Firefox/Features/50ms ASSERT

Feature	Status	ETA	Owner
ASSERT when UI is delayed by more than 50ms	Project proposal written	2011-04-29	dietrich

Summary

Any time the user interface takes more than 50ms to respond to an action, it can appear sluggish to the user. To determine how often this happens, and what parts of our code are frequent offenders, we should add the ability to detect when the main-thread event loop is delayed by more than 50ms and log it as an ASSERT.

Release Requirements

• does not affect performance in production or beta builds
• can be logged to screen or file
• logging has been added to all primary user interface events

Next Steps

• complete project definition (ETA: 2011/04/01)
• work with UX to identify 15 primary UI events (ETA: 2011/04/01)
• add observers (see bug 601268) to primary UI events (ETA: 2011/04/15)
• verify logging results are useful (ETA: 2011/04/15)
• add observers to as many other UI events as required (ETA: 2011/04/29)

Related Bugs & Dependencies

Tracking Bugs

• TBD - main project tracking bug

Related Bugs

• bug 601268 - adds "canary in a coal mine" instrumentation to nsThread.cpp
• bug 606574 - adds ability to report information in Talos

Related Documents

• no test plan needed
• no product marketing plan needed

Team

Anyone interested in this project is encouraged to jump in and get involved. The list here is to provide contact and ownership information:

• Development Lead: dietrich
• Infrastructure Lead: ted

Designs

No designs required

Goals/Use Cases

• provide insight to developers into what is causing the Firefox user interface to feel slow or unresponsive to users
• identify high impact areas for UI responsiveness work

Non-Goals

• provide information to end-users about what is causing Firefox to feel slow or unresponsive
• provide UI profiling

Other Documentation

• Jakob Neilson's UseIt article on Response Time Limits for User Interfaces