about kernel module speed,

Dragonfly

somebody ask module speed comparing with linked into kernel image. so c&p from Understanding Linux kernel.

No performance penalty
Once linked in, the object code of a module is equivalent to the object code of the statically linked kernel. Therefore, no explicit message passing is required when the functions of the module are invoked.[7]
[7] A small performance penalty occurs when the module is linked and unlinked. However, this penalty can be compared to the penalty caused by the creation and deletion of system processes in microkernel operating systems.