Update TopologyManager single-numa-node logic to handle "don't cares"

The logic has been updated to match the logic of the best-effort policy
except in two places:

1) The hint filtering frunction has been updated to allow "don't care"
hints encoded with a `nil` affinity mask, to pass through the filter in
addition to hints that have just a single NUMA bit set.

2) After calculating the `bestHint` we transform "don't care" affinities
encoded as having all NUMA bits set in their affinity masks into "don't
care" affinities encoded as `nil`.

pkg/kubelet/cm/topologymanager/policy_single_numa_node.go

@@ -18,6 +18,7 @@ package topologymanager
 
 import (
 	"k8s.io/klog"
+	"k8s.io/kubernetes/pkg/kubelet/cm/topologymanager/bitmask"
 	"k8s.io/kubernetes/pkg/kubelet/lifecycle"
 )
 
@@ -59,95 +60,100 @@ func (p *singleNumaNodePolicy) filterHints(allResourcesHints [][]TopologyHint) [
 	for _, oneResourceHints := range allResourcesHints {
 		var filtered []TopologyHint
 		for _, hint := range oneResourceHints {
+			if hint.NUMANodeAffinity == nil && hint.Preferred == true {
+				filtered = append(filtered, hint)
+			}
 			if hint.NUMANodeAffinity != nil && hint.NUMANodeAffinity.Count() == 1 && hint.Preferred == true {
 				filtered = append(filtered, hint)
 			}
 		}
-
 		filteredResourcesHints = append(filteredResourcesHints, filtered)
 	}
 	return filteredResourcesHints
 }
 
 func (p *singleNumaNodePolicy) mergeProvidersHints(providersHints []map[string][]TopologyHint) TopologyHint {
+	// Set the default affinity as an any-numa affinity containing the list
+	// of NUMA Nodes available on this machine.
+	defaultAffinity, _ := bitmask.NewBitMask(p.numaNodes...)
+
 	// Loop through all provider hints and save an accumulated list of the
 	// hints returned by each hint provider. If no hints are provided, assume
 	// that provider has no preference for topology-aware allocation.
-	var allResourcesHints [][]TopologyHint
+	var allProviderHints [][]TopologyHint
 	for _, hints := range providersHints {
+		// If hints is nil, insert a single, preferred any-numa hint into allProviderHints.
 		if len(hints) == 0 {
-			klog.Infof("[topologymanager] Hint Provider has no preference for NUMA affinity with any resource, " +
-				"skipping.")
+			klog.Infof("[topologymanager] Hint Provider has no preference for NUMA affinity with any resource")
+			allProviderHints = append(allProviderHints, []TopologyHint{{nil, true}})
 			continue
 		}
 
 		// Otherwise, accumulate the hints for each resource type into allProviderHints.
 		for resource := range hints {
 			if hints[resource] == nil {
-				klog.Infof("[topologymanager] Hint Provider has no preference for NUMA affinity with resource "+
-					"'%s', skipping.", resource)
+				klog.Infof("[topologymanager] Hint Provider has no preference for NUMA affinity with resource '%s'", resource)
+				allProviderHints = append(allProviderHints, []TopologyHint{{nil, true}})
 				continue
 			}
 
 			if len(hints[resource]) == 0 {
-				klog.Infof("[topologymanager] Hint Provider has no possible NUMA affinities for resource '%s'",
-					resource)
-				// return defaultHint which will fail pod admission
-				return TopologyHint{}
+				klog.Infof("[topologymanager] Hint Provider has no possible NUMA affinities for resource '%s'", resource)
+				allProviderHints = append(allProviderHints, []TopologyHint{{nil, false}})
+				continue
 			}
-			klog.Infof("[topologymanager] TopologyHints for resource '%v': %v", resource, hints[resource])
-			allResourcesHints = append(allResourcesHints, hints[resource])
+
+			allProviderHints = append(allProviderHints, hints[resource])
 		}
 	}
-	// In case allProviderHints length is zero it means that we have no
-	// preference for NUMA affinity. In that case update default hint preferred
-	// to true to allow scheduling.
-	if len(allResourcesHints) == 0 {
-		klog.Infof("[topologymanager] No preference for NUMA affinity from all providers")
-		return TopologyHint{nil, true}
-	}
 
