2010/5/22 William Pietri william@scissor.com:
I don't know how useful it is, but recently I helped a client build some JS-based, in-browser page load performance monitoring. It tracks various rendering events of a chosen percentage of pageviews. The only server-side code processes web server logs in batch, so it is pretty low impact, and works with cached pages. It's been served in a few hundred million pageviews with no obvious problems yet.
I think most of the server-side code is pretty particular to their needs, but if somebody wants it for Wikipedia, I'm sure they'd be willing to give up the client-side stuff and my rough-and-ready initial pass at the log parsing, which is in Ruby. If that's useful, let me know off-list and I'll ask 'em for permission.
I'm not sure we need this. I don't see a reason why one of us usability developers can't just load pages, find out whether they're slower, and where the slowness is. If the slowness is present for everyone (many different people reporting slowness seems to indicate that, and I have no reason to believe otherwise) you don't need to jump through hoops to gather data from random users when you can easily reproduce it yourself.
Roan Kattouw (Catrope)