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

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Message-ID: <20170818164506.GO28715@tassilo.jf.intel.com>
Date:   Fri, 18 Aug 2017 09:45:06 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
Cc:     Mel Gorman <mgorman@...hsingularity.net>,
        "Liang, Kan" <kan.liang@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...e.hu>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>, Jan Kara <jack@...e.cz>,
        linux-mm <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] sched/wait: Break up long wake list walk

> Still, I don't think this problem is THP specific.  If there is a hot
> regular page getting migrated, we'll also see many threads get
> queued up quickly.  THP may have made the problem worse as migrating
> it takes a longer time, meaning more threads could get queued up.

Also THP probably makes more threads collide because the pages are larger.
But still it can all happen even without THP.

-Andi