Mercurial > hg > graal-compiler
view src/share/vm/gc_implementation/g1/heapRegionRemSet.hpp @ 342:37f87013dfd8
6711316: Open source the Garbage-First garbage collector
Summary: First mercurial integration of the code for the Garbage-First garbage collector.
Reviewed-by: apetrusenko, iveresov, jmasa, sgoldman, tonyp, ysr
author | ysr |
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date | Thu, 05 Jun 2008 15:57:56 -0700 |
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children | fe3d7c11b4b7 |
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/* * Copyright 2001-2007 Sun Microsystems, Inc. All Rights Reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, * CA 95054 USA or visit www.sun.com if you need additional information or * have any questions. * */ // Remembered set for a heap region. Represent a set of "cards" that // contain pointers into the owner heap region. Cards are defined somewhat // abstractly, in terms of what the "BlockOffsetTable" in use can parse. class G1CollectedHeap; class G1BlockOffsetSharedArray; class HeapRegion; class HeapRegionRemSetIterator; class PosParPRT; class SparsePRT; // The "_coarse_map" is a bitmap with one bit for each region, where set // bits indicate that the corresponding region may contain some pointer // into the owning region. // The "_fine_grain_entries" array is an open hash table of PerRegionTables // (PRTs), indicating regions for which we're keeping the RS as a set of // cards. The strategy is to cap the size of the fine-grain table, // deleting an entry and setting the corresponding coarse-grained bit when // we would overflow this cap. // We use a mixture of locking and lock-free techniques here. We allow // threads to locate PRTs without locking, but threads attempting to alter // a bucket list obtain a lock. This means that any failing attempt to // find a PRT must be retried with the lock. It might seem dangerous that // a read can find a PRT that is concurrently deleted. This is all right, // because: // // 1) We only actually free PRT's at safe points (though we reuse them at // other times). // 2) We find PRT's in an attempt to add entries. If a PRT is deleted, // it's _coarse_map bit is set, so the that we were attempting to add // is represented. If a deleted PRT is re-used, a thread adding a bit, // thinking the PRT is for a different region, does no harm. class OtherRegionsTable: public CHeapObj { friend class HeapRegionRemSetIterator; G1CollectedHeap* _g1h; Mutex _m; HeapRegion* _hr; // These are protected by "_m". BitMap _coarse_map; size_t _n_coarse_entries; static jint _n_coarsenings; PosParPRT** _fine_grain_regions; size_t _n_fine_entries; #define SAMPLE_FOR_EVICTION 1 #if SAMPLE_FOR_EVICTION size_t _fine_eviction_start; static size_t _fine_eviction_stride; static size_t _fine_eviction_sample_size; #endif SparsePRT _sparse_table; // These are static after init. static size_t _max_fine_entries; static size_t _mod_max_fine_entries_mask; // Requires "prt" to be the first element of the bucket list appropriate // for "hr". If this list contains an entry for "hr", return it, // otherwise return "NULL". PosParPRT* find_region_table(size_t ind, HeapRegion* hr) const; // Find, delete, and return a candidate PosParPRT, if any exists, // adding the deleted region to the coarse bitmap. Requires the caller // to hold _m, and the fine-grain table to be full. PosParPRT* delete_region_table(); // If a PRT for "hr" is in the bucket list indicated by "ind" (which must // be the correct index for "hr"), delete it and return true; else return // false. bool del_single_region_table(size_t ind, HeapRegion* hr); static jint _cache_probes; static jint _cache_hits; // Indexed by thread X heap region, to minimize thread contention. static int** _from_card_cache; static size_t _from_card_cache_max_regions; static size_t _from_card_cache_mem_size; public: OtherRegionsTable(HeapRegion* hr); HeapRegion* hr() const { return _hr; } // For now. Could "expand" some tables in the future, so that this made // sense. void add_reference(oop* from, int tid); void add_reference(oop* from) { return add_reference(from, 0); } // Removes any entries shown by the given bitmaps to contain only dead // objects. void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm); // Not const because it takes a lock. size_t occupied() const; size_t occ_fine() const; size_t occ_coarse() const; size_t occ_sparse() const; static jint n_coarsenings() { return _n_coarsenings; } // Returns size in bytes. // Not const because it takes a lock. size_t mem_size() const; static size_t static_mem_size(); static size_t fl_mem_size(); bool