DaemonGuard: Enabling O/S-Orchestrated Fine-Grained Software-Based Selective-Testing in Multi-/Many-Core Microprocessors

As technology scales deep into the sub-micron regime, transistors become less reliable. Future systems are widely predicted to suffer from considerable aging and wear-out effects. This ominous threat has urged system designers to develop effective run-time testing methodologies that can monitor and assess the system's health. In this work, we investigate the potential of online software-based functional testing at the granularity of individual microprocessor core components in multi-/many-core systems. While existing techniques monolithically test the entire core, our approach aims to reduce testing time by avoiding the over-testing of under-utilized units. To facilitate fine-grained testing, we introduce DaemonGuard, a framework that enables the real-time observation of individual sub-core modules and performs on-demand selective testing of only the modules that have recently been stressed. Moreover, we investigate the impact of the cache hierarchy on the testing process and we develop a cache-aware selective testing methodology that significantly expedites the execution of memory-intensive test programs. The monitoring and test-initiation process is orchestrated by a transparent, minimally-intrusive, and lightweight operating system process that observes the utilization of individual datapath components at run-time. We perform a series of experiments using a full-system, execution-driven simulation framework running a commodity operating system, real multi-threaded workloads, and test programs. Our results indicate that operating-system-assisted selective testing at the sub-core level leads to substantial savings in testing time and very low impact on system performance. Additionally, the cache-aware testing technique is shown to be very effective in exploiting the memory hierarchy to further minimize the testing time.