{"id":2138,"date":"2023-04-02T10:07:33","date_gmt":"2023-04-02T02:07:33","guid":{"rendered":"https:\/\/www.appblog.cn\/?p=2138"},"modified":"2023-04-05T19:59:39","modified_gmt":"2023-04-05T11:59:39","slug":"deeply-understand-the-core-knowledge-points-of-jvm","status":"publish","type":"post","link":"https:\/\/www.appblog.cn\/index.php\/2023\/04\/02\/deeply-understand-the-core-knowledge-points-of-jvm\/","title":{"rendered":"\u6df1\u5165\u7406\u89e3JVM\u7684\u6838\u5fc3\u77e5\u8bc6\u70b9"},"content":{"rendered":"<h2>JVM\u6982\u8ff0<\/h2>\n<p>JVM (JAVA \u865a\u62df\u673a)\uff0c\u5b9a\u4e49\u4e86\u4e00\u5957\u7f16\u8bd1\u3001\u52a0\u8f7d\u3001\u89e3\u91ca\u6267\u884cJAVA\u4ee3\u7801\u7684\u89c4\u8303\u3002\u57fa\u4e8e\u8fd9\u5957\u89c4\u8303\u5e02\u573a\u4e0a\u4e0d\u540c\u4ea7\u54c1\u5b9e\u73b0\uff0c\u4f8b\u5982Hotspot\u3001JRockit\u3001J9\u7b49\u3002<\/p>\n<p>\u5176\u7b80\u6613\u5185\u5b58\u4f53\u7cfb\u7ed3\u6784\u5982\u4e0b\uff1a<\/p>\n<p><!-- more --><\/p>\n<p><img decoding=\"async\" src=\"http:\/\/www.yezhou.me\/AppBlog\/images\/Java\/JVM\u7b80\u6613\u5185\u5b58\u4f53\u7cfb\u7ed3\u6784.png\" alt=\"JVM\u7b80\u6613\u5185\u5b58\u4f53\u7cfb\u7ed3\u6784\" \/><\/p>\n<h2>\u5806\u7684\u5185\u5b58\u5212\u5206<\/h2>\n<p><img decoding=\"async\" src=\"http:\/\/www.yezhou.me\/AppBlog\/images\/Java\/JVM\u5806\u5185\u5b58\u5212\u5206.png\" alt=\"JVM\u5806\u5185\u5b58\u5212\u5206\" \/><\/p>\n<p>Java\u5806\u7684\u5185\u5b58\u5212\u5206\u5982\u56fe\u6240\u793a\uff0c\u5206\u522b\u4e3a\u5e74\u8f7b\u4ee3\u3001Old Memory\uff08\u8001\u5e74\u4ee3\uff09\u3001Perm\uff08\u6c38\u4e45\u4ee3\uff09\u3002\u5176\u4e2d\u5728JDK1.8\u4e2d\uff0c\u6c38\u4e45\u4ee3\u88ab\u79fb\u9664\uff0c\u4f7f\u7528MetaSpace\u4ee3\u66ff\u3002<\/p>\n<h3>\u65b0\u751f\u4ee3<\/h3>\n<ul>\n<li>\u4f7f\u7528\u590d\u5236\u6e05\u9664\u7b97\u6cd5\uff08Copinng\u7b97\u6cd5\uff09\uff0c\u539f\u56e0\u662f\u5e74\u8f7b\u4ee3\u6bcf\u6b21GC\u90fd\u8981\u56de\u6536\u5927\u90e8\u5206\u5bf9\u8c61\u3002\u65b0\u751f\u4ee3\u91cc\u9762\u5206\u6210\u4e00\u4efd\u8f83\u5927\u7684Eden\u7a7a\u95f4\u548c\u4e24\u4efd\u8f83\u5c0f\u7684Survivor\u7a7a\u95f4\u3002\u6bcf\u6b21\u53ea\u4f7f\u7528Eden\u548c\u5176\u4e2d\u4e00\u5757Survivor\u7a7a\u95f4\uff0c\u7136\u540e\u5783\u573e\u56de\u6536\u7684\u65f6\u5019\uff0c\u628a\u5b58\u6d3b\u5bf9\u8c61\u653e\u5230\u672a\u4f7f\u7528\u7684Survivor\uff08\u5212\u5206\u51fafrom\u3001to\uff09\u7a7a\u95f4\u4e2d\uff0c\u6e05\u7a7aEden\u548c\u521a\u624d\u4f7f\u7528\u8fc7\u7684Survivor\u7a7a\u95f4<\/li>\n<li>\u5206\u4e3a<code>Eden<\/code>\u3001<code>Survivor From<\/code>\u3001<code>Survivor To<\/code>\uff0c\u6bd4\u4f8b\u9ed8\u8ba4\u4e3a<code>8\uff1a1\uff1a1<\/code><\/li>\n<li>\u5185\u5b58\u4e0d\u8db3\u65f6\u53d1\u751fMinor