On Wed, 21 Jun 2023 14:39:18 GMT, 温绍锦 <d...@openjdk.org> wrote:
>> By optimizing the implementation of java.lang.Long#fastUUID, the performance
>> of the java.util.UUID#toString method can be significantly improved.
>>
>> The following are the test results of JMH:
>>
>> Benchmark Mode Cnt Score Error Units
>> UUIDUtilsBenchmark.new thrpt 5 92676.550 ± 292.213 ops/ms
>> UUIDUtilsBenchmark.original thrpt 5 37040.165 ± 1023.532 ops/ms
>
> 温绍锦 has updated the pull request incrementally with one additional commit
> since the last revision:
>
> add annotation Stable
src/java.base/share/classes/java/lang/Long.java line 548:
> 546: buf[33] = (byte) i14;
> 547: buf[34] = (byte) (i15 >> 8);
> 548: buf[35] = (byte) i15;
You may be able to use `jdk.internal.util.ByteArray` to simplify code and
improve performance:
Suggestion:
ByteArray.setChar(buf, 0, i0);
ByteArray.setChar(buf, 2, i1);
ByteArray.setChar(buf, 4, i2);
ByteArray.setChar(buf, 6, i3);
buf[8] = '-';
ByteArray.setChar(buf, 9, i4);
ByteArray.setChar(buf, 11, i5);
buf[13] = '-';
ByteArray.setChar(buf, 14, i6);
ByteArray.setChar(buf, 16, i7);
buf[18] = '-';
ByteArray.setChar(buf, 19, i8);
ByteArray.setChar(buf, 21, i9);
buf[23] = '-';
ByteArray.setChar(buf, 24, i10);
ByteArray.setChar(buf, 26, i11);
ByteArray.setChar(buf, 28, i12);
ByteArray.setChar(buf, 30, i13);
ByteArray.setChar(buf, 32, i14);
ByteArray.setChar(buf, 34, i15);
I measured the throughput of `UUID::toString()` using JMH on my linux server
(CPU: R7-5800X):
Benchmark Mode Cnt Score Error Units
- UUIDUtilsBenchmark.test thrpt 5 76117.237 ± 461.679 ops/ms
+ UUIDUtilsBenchmark.test thrpt 5 87291.496 ± 729.527 ops/ms
The result of this benchmark test is that using `ByteArray` can improve peak
throughput by nearly 15%.
Note: `ByteArray` uses `VarHandle` internally, and the impact on startup time
is unknown, so more testing is needed.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/14578#discussion_r1237573456
