Re: [RFC] mmap(MAP_CONTIG)

[Mike Kravetz]

On 10/04/2017 04:54 AM, Michal Nazarewicz wrote:
> On Tue, Oct 03 2017, Mike Kravetz wrote:
>> At Plumbers this year, Guy Shattah and Christoph Lameter gave a presentation
>> titled 'User space contiguous memory allocation for DMA' [1].  The slides
>> point out the performance benefits of devices that can take advantage of
>> larger physically contiguous areas.
> 
> Issue I have is that kind of memory needed may depend on a device.  Some
> may require contiguous blocks.  Some may support scatter-gather.  Some
> may be behind IO-MMU and not care either way.
> 
> Furthermore, I feel dÃjà vu.  Wasnât dmabuf supposed to address this
> issue?

Thanks Michal,

I was unaware of dmabuf and am just now looking at capabilities.  The
question is whether or not the IB driver writers requesting mmap(MAP_CONTIG)
functionality could make use of dmabuf.  That is out of my are of expertise,
so I will let them reply.

-- 
Mike Kravetz