1 /*
2 * Copyright (c) 2001, 2015, 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/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 permanent, bool active) :
34 _qset(qset), _buf(NULL), _index(0), _sz(0), _active(active),
35 _permanent(permanent), _lock(NULL)
36 {}
37
38 PtrQueue::~PtrQueue() {
39 assert(_permanent || (_buf == NULL), "queue must be flushed before delete");
40 }
41
42 void PtrQueue::flush_impl() {
43 if (!_permanent && _buf != NULL) {
44 if (_index == _sz) {
45 // No work to do.
46 qset()->deallocate_buffer(_buf);
47 } else {
48 // We must NULL out the unused entries, then enqueue.
49 size_t limit = byte_index_to_index(_index);
50 for (size_t i = 0; i < limit; ++i) {
51 _buf[i] = NULL;
52 }
53 qset()->enqueue_complete_buffer(_buf);
54 }
55 _buf = NULL;
56 _index = 0;
57 }
58 }
59
60
61 void PtrQueue::enqueue_known_active(void* ptr) {
62 assert(_index <= _sz, "Invariant.");
63 assert(_index == 0 || _buf != NULL, "invariant");
64
65 while (_index == 0) {
66 handle_zero_index();
67 }
68
69 assert(_index > 0, "postcondition");
70 _index -= sizeof(void*);
71 _buf[byte_index_to_index(_index)] = ptr;
72 assert(_index <= _sz, "Invariant.");
73 }
74
75 void PtrQueue::locking_enqueue_completed_buffer(void** buf) {
76 assert(_lock->owned_by_self(), "Required.");
77
78 // We have to unlock _lock (which may be Shared_DirtyCardQ_lock) before
79 // we acquire DirtyCardQ_CBL_mon inside enqueue_complete_buffer as they
80 // have the same rank and we may get the "possible deadlock" message
81 _lock->unlock();
82
83 qset()->enqueue_complete_buffer(buf);
84 // We must relock only because the caller will unlock, for the normal
85 // case.
86 _lock->lock_without_safepoint_check();
87 }
88
89
90 PtrQueueSet::PtrQueueSet(bool notify_when_complete) :
91 _max_completed_queue(0),
92 _cbl_mon(NULL), _fl_lock(NULL),
93 _notify_when_complete(notify_when_complete),
94 _sz(0),
95 _completed_buffers_head(NULL),
96 _completed_buffers_tail(NULL),
97 _n_completed_buffers(0),
98 _process_completed_threshold(0), _process_completed(false),
99 _buf_free_list(NULL), _buf_free_list_sz(0)
100 {
101 _fl_owner = this;
102 }
103
104 PtrQueueSet::~PtrQueueSet() {
105 // There are presently only a couple (derived) instances ever
106 // created, and they are permanent, so no harm currently done by
107 // doing nothing here.
108 }
109
110 void PtrQueueSet::initialize(Monitor* cbl_mon,
111 Mutex* fl_lock,
112 size_t process_completed_threshold,
113 size_t max_completed_queue,
114 PtrQueueSet *fl_owner) {
115 _max_completed_queue = max_completed_queue;
116 _process_completed_threshold = process_completed_threshold;
117 _completed_queue_padding = 0;
118 assert(cbl_mon != NULL && fl_lock != NULL, "Init order issue?");
119 _cbl_mon = cbl_mon;
120 _fl_lock = fl_lock;
121 _fl_owner = (fl_owner != NULL) ? fl_owner : this;
122 }
123
124 void** PtrQueueSet::allocate_buffer() {
125 assert(_sz > 0, "Didn't set a buffer size.");
126 MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
127 if (_fl_owner->_buf_free_list != NULL) {
128 void** res = BufferNode::make_buffer_from_node(_fl_owner->_buf_free_list);
129 _fl_owner->_buf_free_list = _fl_owner->_buf_free_list->next();
130 _fl_owner->_buf_free_list_sz--;
131 return res;
132 } else {
133 // Allocate space for the BufferNode in front of the buffer.
134 char *b = NEW_C_HEAP_ARRAY(char, _sz + BufferNode::aligned_size(), mtGC);
135 return BufferNode::make_buffer_from_block(b);
136 }
137 }
138
139 void PtrQueueSet::deallocate_buffer(void** buf) {
140 assert(_sz > 0, "Didn't set a buffer size.");
141 MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
142 BufferNode *node = BufferNode::make_node_from_buffer(buf);
143 node->set_next(_fl_owner->_buf_free_list);
144 _fl_owner->_buf_free_list = node;
145 _fl_owner->_buf_free_list_sz++;
146 }
147
148 void PtrQueueSet::reduce_free_list() {
149 assert(_fl_owner == this, "Free list reduction is allowed only for the owner");
150 // For now we'll adopt the strategy of deleting half.
151 MutexLockerEx x(_fl_lock, Mutex::_no_safepoint_check_flag);
152 size_t n = _buf_free_list_sz / 2;
153 while (n > 0) {
154 assert(_buf_free_list != NULL, "_buf_free_list_sz must be wrong.");
155 void* b = BufferNode::make_block_from_node(_buf_free_list);
156 _buf_free_list = _buf_free_list->next();
157 FREE_C_HEAP_ARRAY(char, b);
158 _buf_free_list_sz --;
159 n--;
160 }
161 }
162
163 void PtrQueue::handle_zero_index() {
164 assert(_index == 0, "Precondition.");
165
166 // This thread records the full buffer and allocates a new one (while
167 // holding the lock if there is one).
