{"id":10006250,"date":"2022-08-19T02:25:44","date_gmt":"2022-08-18T18:25:44","guid":{"rendered":"https:\/\/ityet.com\/?p=10006250"},"modified":"2022-08-19T02:25:44","modified_gmt":"2022-08-18T18:25:44","slug":"%e8%85%be%e8%ae%af%e4%b8%89%e9%9d%a2%ef%bc%9a%e8%bf%9b%e7%a8%8b%e5%86%99%e6%96%87%e4%bb%b6%e8%bf%87%e7%a8%8b%e4%b8%ad%ef%bc%8c%e8%bf%9b%e7%a8%8b%e5%b4%a9%e6%ba%83%e4%ba%86%ef%bc%8c%e6%96%87%e4%bb%b6","status":"publish","type":"post","link":"https:\/\/itmax.cn\/?p=10006250","title":{"rendered":"\u817e\u8baf\u4e09\u9762\uff1a\u8fdb\u7a0b\u5199\u6587\u4ef6\u8fc7\u7a0b\u4e2d\uff0c\u8fdb\u7a0b\u5d29\u6e83\u4e86\uff0c\u6587\u4ef6\u6570\u636e\u4f1a\u4e22\u5417\uff1f"},"content":{"rendered":"<h2>1. Page Cache<\/h2>\n<h3>1.1 Page Cache \u662f\u4ec0\u4e48\uff1f<\/h3>\n<p>\u4e3a\u4e86\u7406\u89e3 Page Cache\uff0c\u6211\u4eec\u4e0d\u59a8\u5148\u770b\u4e00\u4e0b Linux \u7684\u6587\u4ef6 I\/O \u7cfb\u7edf\uff0c\u5982\u4e0b\u56fe\u6240\u793a\uff1a<\/p>\n<p><img decoding=\"async\" referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000042339556\" alt=\"filesystem\" title=\"filesystem\" loading=\"lazy\"><\/p>\n<blockquote><p>Figure1. Linux \u6587\u4ef6 I\/O \u7cfb\u7edf<\/p><\/blockquote>\n<p>\u4e0a\u56fe\u4e2d\uff0c\u7ea2\u8272\u90e8\u5206\u4e3a Page Cache\u3002\u53ef\u89c1 Page Cache \u7684\u672c\u8d28\u662f\u7531 Linux \u5185\u6838\u7ba1\u7406\u7684\u5185\u5b58\u533a\u57df\u3002\u6211\u4eec\u901a\u8fc7 mmap \u4ee5\u53ca buffered I\/O \u5c06\u6587\u4ef6\u8bfb\u53d6\u5230\u5185\u5b58\u7a7a\u95f4\u5b9e\u9645\u4e0a\u90fd\u662f\u8bfb\u53d6\u5230 Page Cache \u4e2d\u3002<\/p>\n<h3>1.2 \u5982\u4f55\u67e5\u770b\u7cfb\u7edf\u7684 Page Cache\uff1f<\/h3>\n<p>\u901a\u8fc7\u8bfb\u53d6 <code>\/proc\/meminfo<\/code> \u6587\u4ef6\uff0c\u80fd\u591f\u5b9e\u65f6\u83b7\u53d6\u7cfb\u7edf\u5185\u5b58\u60c5\u51b5\uff1a<\/p>\n<pre><code>$ cat \/proc\/meminfo\n...\nBuffers:            1224 kB\nCached:           111472 kB\nSwapCached:        36364 kB\nActive:          6224232 kB\nInactive:         979432 kB\nActive(anon):    6173036 kB\nInactive(anon):   927932 kB\nActive(file):      51196 kB\nInactive(file):    51500 kB\n...\nShmem:             10000 kB\n...\nSReclaimable:      43532 kB\n...<\/code><\/pre>\n<p>\u6839\u636e\u4e0a\u9762\u7684\u6570\u636e\uff0c\u4f60\u53ef\u4ee5\u7b80\u5355\u5f97\u51fa\u8fd9\u6837\u7684\u516c\u5f0f\uff08\u7b49\u5f0f\u4e24\u8fb9\u4e4b\u548c\u90fd\u662f 112696 KB\uff09\uff1a<\/p>\n<pre><code>Buffers + Cached + SwapCached = Active(file) + Inactive(file) + Shmem + SwapCached<\/code><\/pre>\n<p>\u4e24\u8fb9\u7b49\u5f0f\u90fd\u662f Page Cache\uff0c\u5373\uff1a<\/p>\n<pre><code>Page Cache = Buffers + Cached + SwapCached<\/code><\/pre>\n<p>\u901a\u8fc7\u9605\u8bfb 1.4 \u4ee5\u53ca 1.5 \u5c0f\u8282\uff0c\u5c31\u80fd\u591f\u7406\u89e3\u4e3a\u4ec0\u4e48 SwapCached \u4e0e Buffers \u4e5f\u662f Page Cache \u7684\u4e00\u90e8\u5206\u3002<\/p>\n<h3>1.3 page \u4e0e Page Cache<\/h3>\n<p>page \u662f\u5185\u5b58\u7ba1\u7406\u5206\u914d\u7684\u57fa\u672c\u5355\u4f4d\uff0c Page Cache \u7531\u591a\u4e2a page \u6784\u6210\u3002page \u5728\u64cd\u4f5c\u7cfb\u7edf\u4e2d\u901a\u5e38\u4e3a 4KB \u5927\u5c0f\uff0832bits\/64bits\uff09\uff0c\u800c Page Cache \u7684\u5927\u5c0f\u5219\u4e3a 4KB \u7684\u6574\u6570\u500d\u3002<\/p>\n<p><strong>\u53e6\u4e00\u65b9\u9762\uff0c\u5e76\u4e0d\u662f\u6240\u6709 page \u90fd\u88ab\u7ec4\u7ec7\u4e3a Page Cache<\/strong>\u3002<\/p>\n<p>Linux \u7cfb\u7edf\u4e0a\u4f9b\u7528\u6237\u53ef\u8bbf\u95ee\u7684\u5185\u5b58\u5206\u4e3a\u4e24\u4e2a\u7c7b\u578b[2]\uff0c\u5373\uff1a<\/p>\n<ul>\n<li>File-backed pages\uff1a\u6587\u4ef6\u5907\u4efd\u9875\u4e5f\u5c31\u662f Page Cache \u4e2d\u7684 page\uff0c\u5bf9\u5e94\u4e8e\u78c1\u76d8\u4e0a\u7684\u82e5\u5e72\u6570\u636e\u5757\uff1b\u5bf9\u4e8e\u8fd9\u4e9b\u9875\u6700\u5927\u7684\u95ee\u9898\u662f\u810f\u9875\u56de\u76d8\uff1b<\/li>\n<li>Anonymous pages\uff1a\u533f\u540d\u9875\u4e0d\u5bf9\u5e94\u78c1\u76d8\u4e0a\u7684\u4efb\u4f55\u78c1\u76d8\u6570\u636e\u5757\uff0c\u5b83\u4eec\u662f\u8fdb\u7a0b\u7684\u8fd0\u884c\u662f\u5185\u5b58\u7a7a\u95f4\uff08\u4f8b\u5982\u65b9\u6cd5\u6808\u3001\u5c40\u90e8\u53d8\u91cf\u8868\u7b49\u5c5e\u6027\uff09\uff1b<\/li>\n<\/ul>\n<p><strong>\u4e3a\u4ec0\u4e48 