{"id":3663,"date":"2019-07-18T17:49:36","date_gmt":"2019-07-18T09:49:36","guid":{"rendered":"https:\/\/damogame.cn\/wordpress\/?p=3663"},"modified":"2019-07-18T17:49:36","modified_gmt":"2019-07-18T09:49:36","slug":"tcmalloc%e8%a7%a3%e5%af%86","status":"publish","type":"post","link":"https:\/\/i007.cc\/wordpress\/archives\/3663","title":{"rendered":"TCMalloc\u89e3\u5bc6"},"content":{"rendered":"<div class=\"show-content\" data-note-content=\"\">\n<p><a href=\"https:\/\/www.jianshu.com\/p\/11082b443ddf\">\u539f\u6587\u5730\u5740<\/a><\/p>\n<div class=\"show-content-free\">\n<h1>\u5199\u5728\u524d\u9762<\/h1>\n<p>\u672c\u6587\u9996\u5148\u7b80\u5355\u4ecb\u7ecdTCMalloc\u53ca\u5176\u4f7f\u7528\u65b9\u6cd5\uff0c\u7136\u540e\u89e3\u91caTCMalloc\u66ff\u4ee3\u7cfb\u7edf\u7684\u5185\u5b58\u5206\u914d\u51fd\u6570\u7684\u539f\u7406\uff0c\u7136\u540e\u4ece\u5b8f\u89c2\u4e0a\u8ba8\u8bba\u5176\u5185\u5b58\u5206\u914d\u7684\u7b56\u7565\uff0c\u5728\u6b64\u4e4b\u540e\u518d\u6df1\u5165\u8ba8\u8bba\u5b9e\u73b0\u7ec6\u8282\u3002<\/p>\n<p>\u6709\u51e0\u70b9\u9700\u8981\u8bf4\u660e\uff1a<\/p>\n<ul>\n<li>\u672c\u6587\u53ea\u8ba8\u8bbagperftools\u4e2dTCMalloc\u90e8\u5206\u7684\u4ee3\u7801\uff0c\u5bf9\u5e94\u7248\u672c<a href=\"https:\/\/github.com\/gperftools\/gperftools\/releases\/tag\/gperftools-2.7\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">gperftools-2.7<\/a>\u3002<\/li>\n<li>\u672c\u6587\u662f\u6839\u636eTCMalloc\u6e90\u7801\u4ee5\u53ca\u7b80\u77ed\u7684<a href=\"https:\/\/gperftools.github.io\/gperftools\/TCMalloc.html\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">\u5b98\u65b9\u4ecb\u7ecd<\/a>\u4f5c\u51fa\u7684\u4e2a\u4eba\u7406\u89e3\uff0c\u96be\u514d\u6709\u7eb0\u6f0f\u4e4b\u5904\uff0c\u4e14\u96be\u4ee5\u8986\u76d6TCMalloc\u7684\u65b9\u65b9\u9762\u9762\uff0c\u4e0d\u8db3\u4e4b\u5904\u8fd8\u8bf7\u5404\u4f4d\u770b\u5b98\u7559\u8a00\u6307\u6b63\u3002<\/li>\n<li>\u9664\u975e\u7279\u522b\u8bf4\u660e\uff0c\u4ee5\u4e0b\u8ba8\u8bba\u5747\u4ee532\u4f4d\u7cfb\u7edf\u3001TCMalloc\u9ed8\u8ba4page\u5927\u5c0f\uff088KB\uff09\u4e3a\u57fa\u7840\uff0c\u4e0d\u540c\u67b6\u6784\u6216\u4e0d\u540cpage\u5927\u5c0f\uff0c\u6709\u4e9b\u76f8\u5173\u6570\u503c\u53ef\u80fd\u4e0d\u4e00\u6837\uff0c\u4f46\u57fa\u672c\u539f\u7406\u662f\u76f8\u4f3c\u7684\u3002<\/li>\n<li>\u4e3a\u4e86\u63a7\u5236\u7bc7\u5e45\uff0c\u6211\u4f1a\u5c3d\u91cf\u5c11\u8d34\u5927\u6bb5\u4ee3\u7801\uff0c\u53ea\u7ed9\u51fa\u5173\u952e\u4ee3\u7801\u7684\u4f4d\u7f6e\u6216\u51fd\u6570\u540d\uff0c\u5404\u4f4d\u770b\u5b98\u53ef\u81ea\u884c\u53c2\u9605TCMalloc\u76f8\u5173\u4ee3\u7801\u3002<\/li>\n<\/ul>\n<h1>TCMalloc\u662f\u4ec0\u4e48<\/h1>\n<p>TCMalloc\u5168\u79f0Thread-Caching Malloc\uff0c\u5373\u7ebf\u7a0b\u7f13\u5b58\u7684malloc\uff0c\u5b9e\u73b0\u4e86\u9ad8\u6548\u7684\u591a\u7ebf\u7a0b\u5185\u5b58\u7ba1\u7406\uff0c\u7528\u4e8e\u66ff\u4ee3\u7cfb\u7edf\u7684\u5185\u5b58\u5206\u914d\u76f8\u5173\u7684\u51fd\u6570\uff08malloc\u3001free\uff0cnew\uff0cnew[]\u7b49\uff09\u3002<\/p>\n<p>TCMalloc\u662fgperftools\u7684\u4e00\u90e8\u5206\uff0c\u9664TCMalloc\u5916\uff0cgperftools\u8fd8\u5305\u62echeap-checker\u3001heap-profiler\u548ccpu-profiler\u3002\u672c\u6587\u53ea\u8ba8\u8bbagperftools\u7684TCMalloc\u90e8\u5206\u3002<\/p>\n<p>git\u4ed3\u5e93\uff1a<a href=\"https:\/\/github.com\/gperftools\/gperftools.git\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">https:\/\/github.com\/gperftools\/gperftools.git<\/a><\/p>\n<p>\u5b98\u65b9\u4ecb\u7ecd\uff1a<a href=\"https:\/\/gperftools.github.io\/gperftools\/TCMalloc.html\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">https:\/\/gperftools.github.io\/gperftools\/TCMalloc.html<\/a>\uff08\u91cc\u9762\u6709\u4e9b\u5185\u5bb9\u5df2\u7ecf\u8fc7\u65f6\u4e86\uff09<\/p>\n<h1>\u5982\u4f55\u4f7f\u7528TCMalloc<\/h1>\n<h2>\u5b89\u88c5<\/h2>\n<p>\u4ee5\u4e0b\u662f\u6bd4\u8f83\u5e38\u89c4\u7684\u5b89\u88c5\u6b65\u9aa4\uff0c\u8be6\u7ec6\u53ef\u53c2\u8003gperftools\u4e2d\u7684<a href=\"https:\/\/github.com\/gperftools\/gperftools\/blob\/master\/INSTALL\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">INSTALL<\/a>\u3002<\/p>\n<ol>\n<li>\u4ecegit\u4ed3\u5e93clone\u7248\u672c\u7684gperftools\u7684\u5b89\u88c5\u4f9d\u8d56autoconf\u3001automake\u3001libtool\uff0c\u4ee5Debian\u4e3a\u4f8b\uff1a\n<pre class=\"hljs bash\"><code class=\"bash\"><span class=\"hljs-comment\"># apt install autoconf automake libtool<\/span><\/code><\/pre>\n<\/li>\n<li>\u751f\u6210configure\u7b49\u4e00\u7cfb\u5217\u6587\u4ef6\n<pre class=\"hljs bash\"><code class=\"bash\">$ .\/autogen.sh\r\n<\/code><\/pre>\n<\/li>\n<li>\u751f\u6210Makefile\n<pre class=\"hljs bash\"><code class=\"bash\">$ .\/configure\r\n<\/code><\/pre>\n<\/li>\n<li>\u7f16\u8bd1\n<pre class=\"hljs bash\"><code class=\"bash\">$ make\r\n<\/code><\/pre>\n<\/li>\n<li>\u5b89\u88c5\n<pre class=\"hljs bash\"><code class=\"bash\"><span class=\"hljs-comment\"># make install<\/span><\/code><\/pre>\n<p>\u9ed8\u8ba4\u5b89\u88c5\u5728<code>\/usr\/local\/<\/code>\u4e0b\u7684\u76f8\u5173\u8def\u5f84\uff08bin\u3001lib\u3001share\uff09\uff0c\u53ef\u5728configure\u65f6\u4ee5<code>--prefix=PATH<\/code>\u6307\u5b9a\u5176\u4ed6\u8def\u5f84\u3002<\/li>\n<\/ol>\n<h3>64\u4f4dLinux\u7cfb\u7edf\u9700\u8981\u6ce8\u610f<\/h3>\n<p>\u572864\u4f4dLinux\u73af\u5883\u4e0b\uff0cgperftools\u4f7f\u7528glibc\u5185\u7f6e\u7684stack-unwinder\u53ef\u80fd\u4f1a\u5f15\u53d1\u6b7b\u9501\uff0c\u56e0\u6b64\u5b98\u65b9\u63a8\u8350\u5728\u914d\u7f6e\u548c\u5b89\u88c5gperftools\u4e4b\u524d\uff0c\u5148\u5b89\u88c5<a href=\"http:\/\/download.savannah.gnu.org\/releases\/libunwind\/libunwind-0.99-beta.tar.gz\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">libunwind-0.99-beta<\/a>\uff0c\u6700\u597d\u5c31\u7528\u8fd9\u4e2a\u7248\u672c\uff0c\u7248\u672c\u592a\u65b0\u6216\u592a\u65e7\u90fd\u53ef\u80fd\u4f1a\u6709\u95ee\u9898\u3002<\/p>\n<p>\u5373\u4fbf\u4f7f\u7528libunwind\uff0c\u572864\u4f4d\u7cfb\u7edf\u4e0a\u8fd8\u662f\u4f1a\u6709\u95ee\u9898\uff0c\u4f46\u53ea\u5f71\u54cdheap-checker\u3001heap-profiler\u548ccpu-profiler\uff0cTCMalloc\u4e0d\u53d7\u5f71\u54cd\uff0c\u56e0\u6b64\u4e0d\u518d\u8d58\u8ff0\uff0c\u611f\u5174\u8da3\u7684\u8bfb\u8005\u53ef\u53c2\u9605gperftools\u7684<a href=\"https:\/\/github.com\/gperftools\/gperftools\/blob\/master\/INSTALL\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">INSTALL<\/a>\u3002<\/p>\n<p>\u5982\u679c\u4e0d\u5e0c\u671b\u5b89\u88c5libunwind\uff0c\u4e5f\u53ef\u4ee5\u7528gperftools\u5185\u7f6e\u7684stack unwinder\uff0c\u4f46\u9700\u8981\u5e94\u7528\u7a0b\u5e8f\u3001TCMalloc\u5e93\u3001\u7cfb\u7edf\u5e93\uff08\u6bd4\u5982libc\uff09\u5728\u7f16\u8bd1\u65f6\u5f00\u542f\u5e27\u6307\u9488\uff08frame pointer\uff09\u9009\u9879\u3002<\/p>\n<p>\u5728x86-64\u4e0b\uff0c\u7f16\u8bd1\u65f6\u5f00\u542f\u5e27\u6307\u9488\u9009\u9879\u5e76\u4e0d\u662f\u9ed8\u8ba4\u884c\u4e3a\u3002\u56e0\u6b64\u9700\u8981\u6307\u5b9a<code>-fno-omit-frame-pointer<\/code>\u7f16\u8bd1\u6240\u6709\u5e94\u7528\u7a0b\u5e8f\uff0c\u7136\u540e\u5728configure\u65f6\u901a\u8fc7<code>--enable-frame-pointers<\/code>\u9009\u9879\u4f7f\u7528\u5185\u7f6e\u7684gperftools stack unwinder\u3002<\/p>\n<h2>\u4f7f\u7528<\/h2>\n<h3>\u4ee5\u52a8\u6001\u5e93\u7684\u65b9\u5f0f<\/h3>\n<p>\u5b89\u88c5\u4e4b\u540e\uff0c\u901a\u8fc7<code>-ltcmalloc<\/code>\u6216<code>-ltcmalloc_minimal<\/code>\u5c06TCMalloc\u94fe\u63a5\u5230\u5e94\u7528\u7a0b\u5e8f\u5373\u53ef\u3002<\/p>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-meta\">#<span class=\"hljs-meta-keyword\">include<\/span> <span class=\"hljs-meta-string\">&lt;stdlib.h&gt;<\/span><\/span>\r\n\r\n<span class=\"hljs-function\"><span class=\"hljs-keyword\">int<\/span> <span class=\"hljs-title\">main<\/span><span class=\"hljs-params\">( <span class=\"hljs-keyword\">int<\/span> argc, <span class=\"hljs-keyword\">char<\/span> *argv[] )<\/span><\/span>{   \r\n    <span class=\"hljs-built_in\">malloc<\/span>(<span class=\"hljs-number\">1<\/span>);\r\n}\r\n<\/code><\/pre>\n<pre class=\"hljs shell\"><code class=\"shell\"><span class=\"hljs-meta\">$<\/span><span class=\"bash\"> g++ -O0 -g -ltcmalloc test.cc &amp;&amp; gdb a.out<\/span><\/code><\/pre>\n<pre class=\"hljs javascript\"><code class=\"javascript\">(gdb) b test.cc:<span class=\"hljs-number\">5<\/span>\r\nBreakpoint <span class=\"hljs-number\">1<\/span> at <span class=\"hljs-number\">0x7af<\/span>: file test.cc, line <span class=\"hljs-number\">5.<\/span>\r\n(gdb) r\r\nStarting program: <span class=\"hljs-regexp\">\/home\/<\/span>wanglong\/test\/https:<span class=\"hljs-comment\">\/\/wallenwang.com\/tcmalloc\/a.out <\/span>\r\n[Thread debugging using libthread_db enabled]\r\nUsing host libthread_db library <span class=\"hljs-string\">\"\/lib\/x86_64-linux-gnu\/libthread_db.so.1\"<\/span>.\r\n\r\nBreakpoint <span class=\"hljs-number\">1<\/span>, main (argc=<span class=\"hljs-number\">1<\/span>, argv=<span class=\"hljs-number\">0x7fffffffddd8<\/span>) at test.cc:<span class=\"hljs-number\">5<\/span>\r\n<span class=\"hljs-number\">5<\/span>           malloc(<span class=\"hljs-number\">1<\/span>);\r\n(gdb) s\r\ntc_malloc (size=<span class=\"hljs-number\">1<\/span>) at src\/tcmalloc.cc:<span class=\"hljs-number\">1892<\/span>\r\n<span class=\"hljs-number\">1892<\/span>      <span class=\"hljs-keyword\">return<\/span> malloc_fast_path&lt;tcmalloc::malloc_oom&gt;(size);\r\n(gdb) \r\n<\/code><\/pre>\n<p>\u901a\u8fc7gdb\u65ad\u70b9\u53ef\u4ee5\u770b\u5230\u5bf9<code>malloc()<\/code>\u7684\u8c03\u7528\u5df2\u7ecf\u66ff\u6362\u4e3aTCMalloc\u7684\u5b9e\u73b0\u3002<\/p>\n<h3>\u4ee5\u9759\u6001\u5e93\u7684\u65b9\u5f0f<\/h3>\n<p>gperftools\u7684<a href=\"https:\/\/github.com\/gperftools\/gperftools\/blob\/master\/README\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">README<\/a>\u4e2d\u8bf4\u9759\u6001\u5e93\u5e94\u8be5\u4f7f\u7528<code>libtcmalloc_and_profiler.a<\/code>\u5e93\u800c\u4e0d\u662f<code>libprofiler.a<\/code>\u548clibtcmalloc.a\uff0c\u4f46\u7b80\u5355\u6d4b\u8bd5\u540e\u8005\u4e5f\u662fOK\u7684\uff0c\u800c\u4e14\u5728\u5b9e\u9645\u9879\u76ee\u4e2d\u4e5f\u662f\u7528\u7684\u540e\u8005\uff0c\u4e0d\u77e5\u9053\u662f\u4e0d\u662f\u6587\u6863\u592a\u8fc7\u8001\u65e7\u4e86\u3002<\/p>\n<pre class=\"hljs shell\"><code class=\"shell\"><span class=\"hljs-meta\">$<\/span><span class=\"bash\"> g++ -O0 -g -pthread test.cc \/usr\/<span class=\"hljs-built_in\">local<\/span>\/lib\/libtcmalloc_and_profiler.a<\/span><\/code><\/pre>\n<p>\u5982\u679c\u4f7f\u7528\u4e86libunwind\uff0c\u9700\u8981\u6307\u5b9a<code>-Wl,--eh-frame-hdr<\/code>\u9009\u9879\uff0c\u4ee5\u786e\u4fddlibunwind\u53ef\u4ee5\u627e\u5230\u7f16\u8bd1\u5668\u751f\u6210\u7684\u4fe1\u606f\u6765\u8fdb\u884c\u6808\u56de\u6eaf\u3002<\/p>\n<p>eh-frame\uff08exception handling frame\uff09\u53c2\u8003\u8d44\u6599\uff1a<\/p>\n<ul>\n<li><a href=\"http:\/\/infocenter.arm.com\/help\/index.jsp?topic=\/com.arm.doc.dui0803d\/pge1446568291678.html\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">http:\/\/infocenter.arm.com\/help\/index.jsp?topic=\/com.arm.doc.dui0803d\/pge1446568291678.html<\/a><\/li>\n<li><a href=\"http:\/\/zhaohongjian000.is-programmer.com\/posts\/29660.html\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">http:\/\/zhaohongjian000.is-programmer.com\/posts\/29660.html<\/a><\/li>\n<li><a href=\"https:\/\/www.cnblogs.com\/catch\/p\/3619379.html\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">https:\/\/www.cnblogs.com\/catch\/p\/3619379.html<\/a><\/li>\n<\/ul>\n<h1>TCMalloc\u662f\u5982\u4f55\u751f\u6548\u7684<\/h1>\n<p>\u4e3a\u4ec0\u4e48\u6307\u5b9a<code>-ltcmalloc<\/code>\u6216\u8005\u4e0e<code>libtcmalloc_and_profiler.a<\/code>\u8fde\u63a5\u4e4b\u540e\uff0c\u5bf9malloc\u3001free\u3001new\u3001delete\u7b49\u7684\u8c03\u7528\u5c31\u7531\u9ed8\u8ba4\u7684libc\u4e2d\u7684\u51fd\u6570\u8c03\u7528\u53d8\u4e3aTCMalloc\u4e2d\u76f8\u5e94\u7684\u51fd\u6570\u8c03\u7528\u4e86\u5462\uff1f\u7b54\u6848\u5728<code>libc_override.h<\/code>\u4e2d\uff0c\u4e0b\u9762\u53ea\u8ba8\u8bba\u5e38\u89c1\u7684\u4e24\u79cd\u60c5\u51b5\uff1a\u4f7f\u7528\u4e86glibc\uff0c\u6216\u8005\u4f7f\u7528\u4e86GCC\u7f16\u8bd1\u5668\u3002\u5176\u4f59\u60c5\u51b5\u53ef\u81ea\u884c\u67e5\u770b\u76f8\u5e94\u7684libc_override\u5934\u6587\u4ef6\u3002<\/p>\n<h2>\u4f7f\u7528glibc\uff08\u4f46\u6ca1\u6709\u4f7f\u7528GCC\u7f16\u8bd1\u5668\uff09<\/h2>\n<p>\u5728glibc\u4e2d\uff0c\u5185\u5b58\u5206\u914d\u76f8\u5173\u7684\u51fd\u6570\u90fd\u662f<a href=\"https:\/\/en.wikipedia.org\/wiki\/Weak_symbol\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">\u5f31\u7b26\u53f7\uff08weak symbol\uff09<\/a>\uff0c\u56e0\u6b64TCMalloc\u53ea\u9700\u8981\u5b9a\u4e49\u81ea\u5df1\u7684\u51fd\u6570\u5c06\u5176\u8986\u76d6\u5373\u53ef\uff0c\u4ee5malloc\u548cfree\u4e3a\u4f8b\uff1a<\/p>\n<p>libc_override_redefine.h<\/p>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-keyword\">extern<\/span> <span class=\"hljs-string\">\"C\"<\/span> { \r\n  <span class=\"hljs-function\"><span class=\"hljs-keyword\">void<\/span>* <span class=\"hljs-title\">malloc<\/span><span class=\"hljs-params\">(<span class=\"hljs-keyword\">size_t<\/span> s)<\/span><\/span>{ <span class=\"hljs-keyword\">return<\/span> tc_malloc(s);       }\r\n  <span class=\"hljs-function\"><span class=\"hljs-keyword\">void<\/span>  <span class=\"hljs-title\">free<\/span><span class=\"hljs-params\">(<span class=\"hljs-keyword\">void<\/span>* p)<\/span><\/span>{ tc_free(p);                }\r\n}  <span class=\"hljs-comment\">\/\/ extern \"C\"<\/span><\/code><\/pre>\n<p>\u53ef\u4ee5\u770b\u5230\uff0cTCMalloc\u5c06<code>malloc()<\/code>\u548c<code>free()<\/code>\u5206\u522b\u5b9a\u4e49\u4e3a\u5bf9<code>tc_malloc()<\/code>\u548c<code>tc_free()<\/code>\u7684\u8c03\u7528\uff0c\u5e76\u5728<code>tc_malloc()<\/code>\u548c<code>tc_free()<\/code>\u4e2d\u5b9e\u73b0\u5177\u4f53\u7684\u5185\u5b58\u5206\u914d\u548c\u56de\u6536\u903b\u8f91\u3002<\/p>\n<p>new\u548cdelete\u4e5f\u7c7b\u4f3c\uff1a<\/p>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-function\"><span class=\"hljs-keyword\">void<\/span>* <span class=\"hljs-keyword\">operator<\/span> <span class=\"hljs-title\">new<\/span><span class=\"hljs-params\">(<span class=\"hljs-keyword\">size_t<\/span> size)<\/span><\/span>{ <span class=\"hljs-keyword\">return<\/span> tc_new(size);       }\r\n<span class=\"hljs-function\"><span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-keyword\">operator<\/span> <span class=\"hljs-title\">delete<\/span><span class=\"hljs-params\">(<span class=\"hljs-keyword\">void<\/span>* p)<\/span> CPP_NOTHROW        <\/span>{ tc_delete(p);              }\r\n<\/code><\/pre>\n<h2>\u4f7f\u7528GCC\u7f16\u8bd1\u5668<\/h2>\n<p>\u5982\u679c\u4f7f\u7528\u4e86GCC\u7f16\u8bd1\u5668\uff0c\u5219\u4f7f\u7528\u5176\u652f\u6301\u7684<a href=\"https:\/\/gcc.gnu.org\/onlinedocs\/gcc-4.7.0\/gcc\/Function-Attributes.html\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">\u51fd\u6570\u5c5e\u6027\uff1aalias<\/a>\u3002<\/p>\n<p>libc_override_gcc_and_weak.h\uff1a<\/p>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-meta\">#<span class=\"hljs-meta-keyword\">define<\/span> ALIAS(tc_fn)   __attribute__ ((alias (#tc_fn), used))<\/span>\r\n\r\n<span class=\"hljs-keyword\">extern<\/span> <span class=\"hljs-string\">\"C\"<\/span> { \r\n  <span class=\"hljs-function\"><span class=\"hljs-keyword\">void<\/span>* <span class=\"hljs-title\">malloc<\/span><span class=\"hljs-params\">(<span class=\"hljs-keyword\">size_t<\/span> size)<\/span> __THROW               <span class=\"hljs-title\">ALIAS<\/span><span class=\"hljs-params\">(tc_malloc)<\/span><\/span>;\r\n  <span class=\"hljs-function\"><span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-title\">free<\/span><span class=\"hljs-params\">(<span class=\"hljs-keyword\">void<\/span>* ptr)<\/span> __THROW                    <span class=\"hljs-title\">ALIAS<\/span><span class=\"hljs-params\">(tc_free)<\/span><\/span>;\r\n}   <span class=\"hljs-comment\">\/\/ extern \"C\"<\/span><\/code><\/pre>\n<p>\u5c06\u5b8f\u5c55\u5f00\uff0c<code>__attribute__ ((alias (\"tc_malloc\"), used))<\/code>\u8868\u660etc_malloc\u662fmalloc\u7684\u522b\u540d\u3002<\/p>\n<p>\u5177\u4f53\u53ef\u53c2\u9605GCC\u76f8\u5173\u6587\u6863\uff1a<\/p>\n<p><strong>alias (&#8220;target&#8221;)<\/strong><br \/>\n\u200b The alias attribute causes the declaration to be emitted as an alias for another symbol, which must be specified. For instance,<br \/>\n\u200b\u00a0<code>void __f () { \/* Do something. *\/; }<\/code><br \/>\n\u200b\u00a0<code>void f () __attribute__ ((weak, alias (\"__f\")));<\/code><br \/>\n\u200b defines\u00a0<code>f<\/code>\u00a0to be a weak alias for\u00a0<code>__f<\/code>. In C++, the mangled name for the target must be used. It is an error if\u00a0<code>__f<\/code>\u00a0is not defined in the same translation unit.