Fast complete memory consistency verification

The verification of an execution against memory consistency is known to be NP-hard. This paper proposes a novel fast memory consistency verification method by identifying a new natural partial order: time order. In multiprocessor systems with store atomicity, a time order restriction exists between two operations whose pending periods are disjoint: the former operation in time order must be observed by the latter operation. Based on the time order restriction, memory consistency verification is localized: for any operation, both inferring related orders and checking related cycles need to take into account only a bounded number of operations. Our method has been implemented in a memory consistency verification tool for CMP (Chip Multi Processor), named LCHECK. The time complexity of the algorithm in LCHECK is O(Cpp2n2) (where C is a constant, p is the number of processors and n is the number of operations) for soundly and completely checking, and O(p3n) for soundly but incompletely checking. LCHECK has been integrated into both pre and post silicon verification platforms of the Godson-3 microprocessor, and many bugs of memory consistency and cache coherence were found with the help of LCHECK.

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