Linking libc dynamically is essentially free. Every program on the system runs it, so almost all its code and clean data pages are already in memory.

As for static libc: please don't do this. A static libc, from a compatibility POV, is just as bad as embedding random SYSENTER instructions in program text. It makes the system much more brittle than it would otherwise be. I understand the desire to package a whole program into a single blob that works on every system, but we should support this use case with strong compatibility guarantees for libc, not with making SYSENTER the permanent support boundary!

When I am god emperor of mankind, on my first day, I will outlaw both static linking of libc and non-PIE main executables.