{"id":446,"date":"2019-02-21T00:16:33","date_gmt":"2019-02-20T16:16:33","guid":{"rendered":"https:\/\/fick707.com\/?p=446"},"modified":"2019-02-21T00:37:51","modified_gmt":"2019-02-20T16:37:51","slug":"nio","status":"publish","type":"post","link":"https:\/\/fick707.com\/?p=446","title":{"rendered":"nio"},"content":{"rendered":"\n<p>\u8f6c\u8f7d\u81ea\uff1ahttps:\/\/mp.weixin.qq.com\/s?__biz=MzU0MzQ5MDA0Mw==&amp;mid=2247483907&amp;idx=1&amp;sn=3d5e1384a36bd59f5fd14135067af1c2&amp;chksm=fb0be897cc7c61815a6a1c3181f3ba3507b199fd7a8c9025e9d8f67b5e9783bc0f0fe1c73903&amp;scene=21#wechat_redirect<\/p>\n\n\n<h2>\u7528\u6237\u7a7a\u95f4\u4ee5\u53ca\u5185\u6838\u7a7a\u95f4\u6982\u5ff5<\/h2>\n<blockquote>\n<p>\u6211\u4eec\u77e5\u9053\u73b0\u5728\u64cd\u4f5c\u7cfb\u7edf\u90fd\u662f\u91c7\u7528\u865a\u62df\u5b58\u50a8\u5668\uff0c\u90a3\u4e48\u5bf932\u4f4d\u64cd\u4f5c\u7cfb\u7edf\u800c\u8a00\uff0c\u5b83\u7684\u5bfb\u5740\u7a7a\u95f4\uff08\u865a\u62df\u5b58\u50a8\u7a7a\u95f4\uff09\u4e3a4G\uff082\u768432\u6b21\u65b9\uff09\u3002\u64cd\u5fc3\u7cfb\u7edf\u7684\u6838\u5fc3\u662f\u5185\u6838\uff0c\u72ec\u7acb\u4e8e\u666e\u901a\u7684\u5e94\u7528\u7a0b\u5e8f\uff0c\u53ef\u4ee5\u8bbf\u95ee\u53d7\u4fdd\u62a4\u7684\u5185\u5b58\u7a7a\u95f4\uff0c\u4e5f\u6709\u8bbf\u95ee\u5e95\u5c42\u786c\u4ef6\u8bbe\u5907\u7684\u6240\u6709\u6743\u9650\u3002\u4e3a\u4e86\u4fdd\u8bc1\u7528\u6237\u8fdb\u7a0b\u4e0d\u80fd\u76f4\u63a5\u64cd\u4f5c\u5185\u6838\uff0c\u4fdd\u8bc1\u5185\u6838\u7684\u5b89\u5168\uff0c\u64cd\u5fc3\u7cfb\u7edf\u5c06\u865a\u62df\u7a7a\u95f4\u5212\u5206\u4e3a\u4e24\u90e8\u5206\uff0c\u4e00\u90e8\u5206\u4e3a\u5185\u6838\u7a7a\u95f4\uff0c\u4e00\u90e8\u5206\u4e3a\u7528\u6237\u7a7a\u95f4\u3002\u9488\u5bf9linux\u64cd\u4f5c\u7cfb\u7edf\u800c\u8a00\uff0c\u5c06\u6700\u9ad8\u76841G\u5b57\u8282\uff08\u4ece\u865a\u62df\u5730\u57400xC0000000\u52300xFFFFFFFF\uff09\uff0c\u4f9b\u5185\u6838\u4f7f\u7528\uff0c\u79f0\u4e3a\u5185\u6838\u7a7a\u95f4\uff0c\u800c\u5c06\u8f83\u4f4e\u76843G\u5b57\u8282\uff08\u4ece\u865a\u62df\u5730\u57400x00000000\u52300xBFFFFFFF\uff09\uff0c\u4f9b\u5404\u4e2a\u8fdb\u7a0b\u4f7f\u7528\uff0c\u79f0\u4e3a\u7528\u6237\u7a7a\u95f4\u3002\u6bcf\u4e2a\u8fdb\u7a0b\u53ef\u4ee5\u901a\u8fc7\u7cfb\u7edf\u8c03\u7528\u8fdb\u5165\u5185\u6838\uff0c\u56e0\u6b64\uff0cLinux\u5185\u6838\u7531\u7cfb\u7edf\u5185\u7684\u6240\u6709\u8fdb\u7a0b\u5171\u4eab\u3002\u4e8e\u662f\uff0c\u4ece\u5177\u4f53\u8fdb\u7a0b\u7684\u89d2\u5ea6\u6765\u770b\uff0c\u6bcf\u4e2a\u8fdb\u7a0b\u53ef\u4ee5\u62e5\u67094G\u5b57\u8282\u7684\u865a\u62df\u7a7a\u95f4\u3002<\/p>\n<\/blockquote>\n<p>\u7a7a\u95f4\u5206\u914d\u5982\u4e0b\u56fe\u6240\u793a\uff1a<img decoding=\"async\" src=\"https:\/\/mmbiz.qpic.cn\/mmbiz_png\/1QxwhpDy7ia1mMN6NlFd3fDIMRY5O2CHeicticSgN0yV4LCskQ1y0PUvDnnngVDqblPA1TQNH29gicOVwPmI4YfY9w\/640\"><\/p>\n<p><strong>\u6709\u4e86\u7528\u6237\u7a7a\u95f4\u548c\u5185\u6838\u7a7a\u95f4\uff0c\u6574\u4e2alinux\u5185\u90e8\u7ed3\u6784\u53ef\u4ee5\u5206\u4e3a\u4e09\u90e8\u5206\uff0c\u4ece\u6700\u5e95\u5c42\u5230\u6700\u4e0a\u5c42\u4f9d\u6b21\u662f\uff1a\u786c\u4ef6&#8211;&gt;\u5185\u6838\u7a7a\u95f4&#8211;&gt;\u7528\u6237\u7a7a\u95f4\u3002<\/strong><\/p>\n<p>\u5982\u4e0b\u56fe\u6240\u793a\uff1a<img decoding=\"async\" src=\"https:\/\/mmbiz.qpic.cn\/mmbiz_png\/1QxwhpDy7ia1mMN6NlFd3fDIMRY5O2CHe9j6jecEPcWWkLGfEmlPUTib41WLcWpmk4h7qgcLJHickWK6bpl54Dw1g\/640\"><\/p>\n<p><strong>\u9700\u8981\u6ce8\u610f\u7684\u7ec6\u8282\u95ee\u9898\uff0c\u4ece\u4e0a\u56fe\u53ef\u4ee5\u770b\u51fa\u5185\u6838\u7684\u7ec4\u6210:<\/strong><\/p>\n<blockquote>\n<p>&nbsp;<\/p>\n<ol class=\"list-paddingleft-2\">\n<li>\n<p>\u5185\u6838\u7a7a\u95f4\u4e2d\u5b58\u653e\u7684\u662f\u5185\u6838\u4ee3\u7801\u548c\u6570\u636e\uff0c\u800c\u8fdb\u7a0b\u7684\u7528\u6237\u7a7a\u95f4\u4e2d\u5b58\u653e\u7684\u662f\u7528\u6237\u7a0b\u5e8f\u7684\u4ee3\u7801\u548c\u6570\u636e\u3002\u4e0d\u7ba1\u662f\u5185\u6838\u7a7a\u95f4\u8fd8\u662f\u7528\u6237\u7a7a\u95f4\uff0c\u5b83\u4eec\u90fd\u5904\u4e8e\u865a\u62df\u7a7a\u95f4\u4e2d\u3002<\/p>\n<\/li>\n<li>\n<p>Linux\u4f7f\u7528\u4e24\u7ea7\u4fdd\u62a4\u673a\u5236\uff1a0\u7ea7\u4f9b\u5185\u6838\u4f7f\u7528\uff0c3\u7ea7\u4f9b\u7528\u6237\u7a0b\u5e8f\u4f7f\u7528\u3002<\/p>\n<\/li>\n<\/ol>\n<\/blockquote>\n<h2>Linux \u7f51\u7edc I\/O\u6a21\u578b<\/h2>\n<p><img decoding=\"async\" src=\"https:\/\/mmbiz.qpic.cn\/mmbiz_png\/1QxwhpDy7ia1mMN6NlFd3fDIMRY5O2CHexeyA1eDGSbNYrT1BibP9nGBiadHA1vHFicQpsJgiaty29e0vpEic2EmTqpQ\/640\"><\/p>\n<p>\u6211\u4eec\u90fd\u77e5\u9053\uff0c\u4e3a\u4e86OS\u7684\u5b89\u5168\u6027\u7b49\u7684\u8003\u8651\uff0c<strong>\u8fdb\u7a0b\u662f\u65e0\u6cd5\u76f4\u63a5\u64cd\u4f5cI\/O\u8bbe\u5907\u7684\uff0c\u5176\u5fc5\u987b\u901a\u8fc7\u7cfb\u7edf\u8c03\u7528\u8bf7\u6c42\u5185\u6838\u6765\u534f\u52a9\u5b8c\u6210I\/O\u52a8\u4f5c\uff0c\u800c\u5185\u6838\u4f1a\u4e3a\u6bcf\u4e2aI\/O\u8bbe\u5907\u7ef4\u62a4\u4e00\u4e2abuffer<\/strong>\u3002 \u5982\u4e0b\u56fe\u6240\u793a\uff1a<\/p>\n<p><img decoding=\"async\" src=\"data:image\/gif;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVQImWNgYGBgAAAABQABh6FO1AAAAABJRU5ErkJggg==\"><\/p>\n<p><strong>\u6574\u4e2a\u8bf7\u6c42\u8fc7\u7a0b\u4e3a\uff1a \u7528\u6237\u8fdb\u7a0b\u53d1\u8d77\u8bf7\u6c42\uff0c\u5185\u6838\u63a5\u53d7\u5230\u8bf7\u6c42\u540e\uff0c\u4eceI\/O\u8bbe\u5907\u4e2d\u83b7\u53d6\u6570\u636e\u5230buffer\u4e2d\uff0c\u518d\u5c06buffer\u4e2d\u7684\u6570\u636ecopy\u5230\u7528\u6237\u8fdb\u7a0b\u7684\u5730\u5740\u7a7a\u95f4\uff0c\u8be5\u7528\u6237\u8fdb\u7a0b\u83b7\u53d6\u5230\u6570\u636e\u540e\u518d\u54cd\u5e94\u5ba2\u6237\u7aef\u3002<\/strong><\/p>\n<p>\u5728\u6574\u4e2a\u8bf7\u6c42\u8fc7\u7a0b\u4e2d\uff0c\u6570\u636e\u8f93\u5165\u81f3buffer\u9700\u8981\u65f6\u95f4\uff0c\u800c\u4ecebuffer\u590d\u5236\u6570\u636e\u81f3\u8fdb\u7a0b\u4e5f\u9700\u8981\u65f6\u95f4\u3002\u56e0\u6b64\u6839\u636e\u5728\u8fd9\u4e24\u6bb5\u65f6\u95f4\u5185\u7b49\u5f85\u65b9\u5f0f\u7684\u4e0d\u540c\uff0cI\/O\u52a8\u4f5c\u53ef\u4ee5\u5206\u4e3a\u4ee5\u4e0b<strong>\u4e94\u79cd\u6a21\u5f0f<\/strong>\uff1a<\/p>\n<blockquote>\n<p>&nbsp;<\/p>\n<ul