On Thu, May 05, 2022 at 11:09:08AM +0100, Stefan Hajnoczi wrote: > On Tue, May 03, 2022 at 09:43:15AM +0200, Lukáš Doktor wrote: > > Hello Mike, Paolo, others, > > > > in my perf pipeline I noticed a regression bisected to the > > f9fc8932b11f3bcf2a2626f567cb6fdd36a33a94 - "thread-posix: remove the posix > > semaphore support" commit and I'd like to ask you to verify it might have > > caused that and eventually consider fixing it. The regression is visible, > > reproducible and clearly bisectable to this commit with the following 2 > > scenarios: > > I can't parse the commit message for > f9fc8932b11f3bcf2a2626f567cb6fdd36a33a94, so it's not 100% clear to me > why it was necessary to remove sem_*() calls. > > util/thread-pool.c uses qemu_sem_*() to notify worker threads when work > becomes available. It makes sense that this operation is > performance-critical and that's why the benchmark regressed.
Doh, I questioned whether the change would have a performance impact, and it wasn't thought to be used in perf critical places https://www.mail-archive.com/qemu-devel@nongnu.org/msg870737.html With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
