
           }
         } else if (DirectSend && !DirectRecv && SrcBuf != Input && ncclShmem.groups[group].dsts[Dst] == nullptr) {
           // For broadcast in CollNet to do empty send
-          ReduceOrCopyMulti<Unroll, RedOp, T, 1, 1, 1, 1, 0>
+          ReduceOrCopyMulti<Unroll, RedOp, T, 1, 1, 1, 1, /*PreOpSrcs*/0>
-            (tid, nworkers, ncclShmem.redOpArgs, postOp,
+            (tid, nworkers, ncclShmem.redOpArgs[0],  nullptr, postOp,
-             Recv, (T const**)ncclShmem.groups[group].srcs,
+             Recv, ncclShmem.groups[group].srcs,
-             Dst, (T**)ncclShmem.groups[group].dsts,
+             Dst, ncclShmem.groups[group].dsts,
              workSize);
         } else {
-          constexpr int PreOpN = SrcBuf != Input ? 0 :
+          constexpr int PreOpSrcs = SrcBuf != Input ? 0 :
                                     DirectRecv*MaxRecv == NCCL_MAX_DIRECT_ARITY ? (1+NCCL_MAX_DIRECT_ARITY) : 1;
-          ReduceOrCopyMulti<Unroll, RedOp, T, Recv+Src, Recv*MaxRecv+Src, Send+Dst, Send*MaxSend+Dst, PreOpN>
+          ReduceOrCopyMulti<Unroll, RedOp, T, Recv+Src, Recv*MaxRecv+Src, Send+Dst, Send*MaxSend+Dst, PreOpSrcs>
-            (tid, nworkers, ncclShmem.redOpArgs, postOp,
+            (tid, nworkers, ncclShmem.redOpArgs[0], ncclShmem.redOpArgs, postOp,
-             Recv*fan.nrecv()+Src, (T const**)ncclShmem.groups[group].srcs,
+             Recv*fan.nrecv()+Src, ncclShmem.groups[group].srcs,
-             Send*fan.nsend()+Dst, (T**)ncclShmem.groups[group].dsts,
+             Send*fan.nsend()+Dst, ncclShmem.groups[group].dsts,
              workSize);
         }
         barrier(); // This barrier has a counterpart in following loop
-        if (Send && (flags & RolePostSend) && index == 0) __threadfence_system();
+        postPeer<Recv, Send>(0 < sliceSize);
-        __syncwarp();
-        postPeer<Recv, Send>();
         offset += sliceSize;
         slice += 1;
       } while (slice < SlicePerChunk && offset < nelem);
@@ -229,9 +279,7 @@ class Primitives<
         waitPeer<DirectRecv, DirectSend, Recv, Send, Src, Dst>(0, 0, 0, 0);
       }
       barrier(); // Has couterpart in preceding worker-only loop.
-      if (Send && (flags & RolePostSend) && sliceSize > 0 && index == 0) __threadfence_system();
+      postPeer<Recv, Send>(0 < sliceSize);
-      __syncwarp();
-      postPeer<Recv, Send>();
       offset += sliceSize;
       slice += 1;
     }
@@ -242,7 +290,7 @@ class Primitives<
   // shift: peer offset to avoid all ranks sending to or receiving from same peer
   template <int DirectRecv1, int DirectSend1, int Recv, int Send>
   __device__ __forceinline__ void
-  ScatterGatherOp(intptr_t inpIx, intptr_t outIx, int totalElem, int peerElem, int skip, int shift, bool postOp) {
+  ScatterGatherOp(intptr_t inpIx, intptr_t outIx, int totalElem, int peerElem, int peerOffset, int skip, int shift, bool postOp) {
     constexpr int DirectRecv = 1 && Direct && DirectRecv1;
     constexpr int DirectSend = 1 && Direct && DirectSend1;
     int offset = 0; // slice offset
@@ -252,12 +300,12 @@ class Primitives<
     #pragma unroll
     for (int slice=0; slice<SlicePerChunk; ++slice) {
       int realSize = max(0, min(dataSize, peerElem-offset));
+      bool fenceNeeded = false;
       if (tid < nworkers) {
         if (Send) {
           // Scatter pre-scales data of input buffer only in non-Direct case
-          constexpr int PreOpN = DirectSend ? 0 : 1;
+          constexpr int PreOpSrcs = DirectSend ? 0 : 1;
           if (flags & RoleInput) ncclShmem.groups[group].srcs[0] = userBuff + inpIx + offset;
-          if (tid == 0) ncclShmem.groups[group].totalSendSize[slice] = 0; // Skip the threadfence
           // realSize is not accurate here; but intra-node does not rely on sizes FIFO
           waitPeer<0, DirectSend, 0, 1, 1, 0>(0, inpIx, offset, realSize);
           subBarrier();
@@ -265,23 +313,23 @@ class Primitives<
           // Loop over peers
           for (int j=0; j<fan.nsend(); j++) {
             int i = (j+shift)%fan.nsend();
-            int peerOffset = i*peerElem;
+            int pOffset = i*peerOffset;
             // Skip the data I am responsible of reducing myself
-            if (skip >= 0 && i >= skip) peerOffset += peerElem;
+            if (skip >= 0 && i >= skip) pOffset += peerElem;
-            const T* src0 = (T*)ncclShmem.groups[group].srcs[0] + peerOffset;
+            void* src0 = (T*)ncclShmem.groups[group].srcs[0] + pOffset;
-            int realPeerSize = min(realSize, totalElem-peerOffset);
+            int realPeerSize = min(realSize, totalElem-pOffset);
             if (realPeerSize > 0 && ncclShmem.groups[group].dsts[i] != nullptr) {
-              ReduceOrCopyMulti<Unroll, RedOp, T, 1, 1, 1, 1, PreOpN>(tid, nworkers, ncclShmem.redOpArgs, false, 1, &src0, 1, (T**)ncclShmem.groups[group].dsts+i, realPeerSize);
+              ReduceOrCopyMulti<Unroll, RedOp, T, 1, 1, 1, 1, PreOpSrcs>(tid, nworkers, ncclShmem.redOpArgs[0], ncclShmem.redOpArgs, false, 1, &src0, 1, ncclShmem.groups[group].dsts+i, realPeerSize);
               // Mark for threadfence at the end
-              if (tid == 0) ncclShmem.groups[group].totalSendSize[slice] += realPeerSize;
+              fenceNeeded |= true;
             }
           }
         } else if (Recv) {
           if (flags & RoleOutput) ncclShmem.groups[group].dsts[0] = userBuff + outIx + offset;
-          int peerOffset = index*peerElem;
+          int pOffset = index*peerOffset;
-          if (skip >= 0 && index >= skip) peerOffset += peerElem;
+          if (skip >= 0 && index >= skip) pOffset += peerElem;
           // Adjust remote index with peer offset in case we are directly pulling from peer's output buffer
-          waitPeer<DirectRecv, 0, 1, 0, 0, 1>(outIx, outIx+peerOffset, offset, realSize);
+          waitPeer<DirectRecv, 0, 1, 0, 0, 1>(outIx, outIx+pOffset, offset, realSize);
           subBarrier();
           if (DirectRecv && ncclShmem.groups[group].srcs[0] == ncclShmem.groups[group].dsts[0]) {
             // Since waitPeer sets srcs[0] to output buffer + offset, we are doing a direct-write based recv
@@ -290,21 +338,17 @@ class Primitives<
             #pragma unroll
             for (int j=0; j<fan.nrecv(); j++) {
               int i = (j+shift)%fan.nrecv();
-              peerOffset = i*peerElem;
+              pOffset = i*peerOffset;
-              if (skip >= 0 && i >= skip) peerOffset += peerElem;
+              if (skip >= 0 && i >= skip) pOffset += peerElem;
-              T* dst0 = (T*)ncclShmem.groups[group].dsts[0] + peerOffset;
+              void* dst0 = (T*)ncclShmem.groups[group].dsts[0] + pOffset;
-              int realPeerSize = min(realSize, totalElem-peerOffset);
+              int realPeerSize = min(realSize, totalElem-pOffset);
-              if (realPeerSize > 0) ReduceOrCopyMulti<Unroll, RedOp, T, 1, 1, 1, 1, 0>(tid, nworkers, ncclShmem.redOpArgs, postOp, 1, (const T**)ncclShmem.groups[group].srcs+i, 1, &dst0, realPeerSize);
+              if (realPeerSize > 0) ReduceOrCopyMulti<Unroll, RedOp, T, 1, 1, 1, 1, /*PreOpSrcs=*/0>(tid, nworkers, ncclShmem.redOpArgs[0], ncclShmem.redOpArgs, postOp, 1, ncclShmem.groups[group].srcs+i, 1, &dst0, realPeerSize);
             }
           }
         }
       }
-      barrier();
+      fenceNeeded = barrierAny(fenceNeeded);
-      // If we indeed send something, threadfence
+      postPeer<Recv, Send>(fenceNeeded);
-      if (Send && (flags & RolePostSend) && ncclShmem.groups[group].totalSendSize[slice] > 0 && index == 0)
-        __threadfence_system();
-      __syncwarp();
-      postPeer<Recv, Send>();
       offset += realSize;
     }
   }
@@ -320,25 +364,33 @@ class Primitives<
       }
       if (flags & RoleWaitRecv) {
         ncclShmem.groups[group].recvConns[index] = conn; // WaitRecv role saves since that's who needs it in setDataPtrs()
+        if ((index == 0) && (flags & RoleWaitRecv)) {
+          if (conn->flags & NCCL_NVLS_MIN_POLL) {
+            flags |= NvlsMinPolling;
+            ncclShmem.groups[group].nvlsRecv = 1;
+          } else {
+            ncclShmem.groups[group].nvlsRecv = 0;
+          }
+        }
         connStepPtr = conn->tail;
-        connStepCache = *connStepPtr;
+        connStepCache = loadStepValue(connStepPtr);
         flags |= (conn->offsFifo != nullptr) ? OffsFifoEnabled : 0;
         if (Direct) {
           // User buffers have been registered
-          if ((conn->direct & (NCCL_IPC_READ|NCCL_IPC_WRITE)) && e != nullptr && e->regUsed) {
+          if ((conn->flags & (NCCL_IPC_READ|NCCL_IPC_WRITE)) && e != nullptr && e->regUsed) {
             if (connIndex == 1 && P2p == 0) {
               flags |= DirectRead;  // scatter-reduce use direct pull
             } else {
               flags |= (e->direct & NCCL_DIRECT_WRITE) ? DirectWrite :
                        (e->direct & NCCL_DIRECT_READ)  ? DirectRead  : 0;
             }
-          } else if (conn->direct & (NCCL_DIRECT_WRITE|NCCL_DIRECT_READ)) {
+          } else if (conn->flags & (NCCL_DIRECT_WRITE|NCCL_DIRECT_READ)) {
             if (connIndex == 1 && P2p == 0) {
               flags |= DirectRead;  // scatter-reduce use direct pull
             } else {
               // direct read not allowed in non-register case
               // otherwise, in one-to-multi send, we could mix empty send and intermediate send
-              flags |= (conn->direct & NCCL_DIRECT_WRITE) ? DirectWrite : 0;
+              flags |= (conn->flags & NCCL_DIRECT_WRITE) ? DirectWrite : 0;
             }
           }
         }
@@ -359,8 +411,9 @@ class Primitives<
       }
       if (flags & RoleWaitSend) {
         ncclShmem.groups[group].sendConns[index] = conn; // WaitSend role saves since that's who needs it in setDataPtrs()
+        flags |= (conn->flags & NCCL_NVLS_MIN_POLL) ? NvlsMinPolling : 0;
         connStepPtr = conn->head;
-        connStepCache = *connStepPtr;
+        connStepCache = loadStepValue(connStepPtr);
         flags |= (conn->offsFifo != nullptr) ? OffsFifoEnabled : 0;
         if (flags & OffsFifoEnabled)
           connOffsFifoPtr = conn->offsFifo;
@@ -371,20 +424,20 @@ class Primitives<
           connSizesFifoPtr = conn->sizesFifo;
         } else if (Direct) {
           // User buffers have been registered
-          if ((conn->direct & (NCCL_IPC_READ|NCCL_IPC_WRITE)) && e != nullptr && e->regUsed) {
+          if ((conn->flags & (NCCL_IPC_READ|NCCL_IPC_WRITE)) && e != nullptr && e->regUsed) {
             if (connIndex == 1 && P2p == 0) {
               flags |= DirectRead;  // scatter-reduce use direct pull
             } else {
               flags |= (e->direct & NCCL_DIRECT_WRITE) ? DirectWrite :
                        (e->direct & NCCL_DIRECT_READ)  ? DirectRead  : 0;
             }
-          } else if (conn->direct & (NCCL_DIRECT_WRITE|NCCL_DIRECT_READ)) {
+          } else if (conn->flags & (NCCL_DIRECT_WRITE|NCCL_DIRECT_READ)) {
             if (connIndex == 1 && P2p == 0) {
               flags |= DirectRead;  // scatter-reduce use direct pull
             } else {
               // direct read not allowed in non-register case
               // otherwise, in one-to-multi send, we could mix empty send and intermediate send
-              flags |= (conn->direct & NCCL_DIRECT_WRITE) ? DirectWrite : 0;
+              flags |= (conn->flags & NCCL_DIRECT_WRITE) ? DirectWrite : 0;
             }
           }
         }
@@ -397,7 +450,7 @@ class Primitives<
       int tid, int nthreads, int const *recvPeers, int const *sendPeers,
       void const *inputBuf, void *outputBuf, uint64_t redOpArg, uint32_t group=0, struct ncclWorkElem* e = nullptr
     ):
-    tid(tid),
+    tid(tid), tidInBlock(threadIdx.x),
     stepSize(ncclShmem.comm.buffSizes[NCCL_PROTO_SIMPLE]/NCCL_STEPS/sizeof(T)) {
 
     // For send operations, we need an extra warp to overlap the threadfence and the copy
@@ -412,7 +465,7 @@ class Primitives<
     this->fan = Fan(nrecv, nsend);
 
     constexpr int ThreadPerSync = 8;
-    static_assert(MaxSend < ThreadPerSync && MaxRecv < ThreadPerSync, "Not enough threads to cover all peers");
+    static_assert(MaxSend <= ThreadPerSync && MaxRecv <= ThreadPerSync, "Not enough threads to cover all peers");
 
     int g = tid / ThreadPerSync;
     int ng = nthreads / ThreadPerSync;
@@ -566,6 +619,9 @@ class Primitives<
     genericOp<0, 1, 0, 1, Input, Output>(inpIx, outIx, remoteOutIx, eltN, postOp);
   }
 
+  __device__ __forceinline__ void recvSend(int eltN, bool postOp=false) {
+    genericOp<0, 0, 1, 1, -1, -1>(-1, -1, -1, eltN, postOp);
+  }
   __device__ __forceinline__ void recvCopySend(intptr_t outIx, int eltN, bool postOp=false) {
     genericOp<0, 0, 1, 1, -1, Output>(-1, outIx, -1, eltN, postOp);
   }
@@ -596,20 +652,20 @@ class Primitives<
   }
 
   __device__ __forceinline__ void
-  scatter(intptr_t inpIx, int totalElem, int peerElem, int skip, int shift) {
+  scatter(intptr_t inpIx, int totalElem, int peerElem, int peerOffset, int skip, int shift) {
-    ScatterGatherOp<0, 0, 0, 1>(inpIx, -1, totalElem, peerElem, skip, shift, /*postOp=*/false);
+    ScatterGatherOp<0, 0, 0, 1>(inpIx, -1, totalElem, peerElem, peerOffset, skip, shift, /*postOp=*/false);
   }
   __device__ __forceinline__ void
-  directScatter(intptr_t inpIx, int totalElem, int peerElem, int skip, int shift) {
+  directScatter(intptr_t inpIx, int totalElem, int peerElem, int peerOffset, int skip, int shift) {
-    ScatterGatherOp<0, 1, 0, 1>(inpIx, -1, totalElem, peerElem, skip, shift, /*postOp=*/false);
+    ScatterGatherOp<0, 1, 0, 1>(inpIx, -1, totalElem, peerElem, peerOffset, skip, shift, /*postOp=*/false);
   }
 
   __device__ __forceinline__ void
-  gather(intptr_t outIx, int totalElem, int peerElem, int skip, int shift, bool postOp=false) {
+  gather(intptr_t outIx, int totalElem, int peerElem, int peerOffset, int skip, int shift, bool postOp=false) {
-    ScatterGatherOp<0, 0, 1, 0>(-1, outIx, totalElem, peerElem, skip, shift, postOp);
+    ScatterGatherOp<0, 0, 1, 0>(-1, outIx, totalElem, peerElem, peerOffset, skip, shift, postOp);
   }
   __device__ __forceinline__ void
-  directGather(intptr_t outIx, int totalElem, int peerElem, int skip, int shift) {
+  directGather(intptr_t outIx, int totalElem, int peerElem, int peerOffset, int skip, int shift) {
-    ScatterGatherOp<1, 0, 1, 0>(-1, outIx, totalElem, peerElem, skip, shift, /*postOp=*/false);
+    ScatterGatherOp<1, 0, 1, 0>(-1, outIx, totalElem, peerElem, peerOffset, skip, shift, /*postOp=*/false);
   }
 };

src/collectives/device/reduce_scatter.h

@@ -87,3 +87,45 @@ struct RunWorkElement<ncclFuncReduceScatter, T, RedOp, NCCL_ALGO_RING, NCCL_PROT
     runRing<T, RedOp, ProtoLL128>(args);
   }
 };
+
+template<typename T, typename RedOp>
+struct RunWorkElement<ncclFuncReduceScatter, T, RedOp, NCCL_ALGO_NVLS, NCCL_PROTO_SIMPLE> {
+  __device__ __forceinline__ void run(ncclWorkElem *args) {
+    const int tid = threadIdx.x;
+    const int bid = args->bid;
+    const int nChannels = args->nChannels;
+    struct ncclNvls* nvls = &ncclShmem.channel.nvls;
+    const ssize_t chunkSize = int(args->lastChunkSize);
+    const ssize_t size = args->count;
+    const ssize_t loopSize = nChannels*chunkSize;
+
+    const int nThreadsScatter = 128 + WARP_SIZE;
+    const int nThreadsReduce = 384;
+    const int tidEndScatter = nThreadsScatter;
+    const int tidEndReduce = tidEndScatter + nThreadsReduce;
+
+    using Proto = ProtoSimple<1, 1>;
+
+    if (tid < tidEndScatter) {
+      // Scatter
+      int group = (0*Proto::MaxGroupWidth) | (0<<16);
+      Primitives<T, RedOp, FanAsymmetric<0, NCCL_MAX_NVLS_ARITY>, /*Direct=*/0, Proto, 0>
+        prims(tid, nThreadsScatter, NULL, nvls->up, args->sendbuff, NULL, args->redOpArg, group, args);
+      for (ssize_t gridOffset = 0; gridOffset < size; gridOffset += loopSize) {
+        ssize_t offset = gridOffset + bid*chunkSize;
+        int nelem = min(chunkSize, size-offset);
+        prims.scatter(offset, nvls->nHeads*size, nelem, size, -1, 0);
+      }
+    } else if (tid < tidEndReduce) {
+      int group = (3*Proto::MaxGroupWidth) | (1<<16);
+      // Reduce through MC
+      Primitives<T, RedOp, FanAsymmetric<1, 0>, /*Direct=*/0, Proto, 0>
+        prims(tid-tidEndScatter, nThreadsReduce, &nvls->down, NULL, NULL, args->recvbuff, args->redOpArg, group, args);
+      for (ssize_t gridOffset = 0; gridOffset < size; gridOffset += loopSize) {
+        ssize_t offset = gridOffset + bid*chunkSize;
+        int nelem = min(chunkSize, size-offset);
+        prims.recv(offset, nelem);
+      }
+    }
+  }
+};

src/collectives/device/sendrecv.h

@@ -13,12 +13,13 @@ struct RunWork<ncclFuncSendRecv, T, RedOp, NCCL_ALGO_RING, NCCL_PROTO_SIMPLE> {
   template<typename Proto>
   __device__ void runSend(const int tid, const int nthreads, const int group, struct ncclWorkElemP2p* args) {
     void* buff = reinterpret_cast<void*>(uintptr_t(args->buffHi32)<<32 | args->buffLo32);
-    size_t count = reinterpret_cast<size_t>(size_t(args->countHi32)<<32 | args->countLo32);
+    ssize_t count = reinterpret_cast<size_t>(size_t(args->countHi32)<<32 | args->countLo32);
     if (args->peer == ncclShmem.comm.rank) {
       struct ncclWorkElemP2p* recvArgs = args-1;
       void* recvBuff = reinterpret_cast<void*>(uintptr_t(recvArgs->buffHi32)<<32 | recvArgs->buffLo32);
       if (buff != recvBuff) {
-        ReduceOrCopyMulti<COLL_UNROLL, RedOp, T, 1, 1, 1, 1, 0>(tid, nthreads, nullptr, false, 1, (const T**)&buff, 1, (T**)&recvBuff, count);
+        ReduceOrCopyMulti<COLL_UNROLL, RedOp, T, 1, 1, 1, 1, /*PreOpSrcs=*/0>
+          (tid, nthreads, 0, nullptr, false, 1, &buff, 1, &recvBuff, count);
       }
     } else {
       int chunkSize = args->chunkSize/sizeof(T);

src/debug.cc

@@ -74,6 +74,8 @@ void ncclDebugInit() {
         mask = NCCL_ALLOC;
       } else if (strcasecmp(subsys, "CALL") == 0) {
         mask = NCCL_CALL;
+      } else if (strcasecmp(subsys, "NVLS") == 0) {
+        mask = NCCL_NVLS;
       } else if (strcasecmp(subsys, "ALL") == 0) {
         mask = NCCL_ALL;
       }

src/enqueue.cc

@@ -32,7 +32,8 @@ struct ncclKernelMatch {
   NCCL_FUNC5(func, TREE,           devredop, type, specialized), \
   NCCL_FUNC5(func, RING,           devredop, type, specialized), \
   NCCL_FUNC5(func, COLLNET_DIRECT, devredop, type, specialized), \
-  NCCL_FUNC5(func, COLLNET_CHAIN,  devredop, type, specialized)
+  NCCL_FUNC5(func, COLLNET_CHAIN,  devredop, type, specialized), \
+  NCCL_FUNC5(func, NVLS,           devredop, type, specialized)
 
 #ifdef __CUDA_BF16_TYPES_EXIST__
   #define HAVE_BFLOAT16 1
@@ -90,34 +91,48 @@ static const ncclKernelMatch ncclKerns[1+ncclNumTypes+NCCL_NUM_FUNCTIONS*ncclNum
 
 static ncclResult_t computeColl(struct ncclInfo* info /* input */, int* workFuncIndex, struct ncclWorkElem* work, struct ncclProxyOp* proxyOp /* output */);
 
-// Determine the maximum kernel stack size of all CUDA kernels
+NCCL_PARAM(L1SharedMemoryCarveout, "L1_SHARED_MEMORY_CARVEOUT", 0);
-size_t ncclKernMaxLocalSize() {
+
-  ncclResult_t res = ncclSuccess;
+// Returns maximum kernel stack size of all CUDA kernels
-  int numNcclKerns = sizeof(ncclKerns)/sizeof(ncclKerns[0]);
+ncclResult_t ncclInitKernelsForDevice(int cudaArch, size_t* maxStackSize) {
+  constexpr int KernelCount = sizeof(ncclKerns)/sizeof(ncclKerns[0]);
+  ncclResult_t result = ncclSuccess;
+
+  if (maxStackSize) *maxStackSize = 0;
+  int carveout = ncclParamL1SharedMemoryCarveout();
+
+  // Keep track if we already visited a function pointer.
+  void* lru[2] = {nullptr, nullptr};
+  for (int i=0; i < KernelCount; i++) {
+    void* fn = ncclKerns[i].kernelFn;
+    if (fn == lru[0] || fn == lru[1]) goto next_kernel;
+    lru[1] = lru[0];
+    lru[0] = fn;
+
+    if (maxStackSize) {
       cudaFuncAttributes attr = {0};
-  size_t max = 0;
+      CUDACHECKGOTO(cudaFuncGetAttributes(&attr, fn), result, ignore0);
-  for (int i = 0; i < numNcclKerns; i++) {
+      if (attr.localSizeBytes > *maxStackSize) *maxStackSize = attr.localSizeBytes;
-    CUDACHECKGOTO(cudaFuncGetAttributes(&attr, ncclKerns[i].kernelFn), res, error);
+    ignore0:;
-    if (attr.localSizeBytes > max) max = attr.localSizeBytes;
     }
 
-error:
+    if (carveout) {
-  return (res != ncclSuccess) ? 0 : max;
+      CUDACHECKGOTO(cudaFuncSetAttribute(fn,
-}
+        cudaFuncAttributePreferredSharedMemoryCarveout, carveout),
-
+        result, ignore1);
-// Set shared memory carveout for the nccl kernels
+    ignore1:;
-ncclResult_t ncclKernSetSharedMemoryCarveout(int carveOut) {
-  ncclResult_t res = ncclSuccess;
-  int numNcclKerns = sizeof(ncclKerns)/sizeof(ncclKerns[0]);
-  for (int i = 0; i < numNcclKerns; i++) {
-    CUDACHECKGOTO(cudaFuncSetAttribute(ncclKerns[i].kernelFn, cudaFuncAttributePreferredSharedMemoryCarveout, carveOut), res, error);
     }
 
-error:
+    if (ncclShmemDynamicSize(cudaArch) != 0) {
-  return res;
+      CUDACHECKGOTO(cudaFuncSetAttribute(fn,
+        cudaFuncAttributeMaxDynamicSharedMemorySize, ncclShmemDynamicSize(cudaArch)),
+        result, next_kernel);
+    }
+  next_kernel:;
+  }
+  return result;
 }
 
-
 /*****************************************************************************/
 /*       Launch system : synchronization and CUDA kernel launch              */
 /*****************************************************************************/
@@ -248,10 +263,9 @@ static ncclResult_t addProxyOpIfNeeded(struct ncclComm* comm, struct ncclKernelP
 static ncclResult_t addCollToPlan(
     struct ncclComm* comm, struct ncclKernelPlan* plan, int* nWorkBudget, int funcIndex,
     struct ncclWorkElem const* workElem, struct ncclProxyOp const* proxyOp,
-    int nBid, size_t bytes, bool regBufUsed, void* regBufSend[], void* regBufRecv[]
+    int nCollChannels, int nBid, size_t bytes, bool regBufUsed, void* regBufSend[], void* regBufRecv[]
   ) {
   struct ncclKernelPlan::Channel *chans = plan->channels;
-  int nCollChannels = comm->nChannels;
 
   // Choose the `nBid` least loaded channels to do the work. This ensures
   // all bids go to different channels in case they need to synchronize.
@@ -268,9 +282,7 @@ static ncclResult_t addCollToPlan(
     }
   }
   // Sort in the rest of the channels. If a channel has less work than the max
-  // member of least[], replace that member and compute the new max. The optimal
+  // member of least[], replace that member and compute the new max.
-  // algorithm uses a max-heap, but for our small sizes I suspect the better
-  // asymptotic complexity would be swamped by the increased instruction complexity.
   for (int c=nBid; c < nCollChannels; c++) {
     if (chans[c].collBytes < maxBytesInLeast) {
       least[maxIndexInLeast] = c;
@@ -541,8 +553,9 @@ static ncclResult_t scheduleCollTasksToPlan(
       info.sliceSteps = head->sliceSteps;
       NCCLCHECK(ncclInfoSetDerived(&info, comm->nRanks));
       if (nAggOps > 1) {
+        int maxChannels = aggInfo.algorithm == NCCL_ALGO_NVLS ? comm->nvlsChannels : comm->nChannels;
         info.nChannels = DIVUP(info.nBytes, bytePerChannel[collNetSupport]);
-        info.nChannels = std::max(1, std::min(info.nChannels, comm->nChannels));
+        info.nChannels = std::max(1, std::min(info.nChannels, maxChannels));
         info.algorithm = aggInfo.algorithm;
         info.protocol = aggInfo.protocol;
         info.nThreads = aggInfo.nThreads;
@@ -565,8 +578,9 @@ static ncclResult_t scheduleCollTasksToPlan(
         NCCLCHECK(registerIntraNodeBuffers(comm, plan, &info, &regBufUsed, regBufSend, regBufRecv));
       }
 
+      int maxChannels = info.algorithm == NCCL_ALGO_NVLS ? comm->nvlsChannels : comm->nChannels;
       NCCLCHECK(addCollToPlan(comm, plan, nWorkBudget, workFuncIndex, &workElem, &proxyOp,
-        info.nChannels, info.nBytes, regBufUsed, regBufSend, regBufRecv));
+        maxChannels, info.nChannels, info.nBytes, regBufUsed, regBufSend, regBufRecv));
       tasks->nTasksColl -= 1;
       tasks->collBytesTotal -= info.nBytes;
       ncclIntruQueueDequeue(&tasks->collQueue);
@@ -856,7 +870,7 @@ static void CUDART_CB hostStreamPlanCallback(void *plan_) {
   struct ncclKernelPlan* plan = (struct ncclKernelPlan*)plan_;
   ncclResult_t result = hostStreamPlanTask(plan->comm, plan);
   if (result != ncclSuccess) {
-    WARN("hostStreamPlanCallback() failed : %s\n", ncclGetErrorString(result));
+    WARN("hostStreamPlanCallback() failed : %s", ncclGetErrorString(result));
   }
 }
 
