1 /*
2 * Copyright (c) 2001, 2017, 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),
37 _active(active),
38 _permanent(permanent),
39 _index(0),
40 _capacity_in_bytes(0),
41 _buf(NULL),
42 _lock(NULL)
43 {}
44
45 PtrQueue::~PtrQueue() {
46 assert(_permanent || (_buf == NULL), "queue must be flushed before delete");
47 }
48
49 void PtrQueue::flush_impl() {
50 if (_buf != NULL) {
51 BufferNode* node = BufferNode::make_node_from_buffer(_buf, index());
52 if (is_empty()) {
53 // No work to do.
54 qset()->deallocate_buffer(node);
55 } else {
56 qset()->enqueue_complete_buffer(node);
57 }
58 _buf = NULL;
59 set_index(0);
60 }
61 }
62
63
64 void PtrQueue::enqueue_known_active(void* ptr) {
65 while (_index == 0) {
66 handle_zero_index();
67 }
68
69 assert(_buf != NULL, "postcondition");
70 assert(index() > 0, "postcondition");
71 assert(index() <= capacity(), "invariant");
72 _index -= _element_size;
73 _buf[index()] = ptr;
74 }
75
76 void PtrQueue::locking_enqueue_completed_buffer(BufferNode* node) {
77 assert(_lock->owned_by_self(), "Required.");
78
79 // We have to unlock _lock (which may be Shared_DirtyCardQ_lock) before
80 // we acquire DirtyCardQ_CBL_mon inside enqueue_complete_buffer as they
81 // have the same rank and we may get the "possible deadlock" message
82 _lock->unlock();
83
84 qset()->enqueue_complete_buffer(node);
85 // We must relock only because the caller will unlock, for the normal
86 // case.
87 _lock->lock_without_safepoint_check();
88 }
89
90
91 BufferNode* BufferNode::allocate(size_t size) {
92 size_t byte_size = size * sizeof(void*);
93 void* data = NEW_C_HEAP_ARRAY(char, buffer_offset() + byte_size, mtGC);
94 return new (data) BufferNode;
95 }
96
97 void BufferNode::deallocate(BufferNode* node) {
98 node->~BufferNode();
99 FREE_C_HEAP_ARRAY(char, node);
100 }
101
102 PtrQueueSet::PtrQueueSet(bool notify_when_complete) :
103 _buffer_size(0),
104 _max_completed_queue(0),
105 _cbl_mon(NULL), _fl_lock(NULL),
106 _notify_when_complete(notify_when_complete),
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 PtrQueueSet::~PtrQueueSet() {
117 // There are presently only a couple (derived) instances ever
118 // created, and they are permanent, so no harm currently done by
119 // doing nothing here.
120 }
121
122 void PtrQueueSet::initialize(Monitor* cbl_mon,
123 Mutex* fl_lock,
124 int process_completed_threshold,
125 int max_completed_queue,
126 PtrQueueSet *fl_owner) {
127 _max_completed_queue = max_completed_queue;
128 _process_completed_threshold = process_completed_threshold;
129 _completed_queue_padding = 0;
130 assert(cbl_mon != NULL && fl_lock != NULL, "Init order issue?");
131 _cbl_mon = cbl_mon;
132 _fl_lock = fl_lock;
133 _fl_owner = (fl_owner != NULL) ? fl_owner : this;
134 }
135
136 void** PtrQueueSet::allocate_buffer() {
137 BufferNode* node = NULL;
138 {
139 MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
140 node = _fl_owner->_buf_free_list;
141 if (node != NULL) {
142 _fl_owner->_buf_free_list = node->next();
143 _fl_owner->_buf_free_list_sz--;
144 }
145 }
146 if (node == NULL) {
147 node = BufferNode::allocate(buffer_size());
148 } else {
149 // Reinitialize buffer obtained from free list.
150 node->set_index(0);
151 node->set_next(NULL);
152 }
153 return BufferNode::make_buffer_from_node(node);
154 }
155
156 void PtrQueueSet::deallocate_buffer(BufferNode* node) {
157 MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
158 node->set_next(_fl_owner->_buf_free_list);
159 _fl_owner->_buf_free_list = node;
160 _fl_owner->_buf_free_list_sz++;
161 }
162
163 void PtrQueueSet::reduce_free_list() {
164 assert(_fl_owner == this, "Free list reduction is allowed only for the owner");
165 // For now we'll adopt the strategy of deleting half.
166 MutexLockerEx x(_fl_lock, Mutex::_no_safepoint_check_flag);
167 size_t n = _buf_free_list_sz / 2;
168 for (size_t i = 0; i < n; ++i) {
169 assert(_buf_free_list != NULL,
170 "_buf_free_list_sz is wrong: " SIZE_FORMAT, _buf_free_list_sz);
171 BufferNode* node = _buf_free_list;
172 _buf_free_list = node->next();
173 _buf_free_list_sz--;
174 BufferNode::deallocate(node);
175 }
176 }
177
178 void PtrQueue::handle_zero_index() {
179 assert(index() == 0, "precondition");
180
181 // This thread records the full buffer and allocates a new one (while
182 // holding the lock if there is one).
183 if (_buf != NULL) {
184 if (!should_enqueue_buffer()) {
185 assert(index() > 0, "the buffer can only be re-used if it's not full");
186 return;
187 }
188
189 if (_lock) {
190 assert(_lock->owned_by_self(), "Required.");
191
192 // The current PtrQ may be the shared dirty card queue and
193 // may be being manipulated by more than one worker thread
194 // during a pause. Since the enqueueing of the completed
195 // buffer unlocks the Shared_DirtyCardQ_lock more than one
196 // worker thread can 'race' on reading the shared queue attributes
197 // (_buf and _index) and multiple threads can call into this
198 // routine for the same buffer. This will cause the completed
199 // buffer to be added to the CBL multiple times.
