1 /*
2 * Copyright (c) 2001, 2017, 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.
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23 */
24
25 #ifndef SHARE_MEMORY_FREELIST_INLINE_HPP
26 #define SHARE_MEMORY_FREELIST_INLINE_HPP
27
28 #include "gc/shared/collectedHeap.hpp"
29 #include "memory/freeList.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 #endif // SHARE_MEMORY_FREELIST_INLINE_HPP