@@ -964,7 +978,7 @@ ncclResult_t ncclLaunchPrepare(struct ncclComm* comm) {
     }
     NCCLCHECKGOTO(ncclStrongStreamWaitStream(tasks->capturingGraph, launchStream, &comm->deviceStream), result, failure);
 
-    if (persistent || comm->persistentRefs != 0) {
+    if (persistent || comm->persistentRefs != 0 || ncclCudaLaunchBlocking) {
       // We have to launch host tasks to push proxy args. We are careful to only
       // do this if necessary since host tasks impose a high performance cost in CUDA.
       bool acquired = false;
@@ -1005,12 +1019,6 @@ ncclResult_t ncclLaunchKernelBefore_NoUncapturedCuda(struct ncclComm* comm, stru
   return ncclSuccess;
 }
 
-#if CUDART_VERSION >= 11080
-#define NCCL_MAX_CGA_CLUSTER_SIZE 8
-#define NCCL_CGA_CLUSTER_SIZE_SM90 4
-NCCL_PARAM(CGAClusterSize, "CGA_CLUSTER_SIZE", -2);
-#endif
-
 #if CUDART_VERSION >= 12000
 // NCCL uses the "Remote" Mem Sync domain by default
 NCCL_PARAM(MemSyncDomain, "MEM_SYNC_DOMAIN", cudaLaunchMemSyncDomainRemote);
@@ -1022,6 +1030,7 @@ ncclResult_t ncclLaunchKernel(struct ncclComm* comm, struct ncclKernelPlan* plan
   cudaStream_t launchStream = tasks->streams->stream;
   dim3 grid = {(unsigned)plan->channelCount, 1, 1};
   dim3 block = {(unsigned)plan->threadPerBlock, 1, 1};
+  size_t smem = ncclShmemDynamicSize(comm->cudaArch);
   void *args[3] = {&comm->devComm, &plan->channelMask, &plan->workHead};
 
   #if CUDART_VERSION >= 11080
@@ -1029,19 +1038,7 @@ ncclResult_t ncclLaunchKernel(struct ncclComm* comm, struct ncclKernelPlan* plan
   NCCLCHECK(ncclCudaDriverVersion(&driverVersion));
   if (driverVersion >= 11080) {
     int compCap = comm->compCap;
-    unsigned int clusterSize = (compCap == 90) ? NCCL_CGA_CLUSTER_SIZE_SM90 : 0;
+    unsigned int clusterSize = (compCap == 90) ? comm->cgaClusterSize : 0;
-    if (ncclParamCGAClusterSize() != -2) {
-      clusterSize = ncclParamCGAClusterSize();
-      if (clusterSize > NCCL_MAX_CGA_CLUSTER_SIZE) {
-        static bool warned = false;
-        if (warned == false) {
-          WARN("NCCL_CGA_CLUSTER_SIZE value %d is too big. Limiting value to %d.",
-               clusterSize, NCCL_MAX_CGA_CLUSTER_SIZE);
-          warned = true;
-        }
-        clusterSize = NCCL_MAX_CGA_CLUSTER_SIZE;
-      }
-    }
 
     cudaLaunchConfig_t launchConfig = {0};
     cudaLaunchAttribute launchAttrs[3];
@@ -1073,6 +1070,7 @@ ncclResult_t ncclLaunchKernel(struct ncclComm* comm, struct ncclKernelPlan* plan
     #endif
     launchConfig.gridDim = grid;
     launchConfig.blockDim = block;
+    launchConfig.dynamicSmemBytes = smem;
     launchConfig.attrs = launchAttrs;
     launchConfig.numAttrs = attrs;
     launchConfig.stream = launchStream;
@@ -1082,12 +1080,12 @@ ncclResult_t ncclLaunchKernel(struct ncclComm* comm, struct ncclKernelPlan* plan
   }
   #endif
   // Standard kernel launch
-  CUDACHECK(cudaLaunchKernel(fn, grid, block, args, 0, launchStream));
+  CUDACHECK(cudaLaunchKernel(fn, grid, block, args, smem, launchStream));
   return ncclSuccess;
 }
 
 ncclResult_t ncclLaunchKernelAfter_NoCuda(struct ncclComm* comm, struct ncclKernelPlan* plan) {
-  if (comm->persistentRefs == 0) { // implies !plan->persistent
+  if (!(plan->persistent || comm->persistentRefs != 0 || ncclCudaLaunchBlocking)) {
     // If this isn't being captured and there aren't any CUDA graphs alive
     // then we don't need to do our proxyOp pushing on the host stream.
     NCCLCHECK(hostStreamPlanTask(comm, plan));
@@ -1161,6 +1159,8 @@ static ncclResult_t getAlgoInfo(struct ncclInfo* info, int collNetTypeSupport, i
     int nAlgos = NCCL_NUM_ALGORITHMS;
     for (int a=0; a<nAlgos; a++) {
       if ((a == NCCL_ALGO_COLLNET_DIRECT || a == NCCL_ALGO_COLLNET_CHAIN) && collNetTypeSupport != 1) continue;
+      if (a == NCCL_ALGO_NVLS && !NCCL_NVLS_SUPPORTS(info->datatype, info->opFull.op)) continue;
+
       for (int p=0; p<NCCL_NUM_PROTOCOLS; p++) {
         float time;
         NCCLCHECK(ncclTopoGetAlgoTime(info, a, p, numPipeOps, &time));
@@ -1193,6 +1193,9 @@ static ncclResult_t getAlgoInfo(struct ncclInfo* info, int collNetTypeSupport, i
       }
       ncSwitch /= 2;
     }
+  } else if (info->algorithm == NCCL_ALGO_NVLS) {
+    // NVLS should not need more than 16 channels to get peak BW.
+    nc = comm->nvlsChannels;
   } else {
     // Ring/Tree channel tuning
     while (info->nBytes < nc*nt*threadThreshold) {
@@ -1207,6 +1210,7 @@ static ncclResult_t getAlgoInfo(struct ncclInfo* info, int collNetTypeSupport, i
     if (info->algorithm == NCCL_ALGO_TREE) nt += 3*WARP_SIZE;
     if (info->algorithm == NCCL_ALGO_COLLNET_DIRECT) nt += 3*WARP_SIZE;
     if (info->algorithm == NCCL_ALGO_COLLNET_CHAIN) nt += 3*WARP_SIZE;
+    if (info->algorithm == NCCL_ALGO_NVLS) nt = NCCL_MAX_NTHREADS;
   }
   nt = nt/WARP_SIZE < 3 ? 3*WARP_SIZE : nt;
   info->nChannels = nc;
@@ -1225,6 +1229,7 @@ static ncclResult_t getPatternInfo(struct ncclInfo* info) {
       info->pattern = ncclPatternRing; break;
     case ncclFuncAllReduce:
       info->pattern =
+        info->algorithm == NCCL_ALGO_NVLS ? ncclPatternNvls :
         info->algorithm == NCCL_ALGO_COLLNET_DIRECT ? ncclPatternCollnetDirect :
         info->algorithm == NCCL_ALGO_COLLNET_CHAIN ? ncclPatternCollnetChain :
         info->algorithm == NCCL_ALGO_TREE ? ncclPatternTreeUpDown :
@@ -1244,6 +1249,7 @@ static ncclResult_t getLoopInfo(struct ncclInfo* info) {
     case ncclPatternPipelineFrom:
     case ncclPatternPipelineTo:
     case ncclPatternCollnetChain:
+    case ncclPatternNvls:
       info->nstepsPerLoop = info-> nchunksPerLoop = 1; break;
     case ncclPatternCollnetDirect:
       info->nstepsPerLoop = 1; info->nchunksPerLoop = info->comm->channels[0].collnetDirect.nHeads; break;
@@ -1319,6 +1325,14 @@ comp_next:
     while (info->nBytes / (info->nChannels*chunkSize) < info->comm->channels[0].collnetChain.depth*8 && chunkSize > 65536) chunkSize /= 2;
     while (info->nBytes / (info->nChannels*chunkSize) < info->comm->channels[0].collnetChain.depth && chunkSize > 32768) chunkSize /= 2;
     work->lastChunkSize = chunkSize / ncclTypeSize(info->datatype);
+  } else if (info->algorithm == NCCL_ALGO_NVLS) {
+    if (chunkSize > 131072) chunkSize = 131072;
+    // Use uint64_t so that concurrentOps*chunkSize*X does not overflow
+    uint64_t concurrentOps = info->nChannels*info->comm->channels[0].nvls.nHeads;
+    if ((info->nBytes < (32 * (concurrentOps*chunkSize))) && (chunkSize > 65536)) chunkSize = 65536;
+    if ((info->nBytes < (8 * (concurrentOps*chunkSize))) && (chunkSize > 32768)) chunkSize = 32768;
+    if ((info->nBytes < (2 * (concurrentOps*chunkSize))) && (chunkSize > 16384)) chunkSize = 16384;
+    work->lastChunkSize = chunkSize / ncclTypeSize(info->datatype);
   } else if (info->protocol == NCCL_PROTO_LL) {
     const ssize_t sliceSize = stepSize*sizeof(uint64_t)/sizeof(union ncclLLFifoLine);
     const ssize_t loopSize = info->nChannels*info->nchunksPerLoop*(ssize_t)sliceSize;
@@ -1618,6 +1632,11 @@ ncclResult_t ncclRedOpDestroy(ncclRedOp_t op, ncclComm_t comm) {
     WARN("ncclRedOpDestroy :  operator is garbage.");
     return ncclInvalidArgument;
   }
+  if (comm == NULL) {
+    WARN("ncclRedOpDestroy : invalid communicator passed.");
+    return ncclInvalidArgument;
+  }
+
   int ix = int(ncclUserRedOpMangle(comm, op)) - int(ncclNumOps);
   if (comm->userRedOpCapacity <= ix || comm->userRedOps[ix].freeNext != -1) {
     WARN("ncclRedOpDestroy : operator unknown to this communicator.");

src/graph/connect.cc

@@ -313,8 +313,8 @@ ncclResult_t ncclTopoPostset(struct ncclComm* comm, int* firstRanks, int* treePa
 
   // Honor NCCL_MIN_NRINGS/NCCL_MAX_NRINGS.
   // We permit combining max, then min, to only use the first channels, then duplicate them.
-  nChannels = comm->nChannels = std::min((int)ncclMaxNchannels(), nChannels);
+  nChannels = comm->nChannels = std::min(std::min(ncclMaxNchannels(), nChannels), comm->maxCTAs);
-  nChannels = comm->nChannels = copyChannels(comm, nChannels, ncclMinNchannels(), ringPrev, ringNext);
+  nChannels = comm->nChannels = copyChannels(comm, nChannels, std::max(ncclMinNchannels(), comm->minCTAs), ringPrev, ringNext);
 
   // Create rings array and check all is fine
   NCCLCHECK(ncclBuildRings(nChannels, rings, comm->rank, comm->nRanks, ringPrev, ringNext));

src/graph/paths.cc

@@ -461,7 +461,7 @@ ncclResult_t ncclTopoGetIntermediateRank(struct ncclTopoSystem* system, int rank
       type = node->type;
     }
     if (type != GPU) {
-      WARN("Could not find intermediate GPU between GPU rank %d and NIC %d\n", rank, netDev);
+      WARN("Could not find intermediate GPU between GPU rank %d and NIC %d", rank, netDev);
       return ncclInternalError;
     }
     *intermediateRank = node->gpu.rank;
@@ -707,6 +707,7 @@ static int nextPow2(int v) {
 }
 
 ncclResult_t ncclTopoComputeP2pChannels(struct ncclComm* comm) {
+  /* here we already honor comm->max/minCTAs for p2pnChannels. */
   comm->p2pnChannels = std::min(comm->nChannels, (int)ncclParamMaxP2pNChannels());
   comm->p2pnChannels = std::max(comm->p2pnChannels, (int)ncclParamMinP2pNChannels());
   int minChannels = comm->p2pnChannels;
@@ -734,7 +735,6 @@ ncclResult_t ncclTopoComputeP2pChannels(struct ncclComm* comm) {
     for (int b=1, mb=(comm->p2pnChannels>>1); b<comm->p2pnChannels; b<<=1, mb>>=1) if (c & b) mirror |= mb;
     comm->p2pChannels[c] = mirror;
   }
-  INFO(NCCL_INIT, "%d coll channels, %d p2p channels, %d p2p channels per peer", comm->nChannels, comm->p2pnChannels, comm->p2pnChannelsPerPeer);
   return ncclSuccess;
 }
 

src/graph/search.cc

@@ -765,7 +765,6 @@ ncclResult_t ncclTopoCompute(ncclTopoSystem* system, struct ncclTopoGraph* graph
 
   if (ngpus == 1) if (graph->pattern != NCCL_TOPO_PATTERN_RING) graph->pattern = NCCL_TOPO_PATTERN_TREE;
 
-  // SPLIT_TREE works better on older archs.
   int ccMin;
   NCCLCHECK(ncclTopoGetCompCap(system, &ccMin, NULL));
 

src/graph/topo.cc

@@ -815,6 +815,6 @@ ncclResult_t ncclTopoGetLocalRank(struct ncclTopoSystem* system, int rank, int*
       return ncclSuccess;
     }
   }
-  WARN("Could not find local GPU with rank %d\n", rank);
+  WARN("Could not find local GPU with rank %d", rank);
   return ncclInternalError;
 }

src/graph/tuning.cc

@@ -53,7 +53,7 @@ ncclResult_t parseList(const char* str, const char* elems[], int nelems, int* li
 
 // Latencies in us, Bandwidths in GB/s
 // Tree { LL, LL128, Simple } , Ring { LL, LL128, Simple }
-static const float baseLat  [NCCL_NUM_ALGORITHMS][NCCL_NUM_PROTOCOLS] = { { 4.4, 4.4,  0 }, { 3.6, 10.0, 8.4 }, { 4.4, 4.4,  0 }, { 4.4, 4.4,  0 }};
+static const float baseLat  [NCCL_NUM_ALGORITHMS][NCCL_NUM_PROTOCOLS] = { { 4.4, 4.4,  0 }, { 3.6, 10.0, 8.4 }, { 4.4, 4.4,  0 }, { 4.4, 4.4,  0 }, { 0, 0, 40.0 }};
 
 // NVLink, PCI, Network
 #define NCCL_HW_NVLINK 0
@@ -63,13 +63,16 @@ static const float baseLat  [NCCL_NUM_ALGORITHMS][NCCL_NUM_PROTOCOLS] = { { 4.4,
 static float hwLat [3][NCCL_NUM_ALGORITHMS][NCCL_NUM_PROTOCOLS] =
 { /* NVLINK */
   { /* Tree (LL/LL128/Simple)*/ { .52, 1.25, 28 }, /* Ring (LL/LL128/Simple)*/ { .47, 1.9, 3.4 },
-    /* CollNetDirect (Simple)*/ { 0, 0, 8.0 }, /* CollNetChain (Simple)*/ { 0, 0, 8.0 } },
+    /* CollNetDirect (Simple)*/ { 0, 0, 8.0 }, /* CollNetChain (Simple)*/ { 0, 0, 8.0 },
+    /* NVLS */ { 0, 0, 0 } },
   /* PCI */
   { /* Tree (LL/LL128/Simple)*/ { 1.0, 1.9, 28 }, /* Ring (LL/LL128/Simple)*/ { 1.0, 2.5, 5.7 },
-    /* CollNetDirect (Simple)*/ { 0, 0, 8.0 }, /* CollNetChain (Simple)*/ { 0, 0, 8.0 } },
+    /* CollNetDirect (Simple)*/ { 0, 0, 8.0 }, /* CollNetChain (Simple)*/ { 0, 0, 8.0 },
+    /* NVLS */ { 0, 0, 0 } },
   /* NET */
   { /* Tree (LL/LL128/Simple)*/ { 5.0, 8.5, 28 }, /* Ring (LL/LL128/Simple)*/ { 2.7, 4.0, 9.6 },
-    /* CollNetDirect (Simple)*/ { 0, 0, 10.7 }, /* CollNetChain (Simple)*/ { 0, 0, 10.7 } }
+    /* CollNetDirect (Simple)*/ { 0, 0, 10.7 }, /* CollNetChain (Simple)*/ { 0, 0, 10.7 },
+    /* NVLS */ { 0, 0, 0 } }
 };
 
 /* Array indexes used below */
@@ -78,7 +81,7 @@ static float hwLat [3][NCCL_NUM_ALGORITHMS][NCCL_NUM_PROTOCOLS] =
 #define HOPPER_COMPCAP_IDX 2
 
 // LL128 max BW per channel
-static const double ll128MaxBwPerCh = 20.0;
+static const double ll128MaxBwPerCh[3] = { 20.0, 20.0, 36.7 };
 static const double llMaxBws[3][3] = {
   /* Volta-N1/Intel-N2/Intel-N4) */ {39.0, 39.0, 20.4},
   /* Ampere-N1/AMD-N2/AMD-N4) */ {87.7, 22.5 /*avg of ring & tree*/, 19.0},
@@ -88,7 +91,7 @@ static const double llMaxBws[3][3] = {
 static const double perChMaxTreeBws[3][3] = {
   /* Volta (N1/N2/N4) */ {26.5, 18.5, 10.0},
   /* Ampere (N1/N2/N4) */ {24.0, 23.6, 17.8},
-  /* Hopper (N1/N2/N4) */ {24.0, 23.6, 17.8},
+  /* Hopper (N1/N2/N4) */ {38.7, 41.4, 33.0},
 };
 
 ncclResult_t ncclTopoTuneModel(struct ncclComm* comm, int minCompCap, int maxCompCap, struct ncclTopoGraph* treeGraph, struct ncclTopoGraph* ringGraph, struct ncclTopoGraph* collNetGraph) {
@@ -98,7 +101,8 @@ ncclResult_t ncclTopoTuneModel(struct ncclComm* comm, int minCompCap, int maxCom
   comm->maxThreads[NCCL_ALGO_TREE][NCCL_PROTO_SIMPLE] =
     getNthreads("NCCL_NTHREADS", ncclParamNthreads(), 2*WARP_SIZE, NCCL_SIMPLE_MAX_NTHREADS, NCCL_SIMPLE_MAX_NTHREADS);
   comm->maxThreads[NCCL_ALGO_COLLNET_DIRECT][NCCL_PROTO_SIMPLE] =
-    comm->maxThreads[NCCL_ALGO_COLLNET_CHAIN][NCCL_PROTO_SIMPLE] = NCCL_SIMPLE_MAX_NTHREADS;
+    comm->maxThreads[NCCL_ALGO_COLLNET_CHAIN][NCCL_PROTO_SIMPLE] =
+    comm->maxThreads[NCCL_ALGO_NVLS][NCCL_PROTO_SIMPLE] = NCCL_SIMPLE_MAX_NTHREADS;
   comm->maxThreads[NCCL_ALGO_RING][NCCL_PROTO_LL] = comm->maxThreads[NCCL_ALGO_TREE][NCCL_PROTO_LL] =
     getNthreads("NCCL_NTHREADS", ncclParamNthreads(), 2*WARP_SIZE, NCCL_LL_MAX_NTHREADS, NCCL_LL_MAX_NTHREADS);
   comm->maxThreads[NCCL_ALGO_RING][NCCL_PROTO_LL128] = comm->maxThreads[NCCL_ALGO_TREE][NCCL_PROTO_LL128] =
@@ -108,7 +112,7 @@ ncclResult_t ncclTopoTuneModel(struct ncclComm* comm, int minCompCap, int maxCom
   int nRanks = comm->nRanks;
   if (nRanks <= 1) return ncclSuccess;
 
-  int compCapIndex = (minCompCap == 80 && maxCompCap == 80) ? AMPERE_COMPCAP_IDX : ((minCompCap == 90 && maxCompCap == 90) ? HOPPER_COMPCAP_IDX : VOLTA_COMPCAP_IDX);
+  int compCapIndex = minCompCap >= 90 ? HOPPER_COMPCAP_IDX : minCompCap >= 80 ? AMPERE_COMPCAP_IDX : VOLTA_COMPCAP_IDX;
   int cpuArch, cpuVendor, cpuModel;
   NCCLCHECK(ncclTopoCpuType(comm->topo, &cpuArch, &cpuVendor, &cpuModel));
   int index2 = nNodes <= 2 ? nNodes-1 : 2;
@@ -120,7 +124,7 @@ ncclResult_t ncclTopoTuneModel(struct ncclComm* comm, int minCompCap, int maxCom
   if (cpuArch == NCCL_TOPO_CPU_ARCH_POWER) hwLat[NCCL_HW_PCI][NCCL_ALGO_TREE][NCCL_PROTO_SIMPLE] = hwLat[NCCL_HW_PCI][NCCL_ALGO_RING][NCCL_PROTO_SIMPLE];
   float ppn = (float)nRanks / nNodes; // if ppn < 2, then we are sending/receiving at the same GPU through the NIC, apply some bw discount
 
-  struct ncclTopoGraph* graphs[NCCL_NUM_ALGORITHMS] = { treeGraph, ringGraph, collNetGraph, collNetGraph };
+  struct ncclTopoGraph* graphs[NCCL_NUM_ALGORITHMS] = { treeGraph, ringGraph, collNetGraph, collNetGraph, ringGraph/* we only need the NVSwitch speed for NVLS*/ };
   int intraHw[NCCL_NUM_ALGORITHMS], hw[NCCL_NUM_ALGORITHMS];
   for (int a=0; a<NCCL_NUM_ALGORITHMS; a++) intraHw[a] = graphs[a]->typeIntra == LINK_NVL ? NCCL_HW_NVLINK : NCCL_HW_PCI;
   for (int a=0; a<NCCL_NUM_ALGORITHMS; a++) hw[a] = nNodes == 1 ? intraHw[a] : NCCL_HW_NET;
@@ -134,20 +138,25 @@ ncclResult_t ncclTopoTuneModel(struct ncclComm* comm, int minCompCap, int maxCom
       nNodes;
 
     for (int a=0; a<NCCL_NUM_ALGORITHMS; a++) {
-      if (coll != ncclFuncAllReduce && a != NCCL_ALGO_RING) continue;
+      if (coll == ncclFuncBroadcast && a != NCCL_ALGO_RING) continue;
+      if (coll == ncclFuncReduce && a != NCCL_ALGO_RING) continue;
+      if (coll == ncclFuncReduceScatter && a != NCCL_ALGO_RING && a != NCCL_ALGO_NVLS) continue;
+      if (coll == ncclFuncAllGather && a != NCCL_ALGO_RING && a != NCCL_ALGO_NVLS) continue;
 
       for (int p=0; p<NCCL_NUM_PROTOCOLS; p++) {
+        if (a == NCCL_ALGO_NVLS && p != NCCL_PROTO_SIMPLE) continue;
         int collnet = (a == NCCL_ALGO_COLLNET_DIRECT || a == NCCL_ALGO_COLLNET_CHAIN) ? 1 : 0;
         float bw = nNodes <= 2 || collnet ? graphs[a]->bwIntra : graphs[a]->bwInter;
         float busBw = graphs[a]->nChannels * bw;
 
         // Various model refinements
         if (compCapIndex == AMPERE_COMPCAP_IDX) busBw = std::min(busBw, 235.0f);
+        if (compCapIndex == HOPPER_COMPCAP_IDX) busBw = std::min(busBw, 370.0f);
         if (a == NCCL_ALGO_RING && p == NCCL_PROTO_LL) { busBw = std::min(llMaxBw, busBw * ((nNodes > 1 || coll == ncclFuncAllReduce || coll == ncclFuncReduce) ? 1.0/4.0 : 1.0/3.0)); }
-        if (a == NCCL_ALGO_RING && p == NCCL_PROTO_LL128) busBw = std::min(busBw * (ppn < 2 ? 0.7 : 0.92 /*120.0/128.0*/), ll128MaxBwPerCh*graphs[a]->nChannels);
+        if (a == NCCL_ALGO_RING && p == NCCL_PROTO_LL128) busBw = std::min(busBw * (ppn < 2 ? 0.7 : 0.92 /*120.0/128.0*/), ll128MaxBwPerCh[compCapIndex]*graphs[a]->nChannels);
         if (a == NCCL_ALGO_TREE) busBw = std::min(busBw*.92, graphs[a]->nChannels*perChMaxTreeBw);
         if (a == NCCL_ALGO_TREE && p == NCCL_PROTO_LL) busBw = std::min(busBw*1.0/3.8, llMaxBw);
-        if (a == NCCL_ALGO_TREE && p == NCCL_PROTO_LL128) busBw = std::min(busBw * (nNodes == 1 ? 7.0/9.0 : 120.0/128.0), ll128MaxBwPerCh*graphs[a]->nChannels);
+        if (a == NCCL_ALGO_TREE && p == NCCL_PROTO_LL128) busBw = std::min(busBw * (nNodes == 1 ? 7.0/9.0 : 120.0/128.0), ll128MaxBwPerCh[compCapIndex]*graphs[a]->nChannels);
         if (a == NCCL_ALGO_COLLNET_DIRECT && p != NCCL_PROTO_SIMPLE) busBw = 0;  // Not used
         if (a == NCCL_ALGO_COLLNET_CHAIN && p != NCCL_PROTO_SIMPLE) busBw = 0;  // Not used
         if (a == NCCL_ALGO_COLLNET_DIRECT && p == NCCL_PROTO_SIMPLE) {
@@ -159,7 +168,10 @@ ncclResult_t ncclTopoTuneModel(struct ncclComm* comm, int minCompCap, int maxCom
         if (a == NCCL_ALGO_COLLNET_CHAIN && p == NCCL_PROTO_SIMPLE) busBw *= .75;
 
         // Convert bus BW to algorithm BW
-        float ratio = (a != NCCL_ALGO_RING) ? .5 : (1.0 * nRanks) / nsteps;
+        float ratio;
+        if (a == NCCL_ALGO_RING) ratio = (1.0 * nRanks) / nsteps;
+        else if (a == NCCL_ALGO_NVLS) ratio = .75;
+        else ratio = .5;
         comm->bandwidths[coll][a][p] = busBw * ratio;
 
         comm->latencies[coll][a][p] = baseLat[a][p];
@@ -195,7 +207,7 @@ ncclResult_t ncclTopoTuneModel(struct ncclComm* comm, int minCompCap, int maxCom
   // Protocols/Algorithms enable/disable, and user overrides.
   // All are enabled except ll128 which is enabled by default only in certain cases.
   int protoEnable[NCCL_NUM_PROTOCOLS] = { 1, 2, 1 };
-  int algoEnable[NCCL_NUM_ALGORITHMS] = { 1, 1, 1, 1 };
+  int algoEnable[NCCL_NUM_ALGORITHMS] = { 1, 1, 1, 1, 1 };
 
   const char *protoStr = getenv("NCCL_PROTO");
   if (protoStr) {
@@ -207,6 +219,10 @@ ncclResult_t ncclTopoTuneModel(struct ncclComm* comm, int minCompCap, int maxCom
     INFO(NCCL_ENV, "NCCL_ALGO set by environment to %s", algoStr);
     NCCLCHECK(parseList(algoStr, ncclAlgoStr, NCCL_NUM_ALGORITHMS, algoEnable));
   }
+
+  // Disable NVLink SHARP if not supported
+  if (comm->nvlsSupport == 0 /* || comm->localRanks <= 2*/) algoEnable[NCCL_ALGO_NVLS] = 0;
+
   // Disable CollNet if it is not supported
   if (comm->collNetSupport == 0) {
     algoEnable[NCCL_ALGO_COLLNET_DIRECT] = 0;
@@ -228,7 +244,7 @@ ncclResult_t ncclTopoTuneModel(struct ncclComm* comm, int minCompCap, int maxCom
     if (pEnable == 2 && p == NCCL_PROTO_LL128) {
       // Enable LL128 by default only on Volta/Ampere/Hopper+NVLink. Other cases are not tested and may cause silent data corruption.
       pEnable = 1;
-      pEnable &= (graphs[a]->typeInter <= PATH_PXB);
+      pEnable &= (graphs[a]->typeInter <= PATH_PXB || (minCompCap >= 90 && graphs[a]->typeInter <= PATH_PXN));
       pEnable &= (graphs[a]->typeIntra <= PATH_NVL);
       pEnable &= (minCompCap == maxCompCap);
       switch (minCompCap) {
@@ -239,8 +255,9 @@ ncclResult_t ncclTopoTuneModel(struct ncclComm* comm, int minCompCap, int maxCom
       }
     }
     if (pEnable == 0) comm->bandwidths[c][a][p] = 0;
-    // Only disable algo for Allreduce since others only have one
+    // Never disable ring for non-allreduce operations. That allows to run real apps with NCCL_ALGO=TREE.
-    if (c == ncclFuncAllReduce && algoEnable[a] == 0) comm->bandwidths[c][a][p] = 0;
+    if (a == NCCL_ALGO_RING && c != ncclFuncAllReduce) continue;
+    if (algoEnable[a] == 0) comm->bandwidths[c][a][p] = 0;
   }
 
   if (comm->rank == 0) {
@@ -284,9 +301,9 @@ ncclResult_t ncclTopoTuneModel(struct ncclComm* comm, int minCompCap, int maxCom
   char* str = getenv("NCCL_THREAD_THRESHOLDS");
   if (str) {
     INFO(NCCL_ENV, "NCCL_THREAD_THRESHOLDS set by environment to %s", str);
-    ssize_t t[NCCL_NUM_ALGORITHMS][NCCL_NUM_PROTOCOLS] = {{ -2, -2, -2 }, { -2, -2, -2 }, { -2, -2, -2 }, { -2, -2, -2 }};
+    ssize_t t[2][NCCL_NUM_PROTOCOLS] = {{ -2, -2, -2 }, { -2, -2, -2 }};
     sscanf(str, "%ld %ld %ld %ld %ld %ld", t[0], t[0]+1, t[0]+2, t[1], t[1]+1, t[1]+2);
-    for (int a=0; a<NCCL_NUM_ALGORITHMS; a++) {
+    for (int a=0; a<2; a++) {
       for (int p=0; p<NCCL_NUM_PROTOCOLS; p++) {
         if (t[a][p] >= 0) comm->threadThresholds[a][p] = t[a][p];
       }
@@ -323,7 +340,9 @@ ncclResult_t ncclTopoGetAlgoTime(struct ncclInfo* info, int algorithm, int proto
   if (algorithm == NCCL_ALGO_TREE && logSize < 23) bw *= treeCorrectionFactor[protocol][logSize];
   if (info->nChannels != 0) bw = bw / info->comm->nChannels * info->nChannels;
   if (algorithm == NCCL_ALGO_RING && protocol == NCCL_PROTO_SIMPLE && info->comm->nNodes > 1
-      && info->coll == ncclFuncAllReduce && info->nBytes >= info->comm->nRanks/16.0*65536) lat *= 1.9; // Plateau effect of ring
+      && info->coll == ncclFuncAllReduce && info->nBytes >= info->comm->nRanks/16.0*65536) {
+    lat *= info->comm->minCompCap < 90 ? 1.9 : 1.5; // Plateau effect of ring
+  }
   // Tree pipelining saves latency in aggregation cases
   int latCount = algorithm == NCCL_ALGO_RING ? numPipeOps : DIVUP(numPipeOps, NCCL_MAX_WORK_ELEMENTS);
   *time = lat * latCount + (info->nBytes) / (1000 * bw);

src/group.cc

@@ -315,7 +315,7 @@ static ncclResult_t groupLaunch(struct ncclAsyncJob *job_) {
             ret = ncclSystemError;
           }
           job->state = ncclGroupJobJoined;
-          if (job->result != ncclSuccess) {
+          if (job->result != ncclSuccess && ret == ncclSuccess) {
             ret = job->result;
             errorJobAbortFlag = true;
           }
@@ -326,7 +326,6 @@ static ncclResult_t groupLaunch(struct ncclAsyncJob *job_) {
 
         if (*groupAbortFlag == true || errorJobAbortFlag == true) {
           *job->abortFlag = 1;
-          ret = ncclInternalError;
         }
 
         job = job->next;

src/include/bootstrap.h

@@ -25,6 +25,7 @@ ncclResult_t bootstrapSend(void* commState, int peer, int tag, void* data, int s
 ncclResult_t bootstrapRecv(void* commState, int peer, int tag, void* data, int size);
 ncclResult_t bootstrapBarrier(void* commState, int *ranks, int rank, int nranks, int tag);
 ncclResult_t bootstrapIntraNodeAllGather(void* commState, int *ranks, int rank, int nranks, void* allData, int size);
+ncclResult_t bootstrapIntraNodeBroadcast(void* commState, int *ranks, int rank, int nranks, int root, void* bcastData, int size);
 ncclResult_t bootstrapClose(void* commState);
 ncclResult_t bootstrapAbort(void* commState);
 #endif

src/include/collectives.h

@@ -53,7 +53,8 @@ struct ncclDevRedOpFull {
   DECL4(func, RING,    devredop, type, undef) \
   DECL4(func, TREE,    devredop, type, undef) \
   DECL4(func, COLLNET_DIRECT, devredop, type, undef) \
-  DECL4(func, COLLNET_CHAIN, devredop, type, undef)
+  DECL4(func, COLLNET_CHAIN, devredop, type, undef) \
+  DECL4(func, NVLS,    devredop, type, undef)
 
