OVS Data Plane Development kit is an enhanced Open vSwitch with Data Plane Development Kit libraries. The DPDK was included to try overcome the performance limitations due to CPU interrupts from the physical NIC.
OVS with DPDK operates entirely in user space. The DPDK Poll Mode Driver (PMD) in OVS polls for data that comes into the physical NIC and processes it. This bypasses the network stack and the need to send an interrupt to the CPU when a packet is received.
DPDK PMD requires one or more CPU cores to dedicated entirely to polling and handling the incoming data. Once the packet is in OVS, it is in user-space and can be switched directly to the required VNF.