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Institute for Computing Systems Architecture

Computer Systems Colloquium

"Parallel Techniques For Large-Scale Performance Analysis"

William Knottenbelt, Department of Computing, Imperial College

3.30 pm, Thursday 2 December

Room 2511, James Clerk Maxwell Building

Abstract

Stochastic performance models provide a formal way of capturing and analysing the complex dynamic behaviour of concurrent systems. Such models can be specified by several high-level formalisms, including Stochastic Petri nets, Queueing networks and Stochastic Process Algebras. Traditionally, performance statistics for these models are derived by generating and then solving a Markov chain corresponding to the model's behaviour at the state transition level. However, workstation memory and compute power are frequently overwhelmed by the sheer number and size of the states in the Markov chain.

This talk presents two parallel and distributed techniques which significantly increase the size of the models that can be analysed using Markov modelling. The techniques address both major phases of the analysis, i.e. construction of the Markov chain from a high-level model (state space generation) and solution of the Markov chain to determine its equilibrium distribution (steady state solution). The methods attack both the space and time requirements of Markov modelling. Space requirements are reduced through the use of probabilistic and disk-based storage schemes. Time requirements are reduced by exploiting the compute power provided by a distributed memory parallel computer or a network of workstations. Neither method places any restrictions on the type of model that can be analysed.

Both techniques have been implemented in C++ on a 16-node Fujitsu AP3000 distributed memory parallel computer, together with other tools required to build a complete parallel performance analysis pipeline. Results show that the methods are capable of analysing very large models, while delivering good speedups and exhibiting good scalability.


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