linux-kernel - Re: [PATCH 5/6] PM/Hibernate: Do not release preallocated memory unnecessarily (rev. 2)

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Message-ID: <20090515131115.GC1976@elf.ucw.cz>
Date:	Fri, 15 May 2009 15:11:16 +0200
From:	Pavel Machek <pavel@....cz>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
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>,
	Nigel Cunningham <nigel@...onice.net>,
	David Rientjes <rientjes@...gle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH 5/6] PM/Hibernate: Do not release preallocated memory
	unnecessarily (rev. 2)

On Thu 2009-05-14 19:52:20, Rafael J. Wysocki wrote:
> On Thursday 14 May 2009, Pavel Machek wrote:
> > Hi!
> > 
> > > Since the hibernation code is now going to use allocations of memory
> > > to make enough room for the image, it can also use the page frames
> > > allocated at this stage as image page frames.  The low-level
> > > hibernation code needs to be rearranged for this purpose, but it
> > > allows us to avoid freeing a great number of pages and allocating
> > > these same pages once again later, so it generally is worth doing.
> > > 
> > > [rev. 2: Take highmem into account correctly.]
> > 
> > I don't get it. What is advantage of this patch? It makes the code
> > more complex... Is it supposed to be faster?
> 
> Yes, in some test cases it is reported to be faster (along with [4/6],
> actually).
> 
> Besides, we'd like to get rid of shrink_all_memory() eventually and it is a
> step in this direction.

Ok, but maybe we should wait with applying this until we have patches
that actually get us rid of shrink_all_memory? Maybe it will not be
feasible for speed reasons after all, or something...
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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