{"id":88220,"date":"2026-07-31T18:40:28","date_gmt":"2026-07-31T10:40:28","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/88220.html"},"modified":"2026-07-31T18:40:28","modified_gmt":"2026-07-31T10:40:28","slug":"%e9%98%bb%e5%a1%9e-i-o%e3%80%81%e9%9d%9e%e9%98%bb%e5%a1%9e-i-o%e3%80%81%e5%90%8c%e6%ad%a5-i-o%e4%b8%8e%e5%bc%82%e6%ad%a5-i-o","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/88220.html","title":{"rendered":"\u963b\u585e I\/O\u3001\u975e\u963b\u585e I\/O\u3001\u540c\u6b65 I\/O\u4e0e\u5f02\u6b65 I\/O"},"content":{"rendered":"<\/p>\n<h4>\u6587\u7ae0\u76ee\u5f55<\/h4>\n<ul>\n<li>\u963b\u585e I\/O\u3001\u975e\u963b\u585e I\/O\u3001\u540c\u6b65 I\/O\u4e0e\u5f02\u6b65 I\/O&#xff1a;\u4ece\u7cfb\u7edf\u8c03\u7528\u5230 Linux \u5185\u6838\u7684\u5b8c\u6574\u89e3\u6790<\/li>\n<li>\n<ul>\n<li>\u4e00\u3001\u4e3a\u4ec0\u4e48\u8fd9\u56db\u4e2a\u6982\u5ff5\u5bb9\u6613\u6df7\u6dc6&#xff1f;<\/li>\n<\/ul>\n<\/li>\n<li>\u4e8c\u3001\u4e00\u6b21\u7f51\u7edc\u8bfb\u53d6\u5230\u5e95\u5305\u542b\u54ea\u4e9b\u9636\u6bb5&#xff1f;<\/li>\n<li>\n<ul>\n<li>2.1 \u7b2c\u4e00\u9636\u6bb5&#xff1a;\u7b49\u5f85\u6570\u636e\u8fdb\u5165\u5185\u6838\u63a5\u6536\u7f13\u51b2\u533a<\/li>\n<li>2.2 \u7b2c\u4e8c\u9636\u6bb5&#xff1a;\u5c06\u6570\u636e\u4ece\u5185\u6838\u7a7a\u95f4\u590d\u5236\u5230\u7528\u6237\u7a7a\u95f4<\/li>\n<\/ul>\n<\/li>\n<li>\u4e09\u3001\u4ec0\u4e48\u662f\u963b\u585e I\/O&#xff1f;<\/li>\n<li>\n<ul>\n<li>3.1 \u963b\u585e I\/O \u7684\u5b9a\u4e49<\/li>\n<li>3.2 \u963b\u585e I\/O \u7684\u6267\u884c\u8fc7\u7a0b<\/li>\n<\/ul>\n<\/li>\n<li>\u56db\u3001\u963b\u585e I\/O \u5230\u5e95\u963b\u585e\u4e86\u4ec0\u4e48&#xff1f;<\/li>\n<li>\n<ul>\n<li>4.1 \u963b\u585e\u7684\u662f\u5f53\u524d\u8c03\u7528\u7ebf\u7a0b\u7684\u6267\u884c\u6d41<\/li>\n<li>4.2 \u963b\u585e\u7684\u4e0d\u662f\u6574\u4e2a CPU<\/li>\n<li>4.3 \u963b\u585e\u7684\u4e0d\u662f\u6574\u4e2a\u8fdb\u7a0b<\/li>\n<li>4.4 \u963b\u585e\u7684\u4e0d\u662f\u64cd\u4f5c\u7cfb\u7edf\u548c\u7f51\u7edc\u534f\u8bae\u6808<\/li>\n<li>4.5 \u963b\u585e\u7684\u4e0d\u662f\u8fdc\u7aef\u7a0b\u5e8f<\/li>\n<li>4.6 \u963b\u585e I\/O \u7684\u51c6\u786e\u603b\u7ed3<\/li>\n<\/ul>\n<\/li>\n<li>\u4e94\u3001\u201c\u963b\u585e\u201d\u548c\u201c\u6302\u8d77\u201d\u662f\u5426\u5b8c\u5168\u76f8\u540c&#xff1f;<\/li>\n<li>\u516d\u3001\u963b\u585e\u7ebf\u7a0b\u5728\u7b49\u5f85\u65f6\u662f\u5426\u5360\u7528 CPU&#xff1f;<\/li>\n<li>\u4e03\u3001\u963b\u585e I\/O \u662f\u5426\u4e00\u5b9a\u4f1a\u6c38\u4e45\u963b\u585e&#xff1f;<\/li>\n<li>\u516b\u3001\u4ec0\u4e48\u662f\u975e\u963b\u585e I\/O&#xff1f;<\/li>\n<li>\n<ul>\n<li>8.1 \u975e\u963b\u585e I\/O \u7684\u5b9a\u4e49<\/li>\n<li>8.2 \u5982\u4f55\u5c06 Socket \u8bbe\u7f6e\u4e3a\u975e\u963b\u585e&#xff1f;<\/li>\n<li>8.3 \u975e\u963b\u585e\u8bfb\u53d6\u793a\u4f8b<\/li>\n<\/ul>\n<\/li>\n<li>\u4e5d\u3001\u975e\u963b\u585e I\/O \u662f\u5426\u610f\u5473\u7740\u4e00\u76f4\u5360\u7528 CPU&#xff1f;<\/li>\n<li>\u5341\u3001\u963b\u585e I\/O \u548c\u975e\u963b\u585e I\/O \u7684\u6838\u5fc3\u533a\u522b<\/li>\n<li>\u5341\u4e00\u3001\u963b\u585e I\/O \u7684\u5b8c\u6574\u670d\u52a1\u5668\u793a\u4f8b<\/li>\n<li>\u5341\u4e8c\u3001\u4ec0\u4e48\u662f I\/O \u591a\u8def\u590d\u7528&#xff1f;<\/li>\n<li>\n<ul>\n<li>12.1 &#096;epoll_wait()&#096; \u672c\u8eab\u53ef\u4ee5\u963b\u585e<\/li>\n<li>12.2 \u4e3a\u4ec0\u4e48\u914d\u5408 epoll \u4ecd\u7136\u8981\u8bbe\u7f6e O_NONBLOCK&#xff1f;<\/li>\n<\/ul>\n<\/li>\n<li>\u5341\u4e09\u3001epoll \u5c5e\u4e8e\u5f02\u6b65 I\/O \u5417&#xff1f;<\/li>\n<li>\u5341\u56db\u3001\u4ec0\u4e48\u662f\u540c\u6b65 I\/O&#xff1f;<\/li>\n<li>\n<ul>\n<li>14.1 \u540c\u6b65 I\/O \u7684\u5b9a\u4e49<\/li>\n<li>14.2 \u540c\u6b65\u4e0d\u7b49\u4e8e\u963b\u585e<\/li>\n<\/ul>\n<\/li>\n<li>\u5341\u4e94\u3001\u4ec0\u4e48\u662f\u5f02\u6b65 I\/O&#xff1f;<\/li>\n<li>\n<ul>\n<li>15.1 \u5f02\u6b65 I\/O \u7684\u5b9a\u4e49<\/li>\n<li>15.2 \u540c\u6b65 I\/O \u4e0e\u5f02\u6b65 I\/O \u7684\u6838\u5fc3\u533a\u522b<\/li>\n<\/ul>\n<\/li>\n<li>\u5341\u516d\u3001Reactor \u4e0e Proactor<\/li>\n<li>\n<ul>\n<li>16.1 Reactor&#xff1a;\u5c31\u7eea\u901a\u77e5<\/li>\n<li>16.2 Proactor&#xff1a;\u5b8c\u6210\u901a\u77e5<\/li>\n<\/ul>\n<\/li>\n<li>\u5341\u4e03\u3001Linux \u4e2d\u6709\u54ea\u4e9b\u5f02\u6b65 I\/O \u6280\u672f&#xff1f;<\/li>\n<li>\u5341\u516b\u3001\u56db\u79cd\u5e38\u89c1 I\/O \u6a21\u578b\u5bf9\u6bd4<\/li>\n<li>\n<ul>\n<li>18.1 \u963b\u585e\u540c\u6b65 I\/O<\/li>\n<li>18.2 \u975e\u963b\u585e\u540c\u6b65 I\/O<\/li>\n<li>18.3 I\/O \u591a\u8def\u590d\u7528<\/li>\n<li>18.4 \u5f02\u6b65 I\/O<\/li>\n<\/ul>\n<\/li>\n<li>\u5341\u4e5d\u3001\u4e24\u4e2a\u7ef4\u5ea6\u5e94\u8be5\u600e\u6837\u7ec4\u5408&#xff1f;<\/li>\n<li>\u4e8c\u5341\u3001\u4e3a\u4ec0\u4e48\u9ad8\u5e76\u53d1\u670d\u52a1\u5668\u901a\u5e38\u4e0d\u7528\u4e00\u8fde\u63a5\u4e00\u7ebf\u7a0b&#xff1f;<\/li>\n<li>\u4e8c\u5341\u4e00\u3001\u4e3a\u4ec0\u4e48\u975e\u963b\u585e I\/O \u9002\u5408\u4e8b\u4ef6\u5faa\u73af&#xff1f;<\/li>\n<li>\u4e8c\u5341\u4e8c\u3001\u975e\u963b\u585e\u5199\u64cd\u4f5c\u8fd8\u8981\u5904\u7406\u201c\u90e8\u5206\u5199\u5165\u201d<\/li>\n<li>\u4e8c\u5341\u4e09\u3001\u963b\u585e\u3001\u975e\u963b\u585e\u3001\u540c\u6b65\u3001\u5f02\u6b65\u7684\u6700\u7ec8\u5bf9\u7167\u8868<\/li>\n<li>\u4e8c\u5341\u56db\u3001\u5e38\u89c1\u9519\u8bef\u8bf4\u6cd5\u4fee\u6b63<\/li>\n<li>\n<ul>\n<li>\u9519\u8bef\u4e00&#xff1a;\u963b\u585e I\/O \u4f1a\u5360\u6ee1 CPU<\/li>\n<li>\u9519\u8bef\u4e8c&#xff1a;\u975e\u963b\u585e I\/O \u4e00\u5b9a\u4f1a\u5360\u6ee1 CPU<\/li>\n<li>\u9519\u8bef\u4e09&#xff1a;epoll \u662f\u5f02\u6b65 I\/O<\/li>\n<li>\u9519\u8bef\u56db&#xff1a;epoll \u901a\u77e5\u53ef\u8bfb\u540e&#xff0c;\u53ef\u4ee5\u653e\u5fc3\u4f7f\u7528\u963b\u585e recv<\/li>\n<li>\u9519\u8bef\u4e94&#xff1a;\u963b\u585e I\/O \u963b\u585e\u7684\u662f CPU<\/li>\n<li>\u9519\u8bef\u516d&#xff1a;\u540c\u6b65\u4e00\u5b9a\u963b\u585e&#xff0c;\u5f02\u6b65\u4e00\u5b9a\u975e\u963b\u585e<\/li>\n<\/ul>\n<\/li>\n<li>\u4e8c\u5341\u4e94\u3001\u7528\u4e00\u53e5\u8bdd\u5206\u522b\u8bb0\u4f4f\u56db\u4e2a\u6982\u5ff5<\/li>\n<li>\n<ul>\n<li>\u963b\u585e I\/O<\/li>\n<li>\u975e\u963b\u585e I\/O<\/li>\n<li>\u540c\u6b65 I\/O<\/li>\n<li>\u5f02\u6b65 I\/O<\/li>\n<\/ul>\n<\/li>\n<li>\u4e8c\u5341\u516d\u3001\u6700\u7ec8\u603b\u7ed3<\/li>\n<\/ul>\n<h2>\u963b\u585e I\/O\u3001\u975e\u963b\u585e I\/O\u3001\u540c\u6b65 I\/O\u4e0e\u5f02\u6b65 I\/O&#xff1a;\u4ece\u7cfb\u7edf\u8c03\u7528\u5230 Linux \u5185\u6838\u7684\u5b8c\u6574\u89e3\u6790<\/h2>\n<h3>\u4e00\u3001\u4e3a\u4ec0\u4e48\u8fd9\u56db\u4e2a\u6982\u5ff5\u5bb9\u6613\u6df7\u6dc6&#xff1f;<\/h3>\n<p>\u7f51\u7edc\u7f16\u7a0b\u4e2d\u7ecf\u5e38\u51fa\u73b0\u56db\u4e2a\u672f\u8bed&#xff1a;<\/p>\n<ul>\n<li>\u963b\u585e I\/O&#xff0c;Blocking I\/O<\/li>\n<li>\u975e\u963b\u585e I\/O&#xff0c;Non-blocking I\/O<\/li>\n<li>\u540c\u6b65 I\/O&#xff0c;Synchronous I\/O<\/li>\n<li>\u5f02\u6b65 I\/O&#xff0c;Asynchronous I\/O<\/li>\n<\/ul>\n<p>\u5f88\u591a\u4eba\u4f1a\u628a\u5b83\u4eec\u7b80\u5355\u7406\u89e3\u4e3a&#xff1a;<\/p>\n<p>\u963b\u585e &#061; \u540c\u6b65<br \/>\n\u975e\u963b\u585e &#061; \u5f02\u6b65<\/p>\n<p>\u8fd9\u662f\u9519\u8bef\u7684\u3002<\/p>\n<p>\u5b83\u4eec\u63cf\u8ff0\u7684\u662f\u4e24\u4e2a\u4e0d\u540c\u7ef4\u5ea6&#xff1a;<\/p>\n<p>\u963b\u585e \/ \u975e\u963b\u585e<br \/>\n    \u5173\u6ce8&#xff1a;\u8c03\u7528\u7ebf\u7a0b\u5728\u7b49\u5f85\u671f\u95f4\u662f\u5426\u505c\u5728\u7cfb\u7edf\u8c03\u7528\u4e2d\u3002<\/p>\n<p>\u540c\u6b65 \/ \u5f02\u6b65<br \/>\n    \u5173\u6ce8&#xff1a;I\/O \u64cd\u4f5c\u6700\u7ec8\u7531\u8c01\u5b8c\u6210&#xff0c;\u4ee5\u53ca\u5e94\u7528\u7a0b\u5e8f\u5982\u4f55\u83b7\u5f97\u5b8c\u6210\u7ed3\u679c\u3002<\/p>\n<p>\u56e0\u6b64&#xff1a;<\/p>\n<p>\u963b\u585e\u4e0e\u975e\u963b\u585e&#xff1a;\u63cf\u8ff0\u7ebf\u7a0b\u7b49\u5f85\u65b9\u5f0f<br \/>\n\u540c\u6b65\u4e0e\u5f02\u6b65&#xff1a;\u63cf\u8ff0 I\/O \u5b8c\u6210\u65b9\u5f0f<\/p>\n<p>Linux \u4e2d\u5e38\u89c1\u7684 select\u3001poll\u3001epoll&#xff0c;\u867d\u7136\u901a\u5e38\u914d\u5408\u975e\u963b\u585e\u5957\u63a5\u5b57\u548c\u4e8b\u4ef6\u9a71\u52a8\u7a0b\u5e8f\u4f7f\u7528&#xff0c;\u4f46\u4ece\u4e25\u683c\u7684 I\/O \u6a21\u578b\u5206\u7c7b\u6765\u770b&#xff0c;\u5b83\u4eec\u4ecd\u7136\u5c5e\u4e8e\u540c\u6b65 I\/O\u3002<\/p>\n<hr \/>\n<h2>\u4e8c\u3001\u4e00\u6b21\u7f51\u7edc\u8bfb\u53d6\u5230\u5e95\u5305\u542b\u54ea\u4e9b\u9636\u6bb5&#xff1f;<\/h2>\n<p>\u8981\u7406\u89e3\u56db\u4e2a\u6982\u5ff5&#xff0c;\u5fc5\u987b\u5148\u770b\u4e00\u6b21 recv() \u6216 read() \u7684\u5b8c\u6574\u8fc7\u7a0b\u3002<\/p>\n<p>\u5047\u8bbe\u7a0b\u5e8f\u6267\u884c&#xff1a;<\/p>\n<p><span class=\"token keyword\">char<\/span> buffer<span class=\"token punctuation\">[<\/span><span class=\"token number\">4096<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><br \/>\nssize_t n <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">recv<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> buffer<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>buffer<span class=\"token punctuation\">)<\/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>\u5bf9\u4e8e TCP Socket&#xff0c;\u8bfb\u53d6\u8fc7\u7a0b\u5927\u81f4\u5206\u4e3a\u4e24\u4e2a\u9636\u6bb5\u3002<\/p>\n<h3>2.1 \u7b2c\u4e00\u9636\u6bb5&#xff1a;\u7b49\u5f85\u6570\u636e\u8fdb\u5165\u5185\u6838\u63a5\u6536\u7f13\u51b2\u533a<\/h3>\n<p>\u7f51\u7edc\u6570\u636e\u9996\u5148\u7ecf\u8fc7&#xff1a;<\/p>\n<p>\u8fdc\u7a0b\u4e3b\u673a<br \/>\n   \u2502<br \/>\n   \u25bc<br \/>\n\u7269\u7406\u7f51\u7edc<br \/>\n   \u2502<br \/>\n   \u25bc<br \/>\n\u672c\u673a\u7f51\u5361<br \/>\n   \u2502<br \/>\n   \u25bc<br \/>\n\u7f51\u5361\u9a71\u52a8<br \/>\n   \u2502<br \/>\n   \u25bc<br \/>\nLinux \u7f51\u7edc\u534f\u8bae\u6808<br \/>\n   \u2502<br \/>\n   \u25bc<br \/>\nSocket \u5185\u6838\u63a5\u6536\u7f13\u51b2\u533a<\/p>\n<p>\u6b64\u65f6\u6570\u636e\u8fd8\u6ca1\u6709\u8fdb\u5165\u7528\u6237\u7a0b\u5e8f\u7684 buffer\u3002<\/p>\n<p>\u5982\u679c Socket \u63a5\u6536\u7f13\u51b2\u533a\u4e3a\u7a7a&#xff0c;\u8bf4\u660e\u5f53\u524d\u6ca1\u6709\u6570\u636e\u53ef\u4ee5\u8bfb\u53d6\u3002<\/p>\n<hr \/>\n<h3>2.2 \u7b2c\u4e8c\u9636\u6bb5&#xff1a;\u5c06\u6570\u636e\u4ece\u5185\u6838\u7a7a\u95f4\u590d\u5236\u5230\u7528\u6237\u7a7a\u95f4<\/h3>\n<p>\u5f53\u5185\u6838\u63a5\u6536\u7f13\u51b2\u533a\u4e2d\u5df2\u6709\u6570\u636e\u540e&#xff0c;\u5185\u6838\u8fd8\u9700\u8981\u6267\u884c&#xff1a;<\/p>\n<p>Socket \u5185\u6838\u63a5\u6536\u7f13\u51b2\u533a<br \/>\n          \u2502<br \/>\n          \u2502 copy_to_user<br \/>\n          \u25bc<br \/>\n\u7528\u6237\u7a0b\u5e8f buffer<\/p>\n<p>\u53ea\u6709\u5b8c\u6210\u8fd9\u4e00\u6b65&#xff0c;recv() \u624d\u80fd\u5411\u7528\u6237\u7a0b\u5e8f\u8fd4\u56de\u8bfb\u53d6\u5230\u7684\u5b57\u8282\u6570\u3002<\/p>\n<p>\u56e0\u6b64&#xff0c;\u4e00\u6b21\u4f20\u7edf