[2.6.18-rc6] ext3 memory leak

[2.6.18-rc6] ext3 memory leak

[Guennadi Liakhovetski]

Hi all,

this looks like a serious problem to be fixed before 2.6.18 final and 
backported to 2.6.17.*. Or a case of me misunderstanding something, in 
which case, please, let me know.

I've reported before in thread "[2.6.17.4] slabinfo.buffer_head increases" 
a memory leak in ext3. Today I verified it is still present in 2.6.18-rc6.

A short description: as long as write accesses are made on an ext3 
filesystem /proc/slabinfo buffer_head increases unboundedly. This 
behaviour is not observed with another journalling filesystems (e.g., 
reiserfs), or if ext3 is mounted as ext2.

As it seems serious enough to me I'm sending it to ext3 maintainers.

Thanks
Guennadi
---------------------------------
Guennadi Liakhovetski, Ph.D.
DSA Daten- und Systemtechnik GmbH
Pascalstr. 28
D-52076 Aachen
Germany

Re: [2.6.18-rc6] ext3 memory leak

[Gene Heskett]

On Thursday 07 September 2006 07:10, Guennadi Liakhovetski wrote:
>Hi all,
>
>this looks like a serious problem to be fixed before 2.6.18 final and
>backported to 2.6.17.*. Or a case of me misunderstanding something, in
>which case, please, let me know.
>
>I've reported before in thread "[2.6.17.4] slabinfo.buffer_head
> increases" a memory leak in ext3. Today I verified it is still present
> in 2.6.18-rc6.
>
>A short description: as long as write accesses are made on an ext3
>filesystem /proc/slabinfo buffer_head increases unboundedly. This
>behaviour is not observed with another journalling filesystems (e.g.,
>reiserfs), or if ext3 is mounted as ext2.
>
What would you call the 'get excited' level?  Here, with about 12 hours of 
uptime (I had an unlogged machine shutdown while I was offsite yesterday), 
I'm showing 

buffer_head        67158  67158     48   78    1 : tunables  120   60    
0 : slabdata    861    861      0

There are other entries that are larger here.  However I do note that its 
growing on a per cycle basis as fetchmail is doing its thing every 90 
seconds.  Now its
buffer_head        67672  67704     48   78    1 : tunables  120   60    
0 : slabdata    868    868      0

So perhaps thats why it did the shutdown?  With absolutely zip in the logs?

Although, my firewall box was also reset/rebooted about the same time as 
this ones powerdown according to an uptime report on it just now, so my 
ups must not be doing its thing correctly.

>As it seems serious enough to me I'm sending it to ext3 maintainers.
>
>Thanks
>Guennadi
>---------------------------------
>Guennadi Liakhovetski, Ph.D.
>DSA Daten- und Systemtechnik GmbH
>Pascalstr. 28
>D-52076 Aachen
>Germany
>-
>To unsubscribe from this list: send the line "unsubscribe linux-kernel"
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>More majordomo info at  http://vger.kernel.org/majordomo-info.html
>Please read the FAQ at  http://www.tux.org/lkml/

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Yahoo.com and AOL/TW attorneys please note, additions to the above
message by Gene Heskett are:
Copyright 2006 by Maurice Eugene Heskett, all rights reserved.

Re: [2.6.18-rc6] ext3 memory leak

[Guennadi Liakhovetski]

On Thu, 7 Sep 2006, Guennadi Liakhovetski wrote:

> I've reported before in thread "[2.6.17.4] slabinfo.buffer_head increases" a 
> memory leak in ext3. Today I verified it is still present in 2.6.18-rc6.

No, sorry, I cannot seem to reproduce it under -rc6. It seems to stabilize 
eventually. But it doesn't under -rc2. I looked through all commits to 
ext3 code between -rc2 and -rc6 and I don't see any obvious reasons why a 
memory leak may have been fixed. Unless somebody can sched some light on 
this, I'll try to upgrade the problematic system to -rc6 tomorrow.

Just to be quite sure - this cannot (or is very unlikely to) be a libc 
bug, right?

