Marauder: Synergized Caching and Prefetching for Low-Risk Mobile App Acceleration

https://dl.acm.org/doi/10.1145/3458864.3466866

• Apps dominate mobile usage and are projected to continue doing so

• App responsiveness is well-studied

  • Are apps meeting expectations?

• Measuring app performance

  • 50 apps across categories (Humanoid)

  • Origin servers

  • Record screen and compute IRT (Interaction Response Time)

  • Real phones, live networks, live origin servers and realistic interaction traces

• App performance today

  • 2.9s median on LTE: too slow for users today!

  • Why isn't it better?

    • Which is bigger contributor to delay? network or compute?

      • Network causes 64% of the delay on LTE

      • Improving network performance

        • Caching

          • Store previously fetched content to speedup subsequent fetches

          • Developer specified TTLs

          • Understanding Caching

            • 28% of resources in median interaction from cache --> 44% IRT improvement over no-cache

            • 2x resources unchanged in cache --> 58% IRT improvement over no-cache

          • Cache TTLs are hard to set?

            • Can caching be used optimally?

            • Developers need to set TTLs such that it precisely expires when content changes

              • Ideal TTLs for a given resource vary significantly

              • High TTL --> good cache performance --> stale content

              • Low TTL --> fresh content --> poor cache performance

        • Prefetching

          • Load content ahead-of-time by predicting users' needs

          • Understanding prefetching

            • 4 apps use prefetching

              • Load content in background periodically

              • Avoid network fetches during interaction

              • Speedups above 60%, however, up to 4x extra data usage. Difficult to predict user interactions.

      • Goal: extract benefits while minimizing drawbacks

      • Marauder

        • Not rely on developers

        • Work with existing apps and servers

      • Insights

        • Text files are important

        • Text files catalog resources --> prefetching opportunities

        • Small size of important text files --> refresh in the background

        • Inefficient TTLs --> low cost TTL extensions

        • Stability of referenced resources --> prefetching even with uncacheable text files

      • 
      • Evaluation

        • Speeds up interactions by 27.4%

        • 1.18x median data usage, JIT prefetching is the larger contributor

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