Q2.12: Scheduler Inputs

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Resource: Q2.12
Name: Scheduler Inputs
Date: 01-06-2012
Speaker: Vincent Guittot

Published in: Technology
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Q2.12: Scheduler Inputs

  1. 1. Vincent Guittot Linaro Power Management Working Group Which inputs for the scheduler ? Vincent Guittot <vincent.guittot@linaro.org> Linaro Power Management Working Group
  2. 2. Vincent Guittot Linaro Power Management Working Group Which inputs for the scheduler ?  Accurate load tracking  Sharing clock  Sharing Idle state  Sharing cache  Thermal constraint  Keep it simple  Others
  3. 3. Vincent Guittot Linaro Power Management Working Group Accurate load  Per task load tracking patch-set – From Paul Turner – Differentiate short and long running tasks – Improve the task load migration  tick_sched monitors idle/run time – /proc/stat – cpufreq load monitoring  Unify load monitoring
  4. 4. Vincent Guittot Linaro Power Management Working Group CPU clock  Get the clock sharing topology – Which CPUs share the same clock – Helpful for power saving – cpufreq has got such information • cpus and cpus_related mask  Get current clock rate of a CPU – Useful for more accurate load tracking
  5. 5. Vincent Guittot Linaro Power Management Working Group CPU idle  Get the idle state sharing topology – Which CPUs shares their idle states level  Get the current idle state of a CPU – Improve both performance and powersaving  How many level is needed ? – Keep it as simple as a cpumask ● Coupled cpuidle provide such information – Make it more generic at cpuidle core level ?
  6. 6. Vincent Guittot Linaro Power Management Working Group Cache  Included in the share resources flag – Currently the MC level – Is it always true for ARM ?
  7. 7. Vincent Guittot Linaro Power Management Working Group Thermal  Thermal constraint on CPU – Reduce Max freq → reduce cpu_power – Depend of the time scale
  8. 8. Vincent Guittot Linaro Power Management Working Group Keep it simple  Scheduler performance is sensible – Avoid large X*Y matrix computation – Make it as simple a CPU mask manipulation
  9. 9. Vincent Guittot Linaro Power Management Working Group Other  Any other input ?
  10. 10. Vincent Guittot Linaro Power Management Working Group QUESTIONS ?
  11. 11. Vincent Guittot Linaro Power Management Working Group THANK YOU

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