Worst-case execution time analysis for a Java processor

In this paper, we propose a solution for a worst-case execution time (WCET) analyzable Java system: a combination of a time predictable Java processor and a tool that performsWCET analysis at Java bytecode level. We present a Java processor, called JOP, designed for time-predictable execution of real-time tasks. The execution time of bytecodes, the instructions of the Java virtual machine, is known cycle accurately for JOP. Therefore, JOP simplifies the low-level WCET analysis. A method cache, which fills whole Java methods into the cache, simplifies cache analysis. TheWCET analysis tool is based on integer linear programming. The tool performs the low-level analysis at the bytecode level and integrates the method cache analysis. An integrated data-flow analysis performs receiver type analysis for dynamic method dispatches and loop bound analysis. Furthermore, a model checking approach to WCET analysis is presented where the method cache can be exactly simulated. The combination of the time-predictable Java processor and the WCET analysis tool is evaluated with standard WCET benchmarks and three real-time applications. The WCET friendly architecture of JOP and the integrated method cache analysis yield tight WCET bounds. Comparing the exact, but expensive, model checking based analysis of the method cache with the static approach demonstrates that the static approximation of the method cache is sufficiently tight for practical purposes.