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

[Guy Shattah]

> On Tue, Oct 17 2017, Guy Shattah wrote:
> > Are you going to be OK with kernel API which implements contiguous
> > memory allocation?  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.
> 
> What you describe sounds like CMA.  It may be far from perfect but itâs there
> already and drivers which need contiguous memory can allocate it.
> 

1. CMA has to preconfigured. We're suggesting mechanism that works 'out of the box'
2. Due to the pre-allocation techniques CMA imposes limitation on maximum 
   allocated memory. RDMA users often require 1Gb or more, sometimes more.
3. CMA reserves memory in advance, our suggestion is using existing kernel memory
     mechanisms (THP for example) to allocate memory. 

Guy