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_implementation/g1/g1CollectedHeap.inline.hpp" 27 #include "gc_implementation/g1/satbQueue.hpp" 28 #include "memory/allocation.inline.hpp" 29 #include "memory/sharedHeap.hpp" 30 #include "oops/oop.inline.hpp" 31 #include "runtime/mutexLocker.hpp" 32 #include "runtime/thread.hpp" 33 #include "runtime/vmThread.hpp" 34 35 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC 36 37 void ObjPtrQueue::flush() { 38 // Filter now to possibly save work later. If filtering empties the 39 // buffer then flush_impl can deallocate the buffer. 40 filter(); 41 flush_impl(); 42 } 43 44 // Return true if a SATB buffer entry refers to an object that 45 // requires marking. 46 // 47 // The entry must point into the G1 heap. In particular, it must not 48 // be a NULL pointer. NULL pointers are pre-filtered and never 49 // inserted into a SATB buffer. 50 // 51 // An entry that is below the NTAMS pointer for the containing heap 52 // region requires marking. Such an entry must point to a valid object. 53 // 54 // An entry that is at least the NTAMS pointer for the containing heap 55 // region might be any of the following, none of which should be marked. 56 // 57 // * A reference to an object allocated since marking started. 58 // According to SATB, such objects are implicitly kept live and do 59 // not need to be dealt with via SATB buffer processing. 60 // 61 // * A reference to a young generation object. Young objects are 62 // handled separately and are not marked by concurrent marking. 63 // 64 // * A stale reference to a young generation object. If a young 65 // generation object reference is recorded and not filtered out 66 // before being moved by a young collection, the reference becomes 67 // stale. 68 // 69 // * A stale reference to an eagerly reclaimed humongous object. If a 70 // humongous object is recorded and then reclaimed, the reference 71 // becomes stale. 72 // 73 // The stale reference cases are implicitly handled by the NTAMS 74 // comparison. Because of the possibility of stale references, buffer 75 // processing must be somewhat circumspect and not assume entries 76 // in an unfiltered buffer refer to valid objects. 77 78 inline bool requires_marking(const void* entry, G1CollectedHeap* heap) { 79 // Includes rejection of NULL pointers. 80 assert(heap->is_in_reserved(entry), 81 err_msg("Non-heap pointer in SATB buffer: " PTR_FORMAT, p2i(entry))); 82 83 HeapRegion* region = heap->heap_region_containing_raw(entry); 84 assert(region != NULL, err_msg("No region for " PTR_FORMAT, p2i(entry))); 85 if (entry >= region->next_top_at_mark_start()) { 86 return false; 87 } 88 89 assert(((oop)entry)->is_oop(true /* ignore mark word */), 90 err_msg("Invalid oop in SATB buffer: " PTR_FORMAT, p2i(entry))); 91 92 return true; 93 } 94 95 // This method removes entries from a SATB buffer that will not be 96 // useful to the concurrent marking threads. Entries are retained if 97 // they require marking and are not already marked. Retained entries 98 // are compacted toward the top of the buffer. 99 100 void ObjPtrQueue::filter() { 101 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 102 void** buf = _buf; 103 size_t sz = _sz; 104 105 if (buf == NULL) { 106 // nothing to do 107 return; 108 } 109 110 // Used for sanity checking at the end of the loop. 111 debug_only(size_t entries = 0; size_t retained = 0;) 112 113 size_t i = sz; 114 size_t new_index = sz; 115 116 while (i > _index) { 117 assert(i > 0, "we should have at least one more entry to process"); 118 i -= oopSize; 119 debug_only(entries += 1;) 120 void** p = &buf[byte_index_to_index((int) i)]; 121 void* entry = *p; 122 // NULL the entry so that unused parts of the buffer contain NULLs 123 // at the end. If we are going to retain it we will copy it to its 124 // final place. If we have retained all entries we have visited so 125 // far, we'll just end up copying it to the same place. 