Predictable transactional memory architecture for hierarchical mixed-criticality systems

A transactional memory simplifies the concurrency management in multicore systems by permitting sets of load and store instructions to be executed in an atomic way. The correct results for concurrent transactions and the execution time strongly depend on the coherency potentials, rollback capabilities and strategies of the transactional memory. A transactional memory can be implemented as a Hardware Transactional Memory (HTM), as a Software Transactional Memory (STM), or as a hybrid combination of both called Hybrid Transactional Memory (HyTM). STM is the most common implementation of the transactional memory models, which is slower but simpler and more flexible than hardware transactional memories. HyTM is an approach that combines both STM and HTM by using architectural support to accelerate particular algorithms of the STM or by allowing hardware and software transactions to operate in the same address space. Mixed-Criticality Systems (MCSs) combine applications and subsystems at different levels of criticality on multicore systems. The development of such a safety-critical architecture requires a transactional memory architecture that guarantees the predictability, fault isolation and heterogeneity of concurrent safety-critical subsystems. Available transactional memory architectures do not support mixed-criticality at the chip level. Additionally, existing memory solutions spanning from multi-core chips to the cluster level are missing. A hierarchical transactional memory protocol is required to provide hierarchical support at all levels of the system architecture. In this dissertation, two transactional memory architectures are proposed, namely a transactional memory for chip level architectures and a hierarchical transactional memory architecture for both multi-core chips and the cluster level. In case of the chip-level transactional memory architecture, the predictability of the memory operations is guaranteed based on a global time base and the interarrival times of transactions. Different roll-back strategies with selective committing/aborting of requests are introduced based on the criticality of the components. This requires additional functionalities of the transactional memory such as temporal and spatial partitioning. The hierarchical solution extends the previously mentioned properties and services to a hierarchical transactional memory protocol that guarantees the requirements for distributed