Re: regression: 100% io-wait with 2.6.24-rcX

Mike Snitzer
2008-01-16T16:28:25Z

On Jan 16, 2008 9:15 AM, Martin Knoblauch <spamtrap@knobisoft.de> wrote:
> ----- Original Message ----
> > From: Fengguang Wu <wfg@mail.ustc.edu.cn>
> > To: Martin Knoblauch <knobi@knobisoft.de>
> > Cc: Mike Snitzer <snitzer@gmail.com>; Peter Zijlstra <peterz@infradead.org>; jplatte@naasa.net; Ingo Molnar <mingo@elte.hu>; linux-kernel@vger.kernel.org; "linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>; Linus Torvalds <torvalds@linux-foundation.org>
> > 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.

Fengguang's latest writeback patch applies cleanly, builds, boots on 2.6.24-rc8.

I'll be able to share ext3 performance results (relative to 2.6.24-rc7) shortly.

Mike
>
>
> > 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 */
> >
> >
> >
>
>
>