leveraging smart phones to reduce mobility footprints stephen smaldone †, benjamin gilbert ‡,...
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Leveraging Smart Phones to Reduce Mobility Leveraging Smart Phones to Reduce Mobility FootprintsFootprints
Stephen Smaldone†, Benjamin Gilbert‡, Nilton Bila*, Liviu Iftode†, Eyal de Lara*, and Mahadev Satyanarayanan‡
†Rutgers University, ‡Carnegie Mellon University, *University of Toronto
June 23, 2009 MobiSys 2009 2
Traditional Mobile ComputingTraditional Mobile Computing
• Carry-Everything (on your laptop)• Primary advantage – Have all personal data, files, applications,
preferences, etc., instantaneously/immediately available • Primary disadvantage – Too “heavy”
June 23, 2009 MobiSys 2009 3
Carry-Nothing: Internet Suspend/ResumeCarry-Nothing: Internet Suspend/Resume®® (ISR) (ISR)
• Use stateless VM-enabled client stations and suspend/resume state from a server over the Internet
• ISR Parcel = VM State (memory image, disk, etc.)• Primary advantage – Carry nothing• Primary disadvantage – Depends on connectivity
ISR Client Station #1 ISR Client Station #2
SuspendResumeISR Parcel
ISR Parcel
ISR Server
June 23, 2009 MobiSys 2009 4
Existing ISR OptimizationsExisting ISR Optimizations
• On-demand disk fetching• Look-aside caching / Content-addressable storage
• Certain problems still persist– Does not work in the absence of Internet connectivity– Suspend and Resume latencies can be intolerable to users
June 23, 2009 MobiSys 2009 5
The Opportunity: SmartphoneThe Opportunity: Smartphone
• Device that people already carry• Provides ample storage• Provides multiple modes of connectivity• Light-weight (very small mobility footprint)
June 23, 2009 MobiSys 2009 6
Horatio: Mobile Self-Cleaning CacheHoratio: Mobile Self-Cleaning Cache
Fast Suspend Lazy Self-Cleaning Multiple Resume Options
3G / WiFi
Time
ISR Client Station #1 ISR Client Station #2
ISR Server
June 23, 2009 MobiSys 2009 7
Our ContributionsOur Contributions
1. Mobile self-cleaning cache (Horatio)
2. Design and prototype implementation on smartphones
3. Evaluation that demonstrates usability benefits
4. Suggestions to improve current smartphones for better mobile self-cleaning cache performance
June 23, 2009 MobiSys 2009 8
OutlineOutline
• Introduction• Horatio Design and Implementation• Evaluation and Results• Related Work• Conclusions and Future Work
June 23, 2009 MobiSys 2009 9
Horatio Design GoalsHoratio Design Goals
1. Reduce Latency– Fast suspends and resumes
2. Preserve ISR Reliability– Clean state as soon as possible
3. Conserve Battery and Storage– Store and transfer as little as possible
Key Design Principle:• Separation of Control and Data
June 23, 2009 MobiSys 2009 10
Control/Data SeparationControl/Data Separation
• Ownership Nonce – 10 bytes• Keyring – 5.5 MB• Configuration File – 500 bytes
• Ownership Nonce – 10 bytes• Keyring – 5.5 MB• Configuration File – 500 bytes
ISR Parcel
• Disk Image – 4 GB• Memory Image – 200 MB
• Disk Image – 4 GB• Memory Image – 200 MB
Parcel Control Parcel Data
• Small• Defines parcel ownership• Trusted (used to validate data)
• As large as necessary• Can be (partially) replicated• Encrypted• Possibly untrusted
June 23, 2009 MobiSys 2009 11
Control/Data Separation: How it WorksControl/Data Separation: How it Works
Fast+Lazy Suspends Efficient Self-Cleaning Efficient Resume
Parcel Data
Parcel Control
Time
ISR Server
June 23, 2009 MobiSys 2009 12
Control/Data Separation: BenefitsControl/Data Separation: Benefits
• Saves Horatio’s battery– At suspend: state transferred to Horatio (acts as receiver)
– During self-cleaning: control state transferred from Horatio (acts as transmitter)
– At resume: data state can be transferred from server
• Client can transfer state to server without impacting suspend time– Client station can transfer data state to server after user
leaves (lazy suspend)
– Trust is not an issue, Horatio will validate later (using control state)
June 23, 2009 MobiSys 2009 13
Additional Horatio OptimizationsAdditional Horatio Optimizations
• Memory image differencing– Transfer only dirty memory state as diffs during
suspends and resumes– Require basis memory image to be cached at resume
site
• Eager state transfer during client session– Transfer dirty state in the background– May result in transferring more data than necessary
due to overwrites
June 23, 2009 MobiSys 2009 14
OutlineOutline
• Introduction• Horatio Design and Implementation• Evaluation and Results• Related Work• Conclusions and Future Work
