Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750720AbWJLTzB (ORCPT ); Thu, 12 Oct 2006 15:55:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750783AbWJLTzA (ORCPT ); Thu, 12 Oct 2006 15:55:00 -0400 Received: from mustang.oldcity.dca.net ([216.158.38.3]:37787 "HELO mustang.oldcity.dca.net") by vger.kernel.org with SMTP id S1750720AbWJLTzA (ORCPT ); Thu, 12 Oct 2006 15:55:00 -0400 Subject: Re: USB performance bug since kernel 2.6.13 (CRITICAL???) From: Lee Revell To: Open Source Cc: linux-usb-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org In-Reply-To: <20061012193313.4281.qmail@web58107.mail.re3.yahoo.com> References: <20061012193313.4281.qmail@web58107.mail.re3.yahoo.com> Content-Type: text/plain Date: Thu, 12 Oct 2006 15:55:55 -0400 Message-Id: <1160682956.24931.75.camel@mindpipe> Mime-Version: 1.0 X-Mailer: Evolution 2.6.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 896 Lines: 20 On Thu, 2006-10-12 at 12:33 -0700, Open Source wrote: > I am using a device that submits URBs asynchronously using the libusb > devio infrastructure. In version 2.6.12 I am able to submit and reap > URBs for my particular application at a transaction rate of one per > millisecond. A transaction consists of a single WRITE URB (< 512 > bytes) followed by a single READ URB (1024 bytes). Once I upgrade to > version 2.6.13, the transactional rate drops to one per 4 > milliseconds! The kernel's internal tick rate was lowered from 1000Hz to 250Hz starting with 2.6.13. Rebuild with CONFIG_HZ=1000 and the performance should return to normal. Lee - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/