1 /* 2 * Copyright (c) 2001, 2014, 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 // The buffer might contain refs into the CSet. We have to filter it 39 // first before we flush it, otherwise we might end up with an 40 // enqueued buffer with refs into the CSet which breaks our invariants. 41 filter(); 42 PtrQueue::flush(); 43 } 44 45 // This method removes entries from an SATB buffer that will not be 46 // useful to the concurrent marking threads. An entry is removed if it 47 // satisfies one of the following conditions: 48 // 49 // * it points to an object outside the G1 heap (G1's concurrent 50 // marking only visits objects inside the G1 heap), 51 // * it points to an object that has been allocated since marking 52 // started (according to SATB those objects do not need to be 53 // visited during marking), or 54 // * it points to an object that has already been marked (no need to 55 // process it again). 56 // 57 // The rest of the entries will be retained and are compacted towards 58 // the top of the buffer. Note that, because we do not allow old 59 // regions in the CSet during marking, all objects on the CSet regions 60 // are young (eden or survivors) and therefore implicitly live. So any 61 // references into the CSet will be removed during filtering. 62 63 void ObjPtrQueue::filter() { 64 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 65 void** buf = _buf; 66 size_t sz = _sz; 67 68 if (buf == NULL) { 69 // nothing to do 70 return; 71 } 72 73 // Used for sanity checking at the end of the loop. 74 debug_only(size_t entries = 0; size_t retained = 0;) 75 76 size_t i = sz; 77 size_t new_index = sz; 78 79 while (i > _index) { 80 assert(i > 0, "we should have at least one more entry to process"); 81 i -= oopSize; 82 debug_only(entries += 1;) 83 oop* p = (oop*) &buf[byte_index_to_index((int) i)]; 84 oop obj = *p; 85 // NULL the entry so that unused parts of the buffer contain NULLs 86 // at the end. If we are going to retain it we will copy it to its 87 // final place. If we have retained all entries we have visited so 88 // far, we'll just end up copying it to the same place. 89 *p = NULL; 90 91 bool retain = g1h->is_obj_ill(obj); 92 if (retain) { 93 assert(new_index > 0, "we should not have already filled up the buffer"); 94 new_index -= oopSize; 95 assert(new_index >= i, 96 "new_index should never be below i, as we always compact 'up'"); 97 oop* new_p = (oop*) &buf[byte_index_to_index((int) new_index)]; 98 assert(new_p >= p, "the destination location should never be below " 99 "the source as we always compact 'up'"); 100 assert(*new_p == NULL, 101 "we should have already cleared the destination location"); 102 *new_p = obj; 103 debug_only(retained += 1;) 104 } 105 } 106 107 #ifdef ASSERT 108 size_t entries_calc = (sz - _index) / oopSize; 109 assert(entries == entries_calc, "the number of entries we counted " 110 "should match the number of entries we calculated"); 111 size_t retained_calc = (sz - new_index) / oopSize; 112 assert(retained == retained_calc, "the number of retained entries we counted " 113 "should match the number of retained entries we calculated"); 114 #endif // ASSERT 115 116 _index = new_index; 117 } 118 119 // This method will first apply the above filtering to the buffer. If 120 // post-filtering a large enough chunk of the buffer has been cleared 121 // we can re-use the buffer (instead of enqueueing it) and we can just 122 // allow the mutator to carry on executing using the same buffer 123 // instead of replacing it. 124 125 bool ObjPtrQueue::should_enqueue_buffer() { 126 assert(_lock == NULL || _lock->owned_by_self(), 127 "we should have taken the lock before calling this"); 128 129 // Even if G1SATBBufferEnqueueingThresholdPercent == 0 we have to 130 // filter the buffer given that this will remove any references into 131 // the CSet as we currently assume that no such refs will appear in 132 // enqueued buffers. 