1 /* 2 * Copyright (c) 2001, 2012, 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 void ObjPtrQueue::flush() { 36 // The buffer might contain refs into the CSet. We have to filter it 37 // first before we flush it, otherwise we might end up with an 38 // enqueued buffer with refs into the CSet which breaks our invariants. 39 filter(); 40 PtrQueue::flush(); 41 } 42 43 // This method removes entries from an SATB buffer that will not be 44 // useful to the concurrent marking threads. An entry is removed if it 45 // satisfies one of the following conditions: 46 // 47 // * it points to an object outside the G1 heap (G1's concurrent 48 // marking only visits objects inside the G1 heap), 49 // * it points to an object that has been allocated since marking 50 // started (according to SATB those objects do not need to be 51 // visited during marking), or 52 // * it points to an object that has already been marked (no need to 53 // process it again). 54 // 55 // The rest of the entries will be retained and are compacted towards 56 // the top of the buffer. Note that, because we do not allow old 57 // regions in the CSet during marking, all objects on the CSet regions 58 // are young (eden or survivors) and therefore implicitly live. So any 59 // references into the CSet will be removed during filtering. 60 61 void ObjPtrQueue::filter() { 62 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 63 void** buf = _buf; 64 size_t sz = _sz; 65 66 if (buf == NULL) { 67 // nothing to do 68 return; 69 } 70 71 // Used for sanity checking at the end of the loop. 72 debug_only(size_t entries = 0; size_t retained = 0;) 73 74 size_t i = sz; 75 size_t new_index = sz; 76 77 while (i > _index) { 78 assert(i > 0, "we should have at least one more entry to process"); 79 i -= oopSize; 80 debug_only(entries += 1;) 81 oop* p = (oop*) &buf[byte_index_to_index((int) i)]; 82 oop obj = *p; 83 // NULL the entry so that unused parts of the buffer contain NULLs 84 // at the end. If we are going to retain it we will copy it to its 85 // final place. If we have retained all entries we have visited so 86 // far, we'll just end up copying it to the same place. 87 *p = NULL; 88 89 bool retain = g1h->is_obj_ill(obj); 90 if (retain) { 91 assert(new_index > 0, "we should not have already filled up the buffer"); 92 new_index -= oopSize; 93 assert(new_index >= i, 94 "new_index should never be below i, as we alwaysr compact 'up'"); 95 oop* new_p = (oop*) &buf[byte_index_to_index((int) new_index)]; 96 assert(new_p >= p, "the destination location should never be below " 97 "the source as we always compact 'up'"); 98 assert(*new_p == NULL, 99 "we should have already cleared the destination location"); 100 *new_p = obj; 101 debug_only(retained += 1;) 102 } 103 } 104 105 #ifdef ASSERT 106 size_t entries_calc = (sz - _index) / oopSize; 107 assert(entries == entries_calc, "the number of entries we counted " 108 "should match the number of entries we calculated"); 109 size_t retained_calc = (sz - new_index) / oopSize; 110 assert(retained == retained_calc, "the number of retained entries we counted " 111 "should match the number of retained entries we calculated"); 112 #endif // ASSERT 113 114 _index = new_index; 115 } 116 117 // This method will first apply the above filtering to the buffer. If 118 // post-filtering a large enough chunk of the buffer has been cleared 119 // we can re-use the buffer (instead of enqueueing it) and we can just 120 // allow the mutator to carry on executing using the same buffer 121 // instead of replacing it. 122 123 bool ObjPtrQueue::should_enqueue_buffer() { 124 assert(_lock == NULL || _lock->owned_by_self(), 125 "we should have taken the lock before calling this"); 126 127 // Even if G1SATBBufferEnqueueingThresholdPercent == 0 we have to 128 // filter the buffer given that this will remove any references into 129 // the CSet as we currently assume that no such refs will appear in 130 // enqueued buffers. 131 132 // This method should only be called if there is a non-NULL buffer 133 // that is full. 134 assert(_index == 0, "pre-condition"); 135 assert(_buf != NULL, "pre-condition"); 136 137 filter(); 138 139 size_t sz = _sz; 140 size_t all_entries = sz / oopSize; 141 size_t retained_entries = (sz - _index) / oopSize; 142 size_t perc = retained_entries * 100 / all_entries; 143 bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent; 144 return should_enqueue; 145 } 146 147 void ObjPtrQueue::apply_closure(ObjectClosure* cl) { 148 if (_buf != NULL) { 149 apply_closure_to_buffer(cl, _buf, _index, _sz); 150 } 151 } 152 153 void ObjPtrQueue::apply_closure_and_empty(ObjectClosure* cl) { 154 if (_buf != NULL) { 155 apply_closure_to_buffer(cl, _buf, _index, _sz); 156 _index = _sz; 157 } 158 } 159 160 void ObjPtrQueue::apply_closure_to_buffer(ObjectClosure* cl, 161 void** buf, size_t index, size_t sz) { 162 if (cl == NULL) return; 163 for (size_t i = index; i < sz; i += oopSize) { 164 oop obj = (oop)buf[byte_index_to_index((int)i)]; 165 // There can be NULL entries because of destructors. 