Performance analysis of coherency control policies through lock retention

Abstract

Buffer coherency control can be achieved through retaining a lock (shared, exclusive, etc. ) on each page in the buffer, even after the requesting transaction has committed. Depending upon the lock mode held for retention and the compatibility of lock modes specified, different retention policies can be devised. In addition to tracking the validity of the builered data granules, additional capabilities can be provided such as deferred writes to support no-force policy on commit, (node) location identification of valid granules to support remote memory accesses, and shared/exclusive lock ret ention to reduce the number of global lock requests for concurrency control. However, these can have serious implications not only on the performance but also on the recovery complexity. In this paper, five different integrated coherency policies are considered. We classify these policies into three different cat egories according to their recovery requirements. A performance study based on analytic models is provided to understand the trade-offs on both maximum throughputs and response times of the policies with a similar level of recovery complexity and the performance gain achievable through increasing the level of recovery complexity.