 #if defined(__CUDA_BF16_TYPES_EXIST__)
 #define DECL2(func, devredop, undefForFloat) \
@@ -121,4 +122,13 @@ extern __device__ void NCCL_ONERANK_REDUCE_NAME(PreMulSum, double)();
 #define REDUCE_CHUNKSTEPS 1
 #define NCCL_MAX_SLICE_PER_CHUNK 2  // max value for CHUNKSTEPS/SLICESTEPS, must accord with above
 
+// We can't use the enum identifiers like ncclSum, ncclFloat, etc since this
+// macro will be used in preprocessor conditionals where enums have no meaning.
+#define NCCL_NVLS_SUPPORTS(/*ncclDataType_t*/ type, /*ncclDevRedOp_t*/ red) \
+  (((type==2 || type==3) && (red==0 || red==2 || red==3)) || \
+   ((type==4 || type==5) && (red==0 || red==2 || red==3)) || \
+   ((type==6 || type==9) && (red==0 || red==2 || red==3)) || \
+   (type==7 && red==0) || \
+   (type==8 && red==0))
+
 #endif

src/include/comm.h

@@ -104,6 +104,7 @@ struct ncclChannel {
   struct ncclTree tree;
   struct ncclTree collnetChain;
   struct ncclDirect collnetDirect;
+  struct ncclNvls nvls;
   int id; // index of this channel
   uint32_t workFifoSent; // last used work index+1
   uint64_t p2pOpCount;
@@ -177,8 +178,10 @@ struct ncclComm {
   int nRanks;  // number of GPUs in communicator
   int cudaDev; // my cuda device index
   int compCap; // compute capability of the GPU
+  int minCompCap; // min compute capability in the communicator
   int64_t busId;   // my PCI bus ID in int format
   cpu_set_t cpuAffinity; // CPU affinity of the GPU
+  int cudaArch; // matches __CUDA_ARCH__ of device
 
   int node;
   int nNodes;
@@ -201,6 +204,7 @@ struct ncclComm {
 
   // Channels for collectives
   int nChannels;
+  int nvlsChannels;
   // Channels (per peer) for p2p
   int p2pnChannels;
   int p2pnChannelsPerPeer;
@@ -257,6 +261,10 @@ struct ncclComm {
   int collNetSupport;
   int intraHighestTransportType;
 
+  // NVLink SHARP (NVLS) support
+  int nvlsSupport;
+  void* nvlsResources;
+
   size_t channelSize; // User requested work size (bytes) for channel partitions
 
   // Internal streams
@@ -288,6 +296,11 @@ struct ncclComm {
 
   // communicator mode
   int blocking;
+  // CGA cluster size
+  int cgaClusterSize;
+  int minCTAs, maxCTAs;
+  // network interface name
+  char *netName;
   // initState is to more conveniently reclaim resources when errors happen.
   ncclResult_t initState;
   // flag to indicate if ncclCommFinalize() is called

src/include/cudawrap.h

@@ -73,10 +73,32 @@ DECLARE_CUDA_PFN_EXTERN(cuGetErrorName, 6000);
 DECLARE_CUDA_PFN_EXTERN(cuMemGetAddressRange, 3020);
 DECLARE_CUDA_PFN_EXTERN(cuCtxCreate, 3020);
 DECLARE_CUDA_PFN_EXTERN(cuCtxDestroy, 4000);
+DECLARE_CUDA_PFN_EXTERN(cuCtxGetCurrent, 4000);
 DECLARE_CUDA_PFN_EXTERN(cuCtxSetCurrent, 4000);
+DECLARE_CUDA_PFN_EXTERN(cuCtxGetDevice, 2000);
+// cuMem API support
+DECLARE_CUDA_PFN_EXTERN(cuMemAddressReserve, 10020);
+DECLARE_CUDA_PFN_EXTERN(cuMemAddressFree, 10020);
+DECLARE_CUDA_PFN_EXTERN(cuMemCreate, 10020);
+DECLARE_CUDA_PFN_EXTERN(cuMemGetAllocationGranularity, 10020);
+DECLARE_CUDA_PFN_EXTERN(cuMemExportToShareableHandle, 10020);
+DECLARE_CUDA_PFN_EXTERN(cuMemImportFromShareableHandle, 10020);
+DECLARE_CUDA_PFN_EXTERN(cuMemMap, 10020);
+DECLARE_CUDA_PFN_EXTERN(cuMemRelease, 10020);
+DECLARE_CUDA_PFN_EXTERN(cuMemSetAccess, 10020);
+DECLARE_CUDA_PFN_EXTERN(cuMemUnmap, 10020);
 #if CUDA_VERSION >= 11070
 DECLARE_CUDA_PFN_EXTERN(cuMemGetHandleForAddressRange, 11070); // DMA-BUF support
 #endif
+#if CUDA_VERSION >= 12010
+/* NVSwitch Multicast support */
+DECLARE_CUDA_PFN_EXTERN(cuMulticastAddDevice, 12010);
+DECLARE_CUDA_PFN_EXTERN(cuMulticastBindMem, 12010);
+DECLARE_CUDA_PFN_EXTERN(cuMulticastBindAddr, 12010);
+DECLARE_CUDA_PFN_EXTERN(cuMulticastCreate, 12010);
+DECLARE_CUDA_PFN_EXTERN(cuMulticastGetGranularity, 12010);
+DECLARE_CUDA_PFN_EXTERN(cuMulticastUnbind, 12010);
+#endif
 #endif
 
 /* CUDA Driver functions loaded with dlsym() */
@@ -88,6 +110,7 @@ DECLARE_CUDA_PFN_EXTERN(cuGetProcAddress, 11030);
 ncclResult_t ncclCudaLibraryInit(void);
 
 extern int ncclCudaDriverVersionCache;
+extern bool ncclCudaLaunchBlocking; // initialized by ncclCudaLibraryInit()
 
 inline ncclResult_t ncclCudaDriverVersion(int* driver) {
   int version = __atomic_load_n(&ncclCudaDriverVersionCache, __ATOMIC_RELAXED);
@@ -98,5 +121,4 @@ inline ncclResult_t ncclCudaDriverVersion(int* driver) {
   *driver = version;
   return ncclSuccess;
 }
-
 #endif

src/include/devcomm.h

@@ -15,11 +15,12 @@
 typedef enum { ncclFuncBroadcast, ncclFuncReduce, ncclFuncAllGather, ncclFuncReduceScatter, ncclFuncAllReduce, ncclFuncSendRecv, ncclFuncSend, ncclFuncRecv, ncclNumFuncs} ncclFunc_t;
 extern const char* ncclFuncStr[NCCL_NUM_FUNCTIONS];
 
-#define NCCL_NUM_ALGORITHMS 4 // Tree/Ring/CollNet*
+#define NCCL_NUM_ALGORITHMS 5 // Tree/Ring/CollNet*
 #define NCCL_ALGO_TREE 0
 #define NCCL_ALGO_RING 1
 #define NCCL_ALGO_COLLNET_DIRECT 2
 #define NCCL_ALGO_COLLNET_CHAIN 3
+#define NCCL_ALGO_NVLS 4
 extern const char* ncclAlgoStr[NCCL_NUM_ALGORITHMS];
 
 #define NCCL_NUM_PROTOCOLS 3 // Simple/LL/LL128
@@ -78,6 +79,7 @@ static_assert(NCCL_LL_CLEAN_MASK % NCCL_STEPS == 0, "Invalid NCCL_LL_CLEAN_MASK
 #define NCCL_DIRECT_NIC   0x04
 #define NCCL_IPC_WRITE    0x08
 #define NCCL_IPC_READ     0x10
+#define NCCL_NVLS_MIN_POLL 0x20
 
 struct ncclConnInfo {
   // Regular comm mechanism
@@ -85,7 +87,7 @@ struct ncclConnInfo {
   uint64_t *tail;     // Local for recv, remote for send
   uint64_t *head;     // Local for send, remote for recv
 
-  int direct;         // Direct communication
+  int flags;          // Direct communication / other flags
   int shared;         // Buffers are shared
   void **ptrExchange; // Pointer exchange for direct communication
   uint64_t* redOpArgExchange; // PreOp scaler exchange for direct pull case
@@ -138,13 +140,22 @@ struct ncclTree {
 struct ncclDirect {
   int depth;
   int out;
-  int nHeads;
+  int nHeads;   // Number of parallel N<->1<->net operations we'll do in parallel; size of up/down
-  int headRank;
+  int headRank; // Index in 0..nHeads-1 I am the head rank of. -1 if I'm not a head rank (no local NIC)
-  int shift;
+  int shift;    // Shuffling of send/recv for scatter/gather operations, basically localRank%nHeads
   int up[NCCL_MAX_DIRECT_ARITY];
   int down[NCCL_MAX_DIRECT_ARITY];
 };
 
+#define NCCL_MAX_NVLS_ARITY 8
+struct ncclNvls {
+  int out;
+  int nHeads;   // Number of parallel N<->1<->net operations we'll do in parallel; size of up/down
+  int headRank; // Index in 0..nHeads-1 I am the head rank of. -1 if I'm not a head rank (no local NIC)
+  int up[NCCL_MAX_NVLS_ARITY];
+  int down;
+};
+
 #define NCCL_MAX_CONNS 2
 struct ncclChannelPeer {
   struct ncclConnector send[NCCL_MAX_CONNS];
@@ -264,6 +275,7 @@ struct alignas(16) ncclDevChannel {
   struct ncclTree tree;
   struct ncclTree collnetChain;
   struct ncclDirect collnetDirect;
+  struct ncclNvls nvls;
   uint32_t* workFifoDone; // Location of done counter, device writes index+1 of last work processed
 };
 
@@ -288,4 +300,65 @@ struct alignas(16) ncclDevCommAndChannels {
   struct ncclDevChannel channels[MAXCHANNELS];
 };
 
+#ifdef __CUDA_ARCH__
+  #define NCCL_CUDA_ARCH __CUDA_ARCH__
+#else
+  #define NCCL_CUDA_ARCH 0
+#endif
+
+template<typename T>
+__host__ __device__ constexpr T min_constexpr(T a) { return a; }
+template<typename T, typename ...Ts>
+__host__ __device__ constexpr T min_constexpr(T a, T b, Ts ...c) {
+  return min_constexpr<T>((a < b ? a : b), c...);
+}
+
+template<typename T>
+__host__ __device__ constexpr T max_constexpr(T a) { return a; }
+template<typename T, typename ...Ts>
+__host__ __device__ constexpr T max_constexpr(T a, T b, Ts ...c) {
+  return max_constexpr<T>((a > b ? a : b), c...);
+}
+
+// Calculate the unroll factor given:
+// * bytePerPack: number of bytes accessed per instruction
+// * insns: max permissible unroll value
+// * bytes: desired number of in-flight bytes per iteration ( = unroll*bytePerPack)
+__host__ __device__ constexpr int ncclCalcUnroll(int bytePerPack, int insns, int bytes) {
+  return min_constexpr(insns, (bytes + bytePerPack-1)/bytePerPack);
+}
+
+// Note that all unroll value logic should depend on a given cudaArch argument
+// and not __CUDA_ARCH__ since these need to be host-side executable where the
+// arch value is strictly runtime only. By defaulting to NCCL_CUDA_ARCH, device
+// side code can elide passing the arch for brevity.
+
+__host__ __device__ constexpr int ncclCollUnroll(int cudaArch = NCCL_CUDA_ARCH) {
+  // Our collective unroll should move to the same bytes&insns model as NVLS.
+  return cudaArch >= 800 ? 8 : 4;
+}
+
+__host__ __device__ constexpr int ncclNvlsUnrollBytes(int cudaArch = NCCL_CUDA_ARCH) { return 4*16; }
+__host__ __device__ constexpr int ncclNvlsUnrollInsns(int cudaArch = NCCL_CUDA_ARCH) { return 16; }
+
+__host__ __device__ constexpr int ncclNvlsUnroll(int bytePerPack, int cudaArch = NCCL_CUDA_ARCH) {
+  return ncclCalcUnroll(bytePerPack, ncclNvlsUnrollInsns(cudaArch), ncclNvlsUnrollBytes(cudaArch));
+}
+
+// The amount of dynamic shmem per warp
+__host__ __device__ constexpr int ncclShmemScratchWarpSize(int cudaArch = NCCL_CUDA_ARCH) {
+  return (max_constexpr<int>(
+      /*LL    */0,
+      /*LL128 */(NCCL_LL128_SHMEM_ELEMS_PER_THREAD*WARP_SIZE)*sizeof(uint64_t),
+      /*SIMPLE*/(ncclCollUnroll(cudaArch)*WARP_SIZE + 1)*16,
+      // NVLS needs an extra 16B to read unaligned data.
+      /*NVLS  */WARP_SIZE*(cudaArch >= 900 ? ncclNvlsUnrollBytes(cudaArch) : 0) + 16
+    ) + 15) & -16; // pad to 16 bytes
+}
+
+// The amount of dynamic shmem per block
+__host__ __device__ constexpr int ncclShmemDynamicSize(int cudaArch = NCCL_CUDA_ARCH) {
+  return cudaArch < 700 ? 0 : ncclShmemScratchWarpSize(cudaArch)*(NCCL_MAX_NTHREADS/WARP_SIZE);
+}
+
 #endif

src/include/enqueue.h

@@ -15,8 +15,7 @@
 #define NCCL_MIN_CHANNEL_SIZE (NCCL_LL_THREAD_THRESHOLD*64)
 #define NCCL_AGG_CHANNEL_SIZE (1LL << 21) /* 2 MiB, ideal per-channel size to fully utilize bandwidth */
 
-size_t ncclKernMaxLocalSize();
+ncclResult_t ncclInitKernelsForDevice(int cudaArch, size_t* maxStackSize);
-ncclResult_t ncclKernSetSharedMemoryCarveout(int carveOut);
 ncclResult_t ncclEnqueueCheck(struct ncclInfo* info);
 ncclResult_t ncclLaunchPrepare(struct ncclComm* comm);
 ncclResult_t ncclLaunchKernelBefore_NoUncapturedCuda(struct ncclComm* comm, struct ncclKernelPlan* plan);

src/include/info.h

@@ -24,6 +24,7 @@ typedef enum : uint8_t {
   ncclPatternTreeUpDown,
   ncclPatternCollnetChain,
   ncclPatternCollnetDirect,
+  ncclPatternNvls,
   ncclPatternSend,
   ncclPatternRecv
 } ncclPattern_t;

src/include/ipcsocket.h

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2016-2023, NVIDIA CORPORATION. All rights reserved.
+ *
+ * See COPYRIGHT for license information
+ */
+
+#ifndef NCCL_IPCSOCKET_H
+#define NCCL_IPCSOCKET_H
+
+#include "nccl.h"
+#include <stdio.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/wait.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <memory.h>
+#include <sys/un.h>
+#include <inttypes.h>
+
+#define NCCL_IPC_SOCKNAME_LEN 64
+
+struct ncclIpcSocket {
+  int fd;
+  char socketName[NCCL_IPC_SOCKNAME_LEN];
+  volatile uint32_t* abortFlag;
+};
+
+ncclResult_t ncclIpcSocketInit(struct ncclIpcSocket *handle, int rank, uint64_t hash, volatile uint32_t* abortFlag);
+ncclResult_t ncclIpcSocketClose(struct ncclIpcSocket *handle);
+
+ncclResult_t ncclIpcSocketRecvFd(struct ncclIpcSocket *handle, int *fd);
+ncclResult_t ncclIpcSocketSendFd(struct ncclIpcSocket *handle, const int fd, int rank, uint64_t hash);
+
+#endif /* NCCL_IPCSOCKET_H */

src/include/nccl_net.h

@@ -20,7 +20,7 @@
 #define NCCL_NET_MAX_REQUESTS 8
 
 typedef enum {NCCL_LOG_NONE=0, NCCL_LOG_VERSION=1, NCCL_LOG_WARN=2, NCCL_LOG_INFO=3, NCCL_LOG_ABORT=4, NCCL_LOG_TRACE=5} ncclDebugLogLevel;
-typedef enum {NCCL_INIT=1, NCCL_COLL=2, NCCL_P2P=4, NCCL_SHM=8, NCCL_NET=16, NCCL_GRAPH=32, NCCL_TUNING=64, NCCL_ENV=128, NCCL_ALLOC=256, NCCL_CALL=512, NCCL_ALL=~0} ncclDebugLogSubSys;
+typedef enum {NCCL_INIT=1, NCCL_COLL=2, NCCL_P2P=4, NCCL_SHM=8, NCCL_NET=16, NCCL_GRAPH=32, NCCL_TUNING=64, NCCL_ENV=128, NCCL_ALLOC=256, NCCL_CALL=512, NCCL_PROXY=1024, NCCL_NVLS=2048, NCCL_ALL=~0} ncclDebugLogSubSys;
 
 typedef void (*ncclDebugLogger_t)(ncclDebugLogLevel level, unsigned long flags, const char *file, int line, const char *fmt, ...);
 

src/include/nvtx.h

@@ -7,12 +7,12 @@
 #ifndef NCCL_NVTX_H_
 #define NCCL_NVTX_H_
 
-#include "nvtx3.hpp"
+#include "nvtx3/nvtx3.hpp"
 
-#if __cpp_constexpr >= 201304L && !defined(NVTX3_RELAXED_CONSTEXPR)
+#if __cpp_constexpr >= 201304L && !defined(NVTX3_CONSTEXPR_IF_CPP14)
-#define NVTX3_RELAXED_CONSTEXPR constexpr
+#define NVTX3_CONSTEXPR_IF_CPP14 constexpr
 #else
-#define NVTX3_RELAXED_CONSTEXPR
+#define NVTX3_CONSTEXPR_IF_CPP14
 #endif
 
 // Define all NCCL-provided static schema IDs here (avoid duplicates).
@@ -37,7 +37,7 @@ struct nccl_domain{static constexpr char const* name{"NCCL"};};
 
 class payload_schema {
  public:
-  NVTX3_RELAXED_CONSTEXPR explicit payload_schema(const nvtxPayloadSchemaEntry_t entries[], size_t numEntries, const uint64_t schemaId, const char* schemaName = nullptr) noexcept
+  explicit payload_schema(const nvtxPayloadSchemaEntry_t entries[], size_t numEntries, const uint64_t schemaId, const char* schemaName = nullptr) noexcept
   {
     schema_attr.name = schemaName;
     schema_attr.entries = entries;
@@ -74,11 +74,11 @@ class payload_schema {
 #define NVTX3_FUNC_WITH_PARAMS(ID, S, P) \
   static const payload_schema schema{S, std::extent<decltype(S)>::value, \
     NVTX_PAYLOAD_ENTRY_TYPE_SCHEMA_ID_STATIC_START + NVTX_SID_##ID, #ID}; \
-  static ::nvtx3::v1::registered_string<nccl_domain> const nvtx3_func_name__{__func__}; \
+  static ::nvtx3::v1::registered_string_in<nccl_domain> const nvtx3_func_name__{__func__}; \
   nvtxPayloadData_t nvtx3_bpl__[] = { \
     {NVTX_PAYLOAD_ENTRY_TYPE_SCHEMA_ID_STATIC_START + NVTX_SID_##ID, sizeof(P), &(P)}}; \
-  ::nvtx3::v1::event_attributes nvtx3_func_attr__{nvtx3_func_name__, nvtx3_bpl__}; \
+  ::nvtx3::v1::event_attributes const nvtx3_func_attr__{nvtx3_func_name__, nvtx3_bpl__}; \
-  ::nvtx3::v1::domain_thread_range<nccl_domain> const nvtx3_range__{nvtx3_func_attr__};
+  ::nvtx3::v1::scoped_range_in<nccl_domain> const nvtx3_range__{nvtx3_func_attr__};
 
 extern void initNvtxRegisteredEnums();
 

src/include/nvtx3/nvToolsExt.h

@@ -1,5 +1,5 @@
 /*
-* Copyright 2009-2020  NVIDIA Corporation.  All rights reserved.
+* Copyright 2009-2022  NVIDIA Corporation.  All rights reserved.
 *
 * Licensed under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.

src/include/nvtx3/nvToolsExtCuda.h

@@ -1,5 +1,5 @@
 /*
-* Copyright 2009-2020  NVIDIA Corporation.  All rights reserved.
+* Copyright 2009-2022  NVIDIA Corporation.  All rights reserved.
 *
 * Licensed under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.

src/include/nvtx3/nvToolsExtCudaRt.h

@@ -1,5 +1,5 @@
 /*
-* Copyright 2009-2020  NVIDIA Corporation.  All rights reserved.
+* Copyright 2009-2022  NVIDIA Corporation.  All rights reserved.
 *
 * Licensed under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.

src/include/nvtx3/nvToolsExtOpenCL.h

@@ -1,5 +1,5 @@
 /*
-* Copyright 2009-2020  NVIDIA Corporation.  All rights reserved.
+* Copyright 2009-2022  NVIDIA Corporation.  All rights reserved.
 *
 * Licensed under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.

src/include/nvtx3/nvToolsExtPayload.h

@@ -1,12 +1,12 @@
 /*
-* Copyright 2021  NVIDIA Corporation.  All rights reserved.
+* Copyright 2021-2022  NVIDIA Corporation.  All rights reserved.
 *
 * Licensed under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.
 * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 */
 
-#include "nvtx3/nvToolsExt.h"
+#include "nvToolsExt.h"
 
 #ifndef NVTOOLSEXT_PAYLOAD_H
 #define NVTOOLSEXT_PAYLOAD_H

src/include/nvtx3/nvToolsExtSync.h

@@ -1,5 +1,5 @@
 /*
-* Copyright 2009-2020  NVIDIA Corporation.  All rights reserved.
+* Copyright 2009-2022  NVIDIA Corporation.  All rights reserved.
 *
 * Licensed under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.

src/include/nvtx3/nvtxDetail/nvtxImpl.h

@@ -1,5 +1,5 @@
 /*
-* Copyright 2009-2020  NVIDIA Corporation.  All rights reserved.
+* Copyright 2009-2022  NVIDIA Corporation.  All rights reserved.
 *
 * Licensed under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.

src/include/nvtx3/nvtxDetail/nvtxImplCore.h

@@ -1,5 +1,5 @@
 /*
-* Copyright 2009-2020  NVIDIA Corporation.  All rights reserved.
+* Copyright 2009-2022  NVIDIA Corporation.  All rights reserved.
 *
 * Licensed under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.

src/include/nvtx3/nvtxDetail/nvtxImplCudaRt_v3.h

@@ -1,5 +1,5 @@
 /*
-* Copyright 2009-2020  NVIDIA Corporation.  All rights reserved.
+* Copyright 2009-2022  NVIDIA Corporation.  All rights reserved.
 *
 * Licensed under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.

src/include/nvtx3/nvtxDetail/nvtxImplCuda_v3.h

@@ -1,5 +1,5 @@
 /*
-* Copyright 2009-2020  NVIDIA Corporation.  All rights reserved.
+* Copyright 2009-2022  NVIDIA Corporation.  All rights reserved.
 *
 * Licensed under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.

src/include/nvtx3/nvtxDetail/nvtxImplOpenCL_v3.h

@@ -1,5 +1,5 @@
 /*
-* Copyright 2009-2020  NVIDIA Corporation.  All rights reserved.
+* Copyright 2009-2022  NVIDIA Corporation.  All rights reserved.
 *
 * Licensed under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.

src/include/nvtx3/nvtxDetail/nvtxImplSync_v3.h

@@ -1,5 +1,5 @@
 /*
-* Copyright 2009-2020  NVIDIA Corporation.  All rights reserved.
+* Copyright 2009-2022  NVIDIA Corporation.  All rights reserved.
 *
 * Licensed under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.

src/include/nvtx3/nvtxDetail/nvtxInit.h

@@ -1,5 +1,5 @@
 /*
-* Copyright 2009-2020  NVIDIA Corporation.  All rights reserved.
+* Copyright 2009-2022  NVIDIA Corporation.  All rights reserved.
 *
 * Licensed under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.

src/include/nvtx3/nvtxDetail/nvtxInitDecls.h

@@ -1,5 +1,5 @@
 /*
-* Copyright 2009-2020  NVIDIA Corporation.  All rights reserved.
+* Copyright 2009-2022  NVIDIA Corporation.  All rights reserved.
 *
 * Licensed under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.

src/include/nvtx3/nvtxDetail/nvtxInitDefs.h

@@ -1,5 +1,5 @@
 /*
-* Copyright 2009-2020  NVIDIA Corporation.  All rights reserved.
+* Copyright 2009-2022  NVIDIA Corporation.  All rights reserved.
 *
 * Licensed under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.

src/include/nvtx3/nvtxDetail/nvtxLinkOnce.h

@@ -1,5 +1,5 @@
 /*
-* Copyright 2009-2020  NVIDIA Corporation.  All rights reserved.
+* Copyright 2009-2022  NVIDIA Corporation.  All rights reserved.
 *
 * Licensed under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.

src/include/nvtx3/nvtxDetail/nvtxTypes.h

@@ -1,5 +1,5 @@
 /*
-* Copyright 2009-2020  NVIDIA Corporation.  All rights reserved.
+* Copyright 2009-2022  NVIDIA Corporation.  All rights reserved.
 *
 * Licensed under the Apache License v2.0 with LLVM Exceptions.
 * See https://llvm.org/LICENSE.txt for license information.

src/include/nvtx3/nvtxExtDetail/nvtxExtImplPayload_v1.h

@@ -35,10 +35,11 @@ NVTX_EXT_PAYLOAD_VERSIONED_ID(nvtxExtPayloadSlots)[NVTX3EXT_CBID_PAYLOAD_FN_NUM
 
