1 /* 2 * Copyright (c) 2002, 2008, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 class GCTaskManager; 26 class GCTaskQueue; 27 class OopStack; 28 class ReferenceProcessor; 29 class ParallelScavengeHeap; 30 class PSIsAliveClosure; 31 class PSRefProcTaskExecutor; 32 33 class PSScavenge: AllStatic { 34 friend class PSIsAliveClosure; 35 friend class PSKeepAliveClosure; 36 friend class PSPromotionManager; 37 38 enum ScavengeSkippedCause { 39 not_skipped = 0, 40 to_space_not_empty, 41 promoted_too_large, 42 full_follows_scavenge 43 }; 44 45 // Saved value of to_space->top(), used to prevent objects in to_space from 46 // being rescanned. 47 static HeapWord* _to_space_top_before_gc; 48 49 // Number of consecutive attempts to scavenge that were skipped 50 static int _consecutive_skipped_scavenges; 51 52 53 protected: 54 // Flags/counters 55 static ReferenceProcessor* _ref_processor; // Reference processor for scavenging. 56 static PSIsAliveClosure _is_alive_closure; // Closure used for reference processing 57 static CardTableExtension* _card_table; // We cache the card table for fast access. 58 static bool _survivor_overflow; // Overflow this collection 59 static int _tenuring_threshold; // tenuring threshold for next scavenge 60 static elapsedTimer _accumulated_time; // total time spent on scavenge 61 static HeapWord* _young_generation_boundary; // The lowest address possible for the young_gen. 62 // This is used to decide if an oop should be scavenged, 63 // cards should be marked, etc. 64 static GrowableArray<markOop>* _preserved_mark_stack; // List of marks to be restored after failed promotion 65 static GrowableArray<oop>* _preserved_oop_stack; // List of oops that need their mark restored. 66 static CollectorCounters* _counters; // collector performance counters 67 68 static void clean_up_failed_promotion(); 69 70 static bool should_attempt_scavenge(); 71 72 static HeapWord* to_space_top_before_gc() { return _to_space_top_before_gc; } 73 static inline void save_to_space_top_before_gc(); 74 75 // Private accessors 76 static CardTableExtension* const card_table() { assert(_card_table != NULL, "Sanity"); return _card_table; } 77 78 public: 79 // Accessors 80 static int tenuring_threshold() { return _tenuring_threshold; } 81 static elapsedTimer* accumulated_time() { return &_accumulated_time; } 82 static bool promotion_failed() 83 { return _preserved_mark_stack != NULL; } 84 static int consecutive_skipped_scavenges() 85 { return _consecutive_skipped_scavenges; } 86 87 // Performance Counters 88 static CollectorCounters* counters() { return _counters; } 89 90 // Used by scavenge_contents && psMarkSweep 91 static ReferenceProcessor* const reference_processor() { 92 assert(_ref_processor != NULL, "Sanity"); 93 return _ref_processor; 94 } 95 // Used to add tasks 96 static GCTaskManager* const gc_task_manager(); 97 // The promotion managers tell us if they encountered overflow 98 static void set_survivor_overflow(bool state) { 99 _survivor_overflow = state; 100 } 101 // Adaptive size policy support. When the young generation/old generation 102 // boundary moves, _young_generation_boundary must be reset 103 static void set_young_generation_boundary(HeapWord* v) { 104 _young_generation_boundary = v; 105 } 106 107 // Called by parallelScavengeHeap to init the tenuring threshold 108 static void initialize(); 109 110 // Scavenge entry point 111 static void invoke(); 112 // Return true is a collection was done. Return 113 // false if the collection was skipped. 114 static bool invoke_no_policy(); 115 116 // If an attempt to promote fails, this method is invoked 117 static void oop_promotion_failed(oop obj, markOop obj_mark); 118 119 template <class T> static inline bool should_scavenge(T* p); 120 121 // These call should_scavenge() above and, if it returns true, also check that 122 // the object was not newly copied into to_space. The version with the bool 123 // argument is a convenience wrapper that fetches the to_space pointer from 124 // the heap and calls the other version (if the arg is true). 125 template <class T> static inline bool should_scavenge(T* p, MutableSpace* to_space); 126 template <class T> static inline bool should_scavenge(T* p, bool check_to_space); 127 128 template <class T> inline static void copy_and_push_safe_barrier(PSPromotionManager* pm, T* p); 129 130 // Is an object in the young generation 131 // This assumes that the HeapWord argument is in the heap, 132 // so it only checks one side of the complete predicate. 133 inline static bool is_obj_in_young(HeapWord* o) { 134 const bool result = (o >= _young_generation_boundary); 135 return result; 136 } 137 };