8330802: Desugar switch in Locale::createLocale #18882

cl4es · 2024-04-22T10:34:29Z

This switch expression in Locale::createLocale is causing a somewhat large startup regression on my local system. Desugaring to if statements seem like the right thing to do while we investigate ways to further reduce overheads in SwitchBootstraps.

These numbers are against a baseline which include #18865 and #18845, which already improved the situation:

Name             Cnt          Base         Error           Test         Error         Unit  Change
Perfstartup-Noop  20        40,500 ±       1,942         31,000 ±       2,673        ms/op   1,31x (p = 0,000*)
  :.cycles           143254849,000 ± 3398321,355  102205427,650 ± 2192784,853       cycles   0,71x (p = 0,000*)
  :.instructions     307138448,850 ± 2095834,550  219415574,800 ±  376992,067 instructions   0,71x (p = 0,000*)
  :.taskclock               39,500 ±       1,942         22,500 ±       3,858           ms   0,57x (p = 0,000*)
  * = significant

Comparing to a baseline without those recent improvements the overhead was almost the double:

Name             Cnt          Base         Error           Test         Error         Unit  Change
Perfstartup-Noop  20        50,000 ±       0,000         31,000 ±       2,673        ms/op   1,61x (p = 0,000*)
  :.cycles           187047932,000 ± 3330400,381  102205427,650 ± 2192784,853       cycles   0,55x (p = 0,000*)
  :.instructions     408219060,350 ± 4031173,140  219415574,800 ±  376992,067 instructions   0,54x (p = 0,000*)
  :.taskclock               53,500 ±       4,249         22,500 ±       3,858           ms   0,42x (p = 0,000*)
  * = significant

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Issue

JDK-8330802: Desugar switch in Locale::createLocale (Enhancement - P4)

Reviewers

Alan Bateman (@AlanBateman - Reviewer) ⚠️ Review applies to c4f5ee7c
Chen Liang (@liach - Author)
Roger Riggs (@RogerRiggs - Reviewer)
Naoto Sato (@naotoj - Reviewer)
Mandy Chung (@mlchung - Reviewer)

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bridgekeeper · 2024-04-22T10:34:57Z

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openjdk · 2024-04-22T10:35:23Z

@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:

8330802: Desugar switch in Locale::createLocale

Reviewed-by: alanb, liach, rriggs, naoto, mchung

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 9 new commits pushed to the master branch:

0b9350e: 8322992: Javac fails with StackOverflowError when compiling deeply nested synchronized blocks
20be5e0: 8314846: Do not store Klass::_secondary_super_cache in CDS archive
7e421ce: 8330585: Refactor/rename forwardee handling
3e65d90: 8330820: Remove remnants of operator_new.cpp in build system
936a47d: 8330607: Deprecate -XX:+UseEmptySlotsInSupers
ee7b2e9: 8330051: Small ObjectMonitor spinning code cleanups
3e185c7: 8330154: Serial: Remove TenuredSpace::update_for_block
f889797: 8330463: Rename invalidate() to write_region() in ModRefBarrierSet
c4f5c51: 8330576: ZYoungCompactionLimit should have range check

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openjdk · 2024-04-22T10:36:19Z

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

core-libs
i18n

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing lists. If you would like to change these labels, use the /label pull request command.

mlbridge · 2024-04-22T10:39:18Z

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01: Full - Incremental (0afa47ba)
00: Full (c4f5ee7c)

liach · 2024-04-22T13:05:47Z

src/java.base/share/classes/java/util/Locale.java

+        } else if (key instanceof LocaleKey lk) {
+            return new Locale(lk.base, lk.exts);
+        } else {
+            throw new InternalError("should not happen");


The default branch was required in the switch. Can we simply drop this branch and have a ClassCastException to LocalKey instead?

You mean like so:

private static Locale createLocale(Object key) { if (key instanceof BaseLocale base) { return new Locale(base, null); } LocaleKey lk = (LocaleKey)key; return new Locale(lk.base, lk.exts); }

?

I think this should be alright. The type of the "impossibly" thrown exception would differ.

Yes, just like how jli handles the Class/MethodType union type arguments.

RogerRiggs

LGTM, the CCE is the equivalent of should-not-reach-here.

naotoj

Thanks for the fix, Claes!

mlchung

Looks good.

cl4es · 2024-04-23T07:59:01Z

Thanks for reviewing, everyone!

/integrate

openjdk · 2024-04-23T08:00:08Z

Going to push as commit daa5a4b.
Since your change was applied there have been 16 commits pushed to the master branch:

8961077: 8309259: Reduce calls to MethodHandles.lookup() in jdk.internal.net.http.Stream
574ba14: 8330862: GCBarrierIRExample fails when a different GC is selected via the command line
550a138: 8306928: Duplicate variable assignement in jdk.internal.net.http.AuthenticationFilter#getCredentials
57ebd04: 8330153: C2: dump barrier information for all Mach nodes
58ad399: 8330821: Rename UnsafeCopyMemory
1d52234: 8330704: Clean up non-standard use of /** comments in some langtools tests
83c74d7: 8329717: Missing @since tags in elements in DocumentationTool and Taglet
0b9350e: 8322992: Javac fails with StackOverflowError when compiling deeply nested synchronized blocks
20be5e0: 8314846: Do not store Klass::_secondary_super_cache in CDS archive
7e421ce: 8330585: Refactor/rename forwardee handling
... and 6 more: https://git.openjdk.org/jdk/compare/70acade9f1bd0c7bba25abad0f0d8199715d66d0...master

Your commit was automatically rebased without conflicts.

openjdk · 2024-04-23T08:00:15Z

@cl4es Pushed as commit daa5a4b.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

cl4es added 2 commits April 22, 2024 10:41

Desugar switch in Locale::createLocale

56ebc28

Merge branch 'master' into deswitch

c4f5ee7

openjdk bot added the rfr Pull request is ready for review label Apr 22, 2024

openjdk bot added core-libs core-libs-dev@openjdk.org i18n i18n-dev@openjdk.org labels Apr 22, 2024

AlanBateman approved these changes Apr 22, 2024

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openjdk bot added the ready Pull request is ready to be integrated label Apr 22, 2024

liach reviewed Apr 22, 2024

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Remove InternalError in favor of CCE

0afa47b

liach approved these changes Apr 22, 2024

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RogerRiggs approved these changes Apr 22, 2024

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naotoj approved these changes Apr 22, 2024

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mlchung approved these changes Apr 22, 2024

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openjdk bot added the integrated Pull request has been integrated label Apr 23, 2024

openjdk bot closed this Apr 23, 2024

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Apr 23, 2024

cl4es deleted the deswitch branch April 23, 2024 08:06

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8330802: Desugar switch in Locale::createLocale #18882

8330802: Desugar switch in Locale::createLocale #18882

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8330802: Desugar switch in Locale::createLocale #18882

8330802: Desugar switch in Locale::createLocale #18882

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