Why synchronize on small objects?

Question

How does synchronization block in Java performance depends on object size on which synchronization is being performed?

synchorized (lock) {
    //some code here
}

Imagine lock could be just new Object() as it is used to be or it could be instance of immutable class but with a huge number of fields initialized.

Answer 1

synchronized是不受对象大小影响的对象，因为它是对象上的（小）信号量，性能问题与多个线程如何访问对象有关，换句话说，与应用程序的结构有关。

Answer 2

The synchronization's performance does not depend on the size of the object you're synchronizing on. However, using a "large" object for synchronization may hurt performance in other areas - first, it may take time to initialize it, and second, it will hog memory, causing more page-faults etc. (assuming it's not required by your code regardless, in which case it makes no sense to hold an additional object just for synchronization purposes).