From: Martin Knoblauch Subject: Re: regression: 100% io-wait with 2.6.24-rcX Date: Wed, 16 Jan 2008 06:15:49 -0800 (PST) Message-ID: <230154.6549.qm@web32604.mail.mud.yahoo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Mike Snitzer , Peter Zijlstra , jplatte@naasa.net, Ingo Molnar , linux-kernel@vger.kernel.org, "linux-ext4@vger.kernel.org" , Linus Torvalds To: Fengguang Wu Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org ----- Original Message ---- > From: Fengguang Wu > To: Martin Knoblauch > Cc: Mike Snitzer ; Peter Zijlstra ; jplatte@naasa.net; Ingo Molnar ; linux-kernel@vger.kernel.org; "linux-ext4@vger.kernel.org" ; Linus Torvalds > Sent: Wednesday, January 16, 2008 1:00:04 PM > Subject: Re: regression: 100% io-wait with 2.6.24-rcX > > On Wed, Jan 16, 2008 at 01:26:41AM -0800, Martin Knoblauch wrote: > > > For those interested in using your writeback improvements in > > > production sooner rather than later (primarily with ext3); what > > > recommendations do you have? Just heavily test our own 2.6.24 > + > your > > > evolving "close, but not ready for merge" -mm writeback patchset? > > > > > Hi Fengguang, Mike, > > > > I can add myself to Mikes question. It would be good to know > a > "roadmap" for the writeback changes. Testing 2.6.24-rcX so far has > been > showing quite nice improvement of the overall writeback situation and > it > would be sad to see this [partially] gone in 2.6.24-final. > Linus > apparently already has reverted "...2250b". I will definitely repeat my > tests > with -rc8. and report. > > Thank you, Martin. Can you help test this patch on 2.6.24-rc7? > Maybe we can push it to 2.6.24 after your testing. > Will do tomorrow or friday. Actually a patch against -rc8 would be nicer for me, as I have not looked at -rc7 due to holidays and some of the reported problems with it. Cheers Martin > Fengguang > --- > fs/fs-writeback.c | 17 +++++++++++++++-- > include/linux/writeback.h | 1 + > mm/page-writeback.c | 9 ++++++--- > 3 files changed, 22 insertions(+), 5 deletions(-) > > --- linux.orig/fs/fs-writeback.c > +++ linux/fs/fs-writeback.c > @@ -284,7 +284,16 @@ __sync_single_inode(struct inode *inode, > * soon as the queue becomes uncongested. > */ > inode->i_state |= I_DIRTY_PAGES; > - requeue_io(inode); > + if (wbc->nr_to_write <= 0) > + /* > + * slice used up: queue for next turn > + */ > + requeue_io(inode); > + else > + /* > + * somehow blocked: retry later > + */ > + redirty_tail(inode); > } else { > /* > * Otherwise fully redirty the inode so that > @@ -479,8 +488,12 @@ sync_sb_inodes(struct super_block *sb, s > iput(inode); > cond_resched(); > spin_lock(&inode_lock); > - if (wbc->nr_to_write <= 0) > + if (wbc->nr_to_write <= 0) { > + wbc->more_io = 1; > break; > + } > + if (!list_empty(&sb->s_more_io)) > + wbc->more_io = 1; > } > return; /* Leave any unwritten inodes on s_io */ > } > --- linux.orig/include/linux/writeback.h > +++ linux/include/linux/writeback.h > @@ -62,6 +62,7 @@ struct writeback_control { > unsigned for_reclaim:1; /* Invoked from the page > allocator > */ > unsigned for_writepages:1; /* This is a writepages() call */ > unsigned range_cyclic:1; /* range_start is cyclic */ > + unsigned more_io:1; /* more io to be dispatched */ > }; > > /* > --- linux.orig/mm/page-writeback.c > +++ linux/mm/page-writeback.c > @@ -558,6 +558,7 @@ static void background_writeout(unsigned > global_page_state(NR_UNSTABLE_NFS) < background_thresh > && min_pages <= 0) > break; > + wbc.more_io = 0; > wbc.encountered_congestion = 0; > wbc.nr_to_write = MAX_WRITEBACK_PAGES; > wbc.pages_skipped = 0; > @@ -565,8 +566,9 @@ static void background_writeout(unsigned > min_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write; > if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) { > /* Wrote less than expected */ > - congestion_wait(WRITE, HZ/10); > - if (!wbc.encountered_congestion) > + if (wbc.encountered_congestion || wbc.more_io) > + congestion_wait(WRITE, HZ/10); > + else > break; > } > } > @@ -631,11 +633,12 @@ static void wb_kupdate(unsigned long arg > global_page_state(NR_UNSTABLE_NFS) + > (inodes_stat.nr_inodes - inodes_stat.nr_unused); > while (nr_to_write > 0) { > + wbc.more_io = 0; > wbc.encountered_congestion = 0; > wbc.nr_to_write = MAX_WRITEBACK_PAGES; > writeback_inodes(&wbc); > if (wbc.nr_to_write > 0) { > - if (wbc.encountered_congestion) > + if (wbc.encountered_congestion || wbc.more_io) > congestion_wait(WRITE, HZ/10); > else > break; /* All the old data is written */ > > >