133 134 // This method should only be called if there is a non-NULL buffer 135 // that is full. 136 assert(_index == 0, "pre-condition"); 137 assert(_buf != NULL, "pre-condition"); 138 139 filter(); 140 141 size_t sz = _sz; 142 size_t all_entries = sz / oopSize; 143 size_t retained_entries = (sz - _index) / oopSize; 144 size_t perc = retained_entries * 100 / all_entries; 145 bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent; 146 return should_enqueue; 147 } 148 149 void ObjPtrQueue::apply_closure(ObjectClosure* cl) { 150 if (_buf != NULL) { 151 apply_closure_to_buffer(cl, _buf, _index, _sz); 152 } 153 } 154 155 void ObjPtrQueue::apply_closure_and_empty(ObjectClosure* cl) { 156 if (_buf != NULL) { 157 apply_closure_to_buffer(cl, _buf, _index, _sz); 158 _index = _sz; 159 } 160 } 161 162 void ObjPtrQueue::apply_closure_to_buffer(ObjectClosure* cl, 163 void** buf, size_t index, size_t sz) { 164 if (cl == NULL) return; 165 for (size_t i = index; i < sz; i += oopSize) { 166 oop obj = (oop)buf[byte_index_to_index((int)i)]; 167 // There can be NULL entries because of destructors. 168 if (obj != NULL) { 169 cl->do_object(obj); 170 } 171 } 172 } 173 174 #ifndef PRODUCT 175 // Helpful for debugging 176 177 void ObjPtrQueue::print(const char* name) { 178 print(name, _buf, _index, _sz); 179 } 180 181 void ObjPtrQueue::print(const char* name, 182 void** buf, size_t index, size_t sz) { 183 gclog_or_tty->print_cr(" SATB BUFFER [%s] buf: "PTR_FORMAT" " 184 "index: "SIZE_FORMAT" sz: "SIZE_FORMAT, 185 name, buf, index, sz); 186 } 187 #endif // PRODUCT 188 189 #ifdef ASSERT 190 void ObjPtrQueue::verify_oops_in_buffer() { 191 if (_buf == NULL) return; 192 for (size_t i = _index; i < _sz; i += oopSize) { 193 oop obj = (oop)_buf[byte_index_to_index((int)i)]; 194 assert(obj != NULL && obj->is_oop(true /* ignore mark word */), 195 "Not an oop"); 196 } 197 } 198 #endif 199 200 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 201 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 202 #endif // _MSC_VER 203 204 SATBMarkQueueSet::SATBMarkQueueSet() : 205 PtrQueueSet(), _closure(NULL), _par_closures(NULL), 206 _shared_satb_queue(this, true /*perm*/) { } 207 208 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock, 209 int process_completed_threshold, 210 Mutex* lock) { 211 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1); 212 _shared_satb_queue.set_lock(lock); 213 if (ParallelGCThreads > 0) { 214 _par_closures = NEW_C_HEAP_ARRAY(ObjectClosure*, ParallelGCThreads, mtGC); 215 } 216 } 217 218 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) { 219 DEBUG_ONLY(t->satb_mark_queue().verify_oops_in_buffer();) 220 t->satb_mark_queue().handle_zero_index(); 221 } 222 223 #ifdef ASSERT 224 void SATBMarkQueueSet::dump_active_states(bool expected_active) { 225 gclog_or_tty->print_cr("Expected SATB active state: %s", 226 expected_active ? "ACTIVE" : "INACTIVE"); 227 gclog_or_tty->print_cr("Actual SATB active states:"); 228 gclog_or_tty->print_cr(" Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE"); 229 for (JavaThread* t = Threads::first(); t; t = t->next()) { 230 gclog_or_tty->print_cr(" Thread \"%s\" queue: %s", t->name(), 231 t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE"); 232 } 233 gclog_or_tty->print_cr(" Shared queue: %s", 234 shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE"); 235 } 236 237 void SATBMarkQueueSet::verify_active_states(bool expected_active) { 238 // Verify queue set state 239 if (is_active() != expected_active) { 240 dump_active_states(expected_active); 241 guarantee(false, "SATB queue set has an unexpected active state"); 242 } 243 244 // Verify thread queue states 245 for (JavaThread* t = Threads::first(); t; t = t->next()) { 246 if (t->satb_mark_queue().is_active() != expected_active) { 247 dump_active_states(expected_active); 248 guarantee(false, "Thread SATB queue has an unexpected active state"); 249 } 250 } 251 252 // Verify shared queue state 253 if (shared_satb_queue()->is_active() != expected_active) { 254 dump_active_states(expected_active); 255 guarantee(false, "Shared SATB queue has an unexpected active state"); 256 } 257 } 258 #endif // ASSERT 259 260 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) { 261 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 262 #ifdef ASSERT 263 