Re: xfs cluster rewrites is broken?
From: Alexander Y. Fomichev
Date: Tue Mar 21 2006 - 09:52:57 EST
On Monday 20 March 2006 03:05, David Chinner wrote:
> Hi Alexander,
> On Fri, Mar 17, 2006 at 03:32:03PM +0300, Alexander Y. Fomichev wrote:
> > Hello,
> > Two days ago i've try 2.6.16-rc5 on 2-way dual-core Opteron server
> > and faced with a strange system behaviour.
> > [XFS] cluster rewrites We can cluster mapped pages aswell, this
> > improves
> > performances on rewrites since we can reduce the number of allocator
> > calls.
> FYI, prior to this mod, XFS never clustered rewrites, so it's not
> surprising that this particular issue has only recently come to light.
> > diff -urN a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c
> > --- a/fs/xfs/linux-2.6/xfs_aops.c 2006-03-17 13:13:53.000000000 +0300
> > +++ b/fs/xfs/linux-2.6/xfs_aops.c 2006-03-17 15:12:12.000000000 +0300
> > @@ -616,8 +616,6 @@
> > acceptable = (type == IOMAP_UNWRITTEN);
> > else if (buffer_delay(bh))
> > acceptable = (type == IOMAP_DELAY);
> > - else if (buffer_mapped(bh))
> > - acceptable = (type == 0);
> > else
> > break;
> > } while ((bh = bh->b_this_page) != head);
> Well, that switches off rewrite clustering altogether, so it's
> not surprising that it fixed your problem. It also points out the
> problem as well - we don't every check if the buffer is dirty before
> declaring that the page is acceptible for write clustering.
> The other cases checked here (buffer_unwritten() and buffer_delay())
> are, by defintition, dirty buffers and so they only ever cluster
> dirty pages. buffer_mapped(), OTOH, could be clean or dirty.....
> Can you try the patch below, and see if that fixes the problem
> you are seeing?
Yes, it works as expected. Thank you very mach for quick answer and
Alexander Y. Fomichev <gluk@xxxxxxx>
Public PGP key: http://sysadminday.org.ru/gluk.asc
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