[freezy]

The engine side of the profile build: a version of the player that finds and explains performance problems (stutters, frame pacing, physics stalls, CPU/GPU limits, slow start-up and table loads) on testers' machines and reports them to Sentry. Plan: PROFILE_BUILD_PLAN.md.

For every build

• Start-up timeline: from the process' creation to the menu's first frame, with wall and CPU time per step. It produces one Startup: log line and a Startup diagnostics section.
• Table load timeline: the package reader's steps and the load phases, plus the texture cache result and the load kind. Playable is the first frame after the gamelogic engine started. Settled is the first 3 s window where no frame took over 1.5× its median. The load ends as settled, timeout, failed or cancelled, and logs a line for each.
• SimulationTrace:
  • Players keep a 60 s summary instead of 10 minutes of CSVs. The summary is refreshed every minute on a worker, saved next to the session log, and attached to reports.
  • The rings are per session and are read through a per-slot seqlock.
  • The editor toggle and --simulation-trace still write the CSVs.
• Fixes:
  • The rendered snapshot no longer steps back to an older one.
  • Microsecond timestamps no longer overflow after days of uptime.

For the profile build only (VPE_PROFILE)

• VpeProfiler: an API with conditional methods, so its calls compile out of normal builds. A test checks that, and checks the IL.
• Recorders: per-frame PlayerLoop phase stamps, sections, Unity frame timings matched to frames, and the simulation ticks and lock waits.
• Detectors: stutter, hitch, pacing, simulation stall and slowdown, each with the most likely cause.
• Traces: Perfetto traces of the worst incidents (opens in ui.perfetto.dev), metrics windows, and self-tests (--vpe-test-perf=<mode>|all).

Testing

• 102 EditMode tests pass in the HDRP test project, including new seqlock, timeline and gating tests.
• Both flavors compile.
• A profile build of the HDRP player ran a table with all self-tests. Traces, logs and events went to Sentry.

[greptile-apps]

Confidence Score: 5/5

[Medium impact] The changes since the previous review appear safe to merge.

Summary

Adds startup and table-load timelines, saved simulation summaries, and profile-only frame recording, incident detection, metrics, and Perfetto traces.

• Startup and table loads now show where their time goes.
• Player runs keep a rolling summary of recent simulation timing.
• Profile builds record performance events and explain likely causes.
• Rendered snapshots stay current, and long-running timestamps keep their value.
• Player source lines are normalized without changing game behavior.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart TD
  A[Startup and table-load milestones] --> B[Logs and diagnostics]
  C[Simulation ticks and frames] --> D[Per-session rings]
  D --> E[Saved simulation summary]
  F[Profile-only frame and section recording] --> G[Incident detection]
  D --> G
  G --> H[Metrics and incident reports]
  G --> I[Perfetto trace capture]

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