Why is String.EndsWith() on .NET 8 two times slower than on .NET Framework 4.8, in Chinese and Japanese CultureInfo?

[JasonWei512]

Full test project and result

StringEndsWithBenchmark.zip

Example

On .NET 8 ...

"Hello World".EndsWith("World");

... takes 278% time in Chinese CultureInfo compared to .NET Framework 4.8.

Runtime	CultureInfo	Mean	Error	StdDev	Ratio	RatioSD
.NET 8.0	zh-CN	729.141 ns	5.5568 ns	4.9259 ns	2.78	0.03
.NET Framework 4.8	zh-CN	261.966 ns	2.8408 ns	2.6573 ns	1.00	0.00
.NET 8.0	ja-JP	684.399 ns	7.3567 ns	6.8815 ns	4.10	0.06
.NET Framework 4.8	ja-JP	166.677 ns	2.5655 ns	2.2742 ns	1.00	0.00
.NET 8.0	en-US	8.513 ns	0.0718 ns	0.0672 ns	0.13	0.00
.NET Framework 4.8	en-US	63.882 ns	0.4042 ns	0.3781 ns	1.00	0.00
.NET 8.0	InvariantCulture	8.748 ns	0.1012 ns	0.0898 ns	0.15	0.00
.NET Framework 4.8	InvariantCulture	58.908 ns	0.7907 ns	0.7009 ns	1.00	0.00

Environment

BenchmarkDotNet v0.13.12, Windows 11 (10.0.22631.3007/23H2/2023Update/SunValley3)
AMD Ryzen 7 7840S with Radeon 780M Graphics, 1 CPU, 16 logical and 8 physical cores
  [Host]             : .NET Framework 4.8.1 (4.8.9181.0), X64 RyuJIT VectorSize=256
  .NET 8.0           : .NET 8.0.1 (8.0.123.58001), X64 RyuJIT AVX-512F+CD+BW+DQ+VL+VBMI
  .NET Framework 4.8 : .NET Framework 4.8.1 (4.8.9181.0), X64 RyuJIT VectorSize=256

[huoyaoyuan]

The default globalization implementation is ICU on .NET Core. See https://learn.microsoft.com/dotnet/core/extensions/globalization-icu . You can compare the performance of NLS mode mentioned in the doc.

[hez2010]

You may want to compare string with Ordinal culture to treat string as binary sequence:

"Hello World".EndsWith("World", StringComparison.Ordinal);