Re: [-mm PATCH v2 00/25] get_user_pages() for dax pte and pmd mappings

[Dan Williams <dan.j.williams@intel.com>]

On Mon, Dec 14, 2015 at 6:52 AM, Jeff Moyer <jmoyer@redhat.com> wrote:
> Dan Williams <dan.j.williams@intel.com> writes:
>
>> In the meantime, I expect some would say DAX is a toy as long as it
>> continues to fail at DMA.
>
> I suppose this is the crux of it.  Given that we may be able to migrate
> away from the allocation of storage for temporary data structures in the
> future, and given that admin tooling could hide the undesirable
> configurations, this approach seems workable.

Here's my current thoughts on the tooling for namespace creation:

   ndctl create-namespace

That command by default will create a maximally sized pmem namespace
and set up the struct page memmap by default i.e. it defaults to the
following parameters:

    ndctl create-namespace --type=pmem --mode=memory

The other options for 'mode' are 'safe' and 'raw' where 'safe'
establishes a btt, and 'raw' exposes the full un-decorated capacity of
the namespace.

If you have a pre-existing 'raw' mode pmem namespace, you can convert
it to be enabled for dma, and other capabilities typical memory
possesses, with the following:

    ndctl create-namespace --mode=memory -r namespace0.0

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