From mboxrd@z Thu Jan 1 00:00:00 1970 From: bugzilla-daemon@bugzilla.kernel.org Subject: [Bug 41552] Performance of writing and reading from multiple drives decreases by 40% when going from Linux Kernel 2.6.36.4 to 2.6.37 (and beyond) Date: Mon, 22 Aug 2011 19:25:23 GMT Message-ID: <201108221925.p7MJPNYp020803@demeter2.kernel.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: Received: from demeter2.kernel.org ([140.211.167.42]:49847 "EHLO demeter2.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753189Ab1HVTZX (ORCPT ); Mon, 22 Aug 2011 15:25:23 -0400 Received: from demeter2.kernel.org (localhost.localdomain [127.0.0.1]) by demeter2.kernel.org (8.14.4/8.14.4) with ESMTP id p7MJPNG9020804 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Mon, 22 Aug 2011 19:25:23 GMT In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: linux-scsi@vger.kernel.org https://bugzilla.kernel.org/show_bug.cgi?id=41552 --- Comment #4 from Andrew Morton 2011-08-22 19:25:22 --- (switched to email. Please respond via emailed reply-to-all, not via the bugzilla web interface). On Mon, 22 Aug 2011 15:20:41 GMT bugzilla-daemon@bugzilla.kernel.org wrote: > https://bugzilla.kernel.org/show_bug.cgi?id=41552 > > Summary: Performance of writing and reading from multiple > drives decreases by 40% when going from Linux Kernel > 2.6.36.4 to 2.6.37 (and beyond) > Product: IO/Storage > Version: 2.5 > Kernel Version: 2.6.37 > Platform: All > OS/Version: Linux > Tree: Mainline > Status: NEW > Severity: normal > Priority: P1 > Component: SCSI > AssignedTo: linux-scsi@vger.kernel.org > ReportedBy: mpete_06@hotmail.com > Regression: No > > > We have an application that will write and read from every sector on a drive. > The application can perform these tasks on multiple drives at the same time. > It is designed to run on top of the Linux Kernel, which we periodically update > so that we can get the latest device drivers. When performing the last update > from 2.6.33.2 to 2.6.37, we found that the performance of a set of drives > decreased by some 40% (took 3 hours and 11 minutes to write and read from 5 > drives on 2.6.37 versus 2 hours and 12 minutes on 2.6.33.3). I was able to > determine that the issue was in the 2.6.37 Kernel as I was able to run it with > the 2.6.36.4 kernel, and it had the better performance. After seeing that I/O > throttling was introduced in the 2.6.37 Kernel, I naturally suspected that. > However, by default, all the throttling was turned off (I attached the actual > .config that was used to build the kernel). I then tried to turn on the > throttling and set it to a high number to see what would happen. When I did > that, I was able to reduce the time from 3 hours and 11 minutes to 2 hours and > 50 minutes. There seems to be something there that changed that is impacting > performance on multiple drives. When we do this same test with only one drive, > the performance is identical between the systems. This issue still occurs on > Kernel 3.0.2. > Are you able to determine whether this regression is due to slower reading, to slower writing or to both? Thanks. -- Configure bugmail: https://bugzilla.kernel.org/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are the assignee for the bug.