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From: Mel Gorman <mgorman@techsingularity.net>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Barry Song <song.bao.hua@hisilicon.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Peter Ziljstra <peterz@infradead.org>,
	Aubrey Li <aubrey.li@linux.intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Valentin Schneider <valentin.schneider@arm.com>,
	Ingo Molnar <mingo@redhat.com>,
	Dietmar Eggemann <dietmar.eggemann@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 13:53:58 +0000	[thread overview]
Message-ID: <20201208135358.GJ3371@techsingularity.net> (raw)
In-Reply-To: <CAKfTPtDbUoVSvnjFrpomvTJD0jCA6vH_Y3LP=csW8fHntOG_6A@mail.gmail.com>

On Tue, Dec 08, 2020 at 02:43:10PM +0100, Vincent Guittot wrote:
> On Tue, 8 Dec 2020 at 14:36, Mel Gorman <mgorman@techsingularity.net> wrote:
> >
> > On Tue, Dec 08, 2020 at 02:24:32PM +0100, Vincent Guittot wrote:
> > > > > Nitpick:
> > > > >
> > > > > Since now avg_cost and avg_idle are only used w/ SIS_PROP, they could go
> > > > > completely into the SIS_PROP if condition.
> > > > >
> > > >
> > > > Yeah, I can do that. In the initial prototype, that happened in a
> > > > separate patch that split out SIS_PROP into a helper function and I
> > > > never merged it back. It's a trivial change.
> > >
> > > while doing this, should you also put the update of
> > > this_sd->avg_scan_cost under the SIS_PROP feature ?
> > >
> >
> > It's outside the scope of the series but why not. This?
> >
> > --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>
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 19ca0265f8aa..0fee53b1aae4 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -6176,10 +6176,10 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
> >                         nr = 4;
> >         }
> >
> > -       time = cpu_clock(this);
> 
> I would move it in the if (sched_feat(SIS_PROP)) above.
> 

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
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.

-- 
Mel Gorman
SUSE Labs

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WARNING: multiple messages have this Message-ID (diff)
From: Mel Gorman <mgorman@techsingularity.net>
To: Vincent Guittot <vincent.guittot@linaro.org>
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 13:53:58 +0000	[thread overview]
Message-ID: <20201208135358.GJ3371@techsingularity.net> (raw)
In-Reply-To: <CAKfTPtDbUoVSvnjFrpomvTJD0jCA6vH_Y3LP=csW8fHntOG_6A@mail.gmail.com>

On Tue, Dec 08, 2020 at 02:43:10PM +0100, Vincent Guittot wrote:
> On Tue, 8 Dec 2020 at 14:36, Mel Gorman <mgorman@techsingularity.net> wrote:
> >
> > On Tue, Dec 08, 2020 at 02:24:32PM +0100, Vincent Guittot wrote:
> > > > > Nitpick:
> > > > >
> > > > > Since now avg_cost and avg_idle are only used w/ SIS_PROP, they could go
> > > > > completely into the SIS_PROP if condition.
> > > > >
> > > >
> > > > Yeah, I can do that. In the initial prototype, that happened in a
> > > > separate patch that split out SIS_PROP into a helper function and I
> > > > never merged it back. It's a trivial change.
> > >
> > > while doing this, should you also put the update of
> > > this_sd->avg_scan_cost under the SIS_PROP feature ?
> > >
> >
> > It's outside the scope of the series but why not. This?
> >
> > --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>
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 19ca0265f8aa..0fee53b1aae4 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -6176,10 +6176,10 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
> >                         nr = 4;
> >         }
> >
> > -       time = cpu_clock(this);
> 
> I would move it in the if (sched_feat(SIS_PROP)) above.
> 

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
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.

-- 
Mel Gorman
SUSE Labs

  reply	other threads:[~2020-12-08 13:55 UTC|newest]

Thread overview: 48+ 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 ` Mel Gorman
2020-12-07  9:15 ` [PATCH 1/4] sched/fair: Remove SIS_AVG_CPU Mel Gorman
2020-12-07  9:15   ` Mel Gorman
2020-12-07 15:05   ` Vincent Guittot
2020-12-07 15:05     ` Vincent Guittot
2020-12-08 10:07   ` Dietmar Eggemann
2020-12-08 10:07     ` Dietmar Eggemann
2020-12-08 10:59     ` Mel Gorman
2020-12-08 10:59       ` Mel Gorman
2020-12-08 13:24       ` Vincent Guittot
2020-12-08 13:24         ` Vincent Guittot
2020-12-08 13:36         ` Mel Gorman
2020-12-08 13:36           ` Mel Gorman
2020-12-08 13:43           ` Vincent Guittot
2020-12-08 13:43             ` Vincent Guittot
2020-12-08 13:53             ` Mel Gorman [this message]
2020-12-08 13:53               ` Mel Gorman
2020-12-08 14:47               ` Vincent Guittot
2020-12-08 14:47                 ` Vincent Guittot
2020-12-08 15:12                 ` Mel Gorman
2020-12-08 15:12                   ` Mel Gorman
2020-12-08 15:19                   ` Vincent Guittot
2020-12-08 15:19                     ` Vincent Guittot
2020-12-07  9:15 ` [PATCH 2/4] sched/fair: Do not replace recent_used_cpu with the new target Mel Gorman
2020-12-07  9:15   ` Mel Gorman
2020-12-08  9:57   ` Dietmar Eggemann
2020-12-08  9:57     ` Dietmar Eggemann
2020-12-08 11:02     ` Mel Gorman
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  9:15   ` Mel Gorman
2020-12-07 15:06   ` Vincent Guittot
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  9:15   ` 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 15:04   ` Vincent Guittot
2020-12-07 15:42   ` Mel Gorman
2020-12-07 15:42     ` Mel Gorman
2020-12-08  2:06     ` Li, Aubrey
2020-12-08  2:06       ` Li, Aubrey
  -- strict thread matches above, loose matches on Subject: below --
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 15:34   ` Mel Gorman
2020-12-08 16:13   ` Vincent Guittot
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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