From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with SMTP id F05816B004F for ; Thu, 20 Aug 2009 07:01:24 -0400 (EDT) Received: by yxe14 with SMTP id 14so6483953yxe.12 for ; Thu, 20 Aug 2009 04:01:24 -0700 (PDT) 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 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org 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" List-ID: 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= =3D1, >> > in which case shrink_list() _still_ calls isolate_pages() with the muc= h >> > larger SWAP_CLUSTER_MAX. =C2=A0It effectively scales up the inactive l= ist >> > scan rate by up to 32 times. >> > >> > For example, with 16k inactive pages and DEF_PRIORITY=3D12, (16k >> 12= )=3D4. >> > So when shrink_zone() expects to scan 4 pages in the active/inactive >> > list, it will be scanned SWAP_CLUSTER_MAX=3D32 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 ? >> =3D=3D >> 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=3D1, > in which case shrink_list() _still_ calls isolate_pages() with the much > larger SWAP_CLUSTER_MAX. =C2=A0It 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=3D12, (16k >> 12)= =3D4. > So when shrink_zone() expects to scan 4 pages in the active/inactive > list, it will be scanned SWAP_CLUSTER_MAX=3D32 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 > --- > =C2=A0include/linux/mmzone.h | =C2=A0 =C2=A06 +++++- > =C2=A0mm/page_alloc.c =C2=A0 =C2=A0 =C2=A0 =C2=A0| =C2=A0 =C2=A02 +- > =C2=A0mm/vmscan.c =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0| =C2=A0 20 ++= +++++++++--------- > =C2=A03 files changed, 17 insertions(+), 11 deletions(-) > > --- linux.orig/include/linux/mmzone.h =C2=A0 2009-07-30 10:45:15.00000000= 0 +0800 > +++ linux/include/linux/mmzone.h =C2=A0 =C2=A0 =C2=A0 =C2=A02009-08-20 11= :51:08.000000000 +0800 > @@ -269,6 +269,11 @@ struct zone_reclaim_stat { > =C2=A0 =C2=A0 =C2=A0 =C2=A0 */ > =C2=A0 =C2=A0 =C2=A0 =C2=A0unsigned long =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 recent_rotated[2]; > =C2=A0 =C2=A0 =C2=A0 =C2=A0unsigned long =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 recent_scanned[2]; > + > + =C2=A0 =C2=A0 =C2=A0 /* > + =C2=A0 =C2=A0 =C2=A0 =C2=A0* accumulated for batching > + =C2=A0 =C2=A0 =C2=A0 =C2=A0*/ > + =C2=A0 =C2=A0 =C2=A0 unsigned long =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 n= r_saved_scan[NR_LRU_LISTS]; > =C2=A0}; > > =C2=A0struct zone { > @@ -323,7 +328,6 @@ struct zone { > =C2=A0 =C2=A0 =C2=A0 =C2=A0spinlock_t =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0lru_lock; > =C2=A0 =C2=A0 =C2=A0 =C2=A0struct zone_lru { > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0struct list_head l= ist; > - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 unsigned long nr_saved= _scan; =C2=A0 =C2=A0/* accumulated for batching */ > =C2=A0 =C2=A0 =C2=A0 =C2=A0} lru[NR_LRU_LISTS]; > > =C2=A0 =C2=A0 =C2=A0 =C2=A0struct zone_reclaim_stat reclaim_stat; > --- linux.orig/mm/vmscan.c =C2=A0 =C2=A0 =C2=A02009-08-20 11:48:46.000000= 000 +0800 > +++ linux/mm/vmscan.c =C2=A0 2009-08-20 12:00:55.000000000 +0800 > @@ -1521,6 +1521,7 @@ static void shrink_zone(int priority, st > =C2=A0 =C2=A0 =C2=A0 =C2=A0enum lru_list l; > =C2=A0 =C2=A0 =C2=A0 =C2=A0unsigned long nr_reclaimed =3D sc->nr_reclaime= d; > =C2=A0 =C2=A0 =C2=A0 =C2=A0unsigned long swap_cluster_max =3D sc->swap_cl= uster_max; > + =C2=A0 =C2=A0 =C2=A0 struct zone_reclaim_stat *reclaim_stat =3D get_rec= laim_stat(zone, sc); > =C2=A0 =C2=A0 =C2=A0 =C2=A0int noswap =3D 0; > > =C2=A0 =C2=A0 =C2=A0 =C2=A0/* If we have no swap space, do not bother sca= nning anon pages. */ > @@ -1540,12 +1541,9 @@ static void shrink_zone(int priority, st > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0scan >>=3D priority; > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0scan =3D (scan * percent[file]) / 100; > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0} > - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 if (scanning_global_lr= u(sc)) > - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 nr[l] =3D nr_scan_try_batch(scan, > - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 &zone->lru[l].nr_saved_scan, > - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 swap_cluster_max); > - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 else > - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 nr[l] =3D scan; > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 nr[l] =3D nr_scan_try_= batch(scan, > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 &recl= aim_stat->nr_saved_scan[l], > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 swap_= cluster_max); > =C2=A0 =C2=A0 =C2=A0 =C2=A0} > > =C2=A0 =C2=A0 =C2=A0 =C2=A0while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_= FILE] || > @@ -2128,6 +2126,7 @@ static void shrink_all_zones(unsigned lo > =C2=A0{ > =C2=A0 =C2=A0 =C2=A0 =C2=A0struct zone *zone; > =C2=A0 =C2=A0 =C2=A0 =C2=A0unsigned long nr_reclaimed =3D 0; > + =C2=A0 =C2=A0 =C2=A0 struct zone_reclaim_stat *reclaim_stat; > > =C2=A0 =C2=A0 =C2=A0 =C2=A0for_each_populated_zone(zone) { > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0enum lru_list l; > @@ -2144,11 +2143,14 @@ static void shrink_all_zones(unsigned lo > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0l =3D=3D LRU_ACTIVE_FILE)) > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0continue; > > - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 zone->lru[l].nr_saved_scan +=3D (lru_pages >> prio) + 1; > - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 if (zone->lru[l].nr_saved_scan >=3D nr_pages || pass > 3) { > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 reclaim_stat =3D get_reclaim_stat(zone, sc); > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 reclaim_stat->nr_saved_scan[l] +=3D > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 (lru_pages >> prio) + 1; > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 if (reclaim_stat->nr_saved_scan[l] > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 >=3D nr_pages || pass > 3) { > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0unsigned long nr_to_scan; > > - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 zone->lru[l].nr_saved_scan =3D 0; > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 reclaim_stat->nr_saved_scan[l] =3D 0; > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0nr_to_scan =3D min(nr_pages, lru_page= s); > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0nr_reclaimed +=3D shrink_list(l, nr_t= o_scan, zone, > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0sc, prio); > --- linux.orig/mm/page_alloc.c =C2=A02009-08-20 11:57:54.000000000 +0800 > +++ linux/mm/page_alloc.c =C2=A0 =C2=A0 =C2=A0 2009-08-20 11:58:39.000000= 000 +0800 > @@ -3716,7 +3716,7 @@ static void __paginginit free_area_init_ > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0zone_pcp_init(zone= ); > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0for_each_lru(l) { > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0INIT_LIST_HEAD(&zone->lru[l].list); > - =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 zone->lru[l].nr_saved_scan =3D 0; > + =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 zone->reclaim_stat.nr_saved_scan[l] =3D 0; > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0} > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0zone->reclaim_stat= .recent_rotated[0] =3D 0; > =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0zone->reclaim_stat= .recent_rotated[1] =3D 0; > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. =C2=A0For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org > --=20 Kind regards, Minchan Kim -- 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