# epoll\_wait 偶爾會用很長時間
[TOC]
### 問題描述
epoll\_wait偶爾會用很長時間
### 問題出現的環境背景及自己嘗試過哪些方法
strace 跟蹤
### 相關代碼
~~~
21605 0.000043 semop(38830083, {{0, -1, SEM_UNDO}}, 1) = 0
21605 0.611909 epoll_wait(30, {{EPOLLIN, {u32=25218632, u64=25218632~~~, 4, 10000) = 1
21605 0.103429 accept4(3, {sa_family=AF_INET, sin_port=htons(56826), sin_addr=inet_addr("ip address")}, [16], SOCK_CLOEXEC) = 33
21605 0.000059 semop(38830083, {{0, 1, SEM_UNDO}}, 1) = 0
~~~
### 回復
~~~
epoll_wait 時間很長，說明在這段時間內沒有任何事件發生，epoll 是空閑狀態，這是正常現象。
~~~
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- 歷史：版本更新記錄（1.x）
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