Reference: default JVM heap calculation

[mmahacek]

Update docs to indicate default JVM heap sizing for Elasticsearch, based on code at https://github.com/elastic/elasticsearch/blob/main/distribution/tools/server-cli/src/main/java/org/elasticsearch/server/cli/MachineDependentHeap.java

[Copilot]

Pull Request Overview

This PR updates the Elasticsearch documentation to explain the default JVM heap sizing calculations based on the node's role.

• Adds a new section on default JVM heap sizes.
• Provides distinct sizing guidelines for Master-only, Machine Learning-only, and Data-only nodes.

[elasticsearchmachine]

@mmahacek please enable the option "Allow edits and access to secrets by maintainers" on your PR. For more information, see the documentation.

[elasticsearchmachine]

Pinging @elastic/es-docs (Team:Docs)

[elasticsearchmachine]

Pinging @elastic/es-core-infra (Team:Core/Infra)

[elasticsearchmachine]

Pinging @elastic/core-docs (Team:Docs)

[rjernst]

I'm not sure we want to document these exact percentages/numbers. There's no way to keep them in sync, and the logic is already complex. The point of auto heap sizing is that the user doesn't need to worry about determining how much heap they need, so it's unclear to me what benefit documenting this brings, they shouldn't have to think about it.