Obtaining optimal thresholds for processors with speed-scaling

Ronny J. Polansky, Samyukta Sethuraman, Natarajan Gautam

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


In this research we consider a processor that can operate at multiple speeds and suggest a strategy for optimal speed-scaling. While higher speeds improve latency, they also draw a lot of power. Thus we adopt a threshold-based policy that uses higher speeds under higher workload conditions, and vice versa. However, it is unclear how to select "optimal" thresholds. For that we use a stochastic fluid-flow model with varying processing speeds based on fluid level. First, given a set of thresholds, we develop an approach based on spectral expansion by modeling the evolution of the fluid queue as a semi-Markov process (SMP) and analyzing its performance. While there are techniques based on matrix-analytic methods and forward-backward decomposition, we show that they are not nearly as fast as the spectral-expansion SMP-based approach. Using the performance measures obtained from the SMP model, we suggest an algorithm for selecting the thresholds so that power consumption is minimized, while satisfying a quality-of-service constraint. We illustrate our results using a numerical example.

Original languageEnglish (US)
Pages (from-to)135-155
Number of pages21
JournalElectronic Notes in Theoretical Computer Science
StatePublished - Jan 5 2015
Externally publishedYes


  • Data center
  • Fluid model
  • Power management
  • Quality of service
  • Server speed-scaling
  • Spectral expansion

ASJC Scopus subject areas

  • Theoretical Computer Science
  • General Computer Science


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