1 /*
2 * Copyright (c) 2001, 2010, 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_implementation/concurrentMarkSweep/freeBlockDictionary.hpp"
27 #include "gc_implementation/concurrentMarkSweep/freeList.hpp"
28 #include "memory/sharedHeap.hpp"
29 #include "runtime/globals.hpp"
30 #include "runtime/mutex.hpp"
31 #include "runtime/vmThread.hpp"
32
33 // Free list. A FreeList is used to access a linked list of chunks
34 // of space in the heap. The head and tail are maintained so that
35 // items can be (as in the current implementation) added at the
36 // at the tail of the list and removed from the head of the list to
37 // maintain a FIFO queue.
38
39 FreeList::FreeList() :
40 _head(NULL), _tail(NULL)
41 #ifdef ASSERT
42 , _protecting_lock(NULL)
43 #endif
44 {
45 _size = 0;
46 _count = 0;
47 _hint = 0;
48 init_statistics();
49 }
50
51 FreeList::FreeList(FreeChunk* fc) :
52 _head(fc), _tail(fc)
53 #ifdef ASSERT
54 , _protecting_lock(NULL)
55 #endif
56 {
57 _size = fc->size();
58 _count = 1;
59 _hint = 0;
60 init_statistics();
61 #ifndef PRODUCT
62 _allocation_stats.set_returnedBytes(size() * HeapWordSize);
63 #endif
64 }
65
66 FreeList::FreeList(HeapWord* addr, size_t size) :
67 _head((FreeChunk*) addr), _tail((FreeChunk*) addr)
68 #ifdef ASSERT
69 , _protecting_lock(NULL)
70 #endif
71 {
72 assert(size > sizeof(FreeChunk), "size is too small");
73 head()->setSize(size);
74 _size = size;
75 _count = 1;
76 init_statistics();
77 #ifndef PRODUCT
78 _allocation_stats.set_returnedBytes(_size * HeapWordSize);
79 #endif
80 }
81
82 void FreeList::reset(size_t hint) {
83 set_count(0);
84 set_head(NULL);
85 set_tail(NULL);
86 set_hint(hint);
87 }
88
89 void FreeList::init_statistics(bool split_birth) {
90 _allocation_stats.initialize(split_birth);
91 }
92
93 FreeChunk* FreeList::getChunkAtHead() {
94 assert_proper_lock_protection();
95 assert(head() == NULL || head()->prev() == NULL, "list invariant");
96 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
97 FreeChunk* fc = head();
98 if (fc != NULL) {
99 FreeChunk* nextFC = fc->next();
100 if (nextFC != NULL) {
101 // The chunk fc being removed has a "next". Set the "next" to the
102 // "prev" of fc.
103 nextFC->linkPrev(NULL);
104 } else { // removed tail of list
105 link_tail(NULL);
106 }
107 link_head(nextFC);
108 decrement_count();
109 }
110 assert(head() == NULL || head()->prev() == NULL, "list invariant");
111 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
112 return fc;
113 }
114
115
116 void FreeList::getFirstNChunksFromList(size_t n, FreeList* fl) {
117 assert_proper_lock_protection();
118 assert(fl->count() == 0, "Precondition");
119 if (count() > 0) {
120 int k = 1;
121 fl->set_head(head()); n--;
122 FreeChunk* tl = head();
123 while (tl->next() != NULL && n > 0) {
124 tl = tl->next(); n--; k++;
125 }
126 assert(tl != NULL, "Loop Inv.");
127
128 // First, fix up the list we took from.
129 FreeChunk* new_head = tl->next();
130 set_head(new_head);
131 set_count(count() - k);
132 if (new_head == NULL) {
133 set_tail(NULL);
134 } else {
135 new_head->linkPrev(NULL);
136 }
137 // Now we can fix up the tail.
138 tl->linkNext(NULL);
139 // And return the result.
140 fl->set_tail(tl);
141 fl->set_count(k);
142 }
143 }
144
145 // Remove this chunk from the list
146 void FreeList::removeChunk(FreeChunk*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 FreeChunk* prevFC = fc->prev();
155 FreeChunk* 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->linkPrev(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->linkNext(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->linkPrev(NULL);
178 fc->linkNext(NULL);
179 )
180 assert(fc->isFree(), "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 void FreeList::returnChunkAtHead(FreeChunk* 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 FreeChunk* oldHead = head();
196 assert(chunk != oldHead, "double insertion");
197 chunk->linkAfter(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 DEBUG_ONLY(
205 if (record_return) {
206 increment_returnedBytes_by(size()*HeapWordSize);
207 }
208 )
209 assert(head() == NULL || head()->prev() == NULL, "list invariant");
210 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
211 assert(head() == NULL || head()->size() == size(), "wrong item on list");
212 assert(tail() == NULL || tail()->size() == size(), "wrong item on list");
213 }
214
215 void FreeList::returnChunkAtHead(FreeChunk* chunk) {
216 assert_proper_lock_protection();
217 returnChunkAtHead(chunk, true);
218 }
219
220 // Add this chunk at the tail of the list.
