Question

Example html page that causes high CPU load: http://www.fisiovivax.com/fisioterapia.html

It has JS in it, so I suppose frucade is right.

Thanks jayakumars for your response, though I was already aware of that page and the generic advise is not very helpful in my case.

I'm pretty sure that disabling all plugins would definitely change things and I was more asking how to trace the performance problem down rather than having to go through a long and extensive try&error scheme.

@SirMarius: Yes - it apperas somehow related to specific web pages but not in all cases.

I use FF always with many tabs opened, min 100, sometimes up to 300+. After Updating FF17 to FF18 I've recognized a much more higher CPU-usage.

This issue doesn't occur as long as there are just a few tabs opened, or it doesnt' be of any consequence at least. The CPU-load of FF18 gets higher with each opened tab. When you close the tabs, the CPU-usage also gets normal. There is nearly no Flash-content and just few JS working on the websites (thanks to NoScript and ABP).

The System: i5-CPU, 16GB RAM, Win7 x64

FF17.01: CPU-load 1.0% average at 300 tabs

FF18.01: CPU-load 10.0% average at 300 tabs FF18.01: CPU-load 5.0% average at 150 tabs FF18.01: CPU-load 3.3% average at 100 tabs

A fresh install and disabling all addons (even in Safemode) didn't fix the problem. It seems, that FF is permanetly doing something with the tabs to being able to speedup on user-action. It's all good, as long as there are just a few tabs opened, but it's getting worse with each further opened tab.

I've opened a bug-ticket at https://bugzilla.mozilla.org/show_bug.cgi?id=832864

Try to boot the computer in Windows Safe mode with network support (press F8 on the boot screen) as a test to see if that helps.

I have to keep my system the next few days on, but I'll try your advice as soon as possible. Anyhow, what is your reasoning behind this hint? Any elder FF versions are working fine, and the system is best maintained.

I'd also rather suspect the issue caused by the revamped JavaScript engine rather than any OS issue. @1394: As you bug report was already rejected due to missing details for reproducing it, maybe at least try to assure that you allow FireFox to send performance monitoring data to the developer team (check that it is enabled via preferences > extended (?) > general). I still hope this helps them to spot the issue on their own.

Yes I also suspect that the new JavaScript engine has it's glitches regarding CPU usage. We are developing a website complete in JS and experienced a have CPU load on certain pages (though no JS beside a few AJAX calls was actually executed according to Firebug) though we couldn't figure out yet what the cause of the problem is.

CPU load on certain pages (though no JS beside a few AJAX calls was actually executed according to Firebug) though we couldn't figure out yet what the cause of the problem is.

It may be worth while testing without Firebug installed. I guess Firebug use could itself increase the CPU load in some circumstances.

Same problem here. Firefox 18 consistently uses all cycles of one cpu core. Downgraded to Firefox 16.0.2 and problem's gone even though I'm using exactly the same add-ons.

It is strongly recommended that old versions of Firefox are not used. Unless you re able to take very strong measures to mitigate the risks such as

• using in a Virtual Machine
• having a well rehearsed bare metal restore procedure

As 46 users have now voted me-too in this thread I wonder if anyone is able to give steps to reproduce, preferably whilst in Firefox's safe-mode.

If there is a real problem, a bug could be filed so that it gets developer attention.

If it does not occur in safe mode, then maybe we may discover in this thread what the cause is and share the solution with one-another.

One contender for the problem will be Firefox's new JavaScript handling. As a troubleshooting step that may be turned of by setting javascript.options.methodjit to false using about:config.

• see http://kb.mozillazine.org/Firefox_crashes#JIT_compiler
  • and http://kb.mozillazine.org/About:config

I too am experiencing high CPU usage since the FireFox 18 upgrade. I'm running Windows 7 SP1 x32 on a P4 machine, so the high CPU usage really bogs things down.

As far as I can tell, the performance hit doesn't depend on how many tabs I have open or which websites I visit. Time is the issue. After a few minutes. CPU usage goes above 90% and stays that way whenever I'm doing something in Forefox. It's really frustrating when I can type faster than the program can echo my keystrokes in a form.

