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

[Kelvin Nilsen]

On Wed, 28 Aug 2024 22:43:28 GMT, Satyen Subramaniam <duke 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.

src/hotspot/share/gc/shenandoah/shenandoahEvacInfo.hpp line 2:

> 1: /*
> 2:  * Copyright (c) 2013, 2021, Oracle and/or its affiliates. All rights reserved.

For these files introduced by us, we should put an Amazon copyright notice.  See, for example, shenandoahGenerationallHeuristics.cpp.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/489#discussion_r1735411075
PR Review Comment: https://git.openjdk.org/shenandoah/pull/489#discussion_r1735412641