1 /*
2 * Copyright (c) 2001, 2008, 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 "incls/_precompiled.incl"
26 # include "incls/_freeList.cpp.incl"
27
28 // Free list. A FreeList is used to access a linked list of chunks
29 // of space in the heap. The head and tail are maintained so that
30 // items can be (as in the current implementation) added at the
31 // at the tail of the list and removed from the head of the list to
32 // maintain a FIFO queue.
33
34 FreeList::FreeList() :
35 _head(NULL), _tail(NULL)
36 #ifdef ASSERT
37 , _protecting_lock(NULL)
38 #endif
39 {
40 _size = 0;
41 _count = 0;
42 _hint = 0;
43 init_statistics();
44 }
45
46 FreeList::FreeList(FreeChunk* fc) :
47 _head(fc), _tail(fc)
48 #ifdef ASSERT
49 , _protecting_lock(NULL)
50 #endif
51 {
52 _size = fc->size();
53 _count = 1;
54 _hint = 0;
55 init_statistics();
56 #ifndef PRODUCT
57 _allocation_stats.set_returnedBytes(size() * HeapWordSize);
58 #endif
59 }
60
61 FreeList::FreeList(HeapWord* addr, size_t size) :
62 _head((FreeChunk*) addr), _tail((FreeChunk*) addr)
63 #ifdef ASSERT
64 , _protecting_lock(NULL)
65 #endif
66 {
67 assert(size > sizeof(FreeChunk), "size is too small");
68 head()->setSize(size);
69 _size = size;
70 _count = 1;
71 init_statistics();
72 #ifndef PRODUCT
73 _allocation_stats.set_returnedBytes(_size * HeapWordSize);
74 #endif
75 }
76
77 void FreeList::reset(size_t hint) {
78 set_count(0);
79 set_head(NULL);
80 set_tail(NULL);
81 set_hint(hint);
82 }
83
84 void FreeList::init_statistics(bool split_birth) {
85 _allocation_stats.initialize(split_birth);
86 }
87
88 FreeChunk* FreeList::getChunkAtHead() {
89 assert_proper_lock_protection();
90 assert(head() == NULL || head()->prev() == NULL, "list invariant");
91 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
92 FreeChunk* fc = head();
93 if (fc != NULL) {
94 FreeChunk* nextFC = fc->next();
95 if (nextFC != NULL) {
96 // The chunk fc being removed has a "next". Set the "next" to the
97 // "prev" of fc.
98 nextFC->linkPrev(NULL);
99 } else { // removed tail of list
100 link_tail(NULL);
101 }
102 link_head(nextFC);
103 decrement_count();
104 }
105 assert(head() == NULL || head()->prev() == NULL, "list invariant");
106 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
107 return fc;
108 }
109
110
111 void FreeList::getFirstNChunksFromList(size_t n, FreeList* 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 FreeChunk* 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 FreeChunk* 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->linkPrev(NULL);
131 }
132 // Now we can fix up the tail.
133 tl->linkNext(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 void FreeList::removeChunk(FreeChunk*fc) {
142 assert_proper_lock_protection();
143 assert(head() != NULL, "Remove from empty list");
144 assert(fc != NULL, "Remove a NULL chunk");
145 assert(size() == fc->size(), "Wrong list");
146 assert(head() == NULL || head()->prev() == NULL, "list invariant");
147 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
148
149 FreeChunk* prevFC = fc->prev();
150 FreeChunk* nextFC = fc->next();
151 if (nextFC != NULL) {
152 // The chunk fc being removed has a "next". Set the "next" to the
153 // "prev" of fc.
154 nextFC->linkPrev(prevFC);
155 } else { // removed tail of list
156 link_tail(prevFC);
157 }
158 if (prevFC == NULL) { // removed head of list
159 link_head(nextFC);
160 assert(nextFC == NULL || nextFC->prev() == NULL,
161 "Prev of head should be NULL");
162 } else {
163 prevFC->linkNext(nextFC);
164 assert(tail() != prevFC || prevFC->next() == NULL,
165 "Next of tail should be NULL");
166 }
167 decrement_count();
168 assert(((head() == NULL) + (tail() == NULL) + (count() == 0)) % 3 == 0,
169 "H/T/C Inconsistency");
170 // clear next and prev fields of fc, debug only
171 NOT_PRODUCT(
172 fc->linkPrev(NULL);
173 fc->linkNext(NULL);
174 )
175 assert(fc->isFree(), "Should still be a free chunk");
176 assert(head() == NULL || head()->prev() == NULL, "list invariant");
177 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
178 assert(head() == NULL || head()->size() == size(), "wrong item on list");
179 assert(tail() == NULL || tail()->size() == size(), "wrong item on list");
180 }
181
182 // Add this chunk at the head of the list.
