diff --git a/src/Build/BackEnd/Components/Communications/NodeProviderOutOfProcBase.cs b/src/Build/BackEnd/Components/Communications/NodeProviderOutOfProcBase.cs
index e65f614e08e..501d9ddbbc8 100644
--- a/src/Build/BackEnd/Components/Communications/NodeProviderOutOfProcBase.cs
+++ b/src/Build/BackEnd/Components/Communications/NodeProviderOutOfProcBase.cs
@@ -3,14 +3,13 @@
using System;
using System.Collections.Generic;
+using System.Collections.Concurrent;
using System.Globalization;
using System.IO;
using System.IO.Pipes;
using System.Diagnostics;
using System.Threading;
-#if !FEATURE_APM
using System.Threading.Tasks;
-#endif
using System.Runtime.InteropServices;
#if FEATURE_PIPE_SECURITY
using System.Security.Principal;
@@ -609,8 +608,27 @@ internal class NodeContext
///
/// A buffer typically big enough to handle a packet body.
+ /// We use this as a convenient way to manage and cache a byte[] that's resized
+ /// automatically to fit our payload.
+ ///
+ private MemoryStream _readBufferMemoryStream;
+
+ ///
+ /// A reusable buffer for writing packets.
+ ///
+ private MemoryStream _writeBufferMemoryStream;
+
+ ///
+ /// A queue used for enqueuing packets to write to the stream asynchronously.
///
- private byte[] _smallReadBuffer;
+ private BlockingCollection _packetWriteQueue = new BlockingCollection();
+
+ ///
+ /// A task representing the last packet write, so we can chain packet writes one after another.
+ /// We want to queue up writing packets on a separate thread asynchronously, but serially.
+ /// Each task drains the
+ ///
+ private Task _packetWriteDrainTask = Task.CompletedTask;
///
/// Event indicating the node has terminated.
@@ -640,7 +658,9 @@ internal class NodeContext
_serverToClientStream = nodePipe;
_packetFactory = factory;
_headerByte = new byte[5]; // 1 for the packet type, 4 for the body length
- _smallReadBuffer = new byte[1000]; // 1000 was just an average seen on one profile run.
+
+ _readBufferMemoryStream = new MemoryStream();
+ _writeBufferMemoryStream = new MemoryStream();
_nodeTerminated = new ManualResetEvent(false);
_terminateDelegate = terminateDelegate;
_sharedReadBuffer = InterningBinaryReader.CreateSharedBuffer();
@@ -685,16 +705,8 @@ public async Task RunPacketReadLoopAsync()
NodePacketType packetType = (NodePacketType)_headerByte[0];
int packetLength = BitConverter.ToInt32(_headerByte, 1);
- byte[] packetData;
- if (packetLength < _smallReadBuffer.Length)
- {
- packetData = _smallReadBuffer;
- }
- else
- {
- // Preallocated buffer is not large enough to hold the body. Allocate now, but don't hold it forever.
- packetData = new byte[packetLength];
- }
+ _readBufferMemoryStream.SetLength(packetLength);
+ byte[] packetData = _readBufferMemoryStream.GetBuffer();
try
{
@@ -728,54 +740,81 @@ public async Task RunPacketReadLoopAsync()
#endif
///
- /// Sends the specified packet to this node.
+ /// Sends the specified packet to this node asynchronously.
+ /// The method enqueues a task to write the packet and returns
+ /// immediately. This is because SendData() is on a hot path
+ /// under the primary lock (BuildManager's _syncLock)
+ /// and we want to minimize our time there.
