[XFS] Prevent AIL lock contention during transaction completion (b589334c) · Commits · 戴 / test

When hundreds of processors attempt to commit transactions at the same time, they can contend on the AIL lock when updating the tail LSN held in the in-core log structure. At the moment, the tail LSN is only needed when actually writing out an iclog, so it really does not need to be updated on every single transaction completion - only those that result in switching iclogs and flushing them to disk. The result is that we reduce the number of times we need to grab the AIL lock and the log grant lock by up to two orders of magnitude on large processor count machines. The problem has previously been hidden by AIL lock contention walking the AIL list which was recently solved and uncovered this issue. SGI-PV: 975671 SGI-Modid: xfs-linux-melb:xfs-kern:30504a Signed-off-by:

David Chinner <dgc@sgi.com> Signed-off-by:

Tim Shimmin <tes@sgi.com> Signed-off-by:

Lachlan McIlroy <lachlan@sgi.com>

fs/xfs/xfs_log.c

+6 −9

Original line number	Diff line number	Diff line
		@@ -2813,15 +2813,13 @@ xlog_state_put_ticket(xlog_t *log,
		*
		*/
		STATIC int
		xlog_state_release_iclog(xlog_t *log,
		xlog_state_release_iclog(
		xlog_t *log,
		xlog_in_core_t *iclog)
		{
		int sync = 0; /* do we sync? */

		xlog_assign_tail_lsn(log->l_mp);

		spin_lock(&log->l_icloglock);

		if (iclog->ic_state & XLOG_STATE_IOERROR) {
		spin_unlock(&log->l_icloglock);
		return XFS_ERROR(EIO);
		@@ -2833,13 +2831,14 @@ xlog_state_release_iclog(xlog_t *log,

		if (--iclog->ic_refcnt == 0 &&
		iclog->ic_state == XLOG_STATE_WANT_SYNC) {
		/* update tail before writing to iclog */
		xlog_assign_tail_lsn(log->l_mp);
		sync++;
		iclog->ic_state = XLOG_STATE_SYNCING;
		iclog->ic_header.h_tail_lsn = cpu_to_be64(log->l_tail_lsn);
		xlog_verify_tail_lsn(log, iclog, log->l_tail_lsn);
		/* cycle incremented when incrementing curr_block */
		}

		spin_unlock(&log->l_icloglock);

		/*
		@@ -2849,11 +2848,9 @@ xlog_state_release_iclog(xlog_t *log,
		* this iclog has consistent data, so we ignore IOERROR
		* flags after this point.
		*/
		if (sync) {
		if (sync)
		return xlog_sync(log, iclog);
		}
		return 0;

		} /* xlog_state_release_iclog */

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