{"id":502,"date":"2023-07-12T01:36:37","date_gmt":"2023-07-11T17:36:37","guid":{"rendered":"http:\/\/moyisuiying.com\/?p=502"},"modified":"2024-05-27T00:01:01","modified_gmt":"2024-05-26T16:01:01","slug":"%e5%bd%bb%e5%ba%95%e6%90%9e%e6%87%82%e9%9b%b6%e6%8b%b7%e8%b4%9d%ef%bc%88zero-copy%ef%bc%89%e6%8a%80%e6%9c%af","status":"publish","type":"post","link":"http:\/\/moyisuiying.com\/index.php\/os\/502.html","title":{"rendered":"\u5f7b\u5e95\u641e\u61c2\u96f6\u62f7\u8d1d\uff08Zero-Copy\uff09\u6280\u672f"},"content":{"rendered":"\n<h1>1.\u540d\u8bcd\u91ca\u4e49<\/h1>\n\n\n\n<figure class=\"wp-block-table\"><table><thead><tr><th>\u540d\u8bcd<\/th><th>\u91ca\u4e49<\/th><th>\u5f15\u7528\u8d44\u6599<\/th><\/tr><\/thead><tbody><tr><td>\u96f6\u62f7\u8d1d<\/td><td>\uff08\u82f1\u8bed\uff1a<strong>Zero-copy<\/strong>\uff1b\u4e5f\u8bd1<strong>\u96f6\u62f7\u8d1d<\/strong>\uff09\u6280\u672f\u662f\u6307\u8ba1\u7b97\u673a\u6267\u884c\u64cd\u4f5c\u65f6\uff0c<a href=\"https:\/\/zh.wikipedia.org\/wiki\/%E4%B8%AD%E5%A4%AE%E5%A4%84%E7%90%86%E5%99%A8\" target=\"_blank\"  rel=\"nofollow\" >CPU<\/a>\u4e0d\u9700\u8981\u5148\u5c06\u6570\u636e\u4ece\u67d0\u5904<a href=\"https:\/\/zh.wikipedia.org\/wiki\/%E9%9A%8F%E6%9C%BA%E5%AD%98%E5%8F%96%E5%AD%98%E5%82%A8%E5%99%A8\" target=\"_blank\"  rel=\"nofollow\" >\u5185\u5b58<\/a>\u590d\u5236\u5230\u53e6\u4e00\u4e2a\u7279\u5b9a\u533a\u57df\u3002\u8fd9\u79cd\u6280\u672f\u901a\u5e38\u7528\u4e8e\u901a\u8fc7\u7f51\u7edc\u4f20\u8f93\u6587\u4ef6\u65f6\u8282\u7701CPU\u5468\u671f\u548c<a href=\"https:\/\/zh.wikipedia.org\/wiki\/%E5%86%85%E5%AD%98%E5%B8%A6%E5%AE%BD\" target=\"_blank\"  rel=\"nofollow\" >\u5185\u5b58\u5e26\u5bbd<\/a>\u3002<\/td><td><a href=\"https:\/\/zh.wikipedia.org\/wiki\/%E9%9B%B6%E5%A4%8D%E5%88%B6\" target=\"_blank\"  rel=\"nofollow\" >\u96f6\u590d\u5236<\/a><\/td><\/tr><tr><td>DMA<\/td><td><strong>\u76f4\u63a5\u5185\u5b58\u5b58\u53d6<\/strong>\uff08<strong>D<\/strong>irect <strong>M<\/strong>emory <strong>A<\/strong>ccess\uff0c<strong>DMA<\/strong>\uff09\u662f<a href=\"https:\/\/zh.wikipedia.org\/wiki\/%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%A7%91%E5%AD%A6\" target=\"_blank\"  rel=\"nofollow\" >\u8ba1\u7b97\u673a\u79d1\u5b66<\/a>\u4e2d\u7684\u4e00\u79cd\u5185\u5b58\u8bbf\u95ee\u6280\u672f\u3002\u5b83\u5141\u8bb8\u67d0\u4e9b<a href=\"https:\/\/zh.wikipedia.org\/wiki\/%E9%9B%BB%E8%85%A6\" target=\"_blank\"  rel=\"nofollow\" >\u7535\u8111<\/a>\u5185\u90e8\u7684\u786c\u4ef6\u5b50\u7cfb\u7edf\uff08\u7535\u8111\u5916\u8bbe\uff09\uff0c\u53ef\u4ee5\u72ec\u7acb\u5730\u76f4\u63a5\u8bfb\u5199\u7cfb\u7edf<a href=\"https:\/\/zh.wikipedia.org\/wiki\/%E8%A8%98%E6%86%B6%E9%AB%94\" target=\"_blank\"  rel=\"nofollow\" >\u5185\u5b58<\/a>\uff0c\u800c\u4e0d\u9700<a href=\"https:\/\/zh.wikipedia.org\/wiki\/%E4%B8%AD%E5%A4%AE%E8%99%95%E7%90%86%E5%99%A8\" target=\"_blank\"  rel=\"nofollow\" >\u4e2d\u592e\u5904\u7406\u5668<\/a>\uff08CPU\uff09\u4ecb\u5165\u5904\u7406 \u3002\u5728\u540c\u7b49\u7a0b\u5ea6\u7684\u5904\u7406\u5668\u8d1f\u62c5\u4e0b\uff0cDMA\u662f\u4e00\u79cd\u5feb\u901f\u7684\u6570\u636e\u4f20\u9001\u65b9\u5f0f\u3002\u5f88\u591a\u786c\u4ef6\u7684\u7cfb\u7edf\u4f1a\u4f7f\u7528DMA\uff0c\u5305\u542b<a href=\"https:\/\/zh.wikipedia.org\/wiki\/%E7%A1%AC%E7%A2%9F\" target=\"_blank\"  rel=\"nofollow\" >\u786c\u76d8<\/a>\u63a7\u5236\u5668\u3001<a href=\"https:\/\/zh.wikipedia.org\/wiki\/%E7%B9%AA%E5%9C%96%E9%A1%AF%E7%A4%BA%E5%8D%A1\" target=\"_blank\"  rel=\"nofollow\" >\u7ed8\u56fe\u663e\u5361<\/a>\u3001<a href=\"https:\/\/zh.wikipedia.org\/wiki\/%E7%BD%91%E7%BB%9C%E5%8D%A1\" target=\"_blank\"  rel=\"nofollow\" >\u7f51\u5361<\/a>\u548c<a href=\"https:\/\/zh.wikipedia.org\/wiki\/%E5%A3%B0%E5%8D%A1\" target=\"_blank\"  rel=\"nofollow\" >\u58f0\u5361<\/a>\u3002<\/td><td><a href=\"https:\/\/zh.wikipedia.org\/wiki\/%E7%9B%B4%E6%8E%A5%E8%A8%98%E6%86%B6%E9%AB%94%E5%AD%98%E5%8F%96\" target=\"_blank\"  rel=\"nofollow\" >\u76f4\u63a5\u5185\u5b58\u5b58\u53d6<\/a><\/td><\/tr><tr><td>\u7cfb\u7edf\u8c03\u7528<\/td><td><strong>\u7cfb\u7edf\u8c03\u7528<\/strong>\u662f\u64cd\u4f5c\u7cfb\u7edf\u7684\u6700\u5c0f\u529f\u80fd\u5355\u4f4d,\u901a\u8fc7\u63d0\u4f9b\u4e00\u4e9b\u57fa\u672c\u529f\u80fd\u7684\u63a5\u53e3\u4f9b\u5e94\u7528\u7a0b\u5e8f\u8c03\u7528\u6765\u8c03\u5ea6\u5185\u6838\u7a7a\u95f4\u7ba1\u7406\u7684\u8d44\u6e90\u3002 1. \u7cfb\u7edf\u8c03\u7528\u53d1\u751f\u5728\u7528\u6237\u6001\uff0c\u5bf9\u7cfb\u7edf\u8c03\u7528\u7684\u5904\u7406\u53d1\u751f\u5728\u6838\u5fc3\u6001\u3002 2.