Ajax Performance

YUI Profiler

I missed covering the release of the YUI Profiler in 2.4.0, but in YUI 2.5.0 they’ve sweetened the pot further with ProfilerViewer Control, a visual interface to the data collected by Profiler. Together, they provide an advanced, cross browser alternative to the profiling features of Firebug, something that is desperately needed as the complexity of client side applications increases. As great as Firebug is at profiling JS, I’m always worried that the data may not perfectly apply to other browsers. With YUI Profiler, that’s not an issue.

The profiling model differs significantly from Firebug, which runs as a browser extension and can reach deep into browser internals for its metrics. YUI Profiler is running within the JS sandbox, so the user is required to register specific functions for profiling. This limits the profiling from broad spectrum analysis of the whole application to more targeted measurement, but that also serves to limit the performance overhead of the profiling itself. When discussing the jsLex approach to instrumentation, I was worried that the tool itself would significantly impact runtime performance; with YUI Profiler, I don’t think that’s a concern.

I’m a fan of this approach. I like targeted instrumentation, and YUI Profiler falls somewhere in the middle between full browser instrumentation (Firebug, jsLex) and granular instrumentation calls (Firebug Lite). There are definitely advantages in the latter approach, such as the ability to measure the time of network events, such as async network calls, which as far as I can tell isn’t possible with YUI Profiler. That might be a nice, easy addition to the suite.