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 3ABAC6B00EE for ; Mon, 15 Aug 2011 13:16:52 -0400 (EDT) Received: from wpaz33.hot.corp.google.com (wpaz33.hot.corp.google.com [172.24.198.97]) by smtp-out.google.com with ESMTP id p7FHGmmU030295 for ; Mon, 15 Aug 2011 10:16:48 -0700 Received: from qyk36 (qyk36.prod.google.com [10.241.83.164]) by wpaz33.hot.corp.google.com with ESMTP id p7FHFX3D012912 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=NOT) for ; Mon, 15 Aug 2011 10:16:47 -0700 Received: by qyk36 with SMTP id 36so1143029qyk.16 for ; Mon, 15 Aug 2011 10:16:38 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20110815134846.GB13534@localhost> References: <1313189245-7197-1-git-send-email-curtw@google.com> <1313189245-7197-2-git-send-email-curtw@google.com> <20110815134846.GB13534@localhost> Date: Mon, 15 Aug 2011 10:16:38 -0700 Message-ID: Subject: Re: [PATCH 2/2 v2] writeback: Add writeback stats for pages written From: Curt Wohlgemuth Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Wu Fengguang Cc: Christoph Hellwig , Jan Kara , Andrew Morton , Dave Chinner , Michael Rubin , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" Hi Fengguang: Thanks for looking at this. On Mon, Aug 15, 2011 at 6:48 AM, Wu Fengguang wrot= e: > Curt, > > Some thoughts about the interface..before dipping into the code. > > On Sat, Aug 13, 2011 at 06:47:25AM +0800, Curt Wohlgemuth wrote: >> Add a new file, /proc/writeback/stats, which displays > > That's creating a new top directory in /proc. Do you have plans for > adding more files under it? Good question. We have several files under /proc/writeback in our kernels that we created at various times, some of which are probably no longer useful, but others seem to be. For example: - congestion: prints # of calls, # of jiffies slept in congestion_wait() / io_schedule_timeout() from various call points - threshold_dirty : prints the current global FG threshold - threshold_bg : prints the current global BG threshold - pages_cleaned : prints the # pages sent to writeback -- same as 'nr_written' in /proc/vmstat (ours was earlier :-( ) - pages_dirtied (same as nr_dirtied in /proc/vmstat) - prop_vm_XXX : print shift/events from vm_completions and vm_dirties I'm not sure right now if global FG/BG thresholds appear anywhere in a 3.1 kernel; if so, the two threshold files above are superfluous. So are the pages_cleaned/dirtied. The prop_vm files have not proven useful to me. I think the congestion file has a lot of value, especially in an IO-less throttling world... > >> machine global data for how many pages were cleaned for >> which reasons. =A0It also displays some additional counts for >> various writeback events. >> >> These data are also available for each BDI, in >> /sys/block//bdi/writeback_stats . > >> Sample output: >> >> =A0 =A0page: balance_dirty_pages =A0 =A0 =A0 =A0 =A0 2561544 >> =A0 =A0page: background_writeout =A0 =A0 =A0 =A0 =A0 =A0 =A05153 >> =A0 =A0page: try_to_free_pages =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 0 >> =A0 =A0page: sync =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 = =A0 =A0 =A00 >> =A0 =A0page: kupdate =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A01027= 23 >> =A0 =A0page: fdatawrite =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A01228779 >> =A0 =A0page: laptop_periodic =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 0 >> =A0 =A0page: free_more_memory =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A00 >> =A0 =A0page: fs_free_space =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 0 >> =A0 =A0periodic writeback =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0377 >> =A0 =A0single inode wait =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0= 0 >> =A0 =A0writeback_wb wait =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0= 1 > > That's already useful data, and could be further extended (in > future patches) to answer questions like "what's the writeback > efficiency in terms of effective chunk size?" > > So in future there could be lines like > > =A0 =A0pages: balance_dirty_pages =A0 =A0 =A0 =A0 =A0 2561544 > =A0 =A0chunks: balance_dirty_pages =A0 =A0 =A0 =A0 =A0XXXXXXX > =A0 =A0works: balance_dirty_pages =A0 =A0 =A0 =A0 =A0 XXXXXXX > > or even derived lines like > > =A0 =A0pages_per_chunk: balance_dirty_pages =A0 =A0 =A0 =A0 XXXXXXX > =A0 =A0pages_per_work: balance_dirty_pages =A0 =A0 =A0 =A0 =A0XXXXXXX > > Another question is, how can the display format be script friendly? > The current form looks not easily parse-able at least for "cut".. I suppose you mean because of the variable number of tokens. Yeah, this can be hard. Of course, I always just use "awk '{print $NF}'" and it works for me :-) . But I'd be happy to change these to use a consistent # of args. Thanks, Curt > Thanks, > Fengguang > -- 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