From owner-freebsd-questions Fri Nov 2 21:41:40 2001 Delivered-To: freebsd-questions@freebsd.org Received: from mtiwmhc25.worldnet.att.net (mtiwmhc25.worldnet.att.net [204.127.131.50]) by hub.freebsd.org (Postfix) with ESMTP id 3456537B40B for ; Fri, 2 Nov 2001 21:41:37 -0800 (PST) Received: from columbia ([12.93.208.35]) by mtiwmhc25.worldnet.att.net (InterMail vM.4.01.03.27 201-229-121-127-20010626) with SMTP id <20011103054136.UWRO11294.mtiwmhc25.worldnet.att.net@columbia>; Sat, 3 Nov 2001 05:41:36 +0000 From: "Andrew C. Hornback" To: "Mark Hughes" , Subject: RE: SMP kernel with 1 processor.... Date: Sat, 3 Nov 2001 00:40:39 -0500 Message-ID: <000701c1642a$11a7d3e0$6600000a@columbia> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook 8.5, Build 4.71.2173.0 Importance: Normal In-Reply-To: <002d01c16426$b24648d0$0200a8c0@mark2> X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2919.6600 Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG > -----Original Message----- > From: owner-freebsd-questions@FreeBSD.ORG > [mailto:owner-freebsd-questions@FreeBSD.ORG]On Behalf Of Mark Hughes > Sent: Saturday, November 03, 2001 12:16 AM > To: freebsd-questions@FreeBSD.ORG > Subject: SMP kernel with 1 processor.... > > I know it sounds strange, but really it isn't that strange... > > We're just setting up a web server, we're using a dual-processor > server but > initially it will only have one processor in it. What we want to do really > is to set it up for two processors in a way that won't impact the > performance while it is only used with one, so we can add in a second > processor quickly and with minimal downtime when (and if) need be. > > So, is it okay to compile a kernel with the following options uncommented, > and will it impact performance at all to do so: > > # To make an SMP kernel, the next two are needed > #options SMP # Symmetric MultiProcessor Kernel > #options APIC_IO # Symmetric (APIC) I/O > > Also, other than these two options, is there anything else that > needs to be > enabled/disabled to work with SMP? No, that'll set it up as SMP, but I don't think you want to do that. I'm not aware of the hazards of doing such, but I don't think it's a "best practice". Also, how long is it going to take to install a second processor and do a kernel recompile? You've gotta take the machine fully off-line and powered down to add the second proc (unless you're running hardware that allows hot swap of processors, which would be REALLY cool)... And even then, you could compile the SMP kernel and leave it sitting on the machine, run it on a single proc kernel, and switch it over once you've got the second processor in. --- Andy To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message