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 qset()->enqueue_complete_buffer(node);
79 }
80
81
82 BufferNode* BufferNode::allocate(size_t size) {
83 size_t byte_size = size * sizeof(void*);
84 void* data = NEW_C_HEAP_ARRAY(char, buffer_offset() + byte_size, mtGC);
85 return new (data) BufferNode;
86 }
87
88 void BufferNode::deallocate(BufferNode* node) {
89 node->~BufferNode();
90 FREE_C_HEAP_ARRAY(char, node);
91 }
92
93 PtrQueueSet::PtrQueueSet(bool notify_when_complete) :
94 _buffer_size(0),
95 _max_completed_queue(0),
96 _cbl_mon(NULL), _fl_lock(NULL),
97 _notify_when_complete(notify_when_complete),
98 _completed_buffers_head(NULL),
99 _completed_buffers_tail(NULL),
100 _n_completed_buffers(0),
101 _process_completed_threshold(0), _process_completed(false),
102 _buf_free_list(NULL), _buf_free_list_sz(0)
103 {
104 _fl_owner = this;
105 }
106
107 PtrQueueSet::~PtrQueueSet() {
108 // There are presently only a couple (derived) instances ever
109 // created, and they are permanent, so no harm currently done by
110 // doing nothing here.
111 }
112
113 void PtrQueueSet::initialize(Monitor* cbl_mon,
114 Mutex* fl_lock,
115 int process_completed_threshold,
116 int max_completed_queue,
117 PtrQueueSet *fl_owner) {
118 _max_completed_queue = max_completed_queue;
119 _process_completed_threshold = process_completed_threshold;
120 _completed_queue_padding = 0;
121 assert(cbl_mon != NULL && fl_lock != NULL, "Init order issue?");
122 _cbl_mon = cbl_mon;
123 _fl_lock = fl_lock;
124 _fl_owner = (fl_owner != NULL) ? fl_owner : this;
125 }
126
127 void** PtrQueueSet::allocate_buffer() {
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(buffer_size());
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 MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
149 node->set_next(_fl_owner->_buf_free_list);
150 _fl_owner->_buf_free_list = node;
151 _fl_owner->_buf_free_list_sz++;
152 }
153
154 void PtrQueueSet::reduce_free_list() {
155 assert(_fl_owner == this, "Free list reduction is allowed only for the owner");
156 // For now we'll adopt the strategy of deleting half.
157 MutexLockerEx x(_fl_lock, Mutex::_no_safepoint_check_flag);
158 size_t n = _buf_free_list_sz / 2;
159 for (size_t i = 0; i < n; ++i) {
160 assert(_buf_free_list != NULL,
161 "_buf_free_list_sz is wrong: " SIZE_FORMAT, _buf_free_list_sz);
162 BufferNode* node = _buf_free_list;
163 _buf_free_list = node->next();
164 _buf_free_list_sz--;
165 BufferNode::deallocate(node);
166 }
167 }
168
169 void PtrQueue::handle_zero_index() {
170 assert(index() == 0, "precondition");
171
172 // This thread records the full buffer and allocates a new one (while
173 // holding the lock if there is one).
174 if (_buf != NULL) {
175 if (!should_enqueue_buffer()) {
176 assert(index() > 0, "the buffer can only be re-used if it's not full");
177 return;
178 }
179
180 if (_lock) {
181 assert(_lock->owned_by_self(), "Required.");
182
183 BufferNode* node = BufferNode::make_node_from_buffer(_buf, index());
184 _buf = NULL; // clear shared _buf field
185
186 locking_enqueue_completed_buffer(node); // enqueue completed buffer
187 assert(_buf == NULL, "multiple enqueuers appear to be racing");
188 } else {
189 BufferNode* node = BufferNode::make_node_from_buffer(_buf, index());
190 if (qset()->process_or_enqueue_complete_buffer(node)) {
191 // Recycle the buffer. No allocation.
192 assert(_buf == BufferNode::make_buffer_from_node(node), "invariant");
193 assert(capacity() == qset()->buffer_size(), "invariant");
194 reset();
195 return;
196 }
197 }
198 }
199 // Set capacity in case this is the first allocation.
