1601432 - WebRender abnormal high CPU load with JavaScript off

Status: RESOLVED INCOMPLETE

(Core :: Graphics: WebRender, defect, P3)

Description

[Frank]

User Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36

Steps to reproduce:

1. Create fresh new profile.

2. Set the following preferences: gfx.webrender.all=true, javascript.enabled=false.

3. Restart Firefox.

4. Go to: "https://developer.mozilla.org/en-US/docs/Web/HTML/Element"

5. Open terminal, start "top", observe CPU load of "GPU Process" to be constantly abnormally high (80%-100%) without interacting with the page in any way.

6. Enable JavaScript (javascript.enabled=true). Refresh page. Observe CPU load of "GPU Process" to be low.

Additional Information:
OS: Arch Linux
CPU: Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz
GPU: Intel Corporation UHD Graphics 620 (rev 07)
(MESA_LOADER_DRIVER_OVERRIDE="iris")
MESA: 19.2.6

Actual results:

High CPU load (GPU Process) when WebRender is on and JavaScript is off. I noticed this on some Mozilla Developer pages.

Expected results:

With JavaScript off and no page interaction, the GPU Process should be around 0%.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.

Comment 2

[Darkspirit]

There is an animated loading bar at the top.

Comment 3

[Andrew Osmond [:aosmond] (he/him)]

Would you be able to collect a profiler trace? I'm not sure if the regular profiler addon will work with JS enabled (maybe?) but you can also try perf since this is on Linux:

https://github.com/firefox-devtools/profiler/blob/master/docs-user/guide-perf-profiling.md
https://profiler.firefox.com/

Comment 4

[Frank]

Attachment: Profiler trace from command line (bug_1601432.perf)

Profiler trace from command line as requested. All conditions met as described in the steps to reproduce.

Trace is taken on an idle system with only the example site loaded. No interaction with the browser while trace was taken.

Comment 5

[Robert Mader [:rmader]]

Frank, do you still see this? Can't reproduce here.

Comment 6

[BugBot [:suhaib / :marco/ :calixte]]

Clear a needinfo that is pending on an inactive user.

Inactive users most likely will not respond; if the missing information is essential and cannot be collected another way, the bug maybe should be closed as INCOMPLETE.

For more information, please visit auto_nag documentation.