From owner-freebsd-current@FreeBSD.ORG Tue Mar 9 09:29:36 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 4F50416A4CF for ; Tue, 9 Mar 2004 09:29:36 -0800 (PST) Received: from cmsrelay02.mx.net (cmsrelay02.mx.net [165.212.11.111]) by mx1.FreeBSD.org (Postfix) with SMTP id 1228043D46 for ; Tue, 9 Mar 2004 09:29:36 -0800 (PST) (envelope-from noackjr@alumni.rice.edu) Received: from cmsapps01.cms.usa.net (165.212.11.136) by cmsoutbound.mx.net with SMTP; 9 Mar 2004 17:26:03 -0000 Received: from optimator.noacks.org [65.69.1.61] by cmsapps01.cms.usa.net (ASMTP/noackjr@usa.net) via mtad (C8.MAIN.3.13N) with ESMTP id 094iciRAB0082M36; Tue, 09 Mar 2004 17:26:01 GMT X-USANET-Auth: 65.69.1.61 AUTH noackjr@usa.net optimator.noacks.org Received: from localhost (localhost [127.0.0.1]) by optimator.noacks.org (Postfix) with ESMTP id 50E276163; Tue, 9 Mar 2004 11:26:00 -0600 (CST) Received: from optimator.noacks.org ([127.0.0.1]) by localhost (optimator.noacks.org [127.0.0.1]) (amavisd-new, port 10024) with LMTP id 46047-09; Tue, 9 Mar 2004 11:25:59 -0600 (CST) Received: from alumni.rice.edu (optimator [192.168.1.11]) by optimator.noacks.org (Postfix) with ESMTP id F376F615C; Tue, 9 Mar 2004 11:25:58 -0600 (CST) Message-ID: <404DFE26.5060007@alumni.rice.edu> Date: Tue, 09 Mar 2004 11:25:58 -0600 From: Jon Noack User-Agent: Mozilla Thunderbird 0.5+ (Windows/20040305) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Justin Dossey References: In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new at noacks.org cc: freebsd-current@freebsd.org Subject: Re: APIC/SMP on UP? (was Re: Load average with CURRENT) X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list Reply-To: noackjr@alumni.rice.edu List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 09 Mar 2004 17:29:36 -0000 On 3/9/2004 10:17 AM, Justin Dossey wrote: > On Tue, 9 Mar 2004, Conrad Sabatier wrote: >>I've been meaning to ask about this. Is there anything to be gained on a UP >>box by enabling APIC and/or SMP? I'm running on an Athlon here, with ULE: >> >>CPU: AMD Athlon(tm) Processor (998.07-MHz 686-class CPU) >> Origin = "AuthenticAMD" Id = 0x622 Stepping = 2 Features=0x183f9ff >> AMD Features=0xc0400000 > > I'd say yes, there is. APIC reduces interrupt overhead and provides > an on-chip timer. It also provides better interrupt sharing. APIC, yes (see above). SMP incurs a fairly significant amount of overhead (extra locking, etc.). I think I heard something a while back about attempts to selectively enable SMP locking at runtime (so that leaving SMP enabled in GENERIC doesn't hurt so much for UP), but then again that might have been a dream... ;-) In any case, this is what I run on my UP boxes: #options SMP # Symmetric MultiProcessor Kernel device apic # I/O APIC Jon Noack