Add per pipe segment pool (#1800)

src/System.IO.Pipelines.Testing/BufferUtilities.cs

@@ -35,7 +35,8 @@ namespace System.IO.Pipelines.Testing
 
                 // Create a segment that has offset relative to the OwnedMemory and OwnedMemory itself has offset relative to array
                 var ownedBuffer = new OwnedArray<byte>(chars);
-                var current = new BufferSegment(ownedBuffer, length, length * 2);
+                var current = new BufferSegment();
+                current.SetMemory(ownedBuffer, length, length * 2);
                 if (first == null)
                 {
                     first = current;

src/System.IO.Pipelines/System/IO/Pipelines/BufferSegment.cs

@@ -7,8 +7,7 @@ using System.Text;
 
 namespace System.IO.Pipelines
 {
-    // TODO: Pool segments
-    internal class BufferSegment : IDisposable
+    internal class BufferSegment
     {
         /// <summary>
         /// The Start represents the offset into Array where the range of "active" bytes begins. At the point when the block is leased
@@ -44,21 +43,27 @@ namespace System.IO.Pipelines
 
         private Memory<byte> _buffer;
 
-        public BufferSegment(OwnedMemory<byte> buffer)
+        public void SetMemory(OwnedMemory<byte> buffer)
         {
-            _owned = buffer;
-            Start = 0;
-            End = 0;
-
-            _owned.Retain();
-            _buffer = _owned.Memory;
+            SetMemory(buffer, 0, 0);
         }
 
-        public BufferSegment(OwnedMemory<byte> buffer, int start, int end): this(buffer)
+        public void SetMemory(OwnedMemory<byte> buffer, int start, int end, bool readOnly = false)
         {
+            _owned = buffer;
+            _owned.Retain();
+            _buffer = _owned.Memory;
+
+            RunningLength = 0;
             Start = start;
             End = end;
-            ReadOnly = true;
+            Next = null;
+        }
+
+        public void ResetMemory()
+        {
+            _owned.Release();
+            _owned = null;
         }
 
         public Memory<byte> Buffer => _buffer;
@@ -79,17 +84,17 @@ namespace System.IO.Pipelines
         /// </summary>
         public int WritableBytes => _buffer.Length - End;
 
-        public void Dispose()
-        {
-            _owned.Release();
-        }
-
         /// <summary>
         /// ToString overridden for debugger convenience. This displays the "active" byte information in this block as ASCII characters.
         /// </summary>
         /// <returns></returns>
         public override string ToString()
         {
+            if (_owned == null)
+            {
+                return "<NO MEMORY ATTACHED>";
+            }
+
             var builder = new StringBuilder();
             var data = _owned.Memory.Slice(Start, ReadableBytes).Span;
 
@@ -107,24 +112,29 @@ namespace System.IO.Pipelines
 
             if (beginOrig == endOrig)
             {
-                lastSegment = new BufferSegment(beginOrig._owned, beginBuffer.Index, endBuffer.Index);
+                lastSegment = new BufferSegment();
+                lastSegment.SetMemory(beginOrig._owned, beginBuffer.Index, endBuffer.Index);
                 return lastSegment;
             }
 
-            var beginClone = new BufferSegment(beginOrig._owned, beginBuffer.Index, beginOrig.End);
+            var beginClone = new BufferSegment();
+            beginClone.SetMemory(beginOrig._owned, beginBuffer.Index, beginOrig.End);
             var endClone = beginClone;
 
             beginOrig = beginOrig.Next;
 
             while (beginOrig != endOrig)
             {
-                endClone.SetNext(new BufferSegment(beginOrig._owned, beginOrig.Start, beginOrig.End));
+                var next = new BufferSegment();
+                next.SetMemory(beginOrig._owned, beginOrig.Start, beginOrig.End);
+                endClone.SetNext(next);
 
                 endClone = endClone.Next;
                 beginOrig = beginOrig.Next;
             }
 
