From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753835AbZHTLBZ (ORCPT ); Thu, 20 Aug 2009 07:01:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752395AbZHTLBY (ORCPT ); Thu, 20 Aug 2009 07:01:24 -0400 Received: from mail-yw0-f173.google.com ([209.85.211.173]:41494 "EHLO mail-yw0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752334AbZHTLBX convert rfc822-to-8bit (ORCPT ); Thu, 20 Aug 2009 07:01:23 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=jWZIeeD3lApOeyGNFbDtYUj4IQkSShvuc+2TvLw4RTNnAkOS2vqiJQ4gg/TKo842VE V/i/JaPKlyC25IabLoSWMbg+wkv8ph122WcNYQCtfh954AAif9R3WhkmHvy4uSyI9+54 hB5vUnLLSLtehhgOvDOWIJAArcbK8zqHfoaPY= MIME-Version: 1.0 In-Reply-To: <20090820040533.GA27540@localhost> References: <20090820024929.GA19793@localhost> <20090820121347.8a886e4b.kamezawa.hiroyu@jp.fujitsu.com> <20090820040533.GA27540@localhost> Date: Thu, 20 Aug 2009 20:01:21 +0900 Message-ID: <28c262360908200401t41c03ad3n114b24e03b61de08@mail.gmail.com> Subject: Re: [PATCH -v2] mm: do batched scans for mem_cgroup From: Minchan Kim To: Wu Fengguang Cc: KAMEZAWA Hiroyuki , Andrew Morton , Balbir Singh , KOSAKI Motohiro , Rik van Riel , Johannes Weiner , Avi Kivity , Andrea Arcangeli , "Dike, Jeffrey G" , Hugh Dickins , Christoph Lameter , Mel Gorman , LKML , linux-mm , "nishimura@mxp.nes.nec.co.jp" , "lizf@cn.fujitsu.com" , "menage@google.com" Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Wu. On Thu, Aug 20, 2009 at 1:05 PM, Wu Fengguang wrote: > On Thu, Aug 20, 2009 at 11:13:47AM +0800, KAMEZAWA Hiroyuki wrote: >> On Thu, 20 Aug 2009 10:49:29 +0800 >> Wu Fengguang wrote: >> >> > For mem_cgroup, shrink_zone() may call shrink_list() with nr_to_scan=1, >> > in which case shrink_list() _still_ calls isolate_pages() with the much >> > larger SWAP_CLUSTER_MAX.  It effectively scales up the inactive list >> > scan rate by up to 32 times. >> > >> > For example, with 16k inactive pages and DEF_PRIORITY=12, (16k >> 12)=4. >> > So when shrink_zone() expects to scan 4 pages in the active/inactive >> > list, it will be scanned SWAP_CLUSTER_MAX=32 pages in effect. >> > >> > The accesses to nr_saved_scan are not lock protected and so not 100% >> > accurate, however we can tolerate small errors and the resulted small >> > imbalanced scan rates between zones. >> > >> > This batching won't blur up the cgroup limits, since it is driven by >> > "pages reclaimed" rather than "pages scanned". When shrink_zone() >> > decides to cancel (and save) one smallish scan, it may well be called >> > again to accumulate up nr_saved_scan. >> > >> > It could possibly be a problem for some tiny mem_cgroup (which may be >> > _full_ scanned too much times in order to accumulate up nr_saved_scan). >> > >> > CC: Rik van Riel >> > CC: Minchan Kim >> > CC: Balbir Singh >> > CC: KOSAKI Motohiro >> > CC: KAMEZAWA Hiroyuki >> > Signed-off-by: Wu Fengguang >> > --- >> >> Hmm, how about this ? >> == >> Now, nr_saved_scan is tied to zone's LRU. >> But, considering how vmscan works, it should be tied to reclaim_stat. >> >> By this, memcg can make use of nr_saved_scan information seamlessly. > > Good idea, full patch updated with your signed-off-by :) > > Thanks, > Fengguang > --- > mm: do batched scans for mem_cgroup > > For mem_cgroup, shrink_zone() may call shrink_list() with nr_to_scan=1, > in which case shrink_list() _still_ calls isolate_pages() with the much > larger SWAP_CLUSTER_MAX.  It effectively scales up the inactive list > scan rate by up to 32 times. Yes. It can scan 32 times pages in only inactive list, not active list. > For example, with 16k inactive pages and DEF_PRIORITY=12, (16k >> 12)=4. > So when shrink_zone() expects to scan 4 pages in the active/inactive > list, it will be scanned SWAP_CLUSTER_MAX=32 pages in effect. Active list scan would be scanned in 4, inactive list is 32. > > The accesses to nr_saved_scan are not lock protected and so not 100% > accurate, however we can tolerate small errors and the resulted small > imbalanced scan rates between zones. Yes. > This batching won't blur up the cgroup limits, since it is driven by > "pages reclaimed" rather than "pages scanned". When shrink_zone() > decides to cancel (and save) one smallish scan, it may well be called > again to accumulate up nr_saved_scan. You mean nr_scan_try_batch logic ? But that logic works for just global reclaim? Now am I missing something? Could you elaborate more? :) > It could possibly be a problem for some tiny mem_cgroup (which may be > _full_ scanned too much times in order to accumulate