1 /* 2 * Copyright (c) 2001, 2017, 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 "jvm.h" 27 #include "gc/g1/g1CollectedHeap.inline.hpp" 28 #include "gc/g1/satbMarkQueue.hpp" 29 #include "gc/shared/collectedHeap.hpp" 30 #include "memory/allocation.inline.hpp" 31 #include "oops/oop.inline.hpp" 32 #include "runtime/mutexLocker.hpp" 33 #include "runtime/safepoint.hpp" 34 #include "runtime/thread.hpp" 35 #include "runtime/vmThread.hpp" 36 37 SATBMarkQueue::SATBMarkQueue(SATBMarkQueueSet* qset, bool permanent) : 38 // SATB queues are only active during marking cycles. We create 39 // them with their active field set to false. If a thread is 40 // created during a cycle and its SATB queue needs to be activated 41 // before the thread starts running, we'll need to set its active 42 // field to true. This is done in JavaThread::initialize_queues(). 43 PtrQueue(qset, permanent, false /* active */) 44 { } 45 46 void SATBMarkQueue::flush() { 47 // Filter now to possibly save work later. If filtering empties the 48 // buffer then flush_impl can deallocate the buffer. 49 filter(); 50 flush_impl(); 51 } 52 53 // Return true if a SATB buffer entry refers to an object that 54 // requires marking. 55 // 56 // The entry must point into the G1 heap. In particular, it must not 57 // be a NULL pointer. NULL pointers are pre-filtered and never 58 // inserted into a SATB buffer. 59 // 60 // An entry that is below the NTAMS pointer for the containing heap 61 // region requires marking. Such an entry must point to a valid object. 62 // 63 // An entry that is at least the NTAMS pointer for the containing heap 64 // region might be any of the following, none of which should be marked. 65 // 66 // * A reference to an object allocated since marking started. 67 // According to SATB, such objects are implicitly kept live and do 68 // not need to be dealt with via SATB buffer processing. 69 // 70 // * A reference to a young generation object. Young objects are 71 // handled separately and are not marked by concurrent marking. 72 // 73 // * A stale reference to a young generation object. If a young 74 // generation object reference is recorded and not filtered out 75 // before being moved by a young collection, the reference becomes 76 // stale. 77 // 78 // * A stale reference to an eagerly reclaimed humongous object. If a 79 // humongous object is recorded and then reclaimed, the reference 80 // becomes stale. 81 // 82 // The stale reference cases are implicitly handled by the NTAMS 83 // comparison. Because of the possibility of stale references, buffer 84 // processing must be somewhat circumspect and not assume entries 85 // in an unfiltered buffer refer to valid objects. 86 87 inline bool requires_marking(const void* entry, G1CollectedHeap* heap) { 88 // Includes rejection of NULL pointers. 89 assert(heap->is_in_reserved(entry), 90 "Non-heap pointer in SATB buffer: " PTR_FORMAT, p2i(entry)); 91 92 HeapRegion* region = heap->heap_region_containing(entry); 93 assert(region != NULL, "No region for " PTR_FORMAT, p2i(entry)); 94 if (entry >= region->next_top_at_mark_start()) { 95 return false; 96 } 97 98 assert(oopDesc::is_oop(oop(entry), true /* ignore mark word */), 99 "Invalid oop in SATB buffer: " PTR_FORMAT, p2i(entry)); 100 101 return true; 102 } 103 104 inline bool retain_entry(const void* entry, G1CollectedHeap* heap) { 105 return requires_marking(entry, heap) && !heap->isMarkedNext((oop)entry); 106 } 107 108 // This method removes entries from a SATB buffer that will not be 109 // useful to the concurrent marking threads. Entries are retained if 110 // they require marking and are not already marked. Retained entries 111 // are compacted toward the top of the buffer. 