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From: Josh Don <joshdon@google.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Qais Yousef <qais.yousef@arm.com>, Ingo Molnar <mingo@redhat.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Li Zefan <lizefan@huawei.com>, Tejun Heo <tj@kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	cgroups@vger.kernel.org, Paul Turner <pjt@google.com>
Subject: Re: [PATCH v2] sched/cpuset: distribute tasks within affinity masks
Date: Tue, 17 Mar 2020 14:35:32 -0700	[thread overview]
Message-ID: <CABk29NuAYvkqNmZZ6cjZBC6=hv--2siPPjZG-BUpNewxm02O6A@mail.gmail.com> (raw)
In-Reply-To: <20200317192401.GE20713@hirez.programming.kicks-ass.net>

On Wed, Mar 11, 2020 at 7:05 AM Qais Yousef <qais.yousef@arm.com> wrote:
>
> This actually helps me fix a similar problem I faced in RT [1]. If multiple RT
> tasks wakeup at the same time we get a 'thundering herd' issue where they all
> end up going to the same CPU, just to be pushed out again.
>
> Beside this will help fix another problem for RT tasks fitness, which is
> a manifestation of the problem above. If two tasks wake up at the same time and
> they happen to run on a little cpu (but request to run on a big one), one of
> them will end up being migrated because find_lowest_rq() will return the first
> cpu in the mask for both tasks.
>
> I tested the API (not the change in sched/core.c) and it looks good to me.

Nice, glad that the API already has another use case. Thanks for taking a look.

> nit: cpumask_first_and() is better here?

Yea, I would also prefer to use it, but the definition of
cpumask_first_and() follows this section, as it itself uses
cpumask_next_and().

> It might be a good idea to split the API from the user too.

Not sure what you mean by this, could you clarify?

On Tue, Mar 17, 2020 at 12:24 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> > Anyway, for the API.
> >
> > Reviewed-by: Qais Yousef <qais.yousef@arm.com>
> > Tested-by: Qais Yousef <qais.yousef@arm.com>
>
> Thanks guys!

Thanks Peter, any other comments or are you happy with merging this patch as-is?

WARNING: multiple messages have this Message-ID (diff)
From: Josh Don <joshdon-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
To: Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Cc: Qais Yousef <qais.yousef-5wv7dgnIgG8@public.gmane.org>,
	Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Juri Lelli <juri.lelli-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Vincent Guittot
	<vincent.guittot-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
	Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>,
	Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
	Dietmar Eggemann <dietmar.eggemann-5wv7dgnIgG8@public.gmane.org>,
	Steven Rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org>,
	Ben Segall <bsegall-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	Mel Gorman <mgorman-l3A5Bk7waGM@public.gmane.org>,
	linux-kernel
	<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Paul Turner <pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Subject: Re: [PATCH v2] sched/cpuset: distribute tasks within affinity masks
Date: Tue, 17 Mar 2020 14:35:32 -0700	[thread overview]
Message-ID: <CABk29NuAYvkqNmZZ6cjZBC6=hv--2siPPjZG-BUpNewxm02O6A@mail.gmail.com> (raw)
In-Reply-To: <20200317192401.GE20713-Nxj+rRp3nVydTX5a5knrm8zTDFooKrT+cvkQGrU6aU0@public.gmane.org>

On Wed, Mar 11, 2020 at 7:05 AM Qais Yousef <qais.yousef-5wv7dgnIgG8@public.gmane.org> wrote:
>
> This actually helps me fix a similar problem I faced in RT [1]. If multiple RT
> tasks wakeup at the same time we get a 'thundering herd' issue where they all
> end up going to the same CPU, just to be pushed out again.
>
> Beside this will help fix another problem for RT tasks fitness, which is
> a manifestation of the problem above. If two tasks wake up at the same time and
> they happen to run on a little cpu (but request to run on a big one), one of
> them will end up being migrated because find_lowest_rq() will return the first
> cpu in the mask for both tasks.
>
> I tested the API (not the change in sched/core.c) and it looks good to me.

Nice, glad that the API already has another use case. Thanks for taking a look.

> nit: cpumask_first_and() is better here?

Yea, I would also prefer to use it, but the definition of
cpumask_first_and() follows this section, as it itself uses
cpumask_next_and().

> It might be a good idea to split the API from the user too.

Not sure what you mean by this, could you clarify?

On Tue, Mar 17, 2020 at 12:24 PM Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org> wrote:
>
> > Anyway, for the API.
> >
> > Reviewed-by: Qais Yousef <qais.yousef-5wv7dgnIgG8@public.gmane.org>
> > Tested-by: Qais Yousef <qais.yousef-5wv7dgnIgG8@public.gmane.org>
>
> Thanks guys!

Thanks Peter, any other comments or are you happy with merging this patch as-is?

  reply	other threads:[~2020-03-17 21:35 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-11  1:01 [PATCH v2] sched/cpuset: distribute tasks within affinity masks Josh Don
2020-03-11 14:05 ` Qais Yousef
2020-03-11 14:05   ` Qais Yousef
2020-03-17 19:24   ` Peter Zijlstra
2020-03-17 19:24     ` Peter Zijlstra
2020-03-17 21:35     ` Josh Don [this message]
2020-03-17 21:35       ` Josh Don
2020-03-18 11:34       ` Qais Yousef
2020-03-19 22:45         ` Josh Don
2020-03-19 22:45           ` Josh Don
2020-03-20 11:28           ` Qais Yousef
2020-03-20 11:28             ` Qais Yousef
2020-03-20 12:58 ` [tip: sched/core] sched/core: Distribute " tip-bot2 for Paul Turner

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