IOS 7.1.0 startup time slower than 6.5.4

[james-criscuolo]

With the release of 7.1.0, we've finally been able to test our mobile app on ios-v8. We've found that the startup is significantly slower, to the point that if we start our app via push, apple may kill it due to it taking too long.

My coworker has made a test repo showing this difference, along with much higher CPU usage: https://github.com/IanNMarshall/ns-performance-test

Without any flags (uglify, release, etc.) here is the startup time difference using Time Profiler:

And using release flags:

The times are close, but in our app (and likely anything larger than a demo), the difference grows:

I hope we are just missing something, as I was really hoping to see a significant boost across the board moving to v8. Our tests included codecache, and I'm aware the first startup is meant to be slower in that case, the slowness persists to subsequent app loads as well.