Thanks
Guennadi
---------------------------------
Guennadi Liakhovetski, Ph.D.
DSA Daten- und Systemtechnik GmbH
Pascalstr. 28
D-52076 Aachen
Germany

Re: [2.6.18-rc6] ext3 memory leak

[Gene Heskett]

On Thursday 07 September 2006 11:21, Guennadi Liakhovetski wrote:
>On Thu, 7 Sep 2006, Guennadi Liakhovetski wrote:
>> I've reported before in thread "[2.6.17.4] slabinfo.buffer_head
>> increases" a memory leak in ext3. Today I verified it is still present
>> in 2.6.18-rc6.
>
>No, sorry, I cannot seem to reproduce it under -rc6. It seems to
> stabilize eventually. But it doesn't under -rc2. I looked through all
> commits to ext3 code between -rc2 and -rc6 and I don't see any obvious
> reasons why a memory leak may have been fixed. Unless somebody can sched
> some light on this, I'll try to upgrade the problematic system to -rc6
> tomorrow.
>
I just had to restart x because I was playing with keyboard layouts, trying 
to get the alt keys to properly type the 3rd level chars and screwing it 
all up, and when I had done the restart, that line in slabinfo was 
somewhat reset:
[root@coyote root]# grep buffer_head /proc/slabinfo
buffer_head        46789  78858     48   78    1 : tunables  120   60    
0 : slabdata   1011   1011      0

And frankly I don't know enough about it to state it as a fact.  Time will 
tell though.

>Just to be quite sure - this cannot (or is very unlikely to) be a libc
>bug, right?
>
>Thanks
>Guennadi
>---------------------------------
>Guennadi Liakhovetski, Ph.D.
>DSA Daten- und Systemtechnik GmbH
>Pascalstr. 28
>D-52076 Aachen
>Germany
>-
>To unsubscribe from this list: send the line "unsubscribe linux-kernel"
> in the body of a message to majordomo@vger.kernel.org
>More majordomo info at  http://vger.kernel.org/majordomo-info.html
>Please read the FAQ at  http://www.tux.org/lkml/

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Yahoo.com and AOL/TW attorneys please note, additions to the above
message by Gene Heskett are:
Copyright 2006 by Maurice Eugene Heskett, all rights reserved.

Re: [2.6.18-rc6] ext3 memory leak

[Andrew Morton]

On Thu, 7 Sep 2006 17:21:35 +0200 (CEST)
Guennadi Liakhovetski <gl@dsa-ac.de> wrote:

> On Thu, 7 Sep 2006, Guennadi Liakhovetski wrote:
> 
> > I've reported before in thread "[2.6.17.4] slabinfo.buffer_head increases" a 
> > memory leak in ext3. Today I verified it is still present in 2.6.18-rc6.
> 
> No, sorry, I cannot seem to reproduce it under -rc6. It seems to stabilize 
> eventually. But it doesn't under -rc2. I looked through all commits to 
> ext3 code between -rc2 and -rc6 and I don't see any obvious reasons why a 
> memory leak may have been fixed. Unless somebody can sched some light on 
> this, I'll try to upgrade the problematic system to -rc6 tomorrow.
> 
> Just to be quite sure - this cannot (or is very unlikely to) be a libc 
> bug, right?
> 

It is expected that in this situation the number of buffer_head objects will
be approximately equal to the number of pagecache pages.  So once the pagecache
has grown to consume all available memory and the kernel starts to perform pagecache
reclaim, the buffer_head count should stabilise.

Re: [2.6.18-rc6] ext3 memory leak

[Guennadi Liakhovetski]

On Thu, 7 Sep 2006, Andrew Morton wrote:

> It is expected that in this situation the number of buffer_head objects will
> be approximately equal to the number of pagecache pages.  So once the pagecache
> has grown to consume all available memory and the kernel starts to perform pagecache
> reclaim, the buffer_head count should stabilise.

Ok, thanks that's exactly what I had to know - makes sense now.

Sorry for a false alarm.

Thanks
Guennadi
---------------------------------
Guennadi Liakhovetski, Ph.D.
DSA Daten- und Systemtechnik GmbH
Pascalstr. 28
D-52076 Aachen
Germany