RSS HW hashes incoming session by using 5-tuple info and generates interrupts to different CPUs.
RPS, on the other hand, delivers all NIC interrupts to the same CPU, which then uses IPI to distribute the bottom half to other CPUs.
Typically, affinity + RPS is one setup, while RSS is another, and both do not need to be enabled at the same time.
Imho the smp_affinity was also needed for rss to spread load over the irqs.
Is it just me or are current head of RC/main kernels broken on the R4? I see 252mb memory total on modern main builds and this checks out with the dts, dtsi or so depending. Upping the memory via:
memory {
reg = <0x00 0x40000000 0x01 0x00000000>;
};
Works āsort ofā but eventually segfaults or/and crash/reboots or hits recovery, especially if writing to NVMe. I see similar issues in the last OpenWRT release (same issue yet I actually see all the RAM). I see some relatively recent fixes for eg. Ethernet mem space but havenāt done any testing yet as only the release was stable enough for my use case 
EDIT: This may have been something to do with the hardware, after all - I now see 0MB DRAM in the bootloader and it no longer boots at all. Iām returning it.
Yeah thatās just reserved memory lol