performance slopping but actually very informative

2026-09-16 01:21:20 -04:00 · 2026-06-11 14:07:28 -04:00
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+# `/` Performance Investigation Summary
+
+This is the high-level handoff for the default route at:
+
+```sh
+https://rover.otter.land/
+```
+
+The detailed issue writeups live in `perf/issues/`.
+
+## Main Finding
+
+The `/` page is doing too much main-thread work for low-end devices. On the current powerful
+machine it can appear smooth, but CPU throttling shows real risk for mobile and weaker
+computers.
+
+The biggest measured problem is repeated global input listener churn. The broader underlying
+theme is that high-frequency live data and broad React context invalidation cause many parts
+of the page to rerender or recommit DOM attributes.
+
+## Key Measurements
+
+### Clean `/` Profile, 8x Mobile CPU Throttle
+
+Artifact:
+
+```sh
+perf/results/2026-06-11T03-15-51-398Z/report.json
+```
+
+Results:
+
+```txt
+average frame interval: ~140ms
+p95 frame interval:     ~166.8ms
+p99 frame interval:     ~383.4ms
+long tasks:             67
+event listener delta:   +13,481
+JS heap delta:          +22.76MB
+ScriptDuration delta:   ~35.85s
+TaskDuration delta:     ~52.88s
+```
+
+Top notable CPU self-time included:
+
+```txt
+removeEventListener ~1.30s
+addEventListener    ~0.94s
+```
+
+### Listener Audit
+
+Artifact:
+
+```sh
+perf/results/2026-06-11T03-03-31-625Z-listeners/listener-report.json
+```
+
+Worst churn:
+
+```txt
+keydown               adds=8040 removes=8039
+keyup                 adds=8040 removes=8039
+blur                  adds=8040 removes=8039
+gamepadconnected      adds=8040 removes=8039
+gamepaddisconnected   adds=8040 removes=8039
+```
+
+### `/` Runtime Audit, 6x Mobile CPU Throttle, 30s
+
+Artifact:
+
+```sh
+perf/results/2026-06-11T03-21-51-263Z-root-runtime/root-runtime-report.json
+```
+
+Results:
+
+```txt
+average frame interval: ~88ms
+p95 frame interval:     150ms
+p99 frame interval:     183ms
+long tasks:             18
+WebSocket messages:     at least 1000 sampled
+WebSocket bytes:        ~798KB sampled
+DOM mutation records:   41,062
+DOM attribute records:  40,761
+```
+
+Top sampled WebSocket events:
+
+```txt
+log:entry       526
+sensorFrame     306
+commandAck      145
+session:sync      5
+```
+
+### `/` Runtime Audit With Mutation Targets, 6x Mobile CPU Throttle, 18s
+
+Artifact:
+
+```sh
+perf/results/2026-06-11T03-22-44-714Z-root-runtime/root-runtime-report.json
+```
+
+Results:
+
+```txt
+average frame interval: ~116.6ms
+p95 frame interval:     ~166.7ms
+p99 frame interval:     ~316.6ms
+long tasks:             16
+DOM mutation records:   18,758
+DOM attribute records:  18,490
+```
+
+Top WebSocket events:
+
+```txt
+log:entry       850
+sensorFrame     277
+commandAck      200
+session:sync     23
+```
+
+Top mutation targets:
+
+```txt
+input.accent-emerald-400 name       5300
+input.accent-emerald-400 type       2650
+field-input name                    ~1300 each
+div.h-full style                    1238
+path d                              621
+path fill                           619
+```
+
+## Ordered Work Plan
+
+1. Fix `KeyboardInputManager` and `GamepadInputManager` listener churn.
+2. Split/stabilize `ControlContext` so action consumers do not rerender on every state change.
+3. Batch or gate `log:entry` socket updates.
+4. Throttle visual telemetry rendering.
+5. Memoize or lazy-mount `ReplaySourcesPanel`.
+6. Split and memoize chat composer/nickname form.
+7. Clean up or share timers.
+
+## Reproduction Commands
+
+Install Playwright dependency if missing:
+
+```sh
+npm install --prefix perf playwright@1.60.0
+npx playwright install chromium
+```
+
+Clean CPU profile:
+
+```sh
+CPU_THROTTLE=8 VIEWPORT=390x844 MOBILE=1 node perf/live-cpu-profile.mjs https://rover.otter.land/ perf/results
+```
+
+Listener audit:
+
+```sh
+node perf/live-listener-audit.mjs https://rover.otter.land/ perf/results
+```
+
+Runtime audit:
+
+```sh
+CPU_THROTTLE=6 VIEWPORT=390x844 MOBILE=1 SAMPLE_MS=30000 node perf/live-root-runtime-audit.mjs https://rover.otter.land/ perf/results
+```
+
+Runtime audit with shorter mutation target sample:
+
+```sh
+CPU_THROTTLE=6 VIEWPORT=390x844 MOBILE=1 SAMPLE_MS=18000 node perf/live-root-runtime-audit.mjs https://rover.otter.land/ perf/results
+```
+
+## Notes
+
+The `perf/results/2026-06-11T03-11-39-596Z-route-sweep/` route sweep includes `/spectate`,
+`/mini`, `/display`, and `/scanner`. Those are not the current priority. Use them only for
+context.
+