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perf: reduce ConcurrentDictionary closure allocations in hot paths #5210

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thomhurst merged 1 commit into from
Mar 22, 2026
+47 −6
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perf: reduce ConcurrentDictionary closure allocations in hot paths #5210

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43 changes: 39 additions & 4 deletions TUnit.Engine/Services/EventReceiverOrchestrator.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -317,6 +317,11 @@ public ValueTask InvokeFirstTestInSessionEventReceiversAsync(
return default;
}

if (_firstTestInSessionTasks.TryGetValue("session", out var existingTask))
{
return new ValueTask(existingTask);
}

var task = _firstTestInSessionTasks.GetOrAdd("session",
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@hartmair hartmair Mar 22, 2026

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@thomhurst FYI there is also an overload for this, which internally does almost exactly the same, see ConcurrentDictionary.cs:1223.

var task = _firstTestInSessionTasks.GetOrAdd("session",
static (_, args) => InvokeFirstTestInSessionEventReceiversCoreAsync(args.Item1, args.Item2, args.Item2),
(context, sessionContext, cancellationToken));
        return new ValueTask(task);

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@thomhurst thomhurst Mar 22, 2026

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Thanks @hartmair !

_ => InvokeFirstTestInSessionEventReceiversCoreAsync(context, sessionContext, cancellationToken));
return new ValueTask(task);
Expand Down Expand Up @@ -347,6 +352,12 @@ public ValueTask InvokeFirstTestInAssemblyEventReceiversAsync(
}

var assemblyName = assemblyContext.Assembly.GetName().FullName ?? "";

if (_firstTestInAssemblyTasks.TryGetValue(assemblyName, out var existingTask))
{
return new ValueTask(existingTask);
}

var task = _firstTestInAssemblyTasks.GetOrAdd(assemblyName,
_ => InvokeFirstTestInAssemblyEventReceiversCoreAsync(context, assemblyContext, cancellationToken));
return new ValueTask(task);
Expand Down Expand Up @@ -377,6 +388,12 @@ public ValueTask InvokeFirstTestInClassEventReceiversAsync(
}

var classType = classContext.ClassType;

if (_firstTestInClassTasks.TryGetValue(classType, out var existingTask))
{
return new ValueTask(existingTask);
}

var task = _firstTestInClassTasks.GetOrAdd(classType,
_ => InvokeFirstTestInClassEventReceiversCoreAsync(context, classContext, cancellationToken));
return new ValueTask(task);
Expand Down Expand Up @@ -448,7 +465,12 @@ public ValueTask InvokeLastTestInAssemblyEventReceiversAsync(

var assemblyName = assemblyContext.Assembly.GetName().FullName ?? "";

var assemblyCount = _assemblyTestCounts.GetOrAdd(assemblyName, static _ => new Counter()).Decrement();
if (!_assemblyTestCounts.TryGetValue(assemblyName, out var assemblyCounter))
{
assemblyCounter = _assemblyTestCounts.GetOrAdd(assemblyName, static _ => new Counter());
}

var assemblyCount = assemblyCounter.Decrement();

if (assemblyCount == 0)
{
Expand Down Expand Up @@ -491,7 +513,12 @@ public ValueTask InvokeLastTestInClassEventReceiversAsync(

var classType = classContext.ClassType;

var classCount = _classTestCounts.GetOrAdd(classType, static _ => new Counter()).Decrement();
if (!_classTestCounts.TryGetValue(classType, out var classCounter))
{
classCounter = _classTestCounts.GetOrAdd(classType, static _ => new Counter());
}

var classCount = classCounter.Decrement();

if (classCount == 0)
{
Expand Down Expand Up @@ -536,13 +563,21 @@ public void InitializeTestCounts(IEnumerable<TestContext> allTestContexts)

foreach (var group in contexts.GroupBy(c => c.ClassContext.AssemblyContext.Assembly.GetName().FullName))
{
var counter = _assemblyTestCounts.GetOrAdd(group.Key, static _ => new Counter());
if (!_assemblyTestCounts.TryGetValue(group.Key, out var counter))
{
counter = _assemblyTestCounts.GetOrAdd(group.Key, static _ => new Counter());
}

counter.Add(group.Count());
}

foreach (var group in contexts.GroupBy(c => c.ClassContext.ClassType))
{
var counter = _classTestCounts.GetOrAdd(group.Key, static _ => new Counter());
if (!_classTestCounts.TryGetValue(group.Key, out var counter))
{
counter = _classTestCounts.GetOrAdd(group.Key, static _ => new Counter());
}

counter.Add(group.Count());
}
}
Expand Down
2 changes: 1 addition & 1 deletion TUnit.Engine/Services/HookDelegateBuilder.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -50,7 +50,7 @@ public HookDelegateBuilder(EventReceiverOrchestrator eventReceiverOrchestrator,

private static Type GetCachedGenericTypeDefinition(Type type)
{
return _genericTypeDefinitionCache.GetOrAdd(type, t => t.GetGenericTypeDefinition());
return _genericTypeDefinitionCache.GetOrAdd(type, static t => t.GetGenericTypeDefinition());
}

public async ValueTask InitializeAsync()
Expand Down
8 changes: 7 additions & 1 deletion TUnit.Engine/Services/TestExecution/TestExecutionGuard.cs
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Expand Up @@ -12,8 +12,14 @@ internal sealed class TestExecutionGuard

public ValueTask<bool> TryStartExecutionAsync(string testId, Func<ValueTask> executionFunc)
{
// Fast path: check if test is already executing without allocating a TCS
if (_executingTests.TryGetValue(testId, out var existingTcs))
{
return new ValueTask<bool>(WaitForExistingExecutionAsync(existingTcs));
}

var tcs = new TaskCompletionSource<bool>();
var existingTcs = _executingTests.GetOrAdd(testId, tcs);
existingTcs = _executingTests.GetOrAdd(testId, tcs);

if (existingTcs != tcs)
{
Expand Down
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