{"id":1020,"date":"2016-12-18T14:51:31","date_gmt":"2016-12-18T06:51:31","guid":{"rendered":"http:\/\/www.xttblog.com\/?p=1020"},"modified":"2016-12-18T14:51:31","modified_gmt":"2016-12-18T06:51:31","slug":"java%e5%a4%9a%e7%ba%bf%e7%a8%8b%e4%ba%92%e6%96%a5%e5%92%8cjvm%e9%94%81%e6%9c%ba%e5%88%b6","status":"publish","type":"post","link":"https:\/\/www.xttblog.com\/?p=1020","title":{"rendered":"java\u591a\u7ebf\u7a0b\u4e92\u65a5\u548cJVM\u9501\u673a\u5236"},"content":{"rendered":"

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\n\tvm\u89c4\u8303\u4e2d\u53ef\u4ee5\u770b\u5230synchronized\u5728jvm\u91cc\u5b9e\u73b0\u539f\u7406\uff0cjvm\u57fa\u4e8e\u8fdb\u5165\u548c\u9000\u51faMonitor\u5bf9\u8c61\u6765\u5b9e\u73b0\u65b9\u6cd5\u540c\u6b65\u548c\u4ee3\u7801\u5757\u540c\u7684\u3002\u5728\u4ee3\u7801\u540c\u6b65\u7684\u5f00\u59cb\u4f4d\u7f6e\u7ec7\u5165monitorenter,\u5728\u7ed3\u675f\u540c\u6b65\u7684\u4f4d\u7f6e\uff08\u6b63\u5e38\u7ed3\u675f\u548c\u5f02\u5e38\u7ed3\u675f\u5904\uff09\u7ec7\u5165monitorexit\u6307\u4ee4\u5b9e\u73b0\u3002\u7ebf\u7a0b\u6267\u884c\u5230monitorenter\u5904\uff0c\u8bb2\u4f1a\u83b7\u53d6\u9501\u5bf9\u8c61\u9501\u5bf9\u5e94\u7684monitor\u7684\u6240\u6709\u6743\uff0c\u5373\u5c1d\u8bd5\u83b7\u5f97\u5bf9\u8c61\u7684\u9501\u3002\uff08\u4efb\u610f\u5bf9\u8c61\u90fd\u53c8\u4e00\u4e2amonitor\u4e0e\u4e4b\u5173\u8054\uff0c\u5f53\u4e14\u4e00\u4e2amonitor\u88ab\u6301\u6709\u540e\uff0c\u4ed6\u5904\u4e8e\u9501\u5b9a\u72b6\u6001\uff09\n<\/p>\n

\n\tjava\u7684\u591a\u7ebf\u7a0b\u5b89\u5168\u662f\u57fa\u4e8elock\u673a\u5236\u5b9e\u73b0\u7684\uff0c\u800clock\u7684\u6027\u80fd\u5f80\u5f80\u4e0d\u5982\u4eba\u610f\u3002\u539f\u56e0\u662f\uff0cmonitorenter\u4e0emonitorexit\u8fd9\u4e24\u4e2a\u63a7\u5236\u591a\u7ebf\u7a0b\u540c\u6b65\u7684bytecode\u539f\u8bed\uff0c\u662fjvm\u4f9d\u8d56\u64cd\u4f5c\u7cfb\u7edf\u4e92\u65a5\uff08mutex\uff09\u6765\u5b9e\u73b0\u7684\u3002\n<\/p>\n

\n\t\u4e92\u65a5\u662f\u4e00\u79cd\u4f1a\u5bfc\u81f4\u7ebf\u7a0b\u6302\u8d77\uff0c\u5e76\u5728\u8f83\u77ed\u65f6\u95f4\u5185\u53c8\u9700\u8981\u91cd\u65b0\u8c03\u5ea6\u56de\u539f\u7ebf\u7a0b\u7684\uff0c\u8f83\u4e3a\u6d88\u8017\u8d44\u6e90\u7684\u64cd\u4f5c\u3002\n<\/p>\n

\n\t\u4e3a\u4e86\u4f18\u5316java\u7684Lock\u673a\u5236\uff0c\u4ecejava6\u5f00\u59cb\u5f15\u5165\u8f7b\u91cf\u7ea7\u9501\u7684\u6982\u5ff5\u3002\u8f7b\u91cf\u7ea7\u9501\u672c\u610f\u662f\u4e3a\u4e86\u51cf\u5c11\u591a\u7ebf\u7a0b\u8fdb\u5165\u4e92\u65a5\u7684\u51e0\u7387\uff0c\u5e76\u4e0d\u662f\u8981\u66ff\u4ee3\u4e92\u65a5\u3002\u5b83\u5229\u7528\u4e86cpu\u539f\u8bedCompare-And-Swap\uff08cas,\u6c47\u7f16\u6307\u4ee4CMPXCHG\uff09,\u5c1d\u8bd5\u8fdb\u5165\u4e92\u65a5\u524d\uff0c\u8fdb\u884c\u8865\u6551\u3002\n<\/p>\n