 NVTX_LINKONCE_DEFINE_FUNCTION void NVTX_EXT_PAYLOAD_VERSIONED_ID(nvtxExtPayloadInitOnce)()
 {
+    intptr_t* fnSlots = NVTX_EXT_PAYLOAD_VERSIONED_ID(nvtxExtPayloadSlots) + 1;
     nvtxExtModuleSegment_t segment = {
         0, // unused (only one segment)
         NVTX3EXT_CBID_PAYLOAD_FN_NUM,
-        NVTX_EXT_PAYLOAD_VERSIONED_ID(nvtxExtPayloadSlots) + 1
+        fnSlots
     };
 
     nvtxExtModuleInfo_t module = {

src/include/proxy.h

@@ -10,6 +10,7 @@
 #include "devcomm.h"
 #include "info.h"
 #include "socket.h"
+#include "ipcsocket.h"
 #include <pthread.h>
 #include "shm.h"
 
@@ -161,6 +162,31 @@ struct ncclProxyProgressState {
   int nextOps;
 };
 
+// Expected proxy response fifo
+struct ncclExpectedProxyResponse {
+  void*    opId;
+  int      respSize;
+  bool     done;
+  void*    respBuff;
+  struct   ncclExpectedProxyResponse* next;
+};
+
+struct ncclProxyAsyncOp {
+  int type;
+  struct ncclProxyConnection* connection;
+  int reqSize, respSize;
+  char *reqBuff, *respBuff;
+  void* opId;
+  ncclProxyAsyncOp* next;
+};
+
+struct ncclProxyLocalPeer {
+  struct ncclSocket sock;
+  int localRank;
+  ncclProxyAsyncOp* asyncOps;
+  int asyncOpCounter;
+};
+
 struct ncclProxyState {
   // Service thread
   pthread_t thread;
@@ -176,6 +202,9 @@ struct ncclProxyState {
 
   // Progress thread
   struct ncclProxyProgressState progressState;
+
+  // Queue of expected responses from the proxy
+  struct ncclExpectedProxyResponse* expectedResponses;
 };
 
 enum proxyConnectState {
@@ -220,10 +249,19 @@ enum ncclProxyMsgType {
   ncclProxyMsgStart = 5,
   ncclProxyMsgClose = 6,
   ncclProxyMsgAbort = 7,
-  ncclProxyMsgStop = 8
+  ncclProxyMsgStop = 8,
+  ncclProxyMsgConvertFd = 9 // cuMem API support
 };
 
-ncclResult_t ncclProxyCall(struct ncclProxyConnector* proxyConn, int type, void* reqBuff, int reqSize, void* respBuff, int respSize);
+// This function is called by a client of the proxy that needs to invoke any of the non-progress proxyOp types
+// Call this function on the client, supplying a locally unique opId. Then, poll on the return value of
+// ncclPollProxyResponse(), supplying the same opId to confirm the operation has completed
+ncclResult_t ncclProxyCallAsync(struct ncclProxyConnector* proxyConn, int type, void* reqBuff, int reqSize, int respSize, void* opId);
+
+// This function will internally call ncclProxyCallAsync() and spin until ncclPollProxyResponse() confirms the result is received
+ncclResult_t ncclProxyCallBlocking(struct ncclProxyConnector* proxyConn, int type, void* reqBuff, int reqSize, void* respBuff, int respSize);
+ncclResult_t ncclPollProxyResponse(struct ncclProxyConnector* proxyConn, void* respBuff, void* opId);
+
 ncclResult_t ncclProxyDestroy(struct ncclComm* comm);
 ncclResult_t ncclProxyShmUnlink(struct ncclComm* comm);
 #endif

src/include/socket.h

@@ -92,6 +92,6 @@ ncclResult_t ncclSocketProgress(int op, struct ncclSocket* sock, void* ptr, int
 ncclResult_t ncclSocketWait(int op, struct ncclSocket* sock, void* ptr, int size, int* offset);
 ncclResult_t ncclSocketSend(struct ncclSocket* sock, void* ptr, int size);
 ncclResult_t ncclSocketRecv(struct ncclSocket* sock, void* ptr, int size);
-ncclResult_t ncclSocketTryRecv(struct ncclSocket* sock, void* ptr, int size, int* closed);
+ncclResult_t ncclSocketTryRecv(struct ncclSocket* sock, void* ptr, int size, int* closed, bool blocking);
 ncclResult_t ncclSocketClose(struct ncclSocket* sock);
 #endif

src/include/transport.h

@@ -62,7 +62,7 @@ struct ncclTransportComm {
 };
 
 struct ncclTransport {
-  const char name[4];
+  const char name[8];
   ncclResult_t (*canConnect)(int*, struct ncclTopoSystem* topo, struct ncclTopoGraph* graph, struct ncclPeerInfo*, struct ncclPeerInfo*);
   struct ncclTransportComm send;
   struct ncclTransportComm recv;
@@ -71,6 +71,9 @@ struct ncclTransport {
 ncclResult_t ncclTransportP2pConnect(struct ncclComm* comm, int channelId, int nrecv, int* peerRecv, int nsend, int* peerSend, int connIndex);
 ncclResult_t ncclTransportP2pSetup(struct ncclComm* comm, struct ncclTopoGraph* graph, int connIndex, int* highestTransportType=NULL);
 
+ncclResult_t ncclNvlsSetup(struct ncclComm* comm);
+ncclResult_t ncclNvlsFree(struct ncclComm* comm);
+
 enum { collNetRecv=0, collNetSend=1 };
 int ncclTransportCollNetSetup(struct ncclComm* comm, struct ncclTopoGraph* collNetGraph, struct ncclChannel* channel, int masterRank, int masterPeer, int collNetGraphChannelId, int type);
 ncclResult_t ncclTransportCollNetCheck(struct ncclComm* comm, int collNetSetupFail);

src/init.cc

@@ -35,13 +35,13 @@
 #endif
 
 const char* ncclFuncStr[NCCL_NUM_FUNCTIONS] = { "Broadcast", "Reduce", "AllGather", "ReduceScatter", "AllReduce" };
-const char* ncclAlgoStr[NCCL_NUM_ALGORITHMS] = { "Tree", "Ring", "CollNetDirect", "CollNetChain" };
+const char* ncclAlgoStr[NCCL_NUM_ALGORITHMS] = { "Tree", "Ring", "CollNetDirect", "CollNetChain", "NVLS" };
 const char* ncclProtoStr[NCCL_NUM_PROTOCOLS] = { "LL", "LL128", "Simple" };
 
 NCCL_PARAM(GroupCudaStream, "GROUP_CUDA_STREAM", NCCL_GROUP_CUDA_STREAM);
 
 NCCL_PARAM(CheckPointers, "CHECK_POINTERS", 0);
-NCCL_PARAM(CommBlocking, "COMM_BLOCKING", 0);
+NCCL_PARAM(CommBlocking, "COMM_BLOCKING", NCCL_CONFIG_UNDEF_INT);
 
 static uint64_t hashUniqueId(ncclUniqueId const &id) {
   char const *bytes = (char const*)&id;
@@ -67,12 +67,8 @@ ncclResult_t initGdrCopy() {
   return ncclSuccess;
 }
 
-
-NCCL_PARAM(L1SharedMemoryCarveout, "L1_SHARED_MEMORY_CARVEOUT", 0);
-
 pthread_mutex_t initLock = PTHREAD_MUTEX_INITIALIZER;
 static bool initialized = false;
-static size_t maxLocalSizeBytes = 0;
 
 static ncclResult_t ncclInit() {
   if (__atomic_load_n(&initialized, __ATOMIC_ACQUIRE)) return ncclSuccess;
@@ -80,9 +76,6 @@ static ncclResult_t ncclInit() {
   if (!initialized) {
     initEnv();
     initGdrCopy();
-    maxLocalSizeBytes = ncclKernMaxLocalSize();
-    int carveout = ncclParamL1SharedMemoryCarveout();
-    if (carveout) ncclKernSetSharedMemoryCarveout(carveout);
     // Always initialize bootstrap network
     NCCLCHECK(bootstrapNetInit());
     NCCLCHECK(ncclNetPluginInit());
@@ -210,6 +203,8 @@ static ncclResult_t commFree(ncclComm_t comm) {
     NCCLCHECK(ncclStrongStreamDestruct(&comm->deviceStream));
   }
 
+  if (comm->nvlsSupport) NCCLCHECK(ncclNvlsFree(comm));
+
   struct ncclDestructor* dtor = comm->destructorHead;
   while (dtor != nullptr) {
     NCCLCHECK(dtor->fn(dtor));
@@ -220,6 +215,7 @@ static ncclResult_t commFree(ncclComm_t comm) {
   ncclMemoryStackDestruct(&comm->memPermanent);
 
   ncclCudaHostFree((void *)comm->abortFlag);
+  free(comm->netName);
 
   commPoison(comm); // poison comm before free to avoid comm reuse.
   free(comm);
@@ -243,8 +239,8 @@ static ncclResult_t dmaBufSupported(struct ncclComm* comm) {
   int flag = 0;
   CUdevice dev;
   int cudaDriverVersion;
-  CUCHECK(cuDriverGetVersion(&cudaDriverVersion));
+  CUDACHECK(cudaDriverGetVersion(&cudaDriverVersion));
-  if (cudaDriverVersion < 11070) return ncclInternalError;
+  if (CUPFN(cuDeviceGet) == NULL || cudaDriverVersion < 11070) return ncclInternalError;
   CUCHECK(cuDeviceGet(&dev, comm->cudaDev));
   // Query device to see if DMA-BUF support is available
   (void) CUPFN(cuDeviceGetAttribute(&flag, CU_DEVICE_ATTRIBUTE_DMA_BUF_SUPPORTED, dev));
@@ -265,7 +261,7 @@ ncclResult_t ncclCommEnsureReady(ncclComm_t comm) {
     NCCLCHECK(ncclCommGetAsyncError(comm, &ret));
     if (ret != ncclSuccess) {
       /* if ret is not ncclInProgress, we just keep it. */
-      WARN("Attempt to use communicator before the previous operation returned ncclSuccess\n");
+      WARN("Attempt to use communicator before the previous operation returned ncclSuccess");
       if (ret == ncclInProgress) ret = ncclInvalidArgument;
       goto exit;
     }
@@ -395,6 +391,7 @@ static ncclResult_t devCommSetup(ncclComm_t comm) {
     tmpCommAndChans.channels[c].tree = comm->channels[c].tree;
     tmpCommAndChans.channels[c].collnetChain = comm->channels[c].collnetChain;
     tmpCommAndChans.channels[c].collnetDirect = comm->channels[c].collnetDirect;
+    tmpCommAndChans.channels[c].nvls = comm->channels[c].nvls;
     tmpCommAndChans.channels[c].workFifoDone = &comm->workFifoDone[c];
 
     if (comm->channels[c].ring.userRanks != nullptr) {
@@ -521,8 +518,8 @@ static ncclResult_t collNetTrySetup(ncclComm_t comm, struct ncclTopoGraph* collN
     struct ncclChannel* channel = comm->channels + c;
     for (int h = 0; h < nHeads; h++) {
       const int head = heads[h];
-      collNetSetupFail = ncclTransportCollNetSetup(comm, collNetGraph, channel, head, head, h, collNetRecv);
+      collNetSetupFail |= ncclTransportCollNetSetup(comm, collNetGraph, channel, head, head, h, collNetRecv);
-      if (!collNetSetupFail) collNetSetupFail = ncclTransportCollNetSetup(comm, collNetGraph, channel, head, head, h, collNetSend);
+      if (!collNetSetupFail) collNetSetupFail |= ncclTransportCollNetSetup(comm, collNetGraph, channel, head, head, h, collNetSend);
     }
     // Verify CollNet setup across ranks after trying the first channel
     if (c == 0) {
@@ -922,6 +919,8 @@ static ncclResult_t initTransportsRank(struct ncclComm* comm, ncclUniqueId* comm
   // Check if we can setup CollNet
   if (comm->collNetSupport > 0) collNetTrySetup(comm, &collNetGraph);
 
+  NCCLCHECKGOTO(ncclNvlsSetup(comm), ret, fail);
+
   TRACE(NCCL_INIT, "rank %d nranks %d - CONNECTED %d RINGS AND TREES", rank, nranks, comm->nChannels);
 
   // Compute time models for algorithm and protocol combinations
@@ -929,7 +928,7 @@ static ncclResult_t initTransportsRank(struct ncclComm* comm, ncclUniqueId* comm
     int myCompCap = comm->peerInfo[rank].cudaCompCap;
     int minCompCap = myCompCap, maxCompCap = myCompCap;
     for (int i = 0; i < nranks; i++) {
-      minCompCap = std::min(comm->peerInfo[i].cudaCompCap, minCompCap);
+      comm->minCompCap = minCompCap = std::min(comm->peerInfo[i].cudaCompCap, minCompCap);
       maxCompCap = std::max(comm->peerInfo[i].cudaCompCap, maxCompCap);
     }
     NCCLCHECKGOTO(ncclTopoTuneModel(comm, minCompCap, maxCompCap, &treeGraph, &ringGraph, &collNetGraph), ret, fail);
@@ -938,6 +937,8 @@ static ncclResult_t initTransportsRank(struct ncclComm* comm, ncclUniqueId* comm
   // Compute nChannels per peer for p2p
   NCCLCHECKGOTO(ncclTopoComputeP2pChannels(comm), ret, fail);
 
+  INFO(NCCL_INIT, "%d coll channels, %d nvls channels, %d p2p channels, %d p2p channels per peer", comm->nChannels, comm->nvlsChannels, comm->p2pnChannels, comm->p2pnChannelsPerPeer);
+
   do { // Setup p2p structures in comm->tasks
     struct ncclTasks* tasks = &comm->tasks;
     int nRanks = comm->nRanks;
@@ -1004,12 +1005,13 @@ static ncclResult_t initTransportsRank(struct ncclComm* comm, ncclUniqueId* comm
         }
       }
     }
+
     NCCLCHECKGOTO(ncclTransportP2pSetup(comm, NULL, 1), ret, fail);
   }
 
   // Connect to local net proxy
   NCCLCHECKGOTO(ncclProxyConnect(comm, TRANSPORT_NET, 1, comm->rank, &proxyConn), ret, fail);
-  NCCLCHECKGOTO(ncclProxyCall(&proxyConn, ncclProxyMsgSharedInit, &comm->p2pnChannels, sizeof(int), NULL, 0), ret, fail);
+  NCCLCHECKGOTO(ncclProxyCallBlocking(&proxyConn, ncclProxyMsgSharedInit, &comm->p2pnChannels, sizeof(int), NULL, 0), ret, fail);
 
   // Then to remote ones when using PXN
   if (ncclPxnDisable(comm) == 0) {
@@ -1017,7 +1019,7 @@ static ncclResult_t initTransportsRank(struct ncclComm* comm, ncclUniqueId* comm
     NCCLCHECKGOTO(ncclTopoGetPxnRanks(comm, &pxnPeers, &nranks), ret, fail);
     for (int r=0; r<nranks; r++) {
       NCCLCHECKGOTO(ncclProxyConnect(comm, TRANSPORT_NET, 1, pxnPeers[r], &proxyConn), ret, fail);
-      NCCLCHECKGOTO(ncclProxyCall(&proxyConn, ncclProxyMsgSharedInit, &comm->p2pnChannels, sizeof(int), NULL, 0), ret, fail);
+      NCCLCHECKGOTO(ncclProxyCallBlocking(&proxyConn, ncclProxyMsgSharedInit, &comm->p2pnChannels, sizeof(int), NULL, 0), ret, fail);
     }
   }
 
@@ -1065,6 +1067,11 @@ fail:
 }
 
 NCCL_PARAM(SetStackSize, "SET_STACK_SIZE", 0);
+NCCL_PARAM(CGAClusterSize, "CGA_CLUSTER_SIZE", NCCL_CONFIG_UNDEF_INT);
+// Match config max/minCTAs
+NCCL_PARAM(MaxCTAs, "MAX_CTAS", NCCL_CONFIG_UNDEF_INT);
+NCCL_PARAM(MinCTAs, "MIN_CTAS", NCCL_CONFIG_UNDEF_INT);
+#define NCCL_MAX_CGA_CLUSTER_SIZE 8
 
 struct ncclCommInitRankAsyncJob {
   struct ncclAsyncJob base;
@@ -1087,9 +1094,16 @@ static ncclResult_t ncclCommInitRankFunc(struct ncclAsyncJob* job_) {
   ncclUniqueId commId = job->commId; // C++ struct assignment
   int myrank = job->myrank;
   int cudaDev = job->cudaDev;
+  int archMajor, archMinor;
+  size_t maxLocalSizeBytes = 0;
   ncclResult_t res = ncclSuccess;
 
   CUDACHECKGOTO(cudaSetDevice(cudaDev), res, fail);
+  CUDACHECK(cudaDeviceGetAttribute(&archMajor, cudaDevAttrComputeCapabilityMajor, cudaDev));
+  CUDACHECK(cudaDeviceGetAttribute(&archMinor, cudaDevAttrComputeCapabilityMinor, cudaDev));
+  comm->cudaArch = 100*archMajor + 10*archMinor;
+
+  NCCLCHECK(ncclInitKernelsForDevice(comm->cudaArch, &maxLocalSizeBytes));
   // Set the maximum kernel stack size of all kernels to avoid
   // a CUDA memory reconfig on load (c.f. NVSHMEM issue)
   if (maxLocalSizeBytes > 0 && ncclParamSetStackSize() == 1) {
@@ -1114,18 +1128,143 @@ fail:
   goto exit;
 }
 
-static ncclResult_t parseCommConfig(ncclComm_t comm, ncclConfig_t *config) {
+#define NCCL_CONFIG_DEFAULT(config, field, undef, defvalue, fieldStr, format) \
-  ncclResult_t ret = ncclSuccess;
+  if (config->field == undef) { \
-
+    config->field = defvalue; \
-  /* first set configuration */
+  } else { \
-  if (config) {
+    INFO(NCCL_ENV, "Comm config " fieldStr " set to " format, config->field); \
-    comm->blocking = config->blocking;
-  } else {
-    /* default setting of communicator */
-    comm->blocking = 1;
   }
 
+static ncclResult_t parseCommConfig(ncclComm_t comm, ncclConfig_t *config) {
+  ncclResult_t ret = ncclSuccess;
+  /* config must not be NULL in this function */
+  int blockingEnv;
+  int cgaClusterSizeEnv;
+  int minCTAsEnv;
+  int maxCTAsEnv;
+  const char *envNetName, *tmpNetName;
+  ncclConfig_t defaultConfig = NCCL_CONFIG_INITIALIZER;
+  ncclConfig_t internalConfig = NCCL_CONFIG_INITIALIZER;
+  ncclConfig_t *internalConfigPtr;
+  size_t realSize;
+
+  internalConfigPtr = &internalConfig;
+  if (config) {
+    memcpy((void*)&realSize, (void*)config, sizeof(size_t));
+    realSize = realSize > sizeof(ncclConfig_t) ? sizeof(ncclConfig_t) : realSize;
+    memcpy((void*)internalConfigPtr, (void*)config, realSize);
+    if (internalConfigPtr->magic != 0xcafebeef) {
+      WARN("ncclConfig_t argument not initialized via NCCL_CONFIG_INITIALIZER");
+      ret = ncclInvalidArgument;
+      goto fail;
+    }
+
+    /* check version. */
+    if (internalConfigPtr->version < NCCL_VERSION(2, 14, 0)) {
+      internalConfigPtr->blocking = defaultConfig.blocking;
+    }
+
+    if (internalConfigPtr->version < NCCL_VERSION(2, 17, 0)) {
+      internalConfigPtr->cgaClusterSize = defaultConfig.cgaClusterSize;
+      internalConfigPtr->minCTAs = defaultConfig.minCTAs;
+      internalConfigPtr->maxCTAs = defaultConfig.maxCTAs;
+      internalConfigPtr->netName = defaultConfig.netName;
+    }
+  }
+
+  /* check input config attributes, -1 means user-undefined and we should use default value from NCCL. */
+  if (internalConfigPtr->blocking != NCCL_CONFIG_UNDEF_INT && internalConfigPtr->blocking != 0 && internalConfigPtr->blocking != 1) {
+    WARN("Invalid config blocking attribute value %d", internalConfigPtr->blocking);
+    ret = ncclInvalidArgument;
+    goto fail;
+  }
+
+  if (internalConfigPtr->cgaClusterSize != NCCL_CONFIG_UNDEF_INT && internalConfigPtr->cgaClusterSize < 0) {
+    WARN("Invalid config cgaClusterSize attribute value %d", internalConfigPtr->cgaClusterSize);
+    ret = ncclInvalidArgument;
+    goto fail;
+  }
+
+  if ((internalConfigPtr->minCTAs != NCCL_CONFIG_UNDEF_INT &&
+    internalConfigPtr->minCTAs <= 0) ||
+    (internalConfigPtr->maxCTAs != NCCL_CONFIG_UNDEF_INT &&
+      internalConfigPtr->maxCTAs <= 0) ||
+    (internalConfigPtr->minCTAs > internalConfigPtr->maxCTAs)) {
+    WARN("Invalid config min/max channels attribute value %d/%d", internalConfigPtr->minCTAs, internalConfigPtr->maxCTAs);
+    ret = ncclInvalidArgument;
+    goto fail;
+  }
+
+  /* default config value can be tuned on different platform. */
+  NCCL_CONFIG_DEFAULT(internalConfigPtr, blocking, NCCL_CONFIG_UNDEF_INT, 1, "Blocking", "%d");
+  NCCL_CONFIG_DEFAULT(internalConfigPtr, cgaClusterSize, NCCL_CONFIG_UNDEF_INT, 4, "CGA cluster size", "%d");
+  NCCL_CONFIG_DEFAULT(internalConfigPtr, minCTAs, NCCL_CONFIG_UNDEF_INT, 1, "Min CTAs", "%d");
+  NCCL_CONFIG_DEFAULT(internalConfigPtr, maxCTAs, NCCL_CONFIG_UNDEF_INT, MAXCHANNELS, "Max CTAs", "%d");
+  NCCL_CONFIG_DEFAULT(internalConfigPtr, netName, NCCL_CONFIG_UNDEF_PTR, NULL, "Net name", "%s");
+
+  tmpNetName = internalConfigPtr->netName;
+
+  /* assign config to communicator */
+  comm->blocking = internalConfigPtr->blocking;
+  comm->cgaClusterSize = internalConfigPtr->cgaClusterSize;
+  comm->minCTAs = internalConfigPtr->minCTAs;
+  comm->maxCTAs = internalConfigPtr->maxCTAs;
+
+  /* override configuration from env variable. */
+  blockingEnv = ncclParamCommBlocking();
+  if (blockingEnv == 0 || blockingEnv == 1)
+    comm->blocking = blockingEnv;
+
+  cgaClusterSizeEnv = ncclParamCGAClusterSize();
+  if (0 <= cgaClusterSizeEnv && cgaClusterSizeEnv <= NCCL_MAX_CGA_CLUSTER_SIZE) {
+    comm->cgaClusterSize = cgaClusterSizeEnv;
+  } else if (cgaClusterSizeEnv > NCCL_MAX_CGA_CLUSTER_SIZE) {
+    WARN("NCCL_CGA_CLUSTER_SIZE value %d is too big. Limiting value to %d.", cgaClusterSizeEnv, NCCL_MAX_CGA_CLUSTER_SIZE);
+    comm->cgaClusterSize = NCCL_MAX_CGA_CLUSTER_SIZE;
+  }
+
+  minCTAsEnv = ncclParamMinCTAs();
+  if (minCTAsEnv != NCCL_CONFIG_UNDEF_INT) {
+    comm->minCTAs = minCTAsEnv;
+  }
+
+  maxCTAsEnv = ncclParamMaxCTAs();
+  if (maxCTAsEnv != NCCL_CONFIG_UNDEF_INT) {
+    comm->maxCTAs = maxCTAsEnv;
+  }
+
+  /* cap channels if needed */
+  if (comm->minCTAs > MAXCHANNELS) {
+    WARN("minCTAs %d is larger than #channels upper limit %d", comm->minCTAs, MAXCHANNELS);
+    comm->minCTAs = MAXCHANNELS;
+  }
+
+  if (comm->maxCTAs > MAXCHANNELS) {
+    WARN("maxCTAs %d is larger than #channels upper limit %d", comm->maxCTAs, MAXCHANNELS);
+    comm->maxCTAs = MAXCHANNELS;
+  }
+
+  if (comm->minCTAs > comm->maxCTAs) {
+    WARN("minCTAs %d is larger than maxCTAs %d", comm->minCTAs, comm->maxCTAs);
+    ret = ncclInvalidArgument;
+    goto fail;
+  }
+
+  envNetName = getenv("NCCL_NET");
+  if (envNetName)
+    tmpNetName = envNetName;
+  if (tmpNetName != NULL) {
+    int netNameLen = strlen(tmpNetName) + 1;
+    comm->netName = (char*)malloc(netNameLen);
+    memcpy(comm->netName, tmpNetName, netNameLen);
+  } else {
+    comm->netName = NULL;
+  }
+
+exit:
   return ret;
+fail:
+  goto exit;
 }
 
 static void ncclCommInitRankUndo(struct ncclAsyncJob* job_) {
@@ -1151,6 +1290,7 @@ static ncclResult_t ncclCommInitRankDev(ncclComm_t* newcomm, int nranks, ncclUni
   CUDACHECKGOTO(cudaFree(NULL), res, fail);
 
   NCCLCHECKGOTO(PtrCheck(newcomm, "CommInitRank", "newcomm"), res, fail);
+  NCCLCHECKGOTO(PtrCheck(config, "CommInitRank", "config"), res, fail);
   if (nranks < 1 || myrank < 0 || myrank >= nranks) {
     WARN("Invalid rank requested : %d/%d", myrank, nranks);
     res = ncclInvalidArgument;
@@ -1201,12 +1341,13 @@ ncclResult_t ncclCommInitRank(ncclComm_t* newcomm, int nranks, ncclUniqueId comm
   (void)ncclCudaLibraryInit();
 
   int cudaDev;
+  ncclConfig_t config = NCCL_CONFIG_INITIALIZER;
   CUDACHECK(cudaGetDevice(&cudaDev));
 
   NvtxParamsCommInitRank payload{myrank, nranks, cudaDev};
   NVTX3_FUNC_WITH_PARAMS(CommInitRank, CommInitRankSchema, payload)
 
-  NCCLCHECK(ncclCommInitRankDev(newcomm, nranks, commId, myrank, cudaDev, NULL));
+  NCCLCHECK(ncclCommInitRankDev(newcomm, nranks, commId, myrank, cudaDev, &config));
   return ncclSuccess;
 }
 
@@ -1215,6 +1356,7 @@ ncclResult_t ncclCommInitAll(ncclComm_t* comms, int ndev, const int* devlist) {
   ncclResult_t ret = ncclSuccess;
   int totalnDev;
   int *gpuFlags = NULL;
+  ncclConfig_t config = NCCL_CONFIG_INITIALIZER;
 
   constexpr nvtxPayloadSchemaEntry_t CommInitAllSchema[] = {
     {0, NVTX_PAYLOAD_ENTRY_TYPE_INT, "No. of devices"}
@@ -1258,7 +1400,7 @@ ncclResult_t ncclCommInitAll(ncclComm_t* comms, int ndev, const int* devlist) {
   NCCLCHECKGOTO(ncclGroupStart(), ret, fail);
   for (int i=0; i<ndev; i++) {
     // Ignore return codes .. we need to call ncclGroupEnd to clean up anyway
-    ncclCommInitRankDev(comms+i, ndev, uniqueId, i, devlist ? devlist[i] : i, NULL);
+    ncclCommInitRankDev(comms+i, ndev, uniqueId, i, devlist ? devlist[i] : i, &config);
   }
   NCCLCHECKGOTO(ncclGroupEnd(), ret, fail);
 
@@ -1283,39 +1425,16 @@ ncclResult_t ncclCommInitRankConfig(ncclComm_t *newcomm, int nranks, ncclUniqueI
   int cudaDev;
   ncclResult_t ret = ncclSuccess;
   ncclConfig_t internalConfig = NCCL_CONFIG_INITIALIZER;
-  ncclConfig_t *internalConfigPtr;
+  ncclConfig_t *internalConfigPtr = NULL;
-  size_t realSize;
-  int blockingEnv;
-
   NCCLCHECK(ncclGroupStartInternal());
-  internalConfigPtr = &internalConfig;
-  if (config) {
-    memcpy((void*)&realSize, (void*)config, sizeof(size_t));
-    realSize = realSize > sizeof(ncclConfig_t) ? sizeof(ncclConfig_t) : realSize;
-    memcpy((void*)internalConfigPtr, (void*)config, realSize);
-    if (internalConfigPtr->magic != 0xcafebeef) {
-      WARN("ncclConfig_t argument not initialized via NCCL_CONFIG_INITIALIZER");
-      ret = ncclInvalidArgument;
-      goto exit;
-    }
-  }
-
-  /* check input config attributes */
-  if (internalConfigPtr->blocking != 0 && internalConfigPtr->blocking != 1) {
-    WARN("Invalid config blocking attribute value %d", internalConfigPtr->blocking);
-    ret = ncclInvalidArgument;
-    goto exit;
-  }
-
-  /* overwrite configuration from env variable. */
-  blockingEnv = ncclParamCommBlocking();
-  if (blockingEnv != 0 && blockingEnv != 1) {
-    WARN("Invalid NCCL_COMM_BLOCKING value %d", blockingEnv);
-  }
-  if (blockingEnv == 1) internalConfigPtr->blocking = blockingEnv;
 
