Utilizing a Multi-Core System with the Actor Model

typical multi-threaded application in Java contains numerous synchronized methods and statements. They might also contain calls to the methods wait() and notify() that were introduced with Java 1.0, but these methods provide very primitive functionality and are easily misused. Java 5 introduced the java.util.concurrent package, which provides some higher-level abstractions away from wait() and notify(). However, it can still be a challenge to appropriately use the synchronized and volatile keywords. Even when used correctly, getting them used efficiently can require complicated orchestrations of locks.

The biggest criticism of Java's synchronization is performance. Synchronization blocks become overly encompassing too easily. Although a synchronization block on its own is far from slow, when overly encompassing, it becomes a contested synchronization block. Contested synchronized blocks, or other blocking operations, are slow and require the OS to put threads to sleep and use interrupts to activate them. This puts pressure on the scheduler, resulting in significant performance degradation.