200 set_capacity(qset()->buffer_size());
201 // Allocate a new buffer.
202 _buf = qset()->allocate_buffer();
203 reset();
204 }
205
206 bool PtrQueueSet::process_or_enqueue_complete_buffer(BufferNode* node) {
207 if (Thread::current()->is_Java_thread()) {
208 // We don't lock. It is fine to be epsilon-precise here.
209 if (_max_completed_queue == 0 || _max_completed_queue > 0 &&
210 _n_completed_buffers >= _max_completed_queue + _completed_queue_padding) {
211 bool b = mut_process_buffer(node);
212 if (b) {
213 // True here means that the buffer hasn't been deallocated and the caller may reuse it.
214 return true;
215 }
216 }
217 }
218 // The buffer will be enqueued. The caller will have to get a new one.
219 enqueue_complete_buffer(node);
220 return false;
221 }
222
223 void PtrQueueSet::enqueue_complete_buffer(BufferNode* cbn) {
224 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
225 cbn->set_next(NULL);
226 if (_completed_buffers_tail == NULL) {
227 assert(_completed_buffers_head == NULL, "Well-formedness");
228 _completed_buffers_head = cbn;
229 _completed_buffers_tail = cbn;
230 } else {
231 _completed_buffers_tail->set_next(cbn);
232 _completed_buffers_tail = cbn;
233 }
234 _n_completed_buffers++;
235
236 if (!_process_completed && _process_completed_threshold >= 0 &&
237 _n_completed_buffers >= (size_t)_process_completed_threshold) {
238 _process_completed = true;
239 if (_notify_when_complete) {
240 _cbl_mon->notify();
241 }
242 }
243 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
244 }
245
246 size_t PtrQueueSet::completed_buffers_list_length() {
247 size_t n = 0;
248 BufferNode* cbn = _completed_buffers_head;
249 while (cbn != NULL) {
250 n++;
251 cbn = cbn->next();
252 }
253 return n;
254 }
255
256 void PtrQueueSet::assert_completed_buffer_list_len_correct() {
257 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
258 assert_completed_buffer_list_len_correct_locked();
259 }
260
261 void PtrQueueSet::assert_completed_buffer_list_len_correct_locked() {
262 guarantee(completed_buffers_list_length() == _n_completed_buffers,
263 "Completed buffer length is wrong.");
264 }
265
266 void PtrQueueSet::set_buffer_size(size_t sz) {
267 assert(_buffer_size == 0 && sz > 0, "Should be called only once.");
268 _buffer_size = sz;
269 }
270
271 // Merge lists of buffers. Notify the processing threads.
272 // The source queue is emptied as a result. The queues
273 // must share the monitor.
274 void PtrQueueSet::merge_bufferlists(PtrQueueSet *src) {
275 assert(_cbl_mon == src->_cbl_mon, "Should share the same lock");
276 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
277 if (_completed_buffers_tail == NULL) {
278 assert(_completed_buffers_head == NULL, "Well-formedness");
279 _completed_buffers_head = src->_completed_buffers_head;
280 _completed_buffers_tail = src->_completed_buffers_tail;
281 } else {
282 assert(_completed_buffers_head != NULL, "Well formedness");
283 if (src->_completed_buffers_head != NULL) {
284 _completed_buffers_tail->set_next(src->_completed_buffers_head);
285 _completed_buffers_tail = src->_completed_buffers_tail;
286 }
287 }
288 _n_completed_buffers += src->_n_completed_buffers;
289
290 src->_n_completed_buffers = 0;
291 src->_completed_buffers_head = NULL;
292 src->_completed_buffers_tail = NULL;
293
294 assert(_completed_buffers_head == NULL && _completed_buffers_tail == NULL ||
295 _completed_buffers_head != NULL && _completed_buffers_tail != NULL,
296 "Sanity");
297 }
298
299 void PtrQueueSet::notify_if_necessary() {
300 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
301 assert(_process_completed_threshold >= 0, "_process_completed is negative");
302 if (_n_completed_buffers >= (size_t)_process_completed_threshold || _max_completed_queue == 0) {
303 _process_completed = true;
304 if (_notify_when_complete)
305 _cbl_mon->notify();
306 }
307 }