After updating to pve 9 several windows vms stared to experience this issue, not all.
The memory usage of the affected VMs slowly increased, it was shown in the Proxmox graphs.
This was also shown Windows Task Manager however there is no processes using the memory.
Have updated the virtio drivers.
When memory usage approached 100% it started to swapping and CPU load increased significantly.
After setting the min max memory to the same value, the memory was immediately released and became available to the VM again.
This suggest that there is a problem with the memory ballooning.
The memory usage of the affected VMs slowly increased, it was shown in the Proxmox graphs.
This was also shown Windows Task Manager however there is no processes using the memory.
Have updated the virtio drivers.
When memory usage approached 100% it started to swapping and CPU load increased significantly.
After setting the min max memory to the same value, the memory was immediately released and became available to the VM again.
This suggest that there is a problem with the memory ballooning.