Distributed Shared Memory Model Research Articles

OPDSM: A Combinatorial Object-Based and Page-Based DSM Model

Distributed Shared Memory (DSM) system is designed on the basis of page-based, shared-variable-based or object-based access. There are certain advantages and disadvantages of each access methodology. Comparison of such different access types in a distributed environment is based on parameters namely, type of operation (data read or update), maintenance of consistent data copies on all nodes accessing shared data, administration of data manipulations on multi-computers, etc. This paper compares the design and implementation issues for page-based and object-based DSM in a multicomputing environment. The paper also proposes a hybrid model for implementation of a DSM system that combines some features of page-based and object-based access that is focused on efficient data access with optimum performance with respect to memory access and cohesive data/object organization. Thus the hybrid model is proposed to get a common function of data sharing by using the best features of both page-based and object- based DSM models.

An $O(1)$ RMRs Leader Election Algorithm

The leader election problem is a fundamental coordination problem. We present leader election algorithms for multiprocessor systems where processes communicate by reading and writing shared memory asynchronously and do not fail. In particular, we consider the cache-coherent (CC) and distributed shared memory (DSM) models of such systems. We present leader election algorithms that perform a constant number of remote memory references (RMRs) in the worst case. Our algorithms use splitter-like objects [J. Anderson and M. Moir, Sci. Comput. Programming, 25 (1995), pp. 1–39; H. Attiya and A. Fouren, Theory Comput. Syst., 31 (2001), pp. 642–664] in a novel way, by organizing active processes into teams that share work. As there is an $\Omega(\log n)$ lower bound on the RMR complexity of mutual exclusion for n processes using reads and writes only [H. Attiya, D. Hendler, and W. Woelfel, in Proceedings of the ACM Symposium on Theory of Computing, ACM, New York, 2008, pp. 217–226], our result separates the mutual exclusion and leader election problems in terms of RMR complexity in both the CC and DSM models. Our result also implies that any algorithm using reads, writes, and one-time test-and-set objects can be simulated by an algorithm using reads and writes with only a constant blowup of the RMR complexity; proving this is easy in the CC model but presents subtle challenges in the DSM model, as we explain later. Anderson, Herman, and Kim raise the question of whether conditional primitives such as test-and-set and compare-and-swap can be used, along with reads and writes, to solve mutual exclusion with better worst-case RMR complexity than is possible using reads and writes only [Distributed Computing, 16 (2003), pp. 75–110]. We provide a negative answer to this question in the case of implementing one-time test-and-set.