Hitches, loading, and garbage collection

Capture a hitch

1. Set an explicit hitch threshold for the target experience; use stat hitches or stat dumphitches for fast detection where useful.
2. Display stat unitgraph, toggle stat raw, and reproduce the hitch.
3. Add bookmarks immediately before/after the action that triggers it.
4. Trace cpu,frame,bookmark plus only the suspected channel: loadtime, file, or stats.
5. Inspect the exact slow frame and the preceding work; asynchronous requests often cause a later wait.

Symptom routing

Hitch shape	Inspect
first use of asset/effect	async load, shader/PSO readiness, construction, audio decode
periodic spike	GC, streaming update, autosave/telemetry, scheduled subsystem
entering region	World Partition/level/texture/Nanite streaming and file IO
mass spawn/despawn	object construction, registration, physics/nav, GC pressure
camera cut	visibility burst, VSM pages, streaming, post/upscaler history

For loading, correlate Asset Loading events with file reads and Game-thread waits. A long async load is not necessarily a hitch unless the critical thread blocks for it or the workload saturates IO/CPU.

For GC, inspect allocation/object churn before the collection, collection duration, unreachable-object processing, and post-GC work. Reduce avoidable churn or distribute work; do not merely raise the GC interval if that creates a larger eventual pause or excess memory.