linux-kernel - [RFC PATCH 0/4] Reduce worst-case scanning of runqueues in select_idle

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20201207091516.24683-1-mgorman@techsingularity.net>
Date:   Mon,  7 Dec 2020 09:15:12 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Aubrey Li <aubrey.li@...ux.intel.com>,
        Barry Song <song.bao.hua@...ilicon.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Ziljstra <peterz@...radead.org>,
        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>,
        Mel Gorman <mgorman@...hsingularity.net>
Subject: [RFC PATCH 0/4] Reduce worst-case scanning of runqueues in select_idle_sibling

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