linux-kernel - Re: oomkillers gone wild.

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Date:	Fri, 8 Jun 2012 12:57:36 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: oomkillers gone wild.

On Tue, 5 Jun 2012, Dave Jones wrote:

>   OBJS ACTIVE  USE OBJ SIZE  SLABS OBJ/SLAB CACHE SIZE NAME 
> 142524 142420  99%    9.67K  47510	  3   1520320K task_struct
> 142560 142417  99%    1.75K   7920	 18    253440K signal_cache
> 142428 142302  99%    1.19K   5478	 26    175296K task_xstate
> 306064 289292  94%    0.36K   6956	 44    111296K debug_objects_cache
> 143488 143306  99%    0.50K   4484	 32     71744K cred_jar
> 142560 142421  99%    0.50K   4455       32     71280K task_delay_info
> 150753 145021  96%    0.45K   4308	 35     68928K kmalloc-128
> 
> Why so many task_structs ? There's only 128 processes running, and most of them
> are kernel threads.
> 

Do you have CONFIG_OPROFILE enabled?

> /sys/kernel/slab/task_struct/alloc_calls shows..
> 
>  142421 copy_process.part.21+0xbb/0x1790 age=8/19929576/48173720 pid=0-16867 cpus=0-7
> 
> I get the impression that the oom-killer hasn't cleaned up properly after killing some of
> those forked processes.
> 
> any thoughts ?
> 

If we're leaking task_struct's, meaning that put_task_struct() isn't 
actually freeing them when the refcount goes to 0, then it's certainly not 
because of the oom killer which only sends a SIGKILL to the selected 
process.

Have you tried kmemleak?
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