4965777: GC changes to support use of discovered field for pending references
Summary: If and when the reference handler thread is able to use the discovered field to link reference objects in its pending list, so will GC. In that case, GC will scan through this field once a reference object has been placed on the pending list, but not scan that field before that stage, as the field is used by the concurrent GC thread to link discovered objects. When ReferenceHandleR thread does not use the discovered field for the purpose of linking the elements in the pending list, as would be the case in older JDKs, the JVM will fall back to the old behaviour of using the next field for that purpose.
Reviewed-by: jcoomes, mchung, stefank
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#ifndef SHARE_VM_MEMORY_COMPACTPERMGEN_HPP
#define SHARE_VM_MEMORY_COMPACTPERMGEN_HPP
#include "memory/generation.hpp"
#include "memory/permGen.hpp"
class ContigPermSpace;
class CardTableModRefBS;
class CompactingPermGenGen;
class PermanentGenerationSpec;
// A PermGen implemented with a contiguous space.
class CompactingPermGen: public PermGen {
friend class VMStructs;
protected:
// The "generation" view.
OneContigSpaceCardGeneration* _gen;
public:
CompactingPermGen(ReservedSpace rs, ReservedSpace shared_rs,
size_t initial_byte_size, GenRemSet* remset,
PermanentGenerationSpec* perm_spec);
HeapWord* mem_allocate(size_t size);
void compute_new_size();
Generation* as_gen() const { return _gen; }
};
#endif // SHARE_VM_MEMORY_COMPACTPERMGEN_HPP