From: Alex Elder <aelder@sgi.com>
To: Dave Chinner <david@fromorbit.com>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 07/18] xfs: don't use vfs writeback for pure metadata modifications
Date: Tue, 14 Sep 2010 17:12:17 -0500 [thread overview]
Message-ID: <1284502337.9701.89.camel@doink> (raw)
In-Reply-To: <1284461777-1496-8-git-send-email-david@fromorbit.com>
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? Therefore we don't need to rely on the VFS layer to get
the dirty inode pushed out?
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.)
> Hence we can stop marking VFS inodes dirty during transaction commit or when
> changing timestamps during transactions. This will keep the inodes in the
> superblock dirty list to those containing data or unlogged metadata changes.
The code looks fine to me, but I don't know whether the
change it implements is correct or not without digging
in a little deeper.
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
> fs/xfs/linux-2.6/xfs_iops.c | 18 +++++-------------
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next prev parent reply other threads:[~2010-09-14 22:12 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 [this message]
2010-09-15 0:28 ` Dave Chinner
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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