Introduction to NUMA (Non-Uniform Memory Access)

In a typical SMP (Symmetric MultiProcessor architecture), all memory access are posted to the same shared memory bus. This works fine for a relatively small number of CPUs, but the problem with the shared bus appears when you have dozens, even hundreds, of CPUs competing for access to the shared memory bus. This leads to a major performance bottleneck due to the extremely high contention rate between the multiple CPU's onto the single memory bus.

The NUMA architecture was designed to surpass these scalability limits of the SMP architecture. NUMA computers offer the scalability of MPP(Massively Parallel Processing), in that processors can be added and removed at will without loss of efficiency, and the programming ease of SMP where.