Re: does hibernate to disk try hard enough to free memory?

[Rafael J. Wysocki]

On Wednesday, February 23, 2011, Martin Steigerwald wrote:
> Am Tuesday 22 February 2011 schrieb Rafael J. Wysocki:
> > On Tuesday, February 22, 2011, Martin Steigerwald wrote:
> > > Am Tuesday 22 February 2011 schrieb Rafael J. Wysocki:
> > > > On Tuesday, February 22, 2011, Martin Steigerwald wrote:
> > > > > Hi!
> > > > > 
> > > > > Since Radeon KMS I often have it that my ThinkPad T42 with 2 MiB
> > > > > of RAM is not able to allocate memory for the hibernation image.
> > > > > Before KMS hibernation only very rarely failed for that reason.
> > > > > 
> > > > > Often I run without compositing at all as I believe this might
> > > > > spare some pages as well. But this doesn't always help.
> > > > > 
> > > > > It complains that to less pages could be freed. For example with
> > > > > kernel 2.6.37:
> > > > > 
> > > > > Feb 16 00:15:00 shambhala kernel: PM: Creating hibernation image:
> > > > > Feb 16 00:15:00 shambhala kernel: PM: Need to copy 186577 pages
> > > > > Feb 16 00:15:00 shambhala kernel: PM: Normal pages needed: 114411
> > > > > + 1024, available pages: 112767
> > > > > Feb 16 00:15:00 shambhala kernel: PM: Not enough free memory
> > > > > Feb 16 00:15:00 shambhala kernel: PM: Error -12 creating
> > > > > hibernation image Feb 16 00:15:00 shambhala kernel: Extended
> > > > > CMOS year: 2000 Feb 16 00:15:00 shambhala kernel: ACPI: Waking
> > > > > up from system sleep state S4
> > > > > Feb 16 00:15:00 shambhala kernel: PM: early recover of devices
> > > > > complete after 0.376 msecs
> > > > 
> > > > What's the value in /sys/power/image_size?
> > > 
> > > shambhala:~> cat /sys/power/image_size
> > > 844206080
> > > 
> > > Should I try with less?
> > 
> > Yes, please.  Try with 700000000 for example.
> 
> I replaced dropping by settings image_size to this valua and the ThinkPad 
> hibernated with KMail open. Thus seems to work, but I will test a bit 
> further.
> 
> Where does the higher value previously set come from? Autotuning?

Likely.  The number seems to match at least.

> Is there anything that can be improved with autotuning?

We can lower the ratio of the image size to the total RAM.
Alternatively, we can increase SPARE_PAGES.

> If yes, I can file a bug report.

Yes, please.

> Otherwise I just try to find a good value for image size and be 
> done with it.

It would be helpful if you could determine the greatest image size working
for you.

Thanks,
Rafael
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