1 /*
2 * Copyright (c) 2001, 2012, 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/g1/ptrQueue.hpp"
27 #include "memory/allocation.hpp"
28 #include "memory/allocation.inline.hpp"
29 #include "runtime/mutex.hpp"
30 #include "runtime/mutexLocker.hpp"
31 #include "runtime/thread.inline.hpp"
32
33 PtrQueue::PtrQueue(PtrQueueSet* qset, bool perm, bool active) :
34 _qset(qset), _buf(NULL), _index(0), _active(active),
35 _perm(perm), _lock(NULL)
36 {}
37
38 void PtrQueue::flush() {
39 if (!_perm && _buf != NULL) {
40 if (_index == _sz) {
41 // No work to do.
42 qset()->deallocate_buffer(_buf);
43 } else {
44 // We must NULL out the unused entries, then enqueue.
45 for (size_t i = 0; i < _index; i += oopSize) {
46 _buf[byte_index_to_index((int)i)] = NULL;
47 }
48 assert(_buf != NULL, "must be non-null");
49 qset()->enqueue_complete_buffer(_buf);
50 }
51 _buf = NULL;
52 _index = 0;
53 }
54 }
55
56
57 void PtrQueue::enqueue_known_active(void* ptr) {
58 assert(0 <= _index && _index <= _sz, "Invariant.");
59 assert(_index == 0 || _buf != NULL, "invariant");
60
61 while (_index == 0) {
62 handle_zero_index();
63 }
64
65 assert(_index > 0, "postcondition");
66 _index -= oopSize;
67 _buf[byte_index_to_index((int)_index)] = ptr;
68 assert(0 <= _index && _index <= _sz, "Invariant.");
69 }
70
71 void PtrQueue::locking_enqueue_completed_buffer(void** buf) {
72 assert(_lock->owned_by_self(), "Required.");
73
74 // We have to unlock _lock (which may be Shared_DirtyCardQ_lock) before
75 // we acquire DirtyCardQ_CBL_mon inside enqeue_complete_buffer as they
76 // have the same rank and we may get the "possible deadlock" message
77 _lock->unlock();
78
79 qset()->enqueue_complete_buffer(buf);
80 // We must relock only because the caller will unlock, for the normal
81 // case.
82 _lock->lock_without_safepoint_check();
83 }
84
85
86 PtrQueueSet::PtrQueueSet(bool notify_when_complete) :
87 _max_completed_queue(0),
88 _cbl_mon(NULL), _fl_lock(NULL),
89 _notify_when_complete(notify_when_complete),
90 _sz(0),
91 _completed_buffers_head(NULL),
92 _completed_buffers_tail(NULL),
93 _n_completed_buffers(0),
94 _process_completed_threshold(0), _process_completed(false),
95 _buf_free_list(NULL), _buf_free_list_sz(0)
96 {
97 _fl_owner = this;
98 }
99
100 void** PtrQueueSet::allocate_buffer() {
101 assert(_sz > 0, "Didn't set a buffer size.");
102 MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
103 if (_fl_owner->_buf_free_list != NULL) {
104 void** res = BufferNode::make_buffer_from_node(_fl_owner->_buf_free_list);
105 _fl_owner->_buf_free_list = _fl_owner->_buf_free_list->next();
106 _fl_owner->_buf_free_list_sz--;
107 return res;
108 } else {
109 // Allocate space for the BufferNode in front of the buffer.
110 char *b = NEW_C_HEAP_ARRAY(char, _sz + BufferNode::aligned_size(), mtGC);
111 return BufferNode::make_buffer_from_block(b);
112 }
113 }
114
115 void PtrQueueSet::deallocate_buffer(void** buf) {
116 assert(_sz > 0, "Didn't set a buffer size.");
117 MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
118 BufferNode *node = BufferNode::make_node_from_buffer(buf);
119 node->set_next(_fl_owner->_buf_free_list);
120 _fl_owner->_buf_free_list = node;
121 _fl_owner->_buf_free_list_sz++;
122 }
123
124 void PtrQueueSet::reduce_free_list() {
125 assert(_fl_owner == this, "Free list reduction is allowed only for the owner");
126 // For now we'll adopt the strategy of deleting half.
127 MutexLockerEx x(_fl_lock, Mutex::_no_safepoint_check_flag);
128 size_t n = _buf_free_list_sz / 2;
129 while (n > 0) {
130 assert(_buf_free_list != NULL, "_buf_free_list_sz must be wrong.");
131 void* b = BufferNode::make_block_from_node(_buf_free_list);
132 _buf_free_list = _buf_free_list->next();
133 FREE_C_HEAP_ARRAY(char, b, mtGC);
134 _buf_free_list_sz --;
135 n--;
136 }
137 }
138
139 void PtrQueue::handle_zero_index() {
140 assert(_index == 0, "Precondition.");
141
142 // This thread records the full buffer and allocates a new one (while
143 // holding the lock if there is one).
144 if (_buf != NULL) {
145 if (!should_enqueue_buffer()) {
146 assert(_index > 0, "the buffer can only be re-used if it's not full");
147 return;
148 }
149
150 if (_lock) {
151 assert(_lock->owned_by_self(), "Required.");
152
153 // The current PtrQ may be the shared dirty card queue and
154 // may be being manipulated by more than one worker thread
155 // during a pause. Since the enqueuing of the completed
156 // buffer unlocks the Shared_DirtyCardQ_lock more than one
157 // worker thread can 'race' on reading the shared queue attributes
158 // (_buf and _index) and multiple threads can call into this
159 // routine for the same buffer. This will cause the completed
160 // buffer to be added to the CBL multiple times.