-            lastSegment = new BufferSegment(endOrig._owned, endOrig.Start, endBuffer.Index);
+            lastSegment = new BufferSegment();
+            lastSegment.SetMemory(endOrig._owned, endOrig.Start, endBuffer.Index);
             endClone.SetNext(lastSegment);
 
             return beginClone;
@@ -138,6 +148,7 @@ namespace System.IO.Pipelines
             Next = segment;
 
             segment = this;
+
             while (segment.Next != null)
             {
                 segment.Next.RunningLength = segment.RunningLength + segment.ReadableBytes;

src/System.IO.Pipelines/System/IO/Pipelines/Pipe.cs

@@ -14,6 +14,8 @@ namespace System.IO.Pipelines
     /// </summary>
     public class Pipe : IPipe, IPipeReader, IPipeWriter, IReadableBufferAwaiter, IWritableBufferAwaiter
     {
+        private const int SegmentPoolSize = 16;
+
         private static readonly Action<object> _signalReaderAwaitable = state => ((Pipe)state).ReaderCancellationRequested();
         private static readonly Action<object> _signalWriterAwaitable = state => ((Pipe)state).WriterCancellationRequested();
         private static readonly Action<object> _invokeCompletionCallbacks = state => ((PipeCompletionCallbacks)state).Execute();
@@ -35,12 +37,15 @@ namespace System.IO.Pipelines
         private long _length;
         private long _currentWriteLength;
 
+        private int _pooledSegmentCount;
+
         private PipeAwaitable _readerAwaitable;
         private PipeAwaitable _writerAwaitable;
 
         private PipeCompletion _writerCompletion;
         private PipeCompletion _readerCompletion;
 
+        private BufferSegment[] _bufferSegmentPool;
         // The read head which is the extent of the IPipelineReader's consumed bytes
         private BufferSegment _readHead;
 
@@ -85,6 +90,8 @@ namespace System.IO.Pipelines
                 throw new ArgumentException(nameof(options.MaximumSizeHigh) + " should be greater or equal to " + nameof(options.MaximumSizeLow), nameof(options.MaximumSizeHigh));
             }
 
+            _bufferSegmentPool = new BufferSegment[SegmentPoolSize];
+
             _pool = options.BufferPool;
             _maximumSizeHigh = options.MaximumSizeHigh;
             _maximumSizeLow = options.MaximumSizeLow;
@@ -166,8 +173,13 @@ namespace System.IO.Pipelines
             // If inadequate bytes left or if the segment is readonly
             if (bytesLeftInBuffer == 0 || bytesLeftInBuffer < count || segment.ReadOnly)
             {
-                var nextBuffer = _pool.Rent(count);
-                var nextSegment = new BufferSegment(nextBuffer);
+                BufferSegment nextSegment;
+                lock (_sync)
+                {
+                    nextSegment = CreateSegmentUnsynchronized();
+                }
+
+                nextSegment.SetMemory(_pool.Rent(count));
 
                 segment.SetNext(nextSegment);
 
@@ -194,7 +206,8 @@ namespace System.IO.Pipelines
             if (segment == null)
             {
                 // No free tail space, allocate a new segment
-                segment = new BufferSegment(_pool.Rent(count));
+                segment = CreateSegmentUnsynchronized();
+                segment.SetMemory(_pool.Rent(count));
             }
 
             if (_commitHead == null)
@@ -215,6 +228,26 @@ namespace System.IO.Pipelines
             return segment;
         }
 
+        private BufferSegment CreateSegmentUnsynchronized()
+        {
+            if (_pooledSegmentCount > 0)
+            {
+                _pooledSegmentCount--;
+                return _bufferSegmentPool[_pooledSegmentCount];
+            }
+
+            return new BufferSegment();
+        }
+
+        private void ReturnSegmentUnsynchronized(BufferSegment segment)
+        {
+            if (_pooledSegmentCount < _bufferSegmentPool.Length)
+            {
+                _bufferSegmentPool[_pooledSegmentCount] = segment;
+                _pooledSegmentCount++;
+            }
+        }
+
         internal void Append(ReadableBuffer buffer)
         {
             if (buffer.IsEmpty)
@@ -409,7 +442,7 @@ namespace System.IO.Pipelines
 
             if (readerCompleted)
             {
-                Dispose();
+                CompletePipe();
             }
         }
 
@@ -485,12 +518,13 @@ namespace System.IO.Pipelines
                 }
 
                 _readingState.End(ExceptionResource.NoReadToComplete);
-            }
 
-            while (returnStart != null && returnStart != returnEnd)
-            {
-                returnStart.Dispose();
-                returnStart = returnStart.Next;
+                while (returnStart != null && returnStart != returnEnd)
+                {
+                    returnStart.ResetMemory();
+                    ReturnSegmentUnsynchronized(returnStart);
+                    returnStart = returnStart.Next;
+                }
             }
 
