Using Intel® Power Checker to measure the energy performance of a compute-intensive application

Intel® Power Checker provides developers with a quick and easy way to evaluate the idle power efficiency of their applications on mobile platforms with Intel® Core™ processor or Intel® Atom™ technology running the Microsoft Windows* operating system. Any compiled language application, especially those designed to run on technology based on Intel® products and Java Framework applications can be analyzed by Intel Power Checker. The checker can be used with or without a supported external power meter.

The Intel Power Checker 2.0 now supports measurement both on battery and with the system plugged into an external AC power source. External power measurement is only supported on Intel® Second Generation Core processors and if the Intel® Power Gadget software has been installed.

For this article, I took a very compute-intensive parallel application that I wrote to solve instances of the logic puzzle Akari. The code uses a backtracking algorithm to explore how to place light bulbs onto a grid under constraints dictated by the rules of the puzzle and the layout of the puzzle instance. Potentially millions of independent tasks can be generated by the code as the solution space is searched by threads executing those tasks. This solution method is eminently scalable to a large number of threads and is able to keep many cores running at peak speed for a sustained amount of time.

How to Use Intel Power Checker

The Intel Power Checker provides a GUI wizard that leads you through the four steps of power analysis. These four steps in the checker are described below. Before starting the assessment, be sure to know which section of your application (a workload) you want to be measured, as the Power Checker will only measure a 30 second execution interval. (If you want to measure the entire execution workload, you should try some other tool, like Intel Power Gadget.) Your workload could be a compute-intensive portion or an I/O-intense section or just some point in execution that typifies the majority of expected usage.

Step 1: Specifying the Power Meter device

If you have an external power meter attached to your test system, you can select the model being used on the first screen of the wizard. The default is that no external device is being used. For this default case, Intel Power Checker will determine if the system is capable of providing power consumption data and if the correct power driver, EzPwr.sys, is installed. (The driver is part of the default installation of Intel Power Gadget.)

Step 2: Measure System Baseline

The first measurement that the Intel Power Checker will perform is on the next screen within the wizard. This is to measure the baseline power consumption of the hardware without your application running. Prior to this measurement phase any unnecessary processes such as operating system updates, Windows Indexing Service, virus scans, media players, and internet browsers should have been shut down. In other words, to get the most accurate results you should make your test system as idle as possible and ensure that nothing will become a foreground process during your measurement runs.

Once you have a quiescent system, click the “Start” button to begin this phase of the testing. The Intel Power Checker waits 15 seconds to allow the system to come to an idle state before starting the measurements. You need to be sure to position your mouse and the keyboard out of reach, or keep your hands away from them, to avoid any stray contact that might trigger some response from the platform. After the pause, the checker will observe the system for 30 seconds in this idle state. A progress bar will show the time remaining in each part of this phase. Once the baseline data collection is complete, click the “Next” button to proceed to the next phase.

Step 3: Measure Active Application

Before you are taken to the next screen in the wizard, you are instructed to start the application you are interested in measuring. Start up your application and click the “OK” button to advance the GUI to the next screen. Once you have reached the Step 3 screen, use the scroll bar to locate your application in the process list and click on that line to select it. If your application is not listed, click the “Refresh List” button so that your application’s process will be available to select. In addition, you can use the “Apply Filter” button to narrow down the list in order to find your application’s process quickly. .After selecting your application from the list, click “Next” to move on to the data collection for this phase. Before starting the assessment, be sure your application has reached the desired point of measurement. If there are some initial setup computations that are not of interest, you will need to get past this point before letting Intel Power Checker begin measurement. For my Akari application, there is very little setup time. It was typically in the thick of computation by the time I had gotten to the point of selecting the process from the list.

As soon as I could, I clicked the “Start” button to begin capturing measurement data. Since this is one of the crucial power measurements for your application, always begin capturing data after the workload or critical section has begun and make sure this active execution will run longer than the 30 seconds needed to complete the measurement time.

Step 4: Measure Idle Application

The final phase is to measure your application’s idle power consumption. This is another important phase of energy efficiency measurement of an application since your application must not only do efficient computation, but also not waste energy when sitting idle.

This step doesn’t make much sense within my compute-intensive application since there is no idle state of the application. Once you start the application on a given puzzle instance, it simply computes all legal solutions in parallel and then ends. As (multiple) solutions are found, they are printed out by the thread that found it. If there are no solutions, a message is printed just before the application terminates. This latter case describes the workload I used for my tests. Because you must have your application running in “idle” mode for this step, I left the application running at full speed and simply allowed Power Checker to take its measurements.

If your application does have an idle state, perhaps waiting for interaction from the user, the checker will give the system 15 seconds to calm down fully before taking a final 30 second measurement.

Upon completion of this last data collection phase, you will be able to proceed to the results screen within the Intel Power Checker wizard. After all three measurement phases have been completed; a Tool Report File will be generated containing all of the results for later analysis.

