Scheduling Multithreaded Computations by Work Stealing

This paper studies the problem of efficiently scheduling fully strict (i. e. , well-structured) multithreaded computations on parallel computers. A popular and practical method of scheduling this kind of dynamic MIMD-style computation is "work stealing, " in which processors needing work steal computational threads from other processors. In this paper, we give the first provably good work-stealing scheduler for multithreaded computations with dependencies. Specifically, our analysis shows that the expected time T/sub P/ to execute a fully strict computation on P processors using our work-stealing scheduler is T/sub P/=O(T/sub 1//P+T/sub /spl infin//), where T/sub 1/ is the minimum serial execution time of the multithreaded computation and T/sub /spl infin// is the minimum execution time with an infinite number of processors. Moreover, the space S/sub P/ required by the execution satisfies S/sub P//spl les/S/sub 1/P. We also show that the expected total communication of the algorithm is at most O(T/sub /spl infin//S/sub max/P), where S/sub max/ is the size of the largest activation record of any thread, thereby justifying the folk wisdom that work-stealing schedulers are more communication efficient than their work-sharing counterparts. All three of these bounds are existentially optimal to within a constant factor. >

Authors

• Robert D. Blumofe

Keywords

• Processor scheduling
• Yarn
• Concurrent computing
• Scheduling algorithm
• Algorithm design and analysis
• Laboratories
• Computer science
• Dynamic scheduling
• Load management
• Data structures
• Work-stealing
• Parallelization
• Constant Factor
• Total Communication
• Time Step
• Random Variables
• Subtree
• Communication Cost
• Critical Task
• Total Delay
• Execution Steps
• Execution Time Of Algorithm
• Important Lemmas