1 /* 2 * Copyright 2001-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, 20 * CA 95054 USA or visit www.sun.com if you need additional information or 21 * have any questions. 22 * 23 */ 24 25 # include "incls/_precompiled.incl" 26 # include "incls/_freeList.cpp.incl" 27 28 // Free list. A FreeList is used to access a linked list of chunks 29 // of space in the heap. The head and tail are maintained so that 30 // items can be (as in the current implementation) added at the 31 // at the tail of the list and removed from the head of the list to 32 // maintain a FIFO queue. 33 34 FreeList::FreeList() : 35 _head(NULL), _tail(NULL) 36 #ifdef ASSERT 37 , _protecting_lock(NULL) 38 #endif 39 { 40 _size = 0; 41 _count = 0; 42 _hint = 0; 43 init_statistics(); 44 } 45 46 FreeList::FreeList(FreeChunk* fc) : 47 _head(fc), _tail(fc) 48 #ifdef ASSERT 49 , _protecting_lock(NULL) 50 #endif 51 { 52 _size = fc->size(); 53 _count = 1; 54 _hint = 0; 55 init_statistics(); 56 #ifndef PRODUCT 57 _allocation_stats.set_returnedBytes(size() * HeapWordSize); 58 #endif 59 } 60 61 FreeList::FreeList(HeapWord* addr, size_t size) : 62 _head((FreeChunk*) addr), _tail((FreeChunk*) addr) 63 #ifdef ASSERT 64 , _protecting_lock(NULL) 65 #endif 66 { 67 assert(size > sizeof(FreeChunk), "size is too small"); 68 head()->setSize(size); 69 _size = size; 70 _count = 1; 71 init_statistics(); 72 #ifndef PRODUCT 73 _allocation_stats.set_returnedBytes(_size * HeapWordSize); 74 #endif 75 } 76 77 void FreeList::reset(size_t hint) { 78 set_count(0); 79 set_head(NULL); 80 set_tail(NULL); 81 set_hint(hint); 82 } 83 84 void FreeList::init_statistics() { 85 _allocation_stats.initialize(); 86 } 87 88 FreeChunk* FreeList::getChunkAtHead() { 89 assert_proper_lock_protection(); 90 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 91 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 92 FreeChunk* fc = head(); 93 if (fc != NULL) { 94 FreeChunk* nextFC = fc->next(); 95 if (nextFC != NULL) { 96 // The chunk fc being removed has a "next". Set the "next" to the 97 // "prev" of fc. 98 nextFC->linkPrev(NULL); 99 } else { // removed tail of list 100 link_tail(NULL); 101 } 102 link_head(nextFC); 103 decrement_count(); 104 } 105 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 106 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 107 return fc; 108 } 109 110 111 void FreeList::getFirstNChunksFromList(size_t n, FreeList* fl) { 112 assert_proper_lock_protection(); 113 assert(fl->count() == 0, "Precondition"); 114 if (count() > 0) { 115 int k = 1; 116 fl->set_head(head()); n--; 117 FreeChunk* tl = head(); 118 while (tl->next() != NULL && n > 0) { 119 tl = tl->next(); n--; k++; 120 } 121 assert(tl != NULL, "Loop Inv."); 122 123 // First, fix up the list we took from. 124 FreeChunk* new_head = tl->next(); 125 set_head(new_head); 126 set_count(count() - k); 127 if (new_head == NULL) { 128 set_tail(NULL); 129 } else { 130 new_head->linkPrev(NULL); 131 } 132 // Now we can fix up the tail. 133 tl->linkNext(NULL); 134 // And return the result. 135 fl->set_tail(tl); 136 fl->set_count(k); 137 } 138 } 139 140 // Remove this chunk from the list 141 void FreeList::removeChunk(FreeChunk*fc) { 142 assert_proper_lock_protection(); 143 assert(head() != NULL, "Remove from empty list"); 144 assert(fc != NULL, "Remove a NULL chunk"); 145 assert(size() == fc->size(), "Wrong list"); 146 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 147 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 148 149 FreeChunk* prevFC = fc->prev(); 150 FreeChunk* nextFC = fc->next(); 151 if (nextFC != NULL) { 152 // The chunk fc being removed has a "next". Set the "next" to the 153 // "prev" of fc. 154 nextFC->linkPrev(prevFC); 155 } else { // removed tail of list 156 link_tail(prevFC); 157 } 158 if (prevFC == NULL) { // removed head of list 159 link_head(nextFC); 160 assert(nextFC == NULL || nextFC->prev() == NULL, 161 "Prev of head should be NULL"); 162 } else { 163 prevFC->linkNext(nextFC); 164 assert(tail() != prevFC || prevFC->next() == NULL, 165 "Next of tail should be NULL"); 166 } 167 decrement_count(); 168 #define TRAP_CODE 1 169 #if TRAP_CODE 170 if (head() == NULL) { 171 guarantee(tail() == NULL, "INVARIANT"); 172 guarantee(count() == 0, "INVARIANT"); 173 } 174 #endif 175 // clear next and prev fields of fc, debug only 176 NOT_PRODUCT( 177 fc->linkPrev(NULL); 