{"id":76306,"date":"2026-02-22T07:25:20","date_gmt":"2026-02-21T23:25:20","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/76306.html"},"modified":"2026-02-22T07:25:20","modified_gmt":"2026-02-21T23:25:20","slug":"%e3%80%90linux%e3%80%91%e9%ab%98%e5%b9%b6%e5%8f%91%e6%9c%8d%e5%8a%a1%e5%99%a8%e7%9a%84%e8%b5%b7%e7%82%b9%ef%bc%9a%e4%ba%94%e7%a7%8d-io-%e6%a8%a1%e5%9e%8b%e4%b8%8e%e9%9d%9e%e9%98%bb%e5%a1%9e-io","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/76306.html","title":{"rendered":"\u3010Linux\u3011\u9ad8\u5e76\u53d1\u670d\u52a1\u5668\u7684\u8d77\u70b9\uff1a\u4e94\u79cd IO \u6a21\u578b\u4e0e\u975e\u963b\u585e IO \u672c\u8d28\u89e3\u6790"},"content":{"rendered":"<\/p>\n<h4>\u6587\u7ae0\u76ee\u5f55<\/h4>\n<ul>\n<li>\n<ul>\n<li><font face=\"\u6977\u4f53\" color=\"purple\" size=\"5\">\u9ad8\u5e76\u53d1\u670d\u52a1\u5668\u7684\u8d77\u70b9&#xff1a;\u4e94\u79cd IO \u6a21\u578b\u4e0e\u975e\u963b\u585e IO \u672c\u8d28\u89e3\u6790<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" color=\"#984229\" size=\"5\">\u4e00\u3001\u4ece\u9493\u9c7c\u8bf4\u8d77&#xff1a;\u4e94\u79cd IO \u6a21\u578b\u5168\u666f\u56fe<\/font><\/li>\n<li>\n<ul>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">1.1 IO \u7684\u672c\u8d28&#xff1a;\u7b49\u5f85 &#043; \u62f7\u8d1d<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">1.2 \u9493\u9c7c\u6545\u4e8b&#xff1a;\u4e94\u79cd\u6a21\u578b\u7684\u751f\u52a8\u7c7b\u6bd4<\/font><\/li>\n<li>\n<ul>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">1. \u963b\u585e IO&#xff08;Blocking IO&#xff09;<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">2. \u975e\u963b\u585e IO&#xff08;Non-blocking IO&#xff09;<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">3. \u4fe1\u53f7\u9a71\u52a8 IO&#xff08;Signal-driven IO&#xff09;<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">4. IO \u591a\u8def\u8f6c\u63a5&#xff08;IO Multiplexing&#xff09;<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">5. \u5f02\u6b65 IO&#xff08;Asynchronous IO&#xff09;<\/font><\/li>\n<\/ul>\n<\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">1.3 \u4e94\u6bd4<\/font><\/li>\n<\/ul>\n<\/li>\n<li><font face=\"\u6977\u4f53\" color=\"#984229\" size=\"5\">\u4e8c\u3001\u6700\u5bb9\u6613\u641e\u6df7\u7684\u56db\u4e2a\u6982\u5ff5<\/font><\/li>\n<li>\n<ul>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">2.1 \u540c\u6b65 vs \u5f02\u6b65&#xff1a;\u5173\u6ce8\u6d88\u606f\u901a\u4fe1\u673a\u5236<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">2.2 \u963b\u585e vs \u975e\u963b\u585e&#xff1a;\u5173\u6ce8\u7a0b\u5e8f\u7b49\u5f85\u65f6\u7684\u72b6\u6001<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">2.3 \u56db\u8005\u7ec4\u5408&#xff1a;\u5996\u602a\u84b8\u5510\u50e7\u7684\u4f8b\u5b50<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">2.4 \u4ece\u4ee3\u7801\u89d2\u5ea6\u7406\u89e3\u963b\u585e\u548c\u975e\u963b\u585e<\/font><\/li>\n<\/ul>\n<\/li>\n<li><font face=\"\u6977\u4f53\" color=\"#984229\" size=\"5\">\u4e09\u3001\u9ad8\u7ea7 IO \u6982\u5ff5\u68b3\u7406<\/font><\/li>\n<li>\n<ul>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">3.1 \u9ad8\u7ea7 IO \u7684\u5206\u7c7b<\/font><\/li>\n<\/ul>\n<\/li>\n<li><font face=\"\u6977\u4f53\" color=\"#984229\" size=\"5\">\u56db\u3001fcntl&#xff1a;\u5b9e\u73b0\u975e\u963b\u585e IO \u7684\u5229\u5668<\/font><\/li>\n<li>\n<ul>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">4.1 fcntl \u51fd\u6570\u6982\u89c8<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">4.2 fcntl \u7684\u5de5\u4f5c\u539f\u7406<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">4.3 \u5b9e\u73b0 SetNoBlock \u51fd\u6570<\/font><\/li>\n<\/ul>\n<\/li>\n<li><font face=\"\u6977\u4f53\" color=\"#984229\" size=\"5\">\u4e94\u3001\u975e\u963b\u585e IO \u5b9e\u6218&#xff1a;\u8f6e\u8be2\u8bfb\u53d6\u6807\u51c6\u8f93\u5165<\/font><\/li>\n<li>\n<ul>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">5.1 \u573a\u666f\u63cf\u8ff0<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">5.2 \u5b8c\u6574\u4ee3\u7801<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">5.3 \u8fd0\u884c\u6548\u679c\u5206\u6790<\/font><\/li>\n<\/ul>\n<\/li>\n<li><font face=\"\u6977\u4f53\" color=\"#984229\" size=\"5\">\u516d\u3001IO \u6d41\u7a0b\u53ef\u89c6\u5316&#xff1a;\u4ece\u7cfb\u7edf\u8c03\u7528\u5230\u6570\u636e<\/font><\/li>\n<li>\n<ul>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">6.1 \u7f51\u7edc IO \u7684\u5b8c\u6574\u8def\u5f84<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">6.2 \u4e3a\u4ec0\u4e48 IO \u591a\u8def\u8f6c\u63a5\u6700\u9002\u5408\u9ad8\u5e76\u53d1\u670d\u52a1\u5668<\/font><\/li>\n<\/ul>\n<\/li>\n<li><font face=\"\u6977\u4f53\" color=\"#984229\" size=\"5\">\u4e03\u3001\u5e38\u89c1\u95ee\u9898\u4e0e\u6982\u5ff5\u8fa8\u6790<\/font><\/li>\n<li>\n<ul>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">7.1 \u5bb9\u6613\u6df7\u6dc6\u7684\u70b9<\/font><\/li>\n<li>\n<ul>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">1. IO \u591a\u8def\u8f6c\u63a5 vs \u5f02\u6b65 IO&#xff0c;\u8c01\u66f4\u9ad8\u6548&#xff1f;<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">2. IO \u591a\u8def\u8f6c\u63a5\u81ea\u8eab\u662f\u963b\u585e\u7684&#xff0c;\u600e\u4e48\u8bf4\u5b83\u662f&#034;\u975e\u963b\u585e&#034;&#xff1f;<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">3. EAGAIN \u548c EWOULDBLOCK \u7684\u533a\u522b&#xff1f;<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">4. \u4e3a\u4ec0\u4e48 ET \u6a21\u5f0f&#xff08;epoll \u8fb9\u7f18\u89e6\u53d1&#xff09;\u5fc5\u987b\u914d\u975e\u963b\u585e IO&#xff1f;<\/font><\/li>\n<\/ul>\n<\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">7.2 \u5178\u578b\u9762\u8bd5\u9898\u89e3\u6790<\/font><\/li>\n<\/ul>\n<\/li>\n<li><font face=\"\u6977\u4f53\" color=\"#984229\" size=\"5\">\u516b\u3001\u77e5\u8bc6\u70b9\u603b\u7ed3<\/font><\/li>\n<li>\n<ul>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">8.1 \u6838\u5fc3\u8981\u70b9<\/font><\/li>\n<li><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">8.2 \u6982\u5ff5\u8bb0\u5fc6\u6280\u5de7<\/font><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h3><font face=\"\u6977\u4f53\" color=\"purple\" size=\"5\">\u9ad8\u5e76\u53d1\u670d\u52a1\u5668\u7684\u8d77\u70b9&#xff1a;\u4e94\u79cd IO \u6a21\u578b\u4e0e\u975e\u963b\u585e IO \u672c\u8d28\u89e3\u6790<\/font><\/h3>\n<p>&#x1f4ac; \u5f00\u7bc7&#xff1a;\u5982\u679c\u4f60\u5df2\u7ecf\u638c\u63e1\u4e86 socket \u7f16\u7a0b\u7684\u57fa\u7840&#xff0c;\u80fd\u5199\u51fa\u4e00\u4e2a\u7b80\u5355\u7684 TCP \u670d\u52a1\u5668&#xff0c;\u90a3\u606d\u559c\u4f60\u2014\u2014\u4f60\u5df2\u7ecf\u7ad9\u5728\u4e86 Linux \u7f51\u7edc\u7f16\u7a0b\u8fdb\u9636\u7684\u95e8\u53e3\u3002\u6253\u5f00\u8fd9\u6247\u95e8&#xff0c;\u8fce\u63a5\u4f60\u7684\u662f\u4e00\u4e2a\u5173\u4e8e&#034;\u7b49\u5f85&#034;\u548c&#034;\u6548\u7387&#034;\u7684\u54f2\u5b66\u547d\u9898&#xff1a;\u5f53\u7f51\u7edc\u6570\u636e\u8fd8\u6ca1\u6765\u7684\u65f6\u5019&#xff0c;\u7a0b\u5e8f\u8be5\u5e72\u4ec0\u4e48&#xff1f; \u8fd9\u7bc7\u6587\u7ae0\u5c31\u662f\u56de\u7b54\u8fd9\u4e2a\u95ee\u9898\u7684\u3002\u6211\u4eec\u4f1a\u4ece\u4e94\u79cd IO \u6a21\u578b\u7684\u672c\u8d28\u8bb2\u8d77&#xff0c;\u6df1\u5165\u5206\u6790\u540c\u6b65\/\u5f02\u6b65\u3001\u963b\u585e\/\u975e\u963b\u585e\u8fd9\u56db\u4e2a\u5bb9\u6613\u641e\u6df7\u7684\u6982\u5ff5&#xff0c;\u6700\u540e\u843d\u5730\u5230 fcntl \u5b9e\u73b0\u975e\u963b\u585e IO \u7684\u5b8c\u6574\u4ee3\u7801\u3002\u7406\u89e3\u4e86\u8fd9\u7bc7&#xff0c;\u540e\u9762\u7684 select\u3001poll\u3001epoll \u624d\u80fd\u771f\u6b63\u5b66\u8fdb\u53bb\u3002<\/p>\n<p>&#x1f44d; \u70b9\u8d5e\u3001\u6536\u85cf\u4e0e\u5206\u4eab&#xff1a;IO \u6a21\u578b\u662f Linux \u540e\u7aef\u5f00\u53d1\u548c\u9ad8\u6027\u80fd\u670d\u52a1\u5668\u7684\u5fc5\u8003\u70b9&#xff0c;\u641e\u61c2\u4e86\u8fd9\u91cc&#xff0c;\u9762\u8bd5\u5b98\u95ee\u4f60&#034;\u8bf4\u8bf4 epoll \u7684\u5de5\u4f5c\u539f\u7406&#034;\u65f6&#xff0c;\u4f60\u5c31\u80fd\u4ece\u6839\u4e0a\u8bb2\u6e05\u695a&#xff0c;\u800c\u4e0d\u53ea\u662f\u80cc\u51e0\u4e2a\u7ed3\u8bba\u3002<\/p>\n<p>&#x1f680; \u5faa\u5e8f\u6e10\u8fdb&#xff1a;\u6211\u4eec\u5148\u4ece\u4e00\u4e2a\u9493\u9c7c\u7684\u6545\u4e8b\u5f00\u59cb&#xff0c;\u628a\u4e94\u79cd