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Green Computing Power Aware Computing Maziar Goudarzi.

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Presentation on theme: "Green Computing Power Aware Computing Maziar Goudarzi."— Presentation transcript:

1 Green Computing Power Aware Computing Maziar Goudarzi

2 Outline Power Aware Computing Power Management in Computers Acknowledgements: Some slides/parts from

3 Power aware computing –Avoid wasting energy Challenges –Figure out where and why waste happens –Determine how to avoid it Power aware computing are techniques that consider the energy consumption as one of their main constraints P. Ranganathan, "Recipe for Efficiency: Principles of Power-Aware Computing," Communications of the ACM, vol.53, no.4, pp.60-67, April

4 Sources of energy waste Systems designed for most general case –Most aggressive workload performance –Worst-case risk tolerance Components designed by different teams –No component interaction considered Functions of the system as independent modules –No function interaction considered Design focused on performance and availability –Resource waste for small improvements –Component or operation redundancies 4

5 Sources of energy waste General-purpose systems tendency Good performance for several applications Union of maximum requirements of each application class 5

6 Sources of energy waste Optimization for peak performance scenario –Average system utilization low –Benchmarks stress worst-case performance workloads Systems optimized for these scenarios 6

7 Reduction of energy waste Common solutions –Use a more power-efficient alternative –Disable/Scale-down unused resources –Match work to power-efficient resource –Piggyback, or Combination of multiple tasks in single energy event –Design for required functionality 7

8 Reduction of energy waste Coming solutions –Holistic solutions Broad scope of the problem Cross-layer interaction –Trade off some other metric for energy –Optimize energy efficiency for the common case –Spend someone elses power –Spend power to save power 8

9 Requirements Needed irrespective of the approach –Measurement and monitoring –Analysis tools and models –Control algorithms 9

10 Current work on power management CircuitsArchitecture P. Ranganathan, "Recipe for Efficiency: Principles of Power-Aware Computing", Communications of the ACM, vol.53, no.4, pp.60-67, April. 2010

11 Current work on power management Compiler/System P. Ranganathan, "Recipe for Efficiency: Principles of Power-Aware Computing, Communications of the ACM, vol.53, no.4, pp.60-67, April. 2010

12 Limits of Energy Efficiency Richard Feynman (Nobel Physicist) –10 18 –bit op/s per Watt –Billion desktop-class processors in a handheld device Tremendous improvement in components possible Consider non-IT equipments as well: potential is even higher Practically: at least an order of magnitude improvement

13 Coming Next Power management in computers –Processor –Disk –Memory –Network –Display Power management standards 13

14 Green Computing Power Management in Computers

15 Outline Computer components –Processor –Disk –Memory –Network –Display 15

16 Introduction Different levels –Circuits –Architecture –Compilers and Systems This lecture deals with the last level –Focused on techniques and solutions applied to Matthew Garret, Powering Down, Communications of the ACM 51, 9 (September 2008), 42-46

17 Processor Processor does not run at 100% capacity all time Architecture techniques to save up energy –CPU frequency/voltage scaling –Low power mode states Disable functional units not needed –Clock gating –Dissociate from memory bus –Disable part of the cache 17

18 Management at system level HLT (halt) instruction –Allows to indicate that there is nothing to execute –CPU enters halt state until next interrupt –Issued by the operating system Advanced Power Management (APM) –CPU idle / busy calls CPU in low / normal power state Low power state –Clock stopped until next interrupt –Clock slowed down Advanced Configuration and Power Interface (ACPI) –Current specification for energy management –Richer low power modes and frequency/voltage scaling History 18

19 Transition to low power states Power state transitions take time Interruptions may wake up the processor too often –Some interrupts cannot be avoided Interrupts for user interaction, e.g. keyboard –But other interrupts can be adjusted or disabled Regular interrupts such as timers –Sometimes, flaws in the software client more frequently checking for updates than fetching done from the server Processor must remain in idle power state for more than 20 ms to get benefit of it!!! 19

