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Double-sorted Scheduling in Process Cruise Control Environments

Double-sorted Scheduling in Process Cruise Control Environments
Subject:Power Management

Prof. Dr. Frank Bellosa, Dr. Andreas Weißel

Graduand:Sören Finster


Schedulers found in contemporary operating systems try to maximise the throughput and the responsiveness perceived by the user. In this thesis a scheduler policy is introduced which not only tries to fulfil those objectives but also takes the order of task execution into consideration. By keeping strict priority scheduling or by loosening priority restrictions this policy enables the system developer to define a criteria which then affects the order of the schedulers queue. This new scheduler policy is called Double-sorted Scheduling (DSS).

This work uses DSS to extend an existing policy called Process Cruise Control (PCC) which exploits information from embedded hardware monitors to adjust the CPUs core frequency at context switches to the optimal frequency of the next task. PCC allows energy savings of up to 22%. DSS additionally tries to eliminate unnecessary frequency adjustments by ordering tasks according to their optimal frequency.

DSS and PCC were implemented within the Linux kernel on the Intel XScale architecture. Evaluations show that the addition of DSS to the PCC environment results in less frequency adjustments. With this approach, not only the time, but also the power, lost due to unnecessary frequency adjustments is reduced.


  author = {Soeren Finster},
  title = {Double-sorted Scheduling in Process Cruise Control Environments},
  type = {Study Thesis},
  address = {System Architecture Group, University of Karlsruhe, Germany},
  month = nov # "~22",
  year = 2005,
  url = {http://i30www.ira.uka.de/teaching/theses/pasttheses/}