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

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Date:   Tue, 22 Aug 2017 16:08:52 -0500 (CDT)
From:   Christopher Lameter <cl@...ux.com>
To:     Andi Kleen <ak@...ux.intel.com>
cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Liang, Kan" <kan.liang@...el.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Mel Gorman <mgorman@...e.de>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        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

On Tue, 22 Aug 2017, Andi Kleen wrote:

> We only see it on 4S+ today. But systems are always getting larger,
> so what's a large system today, will be a normal medium scale system
> tomorrow.
>
> BTW we also collected PT traces for the long hang cases, but it was
> hard to find a consistent pattern in them.

Hmmm... Maybe it would be wise to limit the pages autonuma can migrate?

If a page has more than 50 refcounts or so then dont migrate it. I think
high number of refcounts and a high frequewncy of calls are reached in
particular for pages of the c library. Attempting to migrate those does
not make much sense anyways because the load may shift and another
function may become popular. We may end up shifting very difficult to
migrate pages back and forth.