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 E01498D003B for ; Thu, 21 Apr 2011 12:41:59 -0400 (EDT) Date: Thu, 21 Apr 2011 18:41:54 +0200 From: Jan Kara Subject: Re: [PATCH 5/6] writeback: try more writeback as long as something was written Message-ID: <20110421164154.GC4476@quack.suse.cz> References: <20110419030003.108796967@intel.com> <20110419030532.778889102@intel.com> <20110419102016.GD5257@quack.suse.cz> <20110419111601.GA18961@localhost> <20110419211008.GD9556@quack.suse.cz> <20110420075053.GB30672@localhost> <20110420152211.GC4991@quack.suse.cz> <20110421033325.GA13764@localhost> <20110421043940.GC22423@infradead.org> <20110421060556.GA24232@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110421060556.GA24232@localhost> Sender: owner-linux-mm@kvack.org List-ID: To: Wu Fengguang Cc: Christoph Hellwig , Jan Kara , Andrew Morton , Mel Gorman , Dave Chinner , Trond Myklebust , Itaru Kitayama , Minchan Kim , LKML , "linux-fsdevel@vger.kernel.org" , Linux Memory Management List On Thu 21-04-11 14:05:56, Wu Fengguang wrote: > On Thu, Apr 21, 2011 at 12:39:40PM +0800, Christoph Hellwig wrote: > > On Thu, Apr 21, 2011 at 11:33:25AM +0800, Wu Fengguang wrote: > > > I collected the writeback_single_inode() traces (patch attached for > > > your reference) each for several test runs, and find much more > > > I_DIRTY_PAGES after patchset. Dave, do you know why there are so many > > > I_DIRTY_PAGES (or radix tag) remained after the XFS ->writepages() call, > > > even for small files? > > > > What is your defintion of a small file? As soon as it has multiple > > extents or holes there's absolutely no way to clean it with a single > > writepage call. > > It's writing a kernel source tree to XFS. You can find in the below > trace that it often leaves more dirty pages behind (indicated by the > I_DIRTY_PAGES flag) after writing as less as 1 page (indicated by the > wrote=1 field). As Dave said, it's probably just a race since XFS redirties the inode on IO completion. So I think the inodes are just small so they have only a few dirty pages so you don't have much to write and they are written and redirtied before you check the I_DIRTY flags. You could use radix tree dirty tag to verify whether there are really dirty pages or not... BTW a quick check of kernel tree shows the following distribution of sizes (in KB): Count KB Cumulative Percent 257 0 0.9% 13309 4 45% 5553 8 63% 2997 12 73% 1879 16 80% 1275 20 83% 987 24 87% 685 28 89% 540 32 91% 387 36 ... 309 40 264 44 249 48 170 52 143 56 144 60 132 64 100 68 ... Total 30155 And the distribution of your 'wrote=xxx' roughly corresponds to this... Honza -- Jan Kara SUSE Labs, CR -- 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