<br \/>\n\u200b Not all target machines support this attribute.<\/p>\n<p><strong>used<\/strong><br \/>\n\u200b This attribute, attached to a function, means that code must be emitted for the function even if it appears that the function is not referenced. This is useful, for example, when the function is referenced only in inline assembly.<br \/>\n\u200b When applied to a member function of a C++ class template, the attribute also means that the function will be instantiated if the class itself is instantiated.<\/p>\n<h1>TCMalloc\u7684\u521d\u59cb\u5316<\/h1>\n<h2>\u4f55\u65f6\u521d\u59cb\u5316<\/h2>\n<p>TCMalloc\u5b9a\u4e49\u4e86\u4e00\u4e2a\u7c7b<code>TCMallocGuard<\/code>\uff0c\u5e76\u5728\u6587\u4ef6tcmalloc.cc\u4e2d\u5b9a\u4e49\u4e86\u8be5\u7c7b\u578b\u7684\u9759\u6001\u53d8\u91cf<code>module_enter_exit_hook<\/code>\uff0c\u5728\u5176\u6784\u9020\u51fd\u6570\u4e2d\u6267\u884cTCMalloc\u7684\u521d\u59cb\u5316\u903b\u8f91\uff0c\u4ee5\u786e\u4fddTCMalloc\u5728<code>main()<\/code>\u51fd\u6570\u4e4b\u524d\u5b8c\u6210\u521d\u59cb\u5316\uff0c\u9632\u6b62\u5728\u521d\u59cb\u5316\u4e4b\u524d\u5c31\u6709\u591a\u4e2a\u7ebf\u7a0b\u3002<\/p>\n<p>tcmalloc.cc\uff1a<\/p>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-keyword\">static<\/span> TCMallocGuard module_enter_exit_hook;\r\n<\/code><\/pre>\n<p>\u5982\u679c\u9700\u8981\u786e\u4fddTCMalloc\u5728\u67d0\u4e9b\u5168\u5c40\u6784\u9020\u51fd\u6570\u8fd0\u884c\u4e4b\u524d\u5c31\u521d\u59cb\u5316\u5b8c\u6210\uff0c\u5219\u9700\u8981\u5728\u6587\u4ef6\u9876\u90e8\u521b\u5efa\u4e00\u4e2a\u9759\u6001TCMallocGuard\u5b9e\u4f8b\u3002<\/p>\n<h2>\u5982\u4f55\u521d\u59cb\u5316<\/h2>\n<p>TCMallocGuard\u7684\u6784\u9020\u51fd\u6570\u5b9e\u73b0\uff1a<\/p>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-keyword\">static<\/span> <span class=\"hljs-keyword\">int<\/span> tcmallocguard_refcount = <span class=\"hljs-number\">0<\/span>;  <span class=\"hljs-comment\">\/\/ no lock needed: runs before main()<\/span>\r\nTCMallocGuard::TCMallocGuard() {\r\n  <span class=\"hljs-keyword\">if<\/span> (tcmallocguard_refcount++ == <span class=\"hljs-number\">0<\/span>) {\r\n    ReplaceSystemAlloc();    <span class=\"hljs-comment\">\/\/ defined in libc_override_*.h<\/span>\r\n    tc_free(tc_malloc(<span class=\"hljs-number\">1<\/span>));\r\n    ThreadCache::InitTSD();\r\n    tc_free(tc_malloc(<span class=\"hljs-number\">1<\/span>));\r\n    <span class=\"hljs-comment\">\/\/ Either we, or debugallocation.cc, or valgrind will control memory<\/span>\r\n    <span class=\"hljs-comment\">\/\/ management.  We register our extension if we're the winner.<\/span>\r\n<span class=\"hljs-meta\">#<span class=\"hljs-meta-keyword\">ifdef<\/span> TCMALLOC_USING_DEBUGALLOCATION<\/span>\r\n    <span class=\"hljs-comment\">\/\/ Let debugallocation register its extension.<\/span>\r\n<span class=\"hljs-meta\">#<span class=\"hljs-meta-keyword\">else<\/span><\/span>\r\n    <span class=\"hljs-keyword\">if<\/span> (RunningOnValgrind()) {\r\n      <span class=\"hljs-comment\">\/\/ Let Valgrind uses its own malloc (so don't register our extension).<\/span>\r\n    } <span class=\"hljs-keyword\">else<\/span> {\r\n      MallocExtension::Register(<span class=\"hljs-keyword\">new<\/span> TCMallocImplementation);\r\n    }\r\n<span class=\"hljs-meta\">#<span class=\"hljs-meta-keyword\">endif<\/span><\/span>\r\n  }\r\n} \r\n<\/code><\/pre>\n<p>\u53ef\u4ee5\u770b\u5230\uff0cTCMalloc\u521d\u59cb\u5316\u7684\u65b9\u5f0f\u662f\u8c03\u7528<code>tc_malloc()<\/code>\u7533\u8bf7\u4e00\u5b57\u8282\u5185\u5b58\u5e76\u968f\u540e\u8c03\u7528<code>tc_free()<\/code>\u5c06\u5176\u91ca\u653e\u3002\u81f3\u4e8e\u4e3a\u4ec0\u4e48\u5728InitTSD\u524d\u540e\u5404\u7533\u8bf7\u91ca\u653e\u4e00\u6b21\uff0c\u4e0d\u592a\u6e05\u695a\uff0c\u731c\u6d4b\u662f\u4e3a\u4e86\u6d4b\u8bd5\u5728TSD\uff08Thread Specific Data\uff0c\u8be6\u89c1\u540e\u6587\uff09\u521d\u59cb\u5316\u4e4b\u524d\u4e5f\u80fd\u6b63\u5e38\u5de5\u4f5c\u3002<\/p>\n<h2>\u521d\u59cb\u5316\u5185\u5bb9<\/h2>\n<p>\u90a3\u4e48TCMalloc\u5728\u521d\u59cb\u5316\u65f6\u90fd\u6267\u884c\u4e86\u54ea\u4e9b\u64cd\u4f5c\u5462\uff1f\u8fd9\u91cc\u5148\u7b80\u5355\u5217\u4e00\u4e0b\uff0c\u540e\u7eed\u8ba8\u8bbaTCMalloc\u7684\u5b9e\u73b0\u7ec6\u8282\u65f6\u518d\u9010\u4e00\u8be6\u7ec6\u8ba8\u8bba\uff1a<\/p>\n<ul>\n<li>\u521d\u59cb\u5316SizeMap\uff08Size Class\uff09<\/li>\n<li>\u521d\u59cb\u5316\u5404\u79cdAllocator<\/li>\n<li>\u521d\u59cb\u5316CentralCache<\/li>\n<li>\u521b\u5efaPageHeap<\/li>\n<\/ul>\n<p>\u603b\u4e4b\u4e00\u53e5\u8bdd\uff0c\u521b\u5efaTCMalloc\u81ea\u8eab\u7684\u4e00\u4e9b\u5143\u6570\u636e\uff0c\u6bd4\u5982\u5212\u5206\u5c0f\u5bf9\u8c61\u7684\u5927\u5c0f\u7b49\u7b49\u3002<\/p>\n<h1>TCMalloc\u7684\u5185\u5b58\u5206\u914d\u7b97\u6cd5\u6982\u89c8<\/h1>\n<p>TCMalloc\u7684<a href=\"https:\/\/gperftools.github.io\/gperftools\/tcmalloc.html\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">\u5b98\u65b9\u4ecb\u7ecd<\/a>\u4e2d\u5c06\u5185\u5b58\u5206\u914d\u79f0\u4e3a<em>Object Allocation<\/em>\uff0c\u672c\u6587\u4e5f\u6cbf\u7528\u8fd9\u79cd\u53eb\u6cd5\uff0c\u5e76\u5c06object\u7ffb\u8bd1\u4e3a<strong>\u5bf9\u8c61<\/strong>\uff0c\u53ef\u4ee5\u5c06\u5176\u7406\u89e3\u4e3a\u5177\u6709\u4e00\u5b9a\u5927\u5c0f\u7684\u5185\u5b58\u3002<\/p>\n<p>\u6309\u7167\u6240\u5206\u914d\u5185\u5b58\u7684\u5927\u5c0f\uff0cTCMalloc\u5c06\u5185\u5b58\u5206\u914d\u5206\u4e3a\u4e09\u7c7b\uff1a<\/p>\n<ul>\n<li>\u5c0f\u5bf9\u8c61\u5206\u914d\uff0c(0, 256KB]<\/li>\n<li>\u4e2d\u5bf9\u8c61\u5206\u914d\uff0c(256KB, 1MB]<\/li>\n<li>\u5927\u5bf9\u8c61\u5206\u914d\uff0c(1MB, +\u221e)<\/li>\n<\/ul>\n<p>\u7b80\u8981\u4ecb\u7ecd\u51e0\u4e2a\u6982\u5ff5\uff0cPage\uff0cSpan\uff0cPageHeap\uff1a<\/p>\n<p>\u4e0e\u64cd\u4f5c\u7cfb\u7edf\u7ba1\u7406\u5185\u5b58\u7684\u65b9\u5f0f\u7c7b\u4f3c\uff0cTCMalloc\u5c06\u6574\u4e2a\u865a\u62df\u5185\u5b58\u7a7a\u95f4\u5212\u5206\u4e3an\u4e2a\u540c\u7b49\u5927\u5c0f\u7684<strong>Page<\/strong>\uff0c\u6bcf\u4e2apage\u9ed8\u8ba48KB\u3002\u53c8\u5c06\u8fde\u7eed\u7684n\u4e2apage\u79f0\u4e3a\u4e00\u4e2a<strong>Span<\/strong>\u3002<\/p>\n<p>TCMalloc\u5b9a\u4e49\u4e86<strong>PageHeap<\/strong>\u7c7b\u6765\u5904\u7406\u5411OS\u7533\u8bf7\u5185\u5b58\u76f8\u5173\u7684\u64cd\u4f5c\uff0c\u5e76\u63d0\u4f9b\u4e86\u4e00\u5c42\u7f13\u5b58\u3002\u53ef\u4ee5\u8ba4\u4e3a\uff0cPageHeap\u5c31\u662f\u6574\u4e2a\u53ef\u4f9b\u5e94\u7528\u7a0b\u5e8f\u52a8\u6001\u5206\u914d\u7684\u5185\u5b58\u7684\u62bd\u8c61\u3002<\/p>\n<p>PageHeap\u4ee5span\u4e3a\u5355\u4f4d\u5411\u7cfb\u7edf\u7533\u8bf7\u5185\u5b58\uff0c\u7533\u8bf7\u5230\u7684span\u53ef\u80fd\u53ea\u6709\u4e00\u4e2apage\uff0c\u4e5f\u53ef\u80fd\u5305\u542bn\u4e2apage\u3002\u53ef\u80fd\u4f1a\u88ab\u5212\u5206\u4e3a\u4e00\u7cfb\u5217\u7684\u5c0f\u5bf9\u8c61\uff0c\u4f9b\u5c0f\u5bf9\u8c61\u5206\u914d\u4f7f\u7528\uff0c\u4e5f\u53ef\u80fd\u5f53\u505a\u4e00\u6574\u5757\u5f53\u505a\u4e2d\u5bf9\u8c61\u6216\u5927\u5bf9\u8c61\u5206\u914d\u3002<\/p>\n<h2>\u5c0f\u5bf9\u8c61\u5206\u914d<\/h2>\n<h3>Size Class<\/h3>\n<p>\u5bf9\u4e8e256KB\u4ee5\u5185\u7684\u5c0f\u5bf9\u8c61\u5206\u914d\uff0cTCMalloc\u6309\u5927\u5c0f\u5212\u5206\u4e8685\u4e2a\u7c7b\u522b\uff08<a href=\"https:\/\/gperftools.github.io\/gperftools\/tcmalloc.html\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">\u5b98\u65b9\u4ecb\u7ecd<\/a>\u4e2d\u8bf4\u662f88\u4e2a\u5de6\u53f3\uff0c\u4f46\u6211\u4e2a\u4eba\u5b9e\u9645\u6d4b\u8bd5\u662f85\u4e2a\uff0c\u4e0d\u5305\u62ec0\u5b57\u8282\u5927\u5c0f\uff09\uff0c\u79f0\u4e3a<strong>Size Class<\/strong>\uff0c\u6bcf\u4e2asize class\u90fd\u5bf9\u5e94\u4e00\u4e2a\u5927\u5c0f\uff0c\u6bd4\u59828\u5b57\u8282\uff0c16\u5b57\u8282\uff0c32\u5b57\u8282\u3002\u5e94\u7528\u7a0b\u5e8f\u7533\u8bf7\u5185\u5b58\u65f6\uff0cTCMalloc\u4f1a\u9996\u5148\u5c06\u6240\u7533\u8bf7\u7684\u5185\u5b58\u5927\u5c0f\u5411\u4e0a\u53d6\u6574\u5230size class\u7684\u5927\u5c0f\uff0c\u6bd4\u59821<sub>8\u5b57\u8282\u4e4b\u95f4\u7684\u5185\u5b58\u7533\u8bf7\u90fd\u4f1a\u5206\u914d8\u5b57\u8282\uff0c9<\/sub>16\u5b57\u8282\u4e4b\u95f4\u90fd\u4f1a\u5206\u914d16\u5b57\u8282\uff0c\u4ee5\u6b64\u7c7b\u63a8\u3002\u56e0\u6b64\u8fd9\u91cc\u4f1a\u4ea7\u751f\u5185\u90e8\u788e\u7247\u3002TCMalloc\u5c06\u8fd9\u91cc\u7684\u5185\u90e8\u788e\u7247\u63a7\u5236\u572812.5%\u4ee5\u5185\uff0c\u5177\u4f53\u7684\u505a\u6cd5\u5728\u8ba8\u8bbasize class\u7684\u5b9e\u73b0\u7ec6\u8282\u65f6\u518d\u8be6\u7ec6\u5206\u6790\u3002<\/p>\n<h3>ThreadCache<\/h3>\n<p>\u5bf9\u4e8e\u6bcf\u4e2a\u7ebf\u7a0b\uff0cTCMalloc\u90fd\u4e3a\u5176\u4fdd\u5b58\u4e86\u4e00\u4efd\u5355\u72ec\u7684\u7f13\u5b58\uff0c\u79f0\u4e4b\u4e3a<strong>ThreadCache<\/strong>\uff0c\u8fd9\u4e5f\u662fTCMalloc\u540d\u5b57\u7684\u7531\u6765\uff08Thread-Caching Malloc\uff09\u3002\u6bcf\u4e2aThreadCache\u4e2d\u5bf9\u4e8e\u6bcf\u4e2asize class\u90fd\u6709\u4e00\u4e2a\u5355\u72ec\u7684<strong>FreeList<\/strong>\uff0c\u7f13\u5b58\u4e86n\u4e2a\u8fd8\u672a\u88ab\u5e94\u7528\u7a0b\u5e8f\u4f7f\u7528\u7684\u7a7a\u95f2\u5bf9\u8c61\u3002<\/p>\n<p>\u5c0f\u5bf9\u8c61\u7684\u5206\u914d\u76f4\u63a5\u4eceThreadCache\u7684FreeList\u4e2d\u8fd4\u56de\u4e00\u4e2a\u7a7a\u95f2\u5bf9\u8c61\uff0c\u76f8\u5e94\u7684\uff0c\u5c0f\u5bf9\u8c61\u7684\u56de\u6536\u4e5f\u662f\u5c06\u5176\u91cd\u65b0\u653e\u56deThreadCache\u4e2d\u5bf9\u5e94\u7684FreeList\u4e2d\u3002<\/p>\n<p>\u7531\u4e8e\u6bcf\u7ebf\u7a0b\u4e00\u4e2aThreadCache\uff0c\u56e0\u6b64\u4eceThreadCache\u4e2d\u53d6\u7528\u6216\u56de\u6536\u5185\u5b58\u662f<strong>\u4e0d\u9700\u8981\u52a0\u9501<\/strong>\u7684\uff0c\u901f\u5ea6\u5f88\u5feb\u3002<\/p>\n<p>\u4e3a\u4e86\u65b9\u4fbf\u7edf\u8ba1\u6570\u636e\uff0c\u5404\u7ebf\u7a0b\u7684ThreadCache\u8fde\u63a5\u6210\u4e00\u4e2a\u53cc\u5411\u94fe\u8868\u3002ThreadCache\u7684\u7ed3\u6784\u793a\u5927\u81f4\u5982\u4e0b\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"1041\" data-height=\"966\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-292e0b53f382ba70.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/1000\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-292e0b53f382ba70.png\" data-original-width=\"1041\" data-original-height=\"966\" data-original-format=\"image\/png\" data-original-filesize=\"299848\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-ThreadCache<\/div>\n<\/div>\n<h3>CentralCache<\/h3>\n<p>\u90a3\u4e48ThreadCache\u4e2d\u7684\u7a7a\u95f2\u5bf9\u8c61\u4ece\u4f55\u800c\u6765\u5462\uff1f\u7b54\u6848\u662f<strong>CentralCache<\/strong>\u2014\u2014\u4e00\u4e2a\u6240\u6709\u7ebf\u7a0b\u516c\u7528\u7684\u7f13\u5b58\u3002<\/p>\n<p>\u4e0eThreadCache\u7c7b\u4f3c\uff0cCentralCache\u4e2d\u5bf9\u4e8e\u6bcf\u4e2asize class\u4e5f\u90fd\u6709\u4e00\u4e2a\u5355\u72ec\u7684\u94fe\u8868\u6765\u7f13\u5b58\u7a7a\u95f2\u5bf9\u8c61\uff0c\u79f0\u4e4b\u4e3a<strong>CentralFreeList<\/strong>\uff0c\u4f9b\u5404\u7ebf\u7a0b\u7684ThreadCache\u4ece\u4e2d\u53d6\u7528\u7a7a\u95f2\u5bf9\u8c61\u3002<\/p>\n<p>\u7531\u4e8e\u662f\u6240\u6709\u7ebf\u7a0b\u516c\u7528\u7684\uff0c\u56e0\u6b64\u4eceCentralCache\u4e2d\u53d6\u7528\u6216\u56de\u6536\u5bf9\u8c61\uff0c\u662f<strong>\u9700\u8981\u52a0\u9501<\/strong>\u7684\u3002\u4e3a\u4e86\u5e73\u644a\u9501\u64cd\u4f5c\u7684\u5f00\u9500\uff0cThreadCache\u4e00\u822c\u4eceCentralCache\u4e2d\u4e00\u6b21\u6027\u53d6\u7528\u6216\u56de\u6536\u591a\u4e2a\u7a7a\u95f2\u5bf9\u8c61\u3002<\/p>\n<p>CentralCache\u5728TCMalloc\u4e2d\u5e76\u4e0d\u662f\u4e00\u4e2a\u7c7b\uff0c\u53ea\u662f\u4e00\u4e2a\u903b\u8f91\u4e0a\u7684\u6982\u5ff5\uff0c\u5176\u672c\u8d28\u662f<strong>CentralFreeList<\/strong>\u7c7b\u578b\u7684\u6570\u7ec4\u3002\u540e\u6587\u4f1a\u8be6\u7ec6\u8ba8\u8bbaCentralCache\u7684\u5185\u90e8\u7ed3\u6784\uff0c\u73b0\u5728\u6682\u4e14\u8ba4\u4e3aCentralCache\u7684<strong>\u7b80\u5316\u7ed3\u6784<\/strong>\u5982\u4e0b\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"309\" data-height=\"312\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-cf81a424c887f821.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/309\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-cf81a424c887f821.png\" data-original-width=\"309\" data-original-height=\"312\" data-original-format=\"image\/png\" data-original-filesize=\"49198\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-CentralCache<\/div>\n<\/div>\n<h3>PageHeap<\/h3>\n<p>CentralCache\u4e2d\u7684\u7a7a\u95f2\u5bf9\u8c61\u53c8\u662f\u4ece\u4f55\u800c\u6765\u5462\uff1f\u7b54\u6848\u662f\u4e4b\u524d\u63d0\u5230\u7684<strong>PageHeap<\/strong>\u2014\u2014TCMalloc\u5bf9\u53ef\u52a8\u6001\u5206\u914d\u7684\u5185\u5b58\u7684\u62bd\u8c61\u3002<\/p>\n<p>\u5f53CentralCache\u4e2d\u7684\u7a7a\u95f2\u5bf9\u8c61\u4e0d\u591f\u7528\u65f6\uff0cCentralCache\u4f1a\u5411PageHeap\u7533\u8bf7\u4e00\u5757\u5185\u5b58\uff08\u53ef\u80fd\u6765\u81eaPageHeap\u7684\u7f13\u5b58\uff0c\u4e5f\u53ef\u80fd\u5411\u7cfb\u7edf\u7533\u8bf7\u65b0\u7684\u5185\u5b58\uff09\uff0c\u5e76\u5c06\u5176\u62c6\u5206\u6210\u4e00\u7cfb\u5217\u7a7a\u95f2\u5bf9\u8c61\uff0c\u6dfb\u52a0\u5230\u5bf9\u5e94size class\u7684CentralFreeList\u4e2d\u3002<\/p>\n<p>PageHeap\u5185\u90e8\u6839\u636e\u5185\u5b58\u5757\uff08span\uff09\u7684\u5927\u5c0f\u91c7\u53d6\u4e86\u4e24\u79cd\u4e0d\u540c\u7684\u7f13\u5b58\u7b56\u7565\u3002128\u4e2apage\u4ee5\u5185\u7684span\uff0c\u6bcf\u4e2a\u5927\u5c0f\u90fd\u7528\u4e00\u4e2a\u94fe\u8868\u6765\u7f13\u5b58\uff0c\u8d85\u8fc7128\u4e2apage\u7684span\uff0c\u5b58\u50a8\u4e8e\u4e00\u4e2a\u6709\u5e8fset\uff08std::set\uff09\u3002\u8ba8\u8bbaTCMalloc\u7684\u5b9e\u73b0\u7ec6\u8282\u65f6\u518d\u5177\u4f53\u5206\u6790\uff0c\u73b0\u5728\u53ef\u4ee5\u8ba4\u4e3aPageHeap\u7684<strong>\u7b80\u5316\u7ed3\u6784<\/strong>\u5982\u4e0b\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"551\" data-height=\"501\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-8dea96f860c251ba.