[Intel-wired-lan] [PATCH v2 bpf 1/5] net: ethtool: add xdp properties flag set

[Saeed Mahameed <saeed@kernel.org>]

On Wed, 2020-12-09 at 08:41 -0700, David Ahern wrote:
> On 12/9/20 4:52 AM, Jesper Dangaard Brouer wrote:
> > > > still load and either share queues across multiple cores or
> > > > restirct
> > > > down to a subset of CPUs.  
> > > 
> > > And that's the missing piece of logic, I suppose.
> > > 
> > > > Do you need 192 cores for a 10gbps nic, probably not.  
> > > 
> > > Let's hear from Jesper :p
> > 
> > LOL - of-cause you don't need 192 cores.  With XDP I will claim
> > that
> > you only need 2 cores (with high GHz) to forward 10gbps wirespeed
> > small
> > packets.
> 
> You don't need 192 for 10G on Rx. However, if you are using
> XDP_REDIRECT
> from VM tap devices the next device (presumably the host NIC) does
> need
> to be able to handle the redirect.
> 
> My personal experience with this one is mlx5/ConnectX4-LX with a
> limit

This limit was removed from mlx5
https://patchwork.ozlabs.org/project/netdev/patch/20200107191335.12272-5-saeedm at mellanox.com/
Note: you still need to use ehttool to increase from 64 to 128 or 96 in
your case.

> of 63 queues and a server with 96 logical cpus. If the vhost thread
> for
> the tap device runs on a cpu that does not have an XDP TX Queue, the
> packet is dropped. This is a really bizarre case to debug as some
> packets go out fine while others are dropped.

I agree, the user experience horrible.