From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261524AbTIKUrF (ORCPT ); Thu, 11 Sep 2003 16:47:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261526AbTIKUrF (ORCPT ); Thu, 11 Sep 2003 16:47:05 -0400 Received: from pc1-cwma1-5-cust4.swan.cable.ntl.com ([80.5.120.4]:56722 "EHLO dhcp23.swansea.linux.org.uk") by vger.kernel.org with ESMTP id S261524AbTIKUrA (ORCPT ); Thu, 11 Sep 2003 16:47:00 -0400 Subject: Re: [PATCH] 2.6 workaround for Athlon/Opteron prefetch errata From: Alan Cox To: bill davidsen Cc: Linux Kernel Mailing List In-Reply-To: References: <99F2150714F93F448942F9A9F112634C0638B196@txexmtae.amd.com> <3F60837D.7000209@pobox.com> <20030911162634.64438c7d.ak@suse.de> <3F6087FC.7090508@pobox.com> Content-Type: text/plain Content-Transfer-Encoding: 7bit Message-Id: <1063313075.3881.4.camel@dhcp23.swansea.linux.org.uk> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.4 (1.4.4-5) Date: Thu, 11 Sep 2003 21:44:35 +0100 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Iau, 2003-09-11 at 20:56, bill davidsen wrote: > | When we know at compile time it's not needed, it should not be enabled. > > Clearly that's right. This buys nothing on CPUs which don't have the > problem, why have *any* overhead in size and speed? It's too bad that > people have to read around all that code, they don't need to give it a > home in their RAM and execute it as well. We have always built kernels that contained the support for older chips. A 586 kernel for example is minutely slowed by the fact it will run on the Pentium Pro. If someone wants to put in clear "this CPU only" stuff as well then fine, but with my distributor hat on I defy you to benchmark the difference in the real world between PIV and PIV with 100 bytes of extra workaround code. You could get that much code back by spending 10 minutes tidying some random other piece of code you use, or shortening a couple of printk messages.