linux-ext4 - Re: [PATCH] jbd2: don't wake kjournald unnecessarily

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Date:	Wed, 19 Dec 2012 09:09:58 +0100
From:	Jan Kara <jack@...e.cz>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>,
	Jan Kara <jack@...e.cz>, Dave Wysochanski <dwysocha@...hat.com>
Subject: Re: [PATCH] jbd2: don't wake kjournald unnecessarily

On Tue 18-12-12 20:59:54, Eric Sandeen wrote:
> Don't send an extra wakeup to kjournald in the case where we
> already have the proper target in j_commit_request, i.e. that
> transaction has already been requested for commit.
> 
> commit deeeaf13 "jbd2: fix fsync() tid wraparound bug" changed
> the logic leading to a wakeup, but it caused some extra wakeups
> which were found to lead to a measurable performance regression.
> 
> Signed-off-by: Eric Sandeen <sandeen@...hat.com>
  Looks good. You can add: Reviewed-by: Jan Kara <jack@...e.cz>

							Honza
> ---
> 
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index dbf41f9..89970d5 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -518,7 +518,8 @@ int __jbd2_log_start_commit(journal_t *journal, tid_t target)
>  	 * currently running transaction (if it exists).  Otherwise,
>  	 * the target tid must be an old one.
>  	 */
> -	if (journal->j_running_transaction &&
> +	if (journal->j_commit_request != target &&
> +	    journal->j_running_transaction &&
>  	    journal->j_running_transaction->t_tid == target) {
>  		/*
>  		 * We want a new commit: OK, mark the request and wakeup the
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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