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From: "valera.mironow at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/106772] atomic<T>::wait shouldn't touch waiter pool if used platform wait
Date: Wed, 28 Sep 2022 22:18:30 +0000 [thread overview]
Message-ID: <bug-106772-4-cK6RMsLc79@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-106772-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106772
--- Comment #20 from Mkkt Bkkt <valera.mironow at gmail dot com> ---
My main concern with this optimization it's not zero-overhead.
It's not necessary when we expect we have some waiters, in that case it just
additional synchronization and contention in waiter pool (that have small fixed
size, just imagine system with 100+ cores, if we have > 16 waiting threads some
of them make fetch_add/sub on the same atomic, that can be expensive,
especially on numa)
And at the same time, I don't understand when I need to notify and cannot know
notification not needed.
I don't understand when it useful.
next prev parent reply other threads:[~2022-09-28 22:18 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-29 12:38 [Bug libstdc++/106772] New: " valera.mironow at gmail dot com
2022-08-29 12:40 ` [Bug libstdc++/106772] " valera.mironow at gmail dot com
2022-08-29 15:12 ` rodgertq at gcc dot gnu.org
2022-09-20 3:38 ` rodgertq at gcc dot gnu.org
2022-09-20 7:39 ` valera.mironow at gmail dot com
2022-09-20 7:47 ` valera.mironow at gmail dot com
2022-09-20 14:14 ` rodgertq at gcc dot gnu.org
2022-09-20 14:20 ` valera.mironow at gmail dot com
2022-09-20 14:23 ` valera.mironow at gmail dot com
2022-09-20 14:27 ` valera.mironow at gmail dot com
2022-09-20 14:36 ` redi at gcc dot gnu.org
2022-09-20 14:40 ` rodgertq at gcc dot gnu.org
2022-09-20 14:54 ` valera.mironow at gmail dot com
2022-09-20 15:45 ` valera.mironow at gmail dot com
2022-09-20 15:55 ` redi at gcc dot gnu.org
2022-09-20 16:00 ` valera.mironow at gmail dot com
2022-09-20 16:05 ` valera.mironow at gmail dot com
2022-09-28 21:54 ` rodgertq at gcc dot gnu.org
2022-09-28 22:00 ` valera.mironow at gmail dot com
2022-09-28 22:04 ` valera.mironow at gmail dot com
2022-09-28 22:18 ` valera.mironow at gmail dot com [this message]
2022-09-28 22:34 ` rodgertq at gcc dot gnu.org
2022-09-28 22:50 ` rodgertq at gcc dot gnu.org
2022-09-28 23:09 ` valera.mironow at gmail dot com
2022-09-28 23:25 ` valera.mironow at gmail dot com
2022-09-28 23:40 ` rodgertq at gcc dot gnu.org
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