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 perm, bool active) : 34 _qset(qset), _buf(NULL), _index(0), _sz(0), _active(active), 35 _perm(perm), _lock(NULL) 36 {} 37 38 PtrQueue::~PtrQueue() { 39 assert(_perm || (_buf == NULL), "queue must be flushed before delete"); 40 } 41 42 void PtrQueue::flush_impl() { 43 if (!_perm && _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 for (size_t i = 0; i < _index; i += oopSize) { 50 _buf[byte_index_to_index((int)i)] = NULL; 51 } 52 qset()->enqueue_complete_buffer(_buf); 53 } 54 _buf = NULL; 55 _index = 0; 56 } 57 } 58 59 60 void PtrQueue::enqueue_known_active(void* ptr) { 61 assert(_index <= _sz, "Invariant."); 62 assert(_index == 0 || _buf != NULL, "invariant"); 63 64 while (_index == 0) { 65 handle_zero_index(); 66 } 67 68 assert(_index > 0, "postcondition"); 69 _index -= oopSize; 70 _buf[byte_index_to_index((int)_index)] = ptr; 71 assert(_index <= _sz, "Invariant."); 72 } 73 74 void PtrQueue::locking_enqueue_completed_buffer(void** buf) { 75 assert(_lock->owned_by_self(), "Required."); 76 77 // We have to unlock _lock (which may be Shared_DirtyCardQ_lock) before 78 // we acquire DirtyCardQ_CBL_mon inside enqueue_complete_buffer as they 79 // have the same rank and we may get the "possible deadlock" message 80 _lock->unlock(); 81 82 qset()->enqueue_complete_buffer(buf); 83 // We must relock only because the caller will unlock, for the normal 84 // case. 85 _lock->lock_without_safepoint_check(); 86 } 87 88 89 PtrQueueSet::PtrQueueSet(bool notify_when_complete) : 90 _max_completed_queue(0), 91 _cbl_mon(NULL), _fl_lock(NULL), 92 _notify_when_complete(notify_when_complete), 93 _sz(0), 94 _completed_buffers_head(NULL), 95 _completed_buffers_tail(NULL), 96 _n_completed_buffers(0), 97 _process_completed_threshold(0), _process_completed(false), 98 _buf_free_list(NULL), _buf_free_list_sz(0) 99 { 100 _fl_owner = this; 101 } 102 103 void** PtrQueueSet::allocate_buffer() { 104 assert(_sz > 0, "Didn't set a buffer size."); 105 MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag); 106 if (_fl_owner->_buf_free_list != NULL) { 107 void** res = BufferNode::make_buffer_from_node(_fl_owner->_buf_free_list); 108 _fl_owner->_buf_free_list = _fl_owner->_buf_free_list->next(); 109 _fl_owner->_buf_free_list_sz--; 110 return res; 111 } else { 112 // Allocate space for the BufferNode in front of the buffer. 113 char *b = NEW_C_HEAP_ARRAY(char, _sz + BufferNode::aligned_size(), mtGC); 114 return BufferNode::make_buffer_from_block(b); 115 } 116 } 117 118 void PtrQueueSet::deallocate_buffer(void** buf) { 119 assert(_sz > 0, "Didn't set a buffer size."); 120 MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag); 121 BufferNode *node = BufferNode::make_node_from_buffer(buf); 122 node->set_next(_fl_owner->_buf_free_list); 123 _fl_owner->_buf_free_list = node; 124 _fl_owner->_buf_free_list_sz++; 125 } 126 127 void PtrQueueSet::reduce_free_list() { 128 assert(_fl_owner == this, "Free list reduction is allowed only for the owner"); 129 // For now we'll adopt the strategy of deleting half. 130 MutexLockerEx x(_fl_lock, Mutex::_no_safepoint_check_flag); 131 size_t n = _buf_free_list_sz / 2; 132 while (n > 0) { 133 assert(_buf_free_list != NULL, "_buf_free_list_sz must be wrong."); 134 void* b = BufferNode::make_block_from_node(_buf_free_list); 135 _buf_free_list = _buf_free_list->next(); 136 FREE_C_HEAP_ARRAY(char, b); 137 _buf_free_list_sz --; 138 n--; 139 } 140 } 141 142 void PtrQueue::handle_zero_index() { 143 assert(_index == 0, "Precondition."); 144 145 // This thread records the full buffer and allocates a new one (while 146 // holding the lock if there is one). 147 if (_buf != NULL) { 148 if (!should_enqueue_buffer()) { 149 assert(_index > 0, "the buffer can only be re-used if it's not full"); 150 return; 151 } 152 153 if (_lock) { 154 assert(_lock->owned_by_self(), "Required."); 155 156 // The current PtrQ may be the shared dirty card queue and 157 // may be being manipulated by more than one worker thread 158 // during a pause. Since the enqueueing of the completed 159 // buffer unlocks the Shared_DirtyCardQ_lock more than one 160 // worker thread can 'race' on reading the shared queue attributes 161 // (_buf and _index) and multiple threads can call into this 162 // routine for the same buffer. This will cause the completed 163 // buffer to be added to the CBL multiple times. 164 165 // We "claim" the current buffer by caching value of _buf in 166 // a local and clearing the field while holding _lock. When 167 // _lock is released (while enqueueing the completed buffer) 168 // the thread that acquires _lock will skip this code, 169 // preventing the subsequent the multiple enqueue, and 170 // install a newly allocated buffer below. 