   (void)ncclCudaLibraryInit();
-  CUDACHECKGOTO(cudaGetDevice(&cudaDev), ret, exit);
+  CUDACHECKGOTO(cudaGetDevice(&cudaDev), ret, fail);
+
+  if (config == NULL)
+    internalConfigPtr = &internalConfig;
+  else
+    internalConfigPtr = config;
   NCCLCHECKGOTO(ncclCommInitRankDev(newcomm, nranks, commId, myrank, cudaDev, internalConfigPtr), ret, fail);
 
 exit:

src/misc/cudawrap.cc

@@ -23,11 +23,33 @@ DECLARE_CUDA_PFN(cuMemGetAddressRange, 3020);
 /* proxy.cc */
 DECLARE_CUDA_PFN(cuCtxCreate, 3020);
 DECLARE_CUDA_PFN(cuCtxDestroy, 4000);
+DECLARE_CUDA_PFN(cuCtxGetCurrent, 4000);
 DECLARE_CUDA_PFN(cuCtxSetCurrent, 4000);
+DECLARE_CUDA_PFN(cuCtxGetDevice, 2000);
+/* cuMem API support */
+DECLARE_CUDA_PFN(cuMemAddressReserve, 10020);
+DECLARE_CUDA_PFN(cuMemAddressFree, 10020);
+DECLARE_CUDA_PFN(cuMemCreate, 10020);
+DECLARE_CUDA_PFN(cuMemGetAllocationGranularity, 10020);
+DECLARE_CUDA_PFN(cuMemExportToShareableHandle, 10020);
+DECLARE_CUDA_PFN(cuMemImportFromShareableHandle, 10020);
+DECLARE_CUDA_PFN(cuMemMap, 10020);
+DECLARE_CUDA_PFN(cuMemRelease, 10020);
+DECLARE_CUDA_PFN(cuMemSetAccess, 10020);
+DECLARE_CUDA_PFN(cuMemUnmap, 10020);
 #if CUDA_VERSION >= 11070
 /* transport/collNet.cc/net.cc*/
 DECLARE_CUDA_PFN(cuMemGetHandleForAddressRange, 11070); // DMA-BUF support
 #endif
+#if CUDA_VERSION >= 12010
+/* NVSwitch Multicast support */
+DECLARE_CUDA_PFN(cuMulticastAddDevice, 12010);
+DECLARE_CUDA_PFN(cuMulticastBindMem, 12010);
+DECLARE_CUDA_PFN(cuMulticastBindAddr, 12010);
+DECLARE_CUDA_PFN(cuMulticastCreate, 12010);
+DECLARE_CUDA_PFN(cuMulticastGetGranularity, 12010);
+DECLARE_CUDA_PFN(cuMulticastUnbind, 12010);
+#endif
 #endif
 
 /* CUDA Driver functions loaded with dlsym() */
@@ -39,6 +61,7 @@ DECLARE_CUDA_PFN(cuGetProcAddress, 11030);
 
 static void *cudaLib;
 int ncclCudaDriverVersionCache = -1;
+bool ncclCudaLaunchBlocking = false;
 
 #if CUDART_VERSION >= 11030
 /*
@@ -62,9 +85,33 @@ static ncclResult_t cudaPfnFuncLoader(void) {
   LOAD_SYM(cuMemGetAddressRange, 3020, 1);
   LOAD_SYM(cuCtxCreate, 3020, 1);
   LOAD_SYM(cuCtxDestroy, 4000, 1);
+  LOAD_SYM(cuCtxGetCurrent, 4000, 1);
   LOAD_SYM(cuCtxSetCurrent, 4000, 1);
+  LOAD_SYM(cuCtxGetDevice, 2000, 1);
+/* cuMem API support */
+#if CUDA_VERSION >= 11030
+  LOAD_SYM(cuMemAddressReserve, 10020, 1);
+  LOAD_SYM(cuMemAddressFree, 10020, 1);
+  LOAD_SYM(cuMemCreate, 10020, 1);
+  LOAD_SYM(cuMemGetAllocationGranularity, 10020, 1);
+  LOAD_SYM(cuMemExportToShareableHandle, 10020, 1);
+  LOAD_SYM(cuMemImportFromShareableHandle, 10020, 1);
+  LOAD_SYM(cuMemMap, 10020, 1);
+  LOAD_SYM(cuMemRelease, 10020, 1);
+  LOAD_SYM(cuMemSetAccess, 10020, 1);
+  LOAD_SYM(cuMemUnmap, 10020, 1);
+#endif
 #if CUDA_VERSION >= 11070
   LOAD_SYM(cuMemGetHandleForAddressRange, 11070, 1); // DMA-BUF support
+#endif
+#if CUDA_VERSION >= 12010
+/* NVSwitch Multicast support */
+  LOAD_SYM(cuMulticastAddDevice, 12010, 1);
+  LOAD_SYM(cuMulticastBindMem, 12010, 1);
+  LOAD_SYM(cuMulticastBindAddr, 12010, 1);
+  LOAD_SYM(cuMulticastCreate, 12010, 1);
+  LOAD_SYM(cuMulticastGetGranularity, 12010, 1);
+  LOAD_SYM(cuMulticastUnbind, 12010, 1);
 #endif
   return ncclSuccess;
 }
@@ -74,6 +121,11 @@ static pthread_once_t initOnceControl = PTHREAD_ONCE_INIT;
 static ncclResult_t initResult;
 
 static void initOnceFunc() {
+  do {
+    char* val = getenv("CUDA_LAUNCH_BLOCKING");
+    ncclCudaLaunchBlocking = val!=nullptr && val[0]!=0 && !(val[0]=='0' && val[1]==0);
+  } while (0);
+
   CUresult res;
   /*
    * Load CUDA driver library
@@ -85,9 +137,10 @@ static void initOnceFunc() {
   else
     snprintf(path, 1024, "%s%s", ncclCudaPath, "libcuda.so");
 
+  (void) dlerror(); // Clear any previous errors
   cudaLib = dlopen(path, RTLD_LAZY);
   if (cudaLib == NULL) {
-    WARN("Failed to find CUDA library (NCCL_CUDA_PATH='%s') : %s", ncclCudaPath ? ncclCudaPath : "", dlerror());
+    WARN("Failed to find CUDA library %s (NCCL_CUDA_PATH='%s') : %s", path, ncclCudaPath ? ncclCudaPath : "", dlerror());
     goto error;
   }
 

src/misc/ipcsocket.cc

@@ -0,0 +1,200 @@
+/*
+ * Copyright (c) 2016-2023, NVIDIA CORPORATION. All rights reserved.
+ *
+ * See COPYRIGHT for license information
+ */
+
+#include "ipcsocket.h"
+#include "utils.h"
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+// Enable Linux abstract socket naming
+#define USE_ABSTRACT_SOCKET
+
+#define NCCL_IPC_SOCKNAME_STR "/tmp/nccl-socket-%d-%lx"
+
+/*
+ * Create a Unix Domain Socket
+ */
+ncclResult_t ncclIpcSocketInit(ncclIpcSocket *handle, int rank, uint64_t hash, volatile uint32_t* abortFlag) {
+  int fd = -1;
+  struct sockaddr_un cliaddr;
+  char temp[NCCL_IPC_SOCKNAME_LEN] = "";
+
+  if (handle == NULL) {
+    return ncclInternalError;
+  }
+
+  handle->fd = -1;
+  handle->socketName[0] = '\0';
+  if ((fd = socket(AF_UNIX, SOCK_DGRAM, 0)) < 0) {
+    WARN("UDS: Socket creation error : %d", errno);
+    return ncclSystemError;
+  }
+
+  bzero(&cliaddr, sizeof(cliaddr));
+  cliaddr.sun_family = AF_UNIX;
+
+  // Create unique name for the socket.
+  int len = snprintf(temp, NCCL_IPC_SOCKNAME_LEN, NCCL_IPC_SOCKNAME_STR, rank, hash);
+  if (len > (sizeof(cliaddr.sun_path) - 1)) {
+    WARN("UDS: Cannot bind provided name to socket. Name too large");
+    return ncclInternalError;
+  }
+#ifndef USE_ABSTRACT_SOCKET
+  unlink(temp);
+#endif
+
+  TRACE(NCCL_INIT, "UDS: Creating socket %s", temp);
+
+  strncpy(cliaddr.sun_path, temp, len);
+#ifdef USE_ABSTRACT_SOCKET
+  cliaddr.sun_path[0] = '\0'; // Linux abstract socket trick
+#endif
+  if (bind(fd, (struct sockaddr *)&cliaddr, sizeof(cliaddr)) < 0) {
+    WARN("UDS: Binding to socket %s failed : %d", temp, errno);
+    close(fd);
+    return ncclSystemError;
+  }
+
+  handle->fd = fd;
+  strcpy(handle->socketName, temp);
+
+  handle->abortFlag = abortFlag;
+  // Mark socket as non-blocking
+  if (handle->abortFlag) {
+    int flags;
+    EQCHECK(flags = fcntl(fd, F_GETFL), -1);
+    SYSCHECK(fcntl(fd, F_SETFL, flags | O_NONBLOCK), "fcntl");
+  }
+
+  return ncclSuccess;
+}
+
+ncclResult_t ncclIpcSocketClose(ncclIpcSocket *handle) {
+  if (handle == NULL) {
+    return ncclInternalError;
+  }
+  if (handle->fd <= 0) {
+    return ncclSuccess;
+  }
+#ifndef USE_ABSTRACT_SOCKET
+  if (handle->socketName[0] != '\0') {
+    unlink(handle->socketName);
+  }
+#endif
+  close(handle->fd);
+
+  return ncclSuccess;
+}
+
+ncclResult_t ncclIpcSocketRecvFd(ncclIpcSocket *handle, int *recvFd) {
+  struct msghdr msg = {0, 0, 0, 0, 0, 0, 0};
+  struct iovec iov[1];
+
+  // Union to guarantee alignment requirements for control array
+  union {
+    struct cmsghdr cm;
+    char control[CMSG_SPACE(sizeof(int))];
+  } control_un;
+
+  struct cmsghdr *cmptr;
+  char dummy_buffer[1];
+  int ret;
+
+  msg.msg_control = control_un.control;
+  msg.msg_controllen = sizeof(control_un.control);
+
+  iov[0].iov_base = (void *)dummy_buffer;
+  iov[0].iov_len = sizeof(dummy_buffer);
+
+  msg.msg_iov = iov;
+  msg.msg_iovlen = 1;
+
+  while ((ret = recvmsg(handle->fd, &msg, 0)) <= 0) {
+    if (errno != EAGAIN && errno != EWOULDBLOCK && errno != EINTR) {
+      WARN("UDS: Receiving data over socket failed : %d", errno);
+      return ncclSystemError;
+    }
+    if (handle->abortFlag && *handle->abortFlag) return ncclInternalError;
+  }
+
+  if (((cmptr = CMSG_FIRSTHDR(&msg)) != NULL) && (cmptr->cmsg_len == CMSG_LEN(sizeof(int)))) {
+    if ((cmptr->cmsg_level != SOL_SOCKET) || (cmptr->cmsg_type != SCM_RIGHTS)) {
+      WARN("UDS: Receiving data over socket failed");
+      return ncclSystemError;
+    }
+
+    memmove(recvFd, CMSG_DATA(cmptr), sizeof(*recvFd));
+  } else {
+    WARN("UDS: Receiving data over socket %s failed", handle->socketName);
+    return ncclSystemError;
+  }
+
+  TRACE(NCCL_INIT|NCCL_P2P, "UDS: Got recvFd %d from socket %s", *recvFd, handle->socketName);
+
+  return ncclSuccess;
+}
+
+ncclResult_t ncclIpcSocketSendFd(ncclIpcSocket *handle, const int sendFd, int rank, uint64_t hash) {
+  struct msghdr msg;
+  struct iovec iov[1];
+  char temp[NCCL_IPC_SOCKNAME_LEN];
+
+  union {
+    struct cmsghdr cm;
+    char control[CMSG_SPACE(sizeof(int))];
+  } control_un;
+
+  struct cmsghdr *cmptr;
+  struct sockaddr_un cliaddr;
+
+  // Construct client address to send this shareable handle to
+  bzero(&cliaddr, sizeof(cliaddr));
+  cliaddr.sun_family = AF_UNIX;
+
+  int len = snprintf(temp, NCCL_IPC_SOCKNAME_LEN, NCCL_IPC_SOCKNAME_STR, rank, hash);
+  if (len > (sizeof(cliaddr.sun_path) - 1)) {
+    WARN("UDS: Cannot connect to provided name for socket. Name too large");
+    return ncclInternalError;
+  }
+  (void) strncpy(cliaddr.sun_path, temp, len);
+
+  TRACE(NCCL_INIT, "UDS: Sending fd %d to UDS socket %s", sendFd, temp);
+
+#ifdef USE_ABSTRACT_SOCKET
+  cliaddr.sun_path[0] = '\0'; // Linux abstract socket trick
+#endif
+
+  msg.msg_control = control_un.control;
+  msg.msg_controllen = sizeof(control_un.control);
+
+  cmptr = CMSG_FIRSTHDR(&msg);
+  cmptr->cmsg_len = CMSG_LEN(sizeof(int));
+  cmptr->cmsg_level = SOL_SOCKET;
+  cmptr->cmsg_type = SCM_RIGHTS;
+
+  memmove(CMSG_DATA(cmptr), &sendFd, sizeof(sendFd));
+
+  msg.msg_name = (void *)&cliaddr;
+  msg.msg_namelen = sizeof(struct sockaddr_un);
+
+  iov[0].iov_base = (void *)"";
+  iov[0].iov_len = 1;
+  msg.msg_iov = iov;
+  msg.msg_iovlen = 1;
+  msg.msg_flags = 0;
+
+  ssize_t sendResult;
+  while ((sendResult = sendmsg(handle->fd, &msg, 0)) <= 0) {
+    if (errno != EAGAIN && errno != EWOULDBLOCK && errno != EINTR) {
+      WARN("UDS: Sending data over socket %s failed : %d", temp, errno);
+      return ncclSystemError;
+    }
+    if (handle->abortFlag && *handle->abortFlag) return ncclInternalError;
+  }
+
+  return ncclSuccess;
+}

src/misc/socket.cc

@@ -43,7 +43,7 @@ static ncclResult_t socketProgressOpt(int op, struct ncclSocket* sock, void* ptr
 
 static ncclResult_t socketProgress(int op, struct ncclSocket* sock, void* ptr, int size, int* offset) {
   int closed;
-  NCCLCHECK(socketProgressOpt(op, sock, ptr, size, offset, 0, &closed));
+  NCCLCHECK(socketProgressOpt(op, sock, ptr, size, offset, 0 /*block*/, &closed));
   if (closed) {
     char line[SOCKET_NAME_MAXLEN+1];
     WARN("socketProgress: Connection closed by remote peer %s", ncclSocketToString(&sock->addr, line, 0));
@@ -785,17 +785,34 @@ ncclResult_t ncclSocketRecv(struct ncclSocket* sock, void* ptr, int size) {
 }
 
 // Receive or detect connection closed
-ncclResult_t ncclSocketTryRecv(struct ncclSocket* sock, void* ptr, int size, int* closed) {
+ncclResult_t ncclSocketTryRecv(struct ncclSocket* sock, void* ptr, int size, int* closed, bool blocking) {
   int offset = 0;
   if (sock == NULL) {
     WARN("ncclSocketTryRecv: pass NULL socket");
     return ncclInvalidArgument;
   }
   *closed = 0;
+  // Block until connection closes or nbytes received
+  if (blocking) {
     while (offset < size) {
       NCCLCHECK(socketProgressOpt(NCCL_SOCKET_RECV, sock, ptr, size, &offset, 0, closed));
       if (*closed) return ncclSuccess;
     }
+  } else {
+    NCCLCHECK(socketProgressOpt(NCCL_SOCKET_RECV, sock, ptr, size, &offset, 0, closed));
+    if (*closed) return ncclSuccess;
+
+    // If any bytes were received, block waiting for the rest
+    if (offset > 0) {
+      while (offset < size) {
+        NCCLCHECK(socketProgressOpt(NCCL_SOCKET_RECV, sock, ptr, size, &offset, 0, closed));
+        if (*closed) return ncclSuccess;
+      }
+    // No bytes were received, return ncclInProgress
+    } else {
+      return ncclInProgress;
+    }
+  }
   return ncclSuccess;
 }
 

src/nccl.h.in

@@ -25,8 +25,10 @@
 extern "C" {
 #endif
 
+#include <limits.h>
 /* Opaque handle to communicator */
 typedef struct ncclComm* ncclComm_t;
+#define NCCL_COMM_NULL NULL
 
 #define NCCL_UNIQUE_ID_BYTES 128
 typedef struct { char internal[NCCL_UNIQUE_ID_BYTES]; } ncclUniqueId;
@@ -42,15 +44,22 @@ typedef enum { ncclSuccess                 =  0,
                ncclInProgress              =  7,
                ncclNumResults              =  8 } ncclResult_t;
 
+#define NCCL_CONFIG_UNDEF_INT INT_MIN
+#define NCCL_CONFIG_UNDEF_PTR NULL
+
 /* Communicator configuration. Users can assign value to attributes to specify the
  * behavior of a communicator. */
-typedef struct ncclConfig_v21400 {
+typedef struct ncclConfig_v21700 {
   /* attributes that users should never touch. */
   size_t size;
   unsigned int magic;
   unsigned int version;
   /* attributes that users are able to customize. */
   int blocking;
+  int cgaClusterSize;
+  int minCTAs;
+  int maxCTAs;
+  const char *netName;
 } ncclConfig_t;
 
 /* Config initializer must be assigned to initialize config structure when it is created.
@@ -59,7 +68,11 @@ typedef struct ncclConfig_v21400 {
   sizeof(ncclConfig_t), /* size */                                      \
   0xcafebeef,           /* magic */                                     \
   NCCL_VERSION(NCCL_MAJOR, NCCL_MINOR, NCCL_PATCH), /* version */       \
-  1                     /* blocking */                                  \
+  NCCL_CONFIG_UNDEF_INT,                    /* blocking */              \
+  NCCL_CONFIG_UNDEF_INT,                    /* cgaClusterSize */        \
+  NCCL_CONFIG_UNDEF_INT,                    /* minCTAs */               \
+  NCCL_CONFIG_UNDEF_INT,                    /* maxCTAs */               \
+  NCCL_CONFIG_UNDEF_PTR                     /* netName */               \
 }
 
 /* Return the NCCL_VERSION_CODE of the NCCL library in the supplied integer.

src/net.cc

@@ -176,14 +176,8 @@ ncclResult_t ncclNetPluginInit() {
   }
   void* netPluginLib = dlopen(ncclNetPluginName, RTLD_NOW | RTLD_LOCAL);
   if (netPluginLib == nullptr) {
-    // dlopen does not guarantee to set errno, but dlerror only gives us a
+    INFO(NCCL_INIT|NCCL_NET, "NET/Plugin : Plugin load (%s) returned %d : %s", ncclNetPluginName, errno, dlerror());
-    // string, so checking errno doesn't hurt to try to provide a better
+    INFO(NCCL_INIT|NCCL_NET, "NET/Plugin : No plugin found, using internal implementation");
-    // error message
-    if (errno == ENOENT) {
-      INFO(NCCL_INIT|NCCL_NET, "NET/Plugin : No plugin found (%s), using internal implementation", ncclNetPluginName);
-    } else {
-      INFO(NCCL_INIT|NCCL_NET, "NET/Plugin : Plugin load returned %d : %s.", errno, dlerror());
-    }
     return ncclSuccess;
   }
 
@@ -264,9 +258,10 @@ static ncclResult_t collNetGetState(int i, enum ncclNetState* state) {
 
 ncclResult_t ncclNetInit(struct ncclComm* comm) {
   // Initialize main communication network
-  char* netName = getenv("NCCL_NET");
+  char* netName;
   bool ok = false;
 
+  netName = comm->netName;
   for (int i=0; i<3; i++) {
     if (ncclNets[i] == nullptr) continue;
     enum ncclNetState state;
@@ -324,9 +319,26 @@ ncclResult_t ncclGpuGdrSupport(struct ncclComm* comm, int* gdrSupport) {
     ncclResult_t ret;
     ncclDebugNoWarn = NCCL_NET;
     NCCLCHECKGOTO(ncclNetListen(comm, dev, &handle, &lComm), ret, cleanup1);
-    NCCLWAITGOTO(ncclNetConnect(comm, dev, &handle, &sComm), sComm != NULL, comm->abortFlag, ret, cleanup2);
+
-    NCCLWAITGOTO(ncclNetAccept(comm, lComm, &rComm), rComm != NULL, comm->abortFlag, ret, cleanup3);
+    bool connected;
-    CUDACHECKGOTO(cudaMalloc(&gpuPtr, GPU_BUF_SIZE), ret, cleanup4);
+    connected = false;
+    while (!connected) {
+
+      // If we're aborting now, skip to cleanup
+      if (*comm->abortFlag) {
+        goto cleanup2;
+      }
+
+      if (sComm == NULL)
+        NCCLCHECKGOTO(ncclNetConnect(comm, dev, &handle, &sComm), ret, cleanup2);
+
+      if (rComm == NULL)
+        NCCLCHECKGOTO(ncclNetAccept(comm, lComm, &rComm), ret, cleanup2);
+
+      connected = (rComm != NULL) && (sComm != NULL);
+    }
+
+    CUDACHECKGOTO(cudaMalloc(&gpuPtr, GPU_BUF_SIZE), ret, cleanup2);
     if (ncclNetRegMr(comm, sComm, gpuPtr, GPU_BUF_SIZE, NCCL_PTR_CUDA, &mHandle) == ncclSuccess) {
       NCCLCHECK(ncclNetDeregMr(comm, sComm, mHandle));
       NCCLCHECK(ncclNetRegMr(comm, rComm, gpuPtr, GPU_BUF_SIZE, NCCL_PTR_CUDA, &mHandle));
@@ -335,11 +347,11 @@ ncclResult_t ncclGpuGdrSupport(struct ncclComm* comm, int* gdrSupport) {
     }
     ncclDebugNoWarn = 0;
     CUDACHECK(cudaFree(gpuPtr));
-cleanup4:
-    NCCLCHECK(ncclNetCloseRecv(comm, rComm));
-cleanup3:
-    NCCLCHECK(ncclNetCloseSend(comm, sComm));
 cleanup2:
+    if (rComm != NULL)
+      NCCLCHECK(ncclNetCloseRecv(comm, rComm));
+    if (sComm != NULL)
+      NCCLCHECK(ncclNetCloseSend(comm, sComm));
     NCCLCHECK(ncclNetCloseListen(comm, lComm));
 cleanup1:
     break;

src/proxy.cc

@@ -14,6 +14,7 @@
 #include "timer.h"
 
 #include <sys/syscall.h>
+#include <assert.h>
 
 enum { proxyRecv=0, proxySend=1 };
 
@@ -37,6 +38,155 @@ struct ncclProxyPool {
   struct ncclProxyArgs elems[PROXYARGS_ALLOCATE_SIZE];
 };
 
+static void expectedProxyResponseFree(struct ncclProxyState* state) {
+  struct ncclExpectedProxyResponse* elem = state->expectedResponses;
+  struct ncclExpectedProxyResponse* prev = NULL;
+
+  while (elem) {
+    prev = elem;
+    elem = elem->next;
+    free(prev->respBuff);
+    free(prev);
+  }
+}
+
+static ncclResult_t expectedProxyResponseStore(struct ncclProxyState* state, void* opId, void* respBuff, int respSize) {
+  struct ncclExpectedProxyResponse* elem = state->expectedResponses;
+  while (elem) {
+    if (elem->opId == opId) {
+      if (respSize != elem->respSize) {
+        WARN("Mismatched response size for opId=%p", opId);
+        return ncclInternalError;
+      }
+
+      if (elem->done) {
+        WARN("Storing response for already completed opId=%p", opId);
+        return ncclInternalError;
+      }
+
+      memcpy(elem->respBuff, respBuff, respSize);
+      elem->done = true;
+      return ncclSuccess;
+    }
+    elem = elem->next;
+  }
+
+  WARN("Proxy response for opId=%p doesn't match any expected response", opId);
+  return ncclInternalError;
+}
+
+static ncclResult_t expectedProxyResponseEnqueue(struct ncclProxyState* state, void* opId, int respSize, void* respData, int respDataSize) {
+  struct ncclExpectedProxyResponse* ex;
+  NCCLCHECK(ncclCalloc(&ex, 1));
+  ex->opId = opId;
+
+  // Pre-alloc response buffer
+  ex->respBuff = malloc(respSize);
+  ex->respSize = respSize;
+  ex->done     = false;
+  if (respData) {
+    memcpy(ex->respBuff, respData, respDataSize);
+    ex->done = true;
+  }
+
+  // Enqueue
+  struct ncclExpectedProxyResponse* list = state->expectedResponses;
+  if (list == NULL) {
+    state->expectedResponses = ex;
+    return ncclSuccess;
+  }
+  while (list->next) list = list->next;
+  list->next = ex;
+  return ncclSuccess;
+}
+
+static ncclResult_t expectedProxyResponseDequeue(struct ncclProxyState* state, void* opId, void* respBuff, int* found) {
+  struct ncclExpectedProxyResponse* elem = state->expectedResponses;
+  struct ncclExpectedProxyResponse* prev = NULL;
+  *found = 0;
+  while (elem) {
+    if ((elem->opId == opId) && elem->done) {
+      if (prev == NULL) {
+        state->expectedResponses = elem->next;
+      } else {
+        prev->next = elem->next;
+      }
+      memcpy(respBuff, elem->respBuff, elem->respSize);
+      free(elem->respBuff);
+      free(elem);
+      *found = 1;
+      return ncclSuccess;
+    }
+    prev = elem;
+    elem = elem->next;
+  }
+  return ncclSuccess;
+}
+
+static ncclResult_t expectedProxyResponseRemove(struct ncclProxyState* state, void* opId) {
+  struct ncclExpectedProxyResponse* elem = state->expectedResponses;
+  struct ncclExpectedProxyResponse* prev = NULL;
+  while (elem) {
+    if (elem->opId == opId) {
+      if (prev == NULL) {
+        state->expectedResponses = elem->next;
+      } else {
+        prev->next = elem->next;
+      }
+      free(elem->respBuff);
+      free(elem);
+      return ncclSuccess;
+    }
+    prev = elem;
+    elem = elem->next;
+  }
+  WARN("Couldn't find opId=%p", opId);
+  return ncclInternalError;
+}
+
+static ncclResult_t asyncProxyOpEnqueue(struct ncclProxyLocalPeer* peer, ncclProxyAsyncOp* op) {
+  ncclProxyAsyncOp* list = peer->asyncOps;
+  if (list == NULL) {
+    peer->asyncOps = op;
+    return ncclSuccess;
+  }
+  while (list->next) list = list->next;
+  list->next = op;
+  return ncclSuccess;
+}
+
+static ncclResult_t asyncProxyOpDequeue(struct ncclProxyLocalPeer* peer, ncclProxyAsyncOp* op) {
+  struct ncclProxyAsyncOp* elem = peer->asyncOps;
+  struct ncclProxyAsyncOp* prev = NULL;
+  while (elem) {
+    if (elem->opId == op->opId) {
+      if (prev == NULL) {
+        peer->asyncOps = elem->next;
+      } else {
+        prev->next = elem->next;
+      }
+
+      if (elem->reqBuff) {
+        free(elem->reqBuff);
+      }
+      if (elem->respBuff) {
+        free(elem->respBuff);
+      }
+      free(elem);
+
+      return ncclSuccess;
+    }
+    prev = elem;
+    elem = elem->next;
+  }
+  if (op) {
+    WARN("Attempting to dequeue nonexistent async opId=%p", op->opId);
+  } else {
+    WARN("Attempting to dequeue null operation");
+  }
+  return ncclInternalError;
+}
+
 static ncclResult_t allocateArgs(struct ncclProxyProgressState* state, struct ncclProxyArgs** argsptr) {
   struct ncclProxyArgs* elem;
   if (state->pool == NULL) {
@@ -86,7 +236,7 @@ ncclResult_t getOpIndex(struct ncclProxyArgs* op, struct ncclProxyProgressState*
     pool = pool->next;
     p++;
   }
-  WARN("Could not find pool of op %p\n", op);
+  WARN("Could not find pool of op %p", op);
   return ncclInternalError;
 }
 
@@ -140,7 +290,7 @@ ncclResult_t dumpProxyState(struct ncclProxyProgressState* state) {
       nextOp->state |= OP_SEEN;
       printf("\n");
       if (nextOp->next) {
-        WARN("Inactive op has next set!\n");
+        WARN("Inactive op has next set!");
       }
       nextOp = nextOp->nextPeer;
     }
@@ -337,7 +487,7 @@ ncclResult_t ncclLocalOpAppend(struct ncclComm* comm, struct ncclProxyConnector*
       }
     }
     if (lastOp == -1) {
-      WARN("Unable to post incomplete proxy op chain %d..%d (opCount %ld)\n", proxyOps->nextOps, proxyOps->nextOpsEnd, lastOpCount);
+      WARN("Unable to post incomplete proxy op chain %d..%d (opCount %ld)", proxyOps->nextOps, proxyOps->nextOpsEnd, lastOpCount);
       return ncclInternalError;
     }
     // Cut chain at lastOp
@@ -770,19 +920,6 @@ ncclResult_t ncclProxyProgressDestroy(struct ncclComm* comm) {
   return ncclSuccess;
 }
 
