powermetrics is a Mac-only command-line utility that provides many high-quality power-related measurements. It is most useful for getting CPU, GPU and wakeup measurements in a precise and easily scriptable fashion (unlike Activity Monitor and top) especially in combination with rapl via the mach power command. This document describes the version of powermetrics that comes with Mac OS 10.10. The one that comes with 10.9 is less powerful.
Note: The power profiling overview is worth reading at this point if you haven't already. It may make parts of this document easier to understand.
Quick start
powermetrics provides a vast number of measurements. The following command encompasses the most useful ones:
sudo powermetrics --samplers tasks --show-process-coalition --show-process-gpu -n 1 -i 5000
--samplers taskstells it to just do per-process measurements.--show-process-coalition--show-process-gputells it to show per-process GPU measurements.-n 1tells it to take one sample and then stop.-i 5000tells it to use a sample length of 5 seconds (5000 ms). Change this number to get shorter or longer samples.
The following is example output from such an invocation:
*** Sampled system activity (Fri Sep 4 17:15:14 2015 +1000) (5009.63ms elapsed) *** *** Running tasks *** Name ID CPU ms/s User% Deadlines (<2 ms, 2-5 ms) Wakeups (Intr, Pkg idle) GPU ms/s com.apple.Terminal 293 447.66 274.83 120.35 221.74 firefox 84627 77.59 55.55 15.37 2.59 91.42 42.12 204.47 plugin-container 84628 377.22 37.18 43.91 18.56 178.65 75.85 17.29 Terminal 694 9.86 79.94 0.00 0.00 4.39 2.20 0.00 powermetrics 84694 1.21 31.53 0.00 0.00 0.20 0.20 0.00 com.google.Chrome 489 233.83 48.10 25.95 0.00 Google Chrome Helper 84688 181.57 92.81 0.00 0.00 23.95 12.77 0.00 Google Chrome 84681 57.26 76.07 4.39 0.00 23.75 12.97 0.00 Google Chrome Helper 84685 0.13 48.08 0.00 0.00 0.40 0.20 0.00 kernel_coalition 1 128.64 780.19 330.52 0.00 kernel_task 0 109.97 0.00 0.20 0.00 779.47 330.35 0.00 launchd 1 18.88 2.44 0.00 0.00 0.40 0.20 0.00 com.apple.Safari 488 90.60 108.58 56.48 26.65 com.apple.WebKit.WebContent 84679 64.21 84.69 0.00 0.00 104.19 54.89 26.66 com.apple.WebKit.Networking 84678 26.89 58.89 0.40 0.00 1.60 0.00 0.00 Safari 84676 1.56 55.74 0.00 0.00 2.59 1.40 0.00 com.apple.Safari.SearchHelper 84690 0.15 49.49 0.00 0.00 0.20 0.20 0.00 org.mozilla.firefox 482 76.56 124.34 63.47 0.00 firefox 84496 76.70 89.18 10.58 5.59 124.55 63.48 0.00
This sample was taken while the following programs were running:
- Firefox Beta (single process, invoked from the Mac OS dock, shown in the
org.mozilla.firefoxcoalition.) - Firefox Nightly (multi-process, invoked from the command line, shown in the
com.apple.Terminalcoalition.) - Google Chrome.
- Safari.
The grouping of parent and child processes (in coalitions) is obvious. The meaning of the columns is as follows.
- Name: Coalition/process name. Process names within coalitions are indented.
- ID: Coalition/process ID number.
- CPU ms/s: CPU time used by the coalition/process, per second, during the sample period. The sum of the process values typically exceeds the coalition value slightly, for unknown reasons.
- User%: Percentage of that CPU time spent in user space (as opposed to kernel mode.)
- Deadlines (<2 ms, 2-5 ms): These two columns count how many "short" timers woke up threads in the process, per second, during the sample period. High frequency timers, which typically have short time-to-deadlines, can cause high power consumption and should be avoided if possible.
- Wakeups (Intr, Pkg idle): These two columns count how many wakeups occurred, per second, during the sample period. The first column counts interrupt-level wakeups that resulted in a thread being dispatched in the process. The second column counts "package idle exit" wakeups, which wake up the entire package as opposed to just a single core; such wakeups are particularly expensive, and this count is a subset of the first column's count.
