RFR: 8318026: jcmd should provide access to low-level JVM debug information

[Kevin Walls]

On Sun, 4 Feb 2024 23:07:27 GMT, David Holmes <dholmes at openjdk.org> wrote:

> > not including them in the jcmd help output, is to remind us they are not general customer-facing tools.
> 
> Then who are they for? and do they really belong in the `jcmd` tool, or is that just convenient?
> 
> Without help information who will know what can be done with this tool?

I want to suggest that these commands are not for everybody.  But people investigating bugs in detail, including JVM crashes, might find these appealing, and should find the jcmd interface convenient. (It is convenient for the user, and also convenient to implement.)

Proposing not having them in the standard jcmd help: I don't think most users should be attaching debuggers to their production JVMs, and I don't think most users should be doing these debug operations via jcmd on the same JVM.   But we have a variety of expert users who want certain information.

But I do think we should find other ways of documenting this, which might include our existing Troubleshooting Guide, but  might well be something else.

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PR Comment: https://git.openjdk.org/jdk/pull/17655#issuecomment-1926559303