From: Peter Zijlstra <peterz@infradead.org>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Yuyang Du <yuyang.du@intel.com>, 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 3/4] sched,cgroup: Fix cpu_cgroup_fork()
Date: Fri, 17 Jun 2016 16:06:06 +0200 [thread overview]
Message-ID: <20160617140606.GR30154@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <CAKfTPtAuh2=V5PXFc0jL7m1FphUAM-O0P=3wya7NYXLF0JVtcw@mail.gmail.com>
On Fri, Jun 17, 2016 at 03:58:37PM +0200, Vincent Guittot wrote:
> On 17 June 2016 at 14:01, Peter Zijlstra <peterz@infradead.org> wrote:
> > From: Vincent Guittot <vincent.guittot@linaro.org>
> >
> > A new fair task is detached and attached from/to task_group with:
> >
> > cgroup_post_fork()
> > ss->fork(child) := cpu_cgroup_fork()
> > sched_move_task()
> > task_move_group_fair()
> >
> > Which is wrong, because at this point in fork() the task isn't fully
> > initialized and it cannot 'move' to another group, because its not
> > attached to any group as yet.
> >
> > In fact, cpu_cgroup_fork needs a small part of sched_move_task so we
> > can just call this small part directly instead sched_move_task. And
> > the task doesn't really migrate because it is not yet attached so we
> > need the sequence:
> >
> > do_fork()
> > sched_fork()
> > __set_task_cpu()
> >
> > cgroup_post_fork()
> > set_task_rq() # set task group and runqueue
> >
> > wake_up_new_task()
> > select_task_rq() can select a new cpu
> > __set_task_cpu
> > post_init_entity_util_avg
> > attach_task_cfs_rq()
> > activate_task
> > enqueue_task
> >
> > This patch makes that happen.
> >
>
> With this patch and patch 1, the fork sequence looks correct in my test
>
> > Maybe-Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
>
> You can remove the Maybe if you want
Thanks!
next prev parent reply other threads:[~2016-06-17 14:06 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-17 12:01 [PATCH 0/4] sched/fair: Fix PELT wobblies Peter Zijlstra
2016-06-17 12:01 ` [PATCH 1/4] sched: Optimize fork() paths Peter Zijlstra
2016-06-17 12:01 ` [PATCH 2/4] sched/fair: Fix PELT integrity for new groups Peter Zijlstra
2016-06-17 13:51 ` Vincent Guittot
2016-06-17 12:01 ` [PATCH 3/4] sched,cgroup: Fix cpu_cgroup_fork() Peter Zijlstra
2016-06-17 13:58 ` Vincent Guittot
2016-06-17 14:06 ` Peter Zijlstra [this message]
2016-06-17 12:01 ` [PATCH 4/4] sched,fair: Fix PELT integrity for new tasks Peter Zijlstra
2016-06-17 14:09 ` Vincent Guittot
2016-06-17 14:28 ` Peter Zijlstra
2016-06-17 16:02 ` Peter Zijlstra
2016-06-17 16:14 ` Vincent Guittot
2016-06-17 16:18 ` Peter Zijlstra
2016-06-19 22:55 ` Yuyang Du
2016-06-20 9:23 ` Vincent Guittot
2016-06-20 9:52 ` Peter Zijlstra
2016-06-20 10:07 ` Vincent Guittot
2016-06-21 11:43 ` Peter Zijlstra
2016-06-21 12:36 ` Vincent Guittot
2016-06-21 12:47 ` Peter Zijlstra
2016-06-21 12:56 ` Vincent Guittot
2016-06-20 11:35 ` Dietmar Eggemann
2016-06-20 12:35 ` Vincent Guittot
2016-06-20 14:49 ` Dietmar Eggemann
2016-06-21 8:41 ` Peter Zijlstra
2016-06-21 4:51 ` Yuyang Du
2016-06-24 13:03 ` Peter Zijlstra
2016-08-09 23:19 ` Yuyang Du
2016-06-21 13:17 ` Peter Zijlstra
2016-06-21 13:29 ` Vincent Guittot
2016-06-22 11:46 ` Peter Zijlstra
2016-06-23 15:35 ` Dietmar Eggemann
2016-06-23 17:15 ` Peter Zijlstra
2016-06-20 14:27 ` Peter Zijlstra
2016-06-23 11:19 ` Peter Zijlstra
2016-08-01 7:30 ` Wanpeng Li
2016-08-01 9:31 ` Mike Galbraith
2016-08-01 9:56 ` Wanpeng Li
2016-08-01 11:52 ` Mike Galbraith
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