From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id E6B8F6B004F for ; Thu, 20 Aug 2009 00:08:54 -0400 (EDT) Received: from m5.gw.fujitsu.co.jp ([10.0.50.75]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id n7K48svO007372 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Thu, 20 Aug 2009 13:08:54 +0900 Received: from smail (m5 [127.0.0.1]) by outgoing.m5.gw.fujitsu.co.jp (Postfix) with ESMTP id 0355C45DE56 for ; Thu, 20 Aug 2009 13:08:54 +0900 (JST) Received: from s5.gw.fujitsu.co.jp (s5.gw.fujitsu.co.jp [10.0.50.95]) by m5.gw.fujitsu.co.jp (Postfix) with ESMTP id BDC1245DE4E for ; Thu, 20 Aug 2009 13:08:53 +0900 (JST) Received: from s5.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s5.gw.fujitsu.co.jp (Postfix) with ESMTP id 9968D1DB8062 for ; Thu, 20 Aug 2009 13:08:53 +0900 (JST) Received: from m107.s.css.fujitsu.com (m107.s.css.fujitsu.com [10.249.87.107]) by s5.gw.fujitsu.co.jp (Postfix) with ESMTP id 2FAB81DB803F for ; Thu, 20 Aug 2009 13:08:53 +0900 (JST) Date: Thu, 20 Aug 2009 13:06:55 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH -v2] mm: do batched scans for mem_cgroup Message-Id: <20090820130655.7b5e460c.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090820040533.GA27540@localhost> References: <20090820024929.GA19793@localhost> <20090820121347.8a886e4b.kamezawa.hiroyu@jp.fujitsu.com> <20090820040533.GA27540@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Wu Fengguang Cc: 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" List-ID: On Thu, 20 Aug 2009 12:05:33 +0800 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 :) > looks nice :) thanks, -Kame > 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. > > 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 > 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. 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