X64 - Too many methods JITted on startup for blank console application

Using this example:

namespace HelloWorldStartup
{
    internal class Program
    {
        static void Main(string[] args)
        {
        }
    }
}

The CPU I used was an AMD 7950X.
X64 - With DOTNET_JitDisasmSummary=1 it shows this number of methods (this is with R2R):

   1: JIT compiled System.Runtime.CompilerServices.CastHelpers:StelemRef(System.Array,long,System.Object) [Tier1, IL size=88, code size=93]
   2: JIT compiled System.Runtime.CompilerServices.CastHelpers:LdelemaRef(System.Array,long,ulong) [Tier1, IL size=44, code size=44]
   3: JIT compiled System.SpanHelpers:IndexOfNullCharacter(ulong) [Tier1, IL size=805, code size=391]
   4: JIT compiled System.Guid:TryFormatCore[ushort](System.Span`1[ushort],byref,int) [Tier0, IL size=894, code size=892]
   5: JIT compiled System.Number:UInt32ToDecChars[ushort](ulong,uint) [Tier0, IL size=114, code size=253]
   6: JIT compiled System.ArgumentOutOfRangeException:ThrowIfNegative[int](int,System.String) [Tier0, IL size=22, code size=50]
   7: JIT compiled System.Text.Unicode.Utf16Utility:GetPointerToFirstInvalidChar(ulong,int,byref,byref) [Tier0, IL size=994, code size=1101]
   8: JIT compiled System.Text.Ascii:NarrowUtf16ToAscii(ulong,ulong,ulong) [Tier0, IL size=491, code size=594]
   9: JIT compiled System.SpanHelpers:IndexOfNullByte(ulong) [Tier1, IL size=844, code size=459]
  10: JIT compiled System.PackedSpanHelpers:IndexOf[System.SpanHelpers+DontNegate`1[short]](byref,short,int) [Tier0, IL size=698, code size=1631]
  11: JIT compiled System.PackedSpanHelpers:PackSources(System.Runtime.Intrinsics.Vector256`1[short],System.Runtime.Intrinsics.Vector256`1[short]) [Tier0, IL size=13, code size=52]
  12: JIT compiled System.PackedSpanHelpers:ComputeFirstIndexOverlapped(byref,byref,byref,System.Runtime.Intrinsics.Vector256`1[ubyte]) [Tier0, IL size=52, code size=124]
  13: JIT compiled System.PackedSpanHelpers:FixUpPackedVector256Result(System.Runtime.Intrinsics.Vector256`1[ubyte]) [Tier0, IL size=22, code size=42]
  14: JIT compiled System.SpanHelpers:LastIndexOfValueType[short,System.SpanHelpers+DontNegate`1[short]](byref,short,int) [Tier1, IL size=963, code size=419]
  15: JIT compiled System.Text.Ascii:WidenAsciiToUtf16(ulong,ulong,ulong) [Tier0, IL size=604, code size=1425]
  16: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Level(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=27]
  17: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Message(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=28]
  18: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Task(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=27]
  19: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Opcode(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=27]
  20: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Version(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=28]
  21: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Keywords(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=28]
  22: JIT compiled System.Number:Int64ToHexChars[ushort](ulong,ulong,int,int) [Tier0, IL size=67, code size=252]
  23: JIT compiled System.SpanHelpers:IndexOfAnyInRangeUnsignedNumber[ushort,System.SpanHelpers+DontNegate`1[ushort]](byref,ushort,ushort,int) [Tier0, IL size=142, code size=190]
  24: JIT compiled System.PackedSpanHelpers:IndexOfAnyInRange[System.SpanHelpers+DontNegate`1[short]](byref,short,short,int) [Tier0, IL size=659, code size=1600]
  25: JIT compiled System.SpanHelpers:SequenceCompareTo(byref,int,byref,int) [Tier1, IL size=568, code size=329]
  26: JIT compiled HelloWorldStartup.Program:Main(System.String[]) [Tier0, IL size=1, code size=10]

