linux-kernel - Re: [PATCH 3/3] sched: limit cpu search and rotate search window for scalability

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Message-ID: <bdea99d5-a0cd-1f60-e58a-0cc8e4dd6318@oracle.com>
Date:   Tue, 24 Apr 2018 15:48:41 -0700
From:   Subhra Mazumdar <subhra.mazumdar@...cle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, mingo@...hat.com,
        daniel.lezcano@...aro.org, steven.sistare@...cle.com,
        dhaval.giani@...cle.com, rohit.k.jain@...cle.com
Subject: Re: [PATCH 3/3] sched: limit cpu search and rotate search window for
 scalability



On 04/24/2018 05:48 AM, Peter Zijlstra wrote:
> On Mon, Apr 23, 2018 at 05:41:16PM -0700, subhra mazumdar wrote:
>> Lower the lower limit of idle cpu search in select_idle_cpu() and also put
>> an upper limit. This helps in scalability of the search by restricting the
>> search window. Also rotating the search window with help of next_cpu
>> ensures any idle cpu is eventually found in case of high load.
> So this patch does 2 (possibly 3) things, that's not good.
During testing I did try with first only restricting the search window.
That alone wasn't enough to give the full benefit, rotating search window
was essential to get best results. I will break this up in next version.