Performance Profiling

Use this skill to diagnose Apple app performance issues systematically, pick the right profiling workflow, apply targeted fixes, and verify the change with real measurements.

Decision Tree

Choose the reference file before changing code:

What performance problem are you investigating?

+ App hangs, stutters, dropped frames, slow UI, high CPU
  -> Read references/time-profiler.md

+ High memory, leaks, OOM crashes, growing footprint
  -> Read references/memory-profiling.md

+ Slow cold launch, warm launch, resume, or time to first frame
  -> Read references/launch-optimization.md

+ Battery drain, thermal throttling, background energy, network waste
  -> Read references/energy-diagnostics.md

+ General "app feels slow"
  -> Start with references/time-profiler.md, then references/memory-profiling.md

+ Pre-release performance audit
  -> Read all reference files and use the review checklist below

Quick Reference

Problem	Instrument / Tool	Key Metric	Reference
UI hangs over 250 ms	Time Profiler + Hangs	Hang duration, main thread stack	references/time-profiler.md
High CPU usage	Time Profiler	CPU percent by function, call tree weight	references/time-profiler.md
Memory leak	Leaks + Memory Graph	Leaked bytes, retain cycle paths	references/memory-profiling.md
Memory growth	Allocations	Live bytes, generation analysis	references/memory-profiling.md
Slow launch	App Launch	Time to first frame, pre-main, post-main	references/launch-optimization.md
Battery drain	Energy Log	Energy impact, CPU/GPU/network activity	references/energy-diagnostics.md
Thermal issues	Activity Monitor, Instruments	Thermal state transitions	references/energy-diagnostics.md
Network waste	Network profiler	Redundant fetches, payload size	references/energy-diagnostics.md

Workflow