document: Design and implementation of a feedback controller for slowdown differentiation on internet servers Proportional slowdown differentiation ( PSD ) aims to maintain slowdown ratios between different classes of clients according to their pre-specified differentiation parameters . In this paper , we design a feedback controller to allocate processing rate on Internet servers for PSD . In this approach , the processing rate of a class is adjusted by an integral feedback controller according to the difference between the target slowdown ratio and the achieved one . The initial rate class is estimated based on predicted workload using queueing theory . We implement the feedback controller in an Apache Web server . The experimental results under various environments demonstrate the controller 's effectiveness and robustness .
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