{"id":107763,"date":"2026-09-20T09:40:58","date_gmt":"2026-09-20T01:40:58","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/107763.html"},"modified":"2026-09-20T09:40:58","modified_gmt":"2026-09-20T01:40:58","slug":"markword%e5%9c%a8%e7%b4%a7%e5%87%91%e5%af%b9%e8%b1%a1%e5%a4%b4%e4%b8%8a%e7%9a%84%e5%ae%9e%e7%8e%b0%e5%8e%9f%e7%90%86%e5%89%96%e6%9e%90","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/107763.html","title":{"rendered":"Markword\u5728\u7d27\u51d1\u5bf9\u8c61\u5934\u4e0a\u7684\u5b9e\u73b0\u539f\u7406\u5256\u6790"},"content":{"rendered":"<\/p>\n<h4>Markword\u5728\u7d27\u51d1\u5bf9\u8c61\u5934\u4e0a\u7684\u5b9e\u73b0\u539f\u7406\u5256\u6790<\/h4>\n<ul>\n<li>\u524d\u8a00<\/li>\n<li>Markword\u5728\u7d27\u51d1\u5bf9\u8c61\u5934\u4e0a\u7684\u5b9e\u73b0\u539f\u7406<\/li>\n<li>\n<ul>\n<li>\u4f20\u7edf\u504f\u5411\u9501\/\u8f7b\u91cf\u7ea7\u9501\u5bf9 Mark Word \u7684\u7269\u7406\u8986\u5199\u56f0\u5883<\/li>\n<li>\n<ul>\n<li>\u4f20\u7edf\u8f7b\u91cf\u7ea7\u9501\u7684\u8986\u5199\u673a\u5236 (HotSpot Legacy)<\/li>\n<li>\u963b\u788d Compact Object Headers (Lilliput) \u7684\u6839\u672c\u77db\u76fe<\/li>\n<\/ul>\n<\/li>\n<li>LockStack \u5982\u4f55\u5b9e\u73b0\u201c\u89e3\u8026\u201d\u5e76\u817e\u51fa Bit \u7a7a\u95f4<\/li>\n<li>HotSpot \u6e90\u7801\u7ea7\u8be6\u7ec6\u5256\u6790<\/li>\n<li>\n<ul>\n<li>1. &#096;LockStack&#096; \u7ebf\u7a0b\u5c40\u90e8\u6570\u636e\u7ed3\u6784<\/li>\n<li>\n<ul>\n<li>\u8bbe\u8ba1\u7cbe\u9ad3<\/li>\n<\/ul>\n<\/li>\n<li>2. Project Lilliput \u4e2d\u7684 Mark Word \u4f4d\u56fe\u7ed3\u6784\u5b9a\u4e49<\/li>\n<li>3. LightweightSynchronizer \u52a0\u9501\u4e0e\u89e3\u9501\u4ee3\u7801\u8def\u5f84<\/li>\n<li>\n<ul>\n<li>\u52a0\u9501\u5b9e\u73b0&#xff1a;&#096;LightweightSynchronizer::enter&#096;<\/li>\n<li>\u89e3\u9501\u5b9e\u73b0&#xff1a;&#096;LightweightSynchronizer::exit&#096;<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<\/li>\n<li>C2 \u7f16\u8bd1\u5668\u4e0e JIT \u6c47\u7f16\u7ea7 Fast-Path \u5c55\u5f00<\/li>\n<li>\n<ul>\n<li>C2 \u751f\u6210\u7684 FastLock \u673a\u5668\u7801\u6307\u4ee4\u903b\u8f91<\/li>\n<\/ul>\n<\/li>\n<li>\u65b0\u65e7\u8f7b\u91cf\u7ea7\u9501\u673a\u5236\u5bf9\u6bd4<\/li>\n<li>\u603b\u7ed3<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<hr \/>\n<h2>\u524d\u8a00<\/h2>\n<p>\u672c\u6587\u65e8\u5728\u8bb0\u5f55\u8fd1\u671f\u7814\u8bfbJava\u6e90\u7801\u7684\u5b66\u4e60\u5fc3\u5f97\u4e0e\u7591\u96be\u95ee\u9898\u3002\u7531\u4e8e\u4e2a\u4eba\u7406\u89e3\u6c34\u5e73\u6709\u9650&#xff0c;\u6587\u4e2d\u5185\u5bb9\u96be\u514d\u5b58\u5728\u758f\u6f0f&#xff0c;\u6073\u8bf7\u8bfb\u8005\u4e0d\u541d\u6307\u6b63\u3002<\/p>\n<h2>Markword\u5728\u7d27\u51d1\u5bf9\u8c61\u5934\u4e0a\u7684\u5b9e\u73b0\u539f\u7406<\/h2>\n<h3>\u4f20\u7edf\u504f\u5411\u9501\/\u8f7b\u91cf\u7ea7\u9501\u5bf9 Mark Word \u7684\u7269\u7406\u8986\u5199\u56f0\u5883<\/h3>\n<p>\u5728 JDK 21 \u5f15\u5165 Thread-Local Lock Stack (LockStack) \u4ee5\u53ca Project Lilliput (JEP 450) \u843d\u5730\u524d&#xff0c;HotSpot JVM \u7684\u4f20\u7edf\u8f7b\u91cf\u7ea7\u9501&#xff08;BasicLock \/ Displaced Mark Word \u673a\u5236&#xff09;\u5728\u5bf9\u8c61\u5934\u7a7a\u95f4\u5206\u914d\u4e0a\u5b58\u5728\u65e0\u6cd5\u8c03\u548c\u7684\u7269\u7406\u51b2\u7a81\u3002<\/p>\n<h4>\u4f20\u7edf\u8f7b\u91cf\u7ea7\u9501\u7684\u8986\u5199\u673a\u5236 (HotSpot Legacy)<\/h4>\n<p>\u5728\u4f20\u7edf 64 \u4f4d HotSpot \u67b6\u6784\u4e2d&#xff0c;\u5bf9\u8c61\u7684 Mark Word \u5360\u636e 64 \u4f4d&#xff0c;\u5176\u5e03\u5c40\u968f\u7740\u9501\u72b6\u6001\u52a8\u6001\u53d8\u5316\u3002\u5f53\u4e00\u4e2a\u5bf9\u8c61\u5904\u4e8e\u65e0\u9501\u72b6\u6001&#xff08;Unlocked, 001&#xff09;\u65f6&#xff0c;Mark Word \u5b58\u653e HashCode\u3001GC Age \u7b49\u4fe1\u606f&#xff1b;\u4e00\u65e6\u88ab\u7ebf\u7a0b\u901a\u8fc7 CAS \u52a0\u8f7b\u91cf\u7ea7\u9501&#xff0c;Mark Word \u7684\u5168\u90e8 64 \u4f4d\u5c06\u88ab\u6574\u4f53\u66ff\u6362\u3002<\/p>\n<p>\u5728 src\/hotspot\/share\/oops\/markWord.hpp \u7684\u4f20\u7edf\u5b9a\u4e49\u4e2d&#xff1a;<\/p>\n<p><span class=\"token comment\">\/\/ \u4f20\u7edf 64 \u4f4d Mark Word \u4f4d\u56fe\u7ed3\u6784:<\/span><br \/>\n<span class=\"token comment\">\/\/  Unlocked:      [ unused:25 | identity_hash:31 | age:4 | biased_lock:1 | lock:2 (01) ]<\/span><br \/>\n<span class=\"token comment\">\/\/  Lightweight:   [ ptr_to_basic_lock:62                                 | lock:2 (00) ]<\/span><br \/>\n<span class=\"token comment\">\/\/  Inflated:      [ ptr_to_object_monitor:62                             | lock:2 (10) ]<\/span><\/p>\n<p>\u5f53\u52a0\u9501\u65f6&#xff0c;VM \u4f1a\u5728\u5f53\u524d Java \u7ebf\u7a0b\u7684 C-Stack \u6808\u5e27\u4e2d\u5206\u914d\u4e00\u4e2a BasicLock&#xff08;\u5305\u542b _displaced_header&#xff09;&#xff0c;\u5e76\u5c06\u5bf9\u8c61\u7684\u539f\u59cb Mark Word \u590d\u5236\u5230\u8be5\u6808\u5e27\u69fd\u4f4d\u4e2d\u3002\u968f\u540e&#xff0c;\u901a\u8fc7 CAS \u64cd\u4f5c\u5c06\u5bf9\u8c61\u7684 Mark Word \u66ff\u6362\u4e3a\u6307\u5411\u8be5 BasicLock \u7684 64 \u4f4d\u5185\u5b58\u6307\u9488&#xff1a;<\/p>\n<p><span class=\"token comment\">\/\/ src\/hotspot\/share\/runtime\/synchronizer.cpp (Legacy Fast Enter)<\/span><br \/>\n<span class=\"token keyword\">void<\/span> <span class=\"token class-name\">ObjectSynchronizer<\/span><span class=\"token double-colon punctuation\">::<\/span><span class=\"token function\">fast_enter<\/span><span class=\"token punctuation\">(<\/span>Handle obj<span class=\"token punctuation\">,<\/span> BasicLock<span class=\"token operator\">*<\/span> lock<span class=\"token punctuation\">,<\/span> <span class=\"token keyword\">bool<\/span> attempt_rebias<span class=\"token punctuation\">,<\/span> TRAPS<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n  markWord mark <span class=\"token operator\">&#061;<\/span> obj<span class=\"token operator\">-&gt;<\/span><span class=\"token function\">mark<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n  <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>mark<span class=\"token punctuation\">.