1166286 - [Metrics] Track the jank as a histogram to monitor Gaia Apps

Status: RESOLVED DUPLICATE of bug 1183101

(Firefox OS Graveyard :: Gaia::System, defect)

Description

[Tamara Hills [:thills]]

As part of architecture validation, we want to track the jank on a per application basis.  This would be tracked as a histogram and sent to the Telemetry server.

Comment 1

[Russ Nicoletti [:russn]]

Jan, how much work would do you think it would be to track jank per context/frame?

Comment 2

[Jan Keromnes [:janx]]

Russ, I'll have a chat with Vivien about this soon, and then I'll reply here (leaving needinfo).

Comment 3

[Jan Keromnes [:janx]]

Tracking event loop lag (aka "jank") can already easily be done by the HUD on a per-app basis. With bug 1166295, it will be easy to send per-app janks to Telemetry.

It could be possible to get a more precise origin for a lag (e.g. UI lag vs worker lag) but the problem is that there is only one event loop per JS runtime. Inside a top-level content (what the HUD tracks individually as an app's "frame"), there can be many nested iframes and attached workers. The workers will use separate event loops, but all the iframes will share a single event loop.

By making the eventlooplag devtools actor[1] give precise origin information, it could be possible to single out worker-lags from other lags, but I think it won't be easy to find out which particular iframe caused a UI-lag (we could guess that it wasn't caused by inactive iframes, but this will probably be tricky).

[1] The eventlooplag devtools actor https://dxr.mozilla.org/mozilla-central/source/toolkit/devtools/server/actors/eventlooplag.js