[Feature]: Add a way to bypass RAM check for systems with ZFS

[janek202]

Is there no existing feature request for this?

• I have searched the existing feature requests

Is your proposal related to a problem?

The script checks for the amount of available memory, before running the VM.
However, on systems with ZFS, ARC memory is marked as used, but is released as needed.
This means the real available memory amount is bigger than reported by free.

Describe the solution you'd like.

Add an environment variable, that would disable this check.
Alternatively, it could check for Total memory in the system.

Describe alternatives you've considered.

As a workaround, before running the VM, I use head -c 4G /dev/zero | tail to temporarily allocate memory in a dummy process, so gets freed, when I exit it.

Additional context

No response

[kroese]

Good point! But to check for Total Memory is not really an alternative, because QEMU needs to allocate the RAM and thats why I check how much is available. You can have lots of RAM in total, but almost nothing available.

If you plan to run this container continously 24/7, the obvious solution would be to lower the amount that you configured for ZFS/ARC, so that there is always enough room for the container. That should have no downsides at all, since ZFS would not have been able to use it anyway while the container is running.

If you only want to run the container periodically, then a feature to disable the memory check would make sense. I will add a flag for that in the next release (might take a while).

[janek202]

Thanks for a reply.

Good point! But to check for Total Memory is not really an alternative, because QEMU needs to allocate the RAM and thats why I check how much is available. You can have lots of RAM in total, but almost nothing available.

Yes, I worded it poorly. I meant, to introduce an environmental variable that would change which value from free is used, or disable the check entirely.
The current behavior makes sense in majority of systems, and I think it should stay unchanged, as a default. :)

I only run this container periodically, not 24/7, that's why I run into this issue.

[kroese]

If you re-pull the latest image and set:

environment:
  RAM_CHECK: "N"

it should skip the check now. Please let me know if it works!

[janek202]

It seems to be working, thank you!

I got the error, re-pulled the image, started the container, and Windows booted just fine.

[nazdridoy]

environment

where are the scripts that checks for RAM?

[kroese]

https://github.com/qemus/qemu-docker/blob/master/src/config.sh

[nazdridoy]

found it. thanks