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/551\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-8dea96f860c251ba.png\" data-original-width=\"551\" data-original-height=\"501\" data-original-format=\"image\/png\" data-original-filesize=\"82000\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-PageHeap<\/div>\n<\/div>\n<h3>\u5185\u5b58\u56de\u6536<\/h3>\n<p>\u4e0a\u9762\u8bf4\u7684\u90fd\u662f\u5185\u5b58\u5206\u914d\uff0c\u5185\u5b58\u56de\u6536\u7684\u60c5\u51b5\u662f\u600e\u6837\u7684\uff1f<\/p>\n<p>\u5e94\u7528\u7a0b\u5e8f\u8c03\u7528free()\u6216delete\u4e00\u4e2a\u5c0f\u5bf9\u8c61\u65f6\uff0c\u4ec5\u4ec5\u662f\u5c06\u5176\u63d2\u5165\u5230ThreadCache\u4e2d\u5176size class\u5bf9\u5e94\u7684FreeList\u4e2d\u800c\u5df2\uff0c\u4e0d\u9700\u8981\u52a0\u9501\uff0c\u56e0\u6b64\u901f\u5ea6\u4e5f\u662f\u975e\u5e38\u5feb\u7684\u3002<\/p>\n<p>\u53ea\u6709\u5f53\u6ee1\u8db3\u4e00\u5b9a\u7684\u6761\u4ef6\u65f6\uff0cThreadCache\u4e2d\u7684\u7a7a\u95f2\u5bf9\u8c61\u624d\u4f1a\u91cd\u65b0\u653e\u56deCentralCache\u4e2d\uff0c\u4ee5\u4f9b\u5176\u4ed6\u7ebf\u7a0b\u53d6\u7528\u3002\u540c\u6837\u7684\uff0c\u5f53\u6ee1\u8db3\u4e00\u5b9a\u6761\u4ef6\u65f6\uff0cCentralCache\u4e2d\u7684\u7a7a\u95f2\u5bf9\u8c61\u4e5f\u4f1a\u8fd8\u7ed9PageHeap\uff0cPageHeap\u518d\u8fd8\u7ed9\u7cfb\u7edf\u3002<\/p>\n<p>\u5185\u5b58\u5728\u8fd9\u4e9b\u7ec4\u4ef6\u4e4b\u95f4\u7684\u79fb\u52a8\u4f1a\u5728\u540e\u6587\u8be6\u7ec6\u8ba8\u8bba\uff0c\u73b0\u5728\u5148\u5ffd\u7565\u8fd9\u4e9b\u7ec6\u8282\u3002<\/p>\n<h3>\u5c0f\u7ed3<\/h3>\n<p>\u603b\u7ed3\u4e00\u4e0b\uff0c\u5c0f\u5bf9\u8c61\u5206\u914d\u6d41\u7a0b\u5927\u81f4\u5982\u4e0b\uff1a<\/p>\n<ul>\n<li>\u5c06\u8981\u5206\u914d\u7684\u5185\u5b58\u5927\u5c0f\u6620\u5c04\u5230\u5bf9\u5e94\u7684size class\u3002<\/li>\n<li>\u67e5\u770bThreadCache\u4e2d\u8be5size class\u5bf9\u5e94\u7684FreeList\u3002<\/li>\n<li>\u5982\u679cFreeList\u975e\u7a7a\uff0c\u5219\u79fb\u9664FreeList\u7684\u7b2c\u4e00\u4e2a\u7a7a\u95f2\u5bf9\u8c61\u5e76\u5c06\u5176\u8fd4\u56de\uff0c\u5206\u914d\u7ed3\u675f\u3002<\/li>\n<li>\u5982\u679cFreeList\u662f\u7a7a\u7684\uff1a\n<ul>\n<li>\u4eceCentralCache\u4e2dsize class\u5bf9\u5e94\u7684CentralFreeList\u83b7\u53d6\u4e00\u5806\u7a7a\u95f2\u5bf9\u8c61\u3002\n<ul>\n<li>\u5982\u679cCentralFreeList\u4e5f\u662f\u7a7a\u7684\uff0c\u5219\uff1a\n<ul>\n<li>\u5411PageHeap\u7533\u8bf7\u4e00\u4e2aspan\u3002<\/li>\n<li>\u62c6\u5206\u6210size class\u5bf9\u5e94\u5927\u5c0f\u7684\u7a7a\u95f2\u5bf9\u8c61\uff0c\u653e\u5165CentralFreeList\u4e2d\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<li>\u5c06\u8fd9\u5806\u5bf9\u8c61\u653e\u7f6e\u5230ThreadCache\u4e2dsize class\u5bf9\u5e94\u7684FreeList\u4e2d\uff08\u7b2c\u4e00\u4e2a\u5bf9\u8c61\u9664\u5916\uff09\u3002<\/li>\n<li>\u8fd4\u56de\u4eceCentralCache\u83b7\u53d6\u7684\u7b2c\u4e00\u4e2a\u5bf9\u8c61\uff0c\u5206\u914d\u7ed3\u675f\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h2>\u4e2d\u5bf9\u8c61\u5206\u914d<\/h2>\n<p>\u8d85\u8fc7256KB\u4f46\u4e0d\u8d85\u8fc71MB\uff08128\u4e2apage\uff09\u7684\u5185\u5b58\u5206\u914d\u88ab\u8ba4\u4e3a\u662f\u4e2d\u5bf9\u8c61\u5206\u914d\uff0c\u91c7\u53d6\u4e86\u4e0e\u5c0f\u5bf9\u8c61\u4e0d\u540c\u7684\u5206\u914d\u7b56\u7565\u3002<\/p>\n<p>\u9996\u5148\uff0cTCMalloc\u4f1a\u5c06\u5e94\u7528\u7a0b\u5e8f\u6240\u8981\u7533\u8bf7\u7684\u5185\u5b58\u5927\u5c0f\u5411\u4e0a\u53d6\u6574\u5230<strong>\u6574\u6570\u4e2apage<\/strong>\uff08\u56e0\u6b64\uff0c\u8fd9\u91cc\u4f1a\u4ea7\u751f1B~8KB\u7684\u5185\u90e8\u788e\u7247\uff09\u3002\u4e4b\u540e\u7684\u64cd\u4f5c\u8868\u9762\u4e0a\u975e\u5e38\u7b80\u5355\uff0c\u5411PageHeap\u7533\u8bf7\u4e00\u4e2a\u6307\u5b9apage\u6570\u91cf\u7684span\u5e76\u8fd4\u56de\u5176\u8d77\u59cb\u5730\u5740\u5373\u53ef\uff1a<\/p>\n<pre class=\"hljs php\"><code class=\"php\">Span* span = <span class=\"hljs-keyword\">Static<\/span>::pageheap()-&gt;New(num_pages);\r\nresult = (PREDICT_FALSE(span == <span class=\"hljs-keyword\">NULL<\/span>) ? <span class=\"hljs-keyword\">NULL<\/span> : SpanToMallocResult(span));\r\n<span class=\"hljs-keyword\">return<\/span> result;\r\n<\/code><\/pre>\n<p>\u95ee\u9898\u5728\u4e8e\uff0cPageHeap\u662f\u5982\u4f55\u7ba1\u7406\u8fd9\u4e9bspan\u7684\uff1f\u5373<code>PageHeap::New()<\/code>\u662f\u5982\u4f55\u5b9e\u73b0\u7684\u3002<\/p>\n<p>\u524d\u6587\u8bf4\u5230\uff0cPageHeap\u63d0\u4f9b\u4e86\u4e00\u5c42\u7f13\u5b58\uff0c\u56e0\u6b64<code>PageHeap::New()<\/code>\u5e76\u975e\u6bcf\u6b21\u90fd\u5411\u7cfb\u7edf\u7533\u8bf7\u5185\u5b58\uff0c\u4e5f\u53ef\u80fd\u76f4\u63a5\u4ece\u7f13\u5b58\u4e2d\u5206\u914d\u3002<\/p>\n<p>\u5bf9128\u4e2apage\u4ee5\u5185\u7684span\u548c\u8d85\u8fc7128\u4e2apage\u7684span\uff0cPageHeap\u91c7\u53d6\u7684\u7f13\u5b58\u7b56\u7565\u4e0d\u4e00\u6837\u3002\u4e3a\u4e86\u63cf\u8ff0\u65b9\u4fbf\uff0c\u4ee5\u4e0b\u5c06128\u4e2apage\u4ee5\u5185\u7684span\u79f0\u4e3a\u5c0fspan\uff0c\u5927\u4e8e128\u4e2apage\u7684span\u79f0\u4e3a\u5927span\u3002<\/p>\n<p>\u5148\u6765\u770b\u5c0fspan\u662f\u5982\u4f55\u7ba1\u7406\u7684\uff0c\u5927span\u7684\u7ba1\u7406\u653e\u5728\u5927\u5bf9\u8c61\u5206\u914d\u4e00\u8282\u4ecb\u7ecd\u3002<\/p>\n<p>PageHeap\u4e2d\u6709128\u4e2a\u5c0fspan\u7684\u94fe\u8868\uff0c\u5206\u522b\u5bf9\u5e941~128\u4e2apage\u7684span\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"551\" data-height=\"391\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-c8497aea41abd3b2.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/551\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-c8497aea41abd3b2.png\" data-original-width=\"551\" data-original-height=\"391\" data-original-format=\"image\/png\" data-original-filesize=\"64620\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-SpanList<\/div>\n<\/div>\n<p>\u5047\u8bbe\u8981\u5206\u914d\u4e00\u5757\u5185\u5b58\uff0c\u5176\u5927\u5c0f\u7ecf\u8fc7\u5411\u4e0a\u53d6\u6574\u4e4b\u540e\u5bf9\u5e94k\u4e2apage\uff0c\u56e0\u6b64\u9700\u8981\u4ecePageHeap\u53d6\u4e00\u4e2a\u5927\u5c0f\u4e3ak<\/p>\n<p>\u4e2apage\u7684span\uff0c\u8fc7\u7a0b\u5982\u4e0b\uff1a<\/p>\n<ul>\n<li>\u4ecek\u4e2apage\u7684span\u94fe\u8868\u5f00\u59cb\uff0c\u5230128\u4e2apage\u7684span\u94fe\u8868\uff0c\u6309\u987a\u5e8f\u627e\u5230\u7b2c\u4e00\u4e2a\u975e\u7a7a\u94fe\u8868\u3002<\/li>\n<li>\u53d6\u51fa\u8fd9\u4e2a\u975e\u7a7a\u94fe\u8868\u4e2d\u7684\u4e00\u4e2aspan\uff0c\u5047\u8bbe\u6709n\u4e2apage\uff0c\u5c06\u8fd9\u4e2aspan\u62c6\u5206\u6210\u4e24\u4e2aspan\uff1a\n<ul>\n<li>\u4e00\u4e2aspan\u5927\u5c0f\u4e3ak\u4e2apage\uff0c\u4f5c\u4e3a\u5206\u914d\u7ed3\u679c\u8fd4\u56de\u3002<\/li>\n<li>\u53e6\u4e00\u4e2aspan\u5927\u5c0f\u4e3an &#8211; k\u4e2apage\uff0c\u91cd\u65b0\u63d2\u5165\u5230n &#8211; k\u4e2apage\u7684span\u94fe\u8868\u4e2d\u3002<\/li>\n<\/ul>\n<\/li>\n<li>\u5982\u679c\u627e\u4e0d\u5230\u975e\u7a7a\u94fe\u8868\uff0c\u5219\u5c06\u8fd9\u6b21\u5206\u914d\u770b\u505a\u662f\u5927\u5bf9\u8c61\u5206\u914d\uff0c\u5206\u914d\u8fc7\u7a0b\u8be6\u89c1\u4e0b\u6587\u3002<\/li>\n<\/ul>\n<h2>\u5927\u5bf9\u8c61\u5206\u914d<\/h2>\n<p>\u8d85\u8fc71MB\uff08128\u4e2apage\uff09\u7684\u5185\u5b58\u5206\u914d\u88ab\u8ba4\u4e3a\u662f\u5927\u5bf9\u8c61\u5206\u914d\uff0c\u4e0e\u4e2d\u5bf9\u8c61\u5206\u914d\u7c7b\u4f3c\uff0c\u4e5f\u662f\u5148\u5c06\u6240\u8981\u5206\u914d\u7684\u5185\u5b58\u5927\u5c0f\u5411\u4e0a\u53d6\u6574\u5230\u6574\u6570\u4e2apage\uff0c\u5047\u8bbe\u662fk\u4e2apage\uff0c\u7136\u540e\u5411PageHeap\u7533\u8bf7\u4e00\u4e2ak\u4e2apage\u5927\u5c0f\u7684span\u3002<\/p>\n<p>\u5bf9\u4e8e\u4e2d\u5bf9\u8c61\u7684\u5206\u914d\uff0c\u5982\u679c\u4e0a\u8ff0\u7684span\u94fe\u8868\u65e0\u6cd5\u6ee1\u8db3\uff0c\u4e5f\u4f1a\u88ab\u5f53\u505a\u662f\u5927\u5bf9\u8c61\u6765\u5904\u7406\u3002\u4e5f\u5c31\u662f\u8bf4\uff0cTCMalloc\u5728\u6e90\u7801\u5c42\u9762\u5176\u5b9e\u5e76\u6ca1\u6709\u533a\u5206\u4e2d\u5bf9\u8c61\u548c\u5927\u5bf9\u8c61\uff0c\u53ea\u662f\u5bf9\u4e8e\u4e0d\u540c\u5927\u5c0f\u7684span\u7684\u7f13\u5b58\u65b9\u5f0f\u4e0d\u4e00\u6837\u7f62\u4e86\u3002<\/p>\n<p>\u5927\u5bf9\u8c61\u5206\u914d\u7528\u5230\u7684span\u90fd\u662f\u8d85\u8fc7128\u4e2apage\u7684span\uff0c\u5176\u7f13\u5b58\u65b9\u5f0f\u4e0d\u662f\u94fe\u8868\uff0c\u800c\u662f\u4e00\u4e2a\u6309span\u5927\u5c0f\u6392\u5e8f\u7684<strong>\u6709\u5e8fset<\/strong>\uff08std::set\uff09\uff0c\u4ee5\u4fbf\u6309\u5927\u5c0f\u8fdb\u884c\u641c\u7d22\u3002<\/p>\n<p>\u5047\u8bbe\u8981\u5206\u914d\u4e00\u5757\u8d85\u8fc71MB\u7684\u5185\u5b58\uff0c\u5176\u5927\u5c0f\u7ecf\u8fc7\u5411\u4e0a\u53d6\u6574\u4e4b\u540e\u5bf9\u5e94k\u4e2apage\uff08k&gt;128\uff09\uff0c\u6216\u8005\u662f\u8981\u5206\u914d\u4e00\u57571MB\u4ee5\u5185\u7684\u5185\u5b58\uff0c\u4f46\u65e0\u6cd5\u7531\u4e2d\u5bf9\u8c61\u5206\u914d\u903b\u8f91\u6765\u6ee1\u8db3\uff0c\u6b64\u65f6k &lt;= 128\u3002\u4e0d\u7ba1\u54ea\u79cd\u60c5\u51b5\uff0c\u90fd\u662f\u8981\u4ecePageHeap\u7684span set\u4e2d\u53d6\u4e00\u4e2a\u5927\u5c0f\u4e3ak\u4e2apage\u7684span\uff0c\u5176\u8fc7\u7a0b\u5982\u4e0b\uff1a<\/p>\n<ul>\n<li>\u641c\u7d22set\uff0c\u627e\u5230\u4e0d\u5c0f\u4e8ek\u4e2apage\u7684\u6700\u5c0f\u7684span\uff08<strong>best-fit<\/strong>\uff09\uff0c\u5047\u8bbe\u8be5span\u6709n\u4e2apage\u3002<\/li>\n<li>\u5c06\u8fd9\u4e2aspan\u62c6\u5206\u4e3a\u4e24\u4e2aspan\uff1a\n<ul>\n<li>\u4e00\u4e2aspan\u5927\u5c0f\u4e3ak\u4e2apage\uff0c\u4f5c\u4e3a\u7ed3\u679c\u8fd4\u56de\u3002<\/li>\n<li>\u53e6\u4e00\u4e2aspan\u5927\u5c0f\u4e3an &#8211; k\u4e2apage\uff0c\u5982\u679cn &#8211; k &gt; 128\uff0c\u5219\u5c06\u5176\u63d2\u5165\u5230\u5927span\u7684set\u4e2d\uff0c\u5426\u5219\uff0c\u5c06\u5176\u63d2\u5165\u5230\u5bf9\u5e94\u7684\u5c0fspan\u94fe\u8868\u4e2d\u3002<\/li>\n<\/ul>\n<\/li>\n<li>\u5982\u679c\u627e\u4e0d\u5230\u5408\u9002\u7684span\uff0c\u5219\u4f7f\u7528sbrk\u6216mmap\u5411\u7cfb\u7edf\u7533\u8bf7\u65b0\u7684\u5185\u5b58\u4ee5\u751f\u6210\u65b0\u7684span\uff0c\u5e76\u91cd\u65b0\u6267\u884c\u4e2d\u5bf9\u8c61\u6216\u5927\u5bf9\u8c61\u7684\u5206\u914d\u7b97\u6cd5\u3002<\/li>\n<\/ul>\n<h2>\u5c0f\u7ed3<\/h2>\n<p>\u4ee5\u4e0a\u8ba8\u8bba\u5ffd\u7565\u4e86\u5f88\u591a\u5b9e\u73b0\u4e0a\u7684\u7ec6\u8282\uff0c\u6bd4\u5982PageHeap\u5bf9span\u7684\u7ba1\u7406\u8fd8\u533a\u5206\u4e86normal\u72b6\u6001\u7684span\u548creturned\u72b6\u6001\u7684span\uff0c\u63a5\u4e0b\u6765\u4f1a\u8be6\u7ec6\u5206\u6790\u8fd9\u4e9b\u7ec6\u8282\u3002<\/p>\n<p>\u5728\u6b64\u4e4b\u524d\uff0c\u753b\u5f20\u56fe\u6982\u62ec\u4e0bTCMalloc\u7684\u7ba1\u7406\u5185\u5b58\u7684\u7b56\u7565\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"1247\" data-height=\"481\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-1e077643e9161e4e.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/1000\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-1e077643e9161e4e.png\" data-original-width=\"1247\" data-original-height=\"481\" data-original-format=\"image\/png\" data-original-filesize=\"266812\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-Overview<\/div>\n<\/div>\n<p>\u53ef\u4ee5\u770b\u5230\uff0c\u4e0d\u8d85\u8fc7256KB\u7684\u5c0f\u5bf9\u8c61\u5206\u914d\uff0c\u5728\u5e94\u7528\u7a0b\u5e8f\u548c\u5185\u5b58\u4e4b\u95f4\u5176\u5b9e\u6709\u4e09\u5c42\u7f13\u5b58\uff1aPageHeap\u3001CentralCache\u3001ThreadCache\u3002\u800c\u4e2d\u5bf9\u8c61\u548c\u5927\u5bf9\u8c61\u5206\u914d\uff0c\u5219\u53ea\u6709PageHeap\u4e00\u5c42\u7f13\u5b58\u3002<\/p>\n<h1>TCMalloc\u7684\u5b9e\u73b0\u7ec6\u8282<\/h1>\n<p>\u7b97\u6cd5\u6982\u89c8\u4e00\u8282\u6d89\u53ca\u5230\u4e86\u5f88\u591a\u6982\u5ff5\uff0c\u6bd4\u5982Page\uff0cSpan\uff0cSize Class\uff0cPageHeap\uff0cThreadCache\u7b49\uff0c\u4f46\u53ea\u662f\u7c97\u7565\u7684\u4e00\u63d0\uff0c\u672c\u8282\u5c06\u8be6\u7ec6\u8ba8\u8bba\u8fd9\u4e9b\u6982\u5ff5\u6240\u6d89\u53ca\u7684\u5b9e\u73b0\u7ec6\u8282\u3002<\/p>\n<h2>Page<\/h2>\n<p><strong>Page\u662fTCMalloc\u7ba1\u7406\u5185\u5b58\u7684\u57fa\u672c\u5355\u4f4d<\/strong>\uff08\u8fd9\u91cc\u7684page\u8981\u533a\u5206\u4e8e\u64cd\u4f5c\u7cfb\u7edf\u7ba1\u7406\u865a\u62df\u5185\u5b58\u7684page\uff09\uff0cpage\u7684\u9ed8\u8ba4\u5927\u5c0f\u4e3a8KB\uff0c\u53ef\u5728configure\u65f6\u901a\u8fc7\u9009\u9879\u8c03\u6574\u4e3a32KB\u621664KB\u3002<\/p>\n<pre class=\"hljs shell\"><code class=\"shell\">.\/configure &lt;other flags&gt; --with-tcmalloc-pagesize=32 (or 64)\r\n<\/code><\/pre>\n<p>page\u8d8a\u5927\uff0cTCMalloc\u7684\u901f\u5ea6\u76f8\u5bf9\u8d8a\u5feb\uff0c\u4f46\u5176\u5360\u7528\u7684\u5185\u5b58\u4e5f\u4f1a\u8d8a\u9ad8\u3002\u7b80\u5355\u8bf4\uff0c\u5c31\u662f\u7a7a\u95f4\u6362\u65f6\u95f4\u7684\u9053\u7406\u3002\u9ed8\u8ba4\u7684page\u5927\u5c0f\u901a\u8fc7\u51cf\u5c11\u5185\u5b58\u788e\u7247\u6765\u6700\u5c0f\u5316\u5185\u5b58\u4f7f\u7528\uff0c\u4f46\u8ddf\u8e2a\u8fd9\u4e9bpage\u4f1a\u82b1\u8d39\u66f4\u591a\u7684\u65f6\u95f4\u3002\u4f7f\u7528\u66f4\u5927\u7684page\u5219\u4f1a\u5e26\u6765\u66f4\u591a\u7684\u5185\u5b58\u788e\u7247\uff0c\u4f46\u901f\u5ea6\u4e0a\u4f1a\u6709\u6240\u63d0\u5347\u3002\u5b98\u65b9\u6587\u6863\u7ed9\u51fa\u7684\u6570\u636e\u662f\u5728\u67d0\u4e9bgoogle\u5e94\u7528\u4e0a\u67093%~5%\u7684\u901f\u5ea6\u63d0\u5347\u3002<\/p>\n<h3>PageID<\/h3>\n<p>TCMalloc\u5e76\u975e\u53ea\u5c06\u5806\u5185\u5b58\u770b\u505a\u662f\u4e00\u4e2a\u4e2a\u7684page\uff0c\u800c\u662f\u5c06\u6574\u4e2a\u865a\u62df\u5185\u5b58\u7a7a\u95f4\u90fd\u770b\u505a\u662fpage\u7684\u96c6\u5408\u3002\u4ece\u5185\u5b58\u5730\u57400x0\u5f00\u59cb\uff0c\u6bcf\u4e2apage\u5bf9\u5e94\u4e00\u4e2a\u9012\u589e\u7684PageID\uff0c\u5982\u4e0b\u56fe\uff08\u4ee532\u4f4d\u7cfb\u7edf\u4e3a\u4f8b\uff09\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"634\" data-height=\"128\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-f9b9ae429acdc54e.