\u6267\u884c\u9677\u5165\u6307\u4ee4\u4f1a\u4ea7\u751f\u5185\u4e2d\u65ad\uff0c\u4f7f\u5904\u7406\u5668\u4ece\u7528\u6237\u6001\u8fdb\u5165\u6838\u5fc3\u6001\u3002<\/td><td><\/td><\/tr><tr><td>CPU\u4e0a\u4e0b<\/td><td>CPU\u5728\u8fd0\u884c\u4e00\u4e2a\u4efb\u52a1\u4e4b\u524d\uff0c\u8981\u77e5\u9053\u4efb\u52a1\u4ece\u54ea\u91cc\u52a0\u8f7d\u3001\u4ece\u54ea\u91cc\u5f00\u59cb\u8fd0\u884c\uff0c\u8fd9\u4e9b\u6570\u636e\u90fd\u5b58\u653e\u5728<strong>CPU\u5bc4\u5b58\u5668\u548c\u7a0b\u5e8f\u8ba1\u6570\u5668\uff08Program Counter\uff0cPC\uff09<\/strong>\u4e2d\u3002CPU\u5bc4\u5b58\u5668\uff0c\u662fCPU\u672c\u8eab\u542b\u6709\u7684\u5bb9\u91cf\u5c0f\uff0c\u901f\u5ea6\u5feb\u7684\u5185\u5b58\u6a21\u5757\u3002PC\u662f\u7528\u6765\u5b58\u50a8CPU\u6b63\u5728\u6267\u884c\u7684\u6216\u5373\u5c06\u6267\u884c\u7684\u6307\u4ee4\u7684\u4f4d\u7f6e\u3002\u8fd9\u4e9b\u6570\u636e\u90fd\u662fCPU\u6267\u884c\u4e00\u4e2a\u4efb\u52a1\u4f9d\u8d56\u7684\u5fc5\u8981\u73af\u5883\uff0c\u79f0\u4e4b\u4e3aCPU\u4e0a\u4e0b\u6587\u3002<\/td><td><\/td><\/tr><tr><td>CPU\u4e0a\u4e0b\u6587\u5207\u6362<\/td><td>\u5148\u628a\u5f53\u524d\u4efb\u52a1\u7684CPU\u4e0a\u4e0b\u6587\u4fdd\u5b58\u8d77\u6765\uff0c\u7136\u540e\u52a0\u8f7d\u5373\u5c06\u8fd0\u884c\u4efb\u52a1\u7684\u4e0a\u4e0b\u6587\u7684\u8fc7\u7a0b\uff0c\u79f0\u4e3a<strong>CPU\u4e0a\u4e0b\u6587\u5207\u6362<\/strong>\u3002\u8fd9\u4e9b\u4fdd\u5b58\u4e0b\u6765\u7684\u4e0a\u4e0b\u6587\uff0c\u5c06\u88ab\u5b58\u50a8\u5728\u5185\u6838\u4e2d\uff0c\u5728CPU\u91cd\u65b0\u6267\u884c\u5176\u5bf9\u5e94\u7684\u4efb\u52a1\u65f6\uff0c\u518d\u6b21\u52a0\u8f7d\u3002\u8fd9\u6837\u4fdd\u8bc1\u4e86\u903b\u8f91\u6267\u884c\u7684\u8fde\u7eed\u6027\u3002CPU\u4e0a\u4e0b\u6587\u5207\u6362\u5206\u4e3a\uff1a\u8fdb\u7a0b\u4e0a\u4e0b\u6587\u5207\u6362\u3001\u7ebf\u7a0b\u4e0a\u4e0b\u6587\u5207\u6362\u3001\u534f\u7a0b\u4e0a\u4e0b\u6587\u5207\u6362\u3001\u4e2d\u65ad\u4e0a\u4e0b\u6587\u5207\u6362\u3002<\/td><td><\/td><\/tr><tr><td>\u7cfb\u7edf\u8c03\u7528\u4e0a\u4e0b\u6587\u5207\u6362<\/td><td>\u901a\u8fc7\u7cfb\u7edf\u8c03\u7528\u4ece\u7528\u6237\u6001\u5207\u6362\u5230\u5185\u6838\u6001\u65f6\u5019CPU\u5c06\u4f1a\u8fdb\u884c\u4e0a\u4e0b\u6587\u5207\u6362\u3002\u7cfb\u7edf\u8c03\u7528\u7684\u8fc7\u7a0b\uff0c\u5176\u5b9e\u662f\u53d1\u751f\u4e86\u4e24\u6b21 CPU \u4e0a\u4e0b\u6587\u5207\u6362<strong>\u3002\uff08\u7528\u6237\u6001-\u5185\u6838\u6001-\u7528\u6237\u6001\uff09\u3002\u7cfb\u7edf\u8c03\u7528\u8fc7\u7a0b\u4e2d\uff0c\u5e76\u4e0d\u4f1a\u6d89\u53ca\u5230\u865a\u62df\u5185\u5b58\u7b49\u8fdb\u7a0b\u7528\u6237\u6001\u7684\u8d44\u6e90\uff0c\u4e5f\u4e0d\u4f1a\u5207\u6362\u8fdb\u7a0b<\/strong>\u3002\u8fd9\u8ddf\u6211\u4eec\u901a\u5e38\u6240\u8bf4\u7684\u8fdb\u7a0b\u4e0a\u4e0b\u6587\u5207\u6362\u662f\u4e0d\u4e00\u6837\u7684\uff1a<strong>\u8fdb\u7a0b\u4e0a\u4e0b\u6587\u5207\u6362\uff0c\u662f\u6307\u4ece\u4e00\u4e2a\u8fdb\u7a0b\u5207\u6362\u5230\u53e6\u4e00\u4e2a\u8fdb\u7a0b\u8fd0\u884c\uff1b\u800c\u7cfb\u7edf\u8c03\u7528\u8fc7\u7a0b\u4e2d\u4e00\u76f4\u662f\u540c\u4e00\u4e2a\u8fdb\u7a0b\u5728\u8fd0\u884c\u3002<\/strong>\u6240\u4ee5\uff0c<strong>\u7cfb\u7edf\u8c03\u7528\u8fc7\u7a0b\u901a\u5e38\u79f0\u4e3a\u7279\u6743\u6a21\u5f0f\u5207\u6362\uff0c\u800c\u4e0d\u662f\u4e0a\u4e0b\u6587\u5207\u6362\u3002\u7cfb\u7edf\u8c03\u7528\u5c5e\u4e8e\u540c\u8fdb\u7a0b\u5185\u7684 CPU \u4e0a\u4e0b\u6587\u5207\u6362<\/strong>\u3002\u4f46\u5b9e\u9645\u4e0a\uff0c\u7cfb\u7edf\u8c03\u7528\u8fc7\u7a0b\u4e2d\uff0cCPU \u7684\u4e0a\u4e0b\u6587\u5207\u6362\u8fd8\u662f\u65e0\u6cd5\u907f\u514d\u7684\u3002<\/td><td><\/td><\/tr><tr><td><\/td><td><\/td><td><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h1>2.\u4e3a\u4ec0\u4e48\u8981\u6709\u7cfb\u7edf\u8c03\u7528<\/h1>\n\n\n\n<h2>2.1 \u4e0d\u540c\u6307\u4ee4\u96c6\u67b6\u6784\u4e0b\u7684Linux\u64cd\u4f5c\u7cfb\u7edf\u7279\u6743\u7b49\u7ea7<\/h2>\n\n\n\n<h3>2.1.1 X86\u7cfb\u5217<\/h3>\n\n\n\n<p>x86 \u7684\u4fdd\u62a4\u6a21\u5f0f\u4e2d\uff0c\u6709\u56db\u79cd\u7279\u6743\u7b49\u7ea7\u3002Linux \u4f7f\u7528 Ring 0 \u548c Ring 3\uff1a<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img   class=\"lazyload\" data-src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307112152494.png\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/moezx\/cdn@3.0.2\/img\/svg\/loader\/trans.ajax-spinner-preloader.svg\" onerror=\"imgError(this)\"  alt=\"image-20230711215223420\"\/><\/figure >\n<noscript><img src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307112152494.png\" alt=\"image-20230711215223420\"\/><\/figure><\/noscript>\n\n\n\n<ol><li>Ring 0 \u662f\u5185\u6838\u7a7a\u95f4\uff0c\u5177\u6709\u6700\u9ad8\u6743\u9650\uff0c\u53ef\u8bbf\u95ee\u6240\u6709\u786c\u4ef6\u8d44\u6e90.\u901a\u5e38\uff0c\u56e0\u4e3a\u64cd\u4f5c\u7cfb\u7edf\u662f\u4e3a\u6240\u6709\u7a0b\u5e8f\u670d\u52a1\u7684\uff0c\u53ef\u9760\u6027\u6700\u9ad8\uff0c\u800c\u4e14\u5fc5\u987b\u5bf9\u8f6f\u786c\u4ef6\u6709\u5b8c\u5168\u7684\u63a7\u5236\u6743\uff0c\u6240\u4ee5\u5b83\u7684\u4e3b\u4f53\u90e8\u5206\u5fc5\u987b\u62e5\u6709\u7279\u6743\u7ea7Ring 0\uff0c\u5e76\u5904\u4e8e\u6574\u4e2a\u73af\u5f62\u7ed3\u6784\u7684\u4e2d\u5fc3\u3002\u4e5f\u6b63\u662f\u56e0\u4e3a\u8fd9\u6837\uff0c\u64cd\u4f5c\u7cfb\u7edf\u7684\u4e3b\u4f53\u90e8\u5206\u901a\u5e38\u53c8\u88ab\u79f0\u505a\u5185\u6838(Kernel\u3001 Core)\u3002\u800c\u7279\u6743\u7ea7Ring 1\u548cRing 2\u901a\u5e38\u8d4b\u4e88\u90a3\u4e9b\u53ef\u9760\u6027\u4e0d\u5982\u5185\u6838\u7684\u7cfb\u7edf\u670d\u52a1\u7a0b\u5e8f\uff0c\u6bd4\u8f83\u5178\u578b\u7684\u5c31\u662f\u8bbe\u5907\u9a71\u52a8\u7a0b\u5e8f\u3002\u5f53\u7136\uff0c\u5728\u5f88\u591a\u6bd4\u8f83\u6d41\u884c\u7684\u64cd\u4f5c\u7cfb\u7edf\u4e2d\uff0c\u9a71\u52a8\u7a0b\u5e8f\u4e0e\u5185\u6838\u7684\u7279\u6743\u7ea7\u522b\u76f8\u540c\uff0c\u90fd\u662fRing 