linux-kernel - Re: [PATCH 0/5] memcg/kmem: switch to white list policy

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Message-ID: <20151109203053.GD28507@mtj.duckdns.org>
Date:	Mon, 9 Nov 2015 15:30:53 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Vladimir Davydov <vdavydov@...tuozzo.com>
Cc:	Michal Hocko <mhocko@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Greg Thelen <gthelen@...gle.com>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] memcg/kmem: switch to white list policy

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
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