{"id":2168,"date":"2021-06-12T22:32:03","date_gmt":"2021-06-12T14:32:03","guid":{"rendered":"https:\/\/coderbee.net\/?p=2168"},"modified":"2021-06-12T22:32:03","modified_gmt":"2021-06-12T14:32:03","slug":"%e6%96%b0%e4%b8%80%e4%bb%a3-gc-%e7%a5%9e%e5%99%a8-zgc","status":"publish","type":"post","link":"https:\/\/coderbee.net\/index.php\/jvm\/20210612\/2168","title":{"rendered":"\u65b0\u4e00\u4ee3 GC \u795e\u5668 ZGC"},"content":{"rendered":"<h1>0. \u6807\u8bb0-\u590d\u5236\u7b97\u6cd5<\/h1>\n<p>\u6807\u8bb0-\u590d\u5236\u7b97\u6cd5\u5206\u4e09\u4e2a\u9636\u6bb5\uff1a<\/p>\n<ul>\n<li>\u6807\u8bb0\u9636\u6bb5\uff1a\u4ece GC Roots \u51fa\u53d1\uff0c\u6807\u8bb0\u5b58\u6d3b\u5bf9\u8c61\u3002<\/li>\n<li>\u8f6c\u79fb\u9636\u6bb5\uff1a\u628a\u5b58\u6d3b\u5bf9\u8c61\u590d\u5236\u5230\u65b0\u7684\u5185\u5b58\u5730\u5740\uff0c\u539f\u6765\u7684\u5185\u5b58\u7a7a\u95f4\u53d8\u6210\u53ef\u56de\u6536\u7684\u3002<\/li>\n<li>\u91cd\u5b9a\u4f4d\u9636\u6bb5\uff1a\u5b58\u6d3b\u5bf9\u8c61\u88ab\u590d\u5236\u5230\u5176\u4ed6\u5730\u65b9\u540e\uff0c\u6240\u6709\u6307\u5411\u5bf9\u8c61\u65e7\u5730\u5740\u7684\u6307\u9488\u90fd\u8981\u8c03\u6574\u5230\u5bf9\u8c61\u65b0\u7684\u5730\u5740\u4e0a\u3002<\/li>\n<\/ul>\n<h1>1. \u6982\u8ff0<\/h1>\n<p>Z Garbage Collector\uff0c\u5373ZGC\uff0c\u662f\u4e00\u4e2a\u53ef\u4f38\u7f29\u7684\u3001\u4f4e\u5ef6\u8fdf\u7684\u5783\u573e\u6536\u96c6\u5668\u3002\u53ea\u652f\u6301 64 \u4f4d\u7684\u7cfb\u7edf\u3002<\/p>\n<p>ZGC \u672a\u5206\u4ee3\uff0c\u6bcf\u6b21 GC \u90fd\u662f FullGC \u3002<\/p>\n<h2>1.1 ZGC \u7684\u8bbe\u8ba1\u76ee\u6807<\/h2>\n<ul>\n<li>\u4e9a\u6beb\u79d2\u7ea7\u7684\u6700\u5927\u6682\u505c\u65f6\u95f4\u3002<\/li>\n<li>\u6682\u505c\u65f6\u95f4\u4e0d\u968f\u5806\u3001\u5b58\u6d3b\u5bf9\u8c61\u6570\u91cf\u3001\u6839\u96c6\u5408\u5927\u5c0f\u7684\u589e\u957f\u800c\u589e\u957f\u3002<\/li>\n<li>\u53ef\u5904\u7406\u7684\u5806\u5927\u5c0f\u4ece 8MB \u5230 16TB\u3002<\/li>\n<\/ul>\n<p>\u603b\u7684\u6765\u8bf4\uff0cZGC \u5177\u6709\u5982\u4e0b\u7279\u6027\uff1a<\/p>\n<ul>\n<li>\u5e76\u53d1<\/li>\n<li>\u57fa\u4e8e Region<\/li>\n<li>\u538b\u7f29<\/li>\n<li>NUMA \u53cb\u597d<\/li>\n<li>\u4f7f\u7528\u7740\u8272\u6307\u9488<\/li>\n<li>\u4f7f\u7528\u8bfb\u5c4f\u969c load barriers<\/li>\n<\/ul>\n<p>\u622a\u81f3 JDK 14\uff0cZGC \u5df2\u5728\u4e3b\u6d41\u7684\u64cd\u4f5c\u7cfb\u7edf\u4e0a\u83b7\u5f97\u652f\u6301\u3002<\/p>\n<p><!