e10s Update: June 2

Executive Summary

• Green means GO! For e10s-multi Firefox 54 Beta 1 with 4 content processes. Currently 30% of the 54 Beta population has e10s-Multi enabled as compared to 26% the last week. After four weeks on beta, we have no major issues which would prevent us from shipping release criteria. Scroll below to see more details.

• The Release Plan is to activate e10s multi for 80% of our Release users without add-ons (leaving 20% of users without add-ons with single process). We are going to target 100% of that 80% on Day 1. If something goes awry, we can disable e10s multi with the System Add-On completely or, for a specific population exhibiting issues. The patch for these changes to the system add-on have landed and have been uplifted to 54 bug 1367244. We are working with SV to be sure the changes are validated.

• As of Firefox Release 53 (Mid May) 55% of the total release population have Single-Process e10s (as compared to 52.82 in Firefox 42 in early April). Single process e10s is active for non add-on users, and add-on that are web extensions or SDK add-ons actively marked compatible by the author.

• e10s and A11y for Windows has slipped from Firefox 55 to Firefox 56+ due to the challenges with instability.

e10s-Multi Release Criteria

• [ON TRACK] Stability. We have a tight correlation between single process and multi-process crashes which is good. We decided that the WebExtensions crashes in the content crash rate is being higher than Non Web-Extensions was enough risk to not include WE extensions users in this initial roll-out for Firefox 54. There are a couple of fixes happening: a fix for initial signature which started this conversation bug 1347984 has landed in beta and fixes found in bug 1358879 will also help and shall ship in 55. We haven't seen the improvements we are looking for in telemetry data as of *yet* but are monitoring closely. The shutdown ping has revealed a large increase in shutdown crashes bug 1365123. This is not considered a blocker for MVP in 54. It is in the backlog for 56+.

• [ON TRACK] % of Population shows us that adding MPC=True has increased our exposure. It's also interesting to note that stability for MPC=True is the best of all cohorts because of the inclusion of people who have installed ad blockers. This isn't enough for us to include MPC=True support in release but it's noteworthy.

• [ON TRACK] Performance Telemetry shows us that there is parity between 4 processes and single process e10s so far. This is considered to be meeting our release criteria in that there are not major regressions for our Windows users. We are watching our Mac OS and Linux populations increase in sample size and there are some indications that there is a slight difference between 2 and 4 processes but not enough to block.

• • For tab switching metrics, it's worth noting that only about 3/4 of the beta population are using 3 or fewer tabs so we might find we have different results on release.

• [ON TRACK] Memory Usage is considered to be on track. Our criteria is to be better than Chrome and Eric's latest findings show us that we are. Gabor is adding telemetry so it is easy for us to see how many content processes are running when memory is being measured. When that lands, we will uplift to beta.

Upcoming Decisions and Milestones

• [DONE] A go/no-go decision for doing an initial roll-out for Multi in Firefox 54 will happen no later than June 3rd.
• [DONE] May 23 Compare MPC=data to our current Performance and Stability baseline
• [DONE] The % of Beta Users with e10s-Multi activated in shows us that our initial experiment design doesn't activate E10s-Multi for as many users as we would like. 10% of the population is in the control group and 90% is in test, however, only 46% have e10s active and 21% which is has Multi enabled. We are currently activating e10s-Multi for users who either do not have add-ons installed or who are using WebExtensions only. Product's sentiment is that this approach is too conservative and is evaluating risk vs. reward for expanding the experiment to include MPC=True Add-Ons for e10s Multi. This decision will be made by May 12th.
• [DONE] We should have complete data for our release criteria by EOD May 10

Engineering Status + Schedule

• Firefox 54 is code frozen for Multi.
• We are currently working to land bug 1364849 for Firefox 55. Working with Gabor to get it landed in time for the 55 code freeze.
• Next up: we will be planning for the future Wednesday afternoon in SFO.