Scope-Aware Useful Cache Block Analysis for Data Cache Related Preemption Delay

Static timing analysis is crucial for design of realtime systems. While the worst-case execution time of a task is typically computed or measured in a single task environment, the presence of caches imposes additional cache related preemption delay (CRPD) cost to the lower priority tasks in a preemptive multi-tasking system. In this work, we show that existing instruction CRPD analysis techniques cannot be straightforwardly extended for safe and precise data CRPD analysis. In order to capture the dynamic behavior of the data memory references, we introduce the notion of temporal scopes into the abstract cache state (ACS) to capture the data memory blocks that must or may reside in the cache during certain time intervals of program execution. Based on the improved ACS representation, we present a temporal scope aware useful cache block (UCB) calculation for safe and tight estimation of the data CRPD cost. Experimental results show that the proposed technique leads to substantially tighter CRPD estimation, and is applicable to programs with complex data reference patterns.