Mercurial > hg > graal-compiler
annotate src/share/vm/gc_implementation/parNew/parNewGeneration.cpp @ 1836:894b1d7c7e01
6423256: GC stacks should use a better data structure
6942771: SEGV in ParScanThreadState::take_from_overflow_stack
Reviewed-by: apetrusenko, ysr, pbk
| author | jcoomes |
|---|---|
| date | Tue, 28 Sep 2010 15:56:15 -0700 |
| parents | 8b10f48633dc |
| children | a7214d79fcf1 |
| rev | line source |
|---|---|
| 0 | 1 /* |
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2 * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved. |
| 0 | 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 * | |
|
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
| 0 | 22 * |
| 23 */ | |
| 24 | |
| 25 # include "incls/_precompiled.incl" | |
| 26 # include "incls/_parNewGeneration.cpp.incl" | |
| 27 | |
| 28 #ifdef _MSC_VER | |
| 29 #pragma warning( push ) | |
| 30 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list | |
| 31 #endif | |
| 32 ParScanThreadState::ParScanThreadState(Space* to_space_, | |
| 33 ParNewGeneration* gen_, | |
| 34 Generation* old_gen_, | |
| 35 int thread_num_, | |
| 36 ObjToScanQueueSet* work_queue_set_, | |
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37 Stack<oop>* overflow_stacks_, |
| 0 | 38 size_t desired_plab_sz_, |
| 39 ParallelTaskTerminator& term_) : | |
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40 _to_space(to_space_), _old_gen(old_gen_), _young_gen(gen_), _thread_num(thread_num_), |
| 0 | 41 _work_queue(work_queue_set_->queue(thread_num_)), _to_space_full(false), |
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42 _overflow_stack(overflow_stacks_ ? overflow_stacks_ + thread_num_ : NULL), |
| 0 | 43 _ageTable(false), // false ==> not the global age table, no perf data. |
| 44 _to_space_alloc_buffer(desired_plab_sz_), | |
| 45 _to_space_closure(gen_, this), _old_gen_closure(gen_, this), | |
| 46 _to_space_root_closure(gen_, this), _old_gen_root_closure(gen_, this), | |
| 47 _older_gen_closure(gen_, this), | |
| 48 _evacuate_followers(this, &_to_space_closure, &_old_gen_closure, | |
| 49 &_to_space_root_closure, gen_, &_old_gen_root_closure, | |
| 50 work_queue_set_, &term_), | |
| 51 _is_alive_closure(gen_), _scan_weak_ref_closure(gen_, this), | |
| 52 _keep_alive_closure(&_scan_weak_ref_closure), | |
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53 _promotion_failure_size(0), |
| 0 | 54 _strong_roots_time(0.0), _term_time(0.0) |
| 55 { | |
| 1710 | 56 #if TASKQUEUE_STATS |
| 57 _term_attempts = 0; | |
| 58 _overflow_refills = 0; | |
| 59 _overflow_refill_objs = 0; | |
| 60 #endif // TASKQUEUE_STATS | |
| 61 | |
| 0 | 62 _survivor_chunk_array = |
| 63 (ChunkArray*) old_gen()->get_data_recorder(thread_num()); | |
| 64 _hash_seed = 17; // Might want to take time-based random value. | |
| 65 _start = os::elapsedTime(); | |
| 66 _old_gen_closure.set_generation(old_gen_); | |
| 67 _old_gen_root_closure.set_generation(old_gen_); | |
| 68 } | |
| 69 #ifdef _MSC_VER | |
| 70 #pragma warning( pop ) | |
| 71 #endif | |
| 72 | |
| 73 void ParScanThreadState::record_survivor_plab(HeapWord* plab_start, | |
| 74 size_t plab_word_size) { | |
| 75 ChunkArray* sca = survivor_chunk_array(); | |
| 76 if (sca != NULL) { | |
| 77 // A non-null SCA implies that we want the PLAB data recorded. | |
| 78 sca->record_sample(plab_start, plab_word_size); | |
| 79 } | |
| 80 } | |
| 81 | |
| 82 bool ParScanThreadState::should_be_partially_scanned(oop new_obj, oop old_obj) const { | |
| 83 return new_obj->is_objArray() && | |
| 84 arrayOop(new_obj)->length() > ParGCArrayScanChunk && | |
| 85 new_obj != old_obj; | |
| 86 } | |
| 87 | |
| 88 void ParScanThreadState::scan_partial_array_and_push_remainder(oop old) { | |
| 89 assert(old->is_objArray(), "must be obj array"); | |
| 90 assert(old->is_forwarded(), "must be forwarded"); | |
| 91 assert(Universe::heap()->is_in_reserved(old), "must be in heap."); | |
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92 assert(!old_gen()->is_in(old), "must be in young generation."); |
| 0 | 93 |
| 94 objArrayOop obj = objArrayOop(old->forwardee()); | |
| 95 // Process ParGCArrayScanChunk elements now | |
| 96 // and push the remainder back onto queue | |
| 97 int start = arrayOop(old)->length(); | |
| 98 int end = obj->length(); | |
| 99 int remainder = end - start; | |
| 100 assert(start <= end, "just checking"); | |
| 101 if (remainder > 2 * ParGCArrayScanChunk) { | |
| 102 // Test above combines last partial chunk with a full chunk | |
| 103 end = start + ParGCArrayScanChunk; | |
| 104 arrayOop(old)->set_length(end); | |
| 105 // Push remainder. | |
| 106 bool ok = work_queue()->push(old); | |
| 107 assert(ok, "just popped, push must be okay"); | |
| 108 } else { | |
| 109 // Restore length so that it can be used if there | |
| 110 // is a promotion failure and forwarding pointers | |
| 111 // must be removed. | |
| 112 arrayOop(old)->set_length(end); | |
