From: Peter Zijlstra <peterz@infradead.org>
To: Steve Muckle <steve.muckle@linaro.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 21:35:44 +0200 [thread overview]
Message-ID: <20160330193544.GD407@worktop> (raw)
In-Reply-To: <56F98832.3030207@linaro.org>
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.
next prev parent reply other threads:[~2016-03-30 19:35 UTC|newest]
Thread overview: 35+ 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
2016-03-25 1:01 ` Steve Muckle
2016-03-25 21:24 ` Sai Gurrappadi
2016-03-28 12:02 ` [PATCH 1/2] sched/fair: move cpufreq hook to update_cfs_rq_load_avg() Dietmar Eggemann
2016-03-28 16:34 ` Steve Muckle
2016-03-28 18:30 ` Dietmar Eggemann
2016-03-28 19:38 ` Steve Muckle
2016-03-30 19:35 ` Peter Zijlstra [this message]
2016-03-31 1:42 ` Steve Muckle
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
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