d/freebsd-dev
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

llvm/lld: damage control threading

Browse Source 
See the comment inside.

Reviewed by:	dim
Differential Revision:	https://reviews.freebsd.org/D39389
This commit is contained in:
Mateusz Guzik 2023-04-02 12:38:49 +00:00
parent 2a58b312b6
commit 04bab189b8
1 changed files with 13 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
contrib/llvm-project/llvm/lib/Support/Threading.cpp
View File

@ -62,8 +62,19 @@ unsigned llvm::ThreadPoolStrategy::compute_thread_count() const {
: sys::getHostNumPhysicalCores();
if (MaxThreadCount <= 0)
MaxThreadCount = 1;
if (ThreadsRequested == 0)
return MaxThreadCount;
// Damage control threading.
//
// There are no heuristics to figure out how many threads makes sense to spawn,
// all while rolling with all available hw threads starts being detrimental to
// performance really early.
//
// Work around by putting a hard cap unless the user explicitly requested a certain amount.
//
// See https://discourse.llvm.org/t/avoidable-overhead-from-threading-by-default/69160
// for more details.
if (ThreadsRequested == 0) {
return std::min(MaxThreadCount, 4);
}
if (!Limit)
return ThreadsRequested;
return std::min((unsigned)MaxThreadCount, ThreadsRequested);