---
id: wiki-2026-0508-orinoco
title: Orinoco (V8 GC project)
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [V8 Orinoco, Orinoco GC, Concurrent V8 GC]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [v8, gc, performance, concurrent-marking, runtime]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: cpp
  framework: v8
---

# Orinoco

## 매 한 줄
> **"매 V8의 GC를 stop-the-world에서 incremental · concurrent · parallel multi-threaded GC로 전환한 multi-year 프로젝트."**. 2016년 시작, 2017-2019 Concurrent Marking · Parallel Scavenger · Lazy Sweeping 차례 도입. 2026 현재 V8 13.x base GC architecture가 Orinoco — pause time을 100ms+ → <1ms로 감소.

## 매 핵심

### 매 핵심 기법
- **Parallel Scavenger** (Young Gen): 매 multiple worker가 semi-space copy 병렬화.
- **Concurrent Marking** (Old Gen): 매 worker thread가 mutator와 병행 mark — main thread는 거의 미 pause.
- **Incremental Marking**: 매 mark phase를 여러 작은 chunk로 나눔.
- **Parallel/Concurrent Compaction**: page별 evacuation 병렬화.
- **Lazy Sweeping**: 매 sweep을 allocation 시점까지 지연.
- **Black Allocation**: 매 marking 중 새 alloc은 black (skip).

### 매 write barrier 역할
- 매 mutator가 마크된 object → 비마크 object 참조 추가 시 dirty card 표시.
- 매 concurrent marker가 stale graph 처리.

### 매 응용
1. Chrome — main thread jank 감소, smooth 60fps scroll.
2. Node.js — large heap server에서 long pause 제거.
3. Electron/VSCode — GUI responsiveness 유지.

## 💻 패턴

### Orinoco effect 측정 (Node.js)
```bash
# Major GC pause 분포
node --trace-gc --trace-gc-verbose app.js 2>&1 \
  | grep "Mark-" | awk '{print $5}' \
  | sort -n | uniq -c
# 2026 V8: 대부분 < 1ms, occasional 5ms
```

### Disable concurrent marking (compare)
```bash
node --no-concurrent-marking --trace-gc app.js
# pause time 명백히 증가 (10-50ms 종종)
```

### Per-isolate GC stats
```javascript
import { getHeapStatistics } from 'node:v8';

const before = getHeapStatistics();
heavyWorkload();
const after = getHeapStatistics();
console.log('major_gc count:', after.number_of_native_contexts);
console.log('used:', (after.used_heap_size - before.used_heap_size) / 1e6, 'MB');
```

### Performance.measureUserAgentSpecificMemory (Chrome)
```javascript
// In Chrome with COOP+COEP
if (performance.measureUserAgentSpecificMemory) {
  const result = await performance.measureUserAgentSpecificMemory();
  console.log(result.bytes, result.breakdown);
}
```

### Reduce concurrent-marking pressure
```javascript
// Avoid: huge graph mutation in tight loop
function reseat(arr, n) {
  for (let i = 0; i < n; i++) arr[i] = { ref: arr[(i+1) % n] };
  // many write barriers → marker work spike
}
// Prefer: build once, freeze
const frozen = Object.freeze(buildGraph());
```

### Inspect GC marking phase via perf_hooks
```javascript
import { PerformanceObserver } from 'node:perf_hooks';

const obs = new PerformanceObserver(list => {
  for (const e of list.getEntriesByType('gc')) {
    if (e.detail.kind === 2 /* MARK_SWEEP_COMPACT */)
      console.log('major GC:', e.duration.toFixed(2), 'ms');
  }
});
obs.observe({ entryTypes: ['gc'] });
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| Long pause complaint (UI jank) | check Orinoco enabled (default), profile |
| Embedded V8 (custom flags) | enable concurrent + incremental marking |
| Constrained memory (IoT) | might disable concurrent (extra worker thread) |
| Benchmarking | report w/ default flags + GC trace |

**기본값**: 매 default flags (Orinoco on) — 매 manual disable 회피.

## 🔗 Graph
- 부모: [[Garbage_Collection]] · [[V8 엔진 힙 아키텍처|V8 Heap Architecture]]
- 변형: [[Incremental_Marking]] · [[Concurrent_Marking]] · [[Mark-Sweep]]
- 응용: [[Old_Space]] · [[Pointer_Compression]] · [[Write Barrier|Write_Barrier]]
- Adjacent: [[Generational_Hypothesis]] · [[Snapshots]] · [[Multi-threaded Architecture]]

## 🤖 LLM 활용
**언제**: V8 GC internals 학습, Node.js/Chrome perf 분석, GC pause 회귀 추적.
**언제 X**: non-V8 runtime (Hermes는 별도 GC), Java/Go GC (G1/ZGC/Shenandoah는 다른 design).

## ❌ 안티패턴
- **Disabling concurrent marking blindly**: 매 measurement 없이 — 보통 perf 악화.
- **Huge mutation in hot loop**: 매 write barrier overload.
- **Forcing `global.gc()` 빈번**: 매 production 절대 X — Orinoco가 알아서 함.
- **Confusing minor (scavenge) and major (mark-sweep)**: 매 trace 해석 오류.

## 🧪 검증 / 중복
- Verified (V8 blog "Orinoco" series 2016-2019, V8 source `src/heap/`, Mathias Bynens & Benedikt Meurer talks 2017-2020).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — Orinoco GC project (concurrent/parallel/incremental) |