Applications of SRPT Scheduling with Inaccurate Information

1. Applications of SRPT Scheduling with Inaccurate Information Dong Lu, Peter A. Dinda, Yi Qiao, Huanyuan Sheng*, Fabian E. Bustamante Department of Computer Science *Department of IEMS Northwestern University, U.S.A Overview Although Shortest Remaining Processing Time (SRPT) scheduling was proven to yield minimum response time over 40 years ago, its application in real systems has been rare partly due to the lack of its key parameter - accurate job size information. Our work focuses on the performance of size-based scheduling policies with inaccurate information. We have found that performance depends critically on the accuracy of the job size estimator. • Web server scheduling • Is file size a good estimator of a job’s service time? NOT Really (R  0.14) • P2P server side scheduling • Prediction Module and its interaction with scheduler. PS: Processor sharing SRPT: Ideal SRPT FSP: Ideal Fair Sojourn Protocol SRPT-E: SRPT with estimated job sizes FSP-E: FSP with estimated job sizes • SRPT with even a simple estimator dramatically increases performance.  With our best estimator, the performance is further improved. • Domain-based estimator: much more accurate prediction of the service timeat low overhead. FCFS: First Come First Serve PS: Processor Sharing SRPT-CS: SRPT with requested data chunk sizes SRPT-SS: SRPT with served data chunk sizes SRPT: Ideal SRPT SRPT and FSP outperform PS in both mean response time and slowdown given a reasonably good job size estimator. Please see our paper “Size-based Scheduling Policies with Inaccurate Scheduling Information” in proceedings of MASCOTS ‘04 for details on the performance of SRPT and FSP with inaccurate information. Please see our Tech Report NWU-CS-03-15 “Effects and Implications of File Size/Service Time Correlation on Web Server Scheduling Policies” for details. Please see our paper “Looking at the Server-Side of Peer-to-Peer Systems” in LCR ‘04 for details.