Linux \u4e0d\u628a Page Cache \u79f0\u4e3a block cache\uff0c\u8fd9\u4e0d\u662f\u66f4\u597d\u5417\uff1f<\/strong><\/p>\n<p>\u8fd9\u662f\u56e0\u4e3a\u4ece\u78c1\u76d8\u4e2d\u52a0\u8f7d\u5230\u5185\u5b58\u7684\u6570\u636e\u4e0d\u4ec5\u4ec5\u653e\u5728 Page Cache \u4e2d\uff0c\u8fd8\u653e\u5728 buffer cache \u4e2d\u3002\u4f8b\u5982\u901a\u8fc7 Direct I\/O \u6280\u672f\u7684\u78c1\u76d8\u6587\u4ef6\u5c31\u4e0d\u4f1a\u8fdb\u5165 Page Cache \u4e2d\u3002\u5f53\u7136\uff0c\u8fd9\u4e2a\u95ee\u9898\u4e5f\u6709 Linux \u5386\u53f2\u8bbe\u8ba1\u7684\u539f\u56e0\uff0c\u6bd5\u7adf\u8fd9\u53ea\u662f\u4e00\u4e2a\u79f0\u547c\uff0c\u542b\u4e49\u968f\u7740 Linux \u7cfb\u7edf\u7684\u6f14\u8fdb\u4e5f\u9010\u6e10\u4e0d\u540c\u3002<\/p>\n<hr>\n<p>\u4e0b\u9762\u6bd4\u8f83\u4e00\u4e0b File-backed pages \u4e0e Anonymous pages \u5728 Swap \u673a\u5236\u4e0b\u7684\u6027\u80fd\u3002<\/p>\n<p>\u5185\u5b58\u662f\u4e00\u79cd\u73cd\u60dc\u8d44\u6e90\uff0c\u5f53\u5185\u5b58\u4e0d\u591f\u7528\u65f6\uff0c\u5185\u5b58\u7ba1\u7406\u5355\u5143\uff08Memory Mangament Unit\uff09\u9700\u8981\u63d0\u4f9b\u8c03\u5ea6\u7b97\u6cd5\u6765\u56de\u6536\u76f8\u5173\u5185\u5b58\u7a7a\u95f4\u3002\u5185\u5b58\u7a7a\u95f4\u56de\u6536\u7684\u65b9\u5f0f\u901a\u5e38\u5c31\u662f swap\uff0c\u5373\u4ea4\u6362\u5230\u6301\u4e45\u5316\u5b58\u50a8\u8bbe\u5907\u4e0a\u3002<\/p>\n<p>File-backed pages\uff08Page Cache\uff09\u7684\u5185\u5b58\u56de\u6536\u4ee3\u4ef7\u8f83\u4f4e\u3002 Page Cache \u901a\u5e38\u5bf9\u5e94\u4e8e\u4e00\u4e2a\u6587\u4ef6\u4e0a\u7684\u82e5\u5e72\u987a\u5e8f\u5757\uff0c\u56e0\u6b64\u53ef\u4ee5\u901a\u8fc7\u987a\u5e8f I\/O \u7684\u65b9\u5f0f\u843d\u76d8\u3002\u53e6\u4e00\u65b9\u9762\uff0c\u5982\u679c Page Cache \u4e0a\u6ca1\u6709\u8fdb\u884c\u5199\u64cd\u4f5c\uff08\u6240\u8c13\u7684\u6ca1\u6709\u810f\u9875\uff09\uff0c\u751a\u81f3\u4e0d\u4f1a\u5c06 Page Cache \u56de\u76d8\uff0c\u56e0\u4e3a\u6570\u636e\u7684\u5185\u5bb9\u5b8c\u5168\u53ef\u4ee5\u901a\u8fc7\u518d\u6b21\u8bfb\u53d6\u78c1\u76d8\u6587\u4ef6\u5f97\u5230\u3002<\/p>\n<p>Page Cache \u7684\u4e3b\u8981\u96be\u70b9\u5728\u4e8e\u810f\u9875\u56de\u76d8\uff0c\u8fd9\u4e2a\u5185\u5bb9\u4f1a\u5728\u7b2c\u4e8c\u8282\u8fdb\u884c\u8be6\u7ec6\u8bf4\u660e\u3002<\/p>\n<p>Anonymous pages \u7684\u5185\u5b58\u56de\u6536\u4ee3\u4ef7\u8f83\u9ad8\u3002\u8fd9\u662f\u56e0\u4e3a Anonymous pages \u901a\u5e38\u968f\u673a\u5730\u5199\u5165\u6301\u4e45\u5316\u4ea4\u6362\u8bbe\u5907\u3002\u53e6\u4e00\u65b9\u9762\uff0c\u65e0\u8bba\u662f\u5426\u6709\u5199\u64cd\u4f5c\uff0c\u4e3a\u4e86\u786e\u4fdd\u6570\u636e\u4e0d\u4e22\u5931\uff0cAnonymous pages \u5728 swap \u65f6\u5fc5\u987b\u6301\u4e45\u5316\u5230\u78c1\u76d8\u3002<\/p>\n<h3>1.4 Swap \u4e0e\u7f3a\u9875\u4e2d\u65ad<\/h3>\n<p>Swap \u673a\u5236\u6307\u7684\u662f\u5f53\u7269\u7406\u5185\u5b58\u4e0d\u591f\u7528\uff0c\u5185\u5b58\u7ba1\u7406\u5355\u5143\uff08Memory Mangament Unit\uff0cMMU\uff09\u9700\u8981\u63d0\u4f9b\u8c03\u5ea6\u7b97\u6cd5\u6765\u56de\u6536\u76f8\u5173\u5185\u5b58\u7a7a\u95f4\uff0c\u7136\u540e\u5c06\u6e05\u7406\u51fa\u6765\u7684\u5185\u5b58\u7a7a\u95f4\u7ed9\u5f53\u524d\u5185\u5b58\u7533\u8bf7\u65b9\u3002<\/p>\n<p>Swap \u673a\u5236\u5b58\u5728\u7684\u672c\u8d28\u539f\u56e0\u662f Linux \u7cfb\u7edf\u63d0\u4f9b\u4e86\u865a\u62df\u5185\u5b58\u7ba1\u7406\u673a\u5236\uff0c\u6bcf\u4e00\u4e2a\u8fdb\u7a0b\u8ba4\u4e3a\u5176\u72ec\u5360\u5185\u5b58\u7a7a\u95f4\uff0c\u56e0\u6b64\u6240\u6709\u8fdb\u7a0b\u7684\u5185\u5b58\u7a7a\u95f4\u4e4b\u548c\u8fdc\u8fdc\u5927\u4e8e\u7269\u7406\u5185\u5b58\u3002\u6240\u6709\u8fdb\u7a0b\u7684\u5185\u5b58\u7a7a\u95f4\u4e4b\u548c\u8d85\u8fc7\u7269\u7406\u5185\u5b58\u7684\u90e8\u5206\u5c31\u9700\u8981\u4ea4\u6362\u5230\u78c1\u76d8\u4e0a\u3002<\/p>\n<p>\u64cd\u4f5c\u7cfb\u7edf\u4ee5 page \u4e3a\u5355\u4f4d\u7ba1\u7406\u5185\u5b58\uff0c\u5f53\u8fdb\u7a0b\u53d1\u73b0\u9700\u8981\u8bbf\u95ee\u7684\u6570\u636e\u4e0d\u5728\u5185\u5b58\u65f6\uff0c\u64cd\u4f5c\u7cfb\u7edf\u53ef\u80fd\u4f1a\u5c06\u6570\u636e\u4ee5\u9875\u7684\u65b9\u5f0f\u52a0\u8f7d\u5230\u5185\u5b58\u4e2d\u3002\u4e0a\u8ff0\u8fc7\u7a0b\u88ab\u79f0\u4e3a\u7f3a\u9875\u4e2d\u65ad\uff0c\u5f53\u64cd\u4f5c\u7cfb\u7edf\u53d1\u751f\u7f3a\u9875\u4e2d\u65ad\u65f6\uff0c\u5c31\u4f1a\u901a\u8fc7\u7cfb\u7edf\u8c03\u7528\u5c06 