29-10-2010, 08:00 AM
APPLICATION LEVEL POWER MANAGEMENT
Presented by:-
Neenu V S
Applied Electronics
Colege Of Engineering, Trivandrum
2007-11 batch
APPLICATION LEVEL POWER MANAGEMENT
An approach for reducing power or switching the system to low power state when inactive.
It is applicable in cell phone, mp3 player, portable media player, laptops.
WHY POWER MANAGEMENT IMPORTANT IN MOBILE PROCESSORS??
Reduce overall energy consumption
Prolong battery life for portable and embedded systems
Reduce cooling requirements
Reduce noise.
Reduce operating costs for energy and cooling.
APPLICATION LEVEL POWER MANAGEMENT UNIT
A microcontroller that governs power functions of digital platforms.
This microchip has many similar components to the average computer, including firmware and software, memory, a CPU, input/output functions, timers , as well as analog to digital converters .
Remain active even when the computer is completely shut down, powered by the backup battery.
FUNCTIONS OF PMU
Monitoring power connections and battery charges
Charging batteries when necessary
Controlling power to other integrated circuits
Shutting down unnecessary system components when they are left idle
Controlling sleep and power functions (on and off)
Managing the interface for built in keypad and trackpads on portable computers
Regulating the real-time clock (RTC)
LIMITATIONS
Failure to turn on
Failure to restore from sleep mode
Failure to recognize connected devices (FireWire, USB, etc.)
POWER MANAGEMENT KEYS
Power key
Used both to power on and to power off the computer.
Sleep key
Used to put the computer to sleep, when it uses significantly lower power than when it is active, but can be woken quickly.
Wake key
Wakes the system from standby.
APPLICATION LEVEL POWER MANAGEMENT TECHNIQUES
Static techniques
=>include different low-power modes, on-demand gating of clocks and power domains etc.
Dynamic techniques
=> is to dynamically scale the CPU work frequency and voltage.
DYNAMIC POWER MANAGEMENT FOR PROCESSORS
Dynamic voltage and frequency scaling (DVFS)
=> clock rates and voltages are lowered in software depending on the performance required by the application.
Eg: Advanced RISC machine (ARM)
Digital signal processor (DSP)
Adaptive voltage scaling (AVS)
=>based on variations that come up during chip manufacturing as well as during a device's operational lifetime
Contd….
Dynamic power switching (DPS)
=>determines when a device has completed its current computational tasks and, if it's not needed at the moment, then puts the device into a low power state
DVFS TECHNOLOGY
A CASE STUDY:-
Chameleon: Application-
Level Power Management
CHAMELEON
The chamaleon project successfully demonstrates the benefits of:-
1. Application level networking,
2. Application-level memory management,
3. Application-level file systems, and CPU scheduling
4. Application level power management.
CONTRIBUTIONS
Performance.
Our approach enables each application to make local power management decisions based on its processor demand and processor availability.
Flexibility.
Such an approach enables each application to implement a power management policy that closely matches its energy and performance requirements.
Contd…
Generality.
Our approach is general and do not make specific assumptions about nature of applications.
Modest implementation costs.
The user-level power management policies can be implemented at modest cost.
CHAMELEON ARCHITECTURE
KEY COMPONENTS
Chamaleon consists of 3 key components..
1. An OS interface :- that enables applications to query the kernel for resource usage statistics and to convey their desired power settings to the kernel.
2. A modified CPU scheduler:-that support per- process CPU power settings and application isolation
3. A speed adapter:- that maps application- specified power settings to the nearest CPU speed actually supported by the hardware
KEY STEPS OF A USER LEVEL POWER MANAGEMENT
Estimate processor demand:- a combination
of application-domain knowledge and past CPU usage statistics is used to estimate processor demand in the near future.
Estimate processor availability:- the amount of CPU time that will be available to the application in the presence of other applications is estimated.
Determine processor speed setting:- chooses an speed setting that attempts to “match” the processor demand to the processor availability
APPLICATIONS
Moving Picture Experts Group Video Decoder Tool(soft real-time application)
Videoconferencing Tool(soft real-time application)
Word Processor(interactive best effort application)
Web Browser( event-driven interactive application)
CONCLUSION
Application level power management is a new approach for power management in mobile processors.
Chameleon can extract up to 50 percent of savings when compared to the recently proposed OS-based DVFS techniques
Chameleon imposes negligible overheads and is very effective at scheduling concurrent applications with diverse energy needs.
Our results demonstrate the feasibility and benefits of power management at the application level
References
AMD PowerNow! Technology with optimized power management". AMD.
Desktop and Portable Systems: Second Edition" Edited by Owen W. Linzmayer
K. Flautner, S. Reinhardt, and T. Mudge, “Automatic Performance
Setting for Dynamic Voltage Scaling,” Proc. ACM MobiCom ’01,pp. 260-271, July 2001.
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