1620111 - Avoid synchronous ReadFontList IPC message

Status: RESOLVED FIXED

(Core :: Layout: Text and Fonts, defect)

Description

[Markus Stange [:mstange]]

Profile: https://perfht.ml/2vvhnTm (2ms profiling interval, GeckoView example on a Moto G5, remote debugging enabled)

During content process startup, the content process sends a synchronous IPC message ReadFontList to the parent process. If the parent process happens to be busy at the time, this message can block the content process for an extended time - 450ms in this example.

We should try to eliminate this synchronous message.

Comment 1

[Jonathan Kew [:jfkthame]]

Yeah, this should be feasible: instead of having the content process "pull" the font list by sending a message to the parent (which potentially blocks for a long time, as here), we can make the parent "push" the list as part of the XPCOMProcessAttributes it passes when it starts the child. That's what we do on macOS and Linux (https://searchfox.org/mozilla-central/rev/c79c0d65a183d9d38676855f455a5c6a7f7dadd3/dom/ipc/ContentParent.cpp#2408-2409); we should rearrange the Android code to work the same way.

Comment 2

[Jonathan Kew [:jfkthame]]

Attachment: Bug 1620111 - Eliminate sync-IPC message ReadFontList, instead use SetXPCOMProcessAttributes to pass font list to the child process on Android. r=lsalzman

Comment 3

[Jonathan Kew [:jfkthame]]

This should avoid the extra sync message.

(Markus, if you have a chance to try profiling this for comparison, there's a try build at https://treeherder.mozilla.org/#/jobs?repo=try&revision=2323b23e32532b3b553bbfb22098f6f98387f3f9.)

Comment 4

[Markus Stange [:mstange]]

Works great! Thanks!
Before: https://perfht.ml/39wFgbM After: https://perfht.ml/2wzMkpp
(I applied the patch locally and didn't use the try build.)

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/b2eb9f51db33
Eliminate sync-IPC message ReadFontList, instead use SetXPCOMProcessAttributes to pass font list to the child process on Android. r=lsalzman,froydnj

Comment 6

[Oana Pop-Rus]

https://hg.mozilla.org/mozilla-central/rev/b2eb9f51db33