page \u518d\u6b21\u8bfb\u5230\u5185\u5b58\u4e2d\u3002<\/p>\n<p>\u4f46\u4e3b\u5185\u5b58\u7684\u7a7a\u95f4\u662f\u6709\u9650\u7684\uff0c\u5f53\u4e3b\u5185\u5b58\u4e2d\u4e0d\u5305\u542b\u53ef\u4ee5\u4f7f\u7528\u7684\u7a7a\u95f4\u65f6\uff0c\u64cd\u4f5c\u7cfb\u7edf\u4f1a\u4ece\u9009\u62e9\u5408\u9002\u7684\u7269\u7406\u5185\u5b58\u9875\u9a71\u9010\u56de\u78c1\u76d8\uff0c\u4e3a\u65b0\u7684\u5185\u5b58\u9875\u8ba9\u51fa\u4f4d\u7f6e\uff0c<strong>\u9009\u62e9\u5f85\u9a71\u9010\u9875\u7684\u8fc7\u7a0b\u5728\u64cd\u4f5c\u7cfb\u7edf\u4e2d\u53eb\u505a\u9875\u9762\u66ff\u6362\uff08Page Replacement\uff09<\/strong>\uff0c\u66ff\u6362\u64cd\u4f5c\u53c8\u4f1a\u89e6\u53d1 swap \u673a\u5236\u3002<\/p>\n<p>\u5982\u679c\u7269\u7406\u5185\u5b58\u8db3\u591f\u5927\uff0c\u90a3\u4e48\u53ef\u80fd\u4e0d\u9700\u8981 Swap \u673a\u5236\uff0c\u4f46\u662f Swap \u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\u8fd8\u662f\u6709\u4e00\u5b9a\u4f18\u52bf\uff1a\u5bf9\u4e8e\u6709\u53d1\u751f\u5185\u5b58\u6cc4\u6f0f\u51e0\u7387\u7684\u5e94\u7528\u7a0b\u5e8f\uff08\u8fdb\u7a0b\uff09\uff0cSwap \u4ea4\u6362\u5206\u533a\u66f4\u662f\u91cd\u8981\uff0c\u8fd9\u53ef\u4ee5\u786e\u4fdd\u5185\u5b58\u6cc4\u9732\u4e0d\u81f3\u4e8e\u5bfc\u81f4\u7269\u7406\u5185\u5b58\u4e0d\u591f\u7528\uff0c\u6700\u7ec8\u5bfc\u81f4\u7cfb\u7edf\u5d29\u6e83\u3002\u4f46\u5185\u5b58\u6cc4\u9732\u4f1a\u5f15\u8d77\u9891\u7e41\u7684 swap\uff0c\u6b64\u65f6\u975e\u5e38\u5f71\u54cd\u64cd\u4f5c\u7cfb\u7edf\u7684\u6027\u80fd\u3002<\/p>\n<p>Linux \u901a\u8fc7\u4e00\u4e2a swappiness \u53c2\u6570\u6765\u63a7\u5236 Swap \u673a\u5236[2]\uff1a\u8fd9\u4e2a\u53c2\u6570\u503c\u53ef\u4e3a 0-100\uff0c\u63a7\u5236\u7cfb\u7edf swap \u7684\u4f18\u5148\u7ea7\uff1a<\/p>\n<ul>\n<li>\u9ad8\u6570\u503c\uff1a\u8f83\u9ad8\u9891\u7387\u7684 swap\uff0c\u8fdb\u7a0b\u4e0d\u6d3b\u8dc3\u65f6\u4e3b\u52a8\u5c06\u5176\u8f6c\u6362\u51fa\u7269\u7406\u5185\u5b58\u3002<\/li>\n<li>\u4f4e\u6570\u503c\uff1a\u8f83\u4f4e\u9891\u7387\u7684 swap\uff0c\u8fd9\u53ef\u4ee5\u786e\u4fdd\u4ea4\u4e92\u5f0f\u4e0d\u56e0\u4e3a\u5185\u5b58\u7a7a\u95f4\u9891\u7e41\u5730\u4ea4\u6362\u5230\u78c1\u76d8\u800c\u63d0\u9ad8\u54cd\u5e94\u5ef6\u8fdf\u3002<\/li>\n<\/ul>\n<p><strong>\u6700\u540e\uff0c\u4e3a\u4ec0\u4e48 Buffers \u4e5f\u662f Page Cache \u7684\u4e00\u90e8\u5206\uff1f<\/strong><\/p>\n<p>\u8fd9\u662f\u56e0\u4e3a\u5f53\u533f\u540d\u9875\uff08Inactive(anon) \u4ee5\u53ca Active(anon)\uff09\u5148\u88ab\u4ea4\u6362\uff08swap out\uff09\u5230\u78c1\u76d8\u4e0a\u540e\uff0c\u7136\u540e\u518d\u52a0\u8f7d\u56de\uff08swap in\uff09\u5185\u5b58\u4e2d\uff0c\u7531\u4e8e\u8bfb\u5165\u5230\u5185\u5b58\u540e\u539f\u6765\u7684 Swap File \u8fd8\u5728\uff0c\u6240\u4ee5 SwapCached \u4e5f\u53ef\u4ee5\u8ba4\u4e3a\u662f File-backed page\uff0c\u5373\u5c5e\u4e8e Page Cache\u3002\u8fd9\u4e2a\u8fc7\u7a0b\u5982 Figure 2 \u6240\u793a\u3002<\/p>\n<p><img decoding=\"async\" referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000042339557\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<blockquote><p>Figure2. \u533f\u540d\u9875\u7684\u88ab\u4ea4\u6362\u540e\u4e5f\u662f Page Cache<\/p><\/blockquote>\n<h3>1.5 Page Cache \u4e0e buffer cache<\/h3>\n<p>\u6267\u884c free \u547d\u4ee4\uff0c\u6ce8\u610f\u5230\u4f1a\u6709\u4e24\u5217\u540d\u4e3a buffers \u548c cached\uff0c\u4e5f\u6709\u4e00\u884c\u540d\u4e3a \u201c-\/+ buffers\/cache\u201d\u3002<\/p>\n<pre><code>~ free -m\n             total       used       free     shared    buffers     cached\nMem:        128956      96440      32515          0       5368      39900\n-\/+ buffers\/cache:      51172      77784\nSwap:        16002          0      16001<\/code><\/pre>\n<p>\u5176\u4e2d\uff0ccached \u5217\u8868\u793a\u5f53\u524d\u7684\u9875\u7f13\u5b58\uff08Page Cache\uff09\u5360\u7528\u91cf\uff0cbuffers \u5217\u8868\u793a\u5f53\u524d\u7684\u5757\u7f13\u5b58\uff08buffer