What data is presented

The View Results screen of the Intel Power Checker wizard provides basic information about the software assessment. The type of processor in your system and the type and model of the power source that was used are given. Four numerical values for each of the three measurement phases are presented. These values are:

  • Elapsed Time: The exact number of seconds that each of the phases lasted.
  • Energy Consumption: The rate that the battery was discharged during each of the three phases.
  • Average C3 State Residency: The percentage of time that the system was in the C3 state during the data collection period.
  • Platform Timer Period: The number of milliseconds that the platform timer collected

Typical results would hopefully show a larger percentage of time spent in the C3 State Residency for the application idle time measurement (the middle of the three columns on the View Results screen). As my puzzle solving application was still computing as much as it did in the active execution measurement step, this was not the case for my results. This is atypical for the intended type of applications Intel Power Checker assumes will be measured. Thus, the C3 State Residency values provided by the tool for the idle application were not valid for my particular application.

The name of the report file and the directory to which it will be found are listed on the View Results screen.

Some Caveats

Below are some things you should consider before and during a measurement run using Intel Power Checker.

  • Before you start using Intel Power Checker, be sure your chosen workload will run for at least 30 seconds from the point you wish to measure power consumption. In my case, I required a data set that would force the application to run for at least 75 seconds (30 for active measurement, 15 for idle setup, and 30 for idle measurement) plus the time I needed to click boxes and find my application in the process list. Since I ran the application on several different numbers of threads, I needed to be sure that the fastest execution time was still large enough to get all the timings steps completed during a Intel Power Checker run.
  • Upon starting Intel Power Checker, the checker may first report that the platform timer period is invalid. In this case, some currently running (background) process has changed the default and it will be up to the user to determine which currently running application has changed the value. Once you have identified the culprit you must stop this process or service before restarting Intel Power Checker. If you are unsure about which active process is preventing Intel Power Checker from starting, you will need to turn off processes one at a time and try Intel Power Checker until the error message doesn’t come up.
  • Instructions on the Step 3 screen ask you not to touch the keyboard or mouse. If you are measuring an interactive application or you must interact with the application to generate activity for the full 30 seconds, you will need to touch the keyboard and/or mouse. If possible, a workload that can forego interactivity and still compute for the 30 seconds of measurement time would be best. However, if interaction by the user is part of how the application is utilized, interfacing through peripherals will give you a more accurate measure of the overall energy consumption for typical application usage.
  • A data file is created during each phase of the Intel Power Checker assessment to hold the current information. If you cancel the assessment in any of the three phases then a data file will not be created for that phase. After all three phases have been completed, a Tool Report File, in XML format, will be generated containing all of the results. You can find the name of the report file and where it is located on the View Results screen.
  • The “Submit Results” button on the View Results screen is optional and only intended for members of the Intel® Software Partner Program to submit their measurement results to the program. If you are not a member, do not submit your results. Simply click on the “Close” button after you have examined the results compiled by Intel Power Checker.

Some Results

The purpose of this article is not to determine the best scenario for running my Akari solver application in the most energy efficient way. You will want to do this for your application, though, and this article has given you the background on Intel Power Checker to determine if this checker can help you quantify the current power consumption of your application. Also, as you make modifications to the application you will be able to determine if those changes improve the energy efficiency or cause your application to suck more power than before.

In addition to the average C3 State Residency percentage, the checker delivers the total number of Joules expended during the 30 seconds of execution time measured. From this I can compute the average Watts for execution parts of the application. I have found that a better metric for comparing different applications or different runs of the same application is milliwatt hours (mWh). You need the total execution time of the execution portion of the application to compute this value. Since Intel Power Checker only measures activity in 30 second segments, you will need to have some timing data available, which I happened to have for the different runs I made of my Akari application.

I found significant differences when running with and without Hyper-Threading Technology (HT) turned on. Also, if the platform was running on battery (DC) power or from the wall socket (AC) power, a difference in execution time and power usage was evident. For example, when running with HT on and a full complement of four threads on the 4 logical cores in my system, I saw the AC power run 1.19X faster that when running the same workload on DC power. However, the former run took 1.15X more power.

Comparing results between runs on DC power versus AC power is a not a good comparison, especially in this case. The power source is detected by the system and the processor is allowed to run with Intel® Turbo Boost Technology at a higher frequency if the platform is using external power. Even so, you may need to be concerned about power consumption of your application in both power source circumstances and you will need to run measurement experiments within each setup to gauge how well your application modifications affect overall power consumption.

System Requirements

You can use Intel Power Checker on a laptop or netbook based on Intel® Core™ processor or Intel® Atom™ processor technology. A desktop with an external power meter or a desktop that is capable of providing the power consumption information can also be analyzed. A Java* Runtime Environment (JRE) (version 6 update 11 or higher) is also required to run the checker. Supported operating systems are Microsoft Windows* XP (Service Pack 3), Microsoft Windows Vista* (Service Pack 2), Microsoft Windows* 7 (Service Pack 1 [32-bit and 64-bit]), and Microsoft Windows* Server 2008 R2.

Download link

To download the Intel Power Checker installation package, go to the following link:

/partner/app/software-assessment/. Click on the Intel Power Checker tab to move down to the download link.

Other supporting links

There is a video demonstration of using Intel Power Checker, “A Look at Intel Power Checker,” at the link: /en-us/videos/channel/intel-software-partner-program/a-look-at-the-intel-power-checker/1127786023001. Dave Valdovinos and Taylor Kidd, both from Intel, show off the GUI wizard as it measures the power performance of a game-like application.

For more complete information about compiler optimizations, see our Optimization Notice.

Comments

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when i start my application than after some time the application going to hang.........