linux-kernel - Re: [PATCH 1/2] sched/fair: optimization of update_blocked

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Date:   Fri, 8 Feb 2019 17:51:00 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>,
        Sargun Dhillon <sargun@...gun.me>,
        Xie XiuQi <xiexiuqi@...wei.com>, xiezhipeng1@...wei.com,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 1/2] sched/fair: optimization of update_blocked_averages()

On Fri, Feb 08, 2019 at 05:47:53PM +0100, Vincent Guittot wrote:
> On Fri, 8 Feb 2019 at 17:30, Peter Zijlstra <peterz@...radead.org> wrote:
> > On Fri, Feb 08, 2019 at 04:44:53PM +0100, Vincent Guittot wrote:
> > > On Fri, 8 Feb 2019 at 16:40, Peter Zijlstra <peterz@...radead.org> wrote:

> > > Good point but this should go after the for_each_sched_entity() loop
> >
> > Indeed, but that loop does enqueue and can throttle again, should that
> > not also get that additional list_add_leaf_cfs_rq() loop we added to
> > enqueue_task_fair() to finish the add?
> 
> Initially, I added this additional loop but finally removed it because
> I didn't hit it during my tests. IIRC, we are protected by
> throttle_count in such case, which is not the case when we enqueue a
> task

Fair enough; and the to-be added assert will notify us if we got that
wrong :-)

I'll add the assert, no need to re-send.

Thanks!