class=\"list-paddingleft-2\">\n<li>\n<p><strong>\u963b\u585eI\/O (Blocking I\/O)<\/strong><\/p>\n<\/li>\n<li>\n<p><strong>\u975e\u963b\u585eI\/O (Non-Blocking I\/O)<\/strong><\/p>\n<\/li>\n<li>\n<p><strong>I\/O\u590d\u7528\uff08I\/O Multiplexing)<\/strong><\/p>\n<\/li>\n<li>\n<p><strong>\u4fe1\u53f7\u9a71\u52a8\u7684I\/O (Signal Driven I\/O)<\/strong><\/p>\n<\/li>\n<li>\n<p><strong>\u5f02\u6b65I\/O (Asynchrnous I\/O)<\/strong>&nbsp;<strong>\u8bf4\u660e\uff1a<\/strong>\u5982\u679c\u50cf\u4e86\u89e3\u66f4\u591a\u53ef\u80fd\u9700\u8981linux\/unix\u65b9\u9762\u7684\u77e5\u8bc6\u4e86\uff0c\u53ef\u81ea\u884c\u53bb\u5b66\u4e60\u4e00\u4e9b\u7f51\u7edc\u7f16\u7a0b\u539f\u7406\u5e94\u8be5\u6709\u8be6\u7ec6\u8bf4\u660e\uff0c<strong>\u4e0d\u8fc7\u5bf9\u5927\u591a\u6570java\u7a0b\u5e8f\u5458\u6765\u8bf4\uff0c\u4e0d\u9700\u8981\u4e86\u89e3\u5e95\u5c42\u7ec6\u8282\uff0c\u77e5\u9053\u4e2a\u6982\u5ff5\u5c31\u884c\uff0c\u77e5\u9053\u5bf9\u4e8e\u7cfb\u7edf\u800c\u8a00\uff0c\u5e95\u5c42\u662f\u652f\u6301\u7684<\/strong>\u3002<\/p>\n<\/li>\n<\/ul>\n<p>\u672c\u6587\u6700\u91cd\u8981\u7684\u53c2\u8003\u6587\u732e\u662fRichard Stevens\u7684\u201cUNIX\u00ae Network Programming Volume 1, Third Edition: The Sockets Networking \u201d\uff0c6.2\u8282\u201cI\/O Models \u201d\u3002<\/p>\n<\/blockquote>\n<p><img decoding=\"async\" src=\"https:\/\/mmbiz.qpic.cn\/mmbiz_png\/1QxwhpDy7ia1mMN6NlFd3fDIMRY5O2CHezibSibuE2Zb9VU00LqEcYCRSibqiaYInvpiaaCDWxoCHU6mYZvf8dm7S1Tw\/640\"><\/p>\n<p><img decoding=\"async\" src=\"https:\/\/mmbiz.qpic.cn\/mmbiz_png\/1QxwhpDy7ia1mMN6NlFd3fDIMRY5O2CHeUsBzRH6iaWVIXOzN7aicZWnasnIgpia4dAVS9lxpyZ9zeYUAXEFWltTtA\/640\"><\/p>\n<blockquote>\n<p><strong>\u8bb0\u4f4f\u8fd9\u4e24\u70b9\u5f88\u91cd\u8981<\/strong><\/p>\n<p>1 \u7b49\u5f85\u6570\u636e\u51c6\u5907 (Waiting for the data to be ready) 2 \u5c06\u6570\u636e\u4ece\u5185\u6838\u62f7\u8d1d\u5230\u8fdb\u7a0b\u4e2d (Copying the data from the kernel to the process)<\/p>\n<\/blockquote>\n<h3>\u963b\u585eI\/O (Blocking I\/O)<\/h3>\n<p>\u5728linux\u4e2d\uff0c\u9ed8\u8ba4\u60c5\u51b5\u4e0b\u6240\u6709\u7684socket\u90fd\u662fblocking\uff0c\u4e00\u4e2a\u5178\u578b\u7684\u8bfb\u64cd\u4f5c\u6d41\u7a0b\u5927\u6982\u662f\u8fd9\u6837\uff1a<\/p>\n<p><img decoding=\"async\" src=\"data:image\/gif;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVQImWNgYGBgAAAABQABh6FO1AAAAABJRU5ErkJggg==\"><\/p>\n<p>\u5f53\u7528\u6237\u8fdb\u7a0b\u8c03\u7528\u4e86recvfrom\u8fd9\u4e2a\u7cfb\u7edf\u8c03\u7528\uff0c\u5185\u6838\u5c31\u5f00\u59cb\u4e86IO\u7684\u7b2c\u4e00\u4e2a\u9636\u6bb5\uff1a\u7b49\u5f85\u6570\u636e\u51c6\u5907\u3002\u5bf9\u4e8enetwork io\u6765\u8bf4\uff0c\u5f88\u591a\u65f6\u5019\u6570\u636e\u5728\u4e00\u5f00\u59cb\u8fd8\u6ca1\u6709\u5230\u8fbe\uff08\u6bd4\u5982\uff0c\u8fd8\u6ca1\u6709\u6536\u5230\u4e00\u4e2a\u5b8c\u6574\u7684UDP\u5305\uff09\uff0c\u8fd9\u4e2a\u65f6\u5019\u5185\u6838\u5c31\u8981\u7b49\u5f85\u8db3\u591f\u7684\u6570\u636e\u5230\u6765\u3002\u800c\u5728\u7528\u6237\u8fdb\u7a0b\u8fd9\u8fb9\uff0c\u6574\u4e2a\u8fdb\u7a0b\u4f1a\u88ab\u963b\u585e\u3002\u5f53\u5185\u6838\u4e00\u76f4\u7b49\u5230\u6570\u636e\u51c6\u5907\u597d\u4e86\uff0c\u5b83\u5c31\u4f1a\u5c06\u6570\u636e\u4ece\u5185\u6838\u4e2d\u62f7\u8d1d\u5230\u7528\u6237\u5185\u5b58\uff0c\u7136\u540e\u5185\u6838\u8fd4\u56de\u7ed3\u679c\uff0c\u7528\u6237\u8fdb\u7a0b\u624d\u89e3\u9664block\u7684\u72b6\u6001\uff0c\u91cd\u65b0\u8fd0\u884c\u8d77\u6765\u3002 \u6240\u4ee5\uff0cblocking IO\u7684\u7279\u70b9\u5c31\u662f<strong>\u5728IO\u6267\u884c\u7684\u4e24\u4e2a\u9636\u6bb5\u90fd\u88abblock\u4e86\u3002<\/strong><\/p>\n<h3>\u975e\u963b\u585eI\/O (Non-Blocking I\/O)<\/h3>\n<p>linux\u4e0b\uff0c\u53ef\u4ee5\u901a\u8fc7\u8bbe\u7f6esocket\u4f7f\u5176\u53d8\u4e3anon-blocking\u3002\u5f53\u5bf9\u4e00\u4e2anon-blocking socket\u6267\u884c\u8bfb\u64cd\u4f5c\u65f6\uff0c\u6d41\u7a0b\u662f\u8fd9\u4e2a\u6837\u5b50\uff1a<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/mmbiz.qpic.cn\/mmbiz_png\/1QxwhpDy7ia1mMN6NlFd3fDIMRY5O2CHeZaFIICHTIEPYG1Aqg4fgbpVsQAe6jKfLEYk2ficeWa2PiatVCNSX6HYg\/640\"><\/p>\n<p>\u5f53\u7528\u6237\u8fdb\u7a0b\u8c03\u7528recvfrom\u65f6\uff0c\u7cfb\u7edf\u4e0d\u4f1a\u963b\u585e\u7528\u6237\u8fdb\u7a0b\uff0c\u800c\u662f\u7acb\u523b\u8fd4\u56de\u4e00\u4e2aewouldblock\u9519\u8bef\uff0c\u4ece\u7528\u6237\u8fdb\u7a0b\u89d2\u5ea6\u8bb2 \uff0c\u5e76\u4e0d\u9700\u8981\u7b49\u5f85\uff0c\u800c\u662f\u9a6c\u4e0a\u5c31\u5f97\u5230\u4e86\u4e00\u4e2a\u7ed3\u679c\u3002\u7528\u6237\u8fdb\u7a0b\u5224\u65ad\u6807\u5fd7\u662fewouldblock\u65f6\uff0c\u5c31\u77e5\u9053\u6570\u636e\u8fd8\u6ca1\u51c6\u5907\u597d\uff0c\u4e8e\u662f\u5b83\u5c31\u53ef\u4ee5\u53bb\u505a\u5176\u4ed6\u7684\u4e8b\u4e86\uff0c\u4e8e\u662f\u5b83\u53ef\u4ee5\u518d\u6b21\u53d1\u9001recvfrom\uff0c\u4e00\u65e6\u5185\u6838\u4e2d\u7684\u6570\u636e\u51c6\u5907\u597d\u4e86\u3002\u5e76\u4e14\u53c8\u518d\u6b21\u6536\u5230\u4e86\u7528\u6237\u8fdb\u7a0b\u7684system call\uff0c\u90a3\u4e48\u5b83\u9a6c\u4e0a\u5c31\u5c06\u6570\u636e\u62f7\u8d1d\u5230\u4e86\u7528\u6237\u5185\u5b58\uff0c\u7136\u540e\u8fd4\u56de\u3002<\/p>\n<p>\u5f53\u4e00\u4e2a\u5e94\u7528\u7a0b\u5e8f\u5728\u4e00\u4e2a\u5faa\u73af\u91cc\u5bf9\u4e00\u4e2a\u975e\u963b\u585e\u8c03\u7528recvfrom\uff0c\u6211\u4eec\u79f0\u4e3a\u8f6e\u8be2\u3002\u5e94\u7528\u7a0b\u5e8f\u4e0d\u65ad\u8f6e\u8be2\u5185\u6838\uff0c\u770b\u770b\u662f\u5426\u5df2\u7ecf\u51c6\u5907\u597d\u4e86\u67d0\u4e9b\u64cd\u4f5c\u3002\u8fd9\u901a\u5e38\u662f<strong>\u6d6a\u8d39CPU\u65f6\u95f4<\/strong>\uff0c\u4f46\u8fd9\u79cd\u6a21\u5f0f\u5076\u5c14\u4f1a\u9047\u5230\u3002<\/p>\n<h3>I\/O\u590d\u7528\uff08I\/O Multiplexing)<\/h3>\n<p>IO multiplexing\u8fd9\u4e2a\u8bcd\u53ef\u80fd\u6709\u70b9\u964c\u751f\uff0c\u4f46\u662f\u5982\u679c\u6211\u8bf4select\uff0cepoll\uff0c\u5927\u6982\u5c31\u90fd\u80fd\u660e\u767d\u4e86\u3002\u6709\u4e9b\u5730\u65b9\u4e5f\u79f0\u8fd9\u79cdIO\u65b9\u5f0f\u4e3aevent driven