Socket \u8bfb\u53d6\u53ef\u4ee5\u62bd\u8c61\u4e3a&#xff1a;<\/p>\n<p>\u9636\u6bb5\u4e00&#xff1a;\u7b49\u5f85\u6570\u636e\u51c6\u5907\u5b8c\u6210<br \/>\n\u9636\u6bb5\u4e8c&#xff1a;\u5c06\u6570\u636e\u590d\u5236\u5230\u7528\u6237\u7a7a\u95f4<\/p>\n<p>\u8fd9\u4e24\u4e2a\u9636\u6bb5\u662f\u7406\u89e3\u540c\u6b65\u3001\u5f02\u6b65\u3001\u963b\u585e\u548c\u975e\u963b\u585e\u7684\u5173\u952e\u3002<\/p>\n<hr \/>\n<h2>\u4e09\u3001\u4ec0\u4e48\u662f\u963b\u585e I\/O&#xff1f;<\/h2>\n<h3>3.1 \u963b\u585e I\/O \u7684\u5b9a\u4e49<\/h3>\n<p>\u963b\u585e I\/O \u662f\u6307&#xff1a;<\/p>\n<p>\u5f53\u7ebf\u7a0b\u6267\u884c I\/O \u7cfb\u7edf\u8c03\u7528&#xff0c;\u800c\u5f53\u524d\u65e0\u6cd5\u7acb\u5373\u5b8c\u6210\u8be5\u64cd\u4f5c\u65f6&#xff0c;\u7cfb\u7edf\u8c03\u7528\u4e0d\u4f1a\u7acb\u523b\u8fd4\u56de&#xff0c;\u8c03\u7528\u7ebf\u7a0b\u4f1a\u8fdb\u5165\u7b49\u5f85\u72b6\u6001&#xff0c;\u76f4\u5230\u6570\u636e\u5230\u8fbe\u3001\u8fde\u63a5\u5173\u95ed\u3001\u53d1\u751f\u9519\u8bef\u3001\u6536\u5230\u4fe1\u53f7\u6216\u8005\u8d85\u65f6\u3002<\/p>\n<p>\u4f8b\u5982&#xff1a;<\/p>\n<p><span class=\"token keyword\">char<\/span> buffer<span class=\"token punctuation\">[<\/span><span class=\"token number\">1024<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><br \/>\nssize_t n <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">recv<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> buffer<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>buffer<span class=\"token punctuation\">)<\/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>\u5982\u679c fd \u662f\u963b\u585e Socket&#xff0c;\u5e76\u4e14\u63a5\u6536\u7f13\u51b2\u533a\u4e3a\u7a7a&#xff0c;\u90a3\u4e48 recv() \u4e0d\u4f1a\u7acb\u5373\u8fd4\u56de\u3002<\/p>\n<p>\u5f53\u524d\u7ebf\u7a0b\u4f1a\u505c\u5728\u8fd9\u4e00\u884c&#xff1a;<\/p>\n<p>ssize_t n <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">recv<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> buffer<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>buffer<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n                    <span class=\"token comment\">\/\/ \u7a0b\u5e8f\u6682\u65f6\u65e0\u6cd5\u7ee7\u7eed\u5411\u4e0b\u6267\u884c<\/span><\/p>\n<hr \/>\n<h3>3.2 \u963b\u585e I\/O \u7684\u6267\u884c\u8fc7\u7a0b<\/h3>\n<p>\u5176\u6d41\u7a0b\u53ef\u4ee5\u8868\u793a\u4e3a&#xff1a;<\/p>\n<p>\u7528\u6237\u7ebf\u7a0b\u8c03\u7528 recv()<br \/>\n        \u2502<br \/>\n        \u25bc<br \/>\n\u8fdb\u5165\u5185\u6838\u6001<br \/>\n        \u2502<br \/>\n        \u25bc<br \/>\n\u68c0\u67e5 Socket \u63a5\u6536\u7f13\u51b2\u533a<br \/>\n        \u2502<br \/>\n        \u251c\u2500\u2500 \u6709\u6570\u636e<br \/>\n        \u2502      \u2502<br \/>\n        \u2502      \u25bc<br \/>\n        \u2502   \u590d\u5236\u5230\u7528\u6237\u7a7a\u95f4<br \/>\n        \u2502      \u2502<br \/>\n        \u2502      \u25bc<br \/>\n        \u2502   recv() \u8fd4\u56de<br \/>\n        \u2502<br \/>\n        \u2514\u2500\u2500 \u6ca1\u6709\u6570\u636e<br \/>\n               \u2502<br \/>\n               \u25bc<br \/>\n        \u5c06\u7ebf\u7a0b\u52a0\u5165\u7b49\u5f85\u961f\u5217<br \/>\n               \u2502<br \/>\n               \u25bc<br \/>\n        \u8bbe\u7f6e\u4e3a\u53ef\u7761\u7720\u72b6\u6001<br \/>\n               \u2502<br \/>\n               \u25bc<br \/>\n        \u8c03\u5ea6\u5668\u8fd0\u884c\u5176\u4ed6\u7ebf\u7a0b<br \/>\n               \u2502<br \/>\n               \u25bc<br \/>\n        \u6570\u636e\u5230\u8fbe\u540e\u5524\u9192\u7ebf\u7a0b<br \/>\n               \u2502<br \/>\n               \u25bc<br \/>\n        \u590d\u5236\u6570\u636e\u5230\u7528\u6237\u7a7a\u95f4<br \/>\n               \u2502<br \/>\n               \u25bc<br \/>\n        recv() \u8fd4\u56de<\/p>\n<p>\u5bf9\u5e94\u7684\u7ebf\u7a0b\u72b6\u6001\u53d8\u5316\u5927\u81f4\u662f&#xff1a;<\/p>\n<p>\u8fd0\u884c\u6001<br \/>\n  \u2502<br \/>\n  \u2502 \u8c03\u7528 recv()&#xff0c;\u6682\u65f6\u65e0\u6570\u636e<br \/>\n  \u25bc<br \/>\n\u7761\u7720\u7b49\u5f85\u6001<br \/>\n  \u2502<br \/>\n  \u2502 \u6570\u636e\u5230\u8fbe\u3001\u4fe1\u53f7\u6216\u8d85\u65f6<br \/>\n  \u25bc<br \/>\n\u53ef\u8fd0\u884c\u6001<br \/>\n  \u2502<br \/>\n  \u2502 \u83b7\u5f97 CPU \u65f6\u95f4\u7247<br \/>\n  \u25bc<br \/>\n\u8fd0\u884c\u6001<\/p>\n<p>\u8fd9\u91cc\u7684\u201c\u7761\u7720\u201d\u4e0d\u662f\u7528\u6237\u4ee3\u7801\u4e3b\u52a8\u8c03\u7528 sleep()&#xff0c;\u800c\u662f\u5185\u6838\u5728\u7b49\u5f85\u6761\u4ef6\u4e0d\u6ee1\u8db3\u65f6\u6682\u505c\u5f53\u524d\u7ebf\u7a0b\u7684\u6267\u884c\u3002<\/p>\n<hr \/>\n<h2>\u56db\u3001\u963b\u585e I\/O \u5230\u5e95\u963b\u585e\u4e86\u4ec0\u4e48&#xff1f;<\/h2>\n<p>\u8fd9\u662f\u6700\u5bb9\u6613\u4ea7\u751f\u8bef\u89e3\u7684\u5730\u65b9\u3002<\/p>\n<h3>4.1 \u963b\u585e\u7684\u662f\u5f53\u524d\u8c03\u7528\u7ebf\u7a0b\u7684\u6267\u884c\u6d41<\/h3>\n<p>\u963b\u585e recv() \u4f1a\u963b\u6b62\u5f53\u524d\u7ebf\u7a0b\u7ee7\u7eed\u5411\u4e0b\u6267\u884c&#xff1a;<\/p>\n<p>std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;before recv\\\\n&#034;<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>ssize_t n <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">recv<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> buffer<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>buffer<span class=\"token punctuation\">)<\/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\">\/\/ \u6570\u636e\u6ca1\u6709\u5230\u8fbe\u65f6&#xff0c;\u4e0b\u9762\u8fd9\u884c\u4e0d\u4f1a\u6267\u884c<\/span><br \/>\nstd<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;after recv\\\\n&#034;<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>\u5728 recv() \u8fd4\u56de\u4e4b\u524d&#xff0c;\u8fd9\u4e2a\u7ebf\u7a0b\u4e0d\u80fd\u7ee7\u7eed\u6267\u884c\u540e\u9762\u7684\u4e1a\u52a1\u4ee3\u7801\u3002<\/p>\n<p>\u56e0\u6b64&#xff0c;\u963b\u585e I\/O \u963b\u585e\u7684\u662f&#xff1a;<\/p>\n<p>\u5f53\u524d\u8c03\u7528\u7ebf\u7a0b\u7684\u63a7\u5236\u6d41<\/p>\n<hr \/>\n<h3>4.2 \u963b\u585e\u7684\u4e0d\u662f\u6574\u4e2a CPU<\/h3>\n<p>\u5f53\u524d\u7ebf\u7a0b\u8fdb\u5165\u7761\u7720\u7b49\u5f85\u540e&#xff0c;\u64cd\u4f5c\u7cfb\u7edf\u8c03\u5ea6\u5668\u53ef\u4ee5\u8fd0\u884c\u5176\u4ed6\u7ebf\u7a0b\u6216\u5176\u4ed6\u8fdb\u7a0b\u3002<\/p>\n<p>\u4f8b\u5982&#xff1a;<\/p>\n<p>CPU \u5f53\u524d\u8fd0\u884c\u7ebf\u7a0b A<br \/>\n       \u2502<br \/>\n       \u2502 A \u8c03\u7528\u963b\u585e recv()<br \/>\n       \u25bc<br \/>\n\u7ebf\u7a0b A \u8fdb\u5165\u7b49\u5f85\u72b6\u6001<br \/>\n       \u2502<br \/>\n       \u25bc<br \/>\n\u8c03\u5ea6\u5668\u9009\u62e9\u7ebf\u7a0b B<br \/>\n       \u2502<br \/>\n       \u25bc<br \/>\nCPU \u5f00\u59cb\u8fd0\u884c\u7ebf\u7a0b B<\/p>\n<p>\u56e0\u6b64&#xff1a;<\/p>\n<p>\u9519\u8bef\u7406\u89e3&#xff1a;\u963b\u585e I\/O \u4f1a\u628a CPU \u5361\u4f4f<br \/>\n\u6b63\u786e\u7406\u89e3&#xff1a;\u963b\u585e I\/O \u4f1a\u8ba9\u5f53\u524d\u7ebf\u7a0b\u6682\u65f6\u4e0d\u518d\u5360\u7528 CPU<\/p>\n<p>\u4e25\u683c\u6765\u8bf4&#xff0c;\u7ebf\u7a0b\u8fdb\u5165\u7761\u7720\u548c\u91cd\u65b0\u88ab\u8c03\u5ea6\u4f1a\u4ea7\u751f\u4e00\u5b9a\u7684\u8c03\u5ea6\u4e0e\u4e0a\u4e0b\u6587\u5207\u6362\u5f00\u9500&#xff0c;\u4f46\u5728\u7ebf\u7a0b\u7761\u7720\u671f\u95f4&#xff0c;\u5b83\u4e0d\u4f1a\u6301\u7eed\u6267\u884c\u8f6e\u8be2\u6307\u4ee4\u3002<\/p>\n<hr \/>\n<h3>4.3 \u963b\u585e\u7684\u4e0d\u662f\u6574\u4e2a\u8fdb\u7a0b<\/h3>\n<p>\u5982\u679c\u4e00\u4e2a\u8fdb\u7a0b\u4e2d\u6709\u591a\u4e2a\u7ebf\u7a0b&#xff1a;<\/p>\n<p>\u8fdb\u7a0b<br \/>\n\u251c\u2500\u2500 \u7ebf\u7a0b A&#xff1a;\u963b\u585e\u5728 recv()<br \/>\n\u251c\u2500\u2500 \u7ebf\u7a0b B&#xff1a;\u7ee7\u7eed\u5904\u7406\u4efb\u52a1<br \/>\n\u251c\u2500\u2500 \u7ebf\u7a0b C&#xff1a;\u7ee7\u7eed\u8ba1\u7b97<br \/>\n\u2514\u2500\u2500 \u7ebf\u7a0b D&#xff1a;\u7ee7\u7eed\u54cd\u5e94\u5176\u4ed6\u8fde\u63a5<\/p>\n<p>\u7ebf\u7a0b A \u963b\u585e&#xff0c;\u4e0d\u4ee3\u8868\u7ebf\u7a0b B\u3001C\u3001D \u4e5f\u4f1a\u963b\u585e\u3002<\/p>\n<p>\u9664\u975e\u5176\u4ed6\u7ebf\u7a0b\u9700\u8981\u7b49\u5f85\u7ebf\u7a0b A \u6301\u6709\u7684\u4e92\u65a5\u9501\u6216\u5176\u4ed6\u5171\u4eab\u8d44\u6e90\u3002<\/p>\n<hr \/>\n<h3>4.4 \u963b\u585e\u7684\u4e0d\u662f\u64cd\u4f5c\u7cfb\u7edf\u548c\u7f51\u7edc\u534f\u8bae\u6808<\/h3>\n<p>\u7ebf\u7a0b\u963b\u585e\u540e&#xff0c;\u4ee5\u4e0b\u7ec4\u4ef6\u4ecd\u7136\u7ee7\u7eed\u5de5\u4f5c&#xff1a;<\/p>\n<p>\u7f51\u5361\u7ee7\u7eed\u63a5\u6536\u6570\u636e<br \/>\n\u7f51\u5361\u9a71\u52a8\u7ee7\u7eed\u5904\u7406\u6570\u636e<br \/>\n\u5185\u6838\u7f51\u7edc\u534f\u8bae\u6808\u7ee7\u7eed\u89e3\u6790 TCP \u62a5\u6587<br \/>\n\u5185\u6838\u7ee7\u7eed\u7ef4\u62a4 Socket \u7f13\u51b2\u533a<br \/>\n\u5176\u4ed6\u8fdb\u7a0b\u548c\u7ebf\u7a0b\u7ee7\u7eed\u8fd0\u884c<\/p>\n<p>\u5f53\u6570\u636e\u8fdb\u5165 Socket \u63a5\u6536\u7f13\u51b2\u533a\u540e&#xff0c;\u5185\u6838\u4f1a\u5524\u9192\u7b49\u5f85\u8be5 Socket \u7684\u7ebf\u7a0b\u3002<\/p>\n<hr \/>\n<h3>4.5 \u963b\u585e\u7684\u4e0d\u662f\u8fdc\u7aef\u7a0b\u5e8f<\/h3>\n<p>\u672c\u5730\u7ebf\u7a0b\u963b\u585e\u5728 recv() \u4e0a&#xff0c;\u5e76\u4e0d\u4f1a\u8ba9\u8fdc\u7aef\u7a0b\u5e8f\u81ea\u52a8\u505c\u6b62\u8fd0\u884c\u3002<\/p>\n<p>\u8fdc\u7aef\u4ecd\u7136\u53ef\u4ee5&#xff1a;<\/p>\n<p>\u7ee7\u7eed\u53d1\u9001\u6570\u636e<br \/>\n\u7ee7\u7eed\u6267\u884c\u8ba1\u7b97<br \/>\n\u5173\u95ed\u8fde\u63a5<br \/>\n\u53d1\u9001 FIN \u6216 RST<\/p>\n<hr \/>\n<h3>4.6 \u963b\u585e I\/O \u7684\u51c6\u786e\u603b\u7ed3<\/h3>\n<p>\u963b\u585e I\/O&#xff1a;<\/p>\n<p>\u963b\u585e\u5f53\u524d\u7ebf\u7a0b\u7684\u540e\u7eed\u6267\u884c<br \/>\n\u4e0d\u6301\u7eed\u5360\u7528 CPU \u6267\u884c\u8f6e\u8be2<br \/>\n\u4e0d\u963b\u585e\u5176\u4ed6\u53ef\u8fd0\u884c\u7ebf\u7a0b<br \/>\n\u4e0d\u963b\u585e\u6574\u4e2a\u64cd\u4f5c\u7cfb\u7edf<br \/>\n\u4e0d\u963b\u585e\u7f51\u5361\u548c\u5185\u6838\u534f\u8bae\u6808<\/p>\n<p>\u53ef\u4ee5\u8bb0\u6210\u4e00\u53e5\u8bdd&#xff1a;<\/p>\n<p>\u963b\u585e I\/O \u5361\u4f4f\u7684\u662f\u5f53\u524d\u7ebf\u7a0b\u7684\u4ee3\u7801\u6267\u884c&#xff0c;\u4e0d\u662f\u6574\u53f0\u8ba1\u7b97\u673a\u3002<\/p>\n<hr \/>\n<h2>\u4e94\u3001\u201c\u963b\u585e\u201d\u548c\u201c\u6302\u8d77\u201d\u662f\u5426\u5b8c\u5168\u76f8\u540c&#xff1f;<\/h2>\n<p>\u5728\u5f88\u591a\u53e3\u8bed\u5316\u89e3\u91ca\u4e2d&#xff0c;\u4f1a\u628a\u963b\u585e\u7ebf\u7a0b\u79f0\u4e3a\u201c\u6302\u8d77\u7ebf\u7a0b\u201d\u3002<\/p>\n<p>\u8fd9\u79cd\u8bf4\u6cd5\u4fbf\u4e8e\u7406\u89e3&#xff0c;\u4f46\u4ece\u64cd\u4f5c\u7cfb\u7edf\u672f\u8bed\u4e0a\u770b\u5e76\u4e0d\u5b8c\u5168\u4e25\u8c28\u3002<\/p>\n<p>\u963b\u585e I\/O \u4e2d\u7684\u7ebf\u7a0b\u901a\u5e38\u8fdb\u5165\u7684\u662f&#xff1a;<\/p>\n<p>\u7b49\u5f85\u72b6\u6001<br \/>\n\u7761\u7720\u72b6\u6001<br \/>\nBlocked \/ Sleeping \/ Waiting<\/p>\n<p>\u800c\u201c\u6302\u8d77\u201d\u6709\u65f6\u4e13\u95e8\u8868\u793a&#xff1a;<\/p>\n<p>Suspended<br \/>\nStopped<br \/>\n\u88ab\u8c03\u8bd5\u5668\u6682\u505c<br \/>\n\u6536\u5230 SIGSTOP<br \/>\n\u88ab\u6362\u51fa\u5185\u5b58<\/p>\n<p>\u56e0\u6b64&#xff0c;\u5728\u8ba8\u8bba Linux I\/O \u65f6&#xff0c;\u66f4\u51c6\u786e\u7684\u8868\u8fbe\u662f&#xff1a;<\/p>\n<p>\u5f53\u524d\u7ebf\u7a0b\u56e0\u4e3a\u7b49\u5f85 I\/O \u6761\u4ef6\u800c\u8fdb\u5165\u7761\u7720\u6216\u7b49\u5f85\u72b6\u6001\u3002<\/p>\n<p>\u800c\u4e0d\u662f\u7b80\u5355\u5730\u8bf4\u7ebf\u7a0b\u8fdb\u5165\u4e86\u67d0\u79cd\u7edf\u4e00\u7684\u201c\u6302\u8d77\u6001\u201d\u3002<\/p>\n<hr \/>\n<h2>\u516d\u3001\u963b\u585e\u7ebf\u7a0b\u5728\u7b49\u5f85\u65f6\u662f\u5426\u5360\u7528 CPU&#xff1f;<\/h2>\n<p>\u901a\u5e38\u4e0d\u4f1a\u6301\u7eed\u5360\u7528 CPU\u3002<\/p>\n<p>\u5f53\u7ebf\u7a0b\u56e0\u4e3a\u963b\u585e I\/O \u8fdb\u5165\u7b49\u5f85\u72b6\u6001\u540e&#xff0c;\u5b83\u4e0d\u4f1a\u7559\u5728 CPU \u4e0a\u6267\u884c\u5982\u4e0b\u5faa\u73af&#xff1a;<\/p>\n<p><span class=\"token keyword\">while<\/span> <span class=\"token punctuation\">(<\/span>\u6ca1\u6709\u6570\u636e<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    \u7ee7\u7eed\u68c0\u67e5<span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<p>\u5185\u6838\u4f1a\u8ba9\u5b83\u79bb\u5f00\u5f53\u524d CPU \u7684\u8fd0\u884c\u72b6\u6001&#xff0c;\u7531\u8c03\u5ea6\u5668\u9009\u62e9\u5176\u4ed6\u53ef\u8fd0\u884c\u4efb\u52a1\u3002<\/p>\n<p>\u6982\u5ff5\u4e0a\u7684\u5185\u6838\u903b\u8f91\u7c7b\u4f3c&#xff1a;<\/p>\n<p><span class=\"token keyword\">for<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">;<\/span><span class=\"token punctuation\">;<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token function\">socket_has_data<\/span><span class=\"token punctuation\">(<\/span>sock<span class=\"token punctuation\">)<\/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>    <span class=\"token function\">add_current_to_wait_queue<\/span><span class=\"token punctuation\">(<\/span>sock<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">set_current_state<\/span><span class=\"token punctuation\">(<\/span>SLEEPING<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">schedule<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<p>\u771f\u5b9e Linux \u5185\u6838\u5b9e\u73b0\u8981\u590d\u6742\u5f97\u591a&#xff0c;\u5e76\u4e14\u4f1a\u968f\u5185\u6838\u7248\u672c\u3001\u6587\u4ef6\u7c7b\u578b\u548c\u534f\u8bae\u800c\u53d8\u5316&#xff0c;\u4f46\u6838\u5fc3\u601d\u60f3\u662f&#xff1a;<\/p>\n<p>\u52a0\u5165\u7b49\u5f85\u961f\u5217<br \/>\n\u8bbe\u7f6e\u7b49\u5f85\u72b6\u6001<br \/>\n\u8ba9\u51fa CPU<br \/>\n\u6761\u4ef6\u6ee1\u8db3\u540e\u88ab\u5524\u9192<\/p>\n<hr \/>\n<h2>\u4e03\u3001\u963b\u585e I\/O \u662f\u5426\u4e00\u5b9a\u4f1a\u6c38\u4e45\u963b\u585e&#xff1f;<\/h2>\n<p>\u4e0d\u4e00\u5b9a\u3002<\/p>\n<p>\u963b\u585e\u7cfb\u7edf\u8c03\u7528\u53ef\u80fd\u56e0\u4e3a\u4ee5\u4e0b\u6761\u4ef6\u8fd4\u56de&#xff1a;<\/p>\n<p>1. \u6570\u636e\u5230\u8fbe<br \/>\n2. \u5bf9\u7aef\u6b63\u5e38\u5173\u95ed\u8fde\u63a5<br \/>\n3. \u8fde\u63a5\u53d1\u751f\u9519\u8bef<br \/>\n4. \u6536\u5230\u53ef\u5904\u7406\u4e2d\u65ad\u4fe1\u53f7<br \/>\n5. \u8bbe\u7f6e\u7684\u8d85\u65f6\u65f6\u95f4\u5230\u8fbe<\/p>\n<p>\u4f8b\u5982&#xff0c;\u53ef\u4ee5\u4f7f\u7528 SO_RCVTIMEO \u8bbe\u7f6e Socket \u63a5\u6536\u8d85\u65f6&#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;sys\/socket.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;sys\/time.h&gt;<\/span><\/span><\/p>\n<p>timeval timeout<span class=\"token punctuation\">{<\/span><span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><br \/>\ntimeout<span class=\"token punctuation\">.<\/span>tv_sec <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">5<\/span><span class=\"token punctuation\">;<\/span><br \/>\ntimeout<span class=\"token punctuation\">.<\/span>tv_usec <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token function\">setsockopt<\/span><span class=\"token punctuation\">(<\/span><br \/>\n    fd<span class=\"token punctuation\">,<\/span><br \/>\n    SOL_SOCKET<span class=\"token punctuation\">,<\/span><br \/>\n    SO_RCVTIMEO<span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token operator\">&amp;<\/span>timeout<span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>timeout<span class=\"token punctuation\">)<\/span><br \/>\n<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>\u5982\u679c\u5728\u89c4\u5b9a\u65f6\u95f4\u5185\u6ca1\u6709\u53ef\u8bfb\u53d6\u7684\u6570\u636e&#xff0c;recv() \u901a\u5e38\u8fd4\u56de&#xff1a;<\/p>\n<p><span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><\/p>\n<p>\u5e76\u5c06 errno \u8bbe\u7f6e\u4e3a&#xff1a;<\/p>\n<p>EAGAIN<\/p>\n<p>\u6216\u8005&#xff1a;<\/p>\n<p>EWOULDBLOCK<\/p>\n<p>\u4e0d\u80fd\u7b3c\u7edf\u5730\u8ba4\u4e3a Socket \u63a5\u6536\u8d85\u65f6\u4e00\u5b9a\u8fd4\u56de ETIMEDOUT\u3002\u4e0d\u540c\u7cfb\u7edf\u8c03\u7528\u548c\u4e0d\u540c\u9519\u8bef\u573a\u666f\u53ef\u80fd\u4f7f\u7528\u4e0d\u540c\u9519\u8bef\u7801\u3002<\/p>\n<hr \/>\n<h2>\u516b\u3001\u4ec0\u4e48\u662f\u975e\u963b\u585e I\/O&#xff1f;<\/h2>\n<h3>8.1 \u975e\u963b\u585e I\/O \u7684\u5b9a\u4e49<\/h3>\n<p>\u975e\u963b\u585e I\/O \u662f\u6307&#xff1a;<\/p>\n<p>\u5f53\u7cfb\u7edf\u8c03\u7528\u6682\u65f6\u65e0\u6cd5\u7acb\u5373\u5b8c\u6210\u65f6&#xff0c;\u4e0d\u8ba9\u5f53\u524d\u7ebf\u7a0b\u5728\u8be5\u7cfb\u7edf\u8c03\u7528\u4e2d\u7761\u7720\u7b49\u5f85&#xff0c;\u800c\u662f\u7acb\u5373\u8fd4\u56de\u4e00\u4e2a\u201c\u5f53\u524d\u65e0\u6cd5\u5b8c\u6210\u201d\u7684\u7ed3\u679c\u3002<\/p>\n<p>\u5bf9\u4e8e\u975e\u963b\u585e Socket&#xff0c;\u5982\u679c\u63a5\u6536\u7f13\u51b2\u533a\u4e3a\u7a7a&#xff1a;<\/p>\n<p>ssize_t n <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">recv<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> buffer<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>buffer<span class=\"token punctuation\">)<\/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>\u4f1a\u7acb\u5373\u8fd4\u56de&#xff1a;<\/p>\n<p>n <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><\/p>\n<p>\u5e76\u8bbe\u7f6e&#xff1a;<\/p>\n<p>errno <span class=\"token operator\">&#061;&#061;<\/span> EAGAIN<\/p>\n<p>\u6216\u8005&#xff1a;<\/p>\n<p>errno <span class=\"token operator\">&#061;&#061;<\/span> EWOULDBLOCK<\/p>\n<p>\u8fd9\u8868\u793a&#xff1a;<\/p>\n<p>\u5f53\u524d\u6ca1\u6709\u6570\u636e&#xff0c;\u4e0d\u4ee3\u8868\u8fde\u63a5\u53d1\u751f\u4e86\u9519\u8bef&#xff0c;\u8bf7\u7a0d\u540e\u518d\u8bd5\u3002<\/p>\n<hr \/>\n<h3>8.2 \u5982\u4f55\u5c06 Socket \u8bbe\u7f6e\u4e3a\u975e\u963b\u585e&#xff1f;<\/h3>\n<p>\u53ef\u4ee5\u4f7f\u7528 fcntl()&#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;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;stdexcept&gt;<\/span><\/span><\/p>\n<p><span class=\"token keyword\">void<\/span> <span class=\"token function\">set_nonblocking<\/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> flags <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 number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>flags <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token keyword\">throw<\/span> std<span class=\"token double-colon punctuation\">::<\/span><span class=\"token function\">runtime_error<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;fcntl(F_GETFL) failed&#034;<\/span><span class=\"token punctuation\">)<\/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><span class=\"token function\">fcntl<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> F_SETFL<span class=\"token punctuation\">,<\/span> flags <span class=\"token operator\">|<\/span> O_NONBLOCK<span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token keyword\">throw<\/span> std<span class=\"token double-colon punctuation\">::<\/span><span class=\"token function\">runtime_error<\/span><span class=\"token punctuation\">(<\/span><span class=\"token string\">&#034;fcntl(F_SETFL) failed&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<p>\u6ce8\u610f\u4e0d\u80fd\u76f4\u63a5\u5199\u6210&#xff1a;<\/p>\n<p><span class=\"token function\">fcntl<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> F_SETFL<span class=\"token punctuation\">,<\/span> O_NONBLOCK<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>\u56e0\u4e3a\u8fd9\u6837\u53ef\u80fd\u8986\u76d6\u6587\u4ef6\u63cf\u8ff0\u7b26\u4e0a\u539f\u6709\u7684\u5176\u4ed6\u72b6\u6001\u6807\u5fd7\u3002<\/p>\n<p>\u6b63\u786e\u65b9\u5f0f\u662f&#xff1a;<\/p>\n<p>\u539f\u6709\u6807\u5fd7 <span class=\"token operator\">|<\/span> O_NONBLOCK<\/p>\n<hr \/>\n<h3>8.3 \u975e\u963b\u585e\u8bfb\u53d6\u793a\u4f8b<\/h3>\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;cerrno&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;cstring&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;iostream&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;sys\/socket.h&gt;<\/span><\/span><\/p>\n<p><span class=\"token keyword\">void<\/span> <span class=\"token function\">try_read<\/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\">char<\/span> buffer<span class=\"token punctuation\">[<\/span><span class=\"token number\">4096<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    ssize_t n <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">recv<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> buffer<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>buffer<span class=\"token punctuation\">)<\/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\">if<\/span> <span class=\"token punctuation\">(<\/span>n <span class=\"token operator\">&gt;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;\u8bfb\u53d6\u5230 &#034;<\/span> <span class=\"token operator\">&lt;&lt;<\/span> n <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034; \u5b57\u8282\\\\n&#034;<\/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 keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>n <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        std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;\u5bf9\u7aef\u6b63\u5e38\u5173\u95ed\u8fde\u63a5\\\\n&#034;<\/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 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        std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;\u5f53\u524d\u6ca1\u6709\u6570\u636e&#xff0c;\u7a0d\u540e\u518d\u5c1d\u8bd5\\\\n&#034;<\/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 keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>errno <span class=\"token operator\">&#061;&#061;<\/span> EINTR<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;\u7cfb\u7edf\u8c03\u7528\u88ab\u4fe1\u53f7\u4e2d\u65ad\\\\n&#034;<\/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>    std<span class=\"token double-colon punctuation\">::<\/span>cerr <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;recv failed: &#034;<\/span><br \/>\n              <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span><span class=\"token function\">strerror<\/span><span class=\"token punctuation\">(<\/span>errno<span class=\"token punctuation\">)<\/span><br \/>\n              <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token char\">&#039;\\\\n&#039;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<p>\u975e\u963b\u585e recv() \u4e0d\u4f1a\u56e0\u4e3a\u201c\u5f53\u524d\u6ca1\u6709\u6570\u636e\u201d\u800c\u8ba9\u7ebf\u7a0b\u7761\u7720\u5728\u8fd9\u4e2a\u8c03\u7528\u4e2d\u3002<\/p>\n<hr \/>\n<h2>\u4e5d\u3001\u975e\u963b\u585e I\/O \u662f\u5426\u610f\u5473\u7740\u4e00\u76f4\u5360\u7528 CPU&#xff1f;<\/h2>\n<p>\u4e0d\u610f\u5473\u7740\u3002<\/p>\n<p>\u975e\u963b\u585e\u53ea\u662f\u8bf4&#xff1a;<\/p>\n<p>\u5f53\u524d\u8fd9\u4e00\u6b21 I\/O \u7cfb\u7edf\u8c03\u7528\u65e0\u6cd5\u7acb\u5373\u5b8c\u6210\u65f6&#xff0c;\u4f1a\u7acb\u5373\u8fd4\u56de\u3002<\/p>\n<p>\u5b83\u6ca1\u6709\u89c4\u5b9a\u8c03\u7528\u8005\u63a5\u4e0b\u6765\u5fc5\u987b\u600e\u6837\u505a\u3002<\/p>\n<p>\u8c03\u7528\u8005\u53ef\u4ee5&#xff1a;<\/p>\n<p>1. \u7acb\u5373\u518d\u6b21\u8c03\u7528&#xff0c;\u5f62\u6210\u5fd9\u8f6e\u8be2<br \/>\n2. \u5148\u5904\u7406\u5176\u4ed6\u4efb\u52a1&#xff0c;\u7a0d\u540e\u91cd\u8bd5<br \/>\n3. \u4f7f\u7528 select\u3001poll\u3001epoll \u7b49\u5f85\u5c31\u7eea\u4e8b\u4ef6<br \/>\n4. \u4f7f\u7528\u5b9a\u65f6\u5668\u7a0d\u540e\u91cd\u8bd5<br \/>\n5. \u5c06\u63a7\u5236\u6743\u4ea4\u8fd8\u4e8b\u4ef6\u5faa\u73af<\/p>\n<p>\u56e0\u6b64&#xff0c;\u4e0b\u9762\u8fd9\u79cd\u5199\u6cd5\u4f1a\u5fd9\u7b49&#xff1a;<\/p>\n<p><span class=\"token keyword\">while<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token boolean\">true<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    ssize_t n <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">recv<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> buffer<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>buffer<span class=\"token punctuation\">)<\/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\">if<\/span> <span class=\"token punctuation\">(<\/span>n <span class=\"token operator\">&gt;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">process<\/span><span class=\"token punctuation\">(<\/span>buffer<span class=\"token punctuation\">,<\/span> n<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span> <span class=\"token keyword\">else<\/span> <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><br \/>\n               <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> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token comment\">\/\/ \u4ec0\u4e48\u90fd\u4e0d\u505a&#xff0c;\u7acb\u523b\u7ee7\u7eed\u5faa\u73af<\/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 punctuation\">}<\/span><\/p>\n<p>\u5176\u884c\u4e3a\u662f&#xff1a;<\/p>\n<p>recv()<br \/>\n  \u2502<br \/>\n  \u251c\u2500\u2500 EAGAIN<br \/>\n  \u25bc<br \/>\nrecv()<br \/>\n  \u2502<br \/>\n  \u251c\u2500\u2500 EAGAIN<br \/>\n  \u25bc<br \/>\nrecv()<br \/>\n  \u2502<br \/>\n  \u251c\u2500\u2500 EAGAIN<br \/>\n  \u25bc<br \/>\n\u6301\u7eed\u5360\u7528 CPU<\/p>\n<p>\u4f46\u95ee\u9898\u4e0d\u5728\u4e8e\u201c\u975e\u963b\u585e I\/O \u5fc5\u7136\u6d6a\u8d39 CPU\u201d&#xff0c;\u800c\u5728\u4e8e\u7a0b\u5e8f\u91c7\u7528\u4e86\u9519\u8bef\u7684\u9ad8\u9891\u8f6e\u8be2\u7b56\u7565\u3002<\/p>\n<p>\u6b63\u786e\u7684\u9ad8\u5e76\u53d1\u505a\u6cd5\u901a\u5e38\u662f&#xff1a;<\/p>\n<p>\u975e\u963b\u585e Socket<br \/>\n      &#043;<br \/>\nI\/O \u591a\u8def\u590d\u7528<br \/>\n      &#043;<br \/>\n\u4e8b\u4ef6\u5faa\u73af<\/p>\n<hr \/>\n<h2>\u5341\u3001\u963b\u585e I\/O \u548c\u975e\u963b\u585e I\/O \u7684\u6838\u5fc3\u533a\u522b<\/h2>\n<table>\n<tr>\u6bd4\u8f83\u7ef4\u5ea6\u963b\u585e I\/O\u975e\u963b\u585e I\/O<\/tr>\n<tbody>\n<tr>\n<td>\u5f53\u524d\u6ca1\u6709\u6570\u636e<\/td>\n<td>\u7cfb\u7edf\u8c03\u7528\u7b49\u5f85<\/td>\n<td>\u7cfb\u7edf\u8c03\u7528\u7acb\u5373\u8fd4\u56de<\/td>\n<\/tr>\n<tr>\n<td>\u5f53\u524d\u7ebf\u7a0b<\/td>\n<td>\u8fdb\u5165\u7b49\u5f85\u72b6\u6001<\/td>\n<td>\u53ef\u4ee5\u7ee7\u7eed\u6267\u884c\u5176\u4ed6\u4ee3\u7801<\/td>\n<\/tr>\n<tr>\n<td>\u8fd4\u56de\u7ed3\u679c<\/td>\n<td>\u6570\u636e\u3001\u5173\u95ed\u3001\u9519\u8bef\u3001\u4fe1\u53f7\u6216\u8d85\u65f6<\/td>\n<td>\u901a\u5e38\u8fd4\u56de -1 \u548c EAGAIN<\/td>\n<\/tr>\n<tr>\n<td>\u7b49\u5f85\u671f\u95f4 CPU<\/td>\n<td>\u5f53\u524d\u7ebf\u7a0b\u901a\u5e38\u4e0d\u5360\u7528 CPU<\/td>\n<td>\u7531\u7a0b\u5e8f\u8bbe\u8ba1\u51b3\u5b9a<\/td>\n<\/tr>\n<tr>\n<td>\u662f\u5426\u53ef\u80fd\u5fd9\u7b49<\/td>\n<td>\u901a\u5e38\u4e0d\u4f1a<\/td>\n<td>\u9519\u8bef\u8f6e\u8be2\u65f6\u53ef\u80fd\u53d1\u751f<\/td>\n<\/tr>\n<tr>\n<td>\u7f16\u7a0b\u590d\u6742\u5ea6<\/td>\n<td>\u8f83\u4f4e<\/td>\n<td>\u8f83\u9ad8<\/td>\n<\/tr>\n<tr>\n<td>\u5178\u578b\u6a21\u578b<\/td>\n<td>\u4e00\u8fde\u63a5\u4e00\u7ebf\u7a0b<\/td>\n<td>\u4e8b\u4ef6\u5faa\u73af<\/td>\n<\/tr>\n<tr>\n<td>\u9ad8\u5e76\u53d1\u6269\u5c55\u6027<\/td>\n<td>\u53d7\u7ebf\u7a0b\u6570\u91cf\u9650\u5236<\/td>\n<td>\u901a\u5e38\u66f4\u597d<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<hr \/>\n<h2>\u5341\u4e00\u3001\u963b\u585e I\/O \u7684\u5b8c\u6574\u670d\u52a1\u5668\u793a\u4f8b<\/h2>\n<p>\u4e0b\u9762\u662f\u4e00\u4e2a\u6700\u7b80\u5355\u7684\u963b\u585e\u5f0f TCP \u670d\u52a1\u7aef\u3002<\/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;arpa\/inet.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;cerrno&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;cstring&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;iostream&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;sys\/socket.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><\/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 keyword\">int<\/span> listen_fd <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">socket<\/span><span class=\"token punctuation\">(<\/span>AF_INET<span class=\"token punctuation\">,<\/span> SOCK_STREAM<span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>listen_fd <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        std<span class=\"token double-colon punctuation\">::<\/span>cerr <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;socket failed: &#034;<\/span><br \/>\n                  <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span><span class=\"token function\">strerror<\/span><span class=\"token punctuation\">(<\/span>errno<span class=\"token punctuation\">)<\/span><br \/>\n                  <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token char\">&#039;\\\\n&#039;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token keyword\">int<\/span> reuse <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token function\">setsockopt<\/span><span class=\"token punctuation\">(<\/span><br \/>\n            listen_fd<span class=\"token punctuation\">,<\/span><br \/>\n            SOL_SOCKET<span class=\"token punctuation\">,<\/span><br \/>\n            SO_REUSEADDR<span class=\"token punctuation\">,<\/span><br \/>\n            <span class=\"token operator\">&amp;<\/span>reuse<span class=\"token punctuation\">,<\/span><br \/>\n            <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>reuse<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        std<span class=\"token double-colon punctuation\">::<\/span>cerr <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;setsockopt failed: &#034;<\/span><br \/>\n                  <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span><span class=\"token function\">strerror<\/span><span class=\"token punctuation\">(<\/span>errno<span class=\"token punctuation\">)<\/span><br \/>\n                  <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token char\">&#039;\\\\n&#039;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token function\">close<\/span><span class=\"token punctuation\">(<\/span>listen_fd<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    sockaddr_in server_addr<span class=\"token punctuation\">{<\/span><span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    server_addr<span class=\"token punctuation\">.<\/span>sin_family <span class=\"token operator\">&#061;<\/span> AF_INET<span class=\"token punctuation\">;<\/span><br \/>\n    server_addr<span class=\"token punctuation\">.<\/span>sin_port <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">htons<\/span><span class=\"token punctuation\">(<\/span><span class=\"token number\">8888<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    server_addr<span class=\"token punctuation\">.<\/span>sin_addr<span class=\"token punctuation\">.