Measuring the impact of SR-IOV and virtualization on packet round-trip time
Summary
This paper presents a comprehensive study on the impact of Single Root I/O Virtualization (SR-IOV) and various virtualization technologies on packet round-trip time (RTT) in cloud computing environments. The authors, through a series of controlled experiments, aim to understand the performance implications of SR-IOV when paired with different configurations and loads in a Kernel-based Virtual Machine (KVM) setting.
Main Points
Introduction
- Resource virtualization has proven beneficial across data centers, telecommunications systems, and computer networks.
- Several performance issues need consideration when using virtualization.
- Several networking solutions have emerged
- Virtual Machine Device Queues (VMDQ): offloads packet sorting from the virtual machine manager (VMM), the hypervisor, to the network controller to accelerate network I/O throughput.
- PCI Passthrough and SR-IOV: Both aimed at lowering packet processing latency by acting at the hardware level.
Choosing the appropriate technology for a given use case is still an open research issue.
Virtualization and single root I/O virtualization
Single Root I/O Virtualization (SR-IOV) is a hardware-based networking technology that allows a single physical input/output (I/O) device to present itself as multiple virtual devices with similar capabilities.
As SR-IOV is "simply" a physical technology, there are multiple ways to logically connect it to user space processes. However, regarding interfacing virtual machines and SR-IOV, two main designs dominate the scene.
PCI passthrough
PCI Passthrough
PCI Passthrough is a mechanism that assigns host PCI devices directly to the virtual machines (VMs) and acts as a hypervisor bypass.
- allows a VM to directly connect to the PCI device, behaving as if it was physically connected
- the hypervisor no longer has to perform packet translation between the VM and the host.
Removing the hypervisor from the data plane is a clear step to mitigate performance degradation caused by context switches and memory copies between VMs and the hypervisor during packet processing.
SR-IOV is typically utilized in combination with PCI Passthrough.
Standard virtual drivers
