From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id D4B6B8D003B for ; Thu, 21 Apr 2011 12:04:13 -0400 (EDT) Date: Thu, 21 Apr 2011 18:04:05 +0200 From: Jan Kara Subject: Re: [PATCH 3/6] writeback: sync expired inodes first in background writeback Message-ID: <20110421160405.GB4476@quack.suse.cz> References: <20110419073523.GF23985@dastard> <20110419095740.GC5257@quack.suse.cz> <20110419125616.GA20059@localhost> <20110420012120.GK23985@dastard> <20110420025321.GA14398@localhost> <20110421004547.GD1814@dastard> <20110421020617.GB12191@localhost> <20110421030152.GG1814@dastard> <20110421035954.GA15461@localhost> <20110421041010.GA18710@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110421041010.GA18710@localhost> Sender: owner-linux-mm@kvack.org List-ID: To: Wu Fengguang Cc: Dave Chinner , Jan Kara , Andrew Morton , Mel Gorman , Mel Gorman , Trond Myklebust , Itaru Kitayama , Minchan Kim , LKML , "linux-fsdevel@vger.kernel.org" , Linux Memory Management List On Thu 21-04-11 12:10:11, Wu Fengguang wrote: > > > Still, given wb_writeback() is the only caller of both > > > __writeback_inodes_sb and writeback_inodes_wb(), I'm wondering if > > > moving the queue_io calls up into wb_writeback() would clean up this > > > logic somewhat. I think Jan mentioned doing something like this as > > > well elsewhere in the thread... > > > > Unfortunately they call queue_io() inside the lock.. > > OK, let's try moving up the lock too. Do you like this change? :) > > Thanks, > Fengguang > --- > fs/fs-writeback.c | 22 ++++++---------------- > mm/backing-dev.c | 4 ++++ > 2 files changed, 10 insertions(+), 16 deletions(-) > > --- linux-next.orig/fs/fs-writeback.c 2011-04-21 12:04:02.000000000 +0800 > +++ linux-next/fs/fs-writeback.c 2011-04-21 12:05:54.000000000 +0800 > @@ -591,7 +591,6 @@ void writeback_inodes_wb(struct bdi_writ > > if (!wbc->wb_start) > wbc->wb_start = jiffies; /* livelock avoidance */ > - spin_lock(&inode_wb_list_lock); > > if (list_empty(&wb->b_io)) > queue_io(wb, wbc); > @@ -610,22 +609,9 @@ void writeback_inodes_wb(struct bdi_writ > if (ret) > break; > } > - spin_unlock(&inode_wb_list_lock); > /* Leave any unwritten inodes on b_io */ > } > > -static void __writeback_inodes_sb(struct super_block *sb, > - struct bdi_writeback *wb, struct writeback_control *wbc) > -{ > - WARN_ON(!rwsem_is_locked(&sb->s_umount)); > - > - spin_lock(&inode_wb_list_lock); > - if (list_empty(&wb->b_io)) > - queue_io(wb, wbc); > - writeback_sb_inodes(sb, wb, wbc, true); > - spin_unlock(&inode_wb_list_lock); > -} > - > static inline bool over_bground_thresh(void) > { > unsigned long background_thresh, dirty_thresh; > @@ -652,7 +638,7 @@ static unsigned long writeback_chunk_siz > * The intended call sequence for WB_SYNC_ALL writeback is: > * > * wb_writeback() > - * __writeback_inodes_sb() <== called only once > + * writeback_sb_inodes() <== called only once > * write_cache_pages() <== called once for each inode > * (quickly) tag currently dirty pages > * (maybe slowly) sync all tagged pages > @@ -742,10 +728,14 @@ static long wb_writeback(struct bdi_writ > > retry: > trace_wbc_writeback_start(&wbc, wb->bdi); > + spin_lock(&inode_wb_list_lock); > + if (list_empty(&wb->b_io)) > + queue_io(wb, wbc); > if (work->sb) > - __writeback_inodes_sb(work->sb, wb, &wbc); > + writeback_sb_inodes(work->sb, wb, &wbc, true); > else > writeback_inodes_wb(wb, &wbc); > + spin_unlock(&inode_wb_list_lock); > trace_wbc_writeback_written(&wbc, wb->bdi); > > bdi_update_write_bandwidth(wb->bdi, wbc.wb_start); > --- linux-next.orig/mm/backing-dev.c 2011-04-21 12:06:02.000000000 +0800 > +++ linux-next/mm/backing-dev.c 2011-04-21 12:06:31.000000000 +0800 > @@ -268,7 +268,11 @@ static void bdi_flush_io(struct backing_ > .nr_to_write = 1024, > }; > > + spin_lock(&inode_wb_list_lock); > + if (list_empty(&wb->b_io)) > + queue_io(wb, wbc); > writeback_inodes_wb(&bdi->wb, &wbc); > + spin_unlock(&inode_wb_list_lock); > } Three notes here: 1) You are missing the call to writeback_inodes_wb() in balance_dirty_pages() (the patch should really work for vanilla kernels). 2) The intention of both bdi_flush_io() and balance_dirty_pages() is to write .nr_to_write pages. So they should either do queue_io() unconditionally (I kind of like that for simplicity) or they should requeue once if they have not written enough - otherwise it could happen that they are called just at the moment when b_io contains a single inode with a few dirty pages and they end up doing almost nothing. 3) I guess your patch does not compile because queue_io() is static ;). Honza -- Jan Kara SUSE Labs, CR -- 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