Firefox suddenly took 100% CPU time




a year ago
a year ago


(Reporter: vincent-moz, Unassigned)


({perf, steps-wanted})

52 Branch
perf, steps-wanted

Firefox Tracking Flags

(Not tracked)




a year ago
User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0
Build ID: 20170623152303

Steps to reproduce:

Closed a tab (Twitter on a hashtag).

Actual results:

Firefox suddenly took 100% CPU time (the fan started to make a lot of noise, and htop said that this was due to the firefox process).

Expected results:

Firefox should have still kept almost no CPU time.

The about:performance page said that everything was performing well, with at most 1% CPU for each. So the permanent 100% CPU cannot be explained.

Quitting and restarting Firefox solved the issue.

Comment 1

a year ago

This issue is reproducible?
Keywords: perf

Comment 2

a year ago
No, the issue is not reproducible.


a year ago
Has STR: --- → no
Keywords: steps-wanted
User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:57.0) Gecko/20100101 Firefox/57.0
Build ID: 20170809100326

I have tested your issue on latest Firefox release (54.0.1) and latest Nightly (Build ID: 20170809100326) and could not reproduce it. I have opened multiple Twitter tabs with # groups and close them one by one.

Is this still reproducible on your end ? If yes, can you please retest this using latest Firefox release and latest Nightly build ( and report back the results ? When doing this, please use a new clean Firefox profile, maybe even safe mode, to eliminate custom settings as a possible cause (
Flags: needinfo?(vincent-moz)

Comment 4

a year ago
(In reply to Vlad Bacia-Mociran [:VladB], Desktop Engineering QA from comment #3)
> Is this still reproducible on your end ?

No, I couldn't reproduce it yet.
Flags: needinfo?(vincent-moz)
Based on Comment 4 from the reporter, changing status to RESOLVED-WORKSFORME.

If anyone can still reproduce it on latest versions, feel free to reopen the issue and provide more information.
Last Resolved: a year ago
Resolution: --- → WORKSFORME
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