From: Theodore Ts'o Subject: Re: ext4 write performance regression in 3.6-rc1 Date: Fri, 17 Aug 2012 09:40:39 -0400 Message-ID: <20120817134039.GB11439@thunk.org> References: <20120816024654.GB3781@thunk.org> <20120816111051.GA16036@localhost> <20120816152513.GA31346@thunk.org> <20120817060915.GB28786@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Marti Raudsepp , Kernel hackers , ext4 hackers , maze@google.com, "Shi, Alex" , linux-fsdevel@vger.kernel.org To: Fengguang Wu Return-path: Received: from li9-11.members.linode.com ([67.18.176.11]:45241 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752722Ab2HQNkm (ORCPT ); Fri, 17 Aug 2012 09:40:42 -0400 Content-Disposition: inline In-Reply-To: <20120817060915.GB28786@localhost> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri, Aug 17, 2012 at 02:09:15PM +0800, Fengguang Wu wrote: > Ted, > > I find ext4 write performance dropped by 3.3% on average in the > 3.6-rc1 merge window. xfs and btrfs are fine. > > Two machines are tested. The performance regression happens in the > lkp-nex04 machine, which is equipped with 12 SSD drives. lkp-st02 does > not see regression, which is equipped with HDD drives. I'll continue > to repeat the tests and report variations. Hmm... I've checked out the commits in "git log v3.5..v3.6-rc1 -- fs/ext4 fs/jbd2" and I don't see anything that I would expect would cause that. The are the lock elimination changes for Direct I/O overwrites, but that shouldn't matter for your tests which are measuring buffered writes, correct? Is there any chance you could do me a favor and do a git bisect restricted to commits involving fs/ext4 and fs/jbd2? Many thanks, - Ted