From: Dave Chinner <david@fromorbit.com>
To: Alex Elder <aelder@sgi.com>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 07/18] xfs: don't use vfs writeback for pure metadata modifications
Date: Wed, 15 Sep 2010 10:28:28 +1000 [thread overview]
Message-ID: <20100915002828.GK15695@dastard> (raw)
In-Reply-To: <1284502337.9701.89.camel@doink>
On Tue, Sep 14, 2010 at 05:12:17PM -0500, Alex Elder wrote:
> On Tue, 2010-09-14 at 20:56 +1000, Dave Chinner wrote:
> > From: Dave Chinner <dchinner@redhat.com>
> >
> > Under heavy multi-way parallel create workloads, the VFS struggles to write
> > back all the inodes that have been changed in age order. The bdi flusher thread
> > becomes CPU bound, spending 85% of it's time in the VFS code, mostly traversing
> > the superblock dirty inode list to separate dirty inodes old enough to flush.
> >
> > We already keep an index of all metadata changes in age order - in the AIL -
> > and continued log pressure will do age ordered writeback without any extra
> > overhead at all. If there is no pressure on the log, the xfssyncd will
> > periodically write back metadata in ascending disk address offset order so will
> > be very efficient.
>
> So log pressure will cause the logged updates to the inode to be
> written to disk (in order), which is all we really need. Is that
> right?
Yes. And if there is no log pressure, xfssyncd will do the writeback
in an disk order efficient manner.
> Therefore we don't need to rely on the VFS layer to get
> the dirty inode pushed out?
No. Indeed, for all other types of metadata (btree blocks,
directory/attribute blocks, etc) we already rely on the
xfsaild/xfsbufd to write them out in a timely manner because the VFS
knows nothing about them.
> Is writeback the only reason we should inform the VFS that an
> inode is dirty? (Sorry, I have to leave shortly and don't have
> time to follow this at the moment--I may have to come back to
> this later.)
Yes, pretty much. Take your time - this is one of the more radical
changes in the patch set...
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2010-09-15 0:27 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-14 10:55 [PATCH 0/18] xfs: metadata and buffer cache scalability improvements Dave Chinner
2010-09-14 10:56 ` [PATCH 01/18] xfs: single thread inode cache shrinking Dave Chinner
2010-09-14 18:48 ` Alex Elder
2010-09-14 22:48 ` Dave Chinner
2010-09-14 10:56 ` [PATCH 02/18] xfs: reduce the number of CIL lock round trips during commit Dave Chinner
2010-09-14 14:48 ` Christoph Hellwig
2010-09-14 17:21 ` Alex Elder
2010-09-14 10:56 ` [PATCH 03/18] xfs: remove debug assert for per-ag reference counting Dave Chinner
2010-09-14 14:48 ` Christoph Hellwig
2010-09-14 17:22 ` Alex Elder
2010-09-14 10:56 ` [PATCH 04/18] xfs: lockless per-ag lookups Dave Chinner
2010-09-14 12:35 ` Dave Chinner
2010-09-14 14:50 ` Christoph Hellwig
2010-09-14 17:28 ` Alex Elder
2010-09-14 10:56 ` [PATCH 05/18] xfs: convert inode cache lookups to use RCU locking Dave Chinner
2010-09-14 16:27 ` Christoph Hellwig
2010-09-14 23:17 ` Dave Chinner
2010-09-14 21:23 ` Alex Elder
2010-09-14 23:42 ` Dave Chinner
2010-09-14 10:56 ` [PATCH 06/18] xfs: convert pag_ici_lock to a spin lock Dave Chinner
2010-09-14 21:26 ` Alex Elder
2010-09-14 10:56 ` [PATCH 07/18] xfs: don't use vfs writeback for pure metadata modifications Dave Chinner
2010-09-14 14:54 ` Christoph Hellwig
2010-09-15 0:14 ` Dave Chinner
2010-09-15 0:17 ` Christoph Hellwig
2010-09-14 22:12 ` Alex Elder
2010-09-15 0:28 ` Dave Chinner [this message]
2010-11-08 10:47 ` Christoph Hellwig
2010-09-14 10:56 ` [PATCH 08/18] xfs: rename xfs_buf_get_nodaddr to be more appropriate Dave Chinner
2010-09-14 14:56 ` Christoph Hellwig
2010-09-14 22:14 ` Alex Elder
2010-09-14 10:56 ` [PATCH 09/18] xfs: introduced uncached buffer read primitve Dave Chinner
2010-09-14 14:56 ` Christoph Hellwig
2010-09-14 22:16 ` Alex Elder
2010-09-14 10:56 ` [PATCH 10/18] xfs: store xfs_mount in the buftarg instead of in the xfs_buf Dave Chinner
2010-09-14 14:57 ` Christoph Hellwig
2010-09-14 22:21 ` Alex Elder
2010-09-14 10:56 ` [PATCH 11/18] xfs: kill XBF_FS_MANAGED buffers Dave Chinner
2010-09-14 14:59 ` Christoph Hellwig
2010-09-14 22:26 ` Alex Elder
2010-09-14 10:56 ` [PATCH 12/18] xfs: use unhashed buffers for size checks Dave Chinner
2010-09-14 15:00 ` Christoph Hellwig
2010-09-14 22:29 ` Alex Elder
2010-09-14 10:56 ` [PATCH 13/18] xfs: remove buftarg hash for external devices Dave Chinner
2010-09-14 22:29 ` Alex Elder
2010-09-14 10:56 ` [PATCH 14/18] xfs: convert buffer cache hash to rbtree Dave Chinner
2010-09-14 16:29 ` Christoph Hellwig
2010-09-15 17:46 ` Alex Elder
2010-09-14 10:56 ` [PATCH 15/18] xfs; pack xfs_buf structure more tightly Dave Chinner
2010-09-14 16:30 ` Christoph Hellwig
2010-09-15 18:01 ` Alex Elder
2010-09-14 10:56 ` [PATCH 16/18] xfs: convert xfsbud shrinker to a per-buftarg shrinker Dave Chinner
2010-09-14 16:32 ` Christoph Hellwig
2010-09-15 20:19 ` Alex Elder
2010-09-16 0:28 ` Dave Chinner
2010-09-14 10:56 ` [PATCH 17/18] xfs: add a lru to the XFS buffer cache Dave Chinner
2010-09-14 23:16 ` Christoph Hellwig
2010-09-15 0:05 ` Dave Chinner
2010-09-15 21:28 ` Alex Elder
2010-09-14 10:56 ` [PATCH 18/18] xfs: stop using the page cache to back the " Dave Chinner
2010-09-14 23:20 ` Christoph Hellwig
2010-09-15 0:06 ` Dave Chinner
2010-09-14 14:25 ` [PATCH 0/18] xfs: metadata and buffer cache scalability improvements Christoph Hellwig
2010-09-17 13:21 ` Alex Elder
2010-09-21 2:02 ` Dave Chinner
2010-09-21 16:23 ` Alex Elder
2010-09-21 22:34 ` Dave Chinner
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