Introducing Enhanced Intel SpeedStep to Solaris

Friday Sep 21, 2007

At long last, we've integrated CPU frequency scaling into Solaris. And we're making it available for the first time in SXDE 9/07. Though we've supported CPU power management on SPARC for several years, this is the first time that CPU power management is being made available on Solaris x86.

As the title of this inaugural post suggests, our first Solaris x86 CPU power management offering is for those systems running Solaris on Intel platforms. More specifically, Enhanced Intel SpeedStep on Solaris is only supported on systems running Intel processors that belong to Family 0xF - Models >=0x3 or Family 0x6 - Models >= E. You're probably asking yourself, "What does that mean to me?"

The family/model combinations listed above roughly translate to:

• 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

But the easiest way to tell if your Solaris x86 system supports CPU power management is to display the new supported_frequencies_Hz kstat statistic that has been added to the cpu_info module:

$ kstat -m cpu_info -s supported_frequencies_Hz
module: cpu_info                        instance: 0
name:   cpu_info0                       class:    misc
        supported_frequencies_Hz        2800000000:3200000000

 
module: cpu_info                        instance: 1
name:   cpu_info1                       class:    misc
        supported_frequencies_Hz        2800000000:3200000000

As you can see, there is more than one supported frequency listed for each of the CPU instances above. That means that Solaris supports frequency scaling of those CPUs.

With the knowledge that Solaris supports CPU power management on your system, you may be asking yourself, "How do I turn it on?" We've recently added a couple of new keywords to the power.conf(4) file. The new keywords "cpupm" and "cpu-threshold" can be used to control CPU power management behavior on your Solaris system.

I frequently enable CPU power management on my Pentium 4 system and set its CPU idle threshold by adding the following two entries to my power.conf(4) file:

cpupm            enable
cpu-threshold    15s

When I leave my system idle for 15 seconds or more, I can see the result of my "idleness" by displaying the newly introduced current_clock_Hz kstat statistic:

$ kstat -m cpu_info -s current_clock_Hz 
module: cpu_info                        instance: 0 
name:   cpu_info0                       class:    misc 
        current_clock_Hz                2800000000 
 
module: cpu_info                        instance: 1 
name:   cpu_info1                       class:    misc 
        current_clock_Hz                2800000000

My CPUs have been scaled to run at their lowest supported frequency, 2.8 GHz, and are consuming less power and are generating less heat as a result. Not bad, huh?

Well, if you're not running one of the Intel processors listed above, or if you're running an AMD processor, don't fret. We're busy working on extending our Solaris x86 CPU power management support, so there's a good chance that Solaris will be supporting your processor in one of the upcoming SXDE releases. You're sure to see more posts from me as things progress.

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Posted at 07:53PM Sep 21, 2007 by Mark Haywood in Sun
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