Compositional, dynamic cache management for embedded chip multiprocessors

This paper proposes a dynamic cache repartitioning technique that enhances compositionality on platforms executing media applications with multiple utilization scenarios. The repartitioning among scenarios requires a cache flush, thus two undesired effects may occur: (1) the execution of critical tasks may be disturbed and (2) a performance penalty is involved. To cope with these effects we propose a method which: (1) determines, at design time, the cache footprint of each task, such that it creates the premises for critical tasks safety, and reduces the amount of required flush, and (2) enforces these footprints and further decreases the flush penalty, at run-time. We implement our dynamic cache management strategy on a CAKE multiprocessor with 4 Trimedia cores. The experimental workload consists of 6 multimedia applications, each of which formed by multiple tasks belonging to an extended MediaBench suite. For the repartitioned cache we found on average that: (1) the relative variations of critical tasks execution time are less than 0.1%, regardless the scenario switching frequency, (2) for realistic scenario switching frequencies the inter-task cache interference is at most 4% , and (3) the off-chip memory traffic reduces with 60%, and the performance (in cycles per instructions) enhances with 10%, when compared with the shared cache.