1 /*
2 * Copyright (c) 2001, 2013, 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 qset()->enqueue_complete_buffer(_buf);
49 }
50 _buf = NULL;
51 _index = 0;
52 }
53 }
54
55
56 void PtrQueue::enqueue_known_active(void* ptr) {
57 assert(0 <= _index && _index <= _sz, "Invariant.");
58 assert(_index == 0 || _buf != NULL, "invariant");
59
60 while (_index == 0) {
61 handle_zero_index();
62 }
63
64 assert(_index > 0, "postcondition");
65 _index -= oopSize;
66 _buf[byte_index_to_index((int)_index)] = ptr;
67 assert(0 <= _index && _index <= _sz, "Invariant.");
68 }
69
70 void PtrQueue::locking_enqueue_completed_buffer(void** buf) {
71 assert(_lock->owned_by_self(), "Required.");
72
73 // We have to unlock _lock (which may be Shared_DirtyCardQ_lock) before
74 // we acquire DirtyCardQ_CBL_mon inside enqueue_complete_buffer as they
75 // have the same rank and we may get the "possible deadlock" message
76 _lock->unlock();
77
78 qset()->enqueue_complete_buffer(buf);
79 // We must relock only because the caller will unlock, for the normal
80 // case.
81 _lock->lock_without_safepoint_check();
82 }
83
84
85 PtrQueueSet::PtrQueueSet(bool notify_when_complete) :
86 _max_completed_queue(0),
87 _cbl_mon(NULL), _fl_lock(NULL),
88 _notify_when_complete(notify_when_complete),
89 _sz(0),
90 _completed_buffers_head(NULL),
91 _completed_buffers_tail(NULL),
92 _n_completed_buffers(0),
93 _process_completed_threshold(0), _process_completed(false),
94 _buf_free_list(NULL), _buf_free_list_sz(0)
95 {
96 _fl_owner = this;
97 }
98
99 void** PtrQueueSet::allocate_buffer() {
100 assert(_sz > 0, "Didn't set a buffer size.");
101 MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
102 if (_fl_owner->_buf_free_list != NULL) {
103 void** res = BufferNode::make_buffer_from_node(_fl_owner->_buf_free_list);
104 _fl_owner->_buf_free_list = _fl_owner->_buf_free_list->next();
105 _fl_owner->_buf_free_list_sz--;
106 return res;
107 } else {
108 // Allocate space for the BufferNode in front of the buffer.
109 char *b = NEW_C_HEAP_ARRAY(char, _sz + BufferNode::aligned_size(), mtGC);
110 return BufferNode::make_buffer_from_block(b);
111 }
112 }
113
114 void PtrQueueSet::deallocate_buffer(void** buf) {
115 assert(_sz > 0, "Didn't set a buffer size.");
116 MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
117 BufferNode *node = BufferNode::make_node_from_buffer(buf);
118 node->set_next(_fl_owner->_buf_free_list);
119 _fl_owner->_buf_free_list = node;
120 _fl_owner->_buf_free_list_sz++;
121 }
122
123 void PtrQueueSet::reduce_free_list() {
124 assert(_fl_owner == this, "Free list reduction is allowed only for the owner");
125 // For now we'll adopt the strategy of deleting half.
126 MutexLockerEx x(_fl_lock, Mutex::_no_safepoint_check_flag);
127 size_t n = _buf_free_list_sz / 2;
128 while (n > 0) {
129 assert(_buf_free_list != NULL, "_buf_free_list_sz must be wrong.");
130 void* b = BufferNode::make_block_from_node(_buf_free_list);
131 _buf_free_list = _buf_free_list->next();
132 FREE_C_HEAP_ARRAY(char, b);
133 _buf_free_list_sz --;
134 n--;
135 }
136 }
137
138 void PtrQueue::handle_zero_index() {
139 assert(_index == 0, "Precondition.");
140
141 // This thread records the full buffer and allocates a new one (while
142 // holding the lock if there is one).
143 if (_buf != NULL) {
144 if (!should_enqueue_buffer()) {
145 assert(_index > 0, "the buffer can only be re-used if it's not full");
146 return;
147 }
148
149 if (_lock) {
150 assert(_lock->owned_by_self(), "Required.");
151
152 // The current PtrQ may be the shared dirty card queue and
153 // may be being manipulated by more than one worker thread
154 // during a pause. Since the enqueueing of the completed
155 // buffer unlocks the Shared_DirtyCardQ_lock more than one
156 // worker thread can 'race' on reading the shared queue attributes
157 // (_buf and _index) and multiple threads can call into this
158 // routine for the same buffer. This will cause the completed
159 // buffer to be added to the CBL multiple times.
160
161 // We "claim" the current buffer by caching value of _buf in
162 // a local and clearing the field while holding _lock. When
163 // _lock is released (while enqueueing the completed buffer)
164 // the thread that acquires _lock will skip this code,
165 // preventing the subsequent the multiple enqueue, and
166 // install a newly allocated buffer below.
