Thermally Composable Hybrid Application Mapping for Real-Time Applications in Heterogeneous Many-Core Systems

Modern embedded many-core systems host, among others, real-time applications which must be dynamically launched at run time. To this end, Hybrid Application Mapping (HAM) methodologies combine design-time analysis with runtime mapping techniques to enable dynamic application mapping with performance guarantees, e.g., w.r.t. real-time constraints. They rely on composability to derive the required performance guarantees in an isolated analysis of individual applications at design time. The ongoing process technology downsizing, however, has given rise to an increased on-chip temperature, so that the thermal integrity of the platform must be monitored and enforced at run time by means of Dynamic Thermal Management (DTM) techniques which use countermeasures e.g. DVFS and power gating. This, however, violates composability, as the thermally unsafe behavior of one application may trigger DTM countermeasures that affect other applications running in the thermally affected region which, in turn, may lead to the violation of their real-time constraints. As a remedy, this paper proposes, for the first time, a thermally composable HAM methodology that enforces thermal safety proactively at the launch time of applications and, thereby, prevents DTM interferences which react to thermal violations. To that end, we present (a) a novel thermal-safety analysis that can be integrated into the design-time analysis of HAM and (b) a set of thermal-safety admission checks that can be used at run time when launching an application. By establishing thermal composability among running applications, the proposed HAM approach enables providing thermally safe real-time guarantees for dynamically mapped applications in many-core systems. Experimental results for a variety of hard real-time applications on multiple heterogeneous many-core architectures demonstrate the efficiency and effectiveness of the proposed methodology.