Improved Intel Turbo Boost status/control

[Ian Lepore]

On Mon, 2012-03-12 at 21:15 +0200, Alexander Motin wrote:
> Hi.
> 
> I'd like to note that recent r232793 change to cpufreq(4) in HEAD opened 
> simple access to the  Intel Turbo Boost status/control. I've found that 
> at least two of my desktop systems (based Nehalem and SandyBridge Core 
> i7s) with enabled Intel Turbo Boost in BIOS it is not use it by default, 
> unless powerd is enabled. And before this change it was difficult to 
> detect/fix.
> 
> ACPI reports extra performance level with frequency 1MHz above the 
> nominal to control Intel Turbo Boost operation. It is not a bug, but 
> feature:
> dev.cpu.0.freq_levels: 2934/106000 2933/95000 2800/82000 ...
> In this case value 2933 means 2.93GHz, but 2934 means 3.2-3.6GHz.
> 
> After boot with default settings I see:
> dev.cpu.0.freq: 2933
> , that means Turbo Boost is disabled.
> 
> Enabling powerd or just adding to rc.conf
> performance_cpu_freq="HIGH"
> enables Turbo Boost and adds extra 10-20% to the system performance.
> 
> Turbo Boost operation can be monitored in run-time via the PMC with 
> command that prints number or really executed cycles per CPU core:
> pmcstat -s unhalted-core-cycles -w 1
> 

The r232793 patch applies cleanly to 8-stable and builds just fine, but
after install/reboot I don't see a change in the freq_levels

        revolution > sysctl dev.cpu.0
        dev.cpu.0.%desc: ACPI CPU
        dev.cpu.0.%driver: cpu
        dev.cpu.0.%location: handle=\_PR_.P001
        dev.cpu.0.%pnpinfo: _HID=none _UID=0
        dev.cpu.0.%parent: acpi0
        dev.cpu.0.coretemp.delta: 70
        dev.cpu.0.coretemp.resolution: 1
        dev.cpu.0.coretemp.tjmax: 101.0C
        dev.cpu.0.coretemp.throttle_log: 0
        dev.cpu.0.temperature: 31.0C
        dev.cpu.0.freq: 3333
        dev.cpu.0.freq_levels: 3333/130000 3200/117000 3067/105000
        2933/94000 2800/85000 2667/76000 2533/68000 2400/61000
        2267/54000 2133/48000 2000/43000 1867/39000 1733/35000
        1600/32000 1400/28000 1200/24000 1000/20000 800/16000 600/12000
        400/8000 200/4000
        dev.cpu.0.cx_supported: C1/32 C2/96 C3/128
        dev.cpu.0.cx_lowest: C1
        dev.cpu.0.cx_usage: 100.00% 0.00% 0.00% last 657us
        revolution > 
        

I would have expected a 3334 entry to appear after the reboot.  Is this
expected (like are there other required changes missing in 8-stable), or
do I have something misconfigured?  (I can post more info, but don't
want to spam the list if the answer is going to be "this shouldn't work
in 8.x).

-- Ian