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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
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106772

--- 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 f=
ixed
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 k=
now
notification not needed.
I don't understand when it useful.=