1 #ifdef USE_PRAGMA_IDENT_SRC
2 #pragma ident "@(#)freeList.cpp 1.31 07/05/05 17:05:48 JVM"
3 #endif
4 /*
5 * Copyright 2001-2006 Sun Microsystems, Inc. All Rights Reserved.
6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
7 *
8 * This code is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License version 2 only, as
10 * published by the Free Software Foundation.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
23 * CA 95054 USA or visit www.sun.com if you need additional information or
24 * have any questions.
25 *
26 */
27
28 # include "incls/_precompiled.incl"
29 # include "incls/_freeList.cpp.incl"
30
31 // Free list. A FreeList is used to access a linked list of chunks
32 // of space in the heap. The head and tail are maintained so that
33 // items can be (as in the current implementation) added at the
34 // at the tail of the list and removed from the head of the list to
35 // maintain a FIFO queue.
36
37 FreeList::FreeList() :
38 _head(NULL), _tail(NULL)
39 #ifdef ASSERT
40 , _protecting_lock(NULL)
41 #endif
42 {
43 _size = 0;
44 _count = 0;
45 _hint = 0;
46 init_statistics();
47 }
48
49 FreeList::FreeList(FreeChunk* fc) :
50 _head(fc), _tail(fc)
51 #ifdef ASSERT
52 , _protecting_lock(NULL)
53 #endif
54 {
55 _size = fc->size();
56 _count = 1;
57 _hint = 0;
58 init_statistics();
59 #ifndef PRODUCT
60 _allocation_stats.set_returnedBytes(size() * HeapWordSize);
61 #endif
62 }
63
64 FreeList::FreeList(HeapWord* addr, size_t size) :
65 _head((FreeChunk*) addr), _tail((FreeChunk*) addr)
66 #ifdef ASSERT
67 , _protecting_lock(NULL)
68 #endif
69 {
70 assert(size > sizeof(FreeChunk), "size is too small");
71 head()->setSize(size);
72 _size = size;
73 _count = 1;
74 init_statistics();
75 #ifndef PRODUCT
76 _allocation_stats.set_returnedBytes(_size * HeapWordSize);
77 #endif
78 }
79
80 void FreeList::reset(size_t hint) {
81 set_count(0);
82 set_head(NULL);
83 set_tail(NULL);
84 set_hint(hint);
85 }
86
87 void FreeList::init_statistics() {
88 _allocation_stats.initialize();
89 }
90
91 FreeChunk* FreeList::getChunkAtHead() {
92 assert_proper_lock_protection();
93 assert(head() == NULL || head()->prev() == NULL, "list invariant");
94 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
95 FreeChunk* fc = head();
96 if (fc != NULL) {
97 FreeChunk* 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->linkPrev(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 void FreeList::getFirstNChunksFromList(size_t n, FreeList* 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 FreeChunk* 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 FreeChunk* 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->linkPrev(NULL);
134 }
135 // Now we can fix up the tail.
136 tl->linkNext(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
144 void FreeList::removeChunk(FreeChunk*fc) {
145 assert_proper_lock_protection();
146 assert(head() != NULL, "Remove from empty list");
147 assert(fc != NULL, "Remove a NULL chunk");
148 assert(size() == fc->size(), "Wrong list");
149 assert(head() == NULL || head()->prev() == NULL, "list invariant");
150 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
151
152 FreeChunk* prevFC = fc->prev();
153 FreeChunk* nextFC = fc->next();
154 if (nextFC != NULL) {
155 // The chunk fc being removed has a "next". Set the "next" to the
156 // "prev" of fc.
157 nextFC->linkPrev(prevFC);
158 } else { // removed tail of list
159 link_tail(prevFC);
160 }
161 if (prevFC == NULL) { // removed head of list
162 link_head(nextFC);
163 assert(nextFC == NULL || nextFC->prev() == NULL,
164 "Prev of head should be NULL");
165 } else {
166 prevFC->linkNext(nextFC);
167 assert(tail() != prevFC || prevFC->next() == NULL,
168 "Next of tail should be NULL");
169 }
170 decrement_count();
171 #define TRAP_CODE 1
172 #if TRAP_CODE
173 if (head() == NULL) {
174 guarantee(tail() == NULL, "INVARIANT");
175 guarantee(count() == 0, "INVARIANT");
176 }
177 #endif
178 // clear next and prev fields of fc, debug only
179 NOT_PRODUCT(
180 fc->linkPrev(NULL);
181 fc->linkNext(NULL);
182 )
183 assert(fc->isFree(), "Should still be a free chunk");
184 assert(head() == NULL || head()->prev() == NULL, "list invariant");
185 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
186 assert(head() == NULL || head()->size() == size(), "wrong item on list");
187 assert(tail() == NULL || tail()->size() == size(), "wrong item on list");
188 }
189
190 // Add this chunk at the head of the list.
