Firecracker Balloon only deflating on OOM

[JLucMahop]

Good morning to all,

Please I am currently working on swap behavior of the VM and I want to conduct some experiments on Ballooning.

I notice that it after following the readme from the repo ( balloon.md) My balloon only decrease on guest OOM so after filling the swap if the swap is enabled. Is this a normal behavior ?

Yours sincerely

[JLucMahop]

The firecracker balloon doesn't deflate or inflate automatically, It wait for host directives from the API server for inflation and deflation. The only mechanism automatic deflation happens when Guest is OOM, what is a pretty normal behavior

[Manciukic]

What is your use-case?

You can try out the new reporting feature ¹ of the balloon if you're interested in reclaiming memory from the guest, or in the new memory hotplugging feature ² if you'd like to make more memory available to the guest (but this is also controlled from the host).

Footnotes

1. https://github.com/firecracker-microvm/firecracker/blob/main/docs/ballooning.md#virtio-balloon-free-page-reporting ↩

2. https://github.com/firecracker-microvm/firecracker/blob/main/docs/memory-hotplug.md ↩