On Tue, 2023-03-28 at 16:16 -0700, Jakub Kicinski wrote:

On Tue, 28 Mar 2023 21:59:25 +0200 Felix Fietkau wrote:

quoted

When dealing with few flows or an imbalance on CPU utilization, static RPS
CPU assignment can be too inflexible. Add support for enabling threaded NAPI
for backlog processing in order to allow the scheduler to better balance
processing. This helps better spread the load across idle CPUs.

Can you share some numbers vs a system where RPS only spreads to 
the cores which are not running NAPI?

IMHO you're putting a lot of faith in the scheduler and you need 
to show that it actually does what you say it will do.

I have the same feeling. From your description I think some gain is
possible if there are no other processes running except
ksoftirq/rps/threaded napi. 

I guess that the above is expect average state for a small s/w router,
but if/when routing daemon/igmp proxy/local web server kicks-in you
should notice a measurable higher latency (compared to plain RPS in the
same scenario)???

Cheers,

Paolo