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Subject: Re: [PATCH v3 1/7] sched/fair: Ignore percpu threads for imbalance
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To:     Chandra Sekhar Lingutla <clingutla@codeaurora.org>,
        Valentin Schneider <valentin.schneider@arm.com>,
        linux-kernel@vger.kernel.org
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Morten Rasmussen <morten.rasmussen@arm.com>,
        Qais Yousef <qais.yousef@arm.com>,
        Quentin Perret <qperret@google.com>,
        Pavan Kondeti <pkondeti@codeaurora.org>,
        Rik van Riel <riel@surriel.com>
References: <20210311120527.167870-1-valentin.schneider@arm.com>
 <20210311120527.167870-2-valentin.schneider@arm.com>
 <bdea6c4f-262b-c3cb-637e-d4896e688dd3@arm.com>
 <e113aa70-c26b-c43f-a113-5a3b66793e46@codeaurora.org>
From:   Dietmar Eggemann <dietmar.eggemann@arm.com>
Message-ID: <bdf93696-f863-9029-860f-771432d5ec22@arm.com>
Date:   Tue, 16 Mar 2021 19:59:19 +0100
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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@codeaurora.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().

[...]