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Date: Thu, 14 Sep 2017 11:39:53 -0500 (CDT)
From: Christopher Lameter <cl@linux.com>
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To: Tim Chen <tim.c.chen@linux.intel.com>
cc: Linus Torvalds <torvalds@linux-foundation.org>,
        "Liang, Kan" <kan.liang@intel.com>,
        Mel Gorman <mgorman@techsingularity.net>,
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        Johannes Weiner <hannes@cmpxchg.org>, Jan Kara <jack@suse.cz>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
        Davidlohr Bueso <dave@stgolabs.net>, linux-mm <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2 v2] sched/wait: Introduce lock breaker in
 wake_up_page_bit
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On Wed, 13 Sep 2017, Tim Chen wrote:

> Here's what the customer think happened and is willing to tell us.
> They have a parent process that spawns off 10 children per core and
> kicked them to run. The child processes all access a common library.
> We have 384 cores so 3840 child processes running.  When migration occur on
> a page in the common library, the first child that access the page will
> page fault and lock the page, with the other children also page faulting
> quickly and pile up in the page wait list, till the first child is done.

I think we need some way to avoid migration in cases like this. This is
crazy. Page migration was not written to deal with something like this.