20 تمرین اضافی مصرف توان لپ تاپ یا کامپیوترتان را در حالت idle و نیز در حالتهای مختلف کاری (utilizationهای مختلف) اندازه بگیرید. انرژی مصرف شده برای ورود و خروج به حالت low power را استخراج کنید. حداقل زمان مفید موردنیاز در حالت idle جهت مفید بودن آن را تعیین کنید. همه مراحل و نتایج را با جزئیات گزارش کنید. 20

21 Transition to low power states Example: –An application (e.g. client?) –Approach 1: wakeup every ½ second and do 2ms of work. –Approach 2: wakeup every second and do 4ms of work –Which one is better? An 2.3GHz Opteron X4, 16GB DDR2-667 DRAM, 500GB hard At 100% load: 295W At 0% load: 141W Idle power: a few 10s of Watts(?) Race-to-idle concept 21

22 Timers Events scheduled at a specific time in the future –Example: cursor blinking, time clock ticking... –The event produces a timer interrupt Timer interrupts have a big impact on consumption –Regularly wake up the processor –System has plenty of them Two examples of optimization –Linux tickless kernel –Consolidation of timers 22

23 Linux tickless kernel Traditional kernels had a global timer –Timer ticked and interrupted the CPU periodically Typically at 100 Hz, i.e. 10 ms period –At each tick the kernel checks if an event was scheduled Tickless kernel –No periodic tick –When CPU goes to idle state Global timer reprogrammed Tick the next scheduled event Suresh Siddha,Venkatesh Pallipadi, Arjan Van De Ven, Getting maximum mileage out of tickless, Proceedings of the Linux Symposium, 2007 Kernel Timer at 1000 Hz 23

24 تمرین اضافی روی یک سیستم لینوکس، اثر استفاده از Tickless Kernel را دقیق اندازه گیری و گزارش کنید. 24

25 Consolidation of timers Software makes extensive use of timers –Overwhelming number of interrupts –Solutions Review of periods assigned Consolidation of timers –Application level Developer reduce or group timers –System level Glib library function: g_timeout_add_seconds() Linux kernel: round_jiffies() 25

26 Deferrable (Kernel) Timers Kernel Timers –Non-deferrable –Deferrable Example: –ondemand governer sets cpu-freq according to cpu utilization –Periodically samples CPU utilization Important to service in sub-second time when system busy Could be deferred when system idle Kernel Timer at 1000 Hz 26

27 PowerTOP Information about what causes CPU wake ups 27

28 تمرین اضافی با استفاده از PowerTop حداقل سه راهکار برای کاهش مصرف انرژی در یک دستگاه کامپیوتر (مثل سرور) ارائه داده و آنها را عملی کنید. نتایج را با جزئیات گزارش دهید. 28

29 Outline Power management in computers –Processor –Disk –Memory –Network –Display 29

30 Traditional hard drive Composed of electronic and mechanical parts Most of solutions exploit reduction of consumption of the mechanical parts 30

31 Spin down Switch off the platter spindle motor when inactive –Supported by most operating systems Costs –Reduces hard-drive life expectancy –Uses a lot of energy to spin up –Creates delays (order of seconds) Smart management of I/O to –minimize spin transitions –reduce delays 31

32 I/O management Reads –Each read from disk results in spinning up –Application data optimizations Read all needed data at application startup Read data in big chunks –Operating system optimizations Data cache –File system optimizations Problem –Unix systems record last time a file is accessed –Each read triggers a write Disable the last accessed time or updated with next write 32

33 I/O management Writes –Application optimizations Write-out avoidance –Application can track data to write –At some point follow track to write all required information –Operating system optimizations Data to write can be cached (no spin up) Risk of data loss if system fails –Linux laptop mode write to disk when doing read –Electronics Hard-drive electronics and I/O controller low power modes –I/O controller low power mode can save 0.5 Watts –Typical desktop hard drive between 5 and 15 W 33

