[Devel] Re: [PATCH] Show slab memory usage on OOM and SysRq-M (v3)

[Andrew Morton]

On Wed, 18 Apr 2007 11:13:01 +0400 Pavel Emelianov <xemul at sw.ru> wrote:

> The out_of_memory() function and SysRq-M handler call
> show_mem() to show the current memory usage state.
> 
> This is also helpful to see which slabs are the largest
> in the system.
> 
> Thanks Pekka for good idea of how to make it better.
> 
> The nr_pages is stored on kmem_list3 because:
> 
> 1. as Eric pointed out, we do not want to defeat 
>    NUMA optimizations;
> 2. we do not need for additional LOCK-ed operation on
>    altering this field - l3->list_lock is already taken
>    where needed.
> 
> Made naming more descriptive according to Dave.
> 
> Signed-off-by: Pavel Emelianov <xemul at openvz.org>
> Signed-off-by: Kirill Korotaev <dev at openvz.org>
> Acked-by: Pekka Enberg <penberg at cs.helsinki.fi>
> Cc: Eric Dumazet <dada1 at cosmosbay.com>
> Cc: Dave Hansen <hansendc at us.ibm.com>
> 

This is rather a lot of new code and even new locking.

Any time we actually need this what-the-heck-is-happening-in-slab info, the
reporter is able to work out the problem via /proc/slabinfo.  Either by
taking a look in there before the system dies completely, or by looking in
there after the oom-killing.