Automated construction of javascript benchmarks

1 JavaScript is a highly dynamic language for web-based appli-cations. Innovative implementation techniques for improving its speed and responsiveness have been developed in recent years. In-dustry benchmarks such as WebKit SunSpider are often cited as a measure of the efficacy of these techniques. However, recent stud-ies have shown that these benchmarks fail to accurately represent the dynamic nature of modern JavaScript applications, and so may be poor predictors of real-world performance. Worse, they may guide the development of optimizations which are unhelpful for real applications. Our goal is to develop a tool and techniques to automate the creation of realistic and representative benchmarks from existing web applications. We propose a record-and-replay approach to capture JavaScript sessions which has sufficient fidelity to accurately recreate key characteristics of the original applica-tion, and at the same time is sufficiently flexible that a recording produced on one platform can be replayed on a different one. We describe JSBENCH, a flexible tool for workload capture and bench-mark generation, and demonstrate its use in creating eight bench-marks based on popular sites. Using a variety of runtime metrics collected with instrumented versions of Firefox, Internet Explorer, and Safari, we show that workloads created by JSBENCH match the behavior of the original web applications. 1