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/g1CollectedHeap.inline.hpp" 27 #include "gc/g1/satbQueue.hpp" 28 #include "gc/shared/collectedHeap.hpp" 29 #include "memory/allocation.inline.hpp" 30 #include "oops/oop.inline.hpp" 31 #include "runtime/mutexLocker.hpp" 32 #include "runtime/safepoint.hpp" 33 #include "runtime/thread.hpp" 34 #include "runtime/vmThread.hpp" 35 36 void ObjPtrQueue::flush() { 37 // Filter now to possibly save work later. If filtering empties the 38 // buffer then flush_impl can deallocate the buffer. 39 filter(); 40 flush_impl(); 41 } 42 43 // Return true if a SATB buffer entry refers to an object that 44 // requires marking. 45 // 46 // The entry must point into the G1 heap. In particular, it must not 47 // be a NULL pointer. NULL pointers are pre-filtered and never 48 // inserted into a SATB buffer. 49 // 50 // An entry that is below the NTAMS pointer for the containing heap 51 // region requires marking. Such an entry must point to a valid object. 52 // 53 // An entry that is at least the NTAMS pointer for the containing heap 54 // region might be any of the following, none of which should be marked. 55 // 56 // * A reference to an object allocated since marking started. 57 // According to SATB, such objects are implicitly kept live and do 58 // not need to be dealt with via SATB buffer processing. 59 // 60 // * A reference to a young generation object. Young objects are 61 // handled separately and are not marked by concurrent marking. 62 // 63 // * A stale reference to a young generation object. If a young 64 // generation object reference is recorded and not filtered out 65 // before being moved by a young collection, the reference becomes 66 // stale. 67 // 68 // * A stale reference to an eagerly reclaimed humongous object. If a 69 // humongous object is recorded and then reclaimed, the reference 70 // becomes stale. 71 // 72 // The stale reference cases are implicitly handled by the NTAMS 73 // comparison. Because of the possibility of stale references, buffer 74 // processing must be somewhat circumspect and not assume entries 75 // in an unfiltered buffer refer to valid objects. 76 77 inline bool requires_marking(const void* entry, G1CollectedHeap* heap) { 78 // Includes rejection of NULL pointers. 79 assert(heap->is_in_reserved(entry), 80 "Non-heap pointer in SATB buffer: " PTR_FORMAT, p2i(entry)); 81 82 HeapRegion* region = heap->heap_region_containing_raw(entry); 83 assert(region != NULL, "No region for " PTR_FORMAT, p2i(entry)); 84 if (entry >= region->next_top_at_mark_start()) { 85 return false; 86 } 87 88 assert(((oop)entry)->is_oop(true /* ignore mark word */), 89 "Invalid oop in SATB buffer: " PTR_FORMAT, p2i(entry)); 90 91 return true; 92 } 93 94 // This method removes entries from a SATB buffer that will not be 95 // useful to the concurrent marking threads. Entries are retained if 96 // they require marking and are not already marked. Retained entries 97 // are compacted toward the top of the buffer. 98 99 void ObjPtrQueue::filter() { 100 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 101 void** buf = _buf; 102 size_t sz = _sz; 103 104 if (buf == NULL) { 105 // nothing to do 106 return; 107 } 108 109 // Used for sanity checking at the end of the loop. 110 debug_only(size_t entries = 0; size_t retained = 0;) 111 112 size_t i = sz; 113 size_t new_index = sz; 114 115 while (i > _index) { 116 assert(i > 0, "we should have at least one more entry to process"); 117 i -= oopSize; 118 debug_only(entries += 1;) 119 void** p = &buf[byte_index_to_index((int) i)]; 120 void* entry = *p; 121 // NULL the entry so that unused parts of the buffer contain NULLs 122 // at the end. If we are going to retain it we will copy it to its 123 // final place. If we have retained all entries we have visited so 124 // far, we'll just end up copying it to the same place. 