Re: [RFD] swsusp problem: Drivers allocate much memory during suspend (was: Re: 2.6.21-rc5: swsusp: Not enough free memory)

[Pavel Machek <pavel@ucw.cz>]

Hi!

> > > Well, it looks like someone allocated about 6000 pages after we had freed
> > > enough memory for suspending.
> > 
> > We have a tunable allowance in Suspend2 for this, because fglrx
> > allocates a lot of pages in its suspend routine if DRI is enabled. I
> > think some other drivers do too, but fglrx is the main one I know.
> 
> I wasn't aware of that, thanks for the information.
> 
> I think this means we'll probably need to add a tunable, similar to image_size,
> that will allow the users to specify how much spare memory they want to reserve
> for suspending (instead of the constant PAGES_FOR_IO).  IMO we can call it
> 'spare_memory'.

Just increase PAGES_FOR_IO. This should not be tunable.

> Still, this doesn't look like a real solution, because it would require the
> users affected by this problem to experiment with suspending in order to
> figure out how much spare memory they will need.

Exactly.

> IMO to really fix the problem, we should let the drivers that need much memory
> for suspending allocate it _before_ the memory shrinker is called.  For this
> purpose we can use notifiers that will be called before we start the shrinking
> of memory.  Namely, if a driver needs to allocate substantial amount
> of memory

Yes please. Using that notifier without leaking the memory will be
"interesting" but if someone needs so much memory during suspend, let
them eat their own complexity.

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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