kill all processes in a container in the event of OOM

Set memory.oom.group if using cgroups v2 unified mode so all processes in
the container will be killed together in the event of an OOM kill.

pkg/kubelet/kuberuntime/kuberuntime_container_linux.go

@@ -215,6 +215,15 @@ func (m *kubeGenericRuntimeManager) calculateLinuxResources(cpuRequest, cpuLimit
 		resources.CpuPeriod = cpuPeriod
 	}
 
+	// runc requires cgroupv2 for unified mode
+	if libcontainercgroups.IsCgroup2UnifiedMode() {
+		resources.Unified = map[string]string{
+			// Ask the kernel to kill all processes in the container cgroup in case of OOM.
+			// See memory.oom.group in https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html for
+			// more info.
+			"memory.oom.group": "1",
+		}
+	}
 	return &resources
 }