GC<\/li>\n<\/ul>\n<h3>\u8001\u5e74\u4ee3<\/h3>\n<ul>\n<li>\u91c7\u7528\u6807\u8bb0-\u6574\u7406\u7b97\u6cd5\uff08mark-compact\uff09\uff0c\u539f\u56e0\u662f\u8001\u5e74\u4ee3\u6bcf\u6b21GC\u53ea\u4f1a\u56de\u6536\u5c11\u90e8\u5206\u5bf9\u8c61<\/li>\n<\/ul>\n<h3>Perm\uff1a\u7528\u6765\u5b58\u50a8\u7c7b\u7684\u5143\u6570\u636e\uff0c\u4e5f\u5c31\u662f\u65b9\u6cd5\u533a<\/h3>\n<ul>\n<li>Perm\u7684\u5e9f\u9664\uff1a\u5728JDK1.8\u4e2d\uff0cPerm\u88ab\u66ff\u6362\u6210MetaSpace\uff0cMetaSpace\u5b58\u653e\u5728\u672c\u5730\u5185\u5b58\u4e2d\u3002\u539f\u56e0\u662f\u6c38\u4e45\u4ee3\u8fdb\u573a\u5185\u5b58\u4e0d\u591f\u7528\uff0c\u6216\u8005\u53d1\u751f\u5185\u5b58\u6cc4\u6f0f<\/li>\n<li>MetaSpace\uff08\u5143\u7a7a\u95f4\uff09\uff1a\u5143\u7a7a\u95f4\u7684\u672c\u8d28\u548c\u6c38\u4e45\u4ee3\u7c7b\u4f3c\uff0c\u90fd\u662f\u5bf9JVM\u89c4\u8303\u4e2d\u65b9\u6cd5\u533a\u7684\u5b9e\u73b0\u3002\u4e0d\u8fc7\u5143\u7a7a\u95f4\u4e0e\u6c38\u4e45\u4ee3\u4e4b\u95f4\u6700\u5927\u7684\u533a\u522b\u5728\u4e8e\uff1a<strong>\u5143\u7a7a\u95f4\u5e76\u4e0d\u5728\u865a\u62df\u673a\u4e2d\uff0c\u800c\u662f\u4f7f\u7528\u672c\u5730\u5185\u5b58<\/strong><\/li>\n<\/ul>\n<h2>GC\u5783\u573e\u56de\u6536<\/h2>\n<p>\u5e38\u89c1\u7684\u5783\u573e\u56de\u6536\u7b97\u6cd5\uff1a<\/p>\n<h3>Mark-Sweep\uff08\u6807\u8bb0-\u6e05\u9664\u7b97\u6cd5\uff09<\/h3>\n<ul>\n<li>\u601d\u60f3\uff1a\u6807\u8bb0\u6e05\u9664\u7b97\u6cd5\u5206\u4e3a\u4e24\u4e2a\u9636\u6bb5\uff0c\u6807\u8bb0\u9636\u6bb5\u548c\u6e05\u9664\u9636\u6bb5\u3002\u6807\u8bb0\u9636\u6bb5\u4efb\u52a1\u662f\u6807\u8bb0\u51fa\u6240\u6709\u9700\u8981\u56de\u6536\u7684\u5bf9\u8c61\uff0c\u6e05\u9664\u9636\u6bb5\u5c31\u662f\u6e05\u9664\u88ab\u6807\u8bb0\u5bf9\u8c61\u7684\u7a7a\u95f4<\/li>\n<li>\u4f18\u7f3a\u70b9\uff1a\u5b9e\u73b0\u7b80\u5355\uff0c\u5bb9\u6613\u4ea7\u751f\u5185\u5b58\u788e\u7247<\/li>\n<\/ul>\n<h3>Copying\uff08\u590d\u5236\u6e05\u9664\u7b97\u6cd5\uff09<\/h3>\n<ul>\n<li>\u601d\u60f3\uff1a\u5c06\u53ef\u7528\u5185\u5b58\u5212\u5206\u4e3a\u5927\u5c0f\u76f8\u7b49\u7684\u4e24\u5757\uff0c\u6bcf\u6b21\u53ea\u4f7f\u7528\u5176\u4e2d\u7684\u4e00\u5757\u3002\u5f53\u8fdb\u884c\u5783\u573e\u56de\u6536\u7684\u65f6\u5019\uff0c\u628a\u5176\u4e2d\u5b58\u6d3b\u5bf9\u8c61\u5168\u90e8\u590d\u5236\u5230\u53e6\u5916\u4e00\u5757\u4e2d\uff0c\u7136\u540e\u628a\u5df2\u4f7f\u7528\u7684\u5185\u5b58\u7a7a\u95f4\u4e00\u6b21\u6e05\u7a7a\u6389<\/li>\n<li>\u4f18\u7f3a\u70b9\uff1a\u4e0d\u5bb9\u6613\u4ea7\u751f\u5185\u5b58\u788e\u7247\uff1b\u53ef\u7528\u5185\u5b58\u7a7a\u95f4\u5c11\uff1b\u5b58\u6d3b\u5bf9\u8c61\u591a\u7684\u8bdd\uff0c\u6548\u7387\u4f4e\u4e0b<\/li>\n<\/ul>\n<h3>Mark-Compact\uff08\u6807\u8bb0-\u6574\u7406\u7b97\u6cd5\uff09<\/h3>\n<ul>\n<li>\u601d\u60f3\uff1a\u5148\u6807\u8bb0\u5b58\u6d3b\u5bf9\u8c61\uff0c\u7136\u540e\u628a\u5b58\u6d3b\u5bf9\u8c61\u5411\u4e00\u8fb9\u79fb\u52a8\uff0c\u7136\u540e\u6e05\u7406\u6389\u7aef\u8fb9\u754c\u4ee5\u5916\u7684\u5185\u5b58<\/li>\n<li>\u4f18\u7f3a\u70b9\uff1a\u4e0d\u5bb9\u6613\u4ea7\u751f\u5185\u5b58\u788e\u7247\uff1b\u5185\u5b58\u5229\u7528\u7387\u9ad8\uff1b\u5b58\u6d3b\u5bf9\u8c61\u591a\u5e76\u4e14\u5206\u6563\u7684\u65f6\u5019\uff0c\u79fb\u52a8\u6b21\u6570\u591a\uff0c\u6548\u7387\u4f4e\u4e0b<\/li>\n<\/ul>\n<h3>\u5206\u4ee3\u6536\u96c6\u7b97\u6cd5\uff08\u76ee\