1 /*
2 * Copyright (c) 2001, 2016, 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 #include <new>
34
35 PtrQueue::PtrQueue(PtrQueueSet* qset, bool permanent, bool active) :
36 _qset(qset), _buf(NULL), _index(0), _sz(0), _active(active),
37 _permanent(permanent), _lock(NULL)
38 {}
39
40 PtrQueue::~PtrQueue() {
41 assert(_permanent || (_buf == NULL), "queue must be flushed before delete");
42 }
43
44 void PtrQueue::flush_impl() {
45 if (!_permanent && _buf != NULL) {
46 if (_index == _sz) {
47 // No work to do.
48 qset()->deallocate_buffer(_buf);
49 } else {
50 // We must NULL out the unused entries, then enqueue.
51 size_t limit = byte_index_to_index(_index);
52 for (size_t i = 0; i < limit; ++i) {
53 _buf[i] = NULL;
54 }
55 qset()->enqueue_complete_buffer(_buf);
56 }
57 _buf = NULL;
58 _index = 0;
59 }
60 }
61
62
63 void PtrQueue::enqueue_known_active(void* ptr) {
64 assert(_index <= _sz, "Invariant.");
65 assert(_index == 0 || _buf != NULL, "invariant");
66
67 while (_index == 0) {
68 handle_zero_index();
69 }
70
71 assert(_index > 0, "postcondition");
72 _index -= sizeof(void*);
73 _buf[byte_index_to_index(_index)] = ptr;
74 assert(_index <= _sz, "Invariant.");
75 }
76
77 void PtrQueue::locking_enqueue_completed_buffer(void** buf) {
78 assert(_lock->owned_by_self(), "Required.");
79
80 // We have to unlock _lock (which may be Shared_DirtyCardQ_lock) before
81 // we acquire DirtyCardQ_CBL_mon inside enqueue_complete_buffer as they
82 // have the same rank and we may get the "possible deadlock" message
83 _lock->unlock();
84
85 qset()->enqueue_complete_buffer(buf);
86 // We must relock only because the caller will unlock, for the normal
87 // case.
88 _lock->lock_without_safepoint_check();
89 }
90
91
92 BufferNode* BufferNode::allocate(size_t byte_size) {
93 assert(byte_size > 0, "precondition");
94 assert(is_size_aligned(byte_size, sizeof(void**)),
95 "Invalid buffer size " SIZE_FORMAT, byte_size);
96 void* data = NEW_C_HEAP_ARRAY(char, buffer_offset() + byte_size, mtGC);
97 return new (data) BufferNode;
98 }
99
100 void BufferNode::deallocate(BufferNode* node) {
101 node->~BufferNode();
102 FREE_C_HEAP_ARRAY(char, node);
103 }
104
105 PtrQueueSet::PtrQueueSet(bool notify_when_complete) :
106 _max_completed_queue(0),
107 _cbl_mon(NULL), _fl_lock(NULL),
108 _notify_when_complete(notify_when_complete),
109 _sz(0),
110 _completed_buffers_head(NULL),
111 _completed_buffers_tail(NULL),
112 _n_completed_buffers(0),
113 _process_completed_threshold(0), _process_completed(false),
114 _buf_free_list(NULL), _buf_free_list_sz(0)
115 {
116 _fl_owner = this;
117 }
118
119 PtrQueueSet::~PtrQueueSet() {
120 // There are presently only a couple (derived) instances ever
121 // created, and they are permanent, so no harm currently done by
122 // doing nothing here.
