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 766D46B00B6 for ; Wed, 29 Jul 2009 22:09:26 -0400 (EDT) Date: Thu, 30 Jul 2009 10:09:22 +0800 From: Wu Fengguang Subject: Re: Bug in kernel 2.6.31, Slow wb_kupdate writeout Message-ID: <20090730020922.GD7326@localhost> References: <1786ab030907281211x6e432ba6ha6afe9de73f24e0c@mail.gmail.com> <33307c790907281449k5e8d4f6cib2c93848f5ec2661@mail.gmail.com> <33307c790907290015m1e6b5666x9c0014cdaf5ed08@mail.gmail.com> <20090729114322.GA9335@localhost> <33307c790907291719r2caf7914xb543877464ba6fc2@mail.gmail.com> <33307c790907291828x6906e874l4d75e695116aa874@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <33307c790907291828x6906e874l4d75e695116aa874@mail.gmail.com> Sender: owner-linux-mm@kvack.org To: Martin Bligh Cc: Chad Talbott , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , Michael Rubin , Andrew Morton , "sandeen@redhat.com" , Michael Davidson List-ID: On Thu, Jul 30, 2009 at 09:28:07AM +0800, Martin Bligh wrote: > On Wed, Jul 29, 2009 at 5:19 PM, Martin Bligh wrote: > > BTW, can you explain this code at the bottom of generic_sync_sb_inodes > > for me? > > > > A A A A A A A A if (wbc->nr_to_write <= 0) { > > A A A A A A A A A A A A wbc->more_io = 1; > > A A A A A A A A A A A A break; > > A A A A A A A A } > > > > I don't understand why we are setting more_io here? AFAICS, more_io > > means there's more stuff to write ... I would think we'd set this if > > nr_to_write was > 0 ? > > > > Or just have the section below brought up above this > > break check and do: > > > > if (!list_empty(&sb->s_more_io) || !list_empty(&sb->s_io)) > > A A A A wbc->more_io = 1; > > > > Am I just misunderstanding the intent of more_io ? > > I am thinking along the lines of: On closer looks I found this line: if (inode_dirtied_after(inode, start)) break; In this case "list_empty(&sb->s_io)" is not a good criteria: here we are breaking away for some other reasons, and shall not touch wbc.more_io. So let's stick with the current code? Thanks, Fengguang > @@ -638,13 +609,11 @@ sync_sb_inodes(struct super_block *sb, s > iput(inode); > cond_resched(); > spin_lock(&inode_lock); > - if (wbc->nr_to_write <= 0) { > - wbc->more_io = 1; > + if (wbc->nr_to_write <= 0) > break; > - } > - if (!list_empty(&sb->s_more_io)) > - wbc->more_io = 1; > } > + if (!list_empty(&sb->s_more_io) || !list_empty(&sb->s_io) > + wbc->more_io = 1; > return; /* Leave any unwritten inodes on s_io */ > } -- 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