frame.pacing

Rides UIUpdateLink on the foreground window scene rather than hooking anything the app itself did. One reading per window while frames are being produced, covering how many missed the system’s own completion deadline, how long the Core Animation commit took, and how far ahead of presentation the system expected to be.


Delivery	stream, interval
Mechanism	osWatcher
Requires	iOS 18+, basset 0.1.1+

Real output from basset request get, captured while driving frames with a heavy layout pass:

CAPTURED                  ELAPSED  INSTRUMENT

launch 1845607200054935078
2026-08-23T16:13:24.769Z  +0.0s    render.frame.pacing(displayUpdate)
├─ occurrenceCount                 45
├─ windowNanoseconds               1000823792
├─ deadlineMissCount               1
├─ deadlineOverrunNanoseconds      24878875
├─ totalNanoseconds                72501215
├─ peakNanoseconds                 42303917
└─ presentationLatencyNanoseconds  33333250
2026-08-23T16:13:25.769Z  +1.0s    render.frame.pacing(displayUpdate)
├─ occurrenceCount                 23
├─ windowNanoseconds               999479750
├─ totalNanoseconds                43888081
├─ peakNanoseconds                 15127291
└─ presentationLatencyNanoseconds  33333250
2026-08-23T16:13:26.769Z  +2.0s    render.frame.pacing(displayUpdate)
├─ occurrenceCount                 6
├─ windowNanoseconds               999816000
├─ totalNanoseconds                16326499
├─ peakNanoseconds                 15245750
└─ presentationLatencyNanoseconds  33333250

The first window shows a real deadline miss — deadlineMissCount and deadlineOverrunNanoseconds only appear on a window that had one.

Getting Started

SDK

CLI

Instruments

Reference