{"id":7397,"date":"2023-11-28T18:45:09","date_gmt":"2023-11-28T10:45:09","guid":{"rendered":"https:\/\/wx.kaifamiao.info\/?p=7397"},"modified":"2023-11-28T18:51:25","modified_gmt":"2023-11-28T10:51:25","slug":"java-zhong-dui-xiang-de-nei-cun-bu-ju-le-jie-ma","status":"publish","type":"post","link":"http:\/\/wx.kaifamiao.info\/index.php\/2023\/11\/28\/java-zhong-dui-xiang-de-nei-cun-bu-ju-le-jie-ma\/","title":{"rendered":"Java\u4e2d\u5bf9\u8c61\u7684\u5185\u5b58\u5e03\u5c40\u4e86\u89e3\u5417\uff1f"},"content":{"rendered":"

Java\u4e2d\u901a\u8fc7new \u5173\u952e\u5b57\u521b\u5efa\u4e00\u4e2a\u7c7b\u7684\u5b9e\u4f8b\u5bf9\u8c61\uff0c\u5bf9\u8c61\u5b58\u4e8e\u5185\u5b58\u7684\u5806\u4e2d\u5e76\u7ed9\u5176\u5206\u914d\u4e00\u4e2a\u5185\u5b58\u5730\u5740\uff0c\u90a3\u4e48\u662f\u5426\u60f3\u8fc7\u5982\u4e0b\u8fd9\u4e9b\u95ee\u9898\uff1a<\/p>\n

\u8fd9\u4e2a\u5b9e\u4f8b\u5bf9\u8c61\u662f\u4ee5\u600e\u6837\u7684\u5f62\u6001\u5b58\u5728\u5185\u5b58\u4e2d\u7684\uff1f
\n\u4e00\u4e2aObject\u5bf9\u8c61\u5728\u5185\u5b58\u4e2d\u5360\u7528\u591a\u5927\uff1f
\n\u5bf9\u8c61\u4e2d\u7684\u5c5e\u6027\u662f\u5982\u4f55\u5728\u5185\u5b58\u4e2d\u5206\u914d\u7684\uff1f<\/strong>
\n\"\"<\/p>\n

\u5728JVM\u4e2d\uff0cJava\u5bf9\u8c61\u4fdd\u5b58\u5728\u5806\u4e2d\u65f6\uff0c\u7531\u4ee5\u4e0b\u4e09\u90e8\u5206\u7ec4\u6210\uff1a<\/p>\n

\u5bf9\u8c61\u5934(Object header)<\/strong>:\u5305\u62ec\u4e86\u5173\u4e8e\u5806\u5bf9\u8c61\u7684\u5e03\u5c40\u3001\u7c7b\u578b\u3001GC\u72b6\u6001\u3001\u540c\u6b65\u72b6\u6001\u548c\u6807\u8bc6\u54c8\u5e0c\u7801\u7684\u57fa\u672c\u4fe1\u606f\u3002Java\u5bf9\u8c61\u548cvm\u5185\u90e8\u5bf9\u8c61\u90fd\u6709\u4e00\u4e2a\u5171\u540c\u7684\u5bf9\u8c61\u5934\u683c\u5f0f\u3002
\n\u5b9e\u4f8b\u6570\u636e(Instance Data)<\/strong>:\u4e3b\u8981\u662f\u5b58\u653e\u7c7b\u7684\u6570\u636e\u4fe1\u606f\uff0c\u7236\u7c7b\u7684\u4fe1\u606f\uff0c\u5bf9\u8c61\u5b57\u6bb5\u5c5e\u6027\u4fe1\u606f\u3002
\n\u5bf9\u9f50\u586b\u5145(Padding)<\/strong>:\u4e3a\u4e86\u5b57\u8282\u5bf9\u9f50\uff0c\u586b\u5145\u7684\u6570\u636e\uff0c\u4e0d\u662f\u5fc5\u987b\u7684\u3002
\n\"\"<\/p>\n

\u5982\u679c\u5bf9\u8c61\u662f\u4e00\u4e2aJava\u6570\u7ec4\uff0c\u90a3\u4e48\u5bf9\u8c61\u5934\u4e2d\u8fd8\u5fc5\u987b\u6709\u4e00\u5757\u7528\u4e8e\u8bb0\u5f55\u6570\u7ec4\u957f\u5ea6\u7684\u6570\u636e\uff0c\u56e0\u4e3a\u865a\u62df\u673a\u53ef\u4ee5\u901a\u8fc7\u666e\u901aJava\u5bf9\u8c61\u7684\u5143\u6570\u636e\u4fe1\u606f\u786e\u5b9aJava\u5bf9\u8c61\u7684\u5927\u5c0f\uff0c\u4f46\u662f\u4ece\u6570\u7ec4\u7684\u5143\u6570\u636e\u4e2d\u65e0\u6cd5\u786e\u5b9a\u6570\u7ec4\u7684\u5927\u5c0f\u3002<\/p>\n

