1565019 - High CPU usage in parent process main thread when loading tripadvisor.ca, for over 700ms

Status: NEW

(Core :: Networking, defect, P2)

Description

[Markus Stange [:mstange]]

Here's a profile of loading tripadvisor.ca on my machine: https://perfht.ml/2JvpP9n

A lot of work seems to be happening in the parent process main thread, most of it triggered by initiating network requests. It would be good to reduce the amount of work and/or move it to other threads.

(I'm not expecting any immediate remedies; I'm filing this bug mostly to have an example that I can point others at, and so that we have a profile that we can compare ourselves to, in the future as this improves.)

Comment 1

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

Bugbug thinks this bug is a enhancement, but please change it back in case of error.

Comment 2

[Andrew Creskey [:acreskey]]

The Performance Impact Calculator has determined this bug's performance impact to be high. If you'd like to request re-triage, you can reset the Performance Impact flag to "?" or needinfo the triage sheriff.

Platforms: [x] Windows [x] macOS [x] Linux
Impact on site: Causes noticeable jank
Page load impact: Some
[x] Able to reproduce locally
[x] Bug affects multiple sites

Comment 3

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

The severity field for this bug is set to S3. However, the Performance Impact field flags this bug as having a high impact on the performance.
:valentin, could you consider increasing the severity of this performance-impacting bug? Alternatively, if you think the performance impact is lower than previously assessed, could you request a re-triage from the performance team by setting the Performance Impact flag to ??

For more information, please visit auto_nag documentation.

Comment 4

[Valentin Gosu [:valentin] (he/him)]

Not sure if the profile in comment 0 is still applicable?
It seems a lot of time is spent in "http-on-before-connect" observers - matching WebExtension requests.
I think this can stay S3 for now.

Comment 5

[Andrew Creskey [:acreskey]]

Will re-evaluate impact.

Comment 6

[Marc Leclair [:mleclair]]

The Performance Impact Calculator has determined this bug's performance impact to be low. If you'd like to request re-triage, you can reset the Performance Impact flag to "?" or needinfo the triage sheriff.

Platforms: [x] Windows [x] macOS [x] Linux
Page load impact: Some
Websites affected: Rare

Comment 7

[Andrew Creskey [:acreskey]]

Still seeing significant amount of cpu time dedicated to network activity in the parent process, especially URL classifier
https://share.firefox.dev/3QHGsk7

Comment 8

[Andrew Creskey [:acreskey]]

See also Url classifier delay in bug 1813805.