Analyzing Program Transitions to Compute Benefit of Tolerating Consistency Violation Faults

Synchronization is the Achilles heel of concurrent programs. Synchronization requirement is often used to ensure that the execution of the concurrent program can be serialized. Without synchronization requirement, a program suffers from consistency violations. Recently, it was shown that if programs are designed to tolerate such consistency violation faults (cvf s) then one can obtain substantial performance gain. Previous efforts to analyze the effect of cvf-tolerance are limited to run-time analysis of the program to determine if tolerating cvf s can improve the performance. Such run-time analysis is very expensive and provides limited insight. In this work, we consider the question, 'Can analyzing program transitions predict the benefit of cvf-tolerance?' We find that the answer to this question is affirmative. Specifically, we analyze program transitions to evaluate the cost of a cvf and demonstrate that it can be used to predict the benefit of cvf-tolerance. We also find that when faced with a large state space, partial analysis of the state space (via sampling) also provides the required information to predict the benefit of cvf-tolerance. Furthermore, we observe that the cvf-cost distribution is exponential in nature, i.e., the probability that a cvf has a cost of c is A.B-c, where A and B are constants, i.e., most cvf s cause no/low perturbation whereas a small number of cvf s cause a large perturbation. This opens up new avenues to evaluate the benefit of cvf-tolerance.