I've tried the standard methods of debugging such problems: starting FireFox in Safe Mode, restarting Windows in Safe Mode with networking, etc. Nothing works. I just can't use FireFox 18 on this PC. I'm not crazy about Chrome, but I've resorted to it because FireFox is just too frustrating to use now (although, to be fair, IE9 is even worse with its constant nagging prompts).

I wonder if this is happening because FireFox is being optimized for performance in Windows 8, and performance in earlier OS versions is being placed on lower priority.

Well, that's just speculation. What's the latest? Has anyone had any success dealing with this problem?

Thanks for your time,

Alan Mintaka

General Note to anyone interested in this thread subject

Please turn on Telemetrymobile Desktop Please turn on Telemetry _{2nd edit}
This was brought out because Mozilla Firefox developer were not being immediately notified of regressions that occurred on the Release channel. Unfortunately on the Release channel the option is off by default so some or the rarer problems still may get missed. Please turn it on it helps developers spot this sort of problem. (It also gives you masses of data you can examine to confirm if Firefox is doing badly)

Alan

Have you tried the steps in my post above to turn of the Java script processing. I am still not sure if this thread is just a self selecting collection of users with differing problems or whether is any real underlying single problem that is yet to be identified.

It would be really good if we could get methods of reproducing this problem that everyone could test, and see, then developers would be able to investigate and fix it.

ESR
I do not like recommending this and must say it is not officially recommended in fact

• it is not supported by this site support.mozilla
• Mozilla states individuals should not use it

But as a temporary measure when the only other Firefox option is to downgrade to an insecure Firefox 17, I personally may try Firefox17 ESR, because at least that remains secure until the problem is resolved and you may return to the Release Channel.

BETA Channel - always has secure downgrade option
Another controversial idea, NOT for now but once this issue is resolved. Use the Beta channel (or be brave and use Aurora also). If an issue emerges in future with a new Beta Release, you see it six weeks earlier and have a relatively easy downgrade option to a secure and working Firefox Release Channel. Having more users on the Beta channel helps everyone as problems are more likely to be found and not get out onto releases of Firefox.

I fully agree with John99 points.

• Please enable performance telemetry
• To further pin this issue down we urgently need to provide a reproducible way to demonstrate it
• It's important not to mix different issues.

For example I tried to reproduce the issue with the mentioned URL http://www.fisiovivax.com. But the fact is: This particular website generates a continuous cpu load on all browsers (tested: FF16, Chrome). So the issue there seems to be with the JavaScript code itself, rather than the executing browser.

Personally, I mostly noticed this issue on internal Confluence Wikis, JIRA tracker and Zimbra Webmailer which are not public accessible and hence a bad problem demonstrator.

Furthermore the situation does not stable arise on just visiting a specific page, but a longer interaction before. I mostly notice the issue on sites, which do some have some sort of in-page interaction like updating parts of the page upon a requests rather than delivering a full new page.

Has anybody more easily, accessible samples and use cases, which are know to have worked fine with FF17 an earlier?

I still do suspect, that my specific might be significantly make it worse compared to a vanilla FireFox installation, due to the large set of plugins I use. But to the large auditorium indicates, that I might be wrong regarding this point.

Looking forward for any helpful hints to better demonstrate this issue.

FIREFOX 19
Note there was for instance a bug affecting bookmarks use with fx18 fixed in fx19. Before embarking on serious troubleshooting it is probably worth waiting for fx19. (It is released but linux users may need to wait a day or so)

TELEMETRY
Someone asked me for further details. Whilst the feature was being tested an add-on was required, now I may view my personal data by keying into the address bar about:telemetry The pooled data collected is also of course publicly available (but you need to register and sign in to the site)

• https://wiki.mozilla.org/Telemetry/FAQ
  • Send performance data to Mozilla to help improve Firefox
  • How can I help by submitting mobile performance data?
• https://metrics.mozilla.com/

Hello, I have been experiencing the same problem over the past few days. I noticed that with the most recent update (19.0) matters have improved ever so slightly on the whole, but where some pages are using up to 95% CPU I am noticing a significant adverse effect upon other processes (for example, I thought my soundcard/speakers had fried, only to realise that the high CPU usage from FireFox is causing it to pop and crackle - and yes, I have tested this thoroughly to check this isn't the case...)

