From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 31 Aug 2001 04:27:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 31 Aug 2001 04:27:16 -0400 Received: from t2.redhat.com ([199.183.24.243]:25851 "HELO executor.cambridge.redhat.com") by vger.kernel.org with SMTP id ; Fri, 31 Aug 2001 04:26:58 -0400 Message-ID: <3B8F4A64.8B9DEDE4@redhat.com> Date: Fri, 31 Aug 2001 09:27:16 +0100 From: Arjan van de Ven Reply-To: arjanv@redhat.com Organization: Red Hat, Inc X-Mailer: Mozilla 4.78 [en] (X11; U; Linux 2.4.7-2.9smp i686) X-Accept-Language: en MIME-Version: 1.0 To: Chris Abbey , linux-kernel@vger.kernel.org Subject: Re: Athlon doesn't like Athlon optimisation? In-Reply-To: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Chris Abbey wrote: > > Today, Dan Hollis wrote: > > but where would the finger start pointing then? > > hmm... *compiler optimizations* for a specific family cause > problems on that family, but *compiler optimizations* for > a lesser family don't... I'll admit my kernel h4x0|^ 5k1!!s > aren't on par with most on this list, but has anyone thought > to take a look at the *compiler optimizations* that are > generated? It's not the compiler options. (or at least not alone). I have proof for this, let me explain: For the upcomming Red Hat Linux release an athlon kernel will be included, and due to the people who have this problem, I added a kernel commandline option to disable the optimized page_copy() and clear_page() functions. The use of this option makes the machines, of the people who had this problem, happy again. Now I also wrote the 2 functions in question, and I am very convinced that they are correct. They also work on the vast majority of motherboards, and most of the failure cases are cheaper motherboards (or cheap PSU's). The net effect of using the optimized functions is that the memory bandwidth the CPU uses effecively doubles during COW and page_clear() operations. This puts additional load on the motherboard it seems.... I don't know if it's the voltage regulators or borderline ram chips that give up, but there are people who bought 25 identical machines (for a classroom) and only 1 failed, reproducable. Oh and btw, having these functions is the main reason for enabling the "Athlon" CPU type; that's basically the real difference between a PII and Athlon compiled kernel. Greetings, Arjan van de Ven