From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932537AbWCBVFp (ORCPT ); Thu, 2 Mar 2006 16:05:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932540AbWCBVFp (ORCPT ); Thu, 2 Mar 2006 16:05:45 -0500 Received: from mx1.redhat.com ([66.187.233.31]:26802 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S932537AbWCBVFo (ORCPT ); Thu, 2 Mar 2006 16:05:44 -0500 Date: Thu, 2 Mar 2006 13:05:19 -0800 From: Pete Zaitcev To: =?UTF-8?B?UmVuw6k=?= Rebe Cc: linux-kernel@vger.kernel.org Subject: Re: MAX_USBFS_BUFFER_SIZE Message-Id: <20060302130519.588b18a2.zaitcev@redhat.com> In-Reply-To: References: <200603012116.25869.rene@exactcode.de> <20060301213223.GA17270@kroah.com> Organization: Red Hat, Inc. X-Mailer: Sylpheed version 2.0.4 (GTK+ 2.8.12; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 1 Mar 2006 22:42:35 +0100, René Rebe wrote: > > > drivers/usb/core/devio.c:86 > > > #define MAX_USBFS_BUFFER_SIZE 16384 > So, queing alot URBs is the recommended way to sustain the bus? Allowing > way bigger buffers will not be realistic? Have you ever considered how many TDs have to be allocated to transfer a data buffer this big? No, seriously. If your application cannot deliver the tranfer speeds with 16KB URBs, we ought to consider if the combination of our USB stack, usbfs, libusb and the application ought to get serious performance enhancing surgery. The problem is obviously in the software overhead. -- Pete