u524d\u5927\u90e8\u5206JVM\u7684\u5783\u573e\u6536\u96c6\u5668\u6240\u91c7\u7528\u7684\u7b97\u6cd5\uff09<\/h3>\n<p>\u601d\u60f3\uff1a\u628a\u5806\u5206\u6210\u65b0\u751f\u4ee3\u548c\u8001\u5e74\u4ee3\uff08\u6c38\u4e45\u4ee3\u6307\u7684\u662f\u65b9\u6cd5\u533a\uff09<\/p>\n<ul>\n<li>\u56e0\u4e3a\u65b0\u751f\u4ee3\u6bcf\u6b21\u5783\u573e\u56de\u6536\u90fd\u8981\u56de\u6536\u5927\u90e8\u5206\u5bf9\u8c61\uff0c\u6240\u4ee5\u65b0\u751f\u4ee3\u91c7\u7528Copying\u7b97\u6cd5\u3002\u65b0\u751f\u4ee3\u91cc\u9762\u5206\u6210\u4e00\u4efd\u8f83\u5927\u7684Eden\u7a7a\u95f4\u548c\u4e24\u4efd\u8f83\u5c0f\u7684Survivor\u7a7a\u95f4\u3002\u6bcf\u6b21\u53ea\u4f7f\u7528Eden\u548c\u5176\u4e2d\u4e00\u5757Survivor\u7a7a\u95f4\uff0c\u7136\u540e\u5783\u573e\u56de\u6536\u7684\u65f6\u5019\uff0c\u628a\u5b58\u6d3b\u5bf9\u8c61\u653e\u5230\u672a\u4f7f\u7528\u7684Survivor\uff08\u5212\u5206\u51fafrom\u3001to\uff09\u7a7a\u95f4\u4e2d\uff0c\u6e05\u7a7aEden\u548c\u521a\u624d\u4f7f\u7528\u8fc7\u7684Survivor\u7a7a\u95f4<\/li>\n<li>\u7531\u4e8e\u8001\u5e74\u4ee3\u6bcf\u6b21\u53ea\u56de\u6536\u5c11\u91cf\u7684\u5bf9\u8c61\uff0c\u56e0\u6b64\u91c7\u7528mark-compact\u7b97\u6cd5<\/li>\n<li>\u5728\u5806\u533a\u5916\u6709\u4e00\u4e2a\u6c38\u4e45\u4ee3\u3002\u5bf9\u6c38\u4e45\u4ee3\u7684\u56de\u6536\u4e3b\u8981\u662f\u65e0\u6548\u7684\u7c7b\u548c\u5e38\u91cf<\/li>\n<\/ul>\n<p>\u51e0\u79cd\u4e0d\u540c\u7684\u5783\u573e\u56de\u6536\u7c7b\u578b\uff1a<\/p>\n<ul>\n<li>Minor GC\uff1a\u4ece\u5e74\u8f7b\u4ee3\uff08\u5305\u62ecEden\u3001Survivor\u533a\uff09\u56de\u6536\u5185\u5b58<\/li>\n<li>Major GC\uff1a\u6e05\u7406\u6574\u4e2a\u8001\u5e74\u4ee3\uff0c\u5f53Eden\u533a\u5185\u5b58\u4e0d\u8db3\u65f6\u89e6\u53d1<\/li>\n<li>Full GC\uff1a\u6e05\u7406\u6574\u4e2a\u5806\u7a7a\u95f4\uff0c\u5305\u62ec\u5e74\u8f7b\u4ee3\u548c\u8001\u5e74\u4ee3\u3002\u5f53\u8001\u5e74\u4ee3\u5185\u5b58\u4e0d\u8db3\u65f6\u89e6\u53d1<\/li>\n<\/ul>\n<h2>JVM\u4f18\u5316<\/h2>\n<p>1\u3001\u4e00\u822c\u6765\u8bf4\uff0c\u5f53survivor\u533a\u4e0d\u591f\u5927\u6216\u8005\u5360\u7528\u91cf\u8fbe\u523050%\uff0c\u5c31\u4f1a\u628a\u4e00\u4e9b\u5bf9\u8c61\u653e\u5230\u8001\u5e74\u533a\u3002\u901a\u8fc7\u8bbe\u7f6e\u5408\u7406\u7684eden\u533a\uff0csurvivor\u533a\u53ca\u4f7f\u7528\u7387\uff0c\u53ef\u4ee5\u5c06\u5e74\u8f7b\u5bf9\u8c61\u4fdd\u5b58\u5728\u5e74\u8f7b\u4ee3\uff0c\u4ece\u800c\u907f\u514dfull GC\uff0c\u4f7f\u7528<code>-Xmn<\/code>\u8bbe\u7f6e\u5e74\u8f7b\u4ee3\u7684\u5927\u5c0f<\/p>\n<p>2\u3001\u5bf9\u4e8e\u5360\u7528\u5185\u5b58\u6bd4\u8f83\u591a\u7684\u5927\u5bf9\u8c61\uff0c\u4e00\u822c\u4f1a\u9009\u62e9\u5728\u8001\u5e74\u4ee3\u5206\u914d\u5185\u5b58\u3002\u5982\u679c\u5728\u5e74\u8f7b\u4ee3\u7ed9\u5927\u5bf9\u8c61\u5206\u914d\u5185\u5b58\uff0c\u5e74\u8f7b\u4ee3\u5185\u5b58\u4e0d\u591f\u4e86\uff0c\u5c31\u8981\u5728eden\u533a\u79fb\u52a8\u5927\u91cf\u5bf9\u8c61\u5230\u8001\u5e74\u4ee3\uff0c\u7136\u540e\u8fd9\u4e9b\u79fb\u52a8\u7684\u5bf9\u8c61\u53ef\u80fd\u5f88\u5feb\u6d88\u4ea1\uff0c\u56e0\u6b64\u5bfc\u81f4full