1 /*
   2  * Copyright (c) 2001, 2013, 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 "memory/freeBlockDictionary.hpp"
  27 #include "memory/freeList.hpp"
  28 #include "memory/metachunk.hpp"
  29 #include "memory/sharedHeap.hpp"
  30 #include "runtime/globals.hpp"
  31 #include "runtime/mutex.hpp"
  32 #include "runtime/vmThread.hpp"
  33 #include "utilities/macros.hpp"
  34 
  35 #if INCLUDE_ALL_GCS
  36 #include "gc_implementation/concurrentMarkSweep/freeChunk.hpp"
  37 #endif // INCLUDE_ALL_GCS
  38 
  39 // Free list.  A FreeList is used to access a linked list of chunks
  40 // of space in the heap.  The head and tail are maintained so that
  41 // items can be (as in the current implementation) added at the
  42 // at the tail of the list and removed from the head of the list to
  43 // maintain a FIFO queue.
  44 
  45 template <class Chunk>
  46 FreeList<Chunk>::FreeList() :
  47   _head(NULL), _tail(NULL)
  48 #ifdef ASSERT
  49   , _protecting_lock(NULL)
  50 #endif
  51 {
  52   _size         = 0;
  53   _count        = 0;
  54 }
  55 
  56 template <class Chunk>
  57 void FreeList<Chunk>::link_head(Chunk* v) {
  58   assert_proper_lock_protection();
  59   set_head(v);
  60   // If this method is not used (just set the head instead),
  61   // this check can be avoided.
  62   if (v != NULL) {
  63     v->link_prev(NULL);
  64   }
  65 }
  66 
  67 
  68 
  69 template <class Chunk>
  70 void FreeList<Chunk>::reset() {
  71   // Don't set the _size to 0 because this method is
  72   // used with a existing list that has a size but which has
  73   // been emptied.
  74   // Don't clear the _protecting_lock of an existing list.
  75   set_count(0);
  76   set_head(NULL);
  77   set_tail(NULL);
  78 }
  79 
  80 template <class Chunk>
  81 void FreeList<Chunk>::initialize() {
  82 #ifdef ASSERT
  83   // Needed early because it might be checked in other initializing code.
  84   set_protecting_lock(NULL);
  85 #endif
  86   reset();
  87   set_size(0);
  88 }
  89 
  90 template <class Chunk_t>
  91 Chunk_t* FreeList<Chunk_t>::get_chunk_at_head() {
  92   assert_proper_lock_protection();
  93   assert(head() == NULL || head()->prev() == NULL, "list invariant");
  94   assert(tail() == NULL || tail()->next() == NULL, "list invariant");
  95   Chunk_t* fc = head();
  96   if (fc != NULL) {
  97     Chunk_t* nextFC = fc->next();
  98     if (nextFC != NULL) {
  99       // The chunk fc being removed has a "next".  Set the "next" to the
 100       // "prev" of fc.
 101       nextFC->link_prev(NULL);
 102     } else { // removed tail of list
 103       link_tail(NULL);
 104     }
 105     link_head(nextFC);
 106     decrement_count();
 107   }
 108   assert(head() == NULL || head()->prev() == NULL, "list invariant");
 109   assert(tail() == NULL || tail()->next() == NULL, "list invariant");
 110   return fc;
 111 }
 112 
 113 
 114 template <class Chunk>
 115 void FreeList<Chunk>::getFirstNChunksFromList(size_t n, FreeList<Chunk>* fl) {
 116   assert_proper_lock_protection();
 117   assert(fl->count() == 0, "Precondition");
 118   if (count() > 0) {
 119     int k = 1;
 120     fl->set_head(head()); n--;
 121     Chunk* tl = head();
 122     while (tl->next() != NULL && n > 0) {
 123       tl = tl->next(); n--; k++;
 124     }
 125     assert(tl != NULL, "Loop Inv.");
 126 
 127     // First, fix up the list we took from.
 128     Chunk* new_head = tl->next();
 129     set_head(new_head);
 130     set_count(count() - k);
 131     if (new_head == NULL) {
 132       set_tail(NULL);
 133     } else {
 134       new_head->link_prev(NULL);
 135     }
 136     // Now we can fix up the tail.
 137     tl->link_next(NULL);
 138     // And return the result.
 139     fl->set_tail(tl);
 140     fl->set_count(k);
 141   }
 142 }
 143 
 144 // Remove this chunk from the list
 145 template <class Chunk>
 146 void FreeList<Chunk>::remove_chunk(Chunk*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    Chunk* prevFC = fc->prev();
 155    Chunk* 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->link_prev(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->link_next(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->link_prev(NULL);
 178      fc->link_next(NULL);
 179    )
 180    assert(fc->is_free(), "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 template <class Chunk>
 189 void FreeList<Chunk>::return_chunk_at_head(Chunk* chunk, bool record_return) {
 190   assert_proper_lock_protection();
 191   assert(chunk != NULL, "insert a NULL chunk");
 192   assert(size() == chunk->size(), "Wrong size");
 193   assert(head() == NULL || head()->prev() == NULL, "list invariant");
 194   assert(tail() == NULL || tail()->next() == NULL, "list invariant");
 195 
 196   Chunk* oldHead = head();
 197   assert(chunk != oldHead, "double insertion");
 198   chunk->link_after(oldHead);
 199   link_head(chunk);
 200   if (oldHead == NULL) { // only chunk in list
 201     assert(tail() == NULL, "inconsistent FreeList");
 202     link_tail(chunk);
 203   }
 204   increment_count(); // of # of chunks in list
 205   assert(head() == NULL || head()->prev() == NULL, "list invariant");
 206   assert(tail() == NULL || tail()->next() == NULL, "list invariant");
 207   assert(head() == NULL || head()->size() == size(), "wrong item on list");
 208   assert(tail() == NULL || tail()->size() == size(), "wrong item on list");
 209 }
 210 
 211 template <class Chunk>
 212 void FreeList<Chunk>::return_chunk_at_head(Chunk* chunk) {
 213   assert_proper_lock_protection();
 214   return_chunk_at_head(chunk, true);
 215 }
 216 
 217 // Add this chunk at the tail of the list.
