Merge pull request #4033 from icsharpcode/decompiler-tests-server-gc

Use server GC for the decompiler test suite (workstation GC on the shared Windows CI runner)

.github/workflows/build-ilspy.yml

@@ -99,6 +99,13 @@ jobs:
 
     - name: Execute unit tests
       id: unit-tests
+      # All test hosts of the solution run concurrently on a 4-core runner. Server GC (enabled by
+      # ICSharpCode.Decompiler.Tests for machines it has to itself) keeps that host at 100% CPU
+      # and starves the neighbours: the process-module walks in ILSpy.Tests.Windows blow their
+      # 60 s budget and ILSpy.Tests takes almost twice as long, while the decompiler suite itself
+      # gains little here. The environment variable overrides the runtimeconfig setting.
+      env:
+        DOTNET_gcServer: 0
       run: >
         dotnet test --solution ilspy.sln
         --configuration ${{ matrix.configuration }}

ICSharpCode.Decompiler.Tests/ICSharpCode.Decompiler.Tests.csproj

@@ -18,6 +18,12 @@
 
     <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
 
+    <!-- The suite runs dozens of allocation-heavy decompiles concurrently (one NUnit worker per
+         logical CPU, each roundtrip adding WholeProjectDecompiler's own Parallel.ForEach). Workstation
+         GC stops the whole process for every gen0/gen1 collection any worker triggers; measured on a
+         24-thread machine that was ~300 s of pause in a ~550 s run. Server GC gives each core its own
+         heap and collects in parallel. -->
+    <ServerGarbageCollection>true</ServerGarbageCollection>
     <!-- NU1902/1903 are "Package 'X' has a known security vulnerability". In our tests, we don't care. -->
     <!-- CA1416 fires because the TFM dropped its -windows suffix: Windows-only helpers (SdkUtility,
          Tester.SignAssembly/FindMSBuild/RunWithTestRunner) and Windows-only test inputs (Console.CapsLock