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Power Efficient Computing

Power Efficient Computing. Jason Florack Xiao Xiao Liu Jeremy Winters. Introduction. What is “power efficient computing?” A definition: "A power efficient system consumes the minimum amount of energy required to perform any task." It’s an issue of optimization. Introduction (cont’d).

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Power Efficient Computing

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  1. Power Efficient Computing Jason Florack Xiao Xiao Liu Jeremy Winters

  2. Introduction • What is “power efficient computing?” • A definition: "A power efficient system consumes the minimum amount of energy required to perform any task." • It’s an issue of optimization

  3. Introduction (cont’d) • Trend in energy efficiency: Koomey’s law • Published in a 2011 research paper • Mirrors Moore’s Law • Jonathan Koomey, a Consulting Professor at Stanford, found that the number of computations per joule of energy dissipated has been doubling every 1.57 years since the 1950s

  4. Introduction (cont’d) • Why do we care about power efficiency? • Rise of mobile computing (laptops, smartphones, tablets) • Improvements in batteries vs. processors • Mobile computers must be small and light • Total energy consumption is dramatically increasing, meaning: • Cost of total energy expended is rising • Pollution caused by computing is increasing

  5. Introduction (cont’d) • So… how do we do accomplish “Power Efficient Computing?” • This is the question we will address in today’s talk.

  6. Overview • Advanced Configuration and Power Interface [ACPI] • Aspects of a power-efficient system • 3-D Transistors • Conclusion • Q & A

  7. Advanced Configuration and Power Interface (ACPI)

  8. Advanced Configuration and Power Interface (ACPI) • ACPI is an open standard describing how computer components work together to manage system hardware • One goal of ACPI is to consolidate and improve upon old power and configuration standards for hardware devices • Examples: Advanced Power Management (APM), Plug n Play BIOS, etc.

  9. ACPI (cont’d) • First published in 1996 • Originally developed by Intel, Microsoft, and Toshiba; later joined by HP and Phoenix • Latest version is “Revision 5.0” (12/2011) • All major OS’s, including Windows, FreeBSD, HP-UX, Linux, and PC versions of SunOS have at least some support for ACPI

  10. ACPI (cont’d) • ACPI defines platform-independent interfaces for hardware discovery, configuration, power management, and monitoring • Unlike previous standards, ACPI activities are initiated at the OS level rather than the firmware level • OS-directed Power Management (OSPM) systems can activate ACPI

  11. ACPI (cont’d) • This enables more sophisticated and flexible approaches towards power management • Example #1: OS can direct a CPU to turn itself off when idle to conserve energy, and then quickly return to a working state when needed • Example #2: ACPI will enable manufacturers to produce computers that automatically power up as soon as you touch the keyboard

  12. ACPI (cont’d) • In addition, having the OS handle power management (rather than the devices themselves) is advantageous because the OS’s stability and reliability is no longer dependent on the quality of the device firmware

  13. ACPI (cont’d) • ACPI Software Components • Policy Manager • Sets and monitors system policies • Allows policy changes via User Interface • Device Drivers • ACPI Subsystem • Interact with ACPI hardware source: www.acpi.info

  14. ACPI (cont’d) An ACPI System source: www.acpi.info

  15. ACPI (cont’d) • ACPI manages a system’s various “power states” • Global (G) and Sleep (S) states • G0 (S0): Working • G1 (S1, S2, S3, or S4): Sleeping • G2 (S5): Soft off • G3: Mechanical off • Legacy State • There are device (D), processor (C), and performance (P) states that are managed, too

  16. ACPI (cont’d) • ACPI Global States and Transitions source: www.acpi.info

  17. ACPI (cont’d) • Unfortunately, ACPI doesn’t solve everything • Windows “Insomnia”– PCs are not always able to properly implement power management strategies, for various reasons

  18. ACPI (cont’d) • Causes of Windows “Insomnia:” • Software (media players, anti-virus, screen savers) • Custom Device Drivers • Network activity and traffic • System configuration • Scheduled maintenance tasks • Faulty mice

  19. ACPI (cont’d) • Therefore, there is a significant market for third-party PC power management software • Examples: • IE NightWatchman • Data Synergy PowerMAN • Faronics Power Save • Verdiem SURVERYOR

  20. Energy-Efficient System

  21. Energy-EfficientSystems • A energy-efficient system has three principal aspects: • Power Model • Workload Constraints and Performance Assessment • Energy Optimizer

  22. Power Model • In order to manage the system's hardware for energy efficiency, the system must know the specific power details of the physical devices under its control.  • The per-state power consumption or power range • State-transition latency • State-change energy

  23. Performance Assessment • Goal: to limit the amount of active hardware and reduce its performance so as to minimize energy consumption. - Observe - Prediction - application-level

  24. EnergyOptimization • A dynamic process of adjusting the hardware's performance and availability • The operating system can make such decisions in two ways: • Heuristic Methods • low utilization: downward; high utilization: upward. • Constraints-based Optimization

  25. Processors • Careless activation of hardware when there is no useful work to be done must be eliminated. • Keep hardware quiescent until needed. • Dynamic tick: The "tickless" kernel project in Linux

  26. Storage, memory and I/O Storage • At least two immediate steps - direct attention to energy use in traditional disk-based storage • large inexpensive flash memory devices. Memory • The design of a future-looking virtual memory system that is energy aware and able to adjust physical memory resources while running is an open problem I/O • Unfortunately, little attention has been given

  27. Application Software and Algorithms • The most strategic aspect of energy-efficient computing will be the evolution of application software to facilitate system-wide energy efficiency. 

  28. 3-D Transistors

  29. Transistors • What is a transistor? • A semiconductor device used to amplify and switch electrical signals and power • Invented by researchers at Bell Laboratories • How does it work?

  30. 2-D Transistor Image From Intel Corporation

  31. Improvements in the Third Dimension • Increased current flow from source to drain • More efficient state switching

  32. 3-D Transistor Image From Intel Corporation

  33. 3-D Transistors • What are the benefits? • Lower current leakage • Increased current flow • n vs. _ • Lower voltage operation

  34. 3-D Transistors • 37 % performance increase at low voltages • 50% reduction in power consumption

  35. Conclusion

  36. Conclusion • We’ve shown a few different ways that power-efficient computing can be achieved • Employing ACPI and/or third-party software • Making the entire system more power-efficient • Using 3-D transistors in the processor • There are certainly other ways too

  37. Conclusion (cont’d) • Bottom line: Power efficient computing is important now and in the future, because: • Rise of mobile computing brings challenges not seen in the current desktop computing environment • Processing improvements and demands • Battery technology • Big Data

  38. Conclusion (cont’d) • Increased use of data centers and cloud computing means more energy expended • …and more pollution • Due to the increasingly-ubiquitous presence of computers and mobile devices - even in less developed areas of the word - energy usage will continue to increase if not checked by new strategies

  39. Questions?

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