<\/span><span class=\"token function\">is_unlocked<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token comment\">\/\/ 1. \u5c06\u539f\u59cb Mark Word \u6682\u5b58\u5230 C-Stack \u7684 BasicLock \u69fd\u4f4d<\/span><br \/>\n    lock<span class=\"token operator\">-&gt;<\/span><span class=\"token function\">set_displaced_header<\/span><span class=\"token punctuation\">(<\/span>mark<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token comment\">\/\/ 2. \u5c06\u6574\u4e2a Mark Word \u7f16\u7801\u4e3a\u6307\u5411 BasicLock \u7684\u7269\u7406\u5730\u5740\u6307\u9488 (\u9ad8 62 \u4f4d\u88ab\u5b8c\u5168\u5360\u6ee1)<\/span><br \/>\n    markWord locked_mark <span class=\"token operator\">&#061;<\/span> markWord<span class=\"token double-colon punctuation\">::<\/span><span class=\"token function\">encode_pointer_as_mark<\/span><span class=\"token punctuation\">(<\/span>lock<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>obj<span class=\"token operator\">-&gt;<\/span><span class=\"token function\">cas_set_mark<\/span><span class=\"token punctuation\">(<\/span>locked_mark<span class=\"token punctuation\">,<\/span> mark<span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&#061;&#061;<\/span> mark<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n      <span class=\"token keyword\">return<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u52a0\u9501\u6210\u529f<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n  <span class=\"token punctuation\">}<\/span><br \/>\n  <span class=\"token punctuation\">.<\/span><span class=\"token punctuation\">.<\/span><span class=\"token punctuation\">.<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<h4>\u963b\u788d Compact Object Headers (Lilliput) \u7684\u6839\u672c\u77db\u76fe<\/h4>\n<p>Project Lilliput \u7684\u76ee\u6807\u662f\u5c06 64 \u4f4d Mark Word \u4e0e 32\/64 \u4f4d Klass*&#xff08;\u7c7b\u6307\u9488&#xff09;\u5408\u5e76\u4e3a\u5355\u4e2a 64 \u4f4d\u751a\u81f3 32 \u4f4d\u7684 Compact Header\u3002\u5728 Lilliput \u5e03\u5c40\u4e2d&#xff0c;\u538b\u7f29\u7c7b\u6307\u9488 nKlass \u88ab\u5f3a\u5236\u9759\u6001\u5d4c\u5165\u5728 Mark Word \u7684\u56fa\u5b9a Bit \u4f4d\u533a\u95f4\u5185&#xff08;\u4f8b\u5982\u9ad8 32 \u4f4d\u6216\u4e2d\u95f4 22~32 \u4f4d&#xff09;\u3002<\/p>\n<p>\u5982\u679c\u7ee7\u7eed\u6cbf\u7528\u4f20\u7edf\u7684\u8f7b\u91cf\u7ea7\u9501\u673a\u5236&#xff0c;\u4e00\u65e6\u53d1\u751f\u8f7b\u91cf\u7ea7\u52a0\u9501&#xff0c;markWord::encode_pointer_as_mark(lock) \u4f1a\u5c06 \u5bf9\u8c61\u5934\u7684\u5168\u90e8\u9ad8 62 \u4f4d\u5b8c\u5168\u8986\u76d6 \u4e3a\u6808\u5730\u5740&#xff1a;<\/p>\n<p>&#043;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;-&#043;<br \/>\n| \u4f20\u7edf\u52a0\u9501&#xff1a;62 \u4f4d\u6808\u5730\u5740 (BasicLock*)                         | State |<br \/>\n&#043;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;-&#043;<br \/>\n  \u25b2<br \/>\n  \u2514\u2500 \u8fd9\u79cd\u8986\u76d6\u76f4\u63a5\u62b9\u53bb\u4e86\u5d4c\u5165\u5728 Mark Word \u5185\u90e8\u7684 nKlass (\u7c7b\u6307\u9488)&#xff01;<\/p>\n<p>\u5728\u8f7b\u91cf\u7ea7\u9501\u6301\u6709\u671f\u95f4&#xff0c;\u4efb\u4f55\u4f9d\u8d56 oopDesc::klass() \u7684\u9ad8\u9891\u64cd\u4f5c&#xff08;\u5982 invokevirtual \u865a\u65b9\u6cd5\u67e5\u627e\u3001instanceof \u7c7b\u578b\u68c0\u67e5\u3001GC \u6807\u8bb0\u626b\u63cf&#xff09;\u90fd\u65e0\u6cd5\u76f4\u63a5\u4ece\u5bf9\u8c61\u5934\u8bfb\u53d6 nKlass&#xff0c;\u800c\u5fc5\u987b\u6cbf\u7740 Mark Word \u4e2d\u7684\u6307\u9488\u56de\u6eaf\u5230\u7ebf\u7a0b C-Stack \u5e27\u7684 BasicLock::_displaced_header \u4e2d\u89e3\u5f15\u7528\u8fd8\u539f Klass*\u3002\u8fd9\u5728\u591a\u7ebf\u7a0b\u9ad8\u5e76\u53d1\u573a\u666f\u4e0b\u4f1a\u5bfc\u81f4\u7269\u7406\u5185\u5b58\u56de\u6eaf\u8bbf\u95ee\u7684\u9ad8\u6602\u5f00\u9500&#xff0c;\u4f7f\u5bf9\u8c61\u5934\u538b\u7f29\u5931\u53bb\u5b9e\u7528\u4ef7\u503c\u3002<\/p>\n<hr \/>\n<h3>LockStack \u5982\u4f55\u5b9e\u73b0\u201c\u89e3\u8026\u201d\u5e76\u817e\u51fa Bit \u7a7a\u95f4<\/h3>\n<p>\u4e3a\u4e86\u5f7b\u5e95\u6253\u7834\u201c\u9501\u6307\u9488\u8986\u76d6 Mark Word\u201d\u7684\u67b7\u9501&#xff0c;JDK 21 \u5f15\u5165\u4e86\u5168\u65b0\u7684\u8f7b\u91cf\u7ea7\u9501\u5b9e\u73b0&#xff08;JEP 450 \u524d\u7f6e\u4f9d\u8d56&#xff1a;Fast Lightweight Locking&#xff09;&#xff0c;\u5176\u6838\u5fc3\u6982\u5ff5\u662f Thread-Local Lock Stack (LockStack)\u3002<\/p>\n<p>LockStack \u6539\u53d8\u4e86\u9501\u6240\u6709\u6743\u7684\u8bb0\u5f55\u903b\u8f91&#xff1a;\u53d6\u6d88\u628a\u7ebf\u7a0b\u6808\u5730\u5740\u5199\u56de Mark Word \u7684\u505a\u6cd5&#xff0c;\u6539\u7531 JavaThread \u7ed3\u6784\u5185\u90e8\u7684\u7ebf\u7a0b\u79c1\u6709\u56fa\u5b9a\u6570\u7ec4\u7ef4\u62a4\u9501\u5bf9\u8c61\u5f15\u7528&#xff1b;Mark Word \u5728\u52a0\u9501\u671f\u95f4\u4ec5\u4fee\u6539\u6781\u5c11\u6570 State \u72b6\u6001\u4f4d&#xff0c;\u5185\u90e8\u5305\u542b\u7684 nKlass \u4ee5\u53ca HashCode\/Age \u4f4d\u7a7a\u95f4\u539f\u4f4d\u4fdd\u7559&#xff0c;\u4e0d\u53d1\u751f\u4efb\u4f55\u7834\u574f\u6027\u8986\u5199\u3002<\/p>\n<p>                     Thread-Local Lock Stack \u67b6\u6784\u89e3\u8026<\/p>\n<p>  JavaThread (r15 \u5bc4\u5b58\u5668\u76f4\u63a5\u5b9a\u4f4d)<br \/>\n&#043;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#043;<br \/>\n| &#8230;                                |<br \/>\n| _lock_stack:                       |<br \/>\n|   [ index 0 ]: oop_A (\u5bf9\u8c61A\u6307\u9488)    |<br \/>\n|   [ index 1 ]: oop_B (\u5bf9\u8c61B\u6307\u9488)    | \u2500\u2500\u2510<br \/>\n|   [ index 2 ]: NULL                |   \u2502 \u8bb0\u5f55\u9501\u6240\u6709\u6743<br \/>\n|   _top: 2                          |   \u2502 (\u4e0d\u5360\u7528 Mark Word \u7a7a\u95f4)<br \/>\n&#043;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#043;   \u2502<br \/>\n                                         \u2502<br \/>\n                                         v<br \/>\n                      Java Object Header (Mark Word)<br \/>\n&#043;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;-&#043;<br \/>\n| Hash\/Age\/Self-Lock Bits | nKlass (22-32b)         | Lock State (00)|<br \/>\n&#043;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;-&#043;<br \/>\n                                ^^^^^^^^^^^^^^^^^^<br \/>\n                                nKlass \u539f\u4f4d\u4fdd\u7559&#xff0c;\u672a\u88ab\u7269\u7406\u6307\u9488\u8986\u5199&#xff01;<\/p>\n<hr \/>\n<h3>HotSpot \u6e90\u7801\u7ea7\u8be6\u7ec6\u5256\u6790<\/h3>\n<p>\u5728 JDK 21 \u53ca Lilliput \u5206\u652f\u7684 OpenJDK \u6e90\u7801\u4e2d&#xff0c;\u8be5\u673a\u5236\u7684\u5b9e\u73b0\u5206\u5e03\u5728 lockStack.hpp\u3001markWord.hpp \u548c lightweightSynchronizer.cpp \u7b49\u6a21\u5757\u4e2d\u3002<\/p>\n<h4>1. LockStack \u7ebf\u7a0b\u5c40\u90e8\u6570\u636e\u7ed3\u6784<\/h4>\n<p>\u5728 src\/hotspot\/share\/runtime\/lockStack.hpp \u4e2d&#xff0c;HotSpot \u5c06 LockStack \u4f5c\u4e3a\u4e00\u4e2a\u8fde\u7eed\u7684\u5185\u5b58\u6570\u7ec4\u5d4c\u5165\u5728 JavaThread \u5bf9\u8c61\u5185\u90e8\u3002<\/p>\n<p><span class=\"token comment\">\/\/ src\/hotspot\/share\/runtime\/lockStack.hpp<\/span><\/p>\n<p><span class=\"token keyword\">class<\/span> <span class=\"token class-name\">LockStack<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n  <span class=\"token keyword\">friend<\/span> <span class=\"token keyword\">class<\/span> <span class=\"token class-name\">VMStructs<\/span><span class=\"token punctuation\">;<\/span><br \/>\n  <span class=\"token keyword\">friend<\/span> <span class=\"token keyword\">class<\/span> <span class=\"token class-name\">BytecodeInterpreter<\/span><span class=\"token punctuation\">;<\/span><br \/>\n  <span class=\"token keyword\">friend<\/span> <span class=\"token keyword\">class<\/span> <span class=\"token class-name\">C2FastLockNode<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token keyword\">public<\/span><span class=\"token operator\">:<\/span><br \/>\n  <span class=\"token comment\">\/\/ \u9501\u6808\u56fa\u5b9a\u5bb9\u91cf (8 \u4e2a\u69fd\u4f4d&#xff0c;\u8986\u76d6 99.9% \u4ee5\u4e0a\u7684\u5d4c\u5957\u9501\u573a\u666f)<\/span><br \/>\n  <span class=\"token keyword\">static<\/span> <span class=\"token keyword\">const<\/span> <span class=\"token keyword\">int<\/span> CAPACITY <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">8<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token keyword\">private<\/span><span class=\"token operator\">:<\/span><br \/>\n  <span class=\"token comment\">\/\/ _top \u6307\u5411\u4e0b\u4e00\u4e2a\u53ef\u63d2\u5165\u7684\u6570\u7ec4\u7d22\u5f15&#xff08;\u4ee5 byte offset \u5f62\u5f0f\u5b58\u50a8\u4ee5\u4fbf\u6c47\u7f16\u5b9a\u4f4d&#xff09;<\/span><br \/>\n  <span class=\"token keyword\">uint32_t<\/span> _top<span class=\"token punctuation\">;<\/span><br \/>\n  <span class=\"token comment\">\/\/ \u5b58\u653e\u5df2\u52a0\u9501\u5bf9\u8c61\u7684 oop \u7269\u7406\u6307\u9488\u6570\u7ec4<\/span><br \/>\n  oop _base<span class=\"token punctuation\">[<\/span>CAPACITY<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token keyword\">public<\/span><span class=\"token operator\">:<\/span><br \/>\n  <span class=\"token function\">LockStack<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token operator\">:<\/span> <span class=\"token function\">_top<\/span><span class=\"token punctuation\">(<\/span><span class=\"token function\">offset_to_index<\/span><span class=\"token punctuation\">(<\/span><span class=\"token function\">base_offset<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><span class=\"token punctuation\">}<\/span><\/p>\n<p>  <span class=\"token comment\">\/\/ \u5224\u65ad\u9501\u6808\u662f\u5426\u5df2\u6ee1<\/span><br \/>\n  <span class=\"token keyword\">bool<\/span> <span class=\"token function\">is_full<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token keyword\">const<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token keyword\">return<\/span> _top <span class=\"token operator\">&gt;&#061;<\/span> CAPACITY<span class=\"token punctuation\">;<\/span><br \/>\n  <span class=\"token punctuation\">}<\/span><\/p>\n<p>  <span class=\"token comment\">\/\/ \u5165\u6808\u64cd\u4f5c&#xff1a;\u7ebf\u7a0b\u6210\u529f CAS \u52a0\u9501\u540e\u8c03\u7528<\/span><br \/>\n  <span class=\"token keyword\">void<\/span> <span class=\"token function\">push<\/span><span class=\"token punctuation\">(<\/span>oop o<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token function\">assert<\/span><span class=\"token punctuation\">(<\/span><span class=\"token operator\">!<\/span><span class=\"token function\">is_full<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;lock stack overflow&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token function\">assert<\/span><span class=\"token punctuation\">(<\/span>_base<span class=\"token punctuation\">[<\/span>_top<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token keyword\">nullptr<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;must be empty&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    _base<span class=\"token punctuation\">[<\/span>_top<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> o<span class=\"token punctuation\">;<\/span><br \/>\n    _top<span class=\"token operator\">&#043;&#043;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n  <span class=\"token punctuation\">}<\/span><\/p>\n<p>  <span class=\"token comment\">\/\/ \u68c0\u67e5\u5f53\u524d\u7ebf\u7a0b\u662f\u5426\u6301\u6709\u8be5\u5bf9\u8c61\u7684\u9501<\/span><br \/>\n  <span class=\"token keyword\">bool<\/span> <span class=\"token function\">contains<\/span><span