0\u3002<\/li><li>Ring 3 \u662f\u7528\u6237\u7a7a\u95f4\uff0c\u6743\u9650\u6700\u4f4e\uff0c\u65e0\u6cd5\u76f4\u63a5\u8bbf\u95ee\u786c\u4ef6\u8d44\u6e90\u3002\u5e94\u7528\u7a0b\u5e8f\u7684\u53ef\u9760\u6027\u88ab\u89c6\u4e3a\u662f\u6700\u4f4e\u7684\uff0c\u800c\u4e14\u901a\u5e38\u4e0d\u9700\u8981\u76f4\u63a5\u8bbf\u95ee\u786c\u4ef6\u548c\u4e00\u4e9b\u654f\u611f\u7684\u7cfb\u7edf\u8d44\u6e90\uff0c\u8c03\u7528\u8bbe\u5907\u9a71\u52a8\u7a0b\u5e8f\u6216\u8005\u64cd\u4f5c\u7cfb\u7edf\u4f8b\u7a0b\u5c31\u80fd\u5b8c\u6210\u7edd\u5927\u591a\u6570\u5de5\u4f5c\uff0c\u6545\u8d4b\u4e88\u5b83\u4eec\u6700\u4f4e\u7684\u7279\u6743\u7ea7\u522bRing 3\u3002<\/li><\/ol>\n\n\n\n<h3>2.1.2ARMv8\u7cfb\u5217\u7279\u6743\u7b49\u7ea7<\/h3>\n\n\n\n<figure class=\"wp-block-image\"><img   class=\"lazyload\" data-src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307112217066.png\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/moezx\/cdn@3.0.2\/img\/svg\/loader\/trans.ajax-spinner-preloader.svg\" onerror=\"imgError(this)\"  alt=\"image-20230711221730997\"\/><\/figure >\n<noscript><img src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307112217066.png\" alt=\"image-20230711221730997\"\/><\/figure><\/noscript>\n\n\n\n<ol><li>ARMv8\u7cfb\u5217\u7279\u6743\u7b49\u7ea7\uff08exception Level\uff0c\u7b80\u79f0EL0\uff0cEL1\uff0cEL2\uff0cEL3\uff09\uff0c\u5206\u522b\u7528\u4e8eApp\u3001OS\u3001\u865a\u62df\u5316\u3001\u5b89\u5168<\/li><li>\u4e0d\u540c\u7684ARM\u6307\u4ee4\u96c6\u5bf9\u5e94\u7684\u7279\u6743\u7b49\u7ea7\u4e0d\u4e00\u5b9a\u76f8\u540c\uff0c\u8fd9\u91cc\u4ec5\u4e3e\u4f8bARMv8\u7cfb\u5217\u7684\u3002<\/li><\/ol>\n\n\n\n<h2>2.2\u7528\u6237\u6001\u548c\u5185\u6838\u6001\u4e4b\u95f4\u7684\u5207\u6362<\/h2>\n\n\n\n<p>\u5f53\u7a0b\u5e8f\u901a\u8fc7\u7cfb\u7edf\u8c03\u7528\u4ece\u7528\u6237\u6001\u5207\u6362\u5230\u5185\u6838\u6001,\u90a3\u4e48\u5904\u5728\u7528\u6237\u6001\u7684\u7ebf\u7a0b\u9700\u8981\u5148\u4fdd\u5b58\u5f53\u524d\u7684\u6570\u636e\u4ee5\u53ca\u8fd0\u884c\u7684\u6307\u4ee4,\u65b9\u4fbf\u56de\u5230\u7528\u6237\u6001\u65f6\u7ee7\u7eed\u6267\u884c,\u8fd9\u4e2d\u95f4\u8fd8\u6709\u5f88\u591a\u5176\u4ed6\u7684\u4e8b\u60c5\u9700\u8981\u505a,\u4f8b\u5982CPU\u5bc4\u5b58\u5668\u9700\u8981\u4fdd\u5b58\u548c\u52a0\u8f7d, \u7cfb\u7edf\u8c03\u5ea6\u5668\u7684\u4ee3\u7801\u9700\u8981\u6267\u884c, TLB\u5b9e\u4f8b\u9700\u8981\u91cd\u65b0\u52a0\u8f7d, CPU \u7684pipeline\u9700\u8981\u5237\u6389\u3002<\/p>\n\n\n\n<p>\u4ece\u7528\u6237\u6001\u5230\u5185\u6838\u6001\u7684\u8f6c\u53d8\uff0c\u9700\u8981\u901a\u8fc7<strong>\u7cfb\u7edf\u8c03\u7528<\/strong>\u6765\u5b8c\u6210\u3002\u6bd4\u5982\uff0c\u5f53\u6211\u4eec\u67e5\u770b\u6587\u4ef6\u5185\u5bb9\u65f6\uff0c\u5c31\u9700\u8981\u591a\u6b21\u7cfb\u7edf\u8c03\u7528\u6765\u5b8c\u6210\uff1a\u9996\u5148\u8c03\u7528 open() \u6253\u5f00\u6587\u4ef6\uff0c\u7136\u540e\u8c03\u7528 read() \u8bfb\u53d6\u6587\u4ef6\u5185\u5bb9\uff0c\u5e76\u8c03\u7528 write() \u5c06\u5185\u5bb9\u5199\u5230\u6807\u51c6\u8f93\u51fa\uff0c\u6700\u540e\u518d\u8c03\u7528 close() \u5173\u95ed\u6587\u4ef6\u3002<\/p>\n\n\n\n<h1>3.\u8bfb\u53d6\u78c1\u76d8\u6587\u4ef6\u6570\u636e\u5230\u7528\u6237\u8fdb\u7a0b\u7684\u6d41\u7a0b<\/h1>\n\n\n\n<h2>3.1\u4e0d\u4f7f\u7528DMA<\/h2>\n\n\n\n<figure class=\"wp-block-image\"><img   class=\"lazyload\" data-src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307120017639.png\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/moezx\/cdn@3.0.2\/img\/svg\/loader\/trans.ajax-spinner-preloader.svg\" onerror=\"imgError(this)\"  alt=\"image-20230712001733499\"\/><\/figure >\n<noscript><img src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307120017639.png\" alt=\"image-20230712001733499\"\/><\/figure><\/noscript>\n\n\n\n<ol><li>\u6574\u4e2a\u6570\u636e\u7684\u4f20\u8f93\u8fc7\u7a0b\uff0c\u90fd\u8981\u9700\u8981 CPU \u4eb2\u81ea\u53c2\u4e0e\u642c\u8fd0\u6570\u636e\u7684\u8fc7\u7a0b\uff0c\u800c\u4e14\u8fd9\u4e2a\u8fc7\u7a0b\uff0cCPU \u662f\u4e0d\u80fd\u505a\u5176\u4ed6\u4e8b\u60c5\u7684\u3002<\/li><li>\u8c03\u7528\u4e00\u6b21 read()\u7cfb\u7edf\u8c03\u7528\u9700\u8981 2\u6b21CPU\u4e0a\u4e0b\u6587\u5207\u6362\uff0c2\u6b21CPU\u6570\u636e\u62f7\u8d1d\u3002<\/li><\/ol>\n\n\n\n<h2>3.2\u4f7f\u7528DMA<\/h2>\n\n\n\n<p>\u76f4\u63a5\u5185\u5b58\u8bbf\u95ee\uff08Direct Memory Access\uff09\uff0c\u662f\u4e00\u79cd\u786c\u4ef6\u8bbe\u5907\u7ed5\u5f00CPU\u72ec\u7acb\u76f4\u63a5\u8bbf\u95ee\u5185\u5b58\u7684\u673a\u5236\u3002\u6240\u4ee5DMA\u5728\u4e00\u5b9a\u7a0b\u5ea6\u4e0a\u89e3\u653e\u4e86CPU\uff0c\u628a\u4e4b\u524dCPU\u7684\u6742\u6d3b\u8ba9\u786c\u4ef6\u76f4\u63a5\u81ea\u5df1\u505a\u4e86\uff0c\u63d0\u9ad8\u4e86CPU\u6548\u7387\u3002<\/p>\n\n\n\n<p>\u76ee\u524d\u652f\u6301DMA\u7684\u786c\u4ef6\u5305\u62ec\uff1a\u7f51\u5361\u3001\u58f0\u5361\u3001\u663e\u5361\u3001\u78c1\u76d8\u63a7\u5236\u5668\u7b49\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img   class=\"lazyload\" data-src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307100022825.jpeg\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/moezx\/cdn@3.0.2\/img\/svg\/loader\/trans.ajax-spinner-preloader.svg\" onerror=\"imgError(this)\"  