Antigravity Agent
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10_Wiki/Topics 대규모 정리: - 오류 캡처/미완성 stub 문서 227개 제거 - 교차폴더 중복 43클러스터 병합 (63파일 → redirect) - 링크명 정규화: 깨진 링크 수정·redirect 직결·개념 매핑 ~2,400건 - 카테고리 MOC 6개 신규 생성 - Graph 섹션 미해결 related-keyword 링크 10,058건 제거 Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
172 lines
5.2 KiB
Markdown
172 lines
5.2 KiB
Markdown
---
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id: wiki-2026-0508-call-stack-analysis
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title: Call Stack Analysis
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category: 10_Wiki/Topics
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status: verified
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canonical_id: self
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aliases: [Call Stack, Stack Trace Analysis, Flame Graph, Profiling Stack]
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duplicate_of: none
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source_trust_level: A
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confidence_score: 0.95
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verification_status: applied
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tags: [profiling, performance, flame-graph, debugging, observability]
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raw_sources: []
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last_reinforced: 2026-05-10
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github_commit: pending
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tech_stack:
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language: Polyglot
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framework: perf/eBPF/pprof
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---
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# Call Stack Analysis
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## 매 한 줄
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> **"매 performance bug 의 95% 는 'where is CPU time spent?' — 매 call stack sampling 이 답한다."**. 매 stack trace 를 statistical 하게 sampling → flame graph 로 visualize 하면 hot path 가 즉시 보임. 매 2026 표준 stack 은 Linux perf + eBPF, 매 inferno / pyroscope / Datadog Continuous Profiler.
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## 매 핵심
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### 매 sampling vs instrumentation
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- **Sampling profiler**: 매 N Hz (보통 99/999Hz) 마다 stack capture → low overhead, statistical.
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- **Instrumented profiler**: 매 every entry/exit hook → exact, but 10-100x overhead.
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- **현대 default**: 매 sampling — 매 production-safe.
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### 매 stack source
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- **Frame pointer (RBP) walk**: 매 fastest, requires `-fno-omit-frame-pointer`.
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- **DWARF unwind**: 매 .eh_frame 사용 — frame pointer 불필요하나 expensive.
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- **ORC unwinder**: 매 Linux kernel 의 lightweight DWARF subset.
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- **eBPF stackmap**: 매 user+kernel stack 통합.
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### 매 visualization
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- **Flame graph (Brendan Gregg)**: 매 x=share of samples, y=stack depth, width=hot.
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- **Icicle graph**: 매 flipped flame — root at top.
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- **Differential flame graph**: 매 두 profile diff — perf regression 사냥.
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### 매 응용
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1. **CPU bottleneck 진단**: 매 hot function 식별.
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2. **Lock contention**: 매 off-CPU profile + futex stack.
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3. **GC pressure**: 매 alloc-stack profile.
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4. **Cold start**: 매 startup phase flame graph.
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5. **Continuous profiling**: 매 prod 24/7 sample → regression alerting.
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## 💻 패턴
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### Linux perf — basic
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```bash
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# 30s sample at 99Hz
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perf record -F 99 -a -g --call-graph dwarf -- sleep 30
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perf script > out.stack
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# render
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git clone https://github.com/brendangregg/FlameGraph
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./FlameGraph/stackcollapse-perf.pl out.stack | \
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./FlameGraph/flamegraph.pl > flame.svg
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```
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### eBPF profile (BCC)
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```bash
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profile-bpfcc -F 99 -f 30 > out.folded
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flamegraph.pl out.folded > flame.svg
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# advantages: lower overhead, kernel+user merged
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```
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### Go pprof
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```go
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import _ "net/http/pprof"
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func main() {
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go http.ListenAndServe(":6060", nil)
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// ... app
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}
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```
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```bash
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go tool pprof -http=:8080 http://localhost:6060/debug/pprof/profile?seconds=30
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# interactive flame graph in browser
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```
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### Python py-spy (no code change)
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```bash
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py-spy record -o flame.svg -d 30 --pid $(pgrep -f myapp.py)
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# zero instrumentation, samples a running process
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```
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### Node.js / V8
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```bash
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node --prof app.js
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# ... run workload ...
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node --prof-process isolate-0xNNN-v8.log > profile.txt
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# or 0x: npx 0x -- node app.js
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```
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### JVM async-profiler
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```bash
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# attach to running JVM, 60s flame graph
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asprof -d 60 -f flame.html $PID
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# also captures lock contention, alloc, wall-clock
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```
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### Rust — pprof crate
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```rust
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use pprof::ProtoBuf;
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let guard = pprof::ProfilerGuardBuilder::default()
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.frequency(999)
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.blocklist(&["libc", "libgcc", "pthread"])
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.build()?;
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// ... workload ...
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let report = guard.report().build()?;
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let mut file = std::fs::File::create("profile.pb")?;
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report.pprof()?.encode(&mut file)?;
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```
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### Continuous profiling (Pyroscope / Grafana)
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```yaml
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# pyroscope agent — runs alongside app
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pyroscope:
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server: http://pyroscope:4040
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app_name: api-prod
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spy_name: ebpfspy # auto-detect language
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sample_rate: 100
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```
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### Differential flame graph
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```bash
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./FlameGraph/difffolded.pl before.folded after.folded | \
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./FlameGraph/flamegraph.pl > diff.svg
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# red = got slower, blue = got faster
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```
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## 매 결정 기준
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| 상황 | Tool |
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|---|---|
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| Linux native (C/C++/Rust/Go) | perf + FlameGraph |
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| Container / k8s (no SYS_ADMIN) | pprof endpoint |
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| Python prod | py-spy |
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| JVM prod | async-profiler |
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| Continuous 24/7 | Pyroscope / Datadog |
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| Off-CPU (lock/IO) | offcputime-bpfcc |
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**기본값**: 99Hz sampling → folded → flamegraph.pl. 매 첫 5분 안에 hot path 보임.
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## 🔗 Graph
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- 부모: [[Observability]]
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- 변형: [[Flame_Graph]]
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- Adjacent: [[eBPF]]
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## 🤖 LLM 활용
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**언제**: hot function 분석, regression diff, profile 결과 해석.
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**언제 X**: tail latency / distributed trace (분산 환경은 OpenTelemetry).
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## ❌ 안티패턴
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- **Time.time printf 로그 profiling**: 매 statistical 안 되고 hot loop 망침.
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- **Frame pointer 없는 build**: 매 unwind 망가짐 — `-fno-omit-frame-pointer` 필수.
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- **너무 낮은 sample rate (10Hz)**: 매 30초 = 300 samples — noise dominate.
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- **너무 높은 rate (10kHz)**: 매 self-overhead 가 측정 결과 왜곡.
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- **Single-run profile 만 보기**: 매 variance — minimum 5 runs 권장.
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## 🧪 검증 / 중복
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- Verified (Brendan Gregg "Systems Performance" 2nd ed 2020, Linux perf docs, async-profiler README 2024).
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- 신뢰도 A.
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## 🕓 Changelog
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| 날짜 | 변경 |
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|---|---|
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| 2026-05-08 | Phase 1 |
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| 2026-05-10 | Manual cleanup — sampling profilers, flame graphs, multi-language tooling |
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