cache\uff09\u5360\u7528\u91cf\u3002\u7528\u4e00\u53e5\u8bdd\u6765\u89e3\u91ca\uff1a<strong>Page Cache \u7528\u4e8e\u7f13\u5b58\u6587\u4ef6\u7684\u9875\u6570\u636e\uff0cbuffer cache \u7528\u4e8e\u7f13\u5b58\u5757\u8bbe\u5907\uff08\u5982\u78c1\u76d8\uff09\u7684\u5757\u6570\u636e\u3002<\/strong>\u9875\u662f\u903b\u8f91\u4e0a\u7684\u6982\u5ff5\uff0c\u56e0\u6b64 Page Cache \u662f\u4e0e\u6587\u4ef6\u7cfb\u7edf\u540c\u7ea7\u7684\uff1b\u5757\u662f\u7269\u7406\u4e0a\u7684\u6982\u5ff5\uff0c\u56e0\u6b64 buffer cache \u662f\u4e0e\u5757\u8bbe\u5907\u9a71\u52a8\u7a0b\u5e8f\u540c\u7ea7\u7684\u3002<\/p>\n<p>\u5176\u4e2d\uff0ccached \u5217\u8868\u793a\u5f53\u524d\u7684\u9875\u7f13\u5b58\uff08Page Cache\uff09\u5360\u7528\u91cf\uff0cbuffers \u5217\u8868\u793a\u5f53\u524d\u7684\u5757\u7f13\u5b58\uff08buffer cache\uff09\u5360\u7528\u91cf\u3002\u7528\u4e00\u53e5\u8bdd\u6765\u89e3\u91ca\uff1a<strong>Page Cache \u7528\u4e8e\u7f13\u5b58\u6587\u4ef6\u7684\u9875\u6570\u636e\uff0cbuffer cache \u7528\u4e8e\u7f13\u5b58\u5757\u8bbe\u5907\uff08\u5982\u78c1\u76d8\uff09\u7684\u5757\u6570\u636e\u3002<\/strong>\u9875\u662f\u903b\u8f91\u4e0a\u7684\u6982\u5ff5\uff0c\u56e0\u6b64 Page Cache \u662f\u4e0e\u6587\u4ef6\u7cfb\u7edf\u540c\u7ea7\u7684\uff1b\u5757\u662f\u7269\u7406\u4e0a\u7684\u6982\u5ff5\uff0c\u56e0\u6b64 buffer cache \u662f\u4e0e\u5757\u8bbe\u5907\u9a71\u52a8\u7a0b\u5e8f\u540c\u7ea7\u7684\u3002<\/p>\n<p>Page Cache \u4e0e buffer cache \u7684\u5171\u540c\u76ee\u7684\u90fd\u662f\u52a0\u901f\u6570\u636e I\/O\uff1a\u5199\u6570\u636e\u65f6\u9996\u5148\u5199\u5230\u7f13\u5b58\uff0c\u5c06\u5199\u5165\u7684\u9875\u6807\u8bb0\u4e3a dirty\uff0c\u7136\u540e\u5411\u5916\u90e8\u5b58\u50a8 flush\uff0c\u4e5f\u5c31\u662f\u7f13\u5b58\u5199\u673a\u5236\u4e2d\u7684 write-back\uff08\u53e6\u4e00\u79cd\u662f write-through\uff0cLinux \u9ed8\u8ba4\u60c5\u51b5\u4e0b\u4e0d\u91c7\u7528\uff09\uff1b\u8bfb\u6570\u636e\u65f6\u9996\u5148\u8bfb\u53d6\u7f13\u5b58\uff0c\u5982\u679c\u672a\u547d\u4e2d\uff0c\u518d\u53bb\u5916\u90e8\u5b58\u50a8\u8bfb\u53d6\uff0c\u5e76\u4e14\u5c06\u8bfb\u53d6\u6765\u7684\u6570\u636e\u4e5f\u52a0\u5165\u7f13\u5b58\u3002\u64cd\u4f5c\u7cfb\u7edf\u603b\u662f\u79ef\u6781\u5730\u5c06\u6240\u6709\u7a7a\u95f2\u5185\u5b58\u90fd\u7528\u4f5c Page Cache \u548c buffer cache\uff0c\u5f53\u5185\u5b58\u4e0d\u591f\u7528\u65f6\u4e5f\u4f1a\u7528 LRU \u7b49\u7b97\u6cd5\u6dd8\u6c70\u7f13\u5b58\u9875\u3002<\/p>\n<p>\u5728 Linux 2.4 \u7248\u672c\u7684\u5185\u6838\u4e4b\u524d\uff0cPage Cache \u4e0e buffer cache \u662f\u5b8c\u5168\u5206\u79bb\u7684\u3002\u4f46\u662f\uff0c\u5757\u8bbe\u5907\u5927\u591a\u662f\u78c1\u76d8\uff0c\u78c1\u76d8\u4e0a\u7684\u6570\u636e\u53c8\u5927\u591a\u901a\u8fc7\u6587\u4ef6\u7cfb\u7edf\u6765\u7ec4\u7ec7\uff0c\u8fd9\u79cd\u8bbe\u8ba1\u5bfc\u81f4\u5f88\u591a\u6570\u636e\u88ab\u7f13\u5b58\u4e86\u4e24\u6b21\uff0c\u6d6a\u8d39\u5185\u5b58\u3002<strong>\u6240\u4ee5\u5728 2.4 \u7248\u672c\u5185\u6838\u4e4b\u540e\uff0c\u4e24\u5757\u7f13\u5b58\u8fd1\u4f3c\u878d\u5408\u5728\u4e86\u4e00\u8d77\uff1a\u5982\u679c\u4e00\u4e2a\u6587\u4ef6\u7684\u9875\u52a0\u8f7d\u5230\u4e86 Page Cache\uff0c\u90a3\u4e48\u540c\u65f6 buffer cache \u53ea\u9700\u8981\u7ef4\u62a4\u5757\u6307\u5411\u9875\u7684\u6307\u9488\u5c31\u53ef\u4ee5\u4e86<\/strong>\u3002\u53ea\u6709\u90a3\u4e9b\u6ca1\u6709\u6587\u4ef6\u8868\u793a\u7684\u5757\uff0c\u6216\u8005\u7ed5\u8fc7\u4e86\u6587\u4ef6\u7cfb\u7edf\u76f4\u63a5\u64cd\u4f5c\uff08\u5982dd\u547d\u4ee4\uff09\u7684\u5757\uff0c\u624d\u4f1a\u771f\u6b63\u653e\u5230 buffer cache \u91cc\u3002\u56e0\u6b64\uff0c\u6211\u4eec\u73b0\u5728\u63d0\u8d77 Page Cache\uff0c\u57fa\u672c\u4e0a\u90fd\u540c\u65f6\u6307 Page Cache \u548c buffer cache \u4e24\u8005\uff0c\u672c\u6587\u4e4b\u540e\u4e5f\u4e0d\u518d\u533a\u5206\uff0c\u76f4\u63a5\u7edf\u79f0\u4e3a Page Cache\u3002<\/p>\n<p>\u4e0b\u56fe\u8fd1\u4f3c\u5730\u793a\u51fa 32-bit Linux \u7cfb\u7edf\u4e2d\u53ef\u80fd\u7684\u4e00\u79cd Page Cache \u7ed3\u6784\uff0c\u5176\u4e2d block size \u5927\u5c0f\u4e3a 1KB\uff0cpage size \u5927\u5c0f\u4e3a 4KB\u3002<\/p>\n<p><img decoding=\"async\" referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000042339558\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<p>Page