QEMU Guest using huge amounts of compressed memory on boot

Question

Virt Manager configuration:

Guest memory usage right after booting (nothing is running):

I'm running virt-manager on a standard Ubuntu 17.10 system. In Proxmox, the same general configuration (with ballooning enabled) would allocate 8GB of the host but the guest would have roughly 1-2GB used out of 16GB instead of this.

I'm pretty sure I have all the guest drivers installed. (qemu guest, virtio stuff, balloon driver & service)

This is not my first QEMU VM, but the only one outside of Proxmox (which I'm assuming does some extra stuff that virt-manager doesn't).

What really exacerbates this issue is if I set the Current allocation to 2GB, the guest has about 15.6GB compressed and most software won't launch or run correctly because there's no free system memory...

---

Host:

:~$ free -m
              total        used        free      shared  buff/cache   available
Mem:          32163       20273        8949         176        2940       11325
Swap:          2047           2        2045

Hardly anything is running on the host. It looks like the entire 16GB is getting claimed but simultaneously most of that memory is inaccessible to the guest.

Answer 1

usual and expected behaviour. qemu/kvm allocates the max ram until balloon service is started. afterwards any ram consumed by balloon service is free (from host pov)