Logical clock based Last Update Consistency model for Distributed Shared Memory

Abstract

Excessive locking and cumulative updates in Distributed Shared Memory (DSM) not only reduces the parallelism for block access but also causes a serious degradation in response time for a dense network. This paper proposes a new consistency model in DSM named Last Update Consistency (LUC) model, where the model uses logical clock counter to keep the DSM consistent. The logical clock always increases never decreases. So the increasing order of the logical clock value is used to provide the request to the DSM. In this model, multiple nodes can perform READ operations over the same block at a time. For WRITE operation over the same block, only the last modification will exist and the earlier WRITE operations will be treated as obsolete WRITE and should be discarded. The experimental and analytical analysis showed that the proposed model effectively reduces the unnecessary network traffic and cumulative block updates that exist in the Sequential Consistency Model and Release Consistency Model.