{"id":4833,"date":"2020-02-27T16:27:07","date_gmt":"2020-02-27T08:27:07","guid":{"rendered":"https:\/\/www.xttblog.com\/?p=4833"},"modified":"2020-02-27T16:27:07","modified_gmt":"2020-02-27T08:27:07","slug":"jvm-%e5%9e%83%e5%9c%be%e5%9b%9e%e6%94%b6%e5%ae%9e%e6%88%98","status":"publish","type":"post","link":"https:\/\/www.xttblog.com\/?p=4833","title":{"rendered":"JVM \u5783\u573e\u56de\u6536\u5b9e\u6218"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">\u672c\u6587\u6211\u4eec\u6765\u5b66\u4e60\u4e0b GC \u7684\u5b9e\u6218\u5185\u5bb9\uff0c\u4e3b\u8981\u5305\u62ec\u4ee5\u4e0b\u51e0\u70b9<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>JVM \u53c2\u6570\u7b80\u4ecb<\/li><li>\u53d1\u751f OOM \u7684\u4e3b\u8981\u51e0\u79cd\u573a\u666f\u53ca\u76f8\u5e94\u89e3\u51b3\u65b9\u6848<\/li><li>OOM \u95ee\u9898\u6392\u67e5\u7684\u4e00\u4e9b\u5e38\u7528\u5de5\u5177<\/li><li>GC \u65e5\u5fd7\u683c\u5f0f\u600e\u4e48\u770b<\/li><li>jstat \u4e0e\u53ef\u89c6\u5316 APM \u5de5\u5177\u6784\u5efa<\/li><li>\u518d\u8c08 JVM \u53c2\u6570\u8bbe\u7f6e<\/li><\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">JVM \u53c2\u6570\u7b80\u4ecb<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u5728\u5f00\u59cb\u5b9e\u8df5\u4e4b\u524d\u6211\u4eec\u6709\u5fc5\u8981\u5148\u7b80\u5355\u4e86\u89e3\u4e00\u4e0b JVM \u53c2\u6570\u914d\u7f6e\uff0c\u56e0\u4e3a\u672c\u6587\u4e4b\u540e\u7684\u5b9e\u9a8c\u4e2d\u63d0\u5230\u7684 JVM \u4e2d\u7684\u6808\uff0c\u5806\u5927\u5c0f\uff0c\u4f7f\u7528\u7684\u5783\u573e\u6536\u96c6\u5668\u7b49\u90fd\u9700\u8981\u901a\u8fc7 JVM \u53c2\u6570\u6765\u8bbe\u7f6e<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u5148\u6765\u770b\u4e0b\u5982\u4f55\u8fd0\u884c\u4e00\u4e2a Java \u7a0b\u5e8f<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>public class Test {\n    public static  void main(String[] args) {\n        System.out.println(\"test\");\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u9996\u5148\u6211\u4eec\u901a\u8fc7 javac Test.java \u5c06\u5176\u8f6c\u6210\u5b57\u8282\u7801\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u5176\u6b21\u6211\u4eec\u5f80\u5f80\u4f1a\u8f93\u5165 java Test \u8fd9\u6837\u7684\u547d\u4ee4\u6765\u542f\u52a8 JVM \u8fdb\u7a0b\u6765\u6267\u884c\u6b64\u7a0b\u5e8f,\u5176\u5b9e\u6211\u4eec\u5728\u542f\u52a8 JVM \u8fdb\u7a0b\u7684\u65f6\u5019\uff0c\u53ef\u4ee5\u6307\u5b9a\u76f8\u5e94\u7684 JVM \u7684\u53c2\u6570\uff0c\u5982\u4e0b\u84dd\u8272\u90e8\u5206\u3002<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/jvm0.jpg\" alt=\"\" \/><figcaption>\u542f\u52a8 Java \u7a0b\u5e8f\u6307\u5b9a JVM \u53c2\u6570<\/figcaption><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">\u6307\u5b9a\u8fd9\u4e9b JVM \u53c2\u6570\u6211\u4eec\u5c31\u53ef\u4ee5\u6307\u5b9a\u542f\u52a8 JVM \u8fdb\u7a0b\u4ee5\u54ea\u79cd\u6a21\u5f0f\uff08server \u6216 client\uff09\uff0c\u8fd0\u884c\u65f6\u5206\u914d\u7684\u5806\u5927\u5c0f\uff0c\u6808\u5927\u5c0f\uff0c\u7528\u4ec0\u4e48\u5783\u573e\u6536\u96c6\u5668\u7b49\u7b49\uff0cJVM \u53c2\u6570\u4e3b\u8981\u5206\u4ee5\u4e0b\u4e09\u7c7b\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">1\u3001 \u6807\u51c6\u53c2\u6570\uff08-\uff09\uff0c\u6240\u6709\u7684 JVM \u5b9e\u73b0\u90fd\u5fc5\u987b\u5b9e\u73b0\u8fd9\u4e9b\u53c2\u6570\u7684\u529f\u80fd\uff0c\u800c\u4e14\u5411\u540e\u517c\u5bb9\uff1b\u4f8b\u5982 -verbose:gc\uff08\u8f93\u51fa\u6bcf\u6b21GC\u7684\u76f8\u5173\u60c5\u51b5)<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">2\u3001 \u975e\u6807\u51c6\u53c2\u6570\uff08-X\uff09\uff0c\u9ed8\u8ba4 JVM \u5b9e\u73b0\u8fd9\u4e9b\u53c2\u6570\u7684\u529f\u80fd\uff0c\u4f46\u662f\u5e76\u4e0d\u4fdd\u8bc1\u6240\u6709 JVM \u5b9e\u73b0\u90fd\u6ee1\u8db3\uff0c\u4e14\u4e0d\u4fdd\u8bc1\u5411\u540e\u517c\u5bb9\uff0c\u6808\uff0c\u5806\u5927\u5c0f\u7684\u8bbe\u7f6e\u90fd\u662f\u901a\u8fc7\u8fd9\u4e2a\u53c2\u6570\u6765\u914d\u7f6e\u7684,\u7528\u5f97\u6700\u591a\u7684\u5982\u4e0b\uff1a<\/p>\n\n\n\n<table class=\"wp-block-table\"><thead><tr><th>\u53c2\u6570\u793a\u4f8b<\/th><th>\u8868\u793a\u610f\u4e49<\/th><\/tr><\/thead><tbody><tr><td>-Xms512m<\/td><td>JVM \u542f\u52a8\u65f6\u8bbe\u7f6e\u7684\u521d\u59cb\u5806\u5927\u5c0f\u4e3a 512M<\/td><\/tr><tr><td>-Xmx512m<\/td><td>JVM \u53ef\u5206\u914d\u7684\u6700\u5927\u5806\u5927\u5c0f\u4e3a 512M<\/td><\/tr><tr><td>-Xmn200m<\/td><td>\u8bbe\u7f6e\u7684\u5e74\u8f7b\u4ee3\u5927\u5c0f\u4e3a 200M<\/td><\/tr><tr><td>-Xss128k<\/td><td>\u8bbe\u7f6e\u6bcf\u4e2a\u7ebf\u7a0b\u7684\u6808\u5927\u5c0f\u4e3a 128k<\/td><\/tr><\/tbody><\/table>\n\n\n\n<p class=\"wp-block-paragraph\">3\u3001\u975eStable\u53c2\u6570\uff08-XX\uff09\uff0c\u6b64\u7c7b\u53c2\u6570\u5404\u4e2a jvm \u5b9e\u73b0\u4f1a\u6709\u6240\u4e0d\u540c\uff0c\u5c06\u6765\u53ef\u80fd\u4f1a\u968f\u65f6\u53d6\u6d88\uff0c\u9700\u8981\u614e\u91cd\u4f7f\u7528, -XX:-option \u4ee3\u8868\u5173\u95ed option \u53c2\u6570\uff0c-XX:+option \u4ee3\u8868\u8981\u5173\u95ed option \u53c2\u6570,\u4f8b\u5982\u8981\u542f\u7528\u4e32\u884c GC\uff0c\u5bf9\u5e94\u7684 JVM \u53c2\u6570\u5373\u4e3a -XX:+UseSerialGC\u3002\u975e Stable \u53c2\u6570\u4e3b\u8981\u6709\u4e09\u5927\u7c7b\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u2460\u884c\u4e3a\u53c2\u6570\uff08Behavioral Options\uff09\uff1a\u7528\u4e8e\u6539\u53d8 JVM \u7684\u4e00\u4e9b\u57fa\u7840\u884c\u4e3a\uff0c\u5982\u542f\u7528\u4e32\u884c\/\u5e76\u884c GC\u3002<\/p>\n\n\n\n<table class=\"wp-block-table\"><thead><tr><th>\u53c2\u6570\u793a\u4f8b<\/th><th>\u8868\u793a\u610f\u4e49<\/th><\/tr><\/thead><tbody><tr><td>-XX:-DisableExplicitGC<\/td><td>\u7981\u6b62\u8c03\u7528System.gc()\uff1b\u4f46jvm\u7684gc\u4ecd\u7136\u6709\u6548<\/td><\/tr><tr><td>-XX:-UseConcMarkSweepGC<\/td><td>\u5bf9\u8001\u751f\u4ee3\u91c7\u7528\u5e76\u53d1\u6807\u8bb0\u4ea4\u6362\u7b97\u6cd5\u8fdb\u884cGC<\/td><\/tr><tr><td>-XX:-UseParallelGC<\/td><td>\u542f\u7528\u5e76\u884cGC<\/td><\/tr><tr><td>-XX:-UseParallelOldGC<\/td><td>\u5bf9Full GC\u542f\u7528\u5e76\u884c\uff0c\u5f53-XX:-UseParallelGC\u542f\u7528\u65f6\u8be5\u9879\u81ea\u52a8\u542f\u7528<\/td><\/tr><tr><td>-XX:-UseSerialGC<\/td><td>\u542f\u7528\u4e32\u884cGC<\/td><\/tr><\/tbody><\/table>\n\n\n\n<p class=\"wp-block-paragraph\">\u2461\u6027\u80fd\u8c03\u4f18\uff08Performance Tuning\uff09\uff1a\u7528\u4e8e jvm \u7684\u6027\u80fd\u8c03\u4f18\uff0c\u5982\u8bbe\u7f6e\u65b0\u8001\u751f\u4ee3\u5185\u5b58\u5bb9\u91cf\u6bd4\u4f8b\u3002<\/p>\n\n\n\n<table