<\/span>s_addr <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">htonl<\/span><span class=\"token punctuation\">(<\/span>INADDR_ANY<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token function\">bind<\/span><span class=\"token punctuation\">(<\/span><br \/>\n            listen_fd<span class=\"token punctuation\">,<\/span><br \/>\n            <span class=\"token generic-function\"><span class=\"token function\">reinterpret_cast<\/span><span class=\"token generic class-name\"><span class=\"token operator\">&lt;<\/span>sockaddr<span class=\"token operator\">*<\/span><span class=\"token operator\">&gt;<\/span><\/span><\/span><span class=\"token punctuation\">(<\/span><span class=\"token operator\">&amp;<\/span>server_addr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span><br \/>\n            <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>server_addr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        std<span class=\"token double-colon punctuation\">::<\/span>cerr <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;bind failed: &#034;<\/span><br \/>\n                  <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span><span class=\"token function\">strerror<\/span><span class=\"token punctuation\">(<\/span>errno<span class=\"token punctuation\">)<\/span><br \/>\n                  <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token char\">&#039;\\\\n&#039;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token function\">close<\/span><span class=\"token punctuation\">(<\/span>listen_fd<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token number\">1<\/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><span class=\"token function\">listen<\/span><span class=\"token punctuation\">(<\/span>listen_fd<span class=\"token punctuation\">,<\/span> SOMAXCONN<span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        std<span class=\"token double-colon punctuation\">::<\/span>cerr <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;listen failed: &#034;<\/span><br \/>\n                  <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span><span class=\"token function\">strerror<\/span><span class=\"token punctuation\">(<\/span>errno<span class=\"token punctuation\">)<\/span><br \/>\n                  <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token char\">&#039;\\\\n&#039;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token function\">close<\/span><span class=\"token punctuation\">(<\/span>listen_fd<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;server listening on 0.0.0.0:8888\\\\n&#034;<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    sockaddr_in client_addr<span class=\"token punctuation\">{<\/span><span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    socklen_t client_len <span class=\"token operator\">&#061;<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>client_addr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">int<\/span> client_fd <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">accept<\/span><span class=\"token punctuation\">(<\/span><br \/>\n        listen_fd<span class=\"token punctuation\">,<\/span><br \/>\n        <span class=\"token generic-function\"><span class=\"token function\">reinterpret_cast<\/span><span class=\"token generic class-name\"><span class=\"token operator\">&lt;<\/span>sockaddr<span class=\"token operator\">*<\/span><span class=\"token operator\">&gt;<\/span><\/span><\/span><span class=\"token punctuation\">(<\/span><span class=\"token operator\">&amp;<\/span>client_addr<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span><br \/>\n        <span class=\"token operator\">&amp;<\/span>client_len<br \/>\n    <span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>client_fd <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        std<span class=\"token double-colon punctuation\">::<\/span>cerr <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;accept failed: &#034;<\/span><br \/>\n                  <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span><span class=\"token function\">strerror<\/span><span class=\"token punctuation\">(<\/span>errno<span class=\"token punctuation\">)<\/span><br \/>\n                  <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token char\">&#039;\\\\n&#039;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token function\">close<\/span><span class=\"token punctuation\">(<\/span>listen_fd<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token keyword\">char<\/span> buffer<span class=\"token punctuation\">[<\/span><span class=\"token number\">4096<\/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 boolean\">true<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token comment\">\/\/ client_fd \u9ed8\u8ba4\u662f\u963b\u585e Socket\u3002<\/span><br \/>\n        <span class=\"token comment\">\/\/ \u5f53\u524d\u6ca1\u6709\u6570\u636e\u65f6&#xff0c;\u5f53\u524d\u7ebf\u7a0b\u505c\u5728 recv() \u4e2d\u7b49\u5f85\u3002<\/span><br \/>\n        ssize_t n <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">recv<\/span><span class=\"token punctuation\">(<\/span><br \/>\n            client_fd<span class=\"token punctuation\">,<\/span><br \/>\n            buffer<span class=\"token punctuation\">,<\/span><br \/>\n            <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>buffer<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span><br \/>\n            <span class=\"token number\">0<\/span><br \/>\n        <span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>        <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>n <span class=\"token operator\">&gt;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n            std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;received &#034;<\/span> <span class=\"token operator\">&lt;&lt;<\/span> n <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034; bytes\\\\n&#034;<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>            ssize_t sent <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">send<\/span><span class=\"token punctuation\">(<\/span>client_fd<span class=\"token punctuation\">,<\/span> buffer<span class=\"token punctuation\">,<\/span> n<span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n            <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>sent <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n                std<span class=\"token double-colon punctuation\">::<\/span>cerr <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;send failed: &#034;<\/span><br \/>\n                          <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span><span class=\"token function\">strerror<\/span><span class=\"token punctuation\">(<\/span>errno<span class=\"token punctuation\">)<\/span><br \/>\n                          <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token char\">&#039;\\\\n&#039;<\/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>            <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>n <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            std<span class=\"token double-colon punctuation\">::<\/span>cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;client closed connection\\\\n&#034;<\/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>        <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>errno <span class=\"token operator\">&#061;&#061;<\/span> EINTR<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>        std<span class=\"token double-colon punctuation\">::<\/span>cerr <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;recv failed: &#034;<\/span><br \/>\n                  <span class=\"token operator\">&lt;&lt;<\/span> std<span class=\"token double-colon punctuation\">::<\/span><span class=\"token function\">strerror<\/span><span class=\"token punctuation\">(<\/span>errno<span class=\"token punctuation\">)<\/span><br \/>\n                  <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token char\">&#039;\\\\n&#039;<\/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>    <span class=\"token function\">close<\/span><span class=\"token punctuation\">(<\/span>client_fd<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">close<\/span><span class=\"token punctuation\">(<\/span>listen_fd<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <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<p>\u8fd9\u4e2a\u670d\u52a1\u5668\u53ea\u80fd\u5728\u5f53\u524d\u7ebf\u7a0b\u4e2d\u5904\u7406\u4e00\u4e2a\u5df2\u8fde\u63a5\u5ba2\u6237\u7aef\u3002<\/p>\n<p>\u5f53\u7ebf\u7a0b\u963b\u585e\u5728\u67d0\u4e2a\u5ba2\u6237\u7aef\u7684 recv() \u4e0a\u65f6&#xff0c;\u5b83\u65e0\u6cd5\u5728\u540c\u4e00\u7ebf\u7a0b\u4e2d\u5904\u7406\u5176\u4ed6\u8fde\u63a5\u3002<\/p>\n<p>\u89e3\u51b3\u65b9\u5f0f\u53ef\u4ee5\u662f&#xff1a;<\/p>\n<p>\u65b9\u5f0f\u4e00&#xff1a;\u4e00\u4e2a\u8fde\u63a5\u5bf9\u5e94\u4e00\u4e2a\u8fdb\u7a0b<br \/>\n\u65b9\u5f0f\u4e8c&#xff1a;\u4e00\u4e2a\u8fde\u63a5\u5bf9\u5e94\u4e00\u4e2a\u7ebf\u7a0b<br \/>\n\u65b9\u5f0f\u4e09&#xff1a;\u7ebf\u7a0b\u6c60<br \/>\n\u65b9\u5f0f\u56db&#xff1a;\u975e\u963b\u585e I\/O &#043; I\/O \u591a\u8def\u590d\u7528<br \/>\n\u65b9\u5f0f\u4e94&#xff1a;\u771f\u6b63\u7684\u5f02\u6b65 I\/O<\/p>\n<hr \/>\n<h2>\u5341\u4e8c\u3001\u4ec0\u4e48\u662f I\/O \u591a\u8def\u590d\u7528&#xff1f;<\/h2>\n<p>I\/O \u591a\u8def\u590d\u7528\u7684\u6838\u5fc3\u76ee\u6807\u662f&#xff1a;<\/p>\n<p>\u4f7f\u7528\u4e00\u4e2a\u7ebf\u7a0b\u7b49\u5f85\u591a\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26&#xff0c;\u53ea\u5728\u67d0\u4e9b\u6587\u4ef6\u63cf\u8ff0\u7b26\u5df2\u7ecf\u5c31\u7eea\u65f6&#xff0c;\u518d\u5bf9\u5b83\u4eec\u6267\u884c\u5177\u4f53\u7684 I\/O \u64cd\u4f5c\u3002<\/p>\n<p>Linux \u4e2d\u5e38\u89c1\u7684 I\/O \u591a\u8def\u590d\u7528\u63a5\u53e3\u5305\u62ec&#xff1a;<\/p>\n<p>select<br \/>\npoll<br \/>\nepoll<\/p>\n<p>\u4ee5 epoll \u4e3a\u4f8b&#xff1a;<\/p>\n<p>\u8fde\u63a5 1 \u2500\u2510<br \/>\n\u8fde\u63a5 2 \u2500\u2524<br \/>\n\u8fde\u63a5 3 \u2500\u2524<br \/>\n\u8fde\u63a5 4 \u2500\u2524<br \/>\n&#8230;      \u251c\u2500\u2500 epoll \u2500\u2500 \u901a\u77e5\u5e94\u7528\u7a0b\u5e8f\u54ea\u4e9b fd \u5df2\u5c31\u7eea<br \/>\n\u8fde\u63a5 N \u2500\u2518<\/p>\n<p>\u5e94\u7528\u7ebf\u7a0b\u4e0d\u518d\u5bf9\u4e00\u4e07\u4e2a Socket \u9010\u4e2a\u8c03\u7528 recv() \u8be2\u95ee\u3002<\/p>\n<p>\u800c\u662f\u8c03\u7528&#xff1a;<\/p>\n<p><span class=\"token function\">epoll_wait<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">.<\/span><span class=\"token punctuation\">.<\/span><span class=\"token punctuation\">.