I'm using Allocations template to profile my app on iPhone, but VM Tracker is always empty. Why? How to make it show data?

You have to tell it to take snapshots periodically. Before starting the app...
- Click on the VM Tracker Instrument to activate it.
- Show the Detail View (Command-D) if you don't see it already.
- In the left (blue) side bar, activate "Automatic Snapshotting".
- Run.
Optionally you can choose to take snapshots manually before and after interesting events in your app.
来源:https://stackoverflow.com/questions/11692242/why-vm-tracker-is-empty