Vincent Guittot
Linaro Power Management Working Group
Linaro Connect Q4'12
big.LITTLE mini-summit
Session 2 : Bluesky
What...
Vincent Guittot
Linaro Power Management Working Group
3 Topics
● Correlate scheduler with C-state & P-state
● Scale invari...
Vincent Guittot
Linaro Power Management Working Group
Correlate with C-state and P-state
● C-state can make the difference...
Vincent Guittot
Linaro Power Management Working Group
Correlation with C-state and P-state
● C-State can make the differen...
Vincent Guittot
Linaro Power Management Working Group
Correlate with C-state and P-state
● Scheduler can break cpufreq sta...
Vincent Guittot
Linaro Power Management Working Group
Scaling invariance
● Sysbench tests on TC2
● Linearity with P-State
...
Vincent Guittot
Linaro Power Management Working Group
Scaling invariance
Freq = x
Freq = 2x
Scale invariant load trackingW...
Vincent Guittot
Linaro Power Management Working Group
Differentiate user-space tasks
● Cgroup
● Cpuset
● Nice priority
● F...
Vincent Guittot
Linaro Power Management Working Group
Reference
● [1] : big.LITTLE MP Scheduler/OSPM update on TC2
Vincent Guittot
Linaro Power Management Working Group
Thank you
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LCE12: big.LITTLE Mini-Summit (session two) Blue Sky

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Resource: LCE12
Name: big.LITTLE Mini-Summit (session two) Blue Sky
Date: 01-11-2012
Speaker: Vincent Guittot

Published in: Technology
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LCE12: big.LITTLE Mini-Summit (session two) Blue Sky

  1. 1. Vincent Guittot Linaro Power Management Working Group Linaro Connect Q4'12 big.LITTLE mini-summit Session 2 : Bluesky What would the ideal power-aware kernel do?
  2. 2. Vincent Guittot Linaro Power Management Working Group 3 Topics ● Correlate scheduler with C-state & P-state ● Scale invariance of a load ● How to differentiate user-space tasks
  3. 3. Vincent Guittot Linaro Power Management Working Group Correlate with C-state and P-state ● C-state can make the difference ● The migration on a powered down cluster is costly 900µs off migrate and wake up task on CPU0 schedule task on CPU0 wake up
  4. 4. Vincent Guittot Linaro Power Management Working Group Correlation with C-state and P-state ● C-State can make the difference ● The migration on a shallow C-state is efficient off 76µs migrate & wake up task on CPU0 schedule task on CPU0 wfi
  5. 5. Vincent Guittot Linaro Power Management Working Group Correlate with C-state and P-state ● Scheduler can break cpufreq statistic ● Migration moves the load CPU0 CPU1 OnDemand CPU Load statistic
  6. 6. Vincent Guittot Linaro Power Management Working Group Scaling invariance ● Sysbench tests on TC2 ● Linearity with P-State ● CPU test results are linear ● Memory test results are not linear (8% better) ● Linearity between micro-architecture ● CPU test results : A15 ~ 2 x A7 ● Memory test results : A15 <= A7
  7. 7. Vincent Guittot Linaro Power Management Working Group Scaling invariance Freq = x Freq = 2x Scale invariant load trackingWall clock based load tracking Freq = 2x Freq = x Work achieved Load [1]
  8. 8. Vincent Guittot Linaro Power Management Working Group Differentiate user-space tasks ● Cgroup ● Cpuset ● Nice priority ● Foreground / Background ● Others … ● Qualify a task with resource reservation ● … like deadline scheduler
  9. 9. Vincent Guittot Linaro Power Management Working Group Reference ● [1] : big.LITTLE MP Scheduler/OSPM update on TC2
  10. 10. Vincent Guittot Linaro Power Management Working Group Thank you
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