1 /* 2 * Copyright (c) 2001, 2018, 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/threadSMR.hpp" 36 #include "runtime/vmThread.hpp" 37 38 SATBMarkQueue::SATBMarkQueue(SATBMarkQueueSet* qset, bool permanent) : 39 // SATB queues are only active during marking cycles. We create 40 // them with their active field set to false. If a thread is 41 // created during a cycle and its SATB queue needs to be activated 42 // before the thread starts running, we'll need to set its active 43 // field to true. This is done in G1SATBCardTableLoggingModRefBS:: 44 // on_thread_create(). 45 PtrQueue(qset, permanent, false /* active */) 46 { } 47 48 void SATBMarkQueue::flush() { 49 // Filter now to possibly save work later. If filtering empties the 50 // buffer then flush_impl can deallocate the buffer. 51 filter(); 52 flush_impl(); 53 } 54 55 // Return true if a SATB buffer entry refers to an object that 56 // requires marking. 57 // 58 // The entry must point into the G1 heap. In particular, it must not 59 // be a NULL pointer. NULL pointers are pre-filtered and never 60 // inserted into a SATB buffer. 61 // 62 // An entry that is below the NTAMS pointer for the containing heap 63 // region requires marking. Such an entry must point to a valid object. 64 // 65 // An entry that is at least the NTAMS pointer for the containing heap 66 // region might be any of the following, none of which should be marked. 67 // 68 // * A reference to an object allocated since marking started. 69 // According to SATB, such objects are implicitly kept live and do 70 // not need to be dealt with via SATB buffer processing. 71 // 72 // * A reference to a young generation object. Young objects are 73 // handled separately and are not marked by concurrent marking. 74 // 75 // * A stale reference to a young generation object. If a young 76 // generation object reference is recorded and not filtered out 77 // before being moved by a young collection, the reference becomes 78 // stale. 79 // 80 // * A stale reference to an eagerly reclaimed humongous object. If a 81 // humongous object is recorded and then reclaimed, the reference 82 // becomes stale. 83 // 84 // The stale reference cases are implicitly handled by the NTAMS 85 // comparison. Because of the possibility of stale references, buffer 86 // processing must be somewhat circumspect and not assume entries 87 // in an unfiltered buffer refer to valid objects. 88 89 inline bool requires_marking(const void* entry, G1CollectedHeap* heap) { 90 // Includes rejection of NULL pointers. 91 assert(heap->is_in_reserved(entry), 92 "Non-heap pointer in SATB buffer: " PTR_FORMAT, p2i(entry)); 93 94 HeapRegion* region = heap->heap_region_containing(entry); 95 assert(region != NULL, "No region for " PTR_FORMAT, p2i(entry)); 96 if (entry >= region->next_top_at_mark_start()) { 97 return false; 98 } 99 100 assert(oopDesc::is_oop(oop(entry), true /* ignore mark word */), 101 "Invalid oop in SATB buffer: " PTR_FORMAT, p2i(entry)); 102 103 return true; 104 } 105 106 inline bool retain_entry(const void* entry, G1CollectedHeap* heap) { 107 return requires_marking(entry, heap) && !heap->isMarkedNext((oop)entry); 108 } 109 110 // This method removes entries from a SATB buffer that will not be 111 // useful to the concurrent marking threads. Entries are retained if 112 // they require marking and are not already marked. Retained entries 113 // are compacted toward the top of the buffer. 114 115 void SATBMarkQueue::filter() { 116 G1CollectedHeap* g1h = G1CollectedHeap::heap(); 117 void** buf = _buf; 118 119 if (buf == NULL) { 120 // nothing to do 121 return; 122 } 123 124 // Two-fingered compaction toward the end. 125 void** src = &buf[index()]; 126 void** dst = &buf[capacity()]; 127 assert(src <= dst, "invariant"); 128 for ( ; src < dst; ++src) { 129 // Search low to high for an entry to keep. 130 void* entry = *src; 131 if (retain_entry(entry, g1h)) { 132 // Found keeper. Search high to low for an entry to discard. 133 while (src < --dst) { 134 if (!retain_entry(*dst, g1h)) { 135 *dst = entry; // Replace discard with keeper. 136 break; 137 } 138 } 139 // If discard search failed (src == dst), the outer loop will also end. 140 } 141 } 142 // dst points to the lowest retained entry, or the end of the buffer 143 // if all the entries were filtered out. 144 set_index(dst - buf); 145 } 146 147 // This method will first apply the above filtering to the buffer. If 148 // post-filtering a large enough chunk of the buffer has been cleared 149 // we can re-use the buffer (instead of enqueueing it) and we can just 150 // allow the mutator to carry on executing using the same buffer 151 // instead of replacing it. 152 153 bool SATBMarkQueue::should_enqueue_buffer() { 154 assert(_lock == NULL || _lock->owned_by_self(), 155 "we should have taken the lock before calling this"); 156 157 // If G1SATBBufferEnqueueingThresholdPercent == 0 we could skip filtering. 158 159 // This method should only be called if there is a non-NULL buffer 160 // that is full. 161 assert(index() == 0, "pre-condition"); 162 assert(_buf != NULL, "pre-condition"); 163 164 filter(); 165 166 size_t cap = capacity(); 167 size_t percent_used = ((cap - index()) * 100) / cap; 168 bool should_enqueue = percent_used > G1SATBBufferEnqueueingThresholdPercent; 169 return should_enqueue; 170 } 171 172 void SATBMarkQueue::apply_closure_and_empty(SATBBufferClosure* cl) { 173 assert(SafepointSynchronize::is_at_safepoint(), 174 "SATB queues must only be processed at safepoints"); 175 if (_buf != NULL) { 176 cl->do_buffer(&_buf[index()], size()); 177 reset(); 178 } 179 } 180 181 #ifndef PRODUCT 182 // Helpful for debugging 183 184 static void print_satb_buffer(const char* name, 185 void** buf, 186 size_t index, 187 size_t capacity) { 188 tty->print_cr(" SATB BUFFER [%s] buf: " PTR_FORMAT " index: " SIZE_FORMAT 189 " capacity: " SIZE_FORMAT, 190 name, p2i(buf), index, capacity); 191 } 192 193 void SATBMarkQueue::print(const char* name) { 194 print_satb_buffer(name, _buf, index(), capacity()); 195 } 196 197 #endif // PRODUCT 198 199 SATBMarkQueueSet::SATBMarkQueueSet() : 200 PtrQueueSet(), 201 _shared_satb_queue(this, true /* permanent */) { } 202 203 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock, 204 int process_completed_threshold, 205 Mutex* lock) { 206 PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1); 207 _shared_satb_queue.set_lock(lock); 208 } 209 210 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) { 211 t->satb_mark_queue().handle_zero_index(); 212 } 213 214 #ifdef ASSERT 215 void SATBMarkQueueSet::dump_active_states(bool expected_active) { 216 log_error(gc, verify)("Expected SATB active state: %s", expected_active ? "ACTIVE" : "INACTIVE"); 217 log_error(gc, verify)("Actual SATB active states:"); 218 log_error(gc, verify)(" Queue set: %s", is_active() ? "ACTIVE" : "INACTIVE"); 219 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) { 220 log_error(gc, verify)(" Thread \"%s\" queue: %s", t->name(), t->satb_mark_queue().is_active() ? "ACTIVE" : "INACTIVE"); 221 } 222 log_error(gc, verify)(" Shared queue: %s", shared_satb_queue()->is_active() ? "ACTIVE" : "INACTIVE"); 223 } 224 225 void SATBMarkQueueSet::verify_active_states(bool expected_active) { 226 // Verify queue set state 227 if (is_active() != expected_active) { 228 dump_active_states(expected_active); 229 guarantee(false, "SATB queue set has an unexpected active state"); 230 } 231 232 // Verify thread queue states 233 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) { 234 if (t->satb_mark_queue().is_active() != expected_active) { 235 dump_active_states(expected_active); 236 guarantee(false, "Thread SATB queue has an unexpected active state"); 237 } 238 } 239 240 // Verify shared queue state 241 if (shared_satb_queue()->is_active() != expected_active) { 242 dump_active_states(expected_active); 243 guarantee(false, "Shared SATB queue has an unexpected active state"); 244 } 245 } 246 #endif // ASSERT 247 248 void SATBMarkQueueSet::set_active_all_threads(bool active, bool expected_active) { 249 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 250 #ifdef ASSERT 251 verify_active_states(expected_active); 252 #endif // ASSERT 253 _all_active = active; 254 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) { 255 t->satb_mark_queue().set_active(active); 256 } 257 shared_satb_queue()->set_active(active); 258 } 259 260 void SATBMarkQueueSet::filter_thread_buffers() { 261 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) { 262 t->satb_mark_queue().filter(); 263 } 264 shared_satb_queue()->filter(); 265 } 266 267 bool SATBMarkQueueSet::apply_closure_to_completed_buffer(SATBBufferClosure* cl) { 268 BufferNode* nd = NULL; 269 { 270 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 271 if (_completed_buffers_head != NULL) { 272 nd = _completed_buffers_head; 273 _completed_buffers_head = nd->next(); 274 if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL; 275 _n_completed_buffers--; 276 if (_n_completed_buffers == 0) _process_completed = false; 277 } 278 } 279 if (nd != NULL) { 280 void **buf = BufferNode::make_buffer_from_node(nd); 281 size_t index = nd->index(); 282 size_t size = buffer_size(); 283 assert(index <= size, "invariant"); 284 cl->do_buffer(buf + index, size - index); 285 deallocate_buffer(nd); 286 return true; 287 } else { 288 return false; 289 } 290 } 291 292 #ifndef PRODUCT 293 // Helpful for debugging 294 295 #define SATB_PRINTER_BUFFER_SIZE 256 296 297 void SATBMarkQueueSet::print_all(const char* msg) { 298 char buffer[SATB_PRINTER_BUFFER_SIZE]; 299 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 300 301 tty->cr(); 302 tty->print_cr("SATB BUFFERS [%s]", msg); 303 304 BufferNode* nd = _completed_buffers_head; 305 int i = 0; 306 while (nd != NULL) { 307 void** buf = BufferNode::make_buffer_from_node(nd); 308 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Enqueued: %d", i); 309 print_satb_buffer(buffer, buf, nd->index(), buffer_size()); 310 nd = nd->next(); 311 i += 1; 312 } 313 314 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) { 315 jio_snprintf(buffer, SATB_PRINTER_BUFFER_SIZE, "Thread: %s", t->name()); 316 t->satb_mark_queue().print(buffer); 317 } 318 319 shared_satb_queue()->print("Shared"); 320 321 tty->cr(); 322 } 323 #endif // PRODUCT 324 325 void SATBMarkQueueSet::abandon_partial_marking() { 326 BufferNode* buffers_to_delete = NULL; 327 { 328 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag); 329 while (_completed_buffers_head != NULL) { 330 BufferNode* nd = _completed_buffers_head; 331 _completed_buffers_head = nd->next(); 332 nd->set_next(buffers_to_delete); 333 buffers_to_delete = nd; 334 } 335 _completed_buffers_tail = NULL; 336 _n_completed_buffers = 0; 337 DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked()); 338 } 339 while (buffers_to_delete != NULL) { 340 BufferNode* nd = buffers_to_delete; 341 buffers_to_delete = nd->next(); 342 deallocate_buffer(nd); 343 } 344 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint."); 345 // So we can safely manipulate these queues. 346 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *t = jtiwh.next(); ) { 347 t->satb_mark_queue().reset(); 348 } 349 shared_satb_queue()->reset(); 350 }