https://github.com/MaskRay created https://github.com/llvm/llvm-project/pull/209690
`parallelFor` dispatches its work to the thread pool and blocks the calling thread in the `TaskGroup` destructor until the workers finish. The caller thus stays idle instead of joining the work as modern parallel libraries do, and `numactl -C 0-7 ld.lld --threads=8` ends up slower than `numactl -C 0-8 ld.lld --threads=8`. Run one worker on the calling thread instead. This requires that no `parallelFor` body reads `getThreadIndex()`, which is unset on the caller; the last such user is removed by #209687. In the jobserver mode: only pool workers acquire job slots, so a jobserver-limited process may briefly exceed its granted concurrency by one thread. This is acceptable, better than pessimizing the common non-jobserver case, and parallelFor is unused by jobserver users. _______________________________________________ llvm-branch-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
