Last Friday, Microsoft released an optional update for the latest version of Windows 10, the version 1903 (or May 2019 Update) in the form of the build 18362.329. This patch brought a lot of quality fixes and the release notes didn’t indicate any known issues, but some users have since been complaining about some unusual CPU spikes after installing this update.
In two separate Reddit threads spotted by Windows Latest, users have been discussing these high CPU usage problems, and some of them identified Cortana’s background process (SearchUI.exe) as the culprit. For these users, uninstalling the patch seems to be the only sure way to make things back to normal. It’s hard to know if this is a widespread issue, and we haven’t been seeing unusually high CPU usage after installing the build 18362.329 on one of our PCs.
Interestingly, it seems some Windows Insiders in the Release Preview ring who got access this new optional patch ahead of everyone else noticed that Cortana could cause CPU spikes of between 30% and 40% in this build, even when the digital assistant isn’t being used. Several Feedback Hub items about this issue have been submitted since August, but Microsoft apparently didn’t act on them, maybe because they have remained buried under many other items in the Feedback Hub
As of this writing, Microsoft has yet to acknowledge any problems with this optional update, but the reason these optional “C” and “D” patches that Microsoft ships later in the month (after the “B” releases happening on Patch Tuesday) is because they’re preview-quality updates. “The intent of these releases is to provide visibility into, and enable testing of, the non-security fixes that will be included in the next Update Tuesday release,” explained Mike Fortin / Corporate Vice President, Windows, in a blog post from December 2018.
We'll update this post if Microsoft acknowledges this high CPU usage issue in this latest optional patch, but in the meantime we remind you that you can roll back to previous build if you're seeing unusual CPU spikes in the Windows Task manager. Keep in mind that optional Windows 10 updates can be buggy, and it's fine to keep them as all the new quality fixes will eventually ship in the next Patch Tuesday Update.
Update: Microsoft has finally acknowledged the issue and said that a fix will be available in an upcoming release.
We are currently investigating an issue where users are reporting high CPU usage linked to SeachUI.EXE after installing the optional update on August 30 (KB4512941). We will provide an update in an upcoming release.
— Windows Update (@WindowsUpdate) September 3, 2019