1 /* 2 * Copyright (c) 2001, 2010, 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_implementation/concurrentMarkSweep/freeBlockDictionary.hpp" 27 #include "gc_implementation/concurrentMarkSweep/freeList.hpp" 28 #include "memory/sharedHeap.hpp" 29 #include "runtime/globals.hpp" 30 #include "runtime/mutex.hpp" 31 #include "runtime/vmThread.hpp" 32 33 // Free list. A FreeList is used to access a linked list of chunks 34 // of space in the heap. The head and tail are maintained so that 35 // items can be (as in the current implementation) added at the 36 // at the tail of the list and removed from the head of the list to 37 // maintain a FIFO queue. 38 39 FreeList::FreeList() : 40 _head(NULL), _tail(NULL) 41 #ifdef ASSERT 42 , _protecting_lock(NULL) 43 #endif 44 { 45 _size = 0; 46 _count = 0; 47 _hint = 0; 48 init_statistics(); 49 } 50 51 FreeList::FreeList(FreeChunk* fc) : 52 _head(fc), _tail(fc) 53 #ifdef ASSERT 54 , _protecting_lock(NULL) 55 #endif 56 { 57 _size = fc->size(); 58 _count = 1; 59 _hint = 0; 60 init_statistics(); 61 #ifndef PRODUCT 62 _allocation_stats.set_returnedBytes(size() * HeapWordSize); 63 #endif 64 } 65 66 FreeList::FreeList(HeapWord* addr, size_t size) : 67 _head((FreeChunk*) addr), _tail((FreeChunk*) addr) 68 #ifdef ASSERT 69 , _protecting_lock(NULL) 70 #endif 71 { 72 assert(size > sizeof(FreeChunk), "size is too small"); 73 head()->setSize(size); 74 _size = size; 75 _count = 1; 76 init_statistics(); 77 #ifndef PRODUCT 78 _allocation_stats.set_returnedBytes(_size * HeapWordSize); 79 #endif 80 } 81 82 void FreeList::reset(size_t hint) { 83 set_count(0); 84 set_head(NULL); 85 set_tail(NULL); 86 set_hint(hint); 87 } 88 89 void FreeList::init_statistics(bool split_birth) { 90 _allocation_stats.initialize(split_birth); 91 } 92 93 FreeChunk* FreeList::getChunkAtHead() { 94 assert_proper_lock_protection(); 95 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 96 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 97 FreeChunk* fc = head(); 98 if (fc != NULL) { 99 FreeChunk* nextFC = fc->next(); 100 if (nextFC != NULL) { 101 // The chunk fc being removed has a "next". Set the "next" to the 102 // "prev" of fc. 103 nextFC->linkPrev(NULL); 104 } else { // removed tail of list 105 link_tail(NULL); 106 } 107 link_head(nextFC); 108 decrement_count(); 109 } 110 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 111 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 112 return fc; 113 } 114 115 116 void FreeList::getFirstNChunksFromList(size_t n, FreeList* fl) { 117 assert_proper_lock_protection(); 118 assert(fl->count() == 0, "Precondition"); 119 if (count() > 0) { 120 int k = 1; 121 fl->set_head(head()); n--; 122 FreeChunk* tl = head(); 123 while (tl->next() != NULL && n > 0) { 124 tl = tl->next(); n--; k++; 125 } 126 assert(tl != NULL, "Loop Inv."); 127 128 // First, fix up the list we took from. 129 FreeChunk* new_head = tl->next(); 130 set_head(new_head); 131 set_count(count() - k); 132 if (new_head == NULL) { 133 set_tail(NULL); 134 } else { 135 new_head->linkPrev(NULL); 136 } 137 // Now we can fix up the tail. 138 tl->linkNext(NULL); 139 // And return the result. 