| 113 } | |
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114 |
| 0 | 115 // process our set of indices (include header in first chunk) |
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116 // should make sure end is even (aligned to HeapWord in case of compressed oops) |
| 0 | 117 if ((HeapWord *)obj < young_old_boundary()) { |
| 118 // object is in to_space | |
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119 obj->oop_iterate_range(&_to_space_closure, start, end); |
| 0 | 120 } else { |
| 121 // object is in old generation | |
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122 obj->oop_iterate_range(&_old_gen_closure, start, end); |
| 0 | 123 } |
| 124 } | |
| 125 | |
| 126 | |
| 127 void ParScanThreadState::trim_queues(int max_size) { | |
| 128 ObjToScanQueue* queue = work_queue(); | |
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129 do { |
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130 while (queue->size() > (juint)max_size) { |
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131 oop obj_to_scan; |
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132 if (queue->pop_local(obj_to_scan)) { |
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133 if ((HeapWord *)obj_to_scan < young_old_boundary()) { |
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134 if (obj_to_scan->is_objArray() && |
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135 obj_to_scan->is_forwarded() && |
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136 obj_to_scan->forwardee() != obj_to_scan) { |
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137 scan_partial_array_and_push_remainder(obj_to_scan); |
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138 } else { |
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139 // object is in to_space |
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140 obj_to_scan->oop_iterate(&_to_space_closure); |
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141 } |
| 0 | 142 } else { |
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143 // object is in old generation |
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144 obj_to_scan->oop_iterate(&_old_gen_closure); |
| 0 | 145 } |
| 146 } | |
| 147 } | |
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148 // For the case of compressed oops, we have a private, non-shared |
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149 // overflow stack, so we eagerly drain it so as to more evenly |
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150 // distribute load early. Note: this may be good to do in |
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151 // general rather than delay for the final stealing phase. |
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152 // If applicable, we'll transfer a set of objects over to our |
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153 // work queue, allowing them to be stolen and draining our |
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154 // private overflow stack. |
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155 } while (ParGCTrimOverflow && young_gen()->take_from_overflow_list(this)); |
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156 } |
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157 |
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158 bool ParScanThreadState::take_from_overflow_stack() { |
| 695 | 159 assert(ParGCUseLocalOverflow, "Else should not call"); |
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160 assert(young_gen()->overflow_list() == NULL, "Error"); |
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161 ObjToScanQueue* queue = work_queue(); |
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162 Stack<oop>* const of_stack = overflow_stack(); |
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163 const size_t num_overflow_elems = of_stack->size(); |
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164 const size_t space_available = queue->max_elems() - queue->size(); |
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165 const size_t num_take_elems = MIN3(space_available / 4, |
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166 ParGCDesiredObjsFromOverflowList, |
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167 num_overflow_elems); |
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168 // Transfer the most recent num_take_elems from the overflow |
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169 // stack to our work queue. |
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170 for (size_t i = 0; i != num_take_elems; i++) { |
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171 oop cur = of_stack->pop(); |
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172 oop obj_to_push = cur->forwardee(); |
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173 assert(Universe::heap()->is_in_reserved(