An effective selection policy for load balancing in software DSM

Load balance is an area of current research in software distributed shared memory (DSM) systems. When threads are dynamically migrated from heavily loaded nodes to lightly loaded nodes to achieve load balance, the communication cost of maintaining data consistency is increased if migration threads are carelessly selected. Program performance is degraded when loss from increased communication exceeds the benefit from load balancing. Therefore, load balancing requires careful choice of migration threads. This study addresses the problem with a novel selection policy called Reduce Internode Sharing Cost (RISC). The main characteristic of this thread selection policy is simultaneous consideration of both thread memory access types and global sharing. Experimental application of this policy to a DSM system called Cohesion shows that simultaneous consideration of memory access types and global sharing is necessary for thread selection. RISC can reduce 50% data-consistency communication of benchmark applications during execution of the load balance mechanism.