Cache Partitioning Options for Compositional Multimedia Applications

Abstract

The use of conventional probabilistic cache models in embedded multimedia systems is restricted because the tasks flush each others data out of the cache in an unpredictable manner making the system not compositional. In this way the overall performance is difficult to predict and the integration of new tasks expensive. In a multiprocessor platform the unified levels of cache shared between processors are causing the largest task conflicts. Our proposal is to introduce a compositionality property to the system such that the overall performance can be easily computed if the components’ performance in known. This property is obtained by means of assigning each task their exclusive part of the unified level of cache shared between processors. This article also presents the results of the effect on performance (measured in number of cache misses) of two types of cache partitioning, namely set based and associativity based partitioning, for the case of multimedia applications. Our experiments indicate that when applied to a multiprocessor with memory hierarchy the set based partitioning performs always better that the associativity based partitioning. Moreover set based partitioning typically results in performance gain of up to 35 % less misses, where the associativity based partitioning always results in large performance degradation of 17 % to 150 % more misses, when compared with the shared cache case. I