From: Vincent Donnefort <vincent.donnefort@arm.com>
To: Valentin Schneider <valentin.schneider@arm.com>
Cc: peterz@infradead.org, mingo@redhat.com,
vincent.guittot@linaro.org, linux-kernel@vger.kernel.org,
dietmar.eggemann@arm.com, morten.rasmussen@arm.com,
qperret@google.com
Subject: Re: [PATCH 1/3] sched/fair: Make cpu_overutilized() EAS dependent
Date: Tue, 21 Dec 2021 10:09:08 +0100 [thread overview]
Message-ID: <20211221090444.GA2747@ubiquitous> (raw)
In-Reply-To: <875yrj8acq.mognet@arm.com>
On Mon, Dec 20, 2021 at 05:17:09PM +0000, Valentin Schneider wrote:
> On 20/12/21 12:43, Vincent Donnefort wrote:
> > On a system with Energy Aware Scheduling (EAS), tasks are placed according
> > to their energy consumption estimation and load balancing is disabled to
> > not break that energy biased placement. If the system becomes
> > overutilized, i.e. one of the CPU has too much utilization, energy
> > placement would then be disabled, in favor of Capacity-Aware Scheduling
> > (CAS), including load balancing. This is the sole usage for
> > rd->overutilized. Hence, there is no need to raise it for !EAS systems.
> >
> > Fixes: 2802bf3cd936 ("sched/fair: Add over-utilization/tipping point indicator")
>
> I'm not sure a Fixes: is warranted, this does not fix any misbehaviour or
> performance regression (even if this might gain us a few extra IPS by not
> writing 1's to rd->overutilized on SMP systems, note that this still gives
> us writes of 0's).
I put the tag to make sure this patch would be taken for stable releases
with:
[PATCH 2/3] sched/fair: Fix newidle_balance() for overutilized systems
Without the EAS requirement for cpu_overutilized() (patch 1/3), patch 2/3
could lead to useless newidle_balance() for !EAS systems.
Maybe that means in the end 2/3 and 1/3 should be squashed?
>
> Regardless:
>
> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
>
> > Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com>
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 095b0aa378df..e2f6fa14e5e7 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -5511,7 +5511,8 @@ static inline void hrtick_update(struct rq *rq)
> > #ifdef CONFIG_SMP
> > static inline bool cpu_overutilized(int cpu)
> > {
> > - return !fits_capacity(cpu_util_cfs(cpu), capacity_of(cpu));
> > + return sched_energy_enabled() &&
> > + !fits_capacity(cpu_util_cfs(cpu), capacity_of(cpu));
> > }
> >
> > static inline void update_overutilized_status(struct rq *rq)
> > --
> > 2.25.1
next prev parent reply other threads:[~2021-12-21 9:09 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-20 11:43 [PATCH 0/3] Fix stuck overutilized Vincent Donnefort
2021-12-20 11:43 ` [PATCH 1/3] sched/fair: Make cpu_overutilized() EAS dependent Vincent Donnefort
2021-12-20 17:17 ` Valentin Schneider
2021-12-21 9:09 ` Vincent Donnefort [this message]
2021-12-20 11:43 ` [PATCH 2/3] sched/fair: Fix newidle_balance() for overutilized systems Vincent Donnefort
2021-12-20 17:17 ` Valentin Schneider
2021-12-22 8:14 ` Vincent Guittot
2022-01-10 16:29 ` Vincent Donnefort
2021-12-20 11:43 ` [PATCH 3/3] sched/fair: Do not raise overutilized for idle CPUs Vincent Donnefort
2021-12-20 17:17 ` Valentin Schneider
2021-12-22 8:20 ` Vincent Guittot
2022-01-10 16:40 ` Vincent Donnefort
2022-01-17 10:45 ` Vincent Guittot
2022-01-17 12:18 ` Vincent Donnefort
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=20211221090444.GA2747@ubiquitous \
--to=vincent.donnefort@arm.com \
--cc=dietmar.eggemann@arm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=morten.rasmussen@arm.com \
--cc=peterz@infradead.org \
--cc=qperret@google.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).