From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Pavel Machek <pavel@suse.cz>
Subject: Re: Which is simpler? (Was Re: [Suspend2-devel] Re: [ 00/10] [Suspend2] Modules support.)
Date: Tue, 21 Feb 2006 21:36:11 +0100
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Cc: Andy Lutomirski <luto@myrealbox.com>, Matthias Hensler <matthias@wspse.de>,
       kernel list <linux-kernel@vger.kernel.org>,
       Nigel Cunningham <nigel@suspend2.net>, Sebastian Kgler <sebas@kde.org>
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Hi,

On Tuesday 21 February 2006 12:33, Pavel Machek wrote:
> On Po 20-02-06 20:32:25, Andy Lutomirski wrote:
> > Matthias Hensler wrote:
> > >On Mon, Feb 20, 2006 at 01:53:33AM +0100, Pavel Machek wrote:
> > >
> > >>Only feature I can't do is "save whole pagecache"... and 14000 lines
> > >>of code for _that_ is a bit too much. I could probably patch my kernel
> > >>to dump pagecache to userspace, but I do not think it is worth the
> > >>effort.
> > >
> > >
> > >I do not think that Suspend 2 needs 14000 lines for that, the core is
> > >much smaller. But besides, _not_ saving the pagecache is a really _bad_
> > >idea. I expect to have my system back after resume, in the same state I
> > >had left it prior to suspend. I really do not like it how it is done by
> > >Windows, it is just ugly to have a slowly responding system after
> > >resume, because all caches and buffers are gone.
> > >
> > >I can only speak for myself, but I want to work with my system from the
> > >moment my desktop is back.
> > 
> > I Am Not A VM Hacker, but:
> > 
> > What's the point of saving pagecache during suspend?  This seems like a 
> > total waste.  Why don't we save a list of pages in pagecache to disk,
> > then, after resume, prefetch them all back in.  This will slow down 
> > resume (extra seeks, minimized if we sort the list, and inability
> > to compress these pages), but it will speed up suspend, and it sounds
> > a lot simpler.  There's already a patch to add swap prefetching, and 
> > this can't be much more complicated.
> 
> I'd actually love to see this implemented. It would be useful for
> suspend-to-disk (obviously), but also for benchmarks.

Actually I've been thinking of something similar for some time,
so perhaps we should add this to the todolist somewhere? ;-)

Rafael
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