Cache \u4e2d\u7684\u6bcf\u4e2a\u6587\u4ef6\u90fd\u662f\u4e00\u68f5\u57fa\u6570\u6811\uff08radix tree\uff0c\u672c\u8d28\u4e0a\u662f\u591a\u53c9\u641c\u7d22\u6811\uff09\uff0c\u6811\u7684\u6bcf\u4e2a\u8282\u70b9\u90fd\u662f\u4e00\u4e2a\u9875\u3002\u6839\u636e\u6587\u4ef6\u5185\u7684\u504f\u79fb\u91cf\u5c31\u53ef\u4ee5\u5feb\u901f\u5b9a\u4f4d\u5230\u6240\u5728\u7684\u9875\uff0c\u5982\u4e0b\u56fe\u6240\u793a\u3002\u5173\u4e8e\u57fa\u6570\u6811\u7684\u539f\u7406\u53ef\u4ee5\u53c2\u89c1\u82f1\u6587\u7ef4\u57fa\uff0c\u8fd9\u91cc\u5c31\u4e0d\u7ec6\u8bf4\u4e86\u3002<\/p>\n<p><img decoding=\"async\" referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000042339559\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<h3>1.6 Page Cache \u4e0e\u9884\u8bfb<\/h3>\n<p>\u64cd\u4f5c\u7cfb\u7edf\u4e3a\u57fa\u4e8e Page Cache \u7684\u8bfb\u7f13\u5b58\u673a\u5236\u63d0\u4f9b\u9884\u8bfb\u673a\u5236\uff08PAGE_READAHEAD\uff09\uff0c\u4e00\u4e2a\u4f8b\u5b50\u662f\uff1a<\/p>\n<ul>\n<li>\u7528\u6237\u7ebf\u7a0b\u4ec5\u4ec5\u8bf7\u6c42\u8bfb\u53d6\u78c1\u76d8\u4e0a\u6587\u4ef6 A \u7684 offset \u4e3a 0-3KB \u8303\u56f4\u5185\u7684\u6570\u636e\uff0c\u7531\u4e8e\u78c1\u76d8\u7684\u57fa\u672c\u8bfb\u5199\u5355\u4f4d\u4e3a block\uff084KB\uff09\uff0c\u4e8e\u662f\u64cd\u4f5c\u7cfb\u7edf\u81f3\u5c11\u4f1a\u8bfb 0-4KB \u7684\u5185\u5bb9\uff0c\u8fd9\u6070\u597d\u53ef\u4ee5\u5728\u4e00\u4e2a page \u4e2d\u88c5\u4e0b\u3002<\/li>\n<li>\u4f46\u662f\u64cd\u4f5c\u7cfb\u7edf\u51fa\u4e8e\u5c40\u90e8\u6027\u539f\u7406[3]\u4f1a\u9009\u62e9\u5c06\u78c1\u76d8\u5757 offset [4KB,8KB)\u3001[8KB,12KB) \u4ee5\u53ca [12KB,16KB) \u90fd\u52a0\u8f7d\u5230\u5185\u5b58\uff0c\u4e8e\u662f\u989d\u5916\u5728\u5185\u5b58\u4e2d\u7533\u8bf7\u4e86 3 \u4e2a page\uff1b<\/li>\n<\/ul>\n<p>\u4e0b\u56fe\u4ee3\u8868\u4e86\u64cd\u4f5c\u7cfb\u7edf\u7684\u9884\u8bfb\u673a\u5236\uff1a<\/p>\n<p><img decoding=\"async\" referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000042339560\" alt=\"\" title=\"\" loading=\"lazy\"><\/p>\n<blockquote><p>Figure.\u64cd\u4f5c\u7cfb\u7edf\u7684\u9884\u8bfb\u673a\u5236\uff1b<\/p><\/blockquote>\n<p>\u4e0a\u56fe\u4e2d\uff0c\u5e94\u7528\u7a0b\u5e8f\u5229\u7528 read \u7cfb\u7edf\u8c03\u52a8\u8bfb\u53d6 4KB \u6570\u636e\uff0c\u5b9e\u9645\u4e0a\u5185\u6838\u4f7f\u7528 readahead \u673a\u5236\u5b8c\u6210\u4e86 16KB \u6570\u636e\u7684\u8bfb\u53d6\u3002<\/p>\n<h2>2. Page Cache \u4e0e\u6587\u4ef6\u6301\u4e45\u5316\u7684\u4e00\u81f4\u6027&#038;\u53ef\u9760\u6027<\/h2>\n<p>\u73b0\u4ee3 Linux \u7684 Page Cache \u6b63\u5982\u5176\u540d\uff0c\u662f\u5bf9\u78c1\u76d8\u4e0a page\uff08\u9875\uff09\u7684\u5185\u5b58\u7f13\u5b58\uff0c\u540c\u65f6\u53ef\u4ee5\u7528\u4e8e\u8bfb\/\u5199\u64cd\u4f5c\u3002\u4efb\u4f55\u7cfb\u7edf\u5f15\u5165\u7f13\u5b58\uff0c\u5c31\u4f1a\u5f15\u53d1\u4e00\u81f4\u6027\u95ee\u9898\uff1a\u5185\u5b58\u4e2d\u7684\u6570\u636e\u4e0e\u78c1\u76d8\u4e2d\u7684\u6570\u636e\u4e0d\u4e00\u81f4\uff0c\u4f8b\u5982\u5e38\u89c1\u540e\u7aef\u67b6\u6784\u4e2d\u7684 Redis \u7f13\u5b58\u4e0e MySQL \u6570\u636e\u5e93\u5c31\u5b58\u5728\u4e00\u81f4\u6027\u95ee\u9898\u3002<\/p>\n<p>Linux \u63d0\u4f9b\u591a\u79cd\u673a\u5236\u6765\u4fdd\u8bc1\u6570\u636e\u4e00\u81f4\u6027\uff0c\u4f46\u65e0\u8bba\u662f\u5355\u673a\u4e0a\u7684\u5185\u5b58\u4e0e\u78c1\u76d8\u4e00\u81f4\u6027\uff0c\u8fd8\u662f\u5206\u5e03\u5f0f\u7ec4\u4ef6\u4e2d\u8282\u70b9 1 \u4e0e\u8282\u70b9 2 \u3001\u8282\u70b9 3 \u7684\u6570\u636e\u4e00\u81f4\u6027\u95ee\u9898\uff0c\u7406\u89e3\u7684\u5173\u952e\u662f trade-off\uff1a\u541e\u5410\u91cf\u4e0e\u6570\u636e\u4e00\u81f4\u6027\u4fdd\u8bc1\u662f\u4e00\u5bf9\u77db\u76fe\u3002<\/p>\n<p>\u9996\u5148\uff0c\u9700\u8981\u6211\u4eec\u7406\u89e3\u4e00\u4e0b\u6587\u4ef6\u7684\u6570\u636e\u3002<strong>\u6587\u4ef6 = \u6570\u636e + \u5143\u6570\u636e<\/strong>\u3002\u5143\u6570\u636e\u7528\u6765\u63cf\u8ff0\u6587\u4ef6\u7684\u5404\u79cd\u5c5e\u6027\uff0c\u4e5f\u5fc5\u987b\u5b58\u50a8\u5728\u78c1\u76d8\u4e0a\u3002\u56e0\u6b64\uff0c\u6211\u4eec\u8bf4\u4fdd\u8bc1\u6587\u4ef6\u4e00\u81f4\u6027\u5176\u5b9e\u5305\u542b\u4e86\u4e24\u4e2a\u65b9\u9762\uff1a\u6570\u636e\u4e00\u81f4+\u5143\u6570\u636e\u4e00\u81f4\u3002<\/p>\n<blockquote><p>\u6587\u4ef6\u7684\u5143\u6570\u636e\u5305\u62ec\uff1a\u6587\u4ef6\u5927\u5c0f\u3001\u521b\u5efa\u65f6\u95f4\u3001\u8bbf\u95ee\u65f6\u95f4\u3001\u5c5e\u4e3b\u5c5e\u7ec4\u7b49\u4fe1\u606f\u3002<\/p><\/blockquote>\n<p>\u6211\u4eec\u8003\u8651\u5982\u4e0b\u4e00\u81f4\u6027\u95ee\u9898\uff1a\u5982\u679c\u53d1\u751f\u5199\u64cd\u4f5c\u5e76\u4e14\u5bf9\u5e94\u7684\u6570\u636e\u5728 Page Cache \u4e2d\uff0c\u90a3\u4e48\u5199\u64cd\u4f5c\u5c31\u4f1a\u76f4\u63a5\u4f5c\u7528\u4e8e Page Cache \u4e2d\uff0c\u6b64\u65f6\u5982\u679c\u6570\u636e\u8fd8\u6ca1\u5237\u65b0\u5230\u78c1\u76d8\uff0c\u90a3\u4e48\u5185\u5b58\u4e2d\u7684\u6570\u636e\u5c31\u9886\u5148\u4e8e\u78c1\u76d8\uff0c\u6b64\u65f6\u5bf9\u5e94 page \u5c31\u88ab\u79f0\u4e3a Dirty page\u3002<\/p>\n<p>\u5f53\u524d Linux \u4e0b\u4ee5\u4e24\u79cd\u65b9\u5f0f\u5b9e\u73b0\u6587\u4ef6\u4e00\u81f4\u6027\uff1a<\/p>\n<ol>\n<li><strong>Write Through\uff08\u5199\u7a7f\uff09<\/strong>\uff1a\u5411\u7528\u6237\u5c42\u63d0\u4f9b\u7279\u5b9a\u63a5\u53e3\uff0c\u5e94\u7528\u7a0b\u5e8f\u53ef\u4e3b\u52a8\u8c03\u7528\u63a5\u53e3\u6765\u4fdd\u8bc1\u6587\u4ef6\u4e00\u81f4\u6027\uff1b<\/li>\n<li><strong>Write back\uff08\u5199\u56de\uff09<\/strong>\uff1a\u7cfb\u7edf\u4e2d\u5b58\u5728\u5b9a\u671f\u4efb\u52a1\uff08\u8868\u73b0\u5f62\u5f0f\u4e3a\u5185\u6838\u7ebf\u7a0b\uff09\uff0c\u5468\u671f\u6027\u5730\u540c\u6b65\u6587\u4ef6\u7cfb\u7edf\u4e2d\u6587\u4ef6\u810f\u6570\u636e\u5757\uff0c\u8fd9\u662f\u9ed8\u8ba4\u7684 Linux \u4e00\u81f4\u6027\u65b9\u6848\uff1b<\/li>\n<\/ol>\n<p>\u4e0a\u8ff0\u4e24\u79cd\u65b9\u5f0f\u6700\u7ec8\u90fd\u4f9d\u8d56\u4e8e\u7cfb\u7edf\u8c03\u7528\uff0c\u4e3b\u8981\u5206\u4e3a\u5982\u4e0b\u4e09\u79cd\u7cfb\u7edf\u8c03\u7528\uff1a<\/p>\n<table>\n<thead>\n<tr>\n<th>\u65b9\u6cd5<\/th>\n<th>\u542b\u4e49<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>fsync(intfd)<\/td>\n<td><strong>fsync(fd)\uff1a<\/strong>\u5c06 fd \u4ee3\u8868\u7684\u6587\u4ef6\u7684\u810f\u6570\u636e\u548c\u810f\u5143\u6570\u636e\u5168\u90e8\u5237\u65b0\u81f3\u78c1\u76d8\u4e2d\u3002<\/td>\n<\/tr>\n<tr>\n<td>fdatasync(int fd)<\/td>\n<td><strong>fdatasync(fd)\uff1a<\/strong>\u5c06 fd \u4ee3\u8868\u7684\u6587\u4ef6\u7684\u810f\u6570\u636e\u5237\u65b0\u81f3\u78c1\u76d8\uff0c\u540c\u65f6\u5bf9\u5fc5\u8981\u7684\u5143\u6570\u636e\u5237\u65b0\u81f3\u78c1\u76d8\u4e2d\uff0c\u8fd9\u91cc\u6240\u8bf4\u7684\u5fc5\u8981\u7684\u6982\u5ff5\u662f\u6307\uff1a\u5bf9\u63a5\u4e0b\u6765\u8bbf\u95ee\u6587\u4ef6\u6709\u5173\u952e\u4f5c\u7528\u7684\u4fe1\u606f\uff0c\u5982\u6587\u4ef6\u5927\u5c0f\uff0c\u800c\u6587\u4ef6\u4fee\u6539\u65f6\u95f4\u7b49\u4e0d\u5c5e\u4e8e\u5fc5\u8981\u4fe1\u606f<\/td>\n<\/tr>\n<tr>\n<td>sync()<\/td>\n<td><strong>sync()\uff1a<\/strong>\u5219\u662f\u5bf9\u7cfb\u7edf\u4e2d\u6240\u6709\u7684\u810f\u7684\u6587\u4ef6\u6570\u636e\u5143\u6570\u636e\u5237\u65b0\u81f3\u78c1\u76d8\u4e2d<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u4e0a\u8ff0\u4e09\u79cd\u7cfb\u7edf\u8c03\u7528\u53ef\u4ee5\u5206\u522b\u7531\u7528\u6237\u8fdb\u7a0b\u4e0e\u5185\u6838\u8fdb\u7a0b\u53d1\u8d77\u3002\u4e0b\u9762\u6211\u4eec\u7814\u7a76\u4e00\u4e0b\u5185\u6838\u7ebf\u7a0b\u7684\u76f8\u5173\u7279\u6027\u3002<\/p>\n<ol>\n<li>\u521b\u5efa\u7684\u9488\u5bf9\u56de\u5199\u4efb\u52a1\u7684\u5185\u6838\u7ebf\u7a0b\u6570\u7531\u7cfb\u7edf\u4e2d\u6301\u4e45\u5b58\u50a8\u8bbe\u5907\u51b3\u5b9a\uff0c\u4e3a\u6bcf\u4e2a\u5b58\u50a8\u8bbe\u5907\u521b\u5efa\u5355\u72ec\u7684\u5237\u65b0\u7ebf\u7a0b\uff1b<\/li>\n<li>\u5173\u4e8e\u591a\u7ebf\u7a0b\u7684\u67b6\u6784\u95ee\u9898\uff0cLinux \u5185\u6838\u91c7\u53d6\u4e86 Lighthttp \u7684\u505a\u6cd5\uff0c\u5373\u7cfb\u7edf\u4e2d\u5b58\u5728\u4e00\u4e2a\u7ba1\u7406\u7ebf\u7a0b\u548c\u591a\u4e2a\u5237\u65b0\u7ebf\u7a0b\uff08\u6bcf\u4e2a\u6301\u4e45\u5b58\u50a8\u8bbe\u5907\u5bf9\u5e94\u4e00\u4e2a\u5237\u65b0\u7ebf\u7a0b\uff09\u3002\u7ba1\u7406\u7ebf\u7a0b\u76d1\u63a7\u8bbe\u5907\u4e0a\u7684\u810f\u9875\u9762\u60c5\u51b5\uff0c\u82e5\u8bbe\u5907\u4e00\u6bb5\u65f6\u95f4\u5185\u6ca1\u6709\u4ea7\u751f\u810f\u9875\u9762\uff0c\u5c31\u9500\u6bc1\u8bbe\u5907\u4e0a\u7684\u5237\u65b0\u7ebf\u7a0b\uff1b\u82e5\u76d1\u6d4b\u5230\u8bbe\u5907\u4e0a\u6709\u810f\u9875\u9762\u9700\u8981\u56de\u5199\u4e14\u5c1a\u672a\u4e3a\u8be5\u8bbe\u5907\u521b\u5efa\u5237\u65b0\u7ebf\u7a0b\uff0c\u90a3\u4e48\u521b\u5efa\u5237\u65b0\u7ebf\u7a0b\u5904\u7406\u810f\u9875\u9762\u56de\u5199\u3002\u800c\u5237\u65b0\u7ebf\u7a0b\u7684\u4efb\u52a1\u8f83\u4e3a\u5355\u8c03\uff0c\u53ea\u8d1f\u8d23\u5c06\u8bbe\u5907\u4e2d\u7684\u810f\u9875\u9762\u56de\u5199\u81f3\u6301\u4e45\u5b58\u50a8\u8bbe\u5907\u4e2d\u3002<\/li>\n<li>\n<p>\u5237\u65b0\u7ebf\u7a0b\u5237\u65b0\u8bbe\u5907\u4e0a\u810f\u9875\u9762\u5927\u81f4\u8bbe\u8ba1\u5982\u4e0b\uff1a<\/p>\n<ol>\n<li>\u6bcf\u4e2a\u8bbe\u5907\u4fdd\u5b58\u810f\u6587\u4ef6\u94fe\u8868\uff0c\u4fdd\u5b58\u7684\u662f\u8be5\u8bbe\u5907\u4e0a\u5b58\u50a8\u7684\u810f\u6587\u4ef6\u7684 inode \u8282\u70b9\u3002\u6240\u8c13\u7684\u56de\u5199\u6587\u4ef6\u810f\u9875\u9762\u5373\u56de\u5199\u8be5 inode \u94fe\u8868\u4e0a\u7684\u67d0\u4e9b\u6587\u4ef6\u7684\u810f\u9875\u9762\uff1b<\/li>\n<li>\u7cfb\u7edf\u4e2d\u5b58\u5728\u591a\u4e2a\u56de\u5199\u65f6\u673a\uff0c\u7b2c\u4e00\u662f\u5e94\u7528\u7a0b\u5e8f\u4e3b\u52a8\u8c03\u7528\u56de\u5199\u63a5\u53e3\uff08fsync\uff0cfdatasync \u4ee5\u53ca sync \u7b49\uff09\uff0c\u7b2c\u4e8c\u7ba1\u7406\u7ebf\u7a0b\u5468\u671f\u6027\u5730\u5524\u9192\u8bbe\u5907\u4e0a\u7684\u56de\u5199\u7ebf\u7a0b\u8fdb\u884c\u56de\u5199\uff0c\u7b2c\u4e09\u662f\u67d0\u4e9b\u5e94\u7528\u7a0b\u5e8f\/\u5185\u6838\u4efb\u52a1\u53d1\u73b0\u5185\u5b58\u4e0d\u8db3\u65f6\u8981\u56de\u6536\u90e8\u5206\u7f13\u5b58\u9875\u9762\u800c\u4e8b\u5148\u8fdb\u884c\u810f\u9875\u9762\u56de\u5199\uff0c\u8bbe\u8ba1\u4e00\u4e2a\u7edf\u4e00\u7684\u6846\u67b6\u6765\u7ba1\u7406\u8fd9\u4e9b\u56de\u5199\u4efb\u52a1\u975e\u5e38\u6709\u5fc5\u8981\u3002<\/li>\n<\/ol>\n<\/li>\n<\/ol>\n<p>Write Through \u4e0e Write back \u5728\u6301\u4e45\u5316\u7684\u53ef\u9760\u6027\u4e0a\u6709\u6240\u4e0d\u540c\uff1a<\/p>\n<ul>\n<li>Write Through \u4ee5\u727a\u7272\u7cfb\u7edf I\/O \u541e\u5410\u91cf\u4f5c\u4e3a\u4ee3\u4ef7\uff0c\u5411\u4e0a\u5c42\u5e94\u7528\u786e\u4fdd\u4e00\u65e6\u5199\u5165\uff0c\u6570\u636e\u5c31\u5df2\u7ecf\u843d\u76d8\uff0c\u4e0d\u4f1a\u4e22\u5931\uff1b<\/li>\n<li>Write back \u5728\u7cfb\u7edf\u53d1\u751f\u5b95\u673a\u7684\u60c5\u51b5\u4e0b\u65e0\u6cd5\u786e\u4fdd\u6570\u636e\u5df2\u7ecf\u843d\u76d8\uff0c\u56e0\u6b64\u5b58\u5728\u6570\u636e\u4e22\u5931\u7684\u95ee\u9898\u3002\u4e0d\u8fc7\uff0c\u5728\u7a0b\u5e8f\u6302\u4e86\uff0c\u4f8b\u5982\u88ab kill -9\uff0cPage Cache \u4e2d\u7684\u6570\u636e\u64cd\u4f5c\u7cfb\u7edf\u8fd8\u662f\u4f1a\u786e\u4fdd\u843d\u76d8\uff1b<\/li>\n<\/ul>\n<h2>3. Page Cache \u7684\u4f18\u52a3\u52bf<\/h2>\n<h3>3.1 Page Cache \u7684\u4f18\u52bf<\/h3>\n<p><strong>1.\u52a0\u5feb\u6570\u636e\u8bbf\u95ee<\/strong><\/p>\n<p>\u5982\u679c\u6570\u636e\u80fd\u591f\u5728\u5185\u5b58\u4e2d\u8fdb\u884c\u7f13\u5b58\uff0c\u90a3\u4e48\u4e0b\u4e00\u6b21\u8bbf\u95ee\u5c31\u4e0d\u9700\u8981\u901a\u8fc7\u78c1\u76d8 I\/O \u4e86\uff0c\u76f4\u63a5\u547d\u4e2d\u5185\u5b58\u7f13\u5b58\u5373\u53ef\u3002<\/p>\n<p>\u7531\u4e8e\u5185\u5b58\u8bbf\u95ee\u6bd4\u78c1\u76d8\u8bbf\u95ee\u5feb\u5f88\u591a\uff0c\u56e0\u6b64\u52a0\u5feb\u6570\u636e\u8bbf\u95ee\u662f Page Cache \u7684\u4e00\u5927\u4f18\u52bf\u3002<\/p>\n<p><strong>2.\u51cf\u5c11 I\/O \u6b21\u6570\uff0c\u63d0\u9ad8\u7cfb\u7edf\u78c1\u76d8 I\/O \u541e\u5410\u91cf<\/strong><\/p>\n<p>\u5f97\u76ca\u4e8e Page Cache \u7684\u7f13\u5b58\u4ee5\u53ca\u9884\u8bfb\u80fd\u529b\uff0c\u800c\u7a0b\u5e8f\u53c8\u5f80\u5f80\u7b26\u5408\u5c40\u90e8\u6027\u539f\u7406\uff0c\u56e0\u6b64\u901a\u8fc7\u4e00\u6b21 I\/O \u5c06\u591a\u4e2a page \u88c5\u5165 Page Cache \u80fd\u591f\u51cf\u5c11\u78c1\u76d8 I\/O \u6b21\u6570\uff0c \u8fdb\u800c\u63d0\u9ad8\u7cfb\u7edf\u78c1\u76d8 I\/O \u541e\u5410\u91cf\u3002<\/p>\n<h3>3.2 Page Cache \u7684\u52a3\u52bf<\/h3>\n<p>page cache \u4e5f\u6709\u5176\u52a3\u52bf\uff0c\u6700\u76f4\u63a5\u7684\u7f3a\u70b9\u662f\u9700\u8981\u5360\u7528\u989d\u5916\u7269\u7406\u5185\u5b58\u7a7a\u95f4\uff0c\u7269\u7406\u5185\u5b58\u5728\u6bd4\u8f83\u7d27\u4fcf\u7684\u65f6\u5019\u53ef\u80fd\u4f1a\u5bfc\u81f4\u9891\u7e41\u7684 swap \u64cd\u4f5c\uff0c\u6700\u7ec8\u5bfc\u81f4\u7cfb\u7edf\u7684\u78c1\u76d8 I\/O \u8d1f\u8f7d\u7684\u4e0a\u5347\u3002<\/p>\n<p>Page Cache \u7684\u53e6\u4e00\u4e2a\u7f3a\u9677\u662f\u5bf9\u5e94\u7528\u5c42\u5e76\u6ca1\u6709\u63d0\u4f9b\u5f88\u597d\u7684\u7ba1\u7406 API\uff0c\u51e0\u4e4e\u662f\u900f\u660e\u7ba1\u7406\u3002\u5e94\u7528\u5c42\u5373\u4f7f\u60f3\u4f18\u5316 Page Cache \u7684\u4f7f\u7528\u7b56\u7565\u4e5f\u5f88\u96be\u8fdb\u884c\u3002\u56e0\u6b64\u4e00\u4e9b\u5e94\u7528\u9009\u62e9\u5728\u7528\u6237\u7a7a\u95f4\u5b9e\u73b0\u81ea\u5df1\u7684 page \u7ba1\u7406\uff0c\u800c\u4e0d\u4f7f\u7528 page cache\uff0c\u4f8b\u5982 MySQL InnoDB \u5b58\u50a8\u5f15\u64ce\u4ee5 16KB \u7684\u9875\u8fdb\u884c\u7ba1\u7406\u3002<\/p>\n<p>Page Cache \u6700\u540e\u4e00\u4e2a\u7f3a\u9677\u662f\u5728\u67d0\u4e9b\u5e94\u7528\u573a\u666f\u4e0b\u6bd4 Direct I\/O \u591a\u4e00\u6b21\u78c1\u76d8\u8bfb I\/O \u4ee5\u53ca\u78c1\u76d8\u5199 I\/O\u3002\u8fd9\u4e00\u70b9\u53ef\u4ee5\u53c2\u8003[4]\u3002<\/p>\n<p>\u6765\u6e90\uff1a<a href=\"https:\/\/link.segmentfault.com\/?enc=D3E%2ByX7U8Os0bwaaJ9IOEw%3D%3D.rFJ6x1%2FLXKFTMb9plq1z635lePLADQkm2hPHYkHlgMJ1%2F21dJ2uIZiVzRBWCh1q9CK9qoYBCX3AMJPMsYjW3HqgfP4%2FRVEvqcrza6c5EQEg%3D\" rel=\"nofollow\">https:\/\/spongecaptain.cool\/Si&#8230;<\/a><\/p>\n<p><strong>\u8fd1\u671f\u70ed\u6587\u63a8\u8350\uff1a<\/strong><\/p>\n<p>1.<a href=\"https:\/\/link.segmentfault.com\/?enc=GR1i3hU3rFkIPs3RINou8A%3D%3D.0TFGXYqEDpEdsuMQQp1Ar3XxxYpt2vRkWcpMrGHHZ6c%3D\" rel=\"nofollow\">1,000+ \u9053 Java\u9762\u8bd5\u9898\u53ca\u7b54\u6848\u6574\u7406(2022\u6700\u65b0\u7248)<\/a><\/p>\n<p>2.<a href=\"https:\/\/link.segmentfault.com\/?enc=mrV3gasb3u%2BLH%2F5l%2BCcHFQ%3D%3D.SfbdkAM8GSCzReppzVMjsNlFSAWYptARbnuT7FCrSehWtJmUidOUrDv68Tf%2Bebj%2BooPuX4WSXb%2BbthRmHQCi%2Bw%3D%3D\" rel=\"nofollow\">\u52b2\u7206\uff01Java \u534f\u7a0b\u8981\u6765\u4e86\u3002\u3002\u3002<\/a><\/p>\n<p>3.<a href=\"https:\/\/link.segmentfault.com\/?enc=NlnEKAbmCQxH2zE6DtXnnQ%3D%3D.LG%2BNsdGkhUvyKyGK2bClTgH%2F9w9dbezMh0gGovC8Cc39OzW9IPkLQ2e2ZBLrvKSl\" rel=\"nofollow\">Spring Boot 2.x \u6559\u7a0b\uff0c\u592a\u5168\u4e86\uff01<\/a><\/p>\n<p>4.<a href=\"https:\/\/link.segmentfault.com\/?enc=N2MDPC1kil0q576RpIMTAg%3D%3D.8uKMkR0ksjg8zREgk5R4xu1BNfRvZ3K7lh1AbiHKfF0jV3gndASMYwyaz9sXXoRoqpPdzCfdeTWi01dzkedJyQ%3D%3D\" rel=\"nofollow\">\u522b\u518d\u5199\u6ee1\u5c4f\u7684\u7206\u7206\u7206\u70b8\u7c7b\u4e86\uff0c\u8bd5\u8bd5\u88c5\u9970\u5668\u6a21\u5f0f\uff0c\u8fd9\u624d\u662f\u4f18\u96c5\u7684\u65b9\u5f0f\uff01\uff01<\/a><\/p>\n<p>5.<a href=\"https:\/\/link.segmentfault.com\/?enc=k4peNC%2BnNdDNFgOp3FJbBw%3D%3D.zokZuvOYGoQb36Q04CYqsfnjRwMPMVxQY%2BRjLbnRCFdhmBeoTywHF5JPwEkQQpALUGpz9oJV%2FriEcH0tCT2PW7mjXdnLKzyBtSCsoLKXUmc%3D\" rel=\"nofollow\">\u300aJava\u5f00\u53d1\u624b\u518c\uff08\u5d69\u5c71\u7248\uff09\u300b\u6700\u65b0\u53d1\u5e03\uff0c\u901f\u901f\u4e0b\u8f7d\uff01<\/a><\/p>\n<p>\u89c9\u5f97\u4e0d\u9519\uff0c\u522b\u5fd8\u4e86\u968f\u624b\u70b9\u8d5e+\u8f6c\u53d1\u54e6\uff01<\/p>\n<p><a href=\"https:\/\/segmentfault.com\/a\/1190000042339554\">https:\/\/segmentfault.com\/a\/1190000042339554<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>1. Page Cache 1.1 Page Cache \u662f\u4ec0\u4e48\uff1f \u4e3a\u4e86\u7406\u89e3 Page Cache\uff0c\u6211\u4eec\u4e0d\u59a8\u5148 [&hellip;]<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[],"tags":[],"class_list":["post-10006250","post","type-post","status-publish","format-standard","hentry"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10006250","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=10006250"}],"version-history":[{"count":0,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10006250\/revisions"}],"wp:attachment":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10006250"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10006250"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10006250"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}