             TrySchedule(_writerScheduler, continuation);
@@ -527,7 +561,7 @@ namespace System.IO.Pipelines
 
             if (writerCompleted)
             {
-                Dispose();
+                CompletePipe();
             }
         }
 
@@ -650,7 +684,7 @@ namespace System.IO.Pipelines
             }
         }
 
-        private void Dispose()
+        private void CompletePipe()
         {
             lock (_sync)
             {
@@ -667,7 +701,7 @@ namespace System.IO.Pipelines
                     var returnSegment = segment;
                     segment = segment.Next;
 
-                    returnSegment.Dispose();
+                    returnSegment.ResetMemory();
                 }
 
                 _readHead = null;

src/System.IO.Pipelines/System/IO/Pipelines/PreservedBuffer.cs

@@ -33,7 +33,7 @@ namespace System.IO.Pipelines
             {
                 var returnSegment = returnStart;
                 returnStart = returnStart?.Next;
-                returnSegment?.Dispose();
+                returnSegment?.ResetMemory();
 
                 if (returnSegment == returnEnd)
                 {

src/System.IO.Pipelines/System/IO/Pipelines/ReadableBuffer.cs

@@ -260,9 +260,9 @@ namespace System.IO.Pipelines
 
         private static ReadableBuffer CreateInternal(OwnedMemory<byte> data, int offset, int length)
         {
-            var segment = new BufferSegment(data);
-            segment.Start = offset;
-            segment.End = offset + length;
+            var segment = new BufferSegment();
+            segment.SetMemory(data, offset, offset + length);
+
             return new ReadableBuffer(new ReadCursor(segment, offset), new ReadCursor(segment, offset + length));
         }
 

tests/System.IO.Pipelines.Performance.Tests/PipeThroughput.cs

@@ -77,6 +77,29 @@ namespace System.IO.Pipelines.Performance.Tests
             }
         }
 
+
+        [Benchmark(OperationsPerInvoke = InnerLoopCount)]
+        public void LongWriteInline()
+        {
+            for (int i = 0; i < InnerLoopCount; i++)
+            {
+                for (int j = 0; j < 15; j++)
+                {
+                    var writableBuffer = _pipe.Writer.Alloc(WriteLength);
+                    writableBuffer.Advance(WriteLength);
+                    writableBuffer.Commit();
+                    if (j == 14)
+                    {
+                        writableBuffer.FlushAsync().GetResult();
+                    }
+                }
+
+                var result = _pipe.Reader.ReadAsync().GetResult();
+                var buffer = result.Buffer;
+                _pipe.Reader.Advance(buffer.End, buffer.End);
+            }
+        }
+
         [Benchmark(OperationsPerInvoke = InnerLoopCount)]
         public void WritePlaintextResponse()
         {

tests/System.IO.Pipelines.Performance.Tests/System.IO.Pipelines.Performance.Tests.csproj

@@ -26,7 +26,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="BenchmarkDotNet" Version="0.10.5" />
+    <PackageReference Include="BenchmarkDotNet" Version="0.10.9" />
   </ItemGroup>
 
 </Project>

tests/System.IO.Pipelines.Performance.Tests/configs/CoreConfig.cs

@@ -3,9 +3,11 @@
 
 using BenchmarkDotNet.Columns;
 using BenchmarkDotNet.Configs;
+using BenchmarkDotNet.Diagnosers;
 using BenchmarkDotNet.Engines;
 using BenchmarkDotNet.Jobs;
 using BenchmarkDotNet.Validators;
+using BenchmarkDotNet.Toolchains.CsProj;
 
 namespace System.IO.Pipelines.Performance.Tests
 {
@@ -15,9 +17,11 @@ namespace System.IO.Pipelines.Performance.Tests
         {
             Add(JitOptimizationsValidator.FailOnError);
             Add(StatisticColumn.OperationsPerSecond);
+            Add(MemoryDiagnoser.Default);
 
             Add(Job.Default
                 .With(BenchmarkDotNet.Environments.Runtime.Core)
+                .With(CsProjCoreToolchain.NetCoreApp20)
                 .WithRemoveOutliers(false)
                 .With(new GcMode() { Server = true })
                 .With(RunStrategy.Throughput)