ARM64:

   1: JIT compiled System.Runtime.CompilerServices.CastHelpers:StelemRef(System.Array,long,System.Object) [Tier1, IL size=88, code size=144]
   2: JIT compiled System.Runtime.CompilerServices.CastHelpers:LdelemaRef(System.Array,long,ulong) [Tier1, IL size=44, code size=88]
   3: JIT compiled System.SpanHelpers:IndexOfNullCharacter(ulong) [Tier1, IL size=492, code size=392]
   4: JIT compiled HelloWorldStartup.Program:Main(System.String[]) [Tier0, IL size=1, code size=20]

Problems identified:

Bogus SIMD prereqs (Ensure maxSIMDStructBytes doesn't report compVerifyInstructionSetUnusable #85370)
AggressiveOptimization disables R2R on SpanHelpers (Remove AO from a couple of SpanHelpers methods #85819)
Virtual static methods are not R2R compiled (Casting via generic math doesn't always inline in R2R #84421)
Trimmed SelfContained R2RPublish does not use MIBC data (X64 - Too many methods JITted on startup for blank console application #85791 (comment))
EventSource use of reflection (X64 - Too many methods JITted on startup for blank console application #85791 (comment))
Tracing overhead in general (X64 - Too many methods JITted on startup for blank console application #85791 (comment))

@MihaZupan

@MihaZupan can it be caused by SearchValue preinitializations + AVX2?

@stephentoub

// cc @stephentoub @tannergooding

Seems like R2R gives up on methods parameterized with static abstract interfaces? Methods like UInt32ToDecChars, ThrowIfNegative, and Int64ToHexChars aren't doing anything with AVX2.

I'm curious what's triggering these:

  16: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Level(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=27]
  17: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Message(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=28]
  18: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Task(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=27]
  19: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Opcode(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=27]
  20: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Version(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=28]
  21: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Keywords(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=28]

?

I'm curious what's triggering these:

Extensive use of reflection in EventSource

but no ushort

It's never used with ushort, only byte and char.

🤷 trying to find out who is instanciating that

Did you figure this part out?

Did you figure this part out?

Looks like we have two methods:

System.Guid.TryFormatCore[System.Char](System.Span`1<Char>, Int32 ByRef, System.ReadOnlySpan`1<Char>)
System.Guid.TryFormatCore[System.Char](System.Span`1<Char>, Int32 ByRef, Int32)

the latter fails to pick up R2R version, digging further

Ah, SVM again:

Info: Method `[S.P.CoreLib]System.Guid.TryFormatCore<char>(Span`1<char>,int32&,int32)` 
was not compiled because `SVM` requires runtime JIT

Ah, SVM again

Not following... how does that explain why it compiled a ushort version?

Ah, SVM again

Not following... how does that explain why it compiled a ushort version?

I assume it's just the way it's displayed in the log (char -> ushort) or maybe R2R is smart enough to share a single version for both char and ushort, but the actual reason we see TryFormatCore in JitDisasmSummary is SVM

it's just the way it's displayed in the log

Ok :)

Also, why would those not show up on ARM64... was that also on a different OS and that's impacting what EventSource is doing?

They will show-up while running a PerfView trace:

C:\Users\lolti\OneDrive\Desktop\runtime>dotnet HelloWorldStartup.dll
   1: JIT compiled System.Runtime.CompilerServices.CastHelpers:StelemRef(System.Array,long,System.Object) [Tier1, IL size=88, code size=144]
   2: JIT compiled System.Runtime.CompilerServices.CastHelpers:LdelemaRef(System.Array,long,ulong) [Tier1, IL size=44, code size=88]
   3: JIT compiled System.SpanHelpers:IndexOfNullCharacter(ulong) [Tier1, IL size=492, code size=392]
   4: JIT compiled System.ArgumentOutOfRangeException:ThrowIfNegative[int](int,System.String) [Tier0, IL size=22, code size=80]
   5: JIT compiled System.SpanHelpers:IndexOfNullByte(ulong) [Tier1, IL size=581, code size=504]
   6: JIT compiled System.SpanHelpers:NonPackedIndexOfValueType[short,System.SpanHelpers+DontNegate`1[short]](byref,short,int) [Tier1, IL size=843, code size=404]
   7: JIT compiled System.SpanHelpers:LastIndexOfValueType[short,System.SpanHelpers+DontNegate`1[short]](byref,short,int) [Tier1, IL size=819, code size=384]
   8: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Level(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=56]
   9: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Message(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=56]
  10: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Task(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=56]
  11: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Opcode(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=56]
  12: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Version(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=56]
  13: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Keywords(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=56]
  14: JIT compiled System.SpanHelpers:NonPackedIndexOfAnyInRangeUnsignedNumber[ushort,System.SpanHelpers+DontNegate`1[ushort]](byref,ushort,ushort,int) [Tier0, IL size=294, code size=708]
  15: JIT compiled System.SpanHelpers+DontNegate`1[ushort]:NegateIfNeeded(bool) [Tier0, IL size=2, code size=28]
  16: JIT compiled System.SpanHelpers:SequenceCompareTo(byref,int,byref,int) [Tier1, IL size=287, code size=248]
  17: JIT compiled HelloWorldStartup.Program:Main(System.String[]) [Tier0, IL size=1, code size=20]

C:\Users\lolti\OneDrive\Desktop\runtime>dotnet HelloWorldStartup.dll
   1: JIT compiled System.Runtime.CompilerServices.CastHelpers:StelemRef(System.Array,long,System.Object) [Tier1, IL size=88, code size=144]
   2: JIT compiled System.Runtime.CompilerServices.CastHelpers:LdelemaRef(System.Array,long,ulong) [Tier1, IL size=44, code size=88]
   3: JIT compiled System.SpanHelpers:IndexOfNullCharacter(ulong) [Tier1, IL size=492, code size=392]
   4: JIT compiled HelloWorldStartup.Program:Main(System.String[]) [Tier0, IL size=1, code size=20]

The second run is when I didn't do a perf-view trace.

On my X64 box, even when not running perf-view, the EventSource still gets created, likely from some other program.

For the EventSource ones, anyone know why dotnet app.dll wouldn't show those entries but corerun app.dll would?

My dotnet is from a few weeks ago and my corerun is from a local build, but with an empty Main app, with dotnet app.dll I see:

   1: JIT compiled System.Runtime.CompilerServices.CastHelpers:StelemRef(System.Array,long,System.Object) [Tier1, IL size=88, code size=93]
   2: JIT compiled System.Runtime.CompilerServices.CastHelpers:LdelemaRef(System.Array,long,ulong) [Tier1, IL size=44, code size=44]
   3: JIT compiled System.Guid:TryFormatCore[ushort](System.Span`1[ushort],byref,int) [Tier0, IL size=894, code size=892]
   4: JIT compiled System.Guid:FormatGuidVector128Utf8(System.Guid,bool) [Tier0, IL size=322, code size=584]
   5: JIT compiled System.HexConverter:AsciiToHexVector128(System.Runtime.Intrinsics.Vector128`1[ubyte],System.Runtime.Intrinsics.Vector128`1[ubyte]) [Tier0, IL size=78, code size=359]
   6: JIT compiled System.Runtime.Intrinsics.Vector128:ShuffleUnsafe(System.Runtime.Intrinsics.Vector128`1[ubyte],System.Runtime.Intrinsics.Vector128`1[ubyte]) [Tier0, IL size=41, code size=50]
   7: JIT compiled System.Number:UInt32ToDecChars[ushort](ulong,uint) [Instrumented Tier0, IL size=114, code size=315]
   8: JIT compiled System.ArgumentOutOfRangeException:ThrowIfNegative[int](int,System.String) [Tier0, IL size=22, code size=50]
   9: JIT compiled System.Text.Unicode.Utf16Utility:GetPointerToFirstInvalidChar(ulong,int,byref,byref) [Instrumented Tier0, IL size=994, code size=1296]
  10: JIT compiled System.Text.Ascii:NarrowUtf16ToAscii(ulong,ulong,ulong) [Instrumented Tier0, IL size=558, code size=1384]
  11: JIT compiled System.RuntimeType+RuntimeTypeCache+MemberInfoCache`1[System.__Canon]:AddMethod(System.RuntimeType,long,int) [Instrumented Tier0, IL size=354, code size=1672]
  12: JIT compiled System.SpanHelpers:LastIndexOfValueType[short,System.SpanHelpers+DontNegate`1[short]](byref,short,int) [Instrumented Tier0, IL size=1128, code size=2125]
  13: JIT compiled System.Text.Ascii:WidenAsciiToUtf16(ulong,ulong,ulong) [Instrumented Tier0, IL size=738, code size=1814]
  14: JIT compiled System.PackedSpanHelpers:IndexOf[System.SpanHelpers+DontNegate`1[short]](byref,short,int) [Instrumented Tier0, IL size=977, code size=1912]
  15: JIT compiled System.Number:Int64ToHexChars[ushort](ulong,ulong,int,int) [Instrumented Tier0, IL size=67, code size=313]
  16: JIT compiled System.SpanHelpers:IndexOfAnyInRangeUnsignedNumber[ushort,System.SpanHelpers+DontNegate`1[ushort]](byref,ushort,ushort,int) [Tier0, IL size=142, code size=190]
  17: JIT compiled System.PackedSpanHelpers:IndexOfAnyInRange[System.SpanHelpers+DontNegate`1[short]](byref,short,short,int) [Instrumented Tier0, IL size=972, code size=1810]
  18: JIT compiled Test:Main() [Tier0, IL size=1, code size=6]

and with corerun app.dll I see:

   1: JIT compiled System.Runtime.CompilerServices.CastHelpers:StelemRef(System.Array,long,System.Object) [Tier1, IL size=88, code size=93]
   2: JIT compiled System.Runtime.CompilerServices.CastHelpers:LdelemaRef(System.Array,long,ulong) [Tier1, IL size=44, code size=44]
   3: JIT compiled System.Guid:FormatGuidVector128Utf8(System.Guid,bool) [Tier0, IL size=322, code size=584]
   4: JIT compiled System.HexConverter:AsciiToHexVector128(System.Runtime.Intrinsics.Vector128`1[ubyte],System.Runtime.Intrinsics.Vector128`1[ubyte]) [Tier0, IL size=78, code size=359]
   5: JIT compiled System.Runtime.Intrinsics.Vector128:ShuffleUnsafe(System.Runtime.Intrinsics.Vector128`1[ubyte],System.Runtime.Intrinsics.Vector128`1[ubyte]) [Tier0, IL size=41, code size=50]
   6: JIT compiled System.Text.Unicode.Utf16Utility:GetPointerToFirstInvalidChar(ulong,int,byref,byref) [Instrumented Tier0, IL size=994, code size=1292]
   7: JIT compiled System.RuntimeType+RuntimeTypeCache+MemberInfoCache`1[System.__Canon]:AddMethod(System.RuntimeType,long,int) [Instrumented Tier0, IL size=354, code size=1672]
   8: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Level(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=27]
   9: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Message(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=28]
  10: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Task(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=27]
  11: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Opcode(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=27]
  12: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Version(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=28]
  13: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Keywords(System.Object,System.Object,ulong) [FullOpts, IL size=25, code size=28]
  14: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Level(System.Object,System.Span`1[System.Object]) [FullOpts, IL size=36, code size=40]
  15: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Message(System.Object,System.Span`1[System.Object]) [FullOpts, IL size=26, code size=37]
  16: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Task(System.Object,System.Span`1[System.Object]) [FullOpts, IL size=36, code size=40]
  17: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Opcode(System.Object,System.Span`1[System.Object]) [FullOpts, IL size=36, code size=40]
  18: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Version(System.Object,System.Span`1[System.Object]) [FullOpts, IL size=36, code size=41]
  19: JIT compiled (dynamicClass):InvokeStub_EventAttribute.set_Keywords(System.Object,System.Span`1[System.Object]) [FullOpts, IL size=36, code size=41]
  20: JIT compiled Test:Main() [Tier0, IL size=1, code size=6]