-	allResourcesHints = p.filterHints(allResourcesHints)
-	// If no hints, or there is a resource with empty hints after filtering, then policy
-	// cannot be satisfied
-	if len(allResourcesHints) == 0 {
-		klog.Infof("[topologymanager] No hints that align to a single NUMA node.")
-		return TopologyHint{}
-	}
-	for _, hints := range allResourcesHints {
-		if len(hints) == 0 {
-			klog.Infof("[topologymanager] No hints that align to a single NUMA node for resource.")
-			return TopologyHint{}
-		}
-	}
+	// Filter to only include don't cares and hints with a single NUMA node.
+	allProviderHints = p.filterHints(allProviderHints)
 
 	// Set the bestHint to return from this function as {nil false}.
 	// This will only be returned if no better hint can be found when
 	// merging hints from each hint provider.
-	bestHint := TopologyHint{}
-	iterateAllProviderTopologyHints(allResourcesHints, func(permutation []TopologyHint) {
+	bestHint := TopologyHint{defaultAffinity, false}
+	iterateAllProviderTopologyHints(allProviderHints, func(permutation []TopologyHint) {
+		// Get the NUMANodeAffinity from each hint in the permutation and see if any
+		// of them encode unpreferred allocations.
 		mergedHint := mergePermutation(p.numaNodes, permutation)
-		// Only consider mergedHints that result in a NUMANodeAffinity == 1 to
-		// replace the current defaultHint.
-		if mergedHint.NUMANodeAffinity.Count() != 1 {
+
+		// Only consider mergedHints that result in a NUMANodeAffinity > 0 to
+		// replace the current bestHint.
+		if mergedHint.NUMANodeAffinity.Count() == 0 {
 			return
 		}
 
-		// If the current bestHint NUMANodeAffinity is nil, update bestHint
-		// to the current mergedHint.
-		if bestHint.NUMANodeAffinity == nil {
+		// If the current bestHint is non-preferred and the new mergedHint is
+		// preferred, always choose the preferred hint over the non-preferred one.
+		if mergedHint.Preferred && !bestHint.Preferred {
 			bestHint = mergedHint
 			return
 		}
 
-		// Only consider mergedHints that have a narrower NUMANodeAffinity
-		// than the NUMANodeAffinity in the current bestHint.
+		// If the current bestHint is preferred and the new mergedHint is
+		// non-preferred, never update bestHint, regardless of mergedHint's
+		// narowness.
+		if !mergedHint.Preferred && bestHint.Preferred {
+			return
+		}
+
+		// If mergedHint and bestHint has the same preference, only consider
+		// mergedHints that have a narrower NUMANodeAffinity than the
+		// NUMANodeAffinity in the current bestHint.
 		if !mergedHint.NUMANodeAffinity.IsNarrowerThan(bestHint.NUMANodeAffinity) {
 			return
 		}
+
 		// In all other cases, update bestHint to the current mergedHint
 		bestHint = mergedHint
 	})
+
+	if bestHint.NUMANodeAffinity.IsEqual(defaultAffinity) {
+		bestHint = TopologyHint{nil, bestHint.Preferred}
+	}
+
 	return bestHint
 }
 

pkg/kubelet/cm/topologymanager/policy_single_numa_node_test.go

@@ -77,7 +77,9 @@ func TestPolicySingleNumaNodeFilterHints(t *testing.T) {
 			},
 			expectedResources: [][]TopologyHint{
 				[]TopologyHint(nil),
-				[]TopologyHint(nil),
+				{
+					{NUMANodeAffinity: nil, Preferred: true},
+				},
 			},
 		},
 		{
@@ -98,6 +100,7 @@ func TestPolicySingleNumaNodeFilterHints(t *testing.T) {
 				},
 				{
 					{NUMANodeAffinity: NewTestBitMask(1), Preferred: true},
+					{NUMANodeAffinity: nil, Preferred: true},
 				},
 			},
 		},