linux-kernel - Re: [RFC][PATCH 4/5] PM/Hibernate: Rework shrinking of memory

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Message-Id: <200905072200.30777.rjw@sisk.pl>
Date:	Thu, 7 May 2009 22:00:29 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	nigel@...onice.net
Cc:	pm list <linux-pm@...ts.linux-foundation.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, Pavel Machek <pavel@....cz>
Subject: Re: [RFC][PATCH 4/5] PM/Hibernate: Rework shrinking of memory

On Thursday 07 May 2009, Rafael J. Wysocki wrote:
> On Thursday 07 May 2009, Nigel Cunningham wrote:
> > Hi.
> 
> Hi,
> 
> > On Thu, 2009-05-07 at 00:44 +0200, Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rjw@...k.pl>
> > > 
> > > Rework swsusp_shrink_memory() so that it calls shrink_all_memory()
> > > just once to make some room for the image and then allocates memory
> > > to apply more pressure to the memory management subsystem, if
> > > necessary.
> > > 
> > > Unfortunately, we don't seem to be able to drop shrink_all_memory()
> > > entirely just yet, because that would lead to huge performance
> > > regressions in some test cases.
> > 
> > I know it doesn't fit with your current way of doing things, but have
> > you considered trying larger order allocations as a means of getting
> > memory freed?
> 
> Actually, I was thinking about that.  What's your experience with this
> approach?
> 
> > I have code in tuxonice_prepare_image.c (look for extra_pages_allocated) that
> > might be helpful for this purpose.
> 
> OK, thanks.  I'll have a look at it.

I have tried it, but the results are even worse than with 0-order allocations
only.

So far, I have got the best results with shrink_all_memory() called once and
followed by allocating as much memory as we want to be free using 0-order
allocations.  Like in this patch. :-)

Thanks,
Rafael
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