Re: Userland swsusp failure (mm-related)

[Rafael J. Wysocki]

Hi,

On Tuesday 11 April 2006 23:36, Pavel Machek wrote:
> > > Rafael J. Wysocki wrote:
> > > >>>Well, it looks like we didn't free enough RAM for suspend in this case.
> > > >>>Unfortunately we were below the min watermark for ZONE_NORMAL and
> > > >>>we tried to allocate with GFP_ATOMIC (Nick, shouldn't we fall back to
> > > >>>ZONE_DMA in this case?).
> > > >>>
> > > >>>I think we can safely ignore the watermarks in swsusp, so probably
> > > >>>we can set PF_MEMALLOC for the current task temporarily and reset
> > > >>>it when we have allocated memory.  Pavel, what do you think?
> > > >>
> > > >>Seems little hacky but okay to me.
> > > >>
> > > >>Should not fixing "how much to free" computation to free a bit more be
> > > >>enough to handle this?
> > > > 
> > > > 
> > > > Yes, but in that case we'll leave some memory unused. ;-)
> > > > 
> > > 
> > > Probably doesn't fall back to ZONE_DMA because of lowmem reserve.
> > > Yes, PF_MEMALLOC sounds like it might do what you want. A little
> > > hackish perhaps, but better than putting swsusp special cases
> > > into page_alloc.c.
> > 
> > The appended patch contains the changes I'd like to make.  Pavel, is that
> > acceptable?
> 
> Why is PF_MEMALLOC only neccessary for pagedir allocations, and not
> for normal page allocations, too?

Right, we'll need it untli we finally free the image, so I think it should be
set/reset in disk.c:pm_suspend_disk().

However, there's a problem with this approach wrt the userland suspend, because
we'd have to keep PF_MEMALLOC set accross ioctls and I wouldn't like to do
this.

Well, the alternative solution would be to take the ZONE_DMA's lowmem reserve
into account in our free memory computations.

Greetings,
Rafael
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