Re: [Linaro-mm-sig] [PATCH 08/10] mm: cma: Contiguous Memory Allocator added

[Arnd Bergmann <arnd@arndb.de>]

On Wednesday 22 June 2011, Marek Szyprowski wrote:
> Sounds really good, but it might be really hard to implemnt, at least for
> CMA, because it needs to tweak parameters of memory management internal 
> structures very early, when buddy allocator has not been activated yet.

Why that? I would expect you can do the same that hugepages (used to) do
and just attempt high-order allocations. If they succeed, you can add them
as a CMA region and free them again, into the movable set of pages, otherwise
you just fail the  request from user space when the memory is already
fragmented.
 
> > These essentially fight over the same memory (though things are slightly
> > different with dynamic hugepages), and they all face the same basic problem
> > of getting as much for themselves without starving the other three.
> 
> I'm not sure we can solve all such issues in the first version. Maybe we should
> first have each of the above fully working in mainline separately and then
> start the integration works.

Yes, makes sense. We just need to be careful not to introduce user-visible
interfaces that we cannot change any more in the process.

	Arnd