applications of srpt scheduling with inaccurate information

Applications of SRPT Scheduling with Inaccurate Information Dong Lu, Peter A. Dinda, Yi Qiao, Huanyuan Sheng*, Fabian E. Bustamante P2P server side scheduling • Prediction Module and its interaction with scheduler. Web server scheduling • Is file size a good estimator of a job’s service time? NOT Really (R 0.14) 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. 0.1 1 10 100 1000 0 0.2 0.4 0.6 0.8 1 Correlation CoefficientR M e a n Respo PS SRPT SRPT-E FSP FSP-E 1 10 100 1000 0 10 20 30 40 50 60 70 80 90 100 Job Size Percentile (R=0.7322) Slow do PS SRPT SRPT-E FSP FSP-E 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 Bits used to define a dom ain R (c o rrelatio n co fficien t b etw een actua tim e an d estim ated s e rv ic e tim e) • Domain-based estimator: much more accurate prediction of the service time at low overhead. • SRPT with even a simple estimator dramatically increases performance. With our best estimator, the performance is further improved. 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. Department of Computer Science *Department of IEMS Northwestern University, U.S.A 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. 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 and FSP outperform PS in both mean response time and slowdown given a reasonably good job size estimator. 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

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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 - PowerPoint PPT Presentation

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Page 1: Applications of SRPT Scheduling with Inaccurate Information

Applications of SRPT Scheduling with Inaccurate InformationDong Lu, Peter A. Dinda, Yi Qiao, Huanyuan Sheng*, Fabian E. Bustamante

P2P server side scheduling• Prediction Module and its interaction with

scheduler.

Web server scheduling• Is file size a good estimator of a job’s service

time? NOT Really (R 0.14)

OverviewAlthough 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.

0.1

100

1000

0 0.2 0.4 0.6 0.8 1

Correlation Coefficient R

Mean R

esponse T

ime

PSSRPTSRPT-EFSPFSP-E

100

1000

0 10 20 30 40 50 60 70 80 90 100

Job Size Percentile (R=0.7322)

Slo

wdow

PSSRPTSRPT-EFSPFSP-E

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 2 4 6 8 10 12 14 1618 20 2224 26 2830 32Bits used to define a domain

R (

rrela

tio

n c

off

icie

betw

een

actu

al serv

ice

tim

e a

esti

mate

d s

erv

ice t

ime)

• Domain-based estimator: much more accurate prediction of the service time at low overhead.

• SRPT with even a simple estimator dramatically increases performance. With our best estimator, the performance is further improved.

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.

Department of Computer Science*Department of IEMS Northwestern University, U.S.A

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.

PS: Processor sharingSRPT: Ideal SRPTFSP: Ideal Fair Sojourn ProtocolSRPT-E: SRPT with estimated job sizesFSP-E: FSP with estimated job sizes

SRPT and FSP outperform PS in both mean response time and slowdown given a reasonably good job size estimator.

FCFS: First Come First ServePS: Processor SharingSRPT-CS: SRPT with requested data chunk sizesSRPT-SS: SRPT with served data chunk sizesSRPT: Ideal SRPT

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1 Size-Based Scheduling Policies with Inaccurate Scheduling Information Dong Lu *, Huanyuan Sheng +, Peter A. Dinda * * Prescience Lab, Dept. of Computer

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