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refactor: adjust parallelism handling in TestScheduler for better resource management #3701

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Merged
merged 1 commit into from
Nov 4, 2025
Merged

refactor: adjust parallelism handling in TestScheduler for better resource management #3701

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14 changes: 8 additions & 6 deletions TUnit.Engine/Scheduling/TestScheduler.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -473,13 +473,14 @@ private async Task ExecuteUnlimitedAsync(
List<AbstractExecutableTest> tests,
CancellationToken cancellationToken)
{
// Execute tests without limiters with unlimited parallelism (no global semaphore overhead)
// Execute tests without limiters - still apply global parallelism limit to prevent thread pool saturation
// "Unlimited" means no per-test constraints (ParallelLimiter), not unlimited concurrency
await Parallel.ForEachAsync(
tests,
new ParallelOptions
{
MaxDegreeOfParallelism = _maxParallelism,
CancellationToken = cancellationToken
// No MaxDegreeOfParallelism = unlimited parallelism
},
async (test, ct) =>
{
Expand Down Expand Up @@ -550,10 +551,11 @@ private static int GetMaxParallelism(ILogger logger, ICommandLineOptions command
}
}

// Default: 8x CPU cores (optimized for I/O-bound and async tests)
// Allows higher concurrency for tests with async/await patterns while preventing resource exhaustion
var defaultLimit = Environment.ProcessorCount * 8;
logger.LogDebug($"Maximum parallel tests limit defaulting to {defaultLimit} ({Environment.ProcessorCount} processors * 8)");
// Default: 4x CPU cores (balanced for mixed CPU/I/O workloads)
// Higher values can cause thread pool saturation with many async tests
// Users can override via --maximum-parallel-tests or TUNIT_MAX_PARALLEL_TESTS
var defaultLimit = Environment.ProcessorCount * 4;
logger.LogDebug($"Maximum parallel tests limit defaulting to {defaultLimit} ({Environment.ProcessorCount} processors * 4)");
return defaultLimit;
}
}
75 changes: 75 additions & 0 deletions TUnit.Profile/Program.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -156,3 +156,78 @@ public class MixedWorkloadTests
[Repeat(30)]
public async Task QuickAsyncTest3() { await Task.CompletedTask; _ = 3; }
}

/// <summary>
/// Massive parallel tests similar to benchmark suite - stress tests parallelism
/// with large numbers of CPU-bound, IO-bound, and mixed workload tests
/// </summary>
public class MassiveParallelTests
{
[Test]
[Arguments(1)] [Arguments(2)] [Arguments(3)] [Arguments(4)] [Arguments(5)]
[Arguments(6)] [Arguments(7)] [Arguments(8)] [Arguments(9)] [Arguments(10)]
[Arguments(11)] [Arguments(12)] [Arguments(13)] [Arguments(14)] [Arguments(15)]
[Arguments(16)] [Arguments(17)] [Arguments(18)] [Arguments(19)] [Arguments(20)]
[Arguments(21)] [Arguments(22)] [Arguments(23)] [Arguments(24)] [Arguments(25)]
[Arguments(26)] [Arguments(27)] [Arguments(28)] [Arguments(29)] [Arguments(30)]
[Arguments(31)] [Arguments(32)] [Arguments(33)] [Arguments(34)] [Arguments(35)]
[Arguments(36)] [Arguments(37)] [Arguments(38)] [Arguments(39)] [Arguments(40)]
[Arguments(41)] [Arguments(42)] [Arguments(43)] [Arguments(44)] [Arguments(45)]
[Arguments(46)] [Arguments(47)] [Arguments(48)] [Arguments(49)]
public void Parallel_CPUBound_Test(int taskId)
{
var result = PerformCPUWork(taskId);
var doubled = result * 2;
_ = doubled;
}

[Test]
[Arguments(1)] [Arguments(2)] [Arguments(3)] [Arguments(4)] [Arguments(5)]
[Arguments(6)] [Arguments(7)] [Arguments(8)] [Arguments(9)] [Arguments(10)]
[Arguments(11)] [Arguments(12)] [Arguments(13)] [Arguments(14)] [Arguments(15)]
[Arguments(16)] [Arguments(17)] [Arguments(18)] [Arguments(19)] [Arguments(20)]
[Arguments(21)] [Arguments(22)] [Arguments(23)] [Arguments(24)] [Arguments(25)]
[Arguments(26)] [Arguments(27)] [Arguments(28)] [Arguments(29)] [Arguments(30)]
[Arguments(31)] [Arguments(32)] [Arguments(33)] [Arguments(34)] [Arguments(35)]
[Arguments(36)] [Arguments(37)] [Arguments(38)] [Arguments(39)] [Arguments(40)]
[Arguments(41)] [Arguments(42)] [Arguments(43)] [Arguments(44)] [Arguments(45)]
[Arguments(46)] [Arguments(47)] [Arguments(48)] [Arguments(49)]
public async Task Parallel_IOBound_Test(int taskId)
{
await Task.Delay(50);
var result = await PerformIOWorkAsync(taskId);
var length = result.Length;
_ = length;
}

[Test]
[Arguments(1, 101)] [Arguments(2, 102)] [Arguments(3, 103)] [Arguments(4, 104)]
[Arguments(5, 105)] [Arguments(6, 106)] [Arguments(7, 107)] [Arguments(8, 108)]
[Arguments(9, 109)] [Arguments(10, 110)] [Arguments(11, 111)] [Arguments(12, 112)]
[Arguments(13, 113)] [Arguments(14, 114)] [Arguments(15, 115)] [Arguments(16, 116)]
[Arguments(17, 117)] [Arguments(18, 118)] [Arguments(19, 119)]
public async Task Parallel_Mixed_Test(int cpuValue, int ioValue)
{
var cpuResult = PerformCPUWork(cpuValue);
await Task.Yield();
var ioResult = await PerformIOWorkAsync(ioValue);
var combined = $"{cpuResult}_{ioResult}";
_ = combined;
}

private static int PerformCPUWork(int taskId)
{
var sum = 0;
for (var i = 1; i <= 100; i++)
{
sum += (i * taskId) % 1000;
}
return sum;
}

private static async Task<string> PerformIOWorkAsync(int taskId)
{
await Task.Yield();
return $"Task_{taskId}_Result_{Guid.NewGuid().ToString()[..8]}";
}
}
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