From: Frederic Weisbecker <frederic@kernel.org>
To: Norbert <nbrtt01@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Steven Rostedt <rostedt@goodmis.org>,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Yunfeng Ye <yeyunfeng@huawei.com>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>
Subject: Re: Performance regression: thread wakeup time (latency) increased up to 3x
Date: Sun, 7 Nov 2021 16:56:16 +0100 [thread overview]
Message-ID: <20211107155616.GA269390@lothringen> (raw)
In-Reply-To: <ae2debfb-c780-7164-09ee-ea295004d173@gmail.com>
Hi Norbert,
On Tue, Oct 19, 2021 at 12:01:32AM -0700, Norbert wrote:
>
> On the thought that it might enter deeper idle/wait/sleep states:
>
> The benchmark executes this test in a quite tight loop, except that so far
> it waited 1000 ns (with a mix of pause and rdtsc) before calling futex-wake,
> to make sure the other thread fully enters the futex-wait without taking any
> shortcuts.
>
> Except when this "prepare time" is reduced to less than even 350 ns or so,
> the timings remain the same (they go up before they start going down).
> Surely in this situation the thread is at least not supposed to enter deeper
> states for such short waiting times.
Is it possible for you to share this benchmark so that I can try to reproduce?
Thanks!
next prev parent reply other threads:[~2021-11-07 15:56 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-15 7:43 Performance regression: thread wakeup time (latency) increased up to 3x Norbert
2021-10-15 8:52 ` Peter Zijlstra
2021-10-15 9:36 ` Norbert
2021-10-15 14:04 ` Steven Rostedt
2021-10-16 4:08 ` Norbert
2021-10-18 11:25 ` Peter Zijlstra
2021-10-19 1:56 ` Norbert
2021-10-19 7:01 ` Norbert
2021-11-07 15:56 ` Frederic Weisbecker [this message]
2021-11-08 15:56 ` Norbert
2021-10-22 13:03 ` Rafael J. Wysocki
2021-10-24 5:09 ` Norbert
2021-11-02 1:35 ` Norbert
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