191 void FreeList::returnChunkAtHead(FreeChunk* chunk, bool record_return) {
192 assert_proper_lock_protection();
193 assert(chunk != NULL, "insert a NULL chunk");
194 assert(size() == chunk->size(), "Wrong size");
195 assert(head() == NULL || head()->prev() == NULL, "list invariant");
196 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
197
198 FreeChunk* oldHead = head();
199 assert(chunk != oldHead, "double insertion");
200 chunk->linkAfter(oldHead);
201 link_head(chunk);
202 if (oldHead == NULL) { // only chunk in list
203 assert(tail() == NULL, "inconsistent FreeList");
204 link_tail(chunk);
205 }
206 increment_count(); // of # of chunks in list
207 DEBUG_ONLY(
208 if (record_return) {
209 increment_returnedBytes_by(size()*HeapWordSize);
210 }
211 )
212 assert(head() == NULL || head()->prev() == NULL, "list invariant");
213 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
214 assert(head() == NULL || head()->size() == size(), "wrong item on list");
215 assert(tail() == NULL || tail()->size() == size(), "wrong item on list");
216 }
217
218 void FreeList::returnChunkAtHead(FreeChunk* chunk) {
219 assert_proper_lock_protection();
220 returnChunkAtHead(chunk, true);
221 }
222
223 // Add this chunk at the tail of the list.
224 void FreeList::returnChunkAtTail(FreeChunk* chunk, bool record_return) {
225 assert_proper_lock_protection();
226 assert(head() == NULL || head()->prev() == NULL, "list invariant");
227 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
228 assert(chunk != NULL, "insert a NULL chunk");
229 assert(size() == chunk->size(), "wrong size");
230
231 FreeChunk* oldTail = tail();
232 assert(chunk != oldTail, "double insertion");
233 if (oldTail != NULL) {
234 oldTail->linkAfter(chunk);
235 } else { // only chunk in list
236 assert(head() == NULL, "inconsistent FreeList");
237 link_head(chunk);
238 }
239 link_tail(chunk);
240 increment_count(); // of # of chunks in list
241 DEBUG_ONLY(
242 if (record_return) {
243 increment_returnedBytes_by(size()*HeapWordSize);
244 }
245 )
246 assert(head() == NULL || head()->prev() == NULL, "list invariant");
247 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
248 assert(head() == NULL || head()->size() == size(), "wrong item on list");
249 assert(tail() == NULL || tail()->size() == size(), "wrong item on list");
250 }
251
252 void FreeList::returnChunkAtTail(FreeChunk* chunk) {
253 returnChunkAtTail(chunk, true);
254 }
255
256 void FreeList::prepend(FreeList* fl) {
257 assert_proper_lock_protection();
258 if (fl->count() > 0) {
259 if (count() == 0) {
260 set_head(fl->head());
261 set_tail(fl->tail());
262 set_count(fl->count());
263 } else {
264 // Both are non-empty.
265 FreeChunk* fl_tail = fl->tail();
266 FreeChunk* this_head = head();
267 assert(fl_tail->next() == NULL, "Well-formedness of fl");
268 fl_tail->linkNext(this_head);
269 this_head->linkPrev(fl_tail);
270 set_head(fl->head());
271 set_count(count() + fl->count());
272 }
273 fl->set_head(NULL);
274 fl->set_tail(NULL);
275 fl->set_count(0);
276 }
277 }
278
279 // verifyChunkInFreeLists() is used to verify that an item is in this free list.
280 // It is used as a debugging aid.
281 bool FreeList::verifyChunkInFreeLists(FreeChunk* fc) const {
282 // This is an internal consistency check, not part of the check that the
283 // chunk is in the free lists.
284 guarantee(fc->size() == size(), "Wrong list is being searched");
285 FreeChunk* curFC = head();
286 while (curFC) {
287 // This is an internal consistency check.
288 guarantee(size() == curFC->size(), "Chunk is in wrong list.");
289 if (fc == curFC) {
290 return true;
291 }
292 curFC = curFC->next();
293 }
294 return false;
295 }
296
297 #ifndef PRODUCT
298 void FreeList::assert_proper_lock_protection_work() const {
299 #ifdef ASSERT
300 if (_protecting_lock != NULL &&
301 SharedHeap::heap()->n_par_threads() > 0) {
302 // Should become an assert.
303 guarantee(_protecting_lock->owned_by_self(), "FreeList RACE DETECTED");
304 }
305 #endif
306 }
307 #endif