1819275 - [macOS] Attempt to avoid the main thread being blocked on font-list initialization during startup

Status: RESOLVED FIXED

(Core :: Graphics: Text, defect)

Description

[Jonathan Kew [:jfkthame]]

See profile: https://share.firefox.dev/3ZpfakC

This is a profile of launching a local (opt) mozilla-central build to about:blank.

It's noticeable here that during startup, the main thread is blocked (idle) for around 140ms while it waits for the InitFontList thread to complete.

Comment 1

[Jonathan Kew [:jfkthame]]

Attachment: Bug 1819275 - Don't unconditionally access (and initialize) the platform font list from gfxUserFontSet; it is only required for src:local faces. r=#gfx-reviewers

We register the gfxUserFontSet instance with the platform font list so that it can
be updated when necessary, if the font list changes such that src:local rules might
resolve differently. But if src:local is not used, the font set does not need to
be aware of the platform list, so we can make the connection only when a local
lookup is actually present.

This avoids blocking the main thread during startup, e.g. when we create a font set
for the -moz-bullet dataURI font that is part of the UA stylesheet.

Depends on D171205

Comment 2

[Jonathan Kew [:jfkthame]]

Attachment: Bug 1819275 - Make gfxMacPlatformFontList::LookupSystemFont a static method. r=#gfx-reviewers

This method does not rely on any instance data, it just depends on system font APIs.
So it can be declared as static and used regardless of whether the platform font list
is fully initialized.

This avoids blocking on platform font list initialization when the widget code
calls LookupSystemFont during startup.

Depends on D171206

Comment 3

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:lsalzman, could you have a look please?

For more information, please visit auto_nag documentation.

Comment 4

[BugBot [:suhaib / :marco/ :calixte]]

There are some r+ patches which didn't land and no activity in this bug for 2 weeks.
:jfkthame, could you have a look please?
If you still have some work to do, you can add an action "Plan Changes" in Phabricator.
For more information, please visit auto_nag documentation.

Comment 5

[Jonathan Kew [:jfkthame]]

I was seeing some test failures that proved difficult to resolve; still hoping to get back to this but it can't land as-is.

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/098ce7fab046
Don't unconditionally access (and initialize) the platform font list from gfxUserFontSet; it is only required for src:local faces. r=gfx-reviewers,lsalzman
https://hg.mozilla.org/integration/autoland/rev/f1cebda4f6d6
Make gfxMacPlatformFontList::LookupSystemFont a static method. r=gfx-reviewers,lsalzman

Comment 7

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/098ce7fab046
https://hg.mozilla.org/mozilla-central/rev/f1cebda4f6d6

Comment 8

[Alex Finder]

(In reply to Pulsebot from comment #6)

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/098ce7fab046
Don't unconditionally access (and initialize) the platform font list from
gfxUserFontSet; it is only required for src:local faces.
r=gfx-reviewers,lsalzman
https://hg.mozilla.org/integration/autoland/rev/f1cebda4f6d6
Make gfxMacPlatformFontList::LookupSystemFont a static method.
r=gfx-reviewers,lsalzman

== Change summary for alert #39764 (as of Tue, 03 Oct 2023 10:59:02 GMT) ==

Improvements:

Ratio	Test	Platform	Options	Absolute values (old vs new)
7%	sessionrestore_many_windows	macosx1015-64-shippable-qr	e10s fission stylo webrender-sw	847.21 -> 792.17
5%	sessionrestore	macosx1015-64-shippable-qr	e10s fission stylo webrender	1,096.92 -> 1,043.25
5%	sessionrestore_no_auto_restore	macosx1015-64-shippable-qr	e10s fission stylo webrender	1,113.17 -> 1,061.42
4%	sessionrestore	macosx1015-64-shippable-qr	e10s fission stylo webrender	1,086.25 -> 1,046.92

For up to date results, see: https://treeherder.mozilla.org/perfherder/alerts?id=39764