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From:   Mel Gorman <mgorman@techsingularity.net>
To:     LKML <linux-kernel@vger.kernel.org>
Cc:     Aubrey Li <aubrey.li@linux.intel.com>,
        Barry Song <song.bao.hua@hisilicon.com>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Ziljstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Valentin Schneider <valentin.schneider@arm.com>,
        Linux-ARM <linux-arm-kernel@lists.infradead.org>,
        Mel Gorman <mgorman@techsingularity.net>
Subject: [RFC PATCH 0/4] Reduce worst-case scanning of runqueues in select_idle_sibling
Date:   Mon,  7 Dec 2020 09:15:12 +0000
Message-Id: <20201207091516.24683-1-mgorman@techsingularity.net>
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This is a minimal series to reduce 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 improves the hit rate of p->recent_used_cpu to reduce the amount
	of scanning. It should be relatively uncontroversial

Patch 3-4 scans the runqueues in a single pass for select_idle_core()
	and select_idle_cpu() so runqueues are not scanned twice. It's
	a tradeoff because it benefits deep scans but introduces overhead
	for shallow scans.

Even if patch 3-4 is rejected to allow more time for Aubrey's idle cpu mask
approach to stand on its own, patches 1-2 should be fine. The main decision
with patch 4 is whether select_idle_core() should do a full scan when searching
for an idle core, whether it should be throttled in some other fashion or
whether it should be just left alone.

-- 
2.26.2