MIT Department of Electrical Engineering & Computer Science

E E C S

Home-based Shared Virtual Memory

Liviu Iftode
Princeton University

Tuesday, April 29, 1997
3:00 PM (2:45 refreshments)
Room NE43-518
EECS Special Seminar

Abstract

A shared address space (shared memory) is an attractive programming model for parallel computing because of its simplicity. Hardware-coherent distributed shared memory delivers good performance but incurs a high engineering cost. As the range of parallel applications broadens, demand for shared memory that is not only efficient but also inexpensive is increasing. Shared virtual memory (SVM) is a software technique that provides a coherent shared address space on a network of computers using the operating system's virtual memory mechanism. The SVM implementations with the best performance to date use complex Lazy Release Consistency (LRC) protocols which deliver acceptable performance only on small-scale machines.

In this talk I will discuss how shared virtual memory can be substantially improved by a combination of architectural support, efficient protocols, and further relaxation of the memory consistency model. First, I introduce the AURC (Automatic Update Release Consistency) protocol which uses simple hardware support called automatic update and present preliminary results on SHRIMP, a PC-based multicomputer built at Princeton. Second, I will describe a simple and efficient way to implement Lazy-Release Consistency using a home-based protocol inspired by AURC. Evaluation on a 64-node Intel Paragon shows that home-based LRC greatly improves the scalability of SVM by reducing communication traffic and memory consumption. Finally, I will present a new consistency model called Scope Consistency which can reduce false sharing in home-based protocols. Scope consistency exploits the association of shared data and synchronization but does this implicitly and therefore with less programming complexity than Entry Consistency, a model with similar goals.

URL of this page: http://www-eecs.mit.edu/AY96-97/events/44.html
Created: Apr 21, 1997 | Modified: Jun 24, 1997
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