RFR: JDK-8310502 : Optimization for j.l.Long.fastUUID() [v7]

[Chen Liang]

On Thu, 22 Jun 2023 00:13:06 GMT, 温绍锦 <duke at 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:
> 
>   move HEX256 to LongCache

I've tested the benchmarks and the patch and baseline (with extra stable annotation) with a slightly varied version suitable for gradle run:


package com.alibaba.openjdk;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Fork;
import org.openjdk.jmh.annotations.Measurement;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.OutputTimeUnit;
import org.openjdk.jmh.annotations.Warmup;
import org.openjdk.jmh.infra.Blackhole;

import java.util.UUID;
import java.util.concurrent.TimeUnit;

@BenchmarkMode(Mode.Throughput)
@OutputTimeUnit(TimeUnit.MILLISECONDS)
@Warmup(iterations = 3, time = 10)
@Measurement(iterations = 6, time = 5)
@Fork(1)
public class UUIDUtilsBenchmark {
    public static UUID uuid = UUID.randomUUID();

    @Benchmark
    public void jdk(Blackhole bh) {
        bh.consume(uuid.toString());
    }

    @Benchmark
    public void fast(Blackhole bh) {
        bh.consume(UUIDUtils.fastUUID(uuid));
    }
}

The throughput varies a lot between iterations somehow; the patch and baseline with stable has no significant difference (i.e. within the error range, about 10%)

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PR Comment: https://git.openjdk.org/jdk/pull/14578#issuecomment-1601953110