Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754360Ab0HCDpX (ORCPT ); Mon, 2 Aug 2010 23:45:23 -0400 Received: from e5.ny.us.ibm.com ([32.97.182.145]:45998 "EHLO e5.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753339Ab0HCDpV (ORCPT ); Mon, 2 Aug 2010 23:45:21 -0400 Date: Tue, 3 Aug 2010 09:15:13 +0530 From: Balbir Singh To: KAMEZAWA Hiroyuki Cc: linux-mm@kvack.org, "nishimura@mxp.nes.nec.co.jp" , vgoyal@redhat.com, m-ikeda@ds.jp.nec.com, gthelen@google.com, "akpm@linux-foundation.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH -mm 2/5] use ID in page cgroup Message-ID: <20100803034513.GF3863@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20100802191113.05c982e4.kamezawa.hiroyu@jp.fujitsu.com> <20100802191410.cbf03d67.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20100802191410.cbf03d67.kamezawa.hiroyu@jp.fujitsu.com> User-Agent: Mutt/1.5.20 (2009-12-10) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2309 Lines: 63 * KAMEZAWA Hiroyuki [2010-08-02 19:14:10]: > 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. > > Changelog: 20100730 > - fixed some garbage added by debug code in early stage > > Signed-off-by: KAMEZAWA Hiroyuki > --- > include/linux/page_cgroup.h | 3 ++- > mm/memcontrol.c | 32 +++++++++++++++++++------------- > mm/page_cgroup.c | 2 +- > 3 files changed, 22 insertions(+), 15 deletions(-) > > Index: mmotm-0727/include/linux/page_cgroup.h > =================================================================== > --- mmotm-0727.orig/include/linux/page_cgroup.h > +++ mmotm-0727/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. */ > struct page *page; > struct list_head lru; /* per cgroup LRU list */ > }; Can I recommend that on 64 bit systems, we merge the flag, mem_cgroup and blk_cgroup into one 8 byte value. We could use __attribute("packed") and do something like this struct page_cgroup { unsigned int flags; unsigned short mem_cgroup; unsigned short blk_cgroup; ... } __attribute(("packed")); Then we need to make sure we don't use more that 32 bits for flags, which is very much under control at the moment. This will save us 8 bytes in total on 64 bit systems and nothing on 32 bit systems, but will enable blkio cgroup to co-exist. -- Three Cheers, Balbir -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/