Am 10.06.24 um 14:16 schrieb Jason Gunthorpe:
On Mon, Jun 10, 2024 at 02:07:01AM +0100, Pavel Begunkov wrote:
On 6/10/24 01:37, David Wei wrote:
On 2024-06-07 17:52, Jason Gunthorpe wrote:
IMHO it seems to compose poorly if you can only use the io_uring
lifecycle model with io_uring registered memory, and not with DMABUF
memory registered through Mina's mechanism.
By this, do you mean io_uring must be exclusively used to use this
feature?
And you'd rather see the two decoupled, so userspace can register w/ say
dmabuf then pass it to io_uring?
Personally, I have no clue what Jason means. You can just as
well say that it's poorly composable that write(2) to a disk
cannot post a completion into a XDP ring, or a netlink socket,
or io_uring's main completion queue, or name any other API.
There is no reason you shouldn't be able to use your fast io_uring
completion and lifecycle flow with DMABUF backed memory. Those are not
widly different things and there is good reason they should work
together.
Well there is the fundamental problem that you can't use io_uring to
implement the semantics necessary for a dma_fence.
That's why we had to reject the io_uring work on DMA-buf sharing from
Google a few years ago.
But this only affects the dma_fence synchronization part of DMA-buf, but
*not* the general buffer sharing.
Regards,
Christian.
Pretending they are totally different just because two different
people wrote them is a very siloed view.
The devmem TCP callback can implement it in a way feasible to
the project, but it cannot directly post events to an unrelated
API like io_uring. And devmem attaches buffers to a socket,
for which a ring for returning buffers might even be a nuisance.
If you can't compose your io_uring completion mechanism with a DMABUF
provided backing store then I think it needs more work.
Jason
