What is the difference between cgroups freeze and linux command "Kill - STOP pid" in golang?

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I use this cgroups package.

There are two interfaces I am interested in for type Cgroup. The one is Freeze() error and the other is Thaw() error.The description of them is as follows:

    ...
    // Freeze freezes or pauses all processes inside the cgroup
    Freeze() error
    // Thaw thaw or resumes all processes inside the cgroup
    Thaw() error
    ...

And there are two linux command that can pause and resume a process, which is kill -STOP pid and kill -CONT pid.

I wonder that if there is only one process in a cgroup, does it has any difference between these two ways to pause and resume the process? Thanks.

cgroups go operating-system linux
1 Answers

Both states were introduced in oct. 2016 in containerd/cgroups commit b3f3344 and refer to cgroup v1 self-state

The cgroup freezer is hierarchical.

Freezing a cgroup freezes all tasks beloning to the cgroup and all its descendant cgroups.
Each cgroup has its own state (self-state) and the state inherited from the parent (parent-state).
Iff both states are THAWED, the cgroup is THAWED.

CGroup Freezer states:

freezer.state is only available in non-root cgroups and has three possible values:

  • FROZEN — tasks in the cgroup are suspended.
  • FREEZING — the system is in the process of suspending tasks in the cgroup.
  • THAWED — tasks in the cgroup have resumed.

Meaning (here):

The freezer subsystem is used to suspend and resume processes in the cgroup.

Freezer has a control file: freezer.state, write FROZEN to this file, you can suspend the process in the cgroup, and write THAWED to this file, you can resume the suspended process.

VonC_63090
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