class=\"wp-block-table\"><thead><tr><th>\u53c2\u6570\u793a\u4f8b<\/th><th>\u8868\u793a\u610f\u4e49<\/th><\/tr><\/thead><tbody><tr><td>-XX:MaxHeapFreeRatio=70<\/td><td>GC\u540ejava\u5806\u4e2d\u7a7a\u95f2\u91cf\u5360\u7684\u6700\u5927\u6bd4\u4f8b<\/td><\/tr><tr><td>-XX:NewRatio=2<\/td><td>\u65b0\u751f\u4ee3\u5185\u5b58\u5bb9\u91cf\u4e0e\u8001\u751f\u4ee3\u5185\u5b58\u5bb9\u91cf\u7684\u6bd4\u4f8b<\/td><\/tr><tr><td>-XX:NewSize=2.125m<\/td><td>\u65b0\u751f\u4ee3\u5bf9\u8c61\u751f\u6210\u65f6\u5360\u7528\u5185\u5b58\u7684\u9ed8\u8ba4\u503c<\/td><\/tr><tr><td>-XX:ReservedCodeCacheSize=32m<\/td><td>\u4fdd\u7559\u4ee3\u7801\u5360\u7528\u7684\u5185\u5b58\u5bb9\u91cf<\/td><\/tr><tr><td>-XX:ThreadStackSize=512<\/td><td>\u8bbe\u7f6e\u7ebf\u7a0b\u6808\u5927\u5c0f\uff0c\u82e5\u4e3a0\u5219\u4f7f\u7528\u7cfb\u7edf\u9ed8\u8ba4\u503c<\/td><\/tr><\/tbody><\/table>\n\n\n\n<p class=\"wp-block-paragraph\">\u2462\u8c03\u8bd5\u53c2\u6570\uff08Debugging Options\uff09\uff1a\u4e00\u822c\u7528\u4e8e\u6253\u5f00\u8ddf\u8e2a\u3001\u6253\u5370\u3001\u8f93\u51fa\u7b49 JVM \u53c2\u6570\uff0c\u7528\u4e8e\u663e\u793a JVM \u66f4\u52a0\u8be6\u7ec6\u7684\u4fe1\u606f\u3002<\/p>\n\n\n\n<table class=\"wp-block-table\"><thead><tr><th>\u53c2\u6570\u793a\u4f8b<\/th><th>\u8868\u793a\u610f\u4e49<\/th><\/tr><\/thead><tbody><tr><td>-XX:HeapDumpPath=.\/java_pid.hprof<\/td><td>\u6307\u5b9a\u5bfc\u51fa\u5806\u4fe1\u606f\u65f6\u7684\u8def\u5f84\u6216\u6587\u4ef6\u540d<\/td><\/tr><tr><td>-XX:-HeapDumpOnOutOfMemoryError<\/td><td>\u5f53\u9996\u6b21\u906d\u9047OOM\u65f6\u5bfc\u51fa\u6b64\u65f6\u5806\u4e2d\u76f8\u5173\u4fe1\u606f<\/td><\/tr><tr><td>-XX:-PrintGC<\/td><td>\u6bcf\u6b21GC\u65f6\u6253\u5370\u76f8\u5173\u4fe1\u606f<\/td><\/tr><tr><td>-XX:-PrintGC Details<\/td><td>\u6bcf\u6b21GC\u65f6\u6253\u5370\u8be6\u7ec6\u4fe1\u606f<\/td><\/tr><\/tbody><\/table>\n\n\n\n<p class=\"wp-block-paragraph\">\u660e\u767d\u4e86 JVM \u53c2\u6570\u662f\u5e72\u5565\u7528\u7684\uff0c\u63a5\u4e0b\u6765\u6211\u4eec\u8fdb\u5165\u5b9e\u6218\u6f14\u7ec3,\u4e0b\u6587\u4e2d\u6240\u6709\u7a0b\u5e8f\u8fd0\u884c\u65f6\u5bf9\u5e94\u7684 JVM \u53c2\u6570\u90fd\u4ee5 VM Args \u7684\u5f62\u5f0f\u5199\u5728\u5f00\u5934\u7684\u6ce8\u91ca\u91cc\uff0c\u8bfb\u8005\u5982\u679c\u5728\u6267\u884c\u7a0b\u5e8f\u65f6\u8bb0\u5f97\u8981\u628a\u8fd9\u4e9b JVM \u53c2\u6570\u7ed9\u5e26\u4e0a\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u53d1\u751f OOM \u7684\u4e3b\u8981\u51e0\u79cd\u573a\u666f\u53ca\u76f8\u5e94\u89e3\u51b3\u65b9\u6848<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u6709\u4e9b\u4eba\u53ef\u80fd\u4f1a\u89c9\u5f97\u5947\u602a\uff0c GC \u4e0d\u662f\u4f1a\u81ea\u52a8\u5e2e\u6211\u4eec\u6e05\u7406\u5783\u573e\u4ee5\u817e\u51fa\u4f7f\u7528\u7a7a\u95f4\u5417\uff0c\u600e\u4e48\u8fd8\u4f1a\u53d1\u751f OOM, \u6211\u4eec\u5148\u6765\u770b\u4e0b\u6709\u54ea\u4e9b\u573a\u666f\u4f1a\u53d1\u751f OOM<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">1\u3001Java \u865a\u62df\u673a\u89c4\u8303\u4e2d\u63cf\u8ff0\u5728\u6808\u4e0a\u4e3b\u8981\u4f1a\u53d1\u751f\u4ee5\u4e0b\u4e24\u79cd\u5f02\u5e38<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>StackOverflowError \u5f02\u5e38\u3002\u8fd9\u79cd\u60c5\u51b5\u4e3b\u8981\u662f\u56e0\u4e3a\u5355\u4e2a\u7ebf\u7a0b\u8bf7\u6c42\u6808\u6df1\u5ea6\u5927\u4e8e\u865a\u62df\u673a\u6240\u5141\u8bb8\u7684\u6700\u5927\u6df1\u5ea6\uff08\u5982\u5e38\u7528\u7684\u9012\u5f52\u8c03\u7528\u5c42\u7ea7\u8fc7\u6df1\u7b49\uff09\uff0c\u518d\u6bd4\u5982\u5355\u4e2a\u7ebf\u7a0b\u5b9a\u4e49\u4e86\u5927\u91cf\u7684\u672c\u5730\u53d8\u91cf\uff0c\u5bfc\u81f4\u65b9\u6cd5\u5e27\u4e2d\u672c\u5730\u53d8\u91cf\u8868\u957f\u5ea6\u8fc7\u5927\u7b49\u4e5f\u4f1a\u5bfc\u81f4 StackOverflowError \u5f02\u5e38\uff0c \u4e00\u53e5\u8bdd\uff1a\u5728\u5355\u7ebf\u7a0b\u4e0b\uff0c\u5f53\u6808\u6862\u592a\u5927\u6216\u865a\u62df\u673a\u5bb9\u91cf\u592a\u5c0f\u5bfc\u81f4\u5185\u5b58\u65e0\u6cd5\u5206\u914d\u65f6\uff0c\u90fd\u4f1a\u53d1\u751f StackOverflowError \u5f02\u5e38\u3002<\/li><li><\/li><li>\u865a\u62df\u673a\u5728\u6269\u5c55\u6808\u65f6\u65e0\u6cd5\u7533\u8bf7\u5230\u8db3\u591f\u7684\u5185\u5b58\u7a7a\u95f4\uff0c\u4f1a\u629b\u51fa OOM \u5f02\u5e38<\/li><\/ul>\n\n\n\n<pre class=\"wp-block-code\"><code>\/**\n * VM Args:-Xss160k\n *\/\npublic class Test {\n    private void dontStop() {\n        while(true) {\n        }\n    }\n\n    public void stackLeakByThread() {\n        while (true) {\n            Thread thread = new Thread(new Runnable() {\n                @Override\n                public void run() {\n                    dontStop();\n                }\n            });\n            thread.start();\n        }\n    }\n\n    public static  void main(String[] args) {\n        Test oom = new Test();\n        oom.stackLeakByThread();\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u8fd0\u884c\u4ee5\u4e0a\u4ee3\u7801\u4f1a\u629b\u51fa\u300cjava.lang.OutOfMemoryError: unable to create new native thread\u300d\u7684\u5f02\u5e38\uff0c\u539f\u56e0\u4e0d\u96be\u7406\u89e3\uff0c\u64cd\u4f5c\u7cfb\u7edf\u7ed9\u6bcf\u4e2a\u8fdb\u7a0b\u5206\u914d\u7684\u5185\u5b58\u662f\u6709\u9650\u5236\u7684\uff0c\u6bd4\u5982 32 \u4f4d\u7684 Windows \u9650\u5236\u4e3a 2G,\u865a\u62df\u673a\u63d0\u4f9b\u4e86\u53c2\u6570\u6765\u63a7\u5236 Java \u5806\u548c\u65b9\u6cd5\u7684\u8fd9\u4e24\u90e8\u5185\u5b58\u7684\u6700\u5927\u503c\uff0c\u5269\u4f59\u7684\u5185\u5b58\u4e3a \u300c2G &#8211; Xmx\uff08\u6700\u5927\u5806\u5bb9\u91cf\uff09= \u7ebf\u7a0b\u6570 * \u6bcf\u4e2a\u7ebf\u7a0b\u5206\u914d\u7684\u865a\u62df\u673a\u6808\uff08-Xss)+\u672c\u5730\u65b9\u6cd5\u6808 \u300d\uff08\u7a0b\u5e8f\u8ba1\u6570\u5668\u6d88\u8017\u5185\u5b58\u5f88\u5c11\uff0c\u53ef\u5ffd\u7565\uff09,\u6bcf\u4e2a\u7ebf\u7a0b\u90fd\u4f1a\u88ab\u5206\u914d\u5bf9\u5e94\u7684\u865a\u62df\u673a\u6808\u5927\u5c0f\uff0c\u6240\u4ee5\u603b\u53ef\u521b\u5efa\u7684\u7ebf\u7a0b\u6570\u80af\u5b9a\u662f\u56fa\u5b9a\u7684\uff0c \u50cf\u4ee5\u4e0a\u4ee3\u7801\u8fd9\u6837\u4e0d\u65ad\u5730\u521b\u5efa\u7ebf\u7a0b\u5f53\u7136\u4f1a\u9020\u6210\u6700\u7ec8\u65e0\u6cd5\u5206\u914d\uff0c\u4e0d\u8fc7\u8fd9\u4e5f\u7ed9\u6211\u4eec\u63d0\u4f9b\u4e86\u4e00\u4e2a\u65b0\u601d\u8def\uff0c\u5982\u679c\u662f\u56e0\u4e3a\u5efa\u7acb\u8fc7\u591a\u7684\u7ebf\u7a0b\u5bfc\u81f4\u7684\u5185\u5b58\u6ea2\u51fa\uff0c\u800c\u6211\u4eec\u53c8\u60f3\u591a\u521b\u5efa\u7ebf\u7a0b\uff0c\u53ef\u4ee5\u901a\u8fc7\u51cf\u5c11\u6700\u5927\u5806\uff08-Xms\uff09\u548c\u51cf\u5c11\u865a\u62df\u673a\u6808\u5927\u5c0f\uff08-Xss\uff09\u6765\u5b9e\u73b0\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">2\u3001\u5806\u6ea2\u51fa \uff08java.lang.OutOfMemoryError:Java heap space\uff09<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u4e3b\u8981\u539f\u56e0\u6709\u4e24\u70b9\uff1a<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">1.