False sharing, or destructive interference, can degrade performance. It occurs when two threads use some data (that is not logically shared between the threads) but happen to be located in the same cache line. Imagine what would happen if the two threads are executing on different cores and constantly update the variable that resides on the shared cache line. The threads will invalidate the cache line for each other although there is no true sharing of data between the threads.
False sharing will most likely occur when using global data or dynamically-allocated data that is shared between threads. An example where false sharing is likely to occur is when allocating an array that is shared between threads, but each thread is ...