I have tried disabling Java, which again sees a minimal improvement, but again, not enough to make this any less of an issue.

My main concern is how the consistent high CPU usage inflicted by FireFox seems to limiting my overall use of my laptop. I wonder if anyone has noticed any sound/soundcard related issues?

For the record, I am using Firefox 19.0 on Windows 8 (which has all the latest updates installed). I

Please remember the original suggestion

• that refers to http://kb.mozillazine.org/Firefox_CPU_usage

Also consider looking at the simpler

• Firefox uses too many CPU resources - How to fix

@john99, OK, I've enabled telemetry pre the instructions in the FAQ.

BTW, the link you provide for "Desktop Please turn on telemetry" actually points to the instructions for enabling telemetry on mobile devices (the same link you truck out in the previous sentence).

The link to instructions for desktop clients can be found in the left column of that page. Here's a direct link for anyone who's interested:

Desktop Please turn on telemetry

RE Javascript handling: I'm going to leave that setting alone for the time being in order to provide telemetry for an implementation that has it enabled. I'll turn off the javascript handling after I've used the browser for a few hours, so you can have before/after data for comparison.

Thanks, Alan Mintaka

I went to 90%+ pretty quick, even to reload this page!

I've now changed the javascript preferences shown, per the linked instructions in your message.

Old settings:

javascript.options.methodjit.chrome default boolean true javascript.options.methodjit.content default boolean true javascript.options.methodjit_always default boolean false

New settings:

javascript.options.methodjit.chrome user set boolean false javascript.options.methodjit.content user set boolean false javascript.options.methodjit_always default boolean false

Telemetry is still on. This should generate some before/after results, at any rate.

Thanks, Alan Mintaka

OK, telemetry has been on for over a day now. However when I entered

about:telemetry

in the URL bar, I got this message:

"Problem loading page - The address isn't valid"

Note in my first post that I said I was using FireFox 18. The FAQ doesn't mention that an add-on must be used in order to make the about:telemetry link work in Firefox versions before 19.

I installed the add-on in order to make sure that the telemetry I've been generating with Firefox 18 was actually recorded. After the installation the about:telemetry link started working and I found that telemetry evidently was recorded.

Unfortunately I don't know what to make of the information yet. I did notice at the top of the page two messages followed by a few lines of what look like SQL statements. The messages were:

Slow SQL Statements on Main Thread

Slow SQL Statements on Other Thread

This info was followed by a ton of bar charts, mostly with headers I can't understand.

Should I submit this info somehow, or is it now visible to you guys as well?

Obviously I need to upgrade top FireFox 19. If I do this now, will it erase the telemetry recordings for FireFox 18?

RE the javascript preferences: I didn't notice any change in performance with the Javascript preferences set to FALSE. A few minutes after launching, FireFox started using 90+ % of the CPU continuously, regardless of what I was doing (including just watching the task manager). This wrecked the performance of all other applications on the system, and performance in the browser itself was also lousy.

Thanks for your time,

Alan Mintaka

If about:telemetry is available then you should see it listed on the about:about page (it is there in Firefox 19).

@cor-el,

I'm not sure if you're answering my last post. If you are, I was evidently still editing my message when you posted. I did manage to get about:telemetry to work by installing the add-on for FireFox versions older than 19 (mine is 18).

I'm going to leave 18 installed until I can figure out what to do with the telemetry data. However - would upgrading to 19 blow away the telemetry for 18? I would like to keep it if I can, in the event it proves useful somehow.

Also, note some of the messages I listed in my previous post. Regardless of what all of the barcharts mean, slow SQL response was flagged on the "Main" and "Other" threads.

