linux-kernel - Re: [PATCH v4 2/5] sched/fair: Fix attaching task sched avgs twice when switching to fair or changing task group

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Date:	Wed, 8 Jun 2016 02:16:54 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	Vincent Guittot <vincent.guittot@...aro.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Benjamin Segall <bsegall@...gle.com>,
	Paul Turner <pjt@...gle.com>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Dietmar Eggemann <dietmar.eggemann@....com>
Subject: Re: [PATCH v4 2/5] sched/fair: Fix attaching task sched avgs twice
 when switching to fair or changing task group

On Tue, Jun 07, 2016 at 10:09:14AM +0200, Vincent Guittot wrote:
> >> A much more simple solution would be
> >> to prevent last_update_time to be initialized with this special value.
> >> We can initialize the last_update_time of a sched_entity to 1 as an
> >> example which is easier than these changes.
> >
> > Then at least, we must differentiate CONFIG_FAIR_GROUP_SCHED and
> > !CONFIG_FAIR_GROUP_SCHED. And I am not sure whether this is a simpler
> 
> Why do you want to differentiate ? we already have
> sa->last_update_time = 0; in init_entity_runnable_average. We just
> have to change it by sa->last_update_time = 1;

If !CONFIG_FAIR_GROUP_SCHED, we don't have task_move_group_fair().
If last_update_time != 0, we won't attach it for new task. Correct?