RFR: 8355319: Update Manpage for Compact Object Headers (Production)

[Roman Kennke]

On Tue, 3 Jun 2025 07:40:35 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> I put it there because @coleenp said in the JBS issue: "Since UseCompactObjectHeaders seems more useful than some of the other options in the list (except the JFR and NMT options), I think it should go first." - I can move it down, though.
>> 
>> I don't know what you mean by 'This does not explain at all why someone would want to use, or not use, COH' - I explain right there "Enabling this option reduces memory footprint in the Java heap by 4 bytes per object (on average)." Is this not enough? There is no trade-off (loss of performance or any such issue would be considered a bug, tbh).
>
> If the flag is off by default but apparently only has the benefit of reducing footprint, then the reader will wonder why it is off by default. At the moment this reads like we have a flag that will benefit everyone and yet we expect them to turn it on themselves because for some reason we chose not to. If this is really a no-lose situation we can say something like I did in the Release Note JBS issue i.e. something like "this is a good thing to do but still under evaluation so is off by default for now".

Yes this is really a bit odd. 'Still under evaluation' is also weird considering that we just removed the 'experimental' status, which basically saying 'still under evaluation'. Anyway, I will adopt your wording from the release note and move the text down as you suggested.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25491#discussion_r2123054321