Commit ed1575da authored by Darrick J. Wong's avatar Darrick J. Wong
Browse files

xfs: expose the log push threshold 



Separate the computation of the log push threshold and the push logic in
xlog_grant_push_ail.  This enables higher level code to determine (for
example) that it is holding on to a logged intent item and the log is so
busy that it is more than 75% full.  In that case, it would be desirable
to move the log item towards the head to release the tail, which we will
cover in the next patch.

Signed-off-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: default avatarBrian Foster <bfoster@redhat.com>
parent 4e919af7

fs/xfs/xfs_log.c

+30 −10
Original line number Diff line number Diff line
@@ -1475,14 +1475,14 @@ xlog_commit_record( 
}



/*

 * Push on the buffer cache code if we ever use more than 75% of the on-disk

 * log space.  This code pushes on the lsn which would supposedly free up

 * the 25% which we want to leave free.  We may need to adopt a policy which

 * pushes on an lsn which is further along in the log once we reach the high

 * water mark.  In this manner, we would be creating a low water mark.

 * Compute the LSN that we'd need to push the log tail towards in order to have

 * (a) enough on-disk log space to log the number of bytes specified, (b) at

 * least 25% of the log space free, and (c) at least 256 blocks free.  If the

 * log free space already meets all three thresholds, this function returns

 * NULLCOMMITLSN.

 */

STATIC void

xlog_grant_push_ail(

xfs_lsn_t

xlog_grant_push_threshold(

	struct xlog	*log,

	int		need_bytes)

{
@@ -1508,7 +1508,7 @@ xlog_grant_push_ail( 
	free_threshold = max(free_threshold, (log->l_logBBsize >> 2));

	free_threshold = max(free_threshold, 256);

	if (free_blocks >= free_threshold)

		return;

		return NULLCOMMITLSN;



	xlog_crack_atomic_lsn(&log->l_tail_lsn, &threshold_cycle,

						&threshold_block);
@@ -1528,12 +1528,32 @@ xlog_grant_push_ail( 
	if (XFS_LSN_CMP(threshold_lsn, last_sync_lsn) > 0)

		threshold_lsn = last_sync_lsn;



	return threshold_lsn;

}



/*

 * Push the tail of the log if we need to do so to maintain the free log space

 * thresholds set out by xlog_grant_push_threshold.  We may need to adopt a

 * policy which pushes on an lsn which is further along in the log once we

 * reach the high water mark.  In this manner, we would be creating a low water

 * mark.

 */

STATIC void

xlog_grant_push_ail(

	struct xlog	*log,

	int		need_bytes)

{

	xfs_lsn_t	threshold_lsn;



	threshold_lsn = xlog_grant_push_threshold(log, need_bytes);

	if (threshold_lsn == NULLCOMMITLSN || XLOG_FORCED_SHUTDOWN(log))

		return;



	/*

	 * Get the transaction layer to kick the dirty buffers out to

	 * disk asynchronously. No point in trying to do this if

	 * the filesystem is shutting down.

	 */

	if (!XLOG_FORCED_SHUTDOWN(log))

	xfs_ail_push(log->l_ailp, threshold_lsn);

}

fs/xfs/xfs_log.h

+2 −0
Original line number Diff line number Diff line
@@ -141,4 +141,6 @@ void xfs_log_quiesce(struct xfs_mount *mp); 
bool	xfs_log_check_lsn(struct xfs_mount *, xfs_lsn_t);

bool	xfs_log_in_recovery(struct xfs_mount *);



xfs_lsn_t xlog_grant_push_threshold(struct xlog *log, int need_bytes);



#endif	/* __XFS_LOG_H__ */

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