Mark Word<\/strong>
\n\u7528\u4e8e\u5b58\u50a8\u5bf9\u8c61\u81ea\u8eab\u7684\u8fd0\u884c\u65f6\u6570\u636e\uff0c\u5982\u54c8\u5e0c\u7801(HashCode)\u3001GC\u5206\u4ee3\u5e74\u9f84\u3001\u9501\u72b6\u6001\u6807\u5fd7\u3001\u7ebf\u7a0b\u6301\u6709\u7684\u9501\u3001\u504f\u5411\u7ebf\u7a0bID\u3001\u504f\u5411\u65f6\u95f4\u6233\u7b49\u7b49\u3002
\nMark Word\u572832\u4f4dJVM\u7684\u957f\u5ea6\u662f32bit\uff0c\u572864\u4f4dJVM\u4e2d\u957f\u5ea6\u662f64bit\u3002\u6211\u4eec\u6253\u5f00openjdk\u7684\u6e90\u7801\u5305\uff0c\u5bf9\u5e94\u8def\u5f84\/openjdk\/hotspot\/src\/share\/vm\/oops\uff0cMark Word\u5bf9\u5e94\u5230C++\u7684\u4ee3\u7801MarkOop.hpp\uff0c\u53ef\u4ee5\u4ece\u6ce8\u91ca\u4e2d\u770b\u5230\u5b83\u4eec\u7684\u7ec4\u6210\uff0c\u672c\u9898\u4ee3\u7801\u662f\u57fa\u4e8eJDK1.8\u3002
\nMark Word\u5728\u4e0d\u540c\u7684\u9501\u72b6\u6001\u4e0b\u5b58\u50a8\u7684\u5185\u5bb9\u4e0d\u540c
\n\u572832\u4f4dJVM\u4e2d\u662f\u8fd9\u4e48\u5b58\u7684<\/strong>
\n\"\"<\/p>\n

\u572864\u4f4dJVM\u4e2d\u662f\u8fd9\u4e48\u5b58\u7684<\/strong>
\n\"\"<\/p>\n

\u867d\u7136\u5b83\u4eec\u5728\u4e0d\u540c\u4f4d\u6570\u7684JVM\u4e2d\u957f\u5ea6\u4e0d\u4e00\u6837\uff0c\u4f46\u662f\u57fa\u672c\u7ec4\u6210\u5185\u5bb9\u662f\u4e00\u81f4\u7684\u3002<\/p>\n

