linux-kernel - Re: s2disk hang update

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Message-Id: <201002172058.04043.rjw@sisk.pl>
Date:	Wed, 17 Feb 2010 20:58:03 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Alan Jenkins <sourcejedi.lkml@...glemail.com>
Cc:	Mel Gorman <mel@....ul.ie>, hugh.dickins@...cali.co.uk,
	Pavel Machek <pavel@....cz>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	"linux-kernel" <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>
Subject: Re: s2disk hang update

On Wednesday 17 February 2010, Alan Jenkins wrote:
> On 2/16/10, Rafael J. Wysocki <rjw@...k.pl> wrote:
> > On Tuesday 16 February 2010, Alan Jenkins wrote:
> >> On 2/16/10, Alan Jenkins <sourcejedi.lkml@...glemail.com> wrote:
> >> > On 2/15/10, Rafael J. Wysocki <rjw@...k.pl> wrote:
> >> >> On Tuesday 09 February 2010, Alan Jenkins wrote:
> >> >>> Perhaps I spoke too soon.  I see the same hang if I run too many
> >> >>> applications.  The first hibernation fails with "not enough swap" as
> >> >>> expected, but the second or third attempt hangs (with the same
> >> >>> backtrace
> >> >>> as before).
> >> >>>
> >> >>> The patch definitely helps though.  Without the patch, I see a hang
> >> >>> the
> >> >>> first time I try to hibernate with too many applications running.
> >> >>
> >> >> Well, I have an idea.
> >> >>
> >> >> Can you try to apply the appended patch in addition and see if that
> >> >> helps?
> >> >>
> >> >> Rafael
> >> >
> >> > It doesn't seem to help.
> >>
> >> To be clear: It doesn't stop the hang when I hibernate with too many
> >> applications.
> >>
> >> It does stop the same hang in a different case though.
> >>
> >> 1. boot with init=/bin/bash
> >> 2. run s2disk
> >> 3. cancel the s2disk
> >> 4. repeat steps 2&3
> >>
> >> With the patch, I can run 10s of iterations, with no hang.
> >> Without the patch, it soon hangs, (in disable_nonboot_cpus(), as always).
> >>
> >> That's what happens on 2.6.33-rc7.  On 2.6.30, there is no problem.
> >> On 2.6.31 and 2.6.32 I don't get a hang, but dmesg shows an allocation
> >> failure after a couple of iterations ("kthreadd: page allocation
> >> failure. order:1, mode:0xd0").  It looks like it might be the same
> >> stop_machine thread allocation failure that causes the hang.
> >
> > Have you tested it alone or on top of the previous one?  If you've tested it
> > alone, please apply the appended one in addition to it and retest.
> >
> > Rafael
> 
> I did test with both patches applied together -
> 
> 1. [Update] MM / PM: Force GFP_NOIO during suspend/hibernation and resume
> 2. "reducing the number of pages that we're going to keep preallocated by 20%"

In that case you can try to reduce the number of preallocated pages even more,
ie. change "/ 5" to "/ 2" (for example) in the second patch.

Rafael
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