- Introduced double-buffering to reduce copy overhead and overlap BF16 arithmetic with data prefetching.
- Aimed to improve performance of reduction-based collectives by up to 10%.
- Implemented based on recommendations from Guennadi Riguer (AMD)
- Added --force-reduce-pipeline option to install.sh to activate this optimization for BF16 reductions.
- Feature is disabled by default to prevent regressions with large messages until auto-tuning logic is upstreamed.
---------
Co-authored-by: Jeffrey Novotny <jnovotny@amd.com>
Co-authored-by: Pedram Alizadeh <pmohamma@amd.com>
Prevent initialization failures in certain configurations when attempting
to load fp8-specific symmetric multicast kernels on GPUs older than
Blackwell.
* Support fused all reduce and elementwise operations
Add additional "acc" parameter to RCCL Replayer logs
Add flag which indicates availability of new API
* Fix Recorder json parsing
* Remove unreachable code
* Remove extra acc pointer check
* .
* Revert "[DEVICE] Adding ability to choose unroll factor at runtime (#1734)"
This reverts commit 9d72be7b2f.
* Use noinline to reduce kernels linking time
* Don't use noinline for gfx942 and gfx950 to avoid perf regression
---------
Co-authored-by: AtlantaPepsi <timhu102@amd.com>
Co-authored-by: BertanDogancay <bertan.dogancay@gmail.com>
Boosts single node bfloat16 allreduce performance by up to 20% for some data sizes and provides gating with the RCCL_GFX942_CHEAP_FENCE_OFF environment variable
* Increased max stack size to 640
* Added new binary for executing unit tests
Added new unit tests for argcheck.cc and alt_rsmi.cc files
Modified the method to execute unit tests to cover static methods
by using a bash script to convert static to non-static functions
and variables on the fly restricted to debug build type.
Improve support for DirectNIC (CX8)
* Add support for XDR speed detection.
* When DirectNIC is enabled, report only the RDMA interfaces.
Extend the P2C (PXN over C2C) support to send/receive operations.
Support compilation with GCC 14 (Issues #1743, #1751).
Fix the unloading of network plugins that also provide tuner capability.
Fix the change of the current device across the calls to ncclCommDestroy()
and ncclCommAbort().
A note for users on MNNVL systems: please ensure an adequate stack size for
NCCL threads. While the default Linux stack size limit of 8192 KB is known
to be sufficient, we've seen crashes if the limit is changed to
"unlimited", as it causes the glibc library to unexpectedly *decrease* the
stack size of NCCL's background threads to just 2048 KB. Use "ulimit -s"
in bash to print the current limit; if needed, reset it to 8192 KB using
"ulimit -s 8192" (one also needs to ensure that the new setting is
propagated to other nodes when launching a multi-node NCCL job).
* Add support for extended fine-grained system memory pool
* Use hipHostRegisterUncached
* Add "sc0 sc1" flags for LL store on gfx950
* Update after HIP flag is changed to hipExtHostRegisterUncached
This feature tracks the proxy events and status of each send/recv op. ProxyTrace keeps a fixed number of active ops in host mem and dumps the status of each op when the program crashes or hangs.
Improvements for GB200 systems
* Optimize the network performance by alternating the direction of the
rings and the NIC to GPU assignment across communicators to limit
unnecessary sharing.
* Fix the detection of C2C links in case GPU Direct RDMA is disabled
between a GPU and a NIC.
* Fix PXN support on MNNVL systems, where NCCL would try (and fail) to
share regular host memory across multiple nodes.
* Fix P2C (PXN over C2C), which is now preferred over regular PXN. This
support is currently preliminary and is disabled by default; use
NCCL_PXN_C2C=1 to enable.
Further reduce the overheads of CUDA graph capturing, which increased in
NCCL 2.26.2 for large graphs.
Optimize the network performance on DGX B200 systems by adjusting the
bandwidths provided to the graph search algorithm.
Enable fp8 reductions in symmetric kernels on Blackwell with CUDA 12.8.
Restore the plugin name handling logic to make it possible to specify a
path to the plugin (Issue #1732).
Restore the ability to change NCCL_COLLNET_ENABLE during execution
(Issue #1741).
Add an example tuner plugin with CSV-based overrides.
Remove an x86 dependency from the example profiler.
* First version of new replayer, with comments on future TODOs
* plus minor fixes for UT
* Updated format of recorder, especially in binary department, according to replayer's need
* Reapply "[AG and RS channel tuning] Add thread work threshold to tuning models and precompute reg index in LL128 (#1641)"
This reverts commit 943ad6f7820739385a0b54e81f823d0df1dbf71c.
* Decreasing NCCL_LL128_SHMEM_ELEMS_PER_THREAD from 16 to 8
Mustafa Abduljabbar
Atul Kulkarni
Kamil Iskra
Arm Patinyasakdikul
Wenkai Du
alex-breslow-amd
Rahul Vaidya
Nilesh M Negi
isaki001
Bertan Dogancay
mberenjk
ryanhankins
Dingming Wu
BertanDogancay
Sarat Kamisetty
Tim
Richard Barnes
corey-derochie-amd
Nusrat Islam
Pedram Alizadeh
Avinash