[Openmp-commits] [PATCH] D107656: [OpenMP] Use events and taskyield in target nowait task to unblock host threads

[Ye Luo via Phabricator via Openmp-commits]

ye-luo created this revision.
Herald added subscribers: guansong, yaxunl, mgorny.
ye-luo requested review of this revision.
Herald added a reviewer: jdoerfert.
Herald added a subscriber: sstefan1.

Currently, in a target task, host thread spins when invoking synchronization after kernel/transfer submission.
This patch adds LIBOMPTARGET_USE_NOWAIT_EVENT environment variable to enable the code path to unblock host thread in an deferred target task by recording an event for synchronization and calling taskyield.

Need LIBOMP_USE_HIDDEN_HELPER_TASK=0 KMP_TASK_STEALING_CONSTRAINT=1 and LIBOMPTARGET_USE_NOWAIT_EVENT=1 to make this feature work nicely.
https://github.com/ye-luo/openmp-target/blob/master/hands-on/gemv/7-gemv-omp-target-many-matrices-taskloop/gemv-omp-target-many-matrices-taskloop.cpp
Is the test case I played with.


https://reviews.llvm.org/D107656

Files:
  openmp/libomptarget/include/omptarget.h
  openmp/libomptarget/plugins/cuda/src/rtl.cpp
  openmp/libomptarget/plugins/exports
  openmp/libomptarget/src/CMakeLists.txt
  openmp/libomptarget/src/device.cpp
  openmp/libomptarget/src/device.h
  openmp/libomptarget/src/interface.cpp
  openmp/libomptarget/src/omptarget.cpp
  openmp/libomptarget/src/rtl.cpp
  openmp/libomptarget/src/rtl.h
  openmp/runtime/src/kmp.h
  openmp/runtime/src/kmp_tasking.cpp

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