Integrated Device Scheduling and Processor Voltage Scaling for System-wide Energy Conservation
description
Transcript of Integrated Device Scheduling and Processor Voltage Scaling for System-wide Energy Conservation
Integrated Device Scheduling and Processor Voltage Scaling for System-wide Energy Conservation
Hui Cheng, Steve GoddardComputer Science and Engineering
Univ. of Nebraska-Lincoln
Background Power management
Dynamic power management Task scheduling
EDF+SRP Preemptive scheduling
I/O device scheduling Inter-task device scheduling
Periodic task definition
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Motivation Previous research has focused on:
Energy conservation for the processor Much work has been done on DVS Ignores energy conservation of I/O devices
Energy conservation for I/O devices Most techniques cannot be applied to hard real-time
systems Ignores CPU energy conservation
System-wide energy conservation is needed! How to integrate DVS and DPM?
Device power model
Busy
Active
Idle
High transition overhead
Serving I/O reqs
Ready to
serve
Proportional to the job execution time
High power state
Low power state
Current I/O-based DPMs
System energy
I/O device energy
Processorenergy
Non-preemptive task scheduling
LEDES
MUSCLES
EDS
MDO
Preemptive task scheduling
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Offline scheduling
Online scheduling
ASD Aggressive shut down
Include the transition delay in the WCET Sufficient schedulability condition
Problems: Reduces schedulability for some systems Does not consider the energy penalty
associated with power state transitions
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CEA-EDF vs. EASD
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10.35
0.4
0.45
0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
System utilization
Nor
mili
zed
Ene
rgy
Sav
ing
Mean energy saving under different system utilizations
CEA-EDFEASD
CPU power model Dynamic power consumption
Leakage power consumption
Total power consumption
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Optimal speed CPU speed is critical to achieve system-wide
energy conservation Lowest speed:
Good for saving the dynamic power consumption of CPUs
Highest speed: Good for the energy conservation of devices Good for reducing leakage energy consumption of
CPUs
Optimal speed: the speed to balance the energy consumption of all components.
Optimal speed (cont’d) Active device set
Containing all devices that are in the active state at current time.
Optimal speed Energy efficiency scale:
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Energy efficiency scale examples
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10.5
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2
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Normalized processor speed
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ExampleActive device set
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Opt speed 0.4 0.6 0.9 …
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CPU speed
SYS-EDF The DVS scheduling is based on the
DS algorithm proposed in [1]. High speed
Low speed
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SYS-EDF (cont’d) Use CEA-EDF to schedule devices Keep track of the active device set and
compute/adjust the optimal speed. The processor speed is never set below
the optimal processor speed. Same techniques were used in [2][3]
Only scheduled at scheduling points
Evaluation
0-0.1 0.1-0.2 0.2-0.3 0.3-0.4 0.4-0.5 0.5-0.6 0.6-0.7 0.7-0.8 0.8-0.9 0.9-10
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
System utilization
Nor
mili
zed
Ene
rgy
Sav
ing
Mean energy saving under different system utilizations
CEA-EDFSYS-EDFDS+CEA-EDFDS
Conclusion and future work SYS-EDF = I/O based DPM+DVS+Opt speed Provide more energy savings with respect t
o: DVS-alone I/O based DPM alone The straightforward integration of DVS and DPM
Current and future work Consider the device transition delay in the com
putation of optimal speed. Consider the overhead of adjusting CPU voltage Extend to other task models
References [1] Zhang, F., Chanson, S., Processor Voltage Scheduling for Real-Ti
me Tasks with Non-Preemptible Sections. [2] Jejurikar, R., Pereira, C., Gupta, R., Leakage aware dynamic volta
ge scaling for real-time embedded systems. [3] Zhuo, J., Chakrabarti, C., System-Level Energy-Effcient Dynamic
Task Scheduling. [4] Swaminathan, V., Chakrabarty, K., and Iyengar, S.S., Dynamic I/O
Power Management for Hard Real-time Systems. [5] Swaminathan, V., and Chakrabarty, K., Pruning-based, Energy-o
ptimal, Deterministic I/O Device Scheduling for Hard Real-Time Systems.
Transition overhead
OFF
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2T
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1,2J
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2,1J
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Missed deadline
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ON
CEA-EDF vs. EASD (cont’d)
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
0.9
System utilization
Nor
mili
zed
Ene
rgy
Sav
ing
Mean energy saving under different system utilizations
CEA-EDFEASD