6aae379278
Network user buffer support for collectives * Leverage user buffer registration to achieve zero-copy inter-node communications for Ring, NVLS and Collnet Add RAS subsystem * Create a RAS thread keeping track of all NCCL communicators. * Add a ncclras tool contacting the RAS thread and getting a report. Add fp8 support * Add support for e5m2 and e4m3 8-bit floating point operations. * Use Tree/PAT algorithms when possible for better numerical stability. Add NIC fusion * Add a NET API to ask the network plugin to fuse a set of interfaces together. * Fuse multiple NICs under the same PCI switch as a single, larger NIC. Socket connection failure retry * Retry in case of socket connection failure (unreachable host) * Avoid "Software caused connection abort" errors on retries QP connection failure retry * Retry in case of IB QP connection failure during ibv_modify_qp. NET API improvements * Allow plugins to force a flush in case data and completion ordering is not guaranteed. * Indicate when completion is not needed (e.g. for the LL128 protocol), allowing plugins to skip generating a completion. * Allow for full offload of allgather operations when using one GPU per node. NCCL_ALGO/NCCL_PROTO strict enforcement * Extend NCCL_ALGO/NCCL_PROTO syntax to be able to specify ALGO/PROTO filters for each collective operation. * Strictly enforce the ALGO/PROTO filters, no longer fall back on the ring algorithm when the filtering leaves no option and error out instead. Enable CUMEM host allocations * Use cumem functions for host memory allocation by default. Improved profiler plugin API * Avoid dependencies with NCCL includes. * Add information on whether the buffer is registered or not Adjust PAT tuning * Improve transition between PAT and ring at scale. Fix hangs when running with different CPU architectures * Detect when we use a mix of GPU architectures * Ensure Algo/Proto decisions are made based on that unified state. Fix FD leak in UDS * Fix a leak when mapping buffers intra-node with cumem IPCs. Fix crash when mixing buffer registration and graph buffer registration. * Separate local and graph registration to avoid crashes when we free buffers. Fix user buffer registration with dmabuf * Make ncclSend/ncclRecv communication with buffer registration functional on network plugins relying on dmabuf for buffer registration. Fix crash in IB code caused by uninitialized fields. Fix non-blocking ncclSend/ncclRecv * Fix case where ncclSend/ncclRecv would return ncclSuccess in non-blocking mode even though the operation was not enqueued onto the stream. * Issue #1495 Various compiler tweaks and fixes * PR #758 Fix typo in ncclTopoPrintGraph * Issue #1468
NCCL
Optimized primitives for inter-GPU communication.
Introduction
NCCL (pronounced "Nickel") is a stand-alone library of standard communication routines for GPUs, implementing all-reduce, all-gather, reduce, broadcast, reduce-scatter, as well as any send/receive based communication pattern. It has been optimized to achieve high bandwidth on platforms using PCIe, NVLink, NVswitch, as well as networking using InfiniBand Verbs or TCP/IP sockets. NCCL supports an arbitrary number of GPUs installed in a single node or across multiple nodes, and can be used in either single- or multi-process (e.g., MPI) applications.
For more information on NCCL usage, please refer to the NCCL documentation.
Build
Note: the official and tested builds of NCCL can be downloaded from: https://developer.nvidia.com/nccl. You can skip the following build steps if you choose to use the official builds.
To build the library :
$ cd nccl
$ make -j src.build
If CUDA is not installed in the default /usr/local/cuda path, you can define the CUDA path with :
$ make src.build CUDA_HOME=<path to cuda install>
NCCL will be compiled and installed in build/ unless BUILDDIR is set.
By default, NCCL is compiled for all supported architectures. To accelerate the compilation and reduce the binary size, consider redefining NVCC_GENCODE (defined in makefiles/common.mk) to only include the architecture of the target platform :
$ make -j src.build NVCC_GENCODE="-gencode=arch=compute_70,code=sm_70"
Install
To install NCCL on the system, create a package then install it as root.
Debian/Ubuntu :
$ # Install tools to create debian packages
$ sudo apt install build-essential devscripts debhelper fakeroot
$ # Build NCCL deb package
$ make pkg.debian.build
$ ls build/pkg/deb/
RedHat/CentOS :
$ # Install tools to create rpm packages
$ sudo yum install rpm-build rpmdevtools
$ # Build NCCL rpm package
$ make pkg.redhat.build
$ ls build/pkg/rpm/
OS-agnostic tarball :
$ make pkg.txz.build
$ ls build/pkg/txz/
Tests
Tests for NCCL are maintained separately at https://github.com/nvidia/nccl-tests.
$ git clone https://github.com/NVIDIA/nccl-tests.git
$ cd nccl-tests
$ make
$ ./build/all_reduce_perf -b 8 -e 256M -f 2 -g <ngpus>
Copyright
All source code and accompanying documentation is copyright (c) 2015-2020, NVIDIA CORPORATION. All rights reserved.