up nr_saved_scan). > > CC: Rik van Riel > CC: Minchan Kim > CC: Balbir Singh > CC: KOSAKI Motohiro > Signed-off-by: KAMEZAWA Hiroyuki > Signed-off-by: Wu Fengguang > --- >  include/linux/mmzone.h |    6 +++++- >  mm/page_alloc.c        |    2 +- >  mm/vmscan.c            |   20 +++++++++++--------- >  3 files changed, 17 insertions(+), 11 deletions(-) > > --- linux.orig/include/linux/mmzone.h   2009-07-30 10:45:15.000000000 +0800 > +++ linux/include/linux/mmzone.h        2009-08-20 11:51:08.000000000 +0800 > @@ -269,6 +269,11 @@ struct zone_reclaim_stat { >         */ >        unsigned long           recent_rotated[2]; >        unsigned long           recent_scanned[2]; > + > +       /* > +        * accumulated for batching > +        */ > +       unsigned long           nr_saved_scan[NR_LRU_LISTS]; >  }; > >  struct zone { > @@ -323,7 +328,6 @@ struct zone { >        spinlock_t              lru_lock; >        struct zone_lru { >                struct list_head list; > -               unsigned long nr_saved_scan;    /* accumulated for batching */ >        } lru[NR_LRU_LISTS]; > >        struct zone_reclaim_stat reclaim_stat; > --- linux.orig/mm/vmscan.c      2009-08-20 11:48:46.000000000 +0800 > +++ linux/mm/vmscan.c   2009-08-20 12:00:55.000000000 +0800 > @@ -1521,6 +1521,7 @@ static void shrink_zone(int priority, st >        enum lru_list l; >        unsigned long nr_reclaimed = sc->nr_reclaimed; >        unsigned long swap_cluster_max = sc->swap_cluster_max; > +       struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); >        int noswap = 0; > >        /* If we have no swap space, do not bother scanning anon pages. */ > @@ -1540,12 +1541,9 @@ static void shrink_zone(int priority, st >                        scan >>= priority; >                        scan = (scan * percent[file]) / 100; >                } > -               if (scanning_global_lru(sc)) > -                       nr[l] = nr_scan_try_batch(scan, > -                                                 &zone->lru[l].nr_saved_scan, > -                                                 swap_cluster_max); > -               else > -                       nr[l] = scan; > +               nr[l] = nr_scan_try_batch(scan, > +                                         &reclaim_stat->nr_saved_scan[l], > +                                         swap_cluster_max); >        } > >        while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || > @@ -2128,6 +2126,7 @@ static void shrink_all_zones(unsigned lo >  { >        struct zone *zone; >        unsigned long nr_reclaimed = 0; > +       struct zone_reclaim_stat *reclaim_stat; > >        for_each_populated_zone(zone) { >                enum lru_list l; > @@ -2144,11 +2143,14 @@ static void shrink_all_zones(unsigned lo >                                                l == LRU_ACTIVE_FILE)) >                                continue; > > -                       zone->lru[l].nr_saved_scan += (lru_pages >> prio) + 1; > -                       if (zone->lru[l].nr_saved_scan >= nr_pages || pass > 3) { > +                       reclaim_stat = get_reclaim_stat(zone, sc); > +                       reclaim_stat->nr_saved_scan[l] += > +                                               (lru_pages >> prio) + 1; > +                       if (reclaim_stat->nr_saved_scan[l] > +                                               >= nr_pages || pass > 3) { >                                unsigned long nr_to_scan; > > -                               zone->lru[l].nr_saved_scan = 0; > +                               reclaim_stat->nr_saved_scan[l] = 0; >                                nr_to_scan = min(nr_pages, lru_pages); >                                nr_reclaimed += shrink_list(l, nr_to_scan, zone, >                                                                sc, prio); > --- linux.orig/mm/page_alloc.c  2009-08-20 11:57:54.000000000 +0800 > +++ linux/mm/page_alloc.c       2009-08-20 11:58:39.000000000 +0800 > @@ -3716,7 +3716,7 @@ static void __paginginit free_area_init_ >                zone_pcp_init(zone); >                for_each_lru(l) { >                        INIT_LIST_HEAD(&zone->lru[l].list); > -                       zone->lru[l].nr_saved_scan = 0; > +                       zone->reclaim_stat.nr_saved_scan[l] = 0; >                } >                zone->reclaim_stat.recent_rotated[0] = 0; >                zone->reclaim_stat.recent_rotated[1] = 0; > > -- > 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 > -- Kind regards, Minchan Kim