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From: Viresh Kumar <viresh.kumar@linaro.org>
To: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: linux-kernel@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	linux-pm@vger.kernel.org, Pavan Kondeti <pkondeti@codeaurora.org>,
	"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Joel Fernandes <joelaf@google.com>,
	Patrick Bellasi <patrick.bellasi@arm.com>,
	Quentin Perret <quentin.perret@arm.com>
Subject: Re: [PATCH] Revert "cpufreq: schedutil: Don't restrict kthread to related_cpus unnecessarily"
Date: Tue, 8 May 2018 13:52:42 +0530	[thread overview]
Message-ID: <20180508082242.bre6sjfvefhz6xc3@vireshk-i7> (raw)
In-Reply-To: <20180508073340.13114-1-dietmar.eggemann@arm.com>

On 08-05-18, 08:33, Dietmar Eggemann wrote:
> This reverts commit e2cabe48c20efb174ce0c01190f8b9c5f3ea1d13.
> 
> Lifting the restriction that the sugov kthread is bound to the
> policy->related_cpus for a system with a slow switching cpufreq driver,
> which is able to perform DVFS from any cpu (e.g. cpufreq-dt), is not
> only not beneficial it also harms Enery-Aware Scheduling (EAS) on
> systems with asymmetric cpu capacities (e.g. Arm big.LITTLE).
> 
> The sugov kthread which does the update for the little cpus could
> potentially run on a big cpu. It could prevent that the big cluster goes
> into deeper idle states although all the tasks are running on the little
> cluster.

I think the original patch did the right thing, but that doesn't suit
everybody as you explained.

I wouldn't really revert the patch but fix my platform's cpufreq
driver to set dvfs_possible_from_any_cpu = false, so that other
platforms can still benefit from the original commit.

-- 
viresh

  reply	other threads:[~2018-05-08  8:22 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-08  7:33 Dietmar Eggemann
2018-05-08  8:22 ` Viresh Kumar [this message]
2018-05-08  9:09   ` Dietmar Eggemann
2018-05-08  9:42     ` Quentin Perret
2018-05-13  5:19       ` Joel Fernandes
2018-05-17 19:10         ` Saravana Kannan
2018-05-17 19:13           ` Joel Fernandes
2018-05-08  9:45     ` Viresh Kumar
2018-05-08 10:02       ` Quentin Perret
2018-05-08 10:34         ` Viresh Kumar
2018-05-08 11:00           ` Quentin Perret
2018-05-08 11:14             ` Viresh Kumar
2018-05-08 11:24               ` Quentin Perret
2018-05-08 12:20                 ` Juri Lelli
2018-05-08 20:36           ` Rafael J. Wysocki
2018-05-09  4:55             ` Viresh Kumar
2018-05-08 10:36       ` Dietmar Eggemann
2018-05-08 10:53         ` Viresh Kumar
2018-05-08 12:17           ` Juri Lelli
2018-05-09  4:55 ` Viresh Kumar
2018-05-17 10:32   ` Rafael J. Wysocki

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