IO\u3002\u6211\u4eec\u90fd\u77e5\u9053\uff0cselect\/epoll\u7684\u597d\u5904\u5c31\u5728\u4e8e\u5355\u4e2aprocess\u5c31\u53ef\u4ee5\u540c\u65f6\u5904\u7406\u591a\u4e2a\u7f51\u7edc\u8fde\u63a5\u7684IO\u3002\u5b83\u7684\u57fa\u672c\u539f\u7406\u5c31\u662fselect\/epoll\u8fd9\u4e2afunction\u4f1a\u4e0d\u65ad\u7684\u8f6e\u8be2\u6240\u8d1f\u8d23\u7684\u6240\u6709socket\uff0c\u5f53\u67d0\u4e2asocket\u6709\u6570\u636e\u5230\u8fbe\u4e86\uff0c\u5c31\u901a\u77e5\u7528\u6237\u8fdb\u7a0b\u3002\u5b83\u7684\u6d41\u7a0b\u5982\u56fe\uff1a<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/mmbiz.qpic.cn\/mmbiz_png\/1QxwhpDy7ia1mMN6NlFd3fDIMRY5O2CHebauXwbFRBZCjibSLkpcribiavclnxDTFPLRib6jaFj0daFysibEqKNwibwHg\/640\"><\/p>\n<p>\u5f53\u7528\u6237\u8fdb\u7a0b\u8c03\u7528\u4e86select\uff0c\u90a3\u4e48\u6574\u4e2a\u8fdb\u7a0b\u4f1a\u88abblock\uff0c\u800c\u540c\u65f6\uff0c\u5185\u6838\u4f1a\u201c\u76d1\u89c6\u201d\u6240\u6709select\u8d1f\u8d23\u7684socket\uff0c\u5f53\u4efb\u4f55\u4e00\u4e2asocket\u4e2d\u7684\u6570\u636e\u51c6\u5907\u597d\u4e86\uff0cselect\u5c31\u4f1a\u8fd4\u56de\u3002\u8fd9\u4e2a\u65f6\u5019\u7528\u6237\u8fdb\u7a0b\u518d\u8c03\u7528read\u64cd\u4f5c\uff0c\u5c06\u6570\u636e\u4ece\u5185\u6838\u62f7\u8d1d\u5230\u7528\u6237\u8fdb\u7a0b\u3002 \u8fd9\u4e2a\u56fe\u548cblocking IO\u7684\u56fe\u5176\u5b9e\u5e76\u6ca1\u6709\u592a\u5927\u7684\u4e0d\u540c\uff0c\u4e8b\u5b9e\u4e0a\uff0c\u8fd8\u66f4\u5dee\u4e00\u4e9b\u3002\u56e0\u4e3a\u8fd9\u91cc\u9700\u8981\u4f7f\u7528\u4e24\u4e2asystem call (select \u548c recvfrom)\uff0c\u800cblocking IO\u53ea\u8c03\u7528\u4e86\u4e00\u4e2asystem call (recvfrom)\u3002\u4f46\u662f\uff0c\u7528select\u7684\u4f18\u52bf\u5728\u4e8e\u5b83\u53ef\u4ee5\u540c\u65f6\u5904\u7406\u591a\u4e2aconnection\u3002\uff08\u591a\u8bf4\u4e00\u53e5\u3002\u6240\u4ee5\uff0c\u5982\u679c\u5904\u7406\u7684\u8fde\u63a5\u6570\u4e0d\u662f\u5f88\u9ad8\u7684\u8bdd\uff0c\u4f7f\u7528select\/epoll\u7684web server\u4e0d\u4e00\u5b9a\u6bd4\u4f7f\u7528multi-threading + blocking IO\u7684web server\u6027\u80fd\u66f4\u597d\uff0c\u53ef\u80fd\u5ef6\u8fdf\u8fd8\u66f4\u5927\u3002select\/epoll\u7684\u4f18\u52bf\u5e76\u4e0d\u662f\u5bf9\u4e8e\u5355\u4e2a\u8fde\u63a5\u80fd\u5904\u7406\u5f97\u66f4\u5feb\uff0c\u800c\u662f\u5728\u4e8e\u80fd\u5904\u7406\u66f4\u591a\u7684\u8fde\u63a5\u3002\uff09 \u5728IO multiplexing Model\u4e2d\uff0c\u5b9e\u9645\u4e2d\uff0c\u5bf9\u4e8e\u6bcf\u4e00\u4e2asocket\uff0c\u4e00\u822c\u90fd\u8bbe\u7f6e\u6210\u4e3anon-blocking\uff0c\u4f46\u662f\uff0c\u5982\u4e0a\u56fe\u6240\u793a\uff0c\u6574\u4e2a\u7528\u6237\u7684process\u5176\u5b9e\u662f\u4e00\u76f4\u88abblock\u7684\u3002\u53ea\u4e0d\u8fc7process\u662f\u88abselect\u8fd9\u4e2a\u51fd\u6570block\uff0c\u800c\u4e0d\u662f\u88absocket IO\u7ed9block\u3002<\/p>\n<h4>\u6587\u4ef6\u63cf\u8ff0\u7b26fd<\/h4>\n<p>Linux\u7684\u5185\u6838\u5c06\u6240\u6709\u5916\u90e8\u8bbe\u5907\u90fd\u53ef\u4ee5\u770b\u505a\u4e00\u4e2a\u6587\u4ef6\u6765\u64cd\u4f5c\u3002\u90a3\u4e48\u6211\u4eec\u5bf9\u4e0e\u5916\u90e8\u8bbe\u5907\u7684\u64cd\u4f5c\u90fd\u53ef\u4ee5\u770b\u505a\u5bf9\u6587\u4ef6\u8fdb\u884c\u64cd\u4f5c\u3002\u6211\u4eec\u5bf9\u4e00\u4e2a\u6587\u4ef6\u7684\u8bfb\u5199\uff0c\u90fd\u901a\u8fc7\u8c03\u7528\u5185\u6838\u63d0\u4f9b\u7684\u7cfb\u7edf\u8c03\u7528\uff1b\u5185\u6838\u7ed9\u6211\u4eec\u8fd4\u56de\u4e00\u4e2afilede scriptor\uff08fd,\u6587\u4ef6\u63cf\u8ff0\u7b26\uff09\u3002\u800c\u5bf9\u4e00\u4e2asocket\u7684\u8bfb\u5199\u4e5f\u4f1a\u6709\u76f8\u5e94\u7684\u63cf\u8ff0\u7b26\uff0c\u79f0\u4e3asocketfd(socket\u63cf\u8ff0\u7b26\uff09\u3002\u63cf\u8ff0\u7b26\u5c31\u662f\u4e00\u4e2a\u6570\u5b57\uff0c\u6307\u5411\u5185\u6838\u4e2d\u4e00\u4e2a\u7ed3\u6784\u4f53\uff08\u6587\u4ef6\u8def\u5f84\uff0c\u6570\u636e\u533a\uff0c\u7b49\u4e00\u4e9b\u5c5e\u6027\uff09\u3002\u90a3\u4e48\u6211\u4eec\u7684\u5e94\u7528\u7a0b\u5e8f\u5bf9\u6587\u4ef6\u7684\u8bfb\u5199\u5c31\u901a\u8fc7\u5bf9\u63cf\u8ff0\u7b26\u7684\u8bfb\u5199\u5b8c\u6210\u3002<\/p>\n<h4>select<\/h4>\n<p><strong>\u57fa\u672c\u539f\u7406\uff1a<\/strong>select \u51fd\u6570\u76d1\u89c6\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u52063\u7c7b\uff0c\u5206\u522b\u662fwritefds\u3001readfds\u3001\u548cexceptfds\u3002\u8c03\u7528\u540eselect\u51fd\u6570\u4f1a\u963b\u585e\uff0c\u76f4\u5230\u6709\u63cf\u8ff0\u7b26\u5c31\u7eea\uff08\u6709\u6570\u636e \u53ef\u8bfb\u3001\u53ef\u5199\u3001\u6216\u8005\u6709except\uff09\uff0c\u6216\u8005\u8d85\u65f6\uff08timeout\u6307\u5b9a\u7b49\u5f85\u65f6\u95f4\uff0c\u5982\u679c\u7acb\u5373\u8fd4\u56de\u8bbe\u4e3anull\u5373\u53ef\uff09\uff0c\u51fd\u6570\u8fd4\u56de\u3002\u5f53select\u51fd\u6570\u8fd4\u56de\u540e\uff0c\u53ef\u4ee5\u901a\u8fc7\u904d\u5386fdset\uff0c\u6765\u627e\u5230\u5c31\u7eea\u7684\u63cf\u8ff0\u7b26\u3002<\/p>\n<p>\u7f3a\u70b9: 1\u3001select\u6700\u5927\u7684\u7f3a\u9677\u5c31\u662f\u5355\u4e2a\u8fdb\u7a0b\u6240\u6253\u5f00\u7684FD\u662f\u6709\u4e00\u5b9a\u9650\u5236\u7684\uff0c\u5b83\u7531FDSETSIZE\u8bbe\u7f6e\uff0c32\u4f4d\u673a\u9ed8\u8ba4\u662f1024\u4e2a\uff0c64\u4f4d\u673a\u9ed8\u8ba4\u662f2048\u3002 \u4e00\u822c\u6765\u8bf4\u8fd9\u4e2a\u6570\u76ee\u548c\u7cfb\u7edf\u5185\u5b58\u5173\u7cfb\u5f88\u5927\uff0c\u201d\u5177\u4f53\u6570\u76ee\u53ef\u4ee5cat \/proc\/sys\/fs\/file-max\u5bdf\u770b\u201d\u300232\u4f4d\u673a\u9ed8\u8ba4\u662f1024\u4e2a\u300264\u4f4d\u673a\u9ed8\u8ba4\u662f2048. 