> What does Linux expect to scale up to? Reserving 16 PML4 entries leaves the
There are already (ok non x86-64) systems shipping today with 10+TB of
addressable memory. 100+TB is not that far away with typical
growth rates. Besides there has to be much more in the negative address
space than just direct mapping.
So far we always that 64bit Linux can support upto 1/4*max VA memory.
With your change that formula would be not true anymore.