Electrolysis/Multiple content processes
Goals
After e10s is enabled for all users, the next step is to introduce multiple content processes. The goal is to bring out the most from the multi process architecture we introduced with e10s, gain performance where it's possible and minimize the impact of content process crashes. The challenge is to achieve this without sacrificing the advantage we currently have in memory usage compared to our competitors.
One explicit non-goal of this project is to nest content processes for e.g. iframes. There is work underway to do that in bug 1277066 in parallel to this project.
What to expect
First, we will enable 2 content processes and fix correctness bugs in the DOM and frontend components. Then we will start ramping up the number of content processes while optimizing memory use in order to avoid using too much memory overall. Once we have that we can think about advanced process models, sandboxing and how can we get the most out of multiple content processes.
Roadmap
M1[Nightly bug 1303113]: enable 2 content processes on nightly (Done)
Apart a few corner cases 2 content processes are fairly stable for everyday usage. Our hope is that by enabling 2 content processes on nightly despite a few known issues that will be time consuming to fix (session storage / shared workers) we will get better bug reports early.
- Ignore memory footprint.
- Fix crash report in background tabs bug 1241459
- Known issues that will block riding the train but will not block enabling 2 content processes on nightly:
- Service/Shared workers should run in their own process: bug 1231208
- Some test will need some refactoring: bug 1301015 but for now we will force them to use single content process: bug 1301340
M2[Aurora bug 1304546]: Correctness, Measuring Performance and Memory, and Scaling to 4 Processes
- Measure the memory footprint of content processes
- Measure startup of content process (bug 1336389, bug 1304790)
- Start optimizing memory use
- Prepare to go beyond 2 content processes (aiming for 4 initially bug 1336398).
- Service Workers in it's own content process
- AWSY (bug 1272113)
M3[Beta bug 1304547]: Optimization and Preparing for Release
- Memory optimization
- Performance optimization
- Solidifying Automated tests (working with module owners)
- General Convergence; focusing on quality
Meetings
We are meeting every week at 9am PDT (6pm CEST) starting on June 28.
Memory management
- Memory cost of a content process - relatively high
- Memory usage of e10s compared to other browsers - we're not the worst offender
- Extending Nuwa for all platform does not seem realistic, and since the most memory overhead comes from JS, we should address the problem at JS engine level first. Till Schneidereit suggested lazy cross-process memory sharing.
Testing
- Currently for bc/dt tests we keep content processes alive to fight timeouts
- Areas where additional testing is needed have to be identified.
- Some tests were disabled, re-enabling them is high priority work currently
Bug tracking
- Triage[e10s-multi:?] in whiteboard
Links
- Process Model (2012)
- Recent dev.platform discussion