xfs: improve metadata I/O merging in the elevator

Change all async metadata buffers to use [READ|WRITE]_META I/O types
so that the I/O doesn't get issued immediately. This allows merging of
adjacent metadata requests but still prioritises them over bulk data.
This shows a 10-15% improvement in sequential create speed of small
files.

Don't include the log buffers in this classification - leave them as
sync types so they are issued immediately.

Signed-off-by: Dave Chinner <dgc@sgi.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 4cb1792040e3..600b5b06aaeb 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -1441,6 +1441,7 @@ xlog_sync(xlog_t		*log,
         XFS_BUF_ZEROFLAGS(bp);
         XFS_BUF_BUSY(bp);
         XFS_BUF_ASYNC(bp);
+        bp->b_flags |= XBF_LOG_BUFFER;
         /*
          * Do an ordered write for the log block.
          * Its unnecessary to flush the first split block in the log wrap case.
@@ -1478,6 +1479,7 @@ xlog_sync(xlog_t		*log,
                 XFS_BUF_ZEROFLAGS(bp);
                 XFS_BUF_BUSY(bp);
                 XFS_BUF_ASYNC(bp);
+                bp->b_flags |= XBF_LOG_BUFFER;
                 if (log->l_mp->m_flags & XFS_MOUNT_BARRIER)
                         XFS_BUF_ORDERED(bp);
                 dptr = XFS_BUF_PTR(bp);