The memory has been preallocated to hugetlb (or hugepages). As VM’s are started they’ll take memory from hugepages first.
root@muvirt:/# cat /proc/meminfo | grep Huge
AnonHugePages: 10240 kB
ShmemHugePages: 0 kB
FileHugePages: 0 kB
HugePages_Total: 13341
HugePages_Free: 13291
HugePages_Rsvd: 974
HugePages_Surp: 0
Hugepagesize: 2048 kB
Hugetlb: 27322368 kB
If you want to reduce the preallocation you can adjust it in the configuration (reboot required):
uci get virt.system.hugetlb
26682
uci set virt.system.hugetlb=10240
or under ‘Virtualization->Virtual Machines Global Options’ in LuCI:
