oopMapCache.hpp revision 1472:c18cbe5936b8
1/* 2 * Copyright (c) 1997, 2006, 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// A Cache for storing (method, bci) -> oopMap. 26// The memory management system uses the cache when locating object 27// references in an interpreted frame. 28// 29// OopMapCache's are allocated lazily per instanceKlass. 30 31// The oopMap (InterpreterOopMap) is stored as a bit mask. If the 32// bit_mask can fit into two words it is stored in 33// the _bit_mask array, otherwise it is allocated on the heap. 34// For OopMapCacheEntry the bit_mask is allocated in the C heap 35// because these entries persist between garbage collections. 36// For InterpreterOopMap the bit_mask is allocated in 37// a resource area for better performance. InterpreterOopMap 38// should only be created and deleted during same garbage collection. 39// 40// If ENABBLE_ZAP_DEAD_LOCALS is defined, two bits are used 41// per entry instead of one. In all cases, 42// the first bit is set to indicate oops as opposed to other 43// values. If the second bit is available, 44// it is set for dead values. We get the following encoding: 45// 46// 00 live value 47// 01 live oop 48// 10 dead value 49// 11 <unused> (we cannot distinguish between dead oops or values with the current oop map generator) 50 51 52class OffsetClosure { 53 public: 54 virtual void offset_do(int offset) = 0; 55}; 56 57 58class InterpreterOopMap: ResourceObj { 59 friend class OopMapCache; 60 61 public: 62 enum { 63 N = 2, // the number of words reserved 64 // for inlined mask storage 65 small_mask_limit = N * BitsPerWord, // the maximum number of bits 66 // available for small masks, 67 // small_mask_limit can be set to 0 68 // for testing bit_mask allocation 69 70#ifdef ENABLE_ZAP_DEAD_LOCALS 71 bits_per_entry = 2, 72 dead_bit_number = 1, 73#else 74 bits_per_entry = 1, 75#endif 76 oop_bit_number = 0 77 }; 78 79 private: 80 methodOop _method; // the method for which the mask is valid 81 unsigned short _bci; // the bci for which the mask is valid 82 int _mask_size; // the mask size in bits 83 int _expression_stack_size; // the size of the expression stack in slots 84 85 protected: 86 intptr_t _bit_mask[N]; // the bit mask if 87 // mask_size <= small_mask_limit, 88 // ptr to bit mask otherwise 89 // "protected" so that sub classes can 90 // access it without using trickery in 91 // methd bit_mask(). 92#ifdef ASSERT 93 bool _resource_allocate_bit_mask; 94#endif 95 96 // access methods 97 methodOop method() const { return _method; } 98 void set_method(methodOop v) { _method = v; } 99 int bci() const { return _bci; } 100 void set_bci(int v) { _bci = v; } 101 int mask_size() const { return _mask_size; } 102 void set_mask_size(int v) { _mask_size = v; } 103 int number_of_entries() const { return mask_size() / bits_per_entry; } 104 // Test bit mask size and return either the in-line bit mask or allocated 105 // bit mask. 106 uintptr_t* bit_mask() { return (uintptr_t*)(mask_size() <= small_mask_limit ? (intptr_t)_bit_mask : _bit_mask[0]); } 107 108 // return the word size of_bit_mask. mask_size() <= 4 * MAX_USHORT 109 size_t mask_word_size() { 110 return (mask_size() + BitsPerWord - 1) / BitsPerWord; 111 } 112 113 uintptr_t entry_at(int offset) { int i = offset * bits_per_entry; return bit_mask()[i / BitsPerWord] >> (i % BitsPerWord); } 114 115 void set_expression_stack_size(int sz) { _expression_stack_size = sz; } 116 117#ifdef ENABLE_ZAP_DEAD_LOCALS 118 bool is_dead(int offset) { return (entry_at(offset) & (1 << dead_bit_number)) != 0; } 119#endif 120 121 // Lookup 122 bool match(methodHandle method, int bci) { return _method == method() && _bci == bci; } 123 bool is_empty(); 124 125 // Initialization 126 void initialize(); 127 128 public: 129 InterpreterOopMap(); 130 ~InterpreterOopMap(); 131 132 // Copy the OopMapCacheEntry in parameter "from" into this 133 // InterpreterOopMap. If the _bit_mask[0] in "from" points to 134 // allocated space (i.e., the bit mask was to large to hold 135 // in-line), allocate the space from a Resource area. 136 void resource_copy(OopMapCacheEntry* from); 137 138 void iterate_oop(OffsetClosure* oop_closure); 139 void oop_iterate(OopClosure * blk); 140 void oop_iterate(OopClosure * blk, MemRegion mr); 141 void verify(); 142 void print(); 143 144 bool is_oop (int offset) { return (entry_at(offset) & (1 << oop_bit_number )) != 0; } 145 146 int expression_stack_size() { return _expression_stack_size; } 147 148#ifdef ENABLE_ZAP_DEAD_LOCALS 149 void iterate_all(OffsetClosure* oop_closure, OffsetClosure* value_closure, OffsetClosure* dead_closure); 150#endif 151}; 152 153class OopMapCache : public CHeapObj { 154 private: 155 enum { _size = 32, // Use fixed size for now 156 _probe_depth = 3 // probe depth in case of collisions 157 }; 158 159 OopMapCacheEntry* _array; 160 161 unsigned int hash_value_for(methodHandle method, int bci); 162 OopMapCacheEntry* entry_at(int i) const; 163 164 Mutex _mut; 165 166 void flush(); 167 168 public: 169 OopMapCache(); 170 ~OopMapCache(); // free up memory 171 172 // flush cache entry is occupied by an obsolete method 173 void flush_obsolete_entries(); 174 175 // Returns the oopMap for (method, bci) in parameter "entry". 176 // Returns false if an oop map was not found. 177 void lookup(methodHandle method, int bci, InterpreterOopMap* entry); 178 179 // Compute an oop map without updating the cache or grabbing any locks (for debugging) 180 static void compute_one_oop_map(methodHandle method, int bci, InterpreterOopMap* entry); 181 182 // Helpers 183 // Iterate over the entries in the cached OopMapCacheEntry's 184 void oop_iterate(OopClosure *blk); 185 void oop_iterate(OopClosure *blk, MemRegion mr); 186 void verify(); 187 188 // Returns total no. of bytes allocated as part of OopMapCache's 189 static long memory_usage() PRODUCT_RETURN0; 190}; 191