166 if (obj != NULL) { 167 cl->do_object(obj); 168 } 169 } 170 } 171 172 #ifndef PRODUCT 173 // Helpful for debugging 174 175 void ObjPtrQueue::print(const char* name) { 176 print(name, _buf, _index, _sz); 177 } 178 179 void ObjPtrQueue::print(const char* name, 180 void** buf, size_t index, size_t sz) { 181 gclog_or_tty->print_cr(" SATB BUFFER [%s] buf: "PTR_FORMAT" " 182 "index: "SIZE_FORMAT" sz: "SIZE_FORMAT, 183 name, buf, index, sz); 184 } 185 #endif // PRODUCT 186 187 #ifdef ASSERT 188 void ObjPtrQueue::verify_oops_in_buffer() { 189 if (_buf == NULL) return; 190 for (size_t i = _index; i < _sz; i += oopSize) { 191 oop obj = (oop)_buf[byte_index_to_index((int)i)]; 192 assert(obj != NULL && obj->is_oop(true /* ignore mark word */), 193 "Not an oop"); 194 } 195 } 196 #endif 197 198 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 199 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 200 #endif // _MSC_VER 201 202 SATBMarkQueueSet::SATBMarkQueueSet() : 203 PtrQueueSet(), _closure(NULL), _par_closures(NULL), 204 _shared_satb_queue(this, true /*perm*/) { } 205 206 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock, 207 int process_completed_threshold, 208 Mutex* lock) { 209 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1); 210 _shared_satb_queue.set_lock(lock); 211 if (ParallelGCThreads > 0) { 212 _par_closures = NEW_C_HEAP_ARRAY(ObjectClosure*, ParallelGCThreads, mtGC); 213 } 214 } 215 216 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) { 217 DEBUG_ONLY(t->satb_mark_queue().verify_oops_in_buffer();) 218 t->satb_mark_queue().handle_zero_index(); 219 } 220 221 #ifdef ASSERT 222 void SATBMarkQueueSet::dump_active_values(JavaThread* first, 223 bool expected_active) { 224 gclog_or_tty->print_cr("SATB queue active values for Java Threads"); 225 gclog_or_tty->print_cr(" SATB queue set: active is %s", 226 (is_active()) ? "TRUE" : "FALSE"); 227 gclog_or_tty->print_cr(" expected_active is %s", 228 (expected_active) ? "TRUE" : "FALSE"); 229 for (JavaThread* t = first; t; t = t->next()) { 230 bool active = t->satb_mark_queue().is_active(); 231 gclog_or_tty->print_cr(" thread %s, active is %s", 232 t->name(), (active) ? "TRUE" : "FALSE"); 233 } 234 } 235 #endif // ASSERT 236 237 void SATBMarkQueueSet::set_active_all_threads(bool b, 238 bool expected_active) { 239 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 240 JavaThread* first = Threads::first(); 241 242 #ifdef ASSERT 243 if (_all_active != expected_active) { 244 dump_active_values(first, expected_active); 245 246 // I leave this here as a guarantee, instead of an assert, so 247 // that it will still be compiled in if we choose to uncomment 248 // the #ifdef ASSERT in a product build. The whole block is 249 // within an #ifdef ASSERT so the guarantee will not be compiled 250 // in a product build anyway. 251 guarantee(false, 252 "SATB queue set has an unexpected active value"); 253 } 254 #endif // ASSERT 255 _all_active = b; 256 257 for (JavaThread* t = first; t; t = t->next()) { 258 #ifdef ASSERT 259 bool active = t->satb_mark_queue().is_active(); 260 if (active != expected_active) { 261 dump_active_values(first, expected_active); 262 263 // I leave this here as a guarantee, instead of an assert, so 264 // that it will still be compiled in if we choose to uncomment 265 // the #ifdef ASSERT in a product build. The whole block is 266 // within an #ifdef ASSERT so the guarantee will not be compiled 267 // in a product build anyway. 