bhyve performance issues

Hi,

I have a FreeBSD 14.2 system with two bhyve machines (using vm-bhyve).
Those VMs are completely unrelated: one is a Linux VM for podman builds
- "linux", one is a Windows 10 VM for Microsoft365 backup - "windows".

Whenever I start a build process on "linux" (2 cpus out of 6), the host
system becomes barely usable, with a load average of 40-60. The strange
thing is htop shows me cpu usage of "linux" at 20-30% whereas "windows"
(which is just idling around) starts using roughly ~45% cpu (normally <
10%).

Infos: the host: CPU: AMD Ryzen 5 3600 6-Core Processor, 64GB RAM, 4
slow spinning disks (zfs: striped mirror).

windows vm config:
loader="uefi"
cpu_sockets=1
cpu_cores=4
cpu=4
memory=20480M
network0_type="virtio-net"
network0_switch="public"
disk0_type="virtio-blk"
disk0_name="disk0.img"
uuid="30c90d9a-be0f-11ef-a78a-b42e99a1b9c3"
network0_mac="58:9c:fc:0b:a3:ff"
graphics="yes"
xhci_mouse="yes"
graphics_listen="127.0.0.1"
graphics_port="591"
graphics_vga=io
utctime="no"

linux.cfg:
loader="uefi"
cpu=2
memory=4096M
network0_type="virtio-net"
network0_switch="public"
disk0_type="virtio-blk"
disk0_name="disk0.img"
uuid="5307ee72-be0f-11ef-a78a-b42e99a1b9c3"
network0_mac="58:9c:fc:a7:7b:ef"
graphics="yes"
graphics_listen="127.0.0.1"
graphics_port="5901"
graphics_vga=io

Anyone an idea what could be wrong, or, how to debug this? Thanks!

Regards,
Robert