Electrolysis/Multiple content processes: Difference between revisions

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(Updating M1 link to exclude already fixed bugs from the query)
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== 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.
= Overview =
After e10s is enabled for all users, the next step was 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.


== What to expect ==
The first step was to enable 4 content processes to all users without non WebExtensions based add-ons. Before increasing the number of maximum processes the next step is further optimization. Memory consumption and content process startup time optimization, memory balancing among content processes and user machine based customization based on performance statistics.  
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 ==
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.
=== M1: enable 2 content processes on nightly (target: Firefox 52, tracking: [https://bugzilla.mozilla.org/buglist.cgi?list_id=13206336&status_whiteboard_type=allwordssubstr&status_whiteboard=%5Be10s-multi%3AM1%5D&resolution=---&resolution=FIXED&resolution=INVALID&resolution=WONTFIX&resolution=DUPLICATE&resolution=WORKSFORME&query_format=advanced&bug_status=UNCONFIRMED&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED '''M1''']) ===
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}}
** Session storage is not designed for multiple content processes, next generation DOM storage will fix this problem:  {{bug|1286798}}
** Some test will need some refactoring: {{bug|1301015}} but for now we will force them to use single content process: {{bug|1301340}}


=== M2: preparation for scaling (3 months) ===
= Status =
* Measure the memory footprint of content processes.
{| class="wikitable"
* Start optimizing memory use.
|-
* Strategy to go beyond 2 content processes (aiming for 5 initially).
! Version !! Status
 
|-
=== M3: scaling (ongoing) ===
| 56 || Maximum 4 content processes for all e10s eligible users without any non WebExtension add-ons
* Currently vaguely defined, but the main focus will be memory optimization and the goal is to enable more content processes.
|-
 
| 57 || Maximum 4 content processes for all e10s eligible users
== Meetings ==
|-
We are meeting every other week at 9am PDT (6pm CEST) starting on June 28.
| 58 || No longer relying on the system add-on, prelaunching content process in the background
 
|}
== Core Development Areas ==
== Memory management ==
 
=== Memory management ===
* [http://www.erahm.org/2016/02/11/memory-usage-of-firefox-with-e10s-enabled/ Memory cost of a content process] - relatively high
* [http://www.erahm.org/2016/02/11/memory-usage-of-firefox-with-e10s-enabled/ Memory cost of a content process] - relatively high
* [http://www.erahm.org/2016/02/12/are-they-slim-yet/ Memory usage of e10s compared to other browsers] - we're not the worst offender
* [http://www.erahm.org/2016/02/12/are-they-slim-yet/ 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 [https://bugzilla.mozilla.org/show_bug.cgi?id=876173 lazy cross-process memory sharing].
* [https://bugzilla.mozilla.org/show_bug.cgi?id=1381961 Enabled shared global for JSMs]
== Content process startup time ==
* [https://treeherder.mozilla.org/perf.html#/graphs?series=mozilla-central,1559690,1,1&series=mozilla-central,1559693,1,1&series=mozilla-central,1559696,1,1&series=mozilla-central,1559697,1,1&highlightedRevisions=8a3b8491838e ~300ms] - on most platforms (the OSX issue is investigated under: [https://bugzilla.mozilla.org/show_bug.cgi?id=1404309 bug 1404309])
* The preallocated process manager is enabled from 58


=== Other Problem Areas ===
= Current work =
Areas of the browser which may be incompatible in some way with multiple content processes.
{| class="wikitable"
 
|-
* Shared workers
! Metrics !!
* Service workers
|-
* Session storage
| Talos test to measure parallel page loads || {{Bug|1409002}}
* Plugins
|-
* Browser Content Toolbox (this should be fixed on the back-end already)
| Telemetry probe to measure background process activity || {{Bug|1388280}}
* Printing
|-
* Crashed tab handling, crashed tab page
! Tuning !!
* Crash reporting
|-
 
| Process selection based on memory footprint || {{Bug|1388277}}
== Add-ons ==
|-
* Web extension testing seems to be broken with the multiple content processes
| Restarting troubled processes || {{Bug|1374353}}
* SDK based add-ons probably come with a big memory overhead per process.
|-
* Out of process WE add-ons is not part of the project
| Selecting max content process count based on users machine || ...
* Some add-ons might break because of false assumptions (JSM has to be loaded per process now for example)
|}
 
== Testing ==
* [https://bugzilla.mozilla.org/show_bug.cgi?id=1251962 Existing tests should work with 2 content processes.]
* [https://bugzilla.mozilla.org/show_bug.cgi?id=1251963 Areas where additional testing is needed have to be identified.]
 
== Performance Testing ==
Current Talos tests gives very little information about the difference between one and multiple content processes. We need more tests.


= Future plans =
{| class="wikitable"
{| class="wikitable"
! Memshrink !!
|-
| Compressing strings in JSMs || ...
|-
| Reduce resources loaded in the CP || ...
|-
| Reduce static tables || ...
|-
| Reduce or improve per process caches || ...
|-
! Long term !!
|-
|-
! Some tests should use
| Suspending / Freezing background tabs and processes || ...
multiple tabs simultaneously
! Others are irrelevant
! Additional test we need
|-
|-
| sessionrestore<br>
| Battery life saving mode || ...
sessionrestore_no_auto_restore<br>
tps<br>
tresize<br>
tart<br>
| ts_pain<br>
tsvgx<br>
tsvg-opacity<br>
dromeo<br>
a11y<br>
tscrollx<br>
tresize
| Running active web content
simultaneously in multiple tabs
|-
|-
| Sharing scripts || ...
|}
|}


