[RFC REBASED 5/5] powerpc/mm/slice: use the dynamic high slice size to limit bitmap operations

[Aneesh Kumar K.V]

Christophe Leroy <christophe.leroy at c-s.fr> writes:

> The number of high slices a process might use now depends on its
> address space size, and what allocation address it has requested.
>
> This patch uses that limit throughout call chains where possible,
> rather than use the fixed SLICE_NUM_HIGH for bitmap operations.
> This saves some cost for processes that don't use very large address
> spaces.

I haven't really looked at the final code. One of the issue we had was
with the below scenario.

mmap(addr, len) where addr < 128TB and addr+len > 128TB  We want to make
sure we build the mask such that we don't find the addr available.

-aneesh