--more--><\/p>\n<h2>1.2 ZGC \u5728 JDK \u5404\u7248\u672c\u7684\u6539\u8fdb<\/h2>\n<ul>\n<li>JDK 11\n<ul>\n<li>\u521d\u6b21\u5f15\u8fdb\uff0c\u53ea\u652f\u6301 Linux X64 \u5e73\u53f0\u3002<\/li>\n<li>\u4e0d\u652f\u6301\u7c7b\u5378\u8f7d\uff0c<code>-XX:+ClassUnloading<\/code> \u4e0d\u751f\u6548\u3002<\/li>\n<\/ul>\n<\/li>\n<li>JDK 12\n<ul>\n<li>\u652f\u6301\u5e76\u53d1\u7c7b\u5378\u8f7d\u3002<\/li>\n<li>\u6682\u505c\u65f6\u95f4\u8fdb\u4e00\u6b65\u51cf\u5c11\u3002<\/li>\n<\/ul>\n<\/li>\n<li>JDK 13\n<ul>\n<li>\u652f\u6301\u7684\u5806\u6700\u5927\u5c3a\u5bf8\u4ece 4TB \u589e\u5927\u5230 16TB\u3002<\/li>\n<li>\u652f\u6301 uncommitting unused memory<\/li>\n<li>\u8fdb\u4e00\u6b65\u51cf\u5c11\u4e86 \u8fdb\u5165\u5b89\u5168\u70b9 \u7684\u65f6\u95f4\u3002<\/li>\n<li>\u652f\u6301 Linux\/AArch64 \u5e73\u53f0\u3002<\/li>\n<li>\u652f\u6301\u53c2\u6570 <code>-XX:SoftMaxHeapSIze<\/code>\u3002<\/li>\n<\/ul>\n<\/li>\n<li>JDK 14\n<ul>\n<li>\u652f\u6301 macOS\/Windows \u7cfb\u7edf\u3002<\/li>\n<li>\u652f\u6301\u5fae\u3001\u5c0f\u5806\uff0c\u6700\u5c0f\u652f\u6301 8MB\u3002<\/li>\n<li>\u652f\u6301 JFR \u6cc4\u6f0f\u5256\u6790\u3002<\/li>\n<li>\u652f\u6301\u53d7\u9650\u7684\u3001\u4e0d\u8fde\u7eed\u7684\u5730\u5740\u7a7a\u95f4\u3002<\/li>\n<li>\u652f\u6301\u5e76\u884c pre-touch\uff0c\u4f7f\u7528\u53c2\u6570 <code>-XX:+AlwaysPreTouch<\/code>\u3002<\/li>\n<li>\u6027\u80fd\u548c\u7a33\u5b9a\u6027\u63d0\u5347\u3002<\/li>\n<\/ul>\n<\/li>\n<li>JDK 15\n<ul>\n<li>\u8fbe\u5230\u751f\u4ea7\u53ef\u7528\u7ea7\u522b\u3002<\/li>\n<li>\u63d0\u5347 NUMA \u611f\u77e5\u3002<\/li>\n<li>\u63d0\u5347\u5e76\u53d1\u5206\u914d\u3002<\/li>\n<li>\u652f\u6301\u7c7b\u6570\u636e\u5171\u4eab\uff0cClass Data Sharing, CDS\u3002<\/li>\n<li>Support for placing the heap on NVRAM<\/li>\n<li>\u652f\u6301\u7c7b\u6307\u9488\u538b\u7f29\u3002<\/li>\n<li>Support for incremental uncommit<\/li>\n<li>\u4fee\u590d\u5bf9\u900f\u660e\u5927\u9875\u7684\u652f\u6301\u3002<\/li>\n<li>\u589e\u52a0 JFR \u4e8b\u4ef6\u3002<\/li>\n<\/ul>\n<\/li>\n<li>JDK 