IO \u6a21\u578b\u8bb2\u900f\u5f7b&#xff1b;\u518d\u8fa8\u6790\u540c\u6b65\/\u5f02\u6b65\u3001\u963b\u585e\/\u975e\u963b\u585e\u8fd9\u56db\u4e2a\u6982\u5ff5&#xff1b;\u6700\u540e\u52a8\u624b\u5b9e\u73b0\u975e\u963b\u585e IO&#xff0c;\u4e3a\u540e\u7eed\u7684\u591a\u8def\u590d\u7528\u6253\u597d\u57fa\u7840\u3002<\/p>\n<hr \/>\n<h3><font face=\"\u6977\u4f53\" color=\"#984229\" size=\"5\">\u4e00\u3001\u4ece\u9493\u9c7c\u8bf4\u8d77&#xff1a;\u4e94\u79cd IO \u6a21\u578b\u5168\u666f\u56fe<\/font><\/h3>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">1.1 IO \u7684\u672c\u8d28&#xff1a;\u7b49\u5f85 &#043; \u62f7\u8d1d<\/font><\/h4>\n<p>\u5728\u5c55\u5f00\u4e94\u79cd\u6a21\u578b\u4e4b\u524d&#xff0c;\u6211\u4eec\u5148\u641e\u6e05\u695a\u4e00\u4ef6\u4e8b&#xff1a;\u4e00\u6b21 IO \u64cd\u4f5c&#xff0c;\u5230\u5e95\u53d1\u751f\u4e86\u4ec0\u4e48&#xff1f;<\/p>\n<p>\u65e0\u8bba\u662f\u8bfb\u53d6\u7f51\u7edc\u6570\u636e\u3001\u8bfb\u6587\u4ef6&#xff0c;\u8fd8\u662f\u8bfb\u6807\u51c6\u8f93\u5165&#xff0c;\u672c\u8d28\u4e0a\u90fd\u5206\u4e24\u4e2a\u9636\u6bb5&#xff1a;<\/p>\n<p>\u9636\u6bb5\u4e00&#xff1a;\u7b49\u5f85\u6570\u636e\u5c31\u7eea<br \/>\n\u6570\u636e\u5728\u7f51\u5361\/\u78c1\u76d8\/\u952e\u76d8\u4e0a\u8fd8\u6ca1\u5230\u8fbe&#xff0c;\u5185\u6838\u5728\u7b49<br \/>\n\u2193<br \/>\n\u9636\u6bb5\u4e8c&#xff1a;\u6570\u636e\u62f7\u8d1d<br \/>\n\u5185\u6838\u628a\u5c31\u7eea\u7684\u6570\u636e\u4ece\u5185\u6838\u7f13\u51b2\u533a\u62f7\u8d1d\u5230\u7528\u6237\u7f13\u51b2\u533a<\/p>\n<p>\u8fd9\u4e24\u4e2a\u9636\u6bb5\u7f3a\u4e00\u4e0d\u53ef\u3002\u4e94\u79cd IO \u6a21\u578b\u7684\u533a\u522b&#xff0c;\u5c31\u5728\u4e8e\u8fd9\u4e24\u4e2a\u9636\u6bb5\u662f\u600e\u4e48\u5904\u7406\u7684\u3002<\/p>\n<p>\u4e00\u4e2a\u5173\u952e\u7ed3\u8bba\u5148\u8bb0\u4f4f&#xff1a;\u7b49\u5f85\u6d88\u8017\u7684\u65f6\u95f4&#xff0c;\u5f80\u5f80\u8fdc\u8fdc\u5927\u4e8e\u62f7\u8d1d\u6d88\u8017\u7684\u65f6\u95f4\u3002 \u6240\u4ee5\u8ba9 IO \u66f4\u9ad8\u6548\u7684\u6838\u5fc3\u529e\u6cd5&#xff0c;\u5c31\u662f\u8ba9\u7b49\u5f85\u7684\u65f6\u95f4\u5c3d\u91cf\u5c11\u3002\u4e94\u79cd\u6a21\u578b\u7684\u6f14\u5316&#xff0c;\u90fd\u662f\u56f4\u7ed5\u8fd9\u4e00\u70b9\u5c55\u5f00\u7684\u3002<\/p>\n<hr \/>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">1.2 \u9493\u9c7c\u6545\u4e8b&#xff1a;\u4e94\u79cd\u6a21\u578b\u7684\u751f\u52a8\u7c7b\u6bd4<\/font><\/h4>\n<p>\u5047\u8bbe\u4f60\u8981\u53bb\u9493\u9c7c\u3002\u9c7c\u4ec0\u4e48\u65f6\u5019\u54ac\u94a9&#xff0c;\u4f60\u4e0d\u77e5\u9053&#xff08;\u5c31\u50cf\u7f51\u7edc\u6570\u636e\u4ec0\u4e48\u65f6\u5019\u6765&#xff0c;\u4f60\u4e5f\u4e0d\u77e5\u9053&#xff09;\u3002<\/p>\n<h5><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">1. \u963b\u585e IO&#xff08;Blocking IO&#xff09;<\/font><\/h5>\n<p>\u4f60\u628a\u9c7c\u7aff\u63d2\u8fdb\u6c34\u91cc&#xff0c;\u7136\u540e\u5c31\u5750\u5728\u90a3\u91cc\u7b49&#xff0c;\u54ea\u90fd\u4e0d\u53bb&#xff0c;\u76f4\u5230\u9c7c\u54ac\u94a9\u3002<\/p>\n<p>\u8fd9\u5c31\u662f\u963b\u585e IO&#xff1a;\u8c03\u7528 read() \u4e4b\u540e&#xff0c;\u5982\u679c\u6570\u636e\u8fd8\u6ca1\u6765&#xff0c;\u8fdb\u7a0b\/\u7ebf\u7a0b\u5c31\u88ab\u6302\u8d77&#xff08;\u963b\u585e&#xff09;&#xff0c;\u4ec0\u4e48\u4e5f\u5e72\u4e0d\u4e86&#xff0c;\u76f4\u5230\u5185\u6838\u628a\u6570\u636e\u51c6\u5907\u597d&#xff0c;\u62f7\u8d1d\u5b8c\u6210&#xff0c;read() \u624d\u8fd4\u56de\u3002<\/p>\n<p>\u4f60\u7684\u7a0b\u5e8f                    \u5185\u6838<br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>&#8212; read<span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> \u7cfb\u7edf\u8c03\u7528 &#8212;&#8211;<span class=\"token operator\">&gt;|<\/span><br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span> \u7b49\u5f85\u6570\u636e\u5230\u6765<span class=\"token punctuation\">..<\/span>.<br \/>\n<span class=\"token operator\">|<\/span>      <span class=\"token punctuation\">(<\/span>\u7a0b\u5e8f\u963b\u585e\u5728\u8fd9<span class=\"token punctuation\">)<\/span>       <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span> \u6570\u636e\u5230\u4e86&#xff01;\u5f00\u59cb\u62f7\u8d1d<br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span><span class=\"token operator\">&lt;<\/span>&#8212; \u62f7\u8d1d\u5b8c\u6210&#xff0c;\u8fd4\u56de &#8212;&#8212;-<span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span><\/p>\n<p>\u7279\u70b9&#xff1a;<\/p>\n<ul>\n<li>\u6240\u6709\u5957\u63a5\u5b57\u9ed8\u8ba4\u90fd\u662f\u963b\u585e\u6a21\u5f0f<\/li>\n<li>\u6700\u7b80\u5355\u3001\u6700\u5e38\u89c1<\/li>\n<li>\u7f3a\u70b9\u662f\u4e00\u4e2a\u7ebf\u7a0b\u53ea\u80fd\u76ef\u7740\u4e00\u4e2a IO&#xff0c;\u6548\u7387\u4f4e\u4e0b<\/li>\n<\/ul>\n<hr \/>\n<h5><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">2. \u975e\u963b\u585e IO&#xff08;Non-blocking IO&#xff09;<\/font><\/h5>\n<p>\u4f60\u628a\u9c7c\u7aff\u63d2\u8fdb\u6c34\u91cc&#xff0c;\u6bcf\u9694\u51e0\u79d2\u5c31\u8fc7\u6765\u770b\u4e00\u773c&#xff0c;\u6ca1\u54ac\u94a9\u5c31\u53bb\u65c1\u8fb9\u73a9&#xff0c;\u518d\u56de\u6765\u770b&#xff0c;\u5468\u800c\u590d\u59cb\u3002<\/p>\n<p>\u8fd9\u5c31\u662f\u975e\u963b\u585e IO&#xff1a;\u8c03\u7528 read() \u65f6\u5982\u679c\u6570\u636e\u8fd8\u6ca1\u51c6\u5907\u597d&#xff0c;\u5185\u6838\u76f4\u63a5\u8fd4\u56de\u4e00\u4e2a\u9519\u8bef\u7801 EWOULDBLOCK&#xff0c;\u800c\u4e0d\u662f\u8ba9\u4f60\u7b49\u3002\u7a0b\u5e8f\u53ef\u4ee5\u7ee7\u7eed\u5e72\u522b\u7684\u4e8b&#xff0c;\u4f46\u9700\u8981\u4e0d\u65ad\u5730\u91cd\u590d\u8c03\u7528&#xff08;\u8f6e\u8be2&#xff0c;polling&#xff09;\u3002<\/p>\n<p>\u4f60\u7684\u7a0b\u5e8f                    \u5185\u6838<br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>&#8212; read<span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> &#8212;&#8212;&#8212;&#8211;<span class=\"token operator\">&gt;<\/span>  <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span><span class=\"token operator\">&lt;<\/span>&#8212; EWOULDBLOCK &#8212;&#8212;   <span class=\"token operator\">|<\/span> \u6570\u636e\u8fd8\u6ca1\u6765<br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>&#8212; read<span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> &#8212;&#8212;&#8212;&#8211;<span class=\"token operator\">&gt;<\/span>  <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span><span class=\"token operator\">&lt;<\/span>&#8212; EWOULDBLOCK &#8212;&#8212;   <span class=\"token operator\">|<\/span> \u6570\u636e\u8fd8\u6ca1\u6765<br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>&#8212; read<span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> &#8212;&#8212;&#8212;&#8211;<span class=\"token operator\">&gt;<\/span>  <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span> \u6570\u636e\u6765\u4e86&#xff01;\u62f7\u8d1d\u4e2d<span class=\"token punctuation\">..<\/span>.<br \/>\n<span class=\"token operator\">|<\/span><span class=\"token operator\">&lt;<\/span>&#8212; \u8fd4\u56de\u6570\u636e &#8212;&#8212;&#8212;-   <span class=\"token operator\">|<\/span><\/p>\n<p>\u7279\u70b9&#xff1a;<\/p>\n<ul>\n<li>\u9700\u8981\u7a0b\u5e8f\u4e3b\u52a8\u8f6e\u8be2&#xff0c;\u6d88\u8017 CPU&#xff08;CPU \u4e00\u76f4\u5728\u95ee&#034;\u597d\u4e86\u5417&#xff1f;\u597d\u4e86\u5417&#xff1f;&#034;&#xff09;<\/li>\n<li>\u4e00\u822c\u53ea\u5728\u7279\u5b9a\u573a\u666f\u4e0b\u4f7f\u7528&#xff0c;\u4e0d\u63a8\u8350\u5355\u72ec\u4f7f\u7528<\/li>\n<\/ul>\n<hr \/>\n<h5><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">3. \u4fe1\u53f7\u9a71\u52a8 IO&#xff08;Signal-driven IO&#xff09;<\/font><\/h5>\n<p>\u4f60\u5728\u9c7c\u7aff\u4e0a\u88c5\u4e00\u4e2a\u94c3\u94db&#xff0c;\u9c7c\u54ac\u94a9\u65f6\u94c3\u94db\u4f1a\u54cd&#xff0c;\u4f60\u624d\u8fc7\u6765\u5904\u7406\u3002<\/p>\n<p>\u8fd9\u5c31\u662f\u4fe1\u53f7\u9a71\u52a8 IO&#xff1a;\u7a0b\u5e8f\u5411\u5185\u6838\u6ce8\u518c\u4e00\u4e2a\u4fe1\u53f7\u5904\u7406\u51fd\u6570&#xff08;SIGIO&#xff09;&#xff0c;\u7136\u540e\u7ee7\u7eed\u5e72\u522b\u7684\u4e8b\u3002\u5f53\u6570\u636e\u51c6\u5907\u597d\u65f6&#xff0c;\u5185\u6838\u53d1\u9001 SIGIO \u4fe1\u53f7\u901a\u77e5\u7a0b\u5e8f&#xff0c;\u7a0b\u5e8f\u6536\u5230\u4fe1\u53f7\u540e\u518d\u53bb\u8c03\u7528 read() \u628a\u6570\u636e\u53d6\u8d70\u3002<\/p>\n<p>\u4f60\u7684\u7a0b\u5e8f                    \u5185\u6838<br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span> \u6ce8\u518c SIGIO \u4fe1\u53f7\u5904\u7406\u51fd\u6570   <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>&#8212;\u544a\u8bc9\u6211\u6570\u636e\u6765\u4e86&#8212;&#8212;&#8212;<span class=\"token operator\">&gt;|<\/span><br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span> <span class=\"token punctuation\">(<\/span>\u7a0b\u5e8f\u7ee7\u7eed\u5e72\u5176\u4ed6\u4e8b<span class=\"token punctuation\">)<\/span>         <span class=\"token operator\">|<\/span> \u7b49\u5f85\u6570\u636e<span class=\"token punctuation\">..