123 }
124
125 void PtrQueueSet::initialize(Monitor* cbl_mon,
126 Mutex* fl_lock,
127 int process_completed_threshold,
128 int max_completed_queue,
129 PtrQueueSet *fl_owner) {
130 _max_completed_queue = max_completed_queue;
131 _process_completed_threshold = process_completed_threshold;
132 _completed_queue_padding = 0;
133 assert(cbl_mon != NULL && fl_lock != NULL, "Init order issue?");
134 _cbl_mon = cbl_mon;
135 _fl_lock = fl_lock;
136 _fl_owner = (fl_owner != NULL) ? fl_owner : this;
137 }
138
139 void** PtrQueueSet::allocate_buffer() {
140 assert(_sz > 0, "Didn't set a buffer size.");
141 BufferNode* node = NULL;
142 {
143 MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
144 node = _fl_owner->_buf_free_list;
145 if (node != NULL) {
146 _fl_owner->_buf_free_list = node->next();
147 _fl_owner->_buf_free_list_sz--;
148 }
149 }
150 if (node == NULL) {
151 node = BufferNode::allocate(_sz);
152 } else {
153 // Reinitialize buffer obtained from free list.
154 node->set_index(0);
155 node->set_next(NULL);
156 }
157 return BufferNode::make_buffer_from_node(node);
158 }
159
160 void PtrQueueSet::deallocate_buffer(void** buf) {
161 assert(_sz > 0, "Didn't set a buffer size.");
162 MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
163 BufferNode *node = BufferNode::make_node_from_buffer(buf);
164 node->set_next(_fl_owner->_buf_free_list);
165 _fl_owner->_buf_free_list = node;
166 _fl_owner->_buf_free_list_sz++;
167 }
168
169 void PtrQueueSet::reduce_free_list() {
170 assert(_fl_owner == this, "Free list reduction is allowed only for the owner");
171 // For now we'll adopt the strategy of deleting half.
172 MutexLockerEx x(_fl_lock, Mutex::_no_safepoint_check_flag);
173 size_t n = _buf_free_list_sz / 2;
174 for (size_t i = 0; i < n; ++i) {
175 assert(_buf_free_list != NULL,
176 "_buf_free_list_sz is wrong: " SIZE_FORMAT, _buf_free_list_sz);
177 BufferNode* node = _buf_free_list;
178 _buf_free_list = node->next();
179 _buf_free_list_sz--;
180 BufferNode::deallocate(node);
181 }
182 }
183
184 void PtrQueue::handle_zero_index() {
185 assert(_index == 0, "Precondition.");
186
187 // This thread records the full buffer and allocates a new one (while
188 // holding the lock if there is one).
189 if (_buf != NULL) {
190 if (!should_enqueue_buffer()) {
191 assert(_index > 0, "the buffer can only be re-used if it's not full");
192 return;
193 }
194
195 if (_lock) {
196 assert(_lock->owned_by_self(), "Required.");
197
198 // The current PtrQ may be the shared dirty card queue and
199 // may be being manipulated by more than one worker thread
200 // during a pause. Since the enqueueing of the completed
201 // buffer unlocks the Shared_DirtyCardQ_lock more than one
202 // worker thread can 'race' on reading the shared queue attributes
203 // (_buf and _index) and multiple threads can call into this
204 // routine for the same buffer. This will cause the completed
205 // buffer to be added to the CBL multiple times.
206
207 // We "claim" the current buffer by caching value of _buf in
208 // a local and clearing the field while holding _lock. When
209 // _lock is released (while enqueueing the completed buffer)
210 // the thread that acquires _lock will skip this code,
211 // preventing the subsequent the multiple enqueue, and
212 // install a newly allocated buffer below.
213
214 void** buf = _buf; // local pointer to completed buffer
215 _buf = NULL; // clear shared _buf field
216
217 locking_enqueue_completed_buffer(buf); // enqueue completed buffer
218
219 // While the current thread was enqueueing the buffer another thread
220 // may have a allocated a new buffer and inserted it into this pointer
221 // queue. If that happens then we just return so that the current
222 // thread doesn't overwrite the buffer allocated by the other thread
223 // and potentially losing some dirtied cards.
224
225 if (_buf != NULL) return;
226 } else {
227 if (qset()->process_or_enqueue_complete_buffer(_buf)) {
228 // Recycle the buffer. No allocation.
229 _sz = qset()->buffer_size();
230 _index = _sz;
231 return;
232 }
233 }
234 }
235 // Reallocate the buffer
236 _buf = qset()->allocate_buffer();
237 _sz = qset()->buffer_size();
238 _index = _sz;
239 }
240
241 bool PtrQueueSet::process_or_enqueue_complete_buffer(void** buf) {
242 if (Thread::current()->is_Java_thread()) {
243 // We don't lock. It is fine to be epsilon-precise here.