16\n<ul>\n<li>\u5e76\u884c\u7ebf\u7a0b\u6808\u626b\u63cf(<a href=\"http:\/\/openjdk.java.net\/jeps\/376\">JEP 376<\/a>)<\/li>\n<li>\u652f\u6301\u539f\u4f4d\u8f6c\u79fb\uff0c in-place relocation\u3002<\/li>\n<li>\u6027\u80fd\u63d0\u5347\uff08\u5206\u914d\u3001\u521d\u59cb\u5316\u8f6c\u53d1\u8868\u7b49\uff09\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h2>1.3 ZGC \u76f8\u5173\u53c2\u6570<\/h2>\n<p>ZGC \u76f8\u5173\u53c2\u6570\u6bd4 CMS\/G1 \u90fd\u660e\u663e\u5c11\u5f88\u591a\uff0c\u66f4\u5c11\u7684\u53c2\u6570\u610f\u5473\u7740\u66f4\u6613\u7528\u3002<\/p>\n<p>\u5927\u4f53\u4e0a\u53ef\u4ee5\u5206\u4e3a\u4e09\u7c7b\uff1a\u901a\u7528 GC \u9009\u62e9\u3001ZGC \u9009\u9879\u3001ZGC \u8bca\u65ad\u9009\u9879\u3002<\/p>\n<h3>1.3.1 \u901a\u7528 GC \u9009\u62e9<\/h3>\n<ul>\n<li>-XX:MinHeapSize, -Xms \uff1a\u6700\u5c0f\u5806\u5927\u5c0f<\/li>\n<li>-XX:InitialHeapSize, -Xms \uff1a\u521d\u59cb\u5806\u5927\u5c0f<\/li>\n<li>-XX:MaxHeapSize, -Xmx \uff1a\u6700\u5927\u5806\u5927\u5c0f<\/li>\n<li>-XX:SoftMaxHeapSize \uff1a<\/li>\n<li>-XX:ConcGCThreads\uff1a\u4e0e\u5e94\u7528\u7ebf\u7a0b\u5e76\u53d1\u6267\u884c\u65f6\u7684 GC \u7ebf\u7a0b\u6570\u91cf\uff0c\u9ed8\u8ba4\u4e3a CPU \u4e2a\u6570\u7684 12.5%\u3002<\/li>\n<li>-XX:ParallelGCThreads\uff1aSTW \u65f6 GC \u7ebf\u7a0b\u7684\u6570\u91cf\uff0c\u9ed8\u8ba4\u4e3a CPU \u4e2a\u6570\u7684 60%\u3002<\/li>\n<li>-XX:UseLargePages<\/li>\n<li>-XX:UseTransparentHugePages<\/li>\n<li>-XX:UseNUMA<\/li>\n<li>-XX:SoftRefLRUPolicyMSPerMB<\/li>\n<li>-XX:AllocateHeapAt<\/li>\n<\/ul>\n<h3>1.3.1 ZGC \u9009\u9879<\/h3>\n<ul>\n<li>-XX:ZAllocationSpikeTolerance\uff1a\u7528\u6765\u4f30\u7b97\u5f53\u524d\u5806\u5185\u5b58\u5206\u914d\u901f\u7387\uff0c\u5728\u5f53\u524d\u5269\u4f59\u7684\u5806\u5185\u5b58\u4e0b\uff0c<code>ZAllocationSpikeTolerance<\/code> \u8d8a\u5927\uff0c\u4f30\u7b97\u7684\u8fbe\u5230 OOM \u7684\u65f6\u95f4\u8d8a\u5feb\uff0cZGC \u5c31\u4f1a\u66f4\u65e9\u7b2c\u89e6\u53d1 GC\u3002<\/li>\n<li>-XX:ZCollectionInterval\uff1a<code>ZCollectionInterval<\/code> \u7528\u6765\u6307\u5b9a GC \u53d1\u751f\u7684\u95f4\u9694\uff0c\u4ee5\u79d2\u4e3a\u5355\u4f4d\u89e6\u53d1 GC \u3002<\/li>\n<li>-XX:ZFragmentationLimit<\/li>\n<li>-XX:ZMarkStackSpaceLimit<\/li>\n<li>-XX:ZProactive<\/li>\n<li>-XX:ZUncommit<\/li>\n<li>-XX:ZUncommitDelay<\/li>\n<\/ul>\n<h3>1.3.1 