From: Mel Gorman <mgorman@techsingularity.net>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Aubrey Li <aubrey.li@linux.intel.com>,
mingo@redhat.com, juri.lelli@redhat.com,
vincent.guittot@linaro.org, valentin.schneider@arm.com,
qais.yousef@arm.com, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com,
tim.c.chen@linux.intel.com, linux-kernel@vger.kernel.org,
Mel Gorman <mgorman@suse.de>, Jiang Biao <benbjiang@gmail.com>
Subject: Re: [RFC PATCH v5] sched/fair: select idle cpu from idle cpumask for task wakeup
Date: Mon, 7 Dec 2020 17:10:21 +0000 [thread overview]
Message-ID: <20201207171021.GF3371@techsingularity.net> (raw)
In-Reply-To: <20201207155015.GQ3040@hirez.programming.kicks-ass.net>
On Mon, Dec 07, 2020 at 04:50:15PM +0100, Peter Zijlstra wrote:
> On Wed, Nov 18, 2020 at 12:31:13PM +0800, Aubrey Li wrote:
> > Add idle cpumask to track idle cpus in sched domain. When a CPU
> > enters idle, if the idle driver indicates to stop tick, this CPU
> > is set in the idle cpumask to be a wakeup target. And if the CPU
> > is not in idle, the CPU is cleared in idle cpumask during scheduler
> > tick to ratelimit idle cpumask update.
>
> So this will only have SIS consider CPUs that have the tick stopped?
> That might affect the facebook tail-latency workloads quite a bit.
>
This is the concern I had as well. That's why patch "sched/fair: Avoid
revisiting CPUs multiple times during select_idle_sibling" was created. The
intent was that a mask could be used as a hint about what runqueues to
look at first but continue looking at other runqueues without examining
the same runqueue twice. While the patch would not be merged on its own,
it may still be relevant in the context of an idle CPU mask depending on
how up to date it is.
--
Mel Gorman
SUSE Labs
prev parent reply other threads:[~2020-12-07 17:11 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-18 4:31 [RFC PATCH v5] sched/fair: select idle cpu from idle cpumask for task wakeup Aubrey Li
2020-11-23 9:27 ` Vincent Guittot
2020-11-24 7:01 ` Li, Aubrey
2020-11-24 17:01 ` Vincent Guittot
2020-11-25 2:03 ` Li, Aubrey
2020-11-25 8:31 ` Vincent Guittot
2020-11-25 13:37 ` Li, Aubrey
2020-11-26 8:14 ` Vincent Guittot
2020-11-26 9:35 ` Li, Aubrey
2020-11-26 9:49 ` Vincent Guittot
2020-12-07 15:48 ` Peter Zijlstra
2020-12-07 16:52 ` Valentin Schneider
2020-12-07 18:05 ` Peter Zijlstra
2020-12-07 15:50 ` Peter Zijlstra
2020-12-07 17:10 ` Mel Gorman [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=20201207171021.GF3371@techsingularity.net \
--to=mgorman@techsingularity.net \
--cc=aubrey.li@linux.intel.com \
--cc=benbjiang@gmail.com \
--cc=bsegall@google.com \
--cc=dietmar.eggemann@arm.com \
--cc=juri.lelli@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mgorman@suse.de \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=qais.yousef@arm.com \
--cc=rostedt@goodmis.org \
--cc=tim.c.chen@linux.intel.com \
--cc=valentin.schneider@arm.com \
--cc=vincent.guittot@linaro.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).