1 /* 2 * Copyright (c) 2001, 2010, 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 "incls/_precompiled.incl" 26 #include "incls/_concurrentG1Refine.cpp.incl" 27 28 // Possible sizes for the card counts cache: odd primes that roughly double in size. 29 // (See jvmtiTagMap.cpp). 30 int ConcurrentG1Refine::_cc_cache_sizes[] = { 31 16381, 32771, 76831, 150001, 307261, 32 614563, 1228891, 2457733, 4915219, 9830479, 33 19660831, 39321619, 78643219, 157286461, -1 34 }; 35 36 ConcurrentG1Refine::ConcurrentG1Refine() : 37 _card_counts(NULL), _card_epochs(NULL), 38 _n_card_counts(0), _max_n_card_counts(0), 39 _cache_size_index(0), _expand_card_counts(false), 40 _hot_cache(NULL), 41 _def_use_cache(false), _use_cache(false), 42 _n_periods(0), 43 _threads(NULL), _n_threads(0) 44 { 45 46 // Ergomonically select initial concurrent refinement parameters 47 if (FLAG_IS_DEFAULT(G1ConcRefinementGreenZone)) { 48 FLAG_SET_DEFAULT(G1ConcRefinementGreenZone, MAX2<int>(ParallelGCThreads, 1)); 49 } 50 set_green_zone(G1ConcRefinementGreenZone); 51 52 if (FLAG_IS_DEFAULT(G1ConcRefinementYellowZone)) { 53 FLAG_SET_DEFAULT(G1ConcRefinementYellowZone, green_zone() * 3); 54 } 55 set_yellow_zone(MAX2<int>(G1ConcRefinementYellowZone, green_zone())); 56 57 if (FLAG_IS_DEFAULT(G1ConcRefinementRedZone)) { 58 FLAG_SET_DEFAULT(G1ConcRefinementRedZone, yellow_zone() * 2); 59 } 60 set_red_zone(MAX2<int>(G1ConcRefinementRedZone, yellow_zone())); 61 _n_worker_threads = thread_num(); 62 // We need one extra thread to do the young gen rset size sampling. 63 _n_threads = _n_worker_threads + 1; 64 reset_threshold_step(); 65 66 _threads = NEW_C_HEAP_ARRAY(ConcurrentG1RefineThread*, _n_threads); 67 int worker_id_offset = (int)DirtyCardQueueSet::num_par_ids(); 68 ConcurrentG1RefineThread *next = NULL; 69 for (int i = _n_threads - 1; i >= 0; i--) { 70 ConcurrentG1RefineThread* t = new ConcurrentG1RefineThread(this, next, worker_id_offset, i); 71 assert(t != NULL, "Conc refine should have been created"); 72 assert(t->cg1r() == this, "Conc refine thread should refer to this"); 73 _threads[i] = t; 74 next = t; 75 } 76 } 77 78 void ConcurrentG1Refine::reset_threshold_step() { 79 if (FLAG_IS_DEFAULT(G1ConcRefinementThresholdStep)) { 80 _thread_threshold_step = (yellow_zone() - green_zone()) / (worker_thread_num() + 1); 81 } else { 82 _thread_threshold_step = G1ConcRefinementThresholdStep; 83 } 84 } 85 86 int ConcurrentG1Refine::thread_num() { 87 return MAX2<int>((G1ConcRefinementThreads > 0) ? G1ConcRefinementThreads : ParallelGCThreads, 1); 88 } 89 90 void ConcurrentG1Refine::init() { 91 if (G1ConcRSLogCacheSize > 0) { 92 _g1h = G1CollectedHeap::heap(); 93 _max_n_card_counts = 94 (unsigned) (_g1h->g1_reserved_obj_bytes() >> CardTableModRefBS::card_shift); 95 96 size_t max_card_num = ((size_t)1 << (sizeof(unsigned)*BitsPerByte-1)) - 1; 97 guarantee(_max_n_card_counts < max_card_num, "card_num representation"); 98 99 int desired = _max_n_card_counts / InitialCacheFraction; 100 for (_cache_size_index = 0; 101 _cc_cache_sizes[_cache_size_index] >= 0; _cache_size_index++) { 102 if (_cc_cache_sizes[_cache_size_index] >= desired) break; 103 } 104 _cache_size_index = MAX2(0, (_cache_size_index - 1)); 105 106 int initial_size = _cc_cache_sizes[_cache_size_index]; 107 if (initial_size < 0) initial_size = _max_n_card_counts; 108 109 // Make sure we don't go bigger than we will ever need 110 _n_card_counts = MIN2((unsigned) initial_size, _max_n_card_counts); 111 112 _card_counts = NEW_C_HEAP_ARRAY(CardCountCacheEntry, _n_card_counts); 113 _card_epochs = NEW_C_HEAP_ARRAY(CardEpochCacheEntry, _n_card_counts); 114 115 Copy::fill_to_bytes(&_card_counts[0], 116 _n_card_counts * sizeof(CardCountCacheEntry)); 117 Copy::fill_to_bytes(&_card_epochs[0], _n_card_counts * sizeof(CardEpochCacheEntry)); 118 119 ModRefBarrierSet* bs = _g1h->mr_bs(); 120 guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition"); 121 _ct_bs = (CardTableModRefBS*)bs; 122 _ct_bot = _ct_bs->byte_for_const(_g1h->reserved_region().start()); 123 124 _def_use_cache = true; 125 _use_cache = true; 126 _hot_cache_size = (1 << G1ConcRSLogCacheSize); 127 _hot_cache = NEW_C_HEAP_ARRAY(jbyte*, _hot_cache_size); 128 _n_hot = 0; 129 _hot_cache_idx = 0; 130 131 // For refining the cards in the hot cache in parallel 132 int n_workers = (ParallelGCThreads > 0 ? 