xfs: use a cursor for bulk AIL insertion

Delayed logging can insert tens of thousands of log items into the
AIL at the same LSN. When the committing of log commit records
occur, we can get insertions occurring at an LSN that is not at the
end of the AIL. If there are thousands of items in the AIL on the
tail LSN, each insertion has to walk the AIL to find the correct
place to insert the new item into the AIL. This can consume large
amounts of CPU time and block other operations from occurring while
the traversals are in progress.

To avoid this repeated walk, use a AIL cursor to record
where we should be inserting the new items into the AIL without
having to repeat the walk. The cursor infrastructure already
provides this functionality for push walks, so is a simple extension
of existing code. While this will not avoid the initial walk, it
will avoid repeating it tens of thousands of times during a single
checkpoint commit.

This version includes logic improvements from Christoph Hellwig.

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

1 files changed, 7 insertions, 3 deletions

diff --git a/fs/xfs/xfs_trans_priv.h b/fs/xfs/xfs_trans_priv.h
index 6b164e9e9a1f..c0cb40890329 100644
--- a/fs/xfs/xfs_trans_priv.h
+++ b/fs/xfs/xfs_trans_priv.h
@@ -82,6 +82,7 @@ struct xfs_ail {
 extern struct workqueue_struct  *xfs_ail_wq;    /* AIL workqueue */
 
 void    xfs_trans_ail_update_bulk(struct xfs_ail *ailp,
+                                struct xfs_ail_cursor *cur,
                                 struct xfs_log_item **log_items, int nr_items,
                                 xfs_lsn_t lsn) __releases(ailp->xa_lock);
 static inline void
@@ -90,7 +91,7 @@ xfs_trans_ail_update(
         struct xfs_log_item     *lip,
         xfs_lsn_t               lsn) __releases(ailp->xa_lock)
 {
-        xfs_trans_ail_update_bulk(ailp, &lip, 1, lsn);
+        xfs_trans_ail_update_bulk(ailp, NULL, &lip, 1, lsn);
 }
 
 void    xfs_trans_ail_delete_bulk(struct xfs_ail *ailp,
@@ -111,10 +112,13 @@ xfs_lsn_t		xfs_ail_min_lsn(struct xfs_ail *ailp);
 void                    xfs_trans_unlocked_item(struct xfs_ail *,
                                         xfs_log_item_t *);
 
-struct xfs_log_item     *xfs_trans_ail_cursor_first(struct xfs_ail *ailp,
+struct xfs_log_item *   xfs_trans_ail_cursor_first(struct xfs_ail *ailp,
                                         struct xfs_ail_cursor *cur,
                                         xfs_lsn_t lsn);
-struct xfs_log_item     *xfs_trans_ail_cursor_next(struct xfs_ail *ailp,
+struct xfs_log_item *   xfs_trans_ail_cursor_last(struct xfs_ail *ailp,
+                                        struct xfs_ail_cursor *cur,
+                                        xfs_lsn_t lsn);
+struct xfs_log_item *   xfs_trans_ail_cursor_next(struct xfs_ail *ailp,
                                         struct xfs_ail_cursor *cur);
 void                    xfs_trans_ail_cursor_done(struct xfs_ail *ailp,
                                         struct xfs_ail_cursor *cur);