From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx206.postini.com [74.125.245.206]) by kanga.kvack.org (Postfix) with SMTP id EE83F6B00EF for ; Tue, 6 Mar 2012 20:30:16 -0500 (EST) Received: by iajr24 with SMTP id r24so10240380iaj.14 for ; Tue, 06 Mar 2012 17:30:16 -0800 (PST) Date: Tue, 6 Mar 2012 17:29:46 -0800 (PST) From: Hugh Dickins Subject: Re: [PATCH] memcg: fix mapcount check in move charge code for anonymous page In-Reply-To: <1331076667-11118-1-git-send-email-n-horiguchi@ah.jp.nec.com> Message-ID: References: <1331076667-11118-1-git-send-email-n-horiguchi@ah.jp.nec.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Naoya Horiguchi Cc: Daisuke Nishimura , linux-mm@kvack.org, Andrew Morton , Andrea Arcangeli , KAMEZAWA Hiroyuki , Hillf Danton , linux-kernel@vger.kernel.org On Tue, 6 Mar 2012, Naoya Horiguchi wrote: > > IMO, ideally the charge of shared (both file and anon) pages should > be accounted for all cgroups to which the processes mapping the pages > belong to, where each charge is weighted by inverse number of mapcount. > I think accounting total number of mapcount with another counter does > not work, because the weight of charge depends on each page and the > total count of mapcount doesn't describe the proportion among cgroups. > But anyway, it adds more complexity and needs much work, so is not > a short term fix. That "ideal" complexity was considered before the current memcg approach went in. We elected to go with the less satisfying, but much simpler, single-owner approach, and it does seem to have paid off. I believe that even those who had successfully developed a more complex approach have since abandoned it for performance scalability reasons. Hugh -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org