2\u3001\u5bf9socket\u8fdb\u884c\u626b\u63cf\u65f6\u662f\u7ebf\u6027\u626b\u63cf\uff0c\u5373\u91c7\u7528\u8f6e\u8be2\u7684\u65b9\u6cd5\uff0c\u6548\u7387\u8f83\u4f4e\u3002 \u5f53\u5957\u63a5\u5b57\u6bd4\u8f83\u591a\u7684\u65f6\u5019\uff0c\u6bcf\u6b21select()\u90fd\u8981\u901a\u8fc7\u904d\u5386FDSETSIZE\u4e2aSocket\u6765\u5b8c\u6210\u8c03\u5ea6\uff0c\u4e0d\u7ba1\u54ea\u4e2aSocket\u662f\u6d3b\u8dc3\u7684\uff0c\u90fd\u904d\u5386\u4e00\u904d\u3002\u8fd9\u4f1a\u6d6a\u8d39\u5f88\u591aCPU\u65f6\u95f4\u3002\u201d\u5982\u679c\u80fd\u7ed9\u5957\u63a5\u5b57\u6ce8\u518c\u67d0\u4e2a\u56de\u8c03\u51fd\u6570\uff0c\u5f53\u4ed6\u4eec\u6d3b\u8dc3\u65f6\uff0c\u81ea\u52a8\u5b8c\u6210\u76f8\u5173\u64cd\u4f5c\uff0c\u90a3\u5c31\u907f\u514d\u4e86\u8f6e\u8be2\u201d\uff0c\u8fd9\u6b63\u662fepoll\u4e0ekqueue\u505a\u7684\u3002 3\u3001\u9700\u8981\u7ef4\u62a4\u4e00\u4e2a\u7528\u6765\u5b58\u653e\u5927\u91cffd\u7684\u6570\u636e\u7ed3\u6784\uff0c\u8fd9\u6837\u4f1a\u4f7f\u5f97\u7528\u6237\u7a7a\u95f4\u548c\u5185\u6838\u7a7a\u95f4\u5728\u4f20\u9012\u8be5\u7ed3\u6784\u65f6\u590d\u5236\u5f00\u9500\u5927\u3002<\/p>\n<h4>poll<\/h4>\n<p><strong>\u57fa\u672c\u539f\u7406\uff1a<\/strong>poll\u672c\u8d28\u4e0a\u548cselect\u6ca1\u6709\u533a\u522b\uff0c\u5b83\u5c06\u7528\u6237\u4f20\u5165\u7684\u6570\u7ec4\u62f7\u8d1d\u5230\u5185\u6838\u7a7a\u95f4\uff0c\u7136\u540e\u67e5\u8be2\u6bcf\u4e2afd\u5bf9\u5e94\u7684\u8bbe\u5907\u72b6\u6001\uff0c\u5982\u679c\u8bbe\u5907\u5c31\u7eea\u5219\u5728\u8bbe\u5907\u7b49\u5f85\u961f\u5217\u4e2d\u52a0\u5165\u4e00\u9879\u5e76\u7ee7\u7eed\u904d\u5386\uff0c\u5982\u679c\u904d\u5386\u5b8c\u6240\u6709fd\u540e\u6ca1\u6709\u53d1\u73b0\u5c31\u7eea\u8bbe\u5907\uff0c\u5219\u6302\u8d77\u5f53\u524d\u8fdb\u7a0b\uff0c\u76f4\u5230\u8bbe\u5907\u5c31\u7eea\u6216\u8005\u4e3b\u52a8\u8d85\u65f6\uff0c\u88ab\u5524\u9192\u540e\u5b83\u53c8\u8981\u518d\u6b21\u904d\u5386fd\u3002\u8fd9\u4e2a\u8fc7\u7a0b\u7ecf\u5386\u4e86\u591a\u6b21\u65e0\u8c13\u7684\u904d\u5386\u3002<\/p>\n<p><strong>\u5b83\u6ca1\u6709\u6700\u5927\u8fde\u63a5\u6570\u7684\u9650\u5236\uff0c\u539f\u56e0\u662f\u5b83\u662f\u57fa\u4e8e\u94fe\u8868\u6765\u5b58\u50a8\u7684\uff0c\u4f46\u662f\u540c\u6837\u6709\u4e00\u4e2a\u7f3a\u70b9\uff1a<\/strong>1\u3001\u5927\u91cf\u7684fd\u7684\u6570\u7ec4\u88ab\u6574\u4f53\u590d\u5236\u4e8e\u7528\u6237\u6001\u548c\u5185\u6838\u5730\u5740\u7a7a\u95f4\u4e4b\u95f4\uff0c\u800c\u4e0d\u7ba1\u8fd9\u6837\u7684\u590d\u5236\u662f\u4e0d\u662f\u6709\u610f\u4e49\u3002 2 \u3001poll\u8fd8\u6709\u4e00\u4e2a\u7279\u70b9\u662f\u201c\u6c34\u5e73\u89e6\u53d1\u201d\uff0c\u5982\u679c\u62a5\u544a\u4e86fd\u540e\uff0c\u6ca1\u6709\u88ab\u5904\u7406\uff0c\u90a3\u4e48\u4e0b\u6b21poll\u65f6\u4f1a\u518d\u6b21\u62a5\u544a\u8be5fd\u3002<\/p>\n<p><strong>\u6ce8\u610f\uff1a<\/strong>\u4ece\u4e0a\u9762\u770b\uff0cselect\u548cpoll\u90fd\u9700\u8981\u5728\u8fd4\u56de\u540e\uff0c\u901a\u8fc7\u904d\u5386\u6587\u4ef6\u63cf\u8ff0\u7b26\u6765\u83b7\u53d6\u5df2\u7ecf\u5c31\u7eea\u7684socket\u3002\u4e8b\u5b9e\u4e0a\uff0c\u540c\u65f6\u8fde\u63a5\u7684\u5927\u91cf\u5ba2\u6237\u7aef\u5728\u4e00\u65f6\u523b\u53ef\u80fd\u53ea\u6709\u5f88\u5c11\u7684\u5904\u4e8e\u5c31\u7eea\u72b6\u6001\uff0c\u56e0\u6b64\u968f\u7740\u76d1\u89c6\u7684\u63cf\u8ff0\u7b26\u6570\u91cf\u7684\u589e\u957f\uff0c\u5176\u6548\u7387\u4e5f\u4f1a\u7ebf\u6027\u4e0b\u964d\u3002<\/p>\n<h4>epoll<\/h4>\n<p>epoll\u662f\u57282.6\u5185\u6838\u4e2d\u63d0\u51fa\u7684\uff0c\u662f\u4e4b\u524d\u7684select\u548cpoll\u7684\u589e\u5f3a\u7248\u672c\u3002\u76f8\u5bf9\u4e8eselect\u548cpoll\u6765\u8bf4\uff0cepoll\u66f4\u52a0\u7075\u6d3b\uff0c\u6ca1\u6709\u63cf\u8ff0\u7b26\u9650\u5236\u3002epoll\u4f7f\u7528\u4e00\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\u7ba1\u7406\u591a\u4e2a\u63cf\u8ff0\u7b26\uff0c\u5c06\u7528\u6237\u5173\u7cfb\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u7684\u4e8b\u4ef6\u5b58\u653e\u5230\u5185\u6838\u7684\u4e00\u4e2a\u4e8b\u4ef6\u8868\u4e2d\uff0c\u8fd9\u6837\u5728\u7528\u6237\u7a7a\u95f4\u548c\u5185\u6838\u7a7a\u95f4\u7684copy\u53ea\u9700\u4e00\u6b21\u3002<\/p>\n<p><strong>\u57fa\u672c\u539f\u7406\uff1a<\/strong>epoll\u652f\u6301\u6c34\u5e73\u89e6\u53d1\u548c\u8fb9\u7f18\u89e6\u53d1\uff0c\u6700\u5927\u7684\u7279\u70b9\u5728\u4e8e\u8fb9\u7f18\u89e6\u53d1\uff0c\u5b83\u53ea\u544a\u8bc9\u8fdb\u7a0b\u54ea\u4e9bfd\u521a\u521a\u53d8\u4e3a\u5c31\u7eea\u6001\uff0c\u5e76\u4e14\u53ea\u4f1a\u901a\u77e5\u4e00\u6b21\u3002\u8fd8\u6709\u4e00\u4e2a\u7279\u70b9\u662f\uff0cepoll\u4f7f\u7528\u201c\u4e8b\u4ef6\u201d\u7684\u5c31\u7eea\u901a\u77e5\u65b9\u5f0f\uff0c\u901a\u8fc7epollctl\u6ce8\u518cfd\uff0c\u4e00\u65e6\u8be5fd\u5c31\u7eea\uff0c\u5185\u6838\u5c31\u4f1a\u91c7\u7528\u7c7b\u4f3ccallback\u7684\u56de\u8c03\u673a\u5236\u6765\u6fc0\u6d3b\u8be5fd\uff0cepollwait\u4fbf\u53ef\u4ee5\u6536\u5230\u901a\u77e5\u3002<\/p>\n<p><strong>epoll\u7684\u4f18\u70b9\uff1a<\/strong>1\u3001\u6ca1\u6709\u6700\u5927\u5e76\u53d1\u8fde\u63a5\u7684\u9650\u5236\uff0c\u80fd\u6253\u5f00\u7684FD\u7684\u4e0a\u9650\u8fdc\u5927\u4e8e1024\uff081G\u7684\u5185\u5b58\u4e0a\u80fd\u76d1\u542c\u7ea610\u4e07\u4e2a\u7aef\u53e3\uff09\u3002 2\u3001\u6548\u7387\u63d0\u5347\uff0c\u4e0d\u662f\u8f6e\u8be2\u7684\u65b9\u5f0f\uff0c\u4e0d\u4f1a\u968f\u7740FD\u6570\u76ee\u7684\u589e\u52a0\u6548\u7387\u4e0b\u964d\u3002 \u53ea\u6709\u6d3b\u8dc3\u53ef\u7528\u7684FD\u624d\u4f1a\u8c03\u7528callback\u51fd\u6570\uff1b\u5373Epoll\u6700\u5927\u7684\u4f18\u70b9\u5c31\u5728\u4e8e\u5b83\u53ea\u7ba1\u4f60\u201c\u6d3b\u8dc3\u201d\u7684\u8fde\u63a5\uff0c\u800c\u8ddf\u8fde\u63a5\u603b\u6570\u65e0\u5173\uff0c\u56e0\u6b64\u5728\u5b9e\u9645\u7684\u7f51\u7edc\u73af\u5883\u4e2d\uff0cEpoll\u7684\u6548\u7387\u5c31\u4f1a\u8fdc\u8fdc\u9ad8\u4e8eselect\u548cpoll\u3002 3\u3001\u5185\u5b58\u62f7\u8d1d\uff0c\u5229\u7528mmap()\u6587\u4ef6\u6620\u5c04\u5185\u5b58\u52a0\u901f\u4e0e\u5185\u6838\u7a7a\u95f4\u7684\u6d88\u606f\u4f20\u9012\uff1b\u5373epoll\u4f7f\u7528mmap\u51cf\u5c11\u590d\u5236\u5f00\u9500\u3002<\/p>\n<p><strong>JDK1.5_update10\u7248\u672c\u4f7f\u7528epoll\u66ff\u4ee3\u4e86\u4f20\u7edf\u7684select\/poll\uff0c\u6781\u5927\u7684\u63d0\u5347\u4e86NIO\u901a\u4fe1\u7684\u6027\u80fd\u3002<\/strong><\/p>\n<blockquote>\n<p><strong>\u5907\u6ce8\uff1a<\/strong>JDK NIO\u7684BUG\uff0c\u4f8b\u5982\u81ed\u540d\u662d\u8457\u7684epoll bug\uff0c\u5b83\u4f1a\u5bfc\u81f4Selector\u7a7a\u8f6e\u8be2\uff0c\u6700\u7ec8\u5bfc\u81f4CPU 100%\u3002\u5b98\u65b9\u58f0\u79f0\u5728JDK1.6\u7248\u672c\u7684update18\u4fee\u590d\u4e86\u8be5\u95ee\u9898\uff0c\u4f46\u662f\u76f4\u5230JDK1.7\u7248\u672c\u8be5\u95ee\u9898\u4ecd\u65e7\u5b58\u5728\uff0c\u53ea\u4e0d\u8fc7\u8be5BUG\u53d1\u751f\u6982\u7387\u964d\u4f4e\u4e86\u4e00\u4e9b\u800c\u5df2\uff0c\u5b83\u5e76\u6ca1\u6709\u88ab\u6839\u672c\u89e3\u51b3\u3002<strong>\u8fd9\u4e2a\u53ef\u4ee5\u5728\u540e\u7eednetty\u7cfb\u5217\u91cc\u9762\u8fdb\u884c\u8bf4\u660e\u4e0b\u3002<\/strong><\/p>\n<\/blockquote>\n<h3>\u4fe1\u53f7\u9a71\u52a8\u7684I\/O (Signal Driven I\/O)<\/h3>\n<blockquote>\n<p>\u7531\u4e8esignal driven IO\u5728\u5b9e\u9645\u4e2d\u5e76\u4e0d\u5e38\u7528\uff0c\u6240\u4ee5\u7b80\u5355\u63d0\u4e0b\u3002<\/p>\n<\/blockquote>\n<p><img decoding=\"async\" src=\"https:\/\/mmbiz.qpic.cn\/mmbiz_png\/1QxwhpDy7ia1mMN6NlFd3fDIMRY5O2CHeLKrGQbdFkMD69H2ZPiclicVDoT6M9D6oEnknUicDkCGGorAZFYUOA5xUA\/640\"><\/p>\n<p>\u5f88\u660e\u663e\u53ef\u4ee5\u770b\u51fa\u7528\u6237\u8fdb\u7a0b\u4e0d\u662f\u963b\u585e\u7684\u3002\u9996\u5148\u7528\u6237\u8fdb\u7a0b\u5efa\u7acbSIGIO\u4fe1\u53f7\u5904\u7406\u7a0b\u5e8f\uff0c\u5e76\u901a\u8fc7\u7cfb\u7edf\u8c03\u7528sigaction\u6267\u884c\u4e00\u4e2a\u4fe1\u53f7\u5904\u7406\u51fd\u6570\uff0c\u8fd9\u65f6\u7528\u6237\u8fdb\u7a0b\u4fbf\u53ef\u4ee5\u505a\u5176\u4ed6\u7684\u4e8b\u4e86\uff0c\u4e00\u65e6\u6570\u636e\u51c6\u5907\u597d\uff0c\u7cfb\u7edf\u4fbf\u4e3a\u8be5\u8fdb\u7a0b\u751f\u6210\u4e00\u4e2aSIGIO\u4fe1\u53f7\uff0c\u53bb\u901a\u77e5\u5b83\u6570\u636e\u5df2\u7ecf\u51c6\u5907\u597d\u4e86\uff0c\u4e8e\u662f\u7528\u6237\u8fdb\u7a0b\u4fbf\u8c03\u7528recvfrom\u628a\u6570\u636e\u4ece\u5185\u6838\u62f7\u8d1d\u51fa\u6765\uff0c\u5e76\u8fd4\u56de\u7ed3\u679c\u3002<\/p>\n<h3>\u5f02\u6b65I\/O<\/h3>\n<p>\u4e00\u822c\u6765\u8bf4\uff0c\u8fd9\u4e9b\u51fd\u6570\u901a\u8fc7\u544a\u8bc9\u5185\u6838\u542f\u52a8\u64cd\u4f5c\u5e76\u5728\u6574\u4e2a\u64cd\u4f5c\uff08\u5305\u62ec\u5185\u6838\u7684\u6570\u636e\u5230\u7f13\u51b2\u533a\u7684\u526f\u672c\uff09\u5b8c\u6210\u65f6\u901a\u77e5\u6211\u4eec\u3002\u8fd9\u4e2a\u6a21\u578b\u548c\u524d\u9762\u7684\u4fe1\u53f7\u9a71\u52a8I\/O\u6a21\u578b\u7684\u4e3b\u8981\u533a\u522b\u662f\uff0c\u5728\u4fe1\u53f7\u9a71\u52a8\u7684I\/O\u4e2d\uff0c\u5185\u6838\u544a\u8bc9\u6211\u4eec\u4f55\u65f6\u53ef\u4ee5\u542f\u52a8I\/O\u64cd\u4f5c\uff0c\u4f46\u662f\u5f02\u6b65I\/O\u65f6\uff0c\u5185\u6838\u544a\u8bc9\u6211\u4eec\u4f55\u65f6I\/O\u64cd\u4f5c\u5b8c\u6210\u3002<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/mmbiz.qpic.cn\/mmbiz_png\/1QxwhpDy7ia1mMN6NlFd3fDIMRY5O2CHe3TjSdfSDQFh6bXYtPYzQeb0K2X15TF0vIj6Q1SaMibRtT8iafSiaicSdKg\/640\"><\/p>\n<p>\u5f53\u7528\u6237\u8fdb\u7a0b\u5411\u5185\u6838\u53d1\u8d77\u67d0\u4e2a\u64cd\u4f5c\u540e\uff0c\u4f1a\u7acb\u523b\u5f97\u5230\u8fd4\u56de\uff0c\u5e76\u628a\u6240\u6709\u7684\u4efb\u52a1\u90fd\u4ea4\u7ed9\u5185\u6838\u53bb\u5b8c\u6210\uff08\u5305\u62ec\u5c06\u6570\u636e\u4ece\u5185\u6838\u62f7\u8d1d\u5230\u7528\u6237\u81ea\u5df1\u7684\u7f13\u51b2\u533a\uff09\uff0c\u5185\u6838\u5b8c\u6210\u4e4b\u540e\uff0c\u53ea\u9700\u8fd4\u56de\u4e00\u4e2a\u4fe1\u53f7\u544a\u8bc9\u7528\u6237\u8fdb\u7a0b\u5df2\u7ecf\u5b8c\u6210\u5c31\u53ef\u4ee5\u4e86\u3002<\/p>\n<h3>5\u4e2dI\/O\u6a21\u578b\u7684\u5bf9\u6bd4<\/h3>\n<p><img decoding=\"async\" src=\"data:image\/gif;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVQImWNgYGBgAAAABQABh6FO1AAAAABJRU5ErkJggg==\"><\/p>\n<blockquote>\n<p><strong>\u7ed3\u679c\u8868\u660e\uff1a<\/strong>\u524d\u56db\u4e2a\u6a21\u578b\u4e4b\u95f4\u7684\u4e3b\u8981\u533a\u522b\u662f\u7b2c\u4e00\u9636\u6bb5\uff0c\u56db\u4e2a\u6a21\u578b\u7684\u7b2c\u4e8c\u9636\u6bb5\u662f\u4e00\u6837\u7684\uff1a\u8fc7\u7a0b\u53d7\u963b\u5728\u8c03\u7528recvfrom\u5f53\u6570\u636e\u4ece\u5185\u6838\u62f7\u8d1d\u5230\u7528\u6237\u7f13\u51b2\u533a\u3002\u7136\u800c\uff0c\u5f02\u6b65I\/O\u5904\u7406\u4e24\u4e2a\u9636\u6bb5\uff0c\u4e0e\u524d\u56db\u4e2a\u4e0d\u540c\u3002<\/p>\n<\/blockquote>\n<p><img decoding=\"async\" src=\"data:image\/gif;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVQImWNgYGBgAAAABQABh6FO1AAAAABJRU5ErkJggg==\"><\/p>\n<p><strong>\u4ece\u540c\u6b65\u3001\u5f02\u6b65\uff0c\u4ee5\u53ca\u963b\u585e\u3001\u975e\u963b\u585e\u4e24\u4e2a\u7ef4\u5ea6\u6765\u5212\u5206\u6765\u770b\uff1a<\/strong><\/p>\n<p><img decoding=\"async\" src=\"https:\/\/mmbiz.qpic.cn\/mmbiz_png\/1QxwhpDy7ia1mMN6NlFd3fDIMRY5O2CHeH4ibEJCeGdGtr8sJvwf5Mlic1H0udJvVEqXTIFzLwknlic8KWtLl3OYhA\/640\"><\/p>\n<h2>\u96f6\u62f7\u8d1d<\/h2>\n<p><img decoding=\"async\" src=\"https:\/\/mmbiz.qpic.cn\/mmbiz_png\/1QxwhpDy7ia1mMN6NlFd3fDIMRY5O2CHeD9gicHia6ZuvVj98DwibFfQpoSB5GMkuhhiccfMWO9KhiaFheW1GwIXXHUA\/640\"><\/p>\n<p>CPU\u4e0d\u6267\u884c\u62f7\u8d1d\u6570\u636e\u4ece\u4e00\u4e2a\u5b58\u50a8\u533a\u57df\u5230\u53e6\u4e00\u4e2a\u5b58\u50a8\u533a\u57df\u7684\u4efb\u52a1\uff0c\u8fd9\u901a\u5e38\u7528\u4e8e\u5728\u7f51\u7edc\u4e0a\u4f20\u8f93\u6587\u4ef6\u65f6\u8282\u7701CPU\u5468\u671f\u548c\u5185\u5b58\u5e26\u5bbd\u3002<\/p>\n<h3>\u7f13\u5b58 IO<\/h3>\n<p>\u7f13\u5b58 IO \u53c8\u88ab\u79f0\u4f5c\u6807\u51c6 IO\uff0c\u5927\u591a\u6570\u6587\u4ef6\u7cfb\u7edf\u7684\u9ed8\u8ba4 IO \u64cd\u4f5c\u90fd\u662f\u7f13\u5b58 IO\u3002\u5728 Linux \u7684\u7f13\u5b58 IO \u673a\u5236\u4e2d\uff0c\u64cd\u4f5c\u7cfb\u7edf\u4f1a\u5c06 IO \u7684\u6570\u636e\u7f13\u5b58\u5728\u6587\u4ef6\u7cfb\u7edf\u7684\u9875\u7f13\u5b58\uff08 page cache \uff09\u4e2d\uff0c\u4e5f\u5c31\u662f\u8bf4\uff0c\u6570\u636e\u4f1a\u5148\u88ab\u62f7\u8d1d\u5230\u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u7684\u7f13\u51b2\u533a\u4e2d\uff0c\u7136\u540e\u624d\u4f1a\u4ece\u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u7684\u7f13\u51b2\u533a\u62f7\u8d1d\u5230\u5e94\u7528\u7a0b\u5e8f\u7684\u5730\u5740\u7a7a\u95f4\u3002<\/p>\n<p>\u7f13\u5b58 IO \u7684\u7f3a\u70b9\uff1a\u6570\u636e\u5728\u4f20\u8f93\u8fc7\u7a0b\u4e2d\u9700\u8981\u5728\u5e94\u7528\u7a0b\u5e8f\u5730\u5740\u7a7a\u95f4\u548c\u5185\u6838\u8fdb\u884c\u591a\u6b21\u6570\u636e\u62f7\u8d1d\u64cd\u4f5c\uff0c\u8fd9\u4e9b\u6570\u636e\u62f7\u8d1d\u64cd\u4f5c\u6240\u5e26\u6765\u7684 CPU \u4ee5\u53ca\u5185\u5b58\u5f00\u9500\u662f\u975e\u5e38\u5927\u7684\u3002<\/p>\n<h3>\u96f6\u62f7\u8d1d\u6280\u672f\u5206\u7c7b<\/h3>\n<p>\u96f6\u62f7\u8d1d\u6280\u672f\u7684\u53d1\u5c55\u5f88\u591a\u6837\u5316\uff0c\u73b0\u6709\u7684\u96f6\u62f7\u8d1d\u6280\u672f\u79cd\u7c7b\u4e5f\u975e\u5e38\u591a\uff0c\u800c\u5f53\u524d\u5e76\u6ca1\u6709\u4e00\u4e2a\u9002\u5408\u4e8e\u6240\u6709\u573a\u666f\u7684\u96f6\u62f7\u8d1d\u6280\u672f\u7684\u51fa\u73b0\u3002\u5bf9\u4e8e