From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id EB8586B02A6 for ; Wed, 28 Jul 2010 11:47:17 -0400 (EDT) Message-ID: <4C505025.1040709@ds.jp.nec.com> Date: Wed, 28 Jul 2010 11:43:33 -0400 From: Munehiro Ikeda MIME-Version: 1.0 Subject: Re: [RFC][PATCH 4/7][memcg] memcg use ID in page_cgroup References: <20100727165155.8b458b7f.kamezawa.hiroyu@jp.fujitsu.com> <20100727165629.6f98145c.kamezawa.hiroyu@jp.fujitsu.com> <20100728023904.GE12642@redhat.com> <20100728114402.571b8ec6.kamezawa.hiroyu@jp.fujitsu.com> <20100728031358.GG12642@redhat.com> In-Reply-To: <20100728031358.GG12642@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Vivek Goyal Cc: KAMEZAWA Hiroyuki , "linux-mm@kvack.org" , "nishimura@mxp.nes.nec.co.jp" , "balbir@linux.vnet.ibm.com" , gthelen@google.com, "akpm@linux-foundation.org" , "linux-kernel@vger.kernel.org" List-ID: Vivek Goyal wrote, on 07/27/2010 11:13 PM: > On Wed, Jul 28, 2010 at 11:44:02AM +0900, KAMEZAWA Hiroyuki wrote: >> On Tue, 27 Jul 2010 22:39:04 -0400 >> Vivek Goyal wrote: >> >>> On Tue, Jul 27, 2010 at 04:56:29PM +0900, KAMEZAWA Hiroyuki wrote: >>>> From: KAMEZAWA Hiroyuki >>>> >>>> Now, addresses of memory cgroup can be calculated by their ID without complex. >>>> This patch relplaces pc->mem_cgroup from a pointer to a unsigned short. >>>> On 64bit architecture, this offers us more 6bytes room per page_cgroup. >>>> Use 2bytes for blkio-cgroup's page tracking. More 4bytes will be used for >>>> some light-weight concurrent access. >>>> >>>> We may able to move this id onto flags field but ...go step by step. >>>> >>>> Signed-off-by: KAMEZAWA Hiroyuki >>>> --- >>>> include/linux/page_cgroup.h | 3 ++- >>>> mm/memcontrol.c | 40 +++++++++++++++++++++++++--------------- >>>> mm/page_cgroup.c | 2 +- >>>> 3 files changed, 28 insertions(+), 17 deletions(-) >>>> >>>> Index: mmotm-0719/include/linux/page_cgroup.h >>>> =================================================================== >>>> --- mmotm-0719.orig/include/linux/page_cgroup.h >>>> +++ mmotm-0719/include/linux/page_cgroup.h >>>> @@ -12,7 +12,8 @@ >>>> */ >>>> struct page_cgroup { >>>> unsigned long flags; >>>> - struct mem_cgroup *mem_cgroup; >>>> + unsigned short mem_cgroup; /* ID of assigned memory cgroup */ >>>> + unsigned short blk_cgroup; /* Not Used..but will be. */ >>> >>> So later I shall have to use virtually indexed arrays in blkio controller? >>> Or you are just using virtually indexed arrays for lookup speed and >>> I can continue to use css_lookup() and not worry about using virtually >>> indexed arrays. >>> >> yes. you can use css_lookup() even if it's slow. >> > > Ok. > >>> So the idea is that when a page is allocated, also store the blk_group >>> id and once that page is submitted for writeback, we should be able >>> to associate it to right blkio group? >>> >> blk_cgroup id can be attached whenever you wants. please overwrite >> page_cgroup->blk_cgroup when it's necessary. > >> Did you read Ikeda's patch ? I myself doesn't have patches at this point. >> This is just for make a room for recording blkio-ID, which was requested >> for a year. > > I have not read his patches yet. IIRC, previously there were issues > regarding which group should be charged for the page. The person who > allocated it or the thread which did last write to it etc... I guess > we can sort that out later. Absolutely. iotrack, a part of blkio cgroup for async write patch I posted, charges the thread (in exact, blkio-cgroup to which the thread belongs) which dirtied the page first. Though it should be controversial and we need to discuss who should be charged, adding pc->blk_cgroup has no problem because blkio-cgroup can overwrite it any time, as Kame said above. Beyond that, adding pc->blk_cgroup is a big step for us. Now I encode and store ID in pc->flags. pc->blk_cgroup is more straight and that is what we have been looking forward. Thanks Kame! -- IKEDA, Munehiro NEC Corporation of America m-ikeda@ds.jp.nec.com -- 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