From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id 011775F0001 for ; Tue, 7 Apr 2009 03:01:45 -0400 (EDT) Received: from m2.gw.fujitsu.co.jp ([10.0.50.72]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id n3771g7E018756 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Tue, 7 Apr 2009 16:01:44 +0900 Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 7729545DE5D for ; Tue, 7 Apr 2009 16:01:42 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 46E1E45DE57 for ; Tue, 7 Apr 2009 16:01:42 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 337301DB8040 for ; Tue, 7 Apr 2009 16:01:42 +0900 (JST) Received: from m107.s.css.fujitsu.com (m107.s.css.fujitsu.com [10.249.87.107]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id DA9421DB803E for ; Tue, 7 Apr 2009 16:01:41 +0900 (JST) Date: Tue, 7 Apr 2009 16:00:14 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [RFI] Shared accounting for memory resource controller Message-Id: <20090407160014.8c545c3c.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090407063722.GQ7082@balbir.in.ibm.com> References: <20090407063722.GQ7082@balbir.in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: balbir@linux.vnet.ibm.com Cc: "linux-mm@kvack.org" , Andrew Morton , "lizf@cn.fujitsu.com" , Rik van Riel , Bharata B Rao , Dhaval Giani , KOSAKI Motohiro , "linux-kernel@vger.kernel.org" List-ID: On Tue, 7 Apr 2009 12:07:22 +0530 Balbir Singh wrote: > Hi, All, > > This is a request for input for the design of shared page accounting for > the memory resource controller, here is what I have so far > In my first impression, I think simple counting is impossible. IOW, "usage count" and "shared or not" is very different problem. Assume a page and its page_cgroup. Case 1) 1. a page is mapped by process-X under group-A 2. its mapped by process-Y in group-B (now, shared and charged under group-A) 3. move process-X to group-B 4. now the page is not shared. Case 2) swap is an object which can be shared. Case 3) 1. a page known as "A" is mapped by process-X under group-A. 2. its mapped by process-Y under group-B(now, shared and charged under group-A) 3. Do copy-on-write by process-X. Now, "A" is mapped only by B but accoutned under group-A. This case is ignored intentionally, now. Do you want to call try_charge() both against group-A and group-B under process-X's page fault ? There will be many many corner case. > Motivation for shared page accounting > ------------------------------------- > 1. Memory cgroup administrators will benefit from the knowledge of how > much of the data is shared, it helps size the groups correctly. > 2. We currently report only the pages brought in by the cgroup, knowledge > of shared data will give a complete picture of the actual usage. > Motivation sounds good. But counting this in generic rmap will have tons of troubles and slow-down. I bet we should prepare a file as /proc//cgroup_maps And show RSS/RSS-owned-by-us per process. Maybe this feature will be able to be implemented in 3 days. Thanks, -Kame -- 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