Remote Accesses, which implies that the memory references are frequently to locations on other processors. Synchronization Costs, which denotes the time spent by processors in coordinating the progress of the computation among themselves. False Sharing, which means that two or more processors access different variables that happen to be co located on the same cache block, with at least one of the accesses being a write. Once the write occurs, the entire cache line is invalidated to other processors. Thus, any attempt by the other processors to use another data item in the cache line will require the entire cache line to be updated first.
False sharing is a potential problem in any cache based, shared memory multiprocessor system.