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

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Message-ID: <20190708080836.GW3402@hirez.programming.kicks-ass.net>
Date:   Mon, 8 Jul 2019 10:08:36 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Parth Shah <parth@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org, mingo@...hat.com,
        vincent.guittot@...aro.org, subhra.mazumdar@...cle.com
Subject: Re: [RFC 0/2] Optimize the idle CPU search

On Mon, Jul 08, 2019 at 10:24:30AM +0530, 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.

Have you seen these patches:

  https://lkml.kernel.org/r/20180530142236.667774973@infradead.org

I've meant to get back to that, but never quite had the time :/