244 if (_max_completed_queue == 0 || _max_completed_queue > 0 &&
245 _n_completed_buffers >= _max_completed_queue + _completed_queue_padding) {
246 bool b = mut_process_buffer(buf);
247 if (b) {
248 // True here means that the buffer hasn't been deallocated and the caller may reuse it.
249 return true;
250 }
251 }
252 }
253 // The buffer will be enqueued. The caller will have to get a new one.
254 enqueue_complete_buffer(buf);
255 return false;
256 }
257
258 void PtrQueueSet::enqueue_complete_buffer(void** buf, size_t index) {
259 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
260 BufferNode* cbn = BufferNode::make_node_from_buffer(buf);
261 cbn->set_index(index);
262 cbn->set_next(NULL);
263 if (_completed_buffers_tail == NULL) {
264 assert(_completed_buffers_head == NULL, "Well-formedness");
265 _completed_buffers_head = cbn;
266 _completed_buffers_tail = cbn;
267 } else {
268 _completed_buffers_tail->set_next(cbn);
269 _completed_buffers_tail = cbn;
270 }
271 _n_completed_buffers++;
272
273 if (!_process_completed && _process_completed_threshold >= 0 &&
274 _n_completed_buffers >= _process_completed_threshold) {
275 _process_completed = true;
276 if (_notify_when_complete)
277 _cbl_mon->notify();
278 }
279 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
280 }
281
282 int PtrQueueSet::completed_buffers_list_length() {
283 int n = 0;
284 BufferNode* cbn = _completed_buffers_head;
285 while (cbn != NULL) {
286 n++;
287 cbn = cbn->next();
288 }
289 return n;
290 }
291
292 void PtrQueueSet::assert_completed_buffer_list_len_correct() {
293 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
294 assert_completed_buffer_list_len_correct_locked();
295 }
296
297 void PtrQueueSet::assert_completed_buffer_list_len_correct_locked() {
298 guarantee(completed_buffers_list_length() == _n_completed_buffers,
299 "Completed buffer length is wrong.");
300 }
301
302 void PtrQueueSet::set_buffer_size(size_t sz) {
303 assert(_sz == 0 && sz > 0, "Should be called only once.");
304 _sz = sz * sizeof(void*);
305 }
306
307 // Merge lists of buffers. Notify the processing threads.
308 // The source queue is emptied as a result. The queues
309 // must share the monitor.
310 void PtrQueueSet::merge_bufferlists(PtrQueueSet *src) {
311 assert(_cbl_mon == src->_cbl_mon, "Should share the same lock");
312 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
313 if (_completed_buffers_tail == NULL) {
314 assert(_completed_buffers_head == NULL, "Well-formedness");
315 _completed_buffers_head = src->_completed_buffers_head;
316 _completed_buffers_tail = src->_completed_buffers_tail;
317 } else {
318 assert(_completed_buffers_head != NULL, "Well formedness");
319 if (src->_completed_buffers_head != NULL) {
320 _completed_buffers_tail->set_next(src->_completed_buffers_head);
321 _completed_buffers_tail = src->_completed_buffers_tail;
322 }
323 }
324 _n_completed_buffers += src->_n_completed_buffers;
325
326 src->_n_completed_buffers = 0;
327 src->_completed_buffers_head = NULL;
328 src->_completed_buffers_tail = NULL;
329
330 assert(_completed_buffers_head == NULL && _completed_buffers_tail == NULL ||
331 _completed_buffers_head != NULL && _completed_buffers_tail != NULL,
332 "Sanity");
333 }
334
335 void PtrQueueSet::notify_if_necessary() {
336 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
337 if (_n_completed_buffers >= _process_completed_threshold || _max_completed_queue == 0) {
338 _process_completed = true;
339 if (_notify_when_complete)
340 _cbl_mon->notify();
341 }
342 }