What makes up app launch time and how do you measure it?
Essence
Users perceive launch as the time from tapping the icon to the first meaningful frame. There's a cold launch (no process, data not cached), a warm one (no process, but some data is still in memory) and a resume from the background. Apple's target is roughly 400 ms to the first frame of a cold launch; if launch takes tens of seconds, the system terminates the app (watchdog).
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