[Back port] 8310929: Optimization for integer/long toString

[wenshao]

原来的实现需要两次查表Integer.DigitTens/DigitOnes，新的实现只需要查表一次DecimalDigits#DIGITS，组合Unsafe.putShortUnaligned一次put两个数字，可以提升性能。

[kuaiwei]

原来的实现需要两次查表Integer.DigitTens/DigitOnes，新的实现只需要查表一次DecimalDigits#DIGITS，组合Unsafe.putShortUnaligned一次put两个数字，可以提升性能。

能提供一个性能测试案例吗？

[wenshao]

已经补上，dragoonwell11下怎么跑性能测试？

bash configure --with-jmh=build/jmh/jars

configure: error: unrecognized options: --with-jmh
configure exiting with result code 1

[wenshao]

openjdk/jdk#14699

The performance test results of the latest version (PR Update 20 c0f42a7c ) are as follows:

• baseline https://github.com/wenshao/jdk/tree/baseline_test

1. aliyun_ecs_c8i.xlarge

• cpu : intel xeon sapphire rapids (x64)

-Benchmark               (size)  Mode  Cnt  Score   Error  Units (baseline)
-Integers.toStringBig       500  avgt   15  6.800 ? 0.022  us/op
-Integers.toStringSmall     500  avgt   15  4.792 ? 0.021  us/op
-Integers.toStringTiny      500  avgt   15  3.757 ? 0.081  us/op

+Benchmark               (size)  Mode  Cnt  Score   Error  Units (PR Update 20 c0f42a7c)
+Integers.toStringBig       500  avgt   15  5.894 ? 0.046  us/op (+15.37%)
+Integers.toStringSmall     500  avgt   15  4.027 ? 0.012  us/op (+18.99%)
+Integers.toStringTiny      500  avgt   15  3.491 ? 0.090  us/op (+7.61%)

-Benchmark            (size)  Mode  Cnt  Score   Error  Units (baseline)
-Longs.toStringBig       500  avgt   15  9.213 ? 0.019  us/op
-Longs.toStringSmall     500  avgt   15  4.550 ? 0.016  us/op

+Benchmark            (size)  Mode  Cnt  Score   Error  Units (PR Update 20 c0f42a7c)
+Longs.toStringBig       500  avgt   15  7.507 ? 0.011  us/op (+22.72%)
+Longs.toStringSmall     500  avgt   15  3.967 ? 0.021  us/op (+14.69%)

-Benchmark                            Mode  Cnt   Score   Error  Units (baseline)
-StringBuilders.toStringCharWithInt8  avgt   15  89.187 ? 0.236  ns/op

+Benchmark                            Mode  Cnt   Score   Error  Units (PR Update 20 c0f42a7c)
+StringBuilders.toStringCharWithInt8  avgt   15  36.125 ? 0.309  ns/op (+146.88%)

2. aliyun_ecs_c8y.xlarge

• cpu : aliyun yitian 710 (aarch64)

-Benchmark               (size)  Mode  Cnt   Score   Error  Units (baseline)
-Integers.toStringBig       500  avgt   15  11.649 ? 0.011  us/op
-Integers.toStringSmall     500  avgt   15   6.985 ? 0.018  us/op
-Integers.toStringTiny      500  avgt   15   5.972 ? 0.013  us/op

+Benchmark               (size)  Mode  Cnt  Score   Error  Units (PR Update 20 c0f42a7c)
+Integers.toStringBig       500  avgt   15  8.957 ? 0.026  us/op (+30.05%)
+Integers.toStringSmall     500  avgt   15  6.136 ? 0.018  us/op (+13.83%)
+Integers.toStringTiny      500  avgt   15  5.753 ? 0.026  us/op (+3.80%)

-Benchmark            (size)  Mode  Cnt   Score   Error  Units (baseline)
-Longs.toStringBig       500  avgt   15  14.568 ? 0.021  us/op
-Longs.toStringSmall     500  avgt   15   7.250 ? 0.023  us/op

