CAS-DSM: A Compiler Assisted Software Distributed Shared Memory\ud

Traditional software Distributed Shared Memory (DSM) systems rely on the virtual memory management mechanisms to detect accesses to shared memory locations and maintain their consistency. The resulting involvement of the OS(kernel) and the associated overhead which is significant, can be avoided by careful compile time analysis and code instrumentation. In this paper, we propose such a Compiler Assisted Software support approach (CAS-DSM). In the CAS-DSM implementation, the involvement of the OS kernel is avoided by instrumenting the application code at the source level. The overhead caused by the execution of the instrumented code is reduced through several aggressive compile time optimizations. Finally, we also address the issue of reducing certain overheads in polling-based implementation of receiving asynchronous messages. We used SUIF, a public domain compiler tool, to implement compiletime analysis, instrumentation and optimizations. We modified CVM, a publiclyavailable software DSM to support the instrumentation inserted by the compiler.Detailed performance evaluation of CAS-DSM is reported using a set ofSplash/Splash2 parallel application benchmarks on a distributed memory IBMSP-2 machine. CAS-DSM achieved moderate to good performance improvementsfor most of the applications compared to the original CVM implementation.Reducing the overheads in polling-based implementation improves the performance of CAS-DSM significantly resulting in an overall improvement of 12–52% over the original CVM implementation