How to Shrink Memory baloon in guest ?

[tytanick]

Hi.
About balloonin.
Guest had min 2GB and max 15GB of ram.
Over high usage it grows ram up to 15GB of max size. And it it working ok.
But now i want so shrink this balloon back, how can i do this ?
i am dooing
echo 1 > /proc/sys/vm/drop_caches
echo 2 > /proc/sys/vm/drop_caches
echo 3 > /proc/sys/vm/drop_caches

in gues machine. and the real usage of memory is 4GB / 15 GB

How can i shrink balloon so that Proxmox will only use 4GB and free up the rest 11GB ?

 

[vkhera]

I've seen the memory usage level go down on a VM, but I do not know what conditions make it happen. My guest is FreeBSD 10.2 and has the virtio_balloon driver loaded, which as far as I can determine is how the hypervisor and VM communicate about the memory usage. This part of my knowledge is fuzzy due to opaque documentation on the topic.

 

[spirit]

you can set shares=0, to force the shrink.

with default shares values, it's only shrinking when host memory is near full.

(shares is a weight to known which vm you need to shrink the most)

 

[vkhera]

you can set shares=0, to force the shrink.

with default shares values, it's only shrinking when host memory is near full.

(shares is a weight to known which vm you need to shrink the most)

That's really useful information. I haven't seen it in either of the books or anywhere on the wiki...

Anyhow, is my assumption right that the guest OS needs a virtio balloon driver as well for this to work?

 

[spirit]

Anyhow, is my assumption right that the guest OS needs a virtio balloon driver as well for this to work?

yes, sure.

linux kernel have it by default since 2.6.32 if I remember,

windows need to have a driver + service (see proxmox wiki)

 

[vkhera]

Thanks. I run FreeBSD in my VMs, and have loaded the virtio_balloon.ko module into the kernel. It appears to work based on observation over time.