Over the last couple days I noticed my Firefox getting painfully slow. The weird part was that the rest of my system was responsive. When I opened Activity Monitor it showed 100% CPU usage for Firefox. I decided to do some investigating. I used the ‘Sample Process’ feature in Activity Monitor. After setting the display to ‘Percent of Parent’ I noticed that there was a lot of ‘Flash_EnforceLocalSecurity’ messages which lead me to believe that Flash was the culprit.
I went through my tabs, and sure enough I had lots of Flash open. This pattern kept repeating itself. I’d notice Firefox getting sluggish, close flash web pages and see Firefox performing properly and CPU usage levels back to normal. I found it strange that I could play Hulu and Youtube videos fine. I even went to www.bannerserver.com and found that while Firefox was never using 100% of my CPU. This was baffling me until I figured out what the problem was. This issue only happens when AT&T Uverse flash ads show up.
Not everyone cares to find the root cause of a problem like this. It is also only sporadically reproducible, going to the same website might show different ads each time. I would bet that a lot of people would look at this and say “Firefox is slow”, especially because the ads are there on many different pages. These ads are also not the primary reason someone goes to the page (I’d hope) which means that it is difficult to associate the flash ad with the purpose of their tab if they do try to figure out what the problem is. Having plug-ins in a separate process (Electrolysis) seems like a great idea. I hope that, like Safari on Mac, it shows up as a totally separate process which helps avoid people blaming Firefox for poor performance.
The most annoying part of this whole situation is that I’d love to be a Uverse subscriber. It is bad enough that they aren’t offering it in my area, but to make my browser slower is a slap in the face!
#1 by Thinker on November 25th, 2009
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Just get the AdBlocker Plus plugin for Firefox at https://addons.mozilla.org/en-US/firefox/addon/1865
and no more ads.
#2 by Erunno on November 25th, 2009
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Flash ads you say?
https://addons.mozilla.org/de/firefox/addon/1865
#3 by Thinker on November 25th, 2009
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Re: Erunno…
Yes, any and all ads. Be sure to subscribe to an ad-blocking list (will show up after download). Any ads it misses, just right-click the ad and add it to the banned list. It’s easy!
#4 by sargas on November 25th, 2009
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Guys, I think that a typical firefox user isn’t going to install extensions to block these things, and the point is that this is a real bug in either firefox or flash that is going to be blamed on firefox.
Hell, someone might want to use a useful flash website (a game perhaps) and be hit by this, as there is no reason to think whatever AT&T is doing is specific to ads.
#5 by Clint on November 25th, 2009
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Hey John, if u can grab the swf file from that ad, or even if u can’t, can u file a bug on this and cc me? I’d do it but I’m on my phone. Thanks for figuring this out.
Clint
#6 by Erunno on November 26th, 2009
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@sargas
You’re right, of course. Firefox should perform sufficiently well without any extensions being necessary.
#7 by Jesper on November 29th, 2009
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CPU usage of Flash ads is an increasing problem.
I think this is largely because publishers and ad networks have limits on file size but not on CPU usage. Therefore creative agencies turn to CPU intensive action script in order to produce high quality ads while staying under the file size limit.
#8 by Imalaylic on December 10th, 2009
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