From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753972AbaIXPtk (ORCPT ); Wed, 24 Sep 2014 11:49:40 -0400 Received: from gum.cmpxchg.org ([85.214.110.215]:48580 "EHLO gum.cmpxchg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751902AbaIXPti (ORCPT ); Wed, 24 Sep 2014 11:49:38 -0400 Date: Wed, 24 Sep 2014 11:49:34 -0400 From: Johannes Weiner To: Vladimir Davydov Cc: Andrew Morton , Michal Hocko , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH -mm] memcg: zap memcg_can_account_kmem Message-ID: <20140924154934.GA9670@cmpxchg.org> References: <1411570361-29361-1-git-send-email-vdavydov@parallels.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1411570361-29361-1-git-send-email-vdavydov@parallels.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 24, 2014 at 06:52:41PM +0400, Vladimir Davydov wrote: > memcg_can_account_kmem() returns true iff > > !mem_cgroup_disabled() && !mem_cgroup_is_root(memcg) && > memcg_kmem_is_active(memcg); > > To begin with the !mem_cgroup_is_root(memcg) check is useless, because > one can't enable kmem accounting for the root cgroup (mem_cgroup_write() > returns EINVAL on an attempt to set the limit on the root cgroup). > > Furthermore, the !mem_cgroup_disabled() check also seems to be > redundant. The point is memcg_can_account_kmem() is called from three > places: mem_cgroup_salbinfo_read(), __memcg_kmem_get_cache(), and > __memcg_kmem_newpage_charge(). The latter two functions are only invoked > if memcg_kmem_enabled() returns true, which implies that the memory > cgroup subsystem is enabled. And mem_cgroup_slabinfo_read() shows the > output of memory.kmem.slabinfo, which won't exist if the memory cgroup > is completely disabled. > > So let's substitute all the calls to memcg_can_account_kmem() with plain > memcg_kmem_is_active(), and kill the former. > > Signed-off-by: Vladimir Davydov Yes, the two checks look indeed redundant. Acked-by: Johannes Weiner