171 172 void** buf = _buf; // local pointer to completed buffer 173 _buf = NULL; // clear shared _buf field 174 175 locking_enqueue_completed_buffer(buf); // enqueue completed buffer 176 177 // While the current thread was enqueueing the buffer another thread 178 // may have a allocated a new buffer and inserted it into this pointer 179 // queue. If that happens then we just return so that the current 180 // thread doesn't overwrite the buffer allocated by the other thread 181 // and potentially losing some dirtied cards. 182 183 if (_buf != NULL) return; 184 } else { 185 if (qset()->process_or_enqueue_complete_buffer(_buf)) { 186 // Recycle the buffer. No allocation. 187 _sz = qset()->buffer_size(); 188 _index = _sz; 189 return; 190 } 191 } 192 } 193 // Reallocate the buffer 194 _buf = qset()->allocate_buffer(); 195 _sz = qset()->buffer_size(); 196 _index = _sz; 197 } 198 199 bool PtrQueueSet::process_or_enqueue_complete_buffer(void** buf) { 200 if (Thread::current()->is_Java_thread()) { 201 // We don't lock. It is fine to be epsilon-precise here. 202 if (_max_completed_queue == 0 || _max_completed_queue > 0 && 203 _n_completed_buffers >= _max_completed_queue + _completed_queue_padding) { 204 bool b = mut_process_buffer(buf); 205 if (b) { 206 // True here means that the buffer hasn't been deallocated and the caller may reuse it. 207 return true; 208 } 209 } 210 } 211 // The buffer will be enqueued. The caller will have to get a new one. 212 enqueue_complete_buffer(buf); 213 return false; 214 } 215 216 void PtrQueueSet::enqueue_complete_buffer(void** buf, size_t index) { 217 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 218 BufferNode* cbn = BufferNode::new_from_buffer(buf); 219 cbn->set_index(index); 220 if (_completed_buffers_tail == NULL) { 221 assert(_completed_buffers_head == NULL, "Well-formedness"); 222 _completed_buffers_head = cbn; 223 _completed_buffers_tail = cbn; 224 } else { 225 _completed_buffers_tail->set_next(cbn); 226 _completed_buffers_tail = cbn; 227 } 228 _n_completed_buffers++; 229 230 if (!_process_completed && _process_completed_threshold >= 0 && 231 _n_completed_buffers >= _process_completed_threshold) { 232 _process_completed = true; 233 if (_notify_when_complete) 234 _cbl_mon->notify(); 235 } 236 debug_only(assert_completed_buffer_list_len_correct_locked()); 237 } 238 239 int PtrQueueSet::completed_buffers_list_length() { 240 int n = 0; 241 BufferNode* cbn = _completed_buffers_head; 242 while (cbn != NULL) { 243 n++; 244 cbn = cbn->next(); 245 } 246 return n; 247 } 248 249 void PtrQueueSet::assert_completed_buffer_list_len_correct() { 250 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 251 assert_completed_buffer_list_len_correct_locked(); 252 } 253 254 void PtrQueueSet::assert_completed_buffer_list_len_correct_locked() { 255 guarantee(completed_buffers_list_length() == _n_completed_buffers, 256 "Completed buffer length is wrong."); 257 } 258 259 void PtrQueueSet::set_buffer_size(size_t sz) { 260 assert(_sz == 0 && sz > 0, "Should be called only once."); 261 _sz = sz * oopSize; 262 } 263 264 // Merge lists of buffers. Notify the processing threads. 265 // The source queue is emptied as a result. The queues 266 // must share the monitor. 267 void PtrQueueSet::merge_bufferlists(PtrQueueSet *src) { 268 assert(_cbl_mon == src->_cbl_mon, "Should share the same lock"); 269 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 270 if (_completed_buffers_tail == NULL) { 271 assert(_completed_buffers_head == NULL, "Well-formedness"); 272 _completed_buffers_head = src->_completed_buffers_head; 273 _completed_buffers_tail = src->_completed_buffers_tail; 274 } else { 275 assert(_completed_buffers_head != NULL, "Well formedness"); 276 if (src->_completed_buffers_head != NULL) { 277 _completed_buffers_tail->set_next(src->_completed_buffers_head); 278 _completed_buffers_tail = src->_completed_buffers_tail; 279 } 280 } 281 _n_completed_buffers += src->_n_completed_buffers; 282 283 src->_n_completed_buffers = 0; 284 src->_completed_buffers_head = NULL; 285 src->_completed_buffers_tail = NULL; 286 287 assert(_completed_buffers_head == NULL && _completed_buffers_tail == NULL || 288 _completed_buffers_head != NULL && _completed_buffers_tail != NULL, 289 "Sanity"); 290 } 291 292 void PtrQueueSet::notify_if_necessary() { 293 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 294 if (_n_completed_buffers >= _process_completed_threshold || _max_completed_queue == 0) { 295 _process_completed = true; 296 if (_notify_when_complete) 297 _cbl_mon->notify(); 298 } 299 }