From: Peter Zijlstra <peterz@infradead.org>
To: Valentin Schneider <valentin.schneider@arm.com>
Cc: tglx@linutronix.de, mingo@kernel.org,
linux-kernel@vger.kernel.org, bigeasy@linutronix.de,
qais.yousef@arm.com, swood@redhat.com, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
bristot@redhat.com, vincent.donnefort@arm.com
Subject: Re: [PATCH 7/9] sched: Add migrate_disable()
Date: Thu, 24 Sep 2020 14:35:27 +0200 [thread overview]
Message-ID: <20200924123527.GJ2628@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <jhj5z83mlvu.mognet@arm.com>
On Thu, Sep 24, 2020 at 12:53:25PM +0100, Valentin Schneider wrote:
> > @@ -1830,8 +1892,19 @@ static int migration_cpu_stop(void *data
> > */
> > void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask, u32 flags)
> > {
> > - cpumask_copy(&p->cpus_mask, new_mask);
> > - p->nr_cpus_allowed = cpumask_weight(new_mask);
> > + if (flags & SCA_MIGRATE_DISABLE) {
> > + p->cpus_ptr = new_mask;
> > + p->nr_cpus_allowed = 1;
> > + return;
> > + }
> > +
> > + if (flags & SCA_MIGRATE_ENABLE)
> > + p->cpus_ptr = &p->cpus_mask;
>
> There's that check in __set_cpus_allowed_ptr() that new_mask *must* be
> p->cpus_mask when SCA_MIGRATE_ENABLE; that means we could mayhaps shuffle
> that to:
>
> ---
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 7cb13df48366..e0e4e42c5e32 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1892,18 +1892,14 @@ static int migration_cpu_stop(void *data)
> */
> void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask, u32 flags)
> {
> + if (flags & (SCA_MIGRATE_DISABLE | SCA_MIGRATE_ENABLE))
> p->cpus_ptr = new_mask;
> else
> cpumask_copy(&p->cpus_mask, new_mask);
>
> + if (flags & SCA_MIGRATE_DISABLE)
> + p->nr_cpus_allowed = 1;
> + else if (p->cpus_ptr == &p->cpus_mask)
> p->nr_cpus_allowed = cpumask_weight(p->cpus_ptr);
> }
I'm thinking we should let nr_cpus_allowed reflect ->cpus_mask
unconditionally. See these emails:
https://lkml.kernel.org/r/20200923170809.GY1362448@hirez.programming.kicks-ass.net
https://lkml.kernel.org/r/20200924082717.GA1362448@hirez.programming.kicks-ass.net
Basically we want to keep migrate_disable() tasks elegible for
migration/PULL.
But yes, I think that function can be simplified.
next prev parent reply other threads:[~2020-09-24 12:35 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-21 16:35 [PATCH 0/9] sched: Migrate disable support Peter Zijlstra
2020-09-21 16:35 ` [PATCH 1/9] stop_machine: Add function and caller debug info Peter Zijlstra
2020-09-21 16:35 ` [PATCH 2/9] sched: Fix balance_callback() Peter Zijlstra
2020-09-23 14:08 ` Thomas Gleixner
2020-09-21 16:36 ` [PATCH 3/9] sched/hotplug: Ensure only per-cpu kthreads run during hotplug Peter Zijlstra
2020-09-25 16:38 ` Dietmar Eggemann
2020-10-02 14:20 ` Peter Zijlstra
2020-09-21 16:36 ` [PATCH 4/9] sched/core: Wait for tasks being pushed away on hotplug Peter Zijlstra
2020-09-21 16:36 ` [PATCH 5/9] sched/hotplug: Consolidate task migration on CPU unplug Peter Zijlstra
2020-10-01 17:12 ` Vincent Donnefort
2020-10-02 14:17 ` Peter Zijlstra
2020-09-21 16:36 ` [PATCH 6/9] sched: Massage set_cpus_allowed Peter Zijlstra
2020-09-23 14:07 ` Thomas Gleixner
2020-09-21 16:36 ` [PATCH 7/9] sched: Add migrate_disable() Peter Zijlstra
2020-09-21 19:16 ` Thomas Gleixner
2020-09-21 20:42 ` Daniel Bristot de Oliveira
2020-09-23 8:31 ` Thomas Gleixner
2020-09-23 10:51 ` Daniel Bristot de Oliveira
2020-09-23 17:08 ` peterz
2020-09-23 17:54 ` Daniel Bristot de Oliveira
2020-09-23 7:48 ` peterz
2020-09-24 11:53 ` Valentin Schneider
2020-09-24 12:29 ` Peter Zijlstra
2020-09-24 12:33 ` Valentin Schneider
2020-09-24 12:35 ` Peter Zijlstra [this message]
2020-09-25 16:50 ` Sebastian Andrzej Siewior
2020-10-02 14:21 ` Peter Zijlstra
2020-10-02 14:36 ` Sebastian Andrzej Siewior
2020-09-21 16:36 ` [PATCH 8/9] sched: Fix migrate_disable() vs set_cpus_allowed_ptr() Peter Zijlstra
2020-09-24 19:59 ` Valentin Schneider
2020-09-25 8:43 ` Peter Zijlstra
2020-09-25 10:07 ` Valentin Schneider
2020-09-25 9:05 ` Peter Zijlstra
2020-09-25 9:56 ` Peter Zijlstra
2020-09-25 10:09 ` Valentin Schneider
2020-09-21 16:36 ` [PATCH 9/9] sched/core: Make migrate disable and CPU hotplug cooperative Peter Zijlstra
2020-09-25 9:12 ` [PATCH 0/9] sched: Migrate disable support Dietmar Eggemann
2020-09-25 10:10 ` Peter Zijlstra
2020-09-25 11:58 ` Dietmar Eggemann
2020-09-25 12:19 ` Valentin Schneider
2020-09-25 17:49 ` Valentin Schneider
2020-09-29 9:15 ` Dietmar Eggemann
2020-09-25 18:17 ` Sebastian Andrzej Siewior
2020-09-25 19:32 ` Valentin Schneider
2020-10-02 14:30 ` Peter Zijlstra
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