linux-kernel - Re: [PATCH v2 6/8] sched/fair: use load instead of runnable load

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Message-ID: <20190806160743.GW2332@hirez.programming.kicks-ass.net>
Date:   Tue, 6 Aug 2019 18:07:43 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     linux-kernel@...r.kernel.org, mingo@...hat.com, pauld@...hat.com,
        valentin.schneider@....com, srikar@...ux.vnet.ibm.com,
        quentin.perret@....com, dietmar.eggemann@....com,
        Morten.Rasmussen@....com
Subject: Re: [PATCH v2 6/8] sched/fair: use load instead of runnable load

On Thu, Aug 01, 2019 at 04:40:22PM +0200, Vincent Guittot wrote:
> runnable load has been introduced to take into account the case
> where blocked load biases the load balance decision which was selecting
> underutilized group with huge blocked load whereas other groups were
> overloaded.
> 
> The load is now only used when groups are overloaded. In this case,
> it's worth being conservative and taking into account the sleeping
> tasks that might wakeup on the cpu.

This one scares me a little. I have the feeling I'm missing/forgetting
something.

Also; while the regular load-balance (find-busiest) stuff is now all
aware of idle, this change also impacts wake_affine and find_idlest, and
they've not changed.