linux-kernel - Re: [RFC 0/2] Optimize the idle CPU search

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Message-ID: <839c6cc8-b550-3066-d856-3c8a919cc318@oracle.com>
Date:   Tue, 9 Jul 2019 05:38:10 +0530
From:   Subhra Mazumdar <subhra.mazumdar@...cle.com>
To:     Parth Shah <parth@...ux.ibm.com>, linux-kernel@...r.kernel.org
Cc:     peterz@...radead.org, mingo@...hat.com, vincent.guittot@...aro.org
Subject: Re: [RFC 0/2] Optimize the idle CPU search


On 7/8/19 10:24 AM, Parth Shah wrote:
> When searching for an idle_sibling, scheduler first iterates to search for
> an idle core and then for an idle CPU. By maintaining the idle CPU mask
> while iterating through idle cores, we can mark non-idle CPUs for which
> idle CPU search would not have to iterate through again. This is especially
> true in a moderately load system
>
> Optimize idle CPUs search by marking already found non idle CPUs during
> idle core search. This reduces iteration count when searching for idle
> CPUs, resulting in lower iteration count.
>
I believe this can co-exist with latency-nice? We can derive the 'nr' in
select_idle_cpu from latency-nice and use the new mask to iterate.