Results of Power Management

Ive put Greggś blog on Power Management to use, and here are my impressive results. First of all, I checked my processor type:

bleonard@opensolaris:~$ kstat -m cpu_info -s brand -i 0
module: cpu_info                        instance: 0     
name:   cpu_info0                       class:    misc
        brand                           Intel(r) Core(tm)2 Duo CPU     T7700  @ 2.40GHz

bleonard@opensolaris:~$ 

And then I checked to see if my Core 2 Duo is in the list of processors that support power management:

  • Pentium 4 and Intel Xeon processors
  • Intel Core Solo and Intel Core Duo processors
  • Intel Xeon Processor 5100 Series and Intel Core 2 Duo processors
  • AMD processors with Family >= 0x10 which includes Barcelona and Phenom products.
Excellent, the Intel Core 2 Duo in my Mac fits the bill.

Next, I checked the supported frequencies of my processor:

bleonard@opensolaris:~$ kstat -m cpu_info -s supported_frequencies_Hz -i 0
module: cpu_info                        instance: 0     
name:   cpu_info0                       class:    misc
        supported_frequencies_Hz        800000000:1200000000:1400000000:1600000000:1800000000:2000000000:2200000000:2400000000

bleonard@opensolaris:~$ 

From this I can see that my CPU will scale from 2.4 GHz down to 800 MHz. Letś see where itś currently running w/out power management:

bleonard@opensolaris:~$ kstat -m cpu_info -s current_clock_Hz -i 0
module: cpu_info                        instance: 0     
name:   cpu_info0                       class:    misc
        current_clock_Hz                2400000000

We see itś running at its maximum frequency, 2.4 GHz. After following the steps to enable power management, we can see that it idles down to itś lowest frequency, 800 MHz (shown using a 3 second interval):

bleonard@opensolaris:~$ kstat -m cpu_info -s current_clock_Hz -i 0 3 
module: cpu_info                        instance: 0     
name:   cpu_info0                       class:    misc
        current_clock_Hz                2400000000

module: cpu_info                        instance: 0
name:   cpu_info0                       class:    misc
        current_clock_Hz                2200000000
module: cpu_info                        instance: 0    
name:   cpu_info0                       class:    misc
        current_clock_Hz                2000000000
module: cpu_info                        instance: 0    
name:   cpu_info0                       class:    misc
        current_clock_Hz                1600000000
module: cpu_info                        instance: 0    
name:   cpu_info0                       class:    misc
        current_clock_Hz                1400000000
module: cpu_info                        instance: 0    
name:   cpu_info0                       class:    misc
        current_clock_Hz                800000000
\^C bleonard@opensolaris:~$
Comments:

Another nice option is to use Powertop, available at www.opensolaris.org/os/project/tesla/work/powertop

This app will show you not only the live frequencies, it will show the percentage of time being spent in lower power states.

It will also give you the option of turning on power management if it's not already on!

Posted by Dave Stewart on July 14, 2008 at 12:41 PM GMT #

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