From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Sun, 20 Jan 2008 21:23:24 -0800 (PST) Received: from larry.melbourne.sgi.com (larry.melbourne.sgi.com [134.14.52.130]) by oss.sgi.com (8.12.11.20060308/8.12.11/SuSE Linux 0.7) with SMTP id m0L5NHLP016266 for ; Sun, 20 Jan 2008 21:23:21 -0800 Date: Mon, 21 Jan 2008 16:23:30 +1100 From: David Chinner Subject: [patch] Prevent AIL lock contention during transaction completion Message-ID: <20080121052330.GG155259@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: xfs-bounce@oss.sgi.com Errors-to: xfs-bounce@oss.sgi.com List-Id: xfs To: xfs-dev Cc: xfs-oss 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 oftimes 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 has recently been solved. Signed-off-by: Dave Chinner --- fs/xfs/xfs_log.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) Index: 2.6.x-xfs-new/fs/xfs/xfs_log.c =================================================================== --- 2.6.x-xfs-new.orig/fs/xfs/xfs_log.c 2008-01-21 16:06:27.187549816 +1100 +++ 2.6.x-xfs-new/fs/xfs/xfs_log.c 2008-01-21 16:16:51.804146394 +1100 @@ -2815,15 +2815,13 @@ xlog_state_put_ticket(xlog_t *log, * */ STATIC int -xlog_state_release_iclog(xlog_t *log, - xlog_in_core_t *iclog) +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); @@ -2835,13 +2833,14 @@ 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); /* @@ -2851,11 +2850,9 @@ 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 */