///
/// The packet to send.
public void SendData(INodePacket packet)
{
- MemoryStream writeStream = new MemoryStream();
+ _packetWriteQueue.Add(packet);
+ DrainPacketQueue();
+ }
+
+ ///
+ /// Schedule a task to drain the packet write queue. We could have had a
+ /// dedicated thread that would pump the queue constantly, but
+ /// we don't want to allocate a dedicated thread per node (1MB stack)
+ ///
+ /// Usually there'll be a single packet in the queue, but sometimes
+ /// a burst of SendData comes in, with 10-20 packets scheduled. In this case
+ /// the first scheduled task will drain all of them, and subsequent tasks
+ /// will run on an empty queue. I tried to write logic that avoids queueing
+ /// a new task if the queue is already being drained, but it didn't show any
+ /// improvement and made things more complicated.
+ private void DrainPacketQueue()
+ {
+ // this lock is only necessary to protect a write to _packetWriteDrainTask field
+ lock (_packetWriteQueue)
+ {
+ // average latency between the moment this runs and when the delegate starts
+ // running is about 100-200 microseconds (unless there's thread pool saturation)
+ _packetWriteDrainTask = _packetWriteDrainTask.ContinueWith(_ =>
+ {
+ while (_packetWriteQueue.TryTake(out var packet))
+ {
+ SendDataCore(packet);
+ }
+ }, TaskScheduler.Default);
+ }
+ }
+
+ ///
+ /// Actually writes and sends the packet. This can't be called in parallel
+ /// because it reuses the _writeBufferMemoryStream, and this is why we use
+ /// the _packetWriteDrainTask to serially chain invocations one after another.
+ ///
+ /// The packet to send.
+ private void SendDataCore(INodePacket packet)
+ {
+ MemoryStream writeStream = _writeBufferMemoryStream;
+
+ // clear the buffer but keep the underlying capacity to avoid reallocations
+ writeStream.SetLength(0);
+
ITranslator writeTranslator = BinaryTranslator.GetWriteTranslator(writeStream);
try
{
writeStream.WriteByte((byte)packet.Type);
// Pad for the packet length
- writeStream.Write(BitConverter.GetBytes((int)0), 0, 4);
+ WriteInt32(writeStream, 0);
packet.Translate(writeTranslator);
+ int writeStreamLength = (int)writeStream.Position;
+
// Now plug in the real packet length
writeStream.Position = 1;
- writeStream.Write(BitConverter.GetBytes((int)writeStream.Length - 5), 0, 4);
+ WriteInt32(writeStream, writeStreamLength - 5);
byte[] writeStreamBuffer = writeStream.GetBuffer();
- for (int i = 0; i < writeStream.Length; i += MaxPacketWriteSize)
+ for (int i = 0; i < writeStreamLength; i += MaxPacketWriteSize)
{
- int lengthToWrite = Math.Min((int)writeStream.Length - i, MaxPacketWriteSize);
- if ((int)writeStream.Length - i <= MaxPacketWriteSize)
- {
- // We are done, write the last bit asynchronously. This is actually the general case for
- // most packets in the build, and the asynchronous behavior here is desirable.
-#if FEATURE_APM
- _serverToClientStream.BeginWrite(writeStreamBuffer, i, lengthToWrite, PacketWriteComplete, null);
-#else
- _serverToClientStream.WriteAsync(writeStreamBuffer, i, lengthToWrite);
-#endif
- return;
- }
- else
- {
- // If this packet is longer that we can write in one go, then we need to break it up. We can't
- // return out of this function and let the rest of the system continue because another operation
- // might want to send data immediately afterward, and that could result in overlapping writes
- // to the pipe on different threads.
-#if FEATURE_APM
- IAsyncResult result = _serverToClientStream.BeginWrite(writeStream.GetBuffer(), i, lengthToWrite, null, null);
- _serverToClientStream.EndWrite(result);
-#else
- _serverToClientStream.Write(writeStreamBuffer, i, lengthToWrite);
-#endif
- }
+ int lengthToWrite = Math.Min(writeStreamLength - i, MaxPacketWriteSize);
+ _serverToClientStream.Write(writeStreamBuffer, i, lengthToWrite);
}
}
catch (IOException e)
@@ -789,6 +828,17 @@ public void SendData(INodePacket packet)
}
}
+ ///
+ /// Avoid having a BinaryWriter just to write a 4-byte int
+ ///
+ private void WriteInt32(MemoryStream stream, int value)
+ {
+ stream.WriteByte((byte)value);
+ stream.WriteByte((byte)(value >> 8));
+ stream.WriteByte((byte)(value >> 16));
+ stream.WriteByte((byte)(value >> 24));
+ }
+
///
/// Closes the node's context, disconnecting it from the node.
