From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754429Ab0GZK5y (ORCPT ); Mon, 26 Jul 2010 06:57:54 -0400 Received: from gir.skynet.ie ([193.1.99.77]:37265 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754402Ab0GZK5x (ORCPT ); Mon, 26 Jul 2010 06:57:53 -0400 Date: Mon, 26 Jul 2010 11:57:37 +0100 From: Mel Gorman To: Wu Fengguang Cc: Andrew Morton , Dave Chinner , Jan Kara , Christoph Hellwig , Chris Mason , Jens Axboe , LKML , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 4/6] writeback: sync expired inodes first in background writeback Message-ID: <20100726105736.GM5300@csn.ul.ie> References: <20100722050928.653312535@intel.com> <20100722061822.906037624@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20100722061822.906037624@intel.com> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 22, 2010 at 01:09:32PM +0800, Wu Fengguang wrote: > A background flush work may run for ever. So it's reasonable for it to > mimic the kupdate behavior of syncing old/expired inodes first. > > The policy is > - enqueue all newly expired inodes at each queue_io() time > - retry with halfed expire interval until get some inodes to sync > > CC: Jan Kara > Signed-off-by: Wu Fengguang Ok, intuitively this would appear to tie into pageout where we want older inodes to be cleaned first by background flushers to limit the number of dirty pages encountered by page reclaim. If this is accurate, it should be detailed in the changelog. > --- > fs/fs-writeback.c | 20 ++++++++++++++------ > 1 file changed, 14 insertions(+), 6 deletions(-) > > --- linux-next.orig/fs/fs-writeback.c 2010-07-22 12:56:42.000000000 +0800 > +++ linux-next/fs/fs-writeback.c 2010-07-22 13:07:51.000000000 +0800 > @@ -217,14 +217,14 @@ static void move_expired_inodes(struct l > struct writeback_control *wbc) > { > unsigned long expire_interval = 0; > - unsigned long older_than_this; > + unsigned long older_than_this = 0; /* reset to kill gcc warning */ > LIST_HEAD(tmp); > struct list_head *pos, *node; > struct super_block *sb = NULL; > struct inode *inode; > int do_sb_sort = 0; > > - if (wbc->for_kupdate) { > + if (wbc->for_kupdate || wbc->for_background) { > expire_interval = msecs_to_jiffies(dirty_expire_interval * 10); > older_than_this = jiffies - expire_interval; > } > @@ -232,8 +232,15 @@ static void move_expired_inodes(struct l > while (!list_empty(delaying_queue)) { > inode = list_entry(delaying_queue->prev, struct inode, i_list); > if (expire_interval && > - inode_dirtied_after(inode, older_than_this)) > - break; > + inode_dirtied_after(inode, older_than_this)) { > + if (wbc->for_background && > + list_empty(dispatch_queue) && list_empty(&tmp)) { > + expire_interval >>= 1; > + older_than_this = jiffies - expire_interval; > + continue; > + } else > + break; > + } This needs a comment. I think what it is saying is that if background flush is active but no inodes are old enough, consider newer inodes. This is on the assumption that page reclaim has encountered dirty pages and the dirty inodes are still too young. > if (sb && sb != inode->i_sb) > do_sb_sort = 1; > sb = inode->i_sb; > @@ -521,7 +528,8 @@ void writeback_inodes_wb(struct bdi_writ > > wbc->wb_start = jiffies; /* livelock avoidance */ > spin_lock(&inode_lock); > - if (!wbc->for_kupdate || list_empty(&wb->b_io)) > + > + if (!(wbc->for_kupdate || wbc->for_background) || list_empty(&wb->b_io)) > queue_io(wb, wbc); > > while (!list_empty(&wb->b_io)) { > @@ -550,7 +558,7 @@ static void __writeback_inodes_sb(struct > > wbc->wb_start = jiffies; /* livelock avoidance */ > spin_lock(&inode_lock); > - if (!wbc->for_kupdate || list_empty(&wb->b_io)) > + if (!(wbc->for_kupdate || wbc->for_background) || list_empty(&wb->b_io)) > queue_io(wb, wbc); > writeback_sb_inodes(sb, wb, wbc, true); > spin_unlock(&inode_lock); > > -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab