An Analysis of Exclusive Control Mechanisms

Spin-lock is commonly used for process serialization, where it works well for multi processor systems. Under some conditions however, it may cause an unexpected increase of CPU overhead. To address this problem a simulator has been developed which evaluates various algorithms of the lock/unlock process to determine a method to minimize their affect on the stability and scalability of a system. This paper analyzes the effect of spin-lock, how CPU overhead changes as a function of traffic, by using the simulator. It demonstrates how multiple processors go into ldquobusy waitrdquo, consuming CPU time, and working for nothing, with only a few processors able to advance. The paper also shows how this problem can be solved by capped spin-lock where the spin is capped to a certain limit and a pause is inserted between the spins avoiding unnecessary consumption of CPU power and maintaining scalability over a number of processors.