[Openmp-commits] [PATCH] D148808: [OpenMP][libomptarget][AMDGPU] Enable optional active HSA wait state

Jan-Patrick Lehr via Phabricator via Openmp-commits openmp-commits at lists.llvm.org
Wed Apr 26 02:54:42 PDT 2023

jplehr added a comment.

Thanks for all the comments, I think there is a bit of confusion due to my lack of documentation of the code.

1. Units of the variables: microseconds.
2. Wait state: This indicates whether the HSA runtime should actively wait. As far as I understand it, this means that it will likely not perform a context switch while waiting. This can improve the responsiveness to the signal value change. I did some basic profiles with babelstream using standard waiting and the timeout values we used in the old plugin. I can see improvements in the duration that the system stays within the `hsa_signal_wait_scaqcuire`. This suggests that this is indeed helping with latency, and therefore with the runtime "realizing" that a short running kernel has finished. Babelstream results do reproducibly improve.
3. As a result of 2., I think, we used different values for kernels and data movements, as the idea is that the data transfers may just be a little slower.

I will go ahead and update the patch to address all code-related comments.

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