Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756411Ab1FPLpo (ORCPT ); Thu, 16 Jun 2011 07:45:44 -0400 Received: from cantor2.suse.de ([195.135.220.15]:38019 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755972Ab1FPLpl (ORCPT ); Thu, 16 Jun 2011 07:45:41 -0400 Date: Thu, 16 Jun 2011 13:45:39 +0200 From: Michal Hocko To: Ying Han Cc: Johannes Weiner , KAMEZAWA Hiroyuki , Daisuke Nishimura , Balbir Singh , Andrew Morton , Rik van Riel , Minchan Kim , KOSAKI Motohiro , Mel Gorman , Greg Thelen , Michel Lespinasse , "linux-mm@kvack.org" , linux-kernel Subject: Re: [patch 4/8] memcg: rework soft limit reclaim Message-ID: <20110616114538.GF9840@tiehlicka.suse.cz> References: <1306909519-7286-1-git-send-email-hannes@cmpxchg.org> <1306909519-7286-5-git-send-email-hannes@cmpxchg.org> <20110609150026.GD3994@tiehlicka.suse.cz> <20110610073638.GA15403@tiehlicka.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4120 Lines: 104 On Wed 15-06-11 15:57:59, Ying Han wrote: > On Fri, Jun 10, 2011 at 12:36 AM, Michal Hocko wrote: > > On Thu 09-06-11 17:00:26, Michal Hocko wrote: > >> On Thu 02-06-11 22:25:29, Ying Han wrote: > >> > On Thu, Jun 2, 2011 at 2:55 PM, Ying Han wrote: > >> > > On Tue, May 31, 2011 at 11:25 PM, Johannes Weiner wrote: > >> > >> Currently, soft limit reclaim is entered from kswapd, where it selects > >> [...] > >> > >> diff --git a/mm/vmscan.c b/mm/vmscan.c > >> > >> index c7d4b44..0163840 100644 > >> > >> --- a/mm/vmscan.c > >> > >> +++ b/mm/vmscan.c > >> > >> @@ -1988,9 +1988,13 @@ static void shrink_zone(int priority, struct zone *zone, > >> > >> ? ? ? ? ? ? ? ?unsigned long reclaimed = sc->nr_reclaimed; > >> > >> ? ? ? ? ? ? ? ?unsigned long scanned = sc->nr_scanned; > >> > >> ? ? ? ? ? ? ? ?unsigned long nr_reclaimed; > >> > >> + ? ? ? ? ? ? ? int epriority = priority; > >> > >> + > >> > >> + ? ? ? ? ? ? ? if (mem_cgroup_soft_limit_exceeded(root, mem)) > >> > >> + ? ? ? ? ? ? ? ? ? ? ? epriority -= 1; > >> > > > >> > > Here we grant the ability to shrink from all the memcgs, but only > >> > > higher the priority for those exceed the soft_limit. That is a design > >> > > change > >> > > for the "soft_limit" which giving a hint to which memcgs to reclaim > >> > > from first under global memory pressure. > >> > > >> > > >> > Basically, we shouldn't reclaim from a memcg under its soft_limit > >> > unless we have trouble reclaim pages from others. > >> > >> Agreed. > >> > >> > Something like the following makes better sense: > >> > > >> > diff --git a/mm/vmscan.c b/mm/vmscan.c > >> > index bdc2fd3..b82ba8c 100644 > >> > --- a/mm/vmscan.c > >> > +++ b/mm/vmscan.c > >> > @@ -1989,6 +1989,8 @@ restart: > >> > ? ? ? ? throttle_vm_writeout(sc->gfp_mask); > >> > ?} > >> > > >> > +#define MEMCG_SOFTLIMIT_RECLAIM_PRIORITY ? ? ? 2 > >> > + > >> > ?static void shrink_zone(int priority, struct zone *zone, > >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? struct scan_control *sc) > >> > ?{ > >> > @@ -2001,13 +2003,13 @@ static void shrink_zone(int priority, struct zone *zone, > >> > ? ? ? ? ? ? ? ? unsigned long reclaimed = sc->nr_reclaimed; > >> > ? ? ? ? ? ? ? ? unsigned long scanned = sc->nr_scanned; > >> > ? ? ? ? ? ? ? ? unsigned long nr_reclaimed; > >> > - ? ? ? ? ? ? ? int epriority = priority; > >> > > >> > - ? ? ? ? ? ? ? if (mem_cgroup_soft_limit_exceeded(root, mem)) > >> > - ? ? ? ? ? ? ? ? ? ? ? epriority -= 1; > >> > + ? ? ? ? ? ? ? if (!mem_cgroup_soft_limit_exceeded(root, mem) && > >> > + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? priority > MEMCG_SOFTLIMIT_RECLAIM_PRIORITY) > >> > + ? ? ? ? ? ? ? ? ? ? ? continue; > >> > >> yes, this makes sense but I am not sure about the right(tm) value of the > >> MEMCG_SOFTLIMIT_RECLAIM_PRIORITY. 2 sounds too low. > > > > There is also another problem. I have just realized that this code path > > is shared with the cgroup direct reclaim. We shouldn't care about soft > > limit in such a situation. It would be just a wasting of cycles. So we > > have to: > > > > if (current_is_kswapd() && > > ? ? ? ?!mem_cgroup_soft_limit_exceeded(root, mem) && > > ? ? ? ?priority > MEMCG_SOFTLIMIT_RECLAIM_PRIORITY) > > ? ? ? ?continue; > > Agreed. > > > > > Maybe the condition would have to be more complex for per-cgroup > > background reclaim, though. > > That would be the same logic for per-memcg direct reclaim. In general, > we don't consider soft_limit > unless the global memory pressure. So the condition could be something like: > > > if ( global_reclaim(sc) && > > ? ? ? ?!mem_cgroup_soft_limit_exceeded(root, mem) && > > ? ? ? ?priority > MEMCG_SOFTLIMIT_RECLAIM_PRIORITY) > > ? ? ? ?continue; > > make sense? Yes seems to be more consistent. -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/