761962 - Mediate omtc and out-of-process content

Status: RESOLVED FIXED

(Firefox OS Graveyard :: General, defect)

Description

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

CC'ing folks who are likely to be affected by this.

Until bug 745148 lands, we'll be forced to choose either omtc or out-of-process content.  (Recursive shadow layer txns aren't implemented currently and may never /need/ to be.)  So we have to decide which pref "wins" if both are enabled.

Out-of-process content is currently much more invasive because it affects all the DOM APIs that touch system resources.  Most folks working on electrolyzing DOM APIs don't care about gfx (beyond working/not-working).  So OOP content should win.

(Anyone working on cross-process efficient gfx, like sharing gralloc surfaces, falls into the same bucket.  Cross-*thread* efficient gfx should be a subset of issues of cross-process going forward, for gonk.  We should use the same code for both.  But debugging cross-thread can be easier sometimes.)

This will mean that to force-off OOP content and force-on omtc, you'll need to set
  pref("dom.ipc.tabs.disabled", true);
  pref("layers.offmainthreadcomposition.enabled", true);

in either $gecko/b2g/app/b2g.js or user.js.  (The latter pref will soon be the default for b2g.)

Comment 1

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

Attachment: Prefer out-of-process content to omtc when they contend

Comment 2

[[:fabrice] Fabrice Desré]

Just as a fyi, it's easy to add custom preferences when installing gaia, by adding them in $gaia/custom-prefs.js

They are added to the user.js that is pushed to the profile, so they have to be user_pref().

Comment 3

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

Comment on attachment 630488 [details] [diff] [review]
Prefer out-of-process content to omtc when they contend

Gol'dernit, forget to request review.

Comment 4

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

https://hg.mozilla.org/integration/mozilla-inbound/rev/b9c7e2a573c9

Comment 5

[Ed Morley [:emorley]]

https://hg.mozilla.org/mozilla-central/rev/b9c7e2a573c9

Comment 6

[Dietrich Ayala (:dietrich)]

Required for OMTC, which is required, so blocking+.