Thanks for your time,

Alan Mintaka

I am not sure if any of this will help at all, but it may at least point you at some information sources.

Sorry I do not really understand what all the data is myself, although I can see there is an awful lot of information. All I know about where it is stored is that I can see files in my firefox profile that apparently relate to the telemetry add-on and to the data itself, such as a *savedTelemetry.dat.json apparently includes the raw data for the histograms.

I am not sure if saving old versions of that file and overwriting (rename files as necessary maybe) the current file with it could be used as a method of preserving and viewing the info.

My initial thought was that merely comparing your data with the pooled data probably some would show up as very bad and would at least be quntitative data you would be able to quote when expressing how bad performance was.

I am not a developer but I do note developer info shows it is possible to design specific histograms, and as a separate subject there is the profiler that may be used ( ? on custom builds ? )

1. https://developer.mozilla.org/en-US/docs/Performance/Adding_a_new_Telemetry_probe
2. https://developer.mozilla.org/en-US/docs/Performance/Profiling_with_the_Built-in_Profiler
   & https://developer.mozilla.org/en-US/docs/Performance/Profiling_with_the_Built-in_Profiler_and_Local_Symbols_on_Windows

I am not sure where this may be discussed, although there are a wealth of Mozilla forums and mailing lists.

• http://www.mozilla.org/about/forums/
• and also this blog could have user friendly info and maybe even answer questions on the subject of any regression in performance
  • see https://wiki.mozilla.org/Performance/Snappy
  • http://taras.glek.net/blog/2013/01/28/snappy-number-50-misc-speedups/ (much info in previously used site https://blog.mozilla.org/tglek/ )

Thanks john99,

Those links look pretty good, especially the one for "adding_a_new_telemetry_probe". I didn't know such things could even be done.

For now I'll concentrate on the parts of the telemetry I can read, such as "Slow SQL Response".

Also, and as usual, I wasn't thinking. I'll just save the current about:telemetry page for FF 18 on my HDD and then upgrade to FF19. Who knows, the upgrade may solve the problem on this client.

Thanks for the info,

Alan Mintaka

The upgrade from FF18 to FF19 seems to have solved the problem for now. Performance is much better, even with many open tabs. CPU usage does peak over 90% from time to time, but doesn't stay there longer than a few seconds.

However, I still have the about:config javascript.options.methodjit preferences set to FALSE. I'm going to leave them that way for the time being, until I'm satisfied that the upgrade has made the performance consistently better than it was with FF18. Once I'm satisfied with that, then I'll reset those preferences to TRUE.

I'll post here again if performance goes back down the dumper, with or without those preferences set to TRUE.

Thanks to all who took the time to read my posts and respond!

Alan Mintaka

Glad to see there is some possible improvement.

Might be interesting to see if it is possible to work out which bug may have remedied this, I do not see anything obvious in

• http://www.mozilla.org/en-US/firefox/19.0/releasenotes/buglist.html

On the subject of bugs I see the one filed earlier

• Bug 832864 - FF18 uses much more CPU load than FF17 depending on the number of opened tabs

and mentioned in this thread was closed as not actionable due to lack of: Info & valid STR.

Another tool for checking performance is the new profiler. It is still in development but is being integrated into Firefox and so far has made it into Firefox 20 on the Beta channel, so may be only six weeks away.

• http://anton.kovalyov.net/2013/02/22/remote-profiling/
  • and the earlier Firefox Profiler is now in Nightly!
    http://anton.kovalyov.net/2012/12/17/firefox-profiler/

Original Poster here: I'm still monitoring the behaviour, but similar to Alan it seems, that the latest update to FireFox 19.x may have resolved the issue. If not - I will report back hopefully armed with more details.

As a software developer I'm really keen & looking forward to the upcoming built-in FireFox profiler.

I really want to thank all the people here for the really helpful and in-depth support given here! Even if we could no clearly pin down the issue, this question provided a lot of very helpful pointers and insights into FireFox and their roadmap. My experience outstands all my previous support experiences I ever had, even with highly-paid commercial solution providers.

