linux-kernel - Re: [PATCH 3/5] mm: memcontrol: zap memcg_kmem

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Message-ID: <20160208054857.GC22202@cmpxchg.org>
Date:	Mon, 8 Feb 2016 00:48:57 -0500
From:	Johannes Weiner <hannes@...xchg.org>
To:	Vladimir Davydov <vdavydov@...tuozzo.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...nel.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] mm: memcontrol: zap memcg_kmem_online helper

On Sun, Feb 07, 2016 at 08:27:33PM +0300, Vladimir Davydov wrote:
> As kmem accounting is now either enabled for all cgroups or disabled
> system-wide, there's no point in having memcg_kmem_online() helper -
> instead one can use memcg_kmem_enabled() and mem_cgroup_online(), as
> shrink_slab() now does.
> 
> There are only two places left where this helper is used -
> __memcg_kmem_charge() and memcg_create_kmem_cache(). The former can only
> be called if memcg_kmem_enabled() returned true. Since the cgroup it
> operates on is online, mem_cgroup_is_root() check will be enough.
> 
> memcg_create_kmem_cache() can't use mem_cgroup_online() helper instead
> of memcg_kmem_online(), because it relies on the fact that in
> memcg_offline_kmem() memcg->kmem_state is changed before
> memcg_deactivate_kmem_caches() is called, but there we can just
> open-code the check.
> 
> Signed-off-by: Vladimir Davydov <vdavydov@...tuozzo.com>

Nice. I like the direct check for the root memcg.

Acked-by: Johannes Weiner <hannes@...xchg.org>