Windows 10 V1903 Update KB4512941: Workaround for the Cortana high CPU load issue

[German]Since August 21, 2019, Microsoft has been testing the KB4512941 cumulative update for Windows 10 Version 1903 with insiders. However, the update causes a high CPU load on a core on some systems.


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Update KB4512941: What’s the problem?

Cumulative update KB4512941 is intended to fix some issues in Windows 10, version 1903. Among other things, it is planned that this update will finally fix the issue of the broken sandbox (see my blog post Windows 10 V1903: Update KB4497936 breaks Sandbox).

Microsoft is currently testing this update with Windows insiders only – the first version was released on August 21, 2019. Users who installed the update reported that the search did not work anymore. In addition, Cortana causes a high load on a CPU kernel for some people. I had also reported about this issue within my blog post Windows 10 V1903: Updates KB4512941 and KB4515530. Within this blog post I sketched a workaround (a .reg file to enable Bing search and disable Cortana) that has reduced some people’s core load.

Cause found: Scripts and Cortana Cache

German blog reader Werner B. contacted me 2 days ago by mail and gave me some interesting hints (thanks for that). Werner wrote:

I am a reader of the Windows blog and would like to share some information about a workaround to 100% Cortana CPU load on Windows 1903 KB4512941.

Werner refers to my above mentioned blog post Windows 10 V1903: Updates KB4512941 and KB4515530 where I discussed the high CPU load. During his research, Werner came across a post in the Tenforum that picks up the problem or the cause for the high CPU load. There it says:

Kek. I found what causing problem to Cortana by myself.
The problem is somewhere inside

c:\Windows\SystemApps\Microsoft.Windows.Cortana_cw5n1h2txyewy\cache\

Some scripts cause loop and Cortana is stuck on initialization as I see through Proccess Monitor logs.

The issue seems to be connected to the cache folder used by Cortana, which causes the high cpu load.


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Another workaround

With the above knowledge one could now simply say: Ok, I clear the cache and it’s fixed. Unfortunately this won’t help, because the cache will not be rebuilt if it is deleted or a new cache is created. But there is a workaround that the user has outlined in his comment:

Inserting the folder from prev.version works fine insead of black search window

Btw, looking of meaning “cache”, the folder is not recreated / regenerated by itself after delete

Folder saved from backup of 362.295 build (as I remember): cache.rar – Google Drive

German blog reader Werner confirmed to me that this workaround had helped him:

In a local fresh test installation of 1903 in VMWare the CPU load goes to 100% after installation of KB4512941.

If the cache folder is backed up before installing KB4512941 and the folders are copied back after the update, the CPU load of Cortana (immediately without reboot) goes to 0%.

Werner suggests the following steps to fix the high CPU load issue with update KB4512941:

1. Before installing the KB4512941 update, back up the following cache folder to a local directory (e.g. D:\Backup):
c:\Windows\SystemApps\Microsoft.Windows.Cortana_cw5n1h2txyewy\cache

2. Then install the cumulative update KB4512941 and the SSU.

3. After the update installation, open the cmd.exe command prompt by Run as administrator and execute the following command.

cd c:\Windows\SystemApps\Microsoft.Windows.Cortana_cw5n1h2txyewy\cache
xcopy /o /x /e /h /k D:\backup\cache\*

Here I assume that the path to the backed up cache folder is cleanly adjusted with the second command. The xcopy query j/n/ must be confirmed with ‘a’ (for all). Maybe the workaround is helpful for you and Werner asks if someone can confirm the workaround.

Additional details

Werner sent me the following additional information in the aftermath of the article.

The workaround works with the affected Windows country setting “de-de”, regardless of whether Cortana / Bing search was activated or deactivated by OO Shutup10.

A limitation of the manual overwriting of files in ‘SystemApps’ is that “sfc /scannow” detects and resets the change, whereupon the Cortana bug with high CPU load occurs again.

The cache files of Cortana themselves should not be the sole cause of the error. There is no high CPU load at build 18362.327 if the KB4512941 is directly integrated into an April ISO with 18362.30 using DSIM.

A new installation with such an ISO works without problems. One of the benefits of build 18362.327 is that programs compiled with VisualBasic 6 will work again.

Then there was a hint from Werner about installations where the ‘cache’ folder workaround is active:

Installing install.wim from an ISO with integrated KB451294 (which works for new installations) does not fix the cause of the Cortana bug.
( DISM /Online /Cleanup-Image /RestoreHealth /Source:WIM:D:\sources\install.wim /LimitAccess).

With ‘sfc /scannow’, the cache data that works on freshly installed systems, but which have been updated step by step through the monthly updates, will become active again and lead to the Cortana bug..

Werner concludes: “There may be a way to bring existing systems up to build 18362.327 without a workaround. Thanks for the addition.

Note: Read also my article Windows 10 V1903: High CPU load from Cortana, Search broken, blame August 2019 Updates dealing with the final version of this update.

Addendum 2: I’ve written a brush up with findings reported from my blog readers – and an addendum from Werner – at Windows 10 V1903: MS investigating the Search/Cortana issue (09/03/2019). There you will find also a confirmation, that Microsoft is investigating the issue and plan a fix in upcoming releases.

