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 // 26 // PSPromotionLAB is a parallel scavenge promotion lab. This class acts very 27 // much like a MutableSpace. We couldn't embed a MutableSpace, though, as 28 // it has a considerable number of asserts and invariants that are violated. 29 // 30 31 class ObjectStartArray; 32 33 class PSPromotionLAB : public CHeapObj { 34 protected: 35 static size_t filler_header_size; 36 37 enum LabState { 38 needs_flush, 39 flushed, 40 zero_size 41 }; 42 43 HeapWord* _top; 44 HeapWord* _bottom; 45 HeapWord* _end; 46 LabState _state; 47 48 void set_top(HeapWord* value) { _top = value; } 49 void set_bottom(HeapWord* value) { _bottom = value; } 50 void set_end(HeapWord* value) { _end = value; } 51 52 // The shared initialize code invokes this. 53 debug_only(virtual bool lab_is_valid(MemRegion lab) { return false; }); 54 55 PSPromotionLAB() : _top(NULL), _bottom(NULL), _end(NULL) { } 56 57 public: 58 // Filling and flushing. 59 void initialize(MemRegion lab); 60 61 virtual void flush(); 62 63 // Accessors 64 HeapWord* bottom() const { return _bottom; } 65 HeapWord* end() const { return _end; } 66 HeapWord* top() const { return _top; } 67 68 bool is_flushed() { return _state == flushed; } 69 70 bool unallocate_object(oop obj); 71 72 // Returns a subregion containing all objects in this space. 73 MemRegion used_region() { return MemRegion(bottom(), top()); } 74 75 // Boolean querries. 76 bool is_empty() const { return used() == 0; } 77 bool not_empty() const { return used() > 0; } 78 bool contains(const void* p) const { return _bottom <= p && p < _end; } 79 80 // Size computations. Sizes are in bytes. 81 size_t capacity() const { return byte_size(bottom(), end()); } 82 size_t used() const { return byte_size(bottom(), top()); } 83 size_t free() const { return byte_size(top(), end()); } 84 }; 85 86 class PSYoungPromotionLAB : public PSPromotionLAB { 87 public: 88 PSYoungPromotionLAB() { } 89 90 // Not MT safe 91 HeapWord* allocate(size_t size) { 92 // Can't assert this, when young fills, we keep the LAB around, but flushed. 93 // assert(_state != flushed, "Sanity"); 94 HeapWord* obj = top(); 95 HeapWord* new_top = obj + size; 96 // The 'new_top>obj' check is needed to detect overflow of obj+size. 97 if (new_top > obj && new_top <= end()) { 98 set_top(new_top); 99 assert(is_object_aligned((intptr_t)obj) && is_object_aligned((intptr_t)new_top), 100 "checking alignment"); 101 return obj; 102 } 103 104 return NULL; 105 } 106 107 debug_only(virtual bool lab_is_valid(MemRegion lab)); 108 }; 109 110 class PSOldPromotionLAB : public PSPromotionLAB { 111 private: 112 ObjectStartArray* _start_array; 113 114 public: 115 PSOldPromotionLAB() : _start_array(NULL) { } 116 PSOldPromotionLAB(ObjectStartArray* start_array) : _start_array(start_array) { } 117 118 void set_start_array(ObjectStartArray* start_array) { _start_array = start_array; } 119 120 void flush(); 121 122 // Not MT safe 123 HeapWord* allocate(size_t size) { 124 // Cannot test for this now that we're doing promotion failures 125 // assert(_state != flushed, "Sanity"); 126 assert(_start_array != NULL, "Sanity"); 127 HeapWord* obj = top(); 128 HeapWord* new_top = obj + size; 129 // The 'new_top>obj' check is needed to detect overflow of obj+size. 130 if (new_top > obj && new_top <= end()) { 131 set_top(new_top); 132 assert(is_object_aligned((intptr_t)obj) && is_object_aligned((intptr_t)new_top), 133 "checking alignment"); 134 _start_array->allocate_block(obj); 135 return obj; 136 } 137 138 return NULL; 139 } 140 141 debug_only(virtual bool lab_is_valid(MemRegion lab)); 142 };