Power improvement in the multitasking environment Power Reduction Through Measurement and Modeling of Users and CPUs Bin Lin, Arindam Mallik, Peter A. Dinda, Gokhan Memik and Robert P. Dick Department of EECS, Northwestern University {b-lin, arindam, pdinda, g-memik, dickrp}@northwestern.edu Our work targets power reduction in laptops. Almost all of them use a version of DVFS (Dynamic Voltage and Frequency Scaling). DVFS is an energy-saving technique that consists of varying the frequency and voltage of a microprocessor in real-time according to processing needs. Specifically, existing DVFS techniques select an operating point (CPU frequency and voltage) based on the utilization of the processor. User-driven Frequency Scaling (UDFS) Process-driven Voltage Scaling (PDVS) Current DVFS techniques are pessimistic about the user Most DVFS schemes (e.g., Windows) is only based on CPU utilization Leads to use of higher frequencies than necessary for satisfactory performance Different users have different requirements! Current DVFS techniques are pessimistic about the processor Assume worst-case manufacturing process variation and operating temperature Voltage set for a particular frequency based on loose worst-case bounds given by the processor manufacturer. Leads to higher voltages than necessary for stable operation, especially in low temperatures. User-driven Frequency Scaling (UDFS) User presses button when annoyed with speed of computer Button-press feedback drives model & algorithm that drive frequency setting System adapts to users quickly, leading to a reduced rate of button presses Two adaptive algorithms Example: minimum stable Vdd for different operating frequencies & temperatures in an IBM Laptop Minimum Stable Voltage (MSV) Supply voltage that guarantees correct execution for given processing and environmental conditions. Processors can act flawlessly at lower supply voltages. The extra slack is present due to process variation and temperature. Process-driven Voltage Scaling (PDVS) Customize frequency to voltage mapping to individual processor at every temperature, taking advantage of process variation. An automatic voltage profiler is under development UDFS1 scheme UDFS2 scheme User study Results (UDFS + PDVS) % improvement 4 interaction applications: Windows, Microsoft PowerPoint plus music, 3D Shockwave animation video, and FIFA 2005 20 users: “Power User”, “Typical User”, and “Beginner” 2 adaptive algorithms: UDFS1 and UDFS2. PowerPoint Apps PowerPoint App Average number of user events Measurement 3D Shockwave Used a control agent in Windows to log system frequency and User events during the study Built a framework to measure the power consumption of a notebook while replaying the user study scenario. Power numbers presented are original savings- not analytical improvements 3D Shockwave FIFA game Summary of results Combination of PDVS and the best UDFS scheme reduces measured system power by 49.9% (27.8% PDVS, 22.1% UDFS), averaged across 20 users and 4 representative applications, compared to the Windows XP DVFS scheme. For multitasking environment, power consumption gets reduced by 58.6% and 75.7% by (UDFS1+PDVS) and (UDFS2+PDVS). Average temperature reductions for all three applications – 13.2◦C. This work is in process of technical transfer FIFA game % improvement Runs a program to detect the MSV settings for a particular process Analyses the effect of temperature on the MSV Runs a stability test occasionally to review the reliability of the processor “User-Driven Frequency Scaling”, IEEE Computer Society Computer Architecture Letters, 2006. “Process and User Driven Dynamic Voltage and Frequency Scaling”, Tech. Report NWU-EECS-06-11, EECS Department, Northwestern Univ., Aug. 2006. "Power Reduction Through Measurement and Modeling of Users and CPUs", ACM SIGMETRICS 2007 Publications: Chebyshev bound-based (1 − p) values for difference of means from zero are also shown Power improvement in the multitasking environment