On Thu, 25 Apr 2024 22:26:04 GMT, Claes Redestad <redes...@openjdk.org> wrote:
>> When analyzing (startup) performance of the Classfile API I found this
>> opportunity to further improve `MethodTypeDescImpl::descriptorString`.
>>
>> Performance improves across the board in existing microbenchmarks:
>>
>> Name
>> (descString) Cnt Base Error Test Error Unit Change
>> MethodTypeDescFactories.descriptorString
>> (Ljava/lang/Object;Ljava/lang/String;)I 6 55,179 ± 2,027 32,920 ± 1,189
>> ns/op 1,68x (p = 0,000*)
>> MethodTypeDescFactories.descriptorString
>> ()V 6 17,689 ± 1,871 11,060 ± 0,331 ns/op 1,60x (p = 0,000*)
>> MethodTypeDescFactories.descriptorString
>> ([IJLjava/lang/String;Z)Ljava/util/List; 6 86,627 ± 1,646 41,035 ± 0,636
>> ns/op 2,11x (p = 0,000*)
>> MethodTypeDescFactories.descriptorString
>> ()[Ljava/lang/String; 6 18,305 ± 1,974 13,110 ± 0,089 ns/op 1,40x (p =
>> 0,000*)
>> * = significant
>>
>>
>> The improvement is even more pronounced when running with `-Xint`, which is
>> relevant for reducing startup overheads of early ClassFile API use:
>>
>> Name
>> (descString) Cnt Base Error Test Error Unit Change
>> MethodTypeDescFactories.descriptorString
>> (Ljava/lang/Object;Ljava/lang/String;)I 6 5122,061 ± 81,335 2626,481 ±
>> 101,466 ns/op 1,95x (p = 0,000*)
>> MethodTypeDescFactories.descriptorString
>> ()V 6 3481,316 ± 258,904 1489,267 ± 15,506 ns/op 2,34x (p = 0,000*)
>> MethodTypeDescFactories.descriptorString
>> ([IJLjava/lang/String;Z)Ljava/util/List; 6 7741,081 ± 1628,244 3281,778 ±
>> 41,892 ns/op 2,36x (p = 0,000*)
>> MethodTypeDescFactories.descriptorString
>> ()[Ljava/lang/String; 6 3677,803 ± 63,432 1495,291 ± 8,995 ns/op
>> 2,46x (p = 0,000*)
>> * = significant
>> ```
>>
>> I also applied similar approach to `MethodTypeDesc::displayDescriptor`:
>> while not performance sensitive I think these are so inter-related that it
>> makes sense to implement them in a similar fashion.
>
> Claes Redestad has updated the pull request incrementally with one additional
> commit since the last revision:
>
> Calculate length precisely
src/java.base/share/classes/java/lang/constant/MethodTypeDescImpl.java line 181:
> 179: sb.append(argType.descriptorString());
> 180: }
> 181: desc =
> sb.append(')').append(returnType().descriptorString()).toString();
Nit: the rest of the code (and even the new sizing part you added) uses
`returnType` instead of `returnType()`
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/18945#discussion_r1580229759
