I built a simple web crawler using good old platform threads. It was just a multithreaded crawler, nothing fancy. But then, curiosity…

In multiprocessor systems, processors generally have one or more layers of memory cache, which improves performance both by speeding access to data (because the data is closer to the processor) and reducing traffic on the shared memory bus (because many memory operations can be satisfied by local caches.) Memory caches can improve performance tremendously, but they present a host of new challenges. What, for example, happens when two processors examine the same memory location at the same time? Under what conditions will they see the same value?