200
201 // We "claim" the current buffer by caching value of _buf in
202 // a local and clearing the field while holding _lock. When
203 // _lock is released (while enqueueing the completed buffer)
204 // the thread that acquires _lock will skip this code,
205 // preventing the subsequent the multiple enqueue, and
206 // install a newly allocated buffer below.
207
208 BufferNode* node = BufferNode::make_node_from_buffer(_buf, index());
209 _buf = NULL; // clear shared _buf field
210
211 locking_enqueue_completed_buffer(node); // enqueue completed buffer
212
213 // While the current thread was enqueueing the buffer another thread
214 // may have a allocated a new buffer and inserted it into this pointer
215 // queue. If that happens then we just return so that the current
216 // thread doesn't overwrite the buffer allocated by the other thread
217 // and potentially losing some dirtied cards.
218
219 if (_buf != NULL) return;
220 } else {
221 BufferNode* node = BufferNode::make_node_from_buffer(_buf, index());
222 if (qset()->process_or_enqueue_complete_buffer(node)) {
223 // Recycle the buffer. No allocation.
224 assert(_buf == BufferNode::make_buffer_from_node(node), "invariant");
225 assert(capacity() == qset()->buffer_size(), "invariant");
226 reset();
227 return;
228 }
229 }
230 }
231 // Set capacity in case this is the first allocation.
232 set_capacity(qset()->buffer_size());
233 // Allocate a new buffer.
234 _buf = qset()->allocate_buffer();
235 reset();
236 }
237
238 bool PtrQueueSet::process_or_enqueue_complete_buffer(BufferNode* node) {
239 if (Thread::current()->is_Java_thread()) {
240 // We don't lock. It is fine to be epsilon-precise here.
241 if (_max_completed_queue == 0 || _max_completed_queue > 0 &&
242 _n_completed_buffers >= _max_completed_queue + _completed_queue_padding) {
243 bool b = mut_process_buffer(node);
244 if (b) {
245 // True here means that the buffer hasn't been deallocated and the caller may reuse it.
246 return true;
247 }
248 }
249 }
250 // The buffer will be enqueued. The caller will have to get a new one.
251 enqueue_complete_buffer(node);
252 return false;
253 }
254
255 void PtrQueueSet::enqueue_complete_buffer(BufferNode* cbn) {
256 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
257 cbn->set_next(NULL);
258 if (_completed_buffers_tail == NULL) {
259 assert(_completed_buffers_head == NULL, "Well-formedness");
260 _completed_buffers_head = cbn;
261 _completed_buffers_tail = cbn;
262 } else {
263 _completed_buffers_tail->set_next(cbn);
264 _completed_buffers_tail = cbn;
265 }
266 _n_completed_buffers++;
267
268 if (!_process_completed && _process_completed_threshold >= 0 &&
269 _n_completed_buffers >= (size_t)_process_completed_threshold) {
270 _process_completed = true;
271 if (_notify_when_complete) {
272 _cbl_mon->notify();
273 }
274 }
275 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
276 }
277
278 size_t PtrQueueSet::completed_buffers_list_length() {
279 size_t n = 0;
280 BufferNode* cbn = _completed_buffers_head;
281 while (cbn != NULL) {
282 n++;
283 cbn = cbn->next();
284 }
285 return n;
286 }
287
288 void PtrQueueSet::assert_completed_buffer_list_len_correct() {
289 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
290 assert_completed_buffer_list_len_correct_locked();
291 }
292
293 void PtrQueueSet::assert_completed_buffer_list_len_correct_locked() {
294 guarantee(completed_buffers_list_length() == _n_completed_buffers,
295 "Completed buffer length is wrong.");
296 }
297
298 void PtrQueueSet::set_buffer_size(size_t sz) {
299 assert(_buffer_size == 0 && sz > 0, "Should be called only once.");
300 _buffer_size = sz;
301 }
302
303 // Merge lists of buffers. Notify the processing threads.
304 // The source queue is emptied as a result. The queues
305 // must share the monitor.
306 void PtrQueueSet::merge_bufferlists(PtrQueueSet *src) {
307 assert(_cbl_mon == src->_cbl_mon, "Should share the same lock");
308 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
309 if (_completed_buffers_tail == NULL) {
310 assert(_completed_buffers_head == NULL, "Well-formedness");
311 _completed_buffers_head = src->_completed_buffers_head;
312 _completed_buffers_tail = src->_completed_buffers_tail;
313 } else {
314 assert(_completed_buffers_head != NULL, "Well formedness");
315 if (src->_completed_buffers_head != NULL) {
316 _completed_buffers_tail->set_next(src->_completed_buffers_head);
317 _completed_buffers_tail = src->_completed_buffers_tail;
318 }
319 }
320 _n_completed_buffers += src->_n_completed_buffers;
321
322 src->_n_completed_buffers = 0;
323 src->_completed_buffers_head = NULL;
324 src->_completed_buffers_tail = NULL;
325
326 assert(_completed_buffers_head == NULL && _completed_buffers_tail == NULL ||
327 _completed_buffers_head != NULL && _completed_buffers_tail != NULL,
328 "Sanity");
329 }
330
331 void PtrQueueSet::notify_if_necessary() {
332 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
333 assert(_process_completed_threshold >= 0, "_process_completed is negative");
334 if (_n_completed_buffers >= (size_t)_process_completed_threshold || _max_completed_queue == 0) {
335 _process_completed = true;
336 if (_notify_when_complete)
337 _cbl_mon->notify();
338 }
339 }