AWS OFI RCCL

AWS OFI RCCL is a plug-in which enables EC2 developers to use libfabric as a network provider while running AMD's RCCL based applications.

Overview

Machine learning frameworks running on top of AMD GPUs use a library called RCCL which provides standard collective communication routines for an arbitrary number of GPUs installed across single or multiple nodes.

This project implements a plug-in which maps RCCLs connection-oriented transport APIs to libfabric's connection-less reliable interface. This allows RCCL applications to take benefit of libfabric's transport layer services like reliable message support and operating system bypass.

Requirements

The plug-in currently supports the following distributions:

• Amazon Linux
• Amazon Linux 2
• Redhat Enterprise Linux 7 and 8
• Ubuntu 18.04 and 20.04 LTS
• CentOS 7 and 8

It requires Libfabric and RCCL. Please see the Release notes for information on version compatibility.

Libfabric supports various providers. The plug-in can choose only those which support the following features as defined in the libfabric API documentation.

• Tagged messaging (FI_TAGGED, FI_MSG)
• Data transfer context structures (FI_CONTEXT)
• Reliable datagram endpoints (FI_EP_RDM)
• Send after Send ordering semantics (FI_ORDER_SAS)
• Communication with remote endpoints (FI_REMOTE_COMM)

For GPUDirect RDMA support, it requires these additional features from libfabric providers. If these are not supported by any provider on system, plug-in turns off GPUDirect RDMA support.

• Transfers to/from device memory (FI_HMEM)
• Remote memory operations (FI_RMA, FI_READ)

Getting Started

Dependencies

aws-ofi-rccl requires working installations of RCCL and libfabric. You can find the instructions for installing the first two at RCCL installation and libfabric installation respectively.

Build latest RCCL develop branch

cd ~
git clone https://github.com/ROCmSoftwarePlatform/rccl.git
cd rccl
mkdir build
cd build/
CXX=/opt/rocm-5.2.0/bin/hipcc cmake -DCMAKE_PREFIX_PATH=/opt/rocm/ ..
make -j

Plugin build Instructions

The plugin uses GNU autotools for its build system. You can build it as follows:

$ ./autogen.sh
$ CC=cc ./configure --with-libfabric=/opt/cray/libfabric/1.15.0.0 --with-hip=/opt/rocm-5.2.0 --with-rccl=path-to-rccl-build-folder
$ make
$ sudo make install

"--with-rccl=path-to-rccl-build-folder": Let's suppose we build RCCL at /home/username/rccl/build, then "--with-rccl=/home/username/rccl/build".

If you want to install the plugin in a custom path, use the --prefix configure flag to provide the path. You can also point the build to custom dependencies with the following flags:

  --with-libfabric=PATH   Path to non-standard libfabric installation
  --with-hip=PATH         Path to non-standard ROCm installation
  --with-rccl=PATH        Path to non-standard RCCL installation
  --with-mpi=PATH         Path to non-standard MPI installation

To enable trace messages for debugging (disabled by default), use the following config option:

   --enable-trace         Enable printing trace messages

By default, tests are built. To disable building tests, use the following config option:

   --disable-tests        Disable build of tests.

Plugin Configurations

The plugin allows to configure the following variables at run-time according to your environment.

Parameter	Description	Type	Accepted Value
OFI_NCCL_USE_IPV6_TCP	Allow using endpoints with IPv6 addressing format for TCP provider. Users can specify to use a preferred libfabric provider with `FI_PROVIDER` environment variable.	Boolean	0/1 (Default: 0)
OFI_NCCL_TCP_EXCLUDE_IF	List of interface names to be filtered out for TCP provider. Users can specify to use a preferred libfabric provider with `FI_PROVIDER` environment variable.	String	Comma-separated list of interface names (Default: "lo,docker0")
OFI_NCCL_GDR_FLUSH_DISABLE	Disable flush operation when using GPUDirect.	Boolean	0/1 (Default: 1)
OFI_NCCL_CUDA_FLUSH_ENABLE	When using GPUDirect use the cudaDeviceFlushGPUDirectRDMAWrites to enforce data consistency at the receiving GPU. Requires CUDA 11.3 or later. Note that this function only provides a GPU memory fence and requires that data has already been delivered to GPU memory. Some networks and PCIe configurations require an additional network-level flush that is not provided by this option.	Boolean	0/1 (Default: 0)

Running Unit Tests

Running unit tests requires a working MPI installation and a MPI setup between the communicating hosts. To install MPI, you can use standard packages provided for your linux distribution. Once MPI is setup, you can use commands like below for running any test of your choice.

mpirun -n 2 --host <host-1>,<host-2> $INSTALL_PREFIX/bin/rccl_message_transfer

Note: All tests require 2 MPI ranks to run except ring.c which requires atleast 3 ranks.

Running rccl-perf tests

To run standard rccl-perf tests with the aws-ofi-rccl plugin, you can follow the instructions below.

1. Clone the repository

git clone https://github.com/ROCmSoftwarePlatform/rccl-tests.git

2. Build the tests

cd  rccl-tests/
MPI_HOME=/opt/cray/pe/mpich/8.1.15/ofi/cray/10.0 ROCM_PATH=/opt/rocm-5.2.0 MPI=1 NCCL_HOME=~/rccl/build/ make -j

3. Run perf tests

export NCCL_DEBUG=INFO
export FI_CXI_ATS=0
export LD_LIBRARY_PATH=/home/${USER}/rccl/build:/home/${USER}/aws-ofi-rccl/src/.libs/:/opt/cray/libfabric/1.15.0.0/lib64/:/opt/rocm-5.2.0/lib
export FI_LOG_LEVEL=info
export NCCL_NET_GDR_LEVEL=3

srun -N 4 ~/rccl-tests/build/all_reduce_perf -b 8 -e 1G -f 2 -g 8

If you installed the AWS libfabric plugin in a custom prefix, ensure LD_LIBRARY_PATH is set to include that prefix so the perf test binaries can find the plugin.

Getting Help

If you have any issues in building or using the package or if you think you may have found a bug, please open an issue.

Contributing

Reporting issues and sending pull requests are always welcome. To learn how you can contribute, please look at our contributing guidelines.

License

This library is licensed under the Apache 2.0 License.