From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail203.messagelabs.com (mail203.messagelabs.com [216.82.254.243]) by kanga.kvack.org (Postfix) with ESMTP id A5D5A600365 for ; Tue, 27 Jul 2010 05:45:54 -0400 (EDT) Date: Tue, 27 Jul 2010 10:45:34 +0100 From: Mel Gorman Subject: Re: [PATCH 4/6] writeback: sync expired inodes first in background writeback Message-ID: <20100727094534.GW5300@csn.ul.ie> References: <20100722050928.653312535@intel.com> <20100722061822.906037624@intel.com> <20100726105736.GM5300@csn.ul.ie> <20100726125635.GC11947@localhost> <20100726125954.GT5300@csn.ul.ie> <20100726131152.GF11947@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20100726131152.GF11947@localhost> Sender: owner-linux-mm@kvack.org 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" List-ID: On Mon, Jul 26, 2010 at 09:11:52PM +0800, Wu Fengguang wrote: > On Mon, Jul 26, 2010 at 08:59:55PM +0800, Mel Gorman wrote: > > On Mon, Jul 26, 2010 at 08:56:35PM +0800, Wu Fengguang wrote: > > > > > @@ -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. > > > > > > Yes this should be commented. How about this one? > > > > > > @@ -232,8 +232,20 @@ 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)) > > > + inode_dirtied_after(inode, older_than_this)) { > > > + /* > > > + * background writeback will start with expired inodes, > > > + * and then fresh inodes. This order helps reducing > > > + * the number of dirty pages reaching the end of LRU > > > + * lists and cause trouble to the page reclaim. > > > + */ > > > > s/reducing/reduce/ > > > > Otherwise, it's enough detail to know what is going on. Thanks > > Thanks. Here is the updated patch. > --- > Subject: writeback: sync expired inodes first in background writeback > From: Wu Fengguang > Date: Wed Jul 21 20:11:53 CST 2010 > > 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 > - enqueue all dirty inodes if there are no more expired inodes to sync > > This will help reduce the number of dirty pages encountered by page > reclaim, eg. the pageout() calls. Normally older inodes contain older > dirty pages, which are more close to the end of the LRU lists. So > syncing older inodes first helps reducing the dirty pages reached by > the page reclaim code. > > CC: Jan Kara > Signed-off-by: Wu Fengguang Acked-by: Mel Gorman -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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