From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 5CEC26008E4 for ; Tue, 3 Aug 2010 00:02:29 -0400 (EDT) Received: from d03relay03.boulder.ibm.com (d03relay03.boulder.ibm.com [9.17.195.228]) by e34.co.us.ibm.com (8.14.4/8.13.1) with ESMTP id o733wTC3012196 for ; Mon, 2 Aug 2010 21:58:29 -0600 Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by d03relay03.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o7346qn8103484 for ; Mon, 2 Aug 2010 22:06:53 -0600 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id o7346lmD010686 for ; Mon, 2 Aug 2010 22:06:48 -0600 Date: Tue, 3 Aug 2010 09:36:45 +0530 From: Balbir Singh Subject: Re: [PATCH -mm 5/5] memcg: use spinlock in page_cgroup instead of bit_spinlock Message-ID: <20100803040645.GH3863@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20100802191113.05c982e4.kamezawa.hiroyu@jp.fujitsu.com> <20100802192006.a395889a.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20100802192006.a395889a.kamezawa.hiroyu@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org 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" List-ID: * KAMEZAWA Hiroyuki [2010-08-02 19:20:06]: > From: KAMEZAWA Hiroyuki > > This patch replaces bit_spinlock with spinlock. In general, > spinlock has good functinality than bit_spin_lock and we should use > it if we have a room for it. In 64bit arch, we have extra 4bytes. > Let's use it. > expected effects: > - use better codes. > - ticket lock on x86-64 > - para-vitualization aware lock > etc.. > > Chagelog: 20090729 > - fixed page_cgroup_is_locked(). > > Signed-off-by: KAMEZAWA Hiroyuki > -- The additional space usage is a big concern, I think saving space would be of highest priority. I understand the expected benefits, but a spinlock_t per page_cgroup is quite expensive at the moment. If anything I think it should be a config option under CONFIG_DEBUG or something else to play with and see the side effects. -- Three Cheers, Balbir -- 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