<\/span><span class=\"token punctuation\">)<\/span><\/p>\n<p>\u8ba9\u5185\u6838\u8fd4\u56de\u5df2\u7ecf\u5c31\u7eea\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u3002<\/p>\n<hr \/>\n<h3>12.1 epoll_wait() \u672c\u8eab\u53ef\u4ee5\u963b\u585e<\/h3>\n<p>\u4e00\u4e2a\u5e38\u89c1\u8bef\u533a\u662f&#xff1a;<\/p>\n<p>\u975e\u963b\u585e I\/O &#043; epoll<\/p>\n<p>\u6240\u4ee5\u6574\u4e2a\u7a0b\u5e8f\u4e2d\u6240\u6709\u8c03\u7528\u90fd\u4e0d\u4f1a\u963b\u585e\u3002<\/p>\n<p>\u5b9e\u9645\u4e0a&#xff0c;epoll_wait() \u901a\u5e38\u5c31\u662f\u4e00\u4e2a\u963b\u585e\u7b49\u5f85\u8c03\u7528&#xff1a;<\/p>\n<p><span class=\"token keyword\">int<\/span> ready_count <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">epoll_wait<\/span><span class=\"token punctuation\">(<\/span><br \/>\n    epoll_fd<span class=\"token punctuation\">,<\/span><br \/>\n    events<span class=\"token punctuation\">,<\/span><br \/>\n    max_events<span class=\"token punctuation\">,<\/span><br \/>\n    <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span><br \/>\n<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>\u6700\u540e\u4e00\u4e2a\u53c2\u6570\u4e3a -1 \u8868\u793a&#xff1a;<\/p>\n<p>\u5982\u679c\u5f53\u524d\u6ca1\u6709\u5c31\u7eea\u4e8b\u4ef6&#xff0c;\u5c31\u8ba9\u8c03\u7528\u7ebf\u7a0b\u7b49\u5f85\u3002<\/p>\n<p>\u56e0\u6b64&#xff0c;\u4e00\u4e2a\u5178\u578b\u4e8b\u4ef6\u5faa\u73af\u662f&#xff1a;<\/p>\n<p>epoll_wait() \u963b\u585e\u7b49\u5f85\u4e8b\u4ef6<br \/>\n          \u2502<br \/>\n          \u2502 \u67d0\u4e9b fd \u5c31\u7eea<br \/>\n          \u25bc<br \/>\nepoll_wait() \u8fd4\u56de<br \/>\n          \u2502<br \/>\n          \u25bc<br \/>\n\u5bf9\u5c31\u7eea fd \u6267\u884c\u975e\u963b\u585e recv()<br \/>\n          \u2502<br \/>\n          \u25bc<br \/>\n\u5904\u7406\u5b8c\u6bd5<br \/>\n          \u2502<br \/>\n          \u25bc<br \/>\n\u518d\u6b21\u8fdb\u5165 epoll_wait()<\/p>\n<p>\u8fd9\u79cd\u6a21\u578b\u5e76\u4e0d\u662f\u201c\u7ebf\u7a0b\u6c38\u8fdc\u4e0d\u963b\u585e\u201d&#xff0c;\u800c\u662f&#xff1a;<\/p>\n<p>\u7ebf\u7a0b\u96c6\u4e2d\u963b\u585e\u5728\u4e00\u4e2a\u80fd\u591f\u540c\u65f6\u7b49\u5f85\u5927\u91cf\u8fde\u63a5\u7684 epoll_wait() \u4e0a&#xff0c;\u800c\u4e0d\u662f\u963b\u585e\u5728\u67d0\u4e00\u4e2a\u5177\u4f53\u5ba2\u6237\u7aef\u7684 recv() \u4e0a\u3002<\/p>\n<hr \/>\n<h3>12.2 \u4e3a\u4ec0\u4e48\u914d\u5408 epoll \u4ecd\u7136\u8981\u8bbe\u7f6e O_NONBLOCK&#xff1f;<\/h3>\n<p>\u6709\u4eba\u53ef\u80fd\u8ba4\u4e3a&#xff1a;<\/p>\n<p>epoll \u5df2\u7ecf\u901a\u77e5\u8fd9\u4e2a fd \u53ef\u8bfb&#xff0c;\u76f4\u63a5\u4f7f\u7528\u963b\u585e recv() \u4e0d\u5c31\u53ef\u4ee5\u4e86\u5417&#xff1f;<\/p>\n<p>\u8fd9\u6837\u5e76\u4e0d\u7a33\u59a5\u3002<\/p>\n<p>\u56e0\u4e3a\u201c\u6536\u5230\u53ef\u8bfb\u901a\u77e5\u201d\u548c\u201c\u4e4b\u540e\u6267\u884c recv() \u65f6\u4e00\u5b9a\u4e0d\u4f1a\u7b49\u5f85\u201d\u5e76\u4e0d\u662f\u5b8c\u5168\u7b49\u4ef7\u7684\u3002<\/p>\n<p>\u4e2d\u95f4\u53ef\u80fd\u53d1\u751f&#xff1a;<\/p>\n<p>\u5176\u4ed6\u7ebf\u7a0b\u5148\u8bfb\u53d6\u4e86\u6570\u636e<br \/>\n\u4e8b\u4ef6\u72b6\u6001\u53d1\u751f\u53d8\u5316<br \/>\n\u9519\u8bef\u5904\u7406\u6216\u7ade\u6001\u6761\u4ef6<br \/>\n\u4e00\u6b21\u8bfb\u53d6\u6ca1\u6709\u53d6\u5b8c\u5b8c\u6574\u4e1a\u52a1\u6d88\u606f<br \/>\nET \u6a21\u5f0f\u4e0b\u9700\u8981\u6301\u7eed\u8bfb\u53d6<\/p>\n<p>\u56e0\u6b64&#xff0c;\u751f\u4ea7\u73af\u5883\u901a\u5e38\u4f7f\u7528&#xff1a;<\/p>\n<p>epoll &#043; O_NONBLOCK<\/p>\n<p>\u8bfb\u53d6\u65f6\u5faa\u73af\u5230 EAGAIN&#xff1a;<\/p>\n<p><span class=\"token keyword\">while<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token boolean\">true<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    ssize_t n <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">recv<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> buffer<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">sizeof<\/span><span class=\"token punctuation\">(<\/span>buffer<span class=\"token punctuation\">)<\/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\">if<\/span> <span class=\"token punctuation\">(<\/span>n <span class=\"token operator\">&gt;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">process_data<\/span><span class=\"token punctuation\">(<\/span>buffer<span class=\"token punctuation\">,<\/span> n<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>n <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 function\">close_connection<\/span><span class=\"token punctuation\">(<\/span>fd<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>    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>errno <span class=\"token operator\">&#061;&#061;<\/span> EINTR<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>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\">\/\/ \u5f53\u524d\u53ef\u8bfb\u53d6\u6570\u636e\u5df2\u7ecf\u53d6\u5b8c<\/span><br \/>\n        <span class=\"token keyword\">break<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token function\">close_connection<\/span><span class=\"token punctuation\">(<\/span>fd<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>\u7279\u522b\u662f\u5728 epoll ET&#xff0c;\u4e5f\u5c31\u662f\u8fb9\u7f18\u89e6\u53d1\u6a21\u5f0f\u4e0b&#xff0c;\u901a\u5e38\u5fc5\u987b\u4e00\u76f4\u8bfb\u53d6\u5230 EAGAIN\u3002<\/p>\n<hr \/>\n<h2>\u5341\u4e09\u3001epoll \u5c5e\u4e8e\u5f02\u6b65 I\/O \u5417&#xff1f;<\/h2>\n<p>\u4e25\u683c\u6765\u8bf4&#xff0c;\u4e0d\u5c5e\u4e8e\u3002<\/p>\n<p>epoll \u662f&#xff1a;<\/p>\n<p>I\/O \u5c31\u7eea\u901a\u77e5\u673a\u5236<br \/>\nI\/O \u591a\u8def\u590d\u7528\u673a\u5236<br \/>\nReactor \u6a21\u578b\u7684\u91cd\u8981\u57fa\u7840<\/p>\n<p>\u5b83\u901a\u77e5\u5e94\u7528\u7a0b\u5e8f&#xff1a;<\/p>\n<p>\u67d0\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\u73b0\u5728\u53ef\u80fd\u53ef\u4ee5\u8bfb\u53d6\u6216\u5199\u5165\u4e86\u3002<\/p>\n<p>\u4f46\u771f\u6b63\u7684\u6570\u636e\u8bfb\u53d6\u4ecd\u7136\u9700\u8981\u5e94\u7528\u7a0b\u5e8f\u4e3b\u52a8\u8c03\u7528&#xff1a;<\/p>\n<p><span class=\"token function\">recv<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><br \/>\n<span class=\"token function\">read<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><\/p>\n<p>\u4e5f\u5c31\u662f\u8bf4&#xff1a;<\/p>\n<p>epoll \u53ea\u901a\u77e5\u201c\u53ef\u4ee5\u505a\u201d<br \/>\n\u5e94\u7528\u7a0b\u5e8f\u4ecd\u7136\u9700\u8981\u4eb2\u81ea\u201c\u505a\u201d<\/p>\n<p>\u5176\u6d41\u7a0b\u662f&#xff1a;<\/p>\n<p>\u5185\u6838\u901a\u77e5&#xff1a;fd \u53ef\u8bfb<br \/>\n        \u2502<br \/>\n        \u25bc<br \/>\n\u5e94\u7528\u7a0b\u5e8f\u8c03\u7528 recv()<br \/>\n        \u2502<br \/>\n        \u25bc<br \/>\n\u5185\u6838\u628a\u6570\u636e\u590d\u5236\u5230\u7528\u6237\u7a7a\u95f4<br \/>\n        \u2502<br \/>\n        \u25bc<br \/>\nrecv() \u8fd4\u56de<\/p>\n<p>\u56e0\u6b64&#xff0c;epoll \u901a\u5e38\u88ab\u5f52\u7c7b\u4e3a&#xff1a;<\/p>\n<p>\u540c\u6b65 I\/O \u591a\u8def\u590d\u7528<\/p>\n<p>\u800c\u4e0d\u662f\u4e25\u683c\u610f\u4e49\u4e0a\u7684\u5f02\u6b65 I\/O\u3002<\/p>\n<hr \/>\n<h2>\u5341\u56db\u3001\u4ec0\u4e48\u662f\u540c\u6b65 I\/O&#xff1f;<\/h2>\n<h3>14.1 \u540c\u6b65 I\/O \u7684\u5b9a\u4e49<\/h3>\n<p>\u540c\u6b65 I\/O \u662f\u6307&#xff1a;<\/p>\n<p>\u5e94\u7528\u7a0b\u5e8f\u9700\u8981\u4e3b\u52a8\u6267\u884c I\/O \u7cfb\u7edf\u8c03\u7528&#xff0c;\u5e76\u4e14 I\/O \u64cd\u4f5c\u7684\u5173\u952e\u5b8c\u6210\u8fc7\u7a0b\u53d1\u751f\u5728\u8be5\u8c03\u7528\u8def\u5f84\u4e2d&#xff1b;\u64cd\u4f5c\u5b8c\u6210\u540e&#xff0c;\u7cfb\u7edf\u8c03\u7528\u624d\u628a\u7ed3\u679c\u4ea4\u7ed9\u5e94\u7528\u7a0b\u5e8f\u3002<\/p>\n<p>\u4f20\u7edf\u7684 read()\u3001recv() \u90fd\u5c5e\u4e8e\u540c\u6b65 I\/O\u3002<\/p>\n<p>\u65e0\u8bba Socket \u662f\u963b\u585e\u8fd8\u662f\u975e\u963b\u585e&#xff0c;\u771f\u6b63\u8bfb\u53d6\u6570\u636e\u65f6&#xff0c;\u90fd\u5fc5\u987b\u7531\u5e94\u7528\u7a0b\u5e8f\u6267\u884c&#xff1a;<\/p>\n<p><span class=\"token function\">recv<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> buffer<span class=\"token punctuation\">,<\/span> size<span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>\u5185\u6838\u5728\u8fd9\u4e2a\u8c03\u7528\u8fc7\u7a0b\u4e2d&#xff0c;\u5c06\u6570\u636e\u590d\u5236\u5230\u7528\u6237\u7f13\u51b2\u533a\u3002<\/p>\n<p>\u56e0\u6b64&#xff1a;<\/p>\n<p>\u963b\u585e recv()&#xff1a;\u540c\u6b65 I\/O<br \/>\n\u975e\u963b\u585e recv()&#xff1a;\u4ecd\u7136\u662f\u540c\u6b65 I\/O<br \/>\nepoll &#043; recv()&#xff1a;\u4ecd\u7136\u662f\u540c\u6b65 I\/O<\/p>\n<hr \/>\n<h3>14.2 \u540c\u6b65\u4e0d\u7b49\u4e8e\u963b\u585e<\/h3>\n<p>\u540c\u6b65 I\/O \u53ef\u4ee5\u662f\u963b\u585e\u7684&#xff1a;<\/p>\n<p><span class=\"token function\">recv<\/span><span class=\"token punctuation\">(<\/span>blocking_fd<span class=\"token punctuation\">,<\/span> buffer<span class=\"token punctuation\">,<\/span> size<span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>\u6ca1\u6709\u6570\u636e\u65f6&#xff0c;\u7ebf\u7a0b\u7b49\u5f85\u3002<\/p>\n<p>\u540c\u6b65 I\/O\u4e5f\u53ef\u4ee5\u662f\u975e\u963b\u585e\u7684&#xff1a;<\/p>\n<p><span class=\"token function\">recv<\/span><span class=\"token punctuation\">(<\/span>nonblocking_fd<span class=\"token punctuation\">,<\/span> buffer<span class=\"token punctuation\">,<\/span> size<span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>\u6ca1\u6709\u6570\u636e\u65f6&#xff0c;\u7acb\u5373\u8fd4\u56de EAGAIN\u3002<\/p>\n<p>\u4e24\u8005\u7684\u5171\u540c\u70b9\u662f&#xff1a;<\/p>\n<p>\u6700\u7ec8\u7684\u6570\u636e\u8bfb\u53d6\u4ecd\u7136\u7531\u5e94\u7528\u7a0b\u5e8f\u4e3b\u52a8\u8c03\u7528 recv() \u5b8c\u6210\u3002<\/p>\n<hr \/>\n<h2>\u5341\u4e94\u3001\u4ec0\u4e48\u662f\u5f02\u6b65 I\/O&#xff1f;<\/h2>\n<h3>15.1 \u5f02\u6b65 I\/O \u7684\u5b9a\u4e49<\/h3>\n<p>\u5f02\u6b65 I\/O \u662f\u6307&#xff1a;<\/p>\n<p>\u5e94\u7528\u7a0b\u5e8f\u63d0\u4ea4\u4e00\u4e2a I\/O \u8bf7\u6c42\u540e\u7acb\u5373\u7ee7\u7eed\u6267\u884c\u5176\u4ed6\u4efb\u52a1&#xff0c;\u5185\u6838\u6216 I\/O \u7cfb\u7edf\u5728\u540e\u53f0\u5b8c\u6210\u6574\u4e2a I\/O \u64cd\u4f5c&#xff1b;\u64cd\u4f5c\u5b8c\u6210\u540e&#xff0c;\u518d\u901a\u8fc7\u5b8c\u6210\u4e8b\u4ef6\u3001\u56de\u8c03\u3001\u4fe1\u53f7\u6216\u5b8c\u6210\u961f\u5217\u901a\u77e5\u5e94\u7528\u7a0b\u5e8f\u3002<\/p>\n<p>\u5173\u952e\u533a\u522b\u5728\u4e8e&#xff1a;<\/p>\n<p>\u540c\u6b65 I\/O&#xff1a;<br \/>\n\u5e94\u7528\u7a0b\u5e8f\u7b49\u5230\u201c\u53ef\u4ee5\u8bfb\u53d6\u201d\u540e&#xff0c;\u81ea\u5df1\u8c03\u7528 read\/recv \u5b8c\u6210\u8bfb\u53d6\u3002<\/p>\n<p>\u5f02\u6b65 I\/O&#xff1a;<br \/>\n\u5e94\u7528\u7a0b\u5e8f\u5148\u63d0\u4ea4\u201c\u8bf7\u628a\u6570\u636e\u8bfb\u5230\u8fd9\u4e2a\u7f13\u51b2\u533a\u201d\u7684\u8bf7\u6c42&#xff0c;<br \/>\n\u5185\u6838\u5b8c\u6210\u8bfb\u53d6\u540e\u518d\u901a\u77e5\u5e94\u7528\u7a0b\u5e8f\u3002<\/p>\n<p>\u5f02\u6b65\u8bfb\u53d6\u53ef\u4ee5\u62bd\u8c61\u4e3a&#xff1a;<\/p>\n<p>\u5e94\u7528\u7a0b\u5e8f\u63d0\u4ea4\u5f02\u6b65\u8bfb\u53d6\u8bf7\u6c42<br \/>\n           \u2502<br \/>\n           \u25bc<br \/>\n\u63d0\u4ea4\u51fd\u6570\u8fd4\u56de<br \/>\n           \u2502<br \/>\n           \u251c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500 \u5e94\u7528\u7a0b\u5e8f\u7ee7\u7eed\u5904\u7406\u5176\u4ed6\u4efb\u52a1<br \/>\n           \u2502<br \/>\n           \u25bc<br \/>\n\u5185\u6838\u7b49\u5f85\u6570\u636e\u5230\u8fbe<br \/>\n           \u2502<br \/>\n           \u25bc<br \/>\n\u5185\u6838\u5c06\u6570\u636e\u653e\u5165\u6307\u5b9a\u7f13\u51b2\u533a<br \/>\n           \u2502<br \/>\n           \u25bc<br \/>\n\u5185\u6838\u751f\u6210\u5b8c\u6210\u901a\u77e5<br \/>\n           \u2502<br \/>\n           \u25bc<br \/>\n\u5e94\u7528\u7a0b\u5e8f\u5904\u7406\u5b8c\u6210\u7ed3\u679c<\/p>\n<hr \/>\n<h3>15.2 \u540c\u6b65 I\/O \u4e0e\u5f02\u6b65 I\/O \u7684\u6838\u5fc3\u533a\u522b<\/h3>\n<p>\u540c\u6b65\u975e\u963b\u585e\u6a21\u578b&#xff1a;<\/p>\n<p>\u5e94\u7528\u7a0b\u5e8f&#xff1a;\u6570\u636e\u51c6\u5907\u597d\u4e86\u5417&#xff1f;<br \/>\n\u5185\u6838&#xff1a;\u8fd8\u6ca1\u6709&#xff0c;\u8fd4\u56de