From mboxrd@z Thu Jan 1 00:00:00 1970 From: bugzilla-daemon@bugzilla.kernel.org Subject: [Bug 41552] New: 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 15:20:41 GMT Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: Received: from demeter1.kernel.org ([140.211.167.39]:45799 "EHLO demeter1.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752598Ab1HVPUm (ORCPT ); Mon, 22 Aug 2011 11:20:42 -0400 Received: from demeter1.kernel.org (localhost.localdomain [127.0.0.1]) by demeter1.kernel.org (8.14.4/8.14.4) with ESMTP id p7MFKfM3030636 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Mon, 22 Aug 2011 15:20:41 GMT 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 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. -- Configure bugmail: https://bugzilla.kernel.org/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are the assignee for the bug.