--- old/src/share/vm/memory/referenceProcessor.hpp 2011-09-14 14:54:33.491088488 -0700 +++ new/src/share/vm/memory/referenceProcessor.hpp 2011-09-14 14:54:32.950320210 -0700 @@ -48,18 +48,175 @@ // forward references class ReferencePolicy; class AbstractRefProcTaskExecutor; -class DiscoveredList; + +// List of discovered references. +class DiscoveredList { +public: + DiscoveredList() : _len(0), _compressed_head(0), _oop_head(NULL) { } + oop head() const { + return UseCompressedOops ? oopDesc::decode_heap_oop(_compressed_head) : + _oop_head; + } + HeapWord* adr_head() { + return UseCompressedOops ? (HeapWord*)&_compressed_head : + (HeapWord*)&_oop_head; + } + void set_head(oop o) { + if (UseCompressedOops) { + // Must compress the head ptr. + _compressed_head = oopDesc::encode_heap_oop(o); + } else { + _oop_head = o; + } + } + bool is_empty() const { return head() == NULL; } + size_t length() { return _len; } + void set_length(size_t len) { _len = len; } + void inc_length(size_t inc) { _len += inc; assert(_len > 0, "Error"); } + void dec_length(size_t dec) { _len -= dec; } +private: + // Set value depending on UseCompressedOops. This could be a template class + // but then we have to fix all the instantiations and declarations that use this class. + oop _oop_head; + narrowOop _compressed_head; + size_t _len; +}; + +// Iterator for the list of discovered references. +class DiscoveredListIterator { +private: + DiscoveredList& _refs_list; + HeapWord* _prev_next; + oop _prev; + oop _ref; + HeapWord* _discovered_addr; + oop _next; + HeapWord* _referent_addr; + oop _referent; + OopClosure* _keep_alive; + BoolObjectClosure* _is_alive; + + DEBUG_ONLY( + oop _first_seen; // cyclic linked list check + ) + + NOT_PRODUCT( + size_t _processed; + size_t _removed; + ) + +public: + inline DiscoveredListIterator(DiscoveredList& refs_list, + OopClosure* keep_alive, + BoolObjectClosure* is_alive): + _refs_list(refs_list), + _prev_next(refs_list.adr_head()), + _prev(NULL), + _ref(refs_list.head()), +#ifdef ASSERT + _first_seen(refs_list.head()), +#endif +#ifndef PRODUCT + _processed(0), + _removed(0), +#endif + _next(NULL), + _keep_alive(keep_alive), + _is_alive(is_alive) +{ } + + // End Of List. + inline bool has_next() const { return _ref != NULL; } + + // Get oop to the Reference object. + inline oop obj() const { return _ref; } + + // Get oop to the referent object. + inline oop referent() const { return _referent; } + + // Returns true if referent is alive. + inline bool is_referent_alive() const { + return _is_alive->do_object_b(_referent); + } + + // Loads data for the current reference. + // The "allow_null_referent" argument tells us to allow for the possibility + // of a NULL referent in the discovered Reference object. This typically + // happens in the case of concurrent collectors that may have done the + // discovery concurrently, or interleaved, with mutator execution. + void load_ptrs(DEBUG_ONLY(bool allow_null_referent)); + + // Move to the next discovered reference. + inline void next() { + _prev_next = _discovered_addr; + _prev = _ref; + move_to_next(); + } + + // Remove the current reference from the list + void remove(); + + // Make the Reference object active again. + void make_active(); + + // Make the referent alive. + inline void make_referent_alive() { + if (UseCompressedOops) { + _keep_alive->do_oop((narrowOop*)_referent_addr); + } else { + _keep_alive->do_oop((oop*)_referent_addr); + } + } + + // Update the discovered field. + inline void update_discovered() { + // First _prev_next ref actually points into DiscoveredList (gross). + if (UseCompressedOops) { + if (!oopDesc::is_null(*(narrowOop*)_prev_next)) { + _keep_alive->do_oop((narrowOop*)_prev_next); + } + } else { + if (!oopDesc::is_null(*(oop*)_prev_next)) { + _keep_alive->do_oop((oop*)_prev_next); + } + } + } + + // NULL out referent pointer. + void clear_referent(); + + // Statistics + NOT_PRODUCT( + inline size_t processed() const { return _processed; } + inline size_t removed() const { return _removed; } + ) + + inline void move_to_next() { + if (_ref == _next) { + // End of the list. + _ref = NULL; + } else { + _ref = _next; + } + assert(_ref != _first_seen, "cyclic ref_list