Browsing by Author "Ram, Kaushik Kumar"

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    Efficient virtualization of network interfaces without sacrificing safety and transparency
    (2009) Ram, Kaushik Kumar; Cox, Alan L.
    In modern day data centers economics is motivating server consolidation. Today, machine virtualization is being widely used to implement server consolidation. While great strides have been made in efficient virtualization of the machine's processors and memory, virtualization of I/O devices still incurs significant overheads. Xen uses the driver domain I/O model to support I/O virtualization. This model offers benefits such as fault isolation and device transparency. However, the processing overheads incurred in the driver domain to achieve these benefits limit overall I/O performance. This thesis presents mechanisms and optimizations to reduce the overhead of network interface virtualization when using the driver domain model without sacrificing its benefits. In particular, this thesis demonstrates the effectiveness of two approaches to reduce the CPU overhead of network I/O virtualization. First, Xen is modified to support multi-queue network interfaces to eliminate the software overheads of packet de-multiplexing and copying. Second, a new grant mechanism is developed to reduce memory sharing overheads. This thesis also presents and evaluates a series of optimizations that substantially reduce the I/O virtualization overheads in the guest domain. In combination, these mechanisms and optimizations increase the maximum throughput achieved by guest domains, in the receive path, from 3.0 Gb/s to full 10 Gigabit Ethernet link rates.
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    New Architectures and Mechanisms for the Network Subsystem in Virtualized Servers
    (2013-07-24) Ram, Kaushik Kumar; Cox, Alan L.; Rixner, Scott; Varman, Peter J.
    Machine virtualization has become a cornerstone of modern datacenters. It enables server consolidation as a means to reduce costs and increase efficiencies. The communication endpoints within the datacenter are now virtual machines (VMs), not physical servers. Consequently, the datacenter network now extends into the server and last hop switching occurs inside the server. Today, thanks to increasing core counts on processors, server VM densities are on the rise. This trend is placing enormous pressure on the network I/O subsystem and the last hop virtual switch to support efficient communication, both internal and external to the server. But the current state-of-the-art solutions fall short of these requirements. This thesis presents new architectures and mechanisms for the network subsystem in virtualized servers to build efficient virtualization platforms. Specifically, there are three primary contributions in this thesis. First, it presents a new mechanism to reduce memory sharing overheads in driver domain-based I/O architectures. The key idea is to enable a guest operating system to reuse its I/O buffers that are shared with a driver domain. Second, it describes Hyper-Switch, a highly streamlined, efficient, and scalable software-based virtual switching architecture, specifically for hypervisors that support driver domains. The Hyper-Switch combines the best of the existing architectures by hosting the device drivers in a driver domain to isolate any faults and placing the virtual switch in the hypervisor to perform efficient packet switching. Further, the Hyper-Switch implements several optimizations, such as virtual machine state-aware batching, preemptive copying, and dynamic offloading of packet processing to idle CPU cores, to enable efficient packet processing, better utilization of the available CPU resources, and higher concurrency. This architecture eliminates the memory sharing overheads associated with driver domains. Third, this thesis proposes an alternate virtual switching architecture, called sNICh, which explores the idea of server/switch integration. The sNICh is a combined network interface card (NIC) and datacenter switching accelerator. This takes the Hyper-Switch architecture one step further. It offloads the data plane of the switch to the network device, eliminating driver domains entirely.