To SMP or not to SMP

[Barney Cordoba]

--- On Wed, 1/9/13, sthaug at nethelp.no <sthaug at nethelp.no> wrote:

> From: sthaug at nethelp.no <sthaug at nethelp.no>
> Subject: Re: To SMP or not to SMP
> To: erichsfreebsdlist at alogt.com
> Cc: barney_cordoba at yahoo.com, freebsd-net at freebsd.org, jack.vogel at gmail.com, atkin901 at gmail.com
> Date: Wednesday, January 9, 2013, 9:32 AM
> > > 4BSD runs pretty well with
> an SMP kernel. I can test ULE and compare
> > > easily. A no SMP kernel is problematic as the igb
> driver doesn't seem
> > > to work and my onboard NICs are, sadly, igb. 
> > > 
> > this is bad luck. I know of the kernels as I have had
> SMP and single
> > CPU machines since 4.x times.
> 
> I have had igb working with both SMP and non-SMP kernel for
> at least a
> year or two, 8.x-STABLE. No specific problems.
> 
> Steinar Haug, Nethelp consulting, sthaug at nethelp.no
> 

Maybe a problem with "legacy interrupts" on more modern processors?
I'm using an E5520 and while the NIC inits ok, it just doesnt seem to
gen interrupts. I can't spend much time debugging it....

I notice that HAMMER kernels use MSI/X interrupts whether SMP is enabled
or not, while i386 kernels seem to require APIC. Is there some physical
reason for this?

BC