Reducing Smartphone Application Delay through Read/Write Isolation
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This document discusses reducing delays in smartphone applications through improved storage I/O scheduling. It found that Android devices spend up to 58% of CPU time idling due to storage I/O waits. Reads experience slowdowns of up to 626% when blocked by concurrent writes. It proposes the SmartIO scheduler, which reduces read/write interference through isolation and prioritizing reads. Evaluation showed SmartIO reduced average application launch delays by 21% and run-time delays by 17%.
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Reducing Smartphone Application Delay through Read/Write Isolation
- 1. Reducing Smartphone Application Delay through Read/Write Isolation David T. Nguyen
- 2. David T. Nguyen 2 Figure Courtesy: Facebook Connectivity Lab Real-world Problem: Application Delay
- 3. Introduction Research questions How does disk I/O affect smartphone application response time? How to optimize storage to improve application performance? Contributions First large-scale Android I/O study on 2611 devices Proposed SmartIO scheduler that reduces application delay Evaluation indicates 21% reduced launch and 17% reduced run-time delay David T. Nguyen 3
- 5. 40% devices between 13% and 58% Significant CPU time spent waiting for storage Iowait of 2611 Devices CPU active time spent waiting for storage I/O 5David T. Nguyen
- 6. Seq. reads experience up to 626% slowdown when blocked by concurrent writes (rand. up to 293%) I/O slowdown possible source of worse app launch (reads dominate) I/O Slowdown 6David T. Nguyen
- 7. Slowdown Asymmetry 7 ReadSlowdown = Response time of a read in the presence of a concurrent write / Response time of a read when running alone WriteSlowdown = Response time of a write in the presence of a concurrent read / Response time of a write when running alone David T. Nguyen
- 8. Study Summary Android devices spend up to 58% of CPU active life time idling due to I/O Reads experience up to 626% slowdown when blocked by concurrent writes Large slowdown asymmetry (reads up to 6.15; writes up to 1.6) 8David T. Nguyen
- 9. I/O Scheduler Storage Subsystem Concurrency Profiler I/O Grouping I/O Dispatch I/O Priority Assignment Kernel Space User Space SmartIO David T. Nguyen 9
- 10. FLASH BLOCK DEVICE 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 7 queue queue Idle Best Effort Real-time write read Dispatch Queue Real-time Best Effort Idle 10 David T. Nguyen
- 12. Nexus 4: 1-reader (128MB), 1-writer (128MB) Seq. read slowdown improves from 6.15 to1.72 (gain), write worsens from 1.13 to 1.51 (cost) Rand. read slowdown improves from 3.18 to 1.97 (gain), write worsens from 1.6 to 1.83 (cost) Gain vs. Cost 12David T. Nguyen
- 13. 128MB mixed workload (first 10% reads, then 20%..) With increasing percentage of reads, response time decreases (less writes means less slowdown) By changing scheduler (default CFQ to SmartIO) we achieve on average 49% faster response (max. 66%) Scheduler Comparison 13David T. Nguyen
- 14. Cold launch delays reduced on average by 21% (warm by 13%) Run-time delays reduced by 17% 14David T. Nguyen
- 15. Facebook Inc.s goal: cold launch < 5s on 2012 or newer devices cold launch < 10s on older devices RAZR (2012): 9.9s -> 6.2s Samsung S5 (2014): 3.7s -> 2.3s Facebook Performance 15David T. Nguyen
- 16. Conclusion & Future Work SmartIO Reduces app delays through read/write isolation and higher read priorities Study other stages of app life cycle (install, update, switch, uninstall) Analyze impact of network I/O 16David T. Nguyen
- 17. Acknowledgments Our shepherd Prof. Mahadev Satyanarayanan (CMU) Aaron Carroll (NICTA), Dr. Duy Le (EMC), Dr. Tommy Nguyen (RPI), Mai Anh Do (CNU), Daniel Graham (W&M) 17David T. Nguyen
- 18. Reducing Smartphone Application Delay through Read/Write Isolation David T. Nguyen