class=\"token punctuation\">(<\/span>oop o<span class=\"token punctuation\">)<\/span> <span class=\"token keyword\">const<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token keyword\">for<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">int<\/span> i <span class=\"token operator\">&#061;<\/span> _top <span class=\"token operator\">&#8211;<\/span> <span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span> i <span class=\"token operator\">&gt;&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span> i<span class=\"token operator\">&#8212;<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n      <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>_base<span class=\"token punctuation\">[<\/span>i<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;&#061;<\/span> o<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token keyword\">return<\/span> <span class=\"token boolean\">true<\/span><span class=\"token punctuation\">;<\/span><br \/>\n      <span class=\"token punctuation\">}<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    <span class=\"token keyword\">return<\/span> <span class=\"token boolean\">false<\/span><span class=\"token punctuation\">;<\/span><br \/>\n  <span class=\"token punctuation\">}<\/span><\/p>\n<p>  <span class=\"token comment\">\/\/ \u51fa\u6808\u64cd\u4f5c&#xff1a;\u89e3\u9501\u65f6\u8c03\u7528<\/span><br \/>\n  oop <span class=\"token function\">pop<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token function\">assert<\/span><span class=\"token punctuation\">(<\/span>_top <span class=\"token operator\">&gt;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">,<\/span> <span class=\"token string\">&#034;lock stack underflow&#034;<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    _top<span class=\"token operator\">&#8212;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    oop o <span class=\"token operator\">&#061;<\/span> _base<span class=\"token punctuation\">[<\/span>_top<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    _base<span class=\"token punctuation\">[<\/span>_top<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token keyword\">nullptr<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">return<\/span> o<span class=\"token punctuation\">;<\/span><br \/>\n  <span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<h5>\u8bbe\u8ba1\u7cbe\u9ad3<\/h5>\n<ul>\n<li>CPU Cache Line \u53cb\u597d&#xff1a;_base \u6570\u7ec4\u5b58\u5728\u4e8e\u7ebf\u7a0b\u672c\u8eab\u7684 JavaThread \u5185\u5b58\u7a7a\u95f4\u4e2d&#xff0c;\u5728 x86_64 \u4e0b\u901a\u8fc7 %r15&#xff08;Thread Register&#xff09;\u6216 AArch64 \u4e0b\u7684 x28 \u76f4\u63a5\u5bfb\u5740&#xff0c;\u8bbf\u95ee\u901f\u5ea6\u6781\u5feb\u3002<\/li>\n<li>\u7269\u7406\u8131\u8026&#xff1a;\u9501\u6240\u6709\u6743\u7531 contains(oop) \u9690\u5f0f\u8bc1\u660e\u3002\u5982\u679c\u5bf9\u8c61\u7684 Mark Word \u6807\u5fd7\u4f4d\u5904\u4e8e Lightweight Locked \u72b6\u6001&#xff0c;\u4e14\u5f53\u524d\u7ebf\u7a0b\u7684 LockStack \u5305\u542b\u8be5\u5bf9\u8c61\u5730\u5740&#xff0c;\u5219\u5f53\u524d\u7ebf\u7a0b\u72ec\u5360\u8be5\u9501\u3002Mark Word \u5185\u90e8\u5b8c\u5168\u4e0d\u9700\u8981\u4fdd\u5b58\u4efb\u4f55\u6307\u5411\u7ebf\u7a0b\u6216\u6808\u7684\u7269\u7406\u6307\u9488\u3002<\/li>\n<\/ul>\n<hr \/>\n<h4>2. Project Lilliput \u4e2d\u7684 Mark Word \u4f4d\u56fe\u7ed3\u6784\u5b9a\u4e49<\/h4>\n<p>\u7531\u4e8e LockStack \u63a5\u7ba1\u4e86\u9501\u6240\u6709\u6743\u7684\u7269\u7406\u5b58\u50a8&#xff0c;Mark Word \u817e\u51fa\u4e86\u8d85\u8fc7 60 \u4f4d\u7684\u7a7a\u95f2\u7a7a\u95f4\u3002Project Lilliput \u5728 src\/hotspot\/share\/oops\/markWord.hpp \u4e2d\u5b9a\u4e49\u4e86\u7d27\u51d1\u5bf9\u8c61\u5934\u7684\u4f4d\u5e03\u5c40\u3002<\/p>\n<p><span class=\"token comment\">\/\/ src\/hotspot\/share\/oops\/markWord.hpp (Lilliput Branch \/ Compact Object Headers)<\/span><\/p>\n<p><span class=\"token keyword\">class<\/span> <span class=\"token class-name\">markWord<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n <span class=\"token keyword\">private<\/span><span class=\"token operator\">:<\/span><br \/>\n  uintptr_t _value<span class=\"token punctuation\">;<\/span><\/p>\n<p> <span class=\"token keyword\">public<\/span><span class=\"token operator\">:<\/span><br \/>\n  <span class=\"token comment\">\/\/ &#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;<\/span><br \/>\n  <span class=\"token comment\">\/\/ Lilliput 64 \u4f4d Compact Header \u4f4d\u5206\u5e03\u89c4\u7ea6:<\/span><br \/>\n  <span class=\"token comment\">\/\/<\/span><br \/>\n  <span class=\"token comment\">\/\/ \u4f4d 0 &#8211; 2  : Lock State Bits (\u9501\u72b6\u6001\u6807\u5fd7\u4f4d)<\/span><br \/>\n  <span class=\"token comment\">\/\/             001: Unlocked (\u65e0\u9501)<\/span><br \/>\n  <span class=\"token comment\">\/\/             000: Fast-Locked (Lightweight Locked, \u4f7f\u7528 LockStack)<\/span><br \/>\n  <span class=\"token comment\">\/\/             010: Inflated Monitor (\u81a8\u80c0\u9501&#xff0c;\u6307\u5411 ObjectMonitor)<\/span><br \/>\n  <span class=\"token comment\">\/\/             011: Marked for GC (GC \u6807\u8bb0)<\/span><br \/>\n  <span class=\"token comment\">\/\/ \u4f4d 3 &#8211; 6  : GC Age (\u5bf9\u8c61\u5e74\u9f84)<\/span><br \/>\n  <span class=\"token comment\">\/\/ \u4f4d 7      : Self-Lock \/ Hash-State Bits<\/span><br \/>\n  <span class=\"token comment\">\/\/ \u4f4d 8 &#8211; 39 : nKlass (32-bit Compressed Klass Pointer \u538b\u7f29\u7c7b\u6307\u9488)<\/span><br \/>\n  <span class=\"token comment\">\/\/ \u4f4d 40 &#8211; 63: Identity Hashcode (24-bit \u6563\u5217\u7801\u6216\u884d\u751f\u6807\u8bb0)<\/span><br \/>\n  <span class=\"token comment\">\/\/ &#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;&#8212;<\/span><\/p>\n<p>  <span class=\"token keyword\">static<\/span> <span class=\"token