From: Fengguang Wu Subject: Re: ext4 write performance regression in 3.6-rc1 Date: Fri, 17 Aug 2012 22:13:53 +0800 Message-ID: <20120817141353.GA795@localhost> References: <20120816024654.GB3781@thunk.org> <20120816111051.GA16036@localhost> <20120816152513.GA31346@thunk.org> <20120817060915.GB28786@localhost> <20120817134039.GB11439@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: Theodore Ts'o , Marti Raudsepp , Kernel hackers , ext4 hackers , maze@google.com, "Shi, Alex" , linux-fsdevel@vger.kernel.org Return-path: Content-Disposition: inline In-Reply-To: <20120817134039.GB11439@thunk.org> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Fri, Aug 17, 2012 at 09:40:39AM -0400, Theodore Ts'o wrote: > 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? No problem :) Thanks, Fengguang