Composable many-core systems enable the independent development and analysis of applications which will be executed on a shared platform where the mix of concurrently executed applications may change dynamically at run time. For each individual application, an off-line Design Space Exploration (DSE) is performed to compute several mapping alternatives on the platform, offering Pareto-optimal trade-offs in terms of real-time guarantees, resource usage, etc. At run time, one mapping is then chosen to launch the application on demand. In this context, to enable an independent analysis of each individual application at design time, so-called inter-application isolation schemes are applied which specify temporal or spatial isolation policies between applications. S.o.t.a. composable many-core systems are developed based on a fixed isolation scheme that is exclusively applied to every resource in every mapping of every application and use a timing analysis tailored to that isolation scheme to derive timing guarantees for each mapping. A fixed isolation scheme, however, heavily restricts the explored space of solutions and can, therefore, lead to suboptimality. Lifting this restriction necessitates a timing analysis that is applicable to mappings with an arbitrary mix of isolation schemes on different resources. To address this issue, we present an isolation-aware timing analysis that unlike existing analyses can handle multiple isolation schemes in combination within one mapping and delivers safe yet tight timing bounds by identifying and excluding interference scenarios that can never happen under the given combination of isolation schemes. Based on the timing analysis, we present a DSE which explores the choices of isolation scheme per resource within each mapping. Experimental results demonstrate the advantage of the proposed approach over approaches based on a fixed isolation scheme.
Worst-case timing analysis of applications in multi- many-core systems has long been conducted in two steps: First, a context-independent analysis is applied to bound the WCET of each task in isolation, i.e., in absence of interferences. An overview of tools and methods for context-independent WCET analysis is provided in @cite_63 . Following the context-independent analysis, an interference analysis is performed to bound the additional latencies that may be imposed on shared resources due to external interferences.
@cite_63
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Establishing Worst Case Execution Times (WCET) using Measurement-Based Timing Analysis (MBTA) is only effective if we have reasonable confidence that we have fed the worst case execution trace into the analysis. Therefore for certification, the quality of these traces is of paramount importance. This paper aims to investigate how search algorithms can be used to automatically, and reliably, generate test cases so that appropriate execution traces are available to support MBTA. The work carried out in this paper uses a standard search algorithm and created a number of fitness functions to target the generation of 'good data'. The results are then input into a commercial measurement-based WCET analysis tool. The new fitness functions focus on achieving a combination of full branch coverage and a high number of loop counts, or partial path coverage, however are shown to achieve reliable approximations of the WCET particularly when combined with an MBTA tool. The code items used for the analysis included off the shelf benchmarks, as well as industrial safety-critical aircraft engine control software.