verify_active_states(expected_active); 264 #endif // ASSERT 265 _all_active = active; 266 for (JavaThread* t = Threads::first(); t; t = t->next()) { 267 t->satb_mark_queue().set_active(active); 268 } 269 shared_satb_queue()->set_active(active); 270 } 271 272 void SATBMarkQueueSet::filter_thread_buffers() { 273 for(JavaThread* t = Threads::first(); t; t = t->next()) { 274 t->satb_mark_queue().filter(); 275 } 276 shared_satb_queue()->filter(); 277 } 278 279 void SATBMarkQueueSet::set_closure(ObjectClosure* closure) { 280 _closure = closure; 281 } 282 283 void SATBMarkQueueSet::set_par_closure(int i, ObjectClosure* par_closure) { 284 assert(ParallelGCThreads > 0 && _par_closures != NULL, "Precondition"); 285 _par_closures[i] = par_closure; 286 } 287 288 bool SATBMarkQueueSet::apply_closure_to_completed_buffer_work(bool par, 289 uint worker) { 290 BufferNode* nd = NULL; 291 { 292 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 293 if (_completed_buffers_head != NULL) { 294 nd = _completed_buffers_head; 295 _completed_buffers_head = nd->next(); 296 if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL; 297 _n_completed_buffers--; 298 if (_n_completed_buffers == 0) _process_completed = false; 299 } 300 } 301 ObjectClosure* cl = (par ? _par_closures[worker] : _closure); 302 if (nd != NULL) { 303 void **buf = BufferNode::make_buffer_from_node(nd); 304 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz); 305 deallocate_buffer(buf); 306 return true; 307 } else { 308 return false; 309 } 310 } 311 312 void SATBMarkQueueSet::iterate_completed_buffers_read_only(ObjectClosure* cl) { 313 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 314 assert(cl != NULL, "pre-condition"); 315 316 BufferNode* nd = _completed_buffers_head; 317 while (nd != NULL) { 318 void** buf = BufferNode::make_buffer_from_node(nd); 319 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz); 320 nd = nd->next(); 321 } 322 } 323 324 void SATBMarkQueueSet::iterate_thread_buffers_read_only(ObjectClosure* cl) { 325 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 326 assert(cl != NULL, "pre-condition"); 327 328 for (JavaThread* t = Threads::first(); t; t = t->next()) { 329 t->satb_mark_queue().apply_closure(cl); 330 } 331 shared_satb_queue()->apply_closure(cl); 332 } 333 334 #ifndef PRODUCT 335 // Helpful for debugging 336 337 #define SATB_PRINTER_BUFFER_SIZE 256 338 339 void SATBMarkQueueSet::print_all(const char* msg) { 340 char buffer[SATB_PRINTER_BUFFER_SIZE]; 341 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 342 343 gclog_or_tty->cr(); 344 gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg); 345 346 BufferNode* nd = _completed_buffers_head; 347 int i = 0; 348 while (nd != NULL) { 349 void** buf = BufferNode::make_buffer_from_node(nd); 350 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i); 351 ObjPtrQueue::print(buffer, buf, 0, _sz); 352 nd = nd->next(); 353 i += 1; 354 } 355 356 for (JavaThread* t = Threads::first(); t; t = t->next()) { 357 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name()); 358 t->satb_mark_queue().print(buffer); 359 } 360 361 shared_satb_queue()->print("Shared"); 362 363 gclog_or_tty->cr(); 364 } 365 #endif // PRODUCT 366 367 void SATBMarkQueueSet::abandon_partial_marking() { 368 BufferNode* buffers_to_delete = NULL; 369 { 370 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 371 while (_completed_buffers_head != NULL) { 372 BufferNode* nd = _completed_buffers_head; 373 _completed_buffers_head = nd->next(); 374 nd->set_next(buffers_to_delete); 375 buffers_to_delete = nd; 376 } 377 _completed_buffers_tail = NULL; 378 _n_completed_buffers = 0; 379 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked()); 380 } 381 while (buffers_to_delete != NULL) { 382 BufferNode* nd = buffers_to_delete; 383 buffers_to_delete = nd->next(); 384 deallocate_buffer(BufferNode::make_buffer_from_node(nd)); 385 } 386 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 387 // So we can safely manipulate these queues. 388 for (JavaThread* t = Threads::first(); t; t = t->next()) { 389 t->satb_mark_queue().reset(); 390 } 391 shared_satb_queue()->reset(); 392 }