linux-kernel - Re: [PATCH 1/2 v2] sched/wait: Break up long wake list walk

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Message-ID: <alpine.DEB.2.20.1708251243270.6323@nuc-kabylake>
Date:   Fri, 25 Aug 2017 12:46:12 -0500 (CDT)
From:   Christopher Lameter <cl@...ux.com>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...e.hu>, Andi Kleen <ak@...ux.intel.com>,
        Kan Liang <kan.liang@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>, Jan Kara <jack@...e.cz>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Davidlohr Bueso <dave@...olabs.net>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2 v2] sched/wait: Break up long wake list walk

On Fri, 25 Aug 2017, Tim Chen wrote:

> for a long time.  It is a result of the numa balancing migration of hot
> pages that are shared by many threads.

I think that would also call for some work to limit numa balacing of hot
shared pages. The cache lines of hot pages are likely in present the low
level processor caches anyways so moving them would not cause a
performance benefit. Limiting the migration there could stop wasting a lot
of effort.