I run Windows 8 Pro 64bit on a ~3 year old Sony Vaio.

Pretty much since I installed Windows 8 I get high CPU load when I leave the system alone for a couple of minutes.

The high load will continue (usually one core fully utilized) until there is some user input. In the beginning this was the defrag process, but after fixing that, I am getting high CPU load from the System process.

I have run Windows Performance Recorder - the idle activity sets in about 4 minutes after the last input, the biggest culprit seems to be a function called RtlScrubMemory in the NT kernel: WPA (show large pic)

The system has 8GB RAM, Task Manager shows about 3.5 GB memory use, so memory shortage should not be an issue.

Googling did not really turn up anything useful - any help would be appreciated.

Edit: Here is the ETL file: link

  • What's up with the downvote? Any reason?
    – Martin
    Aug 23, 2013 at 17:24
  • See this question. A Sony Vaio running Vista where the problem was apparently related to a glitch in the WiFi radio logic such that I got 100% on one CPU when the radio was turned off. Installing Windows Process Explorer (free from MS for Vista, at least) made it possible to zero in on the interrupt system, leading to the suspicion that it's an "open" interrupt line causing repeated hardware interrupts, likely due to a WiFi driver glitch. Aug 23, 2013 at 18:15
  • use this command which also traces VirtualAlloc/VirtualFree: pastebin.com/4h2ySm1V Maybe this shwos which other tools allocate memory. Aug 23, 2013 at 21:21

3 Answers 3


ok, because I saw the RtlScrubMemory issue several time I asked Microsoft about it. This functions is used to test the installed RAM.

I saw it when the idle Maintenance kicks up and tries to optimize Windows. Disable the Idle Maintenance task in task scheduler to get rid of it.

  • That seems to help, actually. Did you get any info on what triggers this memory scrubbing spree? Is this is a problem caused by bad RAM?
    – Martin
    Jun 6, 2014 at 16:40
  • I haven't got any details about this function from my Microsoft contact. Jun 7, 2014 at 5:47
  • you saved my time
    – SDJSK
    May 12, 2021 at 7:43

If you happen to be running into this problem on Windows 10, the fix is slightly different. Inside Task Scheduler, the location of the memory test scheduled tasks that are causing problems may be located in:

Task Scheduler Library -> Microsoft -> Windows -> MemoryDiagnostic

(On my system, I did not see any tasks under the "TaskScheduler" folder, which is the folder that some others have mentioned to look in)

Disabling all of the tasks in the MemoryDiagnostic folder has successfully kept my computer from eating CPU (and eventually bluescreening) after a few minutes of inactivity.

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Could be a driver issue (in my experience, when Windows is acting strange, a driver is almost always at fault), you could try binary searching the extraneous drivers and seeing if disabling any of them causes the problem to go away (disable all non-necessary drivers, reboot. If problem goes away, re-enable half of them and see if it returns. Wash, rinse, repeat).

My suspicion would be a network driver, so those are the ones that I'd start with.

Also worth noting that the ETL trace shows fairly high usage from a svchost, which could be what's calling the scrubmemory.

  • the svchost.exe usage comes from Defrag service. but this is fine. Aug 23, 2013 at 21:16

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