Multicore Processors and Scaling

The two big advantages of multicore processors are their ability to run multiple threads and the low synchronization costs between those threads. Synchronization costs govern scaling in two important ways. Low synchronization costs mean that the code will scale more effectively to higher thread counts. A similar reasoning leads to the enticing possibility that low synchronization costs enable developers to produce parallel versions of routines that were previously too small to parallelize. Consequently, there is a fortuitous convergence that processors with low synchronization costs that enable scaling to high thread counts also provide the threads that will perform that scaling.

The low synchronization costs lead to one further advantage for multicore processors. This section has discussed a number of reasons that scaling could be limited, and a number of these are implicitly functions of the communication costs between cores. The most obvious example of this is false sharing.