JS Capsules: A Framework for Capturing Fine-grained JavaScript Memory Measurements for the Mobile Web

Understanding the resource consumption of the mobile web is an important topic that has garnered much attention in recent years. However, existing works mostly focus on the networking or computational aspects of the mobile web and largely ignore memory, which is an important aspect given the mobile web's reliance on resource-heavy JavaScript. In this paper, we propose a framework, called JS Capsules, for characterizing the memory of JavaScript functions and, using this framework, we investigate the key browser mechanics that contribute to the memory overhead. Leveraging our framework on a testbed of Android mobile phones, we conduct measurements of the Alexa top 1K websites. While most existing frameworks focus on V8 - the JavaScript engine used in most popular browsers - in the context of memory, our measurements show that the memory implications of JavaScript extends far beyond V8 due to the cascading effects that certain JavaScript calls have on the browser's rendering mechanics. We quantify and highlight the direct impact that website DOM have on JavaScript memory overhead and present, to our knowledge, the first root-cause analysis to dissect and characterize their impact on JavaScript memory overheads.