Understanding the Performance of DSM Applications

Carnival is a performance measurement and analysis tool that assists users in understanding the performance of DSM applications and protocols Using traces of program executions Carnival presents performance data as a hierarchy of execution pro les During analysis Carnival automates the inference process that relates performance phe nomena to speci c causes in the source code or DSM protocol using techniques that focus on the two most important sources of overhead in DSM systems waiting time analysis identi es the causes of synchroniza tion overhead and produces an explanation for each source of waiting time in the program communication analysis identi es the sequence of requests that result in invalidations and produces an explanation for each source of communication We describe these techniques and their implementation in TreadMarks and show how to use waiting time anal ysis and communication analysis to improve the running time of two programs from the SPLASH application suite when executed on DEC Alphas connected by a DEC Memory Channel network