From 4ebc411cfc0a1306742748c452fac679379d1923 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 17 Mar 2026 08:57:16 +0000
Subject: [PATCH 1/3] Initial plan


From dcff0e9069b9871e5e90fcc27780a3c639872fbf Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 17 Mar 2026 09:06:37 +0000
Subject: [PATCH 2/3] Add three output-reading benchmarks to Perf_Process

Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>
---
 .../System.Diagnostics/Perf_Process.cs        | 44 +++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/src/benchmarks/micro/libraries/System.Diagnostics/Perf_Process.cs b/src/benchmarks/micro/libraries/System.Diagnostics/Perf_Process.cs
index 40bd73d7c0f..ec98837f561 100644
--- a/src/benchmarks/micro/libraries/System.Diagnostics/Perf_Process.cs
+++ b/src/benchmarks/micro/libraries/System.Diagnostics/Perf_Process.cs
@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Runtime.InteropServices;
+using System.Threading.Tasks;
 using BenchmarkDotNet.Attributes;
 using MicroBenchmarks;
 
@@ -80,5 +82,47 @@ public void StartAndWaitForExit()
                 p.WaitForExit();
             }
         }
+
+        private static readonly ProcessStartInfo s_outputStartInfo = new ProcessStartInfo()
+        {
+            FileName = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "cmd" : "sh",
+            Arguments = RuntimeInformation.IsOSPlatform(OSPlatform.Windows)
+                ? "/c for /L %i in (1,1,1000) do @echo Line %i"
+                : "-c \"for i in $(seq 1 1000); do echo Line $i; done\"",
+            RedirectStandardOutput = true,
+            UseShellExecute = false
+        };
+
+        private static readonly DataReceivedEventHandler s_ignoreOutputLine = (sender, e) => { };
+
+        [Benchmark]
+        public void ReadOutputLineByLine()
+        {
+            using var process = new Process();
+            process.StartInfo = s_outputStartInfo;
+            process.OutputDataReceived += s_ignoreOutputLine;
+            process.Start();
+            process.BeginOutputReadLine();
+            process.WaitForExit();
+            process.OutputDataReceived -= s_ignoreOutputLine;
+        }
+
+#if NET
+        [Benchmark]
+        public async Task ReadOutputToEndAsync()
+        {
+            using Process process = Process.Start(s_outputStartInfo);
+            await process.StandardOutput.ReadToEndAsync();
+            process.WaitForExit();
+        }
+#endif
+
+        [Benchmark]
+        public void ReadOutputToEnd()
+        {
+            using Process process = Process.Start(s_outputStartInfo);
+            process.StandardOutput.ReadToEnd();
+            process.WaitForExit();
+        }
     }
 }

From d3c0529b1fd501f4364f623638a29382b7b58b1a Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 17 Mar 2026 09:17:19 +0000
Subject: [PATCH 3/3] Address review feedback: static lambda, discard results,
 WaitForExitAsync

Co-authored-by: adamsitnik <6011991+adamsitnik@users.noreply.github.com>
---
 .../micro/libraries/System.Diagnostics/Perf_Process.cs    | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/benchmarks/micro/libraries/System.Diagnostics/Perf_Process.cs b/src/benchmarks/micro/libraries/System.Diagnostics/Perf_Process.cs
index ec98837f561..6f51abb8e53 100644
--- a/src/benchmarks/micro/libraries/System.Diagnostics/Perf_Process.cs
+++ b/src/benchmarks/micro/libraries/System.Diagnostics/Perf_Process.cs
@@ -93,7 +93,7 @@ public void StartAndWaitForExit()
             UseShellExecute = false
         };
 
-        private static readonly DataReceivedEventHandler s_ignoreOutputLine = (sender, e) => { };
+        private static readonly DataReceivedEventHandler s_ignoreOutputLine = static (sender, e) => { };
 
         [Benchmark]
         public void ReadOutputLineByLine()
@@ -112,8 +112,8 @@ public void ReadOutputLineByLine()
         public async Task ReadOutputToEndAsync()
         {
             using Process process = Process.Start(s_outputStartInfo);
-            await process.StandardOutput.ReadToEndAsync();
-            process.WaitForExit();
+            _ = await process.StandardOutput.ReadToEndAsync();
+            await process.WaitForExitAsync();
         }
 #endif
 
@@ -121,7 +121,7 @@ public async Task ReadOutputToEndAsync()
         public void ReadOutputToEnd()
         {
             using Process process = Process.Start(s_outputStartInfo);
-            process.StandardOutput.ReadToEnd();
+            _ = process.StandardOutput.ReadToEnd();
             process.WaitForExit();
         }
     }