contains_reference(oop* from) const; bool contains_reference_locked(oop* from) const; void clear(); // Specifically clear the from_card_cache. void clear_fcc(); // "from_hr" is being cleared; remove any entries from it. void clear_incoming_entry(HeapRegion* from_hr); // Declare the heap size (in # of regions) to the OtherRegionsTable. // (Uses it to initialize from_card_cache). static void init_from_card_cache(size_t max_regions); // Declares that only regions i s.t. 0 <= i < new_n_regs are in use. // Make sure any entries for higher regions are invalid. static void shrink_from_card_cache(size_t new_n_regs); static void print_from_card_cache(); }; class HeapRegionRemSet : public CHeapObj { friend class VMStructs; friend class HeapRegionRemSetIterator; public: enum Event { Event_EvacStart, Event_EvacEnd, Event_RSUpdateEnd }; private: G1BlockOffsetSharedArray* _bosa; G1BlockOffsetSharedArray* bosa() const { return _bosa; } static bool _par_traversal; OtherRegionsTable _other_regions; // One set bit for every region that has an entry for this one. BitMap _outgoing_region_map; // Clear entries for the current region in any rem sets named in // the _outgoing_region_map. void clear_outgoing_entries(); #if MAYBE // Audit the given card index. void audit_card(size_t card_num, HeapRegion* hr, u2* rc_arr, HeapRegionRemSet* empty_cards, size_t* one_obj_cards); // Assumes that "audit_stage1" has been called for "hr", to set up // "shadow" and "new_rs" appropriately. Identifies individual popular // objects; returns "true" if any are found. bool audit_find_pop(HeapRegion* hr, u2* rc_arr); // Assumes that "audit_stage1" has been called for "hr", to set up // "shadow" and "new_rs" appropriately. Identifies individual popular // objects, and determines the number of entries in "new_rs" if any such // popular objects are ignored. If this is sufficiently small, returns // "false" to indicate that a constraint should not be introduced. // Otherwise, returns "true" to indicate that we should go ahead with // adding the constraint. bool audit_stag(HeapRegion* hr, u2* rc_arr); u2* alloc_rc_array(); SeqHeapRegionRemSet* audit_post(u2* rc_arr, size_t multi_obj_crds, SeqHeapRegionRemSet* empty_cards); #endif enum ParIterState { Unclaimed, Claimed, Complete }; ParIterState _iter_state; // Unused unless G1RecordHRRSOops is true. static const int MaxRecorded = 1000000; static oop** _recorded_oops; static HeapWord** _recorded_cards; static HeapRegion** _recorded_regions; static int _n_recorded; static const int MaxRecordedEvents = 1000; static Event* _recorded_events; static int* _recorded_event_index; static int _n_recorded_events; static void print_event(outputStream* str, Event evnt); public: HeapRegionRemSet(G1BlockOffsetSharedArray* bosa, HeapRegion* hr); static int num_par_rem_sets(); static bool par_traversal() { return _par_traversal; } static void set_par_traversal(bool b); HeapRegion* hr() const { return _other_regions.hr(); } size_t occupied() const { return _other_regions.occupied(); } size_t occ_fine() const { return _other_regions.occ_fine(); } size_t occ_coarse() const { return _other_regions.occ_coarse(); } size_t occ_sparse() const { return _other_regions.occ_sparse(); } static jint n_coarsenings() { return OtherRegionsTable::n_coarsenings(); } /* Used in the sequential case. Returns "true" iff this addition causes the size limit to be reached. */ bool add_reference(oop* from) { _other_regions.add_reference(from); return false; } /* Used in the parallel case. Returns "true" iff this addition causes the size limit to be reached. */ bool add_reference(oop* from, int tid) { _other_regions.add_reference(from, tid); return false; } // Records the fact that the current region contains an outgoing // reference into "to_hr". void add_outgoing_reference(HeapRegion* to_hr); // Removes any entries shown by the given bitmaps to contain only dead // objects. void scrub(CardTableModRefBS* ctbs, BitMap* region_bm, BitMap* card_bm); // The region is being reclaimed; clear its remset, and any mention of // entries for this region in other remsets. void clear(); // Forget any entries due to pointers from "from_hr". void clear_incoming_entry(HeapRegion* from_hr) { _other_regions.clear_incoming_entry(from_hr); } #if 0 virtual void cleanup() = 0; #endif // Should be called from single-threaded code. void init_for_par_iteration(); // Attempt to claim the region. Returns true iff this call caused an // atomic transition from Unclaimed to Claimed. bool claim_iter(); // Sets the iteration state to "complete". void set_iter_complete(); // Returns "true" iff the region's