\u5927\u5bf9\u8c61\u7684\u5206\u914d\uff0c\u6700\u6709\u53ef\u80fd\u7684\u662f\u5927\u6570\u7ec4\u5206\u914d\u3002\u793a\u4f8b\u5982\u4e0b\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\/**\n* VM Args:-Xmx12m\n *\/\nclass OOM {\n    static final int SIZE=2*1024*1024;\n    public static void main(String[] a) {\n        int[] i = new int[SIZE];\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u6211\u4eec\u6307\u5b9a\u4e86\u5806\u5927\u5c0f\u4e3a 12M,\u6267\u884c \u300cjava -Xmx12m OOM\u300d\u547d\u4ee4\u5c31\u53d1\u751f\u4e86 OOM \u5f02\u5e38\uff0c\u5982\u679c\u6307\u5b9a 13M \u5219\u4ee5\u4e0a\u7a0b\u5e8f\u5c31\u80fd\u6b63\u5e38\u6267\u884c\uff0c\u6240\u4ee5\u5bf9\u4e8e\u7531\u4e8e\u5927\u5bf9\u8c61\u5206\u914d\u5bfc\u81f4\u7684\u5806\u6ea2\u51fa\u8fd9\u79cd OOM\uff0c\u6211\u4eec\u4e00\u822c\u91c7\u7528\u589e\u5927\u5806\u5185\u5b58\u7684\u65b9\u5f0f\u6765\u89e3\u51b3\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">2.\u5185\u5b58\u6cc4\u6f0f\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u6211\u4eec\u77e5\u9053\u5728 Java \u4e2d\uff0c\u5f00\u53d1\u8005\u521b\u5efa\u548c\u9500\u6bc1\u5bf9\u8c61\u662f\u4e0d\u9700\u8981\u81ea\u5df1\u5f00\u8f9f\u7a7a\u95f4\u7684\uff0cJVM \u4f1a\u81ea\u52a8\u5e2e\u6211\u4eec\u5b8c\u6210\uff0c\u5728\u5e94\u7528\u7a0b\u5e8f\u6574\u4e2a\u751f\u547d\u5468\u671f\u4e2d\uff0cJVM \u4f1a\u5b9a\u65f6\u68c0\u67e5\u54ea\u4e9b\u5bf9\u8c61\u53ef\u7528\uff0c\u54ea\u4e9b\u4e0d\u518d\u4f7f\u7528\uff0c\u5982\u679c\u5bf9\u8c61\u4e0d\u518d\u4f7f\u7528\u7684\u8bdd\u7406\u8bba\u4e0a\u8fd9\u5757\u5185\u5b58\u4f1a\u88ab\u56de\u6536\u518d\u5229\u7528\uff08\u5373GC\uff09\uff0c\u5982\u679c\u65e0\u6cd5\u56de\u6536\u5c31\u4f1a\u53d1\u751f\u5185\u5b58\u6cc4\u6f0f\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\/**\n* VM Args:-Xmx4m\n *\/\npublic class KeylessEntry {\n    static class Key {\n        Integer id; \n        Key(Integer id) {\n            this.id = id;\n        }  \n        @Override\n        public int hashCode() {\n            return id.hashCode();\n        }\n    }\n    public static void main(String[] args) {\n        Map&lt;Key,String&gt; m = new HashMap&lt;Key,String&gt;();\n        while(true) {\n            for(int i=0;i&lt;10000;i++) {\n                if(!m.containsKey(new Key(i))) {\n                    m.put(new Key(i), \"Number:\" + i);\n                }\n            }\n        }\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u6267\u884c\u4ee5\u4e0a\u4ee3\u7801\u5c31\u4f1a\u53d1\u751f\u5185\u5b58\u6cc4\u6f0f\uff0c\u7b2c\u4e00\u6b21\u5faa\u73af\uff0cmap \u91cc\u5b58\u6709 10000 \u4e2a key value,\u4f46\u4e4b\u540e\u7684\u6bcf\u6b21\u5faa\u73af\u90fd\u4f1a\u65b0\u589e 10000 \u4e2a\u5143\u7d20\uff0c\u56e0\u4e3a Key \u8fd9\u4e2a class \u6f0f\u5199\u4e86 equals \u65b9\u6cd5\uff0c\u5bfc\u81f4\u5bf9\u4e8e\u6bcf\u4e00\u4e2a\u65b0\u521b\u5efa\u7684 new Key(i) \u5bf9\u8c61\uff0c\u5373\u4f7f i \u76f8\u540c\u4e5f\u4f1a\u88ab\u8ba4\u5b9a\u4e3a\u5c5e\u4e8e\u4e24\u4e2a\u4e0d\u540c\u7684\u5bf9\u8c61\uff0c\u8fd9\u6837 m.containsKey(new Key(i)) \u7ed3\u679c\u5747\u4e3a false,\u7ed3\u679c\u5c31\u662f HashMap \u4e2d\u7684\u5143\u7d20\u5c06\u4e00\u76f4\u589e\u52a0\uff0c\u89e3\u51b3\u65b9\u5f0f\u4e5f\u5f88\u7b80\u5355\uff0c\u4e3a Key \u6dfb\u52a0 equals \u65b9\u6cd5\u5373\u53ef\uff0c\u5982\u4e0b\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>@Override\npublic boolean equals(Object o) {\n   boolean response = false;\n   if (o instanceof Key) {\n      response = (((Key)o).id).equals(this.id);\n   }\n   return response;\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5bf9\u4e8e\u8fd9\u79cd\u5185\u5b58\u6cc4\u6f0f\u5bfc\u81f4\u7684 OOM\uff0c \u5355\u7eaf\u5730\u589e\u5927\u5806\u5927\u5c0f\u662f\u65e0\u6cd5\u89e3\u51b3\u6839\u672c\u95ee\u9898\u7684\uff0c\u53ea\u4e0d\u8fc7\u662f\u5ef6\u7f13\u4e86 OOM \u7684\u53d1\u751f\uff0c\u6700\u6839\u672c\u7684\u89e3\u51b3\u65b9\u5f0f\u8fd8\u662f\u8981\u901a\u8fc7 heap dump analyzer \u7b49\u65b9\u5f0f\u6765\u627e\u51fa\u5185\u5b58\u6cc4\u6f0f\u7684\u4ee3\u7801\u6765\u4fee\u590d\u89e3\u51b3\uff0c\u540e\u6587\u4f1a\u7ed9\u51fa\u4e00\u4e2a\u4f8b\u5b50\u6765\u5206\u6790<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">3\u3001java.lang.OutOfMemoryError:GC overhead limit exceeded\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Sun \u5b98\u65b9\u5bf9\u6b64\u7684\u5b9a\u4e49\uff1a\u8d85\u8fc798%\u7684\u65f6\u95f4\u7528\u6765\u505a GC \u5e76\u4e14\u56de\u6536\u4e86\u4e0d\u5230 2% \u7684\u5806\u5185\u5b58\u65f6\u4f1a\u629b\u51fa\u6b64\u5f02\u5e38\uff1a<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/jvm1.jpg\" alt=\"\" \/><figcaption>Time used by GC pauses<\/figcaption><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">\u5bfc\u81f4\u7684\u540e\u679c\u5c31\u662f\u7531\u4e8e\u7ecf\u8fc7\u51e0\u4e2a GC \u540e\u53ea\u56de\u6536\u4e86\u4e0d\u5230 2% \u7684\u5185\u5b58\uff0c\u5806\u5f88\u5feb\u53c8\u4f1a\u88ab\u586b\u6ee1\uff0c\u7136\u540e\u53c8\u9891\u7e41\u53d1\u751f GC\uff0c\u5bfc\u81f4 CPU \u8d1f\u8f7d\u5f88\u5feb\u5c31\u8fbe\u5230 100%\uff0c\u53e6\u5916\u6211\u4eec\u77e5\u9053 GC \u4f1a\u5f15\u8d77 \u300cStop The World \u300d\u7684\u95ee\u9898\uff0c\u963b\u585e\u5de5\u4f5c\u7ebf\u7a0b\uff0c\u6240\u4ee5\u4f1a\u5bfc\u81f4\u4e25\u91cd\u7684\u6027\u80fd\u95ee\u9898\uff0c\u4ea7\u751f\u8fd9\u79cd OOM \u7684\u539f\u56e0\u4e0e\u300cjava.lang.OutOfMemoryError:Java heap space\u300d\u7c7b\u4f3c\uff0c\u4e3b\u8981\u662f\u7531\u4e8e\u5206\u914d\u5927\u5185\u5b58\u6570\u7ec4\u6216\u5185\u5b58\u6cc4\u6f0f\u5bfc\u81f4\u7684\uff0c \u89e3\u51b3\u65b9\u6848\u5982\u4e0b\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\u68c0\u67e5\u9879\u76ee\u4e2d\u662f\u5426\u6709\u5927\u91cf\u7684\u6b7b\u5faa\u73af\u6216\u6709\u4f7f\u7528\u5927\u5185\u5b58\u7684\u4ee3\u7801\uff0c\u4f18\u5316\u4ee3\u7801\u3002<\/li><li>dump \u5185\u5b58\uff08\u540e\u6587\u4f1a\u8bb2\u8ff0\u5982\u4f55 dump \u51fa\u5185\u5b58\uff09\uff0c\u68c0\u67e5\u662f\u5426\u5b58\u5728\u5185\u5b58\u6cc4\u9732\uff0c\u5982\u679c\u6ca1\u6709\uff0c\u53ef\u8003\u8651\u901a\u8fc7 -Xmx \u53c2\u6570\u8bbe\u7f6e\u52a0\u5927\u5185\u5b58\u3002<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">4\u3001java.lang.OutOfMemoryError:Permgen space<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u5728 Java 8 \u4ee5\u524d\u6709\u6c38\u4e45\u4ee3\uff08\u5176\u5b9e\u662f\u7528\u6c38\u4e45\u4ee3\u5b9e\u73b0\u4e86\u65b9\u6cd5\u533a\u7684\u529f\u80fd\uff09\u7684\u6982\u5ff5\uff0c\u5b58\u653e\u4e86\u88ab\u865a\u62df\u673a\u52a0\u8f7d\u7684\u7c7b\uff0c\u5e38\u91cf\uff0c\u9759\u6001\u53d8\u91cf\uff0cJIT \u7f16\u8bd1\u540e\u7684\u4ee3\u7801\u7b49\u4fe1\u606f\uff0c\u6240\u4ee5\u5982\u679c\u9519\u8bef\u5730\u9891\u7e41\u5730\u4f7f\u7528 String.intern() \u65b9\u6cd5\u6216\u8fd0\u884c\u671f\u95f4\u751f\u6210\u4e86\u5927\u91cf\u7684\u4ee3\u7406\u7c7b\u90fd\u6709\u53ef\u80fd\u5bfc\u81f4\u6c38\u4e45\u4ee3\u6ea2\u51fa\uff0c\u89e3\u51b3\u65b9\u6848\u5982\u4e0b\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\u662f\u5426\u6c38\u4e45\u4ee3\u8bbe\u7f6e\u7684\u8fc7\u5c0f\uff0c\u5982\u679c\u53ef\u4ee5\uff0c\u9002\u5e94\u8c03\u5927\u4e00\u70b9<\/li><li>\u68c0\u67e5\u4ee3\u7801\u662f\u5426\u6709\u5927\u91cf\u7684\u53cd\u5c04\u64cd\u4f5c<\/li><li>dump \u4e4b\u540e\u901a\u8fc7 mat \u68c0\u67e5\u662f\u5426\u5b58\u5728\u5927\u91cf\u7531\u4e8e\u53cd\u5c04\u751f\u6210\u7684\u4ee3\u7801\u7c7b<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">5\u3001java.lang.OutOfMemoryError:Requested array size exceeds VM limit<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u8be5\u9519\u8bef\u7531 JVM \u4e2d\u7684 native code \u629b\u51fa\u3002JVM \u5728\u4e3a\u6570\u7ec4\u5206\u914d\u5185\u5b58\u4e4b\u524d\uff0c\u4f1a\u6267\u884c\u57fa\u4e8e\u6240\u5728\u5e73\u53f0\u7684\u68c0\u67e5\uff1a\u5206\u914d\u7684\u6570\u636e\u7ed3\u6784\u662f\u5426\u5728\u6b64\u5e73\u53f0\u4e2d\u662f\u53ef\u5bfb\u5740\u7684\uff0c\u5e73\u53f0\u4e00\u822c\u5141\u8bb8\u5206\u914d\u7684\u6570\u636e\u5927\u5c0f\u5728 1 \u5230 21 \u4ebf\u4e4b\u95f4\uff0c\u5982\u679c\u8d85\u8fc7\u4e86\u8fd9\u4e2a\u6570\u5c31\u4f1a\u629b\u51fa\u8fd9\u79cd\u5f02\u5e38\u3002<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/jvm2.jpg\" alt=\"\" \/><figcaption>java.lang.OutOfMemoryError<\/figcaption><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">\u78b0\u5230\u8fd9\u79cd\u5f02\u5e38\u4e00\u822c\u6211\u4eec\u53ea\u8981\u68c0\u67e5\u4ee3\u7801\u4e2d\u662f\u5426\u6709\u521b\u5efa\u8d85\u5927\u6570\u7ec4\u7684\u5730\u65b9\u5373\u53ef\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">6\u3001java.lang.OutOfMemoryError: Out of swap space<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Java \u5e94\u7528\u542f\u52a8\u7684\u65f6\u5019\u5206\u88ab\u5206\u914d\u4e00\u5b9a\u7684\u5185\u5b58\u7a7a\u95f4(\u901a\u8fc7 -Xmx \u53ca\u5176\u4ed6\u53c2\u6570\u6765\u6307\u5b9a)\uff0c \u5982\u679c JVM \u8981\u6c42\u7684\u603b\u5185\u5b58\u7a7a\u95f4\u5927\u5c0f\u5927\u4e8e\u53ef\u7528\u7684\u672c\u673a\u5185\u5b58\uff0c\u5219\u64cd\u4f5c\u7cfb\u7edf\u4f1a\u5c06\u5185\u5b58\u4e2d\u7684\u90e8\u5206\u6570\u636e\u4ea4\u6362\u5230\u786c\u76d8\u4e0a\u3002<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/jvm3.jpg\" alt=\"\" \/><figcaption>java.lang.OutOfMemoryError: Out of swap space<\/figcaption><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">\u5982\u679c\u6b64\u65f6 swap \u5206\u533a\u5927\u5c0f\u4e0d\u8db3\u6216\u8005\u5176\u4ed6\u8fdb\u7a0b\u8017\u5c3d\u4e86\u672c\u673a\u7684\u5185\u5b58\uff0c\u5219\u4f1a\u53d1\u751f OOM, \u53ef\u4ee5\u901a\u8fc7\u589e\u5927 swap \u7a7a\u95f4\u5927\u5c0f\u6765\u89e3\u51b3,\u4f46\u5982\u679c\u5728\u4ea4\u6362\u7a7a\u95f4\u8fdb\u884c GC \u9020\u6210\u7684 \u300cStop The World\u300d\u589e\u52a0\u5927\u4e2a\u6570\u91cf\u7ea7\uff0c\u6240\u4ee5\u589e\u5927 swap \u7a7a\u95f4\u4e00\u5b9a\u8981\u614e\u91cd\uff0c\u6240\u4ee5\u4e00\u822c\u662f\u901a\u8fc7\u589e\u5927\u672c\u673a\u5185\u5b58\u6216\u4f18\u5316\u7a0b\u5e8f\u51cf\u5c11\u5185\u5b58\u5360\u7528\u6765\u89e3\u51b3\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">7\u3001Out of memory:Kill process or sacrifice child<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u4e3a\u4e86\u7406\u89e3\u8fd9\u4e2a\u5f02\u5e38\uff0c\u6211\u4eec\u9700\u8981\u77e5\u8bc6\u4e00\u4e9b\u64cd\u4f5c\u7cfb\u7edf\u7684\u77e5\u8bc6\uff0c\u6211\u4eec\u77e5\u9053\uff0c\u5728\u64cd\u4f5c\u7cfb\u7edf\u4e2d\u6267\u884c\u7684\u7a0b\u5e8f\uff0c\u90fd\u662f\u4ee5\u8fdb\u7a0b\u7684\u65b9\u5f0f\u8fd0\u884c\u7684\uff0c\u800c\u8fdb\u7a0b\u662f\u7531\u5185\u6838\u8c03\u5ea6\u7684\uff0c\u5728\u5185\u6838\u7684\u8c03\u5ea6\u4efb\u52a1\u4e2d\uff0c\u6709\u4e00\u4e2a\u300cOut of memory killer\u300d\u7684\u8c03\u5ea6\u5668\uff0c\u5b83\u4f1a\u5728\u7cfb\u7edf\u53ef\u7528\u5185\u5b58\u4e0d\u8db3\u65f6\u88ab\u6fc0\u6d3b\uff0c\u7136\u540e\u9009\u62e9\u4e00\u4e2a\u8fdb\u7a0b\u628a\u5b83\u5e72\u6389\uff0c\u54ea\u4e2a\u8fdb\u7a0b\u4f1a\u88ab\u5e72\u6389\u5462\uff0c\u7b80\u5355\u5730\u8bf4\u4f1a\u4f18\u5148\u5e72\u6389\u5360\u7528\u5185\u5b58\u5927\u7684\u5e94\u7528\u578b\u8fdb\u7a0b\u3002<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/jvm4.jpg\" alt=\"\" \/><figcaption>Out of memory:Kill process or sacrifice child<\/figcaption><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">\u89e3\u51b3\u8fd9\u79cd OOM \u6700\u76f4\u63a5\u7b80\u5355\u7684\u65b9\u6cd5\u5c31\u662f\u5347\u7ea7\u5185\u5b58\uff0c\u6216\u8005\u8c03\u6574 OOM Killer \u7684\u4f18\u5148\u7ea7\uff0c\u51cf\u5c11\u5e94\u7528\u7684\u4e0d\u5fc5\u8981\u7684\u5185\u5b58\u4f7f\u7528\u7b49\u7b49\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u770b\u4e86\u4ee5\u4e0a\u7684\u5404\u79cd OOM \u4ea7\u751f\u7684\u60c5\u51b5\uff0c\u53ef\u4ee5\u770b\u51fa\uff1aGC \u548c\u662f\u5426\u53d1\u751f OOM \u6ca1\u6709\u5fc5\u7136\u7684\u56e0\u679c\u5173\u7cfb! GC \u4e3b\u8981\u53d1\u751f\u5728\u5806\u4e0a\uff0c\u800c \u4ece\u4ee5\u4e0a\u5217\u51fa\u7684\u51e0\u79cd\u53d1\u751f OOM \u7684\u573a\u666f\u53ef\u4ee5\u770b\u51fa\uff0c\u7a7a\u95f4\u4e0d\u8db3\u65e0\u6cd5\u518d\u521b\u5efa\u7ebf\u7a0b\uff0c\u6216\u8005\u5b58\u5728\u6b7b\u5faa\u73af\u4e00\u76f4\u5728\u5206\u914d\u5bf9\u8c61\u5bfc\u81f4 GC \u65e0\u6cd5\u56de\u6536\u5bf9\u8c61\u6216\u8005\u4e00\u6b21\u5206\u914d\u5927\u5185\u5b58\u6570\u7ec4\uff08\u8d85\u8fc7\u5806\u7684\u5927\u5c0f\uff09\u7b49\u90fd\u53ef\u80fd\u5bfc\u81f4 OOM, \u6240\u4ee5 OOM \u4e0e GC \u5e76\u6ca1\u6709\u5fc5\u7136\u7684\u56e0\u679c\u5173\u7cfb\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">OOM \u95ee\u9898\u6392\u67e5\u7684\u4e00\u4e9b\u5e38\u7528\u5de5\u5177<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u63a5\u4e0b\u6765\u6211\u4eec\u6765\u770b\u4e0b\u5982\u4f55\u6392\u67e5\u9020\u6210 OOM \u7684\u539f\u56e0\uff0c\u5185\u5b58\u6cc4\u6f0f\u662f\u6700\u5e38\u89c1\u7684\u9020\u6210 OOM \u7684\u4e00\u79cd\u539f\u56e0\uff0c\u6240\u4ee5\u63a5\u4e0b\u6765\u6211\u4eec\u4ee5\u6765\u770b\u770b\u600e\u4e48\u4f7f\u7528\u5de5\u5177\u6765\u6392\u67e5\u8fd9\u79cd\u95ee\u9898,\u4f7f\u7528\u5230\u7684\u5de5\u5177\u4e3b\u8981\u6709\u4e24\u5927\u7c7b<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">1\u3001\u4f7f\u7528 mat\uff08Eclipse Memory Analyzer\uff09 \u6765\u5206\u6790 dump\uff08\u5806\u8f6c\u50a8\u5feb\u7167\uff09 \u6587\u4ef6<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u4e3b\u8981\u6b65\u9aa4\u5982\u4e0b\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\u8fd0\u884c Java \u65f6\u6dfb\u52a0 \u300c-XX:+HeapDumpOnOutOfMemoryError\u300d \u53c2\u6570\u6765\u5bfc\u51fa\u5185\u5b58\u6ea2\u51fa\u65f6\u7684\u5806\u4fe1\u606f\uff0c\u751f\u6210 hrof \u6587\u4ef6, \u6dfb\u52a0 \u300c-XX:HeapDumpPath\u300d\u53ef\u4ee5\u6307\u5b9a hrof \u6587\u4ef6\u7684\u751f\u6210\u8def\u5f84,\u5982\u679c\u4e0d\u6307\u5b9a\u5219 hrof \u6587\u4ef6\u751f\u6210\u5728\u4e0e\u5b57\u8282\u7801\u6587\u4ef6\u76f8\u540c\u7684\u76ee\u5f55\u4e0b<\/li><li>\u4f7f\u7528 MAT\uff08Eclipse Memory Analyzer\uff09\u6765\u5206\u6790 hrof \u6587\u4ef6\uff0c\u67e5\u51fa\u5185\u5b58\u6cc4\u6f0f\u7684\u539f\u56e0<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u63a5\u4e0b\u6765\u6211\u4eec\u5c31\u6765\u770b\u770b\u5982\u4f55\u7528\u4ee5\u4e0a\u7684\u5de5\u5177\u67e5\u770b\u5982\u4e0b\u5185\u5b58\u6cc4\u6f0f\u6848\u4f8b\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\/**\n* VM Args:-Xmx10m\n *\/\nimport java.util.ArrayList;\nimport java.util.List;\npublic class Main {\n    public static void main(String[] args) {\n        List&lt;String&gt; list = new ArrayList&lt;String&gt;();\n        while (true) {\n            list.add(\"OutOfMemoryError soon\");\n        }\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u4e3a\u4e86\u8ba9\u4ee5\u4e0a\u7a0b\u5e8f\u5feb\u901f\u4ea7\u751f OOM, \u6211\u628a\u5806\u5927\u5c0f\u8bbe\u7f6e\u6210\u4e86 10M, \u8fd9\u6837\u6267\u884c \u300cjava -Xmx10m -XX:+HeapDumpOnOutOfMemoryError Main\u300d\u540e\u5f88\u5feb\u5c31\u53d1\u751f\u4e86 OOM\uff0c\u6b64\u65f6\u6211\u4eec\u5c31\u62ff\u5230\u4e86 hrof \u6587\u4ef6\uff0c\u4e0b\u8f7d MAT \u5de5\u5177\uff0c\u6253\u5f00 hrof,\u8fdb\u884c\u5206\u6790\uff0c\u6253\u5f00\u4e4b\u540e\u9009\u62e9 \u300cLeak Suspects Report\u300d\u8fdb\u884c\u5206\u6790\uff0c\u53ef\u4ee5\u770b\u5230\u53d1\u751f OOM \u7684\u7ebf\u7a0b\u7684\u5806\u6808\u4fe1\u606f\uff0c\u660e\u786e\u5b9a\u4f4d\u5230\u662f\u54ea\u4e00\u884c\u9020\u6210\u7684\u3002<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/jvm5.jpg\" alt=\"\" \/><figcaption>java -Xmx10m -XX:+HeapDumpOnOutOfMemoryError Main<\/figcaption><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">2\u3001\u4f7f\u7528 jvisualvm \u6765\u5206\u6790<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u7528\u7b2c\u4e00\u79cd\u65b9\u5f0f\u5fc5\u987b\u7b49 OOM \u540e\u624d\u80fd dump \u51fa hprof \u6587\u4ef6\uff0c\u4f46\u5982\u679c\u6211\u4eec\u60f3\u5728\u8fd0\u884c\u4e2d\u89c2\u5bdf\u5806\u7684\u4f7f\u7528\u60c5\u51b5\u4ee5\u4fbf\u67e5\u51fa\u53ef\u80fd\u7684\u5185\u5b58\u6cc4\u6f0f\u4ee3\u7801\u5c31\u65e0\u80fd\u4e3a\u529b\u4e86\uff0c\u8fd9\u65f6\u6211\u4eec\u53ef\u4ee5\u501f\u52a9 jvisualvm \u8fd9\u6b3e\u5de5\u5177, jvisualvm \u7684\u529f\u80fd\u5f3a\u5927\uff0c\u9664\u4e86\u53ef\u4ee5\u5b9e\u65f6\u76d1\u63a7\u5806\u5185\u5b58\u7684\u4f7f\u7528\u60c5\u51b5\uff0c\u8fd8\u53ef\u4ee5\u8ddf\u8e2a\u5783\u573e\u56de\u6536\uff0c\u8fd0\u884c\u4e2d dump \u4e2d\u5806\u5185\u5b58\u4f7f\u7528\u60c5\u51b5\u3001cpu\u5206\u6790\uff0c\u7ebf\u7a0b\u5206\u6790\u7b49\uff0c\u662f\u67e5\u627e\u5206\u6790\u95ee\u9898\u7684\u5229\u5668\uff0c\u66f4\u9a9a\u7684\u662f\u5b83\u4e0d\u5149\u80fd\u5206\u6790\u672c\u5730\u7684 Java \u7a0b\u5e8f\uff0c\u8fd8\u53ef\u4ee5\u5206\u6790\u7ebf\u4e0a\u7684 Java \u7a0b\u5e8f\u8fd0\u884c\u60c5\u51b5, \u672c\u8eab\u8fd9\u6b3e\u5de5\u5177\u4e5f\u662f\u968f JDK \u53d1\u5e03\u7684\uff0c\u662f\u5b98\u65b9\u529b\u63a8\u7684\u4e00\u6b3e\u8fd0\u884c\u76d1\u89c6\uff0c\u6545\u969c\u5904\u7406\u7684\u795e\u5668\u3002\u6211\u4eec\u6765\u770b\u770b\u5982\u4f55\u7528 jvisualvm \u6765\u5206\u6790\u4e0a\u6587\u6240\u8ff0\u7684\u5b58\u5728\u5185\u5b58\u6cc4\u6f0f\u7684\u5982\u4e0b\u4ee3\u7801\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>import java.util.Map;\nimport java.util.HashMap;\npublic class KeylessEntry {\n    static class Key {\n        Integer id; \n        Key(Integer id) {\n            this.id = id;\n        }  \n        @Override\n        public int hashCode() {\n            return id.hashCode();\n        }\n    }\n    public static void main(String[] args) {\n        Map&lt;Key,String&gt; m = new HashMap&lt;Key,String&gt;();\n        while(true) {\n            for(int i=0;i&lt;10000;i++) {\n                if(!m.containsKey(new Key(i))) {\n                    m.put(new Key(i), \"Number:\" + i);\n                }\n            }\n        }\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u6253\u5f00 jvisualvm \uff08\u7ec8\u7aef\u8f93\u5165 jvisualvm \u6267\u884c\u5373\u53ef\uff09\uff0c\u6253\u5f00\u540e\uff0c\u5c06\u5806\u5927\u5c0f\u8bbe\u7f6e\u4e3a 500M\uff0c\u6267\u884c\u547d\u4ee4 java Xms500m -Xmx500m KeylessEntry\uff0c\u6b64\u65f6\u53ef\u4ee5\u89c2\u5bdf\u5230\u5de6\u8fb9\u51fa\u73b0\u4e86\u5bf9\u5e94\u7684\u5e94\u7528 KeylessEntry,\u53cc\u51fb\u70b9\u51fb open\u3002<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/jvm6.jpg\" alt=\"\" \/><figcaption>jvisualvm<\/figcaption><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">\u6253\u5f00\u4e4b\u540e\u53ef\u4ee5\u770b\u5230\u5c55\u793a\u4e86 CPU\uff0c\u5806\u5185\u5b58\u4f7f\u7528\uff0c\u52a0\u8f7d\u7c7b\u53ca\u7ebf\u7a0b\u7684\u60c5\u51b5\u3002<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/jvm7.jpg\" alt=\"\" \/><figcaption> java