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Commit c35a56a0 authored by Theodore Ts'o's avatar Theodore Ts'o
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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: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent c445e3e0

fs/jbd2/transaction.c

+1 −4
Original line number Diff line number Diff line
@@ -1311,7 +1311,6 @@ int jbd2_journal_stop(handle_t *handle) 
	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 @@ int jbd2_journal_stop(handle_t *handle) 
		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 @@ int jbd2_journal_stop(handle_t *handle) 
			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);