linux-kernel - Re: [PATCH v3 1/7] sched/fair: Ignore percpu threads for imbalance pulls

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Date:   Tue, 16 Mar 2021 19:59:19 +0100
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Chandra Sekhar Lingutla <clingutla@...eaurora.org>,
        Valentin Schneider <valentin.schneider@....com>,
        linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Qais Yousef <qais.yousef@....com>,
        Quentin Perret <qperret@...gle.com>,
        Pavan Kondeti <pkondeti@...eaurora.org>,
        Rik van Riel <riel@...riel.com>
Subject: Re: [PATCH v3 1/7] sched/fair: Ignore percpu threads for imbalance
 pulls

Hi Chandra,

On 16/03/2021 17:03, Chandra Sekhar Lingutla wrote:
> Hi Dietmar,
> 
> On 3/16/2021 9:19 PM, Dietmar Eggemann wrote:
>> On 11/03/2021 13:05, Valentin Schneider wrote:
>>> From: Lingutla Chandrasekhar <clingutla@...eaurora.org>

[...]

>>> CPUs 2-3 as Bigs with below scenario:
>>> - CPU0 doing newly_idle balancing
>>> - CPU1 running percpu kworker and RT task (small tasks)
>> What's the role of the small RT task here in the story?
> This is to satisfy 'busiest->nr_running > 1' checks.

Ah, I see. Forgot about this bit of the story, the 'if
(busiest->nr_running > 1)' in load_balance().

[...]