From: Keith Mannthey Subject: Re: Ext4 performance regression: Post 2.6.30 Date: Wed, 31 Mar 2010 15:14:36 -0700 Message-ID: <1270073676.7193.34.camel@keith-laptop> References: <1269843935.13369.52.camel@keith-laptop> <87f94c371003290810u58f64ce6uc20be6bbac420e73@mail.gmail.com> <1270000565.7193.14.camel@keith-laptop> <4BB2CA41.5050406@redhat.com> <1270072944.7193.29.camel@keith-laptop> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: Eric Sandeen , linux-ext4 To: Greg Freemyer Return-path: Received: from e5.ny.us.ibm.com ([32.97.182.145]:57188 "EHLO e5.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756182Ab0CaWOk (ORCPT ); Wed, 31 Mar 2010 18:14:40 -0400 Received: from d01relay07.pok.ibm.com (d01relay07.pok.ibm.com [9.56.227.147]) by e5.ny.us.ibm.com (8.14.3/8.13.1) with ESMTP id o2VLxxue005731 for ; Wed, 31 Mar 2010 17:59:59 -0400 Received: from d01av02.pok.ibm.com (d01av02.pok.ibm.com [9.56.224.216]) by d01relay07.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o2VMEaMg1347742 for ; Wed, 31 Mar 2010 18:14:36 -0400 Received: from d01av02.pok.ibm.com (loopback [127.0.0.1]) by d01av02.pok.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id o2VMEaXp007950 for ; Wed, 31 Mar 2010 19:14:36 -0300 In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Wed, 2010-03-31 at 18:06 -0400, Greg Freemyer wrote: > On Wed, Mar 31, 2010 at 6:02 PM, Keith Mannthey wrote: > > On Tue, 2010-03-30 at 23:06 -0500, Eric Sandeen wrote: > >> Keith Mannthey wrote: > >> > On Mon, 2010-03-29 at 11:10 -0400, Greg Freemyer wrote: > >> >> On Mon, Mar 29, 2010 at 2:25 AM, Keith Mannthey wrote: > >> >>> > >> >>> After 2.6.30 I am seeing large performance regressions on a raid setup. > >> >>> I am working to publish a larger amount of data but I wanted to get some > >> >>> quick data out about what I am seeing. > >> >>> > >> >> Is mdraid involved? > >> >> > >> >> They added barrier support for some configs after 2.6.30 I believe. > >> >> It can cause a drastic perf change, but it increases reliability and > >> >> is "correct". > >> > > >> > lvm and device mapper are is involved. The git bisect just took me to: > >> > > >> > 374bf7e7f6cc38b0483351a2029a97910eadde1b is first bad commit > >> > commit 374bf7e7f6cc38b0483351a2029a97910eadde1b > >> > Author: Mikulas Patocka > >> > Date: Mon Jun 22 10:12:22 2009 +0100 > >> > > >> > dm: stripe support flush > >> > > >> > Flush support for the stripe target. > >> > > >> > This sets ti->num_flush_requests to the number of stripes and > >> > remaps individual flush requests to the appropriate stripe devices. > >> > > >> > Signed-off-by: Mikulas Patocka > >> > Signed-off-by: Alasdair G Kergon > >> > > >> > :040000 040000 542f4b9b442d1371c6534f333b7e00714ef98609 d490479b660139fc1b6b0ecd17bb58c9e00e597e M drivers > >> > > >> > > >> > This may be correct behavior but the performance penalty in this test > >> > case is pretty high. > >> > > >> > I am going to move back to current kernels and starting looking into > >> > ext4/dm flushing. > >> > >> It would probably be interesting to do a mount -o nobarrier to see if > >> that makes the regression go away. > > > > -o nobarrier takes the regression away with 2.6.34-rc3: > > > > Default mount: ~27500 > > > > -o nobarrier: ~12500 > > > > Barriers on this setup cost ALOT during writes. > > > > Interestingly as well the "mailserver" workload regression is also > > removed by mounting with "-o nobarrier". > > > > I am going to see what impact is seen on a single disk setup. > > > > Thanks, > > Keith Mannthey > > LTC FS-Dev > > I'm curious if your using an internal or external journal? I am unsure. How do I tell? I am using defaults except with the -o nobarrier. I know jdb2 is being used. Thanks, Keith > I'd guess the cost of barriers is much greater with an internal > journal, but I don't recall seeing any benchmarks one way or the > other. > > Greg