To SMP or not to SMP

[Garrett Cooper]

On Jan 8, 2013, at 7:50 AM, Barney Cordoba wrote:

> --- On Mon, 1/7/13, Erich Dollansky <erichsfreebsdlist at alogt.com> wrote:
> 
>> From: Erich Dollansky <erichsfreebsdlist at alogt.com>
>> Subject: Re: To SMP or not to SMP
>> To: "Barney Cordoba" <barney_cordoba at yahoo.com>
>> Cc: freebsd-net at freebsd.org
>> Date: Monday, January 7, 2013, 10:56 PM
>> Hi,
>> 
>> On Mon, 7 Jan 2013 18:25:58 -0800 (PST)
>> Barney Cordoba <barney_cordoba at yahoo.com>
>> wrote:
>> 
>>> I have a situation where I have to run 9.1 on an old
>> single core box.
>>> Does anyone have a handle on whether it's better to
>> build a non SMP
>>> kernel or to just use a standard SMP build with just
>> the one core?
>>> Thanks.
>> 
>> I ran a single CPU version of FreeBSD until my last single
>> CPU got hit
>> by a lightning last April or May without any problems.
>> 
>> I never saw a reason to include the overhead of SMP for this
>> kind of
>> machine and I also never ran into problems with this.
> 
> Another "ass"umption based on logic rather than empirical evidence.

	It isn't really an offhanded assumption because there _is_ additional overhead added into the kernel structures to make things work SMP with locking :). Whether or not it's measurable for you and your applications, I have no idea.
HTH,
-Garrett