starting/stopping Instruments from code on iPhone (iOS)

I don't see any way to start/stop profiling in Instruments from code, which kinda kills its usefulness for me in a large number of situations.. Am I missing something? Does anyone know of a way to do this?

The fallback approach is to grab performance data on my own, without Instruments. Has anyone tried to do this before? By "performance data" I mean counts of events like cache misses, fills, missed branches, etc.

Thanks!

Upda开发者_开发知识库te:

I looked into operating the performance monitor hw directly from code, but, unsurprisingly, it appears to be a no-go. USEREN, the "user enable register" controls access to perfmon registers but is not enabled. It might be possible to run privileged or enable user access with a jailbroken phone, but that's a lot of work for some basic profiling.. ugh.