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/634\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-f9b9ae429acdc54e.png\" data-original-width=\"634\" data-original-height=\"128\" data-original-format=\"image\/png\" data-original-filesize=\"20941\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-Page<\/div>\n<\/div>\n<p>\u5bf9\u4e8e\u4efb\u610f\u5185\u5b58\u5730\u5740<code>ptr<\/code>\uff0c\u90fd\u53ef\u901a\u8fc7\u7b80\u5355\u7684\u79fb\u4f4d\u64cd\u4f5c\u6765\u8ba1\u7b97\u5176\u6240\u5728page\u7684PageID\uff1a<\/p>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-keyword\">static<\/span> <span class=\"hljs-keyword\">const<\/span> <span class=\"hljs-keyword\">size_t<\/span> kPageShift  = <span class=\"hljs-number\">13<\/span>; <span class=\"hljs-comment\">\/\/ page\u5927\u5c0f\uff1a1 &lt;&lt; 13 = 8KB<\/span>\r\n<span class=\"hljs-keyword\">const<\/span> PageID p = <span class=\"hljs-keyword\">reinterpret_cast<\/span>&lt;<span class=\"hljs-keyword\">uintptr_t<\/span>&gt;(ptr) &gt;&gt; kPageShift;\r\n<\/code><\/pre>\n<p>\u5373\uff0c<code>ptr<\/code>\u6240\u5c5epage\u7684PageID\u4e3a<code>ptr \/ page_size<\/code>\u3002<\/p>\n<h2>Span<\/h2>\n<p>\u4e00\u4e2a\u6216\u591a\u4e2a\u8fde\u7eed\u7684Page\u7ec4\u6210\u4e00\u4e2aSpan\uff08a contiguous run of pages\uff09\u3002<strong>TCMalloc\u4ee5Span\u4e3a\u5355\u4f4d\u5411\u7cfb\u7edf\u7533\u8bf7\u5185\u5b58\u3002<\/strong><\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"822\" data-height=\"134\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-329183bf1a5cf33b.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/822\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-329183bf1a5cf33b.png\" data-original-width=\"822\" data-original-height=\"134\" data-original-format=\"image\/png\" data-original-filesize=\"65912\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-Span<\/div>\n<\/div>\n<p>\u5982\u56fe\uff0c\u7b2c\u4e00\u4e2aspan\u5305\u542b2\u4e2apage\uff0c\u7b2c\u4e8c\u4e2a\u548c\u7b2c\u56db\u4e2aspan\u5305\u542b3\u4e2apage\uff0c\u7b2c\u4e09\u4e2aspan\u5305\u542b5\u4e2apage\u3002<\/p>\n<p>\u4e00\u4e2aspan\u8bb0\u5f55\u4e86\u8d77\u59cbpage\u7684PageID\uff08<code>start<\/code>\uff09\uff0c\u4ee5\u53ca\u6240\u5305\u542bpage\u7684\u6570\u91cf\uff08<code>length<\/code>\uff09\u3002<\/p>\n<p>\u4e00\u4e2aspan\u8981\u4e48\u88ab\u62c6\u5206\u6210\u591a\u4e2a\u76f8\u540csize class\u7684\u5c0f\u5bf9\u8c61\u7528\u4e8e\u5c0f\u5bf9\u8c61\u5206\u914d\uff0c\u8981\u4e48\u4f5c\u4e3a\u4e00\u4e2a\u6574\u4f53\u7528\u4e8e\u4e2d\u5bf9\u8c61\u6216\u5927\u5bf9\u8c61\u5206\u914d\u3002\u5f53\u4f5c\u7528\u4f5c\u5c0f\u5bf9\u8c61\u5206\u914d\u65f6\uff0cspan\u7684<code>sizeclass<\/code>\u6210\u5458\u53d8\u91cf\u8bb0\u5f55\u4e86\u5176\u5bf9\u5e94\u7684size class\u3002<\/p>\n<p>span\u4e2d\u8fd8\u5305\u542b\u4e24\u4e2aSpan\u7c7b\u578b\u7684\u6307\u9488\uff08<code>prev<\/code>,\u00a0<code>next<\/code>\uff09\uff0c\u7528\u4e8e\u5c06\u591a\u4e2aspan\u4ee5\u94fe\u8868\u7684\u5f62\u5f0f\u5b58\u50a8\u3002<\/p>\n<h3>span\u7684\u4e09\u79cd\u72b6\u6001<\/h3>\n<p>\u4e00\u4e2aspan\u5904\u4e8e\u4ee5\u4e0b\u4e09\u79cd\u72b6\u6001\u4e2d\u7684\u4e00\u79cd\uff1a<\/p>\n<ul>\n<li>IN_USE<\/li>\n<li>ON_NORMAL_FREELIST<\/li>\n<li>ON_RETURNED_FREELIST<\/li>\n<\/ul>\n<p><code>IN_USE<\/code>\u6bd4\u8f83\u597d\u7406\u89e3\uff0c\u6b63\u5728\u4f7f\u7528\u4e2d\u7684\u610f\u601d\uff0c\u8981\u4e48\u88ab\u62c6\u5206\u6210\u5c0f\u5bf9\u8c61\u5206\u914d\u7ed9CentralCache\u6216\u8005ThreadCache\u4e86\uff0c\u8981\u4e48\u5df2\u7ecf\u5206\u914d\u7ed9\u5e94\u7528\u7a0b\u5e8f\u4e86\u3002\u56e0\u4e3aspan\u662f\u7531PageHeap\u6765\u7ba1\u7406\u7684\uff0c\u56e0\u6b64\u5373\u4f7f\u53ea\u662f\u5206\u914d\u7ed9\u4e86CentralCache\uff0c\u8fd8\u6ca1\u6709\u88ab\u5e94\u7528\u7a0b\u5e8f\u6240\u7533\u8bf7\uff0c\u5728PageHeap\u770b\u6765\uff0c\u4e5f\u662fIN_USE\u4e86\u3002<\/p>\n<p><code>ON_NORMAL_FREELIST<\/code>\u548c<code>ON_RETURNED_FREELIST<\/code>\u90fd\u53ef\u4ee5\u8ba4\u4e3a\u662f\u7a7a\u95f2\u72b6\u6001\uff0c\u533a\u522b\u5728\u4e8e\uff0cON_RETURNED_FREELIST\u662f\u6307span\u5bf9\u5e94\u7684\u5185\u5b58\u5df2\u7ecf\u88abPageHeap\u91ca\u653e\u7ed9\u7cfb\u7edf\u4e86\uff08\u5728Linux\u4e2d\uff0c\u5bf9\u4e8eMAP_PRIVATE|MAP_ANONYMOUS\u7684\u5185\u5b58\u4f7f\u7528madvise\u6765\u5b9e\u73b0\uff09\u3002\u9700\u8981\u6ce8\u610f\u7684\u662f\uff0c\u5373\u4f7f\u5f52\u8fd8\u7ed9\u7cfb\u7edf\uff0c\u5176\u865a\u62df\u5185\u5b58\u5730\u5740\u4f9d\u7136\u662f\u53ef\u8bbf\u95ee\u7684\uff0c\u53ea\u662f\u5bf9\u8fd9\u4e9b\u5185\u5b58\u7684\u4fee\u6539\u4e22\u5931\u4e86\u800c\u5df2\uff0c\u5728\u4e0b\u4e00\u6b21\u8bbf\u95ee\u65f6\u4f1a\u5bfc\u81f4page fault\u4ee5\u75280\u6765\u91cd\u65b0\u521d\u59cb\u5316\u3002<\/p>\n<h3>\u7a7a\u95f2\u5bf9\u8c61\u94fe\u8868<\/h3>\n<p>\u88ab\u62c6\u5206\u6210\u591a\u4e2a\u5c0f\u5bf9\u8c61\u7684span\u8fd8\u5305\u542b\u4e86\u4e00\u4e2a\u8bb0\u5f55\u7a7a\u95f2\u5bf9\u8c61\u7684\u94fe\u8868<code>objects<\/code>\uff0c\u7531CentralFreeList\u6765\u7ef4\u62a4\u3002<\/p>\n<p>\u5bf9\u4e8e\u65b0\u521b\u5efa\u7684span\uff0c\u5c06\u5176\u5bf9\u5e94\u7684\u5185\u5b58\u6309size class\u7684\u5927\u5c0f\u5747\u5206\u6210\u82e5\u5e72\u5c0f\u5bf9\u8c61\uff0c\u5728\u6bcf\u4e00\u4e2a\u5c0f\u5bf9\u8c61\u7684\u8d77\u59cb\u4f4d\u7f6e\u5904\u5b58\u50a8\u4e0b\u4e00\u4e2a\u5c0f\u5bf9\u8c61\u7684\u5730\u5740\uff0c\u9996\u9996\u76f8\u8fde\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"405\" data-height=\"242\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-f75ec63d9fc9575a.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/405\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-f75ec63d9fc9575a.png\" data-original-width=\"405\" data-original-height=\"242\" data-original-format=\"image\/png\" data-original-filesize=\"32586\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-FreshSpan<\/div>\n<\/div>\n<p>\u4f46\u5f53span\u4e2d\u7684\u5c0f\u5bf9\u8c61\u7ecf\u8fc7\u4e00\u7cfb\u5217\u7533\u8bf7\u548c\u56de\u6536\u4e4b\u540e\uff0c\u5176\u987a\u5e8f\u5c31\u4e0d\u786e\u5b9a\u4e86\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"401\" data-height=\"261\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-a7c057c328fabbf6.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/401\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-a7c057c328fabbf6.png\" data-original-width=\"401\" data-original-height=\"261\" data-original-format=\"image\/png\" data-original-filesize=\"51921\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-UsedSpan<\/div>\n<\/div>\n<p>\u53ef\u4ee5\u770b\u5230\uff0c\u6709\u4e9b\u5c0f\u5bf9\u8c61\u5df2\u7ecf\u4e0d\u518d\u7a7a\u95f2\u5bf9\u8c61\u94fe\u8868objects\u4e2d\u4e86\uff0c\u94fe\u8868\u4e2d\u7684\u5143\u7d20\u987a\u5e8f\u4e5f\u5df2\u7ecf\u88ab\u6253\u4e71\u3002<\/p>\n<p>\u7a7a\u95f2\u5bf9\u8c61\u94fe\u8868\u4e2d\u7684\u5143\u7d20\u4e71\u5e8f\u6ca1\u4ec0\u4e48\u5f71\u54cd\uff0c\u56e0\u4e3a\u53ea\u6709\u5f53\u4e00\u4e2aspan\u7684\u6240\u6709\u5c0f\u5bf9\u8c61\u90fd\u88ab\u91ca\u653e\u4e4b\u540e\uff0cCentralFreeList\u624d\u4f1a\u5c06\u5176\u8fd8\u7ed9PageHeap\u3002<\/p>\n<h2>PageMap<\/h2>\n<p>PageMap\u4e4b\u524d\u6ca1\u6709\u63d0\u5230\u8fc7\uff0c\u5b83\u4e3b\u8981\u7528\u4e8e\u89e3\u51b3\u8fd9\u4e48\u4e00\u4e2a\u95ee\u9898\uff1a<strong>\u7ed9\u5b9a\u4e00\u4e2apage\uff0c\u5982\u4f55\u786e\u5b9a\u8fd9\u4e2apage\u5c5e\u4e8e\u54ea\u4e2aspan\uff1f<\/strong><\/p>\n<p>\u5373\uff0cPageMap\u7f13\u5b58\u4e86PageID\u5230Span\u7684\u5bf9\u5e94\u5173\u7cfb\u3002<\/p>\n<p>32\u4f4d\u7cfb\u7edf\u3001x86-64\u3001arm64\u4f7f\u7528\u4e24\u7ea7PageMap\uff0c\u4ee532\u4f4d\u7cfb\u7edf\u4e3a\u4f8b\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"1034\" data-height=\"518\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-9212efc047e395d2.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/1000\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-9212efc047e395d2.png\" data-original-width=\"1034\" data-original-height=\"518\" data-original-format=\"image\/png\" data-original-filesize=\"103864\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-PageMap<\/div>\n<\/div>\n<p>\u5728root_\u6570\u7ec4\u4e2d\u5305\u542b512\u4e2a\u6307\u5411Leaf\u7684\u6307\u9488\uff0c\u6bcf\u4e2aLeaf\u53c8\u662f1024\u4e2avoid*\u7684\u6570\u7ec4\uff0c\u6570\u7ec4\u7d22\u5f15\u4e3aPageID\uff0c\u6570\u7ec4\u5143\u7d20\u4e3apage\u6240\u5c5eSpan\u7684\u6307\u9488\u3002\u4e00\u5171<img decoding=\"async\" class=\"math-inline\" src=\"https:\/\/math.jianshu.com\/math?formula=2%5E%7B19%7D\" alt=\"2^{19}\" \/>\u4e2a\u6570\u7ec4\u5143\u7d20\uff0c\u5bf9\u5e9432\u4f4d\u7cfb\u7edf\u7684<img decoding=\"async\" class=\"math-inline\" src=\"https:\/\/math.jianshu.com\/math?formula=2%5E%7B19%7D\" alt=\"2^{19}\" \/>\u4e2apage\u3002<\/p>\n<p>\u4f7f\u7528\u4e24\u7ea7map\u53ef\u4ee5\u51cf\u5c11TCMalloc\u5143\u6570\u636e\u7684\u5185\u5b58\u5360\u7528\uff0c\u56e0\u4e3a\u521d\u59cb\u53ea\u4f1a\u7ed9\u7b2c\u4e00\u5c42\uff08\u5373root_\u6570\u7ec4\uff09\u5206\u914d\u5185\u5b58\uff082KB\uff09\uff0c\u7b2c\u4e8c\u5c42\u53ea\u6709\u5728\u5b9e\u9645\u7528\u5230\u65f6\u624d\u4f1a\u5b9e\u9645\u5206\u914d\u5185\u5b58\u3002\u800c\u5982\u679c\u521d\u59cb\u5c31\u7ed9<img decoding=\"async\" class=\"math-inline\" src=\"https:\/\/math.jianshu.com\/math?formula=2%5E%7B19%7D\" alt=\"2^{19}\" \/>\u4e2apage\u90fd\u5206\u914d\u5185\u5b58\u7684\u8bdd\uff0c\u5219\u4f1a\u5360\u7528<img decoding=\"async\" class=\"math-inline\" src=\"https:\/\/math.jianshu.com\/math?formula=2%5E%7B19%7D%20*%204%20bytes%20%3D%202MB\" alt=\"2^{19} * 4 bytes = 2MB\" \/>\u7684\u5185\u5b58\u3002<\/p>\n<h2>Size Class<\/h2>\n<p>TCMalloc\u5c06\u6bcf\u4e2a\u5c0f\u5bf9\u8c61\u7684\u5927\u5c0f\uff081B~256KB\uff09\u5206\u4e3a85\u4e2a\u7c7b\u522b\uff08<a href=\"https:\/\/gperftools.github.io\/gperftools\/tcmalloc.html\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">\u5b98\u65b9\u4ecb\u7ecd<\/a>\u4e2d\u8bf4\u662f88\u4e2a\u5de6\u53f3\uff0c\u4f46\u6211\u4e2a\u4eba\u5b9e\u9645\u6d4b\u8bd5\u662f85\u4e2a\uff0c\u4e0d\u5305\u62ec0\u5b57\u8282\u5927\u5c0f\uff09\uff0c\u79f0\u4e4b\u4e3aSize Class\uff0c\u6bcf\u4e2asize class\u4e00\u4e2a\u7f16\u53f7\uff0c\u4ece0\u5f00\u59cb\u9012\u589e\uff08\u5b9e\u9645\u7f16\u53f7\u4e3a0\u7684size class\u662f\u5bf9\u5e940\u5b57\u8282\uff0c\u662f\u6ca1\u6709\u5b9e\u9645\u610f\u4e49\u7684\uff09\u3002<\/p>\n<p>\u4e3e\u4e2a\u4f8b\u5b50\uff0c896\u5b57\u8282\u5bf9\u5e94\u7f16\u53f7\u4e3a30\u7684size class\uff0c\u4e0b\u4e00\u4e2asize class 31\u5927\u5c0f\u4e3a1024\u5b57\u8282\uff0c\u90a3\u4e48897\u5b57\u8282\u52301024\u5b57\u8282\u4e4b\u95f4\u6240\u6709\u7684\u5206\u914d\u90fd\u4f1a\u5411\u4e0a\u820d\u5165\u52301024\u5b57\u8282\u3002<\/p>\n<p><code>SizeMap::Init()<\/code>\u5b9e\u73b0\u4e86\u5bf9size class\u7684\u5212\u5206\uff0c\u89c4\u5219\u5982\u4e0b\uff1a<\/p>\n<h3>\u5212\u5206\u8de8\u5ea6<\/h3>\n<ul>\n<li>16\u5b57\u8282\u4ee5\u5185\uff0c\u6bcf8\u5b57\u8282\u5212\u5206\u4e00\u4e2asize class\u3002\n<ul>\n<li>\u6ee1\u8db3\u8fd9\u79cd\u60c5\u51b5\u7684size class\u53ea\u6709\u4e24\u4e2a\uff1a8\u5b57\u8282\u300116\u5b57\u8282\u3002<\/li>\n<\/ul>\n<\/li>\n<li>16~128\u5b57\u8282\uff0c\u6bcf16\u5b57\u8282\u5212\u5206\u4e00\u4e2asize class\u3002\n<ul>\n<li>\u6ee1\u8db3\u8fd9\u79cd\u60c5\u51b5\u7684size class\u67097\u4e2a\uff1a32, 48, 64, 80, 96, 112, 128\u5b57\u8282\u3002<\/li>\n<\/ul>\n<\/li>\n<li>128B~256KB\uff0c\u6309\u7167\u6bcf\u6b21\u6b65\u8fdb<code>(size \/ 8)<\/code>\u5b57\u8282\u7684\u957f\u5ea6\u5212\u5206\uff0c\u5e76\u4e14\u6b65\u957f\u9700\u8981\u5411\u4e0b\u5bf9\u9f50\u52302\u7684\u6574\u6570\u6b21\u5e42\uff0c\u6bd4\u5982\uff1a\n<ul>\n<li>144\u5b57\u8282\uff1a128 + 128 \/ 8 = 128 + 16 = 144<\/li>\n<li>160\u5b57\u8282\uff1a144 + 144 \/ 8 = 144 + 18 = 144 + 16 = 160<\/li>\n<li>176\u5b57\u8282\uff1a160 + 160 \/ 8 = 160 + 20 = 160 + 16 = 176<\/li>\n<li>\u4ee5\u6b64\u7c7b\u63a8<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h3>\u4e00\u6b21\u79fb\u52a8\u591a\u4e2a\u7a7a\u95f2\u5bf9\u8c61<\/h3>\n<p>ThreadCache\u4f1a\u4eceCentralCache\u4e2d\u83b7\u53d6\u7a7a\u95f2\u5bf9\u8c61\uff0c\u4e5f\u4f1a\u5c06\u8d85\u51fa\u9650\u5236\u7684\u7a7a\u95f2\u5bf9\u8c61\u653e\u56deCentralCache\u3002ThreadCache\u548cCentralCache\u4e4b\u95f4\u7684\u5bf9\u8c61\u79fb\u52a8\u662f<strong>\u6279\u91cf<\/strong>\u8fdb\u884c\u7684\uff0c\u5373\u4e00\u6b21\u79fb\u52a8\u591a\u4e2a\u7a7a\u95f2\u5bf9\u8c61\u3002CentralCache\u7531\u4e8e\u662f\u6240\u6709\u7ebf\u7a0b\u516c\u7528\uff0c\u56e0\u6b64\u5bf9\u5176\u8fdb\u884c\u64cd\u4f5c\u65f6\u9700\u8981\u52a0\u9501\uff0c\u4e00\u6b21\u79fb\u52a8\u591a\u4e2a\u5bf9\u8c61\u53ef\u4ee5<strong>\u5747\u644a\u9501\u64cd\u4f5c\u7684\u5f00\u9500<\/strong>\uff0c\u63d0\u5347\u6548\u7387\u3002<\/p>\n<p>\u90a3\u4e48\u4e00\u6b21\u6279\u91cf\u79fb\u52a8\u591a\u5c11\u5462\uff1f\u6bcf\u6b21\u79fb\u52a864KB\u5927\u5c0f\u7684\u5185\u5b58\uff0c\u5373\u56e0size class\u800c\u5f02\uff0c\u4f46\u81f3\u5c112\u4e2a\uff0c\u81f3\u591a32\u4e2a\uff08\u53ef\u901a\u8fc7\u73af\u5883\u53d8\u91cf<code>TCMALLOC_TRANSFER_NUM_OBJ<\/code>\u8c03\u6574\uff09\u3002<\/p>\n<p>\u79fb\u52a8\u6570\u91cf\u7684\u8ba1\u7b97\u4e5f\u662f\u5728size class\u521d\u59cb\u5316\u7684\u8fc7\u7a0b\u4e2d\u8ba1\u7b97\u5f97\u51fa\u7684\u3002<\/p>\n<h3>\u4e00\u6b21\u7533\u8bf7\u591a\u4e2apage<\/h3>\n<p>\u5bf9\u4e8e\u6bcf\u4e2asize class\uff0cTCMalloc\u5411\u7cfb\u7edf\u7533\u8bf7\u5185\u5b58\u65f6\u4e00\u6b21\u6027\u7533\u8bf7n\u4e2apage\uff08\u4e00\u4e2aspan\uff09\uff0c\u7136\u540e\u5747\u5206\u6210\u591a\u4e2a\u5c0f\u5bf9\u8c61\u8fdb\u884c\u7f13\u5b58\uff0c\u4ee5\u6b64\u6765<strong>\u5747\u644a\u7cfb\u7edf\u8c03\u7528\u7684\u5f00\u9500<\/strong>\u3002<\/p>\n<p>\u4e0d\u540c\u7684size class\u5bf9\u5e94\u7684page\u6570\u91cf\u662f\u4e0d\u540c\u7684\uff0c\u5982\u4f55\u51b3\u5b9an\u7684\u5927\u5c0f\u5462\uff1f\u4ece1\u4e2apage\u5f00\u59cb\u9012\u589e\uff0c\u4e00\u76f4\u5230\u5747\u5206\u6210\u82e5\u5e72\u5c0f\u5bf9\u8c61\u540e\u6240\u5269\u7684\u7a7a\u95f4\u5c0f\u4e8espan\u603b\u5927\u5c0f\u76841\/8\u4e3a\u6b62\uff0c\u56e0\u6b64\uff0c\u6d6a\u8d39\u7684\u5185\u5b58\u88ab\u63a7\u5236\u572812.5%\u4ee5\u5185\u3002\u8fd9\u662fTCMalloc<strong>\u51cf\u5c11\u5185\u90e8\u788e\u7247<\/strong>\u7684\u4e00\u79cd\u63aa\u65bd\u3002<\/p>\n<p>\u53e6\u5916\uff0c\u6240\u5206\u914d\u7684page\u6570\u91cf\u8fd8\u9700\u6ee1\u8db3\u4e00\u6b21\u79fb\u52a8\u591a\u4e2a\u7a7a\u95f2\u5bf9\u8c61\u7684\u6570\u91cf\u8981\u6c42\uff08\u6e90\u7801\u4e2d\u7684\u6ce8\u91ca\u662f\u8fd9\u6837\u8bf4\u7684\uff0c\u4e0d\u8fc7\u5b9e\u9645\u4ee3\u7801\u662f\u6ee1\u8db31\/4\u5373\u53ef\uff0c\u539f\u56e0\u4e0d\u660e\uff09\u3002<\/p>\n<h3>\u5408\u5e76\u64cd\u4f5c<\/h3>\n<p>\u5728\u4e0a\u8ff0\u89c4\u5219\u4e4b\u4e0a\uff0c\u8fd8\u6709\u4e00\u4e2a\u5408\u5e76\u64cd\u4f5c\uff1aTCMalloc\u4f1a\u5c06<strong>\u76f8\u540cpage\u6570\u91cf\uff0c\u76f8\u540c\u5bf9\u8c61\u6570\u91cf<\/strong>\u7684\u76f8\u90bb\u7684size class\u5408\u5e76\u4e3a\u4e00\u4e2asize class\u3002\u6bd4\u5982\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"450\" data-height=\"450\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-67b5372db33b0774.