ULE vs. 4BSD in RELENG_7

[Josh Carroll]

> Thank you, that was very useful.  I may have something to test very soon.

Sounds great Jeff, just say the word when you need someone to do the
testing. I'll be glad to help!

> What would be interesting to know is if the sum of the temperatures is any
> different.  4BSD gets a much more random distribution of load because a
> thread is run on whatever cpu context switches next.  ULE will have
> specific load patterns since it scans lists of cpus in a fixed order to
> assign load.

That seems to correlate with what I'm seeing, since the core that is
"spiking" is cpu0. I will write a little perl script to calculate the
sum periodically and record that. You're right, the one core may be
increasing 1-2 C periodically, but the other cores may remain lower. I
can definitely get you some numbers here.

So I went ahead and ran sysbench to see if changing the
kern.sched.slice value affected that (which I hear is a much more
accurate benchmark of real world MySQL performance than, say,
supersmack). There is a slight hit with the lower slice value, though
it's minimal. Although with 4 threads, the lower slice value actually
increases performance slightly. Here are the results (with 4BSD as a
baseline):

4bsd   ule.13   ule.7
2263.6   2250.36   2265.67
2181.18   2310.02   2300.25
2137.87   2304.04   2269.54
2100.41   2252.04   2249.26

buildworld isn't cooperating for me, but once I iron that out, I'll
post some results there as well :)

Thanks once again for all your efforts Jeff. I (and I'm sure others)
really appreciate your work.

Regards,
Josh