Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261252AbTIGSMH (ORCPT ); Sun, 7 Sep 2003 14:12:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263411AbTIGSMH (ORCPT ); Sun, 7 Sep 2003 14:12:07 -0400 Received: from pc1-cwma1-5-cust4.swan.cable.ntl.com ([80.5.120.4]:51179 "EHLO dhcp23.swansea.linux.org.uk") by vger.kernel.org with ESMTP id S261252AbTIGSL6 (ORCPT ); Sun, 7 Sep 2003 14:11:58 -0400 Subject: Re: RFC: [2.6 patch] better i386 CPU selection From: Alan Cox To: Jamie Lokier Cc: Mikael Pettersson , bunk@fs.tum.de, Linux Kernel Mailing List , robert@schwebel.de, Rusty Russell In-Reply-To: <20030907174341.GA21260@mail.jlokier.co.uk> References: <200309071647.h87Glp4t014359@harpo.it.uu.se> <20030907174341.GA21260@mail.jlokier.co.uk> Content-Type: text/plain Content-Transfer-Encoding: 7bit Message-Id: <1062958188.16972.49.camel@dhcp23.swansea.linux.org.uk> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.4 (1.4.4-4) Date: Sun, 07 Sep 2003 19:09:49 +0100 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1630 Lines: 40 On Sul, 2003-09-07 at 18:43, Jamie Lokier wrote: > 2. The CPU types are not a total order. Say I want a kernel > that supports Athlons and a Centaur for my cluster. What > CPU setting should I use? What CPU setting will give my the best > performing kernel - and is that the same as the one for smallest > kernel? You'd use two kernels. There is no sane other answer to that specific case 8) > But I don't want to compile in support for every x86, > because space is tight, and I want it to run as fast as it > can given that it could run on either of the two chips. The code size differential is noise except for FPU emulation, and thats in part sloppy because we could have __fpuseg and eject it at boot if not needed ;) 386 kernels are slow because of user space handling and lack of bswap 486 kernels basically work on anything just fine > I'm not sure if an Athlon is "lower" than a PII or not.... Which do I > option do I pick, to run on either of those without including > redundant stuff for older CPUs? Right now its ordered 386 - 486 - 586 - 586+TSC - 686 - PPro - PII - PIII - PIV Geode is a branch off 586+TSC and supports 686+ too Athlon branches off from PIII if I remember rightly Winchip branches off from 586 and supports all later x86 too ELAN is its own weird world Xmeta comes off 686 somewhere depending how you handle PGE - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/