Linux \u6765\u8bf4\uff0c\u73b0\u5b58\u7684\u96f6\u62f7\u8d1d\u6280\u672f\u4e5f\u6bd4\u8f83\u591a\uff0c\u8fd9\u4e9b\u96f6\u62f7\u8d1d\u6280\u672f\u5927\u90e8\u5206\u5b58\u5728\u4e8e\u4e0d\u540c\u7684 Linux \u5185\u6838\u7248\u672c\uff0c\u6709\u4e9b\u65e7\u7684\u6280\u672f\u5728\u4e0d\u540c\u7684 Linux \u5185\u6838\u7248\u672c\u95f4\u5f97\u5230\u4e86\u5f88\u5927\u7684\u53d1\u5c55\u6216\u8005\u5df2\u7ecf\u6e10\u6e10\u88ab\u65b0\u7684\u6280\u672f\u6240\u4ee3\u66ff\u3002\u672c\u6587\u9488\u5bf9\u8fd9\u4e9b\u96f6\u62f7\u8d1d\u6280\u672f\u6240\u9002\u7528\u7684\u4e0d\u540c\u573a\u666f\u5bf9\u5b83\u4eec\u8fdb\u884c\u4e86\u5212\u5206\u3002\u6982\u62ec\u8d77\u6765\uff0cLinux \u4e2d\u7684\u96f6\u62f7\u8d1d\u6280\u672f\u4e3b\u8981\u6709\u4e0b\u9762\u8fd9\u51e0\u79cd\uff1a<\/p>\n<ul class=\"list-paddingleft-2\">\n<li>\n<p>\u76f4\u63a5 I\/O\uff1a\u5bf9\u4e8e\u8fd9\u79cd\u6570\u636e\u4f20\u8f93\u65b9\u5f0f\u6765\u8bf4\uff0c\u5e94\u7528\u7a0b\u5e8f\u53ef\u4ee5\u76f4\u63a5\u8bbf\u95ee\u786c\u4ef6\u5b58\u50a8\uff0c\u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u53ea\u662f\u8f85\u52a9\u6570\u636e\u4f20\u8f93\uff1a\u8fd9\u7c7b\u96f6\u62f7\u8d1d\u6280\u672f\u9488\u5bf9\u7684\u662f\u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u5e76\u4e0d\u9700\u8981\u5bf9\u6570\u636e\u8fdb\u884c\u76f4\u63a5\u5904\u7406\u7684\u60c5\u51b5\uff0c\u6570\u636e\u53ef\u4ee5\u5728\u5e94\u7528\u7a0b\u5e8f\u5730\u5740\u7a7a\u95f4\u7684\u7f13\u51b2\u533a\u548c\u78c1\u76d8\u4e4b\u95f4\u76f4\u63a5\u8fdb\u884c\u4f20\u8f93\uff0c\u5b8c\u5168\u4e0d\u9700\u8981 Linux \u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u63d0\u4f9b\u7684\u9875\u7f13\u5b58\u7684\u652f\u6301\u3002<\/p>\n<\/li>\n<li>\n<p>\u5728\u6570\u636e\u4f20\u8f93\u7684\u8fc7\u7a0b\u4e2d\uff0c\u907f\u514d\u6570\u636e\u5728\u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u5730\u5740\u7a7a\u95f4\u7684\u7f13\u51b2\u533a\u548c\u7528\u6237\u5e94\u7528\u7a0b\u5e8f\u5730\u5740\u7a7a\u95f4\u7684\u7f13\u51b2\u533a\u4e4b\u95f4\u8fdb\u884c\u62f7\u8d1d\u3002\u6709\u7684\u65f6\u5019\uff0c\u5e94\u7528\u7a0b\u5e8f\u5728\u6570\u636e\u8fdb\u884c\u4f20\u8f93\u7684\u8fc7\u7a0b\u4e2d\u4e0d\u9700\u8981\u5bf9\u6570\u636e\u8fdb\u884c\u8bbf\u95ee\uff0c\u90a3\u4e48\uff0c\u5c06\u6570\u636e\u4ece Linux \u7684\u9875\u7f13\u5b58\u62f7\u8d1d\u5230\u7528\u6237\u8fdb\u7a0b\u7684\u7f13\u51b2\u533a\u4e2d\u5c31\u53ef\u4ee5\u5b8c\u5168\u907f\u514d\uff0c\u4f20\u8f93\u7684\u6570\u636e\u5728\u9875\u7f13\u5b58\u4e2d\u5c31\u53ef\u4ee5\u5f97\u5230\u5904\u7406\u3002\u5728\u67d0\u4e9b\u7279\u6b8a\u7684\u60c5\u51b5\u4e0b\uff0c\u8fd9\u79cd\u96f6\u62f7\u8d1d\u6280\u672f\u53ef\u4ee5\u83b7\u5f97\u8f83\u597d\u7684\u6027\u80fd\u3002Linux \u4e2d\u63d0\u4f9b\u7c7b\u4f3c\u7684\u7cfb\u7edf\u8c03\u7528\u4e3b\u8981\u6709 mmap()\uff0csendfile() \u4ee5\u53ca splice()\u3002<\/p>\n<\/li>\n<li>\n<p>\u5bf9\u6570\u636e\u5728 Linux \u7684\u9875\u7f13\u5b58\u548c\u7528\u6237\u8fdb\u7a0b\u7684\u7f13\u51b2\u533a\u4e4b\u95f4\u7684\u4f20\u8f93\u8fc7\u7a0b\u8fdb\u884c\u4f18\u5316\u3002\u8be5\u96f6\u62f7\u8d1d\u6280\u672f\u4fa7\u91cd\u4e8e\u7075\u6d3b\u5730\u5904\u7406\u6570\u636e\u5728\u7528\u6237\u8fdb\u7a0b\u7684\u7f13\u51b2\u533a\u548c\u64cd\u4f5c\u7cfb\u7edf\u7684\u9875\u7f13\u5b58\u4e4b\u95f4\u7684\u62f7\u8d1d\u64cd\u4f5c\u3002\u8fd9\u79cd\u65b9\u6cd5\u5ef6\u7eed\u4e86\u4f20\u7edf\u7684\u901a\u4fe1\u65b9\u5f0f\uff0c\u4f46\u662f\u66f4\u52a0\u7075\u6d3b\u3002\u5728Linux \u4e2d\uff0c\u8be5\u65b9\u6cd5\u4e3b\u8981\u5229\u7528\u4e86\u5199\u65f6\u590d\u5236\u6280\u672f\u3002<\/p>\n<\/li>\n<\/ul>\n<p>\u524d\u4e24\u7c7b\u65b9\u6cd5\u7684\u76ee\u7684\u4e3b\u8981\u662f\u4e3a\u4e86\u907f\u514d\u5e94\u7528\u7a0b\u5e8f\u5730\u5740\u7a7a\u95f4\u548c\u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u5730\u5740\u7a7a\u95f4\u8fd9\u4e24\u8005\u4e4b\u95f4\u7684\u7f13\u51b2\u533a\u62f7\u8d1d\u64cd\u4f5c\u3002\u8fd9\u4e24\u7c7b\u96f6\u62f7\u8d1d\u6280\u672f\u901a\u5e38\u9002\u7528\u5728\u67d0\u4e9b\u7279\u6b8a\u7684\u60c5\u51b5\u4e0b\uff0c\u6bd4\u5982\u8981\u4f20\u9001\u7684\u6570\u636e\u4e0d\u9700\u8981\u7ecf\u8fc7\u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u7684\u5904\u7406\u6216\u8005\u4e0d\u9700\u8981\u7ecf\u8fc7\u5e94\u7528\u7a0b\u5e8f\u7684\u5904\u7406\u3002\u7b2c\u4e09\u7c7b\u65b9\u6cd5\u5219\u7ee7\u627f\u4e86\u4f20\u7edf\u7684\u5e94\u7528\u7a0b\u5e8f\u5730\u5740\u7a7a\u95f4\u548c\u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u5730\u5740\u7a7a\u95f4\u4e4b\u95f4\u6570\u636e\u4f20\u8f93\u7684\u6982\u5ff5\uff0c\u8fdb\u800c\u9488\u5bf9\u6570\u636e\u4f20\u8f93\u672c\u8eab\u8fdb\u884c\u4f18\u5316\u3002\u6211\u4eec\u77e5\u9053\uff0c\u786c\u4ef6\u548c\u8f6f\u4ef6\u4e4b\u95f4\u7684\u6570\u636e\u4f20\u8f93\u53ef\u4ee5\u901a\u8fc7\u4f7f\u7528 DMA \u6765\u8fdb\u884c\uff0cDMA \u8fdb\u884c\u6570\u636e\u4f20\u8f93\u7684\u8fc7\u7a0b\u4e2d\u51e0\u4e4e\u4e0d\u9700\u8981CPU\u53c2\u4e0e\uff0c\u8fd9\u6837\u5c31\u53ef\u4ee5\u628a CPU \u89e3\u653e\u51fa\u6765\u53bb\u505a\u66f4\u591a\u5176\u4ed6\u7684\u4e8b\u60c5\uff0c\u4f46\u662f\u5f53\u6570\u636e\u9700\u8981\u5728\u7528\u6237\u5730\u5740\u7a7a\u95f4\u7684\u7f13\u51b2\u533a\u548c Linux \u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u7684\u9875\u7f13\u5b58\u4e4b\u95f4\u8fdb\u884c\u4f20\u8f93\u7684\u65f6\u5019\uff0c\u5e76\u6ca1\u6709\u7c7b\u4f3cDMA \u8fd9\u79cd\u5de5\u5177\u53ef\u4ee5\u4f7f\u7528\uff0cCPU \u9700\u8981\u5168\u7a0b\u53c2\u4e0e\u5230\u8fd9\u79cd\u6570\u636e\u62f7\u8d1d\u64cd\u4f5c\u4e2d\uff0c\u6240\u4ee5\u8fd9\u7b2c\u4e09\u7c7b\u65b9\u6cd5\u7684\u76ee\u7684\u662f\u53ef\u4ee5\u6709\u6548\u5730\u6539\u5584\u6570\u636e\u5728\u7528\u6237\u5730\u5740\u7a7a\u95f4\u548c\u64cd\u4f5c\u7cfb\u7edf\u5185\u6838\u5730\u5740\u7a7a\u95f4\u4e4b\u95f4\u4f20\u9012\u7684\u6548\u7387\u3002<\/p>\n<blockquote>\n<p>\u6ce8\u610f\uff0c\u5bf9\u4e8e\u5404\u79cd\u96f6\u62f7\u8d1d\u673a\u5236\u662f\u5426\u80fd\u591f\u5b9e\u73b0\u90fd\u662f\u4f9d\u8d56\u4e8e\u64cd\u4f5c\u7cfb\u7edf\u5e95\u5c42\u662f\u5426\u63d0\u4f9b\u76f8\u5e94\u7684\u652f\u6301\u3002<\/p>\n<\/blockquote>\n<p><img