[dpdk-dev] [PATCH v12 0/3] mempool: add external mempool manager

[Hunt, David]

On 15/6/2016 11:13 AM, Jan Viktorin wrote:
> Hi,
>
> I've got one last question. Initially, I was interested in creating
> my own external memory provider based on a Linux Kernel driver.
> So, I've got an opened file descriptor that points to a device which
> can mmap a memory regions for me.
>
> ...
> int fd = open("/dev/uio0" ...);
> ...
> rte_mempool *pool = rte_mempool_create_empty(...);
> rte_mempool_set_ops_byname(pool, "uio_allocator_ops");
>
> I am not sure how to pass the file descriptor pointer. I thought it would
> be possible by the rte_mempool_alloc but it's not... Is it possible
> to solve this case?
>
> The allocator is device-specific.
>
> Regards
> Jan

This particular use case is not covered.

We did discuss this before, and an opaque pointer was proposed, but did 
not make it in.
http://article.gmane.org/gmane.comp.networking.dpdk.devel/39821
(and following emails in that thread)

So, the options for this use case are as follows:
1. Use the pool_data to pass data in to the alloc, then set the 
pool_data pointer before coming back from alloc. (It's a bit of a hack, 
but means no code change).
2. Add an extra parameter to the alloc function. The simplest way I can 
think of doing this is to
take the *opaque passed into rte_mempool_populate_phys, and pass it on 
into the alloc function.
This will have minimal impact on the public API,s as there is already an 
opaque there in the _populate_ funcs, we're just
reusing it for the alloc.

Do others think option 2 is OK to add this at this late stage? Even if 
the patch set has already been ACK'd?

Regards,
Dave.