+Benchmark            (size)  Mode  Cnt   Score   Error  Units (PR Update 20 c0f42a7c)
+Longs.toStringBig       500  avgt   15  13.401 ? 0.012  us/op (+8.70%)
+Longs.toStringSmall     500  avgt   15   6.031 ? 0.018  us/op (+20.21%)

-Benchmark                            Mode  Cnt   Score   Error  Units (baseline)
-StringBuilders.toStringCharWithInt8  avgt   15  52.484 ? 0.534  ns/op

+Benchmark                            Mode  Cnt   Score   Error  Units (PR Update 20 c0f42a7c)
+StringBuilders.toStringCharWithInt8  avgt   15  40.410 ? 0.348  ns/op (+29.87%)

3. MacBookPro M1 Pro

-Benchmark               (size)  Mode  Cnt   Score   Error  Units (baseline)
-Integers.toStringBig       500  avgt   15  18.483 ± 2.771  us/op
-Integers.toStringSmall     500  avgt   15   4.435 ± 0.067  us/op
-Integers.toStringTiny      500  avgt   15   2.382 ± 0.063  us/op

+Benchmark               (size)  Mode  Cnt  Score   Error  Units (PR Update 20 c0f42a7c)
+Integers.toStringBig       500  avgt   15  5.392 ? 0.016  us/op (+242.78%)
+Integers.toStringSmall     500  avgt   15  3.201 ? 0.024  us/op (+38.55%)
+Integers.toStringTiny      500  avgt   15  2.141 ? 0.021  us/op (+11.25%)

-Benchmark            (size)  Mode  Cnt  Score   Error  Units (baseline)
-Longs.toStringBig       500  avgt   15  8.336 ± 0.025  us/op
-Longs.toStringSmall     500  avgt   15  4.389 ± 0.018  us/op

+Benchmark            (size)  Mode  Cnt  Score   Error  Units (PR Update 20 c0f42a7c)
+Longs.toStringBig       500  avgt   15  7.706 ? 0.015  us/op (+8.17%)
+Longs.toStringSmall     500  avgt   15  3.094 ? 0.021  us/op (+41.85%)

-Benchmark                            Mode  Cnt    Score    Error  Units (baseline)
-StringBuilders.toStringCharWithInt8  avgt   15  124.316 ± 61.017  ns/op

+Benchmark                            Mode  Cnt   Score    Error  Units (PR Update 20 c0f42a7c)
+StringBuilders.toStringCharWithInt8  avgt   15  44.497 ? 29.741  ns/op (+179.38%)

[JoshuaZhuwj]

Hi wenshao,
I have three minor comments.

1. It would be better to submit your changes as the original commits. I mean separating these changes into two commits (JDK-8310929 and JDK-8315970). In this way, changes will be easier to track and manage.
2. The git commits message should be "[Backport] 8310929: Optimization for Integer.toString" instead of "back port from openjdk, optimization for integer/long toString" otherwise your commits will be blocked by Dragonwell CI tests due to improper commit title.
3. Currently there exist two other issues (JDK-8316582 and JDK-8317329) filed against 8310929. Do we need to incorporate these new changes?

[wenshao]

This BackPort PR merges three PRs (8317329, 8310929, 8317329)

[wenshao]

这个PR合并了原来三个PR：

1. 8310929: Optimization for Integer.toString openjdk/jdk#14699 我提交的第一个版本，这个版本性能比较好，但因为使用了ByteArrayLittleEndian，会影响JVM启动性能。
2. 8315970: Big-endian issues after JDK-8310929 openjdk/jdk#15652 我提交的第二个版本，修复StringUTF16 BigEndian机器下的问题
3. 8316582: Minor startup regression in 22-b15 due JDK-8310929 openjdk/jdk#15836 cl4es修改去掉ByteArrayLittleEndian，但性能会下降（比PR 14699差，但比之前好）。

当前的提交合并了前2个，但和第3个PR 15836的修复方法不同，使用Unsafe代替ByteArrayLittleEndian。性能没有回退，并且不会导致JVM启动变慢。

[wenshao]

JDK 11没有ByteArrayLittleEndian，只能合成一个commit来提交了