Use object pools instead of allocating new lists

src/DotRecast.Core/Buffers/RcObjectPool.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Collections.Generic;
+
+namespace DotRecast.Core.Buffers
+{
+    // This implementation is thread unsafe
+    public class RcObjectPool<T> where T : class
+    {
+        private readonly Queue<T> _items = new Queue<T>();
+        private readonly Func<T> _createFunc;
+
+        public RcObjectPool(Func<T> createFunc)
+        {
+            _createFunc = createFunc;
+        }
+
+        public T Get()
+        {
+            if (_items.TryDequeue(out var result))
+                return result;
+
+            return _createFunc();
+        }
+
+        public void Return(T obj)
+        {
+            _items.Enqueue(obj);
+        }
+    }
+}

src/DotRecast.Detour/DtNodePool.cs

@@ -21,6 +21,7 @@ freely, subject to the following restrictions:
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using DotRecast.Core.Buffers;
 
 namespace DotRecast.Detour
 {
@@ -31,10 +32,12 @@ namespace DotRecast.Detour
         private int m_usedNodesCount;
         private List<DtNode[]> m_buckets;
         private readonly int m_initialBufferCapacityBase;
+        private readonly RcObjectPool<List<DtNode>> m_listPool;
 
         public DtNodePool(int initialBufferCapacityBase = 6) // initial size 64
         {
             m_map = new Dictionary<long, List<DtNode>>();
+            m_listPool = new RcObjectPool<List<DtNode>>(() => new List<DtNode>());
             m_buckets = new List<DtNode[]>();
             m_initialBufferCapacityBase = initialBufferCapacityBase;
         }
@@ -78,6 +81,9 @@ namespace DotRecast.Detour
 
         public void Clear()
         {
+            foreach (var pair in m_map)
+                m_listPool.Return(pair.Value);
+
             m_map.Clear();
             m_usedNodesCount = 0;
         }
@@ -124,7 +130,8 @@ namespace DotRecast.Detour
             }
             else
             {
-                nodes = new List<DtNode>();
+                nodes = m_listPool.Get();
+                nodes.Clear();
                 m_map.Add(id, nodes);
             }