a66996ac10
Knowledge vault (Orion/PARA) migrated from the pre-Orion 484vault on 2026-10-01. Deliberately orphaned: prior history contained a plaintext password and stays local-only on branch archive/pre-boilerplate-history. Secrets and live Hermes state are gitignored.
54 lines
No EOL
3.2 KiB
Markdown
54 lines
No EOL
3.2 KiB
Markdown
```
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Here's the full playbook — symptoms, how we cornered each agent, and the exact
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commands. Paste the "Recipe" part into any agent for another app.
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What was wrong in SatsAmp (3 stacked causes)
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1. Main-thread disk I/O inside composition. StationRepository (~290ms) and
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StreamRepository (~130ms) read SharedPreferences + parse JSON in their
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constructors. Hilt builds singletons lazily, so that cost landed inside the
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first page-visit's tap frame.
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2. Tab taps animated through every intermediate page, composing/disposing
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heavy screens mid-flight, plus the selected-indicator tracked settledPage
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(lags the animation).
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3. Debug-build tax. First-touch class verification + JIT + shader compile
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produced 400-1100ms frames that only exist in debuggable builds. Release (R8 +
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install-time AOT) collapsed p99 from 900ms → 18-65ms.
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Also fixed along the way: an equalizer composable running
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rememberInfiniteTransition in every list row even when paused, one unkeyed
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LazyColumn, missing row placement animations.
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Recipe: diagnose jank in any Android app
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4. Setup. adb devices, note the device. Get tap coordinates once: adb shell
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uiautomator dump /sdcard/ui.xml, pull the bounds of the buttons you'll drive.
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5. Measure per interaction, not lifetime. Stats accumulate — always reset
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right before the action, sleep, then dump:
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adb shell dumpsys gfxinfo <pkg> reset > /dev/null
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adb shell input tap <x> <y>; sleep 2
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adb shell dumpsys gfxinfo <pkg> | grep -E "Total frames|Janky
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frames:|95th|99th|Slow UI|Slow issue|input latency"
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Key fields: Slow UI thread vs GPU percentiles (in the full dump: 90th gpu
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percentile). GPU > 2ms + slow UI thread = CPU-side problem, stop looking at
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overdraw/shaders.
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6. Idle test — rule out runaway animation. Reset, sleep 6, dump. Total frames
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rendered: 0 = rendering is on-demand, nothing spins. Dozens+ frames idle =
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find the rememberInfiniteTransition / ticker that's always mounted.
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7. Isolate tap path vs content path. Tap the already-selected tab. Clean (0
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janky) = the stall is incoming-page work, not ripple/nav handling.
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8. StrictMode — catches main-thread I/O with stack traces. Add in
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Application.onCreate, gated on debuggable, penaltyLog() only (never crash):
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StrictMode.setThreadPolicy(StrictMode.ThreadPolicy.Builder()
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.detectDiskReads().detectDiskWrites().detectNetwork()
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.detectCustomSlowCalls().penaltyLog().build())
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Drive the app, then adb shell logcat -d | grep StrictMode. Look for app frames
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(at com.yourapp...) and durations — ours showed repository constructors at 130-
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290ms firing from hvilViewModel() during composition.
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9. Composition timing probe. Wrap page content: remember { nanoTime() } +
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SideEffect { log(elapsed) }. Ours showed 6-24ms — proving composition was
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innocent and the stall was elsewhere in the frame.
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10. Per-frame table for position. adb shell dumpsys gfxinfo <pkg> framestats,
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find the Flags= rows missed vsync; compare
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PerformTraversalsStart vs IntendedVsync — a big gap before traversals start
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- dumpsys gfxinfo without reset shows lifetime stats — always reset per
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experiment.
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- am profile start/stop produced 0-byte files whenever a tap occurred mid-
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trace on this device; in-app probes (StrictMode, FrameMetrics, SideEffect
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timers) were more reliable than device-side
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``` |