Efficient sequential consistency using conditional fences
Changhui Lin, Vijay Nagarajan, Rajiv Gupta · 2010
Among the various memory consistency models, the sequential consistency (SC) model, in which memory operations appear to take place in the order specified by the program, is the most intuitive and enables programmers to reason about their parallel programs the best. Nevertheless, processor designers often choose to support relaxed memory consistency models because the weaker ordering constraints imposed by such models allow for more instructions to be reordered and enable higher performance. Programs running on machines supporting weaker consistency models, can be transformed into ones in which SC is enforced. The compiler does this by computing a minimal set of memory access pairs whose ordering automatically guarantees SC. To ensure that these memory access pairs are not reordered, memory fences are inserted. Unfortunately, insertion of such memory fences can significantly slowdown the program.