GC\u3002\u901a\u8fc7\u8bbe\u7f6e\u53c2\u6570\uff1a<code>-XX:PetenureSizeThreshold=1000000<\/code>\uff0c\u5355\u4f4d\u4e3aB\uff0c\u6807\u660e\u5bf9\u8c61\u5927\u5c0f\u8d85\u8fc71M\u65f6\uff0c\u5728\u8001\u5e74\u4ee3(tenured)\u5206\u914d\u5185\u5b58\u7a7a\u95f4<\/p>\n<p>3\u3001\u4e00\u822c\u60c5\u51b5\u4e0b\uff0c\u5e74\u8f7b\u5bf9\u8c61\u653e\u5728eden\u533a\uff0c\u5f53\u7b2c\u4e00\u6b21GC\u540e\uff0c\u5982\u679c\u5bf9\u8c61\u8fd8\u5b58\u6d3b\uff0c\u653e\u5230survivor\u533a\uff0c\u6b64\u540e\uff0c\u6bcfGC\u4e00\u6b21\uff0c\u5e74\u9f84\u589e\u52a01\uff0c\u5f53\u5bf9\u8c61\u7684\u5e74\u9f84\u8fbe\u5230\u9608\u503c\uff0c\u5c31\u88ab\u653e\u5230tenured\u8001\u5e74\u533a\u3002\u8fd9\u4e2a\u9608\u503c\u53ef\u4ee5\u540c\u6784<code>-XX:MaxTenuringThreshold<\/code>\u8bbe\u7f6e\u3002\u5982\u679c\u60f3\u8ba9\u5bf9\u8c61\u7559\u5728\u5e74\u8f7b\u4ee3\uff0c\u53ef\u4ee5\u8bbe\u7f6e\u6bd4\u8f83\u5927\u7684\u9608\u503c<\/p>\n<p>4\u3001\u8bbe\u7f6e\u6700\u5c0f\u5806\u548c\u6700\u5927\u5806\uff1a<code>-Xmx<\/code>\u548c<code>-Xms<\/code>\u7a33\u5b9a\u7684\u5806\u5927\u5c0f\u5806\u5783\u573e\u56de\u6536\u662f\u6709\u5229\u7684\uff0c\u83b7\u5f97\u4e00\u4e2a\u7a33\u5b9a\u7684\u5806\u5927\u5c0f\u7684\u65b9\u6cd5\u662f\u8bbe\u7f6e<code>-Xms<\/code>\u548c<code>-Xmx<\/code>\u7684\u503c\u4e00\u6837\uff0c\u5373\u6700\u5927\u5806\u548c\u6700\u5c0f\u5806\u4e00\u6837\uff0c\u5982\u679c\u8fd9\u6837\u8bbe\u7f6e\uff0c\u7cfb\u7edf\u5728\u8fd0\u884c\u65f6\u5806\u5927\u5c0f\u7406\u8bba\u4e0a\u662f\u6052\u5b9a\u7684\uff0c\u7a33\u5b9a\u7684\u5806\u7a7a\u95f4\u53ef\u4ee5\u51cf\u5c11GC\u6b21\u6570\uff0c\u56e0\u6b64\uff0c\u5f88\u591a\u670d\u52a1\u7aef\u90fd\u4f1a\u5c06\u8fd9\u4e24\u4e2a\u53c2\u6570\u8bbe\u7f6e\u4e3a\u4e00\u6837\u7684\u6570\u503c\u3002\u7a33\u5b9a\u7684\u5806\u5927\u5c0f\u867d\u7136\u51cf\u5c11GC\u6b21\u6570\uff0c\u4f46\u662f\u589e\u52a0\u6bcf\u6b21GC\u7684\u65f6\u95f4\uff0c\u56e0\u4e3a\u6bcf\u6b21GC\u8981\u628a\u5806\u7684\u5927\u5c0f\u7ef4\u6301\u5728\u4e00\u4e2a\u533a\u95f4\u5185<\/p>\n<p>5\u3001\u4e00\u4e2a\u4e0d\u7a33\u5b9a\u7684\u5806\u5e76\u975e\u6beb\u65e0\u7528\u5904\u3002\u5728\u7cfb\u7edf\u4e0d\u9700\u8981\u4f7f\u7528\u5927\u5185\u5b58\u7684\u65f6\u5019\uff0c\u538b\u7f29\u5806\u7a7a\u95f4\uff0c\u4f7f\u5f97GC\u6bcf\u6b21\u5e94\u5bf9\u4e00\u4e2a\u8f83\u5c0f\u7684\u5806\u7a7a\u95f4\uff0c\u52a0\u5feb\u5355\u6b21GC\u6b21\u6570\u3002\u57fa\u4e8e\u8fd9\u79cd\u8003\u8651\uff0cJVM\u63d0\u4f9b\u4e24\u4e2a\u53c2\u6570\uff0c\u7528\u4e8e\u538b\u7f29\u548c\u6269\u5c55\u5806\u7a7a\u95f4<\/p>\n<ul>\n<li><code>-XX:MinHeapFreeRatio<\/code> \u53c2\u6570\u7528\u4e8e\u8bbe\u7f6e\u5806\u7a7a\u95f4\u7684\u6700\u5c0f\u7a7a\u95f2\u6bd4\u7387\u3002\u9ed8\u8ba4\u503c\u662f40\uff0c\u5f53\u5806\u7a7a\u95f4\u7684\u7a7a\u95f2\u5185\u5b58\u6bd4\u7387\u5c0f\u4e8e40\uff0cJVM\u4fbf\u4f1a\u6269\u5c55\u5806\u7a7a\u95f4<\/li>\n<li><code>-XX:MaxHeapFreeRatio<\/code> \u53c2\u6570\u7528\u4e8e\u8bbe\u7f6e\u5806\u7a7a\u95f4\u7684\u6700\u5927\u7a7a\u95f2\u6bd4\u7387\u3002\u9ed8\u8ba4\u503c\