diff options
Diffstat (limited to 'docs/performance/intel_power_gadget.md')
| -rw-r--r-- | docs/performance/intel_power_gadget.md | 56 |
1 files changed, 56 insertions, 0 deletions
diff --git a/docs/performance/intel_power_gadget.md b/docs/performance/intel_power_gadget.md new file mode 100644 index 0000000000..74f7801cff --- /dev/null +++ b/docs/performance/intel_power_gadget.md @@ -0,0 +1,56 @@ +# Intel Power Gadget + +[Intel Power Gadget](https://software.intel.com/en-us/articles/intel-power-gadget/) +provides real-time graphs of various power-related measures and +estimates, all taken from the Intel RAPL MSRs. This article provides a +basic introduction. + +**Note**: The [power profiling +overview](power_profiling_overview.md) is +worth reading at this point if you haven\'t already. It may make parts +of this document easier to understand. + +The main strengths of this tool are (a) it works on Windows, unlike most +other power-related tools, and (b) it shows this data in graph form, +which is occasionally useful. On Mac and Linux, `tools/power/rapl` +[](tools_power_rapl.md) is probably a better tool +to use. + +## Understanding the Power Gadget output + +The following screenshot (from the Mac version) demonstrates the +available measurements. + + + +The three panes display the following information: + +- **Power**: Shows power estimates for the package and the cores + (\"IA\"). These are reasonably useful for power profiling purposes, + but Mozilla\'s `rapl` utility provides these along with GPU and RAM + estimates, and in a command-line format that is often easier to use. +- **Frequency**: Shows operating frequency measurements for the cores + (\"IA\") and the GPU (\"GT\"). These measurements aren\'t + particularly useful for power profiling purposes. +- **Temperature**: Shows the package temperature. This is interesting, + but again not useful for power profiling purposes. Specifically, + the temperature is a proxy measurement that is *affected by* + processor power consumption, rather than one that *affects* it, + which makes it even less useful than most proxy measurements. + +Intel Power Gadget can also log these results to a file. This feature +has been used in [energia](https://github.com/mozilla/energia), Roberto +Vitillo\'s tool for systematically measuring differential power usage +between different browsers. (An energia dashboard can be seen +[here](http://people.mozilla.org/~rvitillo/dashboard/); please note that +the data has not been updated since early 2014.) + +Version 3.0 (available on Mac and Windows, but not on Linux) also +exposes an API from which the same measurements can be extracted +programmatically. At one point the Gecko Profiler [used this +API](https://benoitgirard.wordpress.com/2012/06/29/correlating-power-usage-with-performance-data-using-the-gecko-profiler-and-intel-sandy-bridge/) +on Windows to implement experimental package power estimates. +Unfortunately, the Gecko profiler takes 1000 samples per second on +desktop and is CPU intensive and so is likely to skew the RAPL estimates +significantly, so the API integration was removed. The API is otherwise +unlikely to be of interest to Mozilla developers. |