On Wed, 21 Jun 2023 07:58:11 GMT, Alan Bateman <al...@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
>
> src/java.base/share/classes/java/lang/Long.java line 97:
>
>> 95: + (lo < 10 ? '0' + lo : 'a' + lo - 10));
>> 96: }
>> 97: }
>
> Are you checking the impact on startup? I guess I would have expected to see
> it loaded from the CDS archive. Given that the usage is just UUID::toString
> then maybe you could move this to a holder class containing a Stable array,
> at least until there is a better way to have lazily computed constants.
> Another thing to try is moving fastUUID out of Long - moving to an array of
> precomputed hex values means it is not tied to Long internals anymore.
1. HEX256 can be used to optimize all integers to hex strings, such as
Integer#toHexString and Long#toHexString and byte [] to hexstring.
2. i am a newcomer, and i don't understand what 'loaded from the CDS archive'
means, do you mean to use constants instead? such as
HEX256 = new char[]{
12336, 12337, 12338, 12339, 12340, 12341, 12342, 12343, 12344, 12345,
12385, 12386, 12387, 12388, 12389, 12390, 12592, 12593, 12594, 12595,
12596, 12597, 12598, 12599, 12600, 12601, 12641, 12642, 12643, 12644,
12645, 12646, 12848, 12849, 12850, 12851, 12852, 12853, 12854, 12855,
12856, 12857, 12897, 12898, 12899, 12900, 12901, 12902, 13104, 13105,
13106, 13107, 13108, 13109, 13110, 13111, 13112, 13113, 13153, 13154,
13155, 13156, 13157, 13158, 13360, 13361, 13362, 13363, 13364, 13365,
13366, 13367, 13368, 13369, 13409, 13410, 13411, 13412, 13413, 13414,
13616, 13617, 13618, 13619, 13620, 13621, 13622, 13623, 13624, 13625,
13665, 13666, 13667, 13668, 13669, 13670, 13872, 13873, 13874, 13875,
13876, 13877, 13878, 13879, 13880, 13881, 13921, 13922, 13923, 13924,
13925, 13926, 14128, 14129, 14130, 14131, 14132, 14133, 14134, 14135,
14136, 14137, 14177, 14178, 14179, 14180, 14181, 14182, 14384, 14385,
14386, 14387, 14388, 14389, 14390, 14391, 14392, 14393, 14433, 14434,
14435, 14436, 14437, 14438, 14640, 14641, 14642, 14643, 14644, 14645,
14646, 14647, 14648, 14649, 14689, 14690, 14691, 14692, 14693, 14694,
24880, 24881, 24882, 24883, 24884, 24885, 24886, 24887, 24888, 24889,
24929, 24930, 24931, 24932, 24933, 24934, 25136, 25137, 25138, 25139,
25140, 25141, 25142, 25143, 25144, 25145, 25185, 25186, 25187, 25188,
25189, 25190, 25392, 25393, 25394, 25395, 25396, 25397, 25398, 25399,
25400, 25401, 25441, 25442, 25443, 25444, 25445, 25446, 25648, 25649,
25650, 25651, 25652, 25653, 25654, 25655, 25656, 25657, 25697, 25698,
25699, 25700, 25701, 25702, 25904, 25905, 25906, 25907, 25908, 25909,
25910, 25911, 25912, 25913, 25953, 25954, 25955, 25956, 25957, 25958,
26160, 26161, 26162, 26163, 26164, 26165, 26166, 26167, 26168, 26169,
26209, 26210, 26211, 26212, 26213, 26214
};
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/14578#discussion_r1236632961