iteration is complete. bool iter_is_complete(); // Initialize the given iterator to iterate over this rem set. void init_iterator(HeapRegionRemSetIterator* iter) const; #if 0 // Apply the "do_card" method to the start address of every card in the // rem set. Returns false if some application of the closure aborted. virtual bool card_iterate(CardClosure* iter) = 0; #endif // The actual # of bytes this hr_remset takes up. size_t mem_size() { return _other_regions.mem_size() // This correction is necessary because the above includes the second // part. + sizeof(this) - sizeof(OtherRegionsTable); } // Returns the memory occupancy of all static data structures associated // with remembered sets. static size_t static_mem_size() { return OtherRegionsTable::static_mem_size(); } // Returns the memory occupancy of all free_list data structures associated // with remembered sets. static size_t fl_mem_size() { return OtherRegionsTable::fl_mem_size(); } bool contains_reference(oop* from) const { return _other_regions.contains_reference(from); } void print() const; #if MAYBE // We are about to introduce a constraint, requiring the collection time // of the region owning this RS to be <= "hr", and forgetting pointers // from the owning region to "hr." Before doing so, examines this rem // set for pointers to "hr", possibly identifying some popular objects., // and possibly finding some cards to no longer contain pointers to "hr", // // These steps may prevent the the constraint from being necessary; in // which case returns a set of cards now thought to contain no pointers // into HR. In the normal (I assume) case, returns NULL, indicating that // we should go ahead and add the constraint. virtual SeqHeapRegionRemSet* audit(HeapRegion* hr) = 0; #endif // Called during a stop-world phase to perform any deferred cleanups. // The second version may be called by parallel threads after then finish // collection work. static void cleanup(); static void par_cleanup(); // Declare the heap size (in # of regions) to the HeapRegionRemSet(s). // (Uses it to initialize from_card_cache). static void init_heap(size_t max_regions) { OtherRegionsTable::init_from_card_cache(max_regions); } // Declares that only regions i s.t. 0 <= i < new_n_regs are in use. static void shrink_heap(size_t new_n_regs) { OtherRegionsTable::shrink_from_card_cache(new_n_regs); } #ifndef PRODUCT static void print_from_card_cache() { OtherRegionsTable::print_from_card_cache(); } #endif static void record(HeapRegion* hr, oop* f); static void print_recorded(); static void record_event(Event evnt); // Run unit tests. #ifndef PRODUCT static void test(); #endif }; class HeapRegionRemSetIterator : public CHeapObj { // The region over which we're iterating. const HeapRegionRemSet* _hrrs; // Local caching of HRRS fields. const BitMap* _coarse_map; PosParPRT** _fine_grain_regions; G1BlockOffsetSharedArray* _bosa; G1CollectedHeap* _g1h; // The number yielded since initialization. size_t _n_yielded_fine; size_t _n_yielded_coarse; size_t _n_yielded_sparse; // If true we're iterating over the coarse table; if false the fine // table. enum IterState { Sparse, Fine, Coarse }; IterState _is; // In both kinds of iteration, heap offset of first card of current // region. size_t _cur_region_card_offset; // Card offset within cur region. size_t _cur_region_cur_card; // Coarse table iteration fields: // Current region index; int _coarse_cur_region_index; int _coarse_cur_region_cur_card; bool coarse_has_next(size_t& card_index); // Fine table iteration fields: // Index of bucket-list we're working on. int _fine_array_index; // Per Region Table we're doing within current bucket list. PosParPRT* _fine_cur_prt; /* SparsePRT::*/ SparsePRTIter _sparse_iter; void fine_find_next_non_null_prt(); bool fine_has_next(); bool fine_has_next(size_t& card_index); public: // We require an iterator to be initialized before use, so the // constructor does little. HeapRegionRemSetIterator(); void initialize(const HeapRegionRemSet* hrrs); // If there remains one or more cards to be yielded, returns true and // sets "card_index" to one of those cards (which is then considered // yielded.) Otherwise, returns false (and leaves "card_index" // undefined.) bool has_next(size_t& card_index); size_t n_yielded_fine() { return _n_yielded_fine; } size_t n_yielded_coarse() { return _n_yielded_coarse; } size_t n_yielded_sparse() { return _n_yielded_sparse; } size_t n_yielded() { return n_yielded_fine() + n_yielded_coarse() + n_yielded_sparse(); } }; #if 0 class CardClosure: public Closure { public: virtual void do_card(HeapWord* card_start) = 0; }; #endif