<\/span>.<br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span> \u6570\u636e\u6765\u4e86&#xff01;\u53d1\u4fe1\u53f7<br \/>\n<span class=\"token operator\">|<\/span><span class=\"token operator\">&lt;&#061;<\/span><span class=\"token operator\">&#061;<\/span> SIGIO \u4fe1\u53f7 <span class=\"token operator\">&#061;&#061;<\/span><span class=\"token operator\">&#061;&#061;<\/span><span class=\"token operator\">&#061;&#061;<\/span><span class=\"token operator\">&#061;&#061;<\/span><span class=\"token operator\">&#061;&#061;<\/span><span class=\"token operator\">&#061;<\/span><span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>&#8212; read<span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> &#8212;&#8212;&#8212;&#8211;<span class=\"token operator\">&gt;<\/span>  <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span><span class=\"token operator\">&lt;<\/span>&#8212; \u62f7\u8d1d\u5b8c\u6210&#xff0c;\u8fd4\u56de &#8212;&#8212;  <span class=\"token operator\">|<\/span><\/p>\n<p>\u7279\u70b9&#xff1a;<\/p>\n<ul>\n<li>\u7b49\u5f85\u9636\u6bb5\u4e0d\u963b\u585e&#xff0c;\u6bd4\u8f83\u7075\u6d3b<\/li>\n<li>\u4f46\u5728 TCP \u4e2d&#xff0c;\u4fe1\u53f7\u89e6\u53d1\u60c5\u51b5\u590d\u6742&#xff08;\u5404\u79cd\u4e8b\u4ef6\u90fd\u4f1a\u89e6\u53d1&#xff09;&#xff0c;\u5b9e\u9645\u4f7f\u7528\u8f83\u5c11<\/li>\n<\/ul>\n<hr \/>\n<h5><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">4. IO \u591a\u8def\u8f6c\u63a5&#xff08;IO Multiplexing&#xff09;<\/font><\/h5>\n<p>\u4f60\u540c\u65f6\u653e\u4e86 100 \u6839\u9c7c\u7aff&#xff0c;\u7136\u540e\u96c7\u4e86\u4e00\u4e2a\u7ba1\u7406\u5458&#xff08;select\u54ea\u6839\u54ac\u94a9\u4e86\u5c31\u901a\u77e5\u4f60\u53bb\u5904\u7406\u54ea\u6839\u3002&#xff09;<\/p>\n<p>\u8fd9\u5c31\u662f IO \u591a\u8def\u8f6c\u63a5&#xff0c;\u4e5f\u53eb IO \u591a\u8def\u590d\u7528&#xff08;multiplexing&#xff09;\u3002\u8fd9\u624d\u662f\u9ad8\u6027\u80fd\u670d\u52a1\u5668\u7684\u6838\u5fc3\u6280\u672f\u3002<\/p>\n<p>\u4f60\u7684\u7a0b\u5e8f                    \u5185\u6838<br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span> select\/epoll_wait<span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span>      <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>&#8212; \u76d1\u63a7 fd1,fd2<span class=\"token punctuation\">..<\/span>.fd100-<span class=\"token operator\">&gt;|<\/span><br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span> \u7b49\u5f85\u4efb\u4e00 fd \u5c31\u7eea<br \/>\n<span class=\"token operator\">|<\/span>   <span class=\"token punctuation\">(<\/span>\u7a0b\u5e8f\u963b\u585e\u5728 <span class=\"token keyword\">select<\/span><span class=\"token punctuation\">)<\/span>     <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span> fd5 \u5c31\u7eea\u4e86&#xff01;<br \/>\n<span class=\"token operator\">|<\/span><span class=\"token operator\">&lt;<\/span>&#8212; \u8fd4\u56de\u5c31\u7eea\u7684 fd &#8212;&#8212;&#8211;<span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span> \u5bf9 fd5 \u8c03\u7528 read<span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span>        <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>&#8212; read<span class=\"token punctuation\">(<\/span>fd5<span class=\"token punctuation\">)<\/span> &#8212;&#8212;&#8212;-<span class=\"token operator\">&gt;|<\/span><br \/>\n<span class=\"token operator\">|<\/span><span class=\"token operator\">&lt;<\/span>&#8212; \u62f7\u8d1d\u5b8c\u6210&#xff0c;\u8fd4\u56de &#8212;&#8212;&#8211;<span class=\"token operator\">|<\/span><\/p>\n<p>\u7279\u70b9&#xff1a;<\/p>\n<ul>\n<li>\u4e00\u4e2a\u8fdb\u7a0b\u80fd\u5904\u7406\u5927\u91cf\u8fde\u63a5&#xff08;\u8fd9\u5c31\u662f C10K \u95ee\u9898\u7684\u89e3\u51b3\u601d\u8def&#xff09;<\/li>\n<li>select\/poll\/epoll \u662f\u4e09\u79cd\u5b9e\u73b0&#xff0c;\u540e\u9762\u6211\u4eec\u4f1a\u8be6\u7ec6\u8bb2<\/li>\n<li>\u6ce8\u610f&#xff1a;select \u672c\u8eab\u662f\u963b\u585e\u7684&#xff0c;\u4f46\u5b83\u80fd\u540c\u65f6\u76d1\u63a7\u591a\u4e2a fd&#xff0c;\u89e3\u51b3\u4e86&#034;\u4e00\u6b21\u53ea\u80fd\u7b49\u4e00\u4e2a&#034;\u7684\u95ee\u9898<\/li>\n<\/ul>\n<hr \/>\n<h5><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">5. \u5f02\u6b65 IO&#xff08;Asynchronous IO&#xff09;<\/font><\/h5>\n<p>\u4f60\u59d4\u6258\u4e00\u4e2a\u5168\u804c\u52a9\u624b\u53bb\u9493\u9c7c&#xff1a;\u9c7c\u54ac\u94a9\u3001\u6536\u6746\u3001\u5904\u7406\u3001\u653e\u8fdb\u51b0\u7bb1&#xff0c;\u5168\u6d41\u7a0b\u90fd\u7531\u52a9\u624b\u5b8c\u6210&#xff0c;\u6700\u540e\u53ea\u901a\u77e5\u4f60\u201c\u9c7c\u5df2\u7ecf\u5728\u51b0\u7bb1\u91cc\u4e86\u201d\u3002 \u7a0b\u5e8f\u53d1\u8d77 IO \u8bf7\u6c42\u540e\u7acb\u523b\u8fd4\u56de&#xff0c;\u5185\u6838\u8d1f\u8d23\u7b49\u5f85\u6570\u636e\u5c31\u7eea &#043; \u5b8c\u6210\u6570\u636e\u62f7\u8d1d\u5230\u7528\u6237\u7f13\u51b2\u533a&#xff0c;\u5168\u90e8\u5b8c\u6210\u540e\u518d\u901a\u8fc7\u4fe1\u53f7\/\u56de\u8c03\/\u4e8b\u4ef6\u901a\u77e5\u7a0b\u5e8f&#xff1a;\u6570\u636e\u5df2\u7ecf\u53ef\u4ee5\u76f4\u63a5\u7528\u4e86\u3002<\/p>\n<p>\u4e0e\u4fe1\u53f7\u9a71\u52a8 IO \u7684\u5173\u952e\u533a\u522b&#xff1a;<\/p>\n<ul>\n<li>\u4fe1\u53f7\u9a71\u52a8&#xff1a;\u5185\u6838\u544a\u8bc9\u4f60\u201c\u53ef\u4ee5\u5f00\u59cb\u8bfb\u4e86\u201d&#xff0c;\u4f60\u81ea\u5df1 read() \u5b8c\u6210\u62f7\u8d1d<\/li>\n<li>\u5f02\u6b65 IO&#xff1a;\u5185\u6838\u544a\u8bc9\u4f60\u201c\u5df2\u7ecf\u62f7\u8d1d\u597d\u4e86\u201d&#xff0c;\u4f60\u76f4\u63a5\u7528\u7f13\u51b2\u533a\u6570\u636e<\/li>\n<\/ul>\n<p>\u4f60\u7684\u7a0b\u5e8f                    \u5185\u6838<br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span> aio_read<span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span>               <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>&#8212; \u53d1\u51fa IO \u8bf7\u6c42&#xff0c;\u7acb\u5373\u8fd4\u56de-<span class=\"token operator\">&gt;|<\/span><br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span> <span class=\"token punctuation\">(<\/span>\u7a0b\u5e8f\u7ee7\u7eed\u5e72\u5176\u4ed6\u4e8b<span class=\"token punctuation\">)<\/span>         <span class=\"token operator\">|<\/span> \u7b49\u5f85\u6570\u636e &#043; \u62f7\u8d1d<span class=\"token punctuation\">..<\/span>.