Monthly Archives: March 2015

Mozilla Firefox/Platform Engineering Update 39.2

This engineering update is also available on the Platform/2015-03-25 wiki.

Firefox Release Schedule (lmandel)

We shipped two chemspills over the weekend: Firefox 36.0.3 and 36.0.4 (plus Firefox ESR 31.5.2 and 31.5.3)

Firefox 37 is scheduled to be released on March 31. That’s next week! For Firefox 37 Beta/Release, please report any keyboard related issues on OS X such as the keyboard stopping to work and requiring a browser restart.

MemShrink (njn)

jemalloc3 has been disabled again on trunk due to Windows crashes. The heap allocator is a fundamental thing and changing it in a complex program like a browser is hard.

Thanks to Jim Blandy, jemalloc (the old version currently used in Firefox releases, not jemalloc3) is now used as the allocator for the JavaScript shell, instead of the system allocator (bug 1134039). This makes the shell configuration closer to the browser configuration, which will make results more representative. But we don’t yet have data on whether those results have changed significantly due to some OS X problems (bug 1146267). It’s worth repeating: changing the heap allocator is hard.

about:memory now has a “resident-peak” measurement (bug 1145007) on Unix (Linux, OSX, *BSD), which measures peak physical memory usage for the process. It may be useful for detecting short-lived spikes in memory usage.

The new Reader View feature was causing high memory usage on desktop Nightly, but has been fixed in bug 1139678.


In Firefox 37, the Media team is shipping the MSE API (Media Source Extensions, bug 778617) to improve YouTube’s HTML5 video playback on Windows. YouTube will now default to HTML5 video instead of Flash on Windows. MSE for OS X is being tested in Aurora 38.


The Shumway team continues to focus on improving startup performance and Flash ad rendering.

Mozilla Firefox/Platform Engineering Update 39.1

This engineering update is also available on the Platform/2015-03-17 wiki.

Firefox Release Schedule

Only two weeks and two beta builds until Firefox Beta 37 is released. The Tracking Firefox dashboard shows tracked bugs for the Aurora and Beta releases.


RyanVM sends a major shout out to Tim Taubert for being on an orange fixing tear last week.


Mike Hommey enabled jemalloc3 (bug 762449) on Nightly. It’s configured to not ride the trains for now. There are a number of perf regressions and crashes that Mike is diligently working through.


The media team is close to shipping Media Source Extensions (MSE bug 1083588) for YouTube. MSE improves HTML5 video performance as YouTube transitions its default video player from Flash to HTML5 video. The team plans to ship MSE on Windows in Firefox 37, OS X in Firefox 38, and then Linux. Be on the look out for any YouTube bugs, such as videos that won’t load or get stuck rebuffering.


Telemetry and FHR measurements were unified into a single system on Nightly 39 (bug 1069869). The old FHR will still be around for a couple of releases. The unified Telemetry client-side is still being stabilized, so Telemetry from Nightly 39 isn’t reliable yet. Be very careful when interpreting Nightly 39 data!

The unified Telemetry pings are sent to a new Telemetry backend (DataPipeline) which will support streaming analyses. The Telemetry wiki is now up to date with information about Telemetry client-side & server-side workings. We added a Telemetry errata page to help with analyzing Telemetry data.

Many Telemetry histograms will automatically expire in Firefox 40. Check Histograms.json to see if the expiry version of your telemetry probes should updated.

Test results comparing e10s vs non-e10s Talos scores and an explanatory blog post are coming soon. Results in very raw form:

Aaron Klotz created a tool for visualizing Windows attached input queues, as detailed on his blog. Attached input queues can cause odd problems like bug 1105386 where a page won’t load or render if the mouse is not moving.

With bug 1128768, we can now gather information about the amount of jank caused by different types of Flash content. This will be used to quantify the benefit of targeting Shumway at different types of Flash content.

Per-compartment CPU accounting (bug 674779) should land in the next week or two. Use it to report add-ons that use too much CPU or CPOWs (e.g. bug 1136923).


The team’s current focus is playing Flash ads in Shumway instead of Flash. Using Shumway will reduce the number of Flash plugin instantiations, which is correlated with Flash deadlocks, and reduce page jank. Flash ads have also exploited Flash security bugs to install malware. Shumway should protect against many of those exploits.

Shumway now plays IMDb trailer videos on Nightly (bug 1137433) and substantial progress is being made on a verifiable sandboxed. An implementation of AS3’s meta-object protocol that should be pretty faithful to Flash’s an a new Shumway interpreter should land soon. This enables proper handling of SecurityDomains, a crucial Flash security feature.

Mozilla Firefox/Platform Engineering Update 38.3

This engineering update is also available on the Platform/2015-03-03 wiki.

Firefox Release Schedule

The next merge date is March 30, just four weeks away. Firefox 37 and 38 releases have been moved up one week to avoid conflicts with holidays. Firefox 38 will be the “spring thing” Firefox release and the next ESR, retiring ESR 31.

The new “Tracking Firefox” dashboard shows tracked bugs for the Aurora and Beta releases.

Upcoming Outages

The next Tree Closing Window is scheduled for Saturday, March 14.


A new Windows-only “address-space” memory reporter (bug 1134030) landed which may help debug Windows graphics and video memory usage. If you have other ideas on how to measure Windows graphics and video memory usage, contact Nicholas Nethercote.


Shumway has now been enabled (in the Nightly channel only) for playing IMDb trailer videos. Shumway made some headlines a couple weeks ago (TechCrunch and CNET) when it was enabled for playing <a href=""Amazon product tour videos.


Service Workers (bug 1059784) should land soon. (Famous last words.)

IndexedDB performance work will also land soon: bug 866846 will enable SQLite’s WAL journal and bug 1112702 will change transactions to be non-durable. These SQLite options favor performance over durability like Chrome and IE do. They do not increase the risk of database corruption.


Mozilla’s Firefox OS team is at the MWC 2015 (Mobile World Congress) in Barcelona this week, announcing new Firefox OS partners, markets, and hardware form factors. Including sliders and flip phones!

Mozilla is also at GDC 2015 (Game Developer Conference) in San Francisco, where Epic Games and Mozilla announced Unreal Engine 4.7 support for HTML5/WebGL export.