From: Vincent Guittot <vincent.guittot@linaro.org>
To: Yuyang Du <yuyang.du@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Mike Galbraith <umgwanakikbuti@gmail.com>,
Benjamin Segall <bsegall@google.com>,
Paul Turner <pjt@google.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Matt Fleming <matt@codeblueprint.co.uk>
Subject: Re: [PATCH v6 1/4] sched/fair: Fix attaching task sched avgs twice when switching to fair or changing task group
Date: Wed, 15 Jun 2016 16:15:29 +0200 [thread overview]
Message-ID: <CAKfTPtDfTKGgQd=ebiKijA0_nBEKzwHL7W_WnMw6AWaVP=TC-g@mail.gmail.com> (raw)
In-Reply-To: <20160615001818.GL8105@intel.com>
On 15 June 2016 at 02:18, Yuyang Du <yuyang.du@intel.com> wrote:
> On Wed, Jun 15, 2016 at 09:46:53AM +0200, Vincent Guittot wrote:
>> I still have concerned with this change of the behavior that attaches
>> the task only when it is enqueued. The load avg of the task will not
>> be decayed between the time we move it into its new group until its
>> enqueue. With this change, a task's load can stay high whereas it has
>> slept for the last couple of seconds.
>
> The task will be updated when it is moved in the detach, so if it stays
> high, it is highly expected to be enqueued soon. But if the task is never
you can't do such assumption because if it's not enqueued soon (keep
in mind that a 10ms sleep will decay the value by 20% from max),
metrics become just wrong. Furthermore, the load metrics of the task
becomes different between a task being moved or the same task staying
on same cfs_rq.
> enqueued, we don't bother the new gruop cfs_rq.
>
> So this is not perfect, and nothing is perfect, but a simple solution.
next prev parent reply other threads:[~2016-06-15 14:15 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-14 22:21 [PATCH v6 0/4] sched/fair: Fix attach and detach sched avgs for task group change and sched class change Yuyang Du
2016-06-14 22:21 ` [PATCH v6 1/4] sched/fair: Fix attaching task sched avgs twice when switching to fair or changing task group Yuyang Du
2016-06-15 7:46 ` Vincent Guittot
2016-06-15 0:18 ` Yuyang Du
2016-06-15 14:15 ` Vincent Guittot [this message]
2016-06-15 15:22 ` Peter Zijlstra
2016-06-16 1:00 ` Yuyang Du
2016-06-16 16:30 ` Vincent Guittot
2016-06-16 17:17 ` Peter Zijlstra
2016-06-16 18:57 ` Vincent Guittot
2016-06-16 18:51 ` Peter Zijlstra
2016-06-16 19:00 ` Vincent Guittot
2016-06-16 20:07 ` Peter Zijlstra
2016-06-16 21:21 ` Vincent Guittot
2016-06-17 2:12 ` Yuyang Du
2016-06-17 12:00 ` Vincent Guittot
2016-06-17 9:48 ` Peter Zijlstra
2016-06-17 11:31 ` Peter Zijlstra
2016-06-14 22:21 ` [PATCH v6 2/4] sched/fair: Move load and util avgs from wake_up_new_task() to sched_fork() Yuyang Du
2016-06-14 22:21 ` [PATCH v6 3/4] sched/fair: Skip detach sched avgs for new task when changing task groups Yuyang Du
2016-06-14 22:21 ` [PATCH v6 4/4] sched/fair: Add inline to detach_entity_load_evg() Yuyang Du
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