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/450\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-67b5372db33b0774.png\" data-original-width=\"450\" data-original-height=\"450\" data-original-format=\"image\/png\" data-original-filesize=\"85951\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">size_merge<\/div>\n<\/div>\n<p>\u7b2c30\u4e2asize class\u7684\u5bf9\u8c61\u5927\u5c0f\u662f832\u5b57\u8282\uff0cpage\u6570\u91cf\u4e3a1\u4e2a\uff0c\u56e0\u6b64\u5305\u542b8192 \/ 832 = 9\u4e2a\u5c0f\u5bf9\u8c61\u3002<\/p>\n<p>\u7b2c31\u4e2asize class\u5bf9\u5e94\u7684page\u6570\u91cf\uff081\u4e2a\uff09\u548c\u5bf9\u8c61\u6570\u91cf\uff089\u4e2a\uff09\u8ddf\u7b2c30\u4e2asize class\u5b8c\u5168\u4e00\u6837\uff0c\u56e0\u6b64\u7b2c30\u4e2asize class\u548c\u7b2c31\u4e2asize class\u5408\u5e76\uff0c\u6240\u4ee5\u7b2c30\u4e2asize class\u5bf9\u5e94\u7684\u5bf9\u8c61\u5927\u5c0f\u4e3a896\u5b57\u8282\u3002<\/p>\n<p>\u4e0b\u4e00\u4e2asize class\u5bf9\u5e94\u7684\u5bf9\u8c61\u5927\u5c0f\u4e3a1024\u5b57\u8282\uff0cpage\u6570\u91cf\u4e3a1\u4e2a\uff0c\u56e0\u6b64\u5bf9\u8c61\u6570\u91cf\u662f8\u4e2a\uff0c\u8ddf\u7b2c30\u4e2asize class\u7684\u5bf9\u8c61\u6570\u91cf\u4e0d\u4e00\u6837\uff0c\u65e0\u6cd5\u5408\u5e76\u3002<\/p>\n<p>\u6700\u7ec8\uff0c\u7b2c30\u4e2asize class\u5bf9\u5e94\u7684\u5bf9\u8c61\u5927\u5c0f\u4e3a896\u5b57\u8282\u3002<\/p>\n<h3>\u8bb0\u5f55\u6620\u5c04\u5173\u7cfb<\/h3>\n<p>\u7531\u4ee5\u4e0a\u5212\u5206\u89c4\u5219\u53ef\u4ee5\u770b\u5230\uff0c\u4e00\u4e2asize class\u5bf9\u5e94\uff1a<\/p>\n<ul>\n<li>\u4e00\u4e2a\u5bf9\u8c61\u5927\u5c0f<\/li>\n<li>\u4e00\u4e2a\u7533\u8bf7page\u7684\u6570\u91cf<\/li>\n<li>\u4e00\u4e2a\u6279\u91cf\u79fb\u52a8\u5bf9\u8c61\u7684\u6570\u91cf<\/li>\n<\/ul>\n<p>TCMalloc\u5c06size class\u4e0e\u8fd9\u4e9b\u4fe1\u606f\u7684\u6620\u5c04\u5173\u7cfb\u5206\u522b\u8bb0\u5f55\u5728\u4e09\u4e2a\u4ee5size class\u7684\u7f16\u53f7\u4e3a\u7d22\u5f15\u7684\u6570\u7ec4\u4e2d\uff08<code>class_to_size_<\/code>\uff0c<code>num_objects_to_move_<\/code>\uff0c\u00a0<code>class_to_pages_<\/code>\uff09\u3002<\/p>\n<p>\u8fd8\u6709\u4e00\u9879\u975e\u5e38\u91cd\u8981\u7684\u6620\u5c04\u5173\u7cfb\uff1a\u5c0f\u5bf9\u8c61\u5927\u5c0f\u5230size class\u7f16\u53f7\u7684\u6620\u5c04\u3002TCMalloc\u5c06\u5176\u8bb0\u5f55\u5728\u4e00\u4e2a\u4e00\u7ef4\u6570\u7ec4<code>class_array_<\/code>\u4e2d\u3002<\/p>\n<p>256KB\u4ee5\u5185\u90fd\u662f\u5c0f\u5bf9\u8c61\uff0c\u800csize class\u7684\u7f16\u53f7\u7528\u4e00\u4e2a\u5b57\u8282\u5c31\u53ef\u4ee5\u8868\u793a\uff0c\u56e0\u6b64\u5b58\u50a8\u5c0f\u5bf9\u8c61\u5927\u5c0f\u5bf9\u5e94\u7684size class\u7f16\u53f7\u9700\u8981256K\u4e2aunsigned char\uff0c\u5373256KB\u7684\u5185\u5b58\u3002\u4f46\u7531\u4e8esize class\u4e4b\u95f4\u662f\u6709\u95f4\u9694\u7684\uff081024\u5b57\u8282\u4ee5\u5185\u95f4\u9694\u81f3\u5c118\u5b57\u8282\uff0c1024\u4ee5\u4e0a\u95f4\u9694\u81f3\u5c11128\u5b57\u8282\uff09\uff0c\u56e0\u6b64\u53ef\u4ee5\u901a\u8fc7\u7b80\u5355\u7684\u8ba1\u7b97\u5bf9class_array_\u7684\u7d22\u5f15\u8fdb\u884c\u538b\u7f29\uff0c\u4ee5\u51cf\u5c11\u5185\u5b58\u5360\u7528\u3002<\/p>\n<p>\u7ed9\u5b9a\u5927\u5c0fs\uff0c\u5176\u5bf9\u5e94\u7684class_array_\u7d22\u5f15\u8ba1\u7b97\u65b9\u5f0f\u5982\u4e0b\uff1a<\/p>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-comment\">\/\/ s &lt;= 1024<\/span>\r\n<span class=\"hljs-function\"><span class=\"hljs-keyword\">static<\/span> <span class=\"hljs-keyword\">inline<\/span> size_t <span class=\"hljs-title\">SmallSizeClass<\/span><span class=\"hljs-params\">(<span class=\"hljs-keyword\">size_t<\/span> s)<\/span><\/span>{\r\n  <span class=\"hljs-keyword\">return<\/span> (<span class=\"hljs-keyword\">static_cast<\/span>&lt;<span class=\"hljs-keyword\">uint32_t<\/span>&gt;(s) + <span class=\"hljs-number\">7<\/span>) &gt;&gt; <span class=\"hljs-number\">3<\/span>;\r\n}\r\n\r\n<span class=\"hljs-comment\">\/\/ s &gt; 1024<\/span>\r\n<span class=\"hljs-function\"><span class=\"hljs-keyword\">static<\/span> <span class=\"hljs-keyword\">inline<\/span> size_t <span class=\"hljs-title\">LargeSizeClass<\/span><span class=\"hljs-params\">(<span class=\"hljs-keyword\">size_t<\/span> s)<\/span><\/span>{\r\n  <span class=\"hljs-keyword\">return<\/span> (<span class=\"hljs-keyword\">static_cast<\/span>&lt;<span class=\"hljs-keyword\">uint32_t<\/span>&gt;(s) + <span class=\"hljs-number\">127<\/span> + (<span class=\"hljs-number\">120<\/span> &lt;&lt; <span class=\"hljs-number\">7<\/span>)) &gt;&gt; <span class=\"hljs-number\">7<\/span>;\r\n}\r\n<\/code><\/pre>\n<p>\u5f53s = 256KB\u65f6\uff0c\u8ba1\u7b97\u7ed3\u679c\u5373\u4e3a<code>class_array_<\/code>\u7684\u6700\u5927\u7d22\u5f152169\uff0c\u56e0\u6b64\u6570\u7ec4\u7684\u5927\u5c0f\u4e3a2170\u5b57\u8282\u3002<\/p>\n<h3>\u8ba1\u7b97\u4efb\u610f\u5185\u5b58\u5730\u5740\u5bf9\u5e94\u7684\u5bf9\u8c61\u5927\u5c0f<\/h3>\n<p>\u5f53\u5e94\u7528\u7a0b\u5e8f\u8c03\u7528<code>free()<\/code>\u6216<code>delete<\/code>\u91ca\u653e\u5185\u5b58\u65f6\uff0c\u9700\u8981\u6709\u4e00\u79cd\u65b9\u5f0f\u83b7\u53d6\u6240\u8981\u91ca\u653e\u7684\u5185\u5b58\u5730\u5740\u5bf9\u5e94\u7684\u5185\u5b58\u5927\u5c0f\u3002\u7ed3\u5408\u524d\u6587\u6240\u8ff0\u7684\u5404\u79cd\u6620\u5c04\u5173\u7cfb\uff0c\u5728TCMalloc\u4e2d\u6309\u7167\u4ee5\u4e0b\u987a\u5e8f\u8ba1\u7b97\u4efb\u610f\u5185\u5b58\u5730\u5740\u5bf9\u5e94\u7684\u5bf9\u8c61\u5927\u5c0f\uff1a<\/p>\n<ul>\n<li>\u8ba1\u7b97\u7ed9\u5b9a\u5730\u5740\u8ba1\u6240\u5728\u7684PageID\uff08ptr &gt;&gt; 13\uff09<\/li>\n<li>\u4ecePageMap\u4e2d\u67e5\u8be2\u8be5page\u6240\u5728\u7684span<\/li>\n<li>span\u4e2d\u8bb0\u5f55\u4e86size class\u7f16\u53f7<\/li>\n<li>\u6839\u636esize class\u7f16\u53f7\u4ece<code>class_to_size_<\/code>\u6570\u7ec4\u4e2d\u67e5\u8be2\u5bf9\u5e94\u7684\u5bf9\u8c61\u5927\u5c0f<\/li>\n<\/ul>\n<p>\u8fd9\u6837\u505a\u7684\u597d\u5904\u662f\uff1a<strong>\u4e0d\u9700\u8981\u5728\u5185\u5b58\u5757\u7684\u5934\u90e8\u8bb0\u5f55\u5185\u5b58\u5927\u5c0f\uff0c\u51cf\u5c11\u5185\u5b58\u7684\u6d6a\u8d39<\/strong>\u3002<\/p>\n<h3>\u5c0f\u7ed3<\/h3>\n<p>size class\u7684\u5b9e\u73b0\u4e2d\u6709\u5f88\u591a\u7701\u7a7a\u95f4\u7701\u65f6\u95f4\u7684\u505a\u6cd5\uff1a<\/p>\n<ul>\n<li>\u7701\u7a7a\u95f4\n<ul>\n<li>\u63a7\u5236\u5212\u5206\u8de8\u5ea6\u7684\u6700\u5927\u503c\uff088KB\uff09\uff0c\u51cf\u5c11\u5185\u90e8\u788e\u7247<\/li>\n<li>\u63a7\u5236\u4e00\u6b21\u7533\u8bf7page\u7684\u6570\u91cf\uff0c\u51cf\u5c11\u5185\u90e8\u788e\u7247<\/li>\n<li>\u901a\u8fc7\u8ba1\u7b97\u548c\u4e00\u7cfb\u5217\u5143\u6570\u636e\u8bb0\u5f55\u5185\u5b58\u5730\u5740\u5230\u5185\u5b58\u5927\u5c0f\u7684\u6620\u5c04\u5173\u7cfb\uff0c\u907f\u514d\u5728\u5b9e\u9645\u5206\u914d\u7684\u5185\u5b58\u5757\u4e2d\u8bb0\u5f55\u5185\u5b58\u5927\u5c0f\uff0c\u51cf\u5c11\u5185\u5b58\u6d6a\u8d39<\/li>\n<li>\u4e24\u7ea7PageMap\u6216\u4e09\u7ea7PageMap<\/li>\n<li>\u538b\u7f29class_array_<\/li>\n<\/ul>\n<\/li>\n<li>\u7701\u65f6\u95f4\n<ul>\n<li>\u4e00\u6b21\u7533\u8bf7\u591a\u4e2apage<\/li>\n<li>\u4e00\u6b21\u79fb\u52a8\u591a\u4e2a\u7a7a\u95f2\u5bf9\u8c61<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h2>PageHeap<\/h2>\n<p>\u524d\u9762\u4ecb\u7ecd\u7684\u90fd\u662fTCMalloc\u5982\u4f55\u5bf9\u5185\u5b58\u8fdb\u884c\u5212\u5206\uff0c\u63a5\u4e0b\u6765\u770bTCMalloc\u5982\u4f55\u7ba1\u7406\u5982\u6b64\u5212\u5206\u540e\u7684\u5185\u5b58\uff0c\u8fd9\u662fPageHeap\u7684\u4e3b\u8981\u804c\u8d23\u3002<\/p>\n<p>TCMalloc\u6e90\u7801\u4e2d\u5bf9PageHeap\u7684\u6ce8\u91ca\uff1a<\/p>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-comment\">\/\/ -------------------------------------------------------------------------<\/span>\r\n<span class=\"hljs-comment\">\/\/ Page-level allocator<\/span>\r\n<span class=\"hljs-comment\">\/\/  * Eager coalescing<\/span>\r\n<span class=\"hljs-comment\">\/\/<\/span>\r\n<span class=\"hljs-comment\">\/\/ Heap for page-level allocation.  We allow allocating and freeing a<\/span>\r\n<span class=\"hljs-comment\">\/\/ contiguous runs of pages (called a \"span\").<\/span>\r\n<span class=\"hljs-comment\">\/\/ -------------------------------------------------------------------------<\/span><\/code><\/pre>\n<h3>\u7a7a\u95f2Span\u7ba1\u7406\u5668<\/h3>\n<p>\u5982\u524d\u6240\u8ff0\uff0c128page\u4ee5\u5185\u7684span\u79f0\u4e3a\u5c0fspan\uff0c128page\u4ee5\u4e0a\u7684span\u79f0\u4e3a\u5927span\u3002PageHeap\u5bf9\u4e8e\u8fd9\u4e24\u79cdspan\u91c7\u53d6\u4e86\u4e0d\u540c\u7684\u7ba1\u7406\u7b56\u7565\u3002\u5c0fspan\u7528\u94fe\u8868\uff0c\u800c\u4e14\u6bcf\u4e2a\u5927\u5c0f\u7684span\u90fd\u7528\u4e00\u4e2a\u5355\u72ec\u7684\u94fe\u8868\u6765\u7ba1\u7406\u3002\u5927span\u7528std::set\u3002<\/p>\n<p>\u524d\u6587\u6ca1\u6709\u63d0\u5230\u7684\u662f\uff0c\u4ece\u53e6\u4e00\u4e2a\u7ef4\u5ea6\u6765\u770b\uff0cPageHeap\u662f\u5206\u5f00\u7ba1\u7406<code>ON_NORMAL_FREELIST<\/code>\u548c<code>ON_RETURNED_FREELIST<\/code>\u72b6\u6001\u7684span\u7684\u3002\u56e0\u6b64\uff0c\u6bcf\u4e2a\u5c0fspan\u5bf9\u5e94\u4e24\u4e2a\u94fe\u8868\uff0c\u6240\u6709\u5927span\u5bf9\u5e94\u4e24\u4e2aset\u3002<\/p>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-comment\">\/\/ We segregate spans of a given size into two circular linked<\/span>\r\n<span class=\"hljs-comment\">\/\/ lists: one for normal spans, and one for spans whose memory<\/span>\r\n<span class=\"hljs-comment\">\/\/ has been returned to the system.<\/span>\r\n<span class=\"hljs-class\"><span class=\"hljs-keyword\">struct<\/span> <span class=\"hljs-title\">SpanList<\/span> {<\/span>\r\n  Span        normal;\r\n  Span        returned;\r\n};\r\n\r\n<span class=\"hljs-comment\">\/\/ Array mapping from span length to a doubly linked list of free spans<\/span>\r\n<span class=\"hljs-comment\">\/\/<\/span>\r\n<span class=\"hljs-comment\">\/\/ <span class=\"hljs-doctag\">NOTE:<\/span> index 'i' stores spans of length 'i + 1'.<\/span>\r\nSpanList free_[kMaxPages];    <span class=\"hljs-comment\">\/\/ 128<\/span>\r\n\r\n<span class=\"hljs-keyword\">typedef<\/span> <span class=\"hljs-built_in\">std<\/span>::<span class=\"hljs-built_in\">set<\/span>&lt;SpanPtrWithLength, SpanBestFitLess, STLPageHeapAllocator&lt;SpanPtrWithLength, <span class=\"hljs-keyword\">void<\/span>&gt; &gt; SpanSet;\r\n\r\n<span class=\"hljs-comment\">\/\/ Sets of spans with length &gt; kMaxPages.<\/span>\r\n<span class=\"hljs-comment\">\/\/<\/span>\r\n<span class=\"hljs-comment\">\/\/ Rather than using a linked list, we use sets here for efficient<\/span>\r\n<span class=\"hljs-comment\">\/\/ best-fit search.<\/span>\r\nSpanSet large_normal_;\r\nSpanSet large_returned_;\r\n<\/code><\/pre>\n<p>\u56e0\u6b64\uff0c\u5b9e\u9645\u7684PageHeap\u662f\u8fd9\u6837\u7684\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"541\" data-height=\"566\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-1c91a978a3acf40b.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/541\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-1c91a978a3acf40b.png\" data-original-width=\"541\" data-original-height=\"566\" data-original-format=\"image\/png\" data-original-filesize=\"159375\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-PageHeap2<\/div>\n<\/div>\n<h3>Heap\u6bb5\u7684\u4f7f\u7528\u9650\u5236<\/h3>\n<p>\u53ef\u4ee5\u901a\u8fc7<code>FLAGS_tcmalloc_heap_limit_mb<\/code>\u5bf9\u8fdb\u7a0bheap\u6bb5\u7684\u5185\u5b58\u4f7f\u7528\u91cf\u8fdb\u884c\u9650\u5236\uff0c\u9ed8\u8ba4\u503c0\u8868\u793a\u4e0d\u505a\u9650\u5236\u3002\u5982\u679c\u5f00\u542f\u4e86\u9650\u5236\u5e76\u4e14\u5bf9heap\u6bb5\u5185\u5b58\u7684\u4f7f\u7528\u91cf\u63a5\u8fd1\u8fd9\u4e2a\u9650\u5236\u65f6\uff0cTCMalloc\u4f1a\u66f4\u79ef\u6781\u7684\u5c06\u7a7a\u95f2\u5185\u5b58\u91ca\u653e\u7ed9\u7cfb\u7edf\uff0c\u8fdb\u800c\u4f1a\u5f15\u53d1\u66f4\u591a\u7684\u8f6f\u5206\u9875\u9519\u8bef\uff08minor page fault\uff09\u3002<\/p>\n<p>\u4e3a\u4e86\u7b80\u5316\u8ba8\u8bba\uff0c<strong>\u540e\u6587\u5747\u5047\u8bbe\u6ca1\u6709\u5bf9heap\u6bb5\u7684\u5185\u5b58\u4f7f\u7528\u505a\u4efb\u4f55\u9650\u5236<\/strong>\u3002<\/p>\n<h3>\u521b\u5efaSpan<\/h3>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-comment\">\/\/ Allocate a run of \"n\" pages.  Returns zero if out of memory.<\/span>\r\n<span class=\"hljs-comment\">\/\/ Caller should not pass \"n == 0\" -- instead, n should have<\/span>\r\n<span class=\"hljs-comment\">\/\/ been rounded up already.<\/span>\r\n<span class=\"hljs-function\">Span* <span class=\"hljs-title\">New<\/span><span class=\"hljs-params\">(Length n)<\/span><\/span>;\r\n<\/code><\/pre>\n<p>\u521b\u5efaspan\u7684\u8fc7\u7a0b\u5176\u5b9e\u5c31\u662f\u5206\u914d\u4e2d\u5bf9\u8c61\u548c\u5927\u5bf9\u8c61\u7684\u8fc7\u7a0b\uff0c\u5047\u8bbe\u8981\u521b\u5efak\u4e2apage\u5927\u5c0f\u7684span\uff08\u4ee5\u4e0b\u7b80\u79f0\u5927\u5c0f\u4e3ak\u7684span\uff09\uff0c\u8fc7\u7a0b\u5982\u4e0b\uff1a<\/p>\n<h4>\u641c\u7d22\u7a7a\u95f2span<\/h4>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-function\">Span* <span class=\"hljs-title\">SearchFreeAndLargeLists<\/span><span class=\"hljs-params\">(Length n)<\/span><\/span>;\r\n<\/code><\/pre>\n<ol>\n<li>\u641c\u7d22\u7a7a\u95f2span\u94fe\u8868\uff0c\u6309\u7167\u4ee5\u4e0b\u987a\u5e8f\uff0c\u627e\u51fa\u7b2c\u4e00\u4e2a\u4e0d\u5c0f\u4e8ek\u7684span\uff1a\n<ul>\n<li>\u4ece\u5927\u5c0f\u4e3ak\u7684span\u7684\u94fe\u8868\u5f00\u59cb\u4f9d\u6b21\u641c\u7d22<\/li>\n<li>\u5bf9\u4e8e\u67d0\u4e2a\u5927\u5c0f\u7684span\uff0c\u5148\u641cnormal\u94fe\u8868\uff0c\u518d\u641creturned\u94fe\u8868<\/li>\n<\/ul>\n<\/li>\n<li>\u5982\u679cspan\u94fe\u8868\u4e2d\u6ca1\u627e\u5230\u5408\u9002\u7684span\uff0c\u5219\u641c\u7d22\u5b58\u50a8\u5927span\u7684set\uff1a\n<ul>\n<li>\u4ece\u5927\u5c0f\u4e3ak\u7684span\u5f00\u59cb\u641c\u7d22<\/li>\n<li>\u540c\u6837\u5148\u641cnormal\u518d\u641creturned<\/li>\n<li>\u4f18\u5148\u4f7f\u7528\u957f\u5ea6\u6700\u5c0f\u5e76\u4e14\u8d77\u59cb\u5730\u5740\u6700\u5c0f\u7684span\uff08<strong>best-fit<\/strong>\uff09<\/li>\n<\/ul>\n<\/li>\n<li>\u5982\u679c\u901a\u8fc7\u4ee5\u4e0a\u4e24\u6b65\u627e\u5230\u4e86\u4e00\u4e2a\u5927\u5c0f\u4e3am\u7684span\uff0c\u5219\u5c06\u5176\u62c6\u6210\u4e24\u4e2aspan\uff1a\n<ul>\n<li>\u5927\u5c0f\u4e3am &#8211; k\u7684span\u91cd\u65b0\u6839\u636e\u5927\u5c0f\u548c\u72b6\u6001\u653e\u56de\u94fe\u8868\u6216set\u4e2d<\/li>\n<li>\u5927\u5c0f\u4e3ak\u7684span\u4f5c\u4e3a\u7ed3\u679c\u8fd4\u56de\uff0c\u521b\u5efaspan\u7ed3\u675f<\/li>\n<\/ul>\n<\/li>\n<li>\u5982\u679c\u6ca1\u641c\u5230\u5408\u9002\u7684span\uff0c\u5219\u7ee7\u7eed\u540e\u9762\u7684\u6b65\u9aa4\uff1a\u5411\u7cfb\u7edf\u7533\u8bf7\u5185\u5b58\u3002<\/li>\n<\/ol>\n<h4>\u5c0f\u63d2\u66f2\uff1a\u91ca\u653e\u6240\u6709\u7a7a\u95f2\u5185\u5b58<\/h4>\n<pre class=\"hljs cpp\"><code class=\"cpp\">ReleaseAtLeastNPages(<span class=\"hljs-keyword\">static_cast<\/span>&lt;Length&gt;(<span