RFR: 8311207: Cleanup for Optimization for UUID.toString [v9]

[Chen Liang]

On Tue, 5 Sep 2023 02:46:21 GMT, 温绍锦 <duke at openjdk.org> wrote:

>> [PR 14578 ](https://github.com/openjdk/jdk/pull/14578) still has unresolved discussions, continue to make improvements.
>> 
>> # Benchmark Result
>> 
>> 
>> sh make/devkit/createJMHBundle.sh
>> bash configure --with-jmh=build/jmh/jars
>> make test TEST="micro:java.util.UUIDBench.toString"
>> 
>> 
>> ## 1. [aliyun_ecs_c8i.xlarge](https://help.aliyun.com/document_detail/25378.html#c8i)
>> * cpu : intel xeon sapphire rapids (x64)
>> 
>> ``` diff
>> -Benchmark           (size)   Mode  Cnt   Score   Error   Units (baseline)
>> -UUIDBench.toString   20000  thrpt   15  62.019 ± 0.622  ops/us
>> 
>> +Benchmark           (size)   Mode  Cnt   Score   Error   Units
>> +UUIDBench.toString   20000  thrpt   15  82.998 ± 0.739  ops/us (+33.82%)
>> 
>> 
>> ## 2. [aliyun_ecs_c8a.xlarge](https://help.aliyun.com/document_detail/25378.html#c8a)
>> * cpu : amd epc genoa (x64)
>> 
>> ``` diff
>> -Benchmark           (size)   Mode  Cnt   Score   Error   Units (baseline)
>> -UUIDBench.toString   20000  thrpt   15  88.668 ± 0.672  ops/us
>> 
>> +Benchmark           (size)   Mode  Cnt   Score   Error   Units
>> +UUIDBench.toString   20000  thrpt   15  89.229 ± 0.271  ops/us (+0.63%)
>> 
>> 
>> 
>> ## 3. [aliyun_ecs_c8y.xlarge](https://help.aliyun.com/document_detail/25378.html#c8y)
>> * cpu : aliyun yitian 710 (aarch64)
>> ``` diff
>> -Benchmark           (size)   Mode  Cnt   Score   Error   Units (baseline)
>> -UUIDBench.toString   20000  thrpt   15  49.382 ± 2.160  ops/us
>> 
>> +Benchmark           (size)   Mode  Cnt   Score   Error   Units
>> +UUIDBench.toString   20000  thrpt   15  49.636 ± 1.974  ops/us (+0.51%)
>> 
>> 
>> ## 4. MacBookPro M1 Pro
>> ``` diff
>> -Benchmark           (size)   Mode  Cnt    Score   Error   Units (baseline)
>> -UUIDBench.toString   20000  thrpt   15  103.543 ± 0.963  ops/us
>> 
>> +Benchmark           (size)   Mode  Cnt    Score   Error   Units
>> +UUIDBench.toString   20000  thrpt   15  110.976 ± 0.685  ops/us (+7.17%)
>> 
>> 
>> ## 5. Orange Pi 5 Plus
>> 
>> ``` diff
>> -Benchmark           (size)   Mode  Cnt   Score   Error   Units (baseline)
>> -UUIDBench.toString   20000  thrpt   15  33.532 ± 0.396  ops/us
>> 
>> +Benchmark           (size)   Mode  Cnt   Score   Error   Units (PR)
>> +UUIDBench.toString   20000  thrpt   15  33.054 ± 0.190  ops/us (-4.42%)
>
> 温绍锦 has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 11 additional commits since the last revision:
> 
>  - Merge branch 'master' into optimization_for_uuid_to_string
>  - use ByteArrayLittleEndian
>  - fix typo
>  - code style
>  - Explain the rationale
>    
>    Co-authored-by: liach <liach at users.noreply.github.com>
>  - private static final Unsafe
>  - revert to the previous version
>  - Merge pull request #1 from liachmodded/optimization_for_uuid_to_string
>    
>    Suggested HexDigits change
>  - Suggested HexDigits change
>  - use big endian
>  - ... and 1 more: https://git.openjdk.org/jdk/compare/ac7b7229...69962433

src/java.base/share/classes/java/util/HexDigits.java line 68:

> 66: 
> 67:     /**
> 68:      * Return a big-endian packed integer for the 4 ASCII bytes for an input unsigned 2-byte integer.

Suggestion:

     * Returns a little-endian packed integer for the 4 ASCII bytes for an input unsigned 2-byte integer.

src/java.base/share/classes/java/util/HexDigits.java line 77:

> 75: 
> 76:     /**
> 77:      * Return a big-endian packed long for the 8 ASCII bytes for an input unsigned 4-byte integer.

Suggestion:

     * Returns a little-endian packed long for the 8 ASCII bytes for an input unsigned 4-byte integer.

src/java.base/share/classes/java/util/UUID.java line 494:

> 492:                 buf,
> 493:                 24,
> 494:                 HexDigits.packDigits(((int) (lsb >> 40)), (int) (lsb >> 32), ((int) lsb) >> 24, ((int) lsb) >> 16));

Suggestion:

                HexDigits.packDigits((int) (lsb >> 40), (int) (lsb >> 32), ((int) lsb) >> 24, ((int) lsb) >> 16));

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

PR Review Comment: https://git.openjdk.org/jdk/pull/14745#discussion_r1315331223
PR Review Comment: https://git.openjdk.org/jdk/pull/14745#discussion_r1315331130
PR Review Comment: https://git.openjdk.org/jdk/pull/14745#discussion_r1315314460