1 /* 2 * Copyright (c) 2001, 2011, 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 "runtime/mutexLocker.hpp" 31 #include "runtime/thread.hpp" 32 33 // This method removes entries from an SATB buffer that will not be 34 // useful to the concurrent marking threads. An entry is removed if it 35 // satisfies one of the following conditions: 36 // 37 // * it points to an object outside the G1 heap (G1's concurrent 38 // marking only visits objects inside the G1 heap), 39 // * it points to an object that has been allocated since marking 40 // started (according to SATB those objects do not need to be 41 // visited during marking), or 42 // * it points to an object that has already been marked (no need to 43 // process it again). 44 // 45 // The rest of the entries will be retained and are compacted towards 46 // the top of the buffer. If with this filtering we clear a large 47 // enough chunk of the buffer we can re-use it (instead of enqueueing 48 // it) and we can just allow the mutator to carry on executing. 49 50 bool ObjPtrQueue::should_enqueue_buffer() { 51 assert(_lock == NULL || _lock->owned_by_self(), 52 "we should have taken the lock before calling this"); 53 54 // A value of 0 means "don't filter SATB buffers". 55 if (G1SATBBufferEnqueueingThresholdPercent == 0) { 56 return true; 57 } 58 59 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 60 61 // This method should only be called if there is a non-NULL buffer 62 // that is full. 63 assert(_index == 0, "pre-condition"); 64 assert(_buf != NULL, "pre-condition"); 65 66 void** buf = _buf; 67 size_t sz = _sz; 68 69 // Used for sanity checking at the end of the loop. 70 debug_only(size_t entries = 0; size_t retained = 0;) 71 72 size_t i = sz; 73 size_t new_index = sz; 74 75 // Given that we are expecting _index == 0, we could have changed 76 // the loop condition to (i > 0). But we are using _index for 77 // generality. 78 while (i > _index) { 79 assert(i > 0, "we should have at least one more entry to process"); 80 i -= oopSize; 81 debug_only(entries += 1;) 82 oop* p = (oop*) &buf[byte_index_to_index((int) i)]; 83 oop obj = *p; 84 // NULL the entry so that unused parts of the buffer contain NULLs 85 // at the end. If we are going to retain it we will copy it to its 86 // final place. If we have retained all entries we have visited so 87 // far, we'll just end up copying it to the same place. 88 *p = NULL; 89 90 bool retain = g1h->is_obj_ill(obj); 91 if (retain) { 92 assert(new_index > 0, "we should not have already filled up the buffer"); 93 new_index -= oopSize; 94 assert(new_index >= i, 95 "new_index should never be below i, as we alwaysr compact 'up'"); 96 oop* new_p = (oop*) &buf[byte_index_to_index((int) new_index)]; 97 assert(new_p >= p, "the destination location should never be below " 98 "the source as we always compact 'up'"); 99 assert(*new_p == NULL, 100 "we should have already cleared the destination location"); 101 *new_p = obj; 102 debug_only(retained += 1;) 103 } 104 } 105 size_t entries_calc = (sz - _index) / oopSize; 106 assert(entries == entries_calc, "the number of entries we counted " 107 "should match the number of entries we calculated"); 108 size_t retained_calc = (sz - new_index) / oopSize; 109 assert(retained == retained_calc, "the number of retained entries we counted " 110 "should match the number of retained entries we calculated"); 111 size_t perc = retained_calc * 100 / entries_calc; 112 bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent; 113 _index = new_index; 114 115 return should_enqueue; 116 } 117 118 void ObjPtrQueue::apply_closure(ObjectClosure* cl) { 119 if (_buf != NULL) { 120 apply_closure_to_buffer(cl, _buf, _index, _sz); 121 _index = _sz; 122 } 123 } 124 125 void ObjPtrQueue::apply_closure_to_buffer(ObjectClosure* cl, 126 void** buf, size_t index, size_t sz) { 127 if (cl == NULL) return; 128 for (size_t i = index; i < sz; i += oopSize) { 129 oop obj = (oop)buf[byte_index_to_index((int)i)]; 130 // There can be NULL entries because of destructors. 131 if (obj != NULL) { 132 cl->do_object(obj); 133 } 134 } 135 } 136 137 #ifdef ASSERT 138 void ObjPtrQueue::verify_oops_in_buffer() { 139 if (_buf == NULL) return; 140 for (size_t i = _index; i < _sz; i += oopSize) { 141 oop obj = (oop)_buf[byte_index_to_index((int)i)]; 142 assert(obj != NULL && obj->is_oop(true /* ignore mark word */), 143 "Not an oop"); 144 } 145 } 146 #endif 147 148 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away 149 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list 150 #endif // _MSC_VER 151 152 153 SATBMarkQueueSet::SATBMarkQueueSet() : 154 PtrQueueSet(), 155 _closure(NULL), _par_closures(NULL), 156 _shared_satb_queue(this, true /*perm*/) 157 {} 158 159 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock, 160 int process_completed_threshold, 161 Mutex* lock) { 162 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1); 163 _shared_satb_queue.set_lock(lock); 164 if (ParallelGCThreads > 0) { 165 _par_closures = NEW_C_HEAP_ARRAY(ObjectClosure*, ParallelGCThreads); 166 } 167 } 168 169 170 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) { 171 DEBUG_ONLY(t->satb_mark_queue().verify_oops_in_buffer();) 172 t->satb_mark_queue().handle_zero_index(); 173 } 174 175 #ifdef ASSERT 176 void SATBMarkQueueSet::dump_active_values(JavaThread* first, 177 bool expected_active) { 178 gclog_or_tty->print_cr("SATB queue active values for Java Threads"); 179 gclog_or_tty->print_cr(" SATB queue set: active is %s", 180 (is_active()) ? "TRUE" : "FALSE"); 181 gclog_or_tty->print_cr(" expected_active is %s", 182 (expected_active) ? "TRUE" : "FALSE"); 183 for (JavaThread* t = first; t; t = t->next()) { 184 bool active = t->satb_mark_queue().is_active(); 185 gclog_or_tty->print_cr(" thread %s, active is %s", 186 t->name(), (active) ? "TRUE" : "FALSE"); 187 } 188 } 189 #endif // ASSERT 190 191 void SATBMarkQueueSet::set_active_all_threads(bool b, 192 bool expected_active) { 193 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 194 JavaThread* first = Threads::first(); 195 196 #ifdef ASSERT 197 if (_all_active != expected_active) { 198 dump_active_values(first, expected_active); 199 200 // I leave this here as a guarantee, instead of an assert, so 201 // that it will still be compiled in if we choose to uncomment 202 // the #ifdef ASSERT in a product build. The whole block is 203 // within an #ifdef ASSERT so the guarantee will not be compiled 204 // in a product build anyway. 205 guarantee(false, 206 "SATB queue set has an unexpected active value"); 207 } 208 #endif // ASSERT 209 _all_active = b; 210 211 for (JavaThread* t = first; t; t = t->next()) { 212 #ifdef ASSERT 213 bool active = t->satb_mark_queue().is_active(); 214 if (active != expected_active) { 215 dump_active_values(first, expected_active); 216 217 // I leave this here as a guarantee, instead of an assert, so 218 // that it will still be compiled in if we choose to uncomment 219 // the #ifdef ASSERT in a product build. The whole block is 220 // within an #ifdef ASSERT so the guarantee will not be compiled 221 // in a product build anyway. 222 guarantee(false, 223 "thread has an unexpected active value in its SATB queue"); 224 } 225 #endif // ASSERT 226 t->satb_mark_queue().set_active(b); 227 } 228 } 229 230 void SATBMarkQueueSet::set_closure(ObjectClosure* closure) { 231 _closure = closure; 232 } 233 234 void SATBMarkQueueSet::set_par_closure(int i, ObjectClosure* par_closure) { 235 assert(ParallelGCThreads > 0 && _par_closures != NULL, "Precondition"); 236 _par_closures[i] = par_closure; 237 } 238 239 void SATBMarkQueueSet::iterate_closure_all_threads() { 240 for(JavaThread* t = Threads::first(); t; t = t->next()) { 241 t->satb_mark_queue().apply_closure(_closure); 242 } 243 shared_satb_queue()->apply_closure(_closure); 244 } 245 246 void SATBMarkQueueSet::par_iterate_closure_all_threads(int worker) { 247 SharedHeap* sh = SharedHeap::heap(); 248 int parity = sh->strong_roots_parity(); 249 250 for(JavaThread* t = Threads::first(); t; t = t->next()) { 251 if (t->claim_oops_do(true, parity)) { 252 t->satb_mark_queue().apply_closure(_par_closures[worker]); 253 } 254 } 255 // We'll have worker 0 do this one. 256 if (worker == 0) { 257 shared_satb_queue()->apply_closure(_par_closures[0]); 258 } 259 } 260 261 bool SATBMarkQueueSet::apply_closure_to_completed_buffer_work(bool par, 262 int worker) { 263 BufferNode* nd = NULL; 264 { 265 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 266 if (_completed_buffers_head != NULL) { 267 nd = _completed_buffers_head; 268 _completed_buffers_head = nd->next(); 269 if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL; 270 _n_completed_buffers--; 271 if (_n_completed_buffers == 0) _process_completed = false; 272 } 273 } 274 ObjectClosure* cl = (par ? _par_closures[worker] : _closure); 275 if (nd != NULL) { 276 void **buf = BufferNode::make_buffer_from_node(nd); 277 ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz); 278 deallocate_buffer(buf); 279 return true; 280 } else { 281 return false; 282 } 283 } 284 285 void SATBMarkQueueSet::abandon_partial_marking() { 286 BufferNode* buffers_to_delete = NULL; 287 { 288 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 289 while (_completed_buffers_head != NULL) { 290 BufferNode* nd = _completed_buffers_head; 291 _completed_buffers_head = nd->next(); 292 nd->set_next(buffers_to_delete); 293 buffers_to_delete = nd; 294 } 295 _completed_buffers_tail = NULL; 296 _n_completed_buffers = 0; 297 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked()); 298 } 299 while (buffers_to_delete != NULL) { 300 BufferNode* nd = buffers_to_delete; 301 buffers_to_delete = nd->next(); 302 deallocate_buffer(BufferNode::make_buffer_from_node(nd)); 303 } 304 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 305 // So we can safely manipulate these queues. 306 for (JavaThread* t = Threads::first(); t; t = t->next()) { 307 t->satb_mark_queue().reset(); 308 } 309 shared_satb_queue()->reset(); 310 }