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native-app-performance

Native macOS/iOS app performance profiling via xctrace/Time Profiler and CLI-only analysis of Instruments traces. Use when asked to profile, attach, record, or analyze Instruments .trace files, find hotspots, or optimize native app performance without opening Instruments UI.

Published by LeoYeAI ↗LeoYeAI/agent-master-skills

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SKILL.md

name: native-app-performancedescription: Native macOS/iOS app performance profiling via xctrace/Time Profiler and CLI-only analysis of Instruments traces. Use when asked to profile, attach, record, or analyze Instruments .trace files, find hotspots, or optimize native app performance without opening Instruments UI.

Native App Performance (CLI-only)

Goal: record Time Profiler via xctrace, extract samples, symbolicate, and propose hotspots without opening Instruments.

Quick start (CLI)

  1. Record Time Profiler (attach):
# Start app yourself, then attach
xcrun xctrace record --template 'Time Profiler' --time-limit 90s --output /tmp/App.trace --attach <pid>
  1. Record Time Profiler (launch):
xcrun xctrace record --template 'Time Profiler' --time-limit 90s --output /tmp/App.trace --launch -- /path/App.app/Contents/MacOS/App
  1. Extract time samples:
scripts/extract_time_samples.py --trace /tmp/App.trace --output /tmp/time-sample.xml
  1. Get load address for symbolication:
# While app is running
vmmap <pid> | rg -m1 "__TEXT" -n
  1. Symbolicate + rank hotspots:
scripts/top_hotspots.py --samples /tmp/time-sample.xml \
  --binary /path/App.app/Contents/MacOS/App \
  --load-address 0x100000000 --top 30

Workflow notes

  • Always confirm you’re profiling the correct binary (local build vs /Applications). Prefer direct binary path for --launch.
  • Ensure you trigger the slow path during capture (menu open/close, refresh, etc.).
  • If stacks are empty, capture longer or avoid idle sections.
  • xcrun xctrace help record and xcrun xctrace help export show correct flags.

Included scripts

  • scripts/record_time_profiler.sh: record via attach or launch.
  • scripts/extract_time_samples.py: export time-sample XML from a trace.
  • scripts/top_hotspots.py: symbolicate and rank top app frames.

Gotchas

  • ASLR means you must use the runtime __TEXT load address from vmmap.
  • If using a new build, update the --binary path; symbols must match the trace.
  • CLI-only flow: no need to open Instruments if stacks are symbolicated via atos.