///
@@ -887,16 +937,10 @@ private void HeaderReadComplete(IAsyncResult result)
int packetLength = BitConverter.ToInt32(_headerByte, 1);
MSBuildEventSource.Log.PacketReadSize(packetLength);
- byte[] packetData;
- if (packetLength < _smallReadBuffer.Length)
- {
- packetData = _smallReadBuffer;
- }
- else
- {
- // Preallocated buffer is not large enough to hold the body. Allocate now, but don't hold it forever.
- packetData = new byte[packetLength];
- }
+ // Ensures the buffer is at least this length.
+ // It avoids reallocations if the buffer is already large enough.
+ _readBufferMemoryStream.SetLength(packetLength);
+ byte[] packetData = _readBufferMemoryStream.GetBuffer();
_clientToServerStream.BeginRead(packetData, 0, packetLength, BodyReadComplete, new Tuple(packetData, packetLength));
}
diff --git a/src/Shared/NodeEndpointOutOfProcBase.cs b/src/Shared/NodeEndpointOutOfProcBase.cs
index 7bb77dda88f..c58bc449a1c 100644
--- a/src/Shared/NodeEndpointOutOfProcBase.cs
+++ b/src/Shared/NodeEndpointOutOfProcBase.cs
@@ -99,6 +99,16 @@ internal abstract class NodeEndpointOutOfProcBase : INodeEndpoint
///
private SharedReadBuffer _sharedReadBuffer;
+ ///
+ /// A way to cache a byte array when writing out packets
+ ///
+ private MemoryStream _packetStream;
+
+ ///
+ /// A binary writer to help write into
+ ///
+ private BinaryWriter _binaryWriter;
+
#endregion
#region INodeEndpoint Events
@@ -189,6 +199,9 @@ internal void InternalConstruct(string pipeName)
_asyncDataMonitor = new object();
_sharedReadBuffer = InterningBinaryReader.CreateSharedBuffer();
+ _packetStream = new MemoryStream();
+ _binaryWriter = new BinaryWriter(_packetStream);
+
#if FEATURE_PIPE_SECURITY && FEATURE_NAMED_PIPE_SECURITY_CONSTRUCTOR
if (!NativeMethodsShared.IsMono)
{
@@ -590,22 +603,26 @@ private void PacketPumpProc()
INodePacket packet;
while (localPacketQueue.TryDequeue(out packet))
{
- MemoryStream packetStream = new MemoryStream();
+ var packetStream = _packetStream;
+ packetStream.SetLength(0);
+
ITranslator writeTranslator = BinaryTranslator.GetWriteTranslator(packetStream);
packetStream.WriteByte((byte)packet.Type);
// Pad for packet length
- packetStream.Write(BitConverter.GetBytes((int)0), 0, 4);
+ _binaryWriter.Write(0);
// Reset the position in the write buffer.
packet.Translate(writeTranslator);
+ int packetStreamLength = (int)packetStream.Position;
+
// Now write in the actual packet length
packetStream.Position = 1;
- packetStream.Write(BitConverter.GetBytes((int)packetStream.Length - 5), 0, 4);
+ _binaryWriter.Write(packetStreamLength - 5);
- localWritePipe.Write(packetStream.GetBuffer(), 0, (int)packetStream.Length);
+ localWritePipe.Write(packetStream.GetBuffer(), 0, packetStreamLength);
}
}
catch (Exception e)