PowerTOP

PowerTOP v1.1 was released earlier this week. Dave Stewart initially turned me onto PowerTOP with his comment to my Results of Power Management blog. PowerTOP for OpenSolaris stems from what was originally a Linux project - its goal to show you what's chewing up your CPU cycles - especially important for laptop users looking to maximize battery life.

Let's start with the results:

The display can be broken into 5 parts: C States, P States, Wakeups, Power Usage and Top Causes for Wakeups. I'll cover each based on the snapshot above.

C States

Your CPU is either working on something or resting. When it's working, the CPU is in state 0, when it's resting it is in some state greater than 0, depending on how deep it's sleeping. From the snapshot above you see that it's been working about 25% of the time and idle for 75%. Of more interest you can see that it spends on average only 0.6ms resting before it is awoken to work again.

P-States

P-States shows the frequency at which your CPU is currently running. In the snapshot above, I'm currently running at my max speed of 2400 Mhz. But if I sit and let it idle I can watch my CPU step its way down to my lowest supported speed of 800 Mhz. The number is shown as a percentage but I don't see how it would ever be anything other than 100%.

Wakeups

Here we see how many times my machine is awoken per second. According to the PowerTOP website, "When running a full GNOME desktop, 3 wakeups per second is achievable". At 1269 Wakeups per seconds, I'm obviously far from achieving that goal.

The interval is just the refresh interval. The default is 5 seconds and you can control this with the -t option when starting PowerTOP.

Power Usage

As a laptop user (for whom PowerTOP is really targeted), this is the most interesting set of statistics. First you see the ACPI estimate of power usage in watts - obviously the higher this number, the shorter your battery life will be, which is the second statistic given based on the wattage. If you watch your CPU step its way down, you'll also see the wattage decrease and the estimated battery life increase.

Top Causes for Wakeups

This list contains the top items causing your CPU to awaken. The items in this list are over my head, but if you understand this stuff, you can begin to investigate why your battery life sucks and try to take steps to improve it. I found several examples of folks doing just that when doing my research on PowerTOP. 

Suggestions? 

One nice feature the Linux version of PowerTOP has that's missing on OpenSolaris is suggestions on improving power usage. This saves you from having to decipher the cryptic list above. It has been filed as an enhancement request: Include Suggestions. Note, the one suggestion that PowerTOP does make is to enable power management if it is not already turned on:


Installing and Running PowerTOP

Download PowerTOP and save it to your desktop.

Open a terminal and untar the archive:

tar -xf Desktop/SUNWpowertop-1.1_5961.5.11-i386.pkg.tar 

Install the package:

pfexec pkgadd -d SUNWpowertop-1.1_5961.5.11-i386.pkg 

And run:

pfexec powertop


Comments:

Brian - nice post! A very good explanation of the features and benefits of PowerTOP. I gave you some link love over on http://softwareblogs.intel.com/2008/07/25/nice-post-on-powertop/

Posted by Dave Stewart on July 25, 2008 at 03:06 PM GMT #

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