From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id E553A6B02A7 for ; Thu, 5 Aug 2010 20:44:56 -0400 (EDT) Received: from m4.gw.fujitsu.co.jp ([10.0.50.74]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o760iufl011280 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Fri, 6 Aug 2010 09:44:56 +0900 Received: from smail (m4 [127.0.0.1]) by outgoing.m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 6316F45DE79 for ; Fri, 6 Aug 2010 09:44:56 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (s4.gw.fujitsu.co.jp [10.0.50.94]) by m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 3E04E45DE60 for ; Fri, 6 Aug 2010 09:44:56 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 1CC2A1DB803A for ; Fri, 6 Aug 2010 09:44:56 +0900 (JST) Received: from ml14.s.css.fujitsu.com (ml14.s.css.fujitsu.com [10.249.87.104]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id CD3A71DB8040 for ; Fri, 6 Aug 2010 09:44:52 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH 2/2] writeback: Adding pages_dirtied and pages_entered_writeback In-Reply-To: <20100805172711.87c802ca.akpm@linux-foundation.org> References: <20100806091548.31ED.A69D9226@jp.fujitsu.com> <20100805172711.87c802ca.akpm@linux-foundation.org> Message-Id: <20100806093312.31F9.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Fri, 6 Aug 2010 09:44:52 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Andrew Morton Cc: kosaki.motohiro@jp.fujitsu.com, Michael Rubin , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, jack@suse.cz, david@fromorbit.com, hch@lst.de, axboe@kernel.dk List-ID: > On Fri, 6 Aug 2010 09:18:59 +0900 (JST) > KOSAKI Motohiro wrote: > > > > On Thu, Aug 5, 2010 at 4:56 PM, KOSAKI Motohiro > > > wrote: > > > > /proc/vmstat already have both. > > > > > > > > cat /proc/vmstat |grep nr_dirty > > > > cat /proc/vmstat |grep nr_writeback > > > > > > > > Also, /sys/devices/system/node/node0/meminfo show per-node stat. > > > > > > > > Perhaps, I'm missing your point. > > > > > > These only show the number of dirty pages present in the system at the > > > point they are queried. > > > The counter I am trying to add are increasing over time. They allow > > > developers to see rates of pages being dirtied and entering writeback. > > > Which is very helpful. > > > > Usually administrators get the data two times and subtract them. Isn't it sufficient? > > > > Nope. The existing nr_dirty is "number of pages dirtied since boot" > minus "number of pages cleaned since boot". If you do the > wait-one-second-then-subtract thing on nr_dirty, the result is > dirtying-bandwidth minus cleaning-bandwidth, and can't be used to > determine dirtying-bandwidth. Technically, yes. I meant, _now_, typical administrators are using the subtraction. Do you mean this is wrong? or do you mean you have another use case? Just curious. > I can see that a graph of dirtying events versus time could be an > interesting thing. I don't see how it could be obtained using the > existing instrumentation. tracepoints, probably.. I think it depend on frequency of the usecase. If the usecase is enouth major, convenience way (e.g. /proc/vmstat) is very helpful. probably, I haven't understand the usecase of this feature. -- 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