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
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LCE12: big.LITTLE Mini-Summit (session two) Blue Sky
- 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. 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. 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. 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. 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. 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. 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. 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. Vincent Guittot Linaro Power Management Working Group Reference ● [1] : big.LITTLE MP Scheduler/OSPM update on TC2
- 10. Vincent Guittot Linaro Power Management Working Group Thank you