On Sun, 24 Sep 2023 11:59:51 GMT, 温绍锦 <d...@openjdk.org> wrote:

>> @cl4es made performance optimizations for the simple specifiers of 
>> String.format in PR https://github.com/openjdk/jdk/pull/2830. Based on the 
>> same idea, I continued to make improvements. I made patterns like %2d %02d 
>> also be optimized.
>> 
>> The following are the test results based on MacBookPro M1 Pro: 
>> 
>> 
>> -Benchmark                          Mode  Cnt     Score     Error  Units
>> -StringFormat.complexFormat         avgt   15  1862.233 ? 217.479  ns/op
>> -StringFormat.int02Format           avgt   15   312.491 ?  26.021  ns/op
>> -StringFormat.intFormat             avgt   15    84.432 ?   4.145  ns/op
>> -StringFormat.longFormat            avgt   15    87.330 ?   6.111  ns/op
>> -StringFormat.stringFormat          avgt   15    63.985 ?  11.366  ns/op
>> -StringFormat.stringIntFormat       avgt   15    87.422 ?   0.147  ns/op
>> -StringFormat.widthStringFormat     avgt   15   250.740 ?  32.639  ns/op
>> -StringFormat.widthStringIntFormat  avgt   15   312.474 ?  16.309  ns/op
>> 
>> +Benchmark                          Mode  Cnt    Score    Error  Units
>> +StringFormat.complexFormat         avgt   15  740.626 ? 66.671  ns/op 
>> (+151.45)
>> +StringFormat.int02Format           avgt   15  131.049 ?  0.432  ns/op 
>> (+138.46)
>> +StringFormat.intFormat             avgt   15   67.229 ?  4.155  ns/op 
>> (+25.59)
>> +StringFormat.longFormat            avgt   15   66.444 ?  0.614  ns/op 
>> (+31.44)
>> +StringFormat.stringFormat          avgt   15   62.619 ?  4.652  ns/op 
>> (+2.19)
>> +StringFormat.stringIntFormat       avgt   15   89.606 ? 13.966  ns/op 
>> (-2.44)
>> +StringFormat.widthStringFormat     avgt   15   52.462 ? 15.649  ns/op 
>> (+377.95)
>> +StringFormat.widthStringIntFormat  avgt   15  101.814 ?  3.147  ns/op 
>> (+206.91)
>
> 温绍锦 has updated the pull request incrementally with one additional commit 
> since the last revision:
> 
>   refactor and cache single conversion FormatSpecifier

Please don't pile on new refactorings and improvements on a PR that has been 
opened for review. Better to let things brew as a draft for a bit if you're not 
sure you're done before opening the PR for review, then once it's been opened 
(like this one) consider preparing follow-up PR instead of refactoring as you 
go.

Specifically I'm not sure 0d977b2 is a good idea and would like you to roll 
those changes back. Object pooling for trivial, short-lived objects are 
considered an anti-pattern, as they add references to old GC generations and 
share many of the same drawbacks as lookup tables, such as increased cache 
traffic. Showing great wins on microbenchmarks while being a wash or even 
regressing real applications.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/15776#issuecomment-1732562759

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