From 82da1ecbc8effc3d376e9047493538b6b015e379 Mon Sep 17 00:00:00 2001
From: Joseph Doherty <dohejw01@gmail.com>
Date: Wed, 11 Nov 2026 19:30:07 -0500
Subject: [PATCH] perf(scripting): #789 give the Windows worker pipe a 1 MiB
 buffer quota each way

With a zero quota an overlapped write stays pending until the peer has read the
bytes, so the new blocking writer waited out a peer wake-up per frame (windev
closed loop 54k -> 26k evals/s). With a quota the write completes once buffered.

Claude-Session: https://claude.ai/code/session_01GT67AD99zQQqpLCVm3p7xk
---
 .../WorkerPipeSecurity.cs                             | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/Core/ZB.MOM.WW.OtOpcUa.Core.Scripting.OutOfProcess/WorkerPipeSecurity.cs b/src/Core/ZB.MOM.WW.OtOpcUa.Core.Scripting.OutOfProcess/WorkerPipeSecurity.cs
index 5c491e7ab..07cc6c394 100644
--- a/src/Core/ZB.MOM.WW.OtOpcUa.Core.Scripting.OutOfProcess/WorkerPipeSecurity.cs
+++ b/src/Core/ZB.MOM.WW.OtOpcUa.Core.Scripting.OutOfProcess/WorkerPipeSecurity.cs
@@ -50,11 +50,20 @@ internal static class WorkerPipeSecurity
         return security;
     }
 
+    /// <summary>
+    ///     The pipe's buffer quota in each direction (lmxopcua#789). With a quota of 0 an overlapped write stays pending
+    ///     until the peer has READ the bytes, so a blocking writer (<see cref="ZB.MOM.WW.OtOpcUa.Core.Scripting.Protocol.WindowsBlockingPipeStream"/>)
+    ///     would wait out a full peer wake-up per frame — measured on windev as half the closed-loop throughput. With a
+    ///     quota a write completes as soon as the bytes are buffered; a peer that stops reading still fills it and blocks
+    ///     the writer, which the heartbeat monitor ends.
+    /// </summary>
+    internal const int BufferBytes = 1024 * 1024;
+
     /// <summary>Creates the single-instance server end of a worker pipe with <paramref name="security"/>.</summary>
     /// <param name="pipeName">The random pipe name.</param>
     /// <param name="security">The ACL (<see cref="ForCurrentHost"/>).</param>
     /// <returns>The server stream.</returns>
     public static NamedPipeServerStream CreateServer(string pipeName, PipeSecurity security)
         => NamedPipeServerStreamAcl.Create(pipeName, PipeDirection.InOut, maxNumberOfServerInstances: 1,
-            PipeTransmissionMode.Byte, PipeOptions.Asynchronous, inBufferSize: 0, outBufferSize: 0, security);
+            PipeTransmissionMode.Byte, PipeOptions.Asynchronous, inBufferSize: BufferBytes, outBufferSize: BufferBytes, security);
 }