125 *p = NULL; 126 127 if (requires_marking(entry, g1h) && !g1h->isMarkedNext((oop)entry)) { 128 assert(new_index > 0, "we should not have already filled up the buffer"); 129 new_index -= oopSize; 130 assert(new_index >= i, 131 "new_index should never be below i, as we always compact 'up'"); 132 void** new_p = &buf[byte_index_to_index((int) new_index)]; 133 assert(new_p >= p, "the destination location should never be below " 134 "the source as we always compact 'up'"); 135 assert(*new_p == NULL, 136 "we should have already cleared the destination location"); 137 *new_p = entry; 138 debug_only(retained += 1;) 139 } 140 } 141 142 #ifdef ASSERT 143 size_t entries_calc = (sz - _index) / oopSize; 144 assert(entries == entries_calc, "the number of entries we counted " 145 "should match the number of entries we calculated"); 146 size_t retained_calc = (sz - new_index) / oopSize; 147 assert(retained == retained_calc, "the number of retained entries we counted " 148 "should match the number of retained entries we calculated"); 149 #endif // ASSERT 150 151 _index = new_index; 152 } 153 154 // This method will first apply the above filtering to the buffer. If 155 // post-filtering a large enough chunk of the buffer has been cleared 156 // we can re-use the buffer (instead of enqueueing it) and we can just 157 // allow the mutator to carry on executing using the same buffer 158 // instead of replacing it. 159 160 bool ObjPtrQueue::should_enqueue_buffer() { 161 assert(_lock == NULL || _lock->owned_by_self(), 162 "we should have taken the lock before calling this"); 163 164 // If G1SATBBufferEnqueueingThresholdPercent == 0 we could skip filtering. 165 166 // This method should only be called if there is a non-NULL buffer 167 // that is full. 168 assert(_index == 0, "pre-condition"); 169 assert(_buf != NULL, "pre-condition"); 170 171 filter(); 172 173 size_t sz = _sz; 174 size_t all_entries = sz / oopSize; 175 size_t retained_entries = (sz - _index) / oopSize; 176 size_t perc = retained_entries * 100 / all_entries; 177 bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent; 178 return should_enqueue; 179 } 180 181 void ObjPtrQueue::apply_closure_and_empty(SATBBufferClosure* cl) { 182 assert(SafepointSynchronize::is_at_safepoint(), 183 "SATB queues must only be processed at safepoints"); 184 if (_buf != NULL) { 185 assert(_index % sizeof(void*) == 0, "invariant"); 186 assert(_sz % sizeof(void*) == 0, "invariant"); 187 assert(_index <= _sz, "invariant"); 188 cl->do_buffer(_buf + byte_index_to_index((int)_index), 189 byte_index_to_index((int)(_sz - _index))); 190 _index = _sz; 191 } 192 } 193 194 #ifndef PRODUCT 195 // Helpful for debugging 196 197 void ObjPtrQueue::print(const char* name) { 198 print(name, _buf, _index, _sz); 199 } 200 201 void ObjPtrQueue::print(const char* name, 202 void** buf, size_t index, size_t sz) { 203 gclog_or_tty->print_cr(" SATB BUFFER [%s] buf: " PTR_FORMAT " " 204 "index: " SIZE_FORMAT " sz: " SIZE_FORMAT, 205 name, p2i(buf), index, sz); 206 } 207 #endif // PRODUCT 208 209 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 210 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 211 #endif // _MSC_VER 212 213 SATBMarkQueueSet::SATBMarkQueueSet() : 214 PtrQueueSet(), 215 _shared_satb_queue(this, true /*perm*/) { } 216 217 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock, 218 int process_completed_threshold, 219 Mutex* lock) { 220 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1); 221 _shared_satb_queue.set_lock(lock); 222 } 223 224 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) { 225 t->satb_mark_queue().handle_zero_index(); 226 } 227 228 #ifdef ASSERT 229 void SATBMarkQueueSet::dump_active_states(bool expected_active) { 230 gclog_or_tty->print_cr("Expected SATB active state: %s", 231 expected_active ? "ACTIVE" : "INACTIVE"); 232 gclog_or_tty->print_cr("Actual SATB active states:"); 233 gclog_or_tty->print_cr(" Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE"); 234 for (JavaThread* t = Threads::first(); t; t = t->next()) { 235 gclog_or_tty->print_cr(" Thread \"%s\" queue: %s", t->name(), 236 t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE"); 237 } 238 gclog_or_tty->print_cr(" Shared queue: %s", 239 shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE"); 240 } 241 242 void SATBMarkQueueSet::verify_active_states(bool expected_active) { 243 // Verify queue set state 244 if (is_active() != expected_active) { 245 dump_active_states(expected_active); 