From owner-freebsd-current@FreeBSD.ORG Tue Mar 9 17:20:40 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 72F9316A4CE for ; Tue, 9 Mar 2004 17:20:40 -0800 (PST) Received: from lakemtao04.cox.net (lakemtao04.cox.net [68.1.17.241]) by mx1.FreeBSD.org (Postfix) with ESMTP id ED1AE43D39 for ; Tue, 9 Mar 2004 17:20:39 -0800 (PST) (envelope-from conrads@ip68-14-60-78.no.no.cox.net) Received: from ip68-14-60-78.no.no.cox.net ([68.14.60.78]) by lakemtao04.cox.netESMTP <20040310012038.PQHD10652.lakemtao04.cox.net@ip68-14-60-78.no.no.cox.net>; Tue, 9 Mar 2004 20:20:38 -0500 Received: from ip68-14-60-78.no.no.cox.net (localhost [127.0.0.1]) i2A1KcFW049590; Tue, 9 Mar 2004 19:20:38 -0600 (CST) (envelope-from conrads@ip68-14-60-78.no.no.cox.net) Received: (from conrads@localhost)i2A1KXer049589; Tue, 9 Mar 2004 19:20:33 -0600 (CST) (envelope-from conrads) Message-ID: X-Mailer: XFMail 1.5.5 on FreeBSD X-Priority: 3 (Normal) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit MIME-Version: 1.0 In-Reply-To: <404DFE26.5060007@alumni.rice.edu> Date: Tue, 09 Mar 2004 19:20:33 -0600 (CST) From: Conrad Sabatier To: Jon Noack cc: Justin Dossey 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: conrads@cox.net List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 10 Mar 2004 01:20:40 -0000 On 09-Mar-2004 Jon Noack wrote: > 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'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 Interesting. Thanks! -- Conrad Sabatier - "In Unix veritas"