Known Issues
The following is a list of general limitations and known issues of the various components of this HPC-X release.
Reference Number | Issue |
- | Description: In order to get the best performance when running on ConnectX-7 NDR400 fabric, the following parameter should be set with mpirun. mpirun -x UCX_MAX_RNDV_LANES=4 -x UCX_RNDV_THRESH=20k … |
Workaround: N/A | |
Keywords: ConnectX-7; UCX; mpirun | |
Discovered in Version: 2.11 (UCX 1.13) | |
2705762 | Description: UCX job may hang when the DC transport is used. |
Workaround:
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Keywords: UCX | |
Discovered in Version: 2.9 (UCX 1.11) | |
- | Description: Once the TCP detects a “Connection reset by a peer” failure on a connection, it stops sending data, and the MPI/SHMEM application hangs. Error printouts from the UCP/UCT can be seen in the log. |
Workaround: On small scale cases, change the "UCX_TLS=tcp" to "UCX_TLS=sm,tcp" parameter. On larger scales this workaround is not applicable. | |
Keywords: UCX hang | |
Discovered in Version: 2.9 (UCX 1.11) | |
- | Description: NCCL plugin works only with NCCL v2.8 or higher. |
Workaround: Build plugin version v2.0 from the following source. https://github.com/Mellanox/nccl-rdma-sharp-plugins/tree/v2.0.x | |
Keywords: NCCL Plugin | |
Discovered in Version: 2.7 (NCCL 2.1) | |
- | Description: UD timeout error may appear. |
Workaround: Disable the UD transport and use DC instead. Set UCX_TLS=dc_x,self,sm | |
Keywords: UD, DC, timeout, UCX | |
Discovered in Version: 2.7 (UCX 1.9) | |
2235234 | Description: On some platforms, GPUDirect RDMA does not work reliably when the path between HCA and GPU traverses QPI link. |
Workaround: Disable GPUDirect support in UCX by setting UCX_IB_GPU_DIRECT_RDMA=n. | |
Keywords: GPUDirect. RDMA, UCX | |
Discovered in Version: 2.7 (UCX 1.9) | |
4549 | Description: UCX may fail to compile with Clang compiler version 9 if --dynamic-list-data flag is used in the compilation. (Github issue: https://github.com/openucx/ucx/issues/4549) |
Workaround: [optional] Compile UCX without using this flag. However, note that ucx_perftest will not be available for usage. | |
Keywords: Clang compiler, UCX | |
Discovered in Version: 2.6 (UCX 1.8) | |
- | Description: When using GPU memory on an InfiniBand network with GPUDirect enabled yet without gdrcopy library, performance of small messages can be low. |
Workaround: Use the Rendezvous protocol by setting the UCX_RNDV_THRESH parameter to 0. | |
Keywords: GPU, GPUDirect, memory | |
Discovered in Version: 2.6 (UCX 1.8) | |
4105 | Description: Adaptive Routing is not supported when used with OpenSHMEM applications. (Github issue: https://github.com/openucx/ucx/issues/4105) |
Workaround: N/A | |
Keywords: Adaptive Routing, AR, OpenSHMEM, OSHMEM | |
Discovered in Version: 2.5 (OpenSHMEM 1.4) | |
- | Description: In ConnectX-4 and Connect-IB HCAs, when the DC transport is used on a large scale, “Retry exceeded” messages may be printed from UCX. |
Workaround: Configure SL2VL on your OpenSM in the fabric and make UCX use SL=1 when using the InfiniBand transports via '-x UCX_IB_SL=1'. | |
Keywords: UCX, DC transport, ConnectX-4, Connect-IB | |
Discovered in Version: 2.1 (UCX 1.3) | |
- | Description: When UCX requires more memory utilization than the memory space defined in /proc/sys/kernel/shmmni file, the following message is printed from UCX: “... total number of segments in the system (%lu) would exceed the limit in /proc/sys/kernel/shmmni (=%lu)... please check shared memory limits by 'ipcs -l”. |
Workaround: Follow the instructions in the error message above and increase the value of shared memory segments in /proc/sys/kernel/shmmni file. | |
Keywords: UCX, memory | |
Discovered in Version: 2.1 (UCX 1.3) | |
1162 | Description: UCX currently does not support canceling send requests. (Github issue: https://github.com/openucx/ucx/issues/1162) |
Workaround: N/A | |
Keywords: UCX | |
Discovered in Version: 2.0 | |
- | Description: UCX job hangs with SocketDirect/MultiHost/SR-IOV. |
Workaround: Set UCX_IB_ADDR_TYPE=ib_global | |
Keywords: UCX | |
- | Description: As UCX embedded in the HPC-X is compiled with AVX support, UCX cannot be run on hosts without AVX support. In case the AVX is not available, recompile the UCX that is available in the HPC-X with the option: --with-avx=no |
Workaround: Recompile UCX with AVX disabled: $ ./utils/hpcx_rebuild.sh --rebuild-ucx --ucx-extra-config "--with-avx=no" | |
Keywords: UCX |