126 *p = NULL; 127 128 if (requires_marking(entry, g1h) && !g1h->isMarkedNext((oop)entry)) { 129 assert(new_index > 0, "we should not have already filled up the buffer"); 130 new_index -= oopSize; 131 assert(new_index >= i, 132 "new_index should never be below i, as we alwaysr compact 'up'"); 133 void** new_p = &buf[byte_index_to_index((int) new_index)]; 134 assert(new_p >= p, "the destination location should never be below " 135 "the source as we always compact 'up'"); 136 assert(*new_p == NULL, 137 "we should have already cleared the destination location"); 138 *new_p = entry; 139 debug_only(retained += 1;) 140 } 141 } 142 143 #ifdef ASSERT 144 size_t entries_calc = (sz - _index) / oopSize; 145 assert(entries == entries_calc, "the number of entries we counted " 146 "should match the number of entries we calculated"); 147 size_t retained_calc = (sz - new_index) / oopSize; 148 assert(retained == retained_calc, "the number of retained entries we counted " 149 "should match the number of retained entries we calculated"); 150 #endif // ASSERT 151 152 _index = new_index; 153 } 154 155 // This method will first apply the above filtering to the buffer. If 156 // post-filtering a large enough chunk of the buffer has been cleared 157 // we can re-use the buffer (instead of enqueueing it) and we can just 158 // allow the mutator to carry on executing using the same buffer 159 // instead of replacing it. 160 161 bool ObjPtrQueue::should_enqueue_buffer() { 162 assert(_lock == NULL || _lock->owned_by_self(), 163 "we should have taken the lock before calling this"); 164 165 // Even if G1SATBBufferEnqueueingThresholdPercent == 0 we have to 166 // filter the buffer given that this will remove any references into 167 // the CSet as we currently assume that no such refs will appear in 168 // enqueued buffers. 169 170 // This method should only be called if there is a non-NULL buffer 171 // that is full. 172 assert(_index == 0, "pre-condition"); 173 assert(_buf != NULL, "pre-condition"); 174 175 filter(); 176 177 size_t sz = _sz; 178 size_t all_entries = sz / oopSize; 179 size_t retained_entries = (sz - _index) / oopSize; 180 size_t perc = retained_entries * 100 / all_entries; 181 bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent; 182 return should_enqueue; 183 } 184 185 void ObjPtrQueue::apply_closure(ObjectClosure* cl) { 186 if (_buf != NULL) { 187 apply_closure_to_buffer(cl, _buf, _index, _sz); 188 } 189 } 190 191 void ObjPtrQueue::apply_closure_and_empty(ObjectClosure* cl) { 192 if (_buf != NULL) { 193 apply_closure_to_buffer(cl, _buf, _index, _sz); 194 _index = _sz; 195 } 196 } 197 198 void ObjPtrQueue::apply_closure_to_buffer(ObjectClosure* cl, 199 void** buf, size_t index, size_t sz) { 200 if (cl == NULL) return; 201 for (size_t i = index; i < sz; i += oopSize) { 202 oop obj = (oop)buf[byte_index_to_index((int)i)]; 203 // There can be NULL entries because of destructors. 204 if (obj != NULL) { 205 cl->do_object(obj); 206 } 207 } 208 } 209 210 #ifndef PRODUCT 211 // Helpful for debugging 212 213 void ObjPtrQueue::print(const char* name) { 214 print(name, _buf, _index, _sz); 215 } 216 217 void ObjPtrQueue::print(const char* name, 218 void** buf, size_t index, size_t sz) { 219 gclog_or_tty->print_cr(" SATB BUFFER [%s] buf: "PTR_FORMAT" " 220 "index: "SIZE_FORMAT" sz: "SIZE_FORMAT, 221 name, buf, index, sz); 222 } 223 #endif // PRODUCT 224 225 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 226 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 227 #endif // _MSC_VER 228 229 SATBMarkQueueSet::SATBMarkQueueSet() : 230 PtrQueueSet(), _closure(NULL), _par_closures(NULL), 231 _shared_satb_queue(this, true /*perm*/) { } 232 233 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock, 234 int process_completed_threshold, 235 Mutex* lock) { 236 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1); 237 _shared_satb_queue.set_lock(lock); 238 if (ParallelGCThreads > 0) { 239 _par_closures = NEW_C_HEAP_ARRAY(ObjectClosure*, ParallelGCThreads, mtGC); 240 } 241 } 242 243 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) { 244 t->satb_mark_queue().handle_zero_index(); 245 } 246 247 #ifdef ASSERT 248 void SATBMarkQueueSet::dump_active_states(bool expected_active) { 249 gclog_or_tty->print_cr("Expected SATB active state: %s", 250 expected_active ? "ACTIVE" : "INACTIVE"); 251 gclog_or_tty->print_cr("Actual SATB active states:"); 252 gclog_or_tty->print_cr(" Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE"); 253 for (JavaThread* t = Threads::first(); t; t = t->next()) { 254 gclog_or_tty->print_cr(" Thread \"%s\" queue: %s", t->name(), 255 t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE"); 256 } 257 gclog_or_tty->print_cr(" Shared queue: %s", 258 shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE"); 259 } 260 261 void SATBMarkQueueSet::verify_active_states(bool expected_active) { 262 // Verify queue set state 263 if (is_active() != expected_active) { 264 dump_active_states(expected_active); 265 guarantee(false, "SATB queue set has an unexpected active state"); 266 } 267 268 // Verify thread queue states 269 for (JavaThread* t = Threads::first(); t; t = t->next()) { 270 if (t->satb_mark_queue().is_active() != expected_active) { 271 dump_active_states(expected_active); 272 