RFR: 8339197: GenShen: Adding Generation and Evacuation Information JFR Logging

[Kelvin Nilsen]

On Thu, 29 Aug 2024 00:03:06 GMT, Kelvin Nilsen <kdnilsen at openjdk.org> wrote:

>> Adding `ShenandoahEvacInfo` event and modifying existing logging for Concurrent Reset and Final Roots events to include generation for Generational Shenandoah GC.
>
> src/hotspot/share/gc/shenandoah/heuristics/shenandoahGenerationalHeuristics.cpp line 233:
> 
>> 231:     evacInfo.set_regions_freed(free_regions);
>> 232: 
>> 233:     ShenandoahTracer().report_evacuation_info(&evacInfo);
> 
> After we chatted, I thought of one other detail that would be nice to gather in this evacInfo event: regions to be promoted in place.  Associated with this detail, would be nice to know:
> 1. how many regions
> 2. how much garbage is known to exist within these regions
> 3. how much free memory is known to exist within these regions
> Same for humongous regions promoted in place.
> 
> See humongous_regions_promoted, regular_regions_promoted_in_place, regular_regions_promoted_usage.   You might need to add another bookkeeping variable to count regular_regions_promoted_live, tracking regular_regions_promoted_usage.

for humongous_regions_promoted, less important to distinguish used and free, because that memory is "off limits" to allocators.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/489#discussion_r1735411525