EAGAIN\u3002<\/p>\n<p>\u5e94\u7528\u7a0b\u5e8f&#xff1a;\u6570\u636e\u51c6\u5907\u597d\u4e86\u5417&#xff1f;<br \/>\n\u5185\u6838&#xff1a;\u51c6\u5907\u597d\u4e86\u3002<\/p>\n<p>\u5e94\u7528\u7a0b\u5e8f&#xff1a;\u90a3\u6211\u8c03\u7528 recv() \u8bfb\u53d6\u3002<\/p>\n<p>\u5f02\u6b65\u6a21\u578b&#xff1a;<\/p>\n<p>\u5e94\u7528\u7a0b\u5e8f&#xff1a;\u8bf7\u628a\u6570\u636e\u8bfb\u5230\u8fd9\u4e2a\u7f13\u51b2\u533a&#xff0c;\u5b8c\u6210\u540e\u901a\u77e5\u6211\u3002<br \/>\n\u5185\u6838&#xff1a;\u8bf7\u6c42\u5df2\u63a5\u6536\u3002<\/p>\n<p>\u5e94\u7528\u7a0b\u5e8f&#xff1a;\u7ee7\u7eed\u5904\u7406\u5176\u4ed6\u4efb\u52a1\u3002<\/p>\n<p>\u5185\u6838&#xff1a;\u6570\u636e\u8bfb\u53d6\u5b8c\u6210&#xff0c;\u8fd9\u662f\u7ed3\u679c\u3002<\/p>\n<hr \/>\n<h2>\u5341\u516d\u3001Reactor \u4e0e Proactor<\/h2>\n<p>\u540c\u6b65\u4e8b\u4ef6\u9a71\u52a8\u4e0e\u5f02\u6b65 I\/O\u8fd8\u53ef\u4ee5\u5206\u522b\u5bf9\u5e94\u4e24\u4e2a\u7ecf\u5178\u6a21\u578b\u3002<\/p>\n<h3>16.1 Reactor&#xff1a;\u5c31\u7eea\u901a\u77e5<\/h3>\n<p>epoll \u901a\u5e38\u7528\u4e8e\u5b9e\u73b0 Reactor\u3002<\/p>\n<p>\u5185\u6838\u901a\u77e5\u5e94\u7528\u7a0b\u5e8f&#xff1a;\u8fd9\u4e2a fd \u5df2\u7ecf\u53ef\u8bfb<br \/>\n\u5e94\u7528\u7a0b\u5e8f\u81ea\u5df1\u6267\u884c recv()<br \/>\n\u5e94\u7528\u7a0b\u5e8f\u81ea\u5df1\u5904\u7406\u6570\u636e<\/p>\n<p>\u6d41\u7a0b&#xff1a;<\/p>\n<p>\u4e8b\u4ef6\u5c31\u7eea<br \/>\n   \u2502<br \/>\n   \u25bc<br \/>\nReactor \u5206\u53d1\u4e8b\u4ef6<br \/>\n   \u2502<br \/>\n   \u25bc<br \/>\n\u7528\u6237\u4ee3\u7801\u8c03\u7528 recv()<br \/>\n   \u2502<br \/>\n   \u25bc<br \/>\n\u5904\u7406\u8bfb\u53d6\u7ed3\u679c<\/p>\n<p>\u6838\u5fc3\u662f&#xff1a;<\/p>\n<p>\u5185\u6838\u901a\u77e5\u201c\u73b0\u5728\u53ef\u4ee5\u505a\u4e86\u201d&#xff0c;\u5e94\u7528\u7a0b\u5e8f\u8d1f\u8d23\u5b8c\u6210\u5177\u4f53\u64cd\u4f5c\u3002<\/p>\n<hr \/>\n<h3>16.2 Proactor&#xff1a;\u5b8c\u6210\u901a\u77e5<\/h3>\n<p>\u771f\u6b63\u7684\u5f02\u6b65 I\/O \u66f4\u63a5\u8fd1 Proactor\u3002<\/p>\n<p>\u5e94\u7528\u7a0b\u5e8f\u63d0\u4ea4\u8bfb\u53d6\u8bf7\u6c42<br \/>\n\u5185\u6838\u5b8c\u6210\u5b9e\u9645\u8bfb\u53d6<br \/>\n\u5185\u6838\u901a\u77e5\u5e94\u7528\u7a0b\u5e8f&#xff1a;\u8bfb\u53d6\u5df2\u7ecf\u5b8c\u6210<br \/>\n\u5e94\u7528\u7a0b\u5e8f\u76f4\u63a5\u5904\u7406\u7ed3\u679c<\/p>\n<p>\u6d41\u7a0b&#xff1a;<\/p>\n<p>\u63d0\u4ea4\u5f02\u6b65\u64cd\u4f5c<br \/>\n      \u2502<br \/>\n      \u25bc<br \/>\n\u5185\u6838\u6267\u884c I\/O<br \/>\n      \u2502<br \/>\n      \u25bc<br \/>\nI\/O \u5b8c\u6210<br \/>\n      \u2502<br \/>\n      \u25bc<br \/>\nProactor \u5206\u53d1\u5b8c\u6210\u4e8b\u4ef6<br \/>\n      \u2502<br \/>\n      \u25bc<br \/>\n\u7528\u6237\u4ee3\u7801\u5904\u7406\u7ed3\u679c<\/p>\n<p>\u6838\u5fc3\u662f&#xff1a;<\/p>\n<p>\u5185\u6838\u901a\u77e5\u201c\u64cd\u4f5c\u5df2\u7ecf\u505a\u5b8c\u4e86\u201d&#xff0c;\u5e94\u7528\u7a0b\u5e8f\u53ea\u5904\u7406\u5b8c\u6210\u7ed3\u679c\u3002<\/p>\n<hr \/>\n<h2>\u5341\u4e03\u3001Linux \u4e2d\u6709\u54ea\u4e9b\u5f02\u6b65 I\/O \u6280\u672f&#xff1f;<\/h2>\n<p>Linux \u4e2d\u5e38\u89c1\u7684\u76f8\u5173\u673a\u5236\u5305\u62ec&#xff1a;<\/p>\n<p>POSIX AIO<br \/>\nLinux Native AIO<br \/>\nio_uring<\/p>\n<p>\u5176\u4e2d io_uring \u63d0\u4f9b\u4e86\u57fa\u4e8e\u63d0\u4ea4\u961f\u5217\u548c\u5b8c\u6210\u961f\u5217\u7684\u63a5\u53e3&#xff1a;<\/p>\n<p>\u7528\u6237\u7a7a\u95f4\u63d0\u4ea4\u961f\u5217 SQ<br \/>\n          \u2502<br \/>\n          \u25bc<br \/>\n\u5185\u6838\u5904\u7406 I\/O \u8bf7\u6c42<br \/>\n          \u2502<br \/>\n          \u25bc<br \/>\n\u7528\u6237\u7a7a\u95f4\u5b8c\u6210\u961f\u5217 CQ<\/p>\n<p>\u5176\u57fa\u672c\u601d\u60f3\u662f&#xff1a;<\/p>\n<p>1. \u5e94\u7528\u7a0b\u5e8f\u6784\u9020 I\/O \u8bf7\u6c42<br \/>\n2. \u5c06\u8bf7\u6c42\u653e\u5165\u63d0\u4ea4\u961f\u5217<br \/>\n3. \u5185\u6838\u5904\u7406\u8bf7\u6c42<br \/>\n4. \u5b8c\u6210\u540e\u5199\u5165\u5b8c\u6210\u961f\u5217<br \/>\n5. \u5e94\u7528\u7a0b\u5e8f\u8bfb\u53d6\u5b8c\u6210\u7ed3\u679c<\/p>\n<p>\u4e0d\u8fc7\u9700\u8981\u6ce8\u610f&#xff1a;<\/p>\n<p>\u4f7f\u7528 io_uring \u5e76\u4e0d\u81ea\u52a8\u610f\u5473\u7740\u6240\u6709\u64cd\u4f5c\u5728\u6240\u6709\u60c5\u51b5\u4e0b\u90fd\u5b8c\u5168\u5f02\u6b65\u3002<\/p>\n<p>\u5177\u4f53\u884c\u4e3a\u8fd8\u4e0e\u64cd\u4f5c\u7c7b\u578b\u3001\u6587\u4ef6\u7c7b\u578b\u3001\u5185\u6838\u7248\u672c\u3001\u914d\u7f6e\u65b9\u5f0f\u53ca\u662f\u5426\u9700\u8981\u5de5\u4f5c\u7ebf\u7a0b\u56de\u9000\u6709\u5173\u3002<\/p>\n<p>\u4f46\u4ece\u7f16\u7a0b\u6a21\u578b\u4e0a\u770b&#xff0c;\u5b83\u6bd4 epoll &#043; read() \u66f4\u63a5\u8fd1\u5b8c\u6210\u9a71\u52a8\u7684\u5f02\u6b65 I\/O\u3002<\/p>\n<hr \/>\n<h2>\u5341\u516b\u3001\u56db\u79cd\u5e38\u89c1 I\/O \u6a21\u578b\u5bf9\u6bd4<\/h2>\n<h3>18.1 \u963b\u585e\u540c\u6b65 I\/O<\/h3>\n<p>\u8c03\u7528 recv()<br \/>\n    \u2502<br \/>\n    \u25bc<br \/>\n\u7b49\u5f85\u6570\u636e<br \/>\n    \u2502<br \/>\n    \u25bc<br \/>\n\u590d\u5236\u6570\u636e<br \/>\n    \u2502<br \/>\n    \u25bc<br \/>\nrecv() \u8fd4\u56de<\/p>\n<p>\u7279\u70b9&#xff1a;<\/p>\n<p>\u7ebf\u7a0b\u7b49\u5f85<br \/>\n\u8c03\u7528\u7b80\u5355<br \/>\n\u4e00\u4e2a\u7ebf\u7a0b\u540c\u4e00\u65f6\u523b\u901a\u5e38\u53ea\u80fd\u7b49\u5f85\u4e00\u4e2a\u4e3b\u8981\u64cd\u4f5c<\/p>\n<p>\u793a\u4f8b&#xff1a;<\/p>\n<p><span class=\"token function\">recv<\/span><span class=\"token punctuation\">(<\/span>blocking_fd<span class=\"token punctuation\">,<\/span> buffer<span class=\"token punctuation\">,<\/span> size<span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<hr \/>\n<h3>18.2 \u975e\u963b\u585e\u540c\u6b65 I\/O<\/h3>\n<p>\u8c03\u7528 recv()<br \/>\n    \u2502<br \/>\n    \u251c\u2500\u2500 \u6ca1\u6570\u636e&#xff1a;\u7acb\u5373\u8fd4\u56de EAGAIN<br \/>\n    \u2502<br \/>\n    \u2514\u2500\u2500 \u6709\u6570\u636e&#xff1a;\u590d\u5236\u5e76\u8fd4\u56de<\/p>\n<p>\u7279\u70b9&#xff1a;<\/p>\n<p>\u7cfb\u7edf\u8c03\u7528\u4e0d\u56e0\u6682\u65e0\u6570\u636e\u800c\u7761\u7720<br \/>\n\u9700\u8981\u7a0b\u5e8f\u51b3\u5b9a\u4f55\u65f6\u91cd\u8bd5<br \/>\n\u9519\u8bef\u8bbe\u8ba1\u5bb9\u6613\u5f62\u6210\u5fd9\u8f6e\u8be2<\/p>\n<p>\u793a\u4f8b&#xff1a;<\/p>\n<p><span class=\"token function\">recv<\/span><span class=\"token punctuation\">(<\/span>nonblocking_fd<span class=\"token punctuation\">,<\/span> buffer<span class=\"token punctuation\">,<\/span> size<span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<hr \/>\n<h3>18.3 I\/O \u591a\u8def\u590d\u7528<\/h3>\n<p>epoll_wait()<br \/>\n      \u2502<br \/>\n      \u25bc<br \/>\n\u7b49\u5f85\u591a\u4e2a fd<br \/>\n      \u2502<br \/>\n      \u25bc<br \/>\n\u8fd4\u56de\u5c31\u7eea fd<br \/>\n      \u2502<br \/>\n      \u25bc<br \/>\n\u5e94\u7528\u7a0b\u5e8f\u8c03\u7528 recv()<\/p>\n<p>\u7279\u70b9&#xff1a;<\/p>\n<p>\u4e00\u4e2a\u7ebf\u7a0b\u7b49\u5f85\u5927\u91cf\u8fde\u63a5<br \/>\n\u901a\u5e38\u914d\u5408\u975e\u963b\u585e Socket<br \/>\n\u4ecd\u7136\u7531\u5e94\u7528\u7a0b\u5e8f\u4e3b\u52a8\u5b8c\u6210\u8bfb\u53d6<br \/>\n\u5c5e\u4e8e\u540c\u6b65 I\/O<\/p>\n<hr \/>\n<h3>18.4 \u5f02\u6b65 I\/O<\/h3>\n<p>\u63d0\u4ea4\u8bfb\u53d6\u8bf7\u6c42<br \/>\n      \u2502<br \/>\n      \u25bc<br \/>\n\u5e94\u7528\u7a0b\u5e8f\u7ee7\u7eed\u8fd0\u884c<br \/>\n      \u2502<br \/>\n      \u25bc<br \/>\n\u5185\u6838\u5b8c\u6210\u8bfb\u53d6<br \/>\n      \u2502<br \/>\n      \u25bc<br \/>\n\u901a\u77e5\u5e94\u7528\u7a0b\u5e8f\u8bfb\u53d6\u5b8c\u6210<\/p>\n<p>\u7279\u70b9&#xff1a;<\/p>\n<p>\u5b8c\u6210\u9a71\u52a8<br \/>\n\u5185\u6838\u6216 I\/O \u7cfb\u7edf\u5b8c\u6210\u6574\u4e2a\u64cd\u4f5c<br \/>\n\u5e94\u7528\u7a0b\u5e8f\u5904\u7406\u5b8c\u6210\u7ed3\u679c<br \/>\n\u5b9e\u73b0\u4e0e\u72b6\u6001\u7ba1\u7406\u901a\u5e38\u66f4\u52a0\u590d\u6742<\/p>\n<hr \/>\n<h2>\u5341\u4e5d\u3001\u4e24\u4e2a\u7ef4\u5ea6\u5e94\u8be5\u600e\u6837\u7ec4\u5408&#xff1f;<\/h2>\n<p>\u53ef\u4ee5\u7528\u4e0b\u9762\u7684\u5750\u6807\u7406\u89e3&#xff1a;<\/p>\n<p>                         I\/O \u5b8c\u6210\u65b9\u5f0f<br \/>\n                  \u540c\u6b65                  \u5f02\u6b65<br \/>\n             \u250c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u252c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2510<br \/>\n\u963b\u585e\u7b49\u5f85     \u2502 \u963b\u585e recv       \u2502 \u63d0\u4ea4\u5f02\u6b65\u8bf7\u6c42\u540e  \u2502<br \/>\n             \u2502                 \u2502 \u4e3b\u52a8\u7b49\u5f85\u5b8c\u6210    \u2502<br \/>\n             \u251c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u253c\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2524<br \/>\n\u975e\u963b\u585e\u7b49\u5f85   \u2502 O_NONBLOCK      \u2502 \u63d0\u4ea4\u8bf7\u6c42\u540e\u7ee7\u7eed  \u2502<br \/>\n             \u2502 epoll &#043; recv    \u2502 \u5904\u7406\u5176\u4ed6\u4efb\u52a1    \u2502<br \/>\n             \u2514\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2534\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2518<\/p>\n<p>\u5b9e\u9645\u5f00\u53d1\u4e2d\u6700\u5e38\u89c1\u7684\u662f&#xff1a;<\/p>\n<p>\u963b\u585e\u540c\u6b65 I\/O<br \/>\n\u975e\u963b\u585e\u540c\u6b65 I\/O<br \/>\nI\/O \u591a\u8def\u590d\u7528<br \/>\n\u5f02\u6b65\u5b8c\u6210 I\/O<\/p>\n<p>\u201c\u5f02\u6b65\u63a5\u53e3\u63d0\u4ea4\u540e\u7acb\u523b\u7b49\u5f85\u5b8c\u6210\u201d\u867d\u7136\u6280\u672f\u4e0a\u53ef\u4ee5\u505a\u5230&#xff0c;\u4f46\u4f1a\u5931\u53bb\u5927\u90e8\u5206\u5f02\u6b65\u7f16\u7a0b\u7684\u4ef7\u503c\u3002<\/p>\n<hr \/>\n<h2>\u4e8c\u5341\u3001\u4e3a\u4ec0\u4e48\u9ad8\u5e76\u53d1\u670d\u52a1\u5668\u901a\u5e38\u4e0d\u7528\u4e00\u8fde\u63a5\u4e00\u7ebf\u7a0b&#xff1f;<\/h2>\n<p>\u963b\u585e I\/O \u672c\u8eab\u5e76\u4e0d\u4f4e\u6548\u3002<\/p>\n<p>\u5bf9\u4e8e\u5c11\u91cf\u8fde\u63a5&#xff0c;\u963b\u585e\u6a21\u578b\u5f80\u5f80\u5177\u6709\u660e\u663e\u4f18\u52bf&#xff1a;<\/p>\n<p>\u4ee3\u7801\u7b80\u5355<br \/>\n\u5bb9\u6613\u8c03\u8bd5<br \/>\n\u4e1a\u52a1\u6d41\u7a0b\u76f4\u89c2<br \/>\n\u7ebf\u7a0b\u7761\u7720\u671f\u95f4\u4e0d\u5fd9\u7b49<\/p>\n<p>\u95ee\u9898\u4e3b\u8981\u51fa\u73b0\u5728\u8fde\u63a5\u6570\u91cf\u975e\u5e38\u5927\u65f6\u3002<\/p>\n<p>\u5982\u679c\u4e00\u4e07\u4e2a\u8fde\u63a5\u90fd\u4f7f\u7528\u72ec\u7acb\u7ebf\u7a0b&#xff1a;<\/p>\n<p>10000 \u4e2a\u8fde\u63a5<br \/>\n      \u2502<br \/>\n      \u25bc<br \/>\n10000 \u4e2a\u7ebf\u7a0b<br \/>\n      \u2502<br \/>\n      \u251c\u2500\u2500 \u7ebf\u7a0b\u6808\u5730\u5740\u7a7a\u95f4<br \/>\n      \u251c\u2500\u2500 \u5185\u6838\u7ebf\u7a0b\u7ba1\u7406\u7ed3\u6784<br \/>\n      \u251c\u2500\u2500 \u8c03\u5ea6\u5f00\u9500<br \/>\n      \u251c\u2500\u2500 \u4e0a\u4e0b\u6587\u5207\u6362<br \/>\n      \u2514\u2500\u2500 \u7f13\u5b58\u5c40\u90e8\u6027\u4e0b\u964d<\/p>\n<p>\u5e38\u89c1 