VIOMB(4)

📦
version 11.0 · 2 versions
, in nixpkgs unstable

💖 VIOMB(4) — the manual page for the VirtIO memory ballooning driver, bestie edition 🎈

okay so this is the viomb page from the Kernel Interfaces Manual, and it's genuinely one of the cutest little drivers you'll ever meet. it's giving "I return memory to my host like a good little guest" energy and honestly? slay. 🫶

✨ SYNOPSIS ✨

virtio* at pci? dev ? function ?
viomb*  at virtio?

there she is. that's the whole vibe. viomb rides on top of virtio, and virtio attaches to pci? dev ? function ?. nesting dolls but make it kernel. 🪆

🌸 DESCRIPTION 🌸

so virtio(4) is this iconic interface that defines efficient, standard, and extensible I/O between the hypervisor and the virtual machine. and the viomb driver? it's the one that specifically supports the virtio-compliant memory ballooning device. main character energy fr fr. 👑

memory ballooning works like this, step by step, no cap:

  1. the host operator requests a guest to return some amount of memory to the host — via e.g. the Qemu monitor balloon command, iykyk.
  2. the hypervisor sends the request via the VirtIO memory ballooning device.
  3. the guest viomb driver then requests allocation of that amount of physical memory from the NetBSD memory management system. polite but firm. 💅
  4. the viomb device tells the hypervisor the guest physical memory address of the allocated memory via the VirtIO memory ballooning device. full circle moment.

and for the girlies who like to check the receipts 📊:

  • the sysctl node hw.viomb.npages shows the requested number of memory pages to return to the hypervisor.
  • hw.viomb.actual shows the actual number of memory pages that are already returned to the hypervisor.

like, the requested vs. the real. the dream vs. the delivery. we love a transparent queen. ✨

🔍 SEE ALSO 🔍

go give these a little kiss, they're all in the family:

and the source material — Rusty Russell, IBM Corporation, Virtio PCI Card Specification, http://ozlabs.org/~rusty/virtio-spec/. the blueprint. the origin story. 🎀

🦋 HISTORY 🦋

the viomb device driver appeared in NetBSD 6.0. so she's been out here returning memory since way back. legacy icon behavior. 👑

💀 BUGS 💀

ngl the userland interface should be same as the Xen ballooning device. (yes, that's exactly how the original says it — grammatical quirk and all, preserving the vibe.) 🙈

and that's the whole page bestie!! no notes. now go forth and balloon responsibly. 🎈💖

🌈 sign-off: this little treasure comes to us from the Debian source, version dated August 25, 2020, and it's the VIOMB(4) page from the Kernel Interfaces Manual. mwah. 💋

📦 where this page comes from