246 guarantee(false, "SATB queue set has an unexpected active state"); 247 } 248 249 // Verify thread queue states 250 for (JavaThread* t = Threads::first(); t; t = t->next()) { 251 if (t->satb_mark_queue().is_active() != expected_active) { 252 dump_active_states(expected_active); 253 guarantee(false, "Thread SATB queue has an unexpected active state"); 254 } 255 } 256 257 // Verify shared queue state 258 if (shared_satb_queue()->is_active() != expected_active) { 259 dump_active_states(expected_active); 260 guarantee(false, "Shared SATB queue has an unexpected active state"); 261 } 262 } 263 #endif // ASSERT 264 265 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) { 266 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 267 #ifdef ASSERT 268 verify_active_states(expected_active); 269 #endif // ASSERT 270 _all_active = active; 271 for (JavaThread* t = Threads::first(); t; t = t->next()) { 272 t->satb_mark_queue().set_active(active); 273 } 274 shared_satb_queue()->set_active(active); 275 } 276 277 void SATBMarkQueueSet::filter_thread_buffers() { 278 for(JavaThread* t = Threads::first(); t; t = t->next()) { 279 t->satb_mark_queue().filter(); 280 } 281 shared_satb_queue()->filter(); 282 } 283 284 bool SATBMarkQueueSet::apply_closure_to_completed_buffer(SATBBufferClosure* cl) { 285 BufferNode* nd = NULL; 286 { 287 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 288 if (_completed_buffers_head != NULL) { 289 nd = _completed_buffers_head; 290 _completed_buffers_head = nd->next(); 291 if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL; 292 _n_completed_buffers--; 293 if (_n_completed_buffers == 0) _process_completed = false; 294 } 295 } 296 if (nd != NULL) { 297 void **buf = BufferNode::make_buffer_from_node(nd); 298 // Skip over NULL entries at beginning (e.g. push end) of buffer. 299 // Filtering can result in non-full completed buffers; see 300 // should_enqueue_buffer. 301 assert(_sz % sizeof(void*) == 0, "invariant"); 302 size_t limit = ObjPtrQueue::byte_index_to_index((int)_sz); 303 for (size_t i = 0; i < limit; ++i) { 304 if (buf[i] != NULL) { 305 // Found the end of the block of NULLs; process the remainder. 306 cl->do_buffer(buf + i, limit - i); 307 break; 308 } 309 } 310 deallocate_buffer(buf); 311 return true; 312 } else { 313 return false; 314 } 315 } 316 317 #ifndef PRODUCT 318 // Helpful for debugging 319 320 #define SATB_PRINTER_BUFFER_SIZE 256 321 322 void SATBMarkQueueSet::print_all(const char* msg) { 323 char buffer[SATB_PRINTER_BUFFER_SIZE]; 324 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 325 326 gclog_or_tty->cr(); 327 gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg); 328 329 BufferNode* nd = _completed_buffers_head; 330 int i = 0; 331 while (nd != NULL) { 332 void** buf = BufferNode::make_buffer_from_node(nd); 333 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i); 334 ObjPtrQueue::print(buffer, buf, 0, _sz); 335 nd = nd->next(); 336 i += 1; 337 } 338 339 for (JavaThread* t = Threads::first(); t; t = t->next()) { 340 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name()); 341 t->satb_mark_queue().print(buffer); 342 } 343 344 shared_satb_queue()->print("Shared"); 345 346 gclog_or_tty->cr(); 347 } 348 #endif // PRODUCT 349 350 void SATBMarkQueueSet::abandon_partial_marking() { 351 BufferNode* buffers_to_delete = NULL; 352 { 353 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 354 while (_completed_buffers_head != NULL) { 355 BufferNode* nd = _completed_buffers_head; 356 _completed_buffers_head = nd->next(); 357 nd->set_next(buffers_to_delete); 358 buffers_to_delete = nd; 359 } 360 _completed_buffers_tail = NULL; 361 _n_completed_buffers = 0; 362 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked()); 363 } 364 while (buffers_to_delete != NULL) { 365 BufferNode* nd = buffers_to_delete; 366 buffers_to_delete = nd->next(); 367 deallocate_buffer(BufferNode::make_buffer_from_node(nd)); 368 } 369 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 370 // So we can safely manipulate these queues. 371 for (JavaThread* t = Threads::first(); t; t = t->next()) { 372 t->satb_mark_queue().reset(); 373 } 374 shared_satb_queue()->reset(); 375 }