does hibernate to disk try hard enough to free memory?

From: Martin Steigerwald
Date: Tue Feb 22 2011 - 16:00:14 EST

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

This was with:

martin@shambhala:~> cat /proc/version
Linux version 2.6.37-tp42-rtime-00004-g9eb63ce (martin@shambhala) (gcc
version 4.4.5 (Debian 4.4.5-8) ) #1 PREEMPT Thu Jan 13 10:59:19 CET 2011

(vanilla with some recursive mtime patches from Jan Kara, but I had this
with unpatched vanilla 2.6.37/ 2.6.36 and 2.6.33 as well)

Often it is just a free thousand pages that are missing.

With TuxOnIce - my current kernels are not having TuxOnIce compiled in -
there was a specific mention of to less lowmem pages.

A usual situation where it might fail is:

shambhala:~> cat /proc/meminfo
MemTotal: 2073668 kB
MemFree: 257536 kB
Buffers: 26480 kB
Cached: 916328 kB
SwapCached: 27044 kB
Active: 795012 kB
Inactive: 660528 kB
Active(anon): 289056 kB
Inactive(anon): 230280 kB
Active(file): 505956 kB
Inactive(file): 430248 kB
Unevictable: 0 kB
Mlocked: 0 kB
HighTotal: 1187144 kB
HighFree: 158040 kB
LowTotal: 886524 kB
LowFree: 99496 kB
SwapTotal: 4000180 kB
SwapFree: 3797720 kB
Dirty: 10064 kB
Writeback: 0 kB
AnonPages: 496044 kB
Mapped: 64192 kB
Shmem: 6604 kB
Slab: 85540 kB
SReclaimable: 34572 kB
SUnreclaim: 50968 kB
KernelStack: 2776 kB
PageTables: 7412 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 5037012 kB
Committed_AS: 1708672 kB
VmallocTotal: 122880 kB
VmallocUsed: 17320 kB
VmallocChunk: 92856 kB
DirectMap4k: 897016 kB
DirectMap4M: 12288 kB


When I stop Akonadi (with SQlite, not MySQL as backend) - after having
closed all other applications of my KDE 4 desktop - hibernation usually
works.

But I also found that

echo 3 >/proc/sys/vm/drop_caches helps.

echo 1 frees some pages:

shambhala:~> echo 1 > /proc/sys/vm/drop_caches
shambhala:~> cat /proc/meminfo
MemTotal: 2073668 kB
MemFree: 1135132 kB
Buffers: 512 kB
Cached: 71544 kB
SwapCached: 27044 kB
Active: 339008 kB
Inactive: 245784 kB
Active(anon): 289060 kB
Inactive(anon): 230280 kB
Active(file): 49948 kB
Inactive(file): 15504 kB
Unevictable: 0 kB
Mlocked: 0 kB
HighTotal: 1187144 kB
HighFree: 697688 kB
LowTotal: 886524 kB
LowFree: 437444 kB
SwapTotal: 4000180 kB
SwapFree: 3797720 kB
Dirty: 444 kB
Writeback: 0 kB
AnonPages: 496048 kB
Mapped: 64228 kB
Shmem: 6604 kB
Slab: 78844 kB
SReclaimable: 27888 kB
SUnreclaim: 50956 kB
KernelStack: 2776 kB
PageTables: 7412 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 5037012 kB
Committed_AS: 1708672 kB
VmallocTotal: 122880 kB
VmallocUsed: 17320 kB
VmallocChunk: 92856 kB
DirectMap4k: 897016 kB
DirectMap4M: 12288 kB

echo 2 even more:

shambhala:~> echo 2 > /proc/sys/vm/drop_caches
shambhala:~> cat /proc/meminfo
MemTotal: 2073668 kB
MemFree: 1209228 kB
Buffers: 1204 kB
Cached: 71536 kB
SwapCached: 27044 kB
Active: 339024 kB
Inactive: 246456 kB
Active(anon): 289064 kB
Inactive(anon): 230280 kB
Active(file): 49960 kB
Inactive(file): 16176 kB
Unevictable: 0 kB
Mlocked: 0 kB
HighTotal: 1187144 kB
HighFree: 697688 kB
LowTotal: 886524 kB
LowFree: 511540 kB
SwapTotal: 4000180 kB
SwapFree: 3797720 kB
Dirty: 380 kB
Writeback: 0 kB
AnonPages: 496052 kB
Mapped: 64228 kB
Shmem: 6604 kB
Slab: 68036 kB
SReclaimable: 17088 kB
SUnreclaim: 50948 kB
KernelStack: 2776 kB
PageTables: 7412 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 5037012 kB
Committed_AS: 1708672 kB
VmallocTotal: 122880 kB
VmallocUsed: 17320 kB
VmallocChunk: 92856 kB
DirectMap4k: 897016 kB
DirectMap4M: 12288 kB

Thus the machine has 500 MB of free lowmem and over 1 GB of free highmem
of 2 GB of total mem and thus surely should be able to hibernate with ease
IMHO. Which it does then too.

After an echo 3 onto drop_caches hibernation for now *always* worked, even
when I left Akregator running - when often with just one open application
the machine would not hibernate.

So if dropping caches *and* dir entries manually helps hibernation going
why doesn't try PM that hard to free pages in order to let the allocation
of the hibernation image be successful?

Are there any other tips? The machine has a whopping 900 MB of caches and
there is a lot of free memory usually so actually I do not get why there
are any memory issues at all that prevent successful hibernation. I guess
that using a 64 bit machine with more memory and without that hysteric
differentiation between lowmem and highmem pages that I never got coming
from the Amiga will help out all those issues, but still I'd like to know
why its failing with 2 GB of RAM of which 1.5 GB are basically fire -
unless I drop caches and dir entries manually.

I will now continue use

echo 3 > /proc/sys/vm/drop_caches

prior to hibernation to check whether it really fixed memory issues during
hibernation.

Ciao,
--
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7

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