A couple of weeks ago, Microsoft released its monthly Patch Tuesday updates for Windows 10, as well as other supported versions of Windows. It wasn't long before users started to notice that gaming performance was being negatively impacted by an update for the latest versions of Windows 10, however, and even Nvidia recommended users roll back the update in order to get the performance back.
Now, Microsoft seems to have rolled out a fix for this issue, as spotted by BleepingComputer. In the release notes for the update, Microsoft has now listed reduced gaming performance as a known issue, while also stating that it's rolling out a fix for it, but you won't be getting a whole new update for it. Instead, Microsoft is using a new method that was introduced just last month called Known Issue Rollback (KIR).
The way that KIR works is that for updates since Windows 10 version 2004 released, non-security patches are contained by simply not removing the old code. Instead, when a new update is released, the old code is disabled, but kept intact, while the new code takes its place. With this system in place, Microsoft can quickly roll back a single targeted fix should any problems arise, as is the case here.
You do need an internet connection for this to work, as your device needs to connect to Windows Update to detect the configuration change in the cloud. Upon rebooting, the new configuration - which re-enables the old code and disables the new problematic one - is activated, removing the new known issue and reinstating whatever bug it was trying to fix, typically a smaller, less impactful one.
For consumer devices, this will all happen automatically, and Microsoft says it should take up to 24 hours for KIR to roll out to everyone, though it's unclear when exactly it began rolling out. If you're using an enterprise managed device, though, the configuration change will have to be enabled via a group policy. You can learn more about how to deploy a KIR using Group Policy here.
If you'd like to check whether you have received the fix via KIR, you can open the Registry Editor and try to find the following path:
If it exists and is enabled, then you should already have the fix.