Netvsc vs Failsafe Performance

[Stephen Hemminger]

On Thu, 12 Sep 2024 13:47:37 -0700
Nandini Rangaswamy <nandini.rangaswamy at broadcom.com> wrote:

> Thanks for your response Long Li.
> I see with netvsc the maximum number of Tx descriptors is restricted to
> 4096 whereas the number of Rx descriptors is restricted to 8192.
> But, for failsafe PMD , we see that both the number of Txd and Rxd is
> restricted to 8192.
> How is netvsc PMD giving the same performance as failsafe PMD ?
> 
> Regards

I think the limits there were somewhat arbitrary chose with netvsc.
Don't remember a hard reason that would block larger sizes.


Having really big rings won't help performance (i.e BufferBloat) and
could a lot of memory consumption. When all heavy data traffic goes through
the VF and that ring is different. Only DoS attacks should be impacted
by rx/tx descriptor limits in the netvsc device. The linux driver actually
has much smaller buffer.