keyword\">const<\/span> <span class=\"token keyword\">int<\/span> lock_shift              <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><br \/>\n  <span class=\"token keyword\">static<\/span> <span class=\"token keyword\">const<\/span> <span class=\"token keyword\">int<\/span> lock_bits               <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">3<\/span><span class=\"token punctuation\">;<\/span><br \/>\n  <span class=\"token keyword\">static<\/span> <span class=\"token keyword\">const<\/span> uintptr_t lock_mask         <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">right_n_bits<\/span><span class=\"token punctuation\">(<\/span>lock_bits<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>  <span class=\"token keyword\">static<\/span> <span class=\"token keyword\">const<\/span> <span class=\"token keyword\">int<\/span> age_shift               <span class=\"token operator\">&#061;<\/span> lock_bits<span class=\"token punctuation\">;<\/span><br \/>\n  <span class=\"token keyword\">static<\/span> <span class=\"token keyword\">const<\/span> <span class=\"token keyword\">int<\/span> age_bits                <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">4<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>  <span class=\"token comment\">\/\/ nKlass \u5b58\u653e\u533a\u95f4&#xff1a;\u5728\u52a0\u9501\u5168\u751f\u547d\u5468\u671f\u4e2d\u6c38\u4e0d\u88ab\u9501\u6e05\u96f6\u6216\u8986\u76d6<\/span><br \/>\n  <span class=\"token keyword\">static<\/span> <span class=\"token keyword\">const<\/span> <span class=\"token keyword\">int<\/span> nklass_shift            <span class=\"token operator\">&#061;<\/span> lock_bits <span class=\"token operator\">&#043;<\/span> age_bits <span class=\"token operator\">&#043;<\/span> <span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ Bit 8 \u5f00\u59cb<\/span><br \/>\n  <span class=\"token keyword\">static<\/span> <span class=\"token keyword\">const<\/span> <span class=\"token keyword\">int<\/span> nklass_bits             <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">32<\/span><span class=\"token punctuation\">;<\/span>                       <span class=\"token comment\">\/\/ \u5360\u7528 32 \u4f4d<\/span><br \/>\n  <span class=\"token keyword\">static<\/span> <span class=\"token keyword\">const<\/span> uintptr_t nklass_mask       <span class=\"token operator\">&#061;<\/span> <span class=\"token function\">right_n_bits<\/span><span class=\"token punctuation\">(<\/span>nklass_bits<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>  <span class=\"token comment\">\/\/ \u5224\u65ad\u662f\u5426\u4e3a LockStack \u7ba1\u7406\u7684 Fast-Locked \u72b6\u6001<\/span><br \/>\n  <span class=\"token keyword\">bool<\/span> <span class=\"token function\">is_fast_locked<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token keyword\">const<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token keyword\">return<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token function\">value<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&amp;<\/span> lock_mask<span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&#061;&#061;<\/span> lock_state_fast_locked<span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u5373 000 \u72b6\u6001<\/span><br \/>\n  <span class=\"token punctuation\">}<\/span><\/p>\n<p>  <span class=\"token comment\">\/\/ \u6781\u901f\u63d0\u53d6 Klass* \u6307\u9488&#xff08;\u5373\u4f7f\u5728 Fast-Locked \u72b6\u6001\u4e0b\u4f9d\u7136\u6709\u6548&#xff09;<\/span><br \/>\n  narrowKlass <span class=\"token function\">narrow_klass<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token keyword\">const<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token keyword\">return<\/span> <span class=\"token function\">narrowKlass<\/span><span class=\"token punctuation\">(<\/span><span class=\"token function\">assert_unsigned_field_overflow<\/span><span class=\"token punctuation\">(<\/span><span class=\"token function\">value<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&gt;&gt;<\/span> nklass_shift<span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&amp;<\/span> nklass_mask<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n  <span class=\"token punctuation\">}<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<hr \/>\n<h4>3. LightweightSynchronizer \u52a0\u9501\u4e0e\u89e3\u9501\u4ee3\u7801\u8def\u5f84<\/h4>\n<p>\u5728 JDK 21 \u4e2d&#xff0c;\u65e7\u7248\u7684 ObjectSynchronizer::fast_enter \u88ab\u5168\u65b0\u7684 LightweightSynchronizer \u66ff\u6362\u3002\u6e90\u7801\u4f4d\u4e8e src\/hotspot\/share\/runtime\/lightweightSynchronizer.cpp\u3002<\/p>\n<h5>\u52a0\u9501\u5b9e\u73b0&#xff1a;LightweightSynchronizer::enter<\/h5>\n<p><span class=\"token comment\">\/\/ src\/hotspot\/share\/runtime\/lightweightSynchronizer.cpp<\/span><\/p>\n<p><span class=\"token keyword\">void<\/span> <span class=\"token class-name\">LightweightSynchronizer<\/span><span class=\"token double-colon punctuation\">::<\/span><span class=\"token function\">enter<\/span><span class=\"token punctuation\">(<\/span>Handle obj<span class=\"token punctuation\">,<\/span> BasicLock<span class=\"token operator\">*<\/span> lock<span class=\"token punctuation\">,<\/span> JavaThread<span class=\"token operator\">*<\/span> current<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n  markWord mark <span class=\"token operator\">&#061;<\/span> obj<span class=\"token operator\">-&gt;<\/span><span class=\"token function\">mark<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>  <span class=\"token comment\">\/\/ 1. \u65e0\u9501\u72b6\u6001 (Unlocked, 001) \u4e0b\u7684 Fast-Path \u5904\u7f6e<\/span><br \/>\n  <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>mark<span class=\"token punctuation\">.