For the moment, the slow add-on notification mechanism from bug 1071880 is Nightly-only. Filing this bug to determine what blocks it from riding the trains.

So, after much brainstorming inside the perf team, here's the current plan: - let perf monitoring ride the trains with jank monitoring OFF by default, ON only when actively used (i.e., initially when about:performance is open), and CPOW monitoring ON by default; - similarly, let AddonWatcher and Telemetry reporting of slow add-ons ride the trains with jank monitoring OFF by default; - wait until we have improved the performance of jank monitoring to turn it ON by default. To improve performance, I will try to introduce a degree of sampling to activate jank monitoring randomly, for 1 event every N events.

I'd recommend letting this ride to Beta and keeping it off of Release until the performance is improved

(In reply to David Rajchenbach-Teller [:Yoric] (please use "needinfo") from comment #1) > So, after much brainstorming inside the perf team, here's the current plan: > - let perf monitoring ride the trains with jank monitoring OFF by default, > ON only when actively used (i.e., initially when about:performance is open), > and CPOW monitoring ON by default; > - similarly, let AddonWatcher and Telemetry reporting of slow add-ons ride > the trains with jank monitoring OFF by default; > - wait until we have improved the performance of jank monitoring to turn it > ON by default. Any indication of when any of this might happen? Also, can this be implemented in stages - eg, for now can we at least have about:performance page that starts and stops monitoring as the page is open and closed? (With caveat to the user than monitoring may affect performance.) A common use case for this is when a user suddenly finds Firefox dragging, and wants to nail down the tab that is causing it. Even if the API could be in place so addon devs can start making their own user friendly implementations (which is bound to happen anyway) would be a big help. But maybe we are so close to this happening that all of the above is moot?

er, perhaps the comments regarding using about:performance for nailing down hoggy tabs would have been more appropriate in bug 674779?

about:performance is in Firefox 47. As the slow add-on monitor has a **** UX, the add-on watcher itself won't be released yet.

(In reply to David Rajchenbach-Teller [:Yoric] (please use "needinfo") from comment #6) > about:performance is in Firefox 47. Great!

about:performance is being redesigned; mass closing the bugs related to parts of the current about:performance page that we are not keeping. Our goals with the redesign are to reduce the overhead caused by having the page opened, increase the reliability of the displayed information, and make the offered information actionable for most users. The back-end work is being tracked in bug 1419681.