Native app performance

Skill mouadja02/skills/skills/coding/native-app-performance

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npx -y skills add mouadja02/skills --skill native-app-performance

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Native macOS/iOS app performance: xctrace, Time Profiler, traces, hotspot analysis — CLI-only.

SKILL.md

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Native App Performance (CLI-only)

Attribution: Sourced from steipete/agent-scripts by Peter Steinberger.

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

Related skill: For Instruments UI workflows and trace export details, see instruments-profiling.

When to Use

CLI-only profiling without opening Instruments GUI
Symbolicating stack traces with atos and vmmap
Ranking hotspots from xctrace time-profile samples
Headless or SSH-based performance analysis

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

xcrun xctrace export --input /tmp/App.trace \
  --xpath '/trace-toc/run[@number="1"]/data/table[@schema="time-profile"]' \
  --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

# Symbolicate using atos
atos -o /path/App.app/Contents/MacOS/App -l <load-address> <address>

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.

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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