167
168 void** buf = _buf; // local pointer to completed buffer
169 _buf = NULL; // clear shared _buf field
170
171 locking_enqueue_completed_buffer(buf); // enqueue completed buffer
172
173 // While the current thread was enqueueing the buffer another thread
174 // may have a allocated a new buffer and inserted it into this pointer
175 // queue. If that happens then we just return so that the current
176 // thread doesn't overwrite the buffer allocated by the other thread
177 // and potentially losing some dirtied cards.
178
179 if (_buf != NULL) return;
180 } else {
181 if (qset()->process_or_enqueue_complete_buffer(_buf)) {
182 // Recycle the buffer. No allocation.
183 _sz = qset()->buffer_size();
184 _index = _sz;
185 return;
186 }
187 }
188 }
189 // Reallocate the buffer
190 _buf = qset()->allocate_buffer();
191 _sz = qset()->buffer_size();
192 _index = _sz;
193 assert(0 <= _index && _index <= _sz, "Invariant.");
194 }
195
196 bool PtrQueueSet::process_or_enqueue_complete_buffer(void** buf) {
197 if (Thread::current()->is_Java_thread()) {
198 // We don't lock. It is fine to be epsilon-precise here.
199 if (_max_completed_queue == 0 || _max_completed_queue > 0 &&
200 _n_completed_buffers >= _max_completed_queue + _completed_queue_padding) {
201 bool b = mut_process_buffer(buf);
202 if (b) {
203 // True here means that the buffer hasn't been deallocated and the caller may reuse it.
204 return true;
205 }
206 }
207 }
208 // The buffer will be enqueued. The caller will have to get a new one.
209 enqueue_complete_buffer(buf);
210 return false;
211 }
212
213 void PtrQueueSet::enqueue_complete_buffer(void** buf, size_t index) {
214 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
215 BufferNode* cbn = BufferNode::new_from_buffer(buf);
216 cbn->set_index(index);
217 if (_completed_buffers_tail == NULL) {
218 assert(_completed_buffers_head == NULL, "Well-formedness");
219 _completed_buffers_head = cbn;
220 _completed_buffers_tail = cbn;
221 } else {
222 _completed_buffers_tail->set_next(cbn);
223 _completed_buffers_tail = cbn;
224 }
225 _n_completed_buffers++;
226
227 if (!_process_completed && _process_completed_threshold >= 0 &&
228 _n_completed_buffers >= _process_completed_threshold) {
229 _process_completed = true;
230 if (_notify_when_complete)
231 _cbl_mon->notify();
232 }
233 debug_only(assert_completed_buffer_list_len_correct_locked());
234 }
235
236 int PtrQueueSet::completed_buffers_list_length() {
237 int n = 0;
238 BufferNode* cbn = _completed_buffers_head;
239 while (cbn != NULL) {
240 n++;
241 cbn = cbn->next();
242 }
243 return n;
244 }
245
246 void PtrQueueSet::assert_completed_buffer_list_len_correct() {
247 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
248 assert_completed_buffer_list_len_correct_locked();
249 }
250
251 void PtrQueueSet::assert_completed_buffer_list_len_correct_locked() {
252 guarantee(completed_buffers_list_length() == _n_completed_buffers,
253 "Completed buffer length is wrong.");
254 }
255
256 void PtrQueueSet::set_buffer_size(size_t sz) {
257 assert(_sz == 0 && sz > 0, "Should be called only once.");
258 _sz = sz * oopSize;
259 }
260
261 // Merge lists of buffers. Notify the processing threads.
262 // The source queue is emptied as a result. The queues
263 // must share the monitor.
264 void PtrQueueSet::merge_bufferlists(PtrQueueSet *src) {
265 assert(_cbl_mon == src->_cbl_mon, "Should share the same lock");
266 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
267 if (_completed_buffers_tail == NULL) {
268 assert(_completed_buffers_head == NULL, "Well-formedness");
269 _completed_buffers_head = src->_completed_buffers_head;
270 _completed_buffers_tail = src->_completed_buffers_tail;
271 } else {
272 assert(_completed_buffers_head != NULL, "Well formedness");
273 if (src->_completed_buffers_head != NULL) {
274 _completed_buffers_tail->set_next(src->_completed_buffers_head);
275 _completed_buffers_tail = src->_completed_buffers_tail;
276 }
277 }
278 _n_completed_buffers += src->_n_completed_buffers;
279
280 src->_n_completed_buffers = 0;
281 src->_completed_buffers_head = NULL;
282 src->_completed_buffers_tail = NULL;
283
284 assert(_completed_buffers_head == NULL && _completed_buffers_tail == NULL ||
285 _completed_buffers_head != NULL && _completed_buffers_tail != NULL,
286 "Sanity");
287 }
288
289 void PtrQueueSet::notify_if_necessary() {
290 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
291 if (_n_completed_buffers >= _process_completed_threshold || _max_completed_queue == 0) {
292 _process_completed = true;
293 if (_notify_when_complete)
294 _cbl_mon->notify();
295 }
296 }