Software—Practice & Experience
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Most software DSMs use the interrupt mechanism for asynchronous message arrival notification. Interrupt, however, is expensive and may not be available in user-level communication protocols. This paper studies the performance of software DSMs using threads instead of interrupt for communication. We implement three thread communication methods in the JIAJIA software DSM. The first method separates a communication thread from the main thread, the second one divides the communication thread into a sending thread and a receiving thread, and the third method further splits a serving thread from the receiving thread. The effect of the thread communication methods is evaluated in a PC cluster and a cluster of PowerPC workstations with some well-accepted benchmarks. Evaluation results show that the performance of thread communication is slightly worse than that of interrupt communication when there is only one processor to run a process, but is better than that of interrupt communication when there are more than one processors in a node to run a process. The thread communication method with one sending thread and one receiving thread achieves the best performance inthethree thread communication methods. Besides, the effect of the thread communication is also related to the operating system. Analysis of the evaluation results reveals that the waiting time constitutes the major overhead of the execution, and the dominant factor that in uence waiting time is neither the interrupt overhead nor the thread switching overhead but the responsiveness of requests (i.e., whether requests can be processed and replied promptly).