KVM Forum 2019: virtio-vsock in QEMU, Firecracker and Linux

Status, Performance and Challenges

Slides and recording are available for the “virtio-vsock in QEMU, Firecracker and Linux: Status, Performance and Challenges“ talk that Andra Paraschiv and I presented at KVM Forum 2019. This was the 13th edition of the KVM Forum conference. It took place in Lyon, France in October 2019.

We talked about the current status and future works of VSOCK drivers in Linux and how Firecracker and QEMU provides the virtio-vsock device.

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How to measure the boot time of a Linux VM with QEMU/KVM

The stefano-garzarella/qemu-boot-time repository contains a Python perf-script and (Linux, QEMU, SeaBIOS) patches to measure the boot time of a Linux VM with QEMU/KVM.

Using I/O writes, we can trace events to measure the time consumed during the boot phase by the different components:

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qemu  linux  boot 

QEMU 4.0 boots uncompressed Linux x86_64 kernel

QEMU 4.0 is now able to boot directly into the uncompressed Linux x86_64 kernel binary with minimal firmware involvement using the PVH entry point defined in the x86/HVM direct boot ABI. (CONFIG_PVH=y must be enabled in the Linux config file).

The x86/HVM direct boot ABI was initially developed for Xen guests, but with latest changes in both QEMU and Linux, QEMU is able to use that same entry point for booting KVM guests.

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qemu  linux  boot 

iperf3-vsock: how to measure VSOCK performance

The iperf-vsock repository contains few patches to add the support of VSOCK address family to iperf3. In this way iperf3 can be used to measure the performance between guest and host using VSOCK sockets.

The VSOCK address family facilitates communication between virtual machines and the host they are running on.

To test VSOCK sockets (only Linux), you must use the new option --vsock on both server and client. Other iperf3 options (e.g. -t, -l, -P, -R, --bidir) are well supported by VSOCK tests.

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vsock  linux  qemu  net