JDK-8075229 : G1 does not always scan CLDG references to the old gen potentially causing problems with eager reclaim
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 9
  • Priority: P3
  • Status: Open
  • Resolution: Unresolved
  • Submitted: 2015-03-16
  • Updated: 2019-02-11
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Relates :  
G1 does not actually scan all roots during a young gc (not all metadata for example). So if we ever have metadata (from metaspace) pointing directly to humongous object in the java heap we're screwed, because eager reclaim may just remove that object.

(This is due to the assumption that old gen data is not moved during young-only gcs)

Add some verification code for this case.
There may not be any kind of metadata that points to a humongous (type) array; this potential problem came up during discussing another issue and was considered worth noting here.

Preliminary ILW: I: high -> crash L: low -> not known to occur W: med -> disable eager reclaim -> P3