From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Subject: Re: [PATCH 0/5] memcg/kmem: switch to white list policy
Date: Mon, 9 Nov 2015 15:30:53 -0500
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To: Vladimir Davydov <vdavydov-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>
Cc: Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, Greg Thelen <gthelen-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org

Hello, Vladimir.

On Mon, Nov 09, 2015 at 11:12:18PM +0300, Vladimir Davydov wrote:
> Because we won't be able to distinguish kmem_cache_alloc calls that
> should be accounted from those that shouldn't. The problem is if two
> caches
> 
> 	A = kmem_cache_create(...)
> 
> and
> 
> 	B = kmem_cache_create(...)
> 
> happen to be merged, A and B will point to the same kmem_cache struct.
> As a result, there is no way to distinguish
> 
> 	kmem_cache_alloc(A)
> 
> which we want to account from
> 
> 	kmem_cache_alloc(B)
> 
> which we don't.

Hmm.... can't we simply merge among !SLAB_ACCOUNT and SLAB_ACCOUNT
kmem_caches within themselves?  I don't think we'd be losing anything
by restricting merge at that level.  For anything to be tagged
SLAB_ACCOUNT, it has to have a potential to grow enormous after all.

Thanks.

-- 
tejun