From: Steve Muckle <steve.muckle@linaro.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
"Rafael J. Wysocki" <rafael@kernel.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Juri Lelli <Juri.Lelli@arm.com>,
Patrick Bellasi <patrick.bellasi@arm.com>,
Michael Turquette <mturquette@baylibre.com>
Subject: Re: [PATCH 1/2] sched/fair: move cpufreq hook to update_cfs_rq_load_avg()
Date: Wed, 30 Mar 2016 18:42:20 -0700 [thread overview]
Message-ID: <56FC807C.80204@linaro.org> (raw)
In-Reply-To: <20160330193544.GD407@worktop>
On 03/30/2016 12:35 PM, Peter Zijlstra wrote:
> On Mon, Mar 28, 2016 at 12:38:26PM -0700, Steve Muckle wrote:
>> Without covering all the paths where CFS utilization changes it's
>> possible to have to wait up to a tick to act on some changes, since the
>> tick is the only guaranteed regularly-occurring instance of the hook.
>> That's an unacceptable amount of latency IMO...
>
> Note that even with your patches that might still be the case. Remote
> wakeups might not happen on the destination CPU at all, so it might not
> be until the next tick (which always happens locally) that we'll
> 'observe' the utilization change brought with the wakeups.
>
> We could force all the remote wakeups to IPI the destination CPU, but
> that comes at a significant performance cost.
What about only IPI'ing the destination when the utilization change is
known to require a higher CPU frequency?
next prev parent reply other threads:[~2016-03-31 1:42 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-22 0:21 [PATCH 1/2] sched/fair: move cpufreq hook to update_cfs_rq_load_avg() Steve Muckle
2016-03-22 0:21 ` [PATCH 2/2] sched/fair: do not call cpufreq hook unless util changed Steve Muckle
2016-03-24 23:47 ` Sai Gurrappadi
2016-03-24 23:47 ` Sai Gurrappadi
2016-03-25 1:01 ` Steve Muckle
2016-03-25 21:24 ` Sai Gurrappadi
2016-03-25 21:24 ` Sai Gurrappadi
2016-04-23 12:57 ` [tip:sched/core] sched/fair: Do " tip-bot for Steve Muckle
2016-03-28 12:02 ` [PATCH 1/2] sched/fair: move cpufreq hook to update_cfs_rq_load_avg() Dietmar Eggemann
2016-03-28 12:02 ` Dietmar Eggemann
2016-03-28 16:34 ` Steve Muckle
2016-03-28 18:30 ` Dietmar Eggemann
2016-03-28 18:30 ` Dietmar Eggemann
2016-03-28 19:38 ` Steve Muckle
2016-03-30 19:35 ` Peter Zijlstra
2016-03-31 1:42 ` Steve Muckle [this message]
2016-03-31 7:37 ` Peter Zijlstra
2016-03-31 21:26 ` Steve Muckle
2016-04-01 9:20 ` Peter Zijlstra
2016-04-11 19:28 ` Steve Muckle
2016-04-11 21:20 ` Rafael J. Wysocki
2016-04-12 14:29 ` Rafael J. Wysocki
2016-04-12 19:38 ` Steve Muckle
2016-04-13 14:45 ` Rafael J. Wysocki
2016-04-13 17:53 ` Steve Muckle
2016-04-13 19:39 ` Rafael J. Wysocki
2016-04-13 0:08 ` Steve Muckle
2016-04-13 4:48 ` Rafael J. Wysocki
2016-04-13 16:05 ` Rafael J. Wysocki
2016-04-13 16:07 ` Rafael J. Wysocki
2016-04-13 18:06 ` Steve Muckle
2016-04-13 19:50 ` Rafael J. Wysocki
2016-04-20 2:22 ` Steve Muckle
2016-03-31 9:27 ` Vincent Guittot
2016-03-31 9:34 ` Peter Zijlstra
2016-03-31 9:50 ` Vincent Guittot
2016-03-31 10:47 ` Peter Zijlstra
2016-03-31 12:14 ` Vincent Guittot
2016-03-31 12:34 ` Peter Zijlstra
2016-03-31 12:50 ` Vincent Guittot
2016-04-23 12:57 ` [tip:sched/core] sched/fair: Move " tip-bot for Steve Muckle
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=56FC807C.80204@linaro.org \
--to=steve.muckle@linaro.org \
--cc=Juri.Lelli@arm.com \
--cc=dietmar.eggemann@arm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=morten.rasmussen@arm.com \
--cc=mturquette@baylibre.com \
--cc=patrick.bellasi@arm.com \
--cc=peterz@infradead.org \
--cc=rafael@kernel.org \
--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 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.