From: Vincent Guittot <vincent.guittot@linaro.org>
To: Mel Gorman <mgorman@techsingularity.net>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>,
LKML <linux-kernel@vger.kernel.org>,
Aubrey Li <aubrey.li@linux.intel.com>,
Barry Song <song.bao.hua@hisilicon.com>,
Ingo Molnar <mingo@redhat.com>,
Peter Ziljstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Linux-ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 1/4] sched/fair: Remove SIS_AVG_CPU
Date: Tue, 8 Dec 2020 16:19:40 +0100 [thread overview]
Message-ID: <CAKfTPtAUb50SHtDQs0xeehrPGqkyA6HqFQ3=nUbtOCGj62Fc9A@mail.gmail.com> (raw)
In-Reply-To: <20201208151226.GK3371@techsingularity.net>
On Tue, 8 Dec 2020 at 16:12, Mel Gorman <mgorman@techsingularity.net> wrote:
>
> On Tue, Dec 08, 2020 at 03:47:40PM +0100, Vincent Guittot wrote:
> > > I considered it but made the choice to exclude the cost of cpumask_and()
> > > from the avg_scan_cost instead. It's minor but when doing the original
> >
> > At the cost of a less readable code
> >
>
> Slightly less readable, yes.
>
> > > prototype, I didn't think it was appropriate to count the cpumask
> > > clearing as part of the scan cost as it's not directly related.
> >
> > hmm... I think it is because the number of loop is directly related to
> > the allowed cpus
> >
>
> While that is true, the cost of initialising the map is constant and
> what is most important is tracking the scan cost which is variable.
> Without SIS_AVG_CPU, the cpumask init can go before SIS_PROP without any
> penalty so is this version preferable?
yes looks good to me
>
> --8<--
> sched/fair: Move avg_scan_cost calculations under SIS_PROP
>
> As noted by Vincent Guittot, avg_scan_costs are calculated for SIS_PROP
> even if SIS_PROP is disabled. Move the time calculations under a SIS_PROP
> check and while we are at it, exclude the cost of initialising the CPU
> mask from the average scan cost.
>
> Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
> ---
> kernel/sched/fair.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index ac7b34e7372b..5c41875aec23 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6153,6 +6153,8 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
> if (!this_sd)
> return -1;
>
> + cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
> +
> if (sched_feat(SIS_PROP)) {
> u64 avg_cost, avg_idle, span_avg;
>
> @@ -6168,11 +6170,9 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
> nr = div_u64(span_avg, avg_cost);
> else
> nr = 4;
> - }
> -
> - time = cpu_clock(this);
>
> - cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
> + time = cpu_clock(this);
> + }
>
> for_each_cpu_wrap(cpu, cpus, target) {
> if (!--nr)
> @@ -6181,8 +6181,10 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
> break;
> }
>
> - time = cpu_clock(this) - time;
> - update_avg(&this_sd->avg_scan_cost, time);
> + if (sched_feat(SIS_PROP)) {
> + time = cpu_clock(this) - time;
> + update_avg(&this_sd->avg_scan_cost, time);
> + }
>
> return cpu;
> }
next prev parent reply other threads:[~2020-12-08 15:20 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-07 9:15 [RFC PATCH 0/4] Reduce worst-case scanning of runqueues in select_idle_sibling Mel Gorman
2020-12-07 9:15 ` [PATCH 1/4] sched/fair: Remove SIS_AVG_CPU Mel Gorman
2020-12-07 15:05 ` Vincent Guittot
2020-12-08 10:07 ` Dietmar Eggemann
2020-12-08 10:59 ` Mel Gorman
2020-12-08 13:24 ` Vincent Guittot
2020-12-08 13:36 ` Mel Gorman
2020-12-08 13:43 ` Vincent Guittot
2020-12-08 13:53 ` Mel Gorman
2020-12-08 14:47 ` Vincent Guittot
2020-12-08 15:12 ` Mel Gorman
2020-12-08 15:19 ` Vincent Guittot [this message]
2020-12-07 9:15 ` [PATCH 2/4] sched/fair: Do not replace recent_used_cpu with the new target Mel Gorman
2020-12-08 9:57 ` Dietmar Eggemann
2020-12-08 11:02 ` Mel Gorman
2020-12-07 9:15 ` [PATCH 3/4] sched/fair: Return an idle cpu if one is found after a failed search for an idle core Mel Gorman
2020-12-07 15:06 ` Vincent Guittot
2020-12-07 9:15 ` [PATCH 4/4] sched/fair: Avoid revisiting CPUs multiple times during select_idle_sibling Mel Gorman
2020-12-07 15:04 ` [RFC PATCH 0/4] Reduce worst-case scanning of runqueues in select_idle_sibling Vincent Guittot
2020-12-07 15:42 ` Mel Gorman
2020-12-08 2:06 ` Li, Aubrey
2020-12-08 15:34 [PATCH 0/4] Reduce " Mel Gorman
2020-12-08 15:34 ` [PATCH 1/4] sched/fair: Remove SIS_AVG_CPU Mel Gorman
2020-12-08 16:13 ` Vincent Guittot
2021-01-25 8:59 [PATCH v4 0/4] Scan for an idle sibling in a single pass Mel Gorman
2021-01-25 8:59 ` [PATCH 1/4] sched/fair: Remove SIS_AVG_CPU Mel Gorman
2021-01-27 13:51 [PATCH v5 0/4] Scan for an idle sibling in a single pass Mel Gorman
2021-01-27 13:52 ` [PATCH 1/4] sched/fair: Remove SIS_AVG_CPU Mel Gorman
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