268 guarantee(false, 269 "thread has an unexpected active value in its SATB queue"); 270 } 271 #endif // ASSERT 272 t->satb_mark_queue().set_active(b); 273 } 274 } 275 276 void SATBMarkQueueSet::filter_thread_buffers() { 277 for(JavaThread* t = Threads::first(); t; t = t->next()) { 278 t->satb_mark_queue().filter(); 279 } 280 shared_satb_queue()->filter(); 281 } 282 283 void SATBMarkQueueSet::set_closure(ObjectClosure* closure) { 284 _closure = closure; 285 } 286 287 void SATBMarkQueueSet::set_par_closure(int i, ObjectClosure* par_closure) { 288 assert(ParallelGCThreads > 0 && _par_closures != NULL, "Precondition"); 289 _par_closures[i] = par_closure; 290 } 291 292 void SATBMarkQueueSet::iterate_closure_all_threads() { 293 for(JavaThread* t = Threads::first(); t; t = t->next()) { 294 t->satb_mark_queue().apply_closure_and_empty(_closure); 295 } 296 shared_satb_queue()->apply_closure_and_empty(_closure); 297 } 298 299 void SATBMarkQueueSet::par_iterate_closure_all_threads(int worker) { 300 SharedHeap* sh = SharedHeap::heap(); 301 int parity = sh->strong_roots_parity(); 302 303 for(JavaThread* t = Threads::first(); t; t = t->next()) { 304 if (t->claim_oops_do(true, parity)) { 305 t->satb_mark_queue().apply_closure_and_empty(_par_closures[worker]); 306 } 307 } 308 309 // We also need to claim the VMThread so that its parity is updated 310 // otherwise the next call to Thread::possibly_parallel_oops_do inside 311 // a StrongRootsScope might skip the VMThread because it has a stale 312 // parity that matches the parity set by the StrongRootsScope 313 // 314 // Whichever worker succeeds in claiming the VMThread gets to do 315 // the shared queue. 316 317 VMThread* vmt = VMThread::vm_thread(); 318 if (vmt->claim_oops_do(true, parity)) { 319 shared_satb_queue()->apply_closure_and_empty(_par_closures[worker]); 320 } 321 } 322 323 bool SATBMarkQueueSet::apply_closure_to_completed_buffer_work(bool par, 324 int worker) { 325 BufferNode* nd = NULL; 326 { 327 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 328 if (_completed_buffers_head != NULL) { 329 nd = _completed_buffers_head; 330 _completed_buffers_head = nd->next(); 331 if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL; 332 _n_completed_buffers--; 333 if (_n_completed_buffers == 0) _process_completed = false; 334 } 335 } 336 ObjectClosure* cl = (par ? _par_closures[worker] : _closure); 337 if (nd != NULL) { 338 void **buf = BufferNode::make_buffer_from_node(nd); 339 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz); 340 deallocate_buffer(buf); 341 return true; 342 } else { 343 return false; 344 } 345 } 346 347 void SATBMarkQueueSet::iterate_completed_buffers_read_only(ObjectClosure* cl) { 348 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 349 assert(cl != NULL, "pre-condition"); 350 351 BufferNode* nd = _completed_buffers_head; 352 while (nd != NULL) { 353 void** buf = BufferNode::make_buffer_from_node(nd); 354 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz); 355 nd = nd->next(); 356 } 357 } 358 359 void SATBMarkQueueSet::iterate_thread_buffers_read_only(ObjectClosure* cl) { 360 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 361 assert(cl != NULL, "pre-condition"); 362 363 for (JavaThread* t = Threads::first(); t; t = t->next()) { 364 t->satb_mark_queue().apply_closure(cl); 365 } 366 shared_satb_queue()->apply_closure(cl); 367 } 368 369 #ifndef PRODUCT 370 // Helpful for debugging 371 372 #define SATB_PRINTER_BUFFER_SIZE 256 373 374 void SATBMarkQueueSet::print_all(const char* msg) { 375 char buffer[SATB_PRINTER_BUFFER_SIZE]; 376 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 377 378 gclog_or_tty->cr(); 379 gclog_or_tty->print_cr("SATB BUFFERS [%s]", msg); 380 381 BufferNode* nd = _completed_buffers_head; 382 int i = 0; 383 while (nd != NULL) { 384 void** buf = BufferNode::make_buffer_from_node(nd); 385 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i); 386 ObjPtrQueue::print(buffer, buf, 0, _sz); 387 nd = nd->next(); 388 i += 1; 389 } 390 391 for (JavaThread* t = Threads::first(); t; t = t->next()) { 392 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name()); 393 t->satb_mark_queue().print(buffer); 394 } 395 396 shared_satb_queue()->print("Shared"); 397 398 gclog_or_tty->cr(); 399 } 400 #endif // PRODUCT 401 402 void SATBMarkQueueSet::abandon_partial_marking() { 403 BufferNode* buffers_to_delete = NULL; 404 { 405 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 406 while (_completed_buffers_head != NULL) { 407 BufferNode* nd = _completed_buffers_head; 408 _completed_buffers_head = nd->next(); 409 nd->set_next(buffers_to_delete); 410 buffers_to_delete = nd; 411 } 412 _completed_buffers_tail = NULL; 413 _n_completed_buffers = 0; 414 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked()); 415 } 416 while (buffers_to_delete != NULL) { 417 BufferNode* nd = buffers_to_delete; 418 buffers_to_delete = nd->next(); 419 deallocate_buffer(BufferNode::make_buffer_from_node(nd)); 420 } 421 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 422 // So we can safely manipulate these queues. 423 for (JavaThread* t = Threads::first(); t; t = t->next()) { 424 t->satb_mark_queue().reset(); 425 } 426 shared_satb_queue()->reset(); 427 }