112 113 void SATBMarkQueue::filter() { 114 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 115 void** buf = _buf; 116 117 if (buf == NULL) { 118 // nothing to do 119 return; 120 } 121 122 // Two-fingered compaction toward the end. 123 void** src = &buf[index()]; 124 void** dst = &buf[capacity()]; 125 assert(src <= dst, "invariant"); 126 for ( ; src < dst; ++src) { 127 // Search low to high for an entry to keep. 128 void* entry = *src; 129 if (retain_entry(entry, g1h)) { 130 // Found keeper. Search high to low for an entry to discard. 131 while (src < --dst) { 132 if (!retain_entry(*dst, g1h)) { 133 *dst = entry; // Replace discard with keeper. 134 break; 135 } 136 } 137 // If discard search failed (src == dst), the outer loop will also end. 138 } 139 } 140 // dst points to the lowest retained entry, or the end of the buffer 141 // if all the entries were filtered out. 142 set_index(dst - buf); 143 } 144 145 // This method will first apply the above filtering to the buffer. If 146 // post-filtering a large enough chunk of the buffer has been cleared 147 // we can re-use the buffer (instead of enqueueing it) and we can just 148 // allow the mutator to carry on executing using the same buffer 149 // instead of replacing it. 150 151 bool SATBMarkQueue::should_enqueue_buffer() { 152 assert(_lock == NULL || _lock->owned_by_self(), 153 "we should have taken the lock before calling this"); 154 155 // If G1SATBBufferEnqueueingThresholdPercent == 0 we could skip filtering. 156 157 // This method should only be called if there is a non-NULL buffer 158 // that is full. 159 assert(index() == 0, "pre-condition"); 160 assert(_buf != NULL, "pre-condition"); 161 162 filter(); 163 164 size_t cap = capacity(); 165 size_t percent_used = ((cap - index()) * 100) / cap; 166 bool should_enqueue = percent_used > G1SATBBufferEnqueueingThresholdPercent; 167 return should_enqueue; 168 } 169 170 void SATBMarkQueue::apply_closure_and_empty(SATBBufferClosure* cl) { 171 assert(SafepointSynchronize::is_at_safepoint(), 172 "SATB queues must only be processed at safepoints"); 173 if (_buf != NULL) { 174 cl->do_buffer(&_buf[index()], size()); 175 reset(); 176 } 177 } 178 179 #ifndef PRODUCT 180 // Helpful for debugging 181 182 static void print_satb_buffer(const char* name, 183 void** buf, 184 size_t index, 185 size_t capacity) { 186 tty->print_cr(" SATB BUFFER [%s] buf: " PTR_FORMAT " index: " SIZE_FORMAT 187 " capacity: " SIZE_FORMAT, 188 name, p2i(buf), index, capacity); 189 } 190 191 void SATBMarkQueue::print(const char* name) { 192 print_satb_buffer(name, _buf, index(), capacity()); 193 } 194 195 #endif // PRODUCT 196 197 SATBMarkQueueSet::SATBMarkQueueSet() : 198 PtrQueueSet(), 199 _shared_satb_queue(this, true /* permanent */) { } 200 201 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock, 202 int process_completed_threshold, 203 Mutex* lock) { 204 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1); 205 _shared_satb_queue.set_lock(lock); 206 } 207 208 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) { 209 t->satb_mark_queue().handle_zero_index(); 210 } 211 212 #ifdef ASSERT 213 void SATBMarkQueueSet::dump_active_states(bool expected_active) { 214 log_error(gc, verify)("Expected SATB active state: %s", expected_active ? "ACTIVE" : "INACTIVE"); 215 log_error(gc, verify)("Actual SATB active states:"); 216 log_error(gc, verify)(" Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE"); 217 for (JavaThread* t = Threads::first(); t; t = t->next()) { 218 log_error(gc, verify)(" Thread \"%s\" queue: %s", t->name(), t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE"); 219 } 220 log_error(gc, verify)(" Shared queue: %s", shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE"); 221 } 222 223 void SATBMarkQueueSet::verify_active_states(bool expected_active) { 224 // Verify queue set state 225 if (is_active() != expected_active) { 226 dump_active_states(expected_active); 