From: Jan Kara Subject: Re: 3.2 and 3.1 filesystem scalability measurements Date: Tue, 31 Jan 2012 11:53:53 +0100 Message-ID: <20120131105353.GA1278@quack.suse.cz> References: <4F261807.2060108@hp.com> <4F26B395.6020607@gmail.com> <20120131001415.GC9090@dastard> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andreas Dilger , "aziro.linux.adm" , Eric Whitney , Ext4 Developers List , linux-fsdevel@vger.kernel.org To: Dave Chinner Return-path: Received: from cantor2.suse.de ([195.135.220.15]:34610 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753054Ab2AaKx5 (ORCPT ); Tue, 31 Jan 2012 05:53:57 -0500 Content-Disposition: inline In-Reply-To: <20120131001415.GC9090@dastard> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue 31-01-12 11:14:15, Dave Chinner wrote: > I also found this oddity on both XFS and ext4: > > flush-253:32-3400 [001] 1936151.384563: writeback_start: bdi 253:32: sb_dev 0:0 nr_pages=-898403 sync_mode=0 kupdate=0 range_cyclic=1 background=1 reason=background > flush-253:32-3400 [005] 1936151.455845: writeback_start: bdi 253:32: sb_dev 0:0 nr_pages=-911663 sync_mode=0 kupdate=0 range_cyclic=1 background=1 reason=background > flush-253:32-3400 [006] 1936151.596298: writeback_start: bdi 253:32: sb_dev 0:0 nr_pages=-931332 sync_mode=0 kupdate=0 range_cyclic=1 background=1 reason=background > flush-253:32-3400 [006] 1936151.719074: writeback_start: bdi 253:32: sb_dev 0:0 nr_pages=-951001 sync_mode=0 kupdate=0 range_cyclic=1 background=1 reason=background > > That's indicating the work->nr_pages is starting extremely negative, > which should not be the case. The highest I saw was around -2m. > Something is not working right there, as writeback is supposed to > terminate if work->nr_pages < 0.... Ugh, what kernel is this? The tracepoint is just a couple of lines after if (work->nr_pages <= 0) break; so I really don't see how that could happen. Honza -- Jan Kara SUSE Labs, CR