GC Phase Times getter for the Parallel GC

[AlinaHovakimyan]

Parsing seems to be done but getter is missing from GenerationalForwardReference.

[dsgrieve]

The forward references are sort of like builder patterns and are turned into events. For example, here's some code from G1CGForwardReference:

private G1Young buildYoung(G1Young collection) {
    fillInMemoryPoolStats(collection);
    fillInRegionSummary(collection);
    fillInMetaspaceStats(collection);
    fillInPhases(collection);
    if (toSpaceExhausted) collection.toSpaceExhausted();
    if (hasReferenceGCSummary())
        collection.add(generateReferenceGCSummary());
    collection.addCPUSummary(getCPUSummary());
    return collection;
}

There are similar methods for other event types.

The reason we've done this is that events are immutable. To create the immutable event, we collect the data before building the event. This is the purpose of the forward reference. Once the end of the event is parsed, we build the event. This is why there are no getters on the forward references.

If one wants to include more data in the event, no problem. One just need to make sure the data is collected and pushed to the forward reference and then added to the event. Note that events are part of the public API so adding new API is okay but existing methods should not be modified.

This comment applies to the other issues filed regarding missing getters.

[brunoborges]

/relevance-check

[github-actions]

Relevance Assessment: Still Relevant

• Summary: The issue accurately describes a gap that still exists in the codebase — Parallel GC phase times are collected by the parser but never exposed through events or any accessible API.

• Evidence:

  • The phases map in GenerationalForwardReference (line 44) is a ConcurrentHashMap(String, Double) that stores phase data.
  • addFullGCPhase() (line 107) is the only method that interacts with phases — it writes to the map but no getter exists to read from it.
  • In UnifiedGenerationalParser, addFullGCPhase() is called in two places (lines 409 and 423), so parsing does collect the data.
  • However, fillOutFullGC() (line 553–558) — which builds FullGC events from the forward reference — never reads the phases map. The phase data is silently discarded.
  • A comment at line 343–345 explicitly acknowledges this: "the problem is all of the phases have been reported on, this data is floating outside events in our current model — ignore for now…"
  • By contrast, the sibling remarkPhases map has proper getters (getPhaseDuration(), remarkPhases()), and G1's G1GCForwardReference has a full fillInPhases() method that propagates phase data into events.
  • No commits or PRs have addressed this gap since the issue was filed.

• Recommendation: ✅ Keep open — The issue is valid and actionable. Parallel GC phase time data is parsed and stored but never propagated into events, making it inaccessible to consumers. Fixing this would require: (1) adding a getter/stream method for the phases map on GenerationalForwardReference, and (2) updating fillOutFullGC() to populate phase data on the FullGC event (likely requiring a corresponding API addition on the event class, similar to G1's addPhaseDuration).

Generated by Relevance Check Agent for issue #377