140 fl->set_tail(tl); 141 fl->set_count(k); 142 } 143 } 144 145 // Remove this chunk from the list 146 void FreeList::removeChunk(FreeChunk*fc) { 147 assert_proper_lock_protection(); 148 assert(head() != NULL, "Remove from empty list"); 149 assert(fc != NULL, "Remove a NULL chunk"); 150 assert(size() == fc->size(), "Wrong list"); 151 assert(head() == NULL || head()->prev() == NULL, "list invariant"); 152 assert(tail() == NULL || tail()->next() == NULL, "list invariant"); 153 154 FreeChunk* prevFC = fc->prev(); 155 FreeChunk* nextFC = fc->next(); 156 if (nextFC != NULL) { 157 // The chunk fc being removed has a "next". Set the "next" to the 158 // "prev" of fc. 159 nextFC->linkPrev(prevFC); 160 } else { // removed tail of list 161 link_tail(prevFC); 162 } 163 if (prevFC == NULL) { // removed head of list 164 link_head(nextFC); 165 assert(nextFC == NULL || nextFC->prev() == NULL, 166 "Prev of head should be NULL"); 167 } else { 168 prevFC->linkNext(nextFC); 169 assert(tail() != prevFC || prevFC->next() == NULL, 170 "Next of tail should be NULL"); 171 } 172 decrement_count(); 173 assert(((head() == NULL) + (tail() == NULL) + (count() == 0)) % 3 == 0, 174 "H/T/C Inconsistency"); 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::verify_stats() const { 296 // The +1 of the LH comparand is to allow some "looseness" in 297 // checking: we usually call this interface when adding a block 298 // and we'll subsequently update the stats; we cannot update the 299 // stats beforehand because in the case of the large-block BT 300 // dictionary for example, this might be the first block and 301 // in that case there would be no place that we could record 302 // the stats (which are kept in the block itself). 303 assert(_allocation_stats.prevSweep() + _allocation_stats.splitBirths() + 1 // Total Stock + 1 304 >= _allocation_stats.splitDeaths() + (ssize_t)count(), "Conservation Principle"); 305 } 306 307 void FreeList::assert_proper_lock_protection_work() const { 308 assert(_protecting_lock != NULL, "Don't call this directly"); 309 assert(ParallelGCThreads > 0, "Don't call this directly"); 310 Thread* thr = Thread::current(); 311 if (thr->is_VM_thread() || thr->is_ConcurrentGC_thread()) { 312 // assert that we are holding the freelist lock 313 } else if (thr->is_GC_task_thread()) { 314 assert(_protecting_lock->owned_by_self(), "FreeList RACE DETECTED"); 315 } else if (thr->is_Java_thread()) { 316 assert(!SafepointSynchronize::is_at_safepoint(), "Should not be executing"); 317 } else { 318 ShouldNotReachHere(); // unaccounted thread type? 319 } 320 } 321 #endif 322 323 // Print the "label line" for free list stats. 324 void FreeList::print_labels_on(outputStream* st, const char* c) { 325 st->print("%16s\t", c); 326 st->print("%14s\t" "%14s\t" "%14s\t" "%14s\t" "%14s\t" 327 "%14s\t" "%14s\t" "%14s\t" "%14s\t" "%14s\t" "\n", 328 "bfrsurp", "surplus", "desired", "prvSwep", "bfrSwep", 329 "count", "cBirths", "cDeaths", "sBirths", "sDeaths"); 330 } 331 332 // Print the AllocationStats for the given free list. If the second argument 333 // to the call is a non-null string, it is printed in the first column; 334 // otherwise, if the argument is null (the default), then the size of the 335 // (free list) block is printed in the first column. 336 void FreeList::print_on(outputStream* st, const char* c) const { 337 if (c != NULL) { 338 st->print("%16s", c); 339 } else { 340 st->print(SIZE_FORMAT_W(16), size()); 341 } 342 st->print("\t" 343 SSIZE_FORMAT_W(14) "\t" SSIZE_FORMAT_W(14) "\t" SSIZE_FORMAT_W(14) "\t" SSIZE_FORMAT_W(14) "\t" SSIZE_FORMAT_W(14) "\t" 344 SSIZE_FORMAT_W(14) "\t" SSIZE_FORMAT_W(14) "\t" SSIZE_FORMAT_W(14) "\t" SSIZE_FORMAT_W(14) "\t" SSIZE_FORMAT_W(14) "\n", 345 bfrSurp(), surplus(), desired(), prevSweep(), beforeSweep(), 346 count(), coalBirths(), coalDeaths(), splitBirths(), splitDeaths()); 347 }