Provably Efficient Two-Level Adaptive Scheduling

Abstract

Multiprocessor scheduling in a shared multiprogramming environment can be structured in two levels, where a kernel-level job scheduler allots processors to jobs and a user-level thread scheduler maps the ready threads of a job onto the allotted processors. This paper presents two-level scheduling schemes for scheduling multithreaded jobs whose parallelism can change during execution. The AGDEQ algorithm uses dynamic-equipartioning (DEQ) as a job-scheduling policy and an adaptive greedy algorithm (A-Greedy) as the thread scheduler. The ASDEQ algorithm uses DEQ for job scheduling and an adaptive work-stealing algorithm (A-Steal) as the thread scheduler. AGDEQ is suitable for scheduling in centralized scheduling environments, and ASDEQ is suitable for more decentralized settings. Both two-level schedulers achieve O(1)-competitiveness with respect to makespan for any set of multithreaded jobs with arbitrary release time. They are also O(1)- competitive for any batched jobs with respect to mean response time. Moreover, because the length of the scheduling quantum can be adjusted to amortize the cost of context-switching during processor reallocation, our schedulers provide control over the scheduling overhead and ensure effective utilization of processors.