macOS Performance Triage (Apple Silicon)

When to Use This Skill

Platform Guard

macOS-only. powermetrics, sample, spindump, Instruments, and the Apple-Silicon power counters macmon reads are Darwin-specific.

test "$(uname -s)" = "Darwin" || { echo "macos-plugin: not Darwin, refusing"; exit 1; }

Core Insight: triage with the USE method; WindowServer is always downstream

Two ideas drive the whole flow:

1. USE method (Brendan Gregg) — for each resource ask Utilization, Saturation, Errors. A bare ps-by-CPU only answers Utilization. Saturation (run-queue depth, thermal throttle) and Errors (log stream) complete the picture. The method is OS-agnostic; only the tools change.
2. WindowServer never starts its own work. Every cycle it burns was requested by a client app's draw / animation / compositing. Apps build their UI as CALayer hierarchies, hand them to WindowServer via IOSurface, and WindowServer composites (positioning, clipping, masks, shadows, effects) synced to the display refresh. So a hot WindowServer is a symptom — the job is to find the app feeding it (continuous video, GIF/Lottie animation, a software / non-GPU-accelerated render path, layout thrashing).

The deepest tier of Gregg's Linux approach does not transfer: there is no eBPF / bpftrace on macOS. DTrace is the analogue but SIP blocks it from tracing Apple-signed/system processes (including WindowServer) unless SIP is disabled — not worth it for desktop triage. The flow below stays within a normally-secured Mac.

Step 1 — Quick triage: what's hot

Start with a process snapshot, sorted by CPU. -c shows the short command name:

ps -Aceo pid,pcpu,pmem,comm -r | head -16

Then get the Apple-Silicon power/thermal picture. macmon (Rust) is the preferred tool — it reads the same data as powermetrics (per-cluster P/E-core load + frequency, GPU, ANE, package power, temps) but without sudo, via a private IOReport API. One-shot, scriptable snapshot:

macmon pipe -s 1 | jq -c '{cpu_W:.cpu_power, gpu_W:.gpu_power, ane_W:.ane_power, ecpu_usage, pcpu_usage, gpu_usage, temp}'

Live TUI: macmon. Process/thread breakdown TUI: btm (bottom, Rust).

If the tools are missing, offer to install (all Rust, all sudo-free):

brew install macmon bottom samply hyperfine

Read the snapshot:

• A high non-system process at the top → go to Step 3 (profile it) or just identify/close it.
• WindowServer high → Step 2 (attribute it).
• kernel_task high → thermal management throttling a real load; find that load.
• The whole security stack hot together → this is an exec storm, hand off to endpoint-security-cpu.

Common phantom offenders

• OrbStack Helper — quitting the OrbStack app does not stop the VM; the helper reparents to launchd (PPID 1) and keeps eating ~40–50% CPU / ~20% RAM with no visible app. Confirm with ps -Ao pid,ppid,comm | grep -i '[o]rb' (a PPID of 1 is the tell) and stop it with orb stop, not kill. (Disk side of the same tool: macos-disk-usage.)
• A backgrounded Electron app (Slack, Discord, VS Code) animating off-screen.
• A browser tab running video/WebRTC/canvas — see Step 2.

Step 2 — Attribute WindowServer / GPU load to the driving app

There is no single first-party "blame" button; attribute in layers, cheapest first:

1. Per-process GPU cost (the real lever):

   sudo powermetrics --samplers tasks --show-process-gpu -n 1 -i 1000
   

   The app with high GPU here is what's loading WindowServer's compositor.
2. Activity Monitor → add the GPU column, sort descending; the Window Spy picker maps a visible window back to its owning process.
3. Instruments → Core Animation template — layer counts, dropped frames, compositing time (developer-side, if you own the app).
4. Instruments → Metal System Trace — catches software-fallback (non-GPU) render paths and frame-pacing anomalies.
5. Quartz Debug (Xcode Additional Tools) — live "flash dirty regions / overdraw"; visually shows which surfaces re-composite every frame.

Pattern to expect: N live video/WebRTC streams (e.g. a multi-cam call inside a browser/VTT) = N continuously-invalidating Core Animation layers → per-frame recomposition. That is a genuine workload floor, not a fault — confirmed when WindowServer stays hot after you close other GPU consumers.

sample WindowServer 5 and spindump can sample WindowServer itself, but they show its internal compositing stacks, not which client drove the work — use powermetrics --show-process-gpu for attribution, not sample.

Step 3 — Deep profiling: flame graph a specific process

For a CPU-heavy process you own, samply (Rust) is the modern path — samples via Apple's Mach interface (on- and off-CPU), opens in the Firefox Profiler UI (flame graph + timeline + call tree), no sudo, no SIP changes for your own binaries:

samply record ./my-program        # launch + record
samply record --pid 12345         # attach to a running PID

• Instruments is more capable (adds GPU, ANE, Metal, PMC counters) but the UI and xctrace CLI are sluggish, and attaching to other apps needs entitlements.
• cargo flamegraph / FlameGraph + dtrace works for your own code, but SIP makes dtrace-based graphs low-fidelity for anything system-touching, and can't graph WindowServer at all without disabling SIP.
• A Chrome/Electron renderer is sandboxed — samply can't see in usefully; use the app's own chrome://tracing / DevTools Performance tab instead.

For A/B comparing two builds or commands (Gregg-style workload characterization), hyperfine (Rust) gives warmup + statistics:

hyperfine --warmup 3 './old-build args' './new-build args'

Linux → macOS tool map (for transferring Gregg's playbook)

The toolkit (Rust-forward, all sudo-free unless noted)

macmon, bottom, samply, hyperfine install with one line: brew install macmon bottom samply hyperfine. asitop/mactop are older equivalents that require sudo; macmon supersedes them.

Output

Report: the hot process(es) with CPU/GPU/power figures; for a hot WindowServer, the attributed client app and why (animation/video/software-render); the recommended action (close/stop the driver, lower its settings, or profile it); and which tier of tool produced the verdict. Distinguish a genuine workload floor (a live video call) from a fixable runaway (an orphaned VM, a stuck animation).

Related

• macos-performance-benchmark — the proactive baseline companion: run a repeatable, threshold-scored benchmark + diagnostic suite (macmon-first, same toolkit) to establish what "normal" is before triaging a deviation from it.