optimise defaultpreemption: enumerate fewer candidates

Signed-off-by: Adhityaa Chandrasekar <adtac@google.com>

pkg/scheduler/apis/config/validation/validation_pluginargs.go

@@ -26,6 +26,38 @@ import (
 	"k8s.io/kubernetes/pkg/scheduler/apis/config"
 )
 
+// ValidateDefaultPreemptionArgs validates that DefaultPreemptionArgs are correct.
+func ValidateDefaultPreemptionArgs(args config.DefaultPreemptionArgs) error {
+	if err := validateMinCandidateNodesPercentage(args.MinCandidateNodesPercentage); err != nil {
+		return err
+	}
+	if err := validateMinCandidateNodesAbsolute(args.MinCandidateNodesAbsolute); err != nil {
+		return err
+	}
+	if args.MinCandidateNodesPercentage == 0 && args.MinCandidateNodesAbsolute == 0 {
+		return fmt.Errorf("both minCandidateNodesPercentage and minCandidateNodesAbsolute cannot be zero")
+	}
+	return nil
+}
+
+// validateMinCandidateNodesPercentage validates that
+// minCandidateNodesPercentage is within the allowed range.
+func validateMinCandidateNodesPercentage(minCandidateNodesPercentage int32) error {
+	if minCandidateNodesPercentage < 0 || minCandidateNodesPercentage > 100 {
+		return fmt.Errorf("minCandidateNodesPercentage is not in the range [0, 100]")
+	}
+	return nil
+}
+
+// validateMinCandidateNodesAbsolute validates that minCandidateNodesAbsolute
+// is within the allowed range.
+func validateMinCandidateNodesAbsolute(minCandidateNodesAbsolute int32) error {
+	if minCandidateNodesAbsolute < 0 {
+		return fmt.Errorf("minCandidateNodesAbsolute is not in the range [0, inf)")
+	}
+	return nil
+}
+
 // ValidateInterPodAffinityArgs validates that InterPodAffinityArgs are correct.
 func ValidateInterPodAffinityArgs(args config.InterPodAffinityArgs) error {
 	return ValidateHardPodAffinityWeight(field.NewPath("hardPodAffinityWeight"), args.HardPodAffinityWeight)

pkg/scheduler/apis/config/validation/validation_pluginargs_test.go

@@ -24,6 +24,55 @@ import (
 	"k8s.io/kubernetes/pkg/scheduler/apis/config"
 )
 
+func TestValidateDefaultPreemptionArgs(t *testing.T) {
+	cases := map[string]struct {
+		args    config.DefaultPreemptionArgs
+		wantErr string
+	}{
+		"valid args (default)": {
+			args: config.DefaultPreemptionArgs{
+				MinCandidateNodesPercentage: 10,
+				MinCandidateNodesAbsolute:   100,
+			},
+		},
+		"negative minCandidateNodesPercentage": {
+			args: config.DefaultPreemptionArgs{
+				MinCandidateNodesPercentage: -1,
+				MinCandidateNodesAbsolute:   100,
+			},
+			wantErr: "minCandidateNodesPercentage is not in the range [0, 100]",
+		},
+		"minCandidateNodesPercentage over 100": {
+			args: config.DefaultPreemptionArgs{
+				MinCandidateNodesPercentage: 900,
+				MinCandidateNodesAbsolute:   100,
+			},
+			wantErr: "minCandidateNodesPercentage is not in the range [0, 100]",
+		},
+		"negative minCandidateNodesAbsolute": {
+			args: config.DefaultPreemptionArgs{
+				MinCandidateNodesPercentage: 20,
+				MinCandidateNodesAbsolute:   -1,
+			},
+			wantErr: "minCandidateNodesAbsolute is not in the range [0, inf)",
+		},
+		"all zero": {
+			args: config.DefaultPreemptionArgs{
+				MinCandidateNodesPercentage: 0,
+				MinCandidateNodesAbsolute:   0,
+			},
+			wantErr: "both minCandidateNodesPercentage and minCandidateNodesAbsolute cannot be zero",
+		},
+	}
+
+	for name, tc := range cases {
+		t.Run(name, func(t *testing.T) {
+			err := ValidateDefaultPreemptionArgs(tc.args)
+			assertErr(t, tc.wantErr, err)
+		})
+	}
+}
+
 func TestValidateInterPodAffinityArgs(t *testing.T) {
 	cases := map[string]struct {
 		args    config.InterPodAffinityArgs