<br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span> \u5168\u90e8\u5b8c\u6210&#xff01;\u901a\u77e5\u7a0b\u5e8f<br \/>\n<span class=\"token operator\">|<\/span><span class=\"token operator\">&lt;&#061;<\/span><span class=\"token operator\">&#061;<\/span> \u56de\u8c03\/\u4fe1\u53f7 <span class=\"token operator\">&#061;&#061;<\/span><span class=\"token operator\">&#061;&#061;<\/span><span class=\"token operator\">&#061;&#061;<\/span><span class=\"token operator\">&#061;&#061;<\/span><span class=\"token operator\">&#061;&#061;<\/span><span class=\"token operator\">&#061;&#061;<\/span><span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span>                         <span class=\"token operator\">|<\/span><br \/>\n<span class=\"token operator\">|<\/span> \u76f4\u63a5\u4f7f\u7528\u7f13\u51b2\u533a\u91cc\u7684\u6570\u636e     <span class=\"token operator\">|<\/span><\/p>\n<p>\u5f02\u6b65 IO \u662f\u6700\u5f7b\u5e95\u7684\u975e\u963b\u585e&#xff0c;\u4e24\u73b0\u590d\u6742&#xff0c;Linux \u4e0b\u7684 aio \u652f\u6301\u6709\u9650\u3002<\/p>\n<hr \/>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">1.3 \u4e94\u6bd4<\/font><\/h4>\n<table>\n<tr>IO \u6a21\u578b\u7b49\u5f85\u9636\u6bb5\u62f7\u8d1d\u9636\u6bb5\u5178\u578b\u63a5\u53e3\u9002\u7528\u573a\u666f<\/tr>\n<tbody>\n<tr>\n<td>\u963b\u585e IO<\/td>\n<td>\u963b\u585e<\/td>\n<td>\u963b\u585e<\/td>\n<td>read\/write<\/td>\n<td>\u7b80\u5355\u573a\u666f&#xff0c;\u8fde\u63a5\u6570\u5c11<\/td>\n<\/tr>\n<tr>\n<td>\u975e\u963b\u585e IO<\/td>\n<td>\u4e0d\u963b\u585e&#xff08;\u8f6e\u8be2&#xff09;<\/td>\n<td>\u963b\u585e<\/td>\n<td>read &#043; O_NONBLOCK<\/td>\n<td>\u914d\u5408 IO \u591a\u8def\u590d\u7528\u4f7f\u7528<\/td>\n<\/tr>\n<tr>\n<td>\u4fe1\u53f7\u9a71\u52a8 IO<\/td>\n<td>\u4e0d\u963b\u585e&#xff08;\u4fe1\u53f7\u901a\u77e5&#xff09;<\/td>\n<td>\u963b\u585e<\/td>\n<td>SIGIO<\/td>\n<td>\u4f7f\u7528\u8f83\u5c11<\/td>\n<\/tr>\n<tr>\n<td>IO \u591a\u8def\u8f6c\u63a5<\/td>\n<td>\u963b\u585e&#xff08;\u4f46\u76d1\u63a7\u591a\u4e2a&#xff09;<\/td>\n<td>\u963b\u585e<\/td>\n<td>select\/poll\/epoll<\/td>\n<td>\u9ad8\u5e76\u53d1\u670d\u52a1\u5668\u9996\u9009<\/td>\n<\/tr>\n<tr>\n<td>\u5f02\u6b65 IO<\/td>\n<td>\u4e0d\u963b\u585e<\/td>\n<td>\u4e0d\u963b\u585e<\/td>\n<td>aio_read\/aio_write<\/td>\n<td>\u6700\u5f7b\u5e95&#xff0c;\u4f46\u5b9e\u73b0\u590d\u6742<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u4e94\u79cd IO \u6a21\u578b\u7684\u672c\u8d28\u533a\u522b&#xff1a;<br \/>\n\u7b49\u5f85\u9636\u6bb5        \u62f7\u8d1d\u9636\u6bb5<br \/>\n\u963b\u585e IO         \u2588\u2588\u2588\u2588\u2588\u2588\u2588\u2588\u2588\u2588\u2588\u2588\u2588\u2588\u2588\u2588  \u2588\u2588\u2588\u2588<br \/>\n\u975e\u963b\u585e IO       \u2713\u8f6e\u8be2\u2713\u8f6e\u8be2\u2713\u5c31\u7eea<span class=\"token operator\">!<\/span>  \u2588\u2588\u2588\u2588<br \/>\n\u4fe1\u53f7\u9a71\u52a8 IO     &#8212;\u5e72\u5176\u4ed6&#8212;SIGIO<span class=\"token operator\">!<\/span> \u2588\u2588\u2588\u2588<br \/>\nIO \u591a\u8def\u8f6c\u63a5     \u2588\u2588\u2588\u2588<span class=\"token punctuation\">(<\/span>\u591a\u4e2afd<span class=\"token punctuation\">)<\/span>\u2588\u2588\u2588\u2588\u2588  \u2588\u2588\u2588\u2588<br \/>\n\u5f02\u6b65 IO         &#8212;\u5e72\u5176\u4ed6&#8212;\u5b8c\u6210<span class=\"token operator\">!<\/span>  <span class=\"token punctuation\">(<\/span>\u5185\u6838\u5e2e\u4f60\u62f7<span class=\"token punctuation\">)<\/span><\/p>\n<hr \/>\n<h3><font face=\"\u6977\u4f53\" color=\"#984229\" size=\"5\">\u4e8c\u3001\u6700\u5bb9\u6613\u641e\u6df7\u7684\u56db\u4e2a\u6982\u5ff5<\/font><\/h3>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">2.1 \u540c\u6b65 vs \u5f02\u6b65&#xff1a;\u5173\u6ce8\u6d88\u606f\u901a\u4fe1\u673a\u5236<\/font><\/h4>\n<p>\u8fd9\u4e24\u4e2a\u6982\u5ff5\u5728\u4e0d\u540c\u8bed\u5883\u4e0b\u6709\u4e0d\u540c\u542b\u4e49&#xff0c;\u4e00\u5b9a\u8981\u5148\u641e\u6e05\u695a\u80cc\u666f\u3002\u5728 IO \u6a21\u578b\u4e2d&#xff1a;<\/p>\n<p>\u540c\u6b65&#xff08;Synchronous&#xff09;&#xff1a;\u8c03\u7528\u8005\u53d1\u51fa\u8c03\u7528\u540e&#xff0c;\u5728\u6ca1\u6709\u5f97\u5230\u7ed3\u679c\u4e4b\u524d&#xff0c;\u8c03\u7528\u4e0d\u8fd4\u56de\u3002\u8c03\u7528\u8005\u4e3b\u52a8\u7b49\u5f85\u8fd9\u4e2a\u8c03\u7528\u7684\u7ed3\u679c\u3002<\/p>\n<p>\u5f02\u6b65&#xff08;Asynchronous&#xff09;&#xff1a;\u8c03\u7528\u8005\u53d1\u51fa\u8c03\u7528\u540e&#xff0c;\u8c03\u7528\u7acb\u523b\u8fd4\u56de&#xff0c;\u6ca1\u6709\u8fd4\u56de\u7ed3\u679c\u3002\u88ab\u8c03\u7528\u8005\u901a\u8fc7\u72b6\u6001\u901a\u77e5\u6216\u56de\u8c03\u51fd\u6570\u6765\u544a\u77e5\u8c03\u7528\u8005\u7ed3\u679c\u3002<\/p>\n<p>\u91cd\u8981&#xff1a;\u8fd9\u91cc\u7684&#034;\u540c\u6b65\/\u5f02\u6b65&#034;\u662f IO \u901a\u4fe1\u673a\u5236\u7684\u6982\u5ff5&#xff0c;\u8ddf\u591a\u7ebf\u7a0b\u4e2d&#034;\u540c\u6b65\u4e0e\u4e92\u65a5&#034;\u7684&#034;\u540c\u6b65&#034;\u5b8c\u5168\u4e0d\u662f\u4e00\u56de\u4e8b&#xff01;\u591a\u7ebf\u7a0b\u7684\u540c\u6b65\u6307\u7684\u662f\u7ebf\u7a0b\u95f4\u7684\u534f\u4f5c\u6b21\u5e8f\u63a7\u5236&#xff0c;\u5c24\u5176\u662f\u8bbf\u95ee\u4e34\u754c\u8d44\u6e90\u65f6\u7684\u534f\u8c03\u3002\u4ee5\u540e\u770b\u5230&#034;\u540c\u6b65&#034;\u8fd9\u4e2a\u8bcd&#xff0c;\u4e00\u5b9a\u5148\u641e\u6e05\u695a\u5927\u80cc\u666f&#xff01;<\/p>\n<hr \/>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">2.2 \u963b\u585e vs \u975e\u963b\u585e&#xff1a;\u5173\u6ce8\u7a0b\u5e8f\u7b49\u5f85\u65f6\u7684\u72b6\u6001<\/font><\/h4>\n<p>\u963b\u585e&#xff1a;\u8c03\u7528\u7ed3\u679c\u8fd4\u56de\u4e4b\u524d&#xff0c;\u5f53\u524d\u7ebf\u7a0b\u4f1a\u88ab\u6302\u8d77\u3002\u8c03\u7528\u7ebf\u7a0b\u53ea\u6709\u5f97\u5230\u7ed3\u679c\u4e4b\u540e\u624d\u4f1a\u8fd4\u56de\u3002<\/p>\n<p>\u975e\u963b\u585e&#xff1a;\u4e0d\u80fd\u7acb\u523b\u5f97\u5230\u7ed3\u679c\u4e4b\u524d&#xff0c;\u8be5\u8c03\u7528\u4e0d\u4f1a\u963b\u585e\u5f53\u524d\u7ebf\u7a0b&#xff0c;\u76f4\u63a5\u8fd4\u56de&#xff08;\u53ef\u80fd\u5e26\u9519\u8bef\u7801&#xff09;\u3002<\/p>\n<hr \/>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">2.3 \u56db\u8005\u7ec4\u5408&#xff1a;\u5996\u602a\u84b8\u5510\u50e7\u7684\u4f8b\u5b50<\/font><\/h4>\n<p>\u6211\u4eec\u7528\u4e00\u4e2a\u751f\u52a8\u7684\u4f8b\u5b50\u6765\u7406\u89e3\u8fd9\u56db\u4e2a\u6982\u5ff5\u7684\u7ec4\u5408\u5173\u7cfb\u3002<\/p>\n<p>\u5996\u602a\u6293\u5230\u4e86\u5510\u50e7&#xff0c;\u60f3\u84b8\u6765\u5403&#xff0c;\u9505\u5f97\u70e7\u70ed\u3002\u5996\u602a\u6709\u51e0\u79cd\u7b49\u6cd5&#xff1a;<\/p>\n<p>\u963b\u585e &#043; \u540c\u6b65&#xff08;\u50bb\u7b49\u578b&#xff09;&#xff1a; \u5996\u602a\u76ef\u7740\u9505&#xff0c;\u4e00\u76f4\u7b49\u5230\u9505\u70ed&#xff0c;\u5565\u4e5f\u4e0d\u5e72\u3002<\/p>\n<p>\u5996\u602a&#xff1a;&#xff08;\u76ef\u7740\u9505&#xff09;<br \/>\n\u5996\u602a&#xff1a;&#xff08;\u8fd8\u5728\u76ef&#xff09;<br \/>\n\u9505&#xff1a;\u6211\u70ed\u4e86&#xff01;<br \/>\n\u5996\u602a&#xff1a;\u597d&#xff0c;\u4e0b\u4e00\u6b65<\/p>\n<p>\u975e\u963b\u585e &#043; \u540c\u6b65&#xff08;\u8f6e\u8be2\u578b&#xff09;&#xff1a; \u5996\u602a\u6bcf\u9694\u4e00\u4f1a\u95ee\u4e00\u6b21&#034;\u70ed\u4e86\u5417&#034;&#xff0c;\u6ca1\u70ed\u5c31\u53bb\u73a9\u4f1a\u513f&#xff0c;\u518d\u6765\u95ee\u3002\u81ea\u5df1\u4e3b\u52a8\u8f6e\u8be2\u3002<\/p>\n<p>\u5996\u602a&#xff1a;\u70ed\u4e86\u5417&#xff1f;&#xff08;\u6ca1\u70ed&#xff09;\u53bb\u73a9<br \/>\n\u5996\u602a&#xff1a;\u70ed\u4e86\u5417&#xff1f;&#xff08;\u6ca1\u70ed&#xff09;\u53bb\u73a9<br \/>\n\u9505&#xff1a;\u6211\u70ed\u4e86&#xff01;<br \/>\n\u5996\u602a&#xff1a;&#xff08;\u4e0b\u6b21\u6765\u95ee\u65f6&#xff09;\u597d&#xff0c;\u4e0b\u4e00\u6b65<\/p>\n<p>\u975e\u963b\u585e &#043; \u5f02\u6b65&#xff08;\u4fe1\u53f7\u901a\u77e5\u578b&#xff09;&#xff1a; \u5996\u602a\u5e72\u5176\u4ed6\u4e8b&#xff0c;\u9505\u70ed\u4e86\u8ba9\u5c0f\u5996\u602a\u6765\u901a\u77e5\u5b83\u3002\u5996\u602a\u6536\u5230\u901a\u77e5\u540e&#xff0c;\u81ea\u5df1\u53bb\u68c0\u67e5\u3001\u5904\u7406\u3002<\/p>\n<p>\u5996\u602a&#xff1a;\u53bb\u5e72\u522b\u7684\u4e8b\u4e86<br \/>\n\u9505&#xff1a;&#xff08;\u901a\u8fc7\u5c0f\u5996\u602a&#xff09;\u6211\u70ed\u4e86&#xff01;<br \/>\n\u5996\u602a&#xff1a;&#xff08;\u6536\u5230\u901a\u77e5&#xff09;\u6211\u6765\u4e86&#xff0c;\u5f00\u59cb\u4e0b\u4e00\u6b65<\/p>\n<p>\u5b8c\u5168\u5f02\u6b65&#xff08;\u5168\u6258\u7ba1\u578b&#xff09;&#xff1a; \u5996\u602a\u5e72\u522b\u7684\u4e8b&#xff0c;\u4e0d\u53ea\u662f\u7b49\u901a\u77e5&#xff0c;\u800c\u662f\u5168\u7a0b\u6258\u7ba1\u2014\u2014\u8fde\u5510\u50e7\u4e5f\u8ba9\u522b\u4eba\u5904\u7406&#xff0c;\u505a\u597d\u4e86\u901a\u77e5\u5996\u602a\u6765\u5403\u3002<\/p>\n<hr \/>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">2.4 \u4ece\u4ee3\u7801\u89d2\u5ea6\u7406\u89e3\u963b\u585e\u548c\u975e\u963b\u585e<\/font><\/h4>\n<p>\u6765\u770b\u4e00\u4e2a\u76f4\u89c2\u7684\u5bf9\u6bd4&#xff1a;<\/p>\n<p><span class=\"token comment\">\/\/ \u963b\u585e\u8bfb\u53d6&#xff1a;\u5982\u679c\u6ca1\u6709\u6570\u636e&#xff0c;\u7a0b\u5e8f\u5361\u5728 read() \u8fd9\u4e00\u884c<\/span><br \/>\nssize_t n <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">read<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> buf<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>buf<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token comment\">\/\/ \u53ea\u6709\u6570\u636e\u6765\u4e86&#xff0c;\u624d\u80fd\u5230\u8fbe\u4e0b\u4e00\u884c<\/span><\/p>\n<p><span class=\"token comment\">\/\/ \u975e\u963b\u585e\u8bfb\u53d6&#xff1a;\u5982\u679c\u6ca1\u6709\u6570\u636e&#xff0c;\u7acb\u5373\u8fd4\u56de -1&#xff0c;errno &#061; EWOULDBLOCK<\/span><br \/>\nssize_t n <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">read<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> buf<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>buf<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span>  <span class=\"token comment\">\/\/ fd \u8bbe\u7f6e\u4e86 O_NONBLOCK<\/span><br \/>\n<span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>n <span class=\"token operator\">&lt;<\/span> <span class=\"token number\">0<\/span> <span class=\"token operator\">&amp;&amp;<\/span> errno <span class=\"token operator\">&#061;&#061;<\/span> EWOULDBLOCK<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token comment\">\/\/ \u6570\u636e\u8fd8\u6ca1\u6765&#xff0c;\u7a0d\u540e\u91cd\u8bd5<\/span><br \/>\n    <span class=\"token keyword\">continue<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token comment\">\/\/ \u7a0b\u5e8f\u4e0d\u4f1a\u88ab\u5361\u4f4f<\/span><\/p>\n<p>\u963b\u585e\u5c31\u50cf&#034;\u4f60\u4e0d\u7ed9\u6211&#xff0c;\u6211\u5c31\u4e0d\u8d70&#034;&#xff1b;\u975e\u963b\u585e\u5c31\u50cf&#034;\u4f60\u6ca1\u6709\u5c31\u544a\u8bc9\u6211\u4e00\u58f0&#xff0c;\u6211\u5148\u53bb\u5fd9\u522b\u7684&#034;\u3002<\/p>\n<hr \/>\n<h3><font face=\"\u6977\u4f53\" color=\"#984229\" size=\"5\">\u4e09\u3001\u9ad8\u7ea7 IO \u6982\u5ff5\u68b3\u7406<\/font><\/h3>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">3.1 \u9ad8\u7ea7 IO \u7684\u5206\u7c7b<\/font><\/h4>\n<p>Linux \u4e2d&#xff0c;\u9664\u4e86\u57fa\u7840\u7684\u963b\u585e IO&#xff0c;\u4ee5\u4e0b\u90fd\u5c5e\u4e8e\u9ad8\u7ea7 IO&#xff1a;<\/p>\n<table>\n<tr>\u9ad8\u7ea7 IO \u7c7b\u578b\u8bf4\u660e<\/tr>\n<tbody>\n<tr>\n<td>\u975e\u963b\u585e IO<\/td>\n<td>fcntl \u8bbe\u7f6e O_NONBLOCK<\/td>\n<\/tr>\n<tr>\n<td>\u8bb0\u5f55\u9501<\/td>\n<td>fcntl \u7684\u9501\u529f\u80fd<\/td>\n<\/tr>\n<tr>\n<td>IO \u591a\u8def\u8f6c\u63a5<\/td>\n<td>select \/ poll \/ epoll<\/td>\n<\/tr>\n<tr>\n<td>readv \/ writev<\/td>\n<td>\u5206\u6563\u8bfb \/ \u805a\u96c6\u5199<\/td>\n<\/tr>\n<tr>\n<td>\u5b58\u50a8\u6620\u5c04 IO<\/td>\n<td>mmap<\/td>\n<\/tr>\n<tr>\n<td>\u7cfb\u7edf V \u6d41\u673a\u5236<\/td>\n<td>\u8f83\u65e7\u7684\u673a\u5236<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u6211\u4eec\u8fd9\u4e2a\u7cfb\u5217\u7684\u91cd\u70b9&#xff1a;IO \u591a\u8def\u8f6c\u63a5&#xff08;select \u2192 poll \u2192 epoll \u2192 Reactor \u6a21\u5f0f&#xff09;<\/p>\n<hr \/>\n<h3><font face=\"\u6977\u4f53\" color=\"#984229\" size=\"5\">\u56db\u3001fcntl&#xff1a;\u5b9e\u73b0\u975e\u963b\u585e IO \u7684\u5229\u5668<\/font><\/h3>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">4.1 fcntl \u51fd\u6570\u6982\u89c8<\/font><\/h4>\n<p>fcntl \u662f Linux \u4e0b\u64cd\u63a7\u6587\u4ef6\u63cf\u8ff0\u7b26\u5c5e\u6027\u7684\u745e\u58eb\u519b\u5200&#xff0c;\u51fd\u6570\u539f\u578b\u5982\u4e0b&#xff1a;<\/p>\n<p><span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;unistd.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;fcntl.h&gt;<\/span><\/span><\/p>\n<p><span class=\"token keyword\">int<\/span> <span class=\"token function\">fcntl<\/span><span class=\"token punctuation\">(<\/span><span class=\"token keyword\">int<\/span> fd<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">int<\/span> cmd<span class=\"token punctuation\">,<\/span> <span class=\"token punctuation\">.<\/span><span class=\"token punctuation\">.<\/span><span class=\"token punctuation\">.<\/span> <span class=\"token comment\">\/* arg *\/<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>\u6839\u636e cmd \u7684\u4e0d\u540c&#xff0c;\u5b83\u6709\u4e94\u79cd\u529f\u80fd&#xff1a;<\/p>\n<table>\n<tr>cmd\u529f\u80fd<\/tr>\n<tbody>\n<tr>\n<td>F_DUPFD<\/td>\n<td>\u590d\u5236\u6587\u4ef6\u63cf\u8ff0\u7b26<\/td>\n<\/tr>\n<tr>\n<td>F_GETFD \/ F_SETFD<\/td>\n<td>\u83b7\u53d6\/\u8bbe\u7f6e\u6587\u4ef6\u63cf\u8ff0\u7b26\u6807\u8bb0<\/td>\n<\/tr>\n<tr>\n<td>F_GETFL \/ F_SETFL<\/td>\n<td>\u83b7\u53d6\/\u8bbe\u7f6e\u6587\u4ef6\u72b6\u6001\u6807\u8bb0 \u2190 \u6211\u4eec\u7528\u8fd9\u4e2a<\/td>\n<\/tr>\n<tr>\n<td>F_GETOWN \/ F_SETOWN<\/td>\n<td>\u83b7\u53d6\/\u8bbe\u7f6e\u5f02\u6b65 IO \u6240\u6709\u6743<\/td>\n<\/tr>\n<tr>\n<td>F_GETLK \/ F_SETLK \/ F_SETLKW<\/td>\n<td>\u83b7\u53d6\/\u8bbe\u7f6e\u8bb0\u5f55\u9501<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u6211\u4eec\u8981\u5b9e\u73b0\u975e\u963b\u585e IO&#xff0c;\u7528\u7684\u662f\u7b2c\u4e09\u79cd&#xff1a;\u83b7\u53d6\/\u8bbe\u7f6e\u6587\u4ef6\u72b6\u6001\u6807\u8bb0\u3002<\/p>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">4.2 fcntl \u7684\u5de5\u4f5c\u539f\u7406<\/font><\/h4>\n<p>\u6587\u4ef6\u63cf\u8ff0\u7b26\u6709\u4e00\u5957\u72b6\u6001\u6807\u8bb0\u4f4d\u56fe&#xff08;flags&#xff09;&#xff0c;\u8bb0\u5f55\u7740\u8fd9\u4e2a fd \u7684\u5404\u79cd\u5c5e\u6027&#xff0c;\u6bd4\u5982&#xff1a;<\/p>\n<ul>\n<li>O_RDONLY&#xff1a;\u53ea\u8bfb<\/li>\n<li>O_WRONLY&#xff1a;\u53ea\u5199<\/li>\n<li>O_RDWR&#xff1a;\u8bfb\u5199<\/li>\n<li>O_NONBLOCK&#xff1a;\u975e\u963b\u585e \u2190 \u6211\u4eec\u8981\u52a0\u7684<\/li>\n<li>O_APPEND&#xff1a;\u8ffd\u52a0\u5199\u5165<\/li>\n<li>O_ASYNC&#xff1a;\u5f02\u6b65 IO<\/li>\n<\/ul>\n<p>\u60f3\u8ba9\u4e00\u4e2a fd \u53d8\u6210\u975e\u963b\u585e&#xff0c;\u5c31\u662f\u5728\u5b83\u7684\u72b6\u6001\u4f4d\u56fe\u4e0a\u52a0\u4e0a O_NONBLOCK \u8fd9\u4e00\u4f4d\u3002<\/p>\n<p>\u64cd\u4f5c\u6b65\u9aa4&#xff1a;<\/p>\n<li>F_GETFL&#xff1a;\u628a\u5f53\u524d\u7684\u4f4d\u56fe\u53d6\u51fa\u6765<\/li>\n<li>\u628a O_NONBLOCK \u4f4d\u6216\u4e0a\u53bb<\/li>\n<li>F_SETFL&#xff1a;\u628a\u4fee\u6539\u540e\u7684\u4f4d\u56fe\u5199\u56de\u53bb<\/li>\n<p>\u5c31\u50cf\u662f\u7ed9 fd \u8d34\u4e00\u5f20\u6807\u7b7e&#xff1a;\u201c\u4ee5\u540e\u64cd\u4f5c\u6211&#xff0c;\u4e0d\u8981\u7b49&#xff0c;\u6ca1\u6570\u636e\u5c31\u76f4\u63a5\u544a\u8bc9\u6211 EWOULDBLOCK\u201d\u3002<\/p>\n<hr \/>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">4.3 \u5b9e\u73b0 SetNoBlock \u51fd\u6570<\/font><\/h4>\n<p><span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;unistd.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;fcntl.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;cstdio&gt;<\/span><\/span><\/p>\n<p><span class=\"token comment\">\/**<br \/>\n * \u5c06\u6587\u4ef6\u63cf\u8ff0\u7b26\u8bbe\u7f6e\u4e3a\u975e\u963b\u585e\u6a21\u5f0f<br \/>\n * &#064;param fd \u9700\u8981\u8bbe\u7f6e\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26<br \/>\n *\/<\/span><br \/>\n<span class=\"token keyword\">void<\/span> <span class=\"token function\">SetNoBlock<\/span><span class=\"token punctuation\">(<\/span><span class=\"token keyword\">int<\/span> fd<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token comment\">\/\/ \u7b2c\u4e00\u6b65&#xff1a;\u83b7\u53d6\u5f53\u524d\u6587\u4ef6\u72b6\u6001\u6807\u8bb0&#xff08;\u8fd9\u662f\u4e00\u4e2a\u4f4d\u56fe&#xff09;<\/span><br \/>\n    <span class=\"token keyword\">int<\/span> fl <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">fcntl<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> F_GETFL<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>fl <span class=\"token operator\">&lt;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;fcntl F_GETFL&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u7b2c\u4e8c\u6b65&#xff1a;\u5c06 O_NONBLOCK \u4f4d\u6dfb\u52a0\u8fdb\u53bb&#xff08;\u7528\u6309\u4f4d\u6216&#xff0c;\u4e0d\u5f71\u54cd\u5176\u4ed6\u6807\u5fd7\u4f4d&#xff09;<\/span><br \/>\n    <span class=\"token comment\">\/\/ \u9519\u8bef\u793a\u8303&#xff1a;fcntl(fd, F_SETFL, O_NONBLOCK);  \/\/ \u8fd9\u4f1a\u6e05\u9664\u5176\u4ed6\u6240\u6709\u6807\u5fd7&#xff01;<\/span><br \/>\n    <span class=\"token keyword\">int<\/span> ret <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">fcntl<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> F_SETFL<span class=\"token punctuation\">,<\/span> fl <span class=\"token operator\">|<\/span> O_NONBLOCK<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>ret <span class=\"token operator\">&lt;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;fcntl F_SETFL&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<p>\u8b66\u544a&#xff1a;F_SETFL \u65f6\u4e00\u5b9a\u8981\u5148 F_GETFL \u53d6\u51fa\u539f\u6709\u6807\u5fd7&#xff0c;\u518d | \u4e0a O_NONBLOCK&#xff01; \u4e0d\u80fd\u76f4\u63a5 fcntl(fd, F_SETFL, O_NONBLOCK)&#xff0c;\u90a3\u6837\u4f1a\u6e05\u9664 fd \u4e0a\u6240\u6709\u5176\u4ed6\u7684\u6807\u5fd7\u4f4d&#xff08;\u6bd4\u5982 O_RDWR&#xff09;&#xff0c;\u540e\u679c\u4e0d\u53ef\u9884\u6599\u3002<\/p>\n<hr \/>\n<h3><font face=\"\u6977\u4f53\" color=\"#984229\" size=\"5\">\u4e94\u3001\u975e\u963b\u585e IO \u5b9e\u6218&#xff1a;\u8f6e\u8be2\u8bfb\u53d6\u6807\u51c6\u8f93\u5165<\/font><\/h3>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">5.1 \u573a\u666f\u63cf\u8ff0<\/font><\/h4>\n<p>\u6211\u4eec\u6765\u505a\u4e00\u4e2a\u5c0f\u5b9e\u9a8c&#xff1a;\u628a\u6807\u51c6\u8f93\u5165&#xff08;fd &#061; 0&#xff09;\u8bbe\u7f6e\u4e3a\u975e\u963b\u585e&#xff0c;\u7136\u540e\u7528\u5faa\u73af\u8f6e\u8be2\u8bfb\u53d6\u3002\u8fd9\u80fd\u5e2e\u6211\u4eec\u76f4\u89c2\u611f\u53d7\u975e\u963b\u585e IO \u7684\u884c\u4e3a\u3002<\/p>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">5.2 \u5b8c\u6574\u4ee3\u7801<\/font><\/h4>\n<p><span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;stdio.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;unistd.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;fcntl.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;errno.h&gt;<\/span><\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;string.h&gt;<\/span><\/span><\/p>\n<p><span class=\"token comment\">\/**<br \/>\n * \u5c06\u6307\u5b9a\u6587\u4ef6\u63cf\u8ff0\u7b26\u8bbe\u7f6e\u4e3a\u975e\u963b\u585e\u6a21\u5f0f<br \/>\n *\/<\/span><br \/>\n<span class=\"token keyword\">void<\/span> <span class=\"token function\">SetNoBlock<\/span><span class=\"token punctuation\">(<\/span><span class=\"token keyword\">int<\/span> fd<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token keyword\">int<\/span> fl <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">fcntl<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> F_GETFL<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>fl <span class=\"token operator\">&lt;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;fcntl F_GETFL&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    <span class=\"token function\">fcntl<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> F_SETFL<span class=\"token punctuation\">,<\/span> fl <span class=\"token operator\">|<\/span> O_NONBLOCK<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<p><span class=\"token keyword\">int<\/span> <span class=\"token function\">main<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token comment\">\/\/ \u628a\u6807\u51c6\u8f93\u5165 (fd&#061;0) \u8bbe\u4e3a\u975e\u963b\u585e<\/span><br \/>\n    <span class=\"token function\">SetNoBlock<\/span><span class=\"token punctuation\">(<\/span><span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">while<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token keyword\">char<\/span> buf<span class=\"token punctuation\">[<\/span><span class=\"token number\">1024<\/span><span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">{<\/span><span class=\"token number\">0<\/span><span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>        <span class=\"token comment\">\/\/ \u975e\u963b\u585e read&#xff1a;\u6ca1\u6709\u8f93\u5165\u65f6\u7acb\u5373\u8fd4\u56de -1<\/span><br \/>\n        <span class=\"token class-name\">ssize_t<\/span> read_size <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">read<\/span><span class=\"token punctuation\">(<\/span><span class=\"token number\">0<\/span><span class=\"token punctuation\">,<\/span> buf<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>buf<span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&#8211;<\/span> <span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>        <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>read_size <span class=\"token operator\">&lt;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n            <span class=\"token comment\">\/\/ errno &#061;&#061; EWOULDBLOCK \u6216 EAGAIN \u8868\u793a&#034;\u6682\u65f6\u6ca1\u6709\u6570\u636e&#xff0c;\u7a0d\u540e\u91cd\u8bd5&#034;<\/span><br \/>\n            <span class=\"token comment\">\/\/ \u8fd9\u662f\u975e\u963b\u585e IO \u7684&#034;\u6b63\u5e38&#034;\u60c5\u51b5&#xff0c;\u4e0d\u662f\u771f\u6b63\u7684\u9519\u8bef<\/span><br \/>\n            <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>errno <span class=\"token operator\">&#061;&#061;<\/span> EWOULDBLOCK <span class=\"token operator\">||<\/span> errno <span class=\"token operator\">&#061;&#061;<\/span> EAGAIN<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n                <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;[\u8f6e\u8be2] \u6ca1\u6709\u8f93\u5165&#xff0c;\u7b49 1 \u79d2\u540e\u91cd\u8bd5&#8230;\\\\n&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n                <span class=\"token function\">sleep<\/span><span class=\"token punctuation\">(<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n                <span class=\"token keyword\">continue<\/span><span class=\"token punctuation\">;<\/span><br \/>\n            <span class=\"token punctuation\">}<\/span><br \/>\n            <span class=\"token comment\">\/\/ \u5176\u4ed6\u9519\u8bef\u624d\u662f\u771f\u6b63\u7684\u9519\u8bef<\/span><br \/>\n            <span class=\"token function\">perror<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;read&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n            <span class=\"token function\">sleep<\/span><span class=\"token punctuation\">(<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n            <span class=\"token keyword\">continue<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token punctuation\">}<\/span><\/p>\n<p>        <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>read_size <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n            <span class=\"token comment\">\/\/ \u8fd4\u56de 0 \u8868\u793a EOF&#xff08;\u5bf9\u4e8e\u6807\u51c6\u8f93\u5165&#xff0c;\u5c31\u662f Ctrl&#043;D&#xff09;<\/span><br \/>\n            <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;\u68c0\u6d4b\u5230 EOF&#xff0c;\u9000\u51fa\\\\n&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n            <span class=\"token keyword\">break<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token punctuation\">}<\/span><\/p>\n<p>        buf<span class=\"token punctuation\">[<\/span>read_size<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token char\">&#039;\\\\0&#039;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token function\">printf<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;[\u8f93\u5165] %s\\\\n&#034;<\/span><span class=\"token punctuation\">,<\/span> buf<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token keyword\">return<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">5.3 \u8fd0\u884c\u6548\u679c\u5206\u6790<\/font><\/h4>\n<p>\u7f16\u8bd1\u5e76\u8fd0\u884c&#xff1a;<\/p>\n<p>gcc nonblock_stdin.c -o nonblock_stdin<br \/>\n.