161
162 // We "claim" the current buffer by caching value of _buf in
163 // a local and clearing the field while holding _lock. When
164 // _lock is released (while enqueueing the completed buffer)
165 // the thread that acquires _lock will skip this code,
166 // preventing the subsequent the multiple enqueue, and
167 // install a newly allocated buffer below.
168
169 void** buf = _buf; // local pointer to completed buffer
170 _buf = NULL; // clear shared _buf field
171
172 locking_enqueue_completed_buffer(buf); // enqueue completed buffer
173
174 // While the current thread was enqueuing the buffer another thread
175 // may have a allocated a new buffer and inserted it into this pointer
176 // queue. If that happens then we just return so that the current
177 // thread doesn't overwrite the buffer allocated by the other thread
178 // and potentially losing some dirtied cards.
179
180 if (_buf != NULL) return;
181 } else {
182 if (qset()->process_or_enqueue_complete_buffer(_buf)) {
183 // Recycle the buffer. No allocation.
184 _sz = qset()->buffer_size();
185 _index = _sz;
186 return;
187 }
188 }
189 }
190 // Reallocate the buffer
191 _buf = qset()->allocate_buffer();
192 _sz = qset()->buffer_size();
193 _index = _sz;
194 assert(0 <= _index && _index <= _sz, "Invariant.");
195 }
196
197 bool PtrQueueSet::process_or_enqueue_complete_buffer(void** buf) {
198 if (Thread::current()->is_Java_thread()) {
199 // We don't lock. It is fine to be epsilon-precise here.
200 if (_max_completed_queue == 0 || _max_completed_queue > 0 &&
201 _n_completed_buffers >= _max_completed_queue + _completed_queue_padding) {
202 bool b = mut_process_buffer(buf);
203 if (b) {
204 // True here means that the buffer hasn't been deallocated and the caller may reuse it.
205 return true;
206 }
207 }
208 }
209 // The buffer will be enqueued. The caller will have to get a new one.
210 enqueue_complete_buffer(buf);
211 return false;
212 }
213
214 void PtrQueueSet::enqueue_complete_buffer(void** buf, size_t index) {
215 assert(buf != NULL, "must be non-null");
216 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
217 BufferNode* cbn = BufferNode::new_from_buffer(buf);
218 cbn->set_index(index);
219 if (_completed_buffers_tail == NULL) {
220 assert(_completed_buffers_head == NULL, "Well-formedness");
221 _completed_buffers_head = cbn;
222 _completed_buffers_tail = cbn;
223 } else {
224 _completed_buffers_tail->set_next(cbn);
225 _completed_buffers_tail = cbn;
226 }
227 _n_completed_buffers++;
228
229 if (!_process_completed && _process_completed_threshold >= 0 &&
230 _n_completed_buffers >= _process_completed_threshold) {
231 _process_completed = true;
232 if (_notify_when_complete)
233 _cbl_mon->notify();
234 }
235 debug_only(assert_completed_buffer_list_len_correct_locked());
236 }
237
238 int PtrQueueSet::completed_buffers_list_length() {
239 int n = 0;
240 BufferNode* cbn = _completed_buffers_head;
241 while (cbn != NULL) {
242 n++;
243 cbn = cbn->next();
244 }
245 return n;
246 }
247
248 void PtrQueueSet::assert_completed_buffer_list_len_correct() {
249 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
250 assert_completed_buffer_list_len_correct_locked();
251 }
252
253 void PtrQueueSet::assert_completed_buffer_list_len_correct_locked() {
254 guarantee(completed_buffers_list_length() == _n_completed_buffers,
255 "Completed buffer length is wrong.");
256 }
257
258 void PtrQueueSet::set_buffer_size(size_t sz) {
259 assert(_sz == 0 && sz > 0, "Should be called only once.");
260 _sz = sz * oopSize;
261 }
262
263 // Merge lists of buffers. Notify the processing threads.
264 // The source queue is emptied as a result. The queues
265 // must share the monitor.
266 void PtrQueueSet::merge_bufferlists(PtrQueueSet *src) {
267 assert(_cbl_mon == src->_cbl_mon, "Should share the same lock");
268 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
269 if (_completed_buffers_tail == NULL) {
270 assert(_completed_buffers_head == NULL, "Well-formedness");
271 _completed_buffers_head = src->_completed_buffers_head;
272 _completed_buffers_tail = src->_completed_buffers_tail;
273 } else {
274 assert(_completed_buffers_head != NULL, "Well formedness");
275 if (src->_completed_buffers_head != NULL) {
276 _completed_buffers_tail->set_next(src->_completed_buffers_head);
277 _completed_buffers_tail = src->_completed_buffers_tail;
278 }
279 }
280 _n_completed_buffers += src->_n_completed_buffers;
281
282 src->_n_completed_buffers = 0;
283 src->_completed_buffers_head = NULL;
284 src->_completed_buffers_tail = NULL;
285
286 assert(_completed_buffers_head == NULL && _completed_buffers_tail == NULL ||
287 _completed_buffers_head != NULL && _completed_buffers_tail != NULL,
288 "Sanity");
289 }
290
291 void PtrQueueSet::notify_if_necessary() {
292 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
293 if (_n_completed_buffers >= _process_completed_threshold || _max_completed_queue == 0) {
294 _process_completed = true;
295 if (_notify_when_complete)
296 _cbl_mon->notify();
297 }
298 }