Asynchronous I/O비동기 I/O

동기 (Blocking):
  Thread: Read() ──── 대기 ────── 완료 → 다음 작업
  I/O:         ▓▓▓▓▓▓▓▓▓▓

비동기 (Non-blocking):
  Thread: Read() → 다음 작업1 → 다음 작업2 → I/O완료 콜백
  I/O:         ▓▓▓▓▓▓▓▓▓▓ (백그라운드)

import asyncio
import aiohttp

async def fetch(session, url):
    async with session.get(url) as response:
        return await response.text()

async def main():
    urls = [f"https://httpbin.org/delay/1" for _ in range(10)]
    async with aiohttp.ClientSession() as session:
        tasks = [fetch(session, url) for url in urls]
        results = await asyncio.gather(*tasks)  # 동시 실행
    # 10개 요청 ~1초 완료 (순차: 10초)

asyncio.run(main())

// 수천 개 fd를 효율적으로 모니터링 (O(1))
int epfd = epoll_create1(0);
epoll_ctl(epfd, EPOLL_CTL_ADD, sockfd, &event);

while (true) {
    int n = epoll_wait(epfd, events, MAX_EVENTS, -1);
    for (int i = 0; i < n; i++) {
        // 준비된 이벤트 처리
        handle_event(events[i]);
    }
}