I have an Orange Pi with Armbian installed.
I find that when I use a CPU governor called schedutil a process called sugov:0 will exist in top. And the sugov:0 can spend about 13% CPU.
When I use the governor ondemand this process will not exist.
What's this process？ 
Sugov is a kernel thread used in ARM architecture as part of the scheduling governor.
the sugov kthread is a special RT task, which goal is just that to activate a frequency transition
As far as I can tell from the referenced documents the 13% CPU usage is a fake measurement and you needn't be worried about it.
It has a strange name so that grep can now easily find all its references in the kernel source without being overwhelmed by false matches.
References
The other answer described well what's sugov:0, so let me explain further the nature of the displayed %CPU values.
Whatever top(1) or htop(1) report about the percentage of CPU usage is the current state. Thus, if some process or kernel thread uses a certain CPU percentage, that's the case at that very moment, while the very next moment it may use 0% or an ever higher percentage. That's also how bursty or short-lived loads can hide from top(1) or htop(1).
in general, it's much better to get the sense of CPU usage by checking the values in the TIME column in the output of ps(1), in particular ps axuw, becase it accounts for the history of CPU usage for each process since the system has booted up. The TIME column can also be added to what top(1) displays, which is what I have in place with htop(1), for example.
However, short-lived processes can also hide from their exposure through the TIME columns, but that doesn't apply to the question.
