From: Juri Lelli <juri.lelli@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>,
tglx@linutronix.de, mingo@kernel.org,
linux-kernel@vger.kernel.org, bigeasy@linutronix.de,
qais.yousef@arm.com, swood@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, tj@kernel.org
Subject: Re: [PATCH -v2 15/17] sched: Fix migrate_disable() vs rt/dl balancing
Date: Wed, 7 Oct 2020 07:29:35 +0200 [thread overview]
Message-ID: <20201007052935.GK4352@localhost.localdomain> (raw)
In-Reply-To: <20201006144816.GZ2628@hirez.programming.kicks-ass.net>
On 06/10/20 16:48, Peter Zijlstra wrote:
> On Tue, Oct 06, 2020 at 04:37:04PM +0200, Juri Lelli wrote:
> > On 06/10/20 15:48, Peter Zijlstra wrote:
> > > On Tue, Oct 06, 2020 at 12:20:43PM +0100, Valentin Schneider wrote:
> > > >
> > > > On 05/10/20 15:57, Peter Zijlstra wrote:
> > > > > In order to minimize the interference of migrate_disable() on lower
> > > > > priority tasks, which can be deprived of runtime due to being stuck
> > > > > below a higher priority task. Teach the RT/DL balancers to push away
> > > > > these higher priority tasks when a lower priority task gets selected
> > > > > to run on a freshly demoted CPU (pull).
> >
> > Still digesting the whole lot, but can't we "simply" force push the
> > higest prio (that we preempt to make space for the migrate_disabled
> > lower prio) directly to the cpu that would accept the lower prio that
> > cannot move?
> >
> > Asking because AFAIU we are calling find_lock_rq from push_cpu_stop and
> > that selects the best cpu for the high prio. I'm basically wondering if
> > we could avoid moving, potentially multiple, high prio tasks around to
> > make space for a lower prio task.
>
> The intention was to do as you describe in the first paragraph, and
> isn't pull also using find_lock_rq() to select the 'lowest' priority
> runqueue to move the task to?
>
> That is, both actions should end up at the same 'lowest' prio CPU.
>
OK, right. Think there might still be differences, since successive calls
to find_lock_rq() could select different candidates (after the
introduction of cpumask_..._distribute), but that shouldn't really
matter much (also things might have changed in the meanwhile and we
really have to call find_lock_rq again I guess).
next prev parent reply other threads:[~2020-10-07 5:29 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-05 14:57 [PATCH -v2 00/17] sched: Migrate disable support Peter Zijlstra
2020-10-05 14:57 ` [PATCH -v2 01/17] stop_machine: Add function and caller debug info Peter Zijlstra
2020-10-05 14:57 ` [PATCH -v2 02/17] sched: Fix balance_callback() Peter Zijlstra
2020-10-05 14:57 ` [PATCH -v2 03/17] sched/hotplug: Ensure only per-cpu kthreads run during hotplug Peter Zijlstra
2020-10-06 7:25 ` Peter Zijlstra
2020-10-05 14:57 ` [PATCH -v2 04/17] sched/core: Wait for tasks being pushed away on hotplug Peter Zijlstra
2020-10-05 14:57 ` [PATCH -v2 05/17] workqueue: Manually break affinity " Peter Zijlstra
2020-10-05 16:31 ` Tejun Heo
