Native App Performance

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>

2. Record Time Profiler (launch):

xcrun xctrace record --template 'Time Profiler' --time-limit 90s --output /tmp/App.trace --launch -- /path/App.app/Contents/MacOS/App

3. Extract time samples:

scripts/extract_time_samples.py --trace /tmp/App.trace --output /tmp/time-sample.xml

4. Get load address for symbolication:

# While app is running
vmmap <pid> | rg -m1 "__TEXT" -n

5. 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.

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