8292847: Zero: Allow ergonomics to select the GC

[shipilev]

Zero is currently defaulting to Serial GC on all machines, due to the fact that NeverActAsServerClassMachine is true. It is set in compiler_globals.pd under #if !defined(COMPILER1) && !defined(COMPILER2) && !INCLUDE_JVMCI. NeverActAsServerClassMachine mostly affects compiler ergonomics, which Zero does not need, but it also affects the selection of default GC.

After JDK-8256497, we can let Zero default to G1. After JDK-8292329, it would help Zero to use the CDS shared heap.

Additional testing:

• Linux x86_64 Zero fastdebug, make bootcycle-images
• Linux x86_64 Zero fastdebug, tier1 tests (many known failures)

---

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Issue

• JDK-8292847: Zero: Allow ergonomics to select the GC

Reviewers

• Thomas Schatzl (@tschatzl - Reviewer)
• Thomas Stuefe (@tstuefe - Reviewer)

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[shipilev]

Anyone? :)

[openjdk]

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

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

8292847: Zero: Allow ergonomics to select the GC

Reviewed-by: tschatzl, stuefe

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At the time when this comment was updated there had been 391 new commits pushed to the master branch:

• 5285035: 8294075: gtest/AsyncLogGtest crashes with SEGV
• 696287d: 8294037: Using alias template to unify hashtables in AsyncLogWriter
• 48cc156: 8293331: Refactor FileDispatcherImpl into operating system-specific components
• f751e60: 8294197: Zero: JVM_handle_linux_signal should not assume deopt NOPs
• 4a6060b: 8294190: Incorrect check messages in SharedRuntime::generate_uncommon_trap_blob
• 0be2b2c: 8292756: java.lang.AssertionError at at jdk.compiler/com.sun.tools.javac.code.Scope$ScopeImpl.leave(Scope.java:386)
• bc2af47: 8254711: Add java.security.Provider.getService JFR Event
• d781ab0: 8294003: Don't handle si_addr == 0 && si_code == SI_KERNEL SIGSEGVs
• a216960: 8294087: RISC-V: RVC: Fix a potential alignment issue and add more alignment assertions for the patchable calls/nops
• 3fa6778: 8292296: Use multiple threads to process ParallelGC deferred updates
• ... and 381 more: https://git.openjdk.org/jdk/compare/79597f1ea6844f374beeeba219719cd9d5fe7d03...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.

[tstuefe]

This seems fine.

Just wondered whether one could change the definition in compiler_globals_pd.hpp in the #if !defined(COMPILER1) && !defined(COMPILER2) && !INCLUDE_JVMCI section to the same effect.

[shipilev]

Just wondered whether one could change the definition in compiler_globals_pd.hpp in the #if !defined(COMPILER1) && !defined(COMPILER2) && !INCLUDE_JVMCI section to the same effect.

I prefer not to mess with these, because they are part of server/client/etc VM selection ergonomics.

[shipilev]

/integrate

[openjdk]

Going to push as commit 3b476a1.
Since your change was applied there have been 517 commits pushed to the master branch:

• 16047e8: 8292780: misc tests failed "assert(false) failed: graph should be schedulable"
• bf39b18: 8288302: Shenandoah: SIGSEGV in vm maybe related to jit compiling xerces
• f957ce9: 8294564: IGV: IllegalArgumentException for "Difference to current graph"
• ae79af2: 8294740: Add cgroups keyword to TestDockerBasic.java
• 07ed68e: 8288907: serviceability/jvmti/vthread/SuspendResume1/SuspendResume1.java fails with -XX:TieredStopAtLevel=2,3
• 090cdfc: 8294726: Update URLs in minefield tests
• ed40d88: 8276849: Refresh the window icon on graphics configuration changes
• 081691a: 8294593: Check the size of the target on invocations of BigInteger::isProbablePrime
• a4f2078: 8294437: java/nio/channels/FileChannel tests slow on Windows
• c6e3daa: 8242115: C2 SATB barriers are not safepoint-safe
• ... and 507 more: https://git.openjdk.org/jdk/compare/79597f1ea6844f374beeeba219719cd9d5fe7d03...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit 3b476a1.

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