guarantee(false, "Thread SATB queue has an unexpected active state"); 273 } 274 } 275 276 // Verify shared queue state 277 if (shared_satb_queue()->is_active() != expected_active) { 278 dump_active_states(expected_active); 279 guarantee(false, "Shared SATB queue has an unexpected active state"); 280 } 281 } 282 #endif // ASSERT 283 284 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) { 285 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 286 #ifdef ASSERT 287 verify_active_states(expected_active); 288 #endif // ASSERT 289 _all_active = active; 290 for (JavaThread* t = Threads::first(); t; t = t->next()) { 291 t->satb_mark_queue().set_active(active); 292 } 293 shared_satb_queue()->set_active(active); 294 } 295 296 void SATBMarkQueueSet::filter_thread_buffers() { 297 for(JavaThread* t = Threads::first(); t; t = t->next()) { 298 t->satb_mark_queue().filter(); 299 } 300 shared_satb_queue()->filter(); 301 } 302 303 void SATBMarkQueueSet::set_closure(ObjectClosure* closure) { 304 _closure = closure; 305 } 306 307 void SATBMarkQueueSet::set_par_closure(int i, ObjectClosure* par_closure) { 308 assert(ParallelGCThreads > 0 && _par_closures != NULL, "Precondition"); 309 _par_closures[i] = par_closure; 310 } 311 312 bool SATBMarkQueueSet::apply_closure_to_completed_buffer_work(bool par, 313 uint worker) { 314 BufferNode* nd = NULL; 315 { 316 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 317 if (_completed_buffers_head != NULL) { 318 nd = _completed_buffers_head; 319 _completed_buffers_head = nd->next(); 320 if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL; 321 _n_completed_buffers--; 322 if (_n_completed_buffers == 0) _process_completed = false; 323 } 324 } 325 ObjectClosure* cl = (par ? _par_closures[worker] : _closure); 326 if (nd != NULL) { 327 void **buf = BufferNode::make_buffer_from_node(nd); 328 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz); 329 deallocate_buffer(buf); 330 return true; 331 } else { 332 return false; 333 } 334 } 335 336 void SATBMarkQueueSet::iterate_completed_buffers_read_only(ObjectClosure* cl) { 337 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 338 assert(cl != NULL, "pre-condition"); 339 340 BufferNode* nd = _completed_buffers_head; 341 while (nd != NULL) { 342 void** buf = BufferNode::make_buffer_from_node(nd); 343 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz); 344 nd = nd->next(); 345 } 346 } 347 348 void SATBMarkQueueSet::iterate_thread_buffers_read_only(ObjectClosure* cl) { 349 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 350 assert(cl != NULL, "pre-condition"); 351 352 for (JavaThread* t = Threads::first(); t; t = t->next()) { 353 t->satb_mark_queue().apply_closure(cl); 354 } 355 shared_satb_queue()->apply_closure(cl); 356 } 357 358 #ifndef PRODUCT 359 // Helpful for debugging 360 361 #define SATB_PRINTER_BUFFER_SIZE 256 362 363 void SATBMarkQueueSet::print_all(const char* msg) { 364 char buffer[SATB_PRINTER_BUFFER_SIZE]; 365 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 366 367 gclog_or_tty->cr(); 368 gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg); 369 370 BufferNode* nd = _completed_buffers_head; 371 int i = 0; 372 while (nd != NULL) { 373 void** buf = BufferNode::make_buffer_from_node(nd); 374 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i); 375 ObjPtrQueue::print(buffer, buf, 0, _sz); 376 nd = nd->next(); 377 i += 1; 378 } 379 380 for (JavaThread* t = Threads::first(); t; t = t->next()) { 381 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name()); 382 t->satb_mark_queue().print(buffer); 383 } 384 385 shared_satb_queue()->print("Shared"); 386 387 gclog_or_tty->cr(); 388 } 389 #endif // PRODUCT 390 391 void SATBMarkQueueSet::abandon_partial_marking() { 392 BufferNode* buffers_to_delete = NULL; 393 { 394 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 395 while (_completed_buffers_head != NULL) { 396 BufferNode* nd = _completed_buffers_head; 397 _completed_buffers_head = nd->next(); 398 nd->set_next(buffers_to_delete); 399 buffers_to_delete = nd; 400 } 401 _completed_buffers_tail = NULL; 402 _n_completed_buffers = 0; 403 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked()); 404 } 405 while (buffers_to_delete != NULL) { 406 BufferNode* nd = buffers_to_delete; 407 buffers_to_delete = nd->next(); 408 deallocate_buffer(BufferNode::make_buffer_from_node(nd)); 409 } 410 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 411 // So we can safely manipulate these queues. 412 for (JavaThread* t = Threads::first(); t; t = t->next()) { 413 t->satb_mark_queue().reset(); 414 } 415 shared_satb_queue()->reset(); 416 }