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My current app takes for a cold start ~8 seconds and I want to optimize that.
For that reason I added a log entry in my Application onCreate (Application, not Activity)

override fun onCreate() {
        Log.d("myTag", "Calling Application onCreate()")
        ....
}

When looking in the logs and measuring the time, I found out that the above mentioned 8 seconds consist of the following:
Tapping app icon => Application.onCreate = 4 seconds
Application.onCreate => my Activity visible = 4 seconds

I know I can optimize the time from Application.onCreate() onward. It's my code and I can speed this part up.
But how can I optimize the time the system needs until my Application.onCreate is called? Thanks!

maximilian
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  • At least say what kind of operations you are doing on your onCreate() network? database related? local? just creating the layout? what? – javdromero Jul 23 '21 at 14:05
  • @javdromero I was not talking about Activity's onCreate but Application onCreate. I'm doing there initialization of libraries like tracking, networking, etc. – maximilian Jul 26 '21 at 14:05

1 Answers1

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Sounds like a great usecase for systrace. I usually use (at least) the gfx, input, view, wm, am, res, dalvik, bionic, and sched categories. A -b 10000 to ensure a sufficient buffer size doesn't hurt.

You'll get an html file which can be loaded in a browser, or opened through Chrome/Chromium's built-in chrome://tracing page.

At the top, you'll see CPU details like usage% and which thread is running at which time. Then, you'll see all the processes on the device, containing nested colored blocks ("segments") with information about what's currently going on. At the top of each thread, there is a small colored bar: white is "sleeping" (this includes waiting on a mutex), blue is "waiting for CPU", green is "running on CPU".

If there is a segment that seems interesting but you don't understand the exact meaning of, a search for the text at https://cs.android.com/ can be useful.

In any case, my guess is that you either have some library linking or ContentProviders that take time before Application.onCreate. Both of those would be visible in a systrace. And if my guess is wrong, you'll likely find something else. Good luck! :)

(it could also be class initialization... it'll be interesting to hear what you find!)

Snild Dolkow
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  • Thank you @Snild Dolkow! I was able to find out that **opening dex files** took 3 seconds. [Image here](https://i.imgur.com/X6v5Tri.jpg). After little Google, I learned this only happens in _debug_ builds. So I made a release build and the dex file loading is now 100ms. And my app starts way faster. Very interesting learing! Thx! – maximilian Jul 26 '21 at 14:03