1493088 - WebRender Scene receives out of order epoch for async video pipeline

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, enhancement)

Description

[Sotaro Ikeda [:sotaro]]

WebRenderBridgeParent incrementally updates epoch and send to WR. But WebRender Scene some time received epoch that has lower values than the past.

I wonder if the symptom is related to Bug 1477819.

Comment 1

[Sotaro Ikeda [:sotaro]]

It could badly affect to CompositorBridgeParent::NotifyPipelineRendered()

Comment 2

[Sotaro Ikeda [:sotaro]]

I checked if epoch is handled incrementally in WebRender since I saw error of waiting for MozAfterPaint even default m-c code with WebRender. The error happened intermittently.

https://treeherder.mozilla.org/#/jobs?repo=try&selectedJob=200567503&revision=8984c30c0df17a09ea09562ef7e64d9713caedee

Comment 3

[Sotaro Ikeda [:sotaro]]

Attachment: temporal log patch

Comment 4

[Sotaro Ikeda [:sotaro]]

Attachment: temporal log patch

Comment 5

[Sotaro Ikeda [:sotaro]]

I used attachment 9010862 [details] [diff] [review] to check comment 0. And confirmed that epoch could revert sometimes to old values.

Comment 6

[Sotaro Ikeda [:sotaro]]

:nical, can you comment to this bug?

Comment 7

[Nicolas Silva [:nical]]

> I wonder if the symptom is related to Bug 1477819.

Sounds right. Because we have low priority transactions for content, we now get two sequences of monotonically increasing epochs: one for high priority pipelines (UI/video) and one for everything else.
A given WebRenderBridgeParent should still have its epochs increasing monotonically, though. My understanding of CompositorBridgeParent::NotifyPipelineRendered is that because we only dispatch the epoch notifications for the WRBP with the given pipeline id the relaxed ordering should not cause issues.

Does that sound right to you Sotaro?

Comment 8

[Sotaro Ikeda [:sotaro]]

It seems that WebRender needs to handle ordered transaction for each pipeline. But we do not always use high priority for video. It causes unordered transaction at WebRender side.

Comment 9

[Sotaro Ikeda [:sotaro]]

Attachment: patch - Use non low priority transaction for async pipline with ImageBridge

Comment 10

[Sotaro Ikeda [:sotaro]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=ca9f3d1ac94e7eb88c26715e92ed066830535874

Comment 11

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/1dde355c049c
Use non low priority transaction for async pipline with ImageBridge r=nical

Comment 12

[Arthur Iakab [arthur_iakab]]

https://hg.mozilla.org/mozilla-central/rev/1dde355c049c