From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id 5DDAF6B0025 for ; Thu, 5 May 2011 12:47:17 -0400 (EDT) Date: Fri, 6 May 2011 00:47:12 +0800 From: Wu Fengguang Subject: Re: [PATCH 6/6] writeback: refill b_io iff empty Message-ID: <20110505164712.GA2548@localhost> References: <20110420080336.441157866@intel.com> <20110420080918.560499032@intel.com> <20110504073931.GA22675@localhost> <20110505163708.GN5323@quack.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110505163708.GN5323@quack.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Jan Kara Cc: Andrew Morton , Mel Gorman , Mel Gorman , Dave Chinner , Itaru Kitayama , Minchan Kim , Linux Memory Management List , "linux-fsdevel@vger.kernel.org" , LKML On Fri, May 06, 2011 at 12:37:08AM +0800, Jan Kara wrote: > On Wed 04-05-11 15:39:31, Wu Fengguang wrote: > > To help understand the behavior change, I wrote the writeback_queue_io > > trace event, and found very different patterns between > > - vanilla kernel > > - this patchset plus the sync livelock fixes > > > > Basically the vanilla kernel each time pulls a random number of inodes > > from b_dirty, while the patched kernel tends to pull a fixed number of > > inodes (enqueue=1031) from b_dirty. The new behavior is very interesting... > This regularity is really strange. Did you have a chance to look more into > it? I find it highly unlikely that there would be exactly 1031 dirty inodes > in b_dirty list every time you call move_expired_inodes()... Yeah that's the weird point. The other things I noticed are more regular "flusher - dd - flusher - dd - ..." writeout patterns after the patches. In vanilla kernel it behaves more randomly and there are many balance_dirty_pages() IOs from tar. I'll try to collect more traces in ext4 tomorrow. Sorry it's too late for me now. 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