\n\t\u4e3a\u4ec0\u4e48\u8981\u81ea\u65cb\u6216\u8005\u81ea\u9002\u5e94\u81ea\u65cb
\n<\/h2>\n

\n\t\u524d\u9762\u6211\u4eec\u8ba8\u8bba\u4e92\u65a5\u540c\u6b65\u7684\u65f6\u5019\uff0c\u63d0\u5230\u4e86\u4e92\u65a5\u540c\u6b65\u5bf9\u6027\u80fd\u6700\u5927\u7684\u5f71\u54cd\u662f\u963b\u585e\u7684\u5b9e\u73b0\uff0c\u6302\u8d77\u7ebf\u7a0b\u548c\u6062\u590d\u7ebf\u7a0b\u7684\u64cd\u4f5c\u90fd\u9700\u8981\u8f6c\u5165\u5185\u6838\u6001\u4e2d\u5b8c\u6210\uff0c\u8fd9\u4e9b\u64cd\u4f5c\u7ed9\u7cfb\u7edf\u7684\u5e76\u53d1\u6027\u80fd \u5e26\u6765\u4e86\u5f88\u5927\u7684\u538b\u529b\u3002\u540c\u65f6\uff0c\u865a\u62df\u673a\u7684\u5f00\u53d1\u56e2\u961f\u4e5f\u6ce8\u610f\u5230\u5728\u8bb8\u591a\u5e94\u7528\u4e0a\uff0c\u5171\u4eab\u6570\u636e\u7684\u9501\u5b9a\u72b6\u6001\u53ea\u4f1a\u6301\u7eed\u5f88\u77ed\u7684\u4e00\u6bb5\u65f6\u95f4\uff0c\u4e3a\u4e86\u8fd9\u6bb5\u65f6\u95f4\u53bb\u6302\u8d77\u548c\u6062\u590d\u7ebf\u7a0b\u5e76\u4e0d\u503c\u5f97\u3002\u5982 \u679c\u7269\u7406\u673a\u5668\u6709\u4e00\u4e2a\u4ee5\u4e0a\u7684\u5904\u7406\u5668\uff0c\u80fd\u8ba9\u4e24\u4e2a\u6216\u4ee5\u4e0a\u7684\u7ebf\u7a0b\u540c\u65f6\u5e76\u884c\u6267\u884c\uff0c\u6211\u4eec\u5c31\u53ef\u4ee5\u8ba9\u540e\u9762\u8bf7\u6c42\u9501\u7684\u90a3\u4e2a\u7ebf\u7a0b“\u7a0d\u7b49\u4e00\u4f1a”\uff0c\u4f46\u4e0d\u653e\u5f03\u5904\u7406\u5668\u7684\u6267\u884c\u65f6\u95f4\uff0c\u770b\u770b\u6301\u6709 \u9501\u7684\u7ebf\u7a0b\u662f\u5426\u5f88\u5feb\u5c31\u4f1a\u91ca\u653e\u9501\u3002\u4e3a\u4e86\u8ba9\u7ebf\u7a0b\u7b49\u5f85\uff0c\u6211\u4eec\u53ea\u987b\u8ba9\u7ebf\u7a0b\u6267\u884c\u4e00\u4e2a\u5fd9\u5faa\u73af\uff08\u81ea\u65cb\uff09\uff0c\u8fd9\u9879\u6280\u672f\u5c31\u662f\u6240\u8c13\u7684\u81ea\u65cb\u9501\u3002\n<\/p>\n

