Leveraging Smart Phones to Reduce Mobility Footprints Stephen Smaldone †, Benjamin Gilbert ‡, Nilton Bila *, Liviu Iftode †, Eyal de Lara *, and Mahadev Satyanarayanan ‡ † Rutgers University, ‡ Carnegie Mellon University, * University of Toronto

June 23, 2009MobiSys Traditional 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, 2009MobiSys Carry-Nothing: Internet Suspend/Resume ® (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 #1ISR Client Station #2 Suspend Resume ISR Parcel ISR Server

June 23, 2009MobiSys Existing 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, 2009MobiSys The Opportunity: Smartphone Device that people already carry Provides ample storage Provides multiple modes of connectivity Light-weight (very small mobility footprint)

June 23, 2009MobiSys Horatio: Mobile Self-Cleaning Cache Fast SuspendLazy Self-CleaningMultiple Resume Options 3G / WiFi Time ISR Client Station #1 ISR Client Station #2 ISR Server

June 23, 2009MobiSys Our 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, 2009MobiSys 20098Outline Introduction Horatio Design and Implementation Evaluation and Results Related Work Conclusions and Future Work

June 23, 2009MobiSys Horatio 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, 2009MobiSys Control/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 ControlParcel Data Small Defines parcel ownership Trusted (used to validate data) As large as necessary Can be (partially) replicated Encrypted Possibly untrusted

June 23, 2009MobiSys Control/Data Separation: How it Works Fast+Lazy SuspendsEfficient Self-CleaningEfficient Resume Parcel Data Parcel Control Time ISR Server

June 23, 2009MobiSys Control/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, 2009MobiSys Additional 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, 2009MobiSys Outline Introduction Horatio Design and Implementation Evaluation and Results Related Work Conclusions and Future Work

June 23, 2009MobiSys Evaluation 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, 2009MobiSys Evaluation 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, 2009MobiSys Improvement in User Experience Dirty State Size (MB) Horatio Device ISR-1 (No Horatio) N95-WiFi OM-WiFi N95-USB SD-USB Microbenchmark Suspend Results * Values are time measured in minutes

June 23, 2009MobiSys Improvement in User Experience Dirty State Size (MB) Horatio Device ISR-1 (No Horatio)5---- N95-WiFi OM-WiFi N95-USB-4459 SD-USB Microbenchmark Resume Results * Values are time measured in minutes

June 23, 2009MobiSys Realistic Workloads (Macrobenchmarks) Workload NameExecution Time (min) Dirty State (MB) MemoryDisk Word10413 Photo13254 Shop Podcast Video

June 23, 2009MobiSys Improvement in User Experience Macrobenchmark Results

June 23, 2009MobiSys Self-Cleaning Time Dirty State Size (MB) Horatio Device N95-WiFi0.6 minutes2 minutes15 minutes OM-WiFi0.2 minutes1 minute13 minutes N95-3G3 minutes8 minutes1 hour Workload (Dirty State Size) N95-WiFiN95-3G (20 MB) 4 minutes12 minutes Word (44 MB) 16 minutes1 hour Photo (29 MB) 14 minutes1 hour Shop (44 MB) 18 minutes1 hour Podcast (230 MB) 37 minutes2 hours Video (632 MB) 2 hours7 hours

June 23, 2009MobiSys Horatio Battery Consumption Dirty State Size (MB) OperationHoratio Device SuspendN95-WiFi0.2%0.4%3%11% SuspendN95-USB0.1%0.2%0.9%4% ResumeN95-WiFi3%4%5%9% ResumeN95-USB0.6% 0.7%1% Self-CleanN95-WiFi0.2%0.6%6%- Self-CleanN95-3G1%4%28%- * Values are percentage of battery depleted

June 23, 2009MobiSys Eager State Propagation WorkloadLazy State (MB) Suspend State (MB) Eager State (MB) Word Photo Shop

June 23, 2009MobiSys Related Work Remote ( low physical vulnerability) Storage Site Local (h igh network resilience) Local (crisp interaction) Remote (high compute power) Execution Site Classic PC model Laptops SoulPad, MojoPac Remote Execution Cyber Foraging ISR model Thin client model Snowbird Transient Thin Client Horatio

June 23, 2009MobiSys Conclusions 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

Thank You!

June 23, 2009MobiSys Impact on Mobility Footprint Dirty State Size (MB) OperationHoratio Device SuspendN95-WiFi SuspendN95-USB ResumeN95-WiFi ResumeN95-USB Self-CleanN95-WiFi Self-CleanN95-3G * Values are energy measured in Joules

June 23, 2009MobiSys Workload State Generation

June 23, 2009MobiSys Update Locality