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

[Nigel Cunningham <nigel@nigel.suspend2.net>]

Hi.

On Sat, 2007-04-14 at 00:35 +0200, Rafael J. Wysocki wrote:
> On Saturday, 14 April 2007 00:10, Pavel Machek wrote:
> > 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.
> 
> Well, I'm not sure.  First, we don't really know what the value of it should be
> and this alone is a good enough reason for making it tunable, IMHO.  Second, I
> think different systems may need different PAGES_FOR_IO and taking just the
> maximum (even if we learn how much that actually is) seems to be wasteful in
> the vast majority of cases.  Finally, I think it may be possible to speed up
> image saving by increasing PAGES_FOR_IO without playing with the
> image size and we can let the user try it (think of distro kernels that are
> compiled for many different users).

It does vary according to the amount of video memory used for DRM, if I
understand correctly.

Nigel