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