Re: [PATCH 2/2 v2] sched/wait: Introduce lock breaker in wake_up_page_bit

From	Christopher Lameter <cl@linux.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/2 v2] sched/wait: Introduce lock breaker in wake_up_page_bit
Date	2017-09-14 18:50 +0200
Message-ID	<upFuV-7wa-1@gated-at.bofh.it> (permalink)
References	(9 earlier) <ujOhC-2Kk-39@gated-at.bofh.it> <ujRfs-4Ns-21@gated-at.bofh.it> <ujRp8-4QC-7@gated-at.bofh.it> <ujRyO-4TP-11@gated-at.bofh.it> <uprV0-7hc-5@gated-at.bofh.it>
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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.

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Re: [PATCH 2/2 v2] sched/wait: Introduce lock breaker in  wake_up_page_bit Tim Chen <tim.c.chen@linux.intel.com> - 2017-09-14 04:20 +0200
  Re: [PATCH 2/2 v2] sched/wait: Introduce lock breaker in wake_up_page_bit Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-14 04:30 +0200
    Re: [PATCH 2/2 v2] sched/wait: Introduce lock breaker in  wake_up_page_bit Tim Chen <tim.c.chen@linux.intel.com> - 2017-09-14 19:00 +0200
      Re: [PATCH 2/2 v2] sched/wait: Introduce lock breaker in wake_up_page_bit Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-14 19:10 +0200
  Re: [PATCH 2/2 v2] sched/wait: Introduce lock breaker in  wake_up_page_bit Christopher Lameter <cl@linux.com> - 2017-09-14 18:50 +0200

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