1 /* 2 * Copyright (c) 2001, 2015, 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 #include "precompiled.hpp" 26 #include "gc/shared/collectedHeap.hpp" 27 #include "memory/freeBlockDictionary.hpp" 28 #include "memory/freeList.hpp" 29 #include "memory/metachunk.hpp" 30 #include "runtime/globals.hpp" 31 #include "runtime/mutex.hpp" 32 #include "runtime/vmThread.hpp" 33 #include "utilities/macros.hpp" 34 35 // Free list. A FreeList is used to access a linked list of chunks 36 // of space in the heap. The head and tail are maintained so that 37 // items can be (as in the current implementation) added at the 38 // at the tail of the list and removed from the head of the list to 39 // maintain a FIFO queue. 40 41 template <class Chunk> 42 FreeList<Chunk>::FreeList() : 43 _head(NULL), _tail(NULL) 44 #ifdef ASSERT 45 , _protecting_lock(NULL) 46 #endif 47 { 48 _size = 0; 49 _count = 0; 50 } 51 52 template <class Chunk> 53 void FreeList<Chunk>::link_head(Chunk* v) { 54 assert_proper_lock_protection(); 55 set_head(v); 56 // If this method is not used (just set the head instead), 57 // this check can be avoided. 58 if (v != NULL) { 59 v->link_prev(NULL); 60 } 61 } 62 63 64 65 template <class Chunk> 66 void FreeList<Chunk>::reset() { 67 // Don't set the _size to 0 because this method is 68 // used with a existing list that has a size but which has 69 // been emptied. 70 // Don't clear the _protecting_lock of an existing list. 71 set_count(0); 72 set_head(NULL); 73 set_tail(NULL); 74 } 75 76 template <class Chunk> 77 void FreeList<Chunk>::initialize() { 78 #ifdef ASSERT 79 // Needed early because it might be checked in other initializing code. 80 set_protecting_lock(NULL); 81 #endif 82 reset(); 83 set_size(0); 84 } 85 86 template <class Chunk_t> 87 Chunk_t* FreeList<Chunk_t>::get_chunk_at_head() { 88 assert_proper_lock_protection(); 89 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 90 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 91 Chunk_t* fc = head(); 92 if (fc != NULL) { 93 Chunk_t* nextFC = fc->next(); 94 if (nextFC != NULL) { 95 // The chunk fc being removed has a "next". Set the "next" to the 96 // "prev" of fc. 97 nextFC->link_prev(NULL); 98 } else { // removed tail of list 99 link_tail(NULL); 100 } 101 link_head(nextFC); 102 decrement_count(); 103 } 104 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 105 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 106 return fc; 107 } 108 109 110 template <class Chunk> 111 void FreeList<Chunk>::getFirstNChunksFromList(size_t n, FreeList<Chunk>* 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 Chunk* 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 Chunk* 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->link_prev(NULL); 131 } 132 // Now we can fix up the tail. 133 tl->link_next(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 template <class Chunk> 142 void FreeList<Chunk>::remove_chunk(Chunk*fc) { 143 assert_proper_lock_protection(); 144 assert(head() != NULL, "Remove from empty list"); 145 assert(fc != NULL, "Remove a NULL chunk"); 146 assert(size() == fc->size(), "Wrong list"); 147 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 148 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 149 150 Chunk* prevFC = fc->prev(); 151 Chunk* nextFC = fc->next(); 152 if (nextFC != NULL) { 153 // The chunk fc being removed has a "next". Set the "next" to the 154 // "prev" of fc. 155 nextFC->link_prev(prevFC); 156 } else { // removed tail of list 157 link_tail(prevFC); 158 } 159 if (prevFC == NULL) { // removed head of list 160 link_head(nextFC); 161 assert(nextFC == NULL || nextFC->prev() == NULL, 162 "Prev of head should be NULL"); 163 } else { 164 prevFC->link_next(nextFC); 165 assert(tail() != prevFC || prevFC->next() == NULL, 166 "Next of tail should be NULL"); 167 } 168 decrement_count(); 169 assert(((head() == NULL) + (tail() == NULL) + (count() == 0)) % 3 == 0, 170 "H/T/C Inconsistency"); 171 // clear next and prev fields of fc, debug only 172 NOT_PRODUCT( 173 fc->link_prev(NULL); 174 fc->link_next(NULL); 175 ) 176 assert(fc->is_free(), "Should still be a free chunk"); 177 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 178 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 179 assert(head() == NULL || head()->size() == size(), "wrong item on list"); 180 assert(tail() == NULL || tail()->size() == size(), "wrong item on list"); 181 } 182 183 // Add this chunk at the head of the list. 184 template <class Chunk> 185 void FreeList<Chunk>::return_chunk_at_head(Chunk* chunk, bool record_return) { 186 assert_proper_lock_protection(); 187 assert(chunk != NULL, "insert a NULL chunk"); 188 assert(size() == chunk->size(), "Wrong size"); 189 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 190 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 191 192 Chunk* oldHead = head(); 193 assert(chunk != oldHead, "double insertion"); 194 chunk->link_after(oldHead); 195 link_head(chunk); 