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Slow AssemblyLoadContext.StartAssemblyLoad() at startup #45466

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Slow AssemblyLoadContext.StartAssemblyLoad() at startup#45466
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area-Tracing-coreclrenhancementProduct code improvement that does NOT require public API changes/additionstenet-performancePerformance related issue
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@iSazonov

Description

@iSazonov
iSazonov
opened on Dec 2, 2020

Description

Related #44598
I measured PowerShell startup scenario with pwsh -c exit (really start-stop scenario).
One delay in the scenario is in AssemblyLoadContext.StartAssemblyLoad() called from hostpolicy - 59 ms (10%).

image

The StartAssemblyLoad() initializes tracing

runtime/src/coreclr/src/System.Private.CoreLib/src/System/Runtime/Loader/AssemblyLoadContext.CoreCLR.cs

Lines 199 to 206 in 191ea06

private static void StartAssemblyLoad(ref Guid activityId, ref Guid relatedActivityId)
{
// Make sure ActivityTracker is enabled
ActivityTracker.Instance.Enable();
// Don't use trace to TPL event source in ActivityTracker - that event source is a singleton and its instantiation may have triggered the load.
ActivityTracker.Instance.OnStart(NativeRuntimeEventSource.Log.Name, AssemblyLoadName, 0, ref activityId, ref relatedActivityId, EventActivityOptions.Recursive, useTplSource: false);
}

Especially the slow System.Threading.Tasks.TplEventSource..cctor () - 49 ms (8.5%).
(And System.Diagnostics.Tracing.NativeRuntimeEventSource..cctor() too)

image

We can't seem to improve this in PowerShell and I hope it will be improved in .Net in some way. Perhaps it is possible to postpone the initialization or make it async.

Configuration

Used PowerShell 7.2 Preview.1 based on .Net 5.0.

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