linux-kernel - Re: [Bug #13058] First hibernation attempt fails

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Date:	Wed, 22 Apr 2009 13:19:43 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	pavel@....cz, torvalds@...ux-foundation.org, jens.axboe@...cle.com,
	alan-jenkins@...fmail.co.uk, linux-kernel@...r.kernel.org,
	kernel-testers@...r.kernel.org
Subject: Re: [Bug #13058] First hibernation attempt fails

On Wed, 22 Apr 2009 22:11:17 +0200
"Rafael J. Wysocki" <rjw@...k.pl> wrote:

> On Wednesday 22 April 2009, Pavel Machek wrote:
> > Hi!
> > 
> > > Of course, this will protect the calling task from getting oom-killed. 
> > > But it doesn't protect other tasks from getting oom-killed due to the
> > > activity of _this_ task.
> > > 
> > > But I think that problem already exists, and that this proposal doesn't
> > > worsen anything, yes?
> > > 
> > > Or is it the case that all other tasks are safely stuck in the freezer
> > > at this time, so they won't be allocating any memory anyway?
> > 
> > That is the idea, yes. ... but we now have more threads that are not
> > freezable... so they may allocate the memory.
> > 
> > Is it non-feasible to free memory without really going and allocating
> > everything?
> 
> The question is whether there is a point.  In principle we can just go and
> allocate as much as we need upfront.  It shouldn't change anything, because
> we resume and suspend devices after creating the image anyway.
> 
> I think we could try to disable the OOM killer before suspend and just
> allocate the memory for the image right before devices are suspended for the
> first time.
> 

It would be nice to do.

shrink_all_memory() is simply trying to do something which page reclaim
doesn't expect to do (free memory when there's already lots of memory
free).  Consequently it doesn't do it very well, and there's a good
risk that changes to core reclaim will accidentally break
shrink_all_memory().  

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