1 /* 2 * Copyright (c) 2014, 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/g1OopClosures.inline.hpp" 28 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp" 29 #include "oops/oop.inline.hpp" 30 #include "oops/oop.pcgc.inline.hpp" 31 #include "runtime/prefetch.inline.hpp" 32 33 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num, ReferenceProcessor* rp) 34 : _g1h(g1h), 35 _refs(g1h->task_queue(queue_num)), 36 _dcq(&g1h->dirty_card_queue_set()), 37 _ct_bs(g1h->g1_barrier_set()), 38 _g1_rem(g1h->g1_rem_set()), 39 _hash_seed(17), _queue_num(queue_num), 40 _term_attempts(0), 41 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)), 42 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)), 43 _age_table(false), _scanner(g1h, rp), 44 _strong_roots_time(0), _term_time(0), 45 _alloc_buffer_waste(0), _undo_waste(0) { 46 _scanner.set_par_scan_thread_state(this); 47 // we allocate G1YoungSurvRateNumRegions plus one entries, since 48 // we "sacrifice" entry 0 to keep track of surviving bytes for 49 // non-young regions (where the age is -1) 50 // We also add a few elements at the beginning and at the end in 51 // an attempt to eliminate cache contention 52 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length(); 53 uint array_length = PADDING_ELEM_NUM + 54 real_length + 55 PADDING_ELEM_NUM; 56 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC); 57 if (_surviving_young_words_base == NULL) 58 vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR, 59 "Not enough space for young surv histo."); 60 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM; 61 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t)); 62 63 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer; 64 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer; 65 66 _start = os::elapsedTime(); 67 } 68 69 G1ParScanThreadState::~G1ParScanThreadState() { 70 retire_alloc_buffers(); 71 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base, mtGC); 72 } 73 74 void 75 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st) 76 { 77 st->print_raw_cr("GC Termination Stats"); 78 st->print_raw_cr(" elapsed --strong roots-- -------termination-------" 79 " ------waste (KiB)------"); 80 st->print_raw_cr("thr ms ms % ms % attempts" 81 " total alloc undo"); 82 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------" 83 " ------- ------- -------"); 84 } 85 86 void 87 G1ParScanThreadState::print_termination_stats(int i, 88 outputStream* const st) const 89 { 90 const double elapsed_ms = elapsed_time() * 1000.0; 91 const double s_roots_ms = strong_roots_time() * 1000.0; 92 const double term_ms = term_time() * 1000.0; 93 st->print_cr("%3d %9.2f %9.2f %6.2f " 94 "%9.2f %6.2f " SIZE_FORMAT_W(8) " " 95 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7), 96 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms, 97 term_ms, term_ms * 100 / elapsed_ms, term_attempts(), 98 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K, 99 alloc_buffer_waste() * HeapWordSize / K, 100 undo_waste() * HeapWordSize / K); 101 } 102 103 #ifdef ASSERT 104 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const { 105 assert(ref != NULL, "invariant"); 106 assert(UseCompressedOops, "sanity"); 107 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, p2i(ref))); 108 oop p = oopDesc::load_decode_heap_oop(ref); 109 assert(_g1h->is_in_g1_reserved(p), 110 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p))); 111 return true; 112 } 113 114 bool G1ParScanThreadState::verify_ref(oop* ref) const { 115 assert(ref != NULL, "invariant"); 116 if (has_partial_array_mask(ref)) { 117 // Must be in the collection set--it's already been copied. 118 oop p = clear_partial_array_mask(ref); 119 assert(_g1h->obj_in_cs(p), 120 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p))); 121 } else { 122 oop p = oopDesc::load_decode_heap_oop(ref); 123 assert(_g1h->is_in_g1_reserved(p), 124 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p))); 125 } 126 return true; 127 } 128 129 bool G1ParScanThreadState::verify_task(StarTask ref) const { 130 if (ref.is_narrow()) { 131 return verify_ref((narrowOop*) ref); 132 } else { 133 return verify_ref((oop*) ref); 134 } 135 } 136 #endif // ASSERT 137 138 void G1ParScanThreadState::trim_queue() { 139 assert(_evac_failure_cl != NULL, "not set"); 140 141 StarTask ref; 142 do { 143 // Drain the overflow stack first, so other threads can steal. 144 while (_refs->pop_overflow(ref)) { 145 dispatch_reference(ref); 146 } 147 148 while (_refs->pop_local(ref)) { 149 dispatch_reference(ref); 150 } 151 } while (!_refs->is_empty()); 152 } 153 154 oop G1ParScanThreadState::copy_to_survivor_space(oop const old) { 155 size_t word_sz = old->size(); 156 HeapRegion* from_region = _g1h->heap_region_containing_raw(old); 157 // +1 to make the -1 indexes valid... 158 int young_index = from_region->young_index_in_cset()+1; 159 assert( (from_region->is_young() && young_index > 0) || 160 (!from_region->is_young() && young_index == 0), "invariant" ); 161 G1CollectorPolicy* g1p = _g1h->g1_policy(); 162 markOop m = old->mark(); 163 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age() 164 : m->age(); 165 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age, 166 word_sz); 167 HeapWord* obj_ptr = allocate(alloc_purpose, word_sz); 168 #ifndef PRODUCT 169 // Should this evacuation fail? 170 if (_g1h->evacuation_should_fail()) { 171 if (obj_ptr != NULL) { 172 undo_allocation(alloc_purpose, obj_ptr, word_sz); 173 obj_ptr = NULL; 174 } 175 } 176 #endif // !PRODUCT 177 178 if (obj_ptr == NULL) { 179 // The allocation failure may have been caused by attempted allocation of a 180 // humongous object. Detect this and process appropriately. 