Re: OOM triggered with plenty of memory free

[ebiederm@xmission.com (Eric W. Biederman)]

Dave Hansen <dave@linux.vnet.ibm.com> writes:

> On 02/25/2013 10:39 PM, Jonathan Woithe wrote:
>> On Wed, Feb 13, 2013 at 07:14:50AM -0800, Dave Hansen wrote:
>>> David's analysis looks spot-on.  The only other thing I'll add is that
>>> it just looks weird that all three kmalloc() caches are so _even_:
>>>
>>>>> kmalloc-128       1234556 1235168    128   32    1 : tunables    0    0    0 : slabdata  38599  38599      0
>>>>> kmalloc-64        1238117 1238144     64   64    1 : tunables    0    0    0 : slabdata  19346  19346      0
>>>>> kmalloc-32        1236600 1236608     32  128    1 : tunables    0    0    0 : slabdata   9661   9661      0
>>>
>>> It's almost like something goes and does 3 allocations in series and
>>> leaks them all.
> ...
>> Given these observations it seems that 2.6.35.11 was leaking memory,
>> probably as a result of a bug in the fork() execution path.  At this stage
>> kmemleak is not showing the same recurring problem under 3.7.9.
>
> Your kmemleak data shows that the leaks are always from either 'struct
> cred', or 'struct pid'.  Those are _generally_ tied to tasks, but you
> only have a couple thousand task_structs.
>
> My suspicion would be that something is allocating those structures, but
> a refcount got leaked somewhere.  2.6.35.11 is about the same era that
> this code went in:
>
> http://lists.linux-foundation.org/pipermail/containers/2010-June/024720.html
>
> and it deals with both creds and 'struct pid'.  Eric, do you recall any
> bugs like this that got fixed along the way?
>
> I do think it's fairly safe to assume that 3.7.9 doesn't have this
> bug.

I remember that at one point there was a very subtle leak of I think
struct pid.  That leak was not associated with the socket code but
something else.

Eric

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