2nd/10_Wiki/Topic_Programming/Architecture/Hardware.md

---
id: wiki-2026-0508-hardware
title: Hardware
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [Hardware Basics, 하드웨어]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [hardware, performance, systems]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: c
  framework: systems
---

# Hardware

## 매 한 줄
> **"매 software 의 ceiling 은 hardware 의 reality"**. 매 modern stack (cloud LLM, browser, game) 의 performance 는 매 CPU pipeline, cache hierarchy, memory bandwidth, storage tier, NIC, GPU 의 understanding 없이 explain 불가. 2026 시점 Apple M4 Max, Nvidia H200/B200, AMD MI300X, NVMe Gen5 의 가 baseline.

## 매 핵심

### 매 Latency numbers (Jeff Dean, 2026 update)
- L1 cache: ~1 ns
- L2 cache: ~3-4 ns
- L3 cache: ~10-15 ns
- DRAM: ~80-100 ns
- NVMe Gen5 random read: ~10-20 µs
- SSD SATA random read: ~100 µs
- Same-DC RTT: ~0.5 ms
- Cross-region RTT: 50-150 ms

### 매 CPU
- **Pipeline**: fetch, decode, execute, mem, writeback — 매 superscalar + OoO.
- **Branch predictor**: 매 mispredict = 15-20 cycle penalty.
- **SIMD**: AVX-512, NEON, SVE2.
- **NUMA**: multi-socket 시 매 local memory 우선.

### 매 Memory hierarchy
- **Cache line**: 매 64 byte 단위 — 매 false sharing 회피의 단위.
- **TLB**: 매 page translation cache — miss 매 expensive.
- **HBM (GPU)**: H100 80GB @ 3.35 TB/s, B200 192GB @ 8 TB/s.

### 매 Storage / IO
- NVMe Gen5: ~14 GB/s seq, 매 millions IOPS.
- io_uring: 매 syscall 의 batched submission.
- RDMA: 매 kernel bypass network.

### 매 응용
1. Latency-sensitive trading / gaming.
2. ML training (HBM, NVLink).
3. Database (page cache, WAL, SSD wear).
4. Browser rendering (GPU compositing).

## 💻 패턴

### Cache-line aware (false sharing 회피)
```c
#include <stdalign.h>
struct counters {
    alignas(64) _Atomic long a;  // 매 separate cache line
    alignas(64) _Atomic long b;
};
```

### SIMD (AVX2 dot product)
```c
#include <immintrin.h>
float dot(const float* a, const float* b, int n) {
    __m256 acc = _mm256_setzero_ps();
    for (int i = 0; i < n; i += 8) {
        __m256 va = _mm256_loadu_ps(a + i);
        __m256 vb = _mm256_loadu_ps(b + i);
        acc = _mm256_fmadd_ps(va, vb, acc);
    }
    float buf[8]; _mm256_storeu_ps(buf, acc);
    float s = 0; for (int i = 0; i < 8; i++) s += buf[i]; return s;
}
```

### Prefetch hint
```c
for (int i = 0; i < n; i++) {
    __builtin_prefetch(&arr[i + 16]);
    process(arr[i]);
}
```

### Linux perf (hardware counter)
```bash
perf stat -e cycles,instructions,cache-misses,branch-misses ./bench
perf record -g ./bench && perf report
```

### io_uring (high-IOPS read)
```c
struct io_uring ring;
io_uring_queue_init(256, &ring, 0);
struct io_uring_sqe* sqe = io_uring_get_sqe(&ring);
io_uring_prep_read(sqe, fd, buf, len, offset);
io_uring_submit(&ring);
```

### NUMA pin
```bash
numactl --cpunodebind=0 --membind=0 ./server
```

### GPU memcpy bandwidth (CUDA)
```cpp
cudaMemcpyAsync(d_x, h_x, n*sizeof(float), cudaMemcpyHostToDevice, s);
// 매 H100 PCIe Gen5: ~50 GB/s, NVLink: ~900 GB/s
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| Hot loop 의 memory bound | SIMD + cache blocking + prefetch |
| 다중 thread counter | per-thread + cache-line padding |
| Random small IO | NVMe + io_uring |
| Sequential large IO | mmap or O_DIRECT |
| LLM inference | GPU (HBM bw 가 bottleneck) |
| Multi-socket | NUMA pin + local alloc |

**기본값**: 매 측정 먼저 (perf, FlameGraph) — 매 추측 X.

## 🔗 Graph
- 변형: [[GPU]] · [[Memory Hierarchy]]

## 🤖 LLM 활용
**언제**: 매 latency budget 분석, hardware-software co-design, 매 capacity planning.
**언제 X**: 매 high-level CRUD app — 매 framework default 면 충분.

## ❌ 안티패턴
- **False sharing**: 매 동일 cache line 을 multiple thread 가 write.
- **Pointer chasing in hot loop**: 매 cache miss 행렬.
- **Ignoring NUMA**: 매 multi-socket 에서 cross-node 매 access bottleneck.
- **Sync syscall in hot path**: 매 io_uring / batching 으로 amortize.
- **Bandwidth ≠ latency 혼동**: HBM 8 TB/s 라도 매 latency 는 ~수백 ns.

## 🧪 검증 / 중복
- Verified (Hennessy & Patterson *Computer Architecture* 7ed 2024, Intel SDM, Nvidia H200/B200 whitepaper, Linux kernel docs).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — latency numbers + CPU/GPU/NVMe 2026 baseline 정리 |