Message-Id: <201102222159.58546.Martin@lichtvoll.de>
Date:	Tue, 22 Feb 2011 21:59:52 +0100
From:	Martin Steigerwald <Martin@...htvoll.de>
To:	Linux PM mailing list <linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: does hibernate to disk try hard enough to free memory?

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@...mbhala:~> cat /proc/version
Linux version 2.6.37-tp42-rtime-00004-g9eb63ce (martin@...mbhala) (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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