Xms500m -Xmx500m KeylessEntry<\/figcaption><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">\u6ce8\u610f\u770b\u5806\uff08Heap\uff09\u7684\u4f7f\u7528\u60c5\u51b5\uff0c\u4e00\u76f4\u5728\u4e0a\u6da8\u3002<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/jvm8.jpg\" alt=\"\" \/><figcaption>Heap Dump<\/figcaption><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">\u6b64\u65f6\u6211\u4eec\u518d\u70b9\u51fb \u300cHeap Dump\u300d\u3002<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/jvm9.jpg\" alt=\"\" \/><figcaption>\u5185\u5b58\u4e2d\u5bf9\u8c61<\/figcaption><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">\u8fc7\u4e00\u4f1a\u513f\u5373\u53ef\u770b\u5230\u5185\u5b58\u4e2d\u5bf9\u8c61\u7684\u4f7f\u7528\u60c5\u51b5\u3002<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/jvm10.jpg\" alt=\"\" \/><figcaption>HashMap \u5185\u5b58\u6cc4\u9732<\/figcaption><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u770b\u5230\u76f8\u5173\u7684 TreeNode \u6709 291w \u4e2a\uff0c\u8fdc\u8d85\u6b63\u5e38\u60c5\u51b5\u4e0b\u7684 10000 \u4e2a\uff01\u8bf4\u660e HashMap \u4e00\u76f4\u5728\u589e\u957f\uff0c\u81ea\u6b64\u6211\u4eec\u53ef\u4ee5\u5b9a\u4f4d\u51fa\u95ee\u9898\u4ee3\u7801\u6240\u5728\uff01<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">3\u3001\u4f7f\u7528 jps + jmap \u6765\u83b7\u53d6 dump \u6587\u4ef6\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">jps \u53ef\u4ee5\u5217\u51fa\u6b63\u5728\u8fd0\u884c\u7684\u865a\u62df\u673a\u8fdb\u7a0b\uff0c\u5e76\u663e\u793a\u6267\u884c\u865a\u62df\u673a\u4e3b\u7c7b\u53ca\u8fd9\u4e9b\u8fdb\u7a0b\u7684\u672c\u5730\u865a\u62df\u673a\u552f\u4e00 ID\uff0c\u5982\u56fe\u793a\u3002<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/jvm11.jpg\" alt=\"\" \/><figcaption>jps<\/figcaption><\/figure><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">\u62ff\u5230\u8fdb\u7a0b\u7684 pid \u540e\uff0c\u6211\u4eec\u5c31\u53ef\u4ee5\u7528 jmap \u6765 dump \u51fa\u5806\u8f6c\u50a8\u6587\u4ef6\u4e86\uff0c\u6267\u884c\u547d\u4ee4\u5982\u4e0b\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>jmap -dump:format=b,file=heapdump.phrof pid<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u62ff\u5230 dump \u6587\u4ef6\u540e\u6211\u4eec\u5c31\u53ef\u4ee5\u7528 MAT \u5de5\u5177\u6765\u5206\u6790\u4e86\u3002\u4f46\u8fd9\u4e2a\u547d\u4ee4\u5728\u751f\u4ea7\u4e0a\u4e00\u5b9a\u8981\u614e\u7528\uff01\u56e0\u4e3aJVM \u4f1a\u5c06\u6574\u4e2a heap \u7684\u4fe1\u606f dump \u5199\u5165\u5230\u4e00\u4e2a\u6587\u4ef6\uff0cheap \u6bd4\u8f83\u5927\u7684\u8bdd\u4f1a\u5bfc\u81f4\u8fd9\u4e2a\u8fc7\u7a0b\u6bd4\u8f83\u8017\u65f6\uff0c\u5e76\u4e14\u6267\u884c\u8fc7\u7a0b\u4e2d\u4e3a\u4e86\u4fdd\u8bc1 dump \u7684\u4fe1\u606f\u662f\u53ef\u9760\u7684\uff0c\u4f1a\u6682\u505c\u5e94\u7528\uff01<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">GC \u65e5\u5fd7\u683c\u5f0f\u600e\u4e48\u770b<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u63a5\u4e0b\u6765\u6211\u4eec\u770b\u770b GC \u65e5\u5fd7\u600e\u4e48\u770b\uff0c\u65e5\u5fd7\u53ef\u4ee5\u6709\u6548\u5730\u5e2e\u52a9\u6211\u4eec\u5b9a\u4f4d\u95ee\u9898\uff0c\u6240\u4ee5\u641e\u6e05\u695a GC \u65e5\u5fd7\u7684\u683c\u5f0f\u975e\u5e38\u91cd\u8981\uff0c\u6765\u770b\u4e0b\u5982\u4e0b\u4f8b\u5b50\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\/**\n *  VM Args:-verbose:gc -Xms20M -Xmx20M -Xmn10M -XX:+PrintGCDetails -XX:+PrintGCTimeStamps  -XX:+UseSerialGC -XX:SurvivorRatio=8\n *\/\npublic class TestGC {\n    private static final int _1MB = 1024 * 1024;\n    public static void main(String[] args) {\n        byte[] allocation1, allocation2, allocation3, allocation4;\n        allocation1 = new byte[2 * _1MB];\n        allocation2 = new byte[2 * _1MB];\n        allocation3 = new byte[2 * _1MB];\n        allocation4 = new byte[4 * _1MB];    \/\/ \u8fd9\u91cc\u4f1a\u51fa\u73b0\u4e00\u6b21 Minor GC\n    }\n}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u6267\u884c\u4ee5\u4e0a\u4ee3\u7801\uff0c\u4f1a\u8f93\u51fa\u5982\u4e0b GC \u65e5\u5fd7\u4fe1\u606f\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>10.080: 2[GC 3(Allocation Failure) 0.080: 4[DefNew: 56815K-&gt;280K(9216K),6 0.0043690 secs] 76815K-&gt;6424K(19456K), 80.0044111 secs]9 [Times: user=0.00 sys=0.01, real=0.01 secs]<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u4ee5\u4e0a\u662f\u53d1\u751f Minor GC \u7684 GC \u662f\u65e5\u5fd7\uff0c\u5982\u679c\u53d1\u751f Full GC \u5462\uff0c\u683c\u5f0f\u5982\u4e0b\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>10.088: 2[Full GC 3(Allocation Failure) 0.088: 4[Tenured: 50K-&gt;210K(10240K), 60.0009420 secs] 74603K-&gt;210K(19456K), [Metaspace: 2630K-&gt;2630K(1056768K)], 80.0009700 secs]9 [Times: user=0.01 sys=0.00, real=0.02 secs]<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u4e24\u8005\u683c\u5f0f\u5176\u5b9e\u5dee\u4e0d\u591a\uff0c\u4e00\u8d77\u6765\u770b\u770b\uff0c\u4e3b\u8981\u4ee5\u672c\u4f8b\u89e6\u53d1\u7684 Minor GC \u6765\u8bb2\u89e3, \u4ee5\u4e0a\u65e5\u5fd7\u4e2d\u6807\u7684\u6bcf\u4e00\u4e2a\u6570\u5b57\u4e0e\u4ee5\u4e0b\u5e8f\u53f7\u4e00\u4e00\u5bf9\u5e94\u3002<\/p>\n\n\n\n<ol class=\"wp-block-list\"><li>\u5f00\u5934\u7684 0.080\uff0c0.088 \u4ee3\u8868\u4e86 GC \u53d1\u751f\u7684\u65f6\u95f4\uff0c\u8fd9\u4e2a\u6570\u5b57\u7684\u542b\u4e49\u662f\u4ece Java \u865a\u62df\u673a\u542f\u52a8\u4ee5\u6765\u7ecf\u8fc7\u7684\u79d2\u6570<\/li><li>[GC \u6216\u8005 [Full GC \u8bf4\u660e\u4e86\u8fd9\u6b21\u5783\u573e\u6536\u96c6\u7684\u505c\u987f\u7c7b\u578b\uff0c\u6ce8\u610f\u4e0d\u662f\u7528\u6765\u533a\u5206\u65b0\u751f\u4ee3 GC \u8fd8\u662f\u8001\u5e74\u5316 GC \u7684\uff0c\u5982\u679c\u6709 Full\uff0c\u8bf4\u660e\u8fd9\u6b21 GC \u662f\u53d1\u751f\u4e86 Stop The World \u7684\uff0c\u5982\u679c\u662f\u8c03\u7528 System.gc() \u6240\u89e6\u53d1\u7684\u6536\u96c6\uff0c\u8fd9\u91cc\u4f1a\u663e\u793a [Full GC\uff08System\uff09<\/li><li>\u4e4b\u540e\u7684 Allocation Failure \u4ee3\u8868\u4e86\u89e6\u53d1 GC \u7684\u539f\u56e0\uff0c\u5728\u8fd9\u4e2a\u7a0b\u5e8f\u4e2d\u6211\u4eec\u8bbe\u7f6e\u4e86\u65b0\u751f\u4ee3\u7684\u5927\u5c0f\u4e3a 10M\uff08-Xmn10M\uff09\uff0cEden:S0:S1 = 8\uff1a1\uff1a1\uff08-XX:SurvivorRatio=8\uff09\uff0c\u4e5f\u5c31\u662f\u8bf4 Eden \u533a\u5360\u4e86 8M, \u5f53\u5206\u914d