alt=\"img\"\/><\/figure >\n<noscript><img src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307100022825.jpeg\" alt=\"img\"\/><\/figure><\/noscript>\n\n\n\n<p>\u6709\u4e86DMA\u7684\u53c2\u4e0e\u4e4b\u540e\u7684\u6d41\u7a0b\u53d1\u751f\u4e86\u4e00\u4e9b\u53d8\u5316\uff1a<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img   class=\"lazyload\" data-src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307100022794.jpeg\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/moezx\/cdn@3.0.2\/img\/svg\/loader\/trans.ajax-spinner-preloader.svg\" onerror=\"imgError(this)\"  alt=\"img\"\/><\/figure >\n<noscript><img src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307100022794.jpeg\" alt=\"img\"\/><\/figure><\/noscript>\n\n\n\n<p>\u8bfb\u6570\u636e\u8fc7\u7a0b\uff1a<\/p>\n\n\n\n<ul><li>\u5e94\u7528\u7a0b\u5e8f\u8981\u8bfb\u53d6\u78c1\u76d8\u6570\u636e\uff0c\u8c03\u7528read()\u51fd\u6570\u4ece\u800c\u5b9e\u73b0\u7528\u6237\u6001\u5207\u6362\u5185\u6838\u6001\uff0c\u8fd9\u662f\u7b2c1\u6b21\u72b6\u6001\u5207\u6362\uff1b<\/li><li>DMA\u63a7\u5236\u5668\u5c06\u6570\u636e\u4ece\u78c1\u76d8\u62f7\u8d1d\u5230\u5185\u6838\u7f13\u51b2\u533a\uff0c\u8fd9\u662f\u7b2c1\u6b21DMA\u62f7\u8d1d\uff1b<\/li><li>CPU\u5c06\u6570\u636e\u4ece\u5185\u6838\u7f13\u51b2\u533a\u590d\u5236\u5230\u7528\u6237\u7f13\u51b2\u533a\uff0c\u8fd9\u662f\u7b2c1\u6b21CPU\u62f7\u8d1d\uff1b<\/li><li>CPU\u5b8c\u6210\u62f7\u8d1d\u4e4b\u540e\uff0cread()\u51fd\u6570\u8fd4\u56de\u5b9e\u73b0\u7528\u6237\u6001\u5207\u6362\u7528\u6237\u6001\uff0c\u8fd9\u662f\u7b2c2\u6b21\u72b6\u6001\u5207\u6362\uff1b<\/li><\/ul>\n\n\n\n<ol><li>DMA \u6536\u5230\u78c1\u76d8\u7684\u4fe1\u53f7\uff0c\u5c06\u78c1\u76d8\u63a7\u5236\u5668\u7f13\u51b2\u533a\u4e2d\u7684\u6570\u636e\u62f7\u8d1d\u5230\u5185\u6838\u7f13\u51b2\u533a\u4e2d\uff0c\u6b64\u65f6\u4e0d\u5360\u7528 CPU\uff0cCPU \u53ef\u4ee5\u6267\u884c\u5176\u4ed6\u4efb\u52a1\uff1b<\/li><li>\u8c03\u7528\u4e00\u6b21 read()\u7cfb\u7edf\u8c03\u7528\u9700\u8981 2\u6b21CPU\u4e0a\u4e0b\u6587\u5207\u6362\uff0c1\u6b21CPU\u6570\u636e\u62f7\u8d1d,1\u6b21DMA\u6570\u636e\u62f7\u8d1d\uff1b<\/li><\/ol>\n\n\n\n<h1>4.socket\u7f16\u7a0b\u6587\u4ef6\u4f20\u8f93read()+write()\u65b9\u5f0f<\/h1>\n\n\n\n<figure class=\"wp-block-image\"><img   class=\"lazyload\" data-src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307120029156.png\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/moezx\/cdn@3.0.2\/img\/svg\/loader\/trans.ajax-spinner-preloader.svg\" onerror=\"imgError(this)\"  alt=\"image-20230712002919076\"\/><\/figure >\n<noscript><img src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307120029156.png\" alt=\"image-20230712002919076\"\/><\/figure><\/noscript>\n\n\n\n<figure class=\"wp-block-image\"><img   class=\"lazyload\" data-src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307112338412.png\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/moezx\/cdn@3.0.2\/img\/svg\/loader\/trans.ajax-spinner-preloader.svg\" onerror=\"imgError(this)\"  alt=\"image-20230711233831275\"\/><\/figure >\n<noscript><img src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307112338412.png\" alt=\"image-20230711233831275\"\/><\/figure><\/noscript>\n\n\n\n<p>\u8bfb\u6570\u636e\u8fc7\u7a0b\uff1a<\/p>\n\n\n\n<ul><li>\u5e94\u7528\u7a0b\u5e8f\u8981\u8bfb\u53d6\u78c1\u76d8\u6570\u636e\uff0c\u8c03\u7528read()\u51fd\u6570\u4ece\u800c\u5b9e\u73b0\u7528\u6237\u6001\u5207\u6362\u5185\u6838\u6001\uff0c\u8fd9\u662f\u7b2c1\u6b21\u72b6\u6001\u5207\u6362\uff1b<\/li><li>DMA\u63a7\u5236\u5668\u5c06\u6570\u636e\u4ece\u78c1\u76d8\u62f7\u8d1d\u5230\u5185\u6838\u7f13\u51b2\u533a\uff0c\u8fd9\u662f\u7b2c1\u6b21DMA\u62f7\u8d1d\uff1b<\/li><li>CPU\u5c06\u6570\u636e\u4ece\u5185\u6838\u7f13\u51b2\u533a\u590d\u5236\u5230\u7528\u6237\u7f13\u51b2\u533a\uff0c\u8fd9\u662f\u7b2c1\u6b21CPU\u62f7\u8d1d\uff1b<\/li><li>CPU\u5b8c\u6210\u62f7\u8d1d\u4e4b\u540e\uff0cread()\u51fd\u6570\u8fd4\u56de\u5b9e\u73b0\u7528\u6237\u6001\u5207\u6362\u7528\u6237\u6001\uff0c\u8fd9\u662f\u7b2c2\u6b21\u72b6\u6001\u5207\u6362\uff1b<\/li><\/ul>\n\n\n\n<p>\u5199\u6570\u636e\u8fc7\u7a0b\uff1a<\/p>\n\n\n\n<ul><li>\u5e94\u7528\u7a0b\u5e8f\u8981\u5411\u7f51\u5361\u5199\u6570\u636e\uff0c\u8c03\u7528write()\u51fd\u6570\u5b9e\u73b0\u7528\u6237\u6001\u5207\u6362\u5185\u6838\u6001\uff0c\u8fd9\u662f\u7b2c1\u6b21\u5207\u6362\uff1b<\/li><li>CPU\u5c06\u7528\u6237\u7f13\u51b2\u533a\u6570\u636e\u62f7\u8d1d\u5230socket\u7f13\u51b2\u533a\uff0c\u8fd9\u662f\u7b2c1\u6b21CPU\u62f7\u8d1d\uff1b<\/li><li>DMA\u63a7\u5236\u5668\u5c06\u6570\u636e\u4ecesocket\u7f13\u51b2\u533a\u590d\u5236\u5230\u7f51\u5361\uff0c\u8fd9\u662f\u7b2c1\u6b21DMA\u62f7\u8d1d\uff1b<\/li><li>\u5b8c\u6210\u62f7\u8d1d\u4e4b\u540e\uff0cwrite()\u51fd\u6570\u8fd4\u56de\u5b9e\u73b0\u5185\u6838\u6001\u5207\u6362\u7528\u6237\u6001\uff0c\u8fd9\u662f\u7b2c2\u6b21\u5207\u6362\uff1b<\/li><\/ul>\n\n\n\n<ol><li>DMA \u6536\u5230\u78c1\u76d8\u7684\u4fe1\u53f7\uff0c\u5c06\u78c1\u76d8\u63a7\u5236\u5668\u7f13\u51b2\u533a\u4e2d\u7684\u6570\u636e\u62f7\u8d1d\u5230\u5185\u6838\u7f13\u51b2\u533a\u4e2d\uff0c\u6b64\u65f6\u4e0d\u5360\u7528 CPU\uff0cCPU \u53ef\u4ee5\u6267\u884c\u5176\u4ed6\u4efb\u52a1\uff1b<\/li><\/ol>\n\n\n\n<ol start=\"2\"><li>\u8c03\u7528\u4e00\u6b21 read()\u7cfb\u7edf\u8c03\u7528\u9700\u8981 2\u6b21CPU\u4e0a\u4e0b\u6587\u5207\u6362\uff0c1\u6b21CPU\u6570\u636e\u62f7\u8d1d,\uff0c1\u6b21DMA\u6570\u636e\u62f7\u8d1d\uff1b\u8c03\u7528\u4e00\u6b21 write()\u7cfb\u7edf\u8c03\u7528\u9700\u8981 2\u6b21CPU\u4e0a\u4e0b\u6587\u5207\u6362\uff0c1\u6b21CPU\u6570\u636e\u62f7\u8d1d,\uff0c1\u6b21DMA\u6570\u636e\u62f7\u8d1d.