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Update Socket.md

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补充 select/poll 与 epoll 的对比示意图。
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CyC2018
2026-10-25 19:34:21 +08:00
parent f6c77c1cab
commit b3e943b5e6
3 changed files with 89 additions and 0 deletions
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notes/Socket.md
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@@ -234,6 +234,8 @@ epoll_ctl() 用于向内核注册新的描述符或者是改变某个文件描
从上面的描述可以看出，epoll 只需要将描述符从进程缓冲区向内核缓冲区拷贝一次，并且进程不需要通过轮询来获得事件完成的描述符。
<div align="center"> <img src="pics/epoll.png" width="600px"/> </div><br>
epoll 仅适用于 Linux OS。
epoll 比 select 和 poll 更加灵活而且没有描述符数量限制。
notes/pics/epoll.png
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tools/diagram/src/epoll.svg
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<text x="320" y="28" class="title">select / poll 与 epoll</text>
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<text x="30" y="68" class="b">select / poll</text>
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<rect x="95" y="80" width="140" height="34" rx="6" fill="#B0E3E6"/>
<text x="165" y="101.5" class="b c">用户进程</text>
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<text x="300" y="143" class="sub e">用户态</text>
<text x="300" y="163" class="sub e">内核态</text>
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<text x="340" y="68" class="b">epoll</text>
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<text x="610" y="163" class="sub e">内核态</text>
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<text x="104" y="180" class="e sub">每次调用复制</text>
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<rect x="70" y="203" width="160" height="40" rx="6" fill="#B1DDF0"/>
<text x="150" y="221" class="b c">遍历全部描述符</text>
<text x="150" y="236" class="sub c">检查是否就绪</text>
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<text x="200" y="180" class="sub">返回后进程</text>
<text x="200" y="194" class="sub">再遍历一次</text>
<text x="165" y="290" class="c note">每次调用都是 O(N)</text>
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<text x="397" y="180" class="sub mono">epoll_ctl()</text>
<text x="397" y="194" class="sub">注册一次</text>
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<text x="478" y="267" class="c sub">就绪时回调</text>
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