168 if (_buf != NULL) {
169 if (!should_enqueue_buffer()) {
170 assert(_index > 0, "the buffer can only be re-used if it's not full");
171 return;
172 }
173
174 if (_lock) {
175 assert(_lock->owned_by_self(), "Required.");
176
177 // The current PtrQ may be the shared dirty card queue and
178 // may be being manipulated by more than one worker thread
179 // during a pause. Since the enqueueing of the completed
180 // buffer unlocks the Shared_DirtyCardQ_lock more than one
181 // worker thread can 'race' on reading the shared queue attributes
182 // (_buf and _index) and multiple threads can call into this
183 // routine for the same buffer. This will cause the completed
184 // buffer to be added to the CBL multiple times.
185
186 // We "claim" the current buffer by caching value of _buf in
187 // a local and clearing the field while holding _lock. When
188 // _lock is released (while enqueueing the completed buffer)
189 // the thread that acquires _lock will skip this code,
190 // preventing the subsequent the multiple enqueue, and
191 // install a newly allocated buffer below.
192
193 void** buf = _buf; // local pointer to completed buffer
194 _buf = NULL; // clear shared _buf field
195
196 locking_enqueue_completed_buffer(buf); // enqueue completed buffer
197
198 // While the current thread was enqueueing the buffer another thread
199 // may have a allocated a new buffer and inserted it into this pointer
200 // queue. If that happens then we just return so that the current
201 // thread doesn't overwrite the buffer allocated by the other thread
202 // and potentially losing some dirtied cards.
203
204 if (_buf != NULL) return;
205 } else {
206 if (qset()->process_or_enqueue_complete_buffer(_buf)) {
207 // Recycle the buffer. No allocation.
208 _sz = qset()->buffer_size();
209 _index = _sz;
210 return;
211 }
212 }
213 }
214 // Reallocate the buffer
215 _buf = qset()->allocate_buffer();
216 _sz = qset()->buffer_size();
217 _index = _sz;
218 }
219
220 bool PtrQueueSet::process_or_enqueue_complete_buffer(void** buf) {
221 if (Thread::current()->is_Java_thread()) {
222 // We don't lock. It is fine to be epsilon-precise here.
223 if (_max_completed_queue == 0 || _max_completed_queue > 0 &&
224 _n_completed_buffers >= _max_completed_queue + _completed_queue_padding) {
225 bool b = mut_process_buffer(buf);
226 if (b) {
227 // True here means that the buffer hasn't been deallocated and the caller may reuse it.
228 return true;
229 }
230 }
231 }
232 // The buffer will be enqueued. The caller will have to get a new one.
233 enqueue_complete_buffer(buf);
234 return false;
235 }
236
237 void PtrQueueSet::enqueue_complete_buffer(void** buf, size_t index) {
238 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
239 BufferNode* cbn = BufferNode::new_from_buffer(buf);
240 cbn->set_index(index);
241 if (_completed_buffers_tail == NULL) {
242 assert(_completed_buffers_head == NULL, "Well-formedness");
243 _completed_buffers_head = cbn;
244 _completed_buffers_tail = cbn;
245 } else {
246 _completed_buffers_tail->set_next(cbn);
247 _completed_buffers_tail = cbn;
248 }
249 _n_completed_buffers++;
250
251 if (!_process_completed &&
252 _n_completed_buffers >= _process_completed_threshold) {
253 _process_completed = true;
254 if (_notify_when_complete) {
255 _cbl_mon->notify();
256 }
257 }
258 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
259 }
260
261 size_t PtrQueueSet::completed_buffers_list_length() {
262 int n = 0;
263 BufferNode* cbn = _completed_buffers_head;
264 while (cbn != NULL) {
265 n++;
266 cbn = cbn->next();
267 }
268 return n;
269 }
270
271 void PtrQueueSet::assert_completed_buffer_list_len_correct() {
272 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
273 assert_completed_buffer_list_len_correct_locked();
274 }
275
276 void PtrQueueSet::assert_completed_buffer_list_len_correct_locked() {
277 guarantee(completed_buffers_list_length() == _n_completed_buffers,
278 "Completed buffer length is wrong.");
279 }
280
281 void PtrQueueSet::set_buffer_size(size_t sz) {
282 assert(_sz == 0 && sz > 0, "Should be called only once.");
283 _sz = sz * sizeof(void*);
284 }
285
286 // Merge lists of buffers. Notify the processing threads.
287 // The source queue is emptied as a result. The queues
288 // must share the monitor.
289 void PtrQueueSet::merge_bufferlists(PtrQueueSet *src) {
290 assert(_cbl_mon == src->_cbl_mon, "Should share the same lock");
291 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
292 if (_completed_buffers_tail == NULL) {
293 assert(_completed_buffers_head == NULL, "Well-formedness");
294 _completed_buffers_head = src->_completed_buffers_head;
295 _completed_buffers_tail = src->_completed_buffers_tail;
296 } else {
297 assert(_completed_buffers_head != NULL, "Well formedness");
298 if (src->_completed_buffers_head != NULL) {
299 _completed_buffers_tail->set_next(src->_completed_buffers_head);
300 _completed_buffers_tail = src->_completed_buffers_tail;
301 }
302 }
303 _n_completed_buffers += src->_n_completed_buffers;
304
305 src->_n_completed_buffers = 0;
306 src->_completed_buffers_head = NULL;
307 src->_completed_buffers_tail = NULL;
308
309 assert(_completed_buffers_head == NULL && _completed_buffers_tail == NULL ||
310 _completed_buffers_head != NULL && _completed_buffers_tail != NULL,
311 "Sanity");
312 }
313
314 void PtrQueueSet::notify_if_necessary() {
315 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
316 if (_n_completed_buffers >= _process_completed_threshold || _max_completed_queue == 0) {
317 _process_completed = true;
318 if (_notify_when_complete)
319 _cbl_mon->notify();
320 }
321 }