1600418 - Delay during switching tabs (after long browsing session)

Status: RESOLVED INVALID

(Firefox :: Untriaged, defect)

Description

[Cirno]

User Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:70.0) Gecko/20100101 Firefox/70.0

Steps to reproduce:

Sometimes firefox become unresponsive when I open new tabs/switch between tabs. It seems to correlate with how long Firefox has been open and how active/intense I am with my browsing. It usually happens after couple days of browsing without restarting firefox (I put my PC to sleep, so firefox is not closed).

Actual results:

Switching between tabs became slow (about 1 to 2 seconds). It doesn't matter what sites are loaded in tabs, even empty tabs have the same delay. Closing all tabs doesn't fix the issue. The only way I found to fix it is to restart firefox, then switching between tabs became near instantaneous again.

Expected results:

Switching between tabs shouldn't became slow.

Comment 1

[Cirno]

Here I captured switching tabs couple times https://perfht.ml/35INGKE

Comment 2

[Peter Magyari (Desktop QA)]

Hi Cirno,

I wasn't able to reproduce this issue on my end, I've tried it both on Firefox 70.0.1 and Firefox Nightly 73.0a1

Could you check if this also occurs to you while using a new profile? You can find the steps to do that here:
https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles?redirectlocale=en-US&redirectslug=Managing-profiles#w_starting-the-profile-manager

Thanks!

Comment 3

[Peter Magyari (Desktop QA)]

Mike, if you've got the time, could you take a look over the performance profile from Comment 1?

Thanks!

Comment 4

[Cirno]

(In reply to Peter_M from comment #2)

Could you check if this also occurs to you while using a new profile?

Can I use addons on that new profile? Because it can take several days or even up to a week until I catch the bug and using firefox without all addons is inconvenient

Comment 5

[Cirno]

By the way, I have a suspicion that cause of the bug could be the Stylus addon.
Here https://www.reddit.com/r/firefox/comments/cifd2q/major_performance_issues_with_firefox_ui_freezing/
some guy described the same bug, and he was able to find that the cause of it was addon Dark Reader. I do not use Dark Reader, but I have Stylus installed (main purpose of both addons is changing css of pages).
Can you tell from the performance profile whether the slowness is due to that addon or not?

Comment 6

[Mike Conley (:mconley) (:⚙️)]

Wow! The parent process is really bogged down doing style computations. I'm seeing style flushes lasting ~700ms!

Cirno, have you modified the style of the browser in the parent process using a userChrome.css file?

Comment 7

[Cirno]

Attachment: Bug1600418_chromeFolder.zip

Yes, I have restyled scrollbar and context menu. Here the content of chrome folder.

Comment 8

[Mike Conley (:mconley) (:⚙️)]

If you (temporarily) remove those customizations (perhaps by renaming the chrome folder to chrome-disabled or something), does the performance issue go away?

Comment 9

[Cirno]

I'll do it and check. Right now I don't have any performance problems, it usually should pass some time after last browser restart until the bug occurs (and last restart was today after firefox update). I'll report in a few days (or a week)

Comment 10

[Emma Malysz]

Cirno, were you able to reproduce this problem without the customizations?

Marking this as fxperf:p3 until we have additional information.

Comment 11

[Cirno]

No. I tested it about a week and there's no delay. So previous delay was definitely due bugs in my userChrome
I'm sorry for bothering you all, it was my fault. And thank you for help

Comment 12

[Mike Conley (:mconley) (:⚙️)]

Not a problem, thanks for reporting.