133 _g1h->workers()->total_workers() : 1); 134 _hot_cache_par_chunk_size = MAX2(1, _hot_cache_size / n_workers); 135 _hot_cache_par_claimed_idx = 0; 136 } 137 } 138 139 void ConcurrentG1Refine::stop() { 140 if (_threads != NULL) { 141 for (int i = 0; i < _n_threads; i++) { 142 _threads[i]->stop(); 143 } 144 } 145 } 146 147 void ConcurrentG1Refine::reinitialize_threads() { 148 reset_threshold_step(); 149 if (_threads != NULL) { 150 for (int i = 0; i < _n_threads; i++) { 151 _threads[i]->initialize(); 152 } 153 } 154 } 155 156 ConcurrentG1Refine::~ConcurrentG1Refine() { 157 if (G1ConcRSLogCacheSize > 0) { 158 assert(_card_counts != NULL, "Logic"); 159 FREE_C_HEAP_ARRAY(CardCountCacheEntry, _card_counts); 160 assert(_card_epochs != NULL, "Logic"); 161 FREE_C_HEAP_ARRAY(CardEpochCacheEntry, _card_epochs); 162 assert(_hot_cache != NULL, "Logic"); 163 FREE_C_HEAP_ARRAY(jbyte*, _hot_cache); 164 } 165 if (_threads != NULL) { 166 for (int i = 0; i < _n_threads; i++) { 167 delete _threads[i]; 168 } 169 FREE_C_HEAP_ARRAY(ConcurrentG1RefineThread*, _threads); 170 } 171 } 172 173 void ConcurrentG1Refine::threads_do(ThreadClosure *tc) { 174 if (_threads != NULL) { 175 for (int i = 0; i < _n_threads; i++) { 176 tc->do_thread(_threads[i]); 177 } 178 } 179 } 180 181 bool ConcurrentG1Refine::is_young_card(jbyte* card_ptr) { 182 HeapWord* start = _ct_bs->addr_for(card_ptr); 183 HeapRegion* r = _g1h->heap_region_containing(start); 184 if (r != NULL && r->is_young()) { 185 return true; 186 } 187 // This card is not associated with a heap region 188 // so can't be young. 189 return false; 190 } 191 192 jbyte* ConcurrentG1Refine::add_card_count(jbyte* card_ptr, int* count, bool* defer) { 193 unsigned new_card_num = ptr_2_card_num(card_ptr); 194 unsigned bucket = hash(new_card_num); 195 assert(0 <= bucket && bucket < _n_card_counts, "Bounds"); 196 197 CardCountCacheEntry* count_ptr = &_card_counts[bucket]; 198 CardEpochCacheEntry* epoch_ptr = &_card_epochs[bucket]; 199 200 // We have to construct a new entry if we haven't updated the counts 201 // during the current period, or if the count was updated for a 202 // different card number. 203 unsigned int new_epoch = (unsigned int) _n_periods; 204 julong new_epoch_entry = make_epoch_entry(new_card_num, new_epoch); 205 206 while (true) { 207 // Fetch the previous epoch value 208 julong prev_epoch_entry = epoch_ptr->_value; 209 julong cas_res; 210 211 if (extract_epoch(prev_epoch_entry) != new_epoch) { 212 // This entry has not yet been updated during this period. 213 // Note: we update the epoch value atomically to ensure 214 // that there is only one winner that updates the cached 215 // card_ptr value even though all the refine threads share 216 // the same epoch value. 217 218 cas_res = (julong) Atomic::cmpxchg((jlong) new_epoch_entry, 219 (volatile jlong*)&epoch_ptr->_value, 220 (jlong) prev_epoch_entry); 221 222 if (cas_res == prev_epoch_entry) { 223 // We have successfully won the race to update the 224 // epoch and card_num value. Make it look like the 225 // count and eviction count were previously cleared. 226 count_ptr->_count = 1; 227 count_ptr->_evict_count = 0; 228 *count = 0; 229 // We can defer the processing of card_ptr 230 *defer = true; 231 return card_ptr; 232 } 233 // We did not win the race to update the epoch field, so some other 234 // thread must have done it. The value that gets returned by CAS 235 // should be the new epoch value. 