Starting today, FF uses a lot of CPU even when idle




3 years ago
2 years ago


(Reporter: martyn.ayers, Unassigned)


39 Branch

Firefox Tracking Flags

(Not tracked)




3 years ago
User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:39.0) Gecko/20100101 Firefox/39.0
Build ID: 20150630154324

Steps to reproduce:

I'm using FF on a Win7 64-bit Lenovo T410 portable with 8Gb RAM and 4-core i5.  AV is F-Secure.  Win7 updates from MS are up to date.

I just start FF (v.39) and watch the CPU utilisation in Task Manager with no other applications running.

Actual results:

About 30 seconds after starting FF, the CPU utilisation rises from a few percent to 30%+ and stays there for several minutes.  On TaskMan's Processes tab, 27+% of this is attributed to  "firefox.exe *32".  Then it goes through alternating cycles of short periods of 1-2% utilisation before rising again to 27%+.  This behaviour occurs regardless of how many tabs are open in FF and of what sites are open on the tabs.

I've scanned the PC with F-Secure AV, SpyBot Search and Destroy and MalwareBytes premium, all of which are up to date.  None of them finds anything of consequence, just the usual tracking cookie stuff which I allow them to tidy up.  None of this has made any difference to FF's behaviour.  I have rebooted the PC several times, but the behaviour continues.

As noted in the summary, this has only started happening today.  I am running the same FF version on another PC on my LAN and on that, FF has continued to behave normally.

As noted

Expected results:

After starting up FF should settle down to a few % CPU like it usually does.

Comment 1

3 years ago
Is it reproducible:
1) in safe mode:
2) with a fresh profile:
Flags: needinfo?(martyn.ayers)
Hi Martyn,

I didn't managed to reproduce this issue on the latest release(42.0) nor the latest Nightly(45.0a1).

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:42.0) Gecko/20100101 Firefox/42.0
Build ID: 20151029151421

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Firefox/45.0
Build ID: 20151206030448

I've also tried to reproduce it on your specified version of Firefox(39.0), but the CPU load didn't jumped over 2-3%.

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:39.0) Gecko/20100101 Firefox/39.0
Build ID: 20150630154324

Considering this and the fact that the reporter did not responded to Loic's info request, I will mark this bug as RESOLVED WORKSFORME. If you still encounter this issue, please feel free to reopen this bug or file a new one.

Last Resolved: 3 years ago
Resolution: --- → WORKSFORME

Comment 3

3 years ago
It's better to close it as incomplete as the OP didn't reply (but still can do it). ;)
Hi Loic,

Thanks for your suggestion. I will consider your opinion when triaging further bugs.

Flags: needinfo?(martyn.ayers)
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