RFC: Enable sustained performance mode on Android

[JonnyH]

Is this useful? Should we add it to a UI option?

[Techjar]

Devices don't necessarily handle this in a beneficial way, so it should definitely be an option. As for whether its useful, I would say yes as long as we can find some devices which show an improvement with it on.

[zackhow]

The way I understand this is it brings a consistent experience over the course of the activity, that it will drop performance in the short term to prevent slowdowns later due to heating. So instead of 60 fps for 15 minutes -> 30 fps after, you get 45fps for 60 minutes. Either way, most(all?) android phones have trouble even hitting 60fps sustained, so I don't think this is even an option atm. Maybe in two(five...?) years

Looking at the documentation, I'd say we'd want something closer to 'Exclusive core'
https://source.android.com/devices/tech/power/performance#exclusive_core

[Techjar]

@zackhow Doesn't look like that does anything to the CPU governor, and is just a higher level construct for CPU pinning to prevent other threads preempting yours. Not very useful to us, as our problem is aggressive CPU scaling causing stutters.

[Helios747]

It certainly wouldn't hurt. Default it on.

[ghost]

How about this now?

[JosJuice]

I uploaded a rebased version as PR #10206.