8347256: Epsilon: Demote heap size and AlwaysPreTouch warnings to info level

[shipilev]

For Epsilon, we have added log_warning messages when heap size and AlwaysPreTouch configuration is not great with JDK-8232051. Unfortunately, this means we print this warning all the time, even though users might not actually run into problems there, or when users tried to implement these suggestions and still decided to run against them.

I think we want to emit the suggestions in the normal GC log instead, so they are not printed all the time. Additionally, I moved the printing at the end of init logger, so it does not come in the middle of gc,init block.

Output before:

$ java -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC Hello.java 
[0.008s][warning][gc,init] Consider setting -Xms equal to -Xmx to avoid resizing hiccups
[0.008s][warning][gc,init] Consider enabling -XX:+AlwaysPreTouch to avoid memory commit hiccups
Hello!

$ java -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC -Xlog:gc Hello.java 
[0.008s][info][gc] Using Epsilon
[0.008s][warning][gc,init] Consider setting -Xms equal to -Xmx to avoid resizing hiccups
[0.008s][warning][gc,init] Consider enabling -XX:+AlwaysPreTouch to avoid memory commit hiccups
Hello!
[0.757s][info   ][gc     ] Heap: 1024M reserved, 129M (12.60%) committed, 23906K (2.28%) used

Output after:

$ java -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC Hello.java 
Hello!

$ java -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC -Xlog:gc Hello.java 
[0.009s][info][gc] Using Epsilon
[0.009s][info][gc] Consider setting -Xms equal to -Xmx to avoid resizing hiccups
[0.009s][info][gc] Consider enabling -XX:+AlwaysPreTouch to avoid memory commit hiccups
Hello!
[0.753s][info][gc] Heap: 1024M reserved, 129M (12.60%) committed, 23908K (2.28%) used

---

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Issue

• JDK-8347256: Epsilon: Demote heap size and AlwaysPreTouch warnings to info level (Enhancement - P4)

Reviewers

• Thomas Schatzl (@tschatzl - Reviewer)
• Paul Hohensee (@phohensee - Reviewer)

Reviewing

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[bridgekeeper]

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[openjdk]

@shipilev 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:

8347256: Epsilon: Demote heap size and AlwaysPreTouch warnings to info level

Reviewed-by: tschatzl, phh

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 44 new commits pushed to the master branch:

• 931914a: 8340631: assert(reserved_rgn->contain_region(base_addr, size)) failed: Reserved CDS region should contain this mapping region
• 665c39c: 8347375: Extra

  tag in robot specification

• b335ea9: 8347122: Add missing @serial tags to module java.desktop
• df28cec: 8345144: Robot does not specify all causes of IllegalThreadStateException
• 9f3c5f9: 8344907: NullPointerException in Win32ShellFolder2.getSystemIcon when "icon" is null
• 22f70a7: 8321413: IllegalArgumentException: Code length outside the allowed range while creating a jlink image
• 3bfa952: 8283795: Add TLSv1.3 and CNSA 1.0 algorithms to implementation requirements
• 1ef77cd: 8347171: (dc) java/nio/channels/DatagramChannel/InterruptibleOrNot.java fails with virtual thread factory
• 72f1114: 8346705: SNI not sent with Java 22+ using java.net.http.HttpClient.Builder#sslParameters
• cb9a98b: 8347141: Several javac tests compile with an unnecessary -Xlint:-path flag
• ... and 34 more: https://git.openjdk.org/jdk/compare/98724219a87c1cdb1e7942ade1a4d49b201a0a94...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.

[openjdk]

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• hotspot-gc

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[mlbridge]

Webrevs

• 00: Full (061917bd)

[tschatzl]

lgtm.

[shipilev]

Thank you @tschatzl! I think I need another Review to merge this. Thanks!

[shipilev]

Thanks!

/integrate

[openjdk]

Going to push as commit 1a0fe49.
Since your change was applied there have been 49 commits pushed to the master branch:

• 8b07617: 8347345: Remove redundant test policy file from ModelMBeanInfoSupport directory
• f6492aa: 8347279: Problemlist TestEvilSyncBug.java#generational
• 0210a63: 8347379: Problem list failed tests after JDK-8321413
• a9351df: 8346787: Fix two C2 IR matching tests for RISC-V
• 89ee1a5: 8343978: Update the default value of CodeEntryAlignment for Ampere-1A and 1B
• 931914a: 8340631: assert(reserved_rgn->contain_region(base_addr, size)) failed: Reserved CDS region should contain this mapping region
• 665c39c: 8347375: Extra

  tag in robot specification

• b335ea9: 8347122: Add missing @serial tags to module java.desktop
• df28cec: 8345144: Robot does not specify all causes of IllegalThreadStateException
• 9f3c5f9: 8344907: NullPointerException in Win32ShellFolder2.getSystemIcon when "icon" is null
• ... and 39 more: https://git.openjdk.org/jdk/compare/98724219a87c1cdb1e7942ade1a4d49b201a0a94...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit 1a0fe49.

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