adb (Android Debug Bridge, a tool probably familiar to anyone who’s read this far) provides just the thing I needed. Mor

Consistency: Cold start ensures that your app is going through the same set of operations every time it starts. If your app is being launched in a warm start scenario, it is not as obvious which steps are being performed and which are being skipped, so it’s not clear what you are actually timing (and whether you are testing things consistently between repeated runs).

Running this command launches the app (unless the app is already in the foreground, which is not what you want; we’ll deal with that next), and then outputs the following information:

Worst case: By definition, cold start is the worst-case scenario; it is the longest startup duration that your users will see. You need to keep your focus on that worst-case statistic, rather than the best-case warm start situation. You can’t fix the big problems if you ignore them.

In order to force a cold-start situation for every run, you need to kill the app between runs. Again, doing this on the screen (by, say, swiping it out of the Overview list in launcher) would be tedious and error-prone. Once again, adb shell comes to the rescue.

Note: There’s actually a much simpler way to loop start-activity using -S (which force-stops the activity first) and -R COUNT (which runs thestart-activity command COUNT times), so I could have used this instead:

Here’s the final command I used, which includes killing the app, waiting a second, then launching it. I looped it for 100 iterations, which provided a reasonable sample size for my situation:

Both scenarios are valid to test and understand. But in general, testing your startup performance in a cold start scenario is a better place to start, for two main reasons:

There are a couple of different shell commands that can be used to kill activities. The most obvious is adb shell am kill… but it doesn’t actually do the trick. After you’ve launched your application, it’s in the foreground and kill won’t kill the foreground app. Instead, you need the force-quit command:

The last argument is the package component information for your app. You can see that they are the same here as in the ActivityTaskManager log output in the section above.

To convert the output above to just the launch duration, I pipe the output through grep and cut shell commands (there are various ways to do this, I just picked one at random):

Now you have commands that you can run together to launch the app, output the launch duration data, and quit the app, making it ready to launch again. You could type this in the console over and over, but hey, we’re in a shell; let’s put it in a loop and run it repeatedly with just one command.

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is on the most powerful device you have and one that is turned on for most of the day, preferably all day. One of the benefits of this setup is that you will be able to use Jupyter Notebook from any device on your network, but have all the computation happen on the device we configure.

In doing this, you want to avoid running the app too soon after it’s killed, in case there are side-effects associated with the app being torn down (such as the system pulling the Launcher to the foreground as the app is torn down). To do this, I added a second of sleep to insert a small buffer between operations.

Starting: Intent { cmp=com.android.samples.mytest/.MainActivity } Status: ok LaunchState: COLD Activity: com.android.samples.mytest/.MainActivity TotalTime: 1380 WaitTime: 1381 Complete

This means that we don’t have to troll through logcat to get this information. Instead, we can get it directly from the console where we run the launch command. Better yet, we can strip the extraneous text and leave just the launch result, making it easier to extract this data for use elsewhere.