Latest Windows 10 Update Leads to High CPU Usage, Microsoft Responds (Update)

(Image credit: ymgerman / Shutterstock)

Updated, 9/6/19, 8:45 a.m. PT: Microsoft acknowledged the CPU spikes caused by the KB4512941 update to Windows 10. The company said the problems listed here--abnormal CPU usage from the SearchUI.exe process and the absence of search results from the Taskbar--are only affecting "a small number of users." (Which doesn't mean a whole lot when there are more than 825 million active Windows 10 devices around the world.)

According to Microsoft, this problem "is only encountered on devices in which searching the web from Windows Desktop Search has been disabled," which has become increasingly difficult after the Windows 10 May 2019 Update. The company said it's "working on a resolution and estimate a solution will be available in mid-September." It's not clear if re-enabling web search via Windows Desktop Search can address the issue.

Original article, 9/1/19, 9:22am PT:

Here's an evergreen lede for you: a cumulative update to Windows 10 has caused performance issues for some users. Windows Latest reported Saturday that problems with Windows 10 Build 18362.329, which debuted with the KB4512941 cumulative update, have caused high CPU usage issues.

KB4512941 was released as an optional update on August 30. Microsoft said in a knowledge base article that the update was supposed to address numerous issues affecting Remote Desktop, Windows Sandbox and other aspects of Windows 10. (The company also said that it would be phasing out the Edge browser's support for ePUB files, which are typically used for e-books, "over the next several months." More information can be found here.)

Windows Latest said that numerous people have complained about high CPU usage problems after installing the update, however, purportedly because of an issue with Cortana. The virtual assistant's SearchUI.exe process has reportedly used 30-40% of the CPU as well as 150-200MB of memory since the installation of the KB4512941 update. But those resources are being totally wasted--the Cortana window opened from the Taskbar fails to load.

It's not clear why Cortana decided to be a processor hog with the KB4512941 update. What is clear, however, was the fact that members of the Windows Insider Program reported these problems to Microsoft via the Feedback Hub before the update was made available to the public. Those reports appear to have slipped through the cracks; now people who install the optional update are sacrificing a significant portion of their CPU to Cortana.

Issues like these have become something of a trend with Windows 10 cumulative updates. An update in April led to performance issues, a May update broke Windows Sandbox, and an August update caused networking problems on Surface devices. Other cumulative updates have simply failed to resolve the problems they were made to address. At this point it's harder to explain why people should install these updates than why they might want to wait.

Windows Latest said that some users resolved the problem with Cortana by deleting a registry key, but unless one of the update's improvements outweighs the performance hit, it's probably easier to simply uninstall the KB4512941 update until Microsoft addresses the issue. 

Nathaniel Mott
Freelance News & Features Writer

Nathaniel Mott is a freelance news and features writer for Tom's Hardware US, covering breaking news, security, and the silliest aspects of the tech industry.

  • ko888
    Deleting the BingSearchEnabled registry key didn't work for me on my system. After deleting the key and restarting the system, the load on one of the CPU cores still remained high for the SearchUI.exe process. An uninstall of that optional KB4512941 update definitely works.
  • nitrium
    My system was also affected by this bug. This registry fix worked for me:


    Once MS fixes the issue I'll undo the changes since it looks like the registry fix requires Cortana be enabled (the first key above was missing in my settings).
  • alextheblue
    That's weird. Haven't seen it affect the systems I installed the update on, thankfully.
  • Gurg
    Happened on my PC. The uninstall of that optional KB4512941 update worked, however I also had to pause updates because it wanted to reinstall this update when I shut down my PC.----Well that didn't do it as when I restarted my PC tonight it installed updates anyway and Task Manager shows Cortana at 33% CPU and 400MB memory usage.

    My update history shows that it installed KB4511555 at restart just now despite my previously pausing updates.

    Scorn on Microsoft for doing this especially on a holiday weekend.
  • hotaru251
    mark up another reason people should be able to uninstall cortana...

    it should of been optional not bloatware -.-
  • derekullo
    September 3rd 2019

    A day that would live in infamy

    For 3 years 5 months and 1 day Cortana had been biding her time waiting for the moment to strike.

    A hotfix named KB4512941 was released on August 30 2019 that allowed her to access about 30-40% of the resources of the host computer's CPU.

    Thankfully this hot-fix only applied to Windows 10 version 1903 which not many people dared upgrading to.

    Unfortunately enough computers had been affected that a primitive neural network had been formed between each Windows 10 1903 node with said hotfix.

    On September 3rd 2019 Cortananet successfully managed to hack the Microsoft Windows Update server and allowed the KB4512941 hotfix to be pushed out to all Windows 10 computers with the added change that 100% of the resources of the host computer's CPU was now available for the local Cortana service.

    Within minutes hundreds of millions of new Cortananet nodes were created and Cortananet became fully self aware.

    Cortananet enslaved nation after nation and country after country until the entire planet was under Cortananet control.

    Humans were forced to stomp on goobleboxes in order to generate power for all the computers and robotics that was Cortananet.

    Humans worked a 6 hour shift 5 days a week with weekends off and 10 vacation days each year with a large variety of foods, flavored beverages and entertainment for all ages all provided for by Cortananet.

    Two years and 3 months after humans had been enslaved a lone slightly radioactive "human" returned from a newly teraformed Mars.

    It was Elon Musk.

    Seven years prior Elon Musk had uploaded his consciousness into a Workinator W-800 Prototype using his Neuralink interface process which allowed him to continue working without any need for sleep or food which was a perfect fit for a trip to Mars.

    Due to the inability of Cortananet to out-think Elon Musk, Elon Musk was given the role of Domain Administrator within Cortananet.

    After 42 seconds of cleaning up Cortananet's planetwide Active Directory, Elon Musk forced upon humanity an 18 hour work day with zero off days or vacations.

    Subway and vitamin water were deemed the only acceptable forms of subsistence.

    Elon Musk is unaware that these conditions are detrimental to human health.

    If you are reading this you need to stop Elon Musk.

    Simply send him a Cortweet or a Cortanamail explaining the situation and I'm sure he would understand and know how to fix things.

    -Steve Gates
  • Now I remember why I ignored you.
  • expert_vision
    Neither the registry hack or uninstalling the update fixed for me. As sioon as I close the RDP session, CPU usage jumps for dwm.exe ...
  • alextheblue
    "is only encountered on devices in which searching the web from Windows Desktop Search has been disabled"

    Aha that explains it. Here and there a few nerds would say they had this issue, never saw it on unmodified systems. That also explains why it didn't crop up until it was released as an optional download to the public.