[patch 08/22] reduce l_icloglock roundtrips

Christoph Hellwig
2008-12-02T16:11:51Z

[-- Attachment #1: xfs-reduce-log-lock-roundtrips --]
[-- Type: text/plain, Size: 2626 bytes --]

All but one caller of xlog_state_want_sync drop and re-acquire
l_icloglock around the call to it, just so that xlog_state_want_sync can
acquire and drop it.

Move all lock operation out of l_icloglock and assert that the lock is
held when it is called.

Note that it would make sense to extende this scheme to
xlog_state_release_iclog, but the locking in there is more complicated
and we'd like to keep the atomic_dec_and_lock optmization for those
callers not having l_icloglock yet.

(First sent on Semptember 29th)

Signed-off-by: Christoph Hellwig <hch@lst.de>

Index: xfs-master/fs/xfs/xfs_log.c
===================================================================
--- xfs-master.orig/fs/xfs/xfs_log.c 2008-12-02 11:07:00.000000000 +0100
+++ xfs-master/fs/xfs/xfs_log.c 2008-12-02 11:13:33.000000000 +0100
@@ -729,8 +729,8 @@ xfs_log_unmount_write(xfs_mount_t *mp)
spin_lock(&log->l_icloglock);
iclog = log->l_iclog;
atomic_inc(&iclog->ic_refcnt);
- spin_unlock(&log->l_icloglock);
xlog_state_want_sync(log, iclog);
+ spin_unlock(&log->l_icloglock);
error = xlog_state_release_iclog(log, iclog);

spin_lock(&log->l_icloglock);
@@ -767,9 +767,9 @@ xfs_log_unmount_write(xfs_mount_t *mp)
spin_lock(&log->l_icloglock);
iclog = log->l_iclog;
atomic_inc(&iclog->ic_refcnt);
- spin_unlock(&log->l_icloglock);

xlog_state_want_sync(log, iclog);
+ spin_unlock(&log->l_icloglock);
error = xlog_state_release_iclog(log, iclog);

spin_lock(&log->l_icloglock);
@@ -1984,7 +1984,9 @@ xlog_write(xfs_mount_t * mp,
if (iclog->ic_size - log_offset <= sizeof(xlog_op_header_t)) {
xlog_state_finish_copy(log, iclog, record_cnt, data_cnt);
record_cnt = data_cnt = 0;
+ spin_lock(&log->l_icloglock);
xlog_state_want_sync(log, iclog);
+ spin_unlock(&log->l_icloglock);
if (commit_iclog) {
ASSERT(flags & XLOG_COMMIT_TRANS);
*commit_iclog = iclog;
@@ -3193,7 +3195,7 @@ try_again:
STATIC void
xlog_state_want_sync(xlog_t *log, xlog_in_core_t *iclog)
{
- spin_lock(&log->l_icloglock);
+ ASSERT(spin_is_locked(&log->l_icloglock));

if (iclog->ic_state == XLOG_STATE_ACTIVE) {
xlog_state_switch_iclogs(log, iclog, 0);
@@ -3201,10 +3203,7 @@ xlog_state_want_sync(xlog_t *log, xlog_i
ASSERT(iclog->ic_state &
(XLOG_STATE_WANT_SYNC|XLOG_STATE_IOERROR));
}
-
- spin_unlock(&log->l_icloglock);
-} /* xlog_state_want_sync */
-
+}

/*****************************************************************************