== Bug tracking ==
= Bug tracking =
* [https://bugzilla.mozilla.org/buglist.cgi?list_id=13206351&resolution=---&resolution=FIXED&resolution=INVALID&resolution=WONTFIX&resolution=DUPLICATE&resolution=WORKSFORME&status_whiteboard_type=allwordssubstr&query_format=advanced&status_whiteboard=%5Be10s-multi%3AM1%5D&bug_status=UNCONFIRMED&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED '''M1'''] [e10s-multi:M1] in whiteboard
 
* [https://bugzilla.mozilla.org/buglist.cgi?list_id=13072930&resolution=---&resolution=FIXED&resolution=INVALID&resolution=WONTFIX&resolution=DUPLICATE&resolution=WORKSFORME&status_whiteboard_type=allwordssubstr&query_format=advanced&status_whiteboard=%5Be10s-multi%3AM2%5D '''M2'''] [e10s-multi:M2] in whiteboard
== Triage ==
* [https://bugzilla.mozilla.org/buglist.cgi?list_id=13115346&resolution=---&status_whiteboard_type=anywordssubstr&query_format=advanced&status_whiteboard=%5Be10s-multi%3AM%3F%5D%20%5Be10s-multi%3A%3F%5D&bug_status=UNCONFIRMED&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED&bug_status=VERIFIED '''Triage'''][e10s-multi:?] in whiteboard
* [https://bugzilla.mozilla.org/buglist.cgi?list_id=13712205&resolution=---&status_whiteboard_type=anywordssubstr&query_format=advanced&status_whiteboard=e10s-multi%3AM%3F%2C%20e10s-multi%3A%3F Triage list] ('e10s-multi:?' in whiteboard)
* [https://bugzilla.mozilla.org/show_bug.cgi?id=1231208 '''ServiceWorkers meta'''] contact person: Andrea Marchesini
 
* [https://bugzilla.mozilla.org/show_bug.cgi?id=742822 '''LocalStorage refactoring'''] contact person: Jan Varga
== Priorities ==
* [https://bugzilla.mozilla.org/buglist.cgi?priority=P1&list_id=13845618&resolution=---&resolution=FIXED&resolution=INVALID&resolution=WONTFIX&resolution=DUPLICATE&resolution=WORKSFORME&status_whiteboard_type=allwordssubstr&query_format=advanced&status_whiteboard=e10s-multi%3A%2B&bug_status=UNCONFIRMED&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED P1]
* [https://bugzilla.mozilla.org/buglist.cgi?list_id=13845621&status_whiteboard_type=allwordssubstr&status_whiteboard=e10s-multi%3A%2B&priority=P2&resolution=---&resolution=FIXED&resolution=INVALID&resolution=WONTFIX&resolution=DUPLICATE&resolution=WORKSFORME&query_format=advanced&bug_status=UNCONFIRMED&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED P2]
* [https://bugzilla.mozilla.org/buglist.cgi?priority=P3&list_id=13845618&resolution=---&resolution=FIXED&resolution=INVALID&resolution=WONTFIX&resolution=DUPLICATE&resolution=WORKSFORME&status_whiteboard_type=allwordssubstr&query_format=advanced&status_whiteboard=e10s-multi%3A%2B&bug_status=UNCONFIRMED&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED P3]


== Links ==
= Links =
* [https://docs.google.com/a/mozilla.com/document/d/14E5ERudaZrx-qcOLttXGkV6DgHIyp3h9IZoqnhuO7X8/edit Process Model] (2012)
* [https://docs.google.com/a/mozilla.com/document/d/14E5ERudaZrx-qcOLttXGkV6DgHIyp3h9IZoqnhuO7X8/edit Process Model] (2012)
* Recent [https://groups.google.com/forum/#!searchin/mozilla.dev.platform/e10s$20multiple$20processes/mozilla.dev.platform/NHIjpGvOelE/_A9IJWsP0fUJ dev.platform] discussion
* Recent [https://groups.google.com/forum/#!searchin/mozilla.dev.platform/e10s$20multiple$20processes/mozilla.dev.platform/NHIjpGvOelE/_A9IJWsP0fUJ dev.platform] discussion
= Teams =
TBD

Latest revision as of 12:46, 6 November 2017

Overview

After e10s is enabled for all users, the next step was 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.

The first step was to enable 4 content processes to all users without non WebExtensions based add-ons. Before increasing the number of maximum processes the next step is further optimization. Memory consumption and content process startup time optimization, memory balancing among content processes and user machine based customization based on performance statistics.

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.

Status

Version Status
56 Maximum 4 content processes for all e10s eligible users without any non WebExtension add-ons
57 Maximum 4 content processes for all e10s eligible users
58 No longer relying on the system add-on, prelaunching content process in the background

Memory management

Content process startup time

  • ~300ms - on most platforms (the OSX issue is investigated under: bug 1404309)
  • The preallocated process manager is enabled from 58

Current work

Metrics
Talos test to measure parallel page loads bug 1409002
Telemetry probe to measure background process activity bug 1388280
Tuning
Process selection based on memory footprint bug 1388277
Restarting troubled processes bug 1374353
Selecting max content process count based on users machine ...

Future plans

Memshrink
Compressing strings in JSMs ...
Reduce resources loaded in the CP ...
Reduce static tables ...
Reduce or improve per process caches ...
Long term
Suspending / Freezing background tabs and processes ...
Battery life saving mode ...
Sharing scripts ...

Bug tracking

Triage

Priorities

Links

Teams

TBD

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