jbd2: Improve scalability by not taking j_state_lock in jbd2_journal_stop()
One of the most contended locks in the jbd2 layer is j_state_lock when
running dbench. This is especially true if using the real-time kernel
with its "sleeping spinlocks" patch that replaces spinlocks with
priority inheriting mutexes --- but it also shows up on large SMP
benchmarks.
Thanks to John Stultz for pointing this out.
Reviewed by Mingming Cao and Jan Kara.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index bfc70f5..e214d68 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1311,7 +1311,6 @@
if (handle->h_sync)
transaction->t_synchronous_commit = 1;
current->journal_info = NULL;
- spin_lock(&journal->j_state_lock);
spin_lock(&transaction->t_handle_lock);
transaction->t_outstanding_credits -= handle->h_buffer_credits;
transaction->t_updates--;
@@ -1340,8 +1339,7 @@
jbd_debug(2, "transaction too old, requesting commit for "
"handle %p\n", handle);
/* This is non-blocking */
- __jbd2_log_start_commit(journal, transaction->t_tid);
- spin_unlock(&journal->j_state_lock);
+ jbd2_log_start_commit(journal, transaction->t_tid);
/*
* Special case: JBD2_SYNC synchronous updates require us
@@ -1351,7 +1349,6 @@
err = jbd2_log_wait_commit(journal, tid);
} else {
spin_unlock(&transaction->t_handle_lock);
- spin_unlock(&journal->j_state_lock);
}
lock_map_release(&handle->h_lockdep_map);