Virtualization has proven consolidation and isolation benefits, but invariably incurs an overhead. This overhead especially penalizes latency sensitive tasks such as tcp processing, because such processing only occurs when a guest is scheduled. We evaluate a system where tcp is paravirtualized. All guest tcp processing below the socket interface takes place in the hypervisor, which enables rapid response to protocol state changes. We have built Leulo, a prototype hypervisor, and a modified Linux guest kernel that outperforms the Kernel Virtual Machine (KVM) and approaches native performance for certain workloads in an http benchmark.

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Interference from resource sharing can cause unpredictable performance when virtual machines are consolidated on a single machine. We demonstrate performance problems with http streaming in a virtual machine environment, even when no other virtual machines compete for network bandwidth. The paper suggests and evaluates a novel in-hypervisor data streaming service as a remedy to the performance problem. By modifying a Linux guest to exploit this new hypervisor interface, significant performance gains are experienced from a hosted Apache http server.