Re: Userland swsusp failure (mm-related)

[Rafael J. Wysocki]

Hi,

On Wednesday 12 April 2006 00:10, Rafael J. Wysocki wrote:
> 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.

OK, the appended patch subtracts each zone's lowmem reserve for ZONE_NORMAL
from the number of free pages because we are going to allocate from the normal
zone and won't be able to use the lowmem reserves.

Please have a look.

Greetings,
Rafael

---
 kernel/power/swsusp.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletion(-)

Index: linux-2.6.17-rc1-mm2/kernel/power/swsusp.c
===================================================================
--- linux-2.6.17-rc1-mm2.orig/kernel/power/swsusp.c	2006-04-12 07:09:20.000000000 +0200
+++ linux-2.6.17-rc1-mm2/kernel/power/swsusp.c	2006-04-12 07:11:09.000000000 +0200
@@ -192,8 +192,10 @@ int swsusp_shrink_memory(void)
 			PAGES_FOR_IO;
 		tmp = size;
 		for_each_zone (zone)
-			if (!is_highmem(zone))
+			if (!is_highmem(zone) && zone->present_pages > 0) {
 				tmp -= zone->free_pages;
+				tmp += zone->lowmem_reserve[ZONE_NORMAL];
+			}
 		if (tmp > 0) {
 			tmp = shrink_all_memory(SHRINK_BITE);
 			if (!tmp)
-
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