[XFS updates] XFS development tree branch, for-linus, updated. v2.6.34-19477-g51749e4

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The branch, for-linus has been updated
  51749e4 xfs: log IO completion workqueue is a high priority queue
      from  a122eb2fdfd78b58c6dd992d6f4b1aaef667eef9 (commit)

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- Log -----------------------------------------------------------------
commit 51749e47e191db8e588ad5cebea731caf7b705d7
Author: Dave Chinner <dchinner at redhat.com>
Date:   Wed Sep 8 09:00:22 2010 +0000

    xfs: log IO completion workqueue is a high priority queue
    
    The workqueue implementation in 2.6.36-rcX has changed, resulting
    in the workqueues no longer having dedicated threads for work
    processing. This has caused severe livelocks under heavy parallel
    create workloads because the log IO completions have been getting
    held up behind metadata IO completions.  Hence log commits would
    stall, memory allocation would stall because pages could not be
    cleaned, and lock contention on the AIL during inode IO completion
    processing was being seen to slow everything down even further.
    
    By making the log Io completion workqueue a high priority workqueue,
    they are queued ahead of all data/metadata IO completions and
    processed before the data/metadata completions. Hence the log never
    gets stalled, and operations needed to clean memory can continue as
    quickly as possible. This avoids the livelock conditions and allos
    the system to keep running under heavy load as per normal.
    
    Signed-off-by: Dave Chinner <dchinner at redhat.com>
    Reviewed-by: Christoph Hellwig <hch at lst.de>
    Signed-off-by: Alex Elder <aelder at sgi.com>

-----------------------------------------------------------------------

Summary of changes:
 fs/xfs/linux-2.6/xfs_buf.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)


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