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

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Message-id: <20081125224115.GW3186@webber.adilger.int>
Date:	Tue, 25 Nov 2008 15:41:15 -0700
From:	Andreas Dilger <adilger@....com>
To:	Theodore Tso <tytso@....edu>
Cc:	Josef Bacik <jbacik@...hat.com>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH] imporve jbd2 fsync batching

On Nov 25, 2008  05:23 -0500, Theodore Ts'o wrote:
> 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;

Actually, yes.  That is my fault, I'd suggested the original change to
Josef.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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