Java虚拟机使用锁机制来实现多线程共享数据结构的同步.锁机制维护的临界区通常对共享数据结构只进行读操作.只读锁是指当某个线程持有锁在只读临界区时,其他线程可以直接进入只读临界区而无需等待.只读锁能极大地提高锁机制的同步性能.Java虚拟机的锁机制可分为轻量级锁和重量级锁两层,当线程冲突时从轻量级锁转向重量级锁.本文分别从轻量级锁和重量级锁两个层次分别进行只读锁优化.轻量级锁的只读优化算法可以减少原子操作的开销；重量级锁的只读优化算法则可以使多个线程同时在只读临界区中.最后在Java虚拟机HotSpot中实现只读锁优化,并且在龙芯3A上进行实验.性能测试用例包括单线程Java程序、多线程Java程序以及SPECjvm2008.实验结果表明,上述优化方法能极大降低线程进入和退出只读临界区的开销,提高Java虚拟机的同步性能.-Java virtual machine to use locking mechanism to realize multi-thread synchronization. Locking mechanism for shared data structures to maintain the critical area of shared data structures are usually read-only operations. Read-only lock means that when a thread holding a lock on the read-only critical section other threads can go directly to the read-only critical section without waiting. read-only lock can greatly improve the performance of synchronization lock mechanism. locking mechanism for the Java virtual machine can be divided into lightweight and heavyweight locks lock layers, when the thread conflict from the lightweight heavyweight steering lock lock lock this paper from lightweight and heavyweight lock two levels were optimized for read-only lock lightweight lock read-only optimization algorithm can reduce the overhead of atomic operations . heavyweight a read-only lock can enable optimization of multiple threads in the critical region in a read only last a read-only lock to