From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 3 Jun 2001 12:07:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 3 Jun 2001 12:01:47 -0400 Received: from mta1.snfc21.pbi.net ([206.13.28.122]:58568 "EHLO mta1.snfc21.pbi.net") by vger.kernel.org with ESMTP id ; Sun, 3 Jun 2001 12:01:29 -0400 Date: Sun, 03 Jun 2001 09:00:24 -0700 From: David Brownell Subject: Re: [linux-usb-devel] *BAD* impact of usb on PCI performance To: Linux usb mailing list , kernel list Message-id: <013e01c0ec46$4d3727a0$6800000a@brownell.org> MIME-version: 1.0 X-Mailer: Microsoft Outlook Express 5.50.4133.2400 Content-type: text/plain; charset="iso-8859-1" Content-transfer-encoding: 7bit X-MSMail-Priority: Normal X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4133.2400 In-Reply-To: <20010602132200.A186@bug.ucw.cz> X-Priority: 3 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > From: "Georg Acher" > On Sat, Jun 02, 2001 at 01:22:00PM +0200, Pavel Machek wrote: > > > > With Acher's uhci, even ifconfig up of usb-to-usb networking device > > [plusb handled by generic usb-to-usb driver; see -ac series]. > > does 50% slowdown. When fsbr is being used, systems slows down by 350% > > Hm, the 50% make me curious... have to look what's happening... For PL-2301/2302 devices, "ifconfig up" is mostly just posting a bulk read. True with both "usbnet" and its (now obsolete) predecessor drivers "plusb" and (for different devices) "net1080". Laplink-style cables can often support another mode (poll via USB "interrupts", and then issue reads only when data is available) but not every device can work that way (like, I seem to recall, an iPaq PDA). And that'd increase the latency per packet by a couple milliseconds, even when it's possible. > > (running more than 4 times slower than normally. Ouch). > > Blame Intel. Either low latency or low PCI usage, you can choose... This problem is UHCI-specific, not USB-generic, yes? Doesn't happen with OHCI? - Dave