<\/li><li>\u4ece\u8bfb\u53d6\u78c1\u76d8\u6587\u4ef6\u5230\u53d1\u9001\u5230\u7f51\u5361\uff0c\u9700\u8981\u89c1\u8fc74\u6b21CPU\u4e0a\u4e0b\u6587\u5207\u6362\uff0c2\u6b21CPU\u6570\u636e\u62f7\u8d1d\uff0c2\u6b21DMA\u6570\u636e\u62f7\u8d1d<\/li><\/ol>\n\n\n\n<h1>5.\u96f6\u62f7\u8d1d\u6280\u672f\u4f18\u5316\u65b9\u6848<\/h1>\n\n\n\n<p>\u76ee\u524d\u6765\u770b\uff0c\u96f6\u62f7\u8d1d\u6280\u672f\u7684\u51e0\u4e2a\u5b9e\u73b0\u624b\u6bb5\u5305\u62ec\uff1ammap+write\u3001sendfile\u3001sendfile+DMA\u6536\u96c6\u3001splice\u7b49\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img   class=\"lazyload\" data-src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307100028750.jpeg\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/moezx\/cdn@3.0.2\/img\/svg\/loader\/trans.ajax-spinner-preloader.svg\" onerror=\"imgError(this)\"  alt=\"img\"\/><\/figure >\n<noscript><img src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307100028750.jpeg\" alt=\"img\"\/><\/figure><\/noscript>\n\n\n\n<h2>5.1 mmap +write()\u65b9\u5f0f<\/h2>\n\n\n\n<p>mmap\u662fLinux\u63d0\u4f9b\u7684\u4e00\u79cd\u5185\u5b58\u6620\u5c04\u6587\u4ef6\u7684\u673a\u5236\uff0c\u5b83\u5b9e\u73b0\u4e86\u5c06\u5185\u6838\u4e2d\u8bfb\u7f13\u51b2\u533a\u5730\u5740\u4e0e\u7528\u6237\u7a7a\u95f4\u7f13\u51b2\u533a\u5730\u5740\u8fdb\u884c\u6620\u5c04\uff0c\u4ece\u800c\u5b9e\u73b0\u5185\u6838\u7f13\u51b2\u533a\u4e0e\u7528\u6237\u7f13\u51b2\u533a\u7684\u5171\u4eab\u3002<\/p>\n\n\n\n<p>mmap\u5bf9\u5927\u6587\u4ef6\u4f20\u8f93\u6709\u4e00\u5b9a\u4f18\u52bf\uff0c\u4f46\u662f\u5c0f\u6587\u4ef6\u53ef\u80fd\u51fa\u73b0\u788e\u7247\uff0c\u5e76\u4e14\u5728\u591a\u4e2a\u8fdb\u7a0b\u540c\u65f6\u64cd\u4f5c\u6587\u4ef6\u65f6\u53ef\u80fd\u4ea7\u751f\u5f15\u53d1coredump\u7684signal\u3002<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">#include &lt;sys\/mman .h&gt;<br>void* mmap( void *start, size t length, int prot, int flags, int fd,<br>off t offset );<br>int munmap( void *start, size t length );<\/pre>\n\n\n\n<ol><li>start\u53c2\u6570\u5141\u8bb8\u7528\u6237\u4f7f\u7528\u67d0\u4e2a\u7279\u5b9a\u7684\u5730\u5740\u4f5c\u4e3a\u8fd9\u6bb5\u5185\u5b58\u7684\u8d77\u59cb\u5730\u5740\uff0c\u5982\u679c\u5b83\u88ab\u8bbe\u7f6e\u6210NULL\uff0c\u90a3\u4e48\u7cfb\u7edf\u4f1a\u81ea\u52a8\u5206\u914d\u4e00\u4e2a\u5730\u5740\u3002<\/li><li>length\u53c2\u6570\u6307\u5b9a\u5185\u5b58\u6bb5\u7684\u957f\u5ea6\u3002<\/li><li>prot\u53c2\u6570\u7528\u6765\u8bbe\u7f6e\u5185\u5b58\u6bb5\u7684\u8bbf\u95ee\u6743\u9650\u3002PROT_READ\uff08\u5185\u5b58\u6bb5\u53ef\u8bfb\uff09\u3001PROT_WRITE(\u5185\u5b58\u6bb5\u53ef\u5199)\u3001PROT_EXEC(\u5185\u5b58\u6bb5\u53ef\u6267\u884c)\u3001PROT_NONE(\u5185\u5b58\u6bb5\u4e0d\u80fd\u88ab\u8bbf\u95ee)<\/li><li>flags \u53c2\u6570\u63a7\u5236\u5185\u5b58\u6bb5\u5185\u5bb9\u88ab\u4fee\u6539\u540e\u5e8f\u7684\u884c\u4e3a\u3002\u5b83\u53ef\u4ee5\u88ab\u8bbe\u7f6e\u4e3a\u8868 6-1 \u4e2d\u7684\u67d0\u4e9b\u503c(\u8fd9\u91cc\u4ec5\u5217\u51fa\u4e86\u5e38\u7528\u7684\u503c)\u7684\u6309\u4f4d\u6216(\u5176\u4e2d MAP SHARED \u548c MAP PRIVATE \u662f\u65a5\u7684\uff0c\u4e0d\u80fd\u540c\u65f6\u6307\u5b9a)\u3002<img  alt=\"image-20230711000525821\"  class=\"lazyload\" data-src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307110005893.png\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/moezx\/cdn@3.0.2\/img\/svg\/loader\/trans.ajax-spinner-preloader.svg\" onerror=\"imgError(this)\" ><\/li><li>fd \u53c2\u6570\u662f\u88ab\u6620\u5c04\u6587\u4ef6\u5bf9\u5e94\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u3002\u5b83\u4e00\u822c\u901a\u8fc7 pen \u7cfb\u7edf\u8c03\u7528\u83b7\u5f97\u3002<\/li><li>offset \u53c2\u6570\u8bbe\u7f6e\u4ece\u6587\u4ef6\u7684\u4f55\u5904\u5f00\u59cb\u6620\u5c04\uff08\u5bf9\u4e8e\u4e0d\u9700\u8981\u8bfb\u5165\u6574\u4e2a\u6587\u4ef6\u7684\u60c5\u51b5)\u3002<\/li><li>mmap\u51fd\u6570\u6210\u529f\u65f6\u8fd4\u56de\u6307\u5411\u76ee\u6807\u5185\u5b58\u533a\u57df\u7684\u6307\u9488\uff0c\u5931\u8d25\u5219\u8fd4\u56deMAP FAILED((oid*)-1)\u5e76\u8bbe\u7f6eerrno\u3002<\/li><li>munmap \u51fd\u6570\u6210\u529f\u65f6\u8fd4\u56de0\uff0c\u5931\u8d25\u5219\u8fd4\u56de-1\u5e76\u8bbe\u7f6eerrno\u3002<\/li><\/ol >\n<noscript><img alt=\"image-20230711000525821\" src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307110005893.png\"><\/li><li>fd \u53c2\u6570\u662f\u88ab\u6620\u5c04\u6587\u4ef6\u5bf9\u5e94\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u3002\u5b83\u4e00\u822c\u901a\u8fc7 