2020-10-05 14:57 ` [PATCH -v2 06/17] sched/hotplug: Consolidate task migration on CPU unplug Peter Zijlstra
2020-10-05 14:57 ` [PATCH -v2 07/17] sched: Fix hotplug vs CPU bandwidth control Peter Zijlstra
2020-10-06 12:46 ` Vincent Guittot
2020-10-06 13:33 ` Peter Zijlstra
2020-10-09 20:41 ` Dietmar Eggemann
2020-10-12 12:52 ` Peter Zijlstra
2020-10-12 13:18 ` Peter Zijlstra
2020-10-12 14:14 ` Dietmar Eggemann
2020-10-05 14:57 ` [PATCH -v2 08/17] sched: Massage set_cpus_allowed() Peter Zijlstra
2020-10-06 11:20 ` Valentin Schneider
2020-10-05 14:57 ` [PATCH -v2 09/17] sched: Add migrate_disable() Peter Zijlstra
2020-10-06 11:20 ` Valentin Schneider
2020-10-05 14:57 ` [PATCH -v2 10/17] sched: Fix migrate_disable() vs set_cpus_allowed_ptr() Peter Zijlstra
[not found] ` <CH2PR14MB41833F828B4D3BA5A7B6CE7B9A0B0@CH2PR14MB4183.namprd14.prod.outlook.com>
2020-10-12 11:36 ` Peter Zijlstra
[not found] ` <CH2PR14MB4183BF26F02A4AD4F45CADA59A070@CH2PR14MB4183.namprd14.prod.outlook.com>
2020-10-13 13:20 ` Valentin Schneider
2020-10-05 14:57 ` [PATCH -v2 11/17] sched/core: Make migrate disable and CPU hotplug cooperative Peter Zijlstra
2020-10-05 14:57 ` [PATCH -v2 12/17] sched,rt: Use cpumask_any*_distribute() Peter Zijlstra
2020-10-06 14:09 ` Juri Lelli
2020-10-06 14:20 ` Peter Zijlstra
2020-10-06 15:55 ` Qais Yousef
2020-10-07 7:22 ` Peter Zijlstra
2020-10-05 14:57 ` [PATCH -v2 13/17] sched,rt: Use the full cpumask for balancing Peter Zijlstra
2020-10-05 14:57 ` [PATCH -v2 14/17] sched, lockdep: Annotate ->pi_lock recursion Peter Zijlstra
2020-10-05 14:57 ` [PATCH -v2 15/17] sched: Fix migrate_disable() vs rt/dl balancing Peter Zijlstra
2020-10-06 7:59 ` Peter Zijlstra
2020-10-06 13:44 ` Steven Rostedt
2020-10-06 13:50 ` Peter Zijlstra
2020-10-06 11:20 ` Valentin Schneider
2020-10-06 13:48 ` Peter Zijlstra
2020-10-06 14:37 ` Juri Lelli
2020-10-06 14:48 ` Peter Zijlstra
2020-10-07 5:29 ` Juri Lelli [this message]
2020-10-06 16:19 ` Valentin Schneider
2020-10-07 19:22 ` Valentin Schneider
2020-10-07 21:08 ` Peter Zijlstra
2020-10-07 22:32 ` Valentin Schneider
2020-10-08 10:48 ` Sebastian Andrzej Siewior
2020-10-12 9:56 ` Dietmar Eggemann
2020-10-12 11:28 ` Peter Zijlstra
2020-10-12 12:22 ` Dietmar Eggemann
2020-10-05 14:57 ` [PATCH -v2 16/17] sched/proc: Print accurate cpumask vs migrate_disable() Peter Zijlstra
2020-10-05 14:57 ` [PATCH -v2 17/17] sched: Add migrate_disable() tracepoints Peter Zijlstra
2020-10-13 14:01 ` [PATCH 1/2] sched: Deny self-issued __set_cpus_allowed_ptr() when migrate_disable() Valentin Schneider
2020-10-13 14:15 ` Sebastian Andrzej Siewior
2020-10-13 14:21 ` Peter Zijlstra
2020-10-15 9:14 ` Valentin Schneider
2020-10-13 14:22 ` Valentin Schneider
2020-11-11 8:23 ` [tip: sched/core] " tip-bot2 for Valentin Schneider
2020-10-13 14:01 ` [PATCH 2/2] sched: Comment affine_move_task() Valentin Schneider
2020-11-11 8:23 ` [tip: sched/core] " tip-bot2 for Valentin Schneider
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