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_GENMARKSWEEP_HPP
#define SHARE_VM_MEMORY_GENMARKSWEEP_HPP
#include "gc_implementation/shared/markSweep.hpp"
class GenMarkSweep : public MarkSweep {
friend class VM_MarkSweep;
friend class G1MarkSweep;
public:
static void invoke_at_safepoint(int level, ReferenceProcessor* rp,
bool clear_all_softrefs);
private:
// Mark live objects
static void mark_sweep_phase1(int level, bool clear_all_softrefs);
// Calculate new addresses
static void mark_sweep_phase2();
// Update pointers
static void mark_sweep_phase3(int level);
// Move objects to new positions
static void mark_sweep_phase4();
// Temporary data structures for traversal and storing/restoring marks
static void allocate_stacks();
static void deallocate_stacks();
};
#endif // SHARE_VM_MEMORY_GENMARKSWEEP_HPP