Goal: record Time Profiler via xctrace, extract samples, symbolicate, and propose hotspots without opening Instruments.
Quick start (CLI)
- Record Time Profiler (attach):
# Start app yourself, then attach
xcrun xctrace record --template 'Time Profiler' --time-limit 90s --output /tmp/App.trace --attach <pid>
- Record Time Profiler (launch):
xcrun xctrace record --template 'Time Profiler' --time-limit 90s --output /tmp/App.trace --launch -- /path/App.app/Contents/MacOS/App
- Extract time samples:
scripts/extract_time_samples.py --trace /tmp/App.trace --output /tmp/time-sample.xml
- Get load address for symbolication:
# While app is running
vmmap <pid> | rg -m1 "__TEXT" -n
- 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.