Distributed Shared Memory Using Re ective Memory: The LAM System

In the past, acceptance of Distributed Shared Memory (DSM) systems suuered because of poor performance. Performance has primarily been limited by the availability of an interconnect media whose properties are similar to those required by a DSM system. In an eeort to compensate for inappropriate interfaces, sig-niicant research has been devoted to maximizing the utilization of the available interconnect. A class of interconnect media is available that begins to address the inhibitors to DSM performance. These interconnect media have one essential property; the interface is mapped into the address space of the process participating in the DSM system. This project focuses on the development of the LAM DSM system. LAM is a well-balanced hybrid DSM system implemented using Reeective Memory interconnect hardware with a software consistency policy and interface. A distinctive property of this system is that access time is directly proportional to the number of bytes accessed and unrelated to the size of the data structure being accessed. The system architecture, interface and results are described. Additionally, a case is made for the inherent advantage a memory-mapped interconnect has over an interconnect accessed through the operating system and network protocols.