Brief announcement: Persistent unfairness arising from cache residency imbalance

We describe a counter-intuitive performance phenomena relevant to concurrency research. On a modern multicore system with a shared last-level cache, a set of concurrently running identical threads that loop - each accessing the same quantity of distinct thread-private data - can suffer significant relative progress imbalance. If one thread, or a small subset of the threads, manages to transiently enjoy higher cache residency than the other threads, that thread will tend to iterate faster and keep more of its data resident, thus increasing the odds that it will continue to run faster. This emergent behavior tends to be stable over surprisingly long periods. Economic model+somethread(s)randomly become rich +zero-sum game: somebody else become poor+rich stay rich+persistentstratification +Inequality and inequity +http://en.wikipedia.org/wiki/Matthew-effect.