8261254: Initialize charset mapping data lazily

[cl4es]

This patch refactor JDK internal charsets to initialize charset mapping data lazily when needed via holder classes. This means both a startup improvement in some cases, and possible throughput improvements for all DoubleByte-based Charsets.

Testing: tier1-3

---

Progress

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Issue

• JDK-8261254: Initialize charset mapping data lazily

Reviewers

• Alan Bateman (@AlanBateman - Reviewer)
• Johannes Kuhn (@DasBrain - Author)
• Naoto Sato (@naotoj - Reviewer)

Download

$ git fetch https://git.openjdk.java.net/jdk pull/2449/head:pull/2449
$ git checkout pull/2449

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[openjdk]

@cl4es The following labels will be automatically applied to this pull request:

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• core-libs
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[cl4es]

Applications calling Charset.availableCharsets() might see a decent startup improvement (125-190ms -> 57-95ms first call overhead).

All DoubleByte-derived charsets can see a throughput improvement on benchmarks thanks to removing DCL initialization checks with a Holder pattern implementation, which allows static data to be declared final and be more amenable to optimizations:

Before:
Benchmark                                   (charsetName)  Mode  Cnt    Score    Error  Units
StringDecode.WithCharset.decodeCharset              MS932  avgt   15  280.072 ± 17.217  ns/op
StringDecode.WithCharset.decodeCharsetName          MS932  avgt   15  289.368 ± 18.174  ns/op

After:
Benchmark                                   (charsetName)  Mode  Cnt    Score    Error  Units
StringDecode.WithCharset.decodeCharset              MS932  avgt   15  254.906 ± 15.095  ns/op
StringDecode.WithCharset.decodeCharsetName          MS932  avgt   15  268.241 ± 15.725  ns/op

[cl4es]

/label remove build

[openjdk]

@cl4es
The build label was successfully removed.

[mlbridge]

Webrevs

• 00: Full (3ffb1ce)

[AlanBateman]

I wouldn't expect enumerating all charsets with Charset::availableCharsets to be too common but moving the data to holder class looks okay. The missing "final" in a few places was an oversight. The replacement of the foreach and method ref in getServicesCatalog with imperative code is disappointment but okay here.

[openjdk]

@cl4es This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8261254: Initialize charset mapping data lazily

Reviewed-by: alanb, jkuhn, naoto

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 11 new commits pushed to the master branch:

• d6d5d9b: 8261231: Windows IME was disabled after DnD operation
• 29a428f: 8261229: MethodData is not correctly initialized with TieredStopAtLevel=3
• 48c932e: 8231286: HTML font size too large with high-DPI scaling and W3C_LENGTH_UNITS
• dbc35f6: 8261094: Open javax/swing/text/html/CSS/4765271/bug4765271.java
• db0ca2b: 8261161: Clean up warnings in hotspot/jtreg/vmTestbase tests
• 2c28e36: 8237352: Update DatagramSocket to add support for joining multicast groups
• d0a8f2f: 8260593: javac can skip a temporary local variable when pattern matching over a local variable
• deb0544: 8261251: Shenandoah: Use object size for full GC humongous compaction
• d45343e: 8260899: ARM32: SyncOnValueBasedClassTest fails with assert(is_valid()) failed: invalid register
• 9d59dec: 8248876: LoadObject with bad base address created for exec file on linux
• ... and 1 more: https://git.openjdk.java.net/jdk/compare/c5ff454481c8ac2c30abd1fb11bd1cec2c95feeb...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[cl4es]

I spotted usage of this in a real application. While they could work around it and remove the usage to gain an even larger startup win I figured I should do those that can't do so a favor, too.

[DasBrain]

Looks good to me.

[naotoj]

Looks good to me. I initially thought of the same impression as Alan's, i.e., enumerating all charsets is not that common (in fact, same applies to Locale, and I once explored usages and it ended all up in test cases), but if real apps are using it, this is the right way to do so.

[cl4es]

Thanks for reviewing!

/integrate

[openjdk]

@cl4es Since your change was applied there have been 12 commits pushed to the master branch:

• 351d788: 8259074: regex benchmarks and tests
• d6d5d9b: 8261231: Windows IME was disabled after DnD operation
• 29a428f: 8261229: MethodData is not correctly initialized with TieredStopAtLevel=3
• 48c932e: 8231286: HTML font size too large with high-DPI scaling and W3C_LENGTH_UNITS
• dbc35f6: 8261094: Open javax/swing/text/html/CSS/4765271/bug4765271.java
• db0ca2b: 8261161: Clean up warnings in hotspot/jtreg/vmTestbase tests
• 2c28e36: 8237352: Update DatagramSocket to add support for joining multicast groups
• d0a8f2f: 8260593: javac can skip a temporary local variable when pattern matching over a local variable
• deb0544: 8261251: Shenandoah: Use object size for full GC humongous compaction
• d45343e: 8260899: ARM32: SyncOnValueBasedClassTest fails with assert(is_valid()) failed: invalid register
• ... and 2 more: https://git.openjdk.java.net/jdk/compare/c5ff454481c8ac2c30abd1fb11bd1cec2c95feeb...master

Your commit was automatically rebased without conflicts.

Pushed as commit 92c6e6d.

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