2nd/10_Wiki/Topics/Backend/Nodejs Memory Tuning.md

---
id: wiki-2026-0508-nodejs-memory-tuning
title: Node.js Memory Tuning
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [V8 Heap Tuning, Node Heap Limit, max-old-space-size]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [nodejs, v8, performance, memory, gc]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: JavaScript
  framework: Node.js 22 LTS
---

# Node.js Memory Tuning

## 매 한 줄
> **"매 V8 heap 의 explicit budget + GC trace 의 observe"**. Node.js 의 default heap 매 ~4 GB (64-bit) 의 OS-derived — 매 process 의 actual workload 의 맞춰 매 `--max-old-space-size`, `--max-semi-space-size` 의 tune. 2026 Node 22 LTS 의 V8 12.4 — 매 Maglev tier, pointer compression default 의 활용.

## 매 핵심

### 매 V8 heap layout
- **Young generation (semi-space)**: 매 short-lived — 매 Scavenge GC, 매 fast.
- **Old generation**: 매 promoted — 매 Mark-Compact.
- **Code/Map/Large object space**: 매 separate.
- **Pointer compression**: 매 4-byte tagged pointer (4 GB heap 의 limit) — 매 default since Node 14.

### 매 GC modes
- **Scavenge** (minor): 매 ms order, 매 frequent.
- **Mark-Sweep-Compact** (major): 매 100s of ms, 매 STW phase.
- **Concurrent marking**: 매 background — STW 의 reduce.
- **Incremental marking**: 매 chunk-by-chunk.

### 매 응용
1. 큰 JSON parsing — heap 의 raise + streaming parser 의 use.
2. Long-running server — leak detection (heap snapshot diff).
3. Worker thread — per-thread heap budget.
4. Container env (k8s) — request/limit 와 V8 의 align.

## 💻 패턴

### CLI flags (Node 22)
```bash
NODE_OPTIONS="--max-old-space-size=8192 \
              --max-semi-space-size=128 \
              --expose-gc \
              --trace-gc \
              --trace-gc-verbose" \
  node server.js
```

### Container-aware (k8s)
```yaml
env:
  - name: NODE_OPTIONS
    # 매 limit 의 ~80% 의 leave headroom for native + libuv
    value: "--max-old-space-size=3200"
resources:
  limits:
    memory: "4Gi"
```

### Programmatic — heap stats
```js
import v8 from 'node:v8';
import { performance } from 'node:perf_hooks';

setInterval(() => {
  const s = v8.getHeapStatistics();
  console.log({
    used_mb: (s.used_heap_size / 1e6).toFixed(1),
    total_mb: (s.total_heap_size / 1e6).toFixed(1),
    limit_mb: (s.heap_size_limit / 1e6).toFixed(1),
    external_mb: (s.external_memory / 1e6).toFixed(1),
  });
}, 5000);
```

### Heap snapshot on threshold
```js
import v8 from 'node:v8';
import fs from 'node:fs';

function snapshotIfHigh(thresholdRatio = 0.85) {
  const s = v8.getHeapStatistics();
  if (s.used_heap_size / s.heap_size_limit > thresholdRatio) {
    const path = `heap-${Date.now()}.heapsnapshot`;
    v8.writeHeapSnapshot(path);
    console.error('Heap snapshot:', path);
  }
}
setInterval(snapshotIfHigh, 60_000);
```

### GC observer (perf_hooks)
```js
import { PerformanceObserver, constants } from 'node:perf_hooks';

new PerformanceObserver((list) => {
  for (const e of list.getEntries()) {
    const kind = e.detail?.kind;
    if (e.duration > 50) {
      console.warn('Long GC', { kind, ms: e.duration.toFixed(1) });
    }
  }
}).observe({ entryTypes: ['gc'], buffered: false });
```

### Streaming JSON (avoid heap blowup)
```js
import { parser } from 'stream-json';
import { streamArray } from 'stream-json/streamers/StreamArray.js';
import fs from 'node:fs';

fs.createReadStream('big.json')
  .pipe(parser())
  .pipe(streamArray())
  .on('data', ({ value }) => process(value));
```

### Buffer pool tuning
```js
// 매 large Buffer.allocUnsafe 의 pool — > 8KB 매 bypass
import { Buffer } from 'node:buffer';
Buffer.poolSize = 64 * 1024;   // default 8 KB
```

### `--heap-prof` for sampling
```bash
node --heap-prof --heap-prof-interval=524288 server.js
# → Chrome DevTools 의 .heapprofile 의 load
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| Container limit 4 GB | `--max-old-space-size=3200` (~80%) |
| OOM at startup | Streaming parse + lazy load |
| Long GC pauses | Reduce old-gen pressure (pool, reuse) + bigger semi-space |
| Memory leak suspect | Heap snapshot diff (3 snapshots, 30s apart) |
| Worker threads | Per-worker heap budget — sum < container limit |
| > 4 GB heap | `--no-pointer-compression` 의 disable (slower, more RAM) |

**기본값**: `--max-old-space-size = 0.8 × container_limit`, GC trace in prod 의 sample.

## 🔗 Graph
- 부모: [[V8]]
- Adjacent: [[Pointer Compression]]

## 🤖 LLM 활용
**언제**: flag lookup, OOM diagnosis playbook, snapshot 의 interpret.
**언제 X**: 매 specific leak — heap snapshot 의 actual data 의 require.

## ❌ 안티패턴
- **Default heap 의 trust in container**: 매 OOMKilled — explicit `--max-old-space-size`.
- **`global.gc()` polling**: 매 mask 의 leak — root cause 의 fix.
- **Heap limit = container limit**: 매 native + libuv overhead 무시 — 80% 의 leave.
- **Synchronous huge JSON.parse**: 매 STW — streaming parser 의 use.
- **Heap snapshot in hot path**: 매 STW seconds — threshold trigger 의 만.

## 🧪 검증 / 중복
- Verified (nodejs.org docs v22; v8.dev blog; Node Diagnostics Working Group).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — V8 heap tuning + GC trace + snapshot 정리 |