linux-kernel - Re: [PATCH] improve jbd fsync batching

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Message-Id: <20081104011242.cc767dba.akpm@linux-foundation.org>
Date:	Tue, 4 Nov 2008 01:12:42 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Andreas Dilger <adilger@....com>
Cc:	Josef Bacik <jbacik@...hat.com>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
	rwheeler@...hat.com
Subject: Re: [PATCH] improve jbd fsync batching

On Mon, 03 Nov 2008 22:24:28 -0700 Andreas Dilger <adilger@....com> wrote:

> On Nov 03, 2008  12:27 -0800, Andrew Morton wrote:
> > On Tue, 28 Oct 2008 16:16:15 -0400
> > Josef Bacik <jbacik@...hat.com> wrote:
> > > +		spin_lock(&journal->j_state_lock);
> > > +		commit_time = journal->j_average_commit_time;
> > > +		spin_unlock(&journal->j_state_lock);
> > 
> > OK, the lock is needed on 32-bit machines, I guess.
> 
> Should we pessimize the 64-bit performance in that case, for 32-bit
> increasingly rare 32-bit platforms?

In general no.

But spinlocks also do memory ordering stuff on both 32- and 64-bit
machines.  Introducing differences there needs thinking about.

In this case it's fsync which is going to be monster slow anyway.

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