Continuing on the information presented in Part 1: The Symmetric Multi Processor (SMP) scaling problem and Part 2: The Performance Solution as presented by Pyramid Technology, my comments were addressed at the kernel. But what about user processes? Do they also need to use locking?
The answer is yes, if multiple processes share the same physical memory. This can occur with Shared Memory. User space proccesses use Shared Memory so that proccesses can easily and quickly share data. Shared Memory is the fastest Inter Process Communication(IPC) mechanism that can be employed. But it does have a cost (alas nothing is free): lack of synchronization.