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e10s Update: April 8

Executive Summary

  • The biggest news this week is that Product has signed off on APZ being enabled when e10s is enabled. User-visible scrolling is much better with APZ than without for most cases.
  • For Firefox 47, the most likely scenario is still that we continue to conduct A/B Experiments in our beta channel until we can lower our rate of main process, content, and Plugin crashes. IF, the crash rate lowers thanks to the stability fixes/uplifts that have happened as of late, we may be able to extend the experiment for a longer period of time. We will have the final plan by 04/15. Our goal is to expose as many of the eligible population for as many weeks as possible in order to collect a larger data set of telemetry and crash data and to hopefully see a higher return on bug filing related to issues people see. Our latest A/B experiment derived data set indicates we have work to do on stability before we're ready to ship to beta. We are, however, hitting our goals in many areas of our release criteria such as jank and scrolling. We still have work to do in areas such as Startup/Shutdown time, UI Smoothness, Plugin Jank, Memory Usage, and GFX Performance but not to the level that would necessarily block beta.

With the approach of Firefox 47 merging to Beta on April 25, quality and market readiness remain our central focus.

Why yellow? e10s is designated 'yellow' or 'at risk' because:

Incoming data from our latest A/B experiment indicates we have more work to do on the stability side. We also need to tighten up how we are operating by increasing fidelity of our stability data and and reducing latency to measure progress as much as we can.

Next Steps

  • 04/13: e10s stability task force checkpoint
  • 04/15: lock on final plan for Firefox 47 beta

Release Criteria

  • e10s release criteria status
    • We have telemetry data from phase 1 (e10s without APZ) of Beta 46 experiment.
  • Signed off:
    • Jank!
    • Scrolling!
    • Red release criteria:
      • MEMORY_TOTAL: 80% worse. We expected only 10%–25% worse, but 100% regression might be acceptable. TBD.
      • SLOW_SCRIPT_PAGE_COUNT: 0.47 per hour vs 0.36 per hour

Add-Ons + WebExtensions

  • Working on add-on SDK issues mostly related to e10s
  • Outreach to add-on devs to help with e10s compat is ongoing
  • Next steps include getting a pref for testing without a shim

Automated tests

  • Everything we can have enabled in production is enabled, everything else is enabled on a separate branch called 'Ash'.
  • Goal to have all tests be owned by 03/25 (we're close)
  • We would like each directory signed-off by test owners week of 04/07
  • We're tracking all the tests and who owns them, here
  • We are tracking tests that are running and passing on some platforms, but are disabled on others.From a feature coverage point of view, it's in pretty great shape. There's very little that is disabled both on opt *and* debug on a same platform (meaning that that test is not running on this platform). Look for the "Fully disabled in a platform" entries in this spreadsheet.


  • Proposed technical path to encourage a11y clients to communicate directly with the content process bug 1258839. dbolter is getting some first impressions from clients to see if this is a viable approach.
  • We're also looking into Windows touchscreen/a11y compat, see more information as the plan is taking shape, here.


We are at the point where we are setting milestones weekly; given the complexity of deliverables, we are using a Trackback Schedule to keep everything organized.

Release Schedule

Date Trunk Aurora Beta Release
3-07 48 default 47 default 46 A/B Tests 45 off
4-18 49 default 48 default 47 A/B Tests, Possible Rollout (add-ons = ally = no) 46 off
6-07 50 default 49 default 48 Possible Rollout (add-ons + ally = no) 47 off
8-02 51 default 50 default 49 Possible Rollout (add-ons + ally = no) 48 Possible Rollout (add-ons + ally = no)
9-13 52 default 51 default 50 Possible Rollout (add-ons + ally = no) 49 Possible Rollout (add-ons + ally = no)