Enabling WiFi slows down NAT (bcm53xx)

[Rafał Miłecki]

On 13.01.2023 10:27, Rafał Miłecki wrote:
> Then I decided to reproduce manually the slow down.
> 
> That was simple. It's enough to call:
> iw phy phy0 interface add ap0 type __ap
> (without even bringing interface up!)

I noticed that calling
/etc/init.d/network restart
brings back full 940 Mb/s NAT speed and that allowed me to debug this
further.

Here comes explanation:

root at OpenWrt:/# cat /sys/class/net/eth0/queues/rx-0/rps_cpus
0
root at OpenWrt:/# iw phy phy0 interface add ap0 type __ap
root at OpenWrt:/# cat /sys/class/net/eth0/queues/rx-0/rps_cpus
3

When new interface appers, netifd overwrites optimized rps_cpus setup
that comes from target/linux/bcm53xx/base-files/etc/init.d/fastnetwork

https://git.openwrt.org/?p=openwrt/openwrt.git;a=commit;h=fcbd39689ebfef20c62fe3882d51f3af765e8028
("bcm53xx: enable & setup packet steering")

So it's a matter of netifd setup & bcm53xx specific setup script.