Re: [RFC PATCH 3/3] mm/map_contig: Add mmap(MAP_CONTIG) support

[Michal Hocko]

On Tue 17-10-17 10:50:02, Guy Shattah wrote:
[...]
> > Well, we can provide a generic library functions for your driver to use so that
> > you do not have to care about implementation details but I do not think
> > exposing this API to the userspace in a generic fashion is a good idea.
> > Especially when the only usecase that has been thought through so far seems
> > to be a very special HW optimiztion.
> 
> Are you going to be OK with kernel API which implements contiguous
> memory allocation?

We already do have alloc_contig_range. It is a dumb allocator so it is
not very suitable for short term allocations.

> Possibly with mmap style?  Many drivers could utilize it instead of
> having their own weird and possibly non-standard way to allocate
> contiguous memory.  Such API won't be available for user space.

Yes, an mmap helper which performs and enforces some accounting would be a
good start.

> We can begin with implementing kernel API and postpone the userspace
> api discussion for a future date. if it is sufficient. We might not
> have to discuss it at all.

Yeah, that was my thinking as well.
-- 
Michal Hocko
SUSE Labs