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From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Dmitry Torokhov <dtor_core@ameritech.net>
Subject: Re: Which is simpler? (Was Re: [Suspend2-devel] Re: [ 00/10] [Suspend2] Modules support.)
Date: Tue, 21 Feb 2006 21:40:56 +0100
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Cc: Nigel Cunningham <ncunningham@cyclades.com>,
       Andreas Happe <andreashappe@snikt.net>, linux-kernel@vger.kernel.org,
       Suspend2 Devel List <suspend2-devel@lists.suspend2.net>
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On Tuesday 21 February 2006 05:19, Dmitry Torokhov wrote:
> On Monday 20 February 2006 21:57, Nigel Cunningham wrote:
> > For the record, my thinking went: swsusp uses n (12?) bytes of meta data for 
> > every page you save, where as using bitmaps makes that much closer to a 
> > constant value (a small variable amount for recording where the image will be 
> > stored in extents). 12 bytes per page is 3MB/1GB. If swsusp was to add 
> > support for multiple swap partitions or writing to files, those requirements 
> > might be closer to 5MB/GB. 
> 
> 5MB/GB amounts to 0.5% overhead, I don't think you should be concerned here.
> Much more important IMHO is that IIRC swsusp requires to be able to free 1/2
> of the physical memory whuch is hard on low memory boxes.

I see another point in using bitmaps: we could avoid modifying page flags
and use bitmaps to store all of the temporary information.  I thought about
it for some time and I think it's doable.

Greetings,
Rafael