1506084 - Mark font loads with ClassOfService |= TailForbidden

Status: RESOLVED FIXED

(Core :: Layout: Text and Fonts, enhancement, P3)

Description

[Honza Bambas (:mayhemer)]

Because of bug 1501461 we now consider fonts as trackers.  Trackers are tailed.  If fonts are tailed, it may cause visible font fetch/rendering delays.  Fonts should then be explicitly excluded from tailing [1].

Note that I was also experimenting in the past with marking font loads as Unblocked (forbids Tailing too) in bug 1349177, no conclusion made, no tools to measure actual impact.

[1] https://searchfox.org/mozilla-central/rev/17f55aee76b7c4610a974cffd3453454e0c8de7b/netwerk/base/nsIClassOfService.idl#56

Comment 1

[(no longer active)]

Honza, any chance you could find someone from the Necko team to help fix this please?  Thanks!

Comment 2

[Honza Bambas (:mayhemer)]

You mean someone from the font team, no?  I can provide an example, but I would have to look after all the places where font loads are started.  That's more suitable for someone who knows that code than anyone from necko.

An example:
https://searchfox.org/mozilla-central/rev/647b9eb1099e373e079e16f147f74f3d1d65eed3/dom/script/ScriptLoader.cpp#1128-1129,1143

Comment 3

[Jonathan Kew [:jfkthame]]

Offhand, I think font loads are all started via FontFaceSet::StartLoad.[1] I don't see anything related to ClassOfService there at the moment, but it should be trivial to add.

[1] https://searchfox.org/mozilla-central/rev/647b9eb1099e373e079e16f147f74f3d1d65eed3/layout/style/FontFaceSet.cpp#613

Comment 4

[Jonathan Kew [:jfkthame]]

Attachment: Set TailForbidden on class of service for webfont loads

It just wants something like this, I guess?

Comment 5

[Jonathan Kew [:jfkthame]]

Attachment: Set TailForbidden on class of service for webfont loads

Hmm, to actually compile it needs an #include added. Updated patch.

Comment 6

[Honza Bambas (:mayhemer)]

Comment on attachment 9025727 [details] [diff] [review]
Set TailForbidden on class of service for webfont loads

Review of attachment 9025727 [details] [diff] [review]:
-----------------------------------------------------------------

Yes!  Thanks.

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/43db9886e19f
Set TailForbidden on class of service for webfont loads. r=mayhemer

Comment 8

[Razvan Maries]

https://hg.mozilla.org/mozilla-central/rev/43db9886e19f

Comment 9

[(no longer active)]

Thank you both!