From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261670AbTIMQym (ORCPT ); Sat, 13 Sep 2003 12:54:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261692AbTIMQym (ORCPT ); Sat, 13 Sep 2003 12:54:42 -0400 Received: from gprs148-167.eurotel.cz ([160.218.148.167]:16001 "EHLO amd.ucw.cz") by vger.kernel.org with ESMTP id S261670AbTIMQyj (ORCPT ); Sat, 13 Sep 2003 12:54:39 -0400 Date: Sat, 13 Sep 2003 18:54:25 +0200 From: Pavel Machek To: richard.brunner@amd.com Cc: ak@suse.de, davej@redhat.com, torvalds@osdl.org, linux-kernel@vger.kernel.org, akpm@osdl.org Subject: Re: [PATCH] 2.6 workaround for Athlon/Opteron prefetch errata Message-ID: <20030913165425.GC527@elf.ucw.cz> References: <99F2150714F93F448942F9A9F112634C0638B19A@txexmtae.amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <99F2150714F93F448942F9A9F112634C0638B19A@txexmtae.amd.com> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.3i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi! > > > > > What's wrong with the current status quo that just says > > > > > "Athlon prefetch is broken"? > > > > It doesn't fix user space for once. > > > > > > And for another, it cripples the earlier athlons which > > > don't have this > > > errata. Andi's fix at least makes prefetch work again on > > > those boxes. > > > It's also arguable that prefetch() helps the older K7's > > > more than the > > > affected ones. > > > > All Athlons have this Errata. I can trigger it on an old > > 900Mhz pre XP Athlon too. You just have to use 3dnow prefetch > > instead of SSE prefetch. > > > > BTW the older Athlons currently don't use prefetch because > > the alternative > > patcher does not handle 3dnow style prefetch. > > > > Avoiding prefetch for all Athlons and earlier Opterons/Athlon64 > even in the kernel can really tank performance. And as Andi says > it still doesn't solve user mode from hitting the errata. How much speedups can be expected from prefetch? 5%? Pavel -- When do you have a heart between your knees? [Johanka's followup: and *two* hearts?]