no-auto-default still sets IFF_UP
With no-auto-default set, Networkmanger still set IFF_UP thus kernel would allocate the memory resources like ring buffers for the network device in ndo_open. I'm not sure if this is expected or a bug. But I need a way to tell NetworkManager only set IFF_UP for specified interferace. Some NICs consumes a huge amount of memory. For example it's found i40e consumes ~15GB on a power machine. On this machine, i40e manages four interfaces but only one interface has carrier but by default NetworkManager still request IFF_UP set for the other three inactive interfaces. If I manually
ip link set dev down the three inactive interaces, the memory comsumption could be reduced from 16899MB to 5438MB.
Btw, #786 provides another way to address my concern.