From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [patch] mm, memcg: avoid unnecessary function call when memcg is disabled Date: Tue, 20 Nov 2012 13:49:32 -0800 Message-ID: <20121120134932.055bc192.akpm@linux-foundation.org> References: Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" To: David Rientjes Cc: Johannes Weiner , Michal Hocko , KAMEZAWA Hiroyuki , Hugh Dickins , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.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?