<\/span><span class=\"token function\">is_unlocked<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token comment\">\/\/ \u6784\u9020\u5feb\u901f\u52a0\u9501\u7684\u76ee\u6807 markWord&#xff1a;\u4ec5\u5c06\u9501\u6807\u5fd7\u4f4d\u8bbe\u7f6e\u4e3a 000 (Fast-Locked)<\/span><br \/>\n    <span class=\"token comment\">\/\/ \u6ce8\u610f&#xff1a;markWord \u5185\u90e8\u5305\u542b\u7684 nKlass\u3001Age\u3001Hash \u7edd\u5bf9\u6570\u503c\u5b8c\u5168\u4fdd\u6301\u539f\u6837&#xff01;<\/span><br \/>\n    markWord locked_mark <span class=\"token operator\">&#061;<\/span> mark<span class=\"token punctuation\">.<\/span><span class=\"token function\">set_fast_locked<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token comment\">\/\/ \u539f\u5b50 CAS \u66ff\u6362 Mark Word (\u53ea\u4fee\u6539\u72b6\u6001\u4f4d&#xff0c;\u4e0d\u505a\u6307\u9488\u8986\u5199)<\/span><br \/>\n    markWord old_mark <span class=\"token operator\">&#061;<\/span> obj<span class=\"token operator\">-&gt;<\/span><span class=\"token function\">cas_set_mark<\/span><span class=\"token punctuation\">(<\/span>locked_mark<span class=\"token punctuation\">,<\/span> mark<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>old_mark <span class=\"token operator\">&#061;&#061;<\/span> mark<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n      <span class=\"token comment\">\/\/ CAS \u6210\u529f&#xff01;\u5c06\u5bf9\u8c61\u6307\u9488\u63a8\u5165\u5f53\u524d\u7ebf\u7a0b\u7684 LockStack<\/span><br \/>\n      current<span class=\"token operator\">-&gt;<\/span><span class=\"token function\">lock_stack<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">.<\/span><span class=\"token function\">push<\/span><span class=\"token punctuation\">(<\/span><span class=\"token function\">obj<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n      <span class=\"token keyword\">return<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u52a0\u9501\u6210\u529f&#xff0c;\u76f4\u63a5\u8fd4\u56de&#xff0c;\u6ca1\u6709\u7269\u7406 BasicLock \u6307\u9488\u5199\u5165<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    mark <span class=\"token operator\">&#061;<\/span> old_mark<span class=\"token punctuation\">;<\/span><br \/>\n  <span class=\"token punctuation\">}<\/span><\/p>\n<p>  <span class=\"token comment\">\/\/ 2. \u9501\u91cd\u5165 (Reentrant Lock) \u5224\u5b9a<\/span><br \/>\n  <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>mark<span class=\"token punctuation\">.<\/span><span class=\"token function\">is_fast_locked<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&amp;&amp;<\/span> current<span class=\"token operator\">-&gt;<\/span><span class=\"token function\">lock_stack<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">.<\/span><span class=\"token function\">contains<\/span><span class=\"token punctuation\">(<\/span><span class=\"token function\">obj<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token comment\">\/\/ \u5982\u679c\u5f53\u524d\u7ebf\u7a0b\u5df2\u7ecf\u6301\u6709\u8be5\u5bf9\u8c61\u7684\u9501&#xff0c;\u652f\u6301\u9012\u5f52\u52a0\u9501<\/span><br \/>\n    <span class=\"token comment\">\/\/ \u53ea\u9700\u8981\u5411\u7ebf\u7a0b\u7684 LockStack \u4e2d\u518d\u6b21\u538b\u5165\u8be5 oop \u5373\u53ef&#xff0c;Mark Word \u65e0\u9700\u505a\u4efb\u4f55\u4fee\u6539<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token operator\">!<\/span>current<span class=\"token operator\">-&gt;<\/span><span class=\"token function\">lock_stack<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">.<\/span><span class=\"token function\">is_full<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n      current<span class=\"token operator\">-&gt;<\/span><span class=\"token function\">lock_stack<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">.<\/span><span class=\"token function\">push<\/span><span class=\"token punctuation\">(<\/span><span class=\"token function\">obj<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n      <span class=\"token keyword\">return<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    <span class=\"token comment\">\/\/ \u82e5 LockStack \u5df2\u6ee1 (\u8d85\u8fc7 8 \u5c42\u91cd\u5165)&#xff0c;\u9000\u5316\u964d\u7ea7\u5904\u7406&#xff0c;\u89e6\u53d1\u9501\u81a8\u80c0<\/span><br \/>\n  <span class=\"token punctuation\">}<\/span><\/p>\n<p>  <span class=\"token comment\">\/\/ 3. \u6162\u901f\u8def\u5f84 (Slow Path)&#xff1a;\u7ade\u4e89\u5931\u8d25\u6216 LockStack \u6ea2\u51fa&#xff0c;\u81a8\u80c0\u4e3a\u91cd\u91cf\u7ea7\u9501 (ObjectMonitor)<\/span><br \/>\n  <span class=\"token function\">enter_slow<\/span><span class=\"token punctuation\">(<\/span>obj<span class=\"token punctuation\">,<\/span> lock<span class=\"token punctuation\">,<\/span> current<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<h5>\u89e3\u9501\u5b9e\u73b0&#xff1a;LightweightSynchronizer::exit<\/h5>\n<p><span class=\"token comment\">\/\/ src\/hotspot\/share\/runtime\/lightweightSynchronizer.cpp<\/span><\/p>\n<p><span class=\"token keyword\">void<\/span> <span class=\"token class-name\">LightweightSynchronizer<\/span><span class=\"token double-colon punctuation\">::<\/span><span class=\"token function\">exit<\/span><span class=\"token punctuation\">(<\/span>oop obj<span class=\"token punctuation\">,<\/span> current<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n  markWord mark <span class=\"token operator\">&#061;<\/span> obj<span class=\"token operator\">-&gt;<\/span><span class=\"token function\">mark<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>  <span class=\"token comment\">\/\/ \u5982\u679c\u5904\u4e8e Fast-Locked \u72b6\u6001<\/span><br \/>\n  <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>mark<span class=\"token punctuation\">.