From b8c37cfd24a03400e756c02006b5907efd976544 Mon Sep 17 00:00:00 2001
From: Andreas Gehrke <ag@agehrke.com>
Date: Sun, 16 Nov 2025 21:08:52 +0100
Subject: [PATCH 1/2] Avoid unneeded resizes of List when adding from a
 Batch<LogRecord>

---
 .../src/Internals/LogsHelper.cs                                 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/LogsHelper.cs b/sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/LogsHelper.cs
index eb4e2b23e719..71d2e851b588 100644
--- a/sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/LogsHelper.cs
+++ b/sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/LogsHelper.cs
@@ -52,7 +52,7 @@ internal static class LogsHelper
 
         internal static (List<TelemetryItem> TelemetryItems, TelemetrySchemaTypeCounter TelemetrySchemaTypeCounter) OtelToAzureMonitorLogs(Batch<LogRecord> batchLogRecord, AzureMonitorResource? resource, string instrumentationKey)
         {
-            List<TelemetryItem> telemetryItems = new List<TelemetryItem>();
+            List<TelemetryItem> telemetryItems = new List<TelemetryItem>(capacity: (int)batchLogRecord.Count);
             var telemetrySchemaTypeCounter = new TelemetrySchemaTypeCounter();
             TelemetryItem telemetryItem;
 

From 283109b741016341e623d56b4fb479a2f263f6e5 Mon Sep 17 00:00:00 2001
From: Andreas Gehrke <ag@agehrke.com>
Date: Sun, 16 Nov 2025 21:10:01 +0100
Subject: [PATCH 2/2] Remove uneeded mem copy in NDJsonWriter

---
 .../src/Internals/NDJsonWriter.cs             | 25 ++++++++++---------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/NDJsonWriter.cs b/sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/NDJsonWriter.cs
index a70c3f4c4ae1..4740e6168255 100644
--- a/sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/NDJsonWriter.cs
+++ b/sdk/monitor/Azure.Monitor.OpenTelemetry.Exporter/src/Internals/NDJsonWriter.cs
@@ -2,7 +2,7 @@
 // Licensed under the MIT License.
 
 using System;
-using System.IO;
+using System.Buffers;
 using System.Text.Json;
 
 namespace Azure.Monitor.OpenTelemetry.Exporter.Internals
@@ -11,39 +11,40 @@ internal sealed class NDJsonWriter : IDisposable
     {
         private static readonly byte[] s_separator = { (byte)'\n' };
 
+        private readonly Azure.Core.ArrayBufferWriter<byte> _buffer = new();
+
         public NDJsonWriter()
         {
-            Stream = new MemoryStream();
-            JsonWriter = new Utf8JsonWriter(Stream, new JsonWriterOptions() { SkipValidation = true });
+            JsonWriter = new Utf8JsonWriter(_buffer, new JsonWriterOptions() { SkipValidation = true });
         }
 
-        private MemoryStream Stream { get; }
         public Utf8JsonWriter JsonWriter { get; }
 
         public void WriteNewLine()
         {
             JsonWriter.Flush();
             JsonWriter.Reset();
-            Stream.Write(s_separator, 0, 1);
+            _buffer.Write(s_separator);
         }
 
-        public Memory<byte> ToBytes()
+        public ReadOnlyMemory<byte> ToBytes()
         {
             JsonWriter.Flush();
-            return Stream.ToArray();
+            return _buffer.WrittenMemory;
         }
 
         public override string ToString()
         {
-            Stream.Position = 0;
-            using var streamReader = new StreamReader(Stream);
-            return streamReader.ReadToEnd();
+#if NET8_0_OR_GREATER
+            return System.Text.Encoding.UTF8.GetString(_buffer.WrittenSpan);
+#else
+            return System.Text.Encoding.UTF8.GetString(_buffer.WrittenSpan.ToArray());
+#endif
         }
 
         public void Dispose()
         {
-            Stream?.Dispose();
-            JsonWriter?.Dispose();
+            JsonWriter.Dispose();
         }
     }
 }