Evaluation of a Coherence Protocol for Eliminating Passive Sharing in Shared-Bus Multithreaded Multiprocessors

Single-chip multiprocessors and multiple-thread architectures are becoming an affordable solution for high-performance general-purpose workstations and servers. On these machines, the workload is typically constituted of both sequential and parallel applications. Shared-bus shared-memory multithreaded multiprocessor can be used to speed-up the execution of such workload. In this environment, the scheduler takes care of the load balancing by allocating a ready process on the first available processor, thus producing process migration. Process migration and the persistence of private data into different caches produce an undesired sharing, named passive sharing. The copies due to passive sharing produce useless coherence traffic on the bus and coping with such a problem may represent a challenging design problem for these machines. Many protocols use smart solutions to limit the overhead to maintain coherence among shared copies. None of these studies treats passive-sharing directly,