New opt-in system sends performance data to Mozilla
Traditional tools for measuring performance, including benchmarks like SunSpider, don't do a very good job of measuring when Firefox is slow, says Mozilla developer Asa Dotzler. What's needed is real-world usage that reveals where code is slowest, and for that, Mozilla introduced an opt-in feature, called Telemetry, in version 7. Dotzler
explains in his blog
"Telemetry in Firefox is a new technology that allows our developers to build performance tests right into Firefox itself and to have those tests running while users are interacting with Firefox and the Web. These little tests, also called probes, should go completely unnoticed when you're using Firefox but they make note of the time it takes to accomplish certain tasks like establishing a network connection or freeing system memory. If people opt in to sending this anonymous data to Mozilla, like tens of millions do with crash reports already, then our developers can isolate places where Firefox is slow or uses too much memory and can start to remedy them."
Screenshot shows some of the data that Mozilla is gathering from users who opt-in to telemetry.