Microsoft Response
Thank you everyone for providing feedback and submitting traces. Based on your feedback we have identified a change impacting system and games performance for some users starting with Windows 10 Version 1903 (May 2019 update). The change would result in higher system CPU utilization and/or lower game GPU utilization, and thus causing lower framerate in some games. We have a fix for the problem in the next Windows Insider build that will flight to the “Fast” ring (build 18932 and above). You can find instructions on joining the Windows 10 Insider Program here: https://insider.windows.com/en-us/how-to-pc/. After a successful tenure in the insider population, the fix will be deployed as an update to 1903 users at the end of August.
We hope this update resolves your game performance woes that you started experiencing with 1903. If it did not, please file a game performance feedback via https://aka.ms/submitgameperformancefeedback and, importantly, attach a short capture clearly reproducing your problem.
