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xfs: reduce the number of log forces from tail pushing

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The AIL push code will issue a log force on ever single push loop
that it exits and has encountered pinned items. It doesn't rescan
these pinned items until it revisits the AIL from the start. Hence
we only need to force the log once per walk from the start of the
AIL to the target LSN.

This results in numbers like this:

	xs_push_ail_flush.....         1456
	xs_log_force.........          1485

For an 8-way 50M inode create workload - almost all the log forces
are coming from the AIL pushing code.

Reduce the number of log forces by only forcing the log if the
previous walk found pinned buffers. This reduces the numbers to:

	xs_push_ail_flush.....          665
	xs_log_force.........           682

For the same test.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
This commit is contained in:
Dave Chinner
2011-09-30 04:45:03 +00:00
committed by Alex Elder
parent 3815832a2a
commit 670ce93fef
2 changed files with 21 additions and 13 deletions
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fs/xfs/xfs_trans_priv.h
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@@ -71,6 +71,7 @@ struct xfs_ail {
struct delayed_work xa_work;
xfs_lsn_t xa_last_pushed_lsn;
unsigned long xa_flags;
int xa_log_flush;
};
#define XFS_AIL_PUSHING_BIT 0