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authorDavid Chinner <dgc@sgi.com>2008-03-06 13:44:06 +1100
committerLachlan McIlroy <lachlan@redback.melbourne.sgi.com>2008-04-18 11:38:01 +1000
commitb589334c7a1fff85d2f009d5db4c34fad48925e9 (patch)
treebc46a7f50dbc5f8c09e86374cea63192ee2f146b
parent3354040897f828644be6ca5783588e9f64a53b8e (diff)
[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 <dgc@sgi.com> Signed-off-by: Tim Shimmin <tes@sgi.com> Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
-rw-r--r--fs/xfs/xfs_log.c15
1 files changed, 6 insertions, 9 deletions
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 */