MSCCL++
GPU-driven computation & communication stack.
Quick Start
Preliminaries
- OS: tested over Ubuntu 18.04 and 20.04
- Libraries: CUDA >= 11.1.1, libnuma
- GPUs: A100 (TBU: H100)
- Azure SKUs: ND_A100_v4, NDm_A100_v4 (TBD: NC_A100_v4)
Compile Library
Run make in the top directory. To use MPI for test code, pass MPI_HOME (/usr/local/mpi by default). For example:
$ MPI_HOME=/usr/local/mpi make -j
If you do not want to use MPI, pass USE_MPI_FOR_TESTS=0.
# Do not use MPI
$ USE_MPI_FOR_TESTS=0 make -j
make will create a header file build/include/mscclpp.h and a shared library build/lib/libmscclpp.so.
(Optional) Tests
For verification, one can try provided sample code bootstrap_test or p2p_test. First add the MSCCL++ library path to LD_LIBRARY_PATH.
$ export LD_LIBRARY_PATH=$PWD/build/lib:$LD_LIBRARY_PATH
Run tests using MPI:
$ mpirun -np 8 ./build/bin/tests/bootstrap_test 127.0.0.1:50000
$ mpirun -np 8 ./build/bin/tests/p2p_test 127.0.0.1:50000
If tests are compiled without MPI, pass a rank and the number of ranks as the following example. Usage of p2p_test is also the same as bootstrap_test.
# Terminal 1: Rank 0, #Ranks 2
$ ./build/bin/tests/bootstrap_test 127.0.0.1:50000 0 2
# Terminal 2: Rank 1, #Ranks 2
$ ./build/bin/tests/bootstrap_test 127.0.0.1:50000 1 2
Performance
All results from NDv4. "xp-yn" means "x" total GPUs across "y" nodes.
NOTE: NCCL AllGather leverages Ring algorithm instead of all-pairs alike algorithm, which greatly reduces inter-node transmission, causing significant higher performance. MSCCL++ should do something similar in the future
8p-1n
Latency (us)
| Message Size | NCCL AllGather | NCCL AllToAll | MSCCL AllToAll LL | MSCCL AllToAll LL128 | MSCCL AllToAll Simple | MSCCL++ AllGather K0 | MSCCL++ AllGather K1 |
|---|---|---|---|---|---|---|---|
| 1K | 13.12 | 9.61 | 7.76 | 21.06 | 28.50 | 157.91 | 143.21 |
BusBW (GB/s)
| Message Size | NCCL AllGather | NCCL AllToAll | MSCCL AllToAll LL | MSCCL AllToAll LL128 | MSCCL AllToAll Simple | MSCCL++ AllGather K0 | MSCCL++ AllGather K1 |
|---|---|---|---|---|---|---|---|
| 1G | 218.27 | 220.09 | 217.05 | 216.98 | 217.15 | 93.69 | 255.06 |
2p-2n
Latency (us)
| Message Size | NCCL AllGather | NCCL AllToAll | MSCCL AllToAll LL | MSCCL AllToAll LL128 | MSCCL AllToAll Simple | MSCCL++ AllGather K0 | MSCCL++ AllGather K1 |
|---|---|---|---|---|---|---|---|
| 1K | 15.31 | 28.36 | 14.67 | 29.12 | 35.43 | 15.32 | 13.84 |
BusBW (GB/s)
| Message Size | NCCL AllGather | NCCL AllToAll | MSCCL AllToAll LL | MSCCL AllToAll LL128 | MSCCL AllToAll Simple | MSCCL++ AllGather K0 | MSCCL++ AllGather K1 |
|---|---|---|---|---|---|---|---|
| 1G | 15.69 | 16.22 | 13.94 | 13.83 | 14.10 | 23.26 | 23.29 |
16p-2n
Latency (us)
| Message Size | NCCL AllGather | NCCL AllToAll | MSCCL AllToAll LL | MSCCL AllToAll LL128 | MSCCL AllToAll Simple | MSCCL++ AllGather K0 | MSCCL++ AllGather K1 |
|---|---|---|---|---|---|---|---|
| 1K | 31.70 | 45.12 | 22.55 | 39.33 | 56.93 | 159.14 | 230.52 |
BusBW (GB/s)
| Message Size | NCCL AllGather | NCCL AllToAll | MSCCL AllToAll LL | MSCCL AllToAll LL128 | MSCCL AllToAll Simple | MSCCL++ AllGather K0 | MSCCL++ AllGather K1 |
|---|---|---|---|---|---|---|---|
| 1G | 174.28 | 38.30 | 40.17 | 40.18 | 40.23 | 44.08 | 9.31 |
Contributing
This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit https://cla.opensource.microsoft.com.
When you submit a pull request, a CLA bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., status check, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.
This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact opencode@microsoft.com with any additional questions or comments.
Trademarks
This project may contain trademarks or logos for projects, products, or services. Authorized use of Microsoft trademarks or logos is subject to and must follow Microsoft's Trademark & Brand Guidelines. Use of Microsoft trademarks or logos in modified versions of this project must not cause confusion or imply Microsoft sponsorship. Any use of third-party trademarks or logos are subject to those third-party's policies.