allocation4 \u65f6\uff0c\u7531\u4e8e\u5c06\u8981\u5206\u914d\u7684\u603b\u5927\u5c0f\u4e3a 10M,\u8d85\u8fc7\u4e86 Eden \u533a\uff0c\u6240\u4ee5\u6b64\u65f6\u4f1a\u53d1\u751f GC<\/li><li>\u63a5\u4e0b\u6765\u7684 [DefNew\uff0c[Tenured\uff0c[Metaspace \u8868\u793a GC \u53d1\u751f\u7684\u533a\u57df\uff0c\u8fd9\u91cc\u663e\u793a\u7684\u533a\u57df\u540d\u4e0e\u4f7f\u7528\u7684 GC \u6536\u96c6\u5668\u662f\u5bc6\u5207\u76f8\u5173\u7684\uff0c\u5728\u6b64\u4f8b\u4e2d\u7531\u4e8e\u65b0\u751f\u4ee3\u6211\u4eec\u4f7f\u7528\u4e86 Serial \u6536\u96c6\u5668\uff0c\u6b64\u6536\u96c6\u5668\u65b0\u751f\u4ee3\u540d\u4e3a\u300cDefault New Generation\u300d\uff0c\u6240\u4ee5\u663e\u793a\u7684\u662f [DefNew\uff0c\u5982\u679c\u662f ParNew \u6536\u96c6\u5668\uff0c\u65b0\u751f\u4ee3\u540d\u79f0\u5c31\u4f1a\u53d8\u4e3a [ParNew`\uff0c\u610f\u4e3a \u300cParallel New Generation\u300d,\u5982\u679c\u91c7\u7528 \u300cParallel Scavenge\u300d\u6536\u96c6\u5668\uff0c\u5219\u914d\u5957\u7684\u65b0\u751f\u4ee3\u540d\u79f0\u4e3a\u300cPSYoungGen\u300d,\u8001\u5e74\u4ee3\u4e0e\u65b0\u751f\u4ee3\u4e00\u6837\uff0c\u540d\u79f0\u4e5f\u662f\u7531\u6536\u96c6\u5668\u51b3\u5b9a\u7684<\/li><li>\u518d\u5f80\u540e 6815K-&gt;280K(9216K) \u8868\u793a \u300cGC \u524d\u8be5\u5185\u5b58\u533a\u57df\u5df2\u4f7f\u7528\u5bb9\u91cf -&gt; GC \u540e\u8be5\u5185\u5b58\u533a\u57df\u5df2\u4f7f\u7528\u5bb9\u91cf\uff08\u8be5\u5185\u5b58\u533a\u57df\u603b\u5bb9\u91cf\uff09\u300d<\/li><li>0.0043690 secs \u8868\u793a\u8be5\u5757\u5185\u5b58\u533a\u57df GC \u6240\u5360\u7528\u7684\u65f6\u95f4\uff0c\u5355\u4f4d\u662f\u79d2<\/li><li>6815K-&gt;6424K(19456K) \u8868\u793a\u300cGC \u524d Java \u5806\u5df2\u4f7f\u7528\u5bb9\u91cf -&gt; GC \u540e Java \u5806\u5df2\u4f7f\u7528\u5bb9\u91cf\uff08java \u5806\u603b\u5bb9\u91cf\uff09\u300d\u3002<\/li><li>0.0044111 secs \u8868\u793a\u6574\u4e2a GC \u6267\u884c\u65f6\u95f4\uff0c\u6ce8\u610f\u548c 6 \u4e2d 0.0043690 secs \u7684\u533a\u522b\uff0c\u540e\u8005\u4e13\u6307\u76f8\u5173\u533a\u57df\u6240\u82b1\u7684 GC \u65f6\u95f4\uff0c\u800c\u524d\u8005\u6307\u7684 GC \u7684\u6574\u4f53\u5806\u5185\u5b58\u53d8\u5316\u6240\u82b1\u65f6\u95f4\uff08\u65b0\u751f\u4ee3\u4e0e\u8001\u751f\u4ee3\u7684\u7684\u5185\u5b58\u6574\u7406\uff09\uff0c\u6240\u4ee5\u524d\u8005\u662f\u80af\u5b9a\u5927\u4e8e\u540e\u8005\u7684\uff01<\/li><li>\u6700\u540e\u4e00\u4e2a [Times: user=0.01 sys=0.00, real=0.02 secs] \u8fd9\u91cc\u7684 user, sys \u548c real \u4e0eLinux \u7684 time \u547d\u4ee4\u6240\u8f93\u51fa\u7684\u65f6\u95f4\u4e00\u81f4\uff0c\u5206\u522b\u4ee3\u8868\u7528\u6237\u6001\u6d88\u8017\u7684 CPU \u65f6\u95f4\uff0c\u5185\u6838\u6001\u6d88\u8017\u7684 CPU \u65f6\u95f4\uff0c\u548c\u64cd\u4f5c\u4ece\u5f00\u59cb\u5230\u7ed3\u675f\u6240\u7ecf\u8fc7\u7684\u5899\u949f\u65f6\u95f4\uff0c\u5899\u949f\u65f6\u95f4\u5305\u62ec\u5404\u79cd\u975e\u8fd0\u7b97\u7684\u7b49\u5f85\u8017\u65f6\uff0c\u4f8b\u5982\u7b49\u5f85\u78c1\u76d8 I\/O\uff0c\u7b49\u5f85\u7ebf\u7a0b\u963b\u585e\uff0c\u800c CPU \u65f6\u95f4\u4e0d\u5305\u62ec\u8fd9\u4e9b\u8017\u65f6\uff0c\u4f46\u5f53\u7cfb\u7edf\u6709\u591a CPU \u6216\u8005\u591a\u6838\u7684\u8bdd\uff0c\u591a\u7ebf\u7a0b\u64cd\u4f5c\u4f1a\u53e0\u52a0\u8fd9\u4e9b CPU \u65f6\u95f4\uff0c\u6240\u4ee5 user \u6216 sys \u65f6\u95f4\u662f\u53ef\u80fd\u8d85\u8fc7 real \u65f6\u95f4\u7684\u3002<\/li><\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">\u77e5\u9053\u4e86 GC \u65e5\u5fd7\u600e\u4e48\u770b\uff0c\u6211\u4eec\u5c31\u53ef\u4ee5\u6839\u636e GC \u65e5\u5fd7\u6709\u6548\u5b9a\u4f4d\u95ee\u9898\u4e86\uff0c\u5982\u6211\u4eec\u53d1\u73b0 Full GC \u53d1\u751f\u65f6\u95f4\u8fc7\u957f\uff0c\u5219\u7ed3\u5408\u6211\u4eec\u4e0a\u6587\u5e94\u7528\u4e2d\u6253\u5370\u7684 OOM \u65e5\u5fd7\u53ef\u80fd\u53ef\u4ee5\u5feb\u901f\u5b9a\u4f4d\u5230\u95ee\u9898\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">jstat \u4e0e\u53ef\u89c6\u5316 APM \u5de5\u5177\u6784\u5efa<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">jstat \u662f\u7528\u4e8e\u76d1\u89c6\u865a\u62df\u673a\u5404\u79cd\u8fd0\u884c\u72b6\u6001\u4fe1\u606f\u7684\u547d\u4ee4\u884c\u5de5\u5177\uff0c\u53ef\u4ee5\u663e\u793a\u672c\u5730\u6216\u8005\u8fdc\u7a0b\u865a\u62df\u673a\u8fdb\u7a0b\u4e2d\u7684\u7c7b\u52a0\u8f7d\uff0c\u5185\u5b58\uff0c\u5783\u573e\u6536\u96c6\uff0cJIT \u7f16\u8bd1\u7b49\u8fd0\u884c\u6570\u636e\uff0cjstat \u652f\u6301\u5b9a\u65f6\u67e5\u8be2\u76f8\u5e94\u7684\u6307\u6807\uff0c\u5982\u4e0b\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>jstat -gc 2764 250 22<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5b9a\u65f6\u9488\u5bf9 2764 \u8fdb\u7a0b\u8f93\u51fa\u5806\u7684\u5783\u573e\u6536\u96c6\u60c5\u51b5\u7684\u7edf\u8ba1\uff0c\u53ef\u4ee5\u663e\u793a gc \u7684\u4fe1\u606f\uff0c\u67e5\u770bgc\u7684\u6b21\u6570\u53ca\u65f6\u95f4,\u5229\u7528\u8fd9\u4e9b\u6307\u6807\uff0c\u628a\u5b83\u4eec\u53ef\u89c6\u5316\uff0c\u5bf9\u5206\u6790\u95ee\u9898\u4f1a\u6709\u5f88\u5927\u7684\u5e2e\u52a9,\u5982\u56fe\u793a\uff0c\u4e0b\u56fe\u5c31\u662f\u6211\u53f8\u6839\u636e jstat \u505a\u7684\u4e00\u90e8\u5206 gc \u7684\u53ef\u89c6\u5316\u62a5\u8868\uff0c\u80fd\u5feb\u901f\u5b9a\u4f4d\u53d1\u751f\u95ee\u9898\u7684\u95ee\u9898\u70b9\uff0c\u5982\u679c\u5927\u5bb6\u9700\u8981\u505a APM \u53ef\u89c6\u5316\u5de5\u5177\uff0c\u5efa\u8bae\u914d\u5408\u4f7f\u7528 jstat \u6765\u5b8c\u6210\u3002<\/p>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/jvm12.jpg\" alt=\"\" \/><figcaption>jstat<\/figcaption><\/figure><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">\u518d\u8c08 JVM \u53c2\u6570\u8bbe\u7f6e<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u7ecf\u8fc7\u524d\u9762\u5bf9 JVM \u53c2\u6570\u7684\u4ecb\u7ecd\u53ca\u76f8\u5173\u4f8b\u5b50\u7684\u5b9e\u9a8c\uff0c\u76f8\u4fe1\u5927\u5bb6\u5bf9 JVM \u7684\u53c2\u6570\u6709\u4e86\u6bd4\u8f83\u6df1\u523b\u7684\u7406\u89e3\uff0c\u63a5\u4e0b\u6765\u6211\u4eec\u518d\u8c08\u8c08\u5982\u4f55\u8bbe\u7f6e JVM \u53c2\u6570<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">1\u3001\u9996\u5148 Oracle \u5b98\u65b9\u63a8\u8350\u5806\u7684\u521d\u59cb\u5316\u5927\u5c0f\u4e0e\u5806\u53ef\u8bbe\u7f6e\u7684\u6700\u5927\u503c\u4e00\u822c\u662f\u76f8\u7b49\u7684\uff0c\u5373 Xms = Xmx\uff0c\u56e0\u4e3a\u8d77\u59cb\u5806\u5185\u5b58\u592a\u5c0f\uff08Xms\uff09\uff0c\u4f1a\u5bfc\u81f4\u542f\u52a8\u521d\u671f\u9891\u7e41 