- GPU ms/s: GPU time used by the coalition/process, per second, during the sample period.
Other things to note.
- Smaller is better — i.e. results in lower power consumption — for all of these measurements.
- There is some overlap between the two "Deadlines" columns and the two "Wakeups" columns. For example, firing a single sub-2ms deadline can also cause a package idle exit wakeup.
- Many of these measurements are also obtainable by passing the
TASK_POWER_INFOflag and atask_power_infostruct to thetask_infofunction. - By default, the coalitions/processes are sorted by a composite value computed from several factors, though this can be changed via command-line options.
Other measurements
powermetrics can also report measurements of backlight usage, network activity, disk activity, interrupt distribution, device power states, C-state residency, P-state residency, quality of service classes, and thermal pressure. These are less likely to be useful for profiling Firefox, however. Run with the --show-all to see all of these at once, but note that you'll need a very wide window to see all the data.
Also note that powermetrics -h is a better guide to the the command-line options than man powermetrics.
mach power
You can use the mach power command to run powermetrics in combination with rapl in a way that gives the most useful summary measurements for each of Firefox, Chrome and Safari. The following is sample output.
total W = _pkg_ (cores + _gpu_ + other) + _ram_ W #01 17.14 W = 14.98 ( 5.50 + 1.19 + 8.29) + 2.16 W 1 sample taken over a period of 30.000 seconds Name ID CPU ms/s User% Deadlines (<2 ms, 2-5 ms) Wakeups (Intr, Pkg idle) GPU ms/s com.google.Chrome 500 439.64 585.35 218.62 19.17 Google Chrome Helper 67319 284.75 83.03 296.67 0.00 454.05 172.74 0.00 Google Chrome Helper 67304 55.23 64.83 0.03 0.00 9.43 4.33 19.17 Google Chrome 67301 63.77 68.09 29.46 0.13 76.11 22.26 0.00 Google Chrome Helper 67320 38.30 66.70 17.83 0.00 45.78 19.29 0.00 com.apple.WindowServer 68 102.58 112.36 43.15 80.52 WindowServer 141 103.03 58.19 60.48 6.40 112.36 43.15 80.53 com.apple.Safari 499 267.19 110.53 46.05 1.69 com.apple.WebKit.WebContent 67372 190.15 79.34 2.02 0.14 129.28 53.79 2.33 com.apple.WebKit.Networking 67292 65.23 52.74 0.07 0.00 4.33 1.40 0.00 Safari 67290 29.09 77.65 0.23 0.00 7.13 3.37 0.00 com.apple.Safari.SearchHelper 67371 13.88 91.18 0.00 0.00 0.36 0.05 0.00 com.apple.WebKit.WebContent 67297 0.81 56.84 0.10 0.00 2.20 1.30 0.00 com.apple.WebKit.WebContent 67293 0.46 76.40 0.03 0.00 0.57 0.20 0.00 com.apple.WebKit.WebContent 67295 0.24 67.72 0.00 0.00 0.90 0.37 0.00 com.apple.WebKit.WebContent 67298 0.17 59.88 0.00 0.00 0.50 0.13 0.00 com.apple.WebKit.WebContent 67296 0.07 43.51 0.00 0.00 0.10 0.03 0.00 kernel_coalition 1 111.76 724.80 213.09 0.12 kernel_task 0 107.06 0.00 5.86 0.00 724.46 212.99 0.12 org.mozilla.firefox 498 92.17 212.69 75.67 1.81 firefox 63865 61.00 87.18 1.00 0.87 25.79 9.00 1.81 plugin-container 67269 31.49 72.46 1.80 0.00 186.90 66.68 0.00 com.apple.WebKit.Plugin.64 67373 55.55 74.38 0.74 0.00 9.51 3.13 0.02 com.apple.Terminal 109 6.22 0.40 0.23 0.00 Terminal 208 6.25 92.99 0.00 0.00 0.33 0.20 0.00
The rapl output is first, then the powermetrics output. As well as the browser processes, the WindowServer and kernel tasks are shown because browsers often trigger significant load in them.
The default sample period is 30,000 milliseconds (30 seconds), but that can be changed with the -i option.