A formal model of data access for multicore architectures with multilevel caches

Abstract

The performance of software running on parallel or distributed architectures can be severely affected by the location of data. In shared memory multicore architectures, data movement between caches and main memory is driven by data accesses from tasks executing in parallel on different cores and by a protocol to ensure cache coherence. This paper integrates cache coherence in a formal model of data access, to capture such data movement from an application perspective. We develop an executable model which captures cache coherent data movement between different cache levels and main memory, for software described by task-level data access patterns. The proposed model is generic in the number of cache levels and cores, and abstracts from the concrete communication medium. We show that the model guarantees expected correctness properties for cache coherence, in particular data consistency. This paper further presents a proof-of-concept implementation of the proposed model in rewriting logic, which allows different choices for the underlying hardware architecture of dynamically created parallel data access patterns to be specified and compared at the modelling level. • A formal, operational model of data access in multicore architectures with multilevel caches. • Correctness properties of the formal model, expressed as invariants over an arbitrary number of cores and caches. • A proof-of-concept implementation of the model to compare executions based on penalties, an abstract performance indicator.