From: Joel Becker Subject: Re: [PATCH 1/2] ext4: Calculate and verify inode checksums Date: Fri, 8 Apr 2011 11:50:13 -0700 Message-ID: <20110408185013.GB17677@noexit> References: <20110406224410.GB24354@tux1.beaverton.ibm.com> <20110406224547.GT32706@tux1.beaverton.ibm.com> <4D9D0ADB.9010005@oracle.com> <20110407164006.GC24354@tux1.beaverton.ibm.com> <4D9DF01C.6050506@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: djwong@us.ibm.com, Theodore Ts'o , Andreas Dilger , linux-ext4 , linux-kernel To: Sunil Mushran Return-path: Received: from zeniv.linux.org.uk ([195.92.253.2]:34409 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754374Ab1DHSu2 (ORCPT ); Fri, 8 Apr 2011 14:50:28 -0400 Content-Disposition: inline In-Reply-To: <4D9DF01C.6050506@oracle.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: 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 with others." - Ambrose Bierce, The Devil's Dictionary http://www.jlbec.org/ jlbec@evilplan.org