From: Rik van Riel <riel@surriel.com>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Mel Gorman <mgorman@techsingularity.net>,
linux-kernel <linux-kernel@vger.kernel.org>,
Kernel Team <kernel-team@fb.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Valentin Schneider <valentin.schneider@arm.com>
Subject: Re: [PATCH v3] sched/fair: bring back select_idle_smt, but differently
Date: Tue, 06 Apr 2021 11:26:37 -0400 [thread overview]
Message-ID: <1e21aa6ea7de3eae32b29559926d4f0ba5fea130.camel@surriel.com> (raw)
In-Reply-To: <CAKfTPtBvy3Wv=-d5tjrirO3ukBgqV5vM709+_ee+H8LWJsnoLw@mail.gmail.com>
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On Tue, 2021-04-06 at 17:10 +0200, Vincent Guittot wrote:
> On Fri, 26 Mar 2021 at 20:19, Rik van Riel <riel@surriel.com> wrote:
>
> > -static int select_idle_cpu(struct task_struct *p, struct
> > sched_domain *sd, int target)
> > +static int select_idle_cpu(struct task_struct *p, struct
> > sched_domain *sd, int prev, int target)
> > {
> > struct cpumask *cpus =
> > this_cpu_cpumask_var_ptr(select_idle_mask);
> > int i, cpu, idle_cpu = -1, nr = INT_MAX;
> > @@ -6136,23 +6163,32 @@ static int select_idle_cpu(struct
> > task_struct *p, struct sched_domain *sd, int t
> >
> > cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
> >
> > - if (sched_feat(SIS_PROP) && !smt) {
> > - u64 avg_cost, avg_idle, span_avg;
> > + if (!smt) {
> > + if (cpus_share_cache(prev, target)) {
>
> Have you checked the impact on no smt system ? would worth a static
> branch.
>
> Also, this doesn't need to be in select_idle_cpu() which aims to loop
> the sched_domain becaus you only compare target and prev. So you can
> move this call to select_idle_smt() in select_idle_sibling()
After Mel's rewrite, there no longer are calls to
select_idle_core() or select_idle_smt() in select_idle_sibling().
Everything got folded into one single loop in select_idle_cpu()
I would be happy to pull the static branch out of select_idle_smt()
and place it into this if condition, though. You are right that
would save some overhead on non-smt systems.
Peter, would you prefer a follow-up patch for that or a version 4
of the patch?
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next prev parent reply other threads:[~2021-04-06 15:26 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-21 19:03 [PATCH v2] sched/fair: bring back select_idle_smt, but differently Rik van Riel
2021-03-22 11:03 ` Mel Gorman
2021-03-22 15:07 ` Rik van Riel
2021-03-22 15:33 ` Mel Gorman
2021-03-23 2:08 ` Rik van Riel
2021-03-26 19:19 ` [PATCH v3] " Rik van Riel
2021-03-28 15:36 ` Mel Gorman
2021-04-06 15:10 ` Vincent Guittot
2021-04-06 15:26 ` Rik van Riel [this message]
2021-04-06 15:31 ` Vincent Guittot
2021-04-06 15:33 ` Vincent Guittot
2021-04-06 15:55 ` Rik van Riel
2021-04-06 16:13 ` Vincent Guittot
2021-04-07 7:17 ` Peter Zijlstra
2021-04-07 9:41 ` Mel Gorman
2021-04-07 10:15 ` Peter Zijlstra
2021-04-07 10:47 ` Mel Gorman
2021-04-07 12:10 ` Peter Zijlstra
2021-04-07 9:42 ` Vincent Guittot
2021-04-07 9:54 ` Peter Zijlstra
2021-04-07 9:57 ` Vincent Guittot
2021-04-07 10:19 ` Peter Zijlstra
2021-04-07 10:24 ` Vincent Guittot
2021-04-08 15:52 ` Rik van Riel
2021-04-09 11:24 ` [tip: sched/core] sched/fair: Bring back select_idle_smt(), " tip-bot2 for Rik van Riel
2021-04-09 16:14 ` tip-bot2 for Rik van Riel
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