class=\"hljs-number\">0x7fffffff<\/span>));\r\n<\/code><\/pre>\n<p>\u5f53\u6ca1\u6709\u53ef\u7528\u7684\u7a7a\u95f2span\u65f6\uff0c\u9700\u8981\u5411\u7cfb\u7edf\u7533\u8bf7\u65b0\u7684\u5185\u5b58\uff0c\u4f46\u5728\u6b64\u4e4b\u524d\uff0c\u8fd8\u6709\u4e00\u6b21\u907f\u514d\u5411\u7cfb\u7edf\u7533\u8bf7\u65b0\u5185\u5b58\u7684\u673a\u4f1a\uff1a\u91ca\u653e\u6240\u6709\u7a7a\u95f2\u5185\u5b58\u3002\u5411\u7cfb\u7edf\u7533\u8bf7\u7684\u5185\u5b58\u6bcf\u8fbe\u5230128MB\uff0c\u4e14\u7a7a\u95f2\u5185\u5b58\u8d85\u8fc7\u4ece\u7cfb\u7edf\u7533\u8bf7\u7684\u603b\u5185\u5b58\u76841\/4\uff0c\u5c31\u9700\u8981\u5c06\u6240\u6709\u7684\u7a7a\u95f2\u5185\u5b58\u91ca\u653e\u3002<\/p>\n<p>\u56e0\u4e3aTCMalloc\u5c06normal\u548creturned\u7684\u5185\u5b58\u5206\u5f00\u7ba1\u7406\uff0c\u800c\u8fd9\u4e24\u79cd\u5185\u5b58\u4e0d\u4f1a\u5408\u5e76\u5728\u4e00\u8d77\u3002\u56e0\u6b64\uff0c\u53ef\u80fd\u6709\u4e00\u6bb5\u8fde\u7eed\u7684\u7a7a\u95f2\u5185\u5b58\u7b26\u5408\u8981\u6c42\uff08k\u4e2apage\u5927\u5c0f\uff09\uff0c\u4f46\u56e0\u4e3a\u5b83\u65e2\u6709normal\u7684\u90e8\u5206\uff0c\u53c8\u6709returned\u7684\u90e8\u5206\uff0c\u56e0\u6b64\u524d\u9762\u7684\u641c\u7d22\u89c4\u5219\u641c\u4e0d\u5230\u5b83\u3002\u800c\u91ca\u653e\u6240\u6709\u5185\u5b58\u53ef\u4ee5\u5c06normal\u7684\u5185\u5b58\u4e5f\u53d8\u4e3areturned\u7684\uff0c\u7136\u540e\u5c31\u53ef\u4ee5\u5408\u5e76\u4e86\uff08\u5408\u5e76\u89c4\u5219\u8be6\u7ec6\u540e\u6587\u5408\u5e76span\uff09\u3002<\/p>\n<p>\u4e4b\u6240\u4ee5\u63a7\u5236\u5728\u6bcf128MB\u4e00\u6b21\u7684\u9891\u7387\uff0c\u662f\u4e3a\u4e86\u907f\u514d\u9ad8\u9891\u5c0f\u91cf\u7533\u8bf7\u5185\u5b58\u7684\u7a0b\u5e8f\u906d\u53d7\u592a\u591a\u7684minor page fault\u3002<\/p>\n<p>\u91ca\u653e\u5b8c\u6bd5\u540e\uff0c\u4f1a\u6309\u7167\u524d\u9762\u7684\u641c\u7d22\u89c4\u5219\u518d\u6b21\u5c1d\u8bd5\u641c\u7d22\u7a7a\u95f2span\uff0c\u5982\u679c\u8fd8\u641c\u4e0d\u5230\uff0c\u624d\u7ee7\u7eed\u540e\u7eed\u7684\u6b65\u9aa4\u3002<\/p>\n<h4>\u5411\u7cfb\u7edf\u7533\u8bf7\u5185\u5b58<\/h4>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-function\"><span class=\"hljs-keyword\">bool<\/span> <span class=\"hljs-title\">GrowHeap<\/span><span class=\"hljs-params\">(Length n)<\/span><\/span>;\r\n<\/code><\/pre>\n<p>\u627e\u4e0d\u5230\u5408\u9002\u7684\u7a7a\u95f2span\uff0c\u5c31\u53ea\u80fd\u5411\u7cfb\u7edf\u7533\u8bf7\u65b0\u7684\u5185\u5b58\u4e86\u3002<\/p>\n<p>TCMalloc\u4ee5<code>sbrk()<\/code>\u548c<code>mmap()<\/code>\u4e24\u79cd\u65b9\u5f0f\u5411\u7cfb\u7edf\u7533\u8bf7\u5185\u5b58\uff0c\u6240\u7533\u8bf7\u5185\u5b58\u7684\u5927\u5c0f\u548c\u4f4d\u7f6e\u5747\u6309page\u5bf9\u9f50\uff0c\u4f18\u5148\u4f7f\u7528<code>sbrk()<\/code>\uff0c\u7533\u8bf7\u5931\u8d25\u5219\u4f1a\u5c1d\u8bd5\u4f7f\u7528<code>mmap()<\/code>\uff0864\u4f4d\u7cfb\u7edfDebug\u6a21\u5f0f\u4f18\u5148\u4f7f\u7528mmap\uff0c\u539f\u56e0\u8be6\u89c1<code>InitSystemAllocators()<\/code>\u6ce8\u91ca\uff09\u3002<\/p>\n<p>TCMalloc\u5411\u7cfb\u7edf\u7533\u8bf7\u5e94\u7528\u7a0b\u5e8f\u6240\u4f7f\u7528\u7684\u5185\u5b58\u65f6\uff0c<strong>\u6bcf\u6b21\u81f3\u5c11\u5c1d\u8bd5\u7533\u8bf71MB<\/strong>\uff08<code>kMinSystemAlloc<\/code>\uff09\uff0c\u7533\u8bf7TCMalloc\u81ea\u8eab\u5143\u6570\u636e\u6240\u4f7f\u7528\u7684\u5185\u5b58\u65f6\uff0c\u6bcf\u6b21\u81f3\u5c11\u7533\u8bf78MB\uff08<code>kMetadataAllocChunkSize<\/code>\uff09\u3002\u8fd9\u6837\u505a\u6709\u4e24\u70b9\u597d\u5904\uff1a<\/p>\n<ul>\n<li>\u51cf\u5c11\u5916\u90e8\u5185\u5b58\u788e\u7247\uff08\u51cf\u5c11\u6240\u7533\u8bf7\u5185\u5b58\u4e0eTCMalloc\u5143\u6570\u636e\u6240\u5360\u5185\u5b58\u7684\u4ea4\u66ff\uff09<\/li>\n<li>\u5747\u644a\u7cfb\u7edf\u8c03\u7528\u7684\u5f00\u9500\uff0c\u63d0\u5347\u6027\u80fd<\/li>\n<\/ul>\n<p>\u53e6\u5916\uff0c\u5f53<strong>\u4ece\u7cfb\u7edf\u7533\u8bf7\u7684\u603b\u5185\u5b58\u8d85\u8fc7128MB\u65f6\u5c31\u4e3aPageMap\u4e00\u6b21\u6027\u7533\u8bf7\u4e00\u5927\u5757\u5185\u5b58<\/strong>\uff0c\u4fdd\u8bc1\u53ef\u4ee5\u5b58\u50a8\u6240\u6709page\u548cspan\u7684\u5bf9\u5e94\u5173\u7cfb\u3002\u8fd9\u4e00\u4e3e\u63aa\u53ef\u4ee5\u51cf\u5c11TCMalloc\u7684\u5143\u6570\u636e\u5c06\u5185\u5b58\u5206\u5757\u800c\u5bfc\u81f4\u7684\u5916\u90e8\u788e\u7247\u3002\u4ece\u6e90\u7801\u4e2d\u53ef\u4ee5\u53d1\u73b0\uff0c\u4ec5\u572832\u4f4d\u7cfb\u7edf\u4e0b\u624d\u4f1a\u8fd9\u6837\u505a\uff0c\u53ef\u80fd\u662f\u56e0\u4e3a64\u4f4d\u7cfb\u7edf\u5185\u5b58\u7684\u7406\u8bba\u4e0a\u9650\u592a\u5927\uff0c\u4e0d\u592a\u73b0\u5b9e\u3002<\/p>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-comment\">\/\/ bool PageHeap::GrowHeap(Length n);<\/span>\r\n<span class=\"hljs-keyword\">if<\/span> (old_system_bytes &lt; kPageMapBigAllocationThreshold\r\n    &amp;&amp; stats_.system_bytes &gt;= kPageMapBigAllocationThreshold) {\r\n  pagemap_.PreallocateMoreMemory();\r\n}\r\n<\/code><\/pre>\n<h5>sbrk<\/h5>\n<p>\u5148\u6765\u770b\u5982\u4f55\u4f7f\u7528<code>sbrk()<\/code>\u4eceHeap\u6bb5\u7533\u8bf7\u5185\u5b58\uff0c\u4e0b\u56fe\u5c55\u793a\u4e86<code>SbrkSysAllocator::Alloc()<\/code>\u7684\u6267\u884c\u6d41\u7a0b\uff0c\u4e3a\u4e86\u8bf4\u660e\u5916\u90e8\u788e\u7247\u7684\u4ea7\u751f\uff0c\u5e76\u8986\u76d6\u5230<code>SbrkSysAllocator::Alloc()<\/code>\u7684\u5927\u90e8\u5206\u6d41\u7a0b\uff0c\u5047\u8bbepage\u5927\u5c0f\u4e3a8KB\uff0c\u6240\u7533\u8bf7\u7684\u5185\u5b58\u5927\u5c0f\u4e3a16KB\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"962\" data-height=\"503\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-32eb11969d240b94.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/962\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-32eb11969d240b94.png\" data-original-width=\"962\" data-original-height=\"503\" data-original-format=\"image\/png\" data-original-filesize=\"87482\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-SbrkAlloc<\/div>\n<\/div>\n<ol>\n<li>\u5047\u8bbe\u5728\u7533\u8bf7\u5185\u5b58\u4e4b\u524d\uff0cpb\uff08program break\uff0c\u53ef\u4ee5\u8ba4\u4e3a\u662f\u5806\u5185\u5b58\u7684\u4e0a\u8fb9\u754c\uff09\u6307\u5411\u7ea2\u8272\u7bad\u5934\u6240\u793a\u4f4d\u7f6e\uff0c\u5373\u6ca1\u6709\u5728page\u7684\u8fb9\u754c\u5904\u3002<\/li>\n<li>\u7b2c\u4e00\u6b21sbrk\u7533\u8bf716KB\u5185\u5b58\uff0c\u56e0\u6b64pb\u79fb\u81f3\u7eff\u8272\u7bad\u5934\u6240\u793a\u4f4d\u7f6e\u3002<\/li>\n<li>\u7531\u4e8e\u9700\u8981\u5bf9\u7533\u8bf7\u7684\u5185\u5b58\u6309page\u5bf9\u9f50\uff0c\u56e0\u6b64\u9700\u8981\u7b2c\u4e8c\u6b21sbrk\uff0cpb\u6307\u5411\u84dd\u8272\u7bad\u5934\u6240\u793a\u4f4d\u7f6e\uff0cpage\u7684\u8fb9\u754c\u5904\u3002<\/li>\n<li>\u6700\u7ec8\uff0c\u8fd4\u56de\u7684\u5185\u5b58\u5730\u5740\u4e3a\u9ed1\u8272\u7bad\u5934\u6240\u793a\u4f4d\u7f6e\uff0c\u9ed1\u8272\u548c\u84dd\u8272\u7bad\u5934\u4e4b\u95f4\u521a\u597d16KB\u3002<\/li>\n<\/ol>\n<p>\u53ef\u4ee5\u770b\u51fa\uff0c\u7ea2\u8272\u7bad\u5934\u548c\u9ed1\u8272\u7bad\u5934\u4e4b\u95f4\u7684\u5185\u5b58\u5c31\u65e0\u6cd5\u88ab\u4f7f\u7528\u4e86\uff0c\u4ea7\u751f\u4e86<strong>\u5916\u90e8\u788e\u7247<\/strong>\u3002<\/p>\n<h5>mmap<\/h5>\n<p>\u5982\u679c\u4f7f\u7528sbrk\u7533\u8bf7\u5185\u5b58\u5931\u8d25\uff0cTCMalloc\u4f1a\u5c1d\u8bd5\u4f7f\u7528mmap\u6765\u5206\u914d\u3002\u540c\u6837\uff0c\u4e3a\u4e86\u8986\u76d6<code>MmapSysAllocator::Alloc()<\/code>\u7684\u5927\u90e8\u5206\u60c5\u51b5\uff0c\u4e0b\u56fe\u5047\u8bbe\u7cfb\u7edf\u7684page\u4e3a4KB\uff0cTCMalloc\u7684page\u4e3a16KB\uff0c\u7533\u8bf7\u7684\u5185\u5b58\u5927\u5c0f\u4e3a32KB\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"788\" data-height=\"587\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-da50e95f40af9eab.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/788\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-da50e95f40af9eab.png\" data-original-width=\"788\" data-original-height=\"587\" data-original-format=\"image\/png\" data-original-filesize=\"94636\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-MmapAlloc<\/div>\n<\/div>\n<ol>\n<li>\u5047\u8bbe\u5728\u7533\u8bf7\u5185\u5b58\u4e4b\u524d\uff0cmmap\u6bb5\u7684\u8fb9\u754c\u4f4d\u4e8e\u7ea2\u8272\u7bad\u5934\u6240\u793a\u4f4d\u7f6e\u3002<\/li>\n<li>\u7b2c\u4e00\u6b21mmap\uff0c\u4f1a\u572832KB\u7684\u57fa\u7840\u4e0a\uff0c\u591a\u7533\u8bf7(\u5bf9\u9f50\u5927\u5c0f &#8211; \u7cfb\u7edfpage\u5927\u5c0f) = 16 -4 = 12KB\u7684\u5185\u5b58\u3002\u6b64\u65f6mmap\u7684\u8fb9\u754c\u4f4d\u4e8e\u7eff\u8272\u7bad\u5934\u6240\u793a\u4f4d\u7f6e\u3002<\/li>\n<li>\u7136\u540e\u901a\u8fc7\u4e24\u6b21munmap\u5c06\u6240\u7533\u8bf7\u5185\u5b58\u7684\u4e24\u4fa7\u8fb9\u754c\u5206\u522b\u5bf9\u9f50\u5230TCMalloc\u7684page\u8fb9\u754c\u3002<\/li>\n<li>\u6700\u7ec8\u7533\u8bf7\u5230\u7684\u5185\u5b58\u4e3a\u4e24\u4e2a\u84dd\u8272\u7bad\u5934\u4e4b\u95f4\u7684\u90e8\u5206\uff0c\u8fd4\u56de\u5de6\u4fa7\u84dd\u8272\u7bad\u5934\u6240\u6307\u793a\u7684\u5185\u5b58\u5730\u5740\u3002<\/li>\n<\/ol>\n<p>\u5982\u679c\u7533\u8bf7\u5185\u5b58\u6210\u529f\uff0c\u5219\u521b\u5efa\u4e00\u4e2a\u65b0\u7684span\u5e76\u7acb\u5373\u5220\u9664\uff0c\u53ef\u5c06\u5176\u653e\u5165\u7a7a\u95f2span\u7684\u94fe\u8868\u6216set\u4e2d\uff0c\u7136\u540e\u7ee7\u7eed\u540e\u9762\u7684\u6b65\u9aa4\u3002<\/p>\n<h4>\u6700\u540e\u7684\u641c\u7d22<\/h4>\n<p>\u6700\u540e\uff0c\u91cd\u65b0\u641c\u7d22\u4e00\u6b21\u7a7a\u95f2span\uff0c\u5982\u679c\u8fd8\u627e\u4e0d\u5230\u5408\u9002\u7684\u7a7a\u95f2span\uff0c\u90a3\u5c31\u8ba4\u4e3a\u662f\u521b\u5efa\u5931\u8d25\u4e86\u3002<\/p>\n<p>\u81f3\u6b64\uff0c\u521b\u5efaspan\u7684\u64cd\u4f5c\u7ed3\u675f\u3002<\/p>\n<h3>\u5220\u9664Span<\/h3>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-comment\">\/\/ Delete the span \"[p, p+n-1]\".<\/span>\r\n<span class=\"hljs-comment\">\/\/ REQUIRES: span was returned by earlier call to New() and<\/span>\r\n<span class=\"hljs-comment\">\/\/           has not yet been deleted.<\/span>\r\n<span class=\"hljs-function\"><span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-title\">Delete<\/span><span class=\"hljs-params\">(Span* span)<\/span><\/span>;\r\n<\/code><\/pre>\n<p>\u5f53span\u6240\u62c6\u5206\u6210\u7684\u5c0f\u5bf9\u8c61\u5168\u90e8\u88ab\u5e94\u7528\u7a0b\u5e8f\u91ca\u653e\u53d8\u4e3a\u7a7a\u95f2\u5bf9\u8c61\uff0c\u6216\u8005\u4f5c\u4e3a\u4e2d\u5bf9\u8c61\u6216\u5927\u5bf9\u8c61\u4f7f\u7528\u7684span\u88ab\u5e94\u7528\u7a0b\u5e8f\u91ca\u653e\u65f6\uff0c\u9700\u8981\u5c06span\u5220\u9664\u3002\u4e0d\u8fc7\u5e76\u4e0d\u662f\u771f\u6b63\u7684\u5220\u9664\uff0c\u800c\u662f\u653e\u5230\u7a7a\u95f2span\u7684\u94fe\u8868\u6216set\u4e2d\u3002<\/p>\n<p>\u5220\u9664\u7684\u64cd\u4f5c\u975e\u5e38\u7b80\u5355\uff0c\u4f46\u53ef\u80fd\u4f1a\u89e6\u53d1\u5408\u5e76span\u7684\u64cd\u4f5c\uff0c\u4ee5\u53ca\u91ca\u653e\u5185\u5b58\u5230\u7cfb\u7edf\u7684\u64cd\u4f5c\u3002<\/p>\n<h4>\u5408\u5e76Span<\/h4>\n<p>\u5f53span\u88abdelete\u65f6\uff0c\u4f1a\u5c1d\u8bd5\u5411\u524d\u5411\u540e\u5408\u5e76\u4e00\u4e2aspan\u3002<\/p>\n<p>\u5408\u5e76\u89c4\u5219\u5982\u4e0b\uff1a<\/p>\n<ul>\n<li>\u53ea\u6709\u5728\u865a\u62df\u5185\u5b58\u7a7a\u95f4\u4e0a\u8fde\u7eed\u7684span\u624d\u53ef\u4ee5\u88ab\u5408\u5e76\u3002<\/li>\n<li>\u53ea\u6709\u540c\u662fnormal\u72b6\u6001\u7684span\u6216\u540c\u662freturned\u72b6\u6001\u7684span\u624d\u53ef\u4ee5\u88ab\u5408\u5e76\u3002<\/li>\n<\/ul>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"696\" data-height=\"142\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-b5c2296a301bfd96.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/696\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-b5c2296a301bfd96.png\" data-original-width=\"696\" data-original-height=\"142\" data-original-format=\"image\/png\" data-original-filesize=\"20564\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-SpanMerge1<\/div>\n<\/div>\n<p>\u4e0a\u56fe\u4e2d\uff0c\u88ab\u5220\u9664\u7684span\u7684\u524d\u4e00\u4e2aspan\u662fnormal\u72b6\u6001\uff0c\u56e0\u6b64\u53ef\u4ee5\u4e0e\u4e4b\u5408\u5e76\uff0c\u800c\u540e\u4e00\u4e2aspan\u662freturned\u72b6\u6001\uff0c\u65e0\u6cd5\u4e0e\u4e4b\u5408\u5e76\u3002\u5408\u5e76\u64cd\u4f5c\u4e4b\u540e\u5982\u4e0b\u56fe\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"696\" data-height=\"139\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-510c27abd81f1a1a.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/696\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-510c27abd81f1a1a.png\" data-original-width=\"696\" data-original-height=\"139\" data-original-format=\"image\/png\" data-original-filesize=\"12791\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-SpanMerge2<\/div>\n<\/div>\n<p>\u8fd8\u6709\u4e00\u4e2a\u503c\u5f97\u6ce8\u610f\u7684\u5f00\u5173\uff1a<code>aggressive_decommit_<\/code>\uff0c\u5f00\u542f\u540eTCMalloc\u4f1a\u79ef\u6781\u7684\u91ca\u653e\u5185\u5b58\u7ed9\u7cfb\u7edf\uff0c\u9ed8\u8ba4\u662f\u5173\u95ed\u72b6\u6001\uff0c\u53ef\u901a\u8fc7\u4ee5\u4e0b\u65b9\u5f0f\u66f4\u6539\uff1a<\/p>\n<pre class=\"hljs php\"><code class=\"php\">MallocExtension::instance()-&gt;SetNumericProperty(<span class=\"hljs-string\">\"tcmalloc.aggressive_memory_decommit\"<\/span>, value)\r\n<\/code><\/pre>\n<p>\u5f53\u5f00\u542f\u4e86<code>aggressive_decommit_<\/code>\u540e\uff0c\u5220\u9664normal\u72b6\u6001\u7684span\u65f6\u4f1a\u5c1d\u8bd5\u5c06\u5176\u91ca\u653e\u7ed9\u7cfb\u7edf\uff0c\u91ca\u653e\u6210\u529f\u5219\u72b6\u6001\u53d8\u4e3areturned\u3002<\/p>\n<p>\u5728\u5408\u5e76\u65f6\uff0c\u5982\u679c\u88ab\u5220\u9664\u7684span\u6b64\u65f6\u662freturned\u72b6\u6001\uff0c\u5219\u4f1a\u5c06\u4e0e\u5176\u76f8\u90bb\u7684normal\u72b6\u6001\u7684span\u4e5f\u91ca\u653e\u7ed9\u7cfb\u7edf\uff0c\u7136\u540e\u518d\u5c1d\u8bd5\u5408\u5e76\u3002<\/p>\n<p>\u56e0\u6b64\uff0c\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c\u88ab\u5220\u9664\u7684span\u548c\u5176\u524d\u4e00\u4e2aspan\u90fd\u4f1a\u88ab\u66f4\u6539\u4e3areturned\u72b6\u6001\uff0c\u5408\u5e76\u4e4b\u540e\u5982\u4e0b\uff0c\u5373\u4e09\u4e2aspan\u88ab\u5408\u5e76\u6210\u4e3a\u4e00\u4e2aspan\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"696\" data-height=\"139\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-5f5d280cb214ea25.