From: David Chinner Date: Thu, 6 Mar 2008 02:44:06 +0000 (+1100) Subject: [XFS] Prevent AIL lock contention during transaction completion X-Git-Tag: v2.6.26-rc1~1147^2~78 X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=b589334c7a1fff85d2f009d5db4c34fad48925e9;p=linux-2.6-omap-h63xx.git [XFS] Prevent AIL lock contention during transaction completion 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 Signed-off-by: Tim Shimmin Signed-off-by: Lachlan McIlroy --- diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c index 31f2b04f2c9..2e35077ff6b 100644 --- a/fs/xfs/xfs_log.c +++ b/fs/xfs/xfs_log.c @@ -2813,15 +2813,13 @@ 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); @@ -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 */