From 0e57f6a36f9be03e5abb755f524ee91c4aebe854 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Mon, 20 Dec 2010 12:02:19 +1100 Subject: xfs: bulk AIL insertion during transaction commit When inserting items into the AIL from the transaction committed callbacks, we take the AIL lock for every single item that is to be inserted. For a CIL checkpoint commit, this can be tens of thousands of individual inserts, yet almost all of the items will be inserted at the same point in the AIL because they have the same index. To reduce the overhead and contention on the AIL lock for such operations, introduce a "bulk insert" operation which allows a list of log items with the same LSN to be inserted in a single operation via a list splice. To do this, we need to pre-sort the log items being committed into a temporary list for insertion. The complexity is that not every log item will end up with the same LSN, and not every item is actually inserted into the AIL. Items that don't match the commit LSN will be inserted and unpinned as per the current one-at-a-time method (relatively rare), while items that are not to be inserted will be unpinned and freed immediately. Items that are to be inserted at the given commit lsn are placed in a temporary array and inserted into the AIL in bulk each time the array fills up. As a result of this, we trade off AIL hold time for a significant reduction in traffic. lock_stat output shows that the worst case hold time is unchanged, but contention from AIL inserts drops by an order of magnitude and the number of lock traversal decreases significantly. Signed-off-by: Dave Chinner Reviewed-by: Christoph Hellwig --- fs/xfs/xfs_trans.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 78 insertions(+), 1 deletion(-) (limited to 'fs/xfs/xfs_trans.c') diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c index f6d956b7711e..f80a067a4658 100644 --- a/fs/xfs/xfs_trans.c +++ b/fs/xfs/xfs_trans.c @@ -1350,7 +1350,7 @@ xfs_trans_fill_vecs( * they could be immediately flushed and we'd have to race with the flusher * trying to pull the item from the AIL as we add it. */ -void +static void xfs_trans_item_committed( struct xfs_log_item *lip, xfs_lsn_t commit_lsn, @@ -1425,6 +1425,83 @@ xfs_trans_committed( xfs_trans_free(tp); } +static inline void +xfs_log_item_batch_insert( + struct xfs_ail *ailp, + struct xfs_log_item **log_items, + int nr_items, + xfs_lsn_t commit_lsn) +{ + int i; + + spin_lock(&ailp->xa_lock); + /* xfs_trans_ail_update_bulk drops ailp->xa_lock */ + xfs_trans_ail_update_bulk(ailp, log_items, nr_items, commit_lsn); + + for (i = 0; i < nr_items; i++) + IOP_UNPIN(log_items[i], 0); +} + +/* + * Bulk operation version of xfs_trans_committed that takes a log vector of + * items to insert into the AIL. This uses bulk AIL insertion techniques to + * minimise lock traffic. + */ +void +xfs_trans_committed_bulk( + struct xfs_ail *ailp, + struct xfs_log_vec *log_vector, + xfs_lsn_t commit_lsn, + int aborted) +{ +#define LOG_ITEM_BATCH_SIZE 32 + struct xfs_log_item *log_items[LOG_ITEM_BATCH_SIZE]; + struct xfs_log_vec *lv; + int i = 0; + + /* unpin all the log items */ + for (lv = log_vector; lv; lv = lv->lv_next ) { + struct xfs_log_item *lip = lv->lv_item; + xfs_lsn_t item_lsn; + + if (aborted) + lip->li_flags |= XFS_LI_ABORTED; + item_lsn = IOP_COMMITTED(lip, commit_lsn); + + /* item_lsn of -1 means the item was freed */ + if (XFS_LSN_CMP(item_lsn, (xfs_lsn_t)-1) == 0) + continue; + + if (item_lsn != commit_lsn) { + + /* + * Not a bulk update option due to unusual item_lsn. + * Push into AIL immediately, rechecking the lsn once + * we have the ail lock. Then unpin the item. + */ + spin_lock(&ailp->xa_lock); + if (XFS_LSN_CMP(item_lsn, lip->li_lsn) > 0) + xfs_trans_ail_update(ailp, lip, item_lsn); + else + spin_unlock(&ailp->xa_lock); + IOP_UNPIN(lip, 0); + continue; + } + + /* Item is a candidate for bulk AIL insert. */ + log_items[i++] = lv->lv_item; + if (i >= LOG_ITEM_BATCH_SIZE) { + xfs_log_item_batch_insert(ailp, log_items, + LOG_ITEM_BATCH_SIZE, commit_lsn); + i = 0; + } + } + + /* make sure we insert the remainder! */ + if (i) + xfs_log_item_batch_insert(ailp, log_items, i, commit_lsn); +} + /* * Called from the trans_commit code when we notice that * the filesystem is in the middle of a forced shutdown. -- cgit v1.2.3-58-ga151