Re: [PATCH 1/2] ext4: Calculate and verify inode checksums

From: Joel Becker <jlbec@evilplan.org>
To: Sunil Mushran <sunil.mushran@oracle.com>
Cc: djwong@us.ibm.com, "Theodore Ts'o" <tytso@mit.edu>,
	Andreas Dilger <adilger.kernel@dilger.ca>,
	linux-ext4 <linux-ext4@vger.kernel.org>,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] ext4: Calculate and verify inode checksums
Date: Fri, 8 Apr 2011 11:50:13 -0700	[thread overview]
Message-ID: <20110408185013.GB17677@noexit> (raw)
In-Reply-To: <4D9DF01C.6050506@oracle.com>

On Thu, Apr 07, 2011 at 10:10:52AM -0700, Sunil Mushran wrote:
> On 04/07/2011 09:40 AM, Darrick J. Wong wrote:
> >That said, I haven't really quantified the performance impact of this naive
> >approach yet, so I wonder -- did you see a similar scenario with ocfs2, and
> >what kind of performance increase did you get by adapting the code to use the
> >jbd2 trigger?  If there's potentially a large increase, it would be interesting
> >to apply the same conversion to the group descriptor checksumming code too.
> 
> Joel Becker may remember the overhead. He wrote the patch. That said we have few
> differences. ocfs2 has larger (blocksized) inodes. Also, it computes ECC. The code
> is in fs/ocfs2/blockcheck.c.

	ocfs2 does the journal access/journal dirty cycle a lot more
than extN.  I think you'd want to generate your own numbers.

Joel


-- 

"Conservative, n.  A statesman who is enamoured of existing evils,
 as distinguished from the Liberal, who wishes to replace them
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			jlbec@evilplan.org