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

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Message-Id: <20070419220801.2f73083f.akpm@linux-foundation.org>
Date:	Thu, 19 Apr 2007 22:08:01 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Pavel Emelianov <xemul@...ru>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Eric Dumazet <dada1@...mosbay.com>,
	Dave Hansen <hansendc@...ibm.com>, devel@...nvz.org,
	Kirill Korotaev <dev@...nvz.org>
Subject: Re: [PATCH] Show slab memory usage on OOM and SysRq-M (v3)

On Wed, 18 Apr 2007 11:13:01 +0400 Pavel Emelianov <xemul@...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@...nvz.org>
> Signed-off-by: Kirill Korotaev <dev@...nvz.org>
> Acked-by: Pekka Enberg <penberg@...helsinki.fi>
> Cc: Eric Dumazet <dada1@...mosbay.com>
> Cc: Dave Hansen <hansendc@...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.
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