183 void FreeList::returnChunkAtHead(FreeChunk* chunk, bool record_return) {
184 assert_proper_lock_protection();
185 assert(chunk != NULL, "insert a NULL chunk");
186 assert(size() == chunk->size(), "Wrong size");
187 assert(head() == NULL || head()->prev() == NULL, "list invariant");
188 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
189
190 FreeChunk* oldHead = head();
191 assert(chunk != oldHead, "double insertion");
192 chunk->linkAfter(oldHead);
193 link_head(chunk);
194 if (oldHead == NULL) { // only chunk in list
195 assert(tail() == NULL, "inconsistent FreeList");
196 link_tail(chunk);
197 }
198 increment_count(); // of # of chunks in list
199 DEBUG_ONLY(
200 if (record_return) {
201 increment_returnedBytes_by(size()*HeapWordSize);
202 }
203 )
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
210 void FreeList::returnChunkAtHead(FreeChunk* chunk) {
211 assert_proper_lock_protection();
212 returnChunkAtHead(chunk, true);
213 }
214
215 // Add this chunk at the tail of the list.
216 void FreeList::returnChunkAtTail(FreeChunk* chunk, bool record_return) {
217 assert_proper_lock_protection();
218 assert(head() == NULL || head()->prev() == NULL, "list invariant");
219 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
220 assert(chunk != NULL, "insert a NULL chunk");
221 assert(size() == chunk->size(), "wrong size");
222
223 FreeChunk* oldTail = tail();
224 assert(chunk != oldTail, "double insertion");
225 if (oldTail != NULL) {
226 oldTail->linkAfter(chunk);
227 } else { // only chunk in list
228 assert(head() == NULL, "inconsistent FreeList");
229 link_head(chunk);
230 }
231 link_tail(chunk);
232 increment_count(); // of # of chunks in list
233 DEBUG_ONLY(
234 if (record_return) {
235 increment_returnedBytes_by(size()*HeapWordSize);
236 }
237 )
238 assert(head() == NULL || head()->prev() == NULL, "list invariant");
239 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
240 assert(head() == NULL || head()->size() == size(), "wrong item on list");
241 assert(tail() == NULL || tail()->size() == size(), "wrong item on list");
242 }
243
244 void FreeList::returnChunkAtTail(FreeChunk* chunk) {
245 returnChunkAtTail(chunk, true);
246 }
247
248 void FreeList::prepend(FreeList* 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 FreeChunk* fl_tail = fl->tail();
258 FreeChunk* this_head = head();
259 assert(fl_tail->next() == NULL, "Well-formedness of fl");
260 fl_tail->linkNext(this_head);
261 this_head->linkPrev(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 // verifyChunkInFreeLists() is used to verify that an item is in this free list.
272 // It is used as a debugging aid.
273 bool FreeList::verifyChunkInFreeLists(FreeChunk* 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 FreeChunk* 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 #ifndef PRODUCT
290 void FreeList::verify_stats() const {
291 // The +1 of the LH comparand is to allow some "looseness" in
292 // checking: we usually call this interface when adding a block
293 // and we'll subsequently update the stats; we cannot update the
294 // stats beforehand because in the case of the large-block BT
295 // dictionary for example, this might be the first block and
296 // in that case there would be no place that we could record
297 // the stats (which are kept in the block itself).
298 assert(_allocation_stats.prevSweep() + _allocation_stats.splitBirths() + 1 // Total Stock + 1
299 >= _allocation_stats.splitDeaths() + (ssize_t)count(), "Conservation Principle");
300 }
301
302 void FreeList::assert_proper_lock_protection_work() const {
303 assert(_protecting_lock != NULL, "Don't call this directly");
304 assert(ParallelGCThreads > 0, "Don't call this directly");
305 Thread* thr = Thread::current();
306 if (thr->is_VM_thread() || thr->is_ConcurrentGC_thread()) {
307 // assert that we are holding the freelist lock
308 } else if (thr->is_GC_task_thread()) {
309 assert(_protecting_lock->owned_by_self(), "FreeList RACE DETECTED");
310 } else if (thr->is_Java_thread()) {
311 assert(!SafepointSynchronize::is_at_safepoint(), "Should not be executing");
312 } else {
313 ShouldNotReachHere(); // unaccounted thread type?
314 }
315 }
316 #endif
317
318 // Print the "label line" for free list stats.
319 void FreeList::print_labels_on(outputStream* st, const char* c) {
320 st->print("%16s\t", c);
321 st->print("%14s\t" "%14s\t" "%14s\t" "%14s\t" "%14s\t"
322 "%14s\t" "%14s\t" "%14s\t" "%14s\t" "%14s\t" "\n",
323 "bfrsurp", "surplus", "desired", "prvSwep", "bfrSwep",
324 "count", "cBirths", "cDeaths", "sBirths", "sDeaths");
325 }
326
327 // Print the AllocationStats for the given free list. If the second argument
328 // to the call is a non-null string, it is printed in the first column;
329 // otherwise, if the argument is null (the default), then the size of the
330 // (free list) block is printed in the first column.
331 void FreeList::print_on(outputStream* st, const char* c) const {
332 if (c != NULL) {
333 st->print("%16s", c);
334 } else {
335 st->print(SIZE_FORMAT_W(16), size());
336 }
337 st->print("\t"
338 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"
339 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",
340 bfrSurp(), surplus(), desired(), prevSweep(), beforeSweep(),
341 count(), coalBirths(), coalDeaths(), splitBirths(), splitDeaths());
342 }