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#if INCLUDE_ALL_GCS
35#include "gc/cms/freeChunk.hpp"
36#endif // INCLUDE_ALL_GCS
37
38// Free list.  A FreeList is used to access a linked list of chunks
39// of space in the heap.  The head and tail are maintained so that
40// items can be (as in the current implementation) added at the
41// at the tail of the list and removed from the head of the list to
42// maintain a FIFO queue.
43
44template <class Chunk>
45FreeList<Chunk>::FreeList() :
46  _head(NULL), _tail(NULL)
47#ifdef ASSERT
48  , _protecting_lock(NULL)
49#endif
50{
51  _size         = 0;
52  _count        = 0;
53}
54
55template <class Chunk>
56void FreeList<Chunk>::link_head(Chunk* v) {
57  assert_proper_lock_protection();
58  set_head(v);
59  // If this method is not used (just set the head instead),
60  // this check can be avoided.
61  if (v != NULL) {
62    v->link_prev(NULL);
63  }
64}
65
66
67
68template <class Chunk>
69void FreeList<Chunk>::reset() {
70  // Don't set the _size to 0 because this method is
71  // used with a existing list that has a size but which has
72  // been emptied.
73  // Don't clear the _protecting_lock of an existing list.
74  set_count(0);
75  set_head(NULL);
76  set_tail(NULL);
77}
78
79template <class Chunk>
80void FreeList<Chunk>::initialize() {
81#ifdef ASSERT
82  // Needed early because it might be checked in other initializing code.
83  set_protecting_lock(NULL);
84#endif
85  reset();
86  set_size(0);
87}
88
89template <class Chunk_t>
90Chunk_t* FreeList<Chunk_t>::get_chunk_at_head() {
91  assert_proper_lock_protection();
92  assert(head() == NULL || head()->prev() == NULL, "list invariant");
93  assert(tail() == NULL || tail()->next() == NULL, "list invariant");
94  Chunk_t* fc = head();
95  if (fc != NULL) {
96    Chunk_t* nextFC = fc->next();
97    if (nextFC != NULL) {
98      // The chunk fc being removed has a "next".  Set the "next" to the
99      // "prev" of fc.
100      nextFC->link_prev(NULL);
101    } else { // removed tail of list
102      link_tail(NULL);
103    }
104    link_head(nextFC);
105    decrement_count();
106  }
107  assert(head() == NULL || head()->prev() == NULL, "list invariant");
108  assert(tail() == NULL || tail()->next() == NULL, "list invariant");
109  return fc;
110}
111
112
113template <class Chunk>
114void FreeList<Chunk>::getFirstNChunksFromList(size_t n, FreeList<Chunk>* fl) {
115  assert_proper_lock_protection();
116  assert(fl->count() == 0, "Precondition");
117  if (count() > 0) {
118    int k = 1;
119    fl->set_head(head()); n--;
120    Chunk* tl = head();
121    while (tl->next() != NULL && n > 0) {
122      tl = tl->next(); n--; k++;
123    }
124    assert(tl != NULL, "Loop Inv.");
125
126    // First, fix up the list we took from.
127    Chunk* new_head = tl->next();
128    set_head(new_head);
129    set_count(count() - k);
130    if (new_head == NULL) {
131      set_tail(NULL);
132    } else {
133      new_head->link_prev(NULL);
134    }
135    // Now we can fix up the tail.
136    tl->link_next(NULL);
137    // And return the result.
138    fl->set_tail(tl);
139    fl->set_count(k);
140  }
141}
142
143// Remove this chunk from the list
144template <class Chunk>
145void FreeList<Chunk>::remove_chunk(Chunk*fc) {
146   assert_proper_lock_protection();
147   assert(head() != NULL, "Remove from empty list");
148   assert(fc != NULL, "Remove a NULL chunk");
149   assert(size() == fc->size(), "Wrong list");
150   assert(head() == NULL || head()->prev() == NULL, "list invariant");
151   assert(tail() == NULL || tail()->next() == NULL, "list invariant");
152
153   Chunk* prevFC = fc->prev();
154   Chunk* nextFC = fc->next();
155   if (nextFC != NULL) {
156     // The chunk fc being removed has a "next".  Set the "next" to the
157     // "prev" of fc.
158     nextFC->link_prev(prevFC);
159   } else { // removed tail of list
160     link_tail(prevFC);
161   }
162   if (prevFC == NULL) { // removed head of list
163     link_head(nextFC);
164     assert(nextFC == NULL || nextFC->prev() == NULL,
165       "Prev of head should be NULL");
166   } else {
167     prevFC->link_next(nextFC);
168     assert(tail() != prevFC || prevFC->next() == NULL,
169       "Next of tail should be NULL");
170   }
171   decrement_count();
172   assert(((head() == NULL) + (tail() == NULL) + (count() == 0)) % 3 == 0,
173          "H/T/C Inconsistency");
174   // clear next and prev fields of fc, debug only
175   NOT_PRODUCT(
176     fc->link_prev(NULL);
177     fc->link_next(NULL);
178   )
179   assert(fc->is_free(), "Should still be a free chunk");
180   assert(head() == NULL || head()->prev() == NULL, "list invariant");
181   assert(tail() == NULL || tail()->next() == NULL, "list invariant");
182   assert(head() == NULL || head()->size() == size(), "wrong item on list");
183   assert(tail() == NULL || tail()->size() == size(), "wrong item on list");
184}
185
186// Add this chunk at the head of the list.
