Addded cache for subgraph. Before it was deserializing on every frame.

com.unity.shadergraph/Editor/Data/Nodes/Utility/SubGraphNode.cs

         [SerializeField]
         private string m_SerializedSubGraph = string.Empty;
 
+        [NonSerialized]
+        MaterialSubGraphAsset m_SubGraph;
+
         [Serializable]
         private class SubGraphHelper
         {
                 if (string.IsNullOrEmpty(m_SerializedSubGraph))
                     return null;
 
-                var helper = new SubGraphHelper();
-                EditorJsonUtility.FromJsonOverwrite(m_SerializedSubGraph, helper);
-                return helper.subGraph;
+                if (m_SubGraph == null)
+                {
+                    var helper = new SubGraphHelper();
+                    EditorJsonUtility.FromJsonOverwrite(m_SerializedSubGraph, helper);
+                    m_SubGraph = helper.subGraph;
+                }
+
+                return m_SubGraph;
             }
             set
             {
                 var helper = new SubGraphHelper();
                 helper.subGraph = value;
                 m_SerializedSubGraph = EditorJsonUtility.ToJson(helper, true);
+                m_SubGraph = null;
                 UpdateSlots();
 
                 Dirty(ModificationScope.Topological);
             var validNames = new List<int>();
             if (referencedGraph == null)
             {
-                RemoveSlotsNameNotMatching(validNames);
+                RemoveSlotsNameNotMatching(validNames, true);
                 return;
             }