Re: Memory leak makes 'Blast the Bubbles' problematic.

From: Robert Hancock
Date: Wed Jan 13 2010 - 19:56:22 EST

On 01/13/2010 09:48 AM, greg@xxxxxxxxxxxx wrote:
Hi, hope the week is going well for everyone.

Unless I miss my guess there is some type of leak or other memory
anomaly starting in at least late model 2.6.31.x kernels. I took a
snapshot of the behavior on as well since I knew that would be considered long in the tooth by all the informed
intelligentia who would be looking at this...... :-)

The machine in question is an older Dell desktop machine with a 1.7Ghz
Pentium 4 and 756 megabytes of RAM. My wife uses it to run X and play
her Flash games in Firefox. She started chewing on my rear end about
a month ago complaining that her games were running so slow she
couldn't stand it. Rebooting the machine would restore proper
behavior for a short period of time. She logs in and out of X from
text mode so the issue isn't with X and/or Firefox chewing up all the

I booted up a fresh copy of yesterday morning and dropped all
the caches (/proc/sys/vm/drop_caches). I told my wife to play some
games last night so I could instrument the change. This morning I
dropped all the caches and took another snapshot of memory status and
the impact of whatever is happening seems clear, ie:

total used free shared buffers cached
Mem: 774644 308284 466360 0 19116 270120
-/+ buffers/cache: 19048 755596
Swap: 125368 0 125368

total used free shared buffers cached
Mem: 774644 645648 128996 0 155772 294664
-/+ buffers/cache: 195212 579432
Swap: 125368 0 125368

I did a little bit more investigating and I'm suspicious the behavior
is secondary to updatedb running rather anything secondary to X having
been run.

The 'Before' snapshot was taken from logs the system mails me every
night at midnight. That would have been after my wife spent a few
hours playing her Flash games but before updatedb ran.

The kernel is custom compiled for the machine. I'm including the
.config below along with diffs showing before/after memory consumption
status. I also included a 'ps fax' listing of what was running at the
time I took the snapshots. I'd be happy to grab any additional
instrumentation people feel they might need.

I hope all this is helpful since whatever behavior is being tickled
makes recent kernels problematic on this caliber of hardware. Let
alone the effects on my rear end from my beloved not being able to
play 'Blast the Bubbles' the way she would like.

Let me know if I can provide any additional information.

Best wishes for a pleasant afternoon to everyone.


/proc/meminfo diff: -------------------------------------------------------
--- meminfo.txt Tue Jan 12 11:31:48 2010
+++ - Wed Jan 13 09:25:11 2010
@@ -1,35 +1,35 @@
MemTotal: 774644 kB
-MemFree: 719848 kB
-Buffers: 3124 kB
-Cached: 39832 kB
+MemFree: 128800 kB
+Buffers: 155784 kB
+Cached: 294768 kB
SwapCached: 0 kB
-Active: 15968 kB
-Inactive: 30900 kB
-Active(anon): 3912 kB
+Active: 173152 kB
+Inactive: 281488 kB
+Active(anon): 4088 kB
Inactive(anon): 0 kB
-Active(file): 12056 kB
-Inactive(file): 30900 kB
+Active(file): 169064 kB
+Inactive(file): 281488 kB
Unevictable: 0 kB
Mlocked: 0 kB
SwapTotal: 125368 kB
SwapFree: 125368 kB
-Dirty: 12 kB
+Dirty: 4 kB
Writeback: 0 kB
-AnonPages: 3928 kB
-Mapped: 4172 kB
+AnonPages: 4108 kB
+Mapped: 4260 kB
Shmem: 0 kB
-Slab: 4312 kB
-SReclaimable: 1244 kB
-SUnreclaim: 3068 kB
-KernelStack: 536 kB
-PageTables: 400 kB
+Slab: 187472 kB
+SReclaimable: 184256 kB
+SUnreclaim: 3216 kB
+KernelStack: 592 kB
+PageTables: 444 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 512688 kB
-Committed_AS: 9804 kB
+Committed_AS: 11676 kB
VmallocTotal: 254124 kB
VmallocUsed: 212 kB
VmallocChunk: 247300 kB
-DirectMap4k: 5596 kB
-DirectMap2M: 780288 kB
+DirectMap4k: 40412 kB
+DirectMap2M: 745472 kB

It looks like the system accumulated some more dcache entries, but those should presumably get freed up if the system needs the memory. The output of "vmstat 1" while the slowness is occurring might be more interesting..
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