Fix #91958: use mach_timebase_info to determine process time coefficient on macOS

src/libraries/Common/src/Interop/OSX/Interop.Libraries.cs

@@ -10,6 +10,7 @@ internal static partial class Libraries
         internal const string CFNetworkLibrary = "/System/Library/Frameworks/CFNetwork.framework/CFNetwork";
         internal const string libobjc = "/usr/lib/libobjc.dylib";
         internal const string libproc = "/usr/lib/libproc.dylib";
+        internal const string libSystem = "libSystem.dylib";
         internal const string OpenLdap = "libldap.dylib";
         internal const string SystemConfigurationLibrary = "/System/Library/Frameworks/SystemConfiguration.framework/SystemConfiguration";
         internal const string AppleCryptoNative = "libSystem.Security.Cryptography.Native.Apple";

src/libraries/Common/src/Interop/OSX/Interop.libSystem.cs

@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+
+internal static partial class Interop
+{
+    internal static partial class libSystem
+    {
+        [LibraryImport(Interop.Libraries.libSystem)]
+        public static unsafe partial int mach_timebase_info(mach_timebase_info_data_t* info);
+        public struct mach_timebase_info_data_t
+        {
+            public uint numer;
+            public uint denom;
+        }
+    }
+}

src/libraries/System.Diagnostics.Process/src/System.Diagnostics.Process.csproj

@@ -317,6 +317,8 @@
              Link="Common\Interop\OSX\Interop.libproc.cs" />
     <Compile Include="$(CommonPath)Interop\OSX\Interop.libproc.GetProcessInfoById.cs"
              Link="Common\Interop\OSX\Interop.libproc.GetProcessInfoById.cs" />
+    <Compile Include="$(CommonPath)Interop\OSX\Interop.libSystem.cs"
+             Link="Common\Interop\OSX\Interop.Interop.libSystem.cs" />
     <Compile Include="$(CommonPath)Interop\OSX\Interop.Libraries.cs"
              Link="Common\Interop\OSX\Interop.Libraries.cs" />
   </ItemGroup>

src/libraries/System.Diagnostics.Process/src/System/Diagnostics/Process.OSX.cs

@@ -10,6 +10,7 @@ namespace System.Diagnostics
     public partial class Process
     {
         private const int NanosecondsTo100NanosecondsFactor = 100;
+        private static volatile uint s_timeBase_numer, s_timeBase_denom;
 
         private const int MicrosecondsToSecondsFactor = 1_000_000;
 
@@ -23,7 +24,7 @@ public TimeSpan PrivilegedProcessorTime
             {
                 EnsureState(State.HaveNonExitedId);
                 Interop.libproc.rusage_info_v3 info = Interop.libproc.proc_pid_rusage(_processId);
-                return new TimeSpan(Convert.ToInt64(info.ri_system_time / NanosecondsTo100NanosecondsFactor));
+                return MapTime(info.ri_system_time);
             }
         }
 
@@ -65,7 +66,7 @@ public TimeSpan TotalProcessorTime
             {
                 EnsureState(State.HaveNonExitedId);
                 Interop.libproc.rusage_info_v3 info = Interop.libproc.proc_pid_rusage(_processId);
-                return new TimeSpan(Convert.ToInt64((info.ri_system_time + info.ri_user_time) / NanosecondsTo100NanosecondsFactor));
+                return MapTime(info.ri_system_time + info.ri_user_time);
             }
         }
 
@@ -82,7 +83,7 @@ public TimeSpan UserProcessorTime
             {
                 EnsureState(State.HaveNonExitedId);
                 Interop.libproc.rusage_info_v3 info = Interop.libproc.proc_pid_rusage(_processId);
-                return new TimeSpan(Convert.ToInt64(info.ri_user_time / NanosecondsTo100NanosecondsFactor));
+                return MapTime(info.ri_user_time);
             }
         }
 