34 Solid state drives (SSD) Composed only of electronic parts No mechanical parts –Lower consumption than regular HDs –Faster read operations 34

35 Solid state drives (SSD) NAND Flash memory limitations –Writing latency Memory organized in pages (~2KB) and blocks (~128KB) Write a page usually requires –erasure of block –rewrite of the whole block –Finite program-erase cycles Each block can be erased a number of times Require wear leveling techniques to balance erasures 35

36 Outline Power management in computers –Processor –Disk –Memory –Network –Display 36

37 Memory SRAM, Cache –Cache reconfiguration DRAM –SDRAM –DDR SDRAM, 2.5/2.6 V –DDR2, 1.8 V –DDR3, 1.5 V –DDR4, 1.05–1.2 V exp. Sep

38 38

39 DDR Memory Q. Deng, et al., MemScale: Active Low-Power Modes for Main Memory, ASPLOS11. 39

40 Outline Power management in computers –Processor –Disk –Memory –Network –Display 40

41 Network Ethernet is the dominant wired communication technology –Common supported speeds 10-10,000 Mbps –Similar energy consumed with and without data transmission –Idle mode prevents any kind of reception –New standard IEEE 802.3az for low power modes –Typical power: 5-20W (10Gbps NIC) Characterizing 10 Gbps Network Interface Energy Consumption, 41

42 Network Wake on LAN –Technique to wake up a slept machine Network keeps physical interface enabled Magic packet tells the interface to wake up machine Wireless LAN –Physical and routing protocols to optimize consumption 42

43 43

44 تمرین اضافی مصرف روزانه برق یک یا چند دانشکده دانشگاه چقدر است؟ آیا نیروگاه 20 کیلوواتی فعلی مقرون به صرفه است؟ اگر خیر، چرا؟ واگر به صرفه نیست پس به چه علت اجرا می شود؟ اگر بله، چه میزان صرفه جویی صورت می دهد؟ هزینه احداث یک نیروگاه خورشیدی فتوولتائیک 100 مگاواتی چقدر است؟ این هزینه را با یک نوع نیروگاه دیگر مقایسه کنید. 44

45 Outline Power management in computers –Processor –Disk –Memory –Network –Display 45

46 Display Analog displays –VESA Display Power Management Signaling (DPMS) Use H-Sync and V-Sync pins to select power mode Four modes are encoded: On, Stand-By, Suspend, Off Digital displays –DVI Digital Monitor Power Management (DMPM) Use Data port and DDC pin to select power mode –DDC: Display Data Channel. Communicate supported display modes to the adapter and to enable the computer host to adjust monitor parameters Supported modes –Power On –Intermediate Power State (Data port off) –Active-Off (Data port off) –Non-Link Recoverable Off (DDC pin off) Digital Visual Interface specification 1.0 ( 46

47 LCD Display Backlight –The light source can be made up of: Several Light Emitting Diodes (LEDs) An Electroluminescent panel (ELP) One or more Cold Cathode Fluorescent Lamps (CCFLs) One or more Hot Cathode Fluorescent Lamps (HCFLs) One or more External Electrode Fluorescent Lamps (EEFLs) One or more Incandescent light bulbs 47

48 LCD Display Intel –Reduce backlight when most pixels are dark 48

49 One Laptop Per Child 49

50 Graphics Chipsets One Laptop Per Child –Secondary display controller –Framebuffer scan even with CPU in idle mode 50

51 GPU Power 51 geforce-gtx-480, html

52 Graphics Card Systems with dual GPUs –Motherboard integrated GPU –External powerful GPU –System switches off external GPU to save energy Compress frame-buffer contents 52

53 تمرین اضافی جمع آوری کلیه روشهای ممکن مدیریت توان در یک سرور مثل سرورهای دانشکده گزارش جزئیات و اثر قابل انتظار از هریک در صورت امکان، اجرا و اندازه گیری اثر هر یک 53

54 Coming Next Power Management Standards –APM –ACPI 54

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