On 2/16/22 15:08, Yongji Xie wrote:
On Wed, Feb 16, 2022 at 8:06 PM Leon Romanovsky <leon@xxxxxxxxxx> wrote:
On Wed, Feb 16, 2022 at 06:03:29PM +0800, Junji Wei wrote:
On Feb 16, 2022, at 5:48 PM, Leon Romanovsky <leon@xxxxxxxxxx> wrote:
On Wed, Feb 16, 2022 at 04:00:53PM +0800, Junji Wei wrote:
<...>
What is the use case for this virtio-rdma? Especially in context of RXE.
Hmm... yes, we didn’t find one. In passthrough case we can use RXE directly.
It doesn't sound like a good sales pitch.
Maybe I misunderstanded what you mean. We mean we didn’t find a user case
for virtio-rdma with passthrough net device. Do you want to know the user
case for our virtio-rdma(RoCE) proposal?
Yes, please.
I think one point is: when running RDMA accelerated applications in
VM, the virtio-rdma solution should get better performance than RXE
since it has a shorter data path (guest app -> host dpdk, bypass guest
kernel).
And you can (potentially) implement RDMA functionality in the hypervisor
by 'simply' to a memcpy between guests.
(I know it's not simple. But you don't actually need RDMA hardware here
and still should be able to provide RDMA functionality to guests.)
And if you look at the current RoCE CNAs they operate in exactly the
same way; there's a network interface, and _additionally_ an rdma
device. So for the OS both will be detected as distinct devices, who
just happen to run on the same PCI device.
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), GF: Felix Imendörffer