-struct ncclProxyAsyncOp {
-  int type;
-  struct ncclProxyConnection* connection;
-  int reqSize, respSize;
-  char *reqBuff, *respBuff;
-};
-
-struct ncclProxyLocalPeer {
-  struct ncclSocket sock;
-  int localRank;
-  struct ncclProxyAsyncOp asyncOps;
-};
-
 #define NCCL_PROXY_CONN_POOL_SIZE_POW2 7
 #define NCCL_PROXY_CONN_POOL_SIZE (1<<(NCCL_PROXY_CONN_POOL_SIZE_POW2))
 #define NCCL_PROXY_CONN_POOL_MASK ((NCCL_PROXY_CONN_POOL_SIZE)-1)
@@ -790,7 +927,6 @@ struct ncclProxyConnectionPool {
   struct ncclProxyConnection** pools;
   int banks;
   int offset;
-  struct ncclProxyAsyncOp* ops;
 };
 
 static ncclResult_t ncclProxyNewConnection(struct ncclProxyConnectionPool* pool, int* id) {
@@ -888,26 +1024,137 @@ ncclResult_t ncclProxyConnect(struct ncclComm* comm, int transport, int send, in
   return ncclSuccess;
 }
 
-const char* ncclProxyMsgTypeStr[] = { "Unknown", "Init", "SharedInit", "Setup", "Connect", "Start", "Close", "Abort", "Stop" };
+const char* ncclProxyMsgTypeStr[] = { "Unknown", "Init", "SharedInit", "Setup", "Connect", "Start", "Close", "Abort", "Stop", "ConvertFd" };
-ncclResult_t ncclProxyCall(struct ncclProxyConnector* proxyConn, int type, void* reqBuff, int reqSize, void* respBuff, int respSize) {
+ncclResult_t ncclProxyCallAsync(struct ncclProxyConnector* proxyConn, int type, void* reqBuff, int reqSize, int respSize, void* opId) {
   struct ncclSocket* sock;
   ncclResult_t ret = ncclSuccess;
+  void* respData = NULL;
+  int respDataSize = 0;
+  struct ncclComm* comm = proxyConn->comm;
+  struct ncclIpcSocket ipcSock = { 0 };
 
-  if (proxyConn->comm->proxyState.peerSocks == NULL) return ncclInternalError;
+  if (*comm->abortFlag != 0) {
-  sock = proxyConn->comm->proxyState.peerSocks + proxyConn->localRank;
+    WARN("ncclProxyCallAsync() - Saw abortFlag while waiting for proxyThread response");
+    return ncclInternalError;
+  }
+  if (comm->proxyState.peerSocks == NULL) return ncclInternalError;
+
+  sock = comm->proxyState.peerSocks + proxyConn->localRank;
   if (sock == NULL) return ncclInternalError;
+
+  if (type == ncclProxyMsgConvertFd) {
+    // cuMem API support
+    // Create a UDS socket to receive the converted fd
+    NCCLCHECK(ncclIpcSocketInit(&ipcSock, comm->localRank, (uint64_t)proxyConn->connection, comm->abortFlag));
+  }
+
   NCCLCHECKGOTO(ncclSocketSend(sock, &type, sizeof(int)), ret, error);
   NCCLCHECKGOTO(ncclSocketSend(sock, &proxyConn->connection, sizeof(void*)), ret, error);
   NCCLCHECKGOTO(ncclSocketSend(sock, &reqSize, sizeof(int)), ret, error);
   NCCLCHECKGOTO(ncclSocketSend(sock, &respSize, sizeof(int)), ret, error);
   if (reqSize) NCCLCHECKGOTO(ncclSocketSend(sock, reqBuff, reqSize), ret, error);
-  if (respSize) NCCLCHECKGOTO(ncclSocketRecv(sock, respBuff, respSize), ret, error);
+
+  if (type == ncclProxyMsgConvertFd) {
+    // cuMem API support
+    int recvFd = -1;
+    if (reqSize != sizeof(int) || respSize != sizeof(int)) return ncclInternalError;
+    // Receive converted fd over UDS
+    NCCLCHECK(ncclIpcSocketRecvFd(&ipcSock, &recvFd));
+    TRACE(NCCL_NET, "UDS: ConvertFd rank %d returned %p %d", proxyConn->localRank, &recvFd, recvFd);
+    assert(recvFd != -1);
+    respData = &recvFd;
+    respDataSize = sizeof(recvFd);
+    NCCLCHECK(ncclIpcSocketClose(&ipcSock));
+  } else {
+    // Send opId to proxy
+    NCCLCHECKGOTO(ncclSocketSend(sock, &opId, sizeof(opId)), ret, error);
+  }
+  // Add proxyOp to expected response queue
+  NCCLCHECK(expectedProxyResponseEnqueue(&comm->proxyState, opId, respSize, respData, respDataSize));
+
   return ncclSuccess;
 error:
-  WARN("Proxy Call to rank %d failed (%s)", proxyConn->comm->localRankToRank[proxyConn->localRank], ncclProxyMsgTypeStr[type]);
+  NCCLCHECK(ncclIpcSocketClose(&ipcSock));
+  WARN("Proxy Call to rank %d failed (%s)", comm->localRankToRank[proxyConn->localRank], ncclProxyMsgTypeStr[type]);
   return ret;
 }
 
+ncclResult_t ncclPollProxyResponse(struct ncclProxyConnector* proxyConn, void* respBuff, void* opId) {
+  struct ncclComm* comm = proxyConn->comm;
+
+  // Receive the connection pointer from the Proxy
+  if (*comm->abortFlag) {
+    WARN("Comm %p is in abort state", comm);
+    return ncclInternalError;
+  }
+  if (comm->proxyState.peerSocks == NULL) return ncclInternalError;
+
+  // Check response queue
+  int found = 0;
+  NCCLCHECK(expectedProxyResponseDequeue(&comm->proxyState, opId, respBuff, &found));
+  if (found == 0) {
+    // Attempt to read in a new response header from the proxy thread
+    struct ncclSocket* sock = comm->proxyState.peerSocks + proxyConn->localRank;
+
+    void* recvOpId;
+    int offset = 0;
+    if (ncclSuccess != ncclSocketProgress(NCCL_SOCKET_RECV, sock, &recvOpId, sizeof(recvOpId), &offset)) {
+      WARN("Socket recv failed while polling for opId=%p", opId);
+      return ncclInternalError;
+    }
+
+    if (offset == 0) {
+      return ncclInProgress;
+    // If we've returned a partial response, block to receive the rest of it
+    } else if (offset < sizeof(recvOpId)) {
+      while (offset < sizeof(recvOpId))
+        NCCLCHECK(ncclSocketProgress(NCCL_SOCKET_RECV, sock, &recvOpId, sizeof(recvOpId), &offset));
+    }
+
+    INFO(NCCL_PROXY, "ncclPollProxyResponse Recieved new opId=%p", recvOpId);
+
+    // Now do a blocking recv of the response size
+    int respSize = 0;
+    NCCLCHECK(ncclSocketRecv(sock, &respSize, sizeof(respSize)));
+
+    // If there's a respSize to recv
+    if (respSize > 0) {
+      NCCLCHECK(ncclSocketRecv(sock, respBuff, respSize));
+    }
+
+    if (recvOpId == opId) {
+      INFO(NCCL_PROXY, "recvOpId=%p matches expected opId=%p", recvOpId, opId);
+      NCCLCHECK(expectedProxyResponseRemove(&comm->proxyState, recvOpId));
+      return ncclSuccess;
+    } else {
+      INFO(NCCL_PROXY, "Queing opId=%p", recvOpId);
+      // Store the result and mark response as completed
+      NCCLCHECK(expectedProxyResponseStore(&comm->proxyState, recvOpId, respBuff, respSize));
+      return ncclInProgress;
+    }
+  } else {
+    INFO(NCCL_PROXY, "ncclPollProxyResponse Dequeued cached opId=%p", opId);
+  }
+
+  return ncclSuccess;
+}
+
+ncclResult_t ncclProxyCallBlocking(struct ncclProxyConnector* proxyConn, int type, void* reqBuff, int reqSize, void* respBuff, int respSize) {
+  // Alloc some memory to act as a handle
+  void* opId = malloc(1);
+
+  NCCLCHECK(ncclProxyCallAsync(proxyConn, type, reqBuff, reqSize, respSize, opId));
+  ncclResult_t res = ncclInProgress;
+
+  while (res == ncclInProgress) {
+    res = ncclPollProxyResponse(proxyConn, respBuff, opId);
+  }
+
+  free(opId);
+
+  return res;
+}
+
 static ncclResult_t proxyProgressInit(struct ncclComm* comm) {
   struct ncclProxyProgressState* state = &comm->proxyState.progressState;
   if (state->opsPool == NULL) {
@@ -998,16 +1245,55 @@ static ncclResult_t proxyConnSharedInit(struct ncclProxyLocalPeer* peer, struct
   if (reqSize != sizeof(int) || respSize != 0) return ncclInternalError;
   int nChannels;
   NCCLCHECK(ncclSocketRecv(sock, &nChannels, sizeof(int)));
+
+  // Store opId for completion response
+  void* opId;
+  NCCLCHECK(ncclSocketRecv(sock, &opId, sizeof(opId)));
+  INFO(NCCL_PROXY, "proxyConnSharedInit received opId=%p", opId);
+
   if (connection->tcomm->proxySharedInit) NCCLCHECK(connection->tcomm->proxySharedInit(connection, comm, nChannels));
   __atomic_store_n(&connection->state, connSharedInitialized, __ATOMIC_RELEASE);
+
+  // Send the opId for referencing async operation
+  INFO(NCCL_PROXY, "proxyConnSharedInit::ncclSocketSend(opId=%p)", opId);
+  NCCLCHECK(ncclSocketSend(connection->sock, &opId, sizeof(opId)));
+
+  // Send the response size
+  INFO(NCCL_PROXY, "proxyConnSharedInit::ncclSocketSend(op.respSize=%d)", respSize);
+  NCCLCHECK(ncclSocketSend(connection->sock, &respSize, sizeof(respSize)));
+
   return ncclSuccess;
 }
 
-static ncclResult_t proxyProgressAsync(struct ncclProxyAsyncOp* op, struct ncclComm* comm, int* asyncOpCount) {
+// cuMem API support
+static ncclResult_t proxyConvertFd(struct ncclProxyLocalPeer* peer, struct ncclComm* comm) {
+  struct ncclSocket* sock = &peer->sock;
+  uint64_t connection;
+  NCCLCHECK(ncclSocketRecv(sock, &connection, sizeof(uint64_t)));
+  int reqSize, respSize;
+  NCCLCHECK(ncclSocketRecv(sock, &reqSize, sizeof(int)));
+  NCCLCHECK(ncclSocketRecv(sock, &respSize, sizeof(int)));
+  if (reqSize != sizeof(int) || respSize != sizeof(int)) return ncclInternalError;
+
+  int fd;
+  struct ncclIpcSocket ipcSock = { 0 };
+  NCCLCHECK(ncclSocketRecv(sock, &fd, sizeof(int)));
+
+  INFO(NCCL_NET, "UDS: proxyConvertFd received fd %d peer %d connection %lx", fd, peer->localRank, connection);
+  // Send back the converted fd using UDS
+  NCCLCHECK(ncclIpcSocketInit(&ipcSock, comm->localRank, connection^1, comm->abortFlag));
+  NCCLCHECK(ncclIpcSocketSendFd(&ipcSock, fd, peer->localRank, connection));
+  NCCLCHECK(ncclIpcSocketClose(&ipcSock));
+  return ncclSuccess;
+}
+
+static ncclResult_t proxyProgressAsync(struct ncclProxyAsyncOp* op, struct ncclComm* comm, int* asyncOpCount, struct ncclProxyLocalPeer* peer) {
   int done = 1;
   if (op->type == ncclProxyMsgSetup) {
+    INFO(NCCL_PROXY, "proxyProgressAsync::proxySetup() opId=%p", op->opId);
     NCCLCHECK(op->connection->tcomm->proxySetup(op->connection, comm, op->reqBuff, op->reqSize, op->respBuff, op->respSize, &done));
   } else if (op->type == ncclProxyMsgConnect) {
+    INFO(NCCL_PROXY, "proxyProgressAsync::proxyConnect() opId=%p op.reqBuff=%p", op->opId, op->reqBuff);
     NCCLCHECK(op->connection->tcomm->proxyConnect(op->connection, comm, op->reqBuff, op->reqSize, op->respBuff, op->respSize, &done));
   } else return ncclInternalError;
   if (done) {
@@ -1019,27 +1305,34 @@ static ncclResult_t proxyProgressAsync(struct ncclProxyAsyncOp* op, struct ncclC
      * ncclSocketSend might already send the respBuff to the requester. If we still choose
      * to abort and close the connection, it can cause segfault if the requester is using
      * the respBuff. */
-    if (op->respSize) ncclSocketSend(op->connection->sock, op->respBuff, op->respSize);
+
-    if (op->reqBuff) {
+    // Send the opId for referencing async operation
-      free(op->reqBuff);
+    NCCLCHECK(ncclSocketSend(op->connection->sock, &op->opId, sizeof(op->opId)));
-      op->reqBuff = NULL;
+
+    // Send the response size
+    NCCLCHECK(ncclSocketSend(op->connection->sock, &op->respSize, sizeof(op->respSize)));
+
+    if (op->respSize) {
+      // Send the response
+      NCCLCHECK(ncclSocketSend(op->connection->sock, op->respBuff, op->respSize));
     }
-    if (op->respBuff) {
+
-      free(op->respBuff);
+    asyncProxyOpDequeue(peer, op);
-      op->respBuff = NULL;
-    }
-    op->type = 0;
     (*asyncOpCount)--;
+    return ncclSuccess;
+
   } else if (*comm->abortFlag != 0) {
     return ncclInternalError;
   }
 
-  return ncclSuccess;
+  return ncclInProgress;
 }
 
 static ncclResult_t proxyConnSetupConnect(int type, struct ncclProxyLocalPeer* peer, struct ncclProxyConnectionPool* connectionPool, struct ncclComm* comm, int* asyncOpCount) {
   struct ncclSocket* sock = &peer->sock;
-  struct ncclProxyAsyncOp* asyncOp = &peer->asyncOps;
+  struct ncclProxyAsyncOp* asyncOp;
+  NCCLCHECK(ncclCalloc(&asyncOp, 1));
+
   asyncOp->type = type;
   NCCLCHECK(ncclSocketRecv(sock, &asyncOp->connection, sizeof(void*)));
 
@@ -1049,9 +1342,16 @@ static ncclResult_t proxyConnSetupConnect(int type, struct ncclProxyLocalPeer* p
     NCCLCHECK(ncclCalloc(&asyncOp->reqBuff, asyncOp->reqSize));
     NCCLCHECK(ncclSocketRecv(sock, asyncOp->reqBuff, asyncOp->reqSize));
   }
+
+  // Store opId for completion response
+  NCCLCHECK(ncclSocketRecv(sock, &asyncOp->opId, sizeof(asyncOp->opId)));
+
   if (asyncOp->respSize) NCCLCHECK(ncclCalloc(&asyncOp->respBuff, asyncOp->respSize));
+
+  asyncProxyOpEnqueue(peer, asyncOp);
+
   (*asyncOpCount)++;
-  NCCLCHECK(proxyProgressAsync(asyncOp, comm, asyncOpCount));
+  NCCLCHECK(proxyProgressAsync(asyncOp, comm, asyncOpCount, peer));
   return ncclSuccess;
 }
 
@@ -1081,7 +1381,7 @@ void* ncclProxyService(void* _args) {
     pollfds[s].events = POLLHUP|POLLIN;
   }
   if (ncclSocketGetFd(comm->proxyState.listenSock, &pollfds[NCCL_MAX_LOCAL_RANKS].fd) != ncclSuccess) {
-    WARN("[Proxy Service] Get listenSock fd fails\n");
+    WARN("[Proxy Service] Get listenSock fd fails");
     return NULL;
   };
   pollfds[NCCL_MAX_LOCAL_RANKS].events = POLLIN;
@@ -1113,14 +1413,14 @@ void* ncclProxyService(void* _args) {
       }
       if (maxnpeers < s+1) maxnpeers = s+1;
       if (ncclSocketInit(&peers[s].sock) != ncclSuccess) {
-        WARN("[Service thread] Initialize peers[%d].sock fails\n", s);
+        WARN("[Service thread] Initialize peers[%d].sock fails", s);
         return NULL;
       }
       if (ncclSocketAccept(&peers[s].sock, comm->proxyState.listenSock) != ncclSuccess) {
         WARN("[Service thread] Accept failed %s", strerror(errno));
       } else {
         if (ncclSocketGetFd(&peers[s].sock, &pollfds[s].fd) != ncclSuccess) {
-          WARN("[Service thread] Get peers[%d].sock fd fails\n", s);
+          WARN("[Service thread] Get peers[%d].sock fd fails", s);
           return NULL;
         }
         npeers++;
@@ -1130,25 +1430,37 @@ void* ncclProxyService(void* _args) {
     for (int s=0; s<maxnpeers; s++) {
       struct ncclProxyLocalPeer* peer = peers+s;
       struct ncclSocket* sock = &peer->sock;
-      struct ncclProxyAsyncOp* op = &peer->asyncOps;
       int closeConn = 0;
       int type = 0;
       ncclResult_t res = ncclSuccess;
-
       if (pollfds[s].fd == -1) continue;
-      if (op->type != 0) {
+
-        res = proxyProgressAsync(op, comm, &asyncOpCount);
+      // Progress all ops for this ncclProxyLocalPeer
+      ncclProxyAsyncOp* op = peer->asyncOps;
+      while (op != nullptr) {
         type = op->type;
-        if (res != ncclSuccess) closeConn = 1;
+        res = proxyProgressAsync(op, comm, &asyncOpCount, peer);
-      } else if (pollfds[s].revents & POLLIN) {
+        if (res == ncclSuccess || res == ncclInProgress) {
+          op = op->next;
+        } else {
+          // Res is a bad result
+          closeConn = 1;
+          WARN("[Service thread] Error encountered progressing operation=%s, res=%d, closing connection", ncclProxyMsgTypeStr[type], res);
+          break;
+        }
+      }
+
+      // Check for additional ops coming in
+      if (pollfds[s].revents & POLLIN) {
         int closed;
-        if (ncclSocketTryRecv(sock, &type, sizeof(int), &closed) != ncclSuccess) {
+        res = ncclSocketTryRecv(sock, &type, sizeof(int), &closed, false /*blocking*/);
-          WARN("[Service thread] Could not receive type from localRank %d", peer->localRank);
+        if (res != ncclSuccess && res != ncclInProgress) {
+          WARN("[Service thread] Could not receive type from localRank %d, res=%u, closed=%d", peer->localRank, res, closed);
           closeConn = 1;
         } else if (closed) {
           INFO(NCCL_INIT|NCCL_NET, "[Service thread] Connection closed by localRank %d", peer->localRank);
           closeConn = 1;
-        } else {
+        } else if (res == ncclSuccess) { // We received something from the sock
           if (type == ncclProxyMsgStop) {
             stop = 1;
             closeConn = 1;
@@ -1159,30 +1471,32 @@ void* ncclProxyService(void* _args) {
           } else if (type == ncclProxyMsgSharedInit) {
             res = proxyConnSharedInit(peers+s, &connectionPool, comm);
           } else if (type == ncclProxyMsgSetup || type == ncclProxyMsgConnect) {
+            INFO(NCCL_PROXY, "proxyConnSetupConnect for peer->localRank %d,", peer->localRank);
             res = proxyConnSetupConnect(type, peers+s, &connectionPool, comm, &asyncOpCount);
+          } else if (type == ncclProxyMsgConvertFd) {
+            res = proxyConvertFd(peers+s, comm); // cuMem API support
           } else {
-            WARN("[Service thread] Unknown command %d from localRank %d\n", type, peer->localRank);
+            WARN("[Service thread] Unknown command %d from localRank %d", type, peer->localRank);
             closeConn = 1;
           }
+
+          INFO(NCCL_PROXY, "Received and initiated operation=%s res=%d", ncclProxyMsgTypeStr[type], res);
         }
       } else if (pollfds[s].revents & POLLHUP) {
         closeConn = 1;
       }
-      if (res != ncclSuccess) {
+      if (res != ncclSuccess && res != ncclInProgress) {
         WARN("[Proxy Service %d] Failed to execute operation %s from rank %d, retcode %d", comm->rank, ncclProxyMsgTypeStr[type], comm->localRankToRank[peer->localRank], res);
         closeConn = 1;
       }
+
       if (closeConn) {
         ncclSocketClose(sock);
-        if (op->reqBuff) {
+
-          free(op->reqBuff);
+        if (op != nullptr) {
-          op->reqBuff = NULL;
+          asyncProxyOpDequeue(peer, op);
+          asyncOpCount--;
         }
-        if (op->respBuff) {
-          free(op->respBuff);
-          op->respBuff = NULL;
-        }
-        op->type = 0;
         pollfds[s].fd = -1;
         npeers--;
       }
@@ -1250,6 +1564,7 @@ ncclResult_t ncclProxyDestroy(struct ncclComm* comm) {
     free(state->peerSocks);
     free(state->proxyOps);
     free(state->sharedDevMems);
+    expectedProxyResponseFree(state);
   }
   return ncclSuccess;
 }

src/transport.cc

@@ -69,9 +69,12 @@ ncclResult_t ncclTransportP2pSetup(struct ncclComm* comm, struct ncclTopoGraph*
   // Stream used during transport setup; need for P2P pre-connect + CUDA Graph
   ncclResult_t ret = ncclSuccess;
   int highestType = TRANSPORT_P2P;  // track highest transport type
-  struct ncclConnect data[2*MAXCHANNELS];
+  struct ncclConnect** data = (ncclConnect**) malloc(sizeof(ncclConnect*) * comm->nRanks); // Store intermediate send/recvData structs for connect
+  struct ncclConnect** recvData = (ncclConnect**) malloc(sizeof(ncclConnect*) * comm->nRanks); // Points to entries inside data for given recv connection within a channel
+  struct ncclConnect** sendData = (ncclConnect**) malloc(sizeof(ncclConnect*) * comm->nRanks); // Points to entries inside data for given send connection within a channel
 
   NCCLCHECKGOTO(ncclStrongStreamAcquireUncaptured(&comm->hostStream), ret, fail);
+  // First time initialization
   for (int i=1; i<comm->nRanks; i++) {
     int bootstrapTag = (i<<8) + (graph ? graph->id+1 : 0);
     int recvPeer = (comm->rank - i + comm->nRanks) % comm->nRanks;
@@ -79,22 +82,28 @@ ncclResult_t ncclTransportP2pSetup(struct ncclComm* comm, struct ncclTopoGraph*
     uint64_t recvMask = comm->connectRecv[recvPeer];
     uint64_t sendMask = comm->connectSend[sendPeer];
 
-    struct ncclConnect* recvData = data;
+    // Data[i] contains all ncclConnect information for all send and receive connections with a given send and recv peer
+    // This data is packed in the array based on the number of sendChannels and recvChannels connected with these peers
+    // The first N entries contain recvData, connection information for recv connections
+    // The next M entries contain sendData, connection information for send connections
+    // It's not guaranteed that each entry of data has the same number of total or send/recv specific connections
+    data[i] = (ncclConnect*) malloc(sizeof(ncclConnect) * 2*MAXCHANNELS);
+    recvData[i] = data[i];
     int sendChannels = 0, recvChannels = 0;
     int type;
     TIME_START(0);
     for (int c=0; c<MAXCHANNELS; c++) {
       if (recvMask & (1UL<<c)) {
-        NCCLCHECKGOTO(selectTransport<0>(comm, graph, recvData+recvChannels++, c, recvPeer, connIndex, &type), ret, fail);
+        NCCLCHECKGOTO(selectTransport<0>(comm, graph, recvData[i]+recvChannels++, c, recvPeer, connIndex, &type), ret, fail);
         if (type > highestType) highestType = type;
       }
     }
     TIME_STOP(0);
     TIME_START(1);
-    struct ncclConnect* sendData = recvData+recvChannels;
+    sendData[i] = recvData[i]+recvChannels;
     for (int c=0; c<MAXCHANNELS; c++) {
       if (sendMask & (1UL<<c)) {
-        NCCLCHECKGOTO(selectTransport<1>(comm, graph, sendData+sendChannels++, c, sendPeer, connIndex, &type), ret, fail);
+        NCCLCHECKGOTO(selectTransport<1>(comm, graph, sendData[i]+sendChannels++, c, sendPeer, connIndex, &type), ret, fail);
         if (type > highestType) highestType = type;
       }
     }
@@ -103,41 +112,81 @@ ncclResult_t ncclTransportP2pSetup(struct ncclComm* comm, struct ncclTopoGraph*
     TIME_START(2);
     if (sendPeer == recvPeer) {
       if (recvChannels+sendChannels) {
-         NCCLCHECKGOTO(bootstrapSend(comm->bootstrap, recvPeer, bootstrapTag, data, sizeof(struct ncclConnect)*(recvChannels+sendChannels)), ret, fail);
+        NCCLCHECKGOTO(bootstrapSend(comm->bootstrap, recvPeer, bootstrapTag, data[i], sizeof(struct ncclConnect)*(recvChannels+sendChannels)), ret, fail);
-         NCCLCHECKGOTO(bootstrapRecv(comm->bootstrap, recvPeer, bootstrapTag, data, sizeof(struct ncclConnect)*(recvChannels+sendChannels)), ret, fail);
+        NCCLCHECKGOTO(bootstrapRecv(comm->bootstrap, recvPeer, bootstrapTag, data[i], sizeof(struct ncclConnect)*(recvChannels+sendChannels)), ret, fail);
-         sendData = data;
+        sendData[i] = data[i];
-         recvData = data+sendChannels;
+        recvData[i] = data[i]+sendChannels;
       }
     } else {
-      if (recvChannels) NCCLCHECKGOTO(bootstrapSend(comm->bootstrap, recvPeer, bootstrapTag, recvData, sizeof(struct ncclConnect)*recvChannels), ret, fail);
+      if (recvChannels) NCCLCHECKGOTO(bootstrapSend(comm->bootstrap, recvPeer, bootstrapTag, recvData[i], sizeof(struct ncclConnect)*recvChannels), ret, fail);
-      if (sendChannels) NCCLCHECKGOTO(bootstrapSend(comm->bootstrap, sendPeer, bootstrapTag, sendData, sizeof(struct ncclConnect)*sendChannels), ret, fail);
+      if (sendChannels) NCCLCHECKGOTO(bootstrapSend(comm->bootstrap, sendPeer, bootstrapTag, sendData[i], sizeof(struct ncclConnect)*sendChannels), ret, fail);
-      if (sendChannels) NCCLCHECKGOTO(bootstrapRecv(comm->bootstrap, sendPeer, bootstrapTag, sendData, sizeof(struct ncclConnect)*sendChannels), ret, fail);
+      if (sendChannels) NCCLCHECKGOTO(bootstrapRecv(comm->bootstrap, sendPeer, bootstrapTag, sendData[i], sizeof(struct ncclConnect)*sendChannels), ret, fail);
-      if (recvChannels) NCCLCHECKGOTO(bootstrapRecv(comm->bootstrap, recvPeer, bootstrapTag, recvData, sizeof(struct ncclConnect)*recvChannels), ret, fail);
+      if (recvChannels) NCCLCHECKGOTO(bootstrapRecv(comm->bootstrap, recvPeer, bootstrapTag, recvData[i], sizeof(struct ncclConnect)*recvChannels), ret, fail);
     }
     TIME_STOP(2);
+  }
 
-    TIME_START(3);
+  // Loop until all channels with all ranks have been connected
+  bool allChannelsConnected;
+  allChannelsConnected = false;
+  while (!allChannelsConnected) {
+    allChannelsConnected = true;
+    for (int i=1; i<comm->nRanks; i++) {
+      int recvPeer = (comm->rank - i + comm->nRanks) % comm->nRanks;
+      int sendPeer = (comm->rank + i) % comm->nRanks;
+      uint64_t recvMask = comm->connectRecv[recvPeer];
+      uint64_t sendMask = comm->connectSend[sendPeer];
+
+      int sendDataOffset = 0;
+      int recvDataOffset = 0;
       for (int c=0; c<MAXCHANNELS; c++) {
+          TIME_START(3);
           if (sendMask & (1UL<<c)) {
             struct ncclConnector* conn = comm->channels[c].peers[sendPeer].send + connIndex;
-        NCCLCHECKGOTO(conn->transportComm->connect(comm, sendData++, 1, comm->rank, conn), ret, fail);
+            // This connector hasn't completed connection yet
+            if (conn->connected == 0) {
+              NCCLCHECKGOTO(conn->transportComm->connect(comm, sendData[i] + sendDataOffset++, 1, comm->rank, conn), ret, fail);
+              if (ret == ncclSuccess) {
                 conn->connected = 1;
                 CUDACHECKGOTO(cudaMemcpyAsync(&comm->channels[c].devPeers[sendPeer].send[connIndex], &conn->conn, sizeof(struct ncclConnInfo), cudaMemcpyHostToDevice, comm->hostStream.cudaStream), ret, fail);
+              } else if (ret == ncclInProgress) {
+                allChannelsConnected = false;
+              }
             }
           }
           TIME_STOP(3);
+
+          // Start with recv channels
           TIME_START(4);
-    for (int c=0; c<MAXCHANNELS; c++) {
           if (recvMask & (1UL<<c)) {
             struct ncclConnector* conn = comm->channels[c].peers[recvPeer].recv + connIndex;
-        NCCLCHECKGOTO(conn->transportComm->connect(comm, recvData++, 1, comm->rank, conn), ret, fail);
+            // This connector hasn't completed connection yet
+            if (conn->connected == 0) {
+              NCCLCHECKGOTO(conn->transportComm->connect(comm, recvData[i] + recvDataOffset++, 1, comm->rank, conn), ret, fail);
+              if (ret == ncclSuccess) {
                 conn->connected = 1;
                 CUDACHECKGOTO(cudaMemcpyAsync(&comm->channels[c].devPeers[recvPeer].recv[connIndex], &conn->conn, sizeof(struct ncclConnInfo), cudaMemcpyHostToDevice, comm->hostStream.cudaStream), ret, fail);
+              } else if (ret == ncclInProgress) {
+                allChannelsConnected = false;
+              }
             }
           }
           TIME_STOP(4);
-    comm->connectRecv[recvPeer] = comm->connectSend[sendPeer] = 0UL;
       }
+    }
+  }
+
+  // Clear all connect masks and free each connectInfo array
+  for (int i=1; i<comm->nRanks; i++) {
+    int recvPeer = (comm->rank - i + comm->nRanks) % comm->nRanks;
+    int sendPeer = (comm->rank + i) % comm->nRanks;
+    comm->connectRecv[recvPeer] = comm->connectSend[sendPeer] = 0UL;
+    free(data[i]);
+  }
+
+  free(data);
+  free(sendData);
+  free(recvData);
 
   if (highestTransportType != NULL) *highestTransportType = highestType;
   TIME_PRINT("P2P Setup/Connect");

src/transport/coll_net.cc

@@ -152,13 +152,13 @@ static ncclResult_t sendSetup(struct ncclComm* comm, struct ncclTopoGraph* graph
   int proxyRank;
   NCCLCHECK(ncclTopoGetNetDev(comm, myInfo->rank, graph, channelId, -1, &req.netDev, &proxyRank));
   NCCLCHECK(ncclTopoCheckGdr(comm->topo, myInfo->busId, req.netDev, 1, &req.useGdr));
-  send->conn.direct |= req.useGdr ? NCCL_DIRECT_NIC : 0;
+  send->conn.flags |= req.useGdr ? NCCL_DIRECT_NIC : 0;
   // Determine whether we need to flush the GDR buffer on recv or not
   if (req.useGdr) NCCLCHECK(ncclTopoNeedFlush(comm->topo, myInfo->busId, &req.needFlush));
 