236 assert(extract_epoch(cas_res) == new_epoch, "unexpected epoch"); 237 // We could 'continue' here or just re-read the previous epoch value 238 prev_epoch_entry = epoch_ptr->_value; 239 } 240 241 // The epoch entry for card_ptr has been updated during this period. 242 unsigned old_card_num = extract_card_num(prev_epoch_entry); 243 244 // The card count that will be returned to caller 245 *count = count_ptr->_count; 246 247 // Are we updating the count for the same card? 248 if (new_card_num == old_card_num) { 249 // Same card - just update the count. We could have more than one 250 // thread racing to update count for the current card. It should be 251 // OK not to use a CAS as the only penalty should be some missed 252 // increments of the count which delays identifying the card as "hot". 253 254 if (*count < max_jubyte) count_ptr->_count++; 255 // We can defer the processing of card_ptr 256 *defer = true; 257 return card_ptr; 258 } 259 260 // Different card - evict old card info 261 if (count_ptr->_evict_count < max_jubyte) count_ptr->_evict_count++; 262 if (count_ptr->_evict_count > G1CardCountCacheExpandThreshold) { 263 // Trigger a resize the next time we clear 264 _expand_card_counts = true; 265 } 266 267 cas_res = (julong) Atomic::cmpxchg((jlong) new_epoch_entry, 268 (volatile jlong*)&epoch_ptr->_value, 269 (jlong) prev_epoch_entry); 270 271 if (cas_res == prev_epoch_entry) { 272 // We successfully updated the card num value in the epoch entry 273 count_ptr->_count = 0; // initialize counter for new card num 274 jbyte* old_card_ptr = card_num_2_ptr(old_card_num); 275 276 // Even though the region containg the card at old_card_num was not 277 // in the young list when old_card_num was recorded in the epoch 278 // cache it could have been added to the free list and subsequently 279 // added to the young list in the intervening time. See CR 6817995. 280 // We do not deal with this case here - it will be handled in 281 // HeapRegion::oops_on_card_seq_iterate_careful after it has been 282 // determined that the region containing the card has been allocated 283 // to, and it's safe to check the young type of the region. 284 285 // We do not want to defer processing of card_ptr in this case 286 // (we need to refine old_card_ptr and card_ptr) 287 *defer = false; 288 return old_card_ptr; 289 } 290 // Someone else beat us - try again. 291 } 292 } 293 294 jbyte* ConcurrentG1Refine::cache_insert(jbyte* card_ptr, bool* defer) { 295 int count; 296 jbyte* cached_ptr = add_card_count(card_ptr, &count, defer); 297 assert(cached_ptr != NULL, "bad cached card ptr"); 298 299 // We've just inserted a card pointer into the card count cache 300 // and got back the card that we just inserted or (evicted) the 301 // previous contents of that count slot. 302 303 // The card we got back could be in a young region. When the 304 // returned card (if evicted) was originally inserted, we had 305 // determined that its containing region was not young. However 306 // it is possible for the region to be freed during a cleanup 307 // pause, then reallocated and tagged as young which will result 308 // in the returned card residing in a young region. 309 // 310 // We do not deal with this case here - the change from non-young 311 // to young could be observed at any time - it will be handled in 312 // HeapRegion::oops_on_card_seq_iterate_careful after it has been 313 // determined that the region containing the card has been allocated 314 // to. 315 316 // The card pointer we obtained from card count cache is not hot 317 // so do not store it in the cache; return it for immediate 318 // refining. 