GC\uff0c\u8d77\u59cb\u5806\u5185\u5b58\u8f83\u5927\uff08Xmx\uff09\u6709\u52a9\u4e8e\u51cf\u5c11 GC \u6b21\u6570<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">2\u3001\u8c03\u8bd5\u7684\u65f6\u5019\u8bbe\u7f6e\u4e00\u4e9b\u6253\u5370\u53c2\u6570\uff0c\u5982-XX:+PrintClassHistogram -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintHeapAtGC -Xloggc:log\/gc.log\uff0c\u8fd9\u6837\u53ef\u4ee5\u4ecegc.log\u91cc\u770b\u51fa\u4e00\u4e9b\u7aef\u502a\u51fa\u6765<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">3\u3001\u7cfb\u7edf\u505c\u987f\u65f6\u95f4\u8fc7\u957f\u53ef\u80fd\u662f GC \u7684\u95ee\u9898\u4e5f\u53ef\u80fd\u662f\u7a0b\u5e8f\u7684\u95ee\u9898\uff0c\u591a\u7528 jmap \u548c jstack \u67e5\u770b\uff0c\u6216\u8005killall -3 Java\uff0c\u7136\u540e\u67e5\u770b Java \u63a7\u5236\u53f0\u65e5\u5fd7\uff0c\u80fd\u770b\u51fa\u5f88\u591a\u95ee\u9898<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">4\u3001 \u91c7\u7528\u5e76\u53d1\u56de\u6536\u65f6\uff0c\u5e74\u8f7b\u4ee3\u5c0f\u4e00\u70b9\uff0c\u5e74\u8001\u4ee3\u8981\u5927\uff0c\u56e0\u4e3a\u5e74\u8001\u5927\u7528\u7684\u662f\u5e76\u53d1\u56de\u6536\uff0c\u5373\u4f7f\u65f6\u95f4\u957f\u70b9\u4e5f\u4e0d\u4f1a\u5f71\u54cd\u5176\u4ed6\u7a0b\u5e8f\u7ee7\u7eed\u8fd0\u884c\uff0c\u7f51\u7ad9\u4e0d\u4f1a\u505c\u987f<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">5\u3001\u4ed4\u7ec6\u4e86\u89e3\u81ea\u5df1\u7684\u5e94\u7528\uff0c\u5982\u679c\u7528\u4e86\u7f13\u5b58\uff0c\u90a3\u4e48\u5e74\u8001\u4ee3\u5e94\u8be5\u5927\u4e00\u4e9b\uff0c\u7f13\u5b58\u7684 HashMap \u4e0d\u5e94\u8be5\u65e0\u9650\u5236\u957f\uff0c\u5efa\u8bae\u91c7\u7528 LRU \u7b97\u6cd5\u7684 Map \u505a\u7f13\u5b58\uff0cLRUMap \u7684\u6700\u5927\u957f\u5ea6\u4e5f\u8981\u6839\u636e\u5b9e\u9645\u60c5\u51b5\u8bbe\u5b9a<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u8981\u8bbe\u7f6e\u597d\u5404\u79cd JVM \u53c2\u6570\uff0c\u8fd8\u53ef\u4ee5\u5bf9 server \u8fdb\u884c\u538b\u6d4b\uff0c \u9884\u4f30\u81ea\u5df1\u7684\u4e1a\u52a1\u91cf\uff0c\u8bbe\u5b9a\u597d\u4e00\u4e9b JVM \u53c2\u6570\u8fdb\u884c\u538b\u6d4b\u770b\u4e0b\u8fd9\u4e9b\u8bbe\u7f6e\u597d\u7684 JVM \u53c2\u6570\u662f\u5426\u80fd\u6ee1\u8db3\u8981\u6c42<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u603b\u7ed3<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u672c\u6587\u901a\u8fc7\u8be6\u7ec6\u4ecb\u7ecd\u4e86 JVM \u53c2\u6570\u53ca GC \u65e5\u5fd7\uff0c OOM \u53d1\u751f\u7684\u539f\u56e0\u53ca\u76f8\u5e94\u7684\u8c03\u8bd5\u5de5\u5177\uff0c\u76f8\u4fe1\u8bfb\u8005\u5e94\u8be5\u638c\u63e1\u4e86\u57fa\u672c\u7684 MAT\uff0cjvisualvm \u8fd9\u4e9b\u5de5\u5177\u6392\u67e5\u95ee\u9898\u7684\u6280\u5de7\uff0c\u4e0d\u8fc7\u8fd9\u4e9b\u5de5\u5177\u7684\u4ecb\u7ecd\u672c\u6587\u53ea\u662f\u63d0\u5230\u4e86\u4e00\u4e9b\u76ae\u6bdb\uff0c\u5927\u5bb6\u53ef\u4ee5\u5728\u518d\u6df1\u5165\u4e86\u89e3\u76f8\u5e94\u5de5\u5177\u7684\u4e00\u4e9b\u8fdb\u9636\u6280\u80fd\uff0c\u8fd9\u80fd\u5bf9\u81ea\u5df1\u6392\u67e5\u95ee\u9898\u7b49\u5927\u6709\u88e8\u76ca\uff01\u6587\u4e2d\u7684\u4f8b\u5b50\u5927\u5bb6\u53ef\u4ee5\u53bb\u8bd5\u9a8c\u4e00\u4e0b\uff0c\u4fee\u6539\u4e00\u4e0b\u53c2\u6570\u770b\u4e0b\u4f1a\u53d1\u751f\u54ea\u4e9b\u795e\u5947\u7684\u73b0\u8c61\uff0c\u4eb2\u81ea\u52a8\u624b\u505a\u4e00\u904d\u80fd\u5bf9\u6392\u67e5\u95ee\u9898\u7684\u601d\u8def\u66f4\u52a0\u6e05\u6670\u3002<\/p>\n<!-- <audio autoplay=\"autoplay\" height=\"100\" width=\"100\" hidden=\"true\"><source src=\"https:\/\/c.coka.la\/orAvPR.mp3\" type=\"audio\/mp3\"\/><\/audio><img decoding=\"async\" src=\"https:\/\/images.weserv.nl\/?url=https:\/\/ws3.sinaimg.cn\/large\/8fa5dcfcgy1g4em3rzar5j20ib089ae0.jpg\" alt=\"\u4e1a\u4f59\u8349\u516c\u4f17\u53f7\"\/> --><p><!-- <img decoding=\"async\" src=\"https:\/\/raw.githubusercontent.com\/xmt1139057136\/xttblog\/master\/8fa5dcfcgy1g4em3rzar5j20ib089ae0.jpg\" alt=\"\u4e1a\u4f59\u8349\u516c\u4f17\u53f7\"\/>--><img decoding=\"async\" src=\"https:\/\/saas.51autoparts.cn\/api\/admin\/sys-file\/oss\/file?fileName=84db51f8561e448f9a4fda2eff0811f9.jpg\" alt=\"\u4e1a\u4f59\u8349\u516c\u4f17\u53f7\"\/><\/p><p>\u6700\u540e\uff0c\u6b22\u8fce\u5173\u6ce8\u6211\u7684\u4e2a\u4eba\u5fae\u4fe1\u516c\u4f17\u53f7\uff1a\u4e1a\u4f59\u8349\uff08yyucao\uff09\uff01<b>\u53ef\u52a0\u4f5c\u8005\u5fae\u4fe1\u53f7\uff1a<font color=\"red\">xttblog2<\/font>\u3002\u5907\u6ce8\uff1a\u201c1\u201d\uff0c\u6dfb\u52a0\u535a\u4e3b\u5fae\u4fe1\u62c9\u4f60\u8fdb\u5fae\u4fe1\u7fa4\u3002\u5907\u6ce8\u9519\u8bef\u4e0d\u4f1a\u540c\u610f\u597d\u53cb\u7533\u8bf7\u3002<\/b>\u518d\u6b21\u611f\u8c22\u60a8\u7684\u5173\u6ce8\uff01\u540e\u7eed\u6709\u7cbe\u5f69\u5185\u5bb9\u4f1a\u7b2c\u4e00\u65f6\u95f4\u53d1\u7ed9\u60a8\uff01\u539f\u521b\u6587\u7ae0\u6295\u7a3f\u8bf7\u53d1\u9001\u81f3532009913@qq.com\u90ae\u7bb1\u3002\u5546\u52a1\u5408\u4f5c\u4e5f\u53ef\u6dfb\u52a0\u4f5c\u8005\u5fae\u4fe1\u8fdb\u884c\u8054\u7cfb\uff01<\/p><p>\u672c\u6587\u539f\u6587\u51fa\u5904\uff1a<a href=\"https:\/\/www.xttblog.com\">\u4e1a\u4f59\u8349<\/a>\uff1a &raquo; <a href=\"https:\/\/www.xttblog.com\/?p=4833\">JVM \u5783\u573e\u56de\u6536\u5b9e\u6218<\/a><\/p><!-- <div class=\"bd-reward-stl\"><button id=\"bdRewardBtn\"><span><\/span><\/button><\/div> -->","protected":false},"excerpt":{"rendered":"<p>\u672c\u6587\u6211\u4eec\u6765\u5b66\u4e60\u4e0b GC \u7684\u5b9e\u6218\u5185\u5bb9\uff0c\u4e3b\u8981\u5305\u62ec\u4ee5\u4e0b\u51e0\u70b9 JVM \u53c2\u6570\u7b80\u4ecb \u53d1\u751f OOM \u7684\u4e3b\u8981\u51e0\u79cd\u573a\u666f\u53ca\u76f8\u5e94\u89e3\u51b3 [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[201,1846,1844,1706,1699],"class_list":["post-4833","post","type-post","status-publish","format-standard","hentry","category-java","tag-dump","tag-jmap","tag-jps","tag-jstat","tag-jvisualvm"],"_links":{"self":[{"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts\/4833","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=4833"}],"version-history":[{"count":1,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts\/4833\/revisions"}],"predecessor-version":[{"id":4834,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts\/4833\/revisions\/4834"}],"wp:attachment":[{"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4833"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4833"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4833"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}