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