---
id: wiki-2026-0508-v8-javascript-engine
title: V8 JavaScript Engine
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [V8, V8 Engine, Chrome V8]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [v8, javascript, engine, runtime, chrome, node]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: C++
  framework: V8
---

# V8 JavaScript Engine

## 매 한 줄
> **"매 Ignition interpreter + TurboFan / Maglev / Sparkplug 의 매 multi-tier JIT 으로 매 JS 를 native 수준에 도달시키는 엔진"**. 매 Chrome / Edge / Node.js / Deno 의 핵심. 매 2026 기준 Maglev (mid-tier JIT) 와 매 pointer compression 으로 매 startup + memory 모두 개선됨.

## 매 핵심

### 매 Multi-tier compilation
- **Ignition** — bytecode interpreter (fastest startup).
- **Sparkplug** — non-optimizing baseline JIT (V8 9.1+).
- **Maglev** — mid-tier optimizing JIT (V8 11.5+, default 11.9+).
- **TurboFan** — top-tier optimizer (slow compile, fast run).

### 매 Hidden classes & inline caches
- 매 JS object 의 매 shape 추적 (V8 internal "Map").
- 매 same-shape access 는 매 monomorphic IC 로 매 native 속도.
- 매 shape 변경 (속성 추가 순서 다름) 매 → polymorphic / megamorphic.

### 매 GC
- Generational: young (scavenger, Minor MC) + old (Mark-Compact, Mark-Sweep).
- Orinoco — concurrent / parallel / incremental.
- Pointer compression (V8 8.0+) — 35-40% heap 절감.

### 매 응용
1. Browser JS — Chrome, Edge.
2. Server JS — Node.js, Deno (V8 기반).
3. Embedded — Electron, CEF.

## 💻 패턴

### Hidden class 친화적 객체
```javascript
// Good — same shape
function User(id, name) { this.id = id; this.name = name; }

// Bad — shape diverges
function User(id, name) { this.id = id; if (name) this.name = name; }
```

### Monomorphic call site
```javascript
function getX(point) { return point.x; }
// pass only one shape consistently → IC stays monomorphic
const points = Array.from({ length: 1e6 }, (_, i) => ({ x: i, y: i }));
points.forEach(getX);
```

### Avoiding deopt
```javascript
function add(a, b) { return a + b; }
add(1, 2);     // optimized for number
add('a', 'b'); // deopt — TurboFan must reoptimize
```

### V8 inspector / profiling
```bash
node --inspect-brk app.js
# Chrome devtools → Performance → JS samples
```

### V8 flags for diagnosis
```bash
node --trace-opt --trace-deopt app.js
node --print-bytecode app.js
node --allow-natives-syntax  # %OptimizeFunctionOnNextCall
```

### Pointer compression check
```bash
node -p "process.config.variables.v8_enable_pointer_compression"
# 1 → enabled
```

## 매 결정 기준
| 관심사 | Approach |
|---|---|
| Startup 빠름 | Ignition / Sparkplug 충분 |
| Hot loop | Maglev / TurboFan 의 monomorphic 유지 |
| Memory tight | pointer compression + young GC tuning |
| Diagnose perf | `--trace-deopt`, `clinic flame` |

**기본값**: 매 modern V8 default — 매 micro-opt 보다 매 algorithmic 우선.

## 🔗 Graph
- 부모: [[JavaScript]]
- 변형: [[JavaScriptCore]] · [[Hermes]]
- 응용: [[Node.js]] · [[Deno]] · [[Chrome]] · [[Electron]]
- Adjacent: [[JIT Compilation]] · [[Garbage Collection]] · [[Inline Cache]]

## 🤖 LLM 활용
**언제**: 매 perf 분석 가설 세우기, 매 deopt 원인 추정.
**언제 X**: 매 V8 internal 변경 빠름 — 매 매 latest blog 확인 필요.

## ❌ 안티패턴
- **Shape divergence**: 매 conditional property 추가 — 매 polymorphic 유발.
- **delete 연산자**: 매 hidden class transition 강제.
- **`arguments` 변형**: 매 deopt 유발.
- **Try/catch in hot path**: 매 V8 ≤ 7.x 까진 deopt — 매 modern V8 은 ok 이나 매 case-by-case.

## 🧪 검증 / 중복
- Verified (V8 official blog v8.dev, "Maglev" announcement).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — Maglev + pointer compression 반영 |
