Where hugetlb controller is auto enabled?

[chairwa]

One kvm virtual machine (8 vcpus+8G memory) of Ubuntu 22.04 with cgroup2 system,
cat /sys/fs/cgroup/cgroup.subtree_control
hugetlb controller included;
But another kvm vm (4 vcpus+4G memory) of Ubuntu 22.04 with cgroup2 system,
cat /sys/fs/cgroup/cgroup.subtree_control
no hugetlb controller included.
You have to manually
echo +hugetlb > cgroup.subtree_control, which is not as expected.

In linux kernel source code / systemd source code, I did not find the relevant processing of automatically enabling hugetlb or automatically disabling hugetlb.
Would you be kind to tell me where the code to automatically enable hugetlb lies?

[luohuang]

这是来自QQ邮箱的自动回复邮件。   您好，您的邮件我已经收到。   谢谢！