ZGC \u8bca\u65ad\u9009\u9879<\/h3>\n<ul>\n<li>-XX:ZStatisticsInterval<\/li>\n<li>-XX:ZVerifyForwarding<\/li>\n<li>-XX:ZVerifyMarking<\/li>\n<li>-XX:ZVerifyObjects<\/li>\n<li>-XX:ZVerifyRoots<\/li>\n<li>-XX:ZVerifyViews<\/li>\n<\/ul>\n<h3>1.3.1 ZGC \u53c2\u6570\u8c03\u4f18<\/h3>\n<p>ZGC \u53c2\u6570\u4e00\u822c\u53ea\u9700\u8c03\u6574\u5982\u4e0b\u51e0\u4e2a\uff1a<\/p>\n<ul>\n<li>\u5806\u5927\u5c0f\uff1a <code>-Xmx<\/code>\u3002<\/li>\n<li>GC \u89e6\u53d1\u65f6\u673a\uff1a<code>ZAllocationSpikeTolerance<\/code> \u548c <code>ZCollectionInterval<\/code>\u3002<\/li>\n<li>GC \u7ebf\u7a0b\u76f8\u5173\uff1a<code>ParallelGCThreads<\/code>\u548c <code>ConcGCThreads<\/code>\u3002<\/li>\n<\/ul>\n<h1>2. ZGC \u5b9e\u73b0\u7684\u4e00\u4e9b\u57fa\u7840\u7279\u6027<\/h1>\n<h2>2.1 \u7740\u8272\u6307\u9488<\/h2>\n<p>\u7740\u8272\u6307\u9488\u662f ZGC \u7684\u6838\u5fc3\u6982\u5ff5\uff0c\u628a GC \u76f8\u5173\u7684\u5143\u6570\u636e\u5b58\u50a8\u5728\u5bf9\u8c61\u7684\u6307\u9488\u4e0a\u3002<\/p>\n<p>Intel\/AMD 64 \u4f4d\u7684\u5904\u7406\u5668\u76ee\u524d\u90fd\u53ea\u652f\u6301 48 \u4f4d\u7684\u5730\u5740\u7a7a\u95f4\uff0c\u539f\u56e0\u4e3b\u8981\u662f\u73b0\u5728\u4e5f\u7528\u4e0d\u5230 64 \u4f4d\u7684\u5730\u5740\u7a7a\u95f4\uff0c\u786c\u4ef6\u5c31\u6ca1\u5fc5\u8981\u652f\u6301\u3002\u76f8\u5173\u7684\u8ba8\u8bba\u53ef\u4ee5\u770b\u770b <a href=\"https:\/\/www.zhihu.com\/question\/28638698\">\u4e3a\u4ec0\u4e4864\u4f4d\u673a\u6307\u9488\u53ea\u752848\u4e2a\u4f4d\uff1f<\/a><\/p>\n<p>\u4f46\u76ee\u524d\u7edd\u5927\u591a\u6570 JVM \u4e5f\u7528\u4e0d\u5230 48 \u4f4d\u7684\u5730\u5740\u7a7a\u95f4\uff0cZGC \u5c31\u4ece\u4e2d\u62a0\u51fa 4 \u4f4d\u7528\u4e8e\u5b58\u50a8 GC \u7684\u6570\u636e\uff0c\u5269\u4e0b 44 \u4f4d\u7ed9\u5e94\u7528\u4f7f\u7528\uff0c\u4e5f\u5c31\u662f ZGC \u652f\u6301\u5806\u6700\u5927 16TB \u7684\u7531\u6765\u3002<\/p>\n<p>\u56e0\u4e3a\u7740\u8272\u6307\u9488\uff0cZGC \u4e0d\u652f\u630132\u4f4d\u7684\u5e73\u53f0\uff0c\u4e5f\u4e0d\u652f\u6301\u6307\u9488\u538b\u7f29\u3002<\/p>\n<p>\u7740\u8272\u6307\u9488\u7684\u7ed3\u6784\u5982\u4e0b\uff1a<\/p>\n<pre><code>|(16bits)|    (1bit)   |  (1bit)  |  (1bit) |  (1bit) |(44bits,16TB address space)|\n| unused | Finalizable | Remapped | Marked1 | Marked0 | Object Address           |\n<\/code><\/pre>\n<p>ZGC \u5728\u4e0d\u540c\u7684\u6807\u8bb0\u5468\u671f\u3001\u6807\u8bb0\u9636\u6bb5\uff0c\u4f1a\u6539\u53d8 <code>Remapped\/Marked1\/Marked0<\/code> \u7684\u503c\u3002<\/p>\n<p>\u5728\u4efb\u610f\u65f6\u523b\uff0c\u8fd9\u56db\u4e2a\u6807\u5fd7\u4f4d\u6700\u591a\u53ea\u6709\u4e00\u4e2a\u88ab\u7f6e\u4e0a\u3002\u8fd9\u56db\u4e2a\u6807\u5fd7\u4f4d\u5206\u522b\u5bf9\u5e94\u4e00\u4e2a\u89c6\u56fe\uff0c\u56e0\u6b64\uff0c\u5728\u4efb\u610f\u65f6\u523b\uff0c\u53ea\u6709\u4e00\u79cd\u89c6\u56fe\u662f\u751f\u6548\u7684\u3002<\/p>\n<p>\u5728\u6807\u8bb0\u7684\u8fc7\u7a0b\u4e2d\uff0c\u662f\u4e0d\u4f1a\u53bb\u79fb\u52a8\u5bf9\u8c61\u7684\uff0c\u4f46\u6539\u53d8\u8fd9\u51e0\u4e2a\u4f4d\u7684\u503c\u5c31\u76f8\u5f53\u4e8e\u6539\u53d8\u4e86\u5bf9\u8c61\u7684\u4f4d\u7f6e\uff0c\u56e0\u6b64\u9700\u8981\u4e00\u79cd\u624b\u6bb5\u6765\u4fdd\u8bc1\u8bbf\u95ee\u65b0\u7684\u5730\u5740\u4ecd\u7136\u80fd\u8bbf\u95ee\u5230\u539f\u6765\u7684\u5bf9\u8c61\uff0c\u8fd9\u5c31\u5f15\u51fa\u4e86\u5185\u5b58\u591a\u91cd\u6620\u5c04\u3002<\/p>\n<h2>2.2 \u5185\u5b58\u591a\u91cd\u6620\u5c04<\/h2>\n<p>\u5185\u5b58\u591a\u91cd\u6620\u5c04\uff08Multi-Mapping\uff09\u5c06\u591a\u4e2a\u4e0d\u540c\u7684\u865a\u62df\u5185\u5b58\u5730\u5740\u6620\u5c04\u5230\u540c\u4e00\u4e2a\u7269\u7406\u5185\u5b58\u5730\u5740\u4e0a\u3002\u56fe\u793a\u5982\u4e0b\uff0c\u8fd8\u662f\u65e7\u7248\u672c 4TB \u7684\u3002<\/p>\n<p><a href=\"https:\/\/coderbee.net\/wp-content\/uploads\/2021\/06\/heap-multi-mapping.png\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/coderbee.net\/wp-content\/uploads\/2021\/06\/heap-multi-mapping.png\" alt=\"\" width=\"1190\" height=\"566\" class=\"alignnone size-full wp-image-2167\" \/><\/a><\/p>\n<h2>2.3 \u8bfb\u5c4f\u969c\u4e0e\u6307\u9488\u81ea\u6108<\/h2>\n<p>\u5047\u8bbe\u5728\u67d0\u4e00\u8f6e GC \u8fc7\u7a0b\u4e2d\u4f7f\u7528\u7684\u89c6\u56fe\u662f Mark0\uff0c\u5728 GC \u5b8c\u6210\u4e4b\u540e\uff0c\u5bf9\u8c61 A \u6307\u5411\u5bf9\u8c61 B \u7684\u5c5e\u6027\u5b57\u6bb5\u7684\u503c\uff08\u6307\u9488\uff09\u5c31\u662f\u6307\u5411 