1680420 - Too much time spent instantiating fonts on WRWorker threads (causes scrolling latency on Facebook)

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect)

Description

[Markus Stange [:mstange]]

Attachment: Instruments screenshot

Profile from scrolling on Facebook: https://share.firefox.dev/37u6r7h

On Facebook, when performing a sequence of fast-scroll, pause, fast-scroll, pause, the scrolling has a high latency (>100ms). Profiling reveals that this latency is because WR frame building is blocking on font rasterization.

The profile above is unfortunately missing symbols for system libraries.

I'm attaching a screenshot from an Instruments profile to make up for it. The breakdown in Instruments is as follows:

• 57% TBaseFont::GetSymbolicTraits
• 21% CTFontCreateWithGraphicsFont called from core_text::font::new_from_CGFont_with_variations
• 9% CTFontCreateWithGraphicsFont called from process_glyph directly
• 7% CTFontCopyVariationAxes
• 3% CTFontDrawGlyphs
• 2% CTFontGetBoundingRectsForGlyphs
• 1% CTFontGetAdvancesForGlyphs

It seems that we could get rid of 95% here if we held on to certain font objects for longer.

Comment 1

[Henrik Skupin [:whimboo][⌚️UTC+2]]

Could this be the same probem as with Matrix/Elements when trying to use an Emoji in a message? When clicking the smiley to open the emoji popup it takes more than a second to display the emojis on Apple. Note that the file is around 240MB in size.

Comment 2

[Henrik Skupin [:whimboo][⌚️UTC+2]]

Looks like the issue with Elements doesn't always happen. I will keep an eye and file a new bug if it's not related to that specific behavior.

Comment 3

[Markus Stange [:mstange]]

I see similar slowness when switching between github tabs: https://share.firefox.dev/3qtYLdI

Comment 4

[Jeff Muizelaar [:jrmuizel]]

GetSymbolicTraits is called by is_bitmap_font() for every glyph. We should do it once per font.

Comment 5

[Lee Salzman [:lsalzman]]

Attachment: Bug 1680420 - cache CTFontSymbolicTraits in WR CT fonts. r?jrmuizel

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/4d24f069ddd9
cache CTFontSymbolicTraits in WR CT fonts. r=jrmuizel

Comment 7

[Razvan Maries]

https://hg.mozilla.org/mozilla-central/rev/4d24f069ddd9