   NCCLCHECK(ncclTopoGetLocalRank(comm->topo, myInfo->rank, &send->proxyConn.localRank));
   NCCLCHECK(ncclProxyConnect(comm, TRANSPORT_COLLNET, 1, myInfo->rank, &send->proxyConn));
-  NCCLCHECK(ncclProxyCall(&send->proxyConn, ncclProxyMsgSetup, &req, sizeof(req), NULL, 0));
+  NCCLCHECK(ncclProxyCallBlocking(&send->proxyConn, ncclProxyMsgSetup, &req, sizeof(req), NULL, 0));
 
   INFO(NCCL_INIT|NCCL_NET,"CollNet %02d/%1d : %d [send] via COLLNET/%s/%d%s", channelId, connIndex, myInfo->rank, collNetName(comm), req.netDev,
       req.useGdr ? "/GDRDMA" : "");
@@ -171,12 +171,12 @@ static ncclResult_t recvSetup(struct ncclComm* comm, struct ncclTopoGraph* graph
   int proxyRank;
   NCCLCHECK(ncclTopoGetNetDev(comm, myInfo->rank, graph, channelId, -1, &req.netDev, &proxyRank));
   NCCLCHECK(ncclTopoCheckGdr(comm->topo, myInfo->busId, req.netDev, 0, &req.useGdr));
-  recv->conn.direct |= req.useGdr ? NCCL_DIRECT_NIC : 0;
+  recv->conn.flags |= req.useGdr ? NCCL_DIRECT_NIC : 0;
 
   NCCLCHECK(ncclTopoGetLocalRank(comm->topo, myInfo->rank, &recv->proxyConn.localRank));
   NCCLCHECK(ncclProxyConnect(comm, TRANSPORT_COLLNET, 0, myInfo->rank, &recv->proxyConn));
   struct collNetRecvConnectInfo* info = (struct collNetRecvConnectInfo*) connectInfo;
-  NCCLCHECK(ncclProxyCall(&recv->proxyConn, ncclProxyMsgSetup, &req, sizeof(req), &info->collNetHandle, sizeof(collNetHandle_t)));
+  NCCLCHECK(ncclProxyCallBlocking(&recv->proxyConn, ncclProxyMsgSetup, &req, sizeof(req), &info->collNetHandle, sizeof(collNetHandle_t)));
 
   INFO(NCCL_INIT|NCCL_NET,"CollNet %02d/%1d : %d [receive] via COLLNET/%s/%d%s", channelId, connIndex, myInfo->rank, collNetName(comm), req.netDev,
       req.useGdr ? "/GDRDMA" : "");
@@ -221,7 +221,7 @@ static ncclResult_t sendConnect(struct ncclComm* comm, struct ncclConnect* conne
   // We're on the same process as the proxy. We can pass a pointer to a struct.
   struct collNetConnectArgs args = { rank, nranks, connectInfos };
   struct connectMap* map;
-  NCCLCHECK(ncclProxyCall(&send->proxyConn, ncclProxyMsgConnect, &args, sizeof(struct collNetConnectArgs), &map, sizeof(struct connectMap*)));
+  NCCLCHECK(ncclProxyCallBlocking(&send->proxyConn, ncclProxyMsgConnect, &args, sizeof(struct collNetConnectArgs), &map, sizeof(struct connectMap*)));
 
   // If collnet connect failed, propagate error to fallback on regular p2p
   if (map == NULL) return ncclSystemError;
@@ -247,7 +247,7 @@ static ncclResult_t recvConnect(struct ncclComm* comm, struct ncclConnect* conne
   // We're on the same process as the proxy. We can pass a pointer to a struct.
   struct collNetConnectArgs args = { rank, nranks, connectInfos };
   struct connectMap* map;
-  NCCLCHECK(ncclProxyCall(&recv->proxyConn, ncclProxyMsgConnect, &args, sizeof(struct collNetConnectArgs), &map, sizeof(struct connectMap*)));
+  NCCLCHECK(ncclProxyCallBlocking(&recv->proxyConn, ncclProxyMsgConnect, &args, sizeof(struct collNetConnectArgs), &map, sizeof(struct connectMap*)));
 
   // If collnet connect failed, propagate error to fallback on regular p2p
   if (map == NULL) return ncclSystemError;
@@ -410,7 +410,7 @@ static ncclResult_t recvProxySetup(struct ncclProxyConnection* connection, struc
 }
 
 static ncclResult_t sendProxyConnect(struct ncclProxyConnection* connection, struct ncclComm* comm, void* reqBuff, int reqSize, void* respBuff, int respSize, int* done) {
-  if (reqSize != sizeof(struct collNetConnectArgs)) { WARN("sendProxyConnect: reqSize is %d != %ld\n", reqSize, sizeof(struct collNetConnectArgs)); return ncclInternalError; }
+  if (reqSize != sizeof(struct collNetConnectArgs)) { WARN("sendProxyConnect: reqSize is %d != %ld", reqSize, sizeof(struct collNetConnectArgs)); return ncclInternalError; }
   struct collNetConnectArgs* args = (struct collNetConnectArgs*)reqBuff;
   struct collNetSendConnectInfo* info = (struct collNetSendConnectInfo*)(args->connectInfos+args->rank);
 
@@ -426,7 +426,7 @@ static ncclResult_t sendProxyConnect(struct ncclProxyConnection* connection, str
   NCCLCHECK(sharedConnect(comm, resources->netDev, args->connectInfos, args->nranks, args->rank, &resources->collNetComm));
 
   // Collnet connect is allowed to fail. Gracefully handle that case by returning NULL to the caller.
-  if (respSize != sizeof(struct connectMap*)) { WARN("sendProxyConnect: respSize is %d != %ld\n", respSize, sizeof(void*)); return ncclInternalError; }
+  if (respSize != sizeof(struct connectMap*)) { WARN("sendProxyConnect: respSize is %d != %ld", respSize, sizeof(void*)); return ncclInternalError; }
   if (resources->collNetComm == NULL) {
     *((struct connectMap**)respBuff) = NULL;
     return ncclSuccess;
@@ -484,7 +484,7 @@ static ncclResult_t sendProxyConnect(struct ncclProxyConnection* connection, str
 }
 
 static ncclResult_t recvProxyConnect(struct ncclProxyConnection* connection, struct ncclComm* comm, void* reqBuff, int reqSize, void* respBuff, int respSize, int* done) {
-  if (reqSize != sizeof(struct collNetConnectArgs)) { WARN("recvProxyConnect: reqSize is %d != %ld\n", reqSize, sizeof(struct collNetConnectArgs)); return ncclInternalError; }
+  if (reqSize != sizeof(struct collNetConnectArgs)) { WARN("recvProxyConnect: reqSize is %d != %ld", reqSize, sizeof(struct collNetConnectArgs)); return ncclInternalError; }
   struct collNetConnectArgs* args = (struct collNetConnectArgs*)reqBuff;
 
   struct recvResources* resources = (struct recvResources*)(connection->transportResources);
@@ -494,7 +494,7 @@ static ncclResult_t recvProxyConnect(struct ncclProxyConnection* connection, str
   NCCLCHECK(sharedConnect(comm, resources->netDev, args->connectInfos, args->nranks, args->rank, &resources->collNetComm));
 
   // Collnet connect is allowed to fail. Gracefully handle that case by returning NULL to the caller.
-  if (respSize != sizeof(struct connectMap*)) { WARN("sendProxyConnect: respSize is %d != %ld\n", respSize, sizeof(void*)); return ncclInternalError; }
+  if (respSize != sizeof(struct connectMap*)) { WARN("sendProxyConnect: respSize is %d != %ld", respSize, sizeof(void*)); return ncclInternalError; }
   if (resources->collNetComm == NULL) {
     *((struct connectMap**)respBuff) = NULL;
     return ncclSuccess;
@@ -553,7 +553,7 @@ static ncclResult_t recvProxyConnect(struct ncclProxyConnection* connection, str
   for (int p=0; p<NCCL_NUM_PROTOCOLS; p++)
     info->mhandles[p] = resources->mhandles[p];
 
-  if (respSize != sizeof(struct connectMap*)) { WARN("recvProxyConnect: respSize is %d != %ld\n", respSize, sizeof(void*)); return ncclInternalError; }
+  if (respSize != sizeof(struct connectMap*)) { WARN("recvProxyConnect: respSize is %d != %ld", respSize, sizeof(void*)); return ncclInternalError; }
   *((struct connectMap**)respBuff) = &resources->map;
   return ncclSuccess;
 }

src/transport/net.cc

@@ -172,13 +172,13 @@ static ncclResult_t sendSetup(struct ncclComm* comm, struct ncclTopoGraph* graph
   int proxyRank;
   NCCLCHECK(ncclTopoGetNetDev(comm, myInfo->rank, graph, channelId, peerInfo->rank, &req.netDev, &proxyRank));
   NCCLCHECK(ncclTopoCheckGdr(comm->topo, myInfo->busId, req.netDev, 1, &req.useGdr));
-  send->conn.direct |= req.useGdr ? NCCL_DIRECT_NIC : 0;
+  send->conn.flags |= req.useGdr ? NCCL_DIRECT_NIC : 0;
 
   NCCLCHECK(ncclProxyConnect(comm, TRANSPORT_NET, 1, proxyRank, &send->proxyConn));
   req.rank = myInfo->rank;
   NCCLCHECK(ncclTopoGetLocalRank(comm->topo, myInfo->rank, &req.localRank));
   req.remoteRank = peerInfo->rank;
-  NCCLCHECK(ncclProxyCall(&send->proxyConn, ncclProxyMsgSetup, &req, sizeof(req), NULL, 0));
+  NCCLCHECK(ncclProxyCallBlocking(&send->proxyConn, ncclProxyMsgSetup, &req, sizeof(req), NULL, 0));
 
   if (proxyRank == myInfo->rank) {
     INFO(NCCL_INIT|NCCL_NET,"Channel %02d/%d : %d[%lx] -> %d[%lx] [send] via NET/%s/%d%s%s", channelId, connIndex, myInfo->rank, myInfo->busId, peerInfo->rank, peerInfo->busId, ncclNetName(comm), req.netDev,
@@ -218,8 +218,7 @@ static ncclResult_t recvSetup(struct ncclComm* comm, struct ncclTopoGraph* graph
   req.rank = myInfo->rank;
   NCCLCHECK(ncclTopoGetLocalRank(comm->topo, myInfo->rank, &req.localRank));
   req.remoteRank = peerInfo->rank;
-  NCCLCHECK(ncclProxyCall(&recv->proxyConn, ncclProxyMsgSetup, &req, sizeof(req), connectInfo, sizeof(ncclNetHandle_t)));
+  NCCLCHECK(ncclProxyCallBlocking(&recv->proxyConn, ncclProxyMsgSetup, &req, sizeof(req), connectInfo, sizeof(ncclNetHandle_t)));
-
   INFO(NCCL_INIT|NCCL_NET,"Channel %02d/%d : %d[%lx] -> %d[%lx] [receive] via NET/%s/%d%s%s", channelId, connIndex, peerInfo->rank, peerInfo->busId, myInfo->rank, myInfo->busId, ncclNetName(comm), req.netDev,
       req.useGdr ? "/GDRDMA" : "", req.shared ? "/Shared" : "");
   return ncclSuccess;
@@ -264,11 +263,28 @@ static ncclResult_t netDumpMap(struct connectMap* map) {
 }
 
 static ncclResult_t sendConnect(struct ncclComm* comm, struct ncclConnect* connectInfo, int nranks, int rank, struct ncclConnector* send) {
+  struct connectMap* map = (connectMap*) send->transportResources;
+
+  void* opId;
+
+  // map isn't allocated thus this op hasn't been submitted yet
+  if (!map) {
     // Setup device pointers
-  struct connectMap* map;
     NCCLCHECK(ncclCalloc(&map, 1));
     send->transportResources = map;
-  NCCLCHECK(ncclProxyCall(&send->proxyConn, ncclProxyMsgConnect, connectInfo, sizeof(ncclNetHandle_t), map, sizeof(struct connectMap)));
+    opId = send;
+    INFO(NCCL_PROXY, "sendConnect ncclProxyCallAsync opId=%p", opId);
+    NCCLCHECK(ncclProxyCallAsync(&send->proxyConn, ncclProxyMsgConnect, connectInfo, sizeof(ncclNetHandle_t), sizeof(struct connectMap), opId));
+  } else {
+    opId =  send;
+  }
+
+  ncclResult_t ret;
+  NCCLCHECK(ret = ncclPollProxyResponse(&send->proxyConn, map, opId));
+  if (ret == ncclInProgress) {
+    return ret;
+  }
+  INFO(NCCL_PROXY, "sendConnect ncclPollProxyResponse opId=%p", opId);
 
   if (map->sameProcess) {
     if (map->cudaDev != comm->cudaDev) {
@@ -315,10 +331,26 @@ static ncclResult_t sendConnect(struct ncclComm* comm, struct ncclConnect* conne
 
 /* Connect to this peer */
 static ncclResult_t recvConnect(struct ncclComm* comm, struct ncclConnect* connectInfo, int nranks, int rank, struct ncclConnector* recv) {
-  struct connectMap* map;
+  struct connectMap* map = (connectMap*) recv->transportResources;
+  void* opId;
+  if (!map) {
     NCCLCHECK(ncclCalloc(&map, 1));
     recv->transportResources = map;
-  NCCLCHECK(ncclProxyCall(&recv->proxyConn, ncclProxyMsgConnect, connectInfo, sizeof(int), map, sizeof(struct connectMap)));
+    // Use recv connector as unique identifier
+    opId = recv;
+    INFO(NCCL_PROXY, "recvConnect ncclProxyCallAsync opId=%p &recv->proxyConn=%p connectInfo=%p",
+       opId, &recv->proxyConn, connectInfo);
+    NCCLCHECK(ncclProxyCallAsync(&recv->proxyConn, ncclProxyMsgConnect, connectInfo, sizeof(int), sizeof(struct connectMap), opId));
+  } else {
+    opId = recv;
+  }
+
+  ncclResult_t ret;
+  NCCLCHECK(ret = ncclPollProxyResponse(&recv->proxyConn, map, opId));
+  if (ret == ncclInProgress) {
+    return ret;
+  }
+  INFO(NCCL_PROXY, "recvConnect ncclPollProxyResponse opId=%p", opId);
   //NCCLCHECK(netDumpMap(map));
 
   struct ncclSendMem *sendMem = (struct ncclSendMem*) NCCL_NET_MAP_GET_POINTER(map, gpu, sendMem);
@@ -490,12 +522,14 @@ static ncclResult_t recvProxySetup(struct ncclProxyConnection* connection, struc
   if (respSize != sizeof(ncclNetHandle_t)) return ncclInternalError;
   NCCLCHECK(ncclNetListen(comm, req->netDev, respBuff, &resources->netListenComm));
   *done = 1;
+
   return ncclSuccess;
 }
 
 static ncclResult_t sendProxyConnect(struct ncclProxyConnection* connection, struct ncclComm* comm, void* reqBuff, int reqSize, void* respBuff, int respSize, int* done) {
   struct sendResources* resources = (struct sendResources*)(connection->transportResources);
   if (reqSize != sizeof(ncclNetHandle_t)) return ncclInternalError;
+  ncclResult_t ret = ncclSuccess;
 
   if (resources->shared) {
     // Shared buffers
@@ -515,21 +549,22 @@ static ncclResult_t sendProxyConnect(struct ncclProxyConnection* connection, str
         NCCLCHECK(ncclCalloc(progressState->netComms+resources->netDev, comm->nRanks));
       }
       struct ncclSharedNetComms* comms = progressState->netComms[resources->netDev]+resources->remoteRank;
-      if (comms->sendComm[resources->channelId] == NULL) NCCLCHECK(ncclNetConnect(comm, resources->netDev, reqBuff, comms->sendComm+resources->channelId));
+      if (comms->sendComm[resources->channelId] == NULL) ret = ncclNetConnect(comm, resources->netDev, reqBuff, comms->sendComm+resources->channelId);
       resources->netSendComm = comms->sendComm[resources->channelId];
       if (comms->sendComm[resources->channelId]) comms->sendRefCount[resources->channelId]++;
     } else {
-      NCCLCHECK(ncclNetConnect(comm, resources->netDev, reqBuff, &resources->netSendComm));
+      ret = ncclNetConnect(comm, resources->netDev, reqBuff, &resources->netSendComm);
     }
   } else {
     // Connect to remote peer
-    NCCLCHECK(ncclNetConnect(comm, resources->netDev, reqBuff, &resources->netSendComm));
+    ret = ncclNetConnect(comm, resources->netDev, reqBuff, &resources->netSendComm);
     connection->proxyAppendPtr = &connection->proxyAppend;
   }
 
+  NCCLCHECK(ret);
   if (resources->netSendComm == NULL) {
     *done = 0;
-    return ncclSuccess;
+    return ncclInProgress;
   }
   *done = 1;
 
@@ -630,6 +665,7 @@ static ncclResult_t recvProxyConnect(struct ncclProxyConnection* connection, str
   if (reqSize != sizeof(int)) return ncclInternalError;
   struct recvResources* resources = (struct recvResources*)(connection->transportResources);
   resources->proxyRank = *(int*)reqBuff;
+  ncclResult_t ret = ncclSuccess;
 
   // Finish connection establishment from remote peer
   if (resources->shared) {
@@ -650,23 +686,25 @@ static ncclResult_t recvProxyConnect(struct ncclProxyConnection* connection, str
         NCCLCHECK(ncclCalloc(progressState->netComms+resources->netDev, comm->nRanks));
       }
       struct ncclSharedNetComms* comms = progressState->netComms[resources->netDev]+resources->proxyRank;
-      if (comms->recvComm[resources->channelId] == NULL) NCCLCHECK(ncclNetAccept(comm, resources->netListenComm, comms->recvComm+resources->channelId));
+      if (comms->recvComm[resources->channelId] == NULL) ret = ncclNetAccept(comm, resources->netListenComm, comms->recvComm+resources->channelId);
       resources->netRecvComm = comms->recvComm[resources->channelId];
       if (comms->recvComm[resources->channelId]) comms->recvRefCount[resources->channelId]++;
     } else {
-      NCCLCHECK(ncclNetAccept(comm, resources->netListenComm, &resources->netRecvComm));
+      ret = ncclNetAccept(comm, resources->netListenComm, &resources->netRecvComm);
     }
   } else {
     // Connect to remote peer
-    NCCLCHECK(ncclNetAccept(comm, resources->netListenComm, &resources->netRecvComm));
+    ret = ncclNetAccept(comm, resources->netListenComm, &resources->netRecvComm);
     connection->proxyAppendPtr = &connection->proxyAppend;
   }
 
+  NCCLCHECK(ret);
   if (resources->netRecvComm == NULL) {
     *done = 0;
-    return ncclSuccess;
+    return ncclInProgress;
   }
   *done = 1;
+
   NCCLCHECK(ncclNetCloseListen(comm, resources->netListenComm));
 
   // Create structures

src/transport/net_ib.cc

@@ -363,7 +363,9 @@ enum ncclIbCommState {
   ncclIbCommStateAccept = 3,
   ncclIbCommStateSend = 4,
   ncclIbCommStateRecv = 5,
-  ncclIbCommStateConnected = 6,
+  ncclIbCommStateConnecting = 6,
+  ncclIbCommStateConnected = 7,
+  ncclIbCommStatePendingReady = 8,
 };
 
 struct ncclIbCommStage {
@@ -601,6 +603,8 @@ ncclResult_t ncclIbConnect(int dev, void* opaqueHandle, void** sendComm) {
 
   if (stage->state == ncclIbCommStateConnect)    goto ib_connect_check;
   if (stage->state == ncclIbCommStateSend)       goto ib_send;
+  if (stage->state == ncclIbCommStateConnecting) goto ib_connect;
+  if (stage->state == ncclIbCommStateConnected)  goto ib_send_ready;
   if (stage->state != ncclIbCommStateStart) {
     WARN("Error: trying to connect already connected sendComm");
     return ncclInternalError;
@@ -664,11 +668,37 @@ ib_connect_check:
 
 ib_send:
   NCCLCHECK(ncclSocketProgress(NCCL_SOCKET_SEND, &comm->sock, stage->buffer, sizeof(qpInfo), &stage->offset));
-  if (stage->offset != sizeof(qpInfo))
+  if (stage->offset != sizeof(qpInfo)) return ncclSuccess;
-    return ncclSuccess;
+
+  stage->state = ncclIbCommStateConnecting;
+  stage->offset = 0;
+  // Clear the staging buffer for re-use
+  memset(stage->buffer, 0, sizeof(qpInfo));
+
+ib_connect:
+  struct ncclIbQpInfo remQpInfo;
+  NCCLCHECK(ncclSocketProgress(NCCL_SOCKET_RECV, &comm->sock, stage->buffer, sizeof(ncclIbQpInfo), &stage->offset));
+  if (stage->offset != sizeof(remQpInfo)) return ncclSuccess;
+
+  memcpy(&remQpInfo, stage->buffer, sizeof(ncclIbQpInfo));
+
+  for (int q=0; q<comm->nqps; q++) {
+    struct ibv_qp* qp = comm->qps[q];
+    NCCLCHECK(ncclIbRtrQp(qp, remQpInfo.qpn[q], &remQpInfo));
+    NCCLCHECK(ncclIbRtsQp(qp));
+  }
+
+  comm->ready = 1;
+  stage->state = ncclIbCommStateConnected;
+  stage->offset = 0;
+
+ib_send_ready:
+  NCCLCHECK(ncclSocketProgress(NCCL_SOCKET_SEND, &comm->sock, &comm->ready, sizeof(int), &stage->offset));
+  if (stage->offset != sizeof(int)) return ncclSuccess;
 
   free(stage->buffer);
-  stage->state = ncclIbCommStateConnected;
+  stage->state = ncclIbCommStateStart;
+
   *sendComm = comm;
   return ncclSuccess;
 }
@@ -685,8 +715,9 @@ ncclResult_t ncclIbAccept(void* listenComm, void** recvComm) {
   if (stage->state == ncclIbCommStateAccept) goto ib_accept_check;
   if (stage->state == ncclIbCommStateRecv) goto ib_recv;
   if (stage->state == ncclIbCommStateSend) goto ib_send;
+  if (stage->state == ncclIbCommStatePendingReady) goto ib_recv_ready;
   if (stage->state != ncclIbCommStateStart) {
-    WARN("Listencomm in unknown state %d\n", stage->state);
+    WARN("Listencomm in unknown state %d", stage->state);
     return ncclInternalError;
   }
 
@@ -704,10 +735,10 @@ ib_accept_check:
   stage->state = ncclIbCommStateRecv;
   stage->offset = 0;
   NCCLCHECK(ncclIbMalloc((void**)&stage->buffer, sizeof(remQpInfo)));
+
 ib_recv:
   NCCLCHECK(ncclSocketProgress(NCCL_SOCKET_RECV, &rComm->sock, stage->buffer, sizeof(remQpInfo), &stage->offset));
-  if (stage->offset != sizeof(remQpInfo))
+  if (stage->offset != sizeof(remQpInfo)) return ncclSuccess;
-    return ncclSuccess;
 
   /* copy back the received info */
   memcpy(&remQpInfo, stage->buffer, sizeof(struct ncclIbQpInfo));
@@ -780,10 +811,18 @@ ib_recv:
   if (stage->buffer) free(stage->buffer);
   NCCLCHECK(ncclIbMalloc((void**)&stage->buffer, sizeof(struct ncclIbQpInfo)));
   memcpy(stage->buffer, &qpInfo, sizeof(struct ncclIbQpInfo));
+
 ib_send:
   NCCLCHECK(ncclSocketProgress(NCCL_SOCKET_SEND, &rComm->sock, stage->buffer, sizeof(struct ncclIbQpInfo), &stage->offset));
   if (stage->offset < sizeof(struct ncclIbQpInfo)) return ncclSuccess;
 
+  stage->offset = 0;
+  stage->state = ncclIbCommStatePendingReady;
+
+ib_recv_ready:
+  NCCLCHECK(ncclSocketProgress(NCCL_SOCKET_RECV,  &rComm->sock, &rComm->ready, sizeof(int), &stage->offset));
+  if (stage->offset != sizeof(int)) return ncclSuccess;
+
   free(stage->buffer);
   *recvComm = rComm;
 
@@ -815,36 +854,6 @@ ncclResult_t ncclIbFreeRequest(struct ncclIbRequest* r) {
   return ncclSuccess;
 }
 
-ncclResult_t ncclSendCheck(struct ncclIbSendComm* comm) {
-  struct ncclIbQpInfo remQpInfo;
-
-  // Do not block on this receive, return if not ready.
-  int bytes = 0;
-  NCCLCHECK(ncclSocketProgress(NCCL_SOCKET_RECV, &comm->sock, &remQpInfo, sizeof(remQpInfo), &bytes));
-  if (bytes == 0) return ncclSuccess; // Try again later
-  NCCLCHECK(ncclSocketWait(NCCL_SOCKET_RECV, &comm->sock, &remQpInfo, sizeof(remQpInfo), &bytes));
-
-  for (int q=0; q<comm->nqps; q++) {
-    struct ibv_qp* qp = comm->qps[q];
-    NCCLCHECK(ncclIbRtrQp(qp, remQpInfo.qpn[q], &remQpInfo));
-    NCCLCHECK(ncclIbRtsQp(qp));
-  }
-  comm->ready = 1;
-  // Block until this is done. It *should* not block indefinitely.
-  NCCLCHECK(ncclSocketSend(&comm->sock, &comm->ready, sizeof(int)));
-
-  return ncclSuccess;
-}
-
-ncclResult_t ncclRecvCheck(struct ncclIbRecvComm* comm) {
-  // Do not block on this receive, return if not ready.
-  int bytes = 0;
-  NCCLCHECK(ncclSocketProgress(NCCL_SOCKET_RECV, &comm->sock, &comm->ready, sizeof(int), &bytes));
-  if (bytes == 0) return ncclSuccess; // Try again later
-  NCCLCHECK(ncclSocketWait(NCCL_SOCKET_RECV, &comm->sock, &comm->ready, sizeof(int), &bytes));
-  return ncclSuccess;
-}
-
 ncclResult_t ncclIbTest(void* request, int* done, int* size);
 