178 fc->linkNext(NULL); 179 ) 180 assert(fc->isFree(), "Should still be a free chunk"); 181 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 182 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 183 assert(head() == NULL || head()->size() == size(), "wrong item on list"); 184 assert(tail() == NULL || tail()->size() == size(), "wrong item on list"); 185 } 186 187 // Add this chunk at the head of the list. 188 void FreeList::returnChunkAtHead(FreeChunk* chunk, bool record_return) { 189 assert_proper_lock_protection(); 190 assert(chunk != NULL, "insert a NULL chunk"); 191 assert(size() == chunk->size(), "Wrong size"); 192 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 193 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 194 195 FreeChunk* oldHead = head(); 196 assert(chunk != oldHead, "double insertion"); 197 chunk->linkAfter(oldHead); 198 link_head(chunk); 199 if (oldHead == NULL) { // only chunk in list 200 assert(tail() == NULL, "inconsistent FreeList"); 201 link_tail(chunk); 202 } 203 increment_count(); // of # of chunks in list 204 DEBUG_ONLY( 205 if (record_return) { 206 increment_returnedBytes_by(size()*HeapWordSize); 207 } 208 ) 209 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 210 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 211 assert(head() == NULL || head()->size() == size(), "wrong item on list"); 212 assert(tail() == NULL || tail()->size() == size(), "wrong item on list"); 213 } 214 215 void FreeList::returnChunkAtHead(FreeChunk* chunk) { 216 assert_proper_lock_protection(); 217 returnChunkAtHead(chunk, true); 218 } 219 220 // Add this chunk at the tail of the list. 221 void FreeList::returnChunkAtTail(FreeChunk* chunk, bool record_return) { 222 assert_proper_lock_protection(); 223 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 224 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 225 assert(chunk != NULL, "insert a NULL chunk"); 226 assert(size() == chunk->size(), "wrong size"); 227 228 FreeChunk* oldTail = tail(); 229 assert(chunk != oldTail, "double insertion"); 230 if (oldTail != NULL) { 231 oldTail->linkAfter(chunk); 232 } else { // only chunk in list 233 assert(head() == NULL, "inconsistent FreeList"); 234 link_head(chunk); 235 } 236 link_tail(chunk); 237 increment_count(); // of # of chunks in list 238 DEBUG_ONLY( 239 if (record_return) { 240 increment_returnedBytes_by(size()*HeapWordSize); 241 } 242 ) 243 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 244 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 245 assert(head() == NULL || head()->size() == size(), "wrong item on list"); 246 assert(tail() == NULL || tail()->size() == size(), "wrong item on list"); 247 } 248 249 void FreeList::returnChunkAtTail(FreeChunk* chunk) { 250 returnChunkAtTail(chunk, true); 251 } 252 253 void FreeList::prepend(FreeList* fl) { 254 assert_proper_lock_protection(); 255 if (fl->count() > 0) { 256 if (count() == 0) { 257 set_head(fl->head()); 258 set_tail(fl->tail()); 259 set_count(fl->count()); 260 } else { 261 // Both are non-empty. 262 FreeChunk* fl_tail = fl->tail(); 263 FreeChunk* this_head = head(); 264 assert(fl_tail->next() == NULL, "Well-formedness of fl"); 265 fl_tail->linkNext(this_head); 266 this_head->linkPrev(fl_tail); 267 set_head(fl->head()); 268 set_count(count() + fl->count()); 269 } 270 fl->set_head(NULL); 271 fl->set_tail(NULL); 272 fl->set_count(0); 273 } 274 } 275 276 // verifyChunkInFreeLists() is used to verify that an item is in this free list. 277 // It is used as a debugging aid. 278 bool FreeList::verifyChunkInFreeLists(FreeChunk* fc) const { 279 // This is an internal consistency check, not part of the check that the 280 // chunk is in the free lists. 281 guarantee(fc->size() == size(), "Wrong list is being searched"); 282 FreeChunk* curFC = head(); 283 while (curFC) { 284 // This is an internal consistency check. 285 guarantee(size() == curFC->size(), "Chunk is in wrong list."); 286 if (fc == curFC) { 287 return true; 288 } 289 curFC = curFC->next(); 290 } 291 return false; 292 } 293 294 #ifndef PRODUCT 295 void FreeList::assert_proper_lock_protection_work() const { 296 #ifdef ASSERT 297 if (_protecting_lock != NULL && 298 SharedHeap::heap()->n_par_threads() > 0) { 299 // Should become an assert. 300 guarantee(_protecting_lock->owned_by_self(), "FreeList RACE DETECTED"); 301 } 302 #endif 303 } 304 #endif