pen \u7cfb\u7edf\u8c03\u7528\u83b7\u5f97\u3002<\/li><li>offset \u53c2\u6570\u8bbe\u7f6e\u4ece\u6587\u4ef6\u7684\u4f55\u5904\u5f00\u59cb\u6620\u5c04\uff08\u5bf9\u4e8e\u4e0d\u9700\u8981\u8bfb\u5165\u6574\u4e2a\u6587\u4ef6\u7684\u60c5\u51b5)\u3002<\/li><li>mmap\u51fd\u6570\u6210\u529f\u65f6\u8fd4\u56de\u6307\u5411\u76ee\u6807\u5185\u5b58\u533a\u57df\u7684\u6307\u9488\uff0c\u5931\u8d25\u5219\u8fd4\u56deMAP FAILED((oid*)-1)\u5e76\u8bbe\u7f6eerrno\u3002<\/li><li>munmap \u51fd\u6570\u6210\u529f\u65f6\u8fd4\u56de0\uff0c\u5931\u8d25\u5219\u8fd4\u56de-1\u5e76\u8bbe\u7f6eerrno\u3002<\/li><\/ol><\/noscript>\n\n\n\n<figure class=\"wp-block-image\"><img   class=\"lazyload\" data-src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307120107454.png\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/moezx\/cdn@3.0.2\/img\/svg\/loader\/trans.ajax-spinner-preloader.svg\" onerror=\"imgError(this)\"  alt=\"image-20230712010742352\"\/><\/figure >\n<noscript><img src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307120107454.png\" alt=\"image-20230712010742352\"\/><\/figure><\/noscript>\n\n\n\n<p>\u8fd9\u6837\u5c31\u51cf\u5c11\u4e86\u4e00\u6b21\u7528\u6237\u6001\u548c\u5185\u6838\u6001\u7684CPU\u62f7\u8d1d\uff0c\u4f46\u662f\u5728\u5185\u6838\u7a7a\u95f4\u5185\u4ecd\u7136\u6709\u4e00\u6b21CPU\u62f7\u8d1d\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img   class=\"lazyload\" data-src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307100030572.jpeg\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/moezx\/cdn@3.0.2\/img\/svg\/loader\/trans.ajax-spinner-preloader.svg\" onerror=\"imgError(this)\"  alt=\"img\"\/><\/figure >\n<noscript><img src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307100030572.jpeg\" alt=\"img\"\/><\/figure><\/noscript>\n\n\n\n<ol><li>mmap()\u7cfb\u7edf\u8c03\u7528\u9700\u89812\u6b21CPU\u4e0a\u4e0b\u6587\u5207\u6362\uff0c1\u6b21DMA\u6570\u636e\u62f7\u8d1d\uff1bwrite()\u7cfb\u7edf\u8c03\u7528\u9700\u89812\u6b21CPU\u4e0a\u4e0b\u6587\u5207\u6362\uff0c1\u6b21CPU\u6570\u636e\u62f7\u8d1d\uff0c1\u6b21DMA\u6570\u636e\u62f7\u8d1d\u3002<\/li><li>mmap()+write()\u5408\u8d77\u6765\u9700\u89814\u6b21CPU\u4e0a\u4e0b\u6587\u5207\u6362\uff0c1\u6b21CPU\u6570\u636e\u62f7\u8d1d\uff0c2\u6b21DMA\u6570\u636e\u62f7\u8d1d<\/li><\/ol>\n\n\n\n<h2>5.2 sendfile\u65b9\u5f0f<\/h2>\n\n\n\n<p>mmap+write\u65b9\u5f0f\u6709\u4e00\u5b9a\u6539\u8fdb\uff0c\u4f46\u662f\u7531\u7cfb\u7edf\u8c03\u7528\u5f15\u8d77\u7684\u72b6\u6001\u5207\u6362\u5e76\u6ca1\u6709\u51cf\u5c11\u3002<\/p>\n\n\n\n<p>sendfile\u7cfb\u7edf\u8c03\u7528\u662f\u5728 Linux \u5185\u68382.1\u7248\u672c\u4e2d\u88ab\u5f15\u5165\uff0c\u5b83\u5efa\u7acb\u4e86\u4e24\u4e2a\u6587\u4ef6\u4e4b\u95f4\u7684\u4f20\u8f93\u901a\u9053\u3002<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">#include &lt;sys\/sendfile.h&gt; <br>ssize_t sendfile(int out_fd, int in_fd, off t* offset, size t count );<\/pre>\n\n\n\n<ol><li>in_fd \u53c2\u6570\u662f\u5f85\u8bfb\u51fa\u5185\u5bb9\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26;in_fd\u5fc5\u987b\u662f\u4e00\u4e2a\u652f\u6301\u7c7b\u4f3c mmap \u51fd\u6570\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0c\u5373\u5b83\u5fc5\u987b\u6307\u5411\u771f\u5b9e\u7684\u6587\u4ef6\uff0c\u4e0d\u80fd\u662f soket \u548c\u7ba1\u9053.<\/li><li>out_fd \u53c2\u6570\u662f\u5f85\u5199\u5185\u5bb9\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26, out fd\u5219\u5fc5\u987b\u662f\u4e00\u4e2a socket\u6587\u4ef6fd.<\/li><li>offset\u53c2\u6570\u6307\u5b9a\u4ece\u8bfb\u4eba\u6587\u4ef6\u6d41\u7684\u54ea\u4e2a\u4f4d\u7f6e\u5f00\u59cb\u8bfb\uff0c\u5982\u679c\u4e3a\u7a7a\uff0c\u5219\u4f7f\u7528\u8bfb\u4eba\u6587\u4ef6\u6d41\u9ed8\u8ba4\u7684\u8d77\u59cb\u4f4d\u7f6e;<\/li><li>count\u53c2\u6570\u6307\u5b9a\u5728\u6587\u4ef6\u63cf\u8ff0\u7b26 in fd \u548cout fd \u4e4b\u95f4\u4f20\u8f93\u7684\u5b57\u8282\u6570\u3002<\/li><li>sendfile \u6210\u529f\u65f6\u8fd4\u56de\u4f20\u8f93\u7684\u5b57\u8282\u6570\uff0c\u5931\u8d25\u5219\u8fd4\u56de-1\u5e76\u8bbe\u7f6e errno\u3002<\/li><\/ol>\n\n\n\n<p>sendfile\u65b9\u5f0f\u53ea\u4f7f\u7528\u4e00\u4e2a\u51fd\u6570\u5c31\u53ef\u4ee5\u5b8c\u6210\u4e4b\u524d\u7684read+write \u548c mmap+write\u7684\u529f\u80fd\uff0c\u8fd9\u6837\u5c31\u5c11\u4e862\u6b21\u72b6\u6001\u5207\u6362\uff0c\u7531\u4e8e\u6570\u636e\u4e0d\u7ecf\u8fc7\u7528\u6237\u7f13\u51b2\u533a\uff0c\u56e0\u6b64\u8be5\u6570\u636e\u65e0\u6cd5\u88ab\u4fee\u6539\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img   class=\"lazyload\" data-src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307100046688.jpeg\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/moezx\/cdn@3.0.2\/img\/svg\/loader\/trans.ajax-spinner-preloader.svg\" onerror=\"imgError(this)\"  alt=\"img\"\/><\/figure >\n<noscript><img src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307100046688.jpeg\" alt=\"img\"\/><\/figure><\/noscript>\n\n\n\n<figure class=\"wp-block-image\"><img   class=\"lazyload\" data-src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307100047390.jpeg\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/moezx\/cdn@3.0.2\/img\/svg\/loader\/trans.ajax-spinner-preloader.svg\" onerror=\"imgError(this)\"  