Many kudos here especially to John99 and AlanMintaka for their extensive research.

You are welcome, pity we did not get to the bottom of the issue, but most importantly it seems to be resolved by the upgrade.

I'm sorry, but I have to disagree. The issue isn't really fixed.

Yes, FF19 uses less CPU load than FF18, but still much more than FF17 did.

Here my average values: The System: i5-CPU, 16GB RAM, Win7 x64

FF17.01: CPU-load 1.0% average at 300 tabs

FF18.02: CPU-load 10.0% average at 300 tabs

FF19: CPU-load 4.5% average at 300 tabs

So FF19 uses still 3 times more CPU load than FF17 did, both in normal mode and in safety mode with disabled addons. I my opinion, that's not enough to mark the problem as solved.

@1394, What about time slices though? FF19 may be using that much CPU, but does it give up time slices for other processes more efficiently than FF18?

Here's how I opened my last post: "The upgrade from FF18 to FF19 seems to have solved the problem for now. Performance is much better, even with many open tabs. CPU usage does peak over 90% from time to time, but doesn't stay there longer than a few seconds."

My original complaint about the high CPU usage was in reference to how it slowed system performance overall and crippled the other applications that were running. That's not happening with FF19, at least not in any way that I can measure. All I know is that the overall system performance problems went away when I updated to FF19, even though FF19 occasionally peaks the CPU over 90%. That's good enough for me.

@AlanMintaka, well, it's good, that you are now able to work again with your computer with opened Firefox.

For average CPU usage I don't measure the peaks, which still occur from time to time. The peaks can go up to full core usage, so in my case with a 4Core CPU up to 25%.

Once again, good, that with the new upgrade many people can use Firefox furthermore, but the core of the problem doesn't seem to be solved yet. FF19 is still using much more CPU load than FF17, even you are now able to use your PC again.

1394
Have you tried using a clean profile and running in safe mode with no plugins enabled ?

I you are prepared to provide evidence of your figures, and run tests if required then you could consider politely posting your assertion about the performance regression as a comment in one of these blogs

• http://taras.glek.net/ (They are written by a developer working on Firefox performance issues.)

You may get a reply from someone with useful advice.

@John99

Jep, new profile, fresh installation, safe mode, disabled plugins, disabled addons - I've tried everything. FF17 is working well, FF18 eats CPU and FF19 is inbetween.

Are you able to review your average CPU usage with FF19 while opened about 300 tabs? Doesn't matter which ones, just open tabs and check, if your average CPU load gets high. I really think, that the most people are satisfied when they can use their PC in normal way. So they don't care about a few percentage CPU load more or less as long as the PC is still running. However, I'll stay at FF17, but I think I'll change to ESR as long as there is no solution in sight.

Btw, many thanks for your hints, but I'm tired in spending time to try getting FF working in the same way as it's did before they rebuilt the whole JS engine and maybe much more.

I just tried fx20 with 500tabs in one window and another hundred or so other tabs in other windows. Each of the cores stayed under 25% . That could be considered high but hardly causing problems.

Try the blog site I mentioned, you could have come across some as yet unknown regression.

Well, many thanks for testing your FF. So the issue, if Mozilla would call it so, is still alive in FF20. Of course, this issue dosn't cause big problems, you can work furthermore, even, if one of four cores stays permanently on 25% percent. But FF isn't the light-cpu-using-browser anymore as it was before.

Ok, I'll try your blog-site ;) Thanks again

@1394 Opposed to the issue I and Alan had where we actually failed to provide a solid bug report, your issue seems to be very easily reproducible. Please consider that FireFox is a free project and its relevance by user base is vital for keeping the Internet free! Therefore I'd join John99 kind encouragement, if you as a stakeholder in the tab issue could try to bring up this into attention at the right places. This would be great!

1394

 before they rebuilt the whole JS engine 

Note the JIT compiler may be disabled by toggling a pref as mentioned upthread, or by using Safe Mode, so your own tests already suggest this is unlikely to be the cause of any CPU load increase you see.