RFR: 8330677: Add Per-Compilation memory usage to JFR [v2]

[Thomas Stuefe]

On Fri, 26 Apr 2024 13:03:26 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

> Regarding src/hotspot/share/jfr/metadata/metadata.xml , could you label it 'Arena Peak Usage' or something like this ? I would like to have it more clear that it is the peak usage. 

I already find "Arena Usage" to be too long, to be honest. Longer column labels make the JMC table less readable (ideally, one would have a "label," short and descriptive, and a "description," one being the column label, the other, e.g., a tooltip).

And "peak" is really the only option that makes sense here. If you ask someone what they think "usage" means, they will assume its the largest footprint accumulated during compilation over the time span of the compilation, aka peak.

> Did you check my nullptr check related question ? 

I read through the comments twice and did not find a nullptr related question. Which question?

> Otherwise looks okay to me. It is a bit unfortunate that by default , we have now an 'empty' added field in the JFR Compilation event. But it is what it is; any chances that the compiler mem statistics would be enabled by default in the future, or is this considered too costly ?

One synchronization per compilation. So, not that costly, no. It will be enabled by default in debug builds with https://github.com/openjdk/jdk/pull/18969 since it is implied in memlimit.

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PR Comment: https://git.openjdk.org/jdk/pull/18864#issuecomment-2079729123