found"); + NOT_PRODUCT(_processed++); + } + +}; class ReferenceProcessor : public CHeapObj { protected: // Compatibility with pre-4965777 JDK's static bool _pending_list_uses_discovered_field; - MemRegion _span; // (right-open) interval of heap - // subject to wkref discovery - bool _discovering_refs; // true when discovery enabled - bool _discovery_is_atomic; // if discovery is atomic wrt - // other collectors in configuration - bool _discovery_is_mt; // true if reference discovery is MT. + + MemRegion _span; // (right-open) interval of heap + // subject to wkref discovery + + bool _discovering_refs; // true when discovery enabled + bool _discovery_is_atomic; // if discovery is atomic wrt + // other collectors in configuration + bool _discovery_is_mt; // true if reference discovery is MT. + // If true, setting "next" field of a discovered refs list requires // write barrier(s). (Must be true if used in a collector in which // elements of a discovered list may be moved during discovery: for @@ -67,18 +224,19 @@ // long-term concurrent marking phase that does weak reference // discovery.) bool _discovered_list_needs_barrier; - BarrierSet* _bs; // Cached copy of BarrierSet. - bool _enqueuing_is_done; // true if all weak references enqueued - bool _processing_is_mt; // true during phases when - // reference processing is MT. - int _next_id; // round-robin mod _num_q counter in - // support of work distribution - // For collectors that do not keep GC marking information + BarrierSet* _bs; // Cached copy of BarrierSet. + bool _enqueuing_is_done; // true if all weak references enqueued + bool _processing_is_mt; // true during phases when + // reference processing is MT. + int _next_id; // round-robin mod _num_q counter in + // support of work distribution + + // For collectors that do not keep GC liveness information // in the object header, this field holds a closure that // helps the reference processor determine the reachability - // of an oop (the field is currently initialized to NULL for - // all collectors but the CMS collector). + // of an oop. It is currently initialized to NULL for all + // collectors except for CMS and G1. BoolObjectClosure* _is_alive_non_header; // Soft ref clearing policies @@ -102,10 +260,13 @@ DiscoveredList* _discoveredPhantomRefs; public: - int num_q() { return _num_q; } - int max_num_q() { return _max_num_q; } - void set_active_mt_degree(int v) { _num_q = v; } - DiscoveredList* discovered_soft_refs() { return _discoveredSoftRefs; } + static int number_of_subclasses_of_ref() { return (REF_PHANTOM - REF_OTHER); } + + int num_q() { return _num_q; } + int max_num_q() { return _max_num_q; } + void set_active_mt_degree(int v) { _num_q = v; } + DiscoveredList* discovered_soft_refs() { return _discoveredSoftRefs; } + ReferencePolicy* setup_policy(bool always_clear) { _current_soft_ref_policy = always_clear ? _always_clear_soft_ref_policy : _default_soft_ref_policy; @@ -205,6 +366,11 @@ void enqueue_discovered_reflists(HeapWord* pending_list_addr, AbstractRefProcTaskExecutor* task_executor); protected: + // Set the 'discovered' field of the given reference to + // the given value - emitting barriers depending upon + // the value of _discovered_list_needs_barrier. + void set_discovered(oop ref, oop value); + // "Preclean" the given discovered reference list // by removing references with strongly reachable referents. // Currently used in support of CMS only. @@ -290,7 +456,19 @@ void set_span(MemRegion span) { _span = span; } // start and stop weak ref discovery - void enable_discovery() { _discovering_refs = true; } + void enable_discovery(bool verify_disabled, bool check_no_refs) { +#ifdef ASSERT + // Verify that we're not currently discovering refs + assert(!verify_disabled || !_discovering_refs, "nested call?"); + + if (check_no_refs) { + // Verify that the discovered lists are empty + verify_no_references_recorded(); + } +#endif // ASSERT + _discovering_refs = true; + } + void disable_discovery() { _discovering_refs = false; } bool discovery_enabled() { return _discovering_refs; } @@ -365,7 +543,7 @@ ~NoRefDiscovery() { if (_was_discovering_refs) { - _rp->enable_discovery(); + _rp->enable_discovery(true /*verify_disabled*/, false /*check_no_refs*/); } } };