The Windows 10 Creators Update (version 1703) added a new Game Mode which tries to allocate more resources to the current game in focus. This features can cause performance issues with OBS and it is recommended to disable it.
Disabling Game Mode is done differently, depending on your Windows 10 version.
Settings App > Gaming > Game Mode > set Game Mode to "Off"
Game Mode is enabled automatically by Windows if supported by your hardware and needs to be disabled individually per-application or globally using the Registry. It's recommended to disable it globally.
This requires a change in your Registry.
regedit.exe or search for
Registry Editor in the start menu and launch it. This requires administrator access.
In the editor, navigate to
HKEY_CURRENT_USER\Software\Microsoft\GameBar. You can paste this directly into the address bar at the top to go there quickly.
At the folder, look for a key called
AllowAutoGameMode in the right panel. If the key is not there, create it. Right-click inside the right panel and select New > "DWORD (32-bit) Value". Rename the new value to
To disable Game Mode, set this value to 0. To enable Game Mode, set it to 1.
To disable it per-game, open the properties of the game shortcut or executable, go to Compatibility and check "Disable full-screen optimisations"