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1 1 Synchronized synchronized Java ( ) Synchronized Java unlock lock load assign unlock (happen-before) lock Synchronized null " " HotSpot JVM Object Monitor synchronized 1 2 Class synchronized monitor Class Class 3 synchronized synchronized monitor this synchronized monitor.

2 synchronized 2 synchronized JVM j.u.c.lock CPU javap SynchronizedDemo.class monitorenter monitor monitor monitorenter monitor

3 monitor 0 monitor 1 monitor monitor monitor 1 monitor monitor 0 monitor monitorexit monitorexit objectref monitor monitor monitor monitor monitor monitor monitorexit 1 2 Synchronized Synchronized monitor wait/notify monitor wait/notify java.lang.illegalmonitorstateexception javap -v SynchronizedDemo.class

4 monitorenter monitorexit ACC_SYNCHRONIZED JVM ACC_SYNCHRONIZED monitor monitor monitor JVM mutex 3

5 JVM 3 ( ) JVM 8 ( 8 ) 8 synchronized JVM 2 ( 3 ) Mark Word Mark Word hashcode GC ID JVM Java Mark Word 32 Mark Word Mark Word ( 32 )

6 64 Mark Word 64bit 01 ID + ) ID ID ID 3 Mark Word Lock Record 01 Lock Record Mark Word Displaced Mark Word Mark Word Lock Record Lock Record Mark Word Lock Record MarkWord Lock

Word Lock Record Lock Record Owner object mark word Lock Record Lock Record Owner NULL monitor record NULL EntryQ semaphore monitor record RcThis blocked waiting monitor record Nest HashCode HashCode

7 Word Lock Record Lock Record Owner object mark word Lock Record Lock Record Owner NULL monitor record NULL EntryQ semaphore monitor record RcThis blocked waiting monitor record Nest HashCode HashCode GC age Candidate Candidate Monitor Monitor Monitor Synchronized JVM Monitor MonitorEnter MonitorExit MonitorEnter Monitor MonitorExit JVM MonitorEnter MonitorExit Monitor Java Monitor Java Monitor Java Java Monitor Synchronized MarkWord 10 Monitor monitor Hot Spot monitor ObjectMonitor ObjectMonitor

ObjectMonitor _WaitSet EntryList ObjectWaiter ObjectWaiter owner ObjectMonitor _EntryList monitor _Owner monitor owner monitor count 1 wait() monitor owner null

8 ObjectMonitor _WaitSet EntryList ObjectWaiter ObjectWaiter owner ObjectMonitor _EntryList monitor _Owner monitor owner monitor count 1 wait() monitor owner null count 1 WaitSet monitor count monitor( ) Monitor Java Mark Word Synchronized Java notify/notifyall/wait Monitor Monitor JVM Object wait wait notify Object notifyall

9 1 Entry Set( ) Owner 5 3 Wait Set wait 5 Monitor JVM monitor javap - verbose XXX.class

10 synchronized monitorenter monitorexit monitorenter monitorenter monitor monitor monitorenter ( monitor ) JVM method_info ACC_SYNCHRONIZED ACC_SYNCHRONIZED monitor synchronized

11 6 JDK5 CAS JDK5 synchronized J.U.C concurrent JDK6 synchronized JDK5 CAS CAS JDK 1.6 -XX:-UseBiasedLocking 6.1 CPU CPU CPU JDK XX:+UseSpinning JDK XX:PreBlockSpin -XX:PreBlockSpin 10 JDK JDK JDK6 HotSpot A B

JDK5 JDK6 -XX:-UseBiasedLocking ( JVM ) CAS ThreadID CAS CAS CAS / HotSpot / CAS CAS CAS CAS true / CAS SMP SMP CPU BUS BUS CAS Compare-And-Swap CPU CPU CAS JVM

12 JDK5 JDK6 -XX:-UseBiasedLocking ( JVM ) CAS ThreadID CAS CAS CAS / HotSpot / CAS CAS CAS CAS true / CAS SMP SMP CPU BUS BUS CAS Compare-And-Swap CPU CPU CAS JVM AtomicInteger Core1 Core2 Load L1 Cache Core1 L1 Cache Core2 L1 Cache Core2 L1 Cache Cache Cache Cache Core1 Core2 Cache Cache CAS Cache Core CAS CAS Cache ID CAS ThreadID

13 1 Mark Word ID ID ID ID CAS Mark Word ID ID 4 4 CAS 5

14 Mark Word 00 ID

15 Lock Record Mark Word Displaced Mark Word

16 2 Mark Word Lock Record 3 CAS Mark Word Lock Word Lock Record Lock record owner object mark word Mark Word 00 5 Mark Word Lock Word 3 10 Mark Word CAS

17 CAS Displaced Mark Word Mark Word 01 CAS Mark Word CAS CAS CAS A B A B CAS HashCode CAS CAS B CAS HashCode B CAS A A B CAS B A B CAS B 6.5 Synchronized Monitor Mutex Lock Synchronized Mutex Lock 6.6

18 7 JVM JVM JDK API StringBuffer Vector HashTable StringBuffer append() Vector add()

19 JVM vector vectortest() JVM vector 8 9 vector add JVM vector for -> -> CAS CAS 3 HotSpot

20 10 Synchronized ReentrantLock synchronized synchronized cas _owner owner recursions++ _EntryList (_recursions--)

中餐烹調丙級95.6.27.doc

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