221 void FreeList::returnChunkAtTail(FreeChunk* chunk, bool record_return) {
222 assert_proper_lock_protection();
223 assert(head() == NULL || head()->prev() == NULL, "list invariant");
224 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
225 assert(chunk != NULL, "insert a NULL chunk");
226 assert(size() == chunk->size(), "wrong size");
227
228 FreeChunk* oldTail = tail();
229 assert(chunk != oldTail, "double insertion");
230 if (oldTail != NULL) {
231 oldTail->linkAfter(chunk);
232 } else { // only chunk in list
233 assert(head() == NULL, "inconsistent FreeList");
234 link_head(chunk);
235 }
236 link_tail(chunk);
237 increment_count(); // of # of chunks in list
238 DEBUG_ONLY(
239 if (record_return) {
240 increment_returnedBytes_by(size()*HeapWordSize);
241 }
242 )
243 assert(head() == NULL || head()->prev() == NULL, "list invariant");
244 assert(tail() == NULL || tail()->next() == NULL, "list invariant");
245 assert(head() == NULL || head()->size() == size(), "wrong item on list");
246 assert(tail() == NULL || tail()->size() == size(), "wrong item on list");
247 }
248
249 void FreeList::returnChunkAtTail(FreeChunk* chunk) {
250 returnChunkAtTail(chunk, true);
251 }
252
253 void FreeList::prepend(FreeList* fl) {
254 assert_proper_lock_protection();
255 if (fl->count() > 0) {
256 if (count() == 0) {
257 set_head(fl->head());
258 set_tail(fl->tail());
259 set_count(fl->count());
260 } else {
261 // Both are non-empty.
262 FreeChunk* fl_tail = fl->tail();
263 FreeChunk* this_head = head();
264 assert(fl_tail->next() == NULL, "Well-formedness of fl");
265 fl_tail->linkNext(this_head);
266 this_head->linkPrev(fl_tail);
267 set_head(fl->head());
268 set_count(count() + fl->count());
269 }
270 fl->set_head(NULL);
271 fl->set_tail(NULL);
272 fl->set_count(0);
273 }
274 }
275
276 // verifyChunkInFreeLists() is used to verify that an item is in this free list.
277 // It is used as a debugging aid.
278 bool FreeList::verifyChunkInFreeLists(FreeChunk* fc) const {
279 // This is an internal consistency check, not part of the check that the
280 // chunk is in the free lists.
281 guarantee(fc->size() == size(), "Wrong list is being searched");
282 FreeChunk* curFC = head();
283 while (curFC) {
284 // This is an internal consistency check.
285 guarantee(size() == curFC->size(), "Chunk is in wrong list.");
286 if (fc == curFC) {
287 return true;
288 }
289 curFC = curFC->next();
290 }
291 return false;
292 }
293
294 #ifndef PRODUCT
295 void FreeList::verify_stats() const {
296 // The +1 of the LH comparand is to allow some "looseness" in
297 // checking: we usually call this interface when adding a block
298 // and we'll subsequently update the stats; we cannot update the
299 // stats beforehand because in the case of the large-block BT
300 // dictionary for example, this might be the first block and
301 // in that case there would be no place that we could record
302 // the stats (which are kept in the block itself).
303 assert(_allocation_stats.prevSweep() + _allocation_stats.splitBirths() + 1 // Total Stock + 1
304 >= _allocation_stats.splitDeaths() + (ssize_t)count(), "Conservation Principle");
305 }
306
307 void FreeList::assert_proper_lock_protection_work() const {
308 assert(_protecting_lock != NULL, "Don't call this directly");
309 assert(ParallelGCThreads > 0, "Don't call this directly");
310 Thread* thr = Thread::current();
311 if (thr->is_VM_thread() || thr->is_ConcurrentGC_thread()) {
312 // assert that we are holding the freelist lock
313 } else if (thr->is_GC_task_thread()) {
314 assert(_protecting_lock->owned_by_self(), "FreeList RACE DETECTED");
315 } else if (thr->is_Java_thread()) {
316 assert(!SafepointSynchronize::is_at_safepoint(), "Should not be executing");
317 } else {
318 ShouldNotReachHere(); // unaccounted thread type?
319 }
320 }
321 #endif
322
323 // Print the "label line" for free list stats.
324 void FreeList::print_labels_on(outputStream* st, const char* c) {
325 st->print("%16s\t", c);
326 st->print("%14s\t" "%14s\t" "%14s\t" "%14s\t" "%14s\t"
327 "%14s\t" "%14s\t" "%14s\t" "%14s\t" "%14s\t" "\n",
328 "bfrsurp", "surplus", "desired", "prvSwep", "bfrSwep",
329 "count", "cBirths", "cDeaths", "sBirths", "sDeaths");
330 }
331
332 // Print the AllocationStats for the given free list. If the second argument
333 // to the call is a non-null string, it is printed in the first column;
334 // otherwise, if the argument is null (the default), then the size of the
335 // (free list) block is printed in the first column.
336 void FreeList::print_on(outputStream* st, const char* c) const {
337 if (c != NULL) {
338 st->print("%16s", c);
339 } else {
340 st->print(SIZE_FORMAT_W(16), size());
341 }
342 st->print("\t"
343 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"
344 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",
345 bfrSurp(), surplus(), desired(), prevSweep(), beforeSweep(),
346 count(), coalBirths(), coalDeaths(), splitBirths(), splitDeaths());
347 }