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From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Pavel Machek <pavel@ucw.cz>
Subject: Re: [PATCH 5/6] PM/Hibernate: Do not release preallocated memory unnecessarily (rev. 2)
Date: Thu, 14 May 2009 19:52:20 +0200
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Cc: pm list <linux-pm@lists.linux-foundation.org>,
       Wu Fengguang <fengguang.wu@intel.com>,
       Andrew Morton <akpm@linux-foundation.org>,
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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.

Thanks,
Rafael