decoding=\"async\" src=\"https:\/\/mmbiz.qpic.cn\/mmbiz_png\/1QxwhpDy7ia1mMN6NlFd3fDIMRY5O2CHeMibFzY1BGkqLJSFb6vlVCf4n4SheCGR0SLn1bJ1BgDgtkx1fKoUQZ1A\/640\">\u5f53\u5e94\u7528\u7a0b\u5e8f\u8bbf\u95ee\u67d0\u5757\u6570\u636e\u65f6\uff0c\u64cd\u4f5c\u7cfb\u7edf\u9996\u5148\u4f1a\u68c0\u67e5\uff0c\u662f\u4e0d\u662f\u6700\u8fd1\u8bbf\u95ee\u8fc7\u6b64\u6587\u4ef6\uff0c\u6587\u4ef6\u5185\u5bb9\u662f\u5426\u7f13\u5b58\u5728\u5185\u6838\u7f13\u51b2\u533a\uff0c\u5982\u679c\u662f\uff0c\u64cd\u4f5c\u7cfb\u7edf\u5219\u76f4\u63a5\u6839\u636eread\u7cfb\u7edf\u8c03\u7528\u63d0\u4f9b\u7684buf\u5730\u5740\uff0c\u5c06\u5185\u6838\u7f13\u51b2\u533a\u7684\u5185\u5bb9\u62f7\u8d1d\u5230buf\u6240\u6307\u5b9a\u7684\u7528\u6237\u7a7a\u95f4\u7f13\u51b2\u533a\u4e2d\u53bb\u3002\u5982\u679c\u4e0d\u662f\uff0c\u64cd\u4f5c\u7cfb\u7edf\u5219\u9996\u5148\u5c06\u78c1\u76d8\u4e0a\u7684\u6570\u636e\u62f7\u8d1d\u7684\u5185\u6838\u7f13\u51b2\u533a\uff0c\u8fd9\u4e00\u6b65\u76ee\u524d\u4e3b\u8981\u4f9d\u9760DMA\u6765\u4f20\u8f93\uff0c\u7136\u540e\u518d\u628a\u5185\u6838\u7f13\u51b2\u533a\u4e0a\u7684\u5185\u5bb9\u62f7\u8d1d\u5230\u7528\u6237\u7f13\u51b2\u533a\u4e2d\u3002 \u63a5\u4e0b\u6765\uff0cwrite\u7cfb\u7edf\u8c03\u7528\u518d\u628a\u7528\u6237\u7f13\u51b2\u533a\u7684\u5185\u5bb9\u62f7\u8d1d\u5230\u7f51\u7edc\u5806\u6808\u76f8\u5173\u7684\u5185\u6838\u7f13\u51b2\u533a\u4e2d\uff0c\u6700\u540esocket\u518d\u628a\u5185\u6838\u7f13\u51b2\u533a\u7684\u5185\u5bb9\u53d1\u9001\u5230\u7f51\u5361\u4e0a\u3002<\/p>\n<p>\u4ece\u4e0a\u56fe\u4e2d\u53ef\u4ee5\u770b\u51fa\uff0c\u5171\u4ea7\u751f\u4e86\u56db\u6b21\u6570\u636e\u62f7\u8d1d\uff0c\u5373\u4f7f\u4f7f\u7528\u4e86DMA\u6765\u5904\u7406\u4e86\u4e0e\u786c\u4ef6\u7684\u901a\u8baf\uff0cCPU\u4ecd\u7136\u9700\u8981\u5904\u7406\u4e24\u6b21\u6570\u636e\u62f7\u8d1d\uff0c\u4e0e\u6b64\u540c\u65f6\uff0c\u5728\u7528\u6237\u6001\u4e0e\u5185\u6838\u6001\u4e5f\u53d1\u751f\u4e86\u591a\u6b21\u4e0a\u4e0b\u6587\u5207\u6362\uff0c\u65e0\u7591\u4e5f\u52a0\u91cd\u4e86CPU\u8d1f\u62c5\u3002 \u5728\u6b64\u8fc7\u7a0b\u4e2d\uff0c\u6211\u4eec\u6ca1\u6709\u5bf9\u6587\u4ef6\u5185\u5bb9\u505a\u4efb\u4f55\u4fee\u6539\uff0c\u90a3\u4e48\u5728\u5185\u6838\u7a7a\u95f4\u548c\u7528\u6237\u7a7a\u95f4\u6765\u56de\u62f7\u8d1d\u6570\u636e\u65e0\u7591\u5c31\u662f\u4e00\u79cd\u6d6a\u8d39\uff0c\u800c\u96f6\u62f7\u8d1d\u4e3b\u8981\u5c31\u662f\u4e3a\u4e86\u89e3\u51b3\u8fd9\u79cd\u4f4e\u6548\u6027\u3002<\/p>\n<p>### \u8ba9\u6570\u636e\u4f20\u8f93\u4e0d\u9700\u8981\u7ecf\u8fc7user space\uff0c\u4f7f\u7528mmap \u6211\u4eec\u51cf\u5c11\u62f7\u8d1d\u6b21\u6570\u7684\u4e00\u79cd\u65b9\u6cd5\u662f\u8c03\u7528mmap()\u6765\u4ee3\u66ffread\u8c03\u7528\uff1a<\/p>\n<ol class=\"list-paddingleft-2\">\n<li>\n<p><code class=\"\"><span class=\"\">buf <\/span><span class=\"\">=<\/span><span class=\"\"> mmap<\/span><span class=\"\">(<\/span><span class=\"\">diskfd<\/span><span class=\"\">,<\/span><span class=\"\"> len<\/span><span class=\"\">);<\/span><\/code><\/p>\n<\/li>\n<li>\n<p><code class=\"\"><span class=\"\">write<\/span><span class=\"\">(<\/span><span class=\"\">sockfd<\/span><span class=\"\">,<\/span><span class=\"\"> buf<\/span><span class=\"\">,<\/span><span class=\"\"> len<\/span><span class=\"\">);<\/span><\/code><\/p>\n<\/li>\n<\/ol>\n<p>\u5e94\u7528\u7a0b\u5e8f\u8c03\u7528 <code class=\"\"><span class=\"\">mmap<\/span><span class=\"\">()<\/span><\/code>\uff0c\u78c1\u76d8\u4e0a\u7684\u6570\u636e\u4f1a\u901a\u8fc7 <code class=\"\"><span class=\"\">DMA<\/span><\/code>\u88ab\u62f7\u8d1d\u7684\u5185\u6838\u7f13\u51b2\u533a\uff0c\u63a5\u7740\u64cd\u4f5c\u7cfb\u7edf\u4f1a\u628a\u8fd9\u6bb5\u5185\u6838\u7f13\u51b2\u533a\u4e0e\u5e94\u7528\u7a0b\u5e8f\u5171\u4eab\uff0c\u8fd9\u6837\u5c31\u4e0d\u9700\u8981\u628a\u5185\u6838\u7f13\u51b2\u533a\u7684\u5185\u5bb9\u5f80\u7528\u6237\u7a7a\u95f4\u62f7\u8d1d\u3002\u5e94\u7528\u7a0b\u5e8f\u518d\u8c03\u7528 <code class=\"\"><span class=\"\">write<\/span><span class=\"\">()<\/span><\/code>,\u64cd\u4f5c\u7cfb\u7edf\u76f4\u63a5\u5c06\u5185\u6838\u7f13\u51b2\u533a\u7684\u5185\u5bb9\u62f7\u8d1d\u5230 <code class=\"\"><span class=\"\">socket<\/span><\/code>\u7f13\u51b2\u533a\u4e2d\uff0c\u8fd9\u4e00\u5207\u90fd\u53d1\u751f\u5728\u5185\u6838\u6001\uff0c\u6700\u540e\uff0c <code class=\"\"><span class=\"\">socket<\/span><\/code>\u7f13\u51b2\u533a\u518d\u628a\u6570\u636e\u53d1\u5230\u7f51\u5361\u53bb\u3002<\/p>\n<p>\u540c\u6837\u7684\uff0c\u770b\u56fe\u5f88\u7b80\u5355\uff1a<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/mmbiz.qpic.cn\/mmbiz_png\/1QxwhpDy7ia1mMN6NlFd3fDIMRY5O2CHe7H5vYssv9cJfTibV6GCxDKb3UicBlentqlOW68ica0S4ONkWlwK7hkJVA\/640\"><\/p>\n<p>\u4f7f\u7528mmap\u66ff\u4ee3read\u5f88\u660e\u663e\u51cf\u5c11\u4e86\u4e00\u6b21\u62f7\u8d1d\uff0c\u5f53\u62f7\u8d1d\u6570\u636e\u91cf\u5f88\u5927\u65f6\uff0c\u65e0\u7591\u63d0\u5347\u4e86\u6548\u7387\u3002\u4f46\u662f\u4f7f\u7528 <code class=\"\"><span class=\"\">mmap<\/span><\/code>\u662f\u6709\u4ee3\u4ef7\u7684\u3002\u5f53\u4f60\u4f7f\u7528 <code class=\"\"><span class=\"\">mmap<\/span><\/code>\u65f6\uff0c\u4f60\u53ef\u80fd\u4f1a\u9047\u5230\u4e00\u4e9b\u9690\u85cf\u7684\u9677\u9631\u3002\u4f8b\u5982\uff0c\u5f53\u4f60\u7684\u7a0b\u5e8f <code class=\"\"><span class=\"\">map<\/span><\/code>\u4e86\u4e00\u4e2a\u6587\u4ef6\uff0c\u4f46\u662f\u5f53\u8fd9\u4e2a\u6587\u4ef6\u88ab\u53e6\u4e00\u4e2a\u8fdb\u7a0b\u622a\u65ad(truncate)\u65f6, write\u7cfb\u7edf\u8c03\u7528\u4f1a\u56e0\u4e3a\u8bbf\u95ee\u975e\u6cd5\u5730\u5740\u800c\u88ab <code class=\"\"><span class=\"\">SIGBUS<\/span><\/code>\u4fe1\u53f7\u7ec8\u6b62\u3002 <code class=\"\"><span class=\"\">SIGBUS<\/span><\/code>\u4fe1\u53f7\u9ed8\u8ba4\u4f1a\u6740\u6b7b\u4f60\u7684\u8fdb\u7a0b\u5e76\u4ea7\u751f\u4e00\u4e2a <code class=\"\"><span