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Every Joule is Precious Carla Schlatter Ellis Duke University

Explore the importance of reducing energy consumption in computing, including heat reduction, battery life extension, and environmental impact. Learn about hardware and software cooperation and supply-side strategies. Discover the impact of rethinking OS design and explore energy-aware applications. Get insights from the Milly Watt project.

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Every Joule is Precious Carla Schlatter Ellis Duke University

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  1. Every Joule is PreciousCarla Schlatter EllisDuke University Milly Watt Project Systems & Architecture

  2. Energy in Computing Energy for computing is an important problem(& not just for mobile computing) • Reducing heat production and fan noise • Extending battery life for mobile/wireless devices • Conserving energy resources (lessen environmental impact, save on electricity costs) Energy should be a “first class” resource at upper levels of system design

  3. Understanding the Energy Problem Energy (Joules) = Power (watts) * Time (sec) E = P * t Power (watts) = Voltage (volts) * Current (amps) P = V * I Current (amps) = Voltage (volts) / Resistance (ohms) I = V / R

  4. Demand Side:HW Power Budget CPU Cache Memory Bus I/O Bridge I/O Bus Main Memory Disk Controller Graphics Controller Network Interface Graphics Disk Disk Network [Intel targets]

  5. Reducing Demand HW / SW Cooperation • Re-examine interactions between HW and SW, particularly within the resource management functions of the Operating System • Software • High level • Coarse grain • OS, compiler or application • Affect usage patterns Hardware • Voltage Scaling • Clock gating • Power modes: Turning off HW blocks • Low level • Fine grain • Low-power Circuits

  6. Supply Side: Battery Properties Battery models provide strategy:Battery lifetime can be determined by controlling discharge rate.Limiting availability of currentcy.

  7. Battery Discharge Behavior Discharge behavior of lithium-ion cell withVoc = 3V and Vcut = 1V

  8. Energy Goals /Metrics • Battery lifetime (hours) • Energy usage (by fixed task set) (Joules) • Energy * Delay (penalizes achieving energy saving by bad performance) • Work units / joule (e.g. Mbytes/joule or MIPS/joule) • Work / battery discharge. • Thermal limits (constrained power) (Watts)

  9. Energy = S Poweri x Timei To reduce energy used for task: Reduce power cost of power state ithrough better technology. Reduce time spent in the higher cost power states. Amortize transition states, if significant. How to Reduce Energy Consumption? i e powerstates

  10. Energy & the OS Traditionally, the system-wide view of resources and workload demands resides with the OS • Explicitly managing energy will require coordination with typical resource management Energy is not just another resource • Energy has a impact on every other resource of a computing system – it is central. • A focus on energy provides an opportunity to rethink OS design

  11. Traditional Influences in OS Design Scientific computationsDatabase operations Multi-user Workload Services & API Goals/Metrics Internal Structure Policies / Mechanisms Performance asBandwidth and Latency. Hardware Resources Processor, Memory, Disks, Network

  12. Rethinking OS Design What is the impact of changing the primary goal of the OS to energy rather than (speed-based) performance? Affects every aspect of OS services and structure: • Interfaces needed by applications that want to affect power consumption • Internal organization and algorithms • Resource management policies and mechanisms

  13. Rethinking OS Design Productivity applications, Games, Multimedia, Web access, Personal (PDAs), Embedded, E-Commerce. Workload Services & API Goals/Metrics Internal Structure Policies / Mechanisms Energy Hardware Resources Processor, Memory, Disks, Wireless networking, Mic & Speaker, Motors & Sensors, Batteries

  14. Rethinking OS Design Non-energy-awaregeneral purpose applications Workload Services & API Goals/Metrics Internal Structure Policies / Mechanisms Batterylifetime Hardware Resources Battery-powered Laptop

  15. Related Work Energy-unaware OS • Low-power hardware, energy-aware compilers, algorithm development Services (Chase: MUSE) Energy-aware OS with Unaware applications • Per-device solutions (disk spindown, DVS) Energy-aware OS with cooperating Energy-aware Applications • Flinn: Odyssey (fidelity-based), Bellosa: Coop I/O, Nemesis OS

  16. Milly Watt Activities • ECOSystem Explicitly managing energy via the OS (ASPLOS02, USENIX03) • Power-aware memory(ASPLOS00, ISLPED01, PACS02, PACS03) • FaceOff Sensor-based display power management (HOTOS03, Mobisys Context Aware 04)

  17. Milly Watt Activities • ECOSystem Explicitly managing energy via the OS (ASPLOS02, USENIX03) • Power-aware memory(ASPLOS00, ISLPED01, PACS02, PACS03) • FaceOff Sensor-based display power management (HOTOS03, Mobisys Context Aware 04)

  18. Milly Watt Activities • ECOSystem Explicitly managing energy via the OS (ASPLOS02, USENIX03) • Power-aware memory(ASPLOS00, ISLPED01, PACS02, PACS03) • FaceOff Sensor-based display power management (HOTOS03, Mobisys Context Aware 04)

  19. For More Information www.cs.duke.edu/ari/millywatt/ email: carla@cs.duke.edu Experiences in Managing Energy with ECOSystem,Heng Zeng, Carla Ellis, and Alvin Lebeck, IEEE Pervasive Computing, January-March 2005. Currentcy: Unifying Policies for Resource Management,H. Zeng, C. Ellis, A. Lebeck, A. Vahdat, in USENIX 2003 Annual Technical Conference ECOSystem: Managing Energy as a First Class Operating System Resource, H. Zeng, X. Fan, C. Ellis, A. Lebeck, and A. Vahdat, Proceedings of ASPLOS 2002

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