From: Nigel Cunningham <ncunningham@cyclades.com>
Organization: Cyclades Corporation
To: Pavel Machek <pavel@suse.cz>
Subject: Re: Which is simpler? (Was Re: [Suspend2-devel] Re: [ 00/10] [Suspend2] Modules support.)
Date: Thu, 23 Feb 2006 10:39:39 +1000
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Cc: "Rafael J. Wysocki" <rjw@sisk.pl>,
       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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Hi.

On Thursday 23 February 2006 10:33, Pavel Machek wrote:
> Hi!
>
> > > > > > The fact that we use page flags to store some
> > > > > > suspend/resume-related information is a big disadvantage in my
> > > > > > view, and I'd like to get rid of that in the future.  In
> > > > > > principle we could use a bitmap, or rather two of them, to store
> > > > > > the same information independently of the page flags, and if we
> > > > > > use bitmaps for this purpose, we can use them also instead of
> > > > > > PBEs.
> > > > >
> > > > > Well, we "only" use 2 bits... :-).
> > > >
> > > > In my view the problem is this adds constraints that other people
> > > > have to take into account.  Not a good thing if avoidable IMHO.
> > >
> > > Well, I hope that swsusp development will move to userland in future
> > >
> > > :-).
> >
> > I don't get your point. I mean, we're talking about flags that record
> > what pages are going to be in the image, be atomically copied and so on.
> > Are you planning on trying to export the free page information and the
> > like to userspace too, along with atomic copy code?
>
> No, certainly not.
>
> Rafael said something like "being limited is bad, because it makes it
> hard to change in-kernel snapshoting code". My reply was something
> like "I hope people will stop changing in-kernel swsusp code, and hack
> userland instead".
>
> Atomic copy code has to stay with kernel: it needs disabled
> interrupts, access to all the RAM, etc. It screams "kernel code".

Good to know. I was afraid you were losing the plot for a minute there :)

Nigel

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