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Fix perf regression in System.Net.NetworkInformation.PhysicalAddress #40571

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Fix perf regression in System.Net.NetworkInformation.PhysicalAddress #40571

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96c0580
Revert the use of the public hex encoding API to avoid its overhead
tkp1n Aug 6, 2020
26e7276
Encourage inlining to avoid additional call introduced in #39702
tkp1n Aug 8, 2020
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1 change: 1 addition & 0 deletions src/libraries/Common/src/System/HexConverter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -83,6 +83,7 @@ public static void ToCharsBuffer(byte value, Span<char> buffer, int startingInde
buffer[startingIndex] = (char)(packedResult >> 8);
}

[MethodImpl(MethodImplOptions.AggressiveInlining)]
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Was this not getting inlined already? I wonder why

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Methods with loops are generally too large to inline by default.

To confirm, you can try:

  • BDN's inlining diagnoser
  • enable and look at the jit inlining events under perfview
  • Use a checked jit and set COMPlus_JitPrintInlinedMethods=<class_name>.<method name>

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Was this not getting inlined already? I wonder why

It is considered unprofitable... (as per BDN inlining diagnoser)

--------------------
Inliner: System.HexConverter+<>c.<ToString>b__4_0 - instance void  (value class System.Span`1<wchar>,value class System.ValueTuple`3<int,int32,value class Casing>)
Inlinee: System.HexConverter.EncodeToUtf16 - void  (value class System.ReadOnlySpan`1<unsigned int8>,value class System.Span`1<wchar>,value class Casing)
Fail Reason: unprofitable inline
--------------------

public static void EncodeToUtf16(ReadOnlySpan<byte> bytes, Span<char> chars, Casing casing = Casing.Upper)
{
Debug.Assert(chars.Length >= bytes.Length * 2);
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2 changes: 1 addition & 1 deletion ...raries/System.Net.NetworkInformation/src/System/Net/NetworkInformation/PhysicalAddress.cs
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Expand Up @@ -90,7 +90,7 @@ public override bool Equals(object? comparand)

public override string ToString()
{
return Convert.ToHexString(_address.AsSpan());
return HexConverter.ToString(_address.AsSpan(), HexConverter.Casing.Upper);
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It's concerning if the brand new public API is insufficient.

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I'm not concerted as we are talking about nanoseconds here.
A public API with input validation will never be a match for an internal method that gets straight to business. Especially with such short input values (16 bytes).

There is also #39702 to improve things (perf). The initial PR adding the public API was kept simple by design (to get it in for .NET 5).

}

public byte[] GetAddressBytes()
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