The Case of the Sluggish Internet Explorer 7

[Added 2007-01-18: Fix Available for Performance Problems with Internet Explorer 7's Phishing Filter ...]

I like Internet Explorer 7. I've installed it many, many times and on
many systems. I've never had a problem with it. That is, until I had to spend some time working with a web-based application on an Intranet. I had to go through several iterations of repetetive steps in this application. It was the kind of work where it would have been more fun to write a program to achieve the end result, but it would probably have taken more time to write the program than it would to go through the tedious process. That, and the fact that I didn't immediately have access to some of the information that would be required to write the app, prevented me from taking the fun route. So I was stuck copying, clicking, pasting, and... WAITING.

The problem wasn't the responsiveness of the web server - the problem was localized to my system. As I was working on a laptop, I could hear the fan kick into high gear as CPU utilization hit 100%... and stayed there. When I paused for a bit, the CPU usage went back down. So, interacting with the web application was causing the behavior. The task took about 90 minutes to complete, and when I was done, Process Explorer showed iexplore.exe as having used nearly 90 minutes of CPU time. I didn't have this problem with Internet Explorer 6! In communicating with the vendor of the web application, they indicated that they hadn't had problems of this sort in any of their experiences with IE7 or with other customers.

I surmised that there was likely a setting in Internet Explorer 7 that was affecting the performance. But IE7 has no shortage of settings, and to try each one was not a task that I wanted to undertake. I fired up IE7, loaded the web-based app, and started working. Then, while the CPU was taxed, I went to Process Explorer, hit the properties of the iexplore.exe process, and checked the "Threads" tab. There were 89 threads, most having a start address of "ndtll.dll!RtlpWorkerThread", and all vying for CPU time. It appeared that a new thread was created for each request that was made, which seems rather "wasteful". At any rate, RtlpWorkerThread is a private "run-time library" worker thread threadproc function, presumably the threadproc used when one uses the Thread Pool API. The stack of one of these threads at the point that I captured it (obtained with Process Explorer and properly configured debugging symbols) is rather deep:


As you can see, after the thread pool plumbing is out of the way, the first function in the stack is ieapfltr.dll!Evaluator::ContinueProcessingWrapper - a function in ieapfltr.dll. ieapfltr.dll describes itself as "Microsoft Phishing Filter", though I suspect IEAP is an acronym for Internet Explorer Anti-Phishing. At any rate, it certainly seemed that the settings surrounding the (anti)phishing filter would be a good place to start.

I went into "Internet Options" in the Control Panel (Start Run inetcpl.cpl) and hit the "Advanced" tab. Toward the bottom was a setting for the Phishing Filter where there were three options:
-Disable Phishing Filter
-Turn off automatic website checking
-Turn on automatic website checking

Mine was set to "Turn off automatic website checking". I changed it to "Disable Phishing Filter" and hit OK, and re-tried the web application. The application was responsive as ever, and the "excess" threads that were previously being created were nowhere to be seen. Changing the setting back to "Turn off automatic website checking", and hitting the web application again caused iexplore.exe to consume as much of the CPU as it could. It appeared that I found the cause of the sluggish performance.

It is worth noting that in the "Internet Options", on the Security tab, each Internet Explorer Zone has its own setting for the Phishing Filter. If one selects a Zone, and clicks the "Custom level..." button, about 75% of the way down is a setting for "Use Phishing Filter" that has 2 options - Disable or Enable. The setting on the Advanced tab overrides this - if the Security zone setting is set to "Enable" and the Advanced setting is set to "Disable Phishing Filter", the Phishing Filter is disabled for all zones. However, if the Advanced setting is set to "Turn off automatic website checking" or "Turn on automatic website checking", one can exercise more granular control over each Security zone by choosing to enable / disable the filter where it makes sense.



Anonymous said...

I've also experienced a lot of sluggishness from IE7. I've found that it really gets worse the more files you have in your internet temp folder. Clearing my cache seems to clear it up. Unfortunatly IE7 seems to cache everything including multiple copies of whatever site is set to your home page. Had to take yahoo news off my home page. I left it open for a weekend when I first installed it and it too 60 min to clear my cache and my system was so unresponsive it wasn't really useful till it finished and it's a 3.6Ghz with 3GB memory.

Anonymous said...

This is why I'm using FF2 these days.

Anonymous said...

Hi, im Poorguy from the sysinternals forum, remember this thread?, if not check it and read it.


«/\/\Ø|ö±ò\/»®© said...

Hi Poorguy,

I've checked the thread. I regularly use Firefox and IE, but the browser I prefer to use is Avant Browser. Of course, it uses the IE engine, but I like the way Avant does certain things better than Firefox or raw IE. The tabs seem more responsive than Firefox or IE. I haven't used Opera in years; I suppose it's time to give it a shake soon...

Anonymous said...

Hi, Poorguy again, yes, you must give it a shot (Opera), it's very very good (specially when you have a faster connection) :D .

Anonymous said...

holy shi* your blog just helped me fix an IE7 problem which had been plagueing me for months!!! thankyou!