With the development of NFV (Network Function Virtualization) paradigm, networking functions would gradually move from specialized and proprietary hardware to open-source software run over a virtual machine (VM) deployed on commodity hardware. Open vSwitch (OVS) is the most prominent open-source solution implementing a virtual switch, while DPDK (Data Plane Development Kit) is a set of specialized libraries to enhance the performance. In particular, DPDK allows packets to be processed by batches. In this paper, we address the issue of modeling the behavior of a DPDK-based virtual switch. First, we investigate the influence of batch services on the overall performance of a virtual switch. Second, we extend two former analytical models to include the processing of packets by batches. We propose a simple means to do it, and we evaluate the accuracy of our solution on two different scenarios. Numerical results show that, despite its simplicity, our approach provides fairly good results when compared to simulation.