On Sun 24-03-19 11:38:35, Liu Song wrote:
> When t_updates back to zero, it guaranteed wake up process which
> waiting on j_wait_updates. If we triggered a commit start without
> considered t_updates, the commit thread wakes up and find t_updates
> is not zero, it have to wait on it once again. So, add checking code
> to avoid this happen.
>
> Signed-off-by: Liu Song <liu.son...@zte.com.cn>
Do I understand correctly that this is a performance improvement? If yes,
did you measure any benefit of the patch? Because I have some doubts that
t_updates == 0 case is very common.
Honza
> ---
> fs/jbd2/transaction.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
> index 79a028a7a579..e0499fd73b1e 100644
> --- a/fs/jbd2/transaction.c
> +++ b/fs/jbd2/transaction.c
> @@ -144,12 +144,13 @@ static void wait_transaction_locked(journal_t *journal)
> __releases(journal->j_state_lock)
> {
> DEFINE_WAIT(wait);
> - int need_to_start;
> + int need_to_start = 0;
> tid_t tid = journal->j_running_transaction->t_tid;
>
> prepare_to_wait(&journal->j_wait_transaction_locked, &wait,
> TASK_UNINTERRUPTIBLE);
> - need_to_start = !tid_geq(journal->j_commit_request, tid);
> + if (!atomic_read(&journal->j_running_transaction->t_updates))
> + need_to_start = !tid_geq(journal->j_commit_request, tid);
> read_unlock(&journal->j_state_lock);
> if (need_to_start)
> jbd2_log_start_commit(journal, tid);
> --
> 2.19.1
>
>
--
Jan Kara <j...@suse.com>
SUSE Labs, CR