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/696\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-5f5d280cb214ea25.png\" data-original-width=\"696\" data-original-height=\"139\" data-original-format=\"image\/png\" data-original-filesize=\"8689\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-SpanMerge3<\/div>\n<\/div>\n<h4>\u91ca\u653espan<\/h4>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-function\">Length <span class=\"hljs-title\">ReleaseAtLeastNPages<\/span><span class=\"hljs-params\">(Length num_pages)<\/span><\/span>;\r\n<\/code><\/pre>\n<p>\u5728delete\u4e00\u4e2aspan\u65f6\u8fd8\u4f1a\u4ee5\u4e00\u5b9a\u7684\u9891\u7387\u89e6\u53d1\u91ca\u653espan\u7684\u5185\u5b58\u7ed9\u7cfb\u7edf\u7684\u64cd\u4f5c\uff08<code>ReleaseAtLeastNPages()<\/code>\uff09\u3002\u91ca\u653e\u7684\u9891\u7387\u53ef\u4ee5\u901a\u8fc7\u73af\u5883\u53d8\u91cf<code>TCMALLOC_RELEASE_RATE<\/code>\u6765\u4fee\u6539\u3002<strong>\u9ed8\u8ba4\u503c\u4e3a1\uff0c\u8868\u793a\u6bcf\u5220\u96641000\u4e2apage\u5c31\u5c1d\u8bd5\u91ca\u653e\u81f3\u5c111\u4e2apage<\/strong>\uff0c2\u8868\u793a\u6bcf\u5220\u9664500\u4e2apage\u5c1d\u8bd5\u91ca\u653e\u81f3\u5c111\u4e2apage\uff0c\u4f9d\u6b21\u7c7b\u63a8\uff0c10\u8868\u793a\u6bcf\u5220\u9664100\u4e2apage\u5c1d\u8bd5\u91ca\u653e\u81f3\u5c111\u4e2apage\u30020\u8868\u793a\u6c38\u8fdc\u4e0d\u91ca\u653e\uff0c\u503c\u8d8a\u5927\u8868\u793a\u91ca\u653e\u7684\u8d8a\u5feb\uff0c\u5408\u7406\u7684\u53d6\u503c\u533a\u95f4\u4e3a[0, 10]\u3002<\/p>\n<p>\u91ca\u653e\u89c4\u5219\uff1a<\/p>\n<ul>\n<li>\u4ece\u5c0f\u5230\u5927\u5faa\u73af\uff0c\u6309\u987a\u5e8f\u91ca\u653e\u7a7a\u95f2span\uff0c\u76f4\u5230\u91ca\u653e\u7684page\u6570\u91cf\u6ee1\u8db3\u9700\u6c42\u3002<\/li>\n<li>\u591a\u6b21\u8c03\u7528\u4f1a\u4ece\u4e0a\u4e00\u6b21\u5faa\u73af\u7ed3\u675f\u7684\u4f4d\u7f6e\u7ee7\u7eed\u5faa\u73af\uff0c\u800c\u4e0d\u4f1a\u91cd\u65b0\u4ece\u5934\uff081 page\uff09\u5f00\u59cb\u3002<\/li>\n<li>\u91ca\u653e\u7684\u8fc7\u7a0b\u4e2d\u80fd\u5408\u5e76span\u5c31\u5408\u5e76span<\/li>\n<li>\u53ef\u80fd\u91ca\u653e\u5c11\u4e8enum_pages\uff0c\u6ca1\u90a3\u4e48\u591afree\u7684span\u4e86\u3002<\/li>\n<li>\u53ef\u80fd\u91ca\u653e\u591a\u4e8enum_pages\uff0c\u8fd8\u5dee\u4e00\u70b9\u5c31\u591fnum_pages\u4e86\uff0c\u4f46\u521a\u597d\u78b0\u5230\u4e00\u4e2a\u5f88\u5927\u7684span\u3002<\/li>\n<\/ul>\n<p>\u91ca\u653e\u65b9\u5f0f\uff1a<\/p>\n<p>\u5982\u679c\u7cfb\u7edf\u652f\u6301\uff0c\u901a\u8fc7<code>madvise(MADV_DONTNEED)<\/code>\u91ca\u653espan\u5bf9\u5e94\u7684\u5185\u5b58\u3002\u56e0\u6b64\uff0c\u5373\u4f7f\u91ca\u653e\u6210\u529f\uff0c\u5bf9\u5e94\u7684\u865a\u62df\u5185\u5b58\u5730\u5740\u7a7a\u95f4\u4ecd\u7136\u53ef\u8bbf\u95ee\uff0c\u4f46\u5185\u5b58\u7684\u5185\u5bb9\u4f1a\u4e22\u5931\uff0c\u5728\u4e0b\u6b21\u8bbf\u95ee\u65f6\u4f1a\u5bfc\u81f4minor page fault\u4ee5\u75280\u6765\u91cd\u65b0\u521d\u59cb\u5316\u3002<\/p>\n<h2>ThreadCache<\/h2>\n<p>TCMalloc\u5206\u914d\u5c0f\u5bf9\u8c61\u7684\u901f\u5ea6\u662f\u975e\u5e38\u5feb\u7684\uff0c\u8fd9\u5f97\u76ca\u4e8e\u5176\u5bf9\u6bcf\u4e2a\u7ebf\u7a0b\u90fd\u6709\u4e00\u4efd\u5355\u72ec\u7684cache\uff0c\u5373ThreadCache\u3002<\/p>\n<p>ThreadCache\u5176\u5b9e\u5c31\u662f\u4e00\u7ec4FreeList\u800c\u5df2\u3002\u5bf9\u4e8e\u6bcf\u4e2asize class\uff0c\u5728ThreadCache\u4e2d\u90fd\u6709\u4e00\u4e2aFreeList\uff0c\u7f13\u5b58\u4e86\u4e00\u7ec4\u7a7a\u95f2\u5bf9\u8c61\uff0c\u5e94\u7528\u7a0b\u5e8f\u7533\u8bf7256KB\u4ee5\u5185\u7684\u5c0f\u5185\u5b58\u65f6\uff0c\u4f18\u5148\u8fd4\u56deFreeList\u4e2d\u7684\u4e00\u4e2a\u7a7a\u95f2\u5bf9\u8c61\u3002\u56e0\u4e3a\u6bcf\u4e2a\u7ebf\u7a0b\u6bcf\u4e2asize class\u90fd\u6709\u5355\u72ec\u7684FreeList\uff0c\u56e0\u6b64\u8fd9\u4e2a\u8fc7\u7a0b\u662f<strong>\u4e0d\u9700\u8981\u52a0\u9501<\/strong>\u7684\uff0c\u901f\u5ea6\u975e\u5e38\u5feb\u3002<\/p>\n<p>\u5982\u679cFreeList\u4e3a\u7a7a\uff0cTCMalloc\u624d\u4f1a\u4ecesize class\u5bf9\u5e94\u7684CentralFreeList\u4e2d\u83b7\u53d6\u4e00\u7ec4\u7a7a\u95f2\u5bf9\u8c61\u653e\u5165ThreadCache\u7684FreeList\u4e2d\uff0c\u5e76\u5c06\u5176\u4e2d\u4e00\u4e2a\u5bf9\u8c61\u8fd4\u56de\u3002\u4eceCentralFreeList\u4e2d\u83b7\u53d6\u7a7a\u95f2\u5bf9\u8c61<strong>\u9700\u8981\u52a0\u9501<\/strong>\u7684\u3002<\/p>\n<p>\u56de\u987e\u4e0bThreadCache\u7684\u7ed3\u6784\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"1041\" data-height=\"966\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-f83d88901f0eb3b4.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/1000\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-f83d88901f0eb3b4.png\" data-original-width=\"1041\" data-original-height=\"966\" data-original-format=\"image\/png\" data-original-filesize=\"299848\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-ThreadCache<\/div>\n<\/div>\n<p>\u5404\u4e2a\u7ebf\u7a0b\u7684ThreadCache\u4e92\u76f8\u8fde\u63a5\u6210\u4e3a\u4e00\u4e2a\u53cc\u5411\u94fe\u8868\uff0c\u4e3b\u8981\u76ee\u7684\u662f\u4e3a\u4e86\u65b9\u4fbf\u7edf\u8ba1\u4fe1\u606f\u3002<\/p>\n<h3>\u6bcf\u7ebf\u7a0bCache<\/h3>\n<p>\u90a3\u4e48\u6bcf\u4e2a\u7ebf\u7a0b\u4e00\u4e2aThreadCache\u662f\u5982\u4f55\u5b9e\u73b0\u7684\u5462\uff1f<\/p>\n<p>\u8fd9\u4f9d\u8d56\u4e8e\u4e24\u79cd\u6280\u672f\uff1aThread Local Storage\uff08TLS)\uff0c\u548cThread Specific Data\uff08TSD\uff09\u3002\u4e24\u8005\u7684\u529f\u80fd\u57fa\u672c\u662f\u4e00\u6837\u7684\uff0c\u90fd\u662f\u63d0\u4f9b\u6bcf\u7ebf\u7a0b\u5b58\u50a8\u3002TLS\u7528\u8d77\u6765\u66f4\u65b9\u4fbf\uff0c\u8bfb\u53d6\u6570\u636e\u66f4\u5feb\uff0c\u4f46\u5728\u7ebf\u7a0b\u9500\u6bc1\u65f6TLS\u65e0\u6cd5\u6267\u884c\u6e05\u7406\u64cd\u4f5c\uff0c\u800cTSD\u53ef\u4ee5\uff0c\u56e0\u6b64TCMalloc\u4f7f\u7528TSD\u4e3a\u6bcf\u4e2a\u7ebf\u7a0b\u63d0\u4f9b\u4e00\u4e2aThreadCache\uff0c\u5982\u679cTLS\u53ef\u7528\uff0c\u5219\u540c\u65f6\u4f7f\u7528TLS\u4fdd\u5b58\u4e00\u4efd\u62f7\u8d1d\u4ee5\u52a0\u901f\u6570\u636e\u7684\u8bbf\u95ee\u3002<\/p>\n<p>TLS\u548cTSD\u7684\u5177\u4f53\u7ec6\u8282\u53ef\u53c2\u8003<a href=\"http:\/\/man7.org\/tlpi\/\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">\u300aThe Linux Programming Interface\u300b<\/a>\u76f8\u5173\u7ae0\u8282\uff0831.3\uff0c31.4\uff09\uff0c\u672c\u6587\u4e0d\u518d\u5c55\u5f00\u8ba8\u8bba\u3002<\/p>\n<p>\u8be6\u7ec6\u53ef\u53c2\u8003\u6e90\u7801\u4e2d<code>ThreadCache::CreateCacheIfNecessary()<\/code>\u51fd\u6570\u548c<code>threadlocal_data_<\/code>\u53d8\u91cf\u76f8\u5173\u4ee3\u7801\u3002<\/p>\n<h3>\u4f55\u65f6\u521b\u5efaThreadCache<\/h3>\n<p>\u5f53\u67d0\u7ebf\u7a0b\u7b2c\u4e00\u6b21\u7533\u8bf7\u5206\u914d\u5185\u5b58\u65f6\uff0cTCMalloc\u4e3a\u8be5\u7ebf\u7a0b\u521b\u5efa\u5176\u4e13\u5c5e\u7684ThreadCache\uff08<code>ThreadCache::GetCache()<\/code>\u00a0-&gt;\u00a0<code>ThreadCache::CreateCacheIfNecessary()<\/code>\uff09\u3002<\/p>\n<h3>\u4f55\u65f6\u9500\u6bc1ThreadCache<\/h3>\n<p>\u5728TCMalloc\u521d\u59cb\u5316TSD\u65f6\uff0c\u4f1a\u8c03\u7528Pthreads API\u4e2d\u7684<code>pthread_key_create()<\/code>\u521b\u5efaThreadCache\u5bf9\u5e94\u7684key\uff0c\u5e76\u4e14\u6307\u5b9a\u4e86\u9500\u6bc1ThreadCache\u7684\u51fd\u6570<code>ThreadCache::DestroyThreadCache()<\/code>\u3002\u56e0\u6b64\uff0c\u5f53\u4e00\u4e2a\u7ebf\u7a0b\u9500\u6bc1\u65f6\uff0c\u5176\u5bf9\u5e94\u7684ThreadCache\u4f1a\u7531\u8be5\u51fd\u6570\u9500\u6bc1\u3002<\/p>\n<h3>ThreadCache\u7684\u5927\u5c0f<\/h3>\n<p>TCMalloc\u5b9a\u4e49\u4e86\u4e00\u4e9b\u53d8\u91cf\u6765<strong>\u5efa\u8bae<\/strong>ThreadCache\u7684\u5927\u5c0f\u3002\u6ce8\u610f\uff0c\u662f\u5efa\u8bae\uff0c\u800c\u975e\u5f3a\u5236\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u5b9e\u9645\u7684\u5927\u5c0f\u53ef\u80fd\u4f1a\u8d85\u8fc7\u8fd9\u4e9b\u503c\u3002<\/p>\n<p>\u6240\u6709\u7ebf\u7a0b\u7684ThreadCache\u7684\u603b\u5927\u5c0f\u9650\u5236\uff08<code>overall_thread_cache_size_<\/code>\uff09\u9ed8\u8ba4\u4e3a32MB\uff08<code>kDefaultOverallThreadCacheSize<\/code>\uff09\uff0c\u53d6\u503c\u8303\u56f4512KB~1GB\uff0c\u53ef\u4ee5\u901a\u8fc7\u73af\u5883\u53d8\u91cf<code>TCMalloc_MAX_TOTAL_THREAD_CACHE_BYTES<\/code>\u6216\u4ee5\u4e0b\u65b9\u5f0f\u6765\u8fdb\u884c\u8c03\u6574\uff1a<\/p>\n<pre class=\"hljs php\"><code class=\"php\">MallocExtension::instance()-&gt;SetNumericProperty(<span class=\"hljs-string\">\"TCMalloc.max_total_thread_cache_bytes\"<\/span>, value);\r\n<\/code><\/pre>\n<p>\u6bcf\u4e2a\u7ebf\u7a0b\u7684ThreadCache\u7684\u5927\u5c0f\u9650\u5236\u9ed8\u8ba4\u4e3a4MB\uff08<code>kMaxThreadCacheSize<\/code>\uff09\u3002\u8c03\u6574ThreadCache\u603b\u5927\u5c0f\u65f6\uff0c\u4f1a\u4fee\u6539\u6bcf\u4e2aThreadCache\u7684\u5927\u5c0f\u9650\u5236\u5230512KB~4MB\u4e4b\u95f4\u7684\u76f8\u5e94\u503c\u3002<\/p>\n<h3>\u6162\u542f\u52a8\u7b97\u6cd5\uff1aFreeList\u7684\u957f\u5ea6\u63a7\u5236<\/h3>\n<p>\u63a7\u5236ThreadCache\u4e2d\u5404\u4e2aFreeList\u4e2d\u5143\u7d20\u7684\u6570\u91cf\u662f\u5f88\u91cd\u8981\u7684\uff1a<\/p>\n<ul>\n<li>\u592a\u5c0f\uff1a\u4e0d\u591f\u7528\uff0c\u9700\u8981\u7ecf\u5e38\u53bbCentralCache\u83b7\u53d6\u7a7a\u95f2\u5bf9\u8c61\uff0c\u5e26\u9501\u64cd\u4f5c<\/li>\n<li>\u592a\u5927\uff1a\u592a\u591a\u5bf9\u8c61\u5728\u7a7a\u95f2\u5217\u8868\u4e2d\u95f2\u7f6e\uff0c\u6d6a\u8d39\u5185\u5b58<\/li>\n<\/ul>\n<p>\u4e0d\u4ec5\u662f\u5185\u5b58\u5206\u914d\uff0c\u5bf9\u4e8e\u5185\u5b58\u91ca\u653e\u6765\u8bf4\u63a7\u5236FreeList\u7684\u957f\u5ea6\u4e5f\u5f88\u91cd\u8981\uff1a<\/p>\n<ul>\n<li>\u592a\u5c0f\uff1a\u9700\u8981\u7ecf\u5e38\u5c06\u7a7a\u95f2\u5bf9\u8c61\u79fb\u81f3CentralCache\uff0c\u5e26\u9501\u64cd\u4f5c<\/li>\n<li>\u592a\u5927\uff1a\u592a\u591a\u5bf9\u8c61\u5728\u7a7a\u95f2\u5217\u8868\u4e2d\u95f2\u7f6e\uff0c\u6d6a\u8d39\u5185\u5b58<\/li>\n<\/ul>\n<p>\u5e76\u4e14\uff0c\u6709\u4e9b\u7ebf\u7a0b\u7684\u5206\u914d\u548c\u91ca\u653e\u662f\u4e0d\u5bf9\u79f0\u7684\uff0c\u6bd4\u5982\u751f\u4ea7\u8005\u7ebf\u7a0b\u548c\u6d88\u8d39\u8005\u7ebf\u7a0b\uff0c\u8fd9\u4e5f\u662f\u9700\u8981\u8003\u8651\u7684\u4e00\u4e2a\u70b9\u3002<\/p>\n<p>\u7c7b\u4f3cTCP\u7684\u62e5\u585e\u63a7\u5236\u7b97\u6cd5\uff0cTCMalloc\u91c7\u7528\u4e86\u6162\u542f\u52a8\uff08slow start\uff09\u7684\u65b9\u5f0f\u6765\u63a7\u5236FreeList\u7684\u957f\u5ea6\uff0c\u5176\u6548\u679c\u5982\u4e0b\uff1a<\/p>\n<ul>\n<li>FreeList\u88ab\u4f7f\u7528\u7684\u8d8a\u9891\u7e41\uff0c\u6700\u5927\u957f\u5ea6\u5c31\u8d8a\u5927\u3002<\/li>\n<li>\u5982\u679cFreeList\u66f4\u591a\u7684\u7528\u4e8e\u91ca\u653e\u800c\u4e0d\u662f\u5206\u914d\uff0c\u5219\u5176\u6700\u5927\u957f\u5ea6\u5c06\u4ec5\u4f1a\u589e\u957f\u5230\u67d0\u4e00\u4e2a\u70b9\uff0c\u4ee5\u6709\u6548\u7684\u5c06\u6574\u4e2a\u7a7a\u95f2\u5bf9\u8c61\u94fe\u8868\u4e00\u6b21\u6027\u79fb\u52a8\u5230CentralCache\u4e2d\u3002<\/li>\n<\/ul>\n<p>\u5206\u914d\u5185\u5b58\u65f6\u7684\u6162\u542f\u52a8\u4ee3\u7801\u5982\u4e0b\uff08<code>FetchFromCentralCache<\/code>\uff09\uff1a<\/p>\n<pre class=\"hljs php\"><code class=\"php\"><span class=\"hljs-keyword\">const<\/span> int batch_size = <span class=\"hljs-keyword\">Static<\/span>::sizemap()-&gt;num_objects_to_move(cl);\r\n\r\n<span class=\"hljs-comment\">\/\/ Increase max length slowly up to batch_size.  After that,<\/span>\r\n<span class=\"hljs-comment\">\/\/ increase by batch_size in one shot so that the length is a<\/span>\r\n<span class=\"hljs-comment\">\/\/ multiple of batch_size.<\/span>\r\n<span class=\"hljs-keyword\">if<\/span> (<span class=\"hljs-keyword\">list<\/span>-&gt;max_length() &lt; batch_size) {\r\n  <span class=\"hljs-keyword\">list<\/span>-&gt;set_max_length(<span class=\"hljs-keyword\">list<\/span>-&gt;max_length() + <span class=\"hljs-number\">1<\/span>);\r\n} <span class=\"hljs-keyword\">else<\/span> { \r\n  <span class=\"hljs-comment\">\/\/ Don't let the list get too long.  In 32 bit builds, the length<\/span>\r\n  <span class=\"hljs-comment\">\/\/ is represented by a 16 bit int, so we need to watch out for<\/span>\r\n  <span class=\"hljs-comment\">\/\/ integer overflow.<\/span>\r\n  int new_length = min&lt;int&gt;(<span class=\"hljs-keyword\">list<\/span>-&gt;max_length() + batch_size,\r\n                            kMaxDynamicFreeListLength);\r\n  <span class=\"hljs-comment\">\/\/ The list's max_length must always be a multiple of batch_size,<\/span>\r\n  <span class=\"hljs-comment\">\/\/ and kMaxDynamicFreeListLength is not necessarily a multiple<\/span>\r\n  <span class=\"hljs-comment\">\/\/ of batch_size.<\/span>\r\n  new_length -= new_length % batch_size;\r\n  ASSERT(new_length % batch_size == <span class=\"hljs-number\">0<\/span>);\r\n  <span class=\"hljs-keyword\">list<\/span>-&gt;set_max_length(new_length);\r\n}\r\n<\/code><\/pre>\n<p>max_length\u5373\u4e3aFreeList\u7684\u6700\u5927\u957f\u5ea6\uff0c\u521d\u59cb\u503c\u4e3a1\u3002batch_size\u662fsize class\u4e00\u8282\u63d0\u5230\u7684\u4e00\u6b21\u6027\u79fb\u52a8\u7a7a\u95f2\u5bf9\u8c61\u7684\u6570\u91cf\uff0c\u5176\u503c\u56e0size class\u800c\u5f02\u3002<\/p>\n<p>\u53ef\u4ee5\u770b\u5230\uff0c\u53ea\u8981max_length\u6ca1\u6709\u8d85\u8fc7batch_size\uff0c\u6bcf\u5f53FreeList\u4e2d\u6ca1\u6709\u5143\u7d20\u9700\u8981\u4eceCentralCache\u83b7\u53d6\u7a7a\u95f2\u5bf9\u8c61\u65f6\uff08\u5373<code>FetchFromCentralCache<\/code>\uff09\uff0cmax_length\u5c31\u52a01\u3002<\/p>\n<p>\u4e00\u65e6max_length\u8fbe\u5230batch_size\uff0c\u63a5\u4e0b\u6765\u6bcf\u6b21<code>FetchFromCentralCache<\/code>\u5c31\u4f1a\u5bfc\u81f4max_length\u589e\u52a0batch_size\u3002<\/p>\n<p>\u4f46\u5e76\u4e0d\u4f1a\u65e0\u9650\u5236\u7684\u589e\u52a0\uff0c\u6700\u5927\u5230<code>kMaxDynamicFreeListLength<\/code>\uff088192\uff09\uff0c\u4ee5\u907f\u514d\u4eceFreeList\u5411CentralCache\u79fb\u52a8\u5bf9\u8c61\u65f6\uff0c\u56e0\u4e3a\u5bf9\u8c61\u8fc7\u591a\u800c\u8fc7\u957f\u7684\u5360\u7528\u9501\u3002<\/p>\n<p>\u518d\u6765\u770b\u5185\u5b58\u56de\u6536\u65f6\u7684\u60c5\u51b5\uff0c\u6bcf\u6b21\u91ca\u653e\u5c0f\u5bf9\u8c61\uff0c\u90fd\u4f1a\u68c0\u67e5FreeList\u7684\u5f53\u524d\u957f\u5ea6\u662f\u5426\u8d85\u8fc7max_length\uff1a<\/p>\n<pre class=\"hljs php\"><code class=\"php\"><span class=\"hljs-keyword\">if<\/span> (PREDICT_FALSE(length &gt; <span class=\"hljs-keyword\">list<\/span>-&gt;max_length())) {\r\n  ListTooLong(<span class=\"hljs-keyword\">list<\/span>, cl);\r\n  <span class=\"hljs-keyword\">return<\/span>;\r\n} \r\n<\/code><\/pre>\n<p>\u5982\u679c\u8d85\u957f\uff0c\u5219\u6267\u884c\u4ee5\u4e0b\u903b\u8f91\uff1a<\/p>\n<pre class=\"hljs php\"><code class=\"php\">void ThreadCache::ListTooLong(FreeList* <span class=\"hljs-keyword\">list<\/span>, uint32 cl) {\r\n  size_ += <span class=\"hljs-keyword\">list<\/span>-&gt;object_size();\r\n    \r\n  <span class=\"hljs-keyword\">const<\/span> int batch_size = <span class=\"hljs-keyword\">Static<\/span>::sizemap()-&gt;num_objects_to_move(cl);\r\n  ReleaseToCentralCache(<span class=\"hljs-keyword\">list<\/span>, cl, batch_size);\r\n  \r\n  <span class=\"hljs-comment\">\/\/ If the list is too long, we need to transfer some number of<\/span>\r\n  <span class=\"hljs-comment\">\/\/ objects to the central cache.  Ideally, we would transfer<\/span>\r\n  <span class=\"hljs-comment\">\/\/ num_objects_to_move, so the code below tries to make max_length<\/span>\r\n  <span class=\"hljs-comment\">\/\/ converge on num_objects_to_move.<\/span>\r\n      \r\n  <span class=\"hljs-keyword\">if<\/span> (<span class=\"hljs-keyword\">list<\/span>-&gt;max_length() &lt; batch_size) {\r\n    <span class=\"hljs-comment\">\/\/ Slow start the max_length so we don't overreserve.<\/span>\r\n    <span class=\"hljs-keyword\">list<\/span>-&gt;set_max_length(<span class=\"hljs-keyword\">list<\/span>-&gt;max_length() + <span class=\"hljs-number\">1<\/span>);\r\n  } <span class=\"hljs-keyword\">else<\/span> <span class=\"hljs-keyword\">if<\/span> (<span class=\"hljs-keyword\">list<\/span>-&gt;max_length() &gt; batch_size) {\r\n    <span class=\"hljs-comment\">\/\/ If we consistently go over max_length, shrink max_length.  If we don't<\/span>\r\n    <span class=\"hljs-comment\">\/\/ shrink it, some amount of memory will always stay in this freelist.