On Sun, 18 May 2025 12:48:07 GMT, Shaojin Wen <s...@openjdk.org> wrote:
> Through JVM Option +PrintInlining, we found that String has a constructor
> codeSize of 852, which is too large. This caused failed to inline.
>
> The following is the output information of PrintInlining:
>
> @ 9 java.lang.String::<init> (12 bytes) inline (hot)
> !m @ 1 java.nio.charset.Charset::defaultCharset (52 bytes)
> inline (hot)
> ! @ 8 java.lang.String::<init> (852 bytes) failed to
> inline: hot method too big
>
>
> In Java code, the big method that cannot be inlined is the following
> constructor
>
>
> String(Charset charset, byte[] bytes, int offset, int length) {}
>
> The above String constructor is too large; break it down into smaller methods
> with a codeSize under 325 to allow them to be inlined by the C2.
Below are the performance numbers on the MacBook M1 Max. The numbers show that
after the small split method, the performance has been significantly improved.
-# master 6c42856b8d5
-Benchmark (size) Mode Cnt
Score Error Units
-StringConstructor.newStringFromBytes 7 avgt 15
6.628 ± 0.048 ns/op
-StringConstructor.newStringFromBytes 64 avgt 15
10.182 ± 0.079 ns/op
-StringConstructor.newStringFromBytesRanged 7 avgt 15
10.187 ± 0.871 ns/op
-StringConstructor.newStringFromBytesRanged 64 avgt 15
11.304 ± 0.111 ns/op
-StringConstructor.newStringFromBytesRangedWithCharsetUTF8 7 avgt 15
10.869 ± 0.753 ns/op
-StringConstructor.newStringFromBytesRangedWithCharsetUTF8 64 avgt 15
11.348 ± 0.134 ns/op
-StringConstructor.newStringFromBytesWithCharsetNameUTF8 7 avgt 15
9.483 ± 0.119 ns/op
-StringConstructor.newStringFromBytesWithCharsetNameUTF8 64 avgt 15
12.755 ± 0.089 ns/op
-StringConstructor.newStringFromBytesWithCharsetUTF8 7 avgt 15
6.721 ± 0.107 ns/op
-StringConstructor.newStringFromBytesWithCharsetUTF8 64 avgt 15
10.208 ± 0.065 ns/op
+# current 4ebac0ddc64
+Benchmark (size) Mode Cnt
Score Error Units
+StringConstructor.newStringFromBytes 7 avgt 15
4.715 ± 0.029 ns/op +40.57%
+StringConstructor.newStringFromBytes 64 avgt 15
8.019 ± 0.152 ns/op +26.97%
+StringConstructor.newStringFromBytesRanged 7 avgt 15
5.563 ± 0.059 ns/op +83.12%
+StringConstructor.newStringFromBytesRanged 64 avgt 15
9.549 ± 0.217 ns/op +18.37%
+StringConstructor.newStringFromBytesRangedWithCharsetUTF8 7 avgt 15
5.579 ± 0.076 ns/op +94.81%
+StringConstructor.newStringFromBytesRangedWithCharsetUTF8 64 avgt 15
9.407 ± 0.047 ns/op +20.63%
+StringConstructor.newStringFromBytesWithCharsetNameUTF8 7 avgt 15
8.168 ± 0.084 ns/op +16.09%
+StringConstructor.newStringFromBytesWithCharsetNameUTF8 64 avgt 15
12.574 ± 0.268 ns/op + 1.43%
+StringConstructor.newStringFromBytesWithCharsetUTF8 7 avgt 15
4.722 ± 0.043 ns/op +42.33%
+StringConstructor.newStringFromBytesWithCharsetUTF8 64 avgt 15
8.077 ± 0.144 ns/op +26.38%
-------------
PR Comment: https://git.openjdk.org/jdk/pull/25290#issuecomment-2889044580
