linux-ext4 - Re: [PATCH] imporve jbd2 fsync batching

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Message-ID: <20081125102335.GB9882@mit.edu>
Date:	Tue, 25 Nov 2008 05:23:35 -0500
From:	Theodore Tso <tytso@....edu>
To:	Josef Bacik <jbacik@...hat.com>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH] imporve jbd2 fsync batching

On Tue, Nov 04, 2008 at 11:10:25AM -0500, Josef Bacik wrote:
> +	commit_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
> +
> +	/*
> +	 * weight the commit time higher than the average time so we don't
> +	 * react too strongly to vast changes in the commit time
> +	 */
> +	if (likely(journal->j_average_commit_time))
> +		journal->j_average_commit_time = (commit_time*3 +
> +				journal->j_average_commit_time) / 4;

Stupid question... if the goal is to not have the average commit time
not react too strongly to sudden and vast changes to the commit time,
would it be better to do this instead:

> +		journal->j_average_commit_time = (commit_time +
> +				journal->j_average_commit_time*3) / 4;


						    - Ted
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