Mark0 \u89c6\u56fe\u7684\u5730\u5740\u7a7a\u95f4\u3002\u65b0\u4e00\u8f6e GC \u4f7f\u7528\u89c6\u56fe Mark1\uff0c\u5728 GC \u7684\u8fc7\u7a0b\u4e2d\uff0c\u5c31\u9700\u8981\u628a\u6307\u5411 Mark0 \u7684\u6307\u9488\u4fee\u6b63\u4e3a\u6307\u5411 Mark1 \u5730\u5740\u7a7a\u95f4\u7684\u5bf9\u5e94\u503c\u3002\u8fd9\u5c31\u662f\u6307\u9488\u81ea\u6108\u7684\u529f\u80fd\u3002<\/p>\n<p>\u6307\u9488\u81ea\u6108\u7684\u529f\u80fd\u662f\u901a\u8fc7\u8bfb\u5c4f\u969c\u6765\u5b9e\u73b0\u7684\uff0c\u5f53<strong>\u4ece\u5806\u91cc\u8bfb\u53d6\u5230\u4e00\u4e2a\u6307\u9488<\/strong>\u65f6\uff0c\u5982\u679c\u8be5\u6307\u9488\u4e0d\u662f\u6307\u5411\u6700\u65b0\u7684\u5730\u5740\u7a7a\u95f4\uff0c\u5c31\u9700\u8981\u4fee\u6539\u5806\u91cc\u5b58\u50a8\u7684\u6307\u9488\u4e3a\u6b63\u786e\u503c\u3002<\/p>\n<p>\u5982\u679c\u4ece\u5806\u91cc\u8bfb\u53d6\u7684\u662f\u57fa\u672c\u7c7b\u578b\u7684\u503c\uff0c\u662f\u4e0d\u9700\u8981\u8fdb\u884c\u81ea\u6108\u5904\u7406\u7684\u3002<\/p>\n<pre><code>Object o = obj.fieldA;          \/\/ Loading an object reference from heap\n&lt;load barrier needed here&gt;\nObject p = o;                   \/\/ no barrier, not a load from heap\no.doSomething();                \/\/ no barrier, not a load from heap\nint i = obj.fieldB;             \/\/ no barrier, not an object reference\n\nObject a = obj.x;\n&lt;load barrier needed here&gt;      \/\/ a \u7684\u503c\u662f\u6700\u65b0\u7684\uff0cobj.x \u7684\u503c\u81ea\u8eab\u4e5f\u4f1a\u4fee\u6b63\nObject b = obj.x;               \n&lt;load barrier needed here&gt;      \/\/ \u76f4\u63a5\u8d70 FastPath\n<\/code><\/pre>\n<p>\u8bfb\u5c4f\u969c\u7531 JIT \u81ea\u52a8\u63d2\u5165\u5408\u9002\u7684\u4f4d\u7f6e\uff0c\u5982\u4e0b\u793a\u4f8b\uff1a<\/p>\n<pre><code>String n = person.name; \/\/ Loading an object reference from heap\nif (n &amp; bad_bit_mask) {\n    slow_path(register_for(n), address_of(person.name));\n}\n<\/code><\/pre>\n<h1>3. ZGC \u7684 GC \u7b97\u6cd5<\/h1>\n<h2>ZGC \u7684\u6267\u884c\u9636\u6bb5<\/h2>\n<ol>\n<li>\u521d\u59cb\u6807\u8bb0\uff0cSTW\uff1a\u4ece GC Roots \u6807\u8bb0\u76f4\u63a5\u53ef\u8fbe\u7684\u5bf9\u8c61\u3002<\/li>\n<li>\u5e76\u53d1\u6807\u8bb0\/\u5bf9\u8c61\u91cd\u5b9a\u4f4d\uff1a\u8fdb\u884c\u5e76\u53d1\u6807\u8bb0\u3001\u5e76\u4fee\u590d\u6307\u5411\u5df2\u8f6c\u79fb\u5bf9\u8c61\u7684\u6307\u9488\u3002<\/li>\n<li>\u518d\u6807\u8bb0\uff0cSTW\uff1a\u65f6\u95f4\u4e0d\u80fd\u8d85\u8fc7 1ms\uff0c\u8d85\u8fc7 1ms \u91cd\u65b0\u8fdb\u5165\u5e76\u53d1\u6807\u8bb0\u9636\u6bb5\u3002<\/li>\n<li>\u5e76\u53d1\u8f6c\u79fb\u51c6\u5907\uff1a\u5f15\u7528\u5904\u7406\u3001\u7c7b\u5378\u8f7d\u3001\u91cd\u5b9a\u4f4d\u96c6\u5408\u9009\u62e9\u3002<\/li>\n<li>\u521d\u59cb\u8f6c\u79fb\uff0cSTW\uff1a\u8f6c\u79fb\u4ece GC Roots \u76f4\u63a5\u53ef\u8fbe\u7684\u5bf9\u8c61\u3002<\/li>\n<li>\u5e76\u53d1\u8f6c\u79fb\uff1a\u5e76\u53d1\u8f6c\u79fb\u5269\u4f59\u7684\u5f85\u8f6c\u79fb\u5bf9\u8c61\u3002<\/li>\n<\/ol>\n<p>\u5e76\u53d1\u8f6c\u79fb\u5b8c\u6210\u540e\uff0c\u9700\u8981\u4fee\u6b63\u6267\u884c\u88ab\u8f6c\u79fb\u5bf9\u8c61\u7684\u5f15\u7528\uff0c\u8fd9\u4e2a\u8fc7\u7a0b\u662f\u501f\u52a9\u4e0b\u4e00\u8f6e GC \u6807\u8bb0\u9636\u6bb5\uff08\u521d\u59cb\u3001\u5e76\u53d1\uff09\u6765\u5b9e\u73b0\uff0c\u4e0b\u4e00\u8f6e GC \u5468\u671f\u6807\u8bb0\u5b8c\u6210\u540e\u8f6c\u53d1\u8868\u53ef\u4ee5\u6e05\u7a7a\u3002<\/p>\n<p>ZGC \u7684\u5e76\u53d1\u6807\u8bb0\u7b97\u6cd5\u4e5f\u662f\u57fa\u4e8e SATB \uff08Snapshot-At-The-Begining\uff09\u7b97\u6cd5\u7684\u3002<\/p>\n<h1>4. \u5f15\u8d77 ZGC \u505c\u987f\u7684\u5176\u4ed6\u573a\u666f<\/h1>\n<ul>\n<li>\u5185\u5b58\u5206\u914d\u963b\u585e\uff1a\u5f53\u5185\u5b58\u4e0d\u8db3\u65f6\u7ebf\u7a0b\u4f1a\u963b\u585e\u7b49\u5f85 GC \u5b8c\u6210\uff0c\u5173\u952e\u5b57\u662f &#8220;Allocation Stall&#8221;\u3002\u51fa\u73b0\u8fd9\u79cd\u60c5\u51b5\u53ef\u4ee5\u8ba4\u4e3a\u662f\u5806\u7a7a\u95f4\u504f\u5c0f\u6216 concurrent gc threads \u6570\u504f\u5c0f\u3002<\/li>\n<li>\u5b89\u5168\u70b9\uff1a\u6240\u6709\u7ebf\u7a0b\u8fdb\u5165\u5230\u5b89\u5168\u70b9\u540e\u624d\u80fd\u8fdb\u884c GC\uff0cZGC \u5b9a\u671f\u8fdb\u5165\u5b89\u5168\u70b9\u5224\u65ad\u662f\u5426\u9700\u8981 GC\u3002\u5148\u8fdb\u5165\u5b89\u5168\u70b9\u7684\u7ebf\u7a0b\u9700\u8981\u7b49\u5f85\u540e\u8fdb\u5165\u5b89\u5168\u70b9\u7684\u7ebf\u7a0b\u76f4\u5230\u6240\u6709\u7ebf\u7a0b\u6302\u8d77\u3002<\/li>\n<li>dump \u7ebf\u7a0b\u3001\u5185\u5b58\uff1ajstack\u3001jmap \u547d\u4ee4\u3002<\/li>\n<\/ul>\n<h1>5. \u5176\u4ed6<\/h1>\n<p>ZGC \u76ee\u524d\u662f\u4e0d\u5206\u4ee3\u7684\uff0c\u4e5f\u5c31\u662f\u8bf4\u6bcf\u6b21 GC \u90fd\u662f Full GC\u3002\u5982\u679c\u5e94\u7528\u5206\u914d\u5bf9\u8c61\u7684\u901f\u5ea6\u8fdc\u5feb\u4e8e GC \u7684\u8fdb\u5ea6\uff0c\u5c31\u53ef\u80fd\u5bfc\u81f4\u53ef\u7528\u7a7a\u95f4\u7528\u5b8c\u4e86 GC \u8fd8\u6ca1\u5b8c\u6210\uff0c\u5bfc\u81f4\u5e94\u7528\u963b\u585e\u3002<\/p>\n<p>\u76ee\u524d\u7684\u6539\u8fdb\u53ea\u80fd\u662f\u52a0\u5927\u5806\u7a7a\u95f4\u6216\u5c3d\u65e9\u5f00\u59cb GC \u3002<\/p>\n<h1>6. \u53c2\u8003\u8d44\u6599<\/h1>\n<p><a href=\"http:\/\/cr.openjdk.java.net\/~pliden\/slides\/ZGC-PLMeetup-2019.pdf\">The Design of ZGC<\/a><br \/>\n<a href=\"https:\/\/wiki.openjdk.java.net\/display\/zgc\/Main\">ZGC \u5b98\u7f51<\/a><\/p>\n<hr \/>\n<p>\u6b22\u8fce\u5173\u6ce8\u6211\u7684\u5fae\u4fe1\u516c\u4f17\u53f7: <strong>coderbee\u7b14\u8bb0<\/strong> \u3002<br \/>\n<img loading=\"lazy\" decoding=\"async\" width=\"258\" height=\"258\" src=\"https:\/\/coderbee.net\/wp-content\/uploads\/2019\/01\/coderbee-note.jpg\" class=\"alignnone size-full wp-image-1707\" \/><\/p>\n","protected":false},"excerpt":{"rendered":"<p>0. \u6807\u8bb0-\u590d\u5236\u7b97\u6cd5 \u6807\u8bb0-\u590d\u5236\u7b97\u6cd5\u5206\u4e09\u4e2a\u9636\u6bb5\uff1a \u6807\u8bb0\u9636\u6bb5\uff1a\u4ece GC Roots &hellip; <a href=\"https:\/\/coderbee.net\/index.php\/jvm\/20210612\/2168\">\u7ee7\u7eed\u9605\u8bfb <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[96],"tags":[101,343],"_links":{"self":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/2168"}],"collection":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/comments?post=2168"}],"version-history":[{"count":2,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/2168\/revisions"}],"predecessor-version":[{"id":2170,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/2168\/revisions\/2170"}],"wp:attachment":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/media?parent=2168"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/categories?post=2168"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/tags?post=2168"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}