The kernel is mostly concerned with memory management, process management, and file IO, as far as I am aware. You don't need a DLL to do any of those. And even if you did, I have never heard anyone claim that doing so is an issue.

Could you provide a specific example of what you are referring to?

The whole idea of a kernel is to abstract operations like disk IO, memory mapping, and display output away from a program being executed by the kernel. Kernels do this through an API, for example, the API which allows files to be opened and closed. Pretty sure you never needed a DLL to open a file.

a method exposed by a DLL file, a Kernel API, or a BIOS system call (if we were allowed to access BIOS directly), the code exists and executes just the same as far as the processor is concerned.

A DLL is the same thing as a shared library in Linux, and has nothing to do with the kernel.

I'm pretty sure none of this is correct.

Functions, when compiled, are just memory addresses of executable code in RAM. And when you call a function, you're just calling assembler instruction JMP which then executes code at the target address. It doesn't matter if that code at that address is

"It adds an* extra step for every time any application calls the kernel"

I have no idea what this means, could you elaborate?

Calling a function exposed by a DLL should be basically the same performance as calling a function directly compiled into a program, as far as I know.