From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 19C106B0087 for ; Fri, 21 Aug 2009 12:36:46 -0400 (EDT) Received: by gxk12 with SMTP id 12so1198309gxk.4 for ; Fri, 21 Aug 2009 09:36:48 -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: Fri, 21 Aug 2009 12:55:27 +0900 Message-ID: <28c262360908202055u2744879cic989e007867d0599@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: 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 Reviewed-by: Minchan Kim It looks better than now :) I hope you will rewrite description and add test result in changelog. :) Thanks for your great effort. --=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