An efficient CCM KRISHNA for high contention environment and its performance comparison with WDL

Abstract

Commonly known concurrency control mechanisms (CCMs) based on two-phase locking are known to be unsuitable for high contention environment. One of the main reasons for their inefficiency is the high level of wasted work, which occurs because of redundant roll-backs, and inappropriate blocking in resolving conflicts. This happens mainly because these CCMs resolve conflicts using pre-defined policies; an approach which sets a limit on their efficiency. Recently a class of CCM, called Wait Depth Limited (WDL) has appeared in the literature, which claims to overcome some of these problems. We also recognize limitations and unsuitability of commonly known locking based CCMs for high contention environment, and present a class of CCMs called KRISHNA which offers a simple heuristic based and efficient solutions to these problems. We establish our claim with a detail simulation study and show that one of the CCMs of KRISHNA class outperforms WDL class in the majority of high contention environments. We argue that our CCMs are based on a simple approach, and are easy and cheaper to implement.