CPU Manager - Add check to policy.Allocate() for init conatiners

If container allocated CPUs is an init container, release those CPUs
back into the shared pool for re-allocation to next container.

Author: nolancon

pkg/kubelet/cm/cpumanager/cpu_manager.go

@@ -215,22 +215,6 @@ func (m *manager) Allocate(p *v1.Pod, c *v1.Container) error {
 	m.Lock()
 	defer m.Unlock()
 
-	// TODO: Reuse CPUs allocated to init containers to mimic functionality
-	// from previous implementation below. Logic should probably be pushed into
-	// the policy now instead of doing it at this level.
-
-	//// Proactively remove CPUs from init containers that have already run.
-	//// They are guaranteed to have run to completion before any other
-	//// container is run.
-	//for _, initContainer := range p.Spec.InitContainers {
-	//	if c.Name != initContainer.Name {
-	//		err := m.policyRemoveContainerByRef(string(p.UID), initContainer.Name)
-	//		if err != nil {
-	//			klog.Warningf("[cpumanager] unable to remove init container (pod: %s, container: %s, error: %v)", string(p.UID), initContainer.Name, err)
-	//		}
-	//	}
-	//}
-
 	// Call down into the policy to assign this container CPUs if required.
 	err := m.policy.Allocate(m.state, p, c)
 	if err != nil {

pkg/kubelet/cm/cpumanager/policy_static.go

@@ -209,6 +209,17 @@ func (p *staticPolicy) Allocate(s state.State, pod *v1.Pod, container *v1.Contai
 			return err
 		}
 		s.SetCPUSet(string(pod.UID), container.Name, cpuset)
+
+		// Check if the container that has just been allocated resources is an init container.
+		// If so, release its CPUs back into the shared pool so they can be reallocated.
+		for _, initContainer := range pod.Spec.InitContainers {
+			if container.Name == initContainer.Name {
+				if toRelease, ok := s.GetCPUSet(string(pod.UID), container.Name); ok {
+					// Mutate the shared pool, adding released cpus.
+					s.SetDefaultCPUSet(s.GetDefaultCPUSet().Union(toRelease))
+				}
+			}
+		}
 	}
 	// container belongs in the shared pool (nothing to do; use default cpuset)
 	return nil