Merge pull request kubernetes#91918 from alculquicondor/new_max_skew

Use maxSkew in PodTopologySpread scoring as tolerance to skew

Author: k8s-ci-robot

pkg/scheduler/framework/plugins/podtopologyspread/scoring.go

@@ -200,8 +200,7 @@ func (pl *PodTopologySpread) Score(ctx context.Context, cycleState *framework.Cy
 				pair := topologyPair{key: c.TopologyKey, value: tpVal}
 				cnt = *s.TopologyPairToPodCounts[pair]
 			}
-			cnt = adjustForMaxSkew(cnt, int64(c.MaxSkew))
-			score += float64(cnt) * s.TopologyNormalizingWeight[i]
+			score += scoreForCount(cnt, c.MaxSkew, s.TopologyNormalizingWeight[i])
 		}
 	}
 	return int64(score), nil
@@ -287,13 +286,10 @@ func topologyNormalizingWeight(size int) float64 {
 	return math.Log(float64(size + 2))
 }
 
-// adjustForMaxSkew adjusts the number of matching pods in a topology domain
-// using the constraint's maxSkew.
-// Topology domains with less than maxSkew number of pods are considered to have
-// the same priority.
-func adjustForMaxSkew(cnt, maxSkew int64) int64 {
-	if cnt < maxSkew {
-		return maxSkew - 1
-	}
-	return cnt
+// scoreForCount calculates the score based on number of matching pods in a
+// topology domain, the constraint's maxSkew and the topology weight.
+// `maxSkew-1` is added to the score so that differences between topology
+// domains get watered down, controlling the tolerance of the score to skews.
+func scoreForCount(cnt int64, maxSkew int32, tpWeight float64) float64 {
+	return float64(cnt)*tpWeight + float64(maxSkew-1)
 }

pkg/scheduler/framework/plugins/podtopologyspread/scoring_test.go

@@ -314,12 +314,11 @@ func TestPodTopologySpreadScore(t *testing.T) {
 			},
 		},
 		{
-			// matching pods spread as 2/1/0/3.
-			// With maxSkew=2, counts change internally to 2/1/1/3.
 			name: "one constraint on node, all 4 nodes are candidates, maxSkew=2",
 			pod: st.MakePod().Name("p").Label("foo", "").
 				SpreadConstraint(2, v1.LabelHostname, v1.ScheduleAnyway, st.MakeLabelSelector().Exists("foo").Obj()).
 				Obj(),
+			// matching pods spread as 2/1/0/3.
 			existingPods: []*v1.Pod{
 				st.MakePod().Name("p-a1").Node("node-a").Label("foo", "").Obj(),
 				st.MakePod().Name("p-a2").Node("node-a").Label("foo", "").Obj(),
@@ -336,20 +335,19 @@ func TestPodTopologySpreadScore(t *testing.T) {
 			},
 			failedNodes: []*v1.Node{},
 			want: []framework.NodeScore{
-				{Name: "node-a", Score: 60},  // +20, compared to maxSkew=1
-				{Name: "node-b", Score: 100}, // +20, compared to maxSkew=1
+				{Name: "node-a", Score: 50}, // +10, compared to maxSkew=1
+				{Name: "node-b", Score: 83}, // +3, compared to maxSkew=1
 				{Name: "node-c", Score: 100},
-				{Name: "node-d", Score: 20}, // +20, compared to maxSkew=1
+				{Name: "node-d", Score: 16}, // +16, compared to maxSkew=1
 			},
 		},
 		{
-			// matching pods spread as 4/3/2/1.
-			// With maxSkew=3, counts change internally to 4/3/2/2.
 			name: "one constraint on node, all 4 nodes are candidates, maxSkew=3",
 			pod: st.MakePod().Name("p").Label("foo", "").
 				SpreadConstraint(3, v1.LabelHostname, v1.ScheduleAnyway, st.MakeLabelSelector().Exists("foo").Obj()).
 				Obj(),
 			existingPods: []*v1.Pod{
+				// matching pods spread as 4/3/2/1.
 				st.MakePod().Name("p-a1").Node("node-a").Label("foo", "").Obj(),
 				st.MakePod().Name("p-a2").Node("node-a").Label("foo", "").Obj(),
 				st.MakePod().Name("p-a3").Node("node-a").Label("foo", "").Obj(),
@@ -369,9 +367,9 @@ func TestPodTopologySpreadScore(t *testing.T) {
 			},
 			failedNodes: []*v1.Node{},
 			want: []framework.NodeScore{
-				{Name: "node-a", Score: 42},  // +28 compared to maxSkew=1
-				{Name: "node-b", Score: 71},  // +29 compared to maxSkew=1
-				{Name: "node-c", Score: 100}, // +29 compared to maxSkew=1
+				{Name: "node-a", Score: 33}, // +19 compared to maxSkew=1
+				{Name: "node-b", Score: 55}, // +13 compared to maxSkew=1
+				{Name: "node-c", Score: 77}, // +6 compared to maxSkew=1
 				{Name: "node-d", Score: 100},
 			},
 		},