more performance sloptesting

2026-09-16 09:31:20 -04:00 · 2026-06-12 01:01:53 -04:00
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+# `/spectate` CPU Performance Summary
+
+This is the `/spectate` companion to the `/` performance writeups. The testing target
+was the deployed page:
+
+```sh
+https://rover.otter.land/spectate
+```
+
+The most useful artifact for this pass is:
+
+```sh
+perf/results/2026-06-12T04-55-16-888Z-root-runtime/root-runtime-report.json
+```
+
+That run used:
+
+```sh
+CPU_THROTTLE=6 VIEWPORT=390x844 MOBILE=1 SAMPLE_MS=30000 \
+  node perf/live-root-runtime-audit.mjs https://rover.otter.land/spectate perf/results
+```
+
+## High-Level Result
+
+`/spectate` is CPU-heavy for a different reason than `/`.
+
+The `/` page's biggest confirmed issue is global input listener churn. `/spectate` does
+not show that same dominant pattern. The fresh `/spectate` audit had 379 event listeners,
+mostly normal media/image listeners, and no giant add/remove loop.
+
+The `/spectate` hot path is instead a live-display fan-out problem:
+
+- several rover media players are mounted at once
+- each rover card renders live HUD telemetry and a top-down SVG map
+- camera/snapshot frames create new blobs and `img.src` values
+- the route subscribes to broad session/log/chat state while also rendering the whole
+  spectator layout
+- the page maintains several WebRTC players at the same time
+
+## Key Measurements
+
+Fresh `/spectate` runtime audit, 30s, mobile viewport, 6x CPU throttle:
+
+```txt
+TaskDuration:        28.48s over a 30.9s sample
+ScriptDuration:      12.11s
+Long tasks:          81
+Worst long task:     375ms
+Average frame gap:   113.9ms
+p95 frame gap:       233.3ms
+p99 frame gap:       300.0ms
+Nodes:               7,059
+Layout objects:      6,150
+RTCPeerConnections:  6
+LayoutCount:         243
+RecalcStyleCount:    248
+```
+
+The 8x CPU-throttled profile from the earlier route comparison was worse:
+
+```txt
+Task delta:          49.13s over a 52.85s sample
+Script delta:        19.58s
+Layout delta:        516
+Recalc delta:        522
+Node delta:          +3,815
+```
+
+That profile also put `Blob`, `decodeString`, and `setAttribute` in the CPU stack, which
+matches the runtime evidence for camera blobs, socket payload parsing, and SVG/image
+attribute churn.
+
+## Socket And DOM Pressure
+
+The fresh audit captured these live events during the 30s window:
+
+```txt
+sensorFrame:          1,354 events, 2,531,090 bytes
+log:entry:              634 events,   150,179 bytes
+unlabeled binary:       126 events, 11,048,477 bytes
+roomCamera:frame:       117 events
+session:sync:            54 events,   914,000 bytes
+commandAck:              68 events
+roverHostStats:          17 events
+roverSnapshot:frame:      7 events
+```
+
+The most important DOM mutations were:
+
+```txt
+path d:                 2,688 mutations
+path fill:              2,682 mutations
+img.h-full.w-full src:    117 mutations
+span.h-2.w-2 class:       117 mutations
+```
+
+The `path` mutations point strongly at the per-rover `TopDownMap` SVG overlays. The
+`img.src` and blink class mutations point at room camera snapshot rendering.
+
+## Ordered Issue List
+
+1. [Telemetry fan-out and always-on HUD maps](./spectate-issues/001-telemetry-fanout-hud-maps.md)
+2. [Multi-rover WebRTC media fan-out](./spectate-issues/002-multi-rover-webrtc-media-fanout.md)
+3. [Room camera and snapshot object URL churn](./spectate-issues/003-room-camera-snapshot-object-url-churn.md)
+4. [Broad spectator session rerenders](./spectate-issues/004-broad-spectator-session-rerenders.md)
+5. [Shared log/session stream pressure](./spectate-issues/005-shared-log-session-stream-pressure.md)
+6. [Spectator role handshake retries](./spectate-issues/006-spectator-role-handshake-retries.md)
+
+## Upstream Dependency Map
+
+Fixing the `/` backlog first is a good plan.
+
+Likely improved by `/` fixes:
+
+- telemetry visual throttling
+- log batching/gating
+- chat/nickname churn
+- session selector/store improvements
+- generic timer cleanup
+
+Not likely to be fixed by `/` alone:
+
+- several simultaneous WHEP video/audio players
+- per-rover spectator HUD maps
+- room camera snapshot blob/object URL churn
+- spectator role/subscribe handshake behavior
+- mobile policy for how many live feeds should be active at once
+
+## Suggested Re-Test
+
+After each `/spectate` fix, run:
+
+```sh
+CPU_THROTTLE=6 VIEWPORT=390x844 MOBILE=1 SAMPLE_MS=30000 \
+  node perf/live-root-runtime-audit.mjs https://rover.otter.land/spectate perf/results
+```
+
+The most useful numbers to compare:
+
+- `TaskDuration`
+- `ScriptDuration`
+- long task count and worst duration
+- frame average/p95/p99
+- `RTCPeerConnections`
+- `mutationTargets` for `path d`, `path fill`, and `img src`
+- `webSocketEvents` for `sensorFrame`, `log:entry`, `session:sync`, and binary frame volume
+