Using a Vector-Based Approach Using a Vector-Based Approach For Modeling Performance of For Modeling Performance of Distributed SystemsDistributed Systems

Alexandra Fedorova, Margo Seltzer

Harvard University

Problem Domain: Eliminating Problem Domain: Eliminating Performance BottlenecksPerformance Bottlenecks

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?

Eliminating Bottlenecks By Eliminating Bottlenecks By Reconfiguring Hardware Reconfiguring Hardware

Expensive to try outExpensive to try out Difficult to answer “what if” questionsDifficult to answer “what if” questions Difficult to simulateDifficult to simulate

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Vector-based ModelingVector-based Modeling

Successfully used to model performance of Successfully used to model performance of single-threaded applications on stand-alone single-threaded applications on stand-alone systemssystems

Attractive for its elegance and simplicityAttractive for its elegance and simplicity

Can we apply it to distributed Can we apply it to distributed systems?systems?

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Vector-based modelingVector-based modelingsy

stem

vec

tor workload vector

x= Performance

estimateC(op4)

C(op3)

C(op2)

C(op1)

C(op0) N(op4)N(op3)N(op2)N(op1)N(op0)

C(opi) – cost of operation i on this system

N(opi) – number of operations of type i performed by this workload

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The Questions:The Questions:

Can it be applied to distributed systems Can it be applied to distributed systems while retaining the simplicity? while retaining the simplicity? When can it be applied and what are the When can it be applied and what are the

constraints?constraints? Can it be used to cut simulation time?Can it be used to cut simulation time? What changes are necessary in order to What changes are necessary in order to

make it work in this domain?make it work in this domain?

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Horizontal Composition of VectorsHorizontal Composition of Vectors

AA

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BBWorkloadvector A

Systemvector B

A’A’

Workloadvector A

xx

Vertical Composition of VectorsVertical Composition of Vectors

AA

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BBWorkloadvector A

Systemvector B

CCWorkloadvector B

Systemvector C