alt=\"img\"\/><\/figure >\n<noscript><img src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307100047390.jpeg\" alt=\"img\"\/><\/figure><\/noscript>\n\n\n\n<ol><li>sendfile()\u7cfb\u7edf\u8c03\u7528\u9700\u89812\u6b21CPU\u4e0a\u4e0b\u6587\u5207\u6362\uff0c1\u6b21CPU\u6570\u636e\u62f7\u8d1d\uff0c2\u6b21DMA\u6570\u636e\u62f7\u8d1d<\/li><\/ol>\n\n\n\n<h2>5.3 sendfile+DMA\u6536\u96c6<\/h2>\n\n\n\n<p>Linux 2.4 \u5185\u6838\u5bf9 sendfile \u7cfb\u7edf\u8c03\u7528\u8fdb\u884c\u4f18\u5316\uff0c\u4f46\u662f\u9700\u8981\u786c\u4ef6DMA\u63a7\u5236\u5668\u7684\u914d\u5408\u3002<\/p>\n\n\n\n<p>\u5347\u7ea7\u540e\u7684sendfile\u5c06\u5185\u6838\u7a7a\u95f4\u7f13\u51b2\u533a\u4e2d\u5bf9\u5e94\u7684\u6570\u636e\u63cf\u8ff0\u4fe1\u606f\uff08\u6587\u4ef6\u63cf\u8ff0\u7b26\u3001\u5730\u5740\u504f\u79fb\u91cf\u7b49\u4fe1\u606f\uff09\u8bb0\u5f55\u5230socket\u7f13\u51b2\u533a\u4e2d\u3002<\/p>\n\n\n\n<p>DMA\u63a7\u5236\u5668\u6839\u636esocket\u7f13\u51b2\u533a\u4e2d\u7684\u5730\u5740\u548c\u504f\u79fb\u91cf\u5c06\u6570\u636e\u4ece\u5185\u6838\u7f13\u51b2\u533a\u62f7\u8d1d\u5230\u7f51\u5361\u4e2d\uff0c\u4ece\u800c\u7701\u53bb\u4e86\u5185\u6838\u7a7a\u95f4\u4e2d\u4ec5\u52691\u6b21CPU\u62f7\u8d1d\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img   class=\"lazyload\" data-src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307100047613.jpeg\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/moezx\/cdn@3.0.2\/img\/svg\/loader\/trans.ajax-spinner-preloader.svg\" onerror=\"imgError(this)\"  alt=\"img\"\/><\/figure >\n<noscript><img src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307100047613.jpeg\" alt=\"img\"\/><\/figure><\/noscript>\n\n\n\n<blockquote class=\"wp-block-quote\"><p>sendfile()\u7cfb\u7edf\u8c03\u7528\u9700\u89812\u6b21CPU\u4e0a\u4e0b\u6587\u5207\u6362\uff0c0\u6b21CPU\u6570\u636e\u62f7\u8d1d\uff0c2\u6b21DMA\u6570\u636e\u62f7\u8d1d<\/p><\/blockquote>\n\n\n\n<h2>5.4 splice\u65b9\u5f0f<\/h2>\n\n\n\n<p>splice\u7cfb\u7edf\u8c03\u7528\u662fLinux \u5728 2.6 \u7248\u672c\u5f15\u5165\u7684\uff0c\u5176\u4e0d\u9700\u8981\u786c\u4ef6\u652f\u6301\uff0c\u5e76\u4e14\u4e0d\u518d\u9650\u5b9a\u4e8esocket\u4e0a\uff0c\u5b9e\u73b0\u4e24\u4e2a\u666e\u901a\u6587\u4ef6\u4e4b\u95f4\u7684\u6570\u636e\u96f6\u62f7\u8d1d\u3002<\/p>\n\n\n\n<pre class=\"wp-block-preformatted\">#include &lt;fcntl.h&gt;<br>ssize_t splice( int fd_in, loff_t* off_in, int fd_out, loff_t* off_out,size_t len, unsigned int flags );<\/pre>\n\n\n\n<ol><li>fd_in \u53c2\u6570\u662f\u5f85\u8f93\u4eba\u6570\u636e\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u3002\u5982\u679c fd_in \u662f\u4e00\u4e2a\u7ba1\u9053\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0c\u90a3\u4e48off_in\u53c2\u6570\u5fc5\u987b\u88ab\u8bbe\u7f6e\u4e3a NULL\u3002\u5982\u679c fd_in \u4e0d\u662f\u4e00\u4e2a\u9053\u6587\u4ef6\u63cf\u8ff0\u7b26 (\u6bd4\u5982 socket)\uff0c\u90a3\u4e48 off_in\u8868\u793a\u4ece\u8f93\u4eba\u6570\u636e\u6d41\u7684\u4f55\u5904\u5f00\u59cb\u8bfb\u53d6\u6570\u636e\u3002\u6b64\u65f6\uff0c\u82e5 off_in \u88ab\u8bbe\u7f6e\u4e3a NULL\uff0c\u5219\u8868\u793a\u4ece\u8f93\u5165\u6570\u636e\u6d41\u7684\u5f53\u524d\u504f\u79fb\u4f4d\u7f6e\u8bfb\u5165 ;\u82e5 of f_in \u4e0d\u4e3a NULL\uff0c\u5219\u5b83\u5c06\u6307\u51fa\u5177\u4f53\u7684\u504f\u79fb\u4f4d\u7f6e\u3002<\/li><li>fd_out\/off_out \u53c2\u6570\u7684\u542b\u4e49\u4e0e fd_in\/off_in \u76f8\u540c\uff0c\u4e0d\u8fc7\u7528\u4e8e\u8f93\u51fa\u6570\u636e\u6d41.<\/li><li>len \u53c2\u6570\u6307\u5b9a\u79fb\u52a8\u6570\u636e\u7684\u957f\u5ea6.<\/li><li>fags \u53c2\u6570\u5219\u63a7\u5236\u6570\u636e\u5982\u4f55\u79fb\u52a8<\/li><li>\u4f7f\u7528 splice \u51fd\u6570\u65f6\uff0cfd_in \u548c fd_out \u5fc5\u987b\u81f3\u5c11\u6709\u4e00\u4e2a\u662f\u7ba1\u9053\u6587\u4ef6\u63cf\u8ff0\u7b26\u3002splice \u51fd\u6570\u8c03\u7528\u6210\u529f\u65f6\u8fd4\u56de\u79fb\u52a8\u5b57\u8282\u7684\u6570\u91cf\u3002\u5b83\u53ef\u80fd\u8fd4\u56de 0\uff0c\u8868\u793a\u6ca1\u6709\u6570\u636e\u9700\u8981\u79fb\u52a8\uff0c\u8fd9\u53d1\u751f\u5728\u4ece\u7ba1\u9053\u4e2d\u8bfb\u53d6\u6570\u636e (fd_in \u662f\u7ba1\u9053\u6587\u4ef6\u63cf\u8ff0\u7b26)\u800c\u8be5\u7ba1\u9053\u6ca1\u6709\u88ab\u5199\u4eba\u4efb\u4f55\u6570\u636e\u65f6\u3002splice \u51fd\u6570\u5931\u8d25\u65f6\u8fd4\u56de-1\u5e76\u8bbe\u7f6eerrno\u3002<\/li><\/ol>\n\n\n\n<p>splice \u7cfb\u7edf\u8c03\u7528\u53ef\u4ee5\u5728\u5185\u6838\u7f13\u51b2\u533a\u548csocket\u7f13\u51b2\u533a\u4e4b\u95f4\u5efa\u7acb\u7ba1\u9053\u6765\u4f20\u8f93\u6570\u636e\uff0c\u907f\u514d\u4e86\u4e24\u8005\u4e4b\u95f4\u7684 CPU \u62f7\u8d1d\u64cd\u4f5c\u3002<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img   class=\"lazyload\" data-src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307100047358.jpeg\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/moezx\/cdn@3.0.2\/img\/svg\/loader\/trans.ajax-spinner-preloader.svg\" onerror=\"imgError(this)\"  alt=\"img\"\/><\/figure >\n<noscript><img src=\"https:\/\/raw.githubusercontent.com\/LJF2402901363\/typora-images\/main\/202307100047358.jpeg\" alt=\"img\"\/><\/figure><\/noscript>\n\n\n\n<blockquote class=\"wp-block-quote\"><p>splice()\u7cfb\u7edf\u8c03\u7528\u9700\u89812\u6b21CPU\u4e0a\u4e0b\u6587\u5207\u6362\uff0c1\u6b21CPU\u6570\u636e\u62f7\u8d1d\uff0c2\u6b21DMA\u6570\u636e\u62f7\u8d1d<\/p><\/blockquote>\n\n\n\n<h1>6.