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Do not snapshot scheduler cache before starting preemption

pull/564/head
Bobby (Babak) Salamat 2019-01-14 11:12:42 -08:00
parent a2daf66a0d
commit e3f4e1e378
1 changed files with 9 additions and 6 deletions
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15
pkg/scheduler/core/generic_scheduler.go
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@ -272,6 +272,13 @@ func (g *genericScheduler) selectHost(priorityList schedulerapi.HostPriorityList
// returns 1) the node, 2) the list of preempted pods if such a node is found,
// 3) A list of pods whose nominated node name should be cleared, and 4) any
// possible error.
// Preempt does not update its snapshot. It uses the same snapshot used in the
// scheduling cycle. This is to avoid a scenario where preempt finds feasible
// nodes without preempting any pod. When there are many pending pods in the
// scheduling queue a nominated pod will go back to the queue and behind
// other pods with the same priority. The nominated pod prevents other pods from
// using the nominated resources and the nominated pod could take a long time
// before it is retried after many other pending pods.
func (g *genericScheduler) Preempt(pod *v1.Pod, nodeLister algorithm.NodeLister, scheduleErr error) (*v1.Node, []*v1.Pod, []*v1.Pod, error) {
// Scheduler may return various types of errors. Consider preemption only if
// the error is of type FitError.
@ -279,10 +286,6 @@ func (g *genericScheduler) Preempt(pod *v1.Pod, nodeLister algorithm.NodeLister,
if !ok || fitError == nil {
return nil, nil, nil, nil
}
err := g.snapshot()
if err != nil {
return nil, nil, nil, err
}
if !podEligibleToPreemptOthers(pod, g.cachedNodeInfoMap) {
klog.V(5).Infof("Pod %v/%v is not eligible for more preemption.", pod.Namespace, pod.Name)
return nil, nil, nil, nil
@ -1073,7 +1076,7 @@ func nodesWherePreemptionMightHelp(nodes []*v1.Node, failedPredicatesMap FailedP
potentialNodes := []*v1.Node{}
for _, node := range nodes {
unresolvableReasonExist := false
failedPredicates, found := failedPredicatesMap[node.Name]
failedPredicates, _ := failedPredicatesMap[node.Name]
// If we assume that scheduler looks at all nodes and populates the failedPredicateMap
// (which is the case today), the !found case should never happen, but we'd prefer
// to rely less on such assumptions in the code when checking does not impose
@ -1104,7 +1107,7 @@ func nodesWherePreemptionMightHelp(nodes []*v1.Node, failedPredicatesMap FailedP
break
}
}
if !found || !unresolvableReasonExist {
if !unresolvableReasonExist {
klog.V(3).Infof("Node %v is a potential node for preemption.", node.Name)
potentialNodes = append(potentialNodes, node)
}