From: Keith Mannthey Subject: Re: Ext4 performance regression: Post 2.6.30 Date: Tue, 30 Mar 2010 18:56:05 -0700 Message-ID: <1270000565.7193.14.camel@keith-laptop> References: <1269843935.13369.52.camel@keith-laptop> <87f94c371003290810u58f64ce6uc20be6bbac420e73@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: linux-ext4 To: Greg Freemyer Return-path: Received: from e2.ny.us.ibm.com ([32.97.182.142]:41975 "EHLO e2.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757970Ab0CaB4I (ORCPT ); Tue, 30 Mar 2010 21:56:08 -0400 Received: from d01relay07.pok.ibm.com (d01relay07.pok.ibm.com [9.56.227.147]) by e2.ny.us.ibm.com (8.14.3/8.13.1) with ESMTP id o2V1jBg7006012 for ; Tue, 30 Mar 2010 21:45:11 -0400 Received: from d01av01.pok.ibm.com (d01av01.pok.ibm.com [9.56.224.215]) by d01relay07.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o2V1u7OL2117860 for ; Tue, 30 Mar 2010 21:56:07 -0400 Received: from d01av01.pok.ibm.com (loopback [127.0.0.1]) by d01av01.pok.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id o2V1u7mA023064 for ; Tue, 30 Mar 2010 21:56:07 -0400 In-Reply-To: <87f94c371003290810u58f64ce6uc20be6bbac420e73@mail.gmail.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: 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. Thanks, Keith Mannthey