1376044 - APZ takes an appreciable amount of time with WebRender

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect, P1)

Description

[Jeff Muizelaar [:jrmuizel]]

Loading up a Facebook news feed I see 4% being spent in UpdateAPZ and 4.3% being spent in IPC::ParamTraits<mozilla::layers::WebRenderScrollData>::Read()

Some of this looks like region copying which could probably be easy to avoid.

Comment 1

[Jeff Muizelaar [:jrmuizel]]

I see a bunch of time being spent on the child side as well:
 - IPC::ParamTraits<mozilla::layers::WebRenderScrollData>::Write()
 - mozilla::layers::PopulateScrollData()

Comment 2

[Kartikaya Gupta (email:[e-mail])]

Can you share the link to the profile?

Comment 3

[Jeff Muizelaar [:jrmuizel]]

I profiled using Instruments so sharing's a bit of a pain. If you can't reproduce it I'll see what I can come up with. (If you need facebook credentials I have an synthetic account I can share with you)

Comment 4

[Kartikaya Gupta (email:[e-mail])]

I profiled both Facebook initial load as well as scrolling up and down on the news feed as more things loaded and I'm seeing negligible amount of time spent in UpdateAPZ and reading WebRenderScrollData instances. This is on a local macOS opt build with rustc 1.22.1 and opt-level 3. In fact the compositor thread is mostly just idle, even the parts where the content process isn't blocked in JS events has the compositor thread >90% idle.

Initial load: https://perfht.ml/2ikCPDO
Scrolling up and down as things load: https://perfht.ml/2ioiQEe

Are you still seeing this? I'll take a look at the code anyway to see if there's any cleanup that can be done there. I've been meaning to do that anyway since we dropped the layers-full codepaths since the WebRenderScrollData can probably be organized better now.

Comment 5

[Jeff Muizelaar [:jrmuizel]]

This is looking much better now.

Comment 6

[Kartikaya Gupta (email:[e-mail])]

I looked over the code. There's a bit of dead code leftover but otherwise there's not much I can do here until we switch to WR hit testing and drop the event regions stuff in WebRenderCommandBuilder.

Comment 7

[Kartikaya Gupta (email:[e-mail])]

Attachment: Bug 1376044 - Remove dead code left over from layers-full WR implementation.

Review commit: https://reviewboard.mozilla.org/r/204318/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/204318/

Comment 8

[Jeff Muizelaar [:jrmuizel]]

Comment on attachment 8933395 [details]
Bug 1376044 - Remove dead code left over from layers-full WR implementation.

https://reviewboard.mozilla.org/r/204318/#review209882

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/7ad26a049af8
Remove dead code left over from layers-full WR implementation. r=jrmuizel

Comment 10

[Raul Gurzau (:RaulG)]

https://hg.mozilla.org/mozilla-central/rev/7ad26a049af8