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]

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