187template <class Chunk>
188void FreeList<Chunk>::return_chunk_at_head(Chunk* 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  Chunk* oldHead = head();
196  assert(chunk != oldHead, "double insertion");
197  chunk->link_after(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  assert(head() == NULL || head()->prev() == NULL, "list invariant");
205  assert(tail() == NULL || tail()->next() == NULL, "list invariant");
206  assert(head() == NULL || head()->size() == size(), "wrong item on list");
207  assert(tail() == NULL || tail()->size() == size(), "wrong item on list");
208}
209
210template <class Chunk>
211void FreeList<Chunk>::return_chunk_at_head(Chunk* chunk) {
212  assert_proper_lock_protection();
213  return_chunk_at_head(chunk, true);
214}
215
216// Add this chunk at the tail of the list.
217template <class Chunk>
218void FreeList<Chunk>::return_chunk_at_tail(Chunk* chunk, bool record_return) {
219  assert_proper_lock_protection();
220  assert(head() == NULL || head()->prev() == NULL, "list invariant");
221  assert(tail() == NULL || tail()->next() == NULL, "list invariant");
222  assert(chunk != NULL, "insert a NULL chunk");
223  assert(size() == chunk->size(), "wrong size");
224
225  Chunk* oldTail = tail();
226  assert(chunk != oldTail, "double insertion");
227  if (oldTail != NULL) {
228    oldTail->link_after(chunk);
229  } else { // only chunk in list
230    assert(head() == NULL, "inconsistent FreeList");
231    link_head(chunk);
232  }
233  link_tail(chunk);
234  increment_count();  // of # of chunks in list
235  assert(head() == NULL || head()->prev() == NULL, "list invariant");
236  assert(tail() == NULL || tail()->next() == NULL, "list invariant");
237  assert(head() == NULL || head()->size() == size(), "wrong item on list");
238  assert(tail() == NULL || tail()->size() == size(), "wrong item on list");
239}
240
241template <class Chunk>
242void FreeList<Chunk>::return_chunk_at_tail(Chunk* chunk) {
243  return_chunk_at_tail(chunk, true);
244}
245
246template <class Chunk>
247void FreeList<Chunk>::prepend(FreeList<Chunk>* fl) {
248  assert_proper_lock_protection();
249  if (fl->count() > 0) {
250    if (count() == 0) {
251      set_head(fl->head());
252      set_tail(fl->tail());
253      set_count(fl->count());
254    } else {
255      // Both are non-empty.
256      Chunk* fl_tail = fl->tail();
257      Chunk* this_head = head();
258      assert(fl_tail->next() == NULL, "Well-formedness of fl");
259      fl_tail->link_next(this_head);
260      this_head->link_prev(fl_tail);
261      set_head(fl->head());
262      set_count(count() + fl->count());
263    }
264    fl->set_head(NULL);
265    fl->set_tail(NULL);
266    fl->set_count(0);
267  }
268}
269
270// verify_chunk_in_free_lists() is used to verify that an item is in this free list.
271// It is used as a debugging aid.
272template <class Chunk>
273bool FreeList<Chunk>::verify_chunk_in_free_list(Chunk* fc) const {
274  // This is an internal consistency check, not part of the check that the
275  // chunk is in the free lists.
276  guarantee(fc->size() == size(), "Wrong list is being searched");
277  Chunk* curFC = head();
278  while (curFC) {
279    // This is an internal consistency check.
280    guarantee(size() == curFC->size(), "Chunk is in wrong list.");
281    if (fc == curFC) {
282      return true;
283    }
284    curFC = curFC->next();
285  }
286  return false;
287}
288
289#ifdef ASSERT
290template <class Chunk>
291void FreeList<Chunk>::assert_proper_lock_protection_work() const {
292  // Nothing to do if the list has no assigned protecting lock
293  if (protecting_lock() == NULL) {
294    return;
295  }
296
297  Thread* thr = Thread::current();
298  if (thr->is_VM_thread() || thr->is_ConcurrentGC_thread()) {
299    // assert that we are holding the freelist lock
300  } else if (thr->is_GC_task_thread()) {
301    assert(protecting_lock()->owned_by_self(), "FreeList RACE DETECTED");
302  } else if (thr->is_Java_thread()) {
303    assert(!SafepointSynchronize::is_at_safepoint(), "Should not be executing");
304  } else {
305    ShouldNotReachHere();  // unaccounted thread type?
306  }
307}
308#endif
309
310// Print the "label line" for free list stats.
311template <class Chunk>
312void FreeList<Chunk>::print_labels_on(outputStream* st, const char* c) {
313  st->print("%16s\t", c);
314  st->print("%14s\t"    "%14s\t"    "%14s\t"    "%14s\t"    "%14s\t"
315            "%14s\t"    "%14s\t"    "%14s\t"    "%14s\t"    "%14s\t"    "\n",
316            "bfrsurp", "surplus", "desired", "prvSwep", "bfrSwep",
317            "count",   "cBirths", "cDeaths", "sBirths", "sDeaths");
318}
319
320// Print the AllocationStats for the given free list. If the second argument
321// to the call is a non-null string, it is printed in the first column;
322// otherwise, if the argument is null (the default), then the size of the
323// (free list) block is printed in the first column.
324template <class Chunk_t>
325void FreeList<Chunk_t>::print_on(outputStream* st, const char* c) const {
326  if (c != NULL) {
327    st->print("%16s", c);
328  } else {
329    st->print(SIZE_FORMAT_W(16), size());
330  }
331}
332
333template class FreeList<Metablock>;
334template class FreeList<Metachunk>;
335#if INCLUDE_ALL_GCS
336template class FreeList<FreeChunk>;
337#endif // INCLUDE_ALL_GCS
338