u662f70\uff0c\u5f53\u5806\u7a7a\u95f4\u7684\u7a7a\u95f2\u5185\u5b58\u6bd4\u7387\u5927\u4e8e70\uff0cJVM\u4fbf\u4f1a\u538b\u7f29\u5806\u7a7a\u95f4<\/li>\n<li>\u5f53<code>-Xmx<\/code>\u548c<code>-Xms<\/code>\u76f8\u7b49\u65f6\uff0c\u4e0a\u9762\u4e24\u4e2a\u53c2\u6570\u65e0\u6548<\/li>\n<\/ul>\n<p>6\u3001\u901a\u8fc7\u589e\u5927\u541e\u5410\u91cf\u63d0\u9ad8\u7cfb\u7edf\u6027\u80fd\uff0c\u53ef\u4ee5\u901a\u8fc7\u8bbe\u7f6e\u5e76\u884c\u5783\u573e\u56de\u6536\u6536\u96c6\u5668<\/p>\n<ul>\n<li><code>-XX:+UseParallelGC<\/code> \u5e74\u8f7b\u4ee3\u4f7f\u7528\u5e76\u884c\u5783\u573e\u56de\u6536\u6536\u96c6\u5668\u3002\u8fd9\u662f\u4e00\u4e2a\u5173\u6ce8\u541e\u5410\u91cf\u7684\u6536\u96c6\u5668\uff0c\u53ef\u4ee5\u5c3d\u53ef\u80fd\u7684\u51cf\u5c11\u5783\u573e\u56de\u6536\u65f6\u95f4<\/li>\n<li><code>-XX:+UseParallelOldGC<\/code> \u8bbe\u7f6e\u8001\u5e74\u4ee3\u4f7f\u7528\u5e76\u884c\u5783\u573e\u56de\u6536\u6536\u96c6\u5668<\/li>\n<\/ul>\n<p>7\u3001\u5c1d\u8bd5\u4f7f\u7528\u5927\u7684\u5185\u5b58\u5206\u9875\uff1a\u4f7f\u7528\u5927\u7684\u5185\u5b58\u5206\u9875\u589e\u52a0CPU\u7684\u5185\u5b58\u5bfb\u5740\u80fd\u529b\uff0c\u4ece\u800c\u63d0\u5347\u7cfb\u7edf\u7684\u6027\u80fd\u3002<code>-XX:+LargePageSizeInBytes<\/code>\u8bbe\u7f6e\u5185\u5b58\u9875\u7684\u5927\u5c0f<\/p>\n<p>8\u3001\u4f7f\u7528\u975e\u5360\u7528\u7684\u5783\u573e\u6536\u96c6\u5668\u3002<code>-XX:+UseConcMarkSweepGC<\/code>\u8001\u5e74\u4ee3\u4f7f\u7528CMS\u6536\u96c6\u5668\u964d\u4f4e\u505c\u987f<\/p>\n<p>9\u3001<code>-XXSurvivorRatio=3<\/code>\uff0c\u8868\u793a\u5e74\u8f7b\u4ee3\u4e2d\u7684\u5206\u914d\u6bd4\u7387\uff1a<code>survivor:eden = 2:3<\/code><\/p>\n<p>10\u3001JVM\u6027\u80fd\u8c03\u4f18\u7684\u5de5\u5177\uff1a<\/p>\n<p>\uff081\uff09jps\uff08Java Process Status\uff09\uff1a\u8f93\u51faJVM\u4e2d\u8fd0\u884c\u7684\u8fdb\u7a0b\u72b6\u6001\u4fe1\u606f(\u73b0\u5728\u4e00\u822c\u4f7f\u7528jconsole)<br \/>\n\uff082\uff09jstack\uff1a\u67e5\u770bjava\u8fdb\u7a0b\u5185\u7ebf\u7a0b\u7684\u5806\u6808\u4fe1\u606f<br \/>\n\uff083\uff09jmap\uff1a\u7528\u4e8e\u751f\u6210\u5806\u8f6c\u5b58\u5feb\u7167<br \/>\n\uff084\uff09jhat\uff1a\u7528\u4e8e\u5206\u6790jmap\u751f\u6210\u7684\u5806\u8f6c\u5b58\u5feb\u7167\uff08\u4e00\u822c\u4e0d\u63a8\u8350\u4f7f\u7528\uff0c\u800c\u662f\u4f7f\u7528Ecplise Memory Analyzer\uff09<br \/>\n\uff085\uff09jstat\uff1a\u662fJVM\u7edf\u8ba1\u76d1\u6d4b\u5de5\u5177\u3002\u53ef\u4ee5\u7528\u6765\u663e\u793a\u5783\u573e\u56de\u6536\u4fe1\u606f\u3001\u7c7b\u52a0\u8f7d\u4fe1\u606f\u3001\u65b0\u751f\u4ee3\u7edf\u8ba1\u4fe1\u606f\u7b49<br \/>\n\uff086\uff09VisualVM\uff1a\u6545\u969c\u5904\u7406\u5de5\u5177<\/p>\n<h2>\u7c7b\u52a0\u8f7d\u673a\u5236<\/h2>\n<p>1\u3001\u53ef\u4ee5\u5728IDEA\u4e2d<code>Run Configurations<\/code> &#8211;&gt; <code>Configuration<\/code> &#8211;&gt; <code>VM options<\/code>\u4e2d\u8bbe\u7f6e\u53c2\u6570\uff1a<\/p>\n<pre><code>-XX:+TraceClassLoading  \/\/\u67e5\u770b\u7c7b\u7684\u52a0\u8f7d\u987a\u5e8f\n\n-XX:MetaspaceSize=2m  \/\/\u8bbe\u7f6emetaspace\u7684\u5927\u5c0f\n\n-XX:MaxMetaspaceSize=10m  \/\/\u8bbe\u7f6emetaspace\u5927\u5c0f\u7684\u6700\u5927\u503c<\/code><\/pre>\n<p>2\u3001\u6bcf\u4e00\u4e2a\u7c7b\u7684\u6700\u5148\u52a0\u8f7d\u7684\u4e09\u4e2a\u7c7b<\/p>\n<pre><code class=\"language-java\">[Loaded java.lang.Object from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]\n[Loaded java.io.Serializable from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]\n[Loaded java.lang.Comparable from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]\n[Loaded java.lang.CharSequence from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]\n[Loaded java.lang.String from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]\n[Loaded java.lang.reflect.AnnotatedElement from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]\n[Loaded java.lang.reflect.GenericDeclaration from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]\n[Loaded java.lang.reflect.Type from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]\n[Loaded java.lang.Class from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]\n[Loaded java.lang.Cloneable from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]\n[Loaded java.lang.ClassLoader from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]\n[Loaded java.lang.System from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]\n[Loaded java.lang.Throwable from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]\n[Loaded java.lang.Error from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]\n[Loaded java.lang.ThreadDeath from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]\n[Loaded java.lang.Exception from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]\n[Loaded java.lang.RuntimeException from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]\n[Loaded java.lang.SecurityManager from C:\\Program Files\\Java\\jdk1.8.0_231\\jre\\lib\\rt.jar]<\/code><\/pre>\n<p>3\u3001\u7c7b\u52a0\u8f7d\u5668\u628aclass\u6587\u4ef6\u4e2d\u7684\u4e8c\u8fdb\u5236\u6570\u636e\u8bfb\u5165\u5230\u5185\u5b58\u4e2d\uff0c\u5b58\u653e\u5728\u65b9\u6cd5\u533a\uff0c\u7136\u540e\u5728\u5806\u533a\u521b\u5efa\u4e00\u4e2ajava.lang.Class\u5bf9\u8c61\uff0c\u7528\u6765\u5c01\u88c5\u7c7b\u5728\u65b9\u6cd5\u533a\u5185\u7684\u6570\u636e\u7ed3\u6784\u3002\u7c7b\u52a0\u8f7d\u7684\u6b65\u9aa4\u5982\u4e0b\uff1a<\/p>\n<ul>\n<li>\u52a0\u8f7d\uff1a\u67e5\u627e\u5e76\u52a0\u8f7d\u7c7b\u7684\u4e8c\u8fdb\u5236\u6570\u636e\uff08\u628aclass\u6587\u4ef6\u91cc\u9762\u7684\u4fe1\u606f\u52a0\u8f7d\u5230\u5185\u5b58\u91cc\u9762\uff09<\/li>\n<li>\u8fde\u63a5\uff1a\u628a\u5185\u5b58\u4e2d\u7c7b\u7684\u4e8c\u8fdb\u5236\u6570\u636e\u5408\u5e76\u5230\u865a\u62df\u673a\u7684\u8fd0\u884c\u65f6\u73af\u5883\u4e2d<\/li>\n<\/ul>\n<p>\uff081\uff09\u9a8c\u8bc1\uff1a\u786e\u4fdd\u88ab\u52a0\u8f7d\u7684\u7c7b\u7684\u6b63\u786e\u6027\u3002\u5305\u62ec\uff1a<\/p>\n<p>A\u3001\u7c7b\u6587\u4ef6\u7684\u7ed3\u6784\u68c0\u67e5\uff1a\u68c0\u67e5\u662f\u5426\u6ee1\u8db3Java\u7c7b\u6587\u4ef6\u7684\u56fa\u5b9a\u683c\u5f0f<br \/>\nB\u3001\u8bed\u4e49\u68c0\u67e5\uff1a\u786e\u4fdd\u7c7b\u672c\u8eab\u7b26\u5408Java\u7684\u8bed\u6cd5\u89c4\u8303<br \/>\nC\u3001\u5b57\u8282\u7801\u9a8c\u8bc1\uff1a\u786e\u4fdd\u5b57\u8282\u7801\u6d41\u53ef\u4ee5\u88abJava\u865a\u62df\u673a\u5b89\u5168\u7684\u6267\u884c\u3002\u5b57\u8282\u7801\u6d41\u662f\u64cd\u4f5c\u7801\u7ec4\u6210\u7684\u5e8f\u5217\u3002\u6bcf\u4e00\u4e2a\u64cd\u4f5c\u7801\u540e\u9762\u90fd\u4f1a\u8ddf\u7740\u4e00\u4e2a\u6216\u8005\u591a\u4e2a\u64cd\u4f5c\u6570\u3002\u5b57\u8282\u7801\u68c0\u67e5\u8fd9\u4e2a\u6b65\u9aa4\u4f1a\u68c0\u67e5\u6bcf\u4e00\u4e2a\u64cd\u4f5c\u7801\u662f\u5426\u5408\u6cd5<br \/>\nD\u3001\u4e8c\u8fdb\u5236\u517c\u5bb9\u6027\u9a8c\u8bc1\uff1a\u786e\u4fdd\u76f8\u4e92\u5f15\u7528\u7684\u7c7b\u4e4b\u95f4\u662f\u534f\u8c03\u4e00\u81f4\u7684<\/p>\n<p>\uff082\uff09\u51c6\u5907\uff1a\u4e3a\u7c7b\u7684\u9759\u6001\u53d8\u91cf\u5206\u914d\u5185\u5b58\uff0c\u5e76\u5c06\u5176\u521d\u59cb\u5316\u4e3a\u9ed8\u8ba4\u503c<\/p>\n<p>\uff083\uff09\u89e3\u6790\uff1a\u628a\u7c7b\u4e2d\u7684\u7b26\u53f7\u5f15\u7528\u8f6c\u5316\u4e3a\u76f4\u63a5\u5f15\u7528\uff08\u6bd4\u5982\u8bf4\u65b9\u6cd5\u7684\u7b26\u53f7\u5f15\u7528\uff0c\u662f\u6709\u65b9\u6cd5\u540d\u548c\u76f8\u5173\u63cf\u8ff0\u7b26\u7ec4\u6210\uff0c\u5728\u89e3\u6790\u9636\u6bb5\uff0cJVM\u628a\u7b26\u53f7\u5f15\u7528\u66ff\u6362\u6210\u4e00\u4e2a\u6307\u9488\uff0c\u8fd9\u4e2a\u6307\u9488\u5c31\u662f\u76f4\u63a5\u5f15\u7528\uff0c\u5b83\u6307\u5411\u8be5\u7c7b\u7684\u8be5\u65b9\u6cd5\u5728\u65b9\u6cd5\u533a\u4e2d\u7684\u5185\u5b58\u4f4d\u7f6e\uff09<\/p>\n<p>\uff084\uff09\u521d\u59cb\u5316\uff1a\u4e3a\u7c7b\u7684\u9759\u6001\u53d8\u91cf\u8d4b\u4e88\u6b63\u786e\u7684\u521d\u59cb\u503c\u3002\u5f53\u9759\u6001\u53d8\u91cf\u7684\u7b49\u53f7\u53f3\u8fb9\u7684\u503c\u662f\u4e00\u4e2a\u5e38\u91cf\u8868\u8fbe\u5f0f\u65f6\uff0c\u4e0d\u4f1a\u8c03\u7528static\u4ee3\u7801\u5757\u8fdb\u884c\u521d\u59cb\u5316\u3002\u53ea\u6709\u7b49\u53f7\u53f3\u8fb9\u7684\u503c\u662f\u4e00\u4e2a\u8fd0\u884c\u65f6\u8fd0\u7b97\u51fa\u6765\u7684\u503c\uff0c\u624d\u4f1a\u8c03\u7528static\u521d\u59cb\u5316\u3002<\/p>\n<p>4\u3001\u5e38\u89c1\u7684\u4e09\u79cd\u7c7b\u52a0\u8f7d\u5668\uff1a<\/p>\n<ul>\n<li><code>AppClassLoader<\/code>&#8211;\u5e94\u7528\u7c7b\u52a0\u8f7d\u5668\uff0c\u8d1f\u8d23\u52a0\u8f7d\u6211\u4eec\u81ea\u5df1\u5199\u7684\u7c7b<\/li>\n<li><code>ExtClassLoader<\/code>&#8211;\u6269\u5c55\u7c7b\u52a0\u8f7d\u5668\uff0c\u8d1f\u8d23\u52a0\u8f7d\u6269\u5c55\u5305\uff08jre\\lib\\ext*.jar\uff09<\/li>\n<li><code>BootstrapClassLoader<\/code>&#8211;\u6839\u7c7b\u52a0\u8f7d\u5668\uff0c\u8d1f\u8d23\u52a0\u8f7d\u6838\u5fc3\u5305\uff08jre\\lib\\rt.jar\uff09<\/li>\n<\/ul>\n<p>5\u3001\u7c7b\u52a0\u8f7d\u7c7b\u7684\u4e24\u79cd\u65b9\u5f0f\uff1a\u663e\u5f0f\u52a0\u8f7d\u548c\u9690\u5f0f\u52a0\u8f7d<\/p>\n<p>\uff081\uff09\u663e\u5f0f\u52a0\u8f7d<\/p>\n<pre><code class=\"language-java\">class classA {\n    \/\/\u7c7b\u52a0\u8f7d\u65f6\u53ef\u4ee5\u6267\u884c\u9759\u6001\u4ee3\u7801\u5757\uff0c\u4f46\u4e0d\u4e00\u5b9a\u4f1a\u6267\u884c\n    static {\n        System.out.println(11);\n    }\n}\n\n\/\/\u4e0d\u4f1a\u6267\u884c\u9759\u6001\u4ee3\u7801\u5757\nloader.loadClass(&quot;cn.appblog.ClassLoader.classA&quot;);\n\/\/\u4f1a\u6267\u884c\u9759\u6001\u4ee3\u7801\u5757\nClass.forName(&quot;cn.appblog.ClassLoader.classA&quot;, true, loader);\n\/\/\u4e0d\u4f1a\u6267\u884c\u9759\u6001\u4ee3\u7801\u5757\nClass.forName(&quot;cn.appblog.ClassLoader.classA&quot;, false, loader);<\/code><\/pre>\n<p>\uff082\uff09\u9690\u5f0f\u52a0\u8f7d\u7684\u65f6\u673a\uff1a\u9ed8\u8ba4\u90fd\u4f1a\u8fdb\u884c\u521d\u59cb\u5316<\/p>\n<ul>\n<li>\u8bbf\u95ee\u7c7b\u7684\u9759\u6001\u5c5e\u6027\u65f6\u5206\u60c5\u51b5\uff1a\u8bbf\u95eestatic final\u4fee\u9970\u7684\u516b\u79cd\u57fa\u672c\u6570\u636e\u7c7b\u578b\u548c\u5b57\u7b26\u4e32\u65f6\u4e0d\u4f1a\u89e6\u53d1\u7c7b\u7684\u52a0\u8f7d\uff1b\u8bbf\u95eestatic \u4fee\u9970\u7684\u4efb\u610f\u5c5e\u6027\u65f6\u90fd\u4f1a\u89e6\u53d1\u7c7b\u7684\u52a0\u8f7d<\/li>\n<li>\u8bbf\u95ee\u7c7b\u7684\u9759\u6001\u65b9\u6cd5\u4f1a\u89e6\u53d1\u7c7b\u7684\u52a0\u8f7d<\/li>\n<li>\u6784\u5efa\u7c7b\u7684\u5bf9\u8c61\u65f6\u4f1a\u89e6\u53d1\u7c7b\u7684\u52a0\u8f7d<\/li>\n<\/ul>\n<p>6\u3001\u7c7b\u7684\u88ab\u52a8\u52a0\u8f7d\u4e0e\u4e3b\u52a8\u52a0\u8f7d<\/p>\n<pre><code class=\"language-java\">class class1 {\n    static int a = 100;\n    static {\n        System.out.println(&quot;class1.static&quot;);\n    }\n}\n\nclass class2 extends class1 {\n    static {\n        System.out.println(&quot;class2.static&quot;);\n    }\n}\n\npublic class TestClassObject {\n    public static void main(String[] args) {\n        \/\/class1\u4e3a\u4e3b\u52a8\u52a0\u8f7d\uff0cclass2\u4e3a\u88ab\u52a8\u52a0\u8f7d(\u4e0d\u6267\u884cstatic\u521d\u59cb\u5316\u64cd\u4f5c)\n        System.out.println(class2.a);\n    }\n}<\/code><\/pre>\n<pre><code>class1.static\n100<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"<p>JVM\u6982\u8ff0 JVM (JAVA \u865a\u62df\u673a)\uff0c\u5b9a\u4e49\u4e86\u4e00\u5957\u7f16\u8bd1\u3001\u52a0\u8f7d\u3001\u89e3\u91ca\u6267\u884cJAVA\u4ee3\u7801\u7684\u89c4\u8303\u3002\u57fa\u4e8e\u8fd9\u5957\u89c4\u8303\u5e02\u573a\u4e0a [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[419],"tags":[],"class_list":["post-2138","post","type-post","status-publish","format-standard","hentry","category-jvm"],"_links":{"self":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts\/2138","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/comments?post=2138"}],"version-history":[{"count":0,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/posts\/2138\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/media?parent=2138"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/categories?post=2138"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.appblog.cn\/index.php\/wp-json\/wp\/v2\/tags?post=2138"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}