fast/syscall-free gettimeofday ?

there were discussions at some point on an imprecise but
fast implementations of gettimeofday() that would not require
a system call (perhaps mmapping some memory region which
is opportunistically updated).

Does anyone remember what happened about that ?

Otherwise, is there any place in the kernel where i can fetch
a struct timeval which is not off by more than, say 1 tick ?

cheers
luigi