pkg/kubelet/cm: use SkipFreezeOnSet

This is a knob added by runc 1.0.2 specifically for kubernetes,
which tells runc/libcontainer/cgroups/systemd v1 manager to not
freeze the cgroup in Set().

We set this knob here because this code is only used for pods
(rather than containers) management, and in this place we create or
update the pod cgroup with no device limits set, so we can skip the
freeze.

If this knob is not set, libcontainer's cgroup v1 manager tries to
figure out whether the freeze is needed or not, but it's a somewhat
expensive check to perform, thus the knob is a shortcut.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

pkg/kubelet/cm/cgroup_manager_linux.go

@@ -380,6 +380,7 @@ func getSupportedUnifiedControllers() sets.String {
 func (m *cgroupManagerImpl) toResources(resourceConfig *ResourceConfig) *libcontainerconfigs.Resources {
 	resources := &libcontainerconfigs.Resources{
 		SkipDevices:     true,
+		SkipFreezeOnSet: true,
 	}
 	if resourceConfig == nil {
 		return resources