Re: AMD, CPPC, etc

> On my desktop system, using 0 ("auto") mode works quite well: the
> system idles around 80 to 95 watts, and when building ports or
> /usr/src with all 32 CPUs going, gets up to the 320-watt range, all
> without any OS work required.

What's the EPP value you are using?  The default of 0?

Now, the question is: Do you get the same performance with these more power-flexible settings compared to the driver's defaults (which are desired performance set to maximum performance (which reported value do you see for that?) and EPP to 0) when building ports or src on the 32 cores?

> I'm not sure what actually chooses the CPU frequency here.

In auto-mode, the cores auto-tune themselves, so basically a hardware governor is at play.

I suggest you forget about actual frequencies, CPPC can be finer-grained than that, with hardware leveraging other performance mechanisms, even if it seems that, currently, on AMD hardware, performance levels are achieved only through changing frequency.

Regards.

-- 
Olivier Certner