linux-kernel - Re: [PATCH 0/4] Reduce scanning of runqueues in select_idle

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Message-ID: <20201209143748.GP3371@techsingularity.net>
Date:   Wed, 9 Dec 2020 14:37:48 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Peter Ziljstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Aubrey Li <aubrey.li@...ux.intel.com>,
        Barry Song <song.bao.hua@...ilicon.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Linux-ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 0/4] Reduce scanning of runqueues in select_idle_sibling

On Tue, Dec 08, 2020 at 03:34:57PM +0000, Mel Gorman wrote:
> Changelog since v1
> o Drop single-pass patch						(vincent)
> o Scope variables used for SIS_AVG_CPU					(dietmar)
> o Remove redundant assignment						(dietmar
> 
> This reduces the amount of runqueue scanning in select_idle_sibling in
> the worst case.
> 
> Patch 1 removes SIS_AVG_CPU because it's unused.
> 
> Patch 2 moves all SIS_PROP-related calculations under SIS_PROP
> 
> Patch 3 improves the hit rate of p->recent_used_cpu to reduce the amount
> 	of scanning. It should be relatively uncontroversial
> 
> Patch 4 returns an idle candidate if one is found while scanning for a
> 	free core.
> 

Any other objections to the series? Vincent marked 1, 3 and 4 as
reviewed. While patch 2 had some mild cosmetic concerns, I think the
version and how it treats SIS_PROP is fine as it is to keep it
functionally equivalent to !SIS_PROP and without adding too many
SIS_PROP checks.

-- 
Mel Gorman
SUSE Labs