<\/span><span class=\"token function\">is_fast_locked<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    <span class=\"token comment\">\/\/ 1. \u4f18\u5148\u5c1d\u8bd5\u4ece LockStack \u7684\u6808\u9876\u5f39\u51fa\u8be5\u5bf9\u8c61<\/span><br \/>\n    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>current<span class=\"token operator\">-&gt;<\/span><span class=\"token function\">lock_stack<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">.<\/span><span class=\"token function\">peek<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&#061;&#061;<\/span> obj<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n      current<span class=\"token operator\">-&gt;<\/span><span class=\"token function\">lock_stack<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">.<\/span><span class=\"token function\">pop<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>      <span class=\"token comment\">\/\/ \u68c0\u67e5\u5f53\u524d\u7ebf\u7a0b\u7684 LockStack \u4e2d\u662f\u5426\u8fd8\u5b58\u5728\u8be5\u5bf9\u8c61\u7684\u91cd\u5165\u9501<\/span><br \/>\n      <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>current<span class=\"token operator\">-&gt;<\/span><span class=\"token function\">lock_stack<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">.<\/span><span class=\"token function\">contains<\/span><span class=\"token punctuation\">(<\/span>obj<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token keyword\">return<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ \u4ecd\u6709\u5916\u5c42 synchronized \u5757\u6301\u6709\u8be5\u9501&#xff0c;\u89e3\u9501\u76f4\u63a5\u7ed3\u675f<\/span><br \/>\n      <span class=\"token punctuation\">}<\/span><\/p>\n<p>      <span class=\"token comment\">\/\/ 2. \u8fd8\u539f Mark Word \u4e3a Unlocked (001) \u72b6\u6001<\/span><br \/>\n      markWord unlocked_mark <span class=\"token operator\">&#061;<\/span> mark<span class=\"token punctuation\">.<\/span><span class=\"token function\">set_unlocked<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n      <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>obj<span class=\"token operator\">-&gt;<\/span><span class=\"token function\">cas_set_mark<\/span><span class=\"token punctuation\">(<\/span>unlocked_mark<span class=\"token punctuation\">,<\/span> mark<span class=\"token punctuation\">)<\/span> <span class=\"token operator\">&#061;&#061;<\/span> mark<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token keyword\">return<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token comment\">\/\/ CAS \u6210\u529f&#xff0c;\u89e3\u9501\u5b8c\u6210<\/span><br \/>\n      <span class=\"token punctuation\">}<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n  <span class=\"token punctuation\">}<\/span><\/p>\n<p>  <span class=\"token comment\">\/\/ \u9501\u81a8\u80c0\u540e\u7684\u6162\u901f\u89e3\u9501\u8def\u5f84<\/span><br \/>\n  <span class=\"token function\">exit_slow<\/span><span class=\"token punctuation\">(<\/span>obj<span class=\"token punctuation\">,<\/span> current<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<hr \/>\n<h3>C2 \u7f16\u8bd1\u5668\u4e0e JIT \u6c47\u7f16\u7ea7 Fast-Path \u5c55\u5f00<\/h3>\n<p>\u5728\u5e95\u5c42\u5185\u8054\u6c47\u7f16&#xff08;\u4ee5 x86_64 \u4e3a\u4f8b&#xff0c;src\/hotspot\/cpu\/x86\/c2_MacroAssembler_x86.cpp&#xff09;\u4e2d&#xff0c;LockStack \u5c55\u73b0\u51fa\u4e86\u6781\u9ad8\u7684\u6267\u884c\u6548\u7387\u3002C2 \u4e0d\u518d\u9700\u8981\u50cf\u65e7\u7248\u672c\u90a3\u6837\u5728\u5f53\u524d\u6808\u5e27\u7684 BasicLock \u4e2d\u4fdd\u5b58 Displaced Header&#xff0c;\u4ece\u800c\u51cf\u5c11\u4e86\u4e00\u6b21 Stack Memory Store\u3002<\/p>\n<h4>C2 \u751f\u6210\u7684 FastLock \u673a\u5668\u7801\u6307\u4ee4\u903b\u8f91<\/h4>\n<p># \u8f93\u5165: %r12 &#061; \u5bf9\u8c61\u6307\u9488 (oop), %r15 &#061; \u5f53\u524d JavaThread \u6307\u9488<br \/>\n# \u8f93\u51fa: ZF (Zero Flag) \u6807\u5fd7\u4f4d\u8868\u793a CAS \u662f\u5426\u6210\u529f<\/p>\n<p># 1. \u8bfb\u53d6\u5f53\u524d\u5bf9\u8c61\u7684 Mark Word<br \/>\nmovq    0x0(%r12), %rax          # %rax &#061; Mark Word<\/p>\n<p># 2. \u6d4b\u8bd5\u9501\u6807\u5fd7\u4f4d\u662f\u5426\u4e3a Unlocked (001)<br \/>\ntestq   $0x7, %rax               # \u68c0\u67e5\u4f4e 3 \u4f4d<br \/>\njnz     .L_slow_path             # \u975e 001 \u72b6\u6001\u8fdb\u5165 Slow Path<\/p>\n<p># 3. \u6784\u9020 Locked Mark Word: \u4fdd\u6301\u9ad8\u4f4d nKlass\/Hash \u4e0d\u53d8&#xff0c;\u4ec5\u5c06\u4f4e 3 \u4f4d\u8f6c\u4e3a 000<br \/>\nmovq    %rax, %rbx<br \/>\nandq    $~0x7, %rbx              # %rbx &#061; Target Mark Word (Fast-Locked: 000)<\/p>\n<p># 4. \u6267\u884c\u539f\u5b50 CAS \u6307\u4ee4<br \/>\nlock cmpxchgq %rbx, 0x0(%r12)    # \u6bd4\u8f83\u5e76\u4ea4\u6362 Mark Word<br \/>\njnz     .L_slow_path             # CAS \u51b2\u7a81\u8fdb\u5165 Slow Path<\/p>\n<p># 5. CAS \u6210\u529f&#xff1a;\u5c06\u5bf9\u8c61\u5199\u5165 JavaThread \u7684 LockStack<br \/>\nmovl    0x2e0(%r15), %ecx        # \u8bfb\u53d6 thread-&gt;_lock_stack._top offset (\u5047\u8bbe\u504f\u79fb 0x2e0)<br \/>\nmovq    %r12, 0x2e4(%r15, %rcx, 8) # lock_stack._base[top] &#061; oop<br \/>\naddl    $1, 0x2e0(%r15)          # _top&#043;&#043;<br \/>\n# \u5b8c\u6210\u52a0\u9501&#xff0c;\u6ca1\u6709\u5bf9\u7269\u7406 C-Stack \u5e27\u5199\u5165 Displaced Header!