I have noticed severe performance drops from hitting the home button in an app and coming back to it by hitting resume on the Oculus Go. Another weird issue is that it fixes itself if these steps are repeated again. This was repeatable on an empty project with an empty scene (only had camera and light) without the Oculus SDK.
1. Open app
2. Hit the home button once fully loaded
3. Hit resume on the app paused screen
4. Framerate will be lower than it was before.
This varies depending on how many objects are being rendered in a scene, and is not really noticeable in an empty scene until the profiler is used, since it still seems to hover around 60 or slightly below.
This happens in 3 different projects set to non-development build with varying amounts of objects and Unity 2017.4 versions, and happens on the latest 2017.4 build. Earliest tested build that has the issues is Unity 2017.3.0f3
2017.4.34f1, empty scene, cube, and simple canvas, project default settings, Single pass (stereo vs single pass does not matter)
Oculus SDK: None added, using built in oculus support, but appears like it probably happens on any Oculus SDK (Tested an old Oculus SDK and the latest as of 11/26/2019)
Oculus Go Headset versions: 184.108.40.206.450.174044450 (headset 1) and 220.127.116.11.458.183074809 (headset 2)
Since this test project did not have the Oculus SDK, it was running at 60fps. Running it at 72 causes the frame rate to drop to 60fps on a mostly empty scene
The profiling screenshot is from headset 1, but also looks the same on headset 2
It is worth noting that versions tested of Unity 2018.4 appear to not include this issue (2018.4.9f1, 2018.4.13f1), and work perfectly fine as a workaround to this issue