gVisor's architecture is fascinating. Years ago I wrote an essay that was kind of a response to all the cracks about "systemd-kerneld" that have been made over the years. Written in character as "Fake Lennart Poettering", it proposed a strategy, using techniques inspired by NetBSD's rump kernel libraries, to turn systemd into a kernel, which would then load a Linux image into user space and "pass through" all system calls to it except those systemd wanted to intercept. Which is kinda the opposite of what gVisor does!
Some guy on a German Linux forum thought my idea was an actual plan by the systemd team, and another poster had to correct him that the author was "FAKE Lennart Poettering", so the joke either didn't land or landed all too well, depending on your perspective...
What use-cases are there for gVisor on Raspbian, given that the target is a Raspberry Pi?
the simplest one (and the one we're targetting) is multi-tenant services. You want to sandbox your service so that it doesn't affect the rest of the services running.
<shameless plug> We're building a container runtime to do this, and we are comparing alternatives, that's how we got there: https://github.com/urunc-dev/urunc</shameless plug>
Ran gVisor on a Pi 4 cluster for home IoT sandboxing. Memory overhead is real—about 120MB per sandbox vs 15MB for raw containers. On 4GB boards that limits you to ~25 isolated services before OOM kicks in. Also, syscall拦截 adds 30-40% CPU overhead on ARM. Works fine for untrusted Python scripts, but I wouldn’t run anything compute-heavy.
Wouldn’t compute workloads be fine as they should not be syscall bound?
yeap -- compute would be nearly the same. I suspect you need some kind of I/O to make your compute useful (get input for the computation / produce output etc.) so, still, this would have a negative effect overall.
> Fair warning: compiling a kernel on the Pi itself takes several hours.
One nit: this should only take about 40 minutes on a Pi 5, assuming you're compiling with -j6 to use all the cores.
(Still faster to cross-compile)
That is kind of what I was thinking too, and cross-compilation is still the fastest way to build for a different target.
well, the tricky detail here (which we do not mention in the post, our bad) is that we got the raspbian config (cp /boot/config ... .config && make oldconfig) which includes most modules, and that's why it took more.
But yeap, good point about using the -j flag, it really accelerates the build!
Using distcc networked compilation instead of cross-compiling is reasonably fast too and easier to set up if one isn't familiar with either.
the most frustrating part with having to compile a custom kernel is the maintenance burden (packaging/updating etc.), and not the time it takes to build…
I had a similar issue with networking modules for calico (k8s cni) on both rpis and jetson boards…