196 if (oldHead == NULL) { // only chunk in list 197 assert(tail() == NULL, "inconsistent FreeList"); 198 link_tail(chunk); 199 } 200 increment_count(); // of # of chunks in list 201 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 202 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 203 assert(head() == NULL || head()->size() == size(), "wrong item on list"); 204 assert(tail() == NULL || tail()->size() == size(), "wrong item on list"); 205 } 206 207 template <class Chunk> 208 void FreeList<Chunk>::return_chunk_at_head(Chunk* chunk) { 209 assert_proper_lock_protection(); 210 return_chunk_at_head(chunk, true); 211 } 212 213 // Add this chunk at the tail of the list. 214 template <class Chunk> 215 void FreeList<Chunk>::return_chunk_at_tail(Chunk* chunk, bool record_return) { 216 assert_proper_lock_protection(); 217 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 218 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 219 assert(chunk != NULL, "insert a NULL chunk"); 220 assert(size() == chunk->size(), "wrong size"); 221 222 Chunk* oldTail = tail(); 223 assert(chunk != oldTail, "double insertion"); 224 if (oldTail != NULL) { 225 oldTail->link_after(chunk); 226 } else { // only chunk in list 227 assert(head() == NULL, "inconsistent FreeList"); 228 link_head(chunk); 229 } 230 link_tail(chunk); 231 increment_count(); // of # of chunks in list 232 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 233 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 234 assert(head() == NULL || head()->size() == size(), "wrong item on list"); 235 assert(tail() == NULL || tail()->size() == size(), "wrong item on list"); 236 } 237 238 template <class Chunk> 239 void FreeList<Chunk>::return_chunk_at_tail(Chunk* chunk) { 240 return_chunk_at_tail(chunk, true); 241 } 242 243 template <class Chunk> 244 void FreeList<Chunk>::prepend(FreeList<Chunk>* fl) { 245 assert_proper_lock_protection(); 246 if (fl->count() > 0) { 247 if (count() == 0) { 248 set_head(fl->head()); 249 set_tail(fl->tail()); 250 set_count(fl->count()); 251 } else { 252 // Both are non-empty. 253 Chunk* fl_tail = fl->tail(); 254 Chunk* this_head = head(); 255 assert(fl_tail->next() == NULL, "Well-formedness of fl"); 256 fl_tail->link_next(this_head); 257 this_head->link_prev(fl_tail); 258 set_head(fl->head()); 259 set_count(count() + fl->count()); 260 } 261 fl->set_head(NULL); 262 fl->set_tail(NULL); 263 fl->set_count(0); 264 } 265 } 266 267 // verify_chunk_in_free_lists() is used to verify that an item is in this free list. 268 // It is used as a debugging aid. 269 template <class Chunk> 270 bool FreeList<Chunk>::verify_chunk_in_free_list(Chunk* fc) const { 271 // This is an internal consistency check, not part of the check that the 272 // chunk is in the free lists. 273 guarantee(fc->size() == size(), "Wrong list is being searched"); 274 Chunk* curFC = head(); 275 while (curFC) { 276 // This is an internal consistency check. 277 guarantee(size() == curFC->size(), "Chunk is in wrong list."); 278 if (fc == curFC) { 279 return true; 280 } 281 curFC = curFC->next(); 282 } 283 return false; 284 } 285 286 #ifdef ASSERT 287 template <class Chunk> 288 void FreeList<Chunk>::assert_proper_lock_protection_work() const { 289 // Nothing to do if the list has no assigned protecting lock 290 if (protecting_lock() == NULL) { 291 return; 292 } 293 294 Thread* thr = Thread::current(); 295 if (thr->is_VM_thread() || thr->is_ConcurrentGC_thread()) { 296 // assert that we are holding the freelist lock 297 } else if (thr->is_GC_task_thread()) { 298 assert(protecting_lock()->owned_by_self(), "FreeList RACE DETECTED"); 299 } else if (thr->is_Java_thread()) { 300 assert(!SafepointSynchronize::is_at_safepoint(), "Should not be executing"); 301 } else { 302 ShouldNotReachHere(); // unaccounted thread type? 303 } 304 } 305 #endif 306 307 // Print the "label line" for free list stats. 308 template <class Chunk> 309 void FreeList<Chunk>::print_labels_on(outputStream* st, const char* c) { 310 st->print("%16s\t", c); 311 st->print("%14s\t" "%14s\t" "%14s\t" "%14s\t" "%14s\t" 312 "%14s\t" "%14s\t" "%14s\t" "%14s\t" "%14s\t" "\n", 313 "bfrsurp", "surplus", "desired", "prvSwep", "bfrSwep", 314 "count", "cBirths", "cDeaths", "sBirths", "sDeaths"); 315 } 316 317 // Print the AllocationStats for the given free list. If the second argument 318 // to the call is a non-null string, it is printed in the first column; 319 // otherwise, if the argument is null (the default), then the size of the 320 // (free list) block is printed in the first column. 321 template <class Chunk_t> 322 void FreeList<Chunk_t>::print_on(outputStream* st, const char* c) const { 323 if (c != NULL) { 324 st->print("%16s", c); 325 } else { 326 st->print(SIZE_FORMAT_W(16), size()); 327 } 328 } 329 330 template class FreeList<Metablock>; 331 template class FreeList<Metachunk>; 332 #if INCLUDE_ALL_GCS 333 template class FreeList<FreeChunk>; 334 #endif // INCLUDE_ALL_GCS