[G1-Sync] Manual knowledge update

2026-05-09 21:08:02 +09:00
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+---
+id: native-perf-tracing-systrace
+title: Native Perf Tracing — Systrace / Instruments / Perfetto
+category: Coding
+status: draft
+source_trust_level: B
+verification_status: conceptual
+created_at: 2026-05-09
+updated_at: 2026-05-09
+tags: [native, performance, systrace, perfetto, instruments, vibe-coding]
+tech_stack: { language: "Swift / Kotlin", applicable_to: ["iOS", "Android"] }
+applied_in: []
+aliases: [Systrace, Perfetto, Instruments Time Profiler, frame timing, trace]
+---
+
+# Native Perf Tracing
+
+> Frame drop / startup 느림 / scroll jank 분석 = trace tool. **Android: Perfetto / Systrace**. **iOS: Instruments (Time Profiler / SwiftUI / Animation Hitches)**. Custom span 으로 본인 코드도 표시.
+
+## 📖 핵심 개념
+- Frame budget: 60fps = 16.6ms / 120fps = 8.3ms.
+- Jank: budget 초과 = 사용자 보임.
+- Trace: 시간축 위 함수 실행 그래프.
+- Custom span: 라이브러리 / 본인 함수 표시.
+
+## 💻 코드 패턴
+
+### Android — Perfetto (modern)
+```bash
+# Android Studio: Profiler → System Trace
+# 또는 명령행:
+adb shell perfetto --txt -c - --out /data/misc/perfetto-traces/trace -t 10s sched freq idle am wm gfx view binder_driver hal dalvik camera input res memory <<< ''
+```
+
+### Custom trace section (Android)
+```kotlin
+import androidx.tracing.Trace
+
+Trace.beginSection("loadHomeFeed")
+val items = repo.loadFeed()
+Trace.endSection()
+
+// 또는 inline
+Trace.beginAsyncSection("download:image:42", 42)
+download(url) { Trace.endAsyncSection("download:image:42", 42) }
+```
+
+### iOS — Instruments
+```
+Xcode → Product → Profile (⌘I) →
+- Time Profiler: 시간 소요 함수
+- Animation Hitches: 60fps 깬 frame
+- SwiftUI: View 재계산
+- Network: 요청 latency
+- Allocations: 메모리
+```
+
+### iOS — os_signpost (custom span)
+```swift
+import os.signpost
+
+let log = OSLog(subsystem: "com.app", category: .pointsOfInterest)
+let id = OSSignpostID(log: log)
+
+os_signpost(.begin, log: log, name: "loadFeed", signpostID: id)
+let items = await loadFeed()
+os_signpost(.end, log: log, name: "loadFeed", signpostID: id)
+```
+
+Instruments → os_signpost instrument 추가하면 timeline 에 보임.
+
+### Frame timing (iOS)
+```swift
+let displayLink = CADisplayLink(target: self, selector: #selector(tick))
+displayLink.add(to: .main, forMode: .common)
+
+@objc func tick(_ dl: CADisplayLink) {
+    let frameDuration = dl.targetTimestamp - dl.timestamp
+    if frameDuration > 1.0 / 60.0 + 0.005 { print("hitch") }
+}
+```
+
+### Frame timing (Android)
+```kotlin
+Choreographer.getInstance().postFrameCallback(object : FrameCallback {
+    var last = 0L
+    override fun doFrame(now: Long) {
+        if (last > 0) {
+            val ms = (now - last) / 1_000_000
+            if (ms > 16) Log.d("frame", "jank $ms ms")
+        }
+        last = now
+        Choreographer.getInstance().postFrameCallback(this)
+    }
+})
+```
+
+### App startup tracing
+```kotlin
+// AndroidX Startup Initializer 또는 manual
+class App : Application() {
+    override fun onCreate() {
+        Trace.beginSection("App.onCreate")
+        super.onCreate()
+        // ...
+        Trace.endSection()
+    }
+}
+```
+
+## 🤔 의사결정 기준
+| 분석 대상 | 도구 |
+|---|---|
+| Scroll jank | Systrace/Perfetto + Choreographer (Android) / Instruments Animation Hitches (iOS) |
+| Cold startup | Systrace boot to firstFrame / iOS Launch Time |
+| 함수 hot path | Time Profiler (iOS) / CPU Profiler (Android) |
+| 사용자 본인 함수 표시 | Trace.beginSection / os_signpost |
+| 네트워크 latency | Charles / 본인 SDK observability |
+
+## ❌ 안티패턴
+- **Trace section 안 닫음**: timeline 깨짐.
+- **Profile build 안 씀**: debug 는 느림 — release 또는 profile build 사용.
+- **profile 상태 의존**: profiler attach 자체가 영향. 상대 비교만.
+- **시작 측정 — emulator 만**: 실기와 다름.
+- **로그로 시간 측정**: I/O 자체가 시간. 표시 적은 trace API.
+- **첫 측정만 보기**: warm-up 필요. 5번 평균.
+
+## 🤖 LLM 활용 힌트
+- iOS = os_signpost + Instruments. Android = Trace + Perfetto.
+- Frame budget 16.6ms 기준 비교.
+
+## 🔗 관련 문서
+- [[Native_Memory_Profiling]]
+- [[Native_ANR_Freeze_Debugging]]
+- [[Native_Battery_Network_Profiling]]