From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id DAAF46B0131 for ; Sun, 17 Oct 2010 20:25:17 -0400 (EDT) Received: from m4.gw.fujitsu.co.jp ([10.0.50.74]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o9I0PEUZ018807 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Mon, 18 Oct 2010 09:25:15 +0900 Received: from smail (m4 [127.0.0.1]) by outgoing.m4.gw.fujitsu.co.jp (Postfix) with ESMTP id A795345DE7D for ; Mon, 18 Oct 2010 09:25:14 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (s4.gw.fujitsu.co.jp [10.0.50.94]) by m4.gw.fujitsu.co.jp (Postfix) with ESMTP id E414F45DE4D for ; Mon, 18 Oct 2010 09:25:13 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id AB26FEF8005 for ; Mon, 18 Oct 2010 09:25:13 +0900 (JST) Received: from ml14.s.css.fujitsu.com (ml14.s.css.fujitsu.com [10.249.87.104]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 2A5C71DB8037 for ; Mon, 18 Oct 2010 09:25:13 +0900 (JST) Date: Mon, 18 Oct 2010 09:19:48 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [RFC][PATCH 2/2] memcg: new lock for mutual execution of account_move and file stats Message-Id: <20101018091948.6314175a.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: References: <20101015170627.e5033fa4.kamezawa.hiroyu@jp.fujitsu.com> <20101015171225.70d4ca8f.kamezawa.hiroyu@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "nishimura@mxp.nes.nec.co.jp" , "balbir@linux.vnet.ibm.com" , Greg Thelen , "akpm@linux-foundation.org" List-ID: On Sun, 17 Oct 2010 14:35:47 +0900 Minchan Kim wrote: > On Sun, Oct 17, 2010 at 2:33 PM, Minchan Kim wrote: > > On Fri, Oct 15, 2010 at 5:12 PM, KAMEZAWA Hiroyuki > > wrote: > >> From: KAMEZAWA Hiroyuki > >> > >> When we try to enhance page's status update to support other flags, > >> one of problem is updating status from IRQ context. > >> > >> Now, mem_cgroup_update_file_stat() takes lock_page_cgroup() to avoid > >> race with _account move_. IOW, there are no races with charge/uncharge > >> in nature. Considering an update from IRQ context, it seems better > >> to disable IRQ at lock_page_cgroup() to avoid deadlock. > >> > >> But lock_page_cgroup() is used too widerly and adding IRQ disable > >> there makes the performance bad. To avoid the big hammer, this patch > >> adds a new lock for update_stat(). > >> > >> This lock is for mutual execustion of updating stat and accout moving. > >> This adds a new lock to move_account..so, this makes move_account slow. > >> But considering trade-off, I think it's acceptable. > >> > >> A score of moving 8GB anon pages, 8cpu Xeon(3.1GHz) is here. > >> > >> [before patch] (mmotm + optimization patch (#1 in this series) > >> [root@bluextal kamezawa]# time echo 2257 > /cgroup/B/tasks > >> > >> real A A 0m0.694s > >> user A A 0m0.000s > >> sys A A 0m0.683s > >> > >> [After patch] > >> [root@bluextal kamezawa]# time echo 2238 > /cgroup/B/tasks > >> > >> real A A 0m0.741s > >> user A A 0m0.000s > >> sys A A 0m0.730s > >> > >> This moves 8Gbytes == 2048k pages. But no bad effects to codes > >> other than "move". > >> > >> Signed-off-by: KAMEZAWA Hiroyuki > > > > It looks good than old approach. > > Just a below nitpick. > > > >> --- > >> A include/linux/page_cgroup.h | A 29 +++++++++++++++++++++++++++++ > >> A mm/memcontrol.c A A A A A A | A 11 +++++++++-- > >> A 2 files changed, 38 insertions(+), 2 deletions(-) > >> > >> Index: mmotm-1013/include/linux/page_cgroup.h > >> =================================================================== > >> --- mmotm-1013.orig/include/linux/page_cgroup.h > >> +++ mmotm-1013/include/linux/page_cgroup.h > >> @@ -36,6 +36,7 @@ struct page_cgroup *lookup_page_cgroup(s > >> A enum { > >> A A A A /* flags for mem_cgroup */ > >> A A A A PCG_LOCK, A /* page cgroup is locked */ > >> + A A A PCG_LOCK_STATS, /* page cgroup's stat accounting flags are locked */ > > > > Hmm, I think naming isn't a good. Aren't both for stat? PCG_LOCK is for page_cgroup->mem_cgroup, not for stat. But hmm...how about { PCG_LOCK /* For CACEH, USED and pc->mem_cgroup */ PCG_CACHE PCG_USED PCG_ACCT_LRU /* no lock is used */ PCG_MOVE_FLAGS_LOCK /* For MAPPED and I/O flags v.s account_move races*/ PCG_FILE_MAPPED, .. PCG_MIGRATION, /* For remembering Page Migration */ } Anyway, documentation should be updated. ... > > As I understand, Both are used for stat. > > One is just used by charge/uncharge and the other is used by > > pdate_file_stat/move_account. > > If you guys who are expert in mcg feel it with easy, I am not against. > > But at least, mcg-not-familiar people like me don't feel it comfortable. > > > > And I think this patch would be better to be part of Greg Thelen's series. > Hmm. Greg, can you merge my new version (I'll post today) into your series ? Thanks, -Kame -- 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