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From: Johannes Weiner <hannes@cmpxchg.org>
To: Chengming Zhou <zhouchengming@bytedance.com>
Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
	vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
	rostedt@goodmis.org, linux-kernel@vger.kernel.org,
	songmuchun@bytedance.com
Subject: Re: [PATCH v2 4/4] psi: Optimize task switch inside shared cgroups
Date: Wed, 3 Mar 2021 09:57:43 -0500	[thread overview]
Message-ID: <YD+j56JtFTfOjNjt@cmpxchg.org> (raw)
In-Reply-To: <20210303034659.91735-5-zhouchengming@bytedance.com>

On Wed, Mar 03, 2021 at 11:46:59AM +0800, Chengming Zhou wrote:
> The commit 36b238d57172 ("psi: Optimize switching tasks inside shared
> cgroups") only update cgroups whose state actually changes during a
> task switch only in task preempt case, not in task sleep case.
> 
> We actually don't need to clear and set TSK_ONCPU state for common cgroups
> of next and prev task in sleep case, that can save many psi_group_change
> especially when most activity comes from one leaf cgroup.
> 
> sleep before:
> psi_dequeue()
>   while ((group = iterate_groups(prev)))  # all ancestors
>     psi_group_change(prev, .clear=TSK_RUNNING|TSK_ONCPU)
> psi_task_switch()
>   while ((group = iterate_groups(next)))  # all ancestors
>     psi_group_change(next, .set=TSK_ONCPU)
> 
> sleep after:
> psi_dequeue()
>   nop
> psi_task_switch()
>   while ((group = iterate_groups(next)))  # until (prev & next)
>     psi_group_change(next, .set=TSK_ONCPU)
>   while ((group = iterate_groups(prev)))  # all ancestors
>     psi_group_change(prev, .clear=common?TSK_RUNNING:TSK_RUNNING|TSK_ONCPU)
> 
> When a voluntary sleep switches to another task, we remove one call of
> psi_group_change() for every common cgroup ancestor of the two tasks.
> 
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

  reply	other threads:[~2021-03-03 18:40 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-03  3:46 [PATCH v2 0/4] psi: Add PSI_CPU_FULL state and some code optimization Chengming Zhou
2021-03-03  3:46 ` [PATCH v2 1/4] psi: Add PSI_CPU_FULL state Chengming Zhou
2021-03-04  9:09   ` [tip: sched/core] " tip-bot2 for Chengming Zhou
2021-03-06 11:42   ` tip-bot2 for Chengming Zhou
2021-03-03  3:46 ` [PATCH v2 2/4] psi: Use ONCPU state tracking machinery to detect reclaim Chengming Zhou
2021-03-03 14:56   ` Johannes Weiner
2021-03-03 15:52   ` Peter Zijlstra
2021-03-04  9:09   ` [tip: sched/core] " tip-bot2 for Chengming Zhou
2021-03-06 11:42   ` tip-bot2 for Chengming Zhou
2021-03-03  3:46 ` [PATCH v2 3/4] psi: pressure states are unlikely Chengming Zhou
2021-03-04  9:09   ` [tip: sched/core] psi: Pressure " tip-bot2 for Johannes Weiner
2021-03-06 11:42   ` tip-bot2 for Johannes Weiner
2021-03-03  3:46 ` [PATCH v2 4/4] psi: Optimize task switch inside shared cgroups Chengming Zhou
2021-03-03 14:57   ` Johannes Weiner [this message]
2021-03-03 15:53   ` Peter Zijlstra
2021-03-03 16:01     ` [External] " Muchun Song
2021-03-04  9:09   ` [tip: sched/core] " tip-bot2 for Chengming Zhou
2021-03-06 11:42   ` tip-bot2 for Chengming Zhou
2021-03-03 14:59 ` [PATCH v2 0/4] psi: Add PSI_CPU_FULL state and some code optimization Johannes Weiner
2021-03-03 15:32   ` Peter Zijlstra
2021-03-03 16:05     ` Peter Zijlstra
2021-03-03 19:38       ` Johannes Weiner
2021-03-04  0:14       ` [External] " Chengming Zhou

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