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 ESMTP id 22A679000C1 for ; Wed, 27 Apr 2011 05:14:58 -0400 (EDT) Received: by vws4 with SMTP id 4so1658965vws.14 for ; Wed, 27 Apr 2011 02:14:56 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20110427174813.8b34df90.kamezawa.hiroyu@jp.fujitsu.com> References: <20110427164708.1143395e.kamezawa.hiroyu@jp.fujitsu.com> <20110427174813.8b34df90.kamezawa.hiroyu@jp.fujitsu.com> Date: Wed, 27 Apr 2011 18:14:56 +0900 Message-ID: Subject: Re: [PATCHv3] memcg: fix get_scan_count for small targets From: Minchan Kim Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: KAMEZAWA Hiroyuki Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , Ying Han , "kosaki.motohiro@jp.fujitsu.com" , "nishimura@mxp.nes.nec.co.jp" , "mgorman@suse.de" On Wed, Apr 27, 2011 at 5:48 PM, KAMEZAWA Hiroyuki wrote: > On Wed, 27 Apr 2011 17:48:18 +0900 > Minchan Kim wrote: > >> On Wed, Apr 27, 2011 at 4:47 PM, KAMEZAWA Hiroyuki >> wrote: >> > At memory reclaim, we determine the number of pages to be scanned >> > per zone as >> > =C2=A0 =C2=A0 =C2=A0 =C2=A0(anon + file) >> priority. >> > Assume >> > =C2=A0 =C2=A0 =C2=A0 =C2=A0scan =3D (anon + file) >> priority. >> > >> > If scan < SWAP_CLUSTER_MAX, the scan will be skipped for this time >> > and priority gets higher. This has some problems. >> > >> > =C2=A01. This increases priority as 1 without any scan. >> > =C2=A0 =C2=A0 To do scan in this priority, amount of pages should be l= arger than 512M. >> > =C2=A0 =C2=A0 If pages>>priority < SWAP_CLUSTER_MAX, it's recorded and= scan will be >> > =C2=A0 =C2=A0 batched, later. (But we lose 1 priority.) >> > =C2=A0 =C2=A0 If memory size is below 16M, pages >> priority is 0 and = no scan in >> > =C2=A0 =C2=A0 DEF_PRIORITY forever. >> > >> > =C2=A02. If zone->all_unreclaimabe=3D=3Dtrue, it's scanned only when p= riority=3D=3D0. >> > =C2=A0 =C2=A0 So, x86's ZONE_DMA will never be recoverred until the us= er of pages >> > =C2=A0 =C2=A0 frees memory by itself. >> > >> > =C2=A03. With memcg, the limit of memory can be small. When using smal= l memcg, >> > =C2=A0 =C2=A0 it gets priority < DEF_PRIORITY-2 very easily and need t= o call >> > =C2=A0 =C2=A0 wait_iff_congested(). >> > =C2=A0 =C2=A0 For doing scan before priorty=3D9, 64MB of memory should= be used. >> > >> > Then, this patch tries to scan SWAP_CLUSTER_MAX of pages in force...wh= en >> > >> > =C2=A01. the target is enough small. >> > =C2=A02. it's kswapd or memcg reclaim. >> > >> > Then we can avoid rapid priority drop and may be able to recover >> > all_unreclaimable in a small zones. And this patch removes nr_saved_sc= an. >> > This will allow scanning in this priority even when pages >> priority >> > is very small. >> > >> > Changelog v2->v3 >> > =C2=A0- removed nr_saved_scan completely. >> > >> > Signed-off-by: KAMEZAWA Hiroyuki >> Reviewed-by: Minchan Kim >> >> The patch looks good to me but I have a nitpick about just coding style. >> How about this? I think below looks better but it's just my private >> opinion and I can't insist on my style. If you don't mind it, ignore. >> > > I did this at the 1st try and got bug.....a variable 'file' here is > reused and now broken. Renaming it with new variable will be ok, but it Right you are. I missed that. :) Thanks. --=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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org