181 if (_g1h->isHumongous(word_sz)) { 182 _g1h->set_humongous_is_live(old); 183 return NULL; 184 } 185 // This will either forward-to-self, or detect that someone else has 186 // installed a forwarding pointer. 187 return _g1h->handle_evacuation_failure_par(this, old); 188 } 189 190 oop obj = oop(obj_ptr); 191 192 // We're going to allocate linearly, so might as well prefetch ahead. 193 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes); 194 195 oop forward_ptr = old->forward_to_atomic(obj); 196 if (forward_ptr == NULL) { 197 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz); 198 199 // alloc_purpose is just a hint to allocate() above, recheck the type of region 200 // we actually allocated from and update alloc_purpose accordingly 201 HeapRegion* to_region = _g1h->heap_region_containing_raw(obj_ptr); 202 alloc_purpose = to_region->is_young() ? GCAllocForSurvived : GCAllocForTenured; 203 204 if (g1p->track_object_age(alloc_purpose)) { 205 // We could simply do obj->incr_age(). However, this causes a 206 // performance issue. obj->incr_age() will first check whether 207 // the object has a displaced mark by checking its mark word; 208 // getting the mark word from the new location of the object 209 // stalls. So, given that we already have the mark word and we 210 // are about to install it anyway, it's better to increase the 211 // age on the mark word, when the object does not have a 212 // displaced mark word. We're not expecting many objects to have 213 // a displaced marked word, so that case is not optimized 214 // further (it could be...) and we simply call obj->incr_age(). 215 216 if (m->has_displaced_mark_helper()) { 217 // in this case, we have to install the mark word first, 218 // otherwise obj looks to be forwarded (the old mark word, 219 // which contains the forward pointer, was copied) 220 obj->set_mark(m); 221 obj->incr_age(); 222 } else { 223 m = m->incr_age(); 224 obj->set_mark(m); 225 } 226 age_table()->add(obj, word_sz); 227 } else { 228 obj->set_mark(m); 229 } 230 231 if (G1StringDedup::is_enabled()) { 232 G1StringDedup::enqueue_from_evacuation(from_region->is_young(), 233 to_region->is_young(), 234 queue_num(), 235 obj); 236 } 237 238 size_t* surv_young_words = surviving_young_words(); 239 surv_young_words[young_index] += word_sz; 240 241 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) { 242 // We keep track of the next start index in the length field of 243 // the to-space object. The actual length can be found in the 244 // length field of the from-space object. 245 arrayOop(obj)->set_length(0); 246 oop* old_p = set_partial_array_mask(old); 247 push_on_queue(old_p); 248 } else { 249 // No point in using the slower heap_region_containing() method, 250 // given that we know obj is in the heap. 251 _scanner.set_region(_g1h->heap_region_containing_raw(obj)); 252 obj->oop_iterate_backwards(&_scanner); 253 } 254 } else { 255 undo_allocation(alloc_purpose, obj_ptr, word_sz); 256 obj = forward_ptr; 257 } 258 return obj; 259 } 260 261 HeapWord* G1ParScanThreadState::allocate_slow(GCAllocPurpose purpose, size_t word_sz) { 262 // We may have reached the slow path because we tried to allocate memory for a 263 // humongous object. This just indicates that that humongous object is live 264 // though. 265 if (_g1h->isHumongous(word_sz)) { 266 return NULL; 267 } 268 HeapWord* obj = NULL; 269 size_t gclab_word_size = _g1h->desired_plab_sz(purpose); 270 if (word_sz * 100 < gclab_word_size * ParallelGCBufferWastePct) { 271 G1ParGCAllocBuffer* alloc_buf = alloc_buffer(purpose); 272 add_to_alloc_buffer_waste(alloc_buf->words_remaining()); 273 alloc_buf->retire(false /* end_of_gc */, false /* retain */); 274 275 HeapWord* buf = _g1h->par_allocate_during_gc(purpose, gclab_word_size); 276 if (buf == NULL) { 277 return NULL; // Let caller handle allocation failure. 278 } 279 // Otherwise. 280 alloc_buf->set_word_size(gclab_word_size); 281 alloc_buf->set_buf(buf); 282 283 obj = alloc_buf->allocate(word_sz); 284 assert(obj != NULL, "buffer was definitely big enough..."); 285 } else { 286 obj = _g1h->par_allocate_during_gc(purpose, word_sz); 287 } 288 return obj; 289 } 290 291 void G1ParScanThreadState::undo_allocation(GCAllocPurpose purpose, HeapWord* obj, size_t word_sz) { 292 if (alloc_buffer(purpose)->contains(obj)) { 293 assert(alloc_buffer(purpose)->contains(obj + word_sz - 1), 294 "should contain whole object"); 295 alloc_buffer(purpose)->undo_allocation(obj, word_sz); 296 } else { 297 CollectedHeap::fill_with_object(obj, word_sz); 298 add_to_undo_waste(word_sz); 299 } 300 } 301 302 HeapWord* G1ParScanThreadState::allocate(GCAllocPurpose purpose, size_t word_sz) { 303 HeapWord* obj = alloc_buffer(purpose)->allocate(word_sz); 304 if (obj != NULL) { 305 return obj; 306 } 307 return allocate_slow(purpose, word_sz); 308 } 309 310 void G1ParScanThreadState::retire_alloc_buffers() { 311 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) { 312 size_t waste = _alloc_buffers[ap]->words_remaining(); 313 add_to_alloc_buffer_waste(waste); 314 _alloc_buffers[ap]->flush_stats_and_retire(_g1h->stats_for_purpose((GCAllocPurpose)ap), 315 true /* end_of_gc */, 316 false /* retain */); 317 } 318 }