\u603b\u7ed3<\/h1>\n\n\n\n<figure class=\"wp-block-table\"><table><thead><tr><th>\u65b9\u6848<\/th><th>CPU\u4e0a\u4e0b\u6587\u5207\u6362\u6b21\u6570<\/th><th>CPU\u62f7\u8d1d\u6b21\u6570<\/th><th>DMA\u62f7\u8d1d\u6b21\u6570<\/th><th>\u5c40\u9650<\/th><\/tr><\/thead><tbody><tr><td>read()+write()\u65b9\u5f0f<\/td><td>4<\/td><td>2<\/td><td>2<\/td><td>CPU\u4e0a\u4e0b\u6587\u5207\u6362\u548cCPU\u62f7\u8d1d\u6570\u636e\u6b21\u6570\u591a\u3002<\/td><\/tr><tr><td>mmap()+write()\u65b9\u5f0f<\/td><td>4<\/td><td>1<\/td><td>2<\/td><td>mmap\u5bf9\u5927\u6587\u4ef6\u4f20\u8f93\u6709\u4e00\u5b9a\u4f18\u52bf\uff0c\u4f46\u662f\u5c0f\u6587\u4ef6\u53ef\u80fd\u51fa\u73b0\u788e\u7247\uff0c\u5e76\u4e14\u5728\u591a\u4e2a\u8fdb\u7a0b\u540c\u65f6\u64cd\u4f5c\u6587\u4ef6\u65f6\u53ef\u80fd\u4ea7\u751f\u5f15\u53d1coredump\u7684signal\u3002<\/td><\/tr><tr><td>sendfile()\u65b9\u5f0f<\/td><td>2<\/td><td>1<\/td><td>2<\/td><td>in_fd \u53c2\u6570\u662f\u5f85\u8bfb\u51fa\u5185\u5bb9\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26;in_fd\u5fc5\u987b\u662f\u4e00\u4e2a\u652f\u6301\u7c7b\u4f3c mmap \u51fd\u6570\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0c\u5373\u5b83\u5fc5\u987b\u6307\u5411\u771f\u5b9e\u7684\u6587\u4ef6\uff0c\u4e0d\u80fd\u662f soket \u548c\u7ba1\u9053. out_fd \u53c2\u6570\u662f\u5f85\u5199\u5185\u5bb9\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26, out fd\u5219\u5fc5\u987b\u662f\u4e00\u4e2a socket\u6587\u4ef6fd.<\/td><\/tr><tr><td>sendfile()+<\/td><td>2<\/td><td>0<\/td><td>2<\/td><td>in_fd \u53c2\u6570\u662f\u5f85\u8bfb\u51fa\u5185\u5bb9\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26;in_fd\u5fc5\u987b\u662f\u4e00\u4e2a\u652f\u6301\u7c7b\u4f3c mmap \u51fd\u6570\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0c\u5373\u5b83\u5fc5\u987b\u6307\u5411\u771f\u5b9e\u7684\u6587\u4ef6\uff0c\u4e0d\u80fd\u662f soket \u548c\u7ba1\u9053. out_fd \u53c2\u6570\u662f\u5f85\u5199\u5185\u5bb9\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26, out fd\u5219\u5fc5\u987b\u662f\u4e00\u4e2a socket\u6587\u4ef6fd.<\/td><\/tr><tr><td>splice()\u65b9\u5f0f<\/td><td>2<\/td><td>0<\/td><td>2<\/td><td>fd_in \u548c fd_out \u5fc5\u987b\u81f3\u5c11\u6709\u4e00\u4e2a\u662f\u7ba1\u9053\u6587\u4ef6\u63cf\u8ff0\u7b26<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h1>7.\u53c2\u8003\u8d44\u6599<\/h1>\n\n\n\n<ol><li><a href=\"https:\/\/juejin.cn\/post\/7079798898826412062\" target=\"_blank\"  rel=\"nofollow\" >\u4e0a\u4e0b\u6587\u5207\u6362\u603b\u7ed3<\/a><\/li><li><a href=\"https:\/\/zhuanlan.zhihu.com\/p\/590066420?utm_id=0\" target=\"_blank\"  rel=\"nofollow\" >\u3010x86\u3011\u7279\u6743\u7ea7\u522b CPL \/ RPL \/ DPL \/ IOPL<\/a><\/li><li><a href=\"https:\/\/www.zhihu.com\/question\/506495585\" target=\"_blank\"  rel=\"nofollow\" >arm\u4e0b\u6709ring0\u5417\uff1f<\/a><\/li><li><a href=\"https:\/\/www.xiaolincoding.com\/os\/8_network_system\/zero_copy.html#%E4%B8%BA%E4%BB%80%E4%B9%88%E8%A6%81%E6%9C%89-dma-%E6%8A%80%E6%9C%AF\" target=\"_blank\"  rel=\"nofollow\" >\u4ec0\u4e48\u662f\u96f6\u62f7\u8d1d<\/a><\/li><li><a href=\"https:\/\/juejin.cn\/post\/6939881308114354207\" target=\"_blank\"  rel=\"nofollow\" >\u638c\u63e1\u8fd95\u4e2a\u6280\u5de7\uff0c\u5f7b\u5e95\u638c\u63e1Netty\u4e2d\u7684\u96f6\u62f7\u8d1d\uff01<\/a><\/li><\/ol>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>1.\u540d\u8bcd\u91ca\u4e49 \u540d\u8bcd \u91ca\u4e49 \u5f15\u7528\u8d44\u6599 \u96f6\u62f7\u8d1d \uff08\u82f1\u8bed\uff1aZero-copy\uff1b\u4e5f\u8bd1\u96f6\u62f7\u8d1d\uff09\u6280\u672f\u662f\u6307\u8ba1\u7b97\u673a\u6267\u884c\u64cd\u4f5c\u65f6\uff0cCPU\u4e0d\u9700\u8981\u5148\u5c06\u6570\u636e &#8230;<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[72],"tags":[225,224],"_links":{"self":[{"href":"http:\/\/moyisuiying.com\/index.php\/wp-json\/wp\/v2\/posts\/502"}],"collection":[{"href":"http:\/\/moyisuiying.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/moyisuiying.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/moyisuiying.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/moyisuiying.com\/index.php\/wp-json\/wp\/v2\/comments?post=502"}],"version-history":[{"count":2,"href":"http:\/\/moyisuiying.com\/index.php\/wp-json\/wp\/v2\/posts\/502\/revisions"}],"predecessor-version":[{"id":504,"href":"http:\/\/moyisuiying.com\/index.php\/wp-json\/wp\/v2\/posts\/502\/revisions\/504"}],"wp:attachment":[{"href":"http:\/\/moyisuiying.com\/index.php\/wp-json\/wp\/v2\/media?parent=502"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/moyisuiying.com\/index.php\/wp-json\/wp\/v2\/categories?post=502"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/moyisuiying.com\/index.php\/wp-json\/wp\/v2\/tags?post=502"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}