Bug 447667 - Memory leak in kernel-2.6.25.3-18.fc9.x86_64
Memory leak in kernel-2.6.25.3-18.fc9.x86_64
Status: CLOSED WONTFIX
Product: Fedora
Classification: Fedora
Component: kernel (Show other bugs)
9
x86_64 Linux
low Severity medium
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Assigned To: Kernel Maintainer List
Fedora Extras Quality Assurance
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Depends On:
Blocks:
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Reported: 2008-05-20 22:35 EDT by Gordon Messmer
Modified: 2009-07-14 11:47 EDT (History)
3 users (show)

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Fixed In Version:
Doc Type: Bug Fix
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Last Closed: 2009-07-14 11:47:42 EDT
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Attachments (Terms of Use)
copy of /proc/meminfo made before reboot (748 bytes, text/plain)
2008-05-20 22:35 EDT, Gordon Messmer
no flags Details
copy of /proc/slabinfo made before reboot (7.63 KB, text/plain)
2008-05-20 22:36 EDT, Gordon Messmer
no flags Details

  None (edit)
Description Gordon Messmer 2008-05-20 22:35:10 EDT
Description of problem:
This morning I noticed that firefox had crashed overnight, and the desktop was
behaving very slow, as if the machine were swapping heavily.  I expected to see
some bloated process in "top"s output, but after sorting the processes by
memory, I saw nothing unusual.  Applications were fairly normal, but there was
very little free memory.

Next, I turned to /proc/meminfo, and it looks like the kernel had allocated
1.4GB of slab!  According to the slabinfo file, there were nearly 7 million
dentry slabs "active" (if I'm reading it correctly).  I don't really understand
the dentry cache, but it seems odd to have 7M dentry caches when I have fewer
than 500k files and directories total on all of the mounted filesystems.

There's nothing odd in the logs except this:

May 20 03:24:44 herald kernel: printk: 37 messages suppressed.

The kernel didn't print any messages in several hours prior to 3:24, and nothing
afterward until I rebooted the system.  Unfortunately, I didn't check "dmesg"
before rebooting. :(

Not much was running overnight: I was logged in to Gnome, Thunderbird and
Firefox were running, and so was Miro.

Version-Release number of selected component (if applicable):
kernel-2.6.25.3-18.fc9.x86_64

How reproducible:
Unknown
Comment 1 Gordon Messmer 2008-05-20 22:35:10 EDT
Created attachment 306202 [details]
copy of /proc/meminfo made before reboot
Comment 2 Gordon Messmer 2008-05-20 22:36:03 EDT
Created attachment 306203 [details]
copy of /proc/slabinfo made before reboot
Comment 3 Dave Jones 2008-05-20 22:45:18 EDT
if you can reproduce this, do this ..

$ free
$ echo 3 > /proc/sys/vm/drop_caches
$ free

that should purge the dentry cache (and other caches).

They should get reclaimed when something needs memory.  This is the first report
I've seen so far of anything suggesting the kernel is leaking slab objects, and
something like a dentry leak would show up real quick.
Comment 4 Gordon Messmer 2008-05-22 11:14:29 EDT
Out of curiosity: what will purging the caches tell us about the problem?

I understand that cache items should be reclaimed when applications need memory.
 I noticed that nearly all of the "Slab" allocated is marked "SReclaimable". 
All the same, something caused Firefox to exit, and allocated a whole lot of
slab in a short amount of time.  I'd wonder if Firefox was at fault, but I'm not
sure how it would cause the kernel to allocate a large amount of memory.

I haven't seen the problem manifest again, yet, but I'm not certain what caused
it in the first place.
Comment 5 Bob Gustafson 2008-06-26 17:45:13 EDT
I don't know if this is related, but I updated to a new kernel (Fed8) and this
kernel is unusable because of a memory leak. I have 3GB and it takes about 10-20
minutes to fill, then I need to reboot.

I went back a kernel using the boot/grub.conf option.

The kernel with a problem is 2.6.25.6-27.fc8
The kernel that runs ok   is 2.6.25.4-10.fc8

I can provide additional information - let me know.
Comment 6 KOSAKI Motohiro 2008-11-02 05:37:13 EST
hm, I have some guess. (yup it's just _guess_)

1. dentry cache is "name to i-node number transration" cache.
   Then many directory touched some command (e.g. find, updatedb) make bloat dentry cache easily.
   some system run updatedb at midnight by cron. do you do that?

2. SLUB on NUMA dramatically increase dcache fragmentation at special situation. (its problem already fixed on upstream (IIRC 2.6.27)).
   do you have a numa box?
Comment 7 Bug Zapper 2009-06-09 21:03:15 EDT
This message is a reminder that Fedora 9 is nearing its end of life.
Approximately 30 (thirty) days from now Fedora will stop maintaining
and issuing updates for Fedora 9.  It is Fedora's policy to close all
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Comment 8 Bug Zapper 2009-07-14 11:47:42 EDT
Fedora 9 changed to end-of-life (EOL) status on 2009-07-10. Fedora 9 is 
no longer maintained, which means that it will not receive any further 
security or bug fix updates. As a result we are closing this bug.

If you can reproduce this bug against a currently maintained version of 
Fedora please feel free to reopen this bug against that version.

Thank you for reporting this bug and we are sorry it could not be fixed.

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