\/nonblock_stdin<\/p>\n<p>\u8fd0\u884c\u540e\u7684\u884c\u4e3a&#xff1a;<\/p>\n<ul>\n<li>\u5982\u679c\u4f60\u4e0d\u8f93\u5165\u4efb\u4f55\u5185\u5bb9&#xff0c;\u7a0b\u5e8f\u6bcf\u79d2\u6253\u5370\u4e00\u6b21&#034;\u6ca1\u6709\u8f93\u5165&#xff0c;\u7b49 1 \u79d2\u540e\u91cd\u8bd5\u2026&#034;<\/li>\n<li>\u4f60\u8f93\u5165 hello \u5e76\u56de\u8f66&#xff0c;\u7a0b\u5e8f\u7acb\u523b\u6253\u5370 [\u8f93\u5165] hello<\/li>\n<li>\u6309 Ctrl&#043;D&#xff0c;\u7a0b\u5e8f\u9000\u51fa<\/li>\n<\/ul>\n<p>\u8fd9\u4e2a\u4f8b\u5b50\u63ed\u793a\u4e86\u975e\u963b\u585e IO \u7684\u4e24\u4e2a\u5173\u952e\u70b9&#xff1a;<\/p>\n<p>1. EWOULDBLOCK \/ EAGAIN \u4e0d\u662f\u771f\u6b63\u7684\u9519\u8bef<\/p>\n<p>EWOULDBLOCK \u548c EAGAIN \u5728\u73b0\u4ee3 Linux \u4e0a\u662f\u540c\u4e00\u4e2a\u503c<br \/>\n\u542b\u4e49&#xff1a;\u64cd\u4f5c\u4f1a\u963b\u585e&#xff0c;\u4f46 fd \u662f\u975e\u963b\u585e\u7684&#xff0c;\u6240\u4ee5\u76f4\u63a5\u8fd4\u56de\u4e86<br \/>\n\u5904\u7406\u65b9\u5f0f&#xff1a;\u91cd\u8bd5&#xff01;\u8fd9\u662f\u9884\u671f\u5185\u7684\u60c5\u51b5<\/p>\n<p>2. \u975e\u963b\u585e\u8f6e\u8be2\u975e\u5e38\u6d6a\u8d39 CPU<\/p>\n<p>\u5982\u679c\u4f60\u628a sleep(1) \u53bb\u6389&#xff0c;\u8fd9\u4e2a\u7a0b\u5e8f\u4f1a\u4ee5 CPU 100% \u7684\u901f\u5ea6\u72c2\u8f6c&#xff0c;\u4e0d\u505c\u5730\u8be2\u95ee&#034;\u6709\u6570\u636e\u4e86\u5417&#034;\u3002\u8fd9\u5c31\u662f\u975e\u963b\u585e IO \u5355\u72ec\u4f7f\u7528\u7684\u95ee\u9898\u2014\u2014\u8f6e\u8be2\u4f1a\u6d6a\u8d39\u5927\u91cf CPU\u3002<\/p>\n<p>\u6240\u4ee5&#xff0c;\u975e\u963b\u585e IO \u901a\u5e38\u4e0d\u5355\u72ec\u4f7f\u7528&#xff0c;\u800c\u662f\u914d\u5408 IO \u591a\u8def\u8f6c\u63a5&#xff08;select\/poll\/epoll&#xff09;\u4e00\u8d77\u7528\u3002\u540e\u8005\u544a\u8bc9\u4f60\u54ea\u4e2a fd \u6709\u6570\u636e\u4e86&#xff0c;\u4f60\u518d\u53bb\u8bfb\u2014\u2014\u65e2\u4e0d\u6d6a\u8d39 CPU \u7b49\u5f85&#xff0c;\u4e5f\u4e0d\u6d6a\u8d39 CPU \u8f6e\u8be2\u3002<\/p>\n<p>\u6ce8\u610f&#xff1a;\u5728\u7ec8\u7aef\u4e0b&#xff0c;\u6807\u51c6\u8f93\u5165\u9ed8\u8ba4\u6309\u201c\u884c\u201d\u63d0\u4ea4&#xff08;\u56de\u8f66\u624d\u4f1a\u628a\u8fd9\u4e00\u884c\u4ea4\u7ed9\u7a0b\u5e8f&#xff09;&#xff0c;\u6240\u4ee5\u4f60\u770b\u5230\u7684\u662f\u56de\u8f66\u540e read \u624d\u8bfb\u5230\u6570\u636e&#xff1b;\u5982\u679c\u6539\u6210 raw\u6a21\u5f0f&#xff08;termios&#xff09;&#xff0c;\u624d\u53ef\u80fd\u6309\u952e\u7ea7\u522b\u8fd4\u56de\u3002<\/p>\n<hr \/>\n<h3><font face=\"\u6977\u4f53\" color=\"#984229\" size=\"5\">\u516d\u3001IO \u6d41\u7a0b\u53ef\u89c6\u5316&#xff1a;\u4ece\u7cfb\u7edf\u8c03\u7528\u5230\u6570\u636e<\/font><\/h3>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">6.1 \u7f51\u7edc IO \u7684\u5b8c\u6574\u8def\u5f84<\/font><\/h4>\n<p>\u7406\u89e3 IO \u6a21\u578b&#xff0c;\u8fd8\u9700\u8981\u77e5\u9053\u6570\u636e\u662f\u5982\u4f55\u4ece\u7f51\u5361\u5230\u8fbe\u4f60\u7684\u7a0b\u5e8f\u7684&#xff1a;<\/p>\n<p>                    \u7f51\u7edc\u6570\u636e\u5230\u8fbe\u7684\u5b8c\u6574\u8def\u5f84<\/p>\n<p>\u8fdc\u7aef\u4e3b\u673a<br \/>\n   <span class=\"token operator\">|<\/span><br \/>\n   <span class=\"token operator\">|<\/span> \u53d1\u9001\u6570\u636e\u5305<br \/>\n   \u2193<br \/>\n<span class=\"token punctuation\">[<\/span>\u7f51\u5361 NIC<span class=\"token punctuation\">]<\/span><br \/>\n   <span class=\"token operator\">|<\/span><br \/>\n   <span class=\"token operator\">|<\/span> \u786c\u4ef6\u4e2d\u65ad \/ DMA<br \/>\n   \u2193<br \/>\n<span class=\"token punctuation\">[<\/span>\u5185\u6838\u63a5\u6536\u7f13\u51b2\u533a<span class=\"token punctuation\">]<\/span>  \u2190 \u6570\u636e<span class=\"token string\">&#034;\u5c31\u7eea&#034;<\/span>\u5c31\u662f\u6307\u5230\u8fd9\u91cc<br \/>\n   <span class=\"token operator\">|<\/span><br \/>\n   <span class=\"token operator\">|<\/span> \u7cfb\u7edf\u8c03\u7528&#xff08;read\/recv&#xff09;<br \/>\n   \u2193<br \/>\n<span class=\"token punctuation\">[<\/span>\u7528\u6237\u7a7a\u95f4\u7f13\u51b2\u533a<span class=\"token punctuation\">]<\/span>  \u2190 \u4f60\u7684 buf<span class=\"token punctuation\">[<\/span><span class=\"token number\">1024<\/span><span class=\"token punctuation\">]<\/span><br \/>\n   <span class=\"token operator\">|<\/span><br \/>\n   <span class=\"token operator\">|<\/span> \u7a0b\u5e8f\u5904\u7406<br \/>\n   \u2193<br \/>\n<span class=\"token punctuation\">[<\/span>\u4f60\u7684\u4e1a\u52a1\u903b\u8f91<span class=\"token punctuation\">]<\/span><\/p>\n<p>\u7406\u89e3\u4e86\u8fd9\u4e2a\u8def\u5f84&#xff0c;\u4e94\u79cd IO \u6a21\u578b\u7684\u533a\u522b\u5c31\u66f4\u6e05\u6670\u4e86&#xff1a;<\/p>\n<ul>\n<li>\u7b49\u5f85\u9636\u6bb5&#xff1a;\u7b49\u6570\u636e\u4ece\u7f51\u5361\u5230\u8fbe\u5185\u6838\u7f13\u51b2\u533a<\/li>\n<li>\u62f7\u8d1d\u9636\u6bb5&#xff1a;\u628a\u6570\u636e\u4ece\u5185\u6838\u7f13\u51b2\u533a\u62f7\u8d1d\u5230\u7528\u6237\u7f13\u51b2\u533a<\/li>\n<\/ul>\n<hr \/>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">6.2 \u4e3a\u4ec0\u4e48 IO \u591a\u8def\u8f6c\u63a5\u6700\u9002\u5408\u9ad8\u5e76\u53d1\u670d\u52a1\u5668<\/font><\/h4>\n<p>\u5047\u8bbe\u4f60\u7684\u670d\u52a1\u5668\u6709 10000 \u4e2a\u5ba2\u6237\u7aef\u8fde\u63a5&#xff1a;<\/p>\n<p>\u4f20\u7edf\u65b9\u6cd5&#xff08;\u4e00\u8fde\u63a5\u4e00\u7ebf\u7a0b&#xff09;&#xff1a;<\/p>\n<p>\u7ebf\u7a0b <span class=\"token number\">1<\/span>&#xff1a;\u963b\u585e\u7b49 \u5ba2\u6237\u7aef1 \u7684\u6570\u636e<br \/>\n\u7ebf\u7a0b <span class=\"token number\">2<\/span>&#xff1a;\u963b\u585e\u7b49 \u5ba2\u6237\u7aef2 \u7684\u6570\u636e<br \/>\n<span class=\"token punctuation\">..<\/span>.<br \/>\n\u7ebf\u7a0b <span class=\"token number\">10000<\/span>&#xff1a;\u963b\u585e\u7b49 \u5ba2\u6237\u7aef10000 \u7684\u6570\u636e<\/p>\n<ul>\n<li>10000 \u4e2a\u7ebf\u7a0b&#xff01;\u5185\u5b58\u5f00\u9500\u5de8\u5927&#xff0c;\u4e0a\u4e0b\u6587\u5207\u6362\u5f00\u9500\u5927<\/li>\n<li>\u5927\u90e8\u5206\u65f6\u5019\u53ea\u6709\u5c11\u6570\u5ba2\u6237\u7aef\u5728\u6d3b\u8dc3&#xff0c;\u5176\u4ed6\u7ebf\u7a0b\u90fd\u5728\u767d\u767d\u7761\u89c9<\/li>\n<\/ul>\n<p>IO \u591a\u8def\u8f6c\u63a5&#xff08;\u5355\u7ebf\u7a0b\/\u5c11\u91cf\u7ebf\u7a0b &#043; epoll&#xff09;&#xff1a;<\/p>\n<p><span class=\"token number\">1<\/span> \u4e2a\u7ebf\u7a0b&#xff1a;<br \/>\n    epoll_wait<span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> \u76d1\u63a7 <span class=\"token number\">10000<\/span> \u4e2a fd<br \/>\n    \u2193 \u67d0\u51e0\u4e2a fd \u5c31\u7eea\u4e86<br \/>\n    \u5904\u7406\u8fd9\u51e0\u4e2a fd<br \/>\n    \u2193<br \/>\n    \u56de\u5230 epoll_wait<span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> \u7ee7\u7eed\u76d1\u63a7<\/p>\n<ul>\n<li>\u53ea\u7528 1 \u4e2a&#xff08;\u6216\u5c11\u91cf&#xff09;\u7ebf\u7a0b<\/li>\n<li>\u53ea\u5904\u7406\u771f\u6b63\u6709\u6570\u636e\u7684\u8fde\u63a5&#xff0c;\u4e0d\u6d6a\u8d39<\/li>\n<li>\u8fd9\u5c31\u662f Nginx\u3001Redis \u7684\u6838\u5fc3\u539f\u7406<\/li>\n<\/ul>\n<hr \/>\n<h3><font face=\"\u6977\u4f53\" color=\"#984229\" size=\"5\">\u4e03\u3001\u5e38\u89c1\u95ee\u9898\u4e0e\u6982\u5ff5\u8fa8\u6790<\/font><\/h3>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">7.1 \u5bb9\u6613\u6df7\u6dc6\u7684\u70b9<\/font><\/h4>\n<h5><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">1. IO \u591a\u8def\u8f6c\u63a5 vs \u5f02\u6b65 IO&#xff0c;\u8c01\u66f4\u9ad8\u6548&#xff1f;<\/font><\/h5>\n<p>\u5f88\u591a\u4eba\u4ee5\u4e3a\u5f02\u6b65 IO \u6700\u597d&#xff0c;\u5176\u5b9e\u4e0d\u4e00\u5b9a\u3002<\/p>\n<ul>\n<li>IO \u591a\u8def\u8f6c\u63a5&#xff08;\u7279\u522b\u662f epoll&#xff09;\u5728 Linux \u4e0a\u975e\u5e38\u6210\u719f&#xff0c;\u6027\u80fd\u6781\u597d<\/li>\n<li>\u5f02\u6b65 IO&#xff08;aio&#xff09;\u5728 Linux \u4e0a\u7684\u652f\u6301\u76f8\u5bf9\u6709\u9650&#xff0c;\u4e14\u7f16\u7a0b\u590d\u6742\u5ea6\u66f4\u9ad8<\/li>\n<li>Nginx\u3001Redis\u3001Node.js \u90fd\u57fa\u4e8e IO \u591a\u8def\u8f6c\u63a5&#xff0c;\u6ca1\u6709\u7528\u5f02\u6b65 IO<\/li>\n<\/ul>\n<p>\u7ed3\u8bba&#xff1a;epoll &#043; \u975e\u963b\u585e IO \u662f\u76ee\u524d Linux \u9ad8\u6027\u80fd\u670d\u52a1\u5668\u7684\u4e3b\u6d41\u65b9\u6848\u3002 \u975e\u5e38\u9002\u5408&#xff1a;\u8fde\u63a5\u6570\u591a\u3001\u4f46\u540c\u4e00\u65f6\u523b\u771f\u6b63\u6d3b\u8dc3\u7684\u8fde\u63a5\u6bd4\u4f8b\u4e0d\u9ad8\u7684\u573a\u666f<\/p>\n<hr \/>\n<h5><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">2. IO \u591a\u8def\u8f6c\u63a5\u81ea\u8eab\u662f\u963b\u585e\u7684&#xff0c;\u600e\u4e48\u8bf4\u5b83\u662f&#034;\u975e\u963b\u585e&#034;&#xff1f;<\/font><\/h5>\n<p>select\/poll\/epoll_wait \u672c\u8eab\u662f\u963b\u585e\u7684&#xff08;\u5982\u679c\u6ca1\u6709 fd \u5c31\u7eea&#xff0c;\u4f1a\u7b49\u5f85&#xff09;\u3002<\/p>\n<p>\u4f46\u5b83\u7684\u4ef7\u503c\u4e0d\u5728\u4e8e&#034;\u4e0d\u963b\u585e&#034;&#xff0c;\u800c\u5728\u4e8e&#034;\u4e00\u6b21\u76d1\u63a7\u591a\u4e2a