<\/p>\n<hr \/>\n<h3>\u65b0\u65e7\u8f7b\u91cf\u7ea7\u9501\u673a\u5236\u5bf9\u6bd4<\/h3>\n<p>\u4e0b\u8868\u76f4\u89c2\u603b\u7ed3\u4e86\u4e3a\u4f55 LockStack \u80fd\u591f\u6210\u4e3a Lilliput \u5b9e\u73b0 Compact Object Headers \u7684\u51b3\u5b9a\u6027\u57fa\u77f3&#xff1a;<\/p>\n<table>\n<tr>\u7ef4\u5ea6\u4f20\u7edf\u8f7b\u91cf\u7ea7\u9501 (BasicLock)JDK 21&#043; LockStack (Fast Locking)<\/tr>\n<tbody>\n<tr>\n<td>** Mark Word \u5360\u7528\u673a\u5236**<\/td>\n<td>\u5f3a\u884c\u8986\u76d6 Mark Word \u9ad8 62 \u4f4d \u4e3a\u7269\u7406\u6808\u5730\u5740<\/td>\n<td>\u96f6\u6307\u9488\u8986\u76d6&#xff0c;\u4ec5\u66f4\u65b0\u4f4e 3 \u4f4d\u9501\u72b6\u6001\u6807\u5fd7\u4f4d&#xff08;001 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\"><\/p>\n<p>           \u2192<\/p>\n<p>          \\\\rightarrow<\/p>\n<p>       <\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.3669em\"><\/span><span class=\"mrel\">\u2192<\/span><\/span><\/span><\/span><\/span> 000&#xff09;<\/td>\n<\/tr>\n<tr>\n<td>nKlass&#xff08;\u7c7b\u6307\u9488&#xff09;\u5b58\u50a8<\/td>\n<td>\u88ab\u5f3a\u884c\u62b9\u9664&#xff0c;\u5fc5\u987b\u6cbf\u7740\u6808\u6307\u9488\u53bb BasicLock \u76f2\u8ffd<\/td>\n<td>\u6c38\u4e45\u9a7b\u7559 \u5728 Mark Word \u56fa\u5b9a\u7684 Bit \u533a\u95f4\u5185&#xff0c;\u7269\u7406\u4e0a\u6c38\u4e0d\u6bc1\u635f<\/td>\n<\/tr>\n<tr>\n<td>getClass() \u8bfb\u53d6\u5f00\u9500<\/td>\n<td>\u52a0\u9501\u671f\u95f4\u5fc5\u987b\u56de\u6eaf C-Stack \u53d6\u56de\u539f\u59cb Mark Word<\/td>\n<td><span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\"><\/p>\n<p>            O<\/p>\n<p>            (<\/p>\n<p>            1<\/p>\n<p>            )<\/p>\n<p>           O(1)<\/p>\n<p>        <\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">O<\/span><span class=\"mopen\">(<\/span><span class=\"mord\">1<\/span><span class=\"mclose\">)<\/span><\/span><\/span><\/span><\/span> \u65e0\u9501\u8bfb\u53d6&#xff0c;\u4ec5\u9700\u6309\u4f4d\u53f3\u79fb\u4e0e\u63a9\u7801&#xff08;mark &gt;&gt; nklass_shift &amp; mask&#xff09;<\/td>\n<\/tr>\n<tr>\n<td>\u9501\u6240\u6709\u6743\u8bb0\u8f7d\u4f4d\u7f6e<\/td>\n<td>\u5bf9\u8c61\u7684 Mark Word \u5185\u90e8&#xff08;\u5b58\u6808\u5730\u5740&#xff09;<\/td>\n<td>\u7ebf\u7a0b\u79c1\u6709\u7684 JavaThread::_lock_stack \u7ebf\u7a0b\u5c40\u90e8\u6570\u7ec4\u4e2d<\/td>\n<\/tr>\n<tr>\n<td>\u9501\u91cd\u5165\u5904\u7406\u65b9\u5f0f<\/td>\n<td>\u5728 Stack Frame \u538b\u5165 NULL \u5934\u7684 BasicLock \u69fd<\/td>\n<td>\u76f4\u63a5\u5728 LockStack \u6570\u7ec4\u5c3e\u90e8 append \u76ee\u6807\u5bf9\u8c61 oop<\/td>\n<\/tr>\n<tr>\n<td>CPU Cache \u5f71\u54cd<\/td>\n<td>\u9891\u7e41\u5199\u5165\u5f53\u524d\u6808\u5e27 BasicLock \u5185\u5b58\u9875<\/td>\n<td>\u6781\u4f73\u7684 Cache Line \u5c40\u90e8\u6027&#xff0c;\u5b8c\u5168\u5728 %r15 \u7ebf\u7a0b\u7ed3\u6784\u7f13\u5b58\u884c\u5185\u5b8c\u6210<\/td>\n<\/tr>\n<tr>\n<td>\u5bf9 Compact Header \u7684\u652f\u6301<\/td>\n<td>\u7269\u7406\u62d2\u7edd&#xff08;\u4e0d\u53ef\u80fd\u5728 64 \u4f4d\u5185\u5bb9\u7eb3 nKlass&#xff09;<\/td>\n<td>\u5b8c\u5907\u652f\u6301&#xff08;Project Lilliput JEP 450 \u6838\u5fc3\u4f9d\u8d56&#xff09;<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<hr \/>\n<h3>\u603b\u7ed3<\/h3>\n<p>Project Lilliput \u7684\u672c\u8d28\u662f\u5728\u6709\u9650\u7684 64 \u4f4d&#xff08;\u751a\u81f3 32 \u4f4d&#xff09;Word \u7a7a\u95f4\u5185&#xff0c;\u4ee5\u7cbe\u7ec6\u5316 Bit \u62fc\u56fe\u7684\u5f62\u5f0f\u91cd\u65b0\u6784\u5efa Java \u5bf9\u8c61\u5934\u3002<\/p>\n<p>HotSpot \u653e\u5f03\u4f20\u7edf\u7684 BasicLock \u6808\u5730\u5740\u8986\u76d6\u673a\u5236&#xff0c;\u8f6c\u5411\u57fa\u4e8e LockStack \u7684 Thread-Local \u9501\u8ddf\u8e2a&#xff0c;\u5c06\u9501\u6240\u6709\u6743\u72b6\u6001\u4ece\u201c\u5bf9\u8c61\u5934\u8bb0\u8f7d\u201d\u89e3\u8026\u4e3a\u201c\u7ebf\u7a0b\u5c40\u90e8\u6570\u7ec4\u8bb0\u8f7d\u201d\u3002\u8fd9\u4e00\u67b6\u6784\u53d8\u9769\u5f7b\u5e95\u91ca\u653e\u4e86 Mark Word \u4e2d\u88ab\u7269\u7406\u6307\u9488\u9738\u5360\u7684 62 \u4f4d\u7a7a\u95f4&#xff0c;\u4f7f\u538b\u7f29\u7c7b\u6307\u9488 nKlass \u80fd\u591f\u5e73\u6ed1\u3001\u6c38\u4e45\u5730\u5d4c\u5165\u5230\u5bf9\u8c61\u5934\u4e2d&#xff0c;\u4ece\u5e95\u5c42\u5960\u5b9a\u4e86 64 \u4f4d\u7d27\u51d1\u5bf9\u8c61\u5934&#xff08;Compact Object Headers&#xff09;\u7684\u6839\u57fa\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Markword\u5728\u7d27\u51d1\u5bf9\u8c61\u5934\u4e0a\u7684\u5b9e\u73b0\u539f\u7406\u5256\u6790\u524d\u8a00Markword\u5728\u7d27\u51d1\u5bf9\u8c61\u5934\u4e0a\u7684\u5b9e\u73b0\u539f\u7406\u4f20\u7edf\u504f\u5411\u9501\/\u8f7b\u91cf\u7ea7\u9501\u5bf9 Mark Word \u7684\u7269\u7406\u8986\u5199\u56f0\u5883\u4f20\u7edf\u8f7b\u91cf\u7ea7\u9501\u7684\u8986\u5199\u673a\u5236 (HotSpot Legacy)\u963b\u788d Compact Object Headers (Lilliput) \u7684\u6839\u672c\u77db\u76feLockStack \u5982\u4f55\u5b9e\u73b0\u201c\u89e3\u8026\u201d\u5e76\u817e\u51fa Bit \u7a7a\u95f4HotSpot \u6e90\u7801\u7ea7\u8be6\u7ec6\u5256\u67901. LockStack \u7ebf\u7a0b\u5c40\u90e8\u6570\u636e\u7ed3\u6784\u8bbe\u8ba1\u7cbe\u9ad32. Project Lilliput \u4e2d\u7684 Mark W<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[55,174,99,426,58],"topic":[],"class_list":["post-107763","post","type-post","status-publish","format-standard","hentry","category-server","tag-c","tag-java","tag-jvm","tag-linux"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v20.3 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Markword\u5728\u7d27\u51d1\u5bf9\u8c61\u5934\u4e0a\u7684\u5b9e\u73b0\u539f\u7406\u5256\u6790 - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.wsisp.com\/helps\/107763.html\" \/>\n<meta property=\"og:locale\" content=\"zh_CN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Markword\u5728\u7d27\u51d1\u5bf9\u8c61\u5934\u4e0a\u7684\u5b9e\u73b0\u539f\u7406\u5256\u6790 - \u7f51\u7855\u4e92\u8054\u5e2e\u52a9\u4e2d\u5fc3\" \/>\n<meta property=\"og:description\" content=\"Markword\u5728\u7d27\u51d1\u5bf9\u8c61\u5934\u4e0a\u7684\u5b9e\u73b0\u539f\u7406\u5256\u6790\u524d\u8a00Markword\u5728\u7d27\u51d1\u5bf9\u8c61\u5934\u4e0a\u7684\u5b9e\u73b0\u539f\u7406\u4f20\u7edf\u504f\u5411\u9501\/\u8f7b\u91cf\u7ea7\u9501\u5bf9 Mark Word \u7684\u7269\u7406\u8986\u5199\u56f0\u5883\u4f20\u7edf\u8f7b\u91cf\u7ea7\u9501\u7684\u8986\u5199\u673a\u5236 (HotSpot Legacy)\u963b\u788d Compact Object Headers (Lilliput) \u7684\u6839\u672c\u77db\u76feLockStack \u5982\u4f55\u5b9e\u73b0\u201c\u89e3\u8026\u201d\u5e76\u817e\u51fa Bit \u7a7a\u95f4HotSpot \u6e90\u7801\u7ea7\u8be6\u7ec6\u5256\u67901. 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