RE: [virtio-dev] Re: [PATCH v11] virtio-net: support inner header hash

[Parav Pandit <parav@nvidia.com>]

> From: Michael S. Tsirkin <mst@redhat.com>
> Sent: Tuesday, March 21, 2023 3:37 AM
> 
> On Tue, Mar 21, 2023 at 04:19:17AM +0000, Parav Pandit wrote:
> > One (this proposal) is solving spread to different RSS queues.
> 
> Spread is mostly ok with modern protocols though. 
Yes. 
> It seems to optimize for a specific monitoring solution.
> 
Monitoring is a critical part of the infrastructure.
So, if a point solution is useful, at least I don't see a negative of it especially when there is a user of it.

> > Another one is finding out which exact packet to drop/pass when queue usage
> is high. (ebpf/tc other ways to solve it).
> >
> > Ebpf sounds cooler than the real offload implementation in the hw device at
> the current level.
> > I remember Jason's good talk on the ebpf a few years back, which is possible
> when done in sw on the hypervisor.
> 
> I was talking about classic bpf though. no state.
> 
Packet processing logic requires to keep track of past tunnel data and counters across many queues for fairness.
This involves stateful ness of past/current data.

Even with outer header entropy, multiple tunnels can steer to a small set of queues, because num_tunnel >= num_queues.
Hence, fairness is orthogonal.