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Multiprogramming Effects

Multiprogramming can cause parallel applications to behave unpredictably, changing the synchronization behavior in ways that are hard to understand. For example, several experiments indicated that the execution time of Cholesky factorization with a cyclic data distribution is more sensitive to multiprogramming than an implementation using a blocked data distribution. Although a cyclic implementation performs better in the absence of multiprogramming, it often performs worse in the presence of multiprogramming. Using waiting time analysis, we found that the cyclic implementation was more sensitive to multiprogramming because it depends on additional communication and synchronization to balance the load. On a multiprogrammed machine, the additional communication and synchronization create more opportunities for multiprogramming to context switch a process that must synchronize with another, which increases waiting time on another processor.



Wagner Meira
Thu Jan 9 14:27:55 EST 1997