fd&#xff0c;\u53ea\u8981\u6709\u4e00\u4e2a\u5c31\u7eea\u5c31\u8fd4\u56de&#034;\u3002<\/p>\n<p>\u8fd9\u8ba9\u4e00\u4e2a\u7ebf\u7a0b\u80fd\u670d\u52a1\u5927\u91cf\u8fde\u63a5&#xff0c;\u800c\u4e0d\u662f\u4e3a\u6bcf\u4e2a\u8fde\u63a5\u5f00\u4e00\u4e2a\u7ebf\u7a0b\u963b\u585e\u7b49\u5f85\u3002<\/p>\n<hr \/>\n<h5><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">3. EAGAIN \u548c EWOULDBLOCK \u7684\u533a\u522b&#xff1f;<\/font><\/h5>\n<p><span class=\"token comment\">\/\/ \u5728 Linux \u4e0a&#xff0c;\u4e24\u8005\u901a\u5e38\u662f\u540c\u4e00\u4e2a\u503c<\/span><br \/>\n<span class=\"token comment\">\/\/ \/usr\/include\/asm-generic\/errno-base.h:<\/span><br \/>\n<span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">define<\/span> <span class=\"token macro-name\">EWOULDBLOCK<\/span>  <span class=\"token expression\">EAGAIN  <\/span><span class=\"token comment\">\/\/ \u901a\u5e38 EWOULDBLOCK &#061; EAGAIN &#061; 11<\/span><\/span><\/p>\n<p><span class=\"token comment\">\/\/ \u6240\u4ee5\u5904\u7406\u65f6&#xff0c;\u4e24\u4e2a\u90fd\u5224\u65ad\u5c31\u884c&#xff1a;<\/span><br \/>\n<span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>errno <span class=\"token operator\">&#061;&#061;<\/span> EAGAIN <span class=\"token operator\">||<\/span> errno <span class=\"token operator\">&#061;&#061;<\/span> EWOULDBLOCK<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token comment\">\/\/ \u6682\u65f6\u65e0\u6570\u636e&#xff0c;\u91cd\u8bd5<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<hr \/>\n<h5><font face=\"\u6977\u4f53\" size=\"4\" color=\"#336699\">4. \u4e3a\u4ec0\u4e48 ET \u6a21\u5f0f&#xff08;epoll \u8fb9\u7f18\u89e6\u53d1&#xff09;\u5fc5\u987b\u914d\u975e\u963b\u585e IO&#xff1f;<\/font><\/h5>\n<p>\u8fd9\u4e2a\u95ee\u9898\u6211\u4eec\u5728 epoll \u90a3\u7bc7\u4f1a\u6df1\u5165\u8bb2&#xff0c;\u8fd9\u91cc\u5148\u57cb\u4e2a\u4f0f\u7b14\u3002<\/p>\n<p>\u7b80\u5355\u6765\u8bf4&#xff1a;ET \u6a21\u5f0f\u4e0b&#xff0c;\u6570\u636e\u5c31\u7eea\u53ea\u901a\u77e5\u4f60\u4e00\u6b21\u3002\u5982\u679c\u4f60\u7528\u963b\u585e read&#xff0c;\u4e00\u6b21 read \u53ef\u80fd\u6ca1\u8bfb\u5b8c\u6240\u6709\u6570\u636e&#xff0c;\u5269\u4e0b\u7684\u6570\u636e\u5c31\u518d\u4e5f\u7b49\u4e0d\u5230\u901a\u77e5\u4e86&#xff08;ET \u4e0d\u4f1a\u518d\u6b21\u89e6\u53d1&#xff09;\u3002<\/p>\n<p>\u6240\u4ee5 ET \u6a21\u5f0f\u4e0b&#xff0c;\u5fc5\u987b\u7528\u975e\u963b\u585e read&#xff0c;\u5faa\u73af\u8bfb\u76f4\u5230 EAGAIN&#xff0c;\u786e\u4fdd\u628a\u7f13\u51b2\u533a\u7684\u6570\u636e\u4e00\u6b21\u6027\u8bfb\u5b8c\u3002<\/p>\n<hr \/>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">7.2 \u5178\u578b\u9762\u8bd5\u9898\u89e3\u6790<\/font><\/h4>\n<p>Q&#xff1a;\u8bf4\u8bf4 select\u3001poll\u3001epoll \u7684\u533a\u522b\u3002<\/p>\n<p>&#xff08;\u5148\u522b\u6025\u7740\u8bf4&#xff0c;\u4ece\u8fd9\u7bc7\u7684\u57fa\u7840\u5f00\u59cb\u5f15\u5165&#xff09;<\/p>\n<p>\u9996\u5148&#xff0c;\u5b83\u4eec\u90fd\u662f IO \u591a\u8def\u8f6c\u63a5\u7684\u5b9e\u73b0&#xff0c;\u6838\u5fc3\u76ee\u7684\u662f\u8ba9\u4e00\u4e2a\u7ebf\u7a0b\u76d1\u63a7\u591a\u4e2a fd\u3002\u533a\u522b\u5728\u4e8e&#xff1a;<\/p>\n<ul>\n<li>select&#xff1a;\u57fa\u4e8e\u4f4d\u56fe&#xff0c;\u6709 fd \u6570\u91cf\u4e0a\u9650&#xff08;1024\/4096&#xff09;&#xff0c;\u6bcf\u6b21\u90fd\u8981\u62f7\u8d1d\u6574\u4e2a\u4f4d\u56fe\u5230\u5185\u6838&#xff0c;\u8fd4\u56de\u540e\u8fd8\u8981\u904d\u5386\u627e\u5c31\u7eea\u7684 fd<\/li>\n<li>poll&#xff1a;\u89e3\u51b3\u4e86 select \u7684\u6570\u91cf\u9650\u5236&#xff0c;\u7528 pollfd \u6570\u7ec4&#xff0c;\u4f46\u8fd8\u662f\u6bcf\u6b21\u90fd\u8981\u5168\u91cf\u62f7\u8d1d\u548c\u904d\u5386<\/li>\n<li>epoll&#xff1a;\u5185\u6838\u7ef4\u62a4\u7ea2\u9ed1\u6811\u548c\u5c31\u7eea\u961f\u5217&#xff0c;\u53ea\u62f7\u8d1d\u53d8\u5316\u7684 fd&#xff0c;epoll_wait \u76f4\u63a5\u8fd4\u56de\u5c31\u7eea\u7684 fd&#xff0c;\u6027\u80fd\u6700\u597d<\/li>\n<\/ul>\n<p>\u8fd9\u4e9b\u6211\u4eec\u540e\u9762\u4e09\u7bc7\u4f1a\u8be6\u7ec6\u5c55\u5f00\u3002<\/p>\n<hr \/>\n<h3><font face=\"\u6977\u4f53\" color=\"#984229\" size=\"5\">\u516b\u3001\u77e5\u8bc6\u70b9\u603b\u7ed3<\/font><\/h3>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">8.1 \u6838\u5fc3\u8981\u70b9<\/font><\/h4>\n<table>\n<tr>#\u8981\u70b9\u8bf4\u660e<\/tr>\n<tbody>\n<tr>\n<td>1<\/td>\n<td>IO \u4e24\u9636\u6bb5<\/td>\n<td>\u7b49\u5f85\u5c31\u7eea &#043; \u6570\u636e\u62f7\u8d1d&#xff0c;\u7b49\u5f85\u5360\u5927\u5934<\/td>\n<td><\/td>\n<\/tr>\n<tr>\n<td>2<\/td>\n<td>\u4e94\u79cd\u6a21\u578b\u672c\u8d28<\/td>\n<td>\u5bf9\u8fd9\u4e24\u4e2a\u9636\u6bb5\u7684\u4e0d\u540c\u5904\u7406\u7b56\u7565<\/td>\n<td><\/td>\n<\/tr>\n<tr>\n<td>3<\/td>\n<td>\u540c\u6b65\u2260\u963b\u585e<\/td>\n<td>\u540c\u6b65\/\u5f02\u6b65\u5173\u6ce8\u901a\u4fe1\u673a\u5236&#xff0c;\u963b\u585e\/\u975e\u963b\u585e\u5173\u6ce8\u7b49\u5f85\u72b6\u6001<\/td>\n<td><\/td>\n<\/tr>\n<tr>\n<td>4<\/td>\n<td>fcntl \u8bbe\u7f6e\u975e\u963b\u585e<\/td>\n<td>F_GETFL \u53d6\u51fa &#043;  O_NONBLOCK&#043;F_SETFL \u5199\u56de<\/td>\n<td><\/td>\n<\/tr>\n<tr>\n<td>5<\/td>\n<td>EAGAIN \u4e0d\u662f\u9519\u8bef<\/td>\n<td>\u975e\u963b\u585e IO \u4e0b&#034;\u6682\u65e0\u6570\u636e&#034;\u7684\u6b63\u5e38\u8fd4\u56de&#xff0c;\u5e94\u91cd\u8bd5<\/td>\n<td><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h4><font face=\"\u6977\u4f53\" size=\"4\" color=\"#112299\">8.2 \u6982\u5ff5\u8bb0\u5fc6\u6280\u5de7<\/font><\/h4>\n<p>\u8bb0\u4f4f\u8fd9\u5f20\u8868&#xff0c;\u9762\u8bd5\u88ab\u95ee\u5230\u76f4\u63a5\u4e0d\u614c&#xff1a;<\/p>\n<p>\u540c\u6b65\/\u5f02\u6b65 \u2192 \u8c01\u6765\u901a\u77e5\u7ed3\u679c&#xff08;\u8c03\u7528\u8005\u4e3b\u52a8\u7b49 \/ \u88ab\u8c03\u7528\u8005\u6765\u901a\u77e5&#xff09;<br \/>\n\u963b\u585e\/\u975e\u963b\u585e \u2192 \u8c03\u7528\u8005\u7b49\u5f85\u65f6\u7684\u72b6\u6001&#xff08;\u6302\u8d77 \/ \u7ee7\u7eed\u6267\u884c&#xff09;<\/p>\n<p>\u4e94\u79cd\u6a21\u578b\u7684\u533a\u522b \u2192 \u9493\u9c7c\u6545\u4e8b&#xff1a;<br \/>\n  \u963b\u585e <span class=\"token operator\">&#061;<\/span> \u5446\u770b<br \/>\n  \u4fe1\u53f7\u9a71\u52a8 <span class=\"token operator\">&#061;<\/span> \u88c5\u94c3\u94db<br \/>\n  IO\u591a\u8def\u8f6c\u63a5 <span class=\"token operator\">&#061;<\/span> \u96c7\u7ba1\u5bb6\u540c\u65f6\u76ef100\u6839\u7aff<br \/>\n  \u5f02\u6b65IO <span class=\"token operator\">&#061;<\/span> \u5168\u6258\u7ba1&#xff0c;\u641e\u597d\u4e86\u53eb\u4f60<\/p>\n<p>\u540c\u65f6&#xff1a;\u5728IO\u6a21\u578b\u91cc\u9762&#xff0c;\u540c\u6b65\u5f02\u6b65\u7684\u672c\u8d28\u533a\u522b\u8fd8\u6709&#xff1a;<\/p>\n<ul>\n<li>\u540c\u6b65 IO&#xff1a;\u62f7\u8d1d\u9636\u6bb5\u7531\u7528\u6237\u7ebf\u7a0b\u89e6\u53d1&#xff08;read\/recv \u53bb\u62f7\u8d1d&#xff09;<\/li>\n<li>\u5f02\u6b65 IO&#xff1a;\u7b49\u5f85&#043;\u62f7\u8d1d\u90fd\u7531\u5185\u6838\u5b8c\u6210&#xff0c;\u5b8c\u6210\u540e\u901a\u77e5\u7528\u6237\u7ebf\u7a0b<\/li>\n<\/ul>\n<hr \/>\n<p>&#x1f4ac; \u603b\u7ed3&#xff1a;\u8fd9\u7bc7\u6587\u7ae0\u6211\u4eec\u4ece\u6700\u5e95\u5c42\u7684 IO \u4e24\u9636\u6bb5\u6a21\u578b\u51fa\u53d1&#xff0c;\u8d70\u901a\u4e86\u4e94\u79cd IO \u6a21\u578b\u7684\u6f14\u8fdb\u903b\u8f91&#xff0c;\u5398\u6e05\u4e86\u540c\u6b65\/\u5f02\u6b65\u3001\u963b\u585e\/\u975e\u963b\u585e\u8fd9\u56db\u4e2a\u5173\u952e\u6982\u5ff5&#xff0c;\u5e76\u901a\u8fc7 fcntl \u5b9e\u73b0\u4e86\u7b2c\u4e00\u4e2a\u975e\u963b\u585e IO \u7684\u5b9e\u6218\u4ee3\u7801\u3002\u73b0\u5728\u4f60\u5e94\u8be5\u80fd\u6e05\u695a\u5730\u8bf4\u51fa&#xff1a;\u4e3a\u4ec0\u4e48 IO \u591a\u8def\u8f6c\u63a5\u662f\u9ad8\u5e76\u53d1\u670d\u52a1\u5668\u7684\u57fa\u7840&#xff0c;\u4ee5\u53ca\u4e3a\u4ec0\u4e48\u975e\u963b\u585e IO \u901a\u5e38\u8981\u548c\u591a\u8def\u590d\u7528\u914d\u5408\u4f7f\u7528\u3002\u4e0b\u4e00\u7bc7&#xff0c;\u6211\u4eec\u5f00\u59cb\u6df1\u5165 select \u2014\u2014\u5386\u53f2\u6700\u60a0\u4e45\u7684\u591a\u8def\u8f6c\u63a5\u5b9e\u73b0&#xff0c;\u4ece\u5b83\u7684\u4f4d\u56fe\u539f\u7406\u5230\u5b57\u5178\u670d\u52a1\u5668\u7684\u5b8c\u6574\u5b9e\u73b0&#xff0c;\u4e00\u6b65\u6b65\u62c6\u89e3\u3002<\/p>\n<p>&#x1f44d; 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