@@ -109,5 +110,35 @@ private static Interop.libproc.rusage_info_v3 GetCurrentProcessRUsage()
         {
             return Interop.libproc.proc_pid_rusage(Environment.ProcessId);
         }
+
+        private static TimeSpan MapTime(ulong sysTime)
+        {
+            uint denom = s_timeBase_denom;
+            if (denom == default)
+            {
+                Interop.libSystem.mach_timebase_info_data_t timeBase = GetTimeBase();
+                s_timeBase_denom = denom = timeBase.denom;
+                s_timeBase_numer = timeBase.numer;
+            }
+            uint numer = s_timeBase_numer;
+
+            // By dividing by NanosecondsTo100NanosecondsFactor first, we lose some precision, but increase the range
+            // where no overflow will happen.
+            return new TimeSpan(Convert.ToInt64(sysTime / NanosecondsTo100NanosecondsFactor * numer / denom));
+        }
+
+        private static unsafe Interop.libSystem.mach_timebase_info_data_t GetTimeBase()
+        {
+            Interop.libSystem.mach_timebase_info_data_t timeBase = default;
+            var returnCode = Interop.libSystem.mach_timebase_info(&timeBase);
+            Debug.Assert(returnCode == 0, $"Non-zero exit code from mach_timebase_info: {returnCode}");
+            if (returnCode != 0)
+            {
+                // Fallback: let's assume that the time values are in nanoseconds,
+                // i.e. the time base is 1/1.
+                timeBase.numer = timeBase.denom = 1;
+            }
+            return timeBase;
+        }
     }
 }

src/libraries/System.Diagnostics.Process/tests/ProcessTests.Unix.cs

@@ -851,6 +851,39 @@ static void ExecuteChildProcess(string filename, string flags)
             }
         }
 
+        [Fact]
+        [PlatformSpecific(TestPlatforms.OSX)]
+        public unsafe void TestTotalProcessorTimeMacOs()
+        {
+            var rUsage = Interop.libproc.proc_pid_rusage(Environment.ProcessId);
+            var timeBase = new Interop.libSystem.mach_timebase_info_data_t();
+            Interop.libSystem.mach_timebase_info(&timeBase);
+
+            var nativeUserUs = rUsage.ri_user_time / 1000 * timeBase.numer / timeBase.denom;
+            var nativeSystemUs = rUsage.ri_system_time / 1000 * timeBase.numer / timeBase.denom;
+            var nativeTotalUs = nativeSystemUs + nativeUserUs;
+
+            var nativeUserTime = TimeSpan.FromMicroseconds(nativeUserUs);
+            var nativeSystemTime = TimeSpan.FromMicroseconds(nativeSystemUs);
+            var nativeTotalTime = TimeSpan.FromMicroseconds(nativeTotalUs);
+
+            var process = Process.GetCurrentProcess();
+            var managedUserTime = process.UserProcessorTime;
+            var managedSystemTime = process.PrivilegedProcessorTime;
+            var managedTotalTime = process.TotalProcessorTime;
+
+            AssertTime(managedUserTime, nativeUserTime, "user");
+            AssertTime(managedSystemTime, nativeSystemTime, "system");
+            AssertTime(managedTotalTime, nativeTotalTime, "total");
+
+            void AssertTime(TimeSpan managed, TimeSpan native, string label)
+            {
+                Assert.True(
+                    managed >= native,
+                    $"Time '{label}' returned by managed API ({managed}) should be greated or equal to the time returned by native API ({native}).");
+            }
+        }
+
         [ConditionalTheory(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
         [InlineData(true)]
         [InlineData(false)]

src/libraries/System.Diagnostics.Process/tests/Resources/Strings.resx

@@ -120,4 +120,10 @@
   <data name="Argv_IncludeDoubleQuote" xml:space="preserve">
     <value>The argv[0] argument cannot include a double quote.</value>
   </data>
+  <data name="CantGetAllPids" xml:space="preserve">
+    <value>Could not get all running Process IDs.</value>
+  </data>
+  <data name="RUsageFailure" xml:space="preserve">
+    <value>Failed to set or retrieve rusage information. See the error code for OS-specific error information.</value>
+  </data>
 </root>

src/libraries/System.Diagnostics.Process/tests/System.Diagnostics.Process.Tests.csproj

@@ -63,6 +63,12 @@
     <Compile Include="ProcessThreadTests.Unix.cs" />
     <Compile Include="$(CoreLibSharedDir)System\PasteArguments.Unix.cs"
              Link="System\PasteArguments.Unix.cs" />
+    <Compile Include="$(CommonPath)Interop\OSX\Interop.Libraries.cs"
+             Link="Common\Interop\OSX\Interop.Libraries.cs" />
+    <Compile Include="$(CommonPath)Interop\OSX\Interop.libproc.cs"
+             Link="Common\Interop\OSX\Interop.libproc.cs" />
+    <Compile Include="$(CommonPath)Interop\OSX\Interop.libSystem.cs"
+             Link="Common\Interop\OSX\Interop.libSystem.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="$(LibrariesProjectRoot)Microsoft.Win32.Registry\src\Microsoft.Win32.Registry.csproj" />