227 guarantee(false, "SATB queue set has an unexpected active state"); 228 } 229 230 // Verify thread queue states 231 for (JavaThread* t = Threads::first(); t; t = t->next()) { 232 if (t->satb_mark_queue().is_active() != expected_active) { 233 dump_active_states(expected_active); 234 guarantee(false, "Thread SATB queue has an unexpected active state"); 235 } 236 } 237 238 // Verify shared queue state 239 if (shared_satb_queue()->is_active() != expected_active) { 240 dump_active_states(expected_active); 241 guarantee(false, "Shared SATB queue has an unexpected active state"); 242 } 243 } 244 #endif // ASSERT 245 246 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) { 247 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 248 #ifdef ASSERT 249 verify_active_states(expected_active); 250 #endif // ASSERT 251 _all_active = active; 252 for (JavaThread* t = Threads::first(); t; t = t->next()) { 253 t->satb_mark_queue().set_active(active); 254 } 255 shared_satb_queue()->set_active(active); 256 } 257 258 void SATBMarkQueueSet::filter_thread_buffers() { 259 for(JavaThread* t = Threads::first(); t; t = t->next()) { 260 t->satb_mark_queue().filter(); 261 } 262 shared_satb_queue()->filter(); 263 } 264 265 bool SATBMarkQueueSet::apply_closure_to_completed_buffer(SATBBufferClosure* cl) { 266 BufferNode* nd = NULL; 267 { 268 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 269 if (_completed_buffers_head != NULL) { 270 nd = _completed_buffers_head; 271 _completed_buffers_head = nd->next(); 272 if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL; 273 _n_completed_buffers--; 274 if (_n_completed_buffers == 0) _process_completed = false; 275 } 276 } 277 if (nd != NULL) { 278 void **buf = BufferNode::make_buffer_from_node(nd); 279 size_t index = nd->index(); 280 size_t size = buffer_size(); 281 assert(index <= size, "invariant"); 282 cl->do_buffer(buf + index, size - index); 283 deallocate_buffer(nd); 284 return true; 285 } else { 286 return false; 287 } 288 } 289 290 #ifndef PRODUCT 291 // Helpful for debugging 292 293 #define SATB_PRINTER_BUFFER_SIZE 256 294 295 void SATBMarkQueueSet::print_all(const char* msg) { 296 char buffer[SATB_PRINTER_BUFFER_SIZE]; 297 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 298 299 tty->cr(); 300 tty->print_cr("SATB BUFFERS [%s]", msg); 301 302 BufferNode* nd = _completed_buffers_head; 303 int i = 0; 304 while (nd != NULL) { 305 void** buf = BufferNode::make_buffer_from_node(nd); 306 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i); 307 print_satb_buffer(buffer, buf, nd->index(), buffer_size()); 308 nd = nd->next(); 309 i += 1; 310 } 311 312 for (JavaThread* t = Threads::first(); t; t = t->next()) { 313 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name()); 314 t->satb_mark_queue().print(buffer); 315 } 316 317 shared_satb_queue()->print("Shared"); 318 319 tty->cr(); 320 } 321 #endif // PRODUCT 322 323 void SATBMarkQueueSet::abandon_partial_marking() { 324 BufferNode* buffers_to_delete = NULL; 325 { 326 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 327 while (_completed_buffers_head != NULL) { 328 BufferNode* nd = _completed_buffers_head; 329 _completed_buffers_head = nd->next(); 330 nd->set_next(buffers_to_delete); 331 buffers_to_delete = nd; 332 } 333 _completed_buffers_tail = NULL; 334 _n_completed_buffers = 0; 335 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked()); 336 } 337 while (buffers_to_delete != NULL) { 338 BufferNode* nd = buffers_to_delete; 339 buffers_to_delete = nd->next(); 340 deallocate_buffer(nd); 341 } 342 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 343 // So we can safely manipulate these queues. 344 for (JavaThread* t = Threads::first(); t; t = t->next()) { 345 t->satb_mark_queue().reset(); 346 } 347 shared_satb_queue()->reset(); 348 }