From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753615AbYE3Rpe (ORCPT ); Fri, 30 May 2008 13:45:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752488AbYE3RpX (ORCPT ); Fri, 30 May 2008 13:45:23 -0400 Received: from yx-out-2324.google.com ([74.125.44.28]:36210 "EHLO yx-out-2324.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751892AbYE3RpW (ORCPT ); Fri, 30 May 2008 13:45:22 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=m3ci1tQUA3rJT01hcJxTiYmObGLiI6UPsYraEbtiAp9cb5Mz7Cv4x9lzGfDPkPXPbga383Px6rIloADq7g4nJbQ/f2PYvHvWyEaOJaxVKuupfBiNCMWxS/vrtYcrioX+/zB/2k9IcN9lqbR4/8QL2lxRonxnk3j+mlkDEEv/CM0= Message-ID: Date: Fri, 30 May 2008 10:45:12 -0700 From: Leonid To: "Alan Stern" Subject: Re: [GIT PATCH] USB fixes for 2.6.26-rc4 Cc: "Greg KH" , "David Brownell" , "Linus Torvalds" , "Andrew Morton" , linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20080529215808.GA3759@suse.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Alan, Not to be overly pedantic, but you weren't so wrong to be confused on the issue of "regression". Here's the scoop: 1) Kernel versions <= 2.6.24: latency of 2/6/2/6/... uframes pattern observed between packets on the bus for nVIDIA HCs. 2) Kernel versions >= 2.6.26: latency of 8/8/8/8/... uframes pattern observed between packets on the bus for nVIDIA HCs. 3) Post-patch: latency of 1/1/1/1/... uframes on all kernels versions and all HC chipsets. So basically there was a peripheral issue in the EHCI driver between 2.6.24 and 2.6.25 that exacerbated the problem. But the underlying issue was there long before 2.6.25. Dave is quite right that this isn't technically a "regression." The issue itself was a bug (as opposed to a "feature" ;-) ) since the original comments in the code clearly had the right intention, but the code itself did not execute as intended in certain situations. In fact, thinking about it now, this issue could even cause significant performance degradation on nVIDIA HCs if one has multiple devices using the bus at any given time. Given this, it might be best to label the patch "USB: EHCI: fix performance issue" instead of using the word regression. But regardless, we are just worrying about symmantics at this point! :) Hope that helps clarify and put to rest this titling issue once in for all. -Leonid On Thu, May 29, 2008 at 6:44 PM, Alan Stern wrote: > On Thu, 29 May 2008, Greg KH wrote: >> Well, I was misinformed by Alan Stern about this then, sorry for missing >> that you didn't ack this one (you acked the other patches in this series >> though.) > > The notion that this was a regression came about by mistake. It was > stated that 2.6.24 worked better than 2.6.25; apparently that remark > was wrong.