Thread Visualization Tool
Tracing C++ functions to understand how they're threading.
Facebook has lots of internal services which perform back-end functions that are critical to the overall efficiency and performance of the site. Most of these services involve complex systems running hundreds of different threads, and there previously wasn't an easy way to gain insight into whether these threads were running effectively or not. This tool traces C++ function calls and integrates with kernel-level data to produce a visualization that shows when threads are executing, their relationship to each other (spawning/call-backs), when they're scheduled on the CPU, and stack trace data whenever the state of a thread changes.