<\/span>\r\n    <span class=\"hljs-keyword\">list<\/span>-&gt;set_length_overages(<span class=\"hljs-keyword\">list<\/span>-&gt;length_overages() + <span class=\"hljs-number\">1<\/span>);\r\n    <span class=\"hljs-keyword\">if<\/span> (<span class=\"hljs-keyword\">list<\/span>-&gt;length_overages() &gt; kMaxOverages) {\r\n      ASSERT(<span class=\"hljs-keyword\">list<\/span>-&gt;max_length() &gt; batch_size);\r\n      <span class=\"hljs-keyword\">list<\/span>-&gt;set_max_length(<span class=\"hljs-keyword\">list<\/span>-&gt;max_length() - batch_size);\r\n      <span class=\"hljs-keyword\">list<\/span>-&gt;set_length_overages(<span class=\"hljs-number\">0<\/span>);\r\n    }\r\n  }\r\n\r\n  <span class=\"hljs-keyword\">if<\/span> (PREDICT_FALSE(size_ &gt; max_size_)) {\r\n    Scavenge();\r\n  }\r\n}\r\n<\/code><\/pre>\n<p>\u4e0e\u5185\u5b58\u5206\u914d\u7684\u60c5\u51b5\u7c7b\u4f3c\uff0c\u53ea\u8981max_length\u8fd8\u6ca1\u6709\u8fbe\u5230batch_size\uff0c\u6bcf\u5f53FreeList\u7684\u957f\u5ea6\u8d85\u8fc7max_length\uff0cmax_length\u7684\u503c\u5c31\u52a01\u3002<\/p>\n<p>\u5f53max_length\u8fbe\u5230\u6216\u8d85\u8fc7batch_size\u540e\uff0c\u5e76\u4e0d\u4f1a\u7acb\u5373\u8c03\u6574max_length\uff0c\u800c\u662f\u7d2f\u8ba1\u8d85\u8fc73\u6b21\uff08<code>kMaxOverages<\/code>\uff09\u540e\uff0c\u624d\u4f1a\u5c06max_length\u51cf\u5c11batch_size\u3002<\/p>\n<h3>\u5783\u573e\u56de\u6536<\/h3>\n<p>TODO\uff1a\u672c\u8282\u8fd8\u6ca1\u5199\u5b8c\uff0c\u8bf7\u5148\u53c2\u9605<a href=\"https:\/\/gperftools.github.io\/gperftools\/tcmalloc.htm\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">\u5b98\u65b9\u4ecb\u7ecd<\/a>Garbage Collection of Thread Caches\u4e00\u8282\u3002\u3002<\/p>\n<p>\u4eceThreadCache\u4e2d\u56de\u6536\u5783\u573e\u5bf9\u8c61\uff0c\u5c06\u672a\u4f7f\u7528\u7684\u5bf9\u8c61\u8fd4\u56de\u5230CentralFreeList\uff0c\u53ef\u4ee5\u63a7\u5236\u7f13\u5b58\u7684\u5927\u5c0f\u3002<\/p>\n<p>\u4e0d\u540c\u7ebf\u7a0b\u5bf9\u7f13\u5b58\u5927\u5c0f\u7684\u9700\u6c42\u662f\u4e0d\u4e00\u6837\u7684\uff0c\u56e0\u6b64\u4e0d\u80fd\u7edf\u4e00\u5bf9\u5f85\uff1a\u6709\u4e9b\u7ebf\u7a0b\u9700\u8981\u5927\u7684\u7f13\u5b58\uff0c\u6709\u4e9b\u7ebf\u7a0b\u9700\u8981\u5c0f\u7684\u7f13\u5b58\u5373\u53ef\uff0c\u751a\u81f3\u6709\u4e9b\u7ebf\u7a0b\u4e0d\u9700\u8981\u7f13\u5b58\u3002<\/p>\n<p>\u5f53\u4e00\u4e2aThreadCache\u5927\u5c0f\u8d85\u8fc7\u5176max_size_\u65f6\uff0c\u89e6\u53d1\u5783\u573e\u56de\u6536\uff1a<\/p>\n<pre class=\"hljs bash\"><code class=\"bash\"><span class=\"hljs-keyword\">if<\/span> (PREDICT_FALSE(size_ &gt; max_size_)){\r\n  Scavenge();\r\n}\r\n<\/code><\/pre>\n<p>\u53ea\u6709\u5f53\u5e94\u7528\u7a0b\u5e8f\u91ca\u653e\u5185\u5b58\u65f6\uff08<code>ThreadCache::Deallocate()<\/code>\uff09\u624d\u4f1a\u89e6\u53d1\u5783\u573e\u56de\u6536\uff0c\u904d\u5386ThreadCache\u4e2d\u6240\u6709\u7684FreeList\uff0c\u5c06FreeList\u4e2d\u7684\u4e00\u4e9b\u5bf9\u8c61\u79fb\u81f3\u5bf9\u5e94\u7684CentralFreeList\u4e2d\u3002<\/p>\n<p>\u5177\u4f53\u79fb\u52a8\u591a\u5c11\u5bf9\u8c61\u7531\u4f4e\u6c34\u4f4d\u6807\u8bb0L\uff08<code>lowater_<\/code>\uff0c\u6bcf\u4e2aFreeList\u4e00\u4e2a\uff09\u6765\u51b3\u5b9a\u3002L\u8bb0\u5f55\u81ea\u4e0a\u6b21\u5783\u573e\u6536\u96c6\u4ee5\u6765\uff0cFreeList\u7684\u6700\u5c0f\u957f\u5ea6\u3002<\/p>\n<h2>CentralCache<\/h2>\n<p>CentralCache\u662f\u903b\u8f91\u4e0a\u7684\u6982\u5ff5\uff0c\u5176\u672c\u8d28\u662fCentralFreeListPadded\u7c7b\u578b\uff08CentralFreeList\u7684\u5b50\u7c7b\uff0c\u7528\u4e8e64\u5b57\u8282\u5bf9\u9f50\uff09\u7684\u6570\u7ec4\uff0c\u6bcf\u4e2asize class\u5bf9\u5e94\u6570\u7ec4\u4e2d\u7684\u4e00\u4e2a\u5143\u7d20\u3002<\/p>\n<pre class=\"hljs cpp\"><code class=\"cpp\">ATTRIBUTE_HIDDEN <span class=\"hljs-keyword\">static<\/span> CentralFreeListPadded central_cache_[kClassSizesMax];\r\n<\/code><\/pre>\n<p>\u7531\u4e8e\u5404\u7ebf\u7a0b\u516c\u7528\u4e00\u4e2aCentralCache\uff0c\u56e0\u6b64\uff0c\u4f7f\u7528CentralCache\u65f6\u9700\u8981\u52a0\u9501\u3002<\/p>\n<p>\u4ee5\u4e0b\u8ba8\u8bba\u90fd\u662f\u9488\u5bf9\u67d0\u4e00\u4e2asize class\u7684\u3002<\/p>\n<p>CentralFreeList\u4e2d\u7f13\u5b58\u4e86\u4e00\u7cfb\u5217\u5c0f\u5bf9\u8c61\uff0c\u4f9b\u5404\u7ebf\u7a0b\u7684ThreadCache\u53d6\u7528\uff0c\u5404\u7ebf\u7a0b\u4e5f\u4f1a\u5c06\u591a\u4f59\u7684\u7a7a\u95f2\u5c0f\u5bf9\u8c61\u8fd8\u7ed9CentralFreeList\uff0c\u53e6\u5916CentralFreeList\u8fd8\u8d1f\u8d23\u4ecePageHeap\u7533\u8bf7span\u4ee5\u5206\u5272\u6210\u5c0f\u5bf9\u8c61\uff0c\u4ee5\u53ca\u5c06\u4e0d\u518d\u4f7f\u7528\u7684span\u8fd8\u7ed9PageHeap\u3002<\/p>\n<h3>\u7ba1\u7406span<\/h3>\n<p>CentralFreeList\u771f\u6b63\u7ba1\u7406\u7684\u662fspan\uff0c\u800c\u5c0f\u5bf9\u8c61\u662f\u5305\u542b\u5728span\u4e2d\u7684\u7a7a\u95f2\u5bf9\u8c61\u94fe\u8868\u4e2d\u7684\u3002CentralFreeList\u7684<code>empty_<\/code>\u94fe\u8868\u4fdd\u5b58\u4e86\u5df2\u7ecf\u6ca1\u6709\u7a7a\u95f2\u5bf9\u8c61\u53ef\u7528\u7684span\uff0c<code>nonempty_<\/code>\u94fe\u8868\u4fdd\u5b58\u4e86\u8fd8\u6709\u7a7a\u95f2\u5bf9\u8c61\u53ef\u7528\u7684span\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"905\" data-height=\"521\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-6b54a892077d6773.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/905\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-6b54a892077d6773.png\" data-original-width=\"905\" data-original-height=\"521\" data-original-format=\"image\/png\" data-original-filesize=\"152308\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-CentralFreeList<\/div>\n<\/div>\n<h3>CentralFreeList\u2194 PageHeap<\/h3>\n<h4>\u4ecePageHeap\u83b7\u53d6span<\/h4>\n<p>\u5f53ThreadCache\u4eceCentralFreeList\u53d6\u7528\u7a7a\u95f2\u5bf9\u8c61\uff08<code>RemoveRange<\/code>\uff09\uff0c\u4f46CentralFreeList\u7684\u7a7a\u95f2\u5bf9\u8c61\u6570\u91cf\u4e0d\u591f\u65f6\uff0cCentralFreeList\u8c03\u7528<code>Populate()<\/code>\u4ecePageHeap\u7533\u8bf7\u4e00\u4e2aspan\u62c6\u5206\u6210\u82e5\u5e72\u5c0f\u5bf9\u8c61\uff0c\u9996\u9996\u8fde\u63a5\u8bb0\u5f55\u5728span\u7684<code>objects<\/code>\u6307\u9488\u4e2d\uff0c\u5373\u6bcf\u4e2a\u5c0f\u5bf9\u8c61\u7684\u8d77\u59cb\u4f4d\u7f6e\u5904\uff0c\u8bb0\u5f55\u4e86\u4e0b\u4e00\u4e2a\u5c0f\u5bf9\u8c61\u7684\u5730\u5740\u3002\u6b64\u65f6\u7684span\u5982\u4e0b\u56fe\uff1a<\/p>\n<div class=\"image-package\">\n<div class=\"image-container\">\n<div class=\"image-container-fill\"><\/div>\n<div class=\"image-view\" data-width=\"405\" data-height=\"242\"><img decoding=\"async\" class=\"\" src=\"https:\/\/upload-images.jianshu.io\/upload_images\/918432-4dc5c4edab2ca987.png?imageMogr2\/auto-orient\/strip%7CimageView2\/2\/w\/405\/format\/webp\" data-original-src=\"\/\/upload-images.jianshu.io\/upload_images\/918432-4dc5c4edab2ca987.png\" data-original-width=\"405\" data-original-height=\"242\" data-original-format=\"image\/png\" data-original-filesize=\"32586\" \/><\/div>\n<\/div>\n<div class=\"image-caption\">tcmalloc-FreshSpan<\/div>\n<\/div>\n<p>\u53ef\u4ee5\u770b\u5230\uff0c\u6b64\u65f6span\u5305\u542b\u7684\u5bf9\u8c61\u6309\u987a\u5e8f\u8fde\u63a5\u5728\u4e00\u8d77\u3002<\/p>\n<p>\u65b0\u7533\u8bf7\u7684span\u88ab\u653e\u5165CentralFreeList\u7684<code>nonempty_<\/code>\u94fe\u8868\u5934\u90e8\u3002<\/p>\n<h4>\u5c06span\u8fd8\u7ed9PageHeap<\/h4>\n<p>CentralFreeList\u7ef4\u62a4span\u7684\u6210\u5458\u53d8\u91cf<code>refcount<\/code>\uff0c\u7528\u6765\u8bb0\u5f55ThreadCache\u4ece\u4e2d\u83b7\u53d6\u4e86\u591a\u5c11\u5bf9\u8c61\u3002<\/p>\n<p>\u5f53ThreadCache\u5c06\u4e0d\u518d\u4f7f\u7528\u7684\u5bf9\u8c61\u5f52\u8fd8\u7ed9CentralCache\u4ee5\u81f4refcount\u51cf\u4e3a0\uff0c\u5373span\u4e2d\u6240\u6709\u5bf9\u8c61\u90fd\u7a7a\u95f2\u65f6\uff0c\u5219CentralCache\u5c06\u8fd9\u4e2aspan\u8fd8\u7ed9PageHeap\u3002\u622a\u53d6<code>CentralFreeList::ReleaseToSpans()<\/code>\u90e8\u5206\u4ee3\u7801\u5982\u4e0b\uff1a<\/p>\n<pre class=\"hljs php\"><code class=\"php\">span-&gt;refcount--;\r\n<span class=\"hljs-keyword\">if<\/span> (span-&gt;refcount == <span class=\"hljs-number\">0<\/span>) {\r\n  Event(span, <span class=\"hljs-string\">'#'<\/span>, <span class=\"hljs-number\">0<\/span>);\r\n  counter_ -= ((span-&gt;length&lt;&lt;kPageShift) \/\r\n               <span class=\"hljs-keyword\">Static<\/span>::sizemap()-&gt;ByteSizeForClass(span-&gt;sizeclass));\r\n  tcmalloc::DLL_Remove(span);\r\n  --num_spans_;\r\n\r\n  <span class=\"hljs-comment\">\/\/ Release central list lock while operating on pageheap<\/span>\r\n  lock_.Unlock();\r\n  {\r\n    SpinLockHolder h(<span class=\"hljs-keyword\">Static<\/span>::pageheap_lock());\r\n    <span class=\"hljs-keyword\">Static<\/span>::pageheap()-&gt;Delete(span);\r\n  }\r\n  lock_.Lock();\r\n}\r\n<\/code><\/pre>\n<h3>CentralFreeList\u2194ThreadCache<\/h3>\n<p>CentralFreeList\u548cThreadCache\u4e4b\u95f4\u7684\u5bf9\u8c61\u79fb\u52a8\u662f\u6279\u91cf\u8fdb\u884c\u7684\uff1a<\/p>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-comment\">\/\/ Insert the specified range into the central freelist.  N is the number of<\/span>\r\n<span class=\"hljs-comment\">\/\/ elements in the range.  RemoveRange() is the opposite operation.<\/span>\r\n<span class=\"hljs-function\"><span class=\"hljs-keyword\">void<\/span> <span class=\"hljs-title\">InsertRange<\/span><span class=\"hljs-params\">(<span class=\"hljs-keyword\">void<\/span> *start, <span class=\"hljs-keyword\">void<\/span> *end, <span class=\"hljs-keyword\">int<\/span> N)<\/span><\/span>;\r\n\r\n<span class=\"hljs-comment\">\/\/ Returns the actual number of fetched elements and sets *start and *end.<\/span>\r\n<span class=\"hljs-function\"><span class=\"hljs-keyword\">int<\/span> <span class=\"hljs-title\">RemoveRange<\/span><span class=\"hljs-params\">(<span class=\"hljs-keyword\">void<\/span> **start, <span class=\"hljs-keyword\">void<\/span> **end, <span class=\"hljs-keyword\">int<\/span> N)<\/span><\/span>;\r\n<\/code><\/pre>\n<p>start\u548cend\u6307\u5b9a\u5c0f\u5bf9\u8c61\u94fe\u8868\u7684\u8303\u56f4\uff0cN\u6307\u5b9a\u5c0f\u5bf9\u8c61\u7684\u6570\u91cf\u3002\u6279\u91cf\u79fb\u52a8\u5c0f\u5bf9\u8c61\u53ef\u4ee5<strong>\u5747\u644a\u9501\u64cd\u4f5c\u7684\u5f00\u9500<\/strong>\u3002<\/p>\n<h4>ThreadCache\u53d6\u7528\u5c0f\u5bf9\u8c61<\/h4>\n<p>\u5f53ThreadCache\u4e2d\u67d0\u4e2asize class\u6ca1\u6709\u7a7a\u95f2\u5bf9\u8c61\u53ef\u7528\u65f6\uff0c\u9700\u8981\u4eceCentralFreeList\u83b7\u53d6N\u4e2a\u5bf9\u8c61\uff0c\u90a3\u4e48N\u7684\u503c\u662f\u591a\u5c11\u5462\uff1f\u4ece<code>ThreadCache::FetchFromCentralCache()<\/code>\u4e2d\u53ef\u4ee5\u627e\u5230\u7b54\u6848\uff1a<\/p>\n<pre class=\"hljs php\"><code class=\"php\"><span class=\"hljs-keyword\">const<\/span> int batch_size = <span class=\"hljs-keyword\">Static<\/span>::sizemap()-&gt;num_objects_to_move(cl);\r\n<span class=\"hljs-keyword\">const<\/span> int num_to_move = min&lt;int&gt;(<span class=\"hljs-keyword\">list<\/span>-&gt;max_length(), batch_size);\r\nvoid *start, *end;\r\nint fetch_count = <span class=\"hljs-keyword\">Static<\/span>::central_cache()[cl].RemoveRange(&amp;start, &amp;end, num_to_move);\r\n<\/code><\/pre>\n<p>\u79fb\u52a8\u6570\u91cfN\u4e3amax_length\u548cbatch_size\u7684\u6700\u5c0f\u503c\uff08\u4e24\u8005\u7684\u5177\u4f53\u6db5\u4e49\u53c2\u89c1ThreadCache\u6162\u542f\u52a8\u4e00\u8282\uff09\u3002<\/p>\n<p>\u5047\u8bbe\u53ea\u8003\u8651\u5185\u5b58\u5206\u914d\u7684\u60c5\u51b5\uff0c\u4e00\u5f00\u59cb\u79fb\u52a81\u4e2a\uff0c\u7136\u540e\u662f2\u4e2a\u30013\u4e2a\uff0c\u4ee5\u6b64\u7c7b\u63a8\uff0c\u540c\u65f6max_length\u6bcf\u6b21\u4e5f\u52a01\uff0c\u76f4\u5230\u8fbe\u5230batch_size\u540e\uff0c\u6bcf\u6b21\u79fb\u52a8batch_size\u4e2a\u5bf9\u8c61\u3002<\/p>\n<p>CentralFreeList\u548cThreadCache\u4e4b\u95f4\u7684\u5bf9\u8c61\u79fb\u52a8\u6709\u4e2a\u4f18\u5316\u63aa\u65bd\uff0c\u56e0\u4e3a\u5927\u90e8\u5206\u60c5\u51b5\u90fd\u662f\u6bcf\u6b21\u79fb\u52a8batch_size\u4e2a\u5bf9\u8c61\uff0c\u4e3a\u4e86\u51cf\u5c11\u94fe\u8868\u64cd\u4f5c\uff0c\u63d0\u5347\u6548\u7387\uff0cCentralFreeList\u5c06\u79fb\u52a8\u7684batch_size\u4e2a\u5bf9\u8c61\u7684\u94fe\u8868\u7684\u9996\u5c3e\u6307\u9488\u7f13\u5b58\u5728\u4e86TCEntry\u4e2d\u3002\u56e0\u6b64\u540e\u7eed\u53ea\u8981\u9700\u8981\u79fb\u52a8batch_size\u4e2a\u5bf9\u8c61\uff0c\u53ea\u9700\u8981\u64cd\u4f5c\u94fe\u8868\u7684\u9996\u5c3e\u5373\u53ef\u3002<\/p>\n<pre class=\"hljs cpp\"><code class=\"cpp\"><span class=\"hljs-comment\">\/\/ Here we reserve space for TCEntry cache slots.  Space is preallocated<\/span>\r\n<span class=\"hljs-comment\">\/\/ for the largest possible number of entries than any one size class may<\/span>\r\n<span class=\"hljs-comment\">\/\/ accumulate.  Not all size classes are allowed to accumulate<\/span>\r\n<span class=\"hljs-comment\">\/\/ kMaxNumTransferEntries, so there is some wasted space for those size<\/span>\r\n<span class=\"hljs-comment\">\/\/ classes.<\/span>\r\nTCEntry tc_slots_[kMaxNumTransferEntries];\r\n<\/code><\/pre>\n<h4>ThreadCache\u5f52\u8fd8\u5c0f\u5bf9\u8c61<\/h4>\n<p>\u5f53ThreadCache\u4e2d\u7684\u7a7a\u95f2\u5bf9\u8c61\u8fc7\u591a\u65f6\uff08<code>ThreadCache::ListTooLong()<\/code>\uff09\uff0c\u4f1a\u5c06\u4e00\u90e8\u5206\u7a7a\u95f2\u5bf9\u8c61\u653e\u56deCentralFreeList\uff08<code>ThreadCache::ReleaseToCentralCache()<\/code>\uff09\u3002\u5982\u4f55\u5224\u65ad\u7a7a\u95f2\u5bf9\u8c61\u8fc7\u591a\u8bf7\u53c2\u8003ThreadCache\u6162\u542f\u52a8\u4e00\u8282\u3002<\/p>\n<p>\u7ebf\u7a0b\u9500\u6bc1\u4e5f\u4f1a\u5c06\u5176ThreadCache\u4e2d\u6240\u6709\u7684\u7a7a\u95f2\u5bf9\u8c61\u90fd\u653e\u56deCentralFreeList\u3002<\/p>\n<p>\u5982\u679cThreadCache\u7f13\u5b58\u7684\u5185\u5b58\u5927\u5c0f\u8d85\u8fc7\u5176\u5141\u8bb8\u7684\u6700\u5927\u503c\uff0c\u4f1a\u89e6\u53d1GC\u64cd\u4f5c\uff08<code>ThreadCache::Scavenge()<\/code>\uff09\uff0c\u5728\u5176\u4e2d\u4e5f\u4f1a\u5c06\u90e8\u5206\u5c0f\u5bf9\u8c61\u5f52\u8fd8\u7ed9CentralFreeList\uff0c\u5177\u4f53\u8bf7\u53c2\u8003ThreadCache\u5783\u573e\u56de\u6536\u4e00\u8282\u3002<\/p>\n<p>\u5168\u6587\u5b8c\u3002<\/p>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>\u539f\u6587\u5730\u5740 \u5199\u5728\u524d\u9762 \u672c\u6587\u9996\u5148\u7b80\u5355\u4ecb\u7ecdTC<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"colormag_page_container_layout":"default_layout","colormag_page_sidebar_layout":"default_layout","footnotes":""},"categories":[],"tags":[119],"class_list":["post-3663","post","type-post","status-publish","format-standard","hentry","tag-03-"],"_links":{"self":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts\/3663","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/comments?post=3663"}],"version-history":[{"count":0,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts\/3663\/revisions"}],"wp:attachment":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/media?parent=3663"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/categories?post=3663"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/tags?post=3663"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}