Allocation-phase aware thread scheduling policies to improve garbage collection performance

Past studies have shown that objects are created and then die in phases. Thus, one way to sustain good garbage collection efficiency is to have a large enough heap to allow many allocation phases to complete and most of the objects to die before invoking garbage collection. However, such an operating environment is hard to maintain in large multithreaded applications because most typical time-sharing schedulers are not allocation-phase cognizant; i.e., they often schedule threads in a way that prevents them from completing their allocation phases quickly. Thus, when garbage collection is invoked, most allocation phases have yet to be completed, resulting in poor collection efficiency. We introduce two new scheduling strategies, LARF (lower allocation rate first) and MQRR (memory-quantum round robin) designed to be allocation-phase aware by assigning higher execution priority to threads in computation-oriented phases. The simulation results show thatallthe reductions of the garbage collection time in a generational collector can range from 0%-27% when compare to a round robin scheduler. The reductions of the overall execution time and the average thread turnaround time range from -0.1%-3% and -0.1%-13%, respectively.