 /* DMA-BUF support */
@@ -1020,7 +1029,7 @@ ncclResult_t ncclIbMultiSend(struct ncclIbSendComm* comm, int slot) {
 
 ncclResult_t ncclIbIsend(void* sendComm, void* data, int size, int tag, void* mhandle, void** request) {
   struct ncclIbSendComm* comm = (struct ncclIbSendComm*)sendComm;
-  if (comm->ready == 0) NCCLCHECK(ncclSendCheck(comm));
+  if (comm->ready == 0) { WARN("NET/IB: ncclIbIsend() called when comm->ready == 0"); return ncclInternalError; }
   if (comm->ready == 0) { *request = NULL; return ncclSuccess; }
 
   struct ibv_mr* mr = (struct ibv_mr*)mhandle;
@@ -1153,7 +1162,7 @@ ncclResult_t ncclIbPostFifo(struct ncclIbRecvComm* comm, int n, void** data, int
 
 ncclResult_t ncclIbIrecv(void* recvComm, int n, void** data, int* sizes, int* tags, void** mhandles, void** request) {
   struct ncclIbRecvComm* comm = (struct ncclIbRecvComm*)recvComm;
-  if (comm->ready == 0) NCCLCHECK(ncclRecvCheck(comm));
+  if (comm->ready == 0) { WARN("NET/IB: ncclIbIrecv() called when comm->ready == 0"); return ncclInternalError; }
   if (comm->ready == 0) { *request = NULL; return ncclSuccess; }
   if (n > NCCL_NET_IB_MAX_RECVS) return ncclInternalError;
 

src/transport/nvls.cc

@@ -0,0 +1,373 @@
+/*************************************************************************
+ * Copyright (c) 2016-2023, NVIDIA CORPORATION. All rights reserved.
+ *
+ * See LICENSE.txt for license information
+ ************************************************************************/
+
+// Implementation of the NVLink SHARP (NVLS) transport
+
+#include "comm.h"
+#include "graph.h"
+#include "utils.h"
+#include "proxy.h"
+
+#if CUDART_VERSION >= 12010
+
+// Currently we only support POSIX_FILE_DESCRIPTOR handle exchange
+#define USE_POSIX_FD 1
+
+#if USE_POSIX_FD
+#define NVLS_CU_MEM_HANDLE_TYPE CU_MEM_HANDLE_TYPE_POSIX_FILE_DESCRIPTOR
+#else
+#define NVLS_CU_MEM_HANDLE_TYPE CU_MEM_HANDLE_TYPE_NONE
+#endif
+
+ncclResult_t nvlsCanConnect(int* ret, struct ncclTopoSystem* topo, struct ncclTopoGraph* graph, struct ncclPeerInfo* info1, struct ncclPeerInfo* info2) {
+  // This transport cannot be used for p2p
+  *ret = 0;
+  return ncclSuccess;
+}
+
+ncclResult_t nvlsSendFree(struct ncclConnector* send) {
+  return ncclSuccess;
+}
+
+ncclResult_t nvlsRecvFree(struct ncclConnector* recv) {
+  return ncclSuccess;
+}
+
+struct ncclTransport nvlsTransport = {
+  "NVLS",
+  nvlsCanConnect,
+  { NULL, NULL, nvlsSendFree, NULL, NULL, NULL, NULL, NULL },
+  { NULL, NULL, nvlsRecvFree, NULL, NULL, NULL, NULL, NULL }
+};
+
+#define NVLS_HANDLE_SIZE 64
+
+struct nvlsResources {
+  CUmulticastObjectProp properties;
+  CUmemAccessDesc accessDesc;
+  int dev;
+  size_t size;
+  size_t granularity;
+  CUmemGenericAllocationHandle mcHandle; // Multicast handle for NVLS buffer
+  char* mcBuff; // Multicast NVLS buffer address
+  CUmemGenericAllocationHandle ucHandle; // Unicast Handle for NVLS buffer
+  char* ucBuff; // Unicast NVLS buffer address
+};
+
+
+ncclResult_t nvlsGetProperties(struct ncclComm *comm, struct nvlsResources* resources, int dev, int nranks, size_t size) {
+  CUmulticastObjectProp* prop = &resources->properties;
+  memset(prop, 0, sizeof(*prop));
+  prop->size = size;
+  prop->numDevices = nranks;
+  prop->handleTypes = NVLS_CU_MEM_HANDLE_TYPE;
+  prop->flags = 0;
+
+  // Could be changed to CU_MULTICAST_GRANULARITY_MINIMUM when 3418538 resolved
+  CUCHECK(cuMulticastGetGranularity(&resources->granularity, prop, CU_MULTICAST_GRANULARITY_RECOMMENDED));
+
+  ALIGN_SIZE(size, resources->granularity);
+  prop->size = resources->size = size;
+
+  memset(&resources->accessDesc, 0, sizeof(resources->accessDesc));
+  resources->accessDesc.flags = CU_MEM_ACCESS_FLAGS_PROT_READWRITE;
+  resources->accessDesc.location.type = CU_MEM_LOCATION_TYPE_DEVICE;
+  resources->accessDesc.location.id = dev;
+  resources->dev = dev;
+
+  return ncclSuccess;
+}
+
+ncclResult_t nvlsGroupCreate(struct ncclComm *comm, struct nvlsResources* resources, int rank, unsigned int nranks, char* shareableHandle) {
+  size_t size = resources->size;
+
+  // Create a Multicast group
+  CUmulticastObjectProp* prop = &resources->properties;
+
+  INFO(NCCL_NVLS, "NVLS Creating Multicast group nranks %d size %zi on rank %d", nranks, size, rank);
+  CUCHECK(cuMulticastCreate(&resources->mcHandle, prop));
+
+  if (NVLS_CU_MEM_HANDLE_TYPE != CU_MEM_HANDLE_TYPE_NONE) {
+    // Get a handle to pass to other ranks
+    CUCHECK(cuMemExportToShareableHandle(shareableHandle, resources->mcHandle, NVLS_CU_MEM_HANDLE_TYPE, 0));
+  }
+  else {
+    memcpy(shareableHandle, &resources->mcHandle, sizeof(resources->mcHandle));
+  }
+
+  INFO(NCCL_NVLS, "NVLS Created Multicast group %llx nranks %d size %zi on rank %d", resources->mcHandle, nranks, size, rank);
+
+  return ncclSuccess;
+}
+
+ncclResult_t nvlsGroupAddDevice(struct ncclComm *comm, struct nvlsResources* resources) {
+  INFO(NCCL_NVLS, "NVLS group %llx adding dev %d", resources->mcHandle, resources->dev);
+  CUCHECK(cuMulticastAddDevice(resources->mcHandle, resources->dev));
+  return ncclSuccess;
+}
+
+ncclResult_t nvlsGroupUnbind(struct ncclComm *comm, struct nvlsResources* resources) {
+  int dev = resources->dev;
+  size_t size = resources->size;
+  INFO(NCCL_NVLS, "NVLS Unbind MC handle %llx size %zi dev %d", resources->mcHandle, size, dev);
+
+  // Unbind physical memory from group for the given device
+  CUCHECK(cuMulticastUnbind(resources->mcHandle, dev, 0/*mcOffset*/, size));
+
+  return ncclSuccess;
+}
+
+ncclResult_t nvlsGroupConnect(struct ncclComm *comm, struct nvlsResources* resources, int rank, char* shareableHandle) {
+  CUmemAllocationHandleType type = NVLS_CU_MEM_HANDLE_TYPE;
+
+  INFO(NCCL_NVLS, "NVLS importing shareableHandle %p from rank %d", shareableHandle, rank);
+
+  // Import and map the remote memory descriptor to the local GPU
+  if (type == CU_MEM_HANDLE_TYPE_POSIX_FILE_DESCRIPTOR) {
+    // cuMem UDS support
+    int fd = *(int *)shareableHandle;
+    TRACE(NCCL_NVLS, "NVLS rank %d Importing shareable handle from rank %d fd %d", comm->localRank, rank, fd);
+    struct ncclProxyConnector proxyConn;
+    NCCLCHECK(ncclProxyConnect(comm, TRANSPORT_P2P, 1, rank, &proxyConn));
+    TRACE(NCCL_NVLS, "NVLS rank %d request conversion of fd %d from rank %d", comm->localRank, fd, rank);
+    NCCLCHECK(ncclProxyCallBlocking(&proxyConn, ncclProxyMsgConvertFd, shareableHandle, sizeof(int), &fd, sizeof(int)));
+    TRACE(NCCL_NVLS, "NVLS rank %d received converted fd %d from rank %d", comm->localRank, fd, rank);
+    CUCHECK(cuMemImportFromShareableHandle(&resources->mcHandle, (void *)(uintptr_t)fd, type));
+  } else {
+    if (NVLS_CU_MEM_HANDLE_TYPE != CU_MEM_HANDLE_TYPE_NONE) {
+      CUCHECK(cuMemImportFromShareableHandle(&resources->mcHandle, (void *)shareableHandle, type));
+    } else {
+      memcpy(&resources->mcHandle, shareableHandle, sizeof(resources->mcHandle));
+    }
+  }
+  return ncclSuccess;
+}
+
+ncclResult_t nvlsGroupBindMem(struct ncclComm *comm, struct nvlsResources* resources) {
+  size_t size = resources->size;
+  size_t granularity;
+  CUdeviceptr ptr = 0;
+  CUmemAllocationProp prop;
+
+  memset(&prop, 0, sizeof(prop));
+  prop.type = CU_MEM_ALLOCATION_TYPE_PINNED;
+  prop.location.type = CU_MEM_LOCATION_TYPE_DEVICE;
+  prop.location.id = resources->dev;
+  prop.requestedHandleTypes = NVLS_CU_MEM_HANDLE_TYPE;
+  CUCHECK(cuMemGetAllocationGranularity(&granularity, &prop, CU_MEM_ALLOC_GRANULARITY_RECOMMENDED));
+
+  // Map a VA for UC memory
+  CUCHECK(cuMemAddressReserve(&ptr, size, granularity, 0U, 0));
+
+  // Alloc local physical mem for this NVLS group
+  CUCHECK(cuMemCreate(&resources->ucHandle, size, &prop, 0));
+  CUCHECK(cuMemMap(ptr, size, 0, resources->ucHandle, 0));
+  CUCHECK(cuMemSetAccess(ptr, size, &resources->accessDesc, 1));
+  CUDACHECK(cudaMemset((void*)ptr, 0, size));
+  resources->ucBuff = (char*)ptr;
+  INFO(NCCL_NVLS, "NVLS Mapped UC at %p size %zi", resources->ucBuff, size);
+
+  // Bind physical memory to the Multicast group
+  // NB: It will block until all ranks have been added to the Group
+  INFO(NCCL_NVLS, "NVLS Bind mem %p UC handle 0x%llx MC handle 0x%llx size %zi", (void*)ptr, resources->ucHandle, resources->mcHandle, size);
+  CUCHECK(cuMulticastBindMem(resources->mcHandle, 0/*mcOffset*/, resources->ucHandle, 0/*memOffset*/, size, 0/*flags*/));
+
+  return ncclSuccess;
+}
+
+ncclResult_t nvlsGroupMapMem(struct ncclComm *comm, struct nvlsResources* resources) {
+  size_t size = resources->size;
+  CUdeviceptr ptr = 0;
+
+  // Create a VA for the NVLS
+  CUCHECK(cuMemAddressReserve(&ptr, size, resources->granularity, 0U, 0));
+  // Map the VA locally
+  CUCHECK(cuMemMap(ptr, size, 0, resources->mcHandle, 0));
+  resources->mcBuff = (char*)ptr;
+  INFO(NCCL_NVLS, "NVLS Mapped MC buffer at %p size %zi", resources->mcBuff, size);
+
+  // Having completed the BindMem we can now call SetAccess
+  // NB: It will block until all ranks have bound to the Group
+  CUCHECK(cuMemSetAccess((CUdeviceptr)resources->mcBuff, size, &resources->accessDesc, 1));
+
+  return ncclSuccess;
+}
+
+ncclResult_t nvlsGroupUnmapMem(struct ncclComm *comm, struct nvlsResources* resources) {
+  size_t size;
+  CUdeviceptr ptr;
+  INFO(NCCL_NVLS, "NVLS Unmap mem UC handle 0x%llx(%p) MC handle 0x%llx(%p)",
+       resources->ucHandle, resources->ucBuff, resources->mcHandle, resources->mcBuff);
+
+  // Release the UC memory and mapping
+  ptr = (CUdeviceptr)resources->ucBuff;
+  size = resources->size;
+  CUCHECK(cuMemUnmap(ptr, size));
+  CUCHECK(cuMemAddressFree(ptr, size));
+  CUCHECK(cuMemRelease(resources->ucHandle));
+
+  // Release the MC memory and mapping
+  ptr = (CUdeviceptr)resources->mcBuff;
+  size = resources->size;
+  CUCHECK(cuMemUnmap(ptr, size));
+  CUCHECK(cuMemAddressFree(ptr, size));
+  CUCHECK(cuMemRelease(resources->mcHandle));
+
+  return ncclSuccess;
+}
+
+#include "bootstrap.h"
+#include "channel.h"
+
+#define NVLS_MEM_ALIGN_SIZE (1 << 21)
+
+NCCL_PARAM(NvlsChannels, "NVLS_NCHANNELS", 16);
+
+NCCL_PARAM(NvlsEnable, "NVLS_ENABLE", 1);
+
+ncclResult_t ncclNvlsSetup(struct ncclComm* comm) {
+  if (!ncclParamNvlsEnable() || comm->localRanks <= 1 || comm->nNodes>1) return ncclSuccess;
+  CUdevice dev;
+  int driverVersion;
+  if (CUPFN(cuDeviceGet) == NULL) return ncclSuccess;
+  CUCHECK(cuDeviceGet(&dev, comm->cudaDev));
+  CUDACHECK(cudaDriverGetVersion(&driverVersion));
+  comm->nvlsSupport = 0;
+  // NVLS Multicast support requires CUDA12.1 UMD + KMD
+  if (CUPFN(cuMulticastCreate) != NULL && driverVersion >= 12010) {
+    CUCHECK(cuDeviceGetAttribute(&comm->nvlsSupport, CU_DEVICE_ATTRIBUTE_MULTICAST_SUPPORTED, dev));
+  }
+  INFO(NCCL_INIT, "NVLS multicast support is %savailable on dev %d", comm->nvlsSupport ? "" : "not ", dev);
+  if (comm->nvlsSupport == 0) return ncclSuccess;
+
+  int nChannels = comm->nvlsChannels = std::max(comm->minCTAs, std::min(comm->maxCTAs, (int)ncclParamNvlsChannels()));
+  int rank = comm->localRank, nranks = comm->localRanks;
+
+  for (int c=0; c<nChannels; c++) {
+    NCCLCHECK(initChannel(comm, c));
+  }
+  ncclResult_t res = ncclSuccess;
+  struct nvlsResources* resources;
+  NCCLCHECK(ncclCalloc(&resources, 1));
+  comm->nvlsResources = resources;
+
+  size_t buffSize = comm->buffSizes[NCCL_PROTO_SIMPLE];
+  size_t memSize = NVLS_MEM_ALIGN_SIZE;
+  size_t nvlsPerRankSize = nChannels*2*(buffSize+memSize);
+  size_t nvlsTotalSize = nvlsPerRankSize*nranks;
+
+  INFO(NCCL_INIT|NCCL_NVLS, "NVLS comm %p rank %d nranks %d buffSize %zi memSize %zi nvlsPerRankSize %zi nvlsTotalSize %zi",
+       comm, rank, nranks, buffSize, memSize, nvlsPerRankSize, nvlsTotalSize);
+
+  char* nvlsShareableHandle = NULL;
+  NCCLCHECKGOTO(ncclCalloc(&nvlsShareableHandle, NVLS_HANDLE_SIZE), res, cleanup);
+  NCCLCHECKGOTO(nvlsGetProperties(comm, resources, dev, nranks, nvlsTotalSize), res, cleanup);
+  if (rank == 0) {
+    NCCLCHECKGOTO(nvlsGroupCreate(comm, resources, rank, nranks, nvlsShareableHandle), res, cleanup);
+    NCCLCHECKGOTO(bootstrapIntraNodeBroadcast(comm->bootstrap, comm->localRankToRank, rank, nranks, 0, nvlsShareableHandle, NVLS_HANDLE_SIZE), res, cleanup);
+  } else {
+    NCCLCHECKGOTO(bootstrapIntraNodeBroadcast(comm->bootstrap, comm->localRankToRank, rank, nranks, 0, nvlsShareableHandle, NVLS_HANDLE_SIZE), res, cleanup);
+    NCCLCHECKGOTO(nvlsGroupConnect(comm, resources, 0, nvlsShareableHandle), res, cleanup);
+  }
+
+  NCCLCHECKGOTO(nvlsGroupAddDevice(comm, resources), res, cleanup);
+  NCCLCHECKGOTO(nvlsGroupBindMem(comm, resources), res, cleanup);
+  // Local intra-node barrier to ensure everyone has bound their memory to the group
+  NCCLCHECKGOTO(bootstrapBarrier(comm->bootstrap, comm->localRankToRank, comm->localRank, comm->localRanks, comm->localRankToRank[0]), res, cleanup);
+  NCCLCHECKGOTO(nvlsGroupMapMem(comm, resources), res, cleanup);
+
+  for (int c=0; c<nChannels; c++) {
+    struct ncclChannel* channel = comm->channels+c;
+    channel->nvls.nHeads = nranks;
+    for (int i=0; i<NCCL_MAX_NVLS_ARITY; i++) channel->nvls.up[i] = -1;
+    channel->nvls.down = comm->nRanks+1+comm->localRank;
+    channel->nvls.out = -1;       // Network not yet implemented.
+    channel->nvls.headRank = comm->localRank;  // Network not yet implemented.
+  }
+
+  for (int r=0; r<nranks; r++) {
+    int nvlsPeer = comm->nRanks+1+r;
+    for (int c=0; c<nChannels; c++) {
+      struct ncclChannel* channel = comm->channels+c;
+      channel->nvls.up[r] = nvlsPeer;
+
+      char* mem = NULL;
+      struct ncclChannelPeer* peer = channel->peers+nvlsPeer;
+
+      // Reduce UC -> MC
+      mem = resources->ucBuff + (r*2*nChannels+c)*(buffSize+memSize);
+      peer->send[0].transportComm = &nvlsTransport.send;
+      peer->send[0].conn.buffs[NCCL_PROTO_SIMPLE] = mem;
+      peer->send[0].conn.head = (uint64_t*)(mem+buffSize);
+      peer->send[0].conn.tail = (uint64_t*)(mem+buffSize+memSize/2);
+      mem = resources->mcBuff + (r*2*nChannels+c)*(buffSize+memSize);
+      peer->recv[1].transportComm = &nvlsTransport.recv;
+      peer->recv[1].conn.buffs[NCCL_PROTO_SIMPLE] = mem;
+      peer->recv[1].conn.head = (uint64_t*)(mem+buffSize);
+      peer->recv[1].conn.tail = (uint64_t*)(mem+buffSize+memSize/2);
+      peer->recv[1].conn.flags |= NCCL_NVLS_MIN_POLL;
+
+      // Broadcast MC -> UC
+      mem = resources->ucBuff + ((r*2+1)*nChannels+c)*(buffSize+memSize);
+      peer->recv[0].transportComm = &nvlsTransport.recv;
+      peer->recv[0].conn.buffs[NCCL_PROTO_SIMPLE] = mem;
+      peer->recv[0].conn.head = (uint64_t*)(mem+buffSize);
+      peer->recv[0].conn.tail = (uint64_t*)(mem+buffSize+memSize/2);
+      mem = resources->mcBuff + ((r*2+1)*nChannels+c)*(buffSize+memSize);
+      peer->send[1].transportComm = &nvlsTransport.send;
+      peer->send[1].conn.buffs[NCCL_PROTO_SIMPLE] = mem;
+      peer->send[1].conn.head = (uint64_t*)(mem+buffSize);
+      peer->send[1].conn.tail = (uint64_t*)(mem+buffSize+memSize/2);
+      peer->send[1].conn.flags |= NCCL_NVLS_MIN_POLL;
+
+      CUDACHECKGOTO(cudaMemcpyAsync(&comm->channels[c].devPeers[nvlsPeer].send[0], &peer->send[0].conn, sizeof(struct ncclConnInfo), cudaMemcpyHostToDevice, comm->hostStream.cudaStream), res, cleanup);
+      CUDACHECKGOTO(cudaMemcpyAsync(&comm->channels[c].devPeers[nvlsPeer].recv[0], &peer->recv[0].conn, sizeof(struct ncclConnInfo), cudaMemcpyHostToDevice, comm->hostStream.cudaStream), res, cleanup);
+      CUDACHECKGOTO(cudaMemcpyAsync(&comm->channels[c].devPeers[nvlsPeer].send[1], &peer->send[1].conn, sizeof(struct ncclConnInfo), cudaMemcpyHostToDevice, comm->hostStream.cudaStream), res, cleanup);
+      CUDACHECKGOTO(cudaMemcpyAsync(&comm->channels[c].devPeers[nvlsPeer].recv[1], &peer->recv[1].conn, sizeof(struct ncclConnInfo), cudaMemcpyHostToDevice, comm->hostStream.cudaStream), res, cleanup);
+
+      /*INFO(NCCL_INIT|NCCL_NVLS, "Peer %d Channel %d MC buff %p/%p UC Buff %p/%p",
+          nvlsPeer, c,
+          resources->mcBuff + (r*2*nChannels+c)*(buffSize+memSize),
+          resources->mcBuff + ((r*2+1)*nChannels+c)*(buffSize+memSize),
+          resources->ucBuff + (r*2*nChannels+c)*(buffSize+memSize),
+          resources->ucBuff + ((r*2+1)*nChannels+c)*(buffSize+memSize));*/
+    }
+  }
+
+  free(nvlsShareableHandle);
+  return res;
+
+cleanup:
+  comm->nvlsSupport = 0;
+  free(nvlsShareableHandle);
+  return res;
+}
+
+ncclResult_t ncclNvlsFree(struct ncclComm* comm) {
+  struct nvlsResources* resources = (struct nvlsResources*)comm->nvlsResources;
+  if (resources == NULL) return ncclSuccess;
+  NCCLCHECK(nvlsGroupUnbind(comm, resources));
+  NCCLCHECK(nvlsGroupUnmapMem(comm, resources));
+  free(resources);
+  comm->nvlsResources = NULL;
+  return ncclSuccess;
+}
+
+#else
+
+/*
+ * Pre CUDA 12.1 stubs
+ */
+
+ncclResult_t ncclNvlsSetup(struct ncclComm* comm) {
+  return ncclSuccess;
+}
+
+ncclResult_t ncclNvlsFree(struct ncclComm* comm) {
+  return ncclSuccess;
+}
+
+#endif /* CUDA_VERSION >= 12010 */

src/transport/p2p.cc

@@ -239,11 +239,11 @@ ncclResult_t p2pSendSetup(struct ncclComm* comm, struct ncclTopoGraph* graph, st
   if (intermediateRank == -1) {
     info->rank = myInfo->rank;
     if (myInfo->pidHash == peerInfo->pidHash && useMemcpy == 0) {
-      if (ncclParamP2pDirectDisable() == 0) send->conn.direct |= info->read ? NCCL_DIRECT_READ : NCCL_DIRECT_WRITE;
+      if (ncclParamP2pDirectDisable() == 0) send->conn.flags |= info->read ? NCCL_DIRECT_READ : NCCL_DIRECT_WRITE;
       INFO(NCCL_INIT|NCCL_P2P, "Channel %02d/%01d : %d[%lx] -> %d[%lx] via P2P/direct pointer%s",
           channelId, connIndex, myInfo->rank, myInfo->busId, peerInfo->rank, peerInfo->busId, useReadStr);
     } else {
-      send->conn.direct |= info->read ? NCCL_IPC_READ : NCCL_IPC_WRITE;
+      send->conn.flags |= info->read ? NCCL_IPC_READ : NCCL_IPC_WRITE;
       INFO(NCCL_INIT|NCCL_P2P,"Channel %02d/%01d : %d[%lx] -> %d[%lx] via P2P/IPC%s%s",
           channelId, connIndex, myInfo->rank, myInfo->busId, peerInfo->rank, peerInfo->busId, useReadStr, useMemcpy ? "/CE" : "");
     }
@@ -256,11 +256,11 @@ ncclResult_t p2pSendSetup(struct ncclComm* comm, struct ncclTopoGraph* graph, st
 
   NCCLCHECK(ncclProxyConnect(comm, TRANSPORT_P2P, 1, info->rank, &send->proxyConn));
   if (useMemcpy) {
-    NCCLCHECK(ncclProxyCall(&send->proxyConn, ncclProxyMsgSetup, NULL, 0, &resources->proxyInfo, sizeof(struct p2pProxyInfo)));
+    NCCLCHECK(ncclProxyCallBlocking(&send->proxyConn, ncclProxyMsgSetup, NULL, 0, &resources->proxyInfo, sizeof(struct p2pProxyInfo)));
     info->shmSize = resources->proxyInfo.shmSize;
     memcpy(info->shmName, resources->proxyInfo.shmName, sizeof(info->shmName));
   } else {
-    NCCLCHECK(ncclProxyCall(&send->proxyConn, ncclProxyMsgSetup, &sendSize, sizeof(int), &info->p2pBuff, sizeof(struct ncclP2pBuff)));
+    NCCLCHECK(ncclProxyCallBlocking(&send->proxyConn, ncclProxyMsgSetup, &sendSize, sizeof(int), &info->p2pBuff, sizeof(struct ncclP2pBuff)));
     NCCLCHECK(p2pMap(myInfo, comm->peerInfo+info->rank, &info->p2pBuff, (void**)&resources->devMem, &resources->sendMemIpc));
   }
 
@@ -290,16 +290,16 @@ ncclResult_t p2pRecvSetup(struct ncclComm* comm, struct ncclTopoGraph* graph, st
   if (intermediateRank == -1) {
     info->rank = myInfo->rank;
     if (myInfo->pidHash == peerInfo->pidHash && useMemcpy == 0) {
-      if (ncclParamP2pDirectDisable() == 0) recv->conn.direct |= info->read ? NCCL_DIRECT_READ : NCCL_DIRECT_WRITE;
+      if (ncclParamP2pDirectDisable() == 0) recv->conn.flags |= info->read ? NCCL_DIRECT_READ : NCCL_DIRECT_WRITE;
     } else {
-      recv->conn.direct |= info->read ? NCCL_IPC_READ : NCCL_IPC_WRITE;
+      recv->conn.flags |= info->read ? NCCL_IPC_READ : NCCL_IPC_WRITE;
     }
   } else {
     info->rank = intermediateRank;
   }
 
   NCCLCHECK(ncclProxyConnect(comm, TRANSPORT_P2P, 0, info->rank, &recv->proxyConn));
-  NCCLCHECK(ncclProxyCall(&recv->proxyConn, ncclProxyMsgSetup, &recvSize, sizeof(int), &info->p2pBuff, sizeof(struct ncclP2pBuff)));
+  NCCLCHECK(ncclProxyCallBlocking(&recv->proxyConn, ncclProxyMsgSetup, &recvSize, sizeof(int), &info->p2pBuff, sizeof(struct ncclP2pBuff)));
 
   NCCLCHECK(p2pMap(myInfo, comm->peerInfo+info->rank, &info->p2pBuff, (void**)&resources->devMem, &resources->recvMemIpc));
   return ncclSuccess;
@@ -330,7 +330,7 @@ static ncclResult_t p2pSendConnect(struct ncclComm* comm, struct ncclConnect* co
     send->conn.sizesFifo = resources->proxyInfo.ceRecvMem->sizesFifo;
     send->conn.head = &resources->proxyInfo.devShm->sendMem.head;
     // Send SIMPLE buff to proxy, and replace it by local buffer
-    NCCLCHECK(ncclProxyCall(&send->proxyConn, ncclProxyMsgConnect, &send->conn.buffs[NCCL_PROTO_SIMPLE], sizeof(void*), NULL, 0));
+    NCCLCHECK(ncclProxyCallBlocking(&send->proxyConn, ncclProxyMsgConnect, &send->conn.buffs[NCCL_PROTO_SIMPLE], sizeof(void*), NULL, 0));
     send->conn.buffs[NCCL_PROTO_SIMPLE] = resources->proxyInfo.ceDevBuff;
   } else {
     send->conn.tail = &remDevMem->tail;

src/transport/shm.cc

@@ -157,7 +157,7 @@ static ncclResult_t shmSendConnect(struct ncclComm* comm, struct ncclConnect* co
   if (useMemcpySend) {
     NCCLCHECK(ncclProxyConnect(comm, TRANSPORT_SHM, 1, comm->rank, &send->proxyConn));
     struct shmProxyInfo proxyInfo = { NULL, NULL, send->conn.buffs[NCCL_PROTO_SIMPLE], resources->hostMem, resources->remHostMem };
-    NCCLCHECK(ncclProxyCall(&send->proxyConn, ncclProxyMsgConnect, &proxyInfo, sizeof(struct shmProxyInfo), &proxyInfo, sizeof(struct shmProxyInfo)));
+    NCCLCHECK(ncclProxyCallBlocking(&send->proxyConn, ncclProxyMsgConnect, &proxyInfo, sizeof(struct shmProxyInfo), &proxyInfo, sizeof(struct shmProxyInfo)));
     send->conn.buffs[NCCL_PROTO_SIMPLE] = proxyInfo.devFifo;
     send->conn.tail = &proxyInfo.ceRecvMem->tail;
     send->conn.sizesFifo = proxyInfo.ceRecvMem->sizesFifo;
@@ -187,7 +187,7 @@ static ncclResult_t shmRecvConnect(struct ncclComm* comm, struct ncclConnect* co
   if (useMemcpyRecv) {
     NCCLCHECK(ncclProxyConnect(comm, TRANSPORT_SHM, 0, comm->rank, &recv->proxyConn));
     struct shmProxyInfo proxyInfo = { NULL, NULL, recv->conn.buffs[NCCL_PROTO_SIMPLE], resources->remHostMem, resources->hostMem };
-    NCCLCHECK(ncclProxyCall(&recv->proxyConn, ncclProxyMsgConnect, &proxyInfo, sizeof(struct shmProxyInfo), &proxyInfo, sizeof(struct shmProxyInfo)));
+    NCCLCHECK(ncclProxyCallBlocking(&recv->proxyConn, ncclProxyMsgConnect, &proxyInfo, sizeof(struct shmProxyInfo), &proxyInfo, sizeof(struct shmProxyInfo)));
     recv->conn.buffs[NCCL_PROTO_SIMPLE] = proxyInfo.devFifo;
     recv->conn.tail = &proxyInfo.ceRecvMem->tail;
   }