From: Nigel Cunningham <ncunningham@cyclades.com>
Organization: Cyclades Corporation
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Subject: Re: Which is simpler? (Was Re: [Suspend2-devel] Re: [ 00/10] [Suspend2] Modules support.)
Date: Fri, 24 Feb 2006 09:16:15 +1000
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Cc: Pavel Machek <pavel@suse.cz>, Dmitry Torokhov <dtor_core@ameritech.net>,
       Andreas Happe <andreashappe@snikt.net>, linux-kernel@vger.kernel.org,
       Suspend2 Devel List <suspend2-devel@lists.suspend2.net>
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On Friday 24 February 2006 08:37, Rafael J. Wysocki wrote:
> Hi,
>
> On Thursday 23 February 2006 13:17, Pavel Machek wrote:
> > > > Ok, I have no problems with visions.
> > > >
> > > > > I think we should try to get the pagecache stuff right first
> > > > > anyway.
> > > >
> > > > Are you sure it is worth doing? I mean... it only helps on small
> > > > machines, no?
> > > >
> > > > OTOH having it for benchmarks will be nice, and perhaps we could use
> > > > that kind it to speed up boot and similar things...
> > >
> > > Currently some people can't suspend with the mainline code because it
> > > cannot free as much memory as needed on their boxes.  I think we shou=
ld
> > > care for them too.
> >
> > But saving pagecache will not help them *at all*!
> >
> > [Because pagecache is freeable, anyway, so it will be freed. Now... I
> > have seen some problems where free_some_memory did not free enough,
> > and schedule()/retry helped a bit... that probably should be fixed.]
>
> It seems I need to understand correctly what the difference between what
> we do and what Nigel does is.  I thought the Nigel's approach was to save
> some cache pages to disk first and use the memory occupied by them to
> store the image data.  If so, is the page cache involved in that or
> something else?

You're right. The only point I would query is that I'm not sure on terminol=
ogy=20
=2D whether 'page cache' =3D=3D LRU. In case there's any difference, I'll s=
ay that=20
I treat pages on the active and inactive LRU lists separately, saving them =
to=20
disk first and using the memory occupied by them for the atomic copy (with=
=20
the exception, of course, of pages belonging to processes such as userui -=
=20
these are made part of the atomic copy and not overwritten).

Regards,

Nigel

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