From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx171.postini.com [74.125.245.171]) by kanga.kvack.org (Postfix) with SMTP id 55A2F6B005D for ; Tue, 20 Nov 2012 16:49:34 -0500 (EST) Date: Tue, 20 Nov 2012 13:49:32 -0800 From: Andrew Morton Subject: Re: [patch] mm, memcg: avoid unnecessary function call when memcg is disabled Message-Id: <20121120134932.055bc192.akpm@linux-foundation.org> In-Reply-To: References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Johannes Weiner , Michal Hocko , KAMEZAWA Hiroyuki , Hugh Dickins , linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org On Mon, 19 Nov 2012 17:44:34 -0800 (PST) David Rientjes wrote: > While profiling numa/core v16 with cgroup_disable=memory on the command > line, I noticed mem_cgroup_count_vm_event() still showed up as high as > 0.60% in perftop. > > This occurs because the function is called extremely often even when memcg > is disabled. > > To fix this, inline the check for mem_cgroup_disabled() so we avoid the > unnecessary function call if memcg is disabled. > > ... > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -181,7 +181,14 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order, > gfp_t gfp_mask, > unsigned long *total_scanned); > > -void mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx); > +void __mem_cgroup_count_vm_event(struct mm_struct *mm, enum vm_event_item idx); > +static inline void mem_cgroup_count_vm_event(struct mm_struct *mm, > + enum vm_event_item idx) > +{ > + if (mem_cgroup_disabled() || !mm) > + return; > + __mem_cgroup_count_vm_event(mm, idx); > +} Does the !mm case occur frequently enough to justify inlining it, or should that test remain out-of-line? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org