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/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 #ifdef TARGET_OS_FAMILY_linux
32 # include "thread_linux.inline.hpp"
33 #endif
34 #ifdef TARGET_OS_FAMILY_solaris
35 # include "thread_solaris.inline.hpp"
36 #endif
37 #ifdef TARGET_OS_FAMILY_windows
38 # include "thread_windows.inline.hpp"
39 #endif
40
41 PtrQueue::PtrQueue(PtrQueueSet* qset_, bool perm, bool active) :
42 _qset(qset_), _buf(NULL), _index(0), _active(active),
43 _perm(perm), _lock(NULL)
44 {}
45
46 void PtrQueue::flush() {
47 if (!_perm && _buf != NULL) {
48 if (_index == _sz) {
49 // No work to do.
50 qset()->deallocate_buffer(_buf);
51 } else {
52 // We must NULL out the unused entries, then enqueue.
53 for (size_t i = 0; i < _index; i += oopSize) {
54 _buf[byte_index_to_index((int)i)] = NULL;
55 }
56 qset()->enqueue_complete_buffer(_buf);
57 }
58 _buf = NULL;
59 _index = 0;
60 }
61 }
62
63
64 static int byte_index_to_index(int ind) {
65 assert((ind % oopSize) == 0, "Invariant.");
66 return ind / oopSize;
67 }
68
69 static int index_to_byte_index(int byte_ind) {
70 return byte_ind * oopSize;
71 }
72
73 void PtrQueue::enqueue_known_active(void* ptr) {
74 assert(0 <= _index && _index <= _sz, "Invariant.");
75 assert(_index == 0 || _buf != NULL, "invariant");
76
77 while (_index == 0) {
78 handle_zero_index();
79 }
80
81 assert(_index > 0, "postcondition");
82 _index -= oopSize;
83 _buf[byte_index_to_index((int)_index)] = ptr;
84 assert(0 <= _index && _index <= _sz, "Invariant.");
85 }
86
87 void PtrQueue::locking_enqueue_completed_buffer(void** buf) {
88 assert(_lock->owned_by_self(), "Required.");
89
90 // We have to unlock _lock (which may be Shared_DirtyCardQ_lock) before
91 // we acquire DirtyCardQ_CBL_mon inside enqeue_complete_buffer as they
92 // have the same rank and we may get the "possible deadlock" message
93 _lock->unlock();
94
95 qset()->enqueue_complete_buffer(buf);
96 // We must relock only because the caller will unlock, for the normal
97 // case.
98 _lock->lock_without_safepoint_check();
99 }
100
101
102 PtrQueueSet::PtrQueueSet(bool notify_when_complete) :
103 _max_completed_queue(0),
104 _cbl_mon(NULL), _fl_lock(NULL),
105 _notify_when_complete(notify_when_complete),
106 _sz(0),
107 _completed_buffers_head(NULL),
108 _completed_buffers_tail(NULL),
109 _n_completed_buffers(0),
110 _process_completed_threshold(0), _process_completed(false),
111 _buf_free_list(NULL), _buf_free_list_sz(0)
112 {
113 _fl_owner = this;
114 }
115
116 void** PtrQueueSet::allocate_buffer() {
117 assert(_sz > 0, "Didn't set a buffer size.");
118 MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
119 if (_fl_owner->_buf_free_list != NULL) {
120 void** res = BufferNode::make_buffer_from_node(_fl_owner->_buf_free_list);
121 _fl_owner->_buf_free_list = _fl_owner->_buf_free_list->next();
122 _fl_owner->_buf_free_list_sz--;
123 return res;
124 } else {
125 // Allocate space for the BufferNode in front of the buffer.
126 char *b = NEW_C_HEAP_ARRAY(char, _sz + BufferNode::aligned_size());
127 return BufferNode::make_buffer_from_block(b);
128 }
129 }
130
131 void PtrQueueSet::deallocate_buffer(void** buf) {
132 assert(_sz > 0, "Didn't set a buffer size.");
133 MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
134 BufferNode *node = BufferNode::make_node_from_buffer(buf);
135 node->set_next(_fl_owner->_buf_free_list);
136 _fl_owner->_buf_free_list = node;
137 _fl_owner->_buf_free_list_sz++;
138 }
139
140 void PtrQueueSet::reduce_free_list() {
141 assert(_fl_owner == this, "Free list reduction is allowed only for the owner");
142 // For now we'll adopt the strategy of deleting half.
143 MutexLockerEx x(_fl_lock, Mutex::_no_safepoint_check_flag);
144 size_t n = _buf_free_list_sz / 2;
145 while (n > 0) {
146 assert(_buf_free_list != NULL, "_buf_free_list_sz must be wrong.");
147 void* b = BufferNode::make_block_from_node(_buf_free_list);
148 _buf_free_list = _buf_free_list->next();
149 FREE_C_HEAP_ARRAY(char, b);
150 _buf_free_list_sz --;
151 n--;
152 }
153 }
154
155 void PtrQueue::handle_zero_index() {
156 assert(0 == _index, "Precondition.");
157 // This thread records the full buffer and allocates a new one (while
158 // holding the lock if there is one).
159 if (_buf != NULL) {
160 if (_lock) {
161 assert(_lock->owned_by_self(), "Required.");
162
163 // The current PtrQ may be the shared dirty card queue and
164 // may be being manipulated by more than one worker thread
165 // during a pause. Since the enqueuing of the completed
166 // buffer unlocks the Shared_DirtyCardQ_lock more than one
167 // worker thread can 'race' on reading the shared queue attributes
168 // (_buf and _index) and multiple threads can call into this
169 // routine for the same buffer. This will cause the completed
170 // buffer to be added to the CBL multiple times.
