Com Surrogate max CPU and lost window focus

Question

Windows 10
i7 CPU
32G RAM

dllhost.exe Com Surrogate kicks off every few minutes - maxes out my i7 CPU - and steals the focus from whatever window I'm working in... and lasts for a couple of minutes.

The focus can be on any application (browser, notepad, etc.) when Com Surrogate runs and starts hurting me. It does not only happen when switching focus to a File Explorer window.

I do not get any kind of Com Surrogate error - just a really bad desktop denial-of-service.

I've tried all of the internet "fixes" I could find:

- Updated codecs
- Disabled thumbnail creation
- Did the DEP settings
- Checked for malware with multiple antivirus engines
- Process Explorer does not show any image or media file targeted by dllhost.exe

I think this Com Surrogate action is the CPU eating problem...

Process Monitor (different than Process Explorer) shows the dllhost.exe Com Surrogate process going through all of my disk folders every time it is eating my machine. It appears that it is still looking for media files to make thumbnails for - even though it doesn't actually create any thumbnails any more!

Also, how/why the non-visible Com Surrogate process is stealing the active window focus is beyond me.

(FYI... Com Surrogate has run, and maxed out my CPU, eight times while I was trying to type this question.)

Given that information, does anyone have anything new to try?

Answer 1

After a lot of troubleshooting... The solution to this problem is simply to NOT USE Windows File Explorer!

I normally have several File Explorers open, because I am working on several projects at once.

The problem is that, even with [create thumbnails] set to disabled... Com Surrogate runs through EVERY folder that is available under EVERY Windows File Explorer instance - (watch with sysinternals Process Monitor) - even though it won't be creating any thumbnails!

The more instances of Windows File Explorer you have open - the longer it takes for Com Surrogate to look through all of the folders under each of those instances. And since it searches the disk in a very tight loop, you don't really have control until it gets done.

So every time the Windows thumbnail creation instance of Com Surrogate runs (once every few minutes):

- it eats ALL of my i7 cpu
- it takes SEVERAL minutes to complete its USELESS (since [create thumbnails] is turned off) file search
- it steals the focus of the active window that I'm typing into
- it gives the focus to one of the File Explorer instances (whether restored or minimized)
- it sets the coordinates of that File Explorer OFF-SCREEN
- it also sets the File Explorer's window size to a window's minimum size

Because it moves the File Explorer window off-screen... I have to go to Task Bar - get to the File Explorer's context menu - and do a manual MOVE to get it back on-screen - and then manually resize it.

If you don't run Windows File Explorer, Windows thumbnail creation instance of Com Surrogate has nothing to do and leaves your system alone.

I looked at several File Explorer alternatives, but a lot of the ones that have the capabilities that I was looking for are actually JUST WRAPPERS around Windows File Explorer... and they exhibit the same problem that I'm having with Windows File Explorer and Com Surrogate.

There may be others, but so far, the only good alternative that I've found is a product called xplorer². It's a commercial product, but their free, Lite version is more than sufficient for my needs.