Linux \u73af\u5883\u4e2d&#xff0c;\u7ebf\u7a0b\u6808\u4e0a\u9650\u53ef\u80fd\u663e\u793a\u4e3a\u6570 MB&#xff0c;\u4f8b\u5982 8 MB&#xff0c;\u4f46\u8fd9\u901a\u5e38\u4e3b\u8981\u662f\u865a\u62df\u5730\u5740\u7a7a\u95f4\u548c\u6700\u5927\u6808\u8303\u56f4&#xff0c;\u5e76\u4e0d\u8868\u793a\u521b\u5efa\u7ebf\u7a0b\u540e\u4f1a\u7acb\u523b\u4e3a\u6bcf\u4e2a\u7ebf\u7a0b\u63d0\u4ea4\u540c\u7b49\u6570\u91cf\u7684\u7269\u7406\u5185\u5b58\u3002<\/p>\n<p>\u56e0\u6b64&#xff0c;\u4e0d\u80fd\u7b80\u5355\u8ba1\u7b97&#xff1a;<\/p>\n<p>10000 \u00d7 8 MB &#061; 80 GB \u7269\u7406\u5185\u5b58\u7acb\u5373\u88ab\u5360\u7528<\/p>\n<p>\u66f4\u51c6\u786e\u7684\u8bf4\u6cd5\u662f&#xff1a;<\/p>\n<p>\u5927\u91cf\u7ebf\u7a0b\u4f1a\u6d88\u8017\u865a\u62df\u5730\u5740\u7a7a\u95f4\u3001\u5b9e\u9645\u4f7f\u7528\u7684\u6808\u5185\u5b58\u3001\u5185\u6838\u7ebf\u7a0b\u8d44\u6e90&#xff0c;\u5e76\u663e\u8457\u589e\u52a0\u8c03\u5ea6\u548c\u4e0a\u4e0b\u6587\u5207\u6362\u538b\u529b\u3002<\/p>\n<p>\u73b0\u4ee3\u7cfb\u7edf\u5e76\u4e0d\u662f\u521b\u5efa\u4e00\u4e07\u4e2a\u7ebf\u7a0b\u5c31\u4e00\u5b9a\u7acb\u5373\u5d29\u6e83&#xff0c;\u4f46\u7ebf\u7a0b\u6570\u91cf\u8d8a\u591a&#xff0c;\u7cfb\u7edf\u7684\u53ef\u6269\u5c55\u6027\u548c\u5c3e\u5ef6\u8fdf\u901a\u5e38\u8d8a\u96be\u63a7\u5236\u3002<\/p>\n<hr \/>\n<h2>\u4e8c\u5341\u4e00\u3001\u4e3a\u4ec0\u4e48\u975e\u963b\u585e I\/O \u9002\u5408\u4e8b\u4ef6\u5faa\u73af&#xff1f;<\/h2>\n<p>\u975e\u963b\u585e I\/O \u7684\u4e3b\u8981\u4ef7\u503c\u5e76\u4e0d\u662f\u201c\u8bfb\u53d6\u66f4\u5feb\u201d&#xff0c;\u800c\u662f&#xff1a;<\/p>\n<p>\u67d0\u4e00\u4e2a\u8fde\u63a5\u6682\u65f6\u6ca1\u6709\u6570\u636e\u65f6&#xff0c;\u4e0d\u4f1a\u628a\u6574\u4e2a\u4e8b\u4ef6\u5faa\u73af\u56f0\u5728\u8fd9\u4e2a\u8fde\u63a5\u4e0a\u3002<\/p>\n<p>\u4f8b\u5982&#xff0c;\u4e00\u4e2a\u7ebf\u7a0b\u5904\u7406\u4e09\u4e2a\u8fde\u63a5&#xff1a;<\/p>\n<p>\u8fde\u63a5 A&#xff1a;\u6ca1\u6709\u6570\u636e<br \/>\n\u8fde\u63a5 B&#xff1a;\u6709\u6570\u636e<br \/>\n\u8fde\u63a5 C&#xff1a;\u6709\u6570\u636e<\/p>\n<p>\u5982\u679c\u7ebf\u7a0b\u5148\u5bf9\u963b\u585e\u8fde\u63a5 A \u8c03\u7528 recv()&#xff1a;<\/p>\n<p>\u7ebf\u7a0b\u963b\u585e\u5728 A<br \/>\nB \u548c C \u5373\u4f7f\u5df2\u6709\u6570\u636e&#xff0c;\u4e5f\u65e0\u6cd5\u53ca\u65f6\u5904\u7406<\/p>\n<p>\u5982\u679c\u4e09\u4e2a\u8fde\u63a5\u90fd\u662f\u975e\u963b\u585e\u7684&#xff1a;<\/p>\n<p>\u68c0\u67e5 A&#xff1a;EAGAIN&#xff0c;\u8df3\u8fc7<br \/>\n\u5904\u7406 B&#xff1a;\u8bfb\u53d6\u6570\u636e<br \/>\n\u5904\u7406 C&#xff1a;\u8bfb\u53d6\u6570\u636e<\/p>\n<p>\u518d\u914d\u5408 epoll&#xff0c;\u5c31\u4e0d\u9700\u8981\u9010\u4e2a\u65e0\u6548\u68c0\u67e5&#xff1a;<\/p>\n<p>epoll_wait() \u8fd4\u56de B\u3001C<br \/>\n\u53ea\u5904\u7406 B\u3001C<br \/>\n\u4e0d\u68c0\u67e5\u6682\u65f6\u6ca1\u6709\u4e8b\u4ef6\u7684 A<\/p>\n<p>\u8fd9\u5c31\u662f\u4e8b\u4ef6\u9a71\u52a8\u9ad8\u5e76\u53d1\u670d\u52a1\u5668\u7684\u57fa\u672c\u601d\u60f3\u3002<\/p>\n<hr \/>\n<h2>\u4e8c\u5341\u4e8c\u3001\u975e\u963b\u585e\u5199\u64cd\u4f5c\u8fd8\u8981\u5904\u7406\u201c\u90e8\u5206\u5199\u5165\u201d<\/h2>\n<p>\u975e\u963b\u585e I\/O \u4e0d\u53ea\u5f71\u54cd\u8bfb\u53d6&#xff0c;\u4e5f\u5f71\u54cd\u5199\u5165\u3002<\/p>\n<p>\u5047\u8bbe\u6267\u884c&#xff1a;<\/p>\n<p><span class=\"token function\">send<\/span><span class=\"token punctuation\">(<\/span>fd<span class=\"token punctuation\">,<\/span> data<span class=\"token punctuation\">,<\/span> <span class=\"token number\">10000<\/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>\u5373\u4f7f\u5f53\u524d Socket \u53ef\u5199&#xff0c;\u4e5f\u4e0d\u4fdd\u8bc1\u4e00\u6b21\u8c03\u7528\u4e00\u5b9a\u5199\u5165\u5168\u90e8 10000 \u5b57\u8282\u3002<\/p>\n<p>\u53ef\u80fd\u8fd4\u56de&#xff1a;<\/p>\n<p>10000&#xff1a;\u5168\u90e8\u5199\u5165\u5185\u6838\u53d1\u9001\u7f13\u51b2\u533a<br \/>\n3000&#xff1a;\u53ea\u5199\u5165\u4e00\u90e8\u5206<br \/>\n-1 &#043; EAGAIN&#xff1a;\u5f53\u524d\u53d1\u9001\u7f13\u51b2\u533a\u6ca1\u6709\u8db3\u591f\u7a7a\u95f4<\/p>\n<p>\u56e0\u6b64\u5fc5\u987b\u7ef4\u62a4\u53d1\u9001\u72b6\u6001&#xff1a;<\/p>\n<p>std<span class=\"token double-colon punctuation\">::<\/span>size_t offset <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token keyword\">while<\/span> <span class=\"token punctuation\">(<\/span>offset <span class=\"token operator\">&lt;<\/span> data_size<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    ssize_t n <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">send<\/span><span class=\"token punctuation\">(<\/span><br \/>\n        fd<span class=\"token punctuation\">,<\/span><br \/>\n        data <span class=\"token operator\">&#043;<\/span> offset<span class=\"token punctuation\">,<\/span><br \/>\n        data_size <span class=\"token operator\">&#8211;<\/span> offset<span class=\"token punctuation\">,<\/span><br \/>\n        <span class=\"token number\">0<\/span><br \/>\n    <span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>n <span class=\"token operator\">&gt;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        offset <span class=\"token operator\">&#043;&#061;<\/span> <span class=\"token generic-function\"><span class=\"token function\">static_cast<\/span><span class=\"token generic class-name\"><span class=\"token operator\">&lt;<\/span>std<span class=\"token double-colon punctuation\">::<\/span>size_t<span class=\"token operator\">&gt;<\/span><\/span><\/span><span class=\"token punctuation\">(<\/span>n<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>n <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span> <span class=\"token operator\">&amp;&amp;<\/span> errno <span class=\"token operator\">&#061;&#061;<\/span> EINTR<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>n <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token operator\">&#8211;<\/span><span class=\"token number\">1<\/span> <span class=\"token operator\">&amp;&amp;<\/span><br \/>\n        <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> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token comment\">\/\/ \u4fdd\u5b58 offset&#xff0c;\u7b49\u5f85\u4e0b\u4e00\u6b21 EPOLLOUT<\/span><br \/>\n        <span class=\"token keyword\">break<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u5176\u4ed6\u9519\u8bef&#xff0c;\u5173\u95ed\u8fde\u63a5<\/span><br \/>\n    <span class=\"token keyword\">break<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<p>\u56e0\u6b64&#xff0c;\u975e\u963b\u585e\u670d\u52a1\u5668\u901a\u5e38\u9700\u8981\u4e3a\u6bcf\u4e2a\u8fde\u63a5\u7ef4\u62a4&#xff1a;<\/p>\n<p>\u63a5\u6536\u7f13\u51b2\u533a<br \/>\n\u53d1\u9001\u7f13\u51b2\u533a<br \/>\n\u5df2\u53d1\u9001\u504f\u79fb\u91cf<br \/>\n\u534f\u8bae\u89e3\u6790\u72b6\u6001<br \/>\n\u8fde\u63a5\u751f\u547d\u5468\u671f\u72b6\u6001<br \/>\n\u8d85\u65f6\u72b6\u6001<\/p>\n<p>\u8fd9\u4e5f\u662f\u975e\u963b\u585e\u4e8b\u4ef6\u9a71\u52a8\u7a0b\u5e8f\u6bd4\u963b\u585e\u7a0b\u5e8f\u590d\u6742\u7684\u4e3b\u8981\u539f\u56e0\u3002<\/p>\n<hr \/>\n<h2>\u4e8c\u5341\u4e09\u3001\u963b\u585e\u3001\u975e\u963b\u585e\u3001\u540c\u6b65\u3001\u5f02\u6b65\u7684\u6700\u7ec8\u5bf9\u7167\u8868<\/h2>\n<table>\n<tr>\u6982\u5ff5\u6838\u5fc3\u95ee\u9898\u5178\u578b\u884c\u4e3a<\/tr>\n<tbody>\n<tr>\n<td>\u963b\u585e<\/td>\n<td>\u8c03\u7528\u4e0d\u80fd\u7acb\u5373\u5b8c\u6210\u65f6&#xff0c;\u7ebf\u7a0b\u662f\u5426\u7b49\u5f85<\/td>\n<td>\u7ebf\u7a0b\u505c\u5728\u7cfb\u7edf\u8c03\u7528\u4e2d<\/td>\n<\/tr>\n<tr>\n<td>\u975e\u963b\u585e<\/td>\n<td>\u8c03\u7528\u4e0d\u80fd\u7acb\u5373\u5b8c\u6210\u65f6&#xff0c;\u7ebf\u7a0b\u662f\u5426\u7acb\u5373\u5f97\u5230\u7ed3\u679c<\/td>\n<td>\u8fd4\u56de EAGAIN<\/td>\n<\/tr>\n<tr>\n<td>\u540c\u6b65<\/td>\n<td>\u5e94\u7528\u7a0b\u5e8f\u662f\u5426\u9700\u8981\u4e3b\u52a8\u53c2\u4e0e\u5e76\u5b8c\u6210 I\/O \u8c03\u7528<\/td>\n<td>\u5e94\u7528\u8c03\u7528 recv() \u83b7\u53d6\u6570\u636e<\/td>\n<\/tr>\n<tr>\n<td>\u5f02\u6b65<\/td>\n<td>\u63d0\u4ea4\u8bf7\u6c42\u540e&#xff0c;\u662f\u5426\u7531\u5185\u6838\u5b8c\u6210\u5e76\u901a\u77e5\u7ed3\u679c<\/td>\n<td>\u5b8c\u6210\u961f\u5217\u3001\u56de\u8c03\u6216\u5b8c\u6210\u4e8b\u4ef6<\/td>\n<\/tr>\n<tr>\n<td>I\/O \u591a\u8def\u590d\u7528<\/td>\n<td>\u5982\u4f55\u7528\u5c11\u91cf\u7ebf\u7a0b\u7b49\u5f85\u591a\u4e2a fd<\/td>\n<td>select\u3001poll\u3001epoll<\/td>\n<\/tr>\n<tr>\n<td>Reactor<\/td>\n<td>\u901a\u77e5\u64cd\u4f5c\u5df2\u7ecf\u5c31\u7eea<\/td>\n<td>\u5e94\u7528\u7a0b\u5e8f\u6267\u884c\u5b9e\u9645 I\/O<\/td>\n<\/tr>\n<tr>\n<td>Proactor<\/td>\n<td>\u901a\u77e5\u64cd\u4f5c\u5df2\u7ecf\u5b8c\u6210<\/td>\n<td>\u5e94\u7528\u7a0b\u5e8f\u5904\u7406\u5b8c\u6210\u7ed3\u679c<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<hr \/>\n<h2>\u4e8c\u5341\u56db\u3001\u5e38\u89c1\u9519\u8bef\u8bf4\u6cd5\u4fee\u6b63<\/h2>\n<h3>\u9519\u8bef\u4e00&#xff1a;\u963b\u585e I\/O \u4f1a\u5360\u6ee1 CPU<\/h3>\n<p>\u9519\u8bef\u3002<\/p>\n<p>\u963b\u585e\u7ebf\u7a0b\u5728\u7b49\u5f85\u671f\u95f4\u901a\u5e38\u4f1a\u8fdb\u5165\u7761\u7720\u72b6\u6001&#xff0c;\u4e0d\u4f1a\u6301\u7eed\u6267\u884c\u8f6e\u8be2\u6307\u4ee4\u3002<\/p>\n<p>\u51c6\u786e\u8bf4\u6cd5&#xff1a;<\/p>\n<p>\u963b\u585e I\/O \u4f1a\u6682\u505c\u5f53\u524d\u7ebf\u7a0b\u7684\u6267\u884c&#xff0c;\u4f46\u901a\u5e38\u4e0d\u4f1a\u8ba9\u8fd9\u4e2a\u7ebf\u7a0b\u5728\u7b49\u5f85\u671f\u95f4\u6301\u7eed\u5360\u7528 CPU\u3002<\/p>\n<hr \/>\n<h3>\u9519\u8bef\u4e8c&#xff1a;\u975e\u963b\u585e I\/O \u4e00\u5b9a\u4f1a\u5360\u6ee1 CPU<\/h3>\n<p>\u9519\u8bef\u3002<\/p>\n<p>\u53ea\u6709\u7a0b\u5e8f\u4e0d\u65ad\u7acb\u5373\u91cd\u8bd5\u65f6\u624d\u4f1a\u5f62\u6210\u5fd9\u8f6e\u8be2\u3002<\/p>\n<p>\u51c6\u786e\u8bf4\u6cd5&#xff1a;<\/p>\n<p>\u975e\u963b\u585e I\/O \u5141\u8bb8\u8c03\u7528\u7acb\u5373\u8fd4\u56de&#xff0c;\u662f\u5426\u5fd9\u8f6e\u8be2\u53d6\u51b3\u4e8e\u7a0b\u5e8f\u5982\u4f55\u5b89\u6392\u4e0b\u4e00\u6b21\u91cd\u8bd5\u3002<\/p>\n<hr \/>\n<h3>\u9519\u8bef\u4e09&#xff1a;epoll \u662f\u5f02\u6b65 I\/O<\/h3>\n<p>\u4e25\u683c\u6765\u8bf4\u9519\u8bef\u3002<\/p>\n<p>\u51c6\u786e\u8bf4\u6cd5&#xff1a;<\/p>\n<p>epoll \u662f I\/O \u591a\u8def\u590d\u7528\u548c\u5c31\u7eea\u901a\u77e5\u673a\u5236&#xff0c;\u901a\u5e38\u914d\u5408\u540c\u6b65\u975e\u963b\u585e I\/O \u4f7f\u7528\u3002<\/p>\n<hr \/>\n<h3>\u9519\u8bef\u56db&#xff1a;epoll \u901a\u77e5\u53ef\u8bfb\u540e&#xff0c;\u53ef\u4ee5\u653e\u5fc3\u4f7f\u7528\u963b\u585e recv<\/h3>\n<p>\u4e0d\u63a8\u8350\u3002<\/p>\n<p>\u51c6\u786e\u8bf4\u6cd5&#xff1a;<\/p>\n<p>\u4e3a\u907f\u514d\u7ade\u6001\u3001\u4e8b\u4ef6\u72b6\u6001\u53d8\u5316\u4ee5\u53ca ET \u6a21\u5f0f\u8bfb\u53d6\u4e0d\u5b8c\u6574\u7b49\u95ee\u9898&#xff0c;epoll \u7ba1\u7406\u7684 Socket 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