What Does This Do

This PR adds an experimental flag profiling.experimental.ddprof.force_jmethodID to enable ddprof feature that aims to reduce pre-loading jmethodIDs for all classes.

The flag is off (true) by default to preserve current behavior.

Motivation

Preloading all jmethodIDs is proved to be a memory footprint issue. In an extreme case, it consumed 9GB native memory.

ddprof is experimenting a way to lessen dependency on jmethod IDs: none lambda and hidden classes that are loaded by system class loaders (bootstrap, platform and application class loaders), never unloaded. Instead of storing jmethod IDs for the methods of the classes, ddprof stores raw method pointers and resolves at dumping time. Therefore, ddprof does not preload jmethod IDs of none-lambda/hidden classes from those class loaders.

Additional Notes

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Jira ticket: [PROJ-IDENT]