Linear Time Memory Consistency Verification

Abstract

Verifying the execution of a parallel program against a given memory consistency model (memory consistency verification) is a crucial problem in the functional validation of Chip Multiprocessor (CMP). In the absence of additional information, the above problem is known to be NP-hard. By adopting the pending period information, this paper proposes the first linear-time software-based approach to memory consistency verification. Our approach relies on a novel technique called reusable cycle checking, which reuses the previous order information when repeatedly checking cycle at different frontiers. In the context of pending period information, this technique significantly reduces the overall computational costs required by cycle checking, enabling linear-time (in the number of memory operations) memory consistency verification for any given multicore system with a constant number of processors. From a practical perspective, an industrial memory consistency verification tool, named XCHECK, has been developed based on our approach. XCHECK is capable of working with neither test program constraint nor dedicated hardware support in postsilicon verifications of many multiprocessor systems. Experimental results show that XCHECK is 3-10 times faster than a state-of-art software-based approach. XCHECK has been integrated into the verification platforms for an industrial multicore processor Godson-3B, and found several bugs of the design.