The kernel "tick" frequency is all about how often the kernel should check what process is running, what process wants to be running and what to do about it.
Clearly that must be a lot slower than the actual execution rate of instructions on the machine.
If the tick frequency is too low things don't get scheduled as promptly as you might like. That may cause problems with the user interface or with audio/video playing.
If the tick frequency is too fast, then you are spending too much time in the kernel code deciding what to do next. Over all performance of applications becomes slower.
Memory in C++ is a leaky abstraction .