Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

My Windows 7 PC is blocking quite often for a couple of seconds up to half a minute or so. I tried to find the problem with the process monitor by filtering all system calls that take over 2 seconds and find that these always have the following stacktrace segment:

0   fltmgr.sys  FltAcquirePushLockShared
1   fltmgr.sys  FltIsCallbackDataDirty
2   fltmgr.sys  fltmgr.sys

The next frame is NtCreateFile in most cases. The calls take often 2-10 seconds, but sometimes up to 50 seconds on a nearly idle system. The HDD (actually, a solid state disc) does not seem to be the problem - HD Tune shows no problems in the benchmark and the error scan, and Process Explorer also gives no hint of unusual CPU or IO activity. And I am pretty certain it is not a virus or something. :-)

How can I find out the actual problem? Are there any helpful tools?

share|improve this question

Use xperf from the WPT (part of the Windows 8 SDK) to trace disk IO:

Run the script, minimize the CMD Window and when you have the issue again, go back to the cmd, wait 15-20s, press a key to stop logging. Open it with xperfview and look in the Disk IO graph which processes causes the high disk IO.

share|improve this answer
The annoying thing is: there is no high IO or CPU activity. I checked that with process explorer. (I extended the question a little to make that clear.) So that probably would not help, would it? – hstoerr Nov 26 '12 at 20:21
try it out and look if it helps or not. – magicandre1981 Nov 26 '12 at 20:59

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.