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Comment by fulafel | Hacker News Reader

The Andromeda description link explains that there are special OS drivers for it. Anyone know what part of the magic is guest side?

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Which bit are you referring to? I think the blog posts make this a little too abstract. It's virtio-net and as mentioned elsewhere, we like and contribute to the latest kernels to do things like better multiqueue support.

For example, here's the script we install in our guest images and encourage people to run to make sure interrupts are paired to queues: https://github.com/GoogleCloudPlatform/compute-image-package...

Disclosure: I work on Google Cloud but don't know much about networking.

This bit, "Some of the most valuable enhancements enable VMs built on supporting Linux kernels to exploit offload/multi-queue capabilities"

I was wondering what is offloaded. I guess virtio-net is a good keyword, thanks.

At the time Andromeda was originally introduced it took a fairly recent Linux kernel to get support for multi-queue networking and offloads with virtio-net. Today anything even moderately recent has support baked in -- specifically Linux 3.8 and above include multi-queue support (as well as the offloads we support).

In terms of specific offloads, the big ones are TCP segmentation offload (TSO) and TCP large receive offload (LRO). These substantially reduce the compute burden on the guest. Less impactful (although still important) are checksum calculation and verification offload.

(I was the tech lead for the hypervisor side of this launch — Jake, the post's author, leads the fast-path team for the Andromeda software switch)

Oh! I think the acronyms you're looking for are GRO, LRO and whatnot.

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