linux-kernel - Re: [PATCH v3 5/5] sched/fair: Fix use of find_idlest

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Message-ID: <20170831135459.ilgktukuchws2kny@destiny>
Date:   Thu, 31 Aug 2017 09:54:59 -0400
From:   Josef Bacik <josef@...icpanda.com>
To:     Brendan Jackman <brendan.jackman@....com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Josef Bacik <josef@...icpanda.com>,
        Morten Rasmussen <morten.rasmussen@....com>
Subject: Re: [PATCH v3 5/5] sched/fair: Fix use of find_idlest_group when
 local group is idlest

On Thu, Aug 31, 2017 at 12:58:02PM +0100, Brendan Jackman wrote:
> find_idlest_group returns NULL when the local group is idlest. The
> caller then continues the find_idlest_group search at a lower level
> of the current CPU's sched_domain hierarchy. find_idlest_group_cpu is
> not consulted and, crucially, @new_cpu is not updated. This means the
> search is pointless and we return @prev_cpu from select_task_rq_fair.
> 
> This is fixed by initialising @new_cpu to @cpu instead of
> @prev_cpu.
> 

Reviewed-by: Josef Bacik <jbacik@...com>

Thanks,

Josef