[compsciphd]

been out of the space for a bit (though interviewing again, so might get back into it), gvisor at least as the "userspace" hypervisor, seemed to provide minimal value vs modern hypervisor systems with low overhead / quick boot VMs (ala firecracker). With that said, I only looked at it years ago, so I could very well be out of date on it.

Wasn't aware of Nabla, but they seem to be going with the unikernel approach (based on a cursory look at them). Unikernels have been "popular" (i.e. multiple attempts) in the space (mostly to basically run a single process app without any context switches), but it creates a process that is fundamentally different than what you develop and is therefore harder to debug.

while the unikernels might be useful in the high frequency trading space (where any time savings are highly valued), I'm personally more skeptical of them in regular world usage (and to an extent, I think history has born this out, as it doesn't feel like any of the attempts at it, has gotten real traction)

[eyberg]

I think many people (including unikernel proponents themselves) vastly underestimate the amount of work that goes into writing an operating system that can run lots of existing prod workloads.

There is a reason why Linux is over 30 years old and basically owns the server market.

As you note, since it's not really a large existing market you basically have to bootstrap it which makes it that much harder.

We (nanovms.com) are lucky enough to have enough customers that have helped push things forward.

For the record I don't know of any of our customers or users that are using them for HFT purposes - something like 99% of our crowd is on public cloud with plain old webapp servers.

[tptacek]

Modern gVisor uses KVM, not ptrace, for this reason.

[compsciphd]

so I did a check, it would seem that gvisor with kvm, mostly works for bare metal, not on existing VMs (nested virtualization).

https://gvisor.dev/docs/architecture_guide/platforms/

"Note that while running within a nested VM is feasible with the KVM platform, the systrap platform will often provide better performance in such a setup, due to the overhead of nested virtualization."

I'd argue then for most people (unless have your own baremetal hyperscaler farm), one would end up using gvisor without kvm, but speaking from a place of ignorance here, so feel free to correct me.