All of lore.kernel.org
 help / color / mirror / Atom feed
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!

  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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20211107155616.GA269390@lothringen \
    --to=frederic@kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=nbrtt01@gmail.com \
    --cc=peterz@infradead.org \
    --cc=rjw@rjwysocki.net \
    --cc=rostedt@goodmis.org \
    --cc=tglx@linutronix.de \
    --cc=yeyunfeng@huawei.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.