171
172 // We "claim" the current buffer by caching value of _buf in
173 // a local and clearing the field while holding _lock. When
174 // _lock is released (while enqueueing the completed buffer)
175 // the thread that acquires _lock will skip this code,
176 // preventing the subsequent the multiple enqueue, and
177 // install a newly allocated buffer below.
178
179 void** buf = _buf; // local pointer to completed buffer
180 _buf = NULL; // clear shared _buf field
181
182 locking_enqueue_completed_buffer(buf); // enqueue completed buffer
183
184 // While the current thread was enqueuing the buffer another thread
185 // may have a allocated a new buffer and inserted it into this pointer
186 // queue. If that happens then we just return so that the current
187 // thread doesn't overwrite the buffer allocated by the other thread
188 // and potentially losing some dirtied cards.
189
190 if (_buf != NULL) return;
191 } else {
192 if (qset()->process_or_enqueue_complete_buffer(_buf)) {
193 // Recycle the buffer. No allocation.
194 _sz = qset()->buffer_size();
195 _index = _sz;
196 return;
197 }
198 }
199 }
200 // Reallocate the buffer
201 _buf = qset()->allocate_buffer();
202 _sz = qset()->buffer_size();
203 _index = _sz;
204 assert(0 <= _index && _index <= _sz, "Invariant.");
205 }
206
207 bool PtrQueueSet::process_or_enqueue_complete_buffer(void** buf) {
208 if (Thread::current()->is_Java_thread()) {
209 // We don't lock. It is fine to be epsilon-precise here.
210 if (_max_completed_queue == 0 || _max_completed_queue > 0 &&
211 _n_completed_buffers >= _max_completed_queue + _completed_queue_padding) {
212 bool b = mut_process_buffer(buf);
213 if (b) {
214 // True here means that the buffer hasn't been deallocated and the caller may reuse it.
215 return true;
216 }
217 }
218 }
219 // The buffer will be enqueued. The caller will have to get a new one.
220 enqueue_complete_buffer(buf);
221 return false;
222 }
223
224 void PtrQueueSet::enqueue_complete_buffer(void** buf, size_t index) {
225 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
226 BufferNode* cbn = BufferNode::new_from_buffer(buf);
227 cbn->set_index(index);
228 if (_completed_buffers_tail == NULL) {
229 assert(_completed_buffers_head == NULL, "Well-formedness");
230 _completed_buffers_head = cbn;
231 _completed_buffers_tail = cbn;
232 } else {
233 _completed_buffers_tail->set_next(cbn);
234 _completed_buffers_tail = cbn;
235 }
236 _n_completed_buffers++;
237
238 if (!_process_completed && _process_completed_threshold >= 0 &&
239 _n_completed_buffers >= _process_completed_threshold) {
240 _process_completed = true;
241 if (_notify_when_complete)
242 _cbl_mon->notify();
243 }
244 debug_only(assert_completed_buffer_list_len_correct_locked());
245 }
246
247 int PtrQueueSet::completed_buffers_list_length() {
248 int n = 0;
249 BufferNode* cbn = _completed_buffers_head;
250 while (cbn != NULL) {
251 n++;
252 cbn = cbn->next();
253 }
254 return n;
255 }
256
257 void PtrQueueSet::assert_completed_buffer_list_len_correct() {
258 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
259 assert_completed_buffer_list_len_correct_locked();
260 }
261
262 void PtrQueueSet::assert_completed_buffer_list_len_correct_locked() {
263 guarantee(completed_buffers_list_length() == _n_completed_buffers,
264 "Completed buffer length is wrong.");
265 }
266
267 void PtrQueueSet::set_buffer_size(size_t sz) {
268 assert(_sz == 0 && sz > 0, "Should be called only once.");
269 _sz = sz * oopSize;
270 }
271
272 // Merge lists of buffers. Notify the processing threads.
273 // The source queue is emptied as a result. The queues
274 // must share the monitor.
275 void PtrQueueSet::merge_bufferlists(PtrQueueSet *src) {
276 assert(_cbl_mon == src->_cbl_mon, "Should share the same lock");
277 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
278 if (_completed_buffers_tail == NULL) {
279 assert(_completed_buffers_head == NULL, "Well-formedness");
280 _completed_buffers_head = src->_completed_buffers_head;
281 _completed_buffers_tail = src->_completed_buffers_tail;
282 } else {
283 assert(_completed_buffers_head != NULL, "Well formedness");
284 if (src->_completed_buffers_head != NULL) {
285 _completed_buffers_tail->set_next(src->_completed_buffers_head);
286 _completed_buffers_tail = src->_completed_buffers_tail;
287 }
288 }
289 _n_completed_buffers += src->_n_completed_buffers;
290
291 src->_n_completed_buffers = 0;
292 src->_completed_buffers_head = NULL;
293 src->_completed_buffers_tail = NULL;
294
295 assert(_completed_buffers_head == NULL && _completed_buffers_tail == NULL ||
296 _completed_buffers_head != NULL && _completed_buffers_tail != NULL,
297 "Sanity");
298 }
299
300 void PtrQueueSet::notify_if_necessary() {
301 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
302 if (_n_completed_buffers >= _process_completed_threshold || _max_completed_queue == 0) {
303 _process_completed = true;
304 if (_notify_when_complete)
305 _cbl_mon->notify();
306 }
307 }