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Message-ID: <20111229104230.GA20854@tiehlicka.suse.cz>
Date: Thu, 29 Dec 2011 11:42:30 +0100
From: Michal Hocko <mhocko@...e.cz>
To: "Kirill A. Shutemov" <kirill@...temov.name>
Cc: linux-mm@...ck.org, cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org,
containers@...ts.linux-foundation.org,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Balbir Singh <bsingharora@...il.com>,
Johannes Weiner <hannes@...xchg.org>,
Michal Marek <mmarek@...e.cz>, linux-kbuild@...r.kernel.org
Subject: Re: [PATCH] Makefiles: Disable unused-variable warning (was: Re:
[PATCH 1/6] memcg: fix unused variable warning)
On Tue 27-12-11 20:26:13, Kirill A. Shutemov wrote:
> On Tue, Dec 27, 2011 at 02:57:52PM +0100, Michal Hocko wrote:
> > On Sat 24-12-11 05:00:14, Kirill A. Shutemov wrote:
> > > From: "Kirill A. Shutemov" <kirill@...temov.name>
> > >
> > > mm/memcontrol.c: In function ‘memcg_check_events’:
> > > mm/memcontrol.c:784:22: warning: unused variable ‘do_numainfo’ [-Wunused-variable]
> > >
> > > Signed-off-by: Kirill A. Shutemov <kirill@...temov.name>
> > > ---
> > > mm/memcontrol.c | 7 ++++---
> > > 1 files changed, 4 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > > index d643bd6..a5e92bd 100644
> > > --- a/mm/memcontrol.c
> > > +++ b/mm/memcontrol.c
> > > @@ -781,14 +781,15 @@ static void memcg_check_events(struct mem_cgroup *memcg, struct page *page)
> > > /* threshold event is triggered in finer grain than soft limit */
> > > if (unlikely(mem_cgroup_event_ratelimit(memcg,
> > > MEM_CGROUP_TARGET_THRESH))) {
> > > - bool do_softlimit, do_numainfo;
> > > + bool do_softlimit;
> > >
> > > - do_softlimit = mem_cgroup_event_ratelimit(memcg,
> > > - MEM_CGROUP_TARGET_SOFTLIMIT);
> > > #if MAX_NUMNODES > 1
> > > + bool do_numainfo;
> > > do_numainfo = mem_cgroup_event_ratelimit(memcg,
> > > MEM_CGROUP_TARGET_NUMAINFO);
> > > #endif
> > > + do_softlimit = mem_cgroup_event_ratelimit(memcg,
> > > + MEM_CGROUP_TARGET_SOFTLIMIT);
> >
> > I don't like this very much. Maybe we should get rid of both do_* and
> > do it with flags? But maybe it is not worth the additional code at
> > all...
>
> Something like this (untested):
> ====
> From f57e1a2e1aaaa167c75b963d5bf12fcbdd3331b8 Mon Sep 17 00:00:00 2001
> From: "Kirill A. Shutemov" <kirill@...temov.name>
> Date: Tue, 27 Dec 2011 20:17:13 +0200
> Subject: [PATCH] memcg: cleanup memcg_check_events()
>
> Signed-off-by: Kirill A. Shutemov <kirill@...temov.name>
The patch looks correct but I am still not sure this is worth fixing in
the code rather than disabling Wunused-variable.
> ---
> mm/memcontrol.c | 42 ++++++++++++++++++++++++------------------
> 1 files changed, 24 insertions(+), 18 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index d643bd6..40c2236 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -108,11 +108,12 @@ enum mem_cgroup_events_index {
> * than using jiffies etc. to handle periodic memcg event.
> */
> enum mem_cgroup_events_target {
> - MEM_CGROUP_TARGET_THRESH,
> - MEM_CGROUP_TARGET_SOFTLIMIT,
> - MEM_CGROUP_TARGET_NUMAINFO,
> - MEM_CGROUP_NTARGETS,
> + MEM_CGROUP_TARGET_THRESH = BIT(1),
> + MEM_CGROUP_TARGET_SOFTLIMIT = BIT(2),
> + MEM_CGROUP_TARGET_NUMAINFO = BIT(3),
> };
> +#define MEM_CGROUP_NTARGETS 3
> +
> #define THRESHOLDS_EVENTS_TARGET (128)
> #define SOFTLIMIT_EVENTS_TARGET (1024)
> #define NUMAINFO_EVENTS_TARGET (1024)
> @@ -743,7 +744,7 @@ static unsigned long mem_cgroup_nr_lru_pages(struct mem_cgroup *memcg,
> return total;
> }
>
> -static bool mem_cgroup_event_ratelimit(struct mem_cgroup *memcg,
> +static int mem_cgroup_event_ratelimit(struct mem_cgroup *memcg,
> enum mem_cgroup_events_target target)
> {
> unsigned long val, next;
> @@ -766,9 +767,9 @@ static bool mem_cgroup_event_ratelimit(struct mem_cgroup *memcg,
> break;
> }
> __this_cpu_write(memcg->stat->targets[target], next);
> - return true;
> + return target;
> }
> - return false;
> + return 0;
> }
>
> /*
> @@ -777,29 +778,34 @@ static bool mem_cgroup_event_ratelimit(struct mem_cgroup *memcg,
> */
> static void memcg_check_events(struct mem_cgroup *memcg, struct page *page)
> {
> + int flags;
> +
> preempt_disable();
> - /* threshold event is triggered in finer grain than soft limit */
> - if (unlikely(mem_cgroup_event_ratelimit(memcg,
> - MEM_CGROUP_TARGET_THRESH))) {
> - bool do_softlimit, do_numainfo;
> + flags = mem_cgroup_event_ratelimit(memcg, MEM_CGROUP_TARGET_THRESH);
>
> - do_softlimit = mem_cgroup_event_ratelimit(memcg,
> + /*
> + * Threshold event is triggered in finer grain than soft limit
> + * and numainfo
> + */
> + if (unlikely(flags)) {
> + flags |= mem_cgroup_event_ratelimit(memcg,
> MEM_CGROUP_TARGET_SOFTLIMIT);
> #if MAX_NUMNODES > 1
> - do_numainfo = mem_cgroup_event_ratelimit(memcg,
> + flags |= mem_cgroup_event_ratelimit(memcg,
> MEM_CGROUP_TARGET_NUMAINFO);
> #endif
> - preempt_enable();
> + }
> + preempt_enable();
>
> + if (unlikely(flags)) {
> mem_cgroup_threshold(memcg);
> - if (unlikely(do_softlimit))
> + if (unlikely(flags & MEM_CGROUP_TARGET_SOFTLIMIT))
> mem_cgroup_update_tree(memcg, page);
> #if MAX_NUMNODES > 1
> - if (unlikely(do_numainfo))
> + if (unlikely(flags & MEM_CGROUP_TARGET_NUMAINFO))
> atomic_inc(&memcg->numainfo_events);
> #endif
> - } else
> - preempt_enable();
> + }
> }
>
> struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont)
> --
> 1.7.7.3
--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic
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