High cpu usage with Firefox

I have an issue that relates to Firefox and cpu usage. If I open quite a few tabs my system crawls, can be for a while too. I can’t select other windows from the taskbar (well I can eventually) etc because the cpu is maxing out. It’s the cmdagent.exe thats hitting the cpu (along with Firefox of course). I managed to track down what’s causing it.

I have only installed cpf recently, so I figured that’s a good place to start. I decided to switch to Allow All and that fixed the problem, no high cpu usage on cmdagent.exe. So next I tried with just the Application Behaviour Analysis off and it still worked fine. No slow downs. Anyway, I played with those settings I found that it is the Monitor DLL Injections option that causes the cpu usage when opening multiple tabs in Firefox. I can have all the other options on but soon as I turn this on, cpu usage goes right up when opening multiple tabs. This is totally reproducible. If I open the same selection of websites, it’s always this option that causes it and nothing else. It’s definitely the culprit.

So, is there anyway to fix this or is that the only solution for now?

I’m using:
Firefox (This actually might have only started happening when I upgraded from I’ll have to uninstall 7 and reinstall 6 to check. It would be odd though, but I only noticed it in the last couple of days, so it’s possible)
Avast 4.7.871
Spybot S&D Resident

I’ve got the same issue.
Anyways (V) (L) (B) (R)

Hmmm, strange, I have no problems and I have quite a few tabs active, not unusual for me … ain’t computers fun.


I’m not seeing this. Well, I do see CPU spikes in Firefox when I open several tabs in quick succession. But, the CPU is not “maxing out”. I only noticed the CPU spikes with the aid of a monitoring utility, there was no apparent impact on the desktop or in Firefox (pauses, delays, etc…).

What extensions/add-ons do you guys have installed in Firefox?

Nope, it’s not extensions or add-ons. If I start Firefox in safe-mode, which disables all extensions, themes etc, it still does it.

What I probably should have made clear, is that the cpu usage drops back pretty much once all the tabs are loaded, it’s only while they are loading. See, quite often when I’m checking my rss news feeds, I will open quite a few tabs to load. The high cpu usage occurs when I have multiple tabs open and loading at the same time. If you had a super fast connection such that they always load basically instantly (I’m on 1.5mbit ADSL btw), you might not notice it (or you probably don’t have an issue at all, which as someone else mentioned, is the joy of computers :slight_smile: ). So you might have to test by opening multiple data intensive sites. But anyway, it’s definitely noticeable if you have the problem, because everything clearly slows down until it is loaded. Yeah, I probably should have said it’s while the tabs are loading, not just open. Also, sometimes when this happens it appears some tabs timeout (or just load slowly), but this isn’t as regular as the slow downs.

It’s most noticeable if I have 9+ tabs loading (which I often do :slight_smile: ) and the cpu usage on cmdagent.exe can go upto 70% (with more tabs). However, if I turn off the Monitor DLL Injections option then the cpu usage cmdagent.exe doesn’t budge from 0%. I just tried with 16 tabs loading with the option off and the cpu usage was still 0%. Everything loaded nice and fast. With the option on and 16 tabs loading I can get cmdagent.exe to consistently sit between 50% and 70%. The other problem is, sometimes this issue is enough to cause Firefox to complain and then Firefox jumps to almost 100% usage. It stays there until I kill it.

1.5Mb ADSL? Hmm… Then perhaps the problem might be the opposite to what you were thinking here. Since, I’m currently using GRPS dial-up & that’s a fair bit slower than any ADSL. I might not be seeing the problem, because I’m running so slow. :smiley:

I also had this problem with firefox and CPF where on page loading the cpu usage jumps to 100%
when say 70 to 80% of the page has loaded and i’m also on Firefox to be honest i can’t
verify if this was a problem with Monitor DLL Injections option as I uninstalled and returned to kerio
but i do know that this affected me with as little as 1 tab open.