Implement computeHostNumHardwareThreads() for FreeBSD
This retrieves CPU affinity via FreeBSD's cpuset(2) API, and makes
LLVM respect affinity settings configured by the user via the
cpuset(1) command.
In particular, this allows to reduce the number of threads used on
machines with high core counts, which can interact badly with
parallelized build systems. This is particularly noticable with lld,
which spawns lots of threads even for linking e.g. hello_world!
This fix is related to PR48193, but does not adress the more
fundamental problem, which is that LLVM by default grabs as many CPUs
and/or threads as possible.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D92271
Originally by: mjg
MFC after: 1 week
landed upstream:
For llvm's internal function which retrieves the number of available
"hardware threads", use cpuset_getaffinity(2) on FreeBSD, so it will
honor processor sets configured by the cpuset(1) command.
This should make it possible to avoid e.g. lld creating a huge number of
threads on a machine with many cores, even for linking simple programs.
This will also be submitted upstream.
Submitted by: mjg
"hardware threads", use cpuset_getaffinity(2) on FreeBSD, so it will
honor processor sets configured by the cpuset(1) command.
This should make it possible to avoid e.g. lld creating a huge number of
threads on a machine with many cores, even for linking simple programs.
This will also be submitted upstream.
Submitted by: mjg
MFC after: 1 week
master 2e10b7a39b9, the last commit before the llvmorg-12-init tag, from
which release/11.x was branched.
Note that for now, I rolled back all our local changes to make merging
easier, and I will reapply the still-relevant ones after updating to
11.0.0-rc1.
This uses the new layout of the upstream repository, which was recently
migrated to GitHub, and converted into a "monorepo". That is, most of
the earlier separate sub-projects with their own branches and tags were
consolidated into one top-level directory, and are now branched and
tagged together.
Updating the vendor area to match this layout is next.
2019-12-20 19:53:05 +00:00
Renamed from contrib/llvm/lib/Support/Unix/Threading.inc (Browse further)
