1 /* 2 * Copyright (c) 2002, 2012, 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 #ifndef SHARE_VM_GC_IMPLEMENTATION_SHARED_SPACEDECORATOR_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_SHARED_SPACEDECORATOR_HPP 27 28 #include "gc_implementation/shared/mutableSpace.hpp" 29 #include "memory/space.hpp" 30 #include "utilities/globalDefinitions.hpp" 31 32 class SpaceDecorator: public AllStatic { 33 public: 34 // Initialization flags. 35 static const bool Clear = true; 36 static const bool DontClear = false; 37 static const bool Mangle = true; 38 static const bool DontMangle = false; 39 }; 40 41 // Functionality for use with class Space and class MutableSpace. 42 // The approach taken with the mangling is to mangle all 43 // the space initially and then to mangle areas that have 44 // been allocated since the last collection. Mangling is 45 // done in the context of a generation and in the context 46 // of a space. 47 // The space in a generation is mangled when it is first 48 // initialized and when the generation grows. The spaces 49 // are not necessarily up-to-date when this mangling occurs 50 // and the method mangle_region() is used. 51 // After allocations have been done in a space, the space generally 52 // need to be remangled. Remangling is only done on the 53 // recently allocated regions in the space. Typically, that is 54 // the region between the new top and the top just before a 55 // garbage collection. 56 // An exception to the usual mangling in a space is done when the 57 // space is used for an extraordinary purpose. Specifically, when 58 // to-space is used as scratch space for a mark-sweep-compact 59 // collection. 60 // Spaces are mangled after a collection. If the generation 61 // grows after a collection, the added space is mangled as part of 62 // the growth of the generation. No additional mangling is needed when the 63 // spaces are resized after an expansion. 64 // The class SpaceMangler keeps a pointer to the top of the allocated 65 // area and provides the methods for doing the piece meal mangling. 66 // Methods for doing sparces and full checking of the mangling are 67 // included. The full checking is done if DEBUG_MANGLING is defined. 68 // GenSpaceMangler is used with the GenCollectedHeap collectors and 69 // MutableSpaceMangler is used with the ParallelScavengeHeap collectors. 70 // These subclasses abstract the differences in the types of spaces used 71 // by each heap. 72 73 class SpaceMangler: public CHeapObj<mtGC> { 74 friend class VMStructs; 75 76 // High water mark for allocations. Typically, the space above 77 // this point have been mangle previously and don't need to be 78 // touched again. Space below this point has been allocated 79 // and remangling is needed between the current top and this 80 // high water mark. 81 HeapWord* _top_for_allocations; 82 HeapWord* top_for_allocations() { return _top_for_allocations; } 83 84 public: 85 86 // Setting _top_for_allocations to NULL at initialization 87 // makes it always below top so that mangling done as part 88 // of the initialize() call of a space does nothing (as it 89 // should since the mangling is done as part of the constructor 90 // for the space. 91 SpaceMangler() : _top_for_allocations(NULL) {} 92 93 // Methods for top and end that delegate to the specific 94 // space type. 95 virtual HeapWord* top() const = 0; 96 virtual HeapWord* end() const = 0; 97 98 // Return true if q matches the mangled pattern. 99 static bool is_mangled(HeapWord* q) PRODUCT_RETURN0; 100 101 // Used to save the an address in a space for later use during mangling. 102 void set_top_for_allocations(HeapWord* v); 103 104 // Overwrites the unused portion of this space. 105 // Mangle only the region not previously mangled [top, top_previously_mangled) 106 void mangle_unused_area(); 107 // Mangle all the unused region [top, end) 108 void mangle_unused_area_complete(); 109 // Do some sparse checking on the area that should have been mangled. 110 void check_mangled_unused_area(HeapWord* limit) PRODUCT_RETURN; 111 // Do a complete check of the area that should be mangled. 112 void check_mangled_unused_area_complete() PRODUCT_RETURN; 113 114 // Mangle the MemRegion. This is a non-space specific mangler. It 115 // is used during the initial mangling of a space before the space 116 // is fully constructed. Also is used when a generation is expanded 117 // and possibly before the spaces have been reshaped to to the new 118 // size of the generation. 119 static void mangle_region(MemRegion mr) PRODUCT_RETURN; 120 }; 121 122 class ContiguousSpace; 123 124 // For use with GenCollectedHeap's 125 class GenSpaceMangler: public SpaceMangler { 126 ContiguousSpace* _sp; 127 128 ContiguousSpace* sp() { return _sp; } 129 130 HeapWord* top() const { return _sp->top(); } 131 HeapWord* end() const { return _sp->end(); } 132 133 public: 134 GenSpaceMangler(ContiguousSpace* sp) : SpaceMangler(), _sp(sp) {} 135 }; 136 137 // For use with ParallelScavengeHeap's. 138 class MutableSpaceMangler: public SpaceMangler { 139 MutableSpace* _sp; 140 141 MutableSpace* sp() { return _sp; } 142 143 HeapWord* top() const { return _sp->top(); } 144 HeapWord* end() const { return _sp->end(); } 145 146 public: 147 MutableSpaceMangler(MutableSpace* sp) : SpaceMangler(), _sp(sp) {} 148 }; 149 150 #endif // SHARE_VM_GC_IMPLEMENTATION_SHARED_SPACEDECORATOR_HPP