\u9501\u6807\u5fd7\u4f4d(lock)<\/strong>:\u533a\u5206\u9501\u72b6\u6001\uff0c11\u65f6\u8868\u793a\u5bf9\u8c61\u5f85GC\u56de\u6536\u72b6\u6001\uff0c\u53ea\u6709\u6700\u540e2\u4f4d\u9501\u6807\u8bc6(11)\u6709\u6548\u3002
\nbiased_lock:\u662f\u5426\u504f\u5411\u9501\uff0c\u7531\u4e8e\u65e0\u9501\u548c\u504f\u5411\u9501\u7684\u9501\u6807\u8bc6\u90fd\u662f01\uff0c\u6ca1\u529e\u6cd5\u533a\u5206\uff0c\u8fd9\u91cc\u5f15\u5165\u4e00\u4f4d\u7684\u504f\u5411\u9501\u6807\u8bc6\u4f4d\u3002
\n\u5206\u4ee3\u5e74\u9f84(age)<\/strong>:\u8868\u793a\u5bf9\u8c61\u88abGC\u7684\u6b21\u6570\uff0c\u5f53\u8be5\u6b21\u6570\u5230\u8fbe\u9608\u503c\u7684\u65f6\u5019,\u5bf9\u8c61\u5c31\u4f1a\u8f6c\u79fb\u5230\u8001\u5e74\u4ee3\u3002
\n\u5bf9\u8c61\u7684hashcode(hash)<\/strong>:\u8fd0\u884c\u671f\u95f4\u8c03\u7528System.identityHashCode()\u6765\u8ba1\u7b97,\u5ef6\u8fdf\u8ba1\u7b97\uff0c\u5e76\u628a\u7ed3\u679c\u8d4b\u503c\u5230\u8fd9\u91cc\u3002\u5f53\u5bf9\u8c61\u52a0\u9501\u540e\uff0c\u8ba1\u7b97\u7684\u7ed3\u679c31\u4f4d\u4e0d\u591f\u8868\u793a,\u5728\u504f\u5411\u9501\uff0c\u8f7b\u91cf\u9501\uff0c\u91cd\u91cf\u9501\uff0chashcode\u4f1a\u88ab\u8f6c\u79fb\u5230Monitor\u4e2d\u3002
\n\u504f\u5411\u9501\u7684\u7ebf\u7a0bID (JavaThread\uff09<\/strong>:\u504f\u5411\u6a21\u5f0f\u7684\u65f6\u5019\uff0c\u5f53\u67d0\u4e2a\u7ebf\u7a0b\u6301\u6709\u5bf9\u8c61\u7684\u65f6\u5019\uff0c\u5bf9\u8c61\u8fd9\u91cc\u5c31\u4f1a\u88ab\u7f6e\u4e3a\u8be5\u7ebf\u7a0b\u7684ID\u3002\u5728\u540e\u9762\u7684\u64cd\u4f5c\u4e2d\uff0c\u5c31\u65e0\u9700\u518d\u8fdb\u884c\u5c1d\u8bd5
\n\u83b7\u53d6\u9501\u7684\u52a8\u4f5c\u3002
\nepoch<\/strong>:\u504f\u5411\u9501\u5728CAS\u9501\u64cd\u4f5c\u8fc7\u7a0b\u4e2d\uff0c\u504f\u5411\u6027\u6807\u8bc6\uff0c\u8868\u793a\u5bf9\u8c61\u66f4\u504f\u5411\u54ea\u4e2a\u9501\u3002ptr_to_lock_record:\u8f7b\u91cf\u7ea7\u9501\u72b6\u6001\u4e0b\uff0c\u6307\u5411\u6808\u4e2d\u9501\u8bb0\u5f55\u7684\u6307\u9488\u3002\u5f53\u9501\u83b7\u53d6\u662f
\n\u65e0\u7ade\u4e89\u7684\u65f6\uff0cJVM\u4f7f\u7528\u539f\u5b50\u64cd\u4f5c\u800c\u4e0d\u662f OS\u4e92\u65a5\u3002\u8fd9\u79cd\u6280\u672f\u79f0\u4e3a\u8f7b\u91cf\u7ea7\u9501\u5b9a\u3002\u5728\u8f7b\u91cf\u7ea7\u9501\u5b9a\u7684\u60c5\u51b5\u4e0b\uff0cJVM\u901a\u8fc7CAS\u64cd\u4f5c\u5728\u5bf9\u8c61\u7684\u6807\u9898\u5b57\u4e2d\u8bbe\u7f6e\u6307\u5411\u9501\u8bb0\u5f55\u7684\u6307\u9488\u3002
\nptr_to_heavyweight_monitor<\/strong>:\u91cd\u91cf\u7ea7\u9501\u72b6\u6001\u4e0b\uff0c\u6307\u5411\u5bf9\u8c61\u76d1\u89c6\u5668Monitor\u7684\u6307\u9488\u3002\u5982\u679c\u4e24\u4e2a\u4e0d\u540c\u7684\u7ebf\u7a0b\u540c\u65f6\u5728\u540c\u4e00\u4e2a\u5bf9\u8c61\u4e0a\u7ade\u4e89\uff0c\u5219\u5fc5\u987b\u5c06\u8f7b\u91cf\u7ea7\u9501\u5b9a\u5347\u7ea7\u5230Monitor\u4ee5\u7ba1\u7406\u7b49\u5f85\u7684\u7ebf\u7a0b\u3002\u5728\u91cd\u91cf\u7ea7\u9501\u5b9a\u7684\u60c5\u51b5\u4e0b\uff0cJVM\u5728\u5bf9\u8c61\u7684ptr_to_heavyweight_monitor\u8bbe\u7f6e\u6307\u5411Monitor\u7684\u6307\u9488\u3002<\/p>\n

Klass Pointer<\/strong>
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\u5b9e\u4f8b\u6570\u636e<\/strong>
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\u5bf9\u9f50\u6570\u636e<\/strong>
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\n\u6240\u6709\u7684\u5bf9\u8c61\u5206\u914d\u7684\u5b57\u8282\u603bSIZE\u9700\u8981\u662f8\u7684\u500d\u6570\uff0c\u5982\u679c\u524d\u9762\u7684\u5bf9\u8c61\u5934\u548c\u5b9e\u4f8b\u6570\u636e\u5360\u7528\u7684\u603bSIZE\u4e0d\u6ee1\u8db3\u8981\u6c42\uff0c\u5219\u901a\u8fc7\u5bf9\u9f50\u6570\u636e\u6765\u586b\u6ee1\u3002<\/p>\n

\u4e3a\u4ec0\u4e48\u8981\u5bf9\u9f50\u6570\u636e?<\/strong>
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\n\"\"<\/p>\n","protected":false},"excerpt":{"rendered":"

Java\u4e2d\u901a\u8fc7new \u5173\u952e\u5b57\u521b\u5efa\u4e00\u4e2a\u7c7b\u7684\u5b9e\u4f8b\u5bf9\u8c61\uff0c\u5bf9\u8c61\u5b58\u4e8e\u5185\u5b58\u7684\u5806\u4e2d\u5e76\u7ed9\u5176\u5206\u914d\u4e00\u4e2a\u5185\u5b58\u5730\u5740\uff0c\u90a3\u4e48\u662f\u5426\u60f3\u8fc7\u5982\u4e0b\u8fd9 […]<\/p>\n","protected":false},"author":8,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[99],"tags":[],"class_list":["post-7397","post","type-post","status-publish","format-standard","hentry","category-javabase"],"_links":{"self":[{"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/posts\/7397","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/comments?post=7397"}],"version-history":[{"count":1,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/posts\/7397\/revisions"}],"predecessor-version":[{"id":7398,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/posts\/7397\/revisions\/7398"}],"wp:attachment":[{"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/media?parent=7397"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/categories?post=7397"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/tags?post=7397"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}