Instruments 기초: 시간 프로파일러

Instruments가 필요한 이유

// Launch: Xcode → Product → Profile (Cmd+I)
// Choose "Time Profiler" template
// Run your app and exercise the slow path

추적 기록하기

// 1. Connect device or use simulator
// 2. Launch with Profile (Cmd+I)
// 3. Select Time Profiler
// 4. Record for 5-30 seconds
// 5. Stop and analyze

호출 트리 보기

// Call Tree columns:
// Self %: time spent in this function exclusively
// Symbol Name: function or method name
// Expand to see callers/callees

가장 무거운 스택 추적

// In Time Profiler:
// View → Heaviest Stack Trace
// Pinpoints the exact line consuming the most CPU

샘플 필터링하기

// Call Tree options (bottom of Instruments):
// ☑ Invert Call Tree    – shows leaf functions first
// ☑ Hide System Libraries – filters out OS internals

소스로 이동하기

// Double-click → opens file in Xcode at the hot line
// Red/orange annotation shows time spent per line

Time Profiler와 SwiftUI

// Common SwiftUI hot spots:
// - body called 100+ times per second
// - Equatable not implemented, causing unnecessary diffs
// - Heavy computation in body instead of a model

메인 스레드와 백그라운드 비교하기

// Thread lanes: Main Thread, Thread 2, Thread 3...
// Select a thread to see its call tree in isolation

앱 시작 시간을 위한 Time Profiler

// Instruments → File → Launch Profile
// Measures time from process start to first frame render

기준선 설정하기

// Baseline: 45ms for imageLoad()
// After optimization: 8ms for imageLoad()
// Confirm: 5.6x speedup verified in Instruments

정확한 프로파일링을 위한 팁

// Always:
// 1. Use physical device
// 2. Build with Release configuration (Product → Scheme → Edit → Build → Release)
// 3. Repeat measurement 3+ times for consistency

간단한 확인

강의 요약