Networking with 2 CPU(s) is bad. Because the pcb lane on pcie are directly to 1 CPU socket. If all cpu plugged but only 1 pcie, the traffic will flow to another cpu and go back again through a lane called QPI. QPI is natural enemy for networking, latency and jitter. Please read about Networking with NUMA. Or you can take out the cpu that not direct to pci lane you, you will got better performance except your cpu is too old.
I used R620 with FRRouting + dpdk on 2690 v2.
Got 8mpps performance on single core, and got 16mpps on 2 core in same cpu socket. But when i pin 1 core on cross cpu socket its only 12mpps, thats it.