June 23, 2009 MobiSys 2009 15
Evaluation GoalsEvaluation Goals
1. How much does Horatio improve user experience?
2. How effective is self-cleaning in reducing the vulnerability of a Horatio device?
3. What is the impact of Horatio on a user’s smartphone battery?
4. How effective is eager state transfer in reducing suspend latency?
June 23, 2009 MobiSys 2009 16
Evaluation SetupEvaluation Setup
• ISR Parcel– 512 MB Memory Image and 4 GB Disk Image
• ISR Client– 2.33 GHz Core 2 Duo CPU, 3 GB RAM, 250 GB
SATA Disk, USB 2.0, Linux 2.6
• ISR Server– Dual 2.8 GHz Xeon CPUs, 1 GB RAM, 32 GB SCSI
Disk, Linux 2.6
• Horatio Devices– Nokia N95, Openmoko Freerunner, and USB
MicroSD Card
June 23, 2009 MobiSys 2009 17
Improvement in User ExperienceImprovement in User Experience
Dirty State Size (MB)
Horatio Device 1 10 100 500
ISR-1 (No Horatio) 24 25 35 82
N95-WiFi 0.7 1.2 5 21
OM-WiFi 0.6 0.8 4 17
N95-USB 0.5 0.7 2 10
SD-USB 0.4 0.4 0.7 2
Microbenchmark Suspend Results
*Values are time measured in minutes
June 23, 2009 MobiSys 2009 18
Improvement in User ExperienceImprovement in User Experience
Dirty State Size (MB)
Horatio Device 0 1 10 100 500
ISR-1 (No Horatio) 5 - - - -
N95-WiFi - 7 7 9 16
OM-WiFi - 5 5 6 12
N95-USB - 4 4 5 9
SD-USB - 0.6 0.6 0.6 0.9
Microbenchmark Resume Results
*Values are time measured in minutes
June 23, 2009 MobiSys 2009 19
Realistic Workloads (Macrobenchmarks)Realistic Workloads (Macrobenchmarks)
Workload Name Execution Time (min)
Dirty State (MB)
Memory Disk
Email 6 16 3
Word 10 41 3
Photo 13 25 4
Shop 12 31 14
Podcast 7 120 109
Video 40 264 368
June 23, 2009 MobiSys 2009 20
Improvement in User ExperienceImprovement in User Experience
0
500
1000
1500
2000
2500
3000
ISR-1 ISR-10 N95-WiFi SD-USB
Tim
e (
s)
suspend
execution
resume
Macrobenchmark Results
0
2000
4000
6000
8000
10000
12000
ISR-1 ISR-10 N95-WiFi SD-USB
Video
Tim
e (
s)
suspend
execution
resume
June 23, 2009 MobiSys 2009 21
Self-Cleaning TimeSelf-Cleaning Time
Dirty State Size (MB)
Horatio Device 1 10 100
N95-WiFi 0.6 minutes 2 minutes 15 minutes
OM-WiFi 0.2 minutes 1 minute 13 minutes
N95-3G 3 minutes 8 minutes 1 hour
Workload (Dirty State Size) N95-WiFi N95-3G
Email (20 MB) 4 minutes 12 minutes
Word (44 MB) 16 minutes 1 hour
Photo (29 MB) 14 minutes 1 hour
Shop (44 MB) 18 minutes 1 hour
Podcast (230 MB) 37 minutes 2 hours
Video (632 MB) 2 hours 7 hours
June 23, 2009 MobiSys 2009 22
Horatio Battery ConsumptionHoratio Battery Consumption
Dirty State Size (MB)
Operation Horatio Device 1 10 100 500
Suspend N95-WiFi 0.2% 0.4% 3% 11%
Suspend N95-USB 0.1% 0.2% 0.9% 4%
Resume N95-WiFi 3% 4% 5% 9%
Resume N95-USB 0.6% 0.6% 0.7% 1%
Self-Clean N95-WiFi 0.2% 0.6% 6% -
Self-Clean N95-3G 1% 4% 28% -
*Values are percentage of battery depleted
June 23, 2009 MobiSys 2009 23
Eager State PropagationEager State Propagation
Workload Lazy State
(MB)
Suspend State
(MB)
Eager State
(MB)
Email 20 3 130
Word 44 2 221
Photo 28 2 199
Shop 44 29 486
June 23, 2009 MobiSys 2009 24
Related WorkRelated Work
Remote(low physical vulnerability)
Storage Site
Local(high network resilience)
Lo
cal
(cris
p in
tera
ctio
n)R
emo
te(h
igh
com
pute
pow
er)
Ex
ecu
tio
n S
ite
Classic PC modelLaptops
SoulPad, MojoPac
Remote ExecutionCyber Foraging
ISR model
Thin client model
Snowbird Transient Thin Client
Ho
rati
o
June 23, 2009 MobiSys 2009 25
Conclusions and Future WorkConclusions and Future Work
• Reliable and Efficient Carry-Nothing Mobile Computing– Use the smartphone as a self-cleaning mobile cache
to improve ISR
• Experimental Results Demonstrate:– Suspend and resume latencies reduced up to 98%
• Future Work– Prediction of resume location for state prefetching– Horatio user interface– Deployment
June 23, 2009 MobiSys 2009 27
Impact on Mobility FootprintImpact on Mobility Footprint
Dirty State Size (MB)
Operation Horatio Device 1 10 100 500
Suspend N95-WiFi 28 71 400 1789
Suspend N95-USB 12 31 147 609
Resume N95-WiFi 507 613 756 1456
Resume N95-USB 96 97 120 227
Self-Clean N95-WiFi 36 103 916 -
Self-Clean N95-3G 181 565 4553 -
*Values are energy measured in Joules
June 23, 2009 MobiSys 2009 28
Workload State GenerationWorkload State Generation
0
10
20
30
40
50
60
70
1 2 3 4 5 6 7 8 9 10 11 S
Cleaning Cycles
Dir
ty S
tate
(M
B)
Word
Photo
Shop