\n\t\u81ea\u65cb\u9501\u5728JDK 1.4.2\u4e2d\u5c31\u5df2\u7ecf\u5f15\u5165\uff0c\u53ea\u4e0d\u8fc7\u9ed8\u8ba4\u662f\u5173\u95ed\u7684\uff0c\u53ef\u4ee5\u4f7f\u7528-XX:+UseSpinning\u53c2\u6570\u6765\u5f00\u542f\uff0c\u5728JDK 1.6\u4e2d\u5c31\u5df2\u7ecf\u6539\u4e3a\u9ed8\u8ba4\u5f00\u542f\u4e86\u3002\u81ea\u65cb\u7b49\u5f85\u4e0d\u80fd\u4ee3\u66ff\u963b\u585e\uff0c\u4e14\u5148\u4e0d\u8bf4\u5bf9\u5904\u7406\u5668\u6570\u91cf\u7684\u8981\u6c42\uff0c\u81ea\u65cb\u7b49\u5f85\u672c\u8eab\u867d\u7136\u907f\u514d\u4e86\u7ebf\u7a0b\u5207\u6362\u7684\u5f00\u9500\uff0c\u4f46\u5b83\u662f\u8981\u5360\u7528\u5904\u7406\u5668\u65f6\u95f4\u7684\uff0c \u6240\u4ee5\u5982\u679c\u9501\u88ab\u5360\u7528\u7684\u65f6\u95f4\u5f88\u77ed\uff0c\u81ea\u65cb\u7b49\u5f85\u7684\u6548\u679c\u5c31\u4f1a\u975e\u5e38\u597d\uff0c\u53cd\u4e4b\u5982\u679c\u9501\u88ab\u5360\u7528\u7684\u65f6\u95f4\u5f88\u957f\uff0c\u90a3\u4e48\u81ea\u65cb\u7684\u7ebf\u7a0b\u53ea\u4f1a\u767d\u767d\u6d88\u8017\u5904\u7406\u5668\u8d44\u6e90\uff0c\u800c\u4e0d\u4f1a\u505a\u4efb\u4f55\u6709\u7528\u7684\u5de5\u4f5c\uff0c \u53cd\u800c\u4f1a\u5e26\u6765\u6027\u80fd\u7684\u6d6a\u8d39\u3002\u56e0\u6b64\u81ea\u65cb\u7b49\u5f85\u7684\u65f6\u95f4\u5fc5\u987b\u8981\u6709\u4e00\u5b9a\u7684\u9650\u5ea6\uff0c\u5982\u679c\u81ea\u65cb\u8d85\u8fc7\u4e86\u9650\u5b9a\u7684\u6b21\u6570\u4ecd\u7136\u6ca1\u6709\u6210\u529f\u83b7\u5f97\u9501\uff0c\u5c31\u5e94\u5f53\u4f7f\u7528\u4f20\u7edf\u7684\u65b9\u5f0f\u53bb\u6302\u8d77\u7ebf\u7a0b\u4e86\u3002\u81ea\u65cb\u6b21 \u6570\u7684\u9ed8\u8ba4\u503c\u662f10\u6b21\uff0c\u7528\u6237\u53ef\u4ee5\u4f7f\u7528\u53c2\u6570-XX:PreBlockSpin\u6765\u66f4\u6539\u3002\n<\/p>\n

\n\t\u5728JDK 1.6\u4e2d\u5f15\u5165\u4e86\u81ea\u9002\u5e94\u7684\u81ea\u65cb\u9501\u3002\u81ea\u9002\u5e94\u610f\u5473\u7740\u81ea\u65cb\u7684\u65f6\u95f4\u4e0d\u518d\u56fa\u5b9a\u4e86\uff0c\u800c\u662f\u7531\u524d\u4e00\u6b21\u5728\u540c\u4e00\u4e2a\u9501\u4e0a\u7684\u81ea\u65cb\u65f6\u95f4\u53ca\u9501\u7684\u62e5\u6709\u8005\u7684\u72b6\u6001\u6765\u51b3\u5b9a\u3002\u5982\u679c\u5728\u540c\u4e00\u4e2a\u9501\u5bf9\u8c61 \u4e0a\uff0c\u81ea\u65cb\u7b49\u5f85\u521a\u521a\u6210\u529f\u83b7\u5f97\u8fc7\u9501\uff0c\u5e76\u4e14\u6301\u6709\u9501\u7684\u7ebf\u7a0b\u6b63\u5728\u8fd0\u884c\u4e2d\uff0c\u90a3\u4e48\u865a\u62df\u673a\u5c31\u4f1a\u8ba4\u4e3a\u8fd9\u6b21\u81ea\u65cb\u4e5f\u5f88\u6709\u53ef\u80fd\u518d\u6b21\u6210\u529f\uff0c\u8fdb\u800c\u5b83\u5c06\u5141\u8bb8\u81ea\u65cb\u7b49\u5f85\u6301\u7eed\u76f8\u5bf9\u66f4\u957f\u7684\u65f6\u95f4\uff0c \u6bd4\u5982100\u4e2a\u5faa\u73af\u3002\u53e6\u4e00\u65b9\u9762\uff0c\u5982\u679c\u5bf9\u4e8e\u67d0\u4e2a\u9501\uff0c\u81ea\u65cb\u5f88\u5c11\u6210\u529f\u83b7\u5f97\u8fc7\uff0c\u90a3\u5728\u4ee5\u540e\u8981\u83b7\u53d6\u8fd9\u4e2a\u9501\u65f6\u5c06\u53ef\u80fd\u7701\u7565\u6389\u81ea\u65cb\u8fc7\u7a0b\uff0c\u4ee5\u907f\u514d\u6d6a\u8d39\u5904\u7406\u5668\u8d44\u6e90\u3002\u6709\u4e86\u81ea\u9002\u5e94\u81ea \u65cb\uff0c\u968f\u7740\u7a0b\u5e8f\u8fd0\u884c\u548c\u6027\u80fd\u76d1\u63a7\u4fe1\u606f\u7684\u4e0d\u65ad\u5b8c\u5584\uff0c\u865a\u62df\u673a\u5bf9\u7a0b\u5e8f\u9501\u7684\u72b6\u51b5\u9884\u6d4b\u5c31\u4f1a\u8d8a\u6765\u8d8a\u51c6\u786e\uff0c\u865a\u62df\u673a\u5c31\u4f1a\u53d8\u5f97\u8d8a\u6765\u8d8a“\u806a\u660e”\u4e86\u3002\n<\/p>\n

\n\t\u9501\u524a\u9664
\n<\/h2>\n

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