JDK-21+ response-time gc profile uses generational zgc

[carterkozak]

==COMMIT_MSG==
JDK-21+ response-time gc profile uses generational zgc
==COMMIT_MSG==

[changelog-app]

Generate changelog in changelog/@unreleased

What do the change types mean?

• feature: A new feature of the service.
• improvement: An incremental improvement in the functionality or operation of the service.
• fix: Remedies the incorrect behaviour of a component of the service in a backwards-compatible way.
• break: Has the potential to break consumers of this service's API, inclusive of both Palantir services
  and external consumers of the service's API (e.g. customer-written software or integrations).
• deprecation: Advertises the intention to remove service functionality without any change to the
  operation of the service itself.
• manualTask: Requires the possibility of manual intervention (running a script, eyeballing configuration,
  performing database surgery, ...) at the time of upgrade for it to succeed.
• migration: A fully automatic upgrade migration task with no engineer input required.

Note: only one type should be chosen.

How are new versions calculated?

• ❗The break and manual task changelog types will result in a major release!
• 🐛 The fix changelog type will result in a minor release in most cases, and a patch release version for patch branches. This behaviour is configurable in autorelease.
• ✨ All others will result in a minor version release.

Type

• Feature
• Improvement
• Fix
• Break
• Deprecation
• Manual task
• Migration

Description

JDK-21+ response-time gc profile uses generational zgc

Check the box to generate changelog(s)

• Generate changelog entry

[schlosna]

This seems reasonable to me to get a baseline

[schlosna]

notes for myself:

• NUMA is enabled by default:
  https://github.com/openjdk/jdk/blob/a9679acd5c85b88afe827dc55dbe9a78b00c8918/src/hotspot/share/gc/z/zArguments.cpp#L117-L119
• -XX:+UseDynamicNumberOfGCThreads is enabled by default
• -XX:+ClassUnloadingWithConcurrentMark is not yet supported for ZGC from what I can tell.
• -XX:+UseStringDeduplication is available for ZGC in JDK 18+, could enable separately Enable UseStringDeduplication where feasible #1378

[carterkozak]

based on https://www.chriswhocodes.com/corretto_jdk11_options.html -XX:+ClassUnloadingWithConcurrentMark defaults to true (and has since jdk-11, I haven't verified earlier releases).

The zgc documentation suggested that numa support is enabled by default, but turned off if the jvm detects it's not needed, but that UseNUMA flag overrides this behavior: https://wiki.openjdk.org/display/zgc/Main#Main-EnablingNUMASupport

[svc-autorelease]

Released 7.41.0