Memory is not being freed on VZ

[okch-codes]

Discussed in #2720

^{Originally posted by Muzosh October 10, 2024}
I ran some memory intensive task today and it maxed out at 8GB (which was defined in my config). I was this in MacOS Activity Monitor next to a "Virtual Machine Service for limactl" process.

However, once those memory intensive tasks finished, the process stayed at 8GB indefinitely (until colima restart), slowing down my host Mac.

Is this intended behavior? I would expect the process to jump down to some idle value (around ~800-1000MB after fresh start).

[afbjorklund]

It is normal for memory that you dedicate to a virtual machine to be locked, the alternative is a feature*.

* called "ballooning" in QEMU, but I am not sure if it is available in Vz yet? Either way, it is not the default.

[okch-codes]

Apparently it's available but it doesn't work.

[balajiv113]

Yes its a macOS bug. Even docker desktop has the same problem.

Somehow orbstack fixed it with a custom memory management
https://orbstack.dev/blog/dynamic-memory

[afbjorklund]

Lima does create a VZVirtioTraditionalMemoryBalloonDeviceConfiguration, but I am not sure if it is used yet?

https://developer.apple.com/documentation/virtualization/vzvirtiotraditionalmemoryballoondevice