Transcript PowerPoint - The Empathic Systems Project

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)
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
Process-driven Voltage Scaling (PDVS)
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
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.
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.
UDFS1 scheme
Example: minimum stable Vdd for different
operating frequencies & temperatures in an IBM
Laptop
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
UDFS2 scheme
User study
• 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.
% improvement
PowerPoint Apps
Results (UDFS + PDVS)
PowerPoint App
Average number of user events
3D Shockwave
Measurement
1. Used a control agent in Windows to log system frequency and User
events during the study
2. 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
 “User-Driven Frequency Scaling”, IEEE Computer Society Computer Architecture Letters, 2006.
Publications:  “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
FIFA game
% improvement
Chebyshev bound-based (1 − p) values for difference of means from
zero are also shown
Power improvement in the multitasking environment