linux-ext4 - Re: Enable asynchronous commits by default patch revoked?

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Message-ID: <20090902144833.GA29651@zero>
Date:	Wed, 2 Sep 2009 10:48:33 -0400
From:	Tom Vier <nester@...il.com>
To:	Theodore Tso <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: Enable asynchronous commits by default patch revoked?

On Mon, Aug 24, 2009 at 06:07:39PM -0400, Theodore Tso wrote:
> Sure, agreed.  But let's look a bit closer at what "async commit"
> really means.
> 
> What ext3 and ext4 does by default is this:
> 
> 1)  Write data blocks required by data=ordered mode (if any)

Shouldn't there be a write barrier after data blocks, so that the journal
blocks aren't written first? ie, mark the first journal block write with
barrier flag on.

> 2)  Write the journal blocks
> 
> 3)  Wait for the journal blocks to be sent to disk.  (We don't actually
> do a barrier operation), so this just means the blocks have been sent
> to the disk, not necessarily that they are forced to a platter.
> 
> 4)  Write the commit block, with the barrier flag set.
> 
> 5)  Wait for the commit block.

-- 
Tom Vier <nester@...il.com>
DSA Key ID 0x15741ECE
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