From mboxrd@z Thu Jan 1 00:00:00 1970 From: Balbir Singh Subject: Re: [PATCH -mmotm 1/5] memcg: disable irq at page cgroup lock Date: Wed, 17 Mar 2010 17:28:55 +0530 Message-ID: <20100317115855.GS18054__21174.1699059077$1268827291$gmane$org@balbir.in.ibm.com> References: <1268609202-15581-1-git-send-email-arighi@develer.com> <1268609202-15581-2-git-send-email-arighi@develer.com> Reply-To: balbir-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1268609202-15581-2-git-send-email-arighi-vWjgImWzx8FBDgjK7y7TUQ@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Andrea Righi Cc: Daisuke Nishimura , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Trond Myklebust , linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Suleiman Souhlal , Andrew Morton , containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Vivek Goyal List-Id: containers.vger.kernel.org * Andrea Righi [2010-03-15 00:26:38]: > From: KAMEZAWA Hiroyuki > > Now, file-mapped is maintaiend. But more generic update function > will be needed for dirty page accounting. > > For accountig page status, we have to guarantee lock_page_cgroup() > will be never called under tree_lock held. > To guarantee that, we use trylock at updating status. > By this, we do fuzzy accounting, but in almost all case, it's correct. > I don't like this at all, but in almost all cases is not acceptable for statistics, since decisions will be made on them and having them incorrect is really bad. Could we do a form of deferred statistics and fix this. -- Three Cheers, Balbir