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reduce overhead when running in no main thread mode #1502

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Merged
lifengl merged 3 commits into from
Nov 11, 2025
+18 −16
Merged

reduce overhead when running in no main thread mode #1502

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c55a1e3
Do not track nested factory when there is no main thread
Nov 5, 2025
06c475e
Do not turn on SynchronouslyBlockingMainThread flag on when the JTF i…
Nov 5, 2025
d97b477
stop creating main thread synchronization context when running in no …
Nov 5, 2025
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7 changes: 3 additions & 4 deletions src/Microsoft.VisualStudio.Threading/JoinableTask.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,6 @@
using System.Linq;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using JoinRelease = Microsoft.VisualStudio.Threading.JoinableTaskCollection.JoinRelease;
Expand Down Expand Up @@ -147,7 +146,7 @@ internal JoinableTask(JoinableTaskFactory owner, bool synchronouslyBlocking, str
this.state |= JoinableTaskFlags.StartedSynchronously | JoinableTaskFlags.CompletingSynchronously;
}

if (owner.Context.IsOnMainThread)
if (owner.Context.IsOnMainThread && !this.JoinableTaskContext.IsNoOpContext)
{
this.state |= JoinableTaskFlags.StartedOnMainThread;
if (synchronouslyBlocking)
Expand Down Expand Up @@ -321,7 +320,7 @@ internal SynchronizationContext? ApplicableJobSyncContext
{
get
{
if (this.JoinableTaskContext.IsOnMainThread)
if (this.JoinableTaskContext.IsOnMainThread && !this.JoinableTaskContext.IsNoOpContext)
{
if (this.mainThreadJobSyncContext is null)
{
Expand Down Expand Up @@ -977,7 +976,7 @@ internal void CompleteOnCurrentThread()
{
bool onMainThread = false;
JoinableTaskFlags additionalFlags = JoinableTaskFlags.CompletingSynchronously;
if (this.JoinableTaskContext.IsOnMainThread)
if (this.JoinableTaskContext.IsOnMainThread && !this.JoinableTaskContext.IsNoOpContext)
{
additionalFlags |= JoinableTaskFlags.SynchronouslyBlockingMainThread;
onMainThread = true;
Expand Down
27 changes: 15 additions & 12 deletions src/Microsoft.VisualStudio.Threading/JoinableTaskFactory.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -28,7 +28,7 @@ public partial class JoinableTaskFactory
/// </summary>
private readonly JoinableTaskContext owner;

private readonly SynchronizationContext mainThreadJobSyncContext;
private readonly SynchronizationContext? mainThreadJobSyncContext;

/// <summary>
/// The collection to add all created tasks to. May be <see langword="null" />.
Expand Down Expand Up @@ -71,7 +71,7 @@ internal JoinableTaskFactory(JoinableTaskContext owner, JoinableTaskCollection?

this.owner = owner;
this.jobCollection = collection;
this.mainThreadJobSyncContext = new JoinableTaskSynchronizationContext(this);
this.mainThreadJobSyncContext = owner.IsNoOpContext ? null : new JoinableTaskSynchronizationContext(this);
}

/// <summary>
Expand Down Expand Up @@ -1017,20 +1017,23 @@ internal RunFramework(JoinableTaskFactory factory, JoinableTask joinable)
{
JoinableTaskDependencyGraph.AddDependency(this.previousJoinable, joinable);

// By definition we inherit the nesting factories of our immediate nesting task.
ListOfOftenOne<JoinableTaskFactory> nestingFactories = this.previousJoinable.NestingFactories;

// And we may add our immediate nesting parent's factory to the list of
// ancestors if it isn't already in the list.
if (this.previousJoinable.Factory != this.factory)
if (!factory.Context.IsNoOpContext)
{
if (!nestingFactories.Contains(this.previousJoinable.Factory))
// By definition we inherit the nesting factories of our immediate nesting task.
ListOfOftenOne<JoinableTaskFactory> nestingFactories = this.previousJoinable.NestingFactories;

// And we may add our immediate nesting parent's factory to the list of
// ancestors if it isn't already in the list.
if (this.previousJoinable.Factory != this.factory)
{
nestingFactories.Add(this.previousJoinable.Factory);
if (!nestingFactories.Contains(this.previousJoinable.Factory))
{
nestingFactories.Add(this.previousJoinable.Factory);
}
}
}

this.joinable.NestingFactories = nestingFactories;
this.joinable.NestingFactories = nestingFactories;
}
}

if (joinable.GetTokenizedParent() is JoinableTask tokenizedParent)
Expand Down
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