perf: limit initSchema calls from openapi.IsNamespaceScoped

kyaml/openapi/openapi.go

@@ -387,18 +387,40 @@ func GetSchema(s string, schema *spec.Schema) (*ResourceSchema, error) {
 // be true if the resource is namespace-scoped, and false if the type is
 // cluster-scoped.
 func IsNamespaceScoped(typeMeta yaml.TypeMeta) (bool, bool) {
-	if res, f := precomputedIsNamespaceScoped[typeMeta]; f {
-		return res, true
+	if isNamespaceScoped, found := precomputedIsNamespaceScoped[typeMeta]; found {
+		return isNamespaceScoped, found
+	}
+	if isInitSchemaNeededForNamespaceScopeCheck() {
+		initSchema()
 	}
-	return isNamespaceScopedFromSchema(typeMeta)
-}
-
-func isNamespaceScopedFromSchema(typeMeta yaml.TypeMeta) (bool, bool) {
-	initSchema()
 	isNamespaceScoped, found := globalSchema.namespaceabilityByResourceType[typeMeta]
 	return isNamespaceScoped, found
 }
 
+// isInitSchemaNeededForNamespaceScopeCheck returns true if initSchema is needed
+// to ensure globalSchema.namespaceabilityByResourceType is fully populated for
+// cases where a custom or non-default built-in schema is in use.
+func isInitSchemaNeededForNamespaceScopeCheck() bool {
+	schemaLock.Lock()
+	defer schemaLock.Unlock()
+
+	if globalSchema.schemaInit {
+		return false // globalSchema already is initialized.
+	}
+	if customSchema != nil {
+		return true // initSchema is needed.
+	}
+	if kubernetesOpenAPIVersion == "" || kubernetesOpenAPIVersion == kubernetesOpenAPIDefaultVersion {
+		// The default built-in schema is in use. Since
+		// precomputedIsNamespaceScoped aligns with the default built-in schema
+		// (verified by TestIsNamespaceScopedPrecompute), there is no need to
+		// call initSchema.
+		return false
+	}
+	// A non-default built-in schema is in use. initSchema is needed.
+	return true
+}
+
 // IsCertainlyClusterScoped returns true for Node, Namespace, etc. and
 // false for Pod, Deployment, etc. and kinds that aren't recognized in the
 // openapi data. See:

kyaml/openapi/openapi_benchmark_test.go

@@ -5,6 +5,7 @@ package openapi
 
 import (
 	"path/filepath"
+	"sigs.k8s.io/kustomize/kyaml/yaml"
 	"strings"
 	"testing"
 
@@ -31,3 +32,19 @@ func BenchmarkProtoUnmarshal(t *testing.B) {
 		}
 	}
 }
+
+func BenchmarkPrecomputedIsNamespaceScoped(b *testing.B) {
+	testcases := map[string]yaml.TypeMeta{
+		"namespace scoped": {APIVersion: "apps/v1", Kind: "ControllerRevision"},
+		"cluster scoped":   {APIVersion: "rbac.authorization.k8s.io/v1", Kind: "ClusterRole"},
+		"unknown resource": {APIVersion: "custom.io/v1", Kind: "Custom"},
+	}
+	for name, testcase := range testcases {
+		b.Run(name, func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				ResetOpenAPI()
+				_, _ = IsNamespaceScoped(testcase)
+			}
+		})
+	}
+}