RFR: JDK-8310502 : Optimization for j.l.Long.fastUUID() [v8]

[Chen Liang]

On Thu, 22 Jun 2023 07:25:34 GMT, 温绍锦 <duke at openjdk.org> wrote:

>> 温绍锦 has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   fix compile error
>
>> I've tested the benchmarks and the patch and baseline (with extra stable annotation) with a slightly varied version suitable for gradle run:
>> 
>> ```java
>> 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%)
> 
> the performance of this improvement varies among different environments, with a significant improvement on the MacBookPro M1 Max chip (my laptop) and only about 10% improvement on Linux servers (Intel Xeon(Sapphire Rapids) Platinum and Aliyun Yitian 710 arm CPU and Orange Pi 5 Plus).

@wenshao Can you try to just add `@Stable` on `Integer.digits` array and check its benchmark results?

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PR Comment: https://git.openjdk.org/jdk/pull/14578#issuecomment-1602173046