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