Rishabh Daim created OAK-12216:
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Summary: clear Segment cache on successful compaction to prevent
W-TinyLFU admission freeze for new-generation segments
Key: OAK-12216
URL: https://issues.apache.org/jira/browse/OAK-12216
Project: Jackrabbit Oak
Issue Type: Task
Reporter: Rishabh Daim
Assignee: Rishabh Daim
*Segment cache (L2)*: Caffeine W-TinyLFU and Guava LRU only learn about
accesses that go through _SegmentCache.getSegment()_. Production traffic often
hits _SegmentId.getSegment()_ and returns the memoized segment from L1 without
touching L2. That made eviction policies act on stale frequency/recency while
the JVM was still reading “hot” segments from L1 — wrong evictions, extra TAR
reads, and skewed benchmarks vs reality.
This was working for Guava, since it was using the LRU eviction policy.
*Fix*: On every L1 hit, call _SegmentCache.recordHit(SegmentId)_, which
performs _cache.getIfPresent(id)_ on the backing L2 so policies see real usage,
plus existing hit accounting.
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