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comparison src/share/vm/memory/referenceProcessor.hpp @ 3917:eca1193ca245

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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
author ysr
date Wed, 07 Sep 2011 13:55:42 -0700
parents c2bf0120ee5d
children 4dfb2df418f2
comparison
equal deleted inserted replaced
3916:05550041d664 3917:eca1193ca245
50 class AbstractRefProcTaskExecutor; 50 class AbstractRefProcTaskExecutor;
51 class DiscoveredList; 51 class DiscoveredList;
52 52
53 class ReferenceProcessor : public CHeapObj { 53 class ReferenceProcessor : public CHeapObj {
54 protected: 54 protected:
55 // Compatibility with pre-4965777 JDK's
56 static bool _pending_list_uses_discovered_field;
55 MemRegion _span; // (right-open) interval of heap 57 MemRegion _span; // (right-open) interval of heap
56 // subject to wkref discovery 58 // subject to wkref discovery
57 bool _discovering_refs; // true when discovery enabled 59 bool _discovering_refs; // true when discovery enabled
58 bool _discovery_is_atomic; // if discovery is atomic wrt 60 bool _discovery_is_atomic; // if discovery is atomic wrt
59 // other collectors in configuration 61 // other collectors in configuration
109 _always_clear_soft_ref_policy : _default_soft_ref_policy; 111 _always_clear_soft_ref_policy : _default_soft_ref_policy;
110 _current_soft_ref_policy->setup(); // snapshot the policy threshold 112 _current_soft_ref_policy->setup(); // snapshot the policy threshold
111 return _current_soft_ref_policy; 113 return _current_soft_ref_policy;
112 } 114 }
113 115
114 public:
115 // Process references with a certain reachability level. 116 // Process references with a certain reachability level.
116 void process_discovered_reflist(DiscoveredList refs_lists[], 117 void process_discovered_reflist(DiscoveredList refs_lists[],
117 ReferencePolicy* policy, 118 ReferencePolicy* policy,
118 bool clear_referent, 119 bool clear_referent,
119 BoolObjectClosure* is_alive, 120 BoolObjectClosure* is_alive,
295 296
296 // whether discovery is atomic wrt other collectors 297 // whether discovery is atomic wrt other collectors
297 bool discovery_is_atomic() const { return _discovery_is_atomic; } 298 bool discovery_is_atomic() const { return _discovery_is_atomic; }
298 void set_atomic_discovery(bool atomic) { _discovery_is_atomic = atomic; } 299 void set_atomic_discovery(bool atomic) { _discovery_is_atomic = atomic; }
299 300
301 // whether the JDK in which we are embedded is a pre-4965777 JDK,
302 // and thus whether or not it uses the discovered field to chain
303 // the entries in the pending list.
304 static bool pending_list_uses_discovered_field() {
305 return _pending_list_uses_discovered_field;
306 }
307
300 // whether discovery is done by multiple threads same-old-timeously 308 // whether discovery is done by multiple threads same-old-timeously
301 bool discovery_is_mt() const { return _discovery_is_mt; } 309 bool discovery_is_mt() const { return _discovery_is_mt; }
302 void set_mt_discovery(bool mt) { _discovery_is_mt = mt; } 310 void set_mt_discovery(bool mt) { _discovery_is_mt = mt; }
303 311
304 // Whether we are in a phase when _processing_ is MT. 312 // Whether we are in a phase when _processing_ is MT.