Similar issues:
Windows 10 V1903: Update KB4497936 breaks Sandbox
Windows 10 V1903: Updates KB4512941 and KB4515530
Windows 10 V1903 Update KB4512941: Workaround for the Cortana high CPU load issue
Windows 10 V1903: High CPU load from Cortana, Search broken, blame August 2019 Updates


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35 Responses to Windows 10 V1903 Update KB4512941: Workaround for the Cortana high CPU load issue

  1. Pingback: The second August patch for Win10 1903 shoots one core up to 100% utilization @ AskWoody

  2. Pingback: KB4512941 for Windows 10 version 1903 - gHacks Tech News

  3. XSevenX says:

    Hello Guys,

    I got a similar problem after Windows 10 update and this was because of ” BingSearchEnabled” which was set to 0.

    You’ll find it to :
    HKEY_CURRENT_USER, SOFTWARE, Microsoft, Windows, CurrentVersion, Search.

    If you set to 1, disconnect and reconnect you’re session, problem can be solved.

    It’s a bad news because this setting allows cortana to use web results for the search..

    I hope Microsoft will correct this problem because we don’t need to use internet resource to search a file in the pc…

    XSevenX

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  5. Stefan says:

    Mit gpedit funktioniert bei mir überhaupt nichts, nur der o.g. Registry-Hack hat geholfen, und zwar sofort nach einem Reboot.

  6. Pingback: Some Windows 10 users on 1903 are facing high CPU usage after latest cumulative updates - Neowin.net

  7. Klyf Fenderson says:

    While I now have windows search working from the Start Menu by re-enabling Websearch/Bing, it’s still broken in the settings app – which takes forever, then finds nothing. (I’ve rebuilt the search index to no avail).

    For now, the workaround is to just use the regular search to find settings.

    All of these problems only started after KB4512941

  8. Pingback: Some Dwelling windows 10 users on 1903 are facing high CPU usage after newest cumulative updates - Neowin - INFOSHRI

  9. Pingback: Windows 10 Version 1903の累積アップデートKB4512941でCPU負荷が異常に高くなる不具合が発生中か | ソフトアンテナブログ

  10. Sean says:

    I updated to 1903 yesterday and was bugged by Cortana with >40% CPU occupancy.

    The workaround works great for me! I downloaded the cache folder from Google Drive, and use the command to Overwrite the buggy cache folder. Even without restarting, the Cortana process was GONE from Task Manager, and the laptop becomes quite again!

    Thank you very much, and regards to the German blogger!

    • Jiří Procházka says:

      Yes, I followed the same, it is easy fix working without restart. Thank you Born!

  11. Pingback: Algunos usuarios de Windows 10 en 1903 se enfrentan a un alto uso de CPU después de las últimas actualizaciones acumulativas – Noti Max

  12. Kipper says:

    XSevenX, This fix worked for me and seems the most simple fix of all. I was seeing Cortana use 60-90% of my CPU. So bad I had to use an un-updated laptop to find your fix. Thank you most sincerely.

  13. Stella says:

    Microsoft once again deliver their shit as if we were alpha testers. Such incompetence.

  14. Pingback: Windows 10 KB4512941 Update Causing High CPU Usage in Cortana | Bleeping Computer

  15. Khaled Eddeeb says:

    Hi,
    I have the same problem, Cortana high CPU and search box not working after installing KB4512941 , I’m an ordinary user, so please I need help.

  16. Pingback: Windows 10 KB4512941 Update Causing High CPU Usage in Cortana | Learn With Ashik

  17. Pingback: CPU Spike bug in latest Windows 10 1903 update reported to Microsoft | Ghacks.net

  18. Pingback: Windows 10 KB4512941 results in superior CPU utilization by Cortana - BetaNews

  19. Pingback: CPU使用率100%!?直し方を伝授!KB4512941でVB6やらマクロやらの不具合が解消されるけど副作用で不具合が出る件windows10 1903環境 | Theデブ☆マニアックス

  20. LEWIS LIEBENBERG says:

    Microsoft should rather stop with updates, as they don’t know what they are doing. They should get engineers from Apple to show them what to do.

  21. Shyam Reddy says:

    Worked for me, thanks a ton, Guenni!

  22. Another solution that solve problem for Cortana high usage is to go in Windows Parameter ==> Confidentiality then Images. desactivate autorisation access for Cortana solve the problem.

  23. fidodido says:

    Hi,
    swapping cache folder with the one from Google Drive fixed the problem.
    Thank you!

  24. Nope says:

    We should let cortana run, and send MS our engergy bills…

  25. Pingback: A tiny sop to Win10 1903 users bitten by the KB 4512941 Cortana/SearchUI.exe redlining bug – ComputerWorld

  26. Kipper says:

    OK, time for some humour. I used your suggestion XSevenX and it worked like a charm so thank you very much. I posted lower down in error sorry. Anyways, I still had a bit of bad stuttering in my games and on system now and then, though nothing like before. I tried everything from Dism, Sfc, re-installing Graphics drivers, the actual games, even the mouse batteries. Generally trying anything I could figure for almost a day and a half, head in a nose dive and spin. Then it hit me, ching, tilt. Un-installed the USB mouse receiver. Plug it back in and problems gone. Some how the update screwed my adaptor driver and system interupts were screwed up. Just posting this to thank XSevenX for the main fix but you can all have a laugh at my expense into bargain. Also, just in case anyone else is having similar problems, du-huk, you never know.

  27. Ernest says:

    I just simply deleted the Cortana cache with “take ownership” registry tweak, and problem solved.

  28. wim says:

    this caused my network (driver) to fail no more lan or wlan
    rollback fixed it.

  29. Khaled Eddeeb says:

    Many thanks… I got it

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