class=\"\">coredump<\/span><\/code>,\u5982\u679c\u4f60\u7684\u670d\u52a1\u5668\u8fd9\u6837\u88ab\u4e2d\u6b62\u4e86\uff0c\u90a3\u4f1a\u4ea7\u751f\u4e00\u7b14\u635f\u5931\u3002<\/p>\n<p>\u901a\u5e38\u6211\u4eec\u4f7f\u7528\u4ee5\u4e0b\u89e3\u51b3\u65b9\u6848\u907f\u514d\u8fd9\u79cd\u95ee\u9898\uff1a<\/p>\n<ol class=\"list-paddingleft-2\">\n<li>\n<p><strong>\u4e3aSIGBUS\u4fe1\u53f7\u5efa\u7acb\u4fe1\u53f7\u5904\u7406\u7a0b\u5e8f<\/strong>&nbsp;\u5f53\u9047\u5230&nbsp;<code class=\"\"><span class=\"\">SIGBUS<\/span><\/code>\u4fe1\u53f7\u65f6\uff0c\u4fe1\u53f7\u5904\u7406\u7a0b\u5e8f\u7b80\u5355\u5730\u8fd4\u56de\uff0c&nbsp;<code class=\"\"><span class=\"\">write<\/span><\/code>\u7cfb\u7edf\u8c03\u7528\u5728\u88ab\u4e2d\u65ad\u4e4b\u524d\u4f1a\u8fd4\u56de\u5df2\u7ecf\u5199\u5165\u7684\u5b57\u8282\u6570\uff0c\u5e76\u4e14&nbsp;<code class=\"\"><span class=\"\">errno<\/span><\/code>\u4f1a\u88ab\u8bbe\u7f6e\u6210success,\u4f46\u662f\u8fd9\u662f\u4e00\u79cd\u7cdf\u7cd5\u7684\u5904\u7406\u529e\u6cd5\uff0c\u56e0\u4e3a\u4f60\u5e76\u6ca1\u6709\u89e3\u51b3\u95ee\u9898\u7684\u5b9e\u8d28\u6838\u5fc3\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u4f7f\u7528\u6587\u4ef6\u79df\u501f\u9501<\/strong>&nbsp;\u901a\u5e38\u6211\u4eec\u4f7f\u7528\u8fd9\u79cd\u65b9\u6cd5\uff0c\u5728\u6587\u4ef6\u63cf\u8ff0\u7b26\u4e0a\u4f7f\u7528\u79df\u501f\u9501\uff0c\u6211\u4eec\u4e3a\u6587\u4ef6\u5411\u5185\u6838\u7533\u8bf7\u4e00\u4e2a\u79df\u501f\u9501\uff0c\u5f53\u5176\u5b83\u8fdb\u7a0b\u60f3\u8981\u622a\u65ad\u8fd9\u4e2a\u6587\u4ef6\u65f6\uff0c\u5185\u6838\u4f1a\u5411\u6211\u4eec\u53d1\u9001\u4e00\u4e2a\u5b9e\u65f6\u7684&nbsp;<code class=\"\"><span class=\"\">RT_SIGNAL_LEASE<\/span><\/code>\u4fe1\u53f7\uff0c\u544a\u8bc9\u6211\u4eec\u5185\u6838\u6b63\u5728\u7834\u574f\u4f60\u52a0\u6301\u5728\u6587\u4ef6\u4e0a\u7684\u8bfb\u5199\u9501\u3002\u8fd9\u6837\u5728\u7a0b\u5e8f\u8bbf\u95ee\u975e\u6cd5\u5185\u5b58\u5e76\u4e14\u88ab&nbsp;<code class=\"\"><span class=\"\">SIGBUS<\/span><\/code>\u6740\u6b7b\u4e4b\u524d\uff0c\u4f60\u7684&nbsp;<code class=\"\"><span class=\"\">write<\/span><\/code>\u7cfb\u7edf\u8c03\u7528\u4f1a\u88ab\u4e2d\u65ad\u3002&nbsp;<code class=\"\"><span class=\"\">write<\/span><\/code>\u4f1a\u8fd4\u56de\u5df2\u7ecf\u5199\u5165\u7684\u5b57\u8282\u6570\uff0c\u5e76\u4e14\u7f6e&nbsp;<code class=\"\"><span class=\"\">errno<\/span><\/code>\u4e3asuccess\u3002 \u6211\u4eec\u5e94\u8be5\u5728&nbsp;<code class=\"\"><span class=\"\">mmap<\/span><\/code>\u6587\u4ef6\u4e4b\u524d\u52a0\u9501\uff0c\u5e76\u4e14\u5728\u64cd\u4f5c\u5b8c\u6587\u4ef6\u540e\u89e3\u9501\uff1a<\/p>\n<\/li>\n<\/ol>\n<ol class=\"list-paddingleft-2\">\n<li>\n<p><code><span class=\"\">if<\/span><span class=\"\">(<\/span><span class=\"\">fcntl<\/span><span class=\"\">(<\/span><span class=\"\">diskfd<\/span><span class=\"\">,<\/span><span class=\"\"> F_SETSIG<\/span><span class=\"\">,<\/span><span class=\"\"> RT_SIGNAL_LEASE<\/span><span class=\"\">)<\/span> <span class=\"\">==<\/span> <span class=\"\">-<\/span><span class=\"\">1<\/span><span class=\"\">)<\/span> <span class=\"\">{<\/span><\/code><\/p>\n<\/li>\n<li>\n<p><code><span class=\"\"> &nbsp; &nbsp;perror<\/span><span class=\"\">(<\/span><span class=\"\">\"kernel lease set signal\"<\/span><span class=\"\">);<\/span><\/code><\/p>\n<\/li>\n<li>\n<p><code><span class=\"\"> &nbsp; &nbsp;<\/span><span class=\"\">return<\/span> <span class=\"\">-<\/span><span class=\"\">1<\/span><span class=\"\">;<\/span><\/code><\/p>\n<\/li>\n<li>\n<p><code><span class=\"\">}<\/span><\/code><\/p>\n<\/li>\n<li>\n<p><code><span class=\"\">\/* l_type can be F_RDLCK F_WRLCK &nbsp;\u52a0\u9501*\/<\/span><\/code><\/p>\n<\/li>\n<li>\n<p><code><span class=\"\">\/* l_type can be &nbsp;F_UNLCK \u89e3\u9501*\/<\/span><\/code><\/p>\n<\/li>\n<li>\n<p><code><span class=\"\">if<\/span><span class=\"\">(<\/span><span class=\"\">fcntl<\/span><span class=\"\">(<\/span><span class=\"\">diskfd<\/span><span class=\"\">,<\/span><span class=\"\"> F_SETLEASE<\/span><span class=\"\">,<\/span><span class=\"\"> l_type<\/span><span class=\"\">)){<\/span><\/code><\/p>\n<\/li>\n<li>\n<p><code><span class=\"\"> &nbsp; &nbsp;perror<\/span><span class=\"\">(<\/span><span class=\"\">\"kernel lease set type\"<\/span><span class=\"\">);<\/span><\/code><\/p>\n<\/li>\n<li>\n<p><code><span class=\"\"> &nbsp; &nbsp;<\/span><span class=\"\">return<\/span> <span class=\"\">-<\/span><span class=\"\">1<\/span><span class=\"\">;<\/span><\/code><\/p>\n<\/li>\n<li>\n<p><code><span class=\"\">}<\/span><\/code><\/p>\n<\/li>\n<\/ol>","protected":false},"excerpt":{"rendered":"<p>\u8f6c\u8f7d\u81ea\uff1ahttps:\/\/mp.weixin.qq.com\/s?__biz=MzU0MzQ5MDA0M &hellip;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"series":[],"class_list":["post-446","post","type-post","status-publish","format-standard","hentry","category-programmers"],"_links":{"self":[{"href":"https:\/\/fick707.com\/index.php?rest_route=\/wp\/v2\/posts\/446"}],"collection":[{"href":"https:\/\/fick707.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/fick707.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/fick707.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/fick707.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=446"}],"version-history":[{"count":4,"href":"https:\/\/fick707.com\/index.php?rest_route=\/wp\/v2\/posts\/446\/revisions"}],"predecessor-version":[{"id":451,"href":"https:\/\/fick707.com\/index.php?rest_route=\/wp\/v2\/posts\/446\/revisions\/451"}],"wp:attachment":[{"href":"https:\/\/fick707.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=446"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/fick707.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=446"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/fick707.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=446"},{"taxonomy":"series","embeddable":true,"href":"https:\/\/fick707.com\/index.php?rest_route=%2Fwp%2Fv2%2Fseries&post=446"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}