Web Performance Pitfalls

Web performance is widely studied in terms of load times, numbers of objects, object sizes, and total page sizes. However, for all these metrics, there are various definitions, data sources, and measurement tools. These often lead to different results and almost all studies do not provide sufficient details about the definition of metrics and the data sources they use. This hinders reproducibility as well as comparability of the results. This paper revisits the various definitions and quantifies their impact on performance results. To do so we assess Web metrics across a large variety of Web pages. Amazingly, even for such “obvious” metrics as load times, differences can be huge. For example, for more than 50% of the pages, the load times vary by more than 19.1% and for 10% by more than 47% depending on the exact definition of load time. Among the main culprits for such difference are the in-/exclusion of initial redirects and the choice of data source, e.g., Resource Timings API or HTTP Archive (HAR) files. Even “simpler” metrics such as the number of objects per page have a huge variance. For the Alexa 1000, we observed a difference of more than 67 objects for 10% of the pages with a median of 7 objects. This highlights the importance of precisely specifying all metrics including how and from which data source they are computed

BatteryLab: A collaborative platform for power monitoring https://batterylab.dev

Advances in cloud computing have simplified the way that both software development and testing are performed. This is not true for battery testing for which state of the art test-beds simply consist of one phone attached to a power meter. These test-beds have limited resources, access, and are overall hard to maintain; for these reasons, they often sit idle with no experiment to run. In this paper, we propose to share existing battery testbeds and transform them into vantage points of BatteryLab, a power monitoring platform offering heterogeneous devices and testing conditions. We have achieved this vision with a combination of hardware and software which allow to augment existing battery test-beds with remote capabilities. BatteryLab currently counts three vantage points, one in Europe and two in the US, hosting three Android devices and one iPhone 7. We benchmark BatteryLab with respect to the accuracy of its battery readings, system performance, and platform heterogeneity. Next, we demonstrate how measurements can be run atop of BatteryLab by developing the “Web Power Monitor” (WPM), a tool which can measure website power consumption at scale. We released WPM and used it to report on the energy consumption of Alexa’s top 1,000 websites across 3 locations and 4 devices (both Android and iOS)