Rethinking Cloud Network Stacks with Switch Bypass

Virtual switches are one of the most important building blocks in public cloud network stacks as they apply high-level policies to traffic enabling communication between virtual machines (VMs) and the rest of the world. The problem is that virtual switches need CPU cores to process packets and the more cores assigned to them, the less are available to VMs that are rented to customers and hence generate revenue. With this paper, we show that it is potentially possible to find a sweet-spot between performance and costs. The insight is that applications running on VMs are not always using 100% of their CPU processing power: we use this to design switch bypass, a new technique that allow virtual switches to opportunistically offload part of their processing to the virtual NIC drivers associated with guest VMs. Using packet classification as use-case, we show that with switch bypass we obtain a performance boost up to 40% without the need of additional core processing power.