Many of the extraneous entries have been removed due to improvements in corelib, but corerun is showing all of these dynamicClass entries that dotnet isn't. Is it possible this is a regression? Or is there something different between the hosts that would trigger this?

My dotnet is from a few weeks ago

What is your exact dotnet version? I have tried this on .NET 8 P7 bits and I do not see this difference. (I see the event source in both cases.)

I think it is most likely difference in timing or difference in what kind of event providers get enabled on the machine. The managed providers run asynchronously and the process can be exiting before they get a chance to run in one case, but not in the other case. Also, the Windows monitoring software running in the background can be turning the event providers on - for examble, it can say that corerun.exe is unsigned binary so better to monitor to it in detail.

Revisited this on current main (.NET 11, win-x64) with a locally-built R2R corelib + testhost, DOTNET_JitDisasmSummary=1:

Scenario	2023 (X64, this issue)	.NET 11 now
Empty `Main()` / `Main(string[] args)`, no event session	26	1 (`Program:Main`)
Empty, active EventPipe/ETW session	+EventSource stubs	14
`Console.WriteLine("Hello world")`	~30	28

The old empty-app noise -- Guid.TryFormatCore, Number.UInt32ToDecChars<ushort>, Int64ToHexChars, ArgumentOutOfRangeException.ThrowIfNegative<T>, and the pile of SpanHelpers/PackedSpanHelpers/Text.Ascii/CastHelpers methods -- is entirely gone. The structural fixes did it:

Ensure maxSIMDStructBytes doesn't report compVerifyInstructionSetUnusable #85370 removed the bogus SIMD/AVX2 prereqs that made R2R code get rejected and re-JITted at load (the biggest contributor).
Casting via generic math doesn't always inline in R2R #84421 fixed generic-math casting to inline/R2R properly (the recurring SVM requires runtime JIT fallout).
Remove AO from a couple of SpanHelpers methods #85819 dropped aggressive-opt from a couple SpanHelpers methods.

The blank app now JITs exactly one method (Program:Main); even the CastHelpers array helpers no longer show with string[] args.

What remains:

EventSource reflection stubs (InvokeStub_EventAttribute.* + a reflection-cache entry) still get JITted when an event/ETW session is active -- ~12 methods for the empty app. This is environment-dependent and is the item that the EventSource source generator is meant to remove.
The Console.WriteLine case's 28 methods are now all the genuine Console -> ConsolePal -> Kernel32.WriteFile startup path (Tier0), with none of the old generic-math/SVM fallbacks.

So the core complaint here -- a blank app JITting ~26 methods -- is effectively resolved (down to 1). The remaining startup-JIT is the EventSource reflection cost when tracing is enabled, which is tracked separately. Closing as resolved; the EventSource source generator work can be tracked on its own.

Note

Investigation and this write-up were done with the help of GitHub Copilot.

Checked on linux-x64 - just one method is jitted for a hello world (tested the most recent daily build of SDK):

1: JIT compiled Program:<Main>$(System.String[]) [Tier0, IL size=11, code size=37]

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X64 - Too many methods JITted on startup for blank console application #85791

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X64 - Too many methods JITted on startup for blank console application #85791

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EgorBo commented on May 4, 2023

TIHan commented on May 4, 2023

stephentoub commented on May 5, 2023

stephentoub commented on May 5, 2023

jkotas commented on May 5, 2023

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