signifanctly slowdown of FreeBSD 8.0-CURRENT/amd64

[Kip Macy]

>
> I'm running the r193133 amd64 with a custom kernel and all debugging off
> on an AMD Athlon64 3400+ single-core, and I haven't noticed any significant
> slowing, although I haven't been doing any systematic benchmarking.
>
> What would be the penalties of running an SMP -CURRENT kernel on
> single-core hardware with no hyperthreading? Can anyone quantify the
> typical added overhead?  Or, counterintuitively, would an SMP kernel
> be better in some ways?
>

He is trying to diagnose if the problem was introduced by enabling
adaptive spinning on sx locks. They're only enabled on SMP kernels.

Cheers,
Kip