 218 template <class Chunk>
 219 void FreeList<Chunk>::return_chunk_at_tail(Chunk* chunk, bool record_return) {
 220   assert_proper_lock_protection();
 221   assert(head() == NULL || head()->prev() == NULL, "list invariant");
 222   assert(tail() == NULL || tail()->next() == NULL, "list invariant");
 223   assert(chunk != NULL, "insert a NULL chunk");
 224   assert(size() == chunk->size(), "wrong size");
 225 
 226   Chunk* oldTail = tail();
 227   assert(chunk != oldTail, "double insertion");
 228   if (oldTail != NULL) {
 229     oldTail->link_after(chunk);
 230   } else { // only chunk in list
 231     assert(head() == NULL, "inconsistent FreeList");
 232     link_head(chunk);
 233   }
 234   link_tail(chunk);
 235   increment_count();  // of # of chunks in list
 236   assert(head() == NULL || head()->prev() == NULL, "list invariant");
 237   assert(tail() == NULL || tail()->next() == NULL, "list invariant");
 238   assert(head() == NULL || head()->size() == size(), "wrong item on list");
 239   assert(tail() == NULL || tail()->size() == size(), "wrong item on list");
 240 }
 241 
 242 template <class Chunk>
 243 void FreeList<Chunk>::return_chunk_at_tail(Chunk* chunk) {
 244   return_chunk_at_tail(chunk, true);
 245 }
 246 
 247 template <class Chunk>
 248 void FreeList<Chunk>::prepend(FreeList<Chunk>* fl) {
 249   assert_proper_lock_protection();
 250   if (fl->count() > 0) {
 251     if (count() == 0) {
 252       set_head(fl->head());
 253       set_tail(fl->tail());
 254       set_count(fl->count());
 255     } else {
 256       // Both are non-empty.
 257       Chunk* fl_tail = fl->tail();
 258       Chunk* this_head = head();
 259       assert(fl_tail->next() == NULL, "Well-formedness of fl");
 260       fl_tail->link_next(this_head);
 261       this_head->link_prev(fl_tail);
 262       set_head(fl->head());
 263       set_count(count() + fl->count());
 264     }
 265     fl->set_head(NULL);
 266     fl->set_tail(NULL);
 267     fl->set_count(0);
 268   }
 269 }
 270 
 271 // verify_chunk_in_free_lists() is used to verify that an item is in this free list.
 272 // It is used as a debugging aid.
 273 template <class Chunk>
 274 bool FreeList<Chunk>::verify_chunk_in_free_list(Chunk* fc) const {
 275   // This is an internal consistency check, not part of the check that the
 276   // chunk is in the free lists.
 277   guarantee(fc->size() == size(), "Wrong list is being searched");
 278   Chunk* curFC = head();
 279   while (curFC) {
 280     // This is an internal consistency check.
 281     guarantee(size() == curFC->size(), "Chunk is in wrong list.");
 282     if (fc == curFC) {
 283       return true;
 284     }
 285     curFC = curFC->next();
 286   }
 287   return false;
 288 }
 289 
 290 #ifndef PRODUCT
 291 template <class Chunk>
 292 void FreeList<Chunk>::assert_proper_lock_protection_work() const {
 293   assert(protecting_lock() != NULL, "Don't call this directly");
 294   assert(ParallelGCThreads > 0, "Don't call this directly");
 295   Thread* thr = Thread::current();
 296   if (thr->is_VM_thread() || thr->is_ConcurrentGC_thread()) {
 297     // assert that we are holding the freelist lock
 298   } else if (thr->is_GC_task_thread()) {
 299     assert(protecting_lock()->owned_by_self(), "FreeList RACE DETECTED");
 300   } else if (thr->is_Java_thread()) {
 301     assert(!SafepointSynchronize::is_at_safepoint(), "Should not be executing");
 302   } else {
 303     ShouldNotReachHere();  // unaccounted thread type?
 304   }
 305 }
 306 #endif
 307 
 308 // Print the "label line" for free list stats.
 309 template <class Chunk>
 310 void FreeList<Chunk>::print_labels_on(outputStream* st, const char* c) {
 311   st->print("%16s\t", c);
 312   st->print("%14s\t"    "%14s\t"    "%14s\t"    "%14s\t"    "%14s\t"
 313             "%14s\t"    "%14s\t"    "%14s\t"    "%14s\t"    "%14s\t"    "\n",
 314             "bfrsurp", "surplus", "desired", "prvSwep", "bfrSwep",
 315             "count",   "cBirths", "cDeaths", "sBirths", "sDeaths");
 316 }
 317 
 318 // Print the AllocationStats for the given free list. If the second argument
 319 // to the call is a non-null string, it is printed in the first column;
 320 // otherwise, if the argument is null (the default), then the size of the
 321 // (free list) block is printed in the first column.
 322 template <class Chunk_t>
 323 void FreeList<Chunk_t>::print_on(outputStream* st, const char* c) const {
 324   if (c != NULL) {
 325     st->print("%16s", c);
 326   } else {
 327     st->print(SIZE_FORMAT_W(16), size());
 328   }
 329 }
 330 
 331 template class FreeList<Metablock>;
 332 template class FreeList<Metachunk>;
 333 #if INCLUDE_ALL_GCS
 334 template class FreeList<FreeChunk>;
 335 #endif // INCLUDE_ALL_GCS