From: "Jörn Engel" <joern@purestorage.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>
Subject: Re: sched: wakeup setting TIF_NEED_RESCHED too frequently
Date: Wed, 28 Apr 2021 11:51:24 -0700 [thread overview]
Message-ID: <YImurOENWBEg8UP+@cork> (raw)
In-Reply-To: <YIkdDeb9c+XmDRvM@hirez.programming.kicks-ass.net>
On Wed, Apr 28, 2021 at 10:30:05AM +0200, Peter Zijlstra wrote:
>
> set_nr_if_polling() only sets TIF_NEED_RESCHED IFF TIF_POLLING_NRFLAG is
> set. TIF_POLLING_NRFLAG is only set when idle and is then sufficient to
> wake that cpu and reschedule.
>
> If not TIF_POLLING_NRFLAG, then we send an IPI to deal with the
> non-empty wake_list.
Yeah, saw that myself. My explanation of the behaviour is wrong. The
observed behaviour remains, though.
Guess I have to add more instrumentation if I cannot find the cause by
reading the code.
Thank you!
Jörn
--
Optimizations always bust things, because all optimizations are, in
the long haul, a form of cheating, and cheaters eventually get caught.
-- Larry Wall
prev parent reply other threads:[~2021-04-28 18:52 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-27 21:16 sched: wakeup setting TIF_NEED_RESCHED too frequently Jörn Engel
2021-04-28 8:30 ` Peter Zijlstra
2021-04-28 18:51 ` Jörn Engel [this message]
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=YImurOENWBEg8UP+@cork \
--to=joern@purestorage.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
/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.