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Turducken: Hierarchical Power Management for Mobile Devices. Jacob Sorber, Nilanjan Banerjee, Mark Corner, Sami Rollins†. University of Massachusetts, Amherst. http://prisms.cs.umass.edu/hpm. Batteries and Wireless: Two Achilles Heels. Imagine using a laptop like it was a desktop: - PowerPoint PPT Presentation
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University of Massachusetts, Amherst
Turducken: Hierarchical Power
Management for Mobile Devices
Jacob Sorber, Nilanjan Banerjee,
Mark Corner, Sami Rollins†
http://prisms.cs.umass.edu/hpm
Batteries and Wireless: Two Achilles Heels
Imagine using a laptop like it was a desktop:
your mail is always fresh
your file system is always consistent
your web is always prefetched
instant messages are instantaneous
Why isn’t this a reality?
Mobility leads to variable connectivity
Limited energy necessitates shutting laptop off
The result is we don’t even try!
Tension in Maintaining Availability
The laptop can remain active—available for communication
System lifetime is severely limited
The laptop can be suspended—extending lifetime
System is not available
Compromise: wake periodically to communicate
More frequent = more available, shorter lifetime
Less frequent = less available, longer lifetime
The tension remains despite current methods
Don’t know when to wake up
Systems lean toward longer lifetime
Goal: A system that is always available with extended lifetime
Solution: Hierarchical Power Management
Hierarchical Power Management
Combine a range of embedded platforms into a single device
Perform tasks on the tier that best fits the task
Download email using PDA
Download large movies with laptop
Sleep high-power tiers when not needed
Focus on non-interactive use
Provide power-efficiency when NOT in use
Remove the human bottleneck
Allow new laptop functionality
Outline
HPM Design Principles:
Combine the Right Platforms
Use the right device for the job
Decompose Tasks
Design of an HPM Laptop
Implementation of Turducken
Hardware
Software
Experimental Results
Related Work and Conclusions
Combine the Right Platforms
More platforms = more overhead
Size, weight, and complexity
Suspend power
Transition cost between platforms
Still need to support a large range of power modes
Use few devices separated by orders-of-magnitude in power
Use the Right Device for the Job
40W
2W
0.04WSensor
PDA
Laptop
Simple computatio
nand storage
Download Web Pages
Very complex computation
Send/RecvMail
Tasks requiringlarge memory or
storage space
Pow
er
Need
s
Decompose Tasks
Not only separate platforms, but subdivide tasks
Tasks include common subtasks:
Checking for network connectivity
Service Discovery
Check for work to be done
Interact with user
Example:
Mote checks for a network, PDA checks for mail server
Laptop remains asleep until user reads the mail
Outline
HPM Design Principles:
Combine the Right Platforms
Use the right device for the job
Decompose Tasks
Design of an HPM Laptop
Implementation of Turducken
Hardware
Software
Experimental Results
Related Work and Conclusions
HPM Hardware Design
WakeControl
Higher Tier
LowerTier
WakeControl
Local Communication Link
Local Communication Link
Battery
Service Discovery
Task Execution
Tier Hardware (CPU, Memory, Storage)
HPM Software Design
Take advantage of transparent proxies
Proxies periodically perform service discovery and fetch content
Provide it on demand to higher tiers in system
Many applications are already distributed
Lower tiers act as proxy for higher tiers
Little or no application recoding and invisible to users
MailProxy
PDA
MailClient
LaptopMail
Server
Outline
HPM Design Principles:
Combine the Right Platforms
Use the right device for the job
Use the right number of devices
Design of an HPM Laptop
Implementation of Turducken
Hardware
Software
Experimental Results
Related Work and Conclusions
Hardware Implementation
Combines Laptop, PDA, and mote into a laptop
Laptop and PDA communicate via USB
PDA and mote via RS-232
Wakeup using relays
WiFi detector allows mote to detect 802.11 beacons
PDALaptop MoteUSB RS-232
Wake
Hardware Implementation
Applications
Time Synchronization
Can be completely performed by the mote
Lowest tier periodically synchronizes with remote time server
Web Prefetching
More complicated application which requires at least PDA
Mote detects wireless networks
PDA periodically fetches updates to frequently accessed pages
Involves user interaction
Both incoming and outgoing updates
Laptop accesses mail via proxy on the PDA
Evaluating Turducken
How does HPM affect battery lifetime?
Show results for a variety of workloads
Vary the consistency of the application
Vary the availability of the network
Consider three configurations
Laptop
Laptop+Mote
Laptop+PDA+Mote
Experiments take a long time
Extrapolate from a set of measured data points
Effect of Consistency
Measure the impact of maintaining consistency
System wakes periodically—vary frequency
Network is always present
Time Synchronization (please see paper)
Web Prefetching
Laptop routes network traffic through PDA
PDA periodically refreshes expired pages
System wakes with constant rate to send mail (2 min/hr)
PDA periodically checks for new mail and sends pending mail
Results: Web Prefetching
PDA is the right device for the job
For always-on operation, Turducken lasts up to 10 times longer
Wake Interval (minutes)
Lif
eti
me (
hou
rs)
Results: E-Mail
More interactive use reduces opportunities for Turducken to save power
Turducken still lasts up to 6 times longer
Wake Interval (minutes)
Lif
eti
me (
hou
rs)
0
100
200
300
400
500
600
700
Avera
ge P
ow
er
(mW
)
Mote Active
Mote Suspend
PDA Active
PDA Suspend
Laptop Active
Laptop Suspend
Laptop Laptop+Mote
Full Turducken
Power-By-Tier: Web Caching
Laptop+Mote shows cost of adding unnecessary platforms
Turducken replaces 400mW of laptop active power with 25mW on PDA
Laptop suspend power is the greatest limiting factor: try hibernation
Effect of Network Availability
Measure the impact of intermittent connectivity
Network is present with varying probability
Mote wakes at a fixed interval
Only wakes PDA when network is available
Only show results for Web Prefetching
Probability of WiFi
Lif
eti
me (
hou
rs)
Results: Web Prefetching
With no network mote prevents laptop from waking
Turducken performs well over a variety of connectivity patterns
Related Work
Wake-On-Wireless [Shih, et al]
Low-power radio receives wakeup messages
Requires in-network support
Focus on when to wake up
Wireless optimizations [Anand, et al], Disk Spindown [Helmbold, et al], Multiple radios [Pering, et al], Multiple processor cores [Mayo & Ranganathan]
none provide orders-of-magnitude scaling of power
Conclusions
Always-on availability and extended battery life
Hierarchical Power Management
Integrate multiple independent platforms
Pass control between tiers
Suspend unneeded tiers
Use proxy-based approach
Little or no application recoding
Always-on operation for up to 10x as long
University of Massachusetts, Amherst
Turducken: Hierarchical Power
Management for Mobile Devices
Jacob Sorber, Nilanjan Banerjee,
Mark Corner, Sami Rollins†
http://prisms.cs.umass.edu/hpm
Turducken: What’s In The Name?