ConcurrentStack -> ConcurrentQueue

Less allocs on Enqueue vs Push

Author: benaadams

src/Microsoft.AspNet.Server.Kestrel/Infrastructure/MemoryPool2.cs

@@ -52,7 +52,7 @@ public class MemoryPool2 : IDisposable
         /// Thread-safe collection of blocks which are currently in the pool. A slab will pre-allocate all of the block tracking objects
         /// and add them to this collection. When memory is requested it is taken from here first, and when it is returned it is re-added.
         /// </summary>
-        private readonly ConcurrentStack<MemoryPoolBlock2> _blocks = new ConcurrentStack<MemoryPoolBlock2>();
+        private readonly ConcurrentQueue<MemoryPoolBlock2> _blocks = new ConcurrentQueue<MemoryPoolBlock2>();
 
         /// <summary>
         /// Thread-safe collection of slabs which have been allocated by this pool. As long as a slab is in this collection and slab.IsActive, 
@@ -89,7 +89,7 @@ public MemoryPoolBlock2 Lease(int minimumSize = MaxPooledBlockLength)
             }
 
             MemoryPoolBlock2 block;
-            if (_blocks.TryPop(out block))
+            if (_blocks.TryDequeue(out block))
             {
                 // block successfully taken from the stack - return it
                 return block;
@@ -146,7 +146,7 @@ private MemoryPoolBlock2 AllocateSlab()
         public void Return(MemoryPoolBlock2 block)
         {
             block.Reset();
-            _blocks.Push(block);
+            _blocks.Enqueue(block);
         }
 
         protected virtual void Dispose(bool disposing)
@@ -159,7 +159,7 @@ protected virtual void Dispose(bool disposing)
             }
 
             MemoryPoolBlock2 block;
-            while (_blocks.TryPop(out block))
+            while (_blocks.TryDequeue(out block))
             {
                 // Deactivate finalizers
                 block.Dispose();