319 if (count < G1ConcRSHotCardLimit) { 320 return cached_ptr; 321 } 322 323 // Otherwise, the pointer we got from the _card_counts cache is hot. 324 jbyte* res = NULL; 325 MutexLockerEx x(HotCardCache_lock, Mutex::_no_safepoint_check_flag); 326 if (_n_hot == _hot_cache_size) { 327 res = _hot_cache[_hot_cache_idx]; 328 _n_hot--; 329 } 330 // Now _n_hot < _hot_cache_size, and we can insert at _hot_cache_idx. 331 _hot_cache[_hot_cache_idx] = cached_ptr; 332 _hot_cache_idx++; 333 if (_hot_cache_idx == _hot_cache_size) _hot_cache_idx = 0; 334 _n_hot++; 335 336 // The card obtained from the hot card cache could be in a young 337 // region. See above on how this can happen. 338 339 return res; 340 } 341 342 void ConcurrentG1Refine::clean_up_cache(int worker_i, 343 G1RemSet* g1rs, 344 DirtyCardQueue* into_cset_dcq) { 345 assert(!use_cache(), "cache should be disabled"); 346 int start_idx; 347 348 while ((start_idx = _hot_cache_par_claimed_idx) < _n_hot) { // read once 349 int end_idx = start_idx + _hot_cache_par_chunk_size; 350 351 if (start_idx == 352 Atomic::cmpxchg(end_idx, &_hot_cache_par_claimed_idx, start_idx)) { 353 // The current worker has successfully claimed the chunk [start_idx..end_idx) 354 end_idx = MIN2(end_idx, _n_hot); 355 for (int i = start_idx; i < end_idx; i++) { 356 jbyte* entry = _hot_cache[i]; 357 if (entry != NULL) { 358 if (g1rs->concurrentRefineOneCard(entry, worker_i, true)) { 359 // 'entry' contains references that point into the current 360 // collection set. We need to record 'entry' in the DCQS 361 // that's used for that purpose. 362 // 363 // The only time we care about recording cards that contain 364 // references that point into the collection set is during 365 // RSet updating while within an evacuation pause. 366 // In this case worker_i should be the id of a GC worker thread 367 assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause"); 368 assert(worker_i < (int) DirtyCardQueueSet::num_par_ids(), "incorrect worker id"); 369 into_cset_dcq->enqueue(entry); 370 } 371 } 372 } 373 } 374 } 375 } 376 377 void ConcurrentG1Refine::expand_card_count_cache() { 378 if (_n_card_counts < _max_n_card_counts) { 379 int new_idx = _cache_size_index+1; 380 int new_size = _cc_cache_sizes[new_idx]; 381 if (new_size < 0) new_size = _max_n_card_counts; 382 383 // Make sure we don't go bigger than we will ever need 384 new_size = MIN2((unsigned) new_size, _max_n_card_counts); 385 386 // Expand the card count and card epoch tables 387 if (new_size > (int)_n_card_counts) { 388 // We can just free and allocate a new array as we're 389 // not interested in preserving the contents 390 assert(_card_counts != NULL, "Logic!"); 391 assert(_card_epochs != NULL, "Logic!"); 392 FREE_C_HEAP_ARRAY(CardCountCacheEntry, _card_counts); 393 FREE_C_HEAP_ARRAY(CardEpochCacheEntry, _card_epochs); 394 _n_card_counts = new_size; 395 _card_counts = NEW_C_HEAP_ARRAY(CardCountCacheEntry, _n_card_counts); 396 _card_epochs = NEW_C_HEAP_ARRAY(CardEpochCacheEntry, _n_card_counts); 397 _cache_size_index = new_idx; 398 } 399 } 400 } 401 402 void ConcurrentG1Refine::clear_and_record_card_counts() { 403 if (G1ConcRSLogCacheSize == 0) return; 404 405 #ifndef PRODUCT 406 double start = os::elapsedTime(); 407 #endif 408 409 if (_expand_card_counts) { 410 expand_card_count_cache(); 411 _expand_card_counts = false; 412 // Only need to clear the epochs. 413 Copy::fill_to_bytes(&_card_epochs[0], _n_card_counts * sizeof(CardEpochCacheEntry)); 414 } 415 416 int this_epoch = (int) _n_periods; 417 assert((this_epoch+1) <= max_jint, "to many periods"); 418 // Update epoch 419 _n_periods++; 420 421 #ifndef PRODUCT 422 double elapsed = os::elapsedTime() - start; 423 _g1h->g1_policy()->record_cc_clear_time(elapsed * 1000.0); 424 #endif 425 } 426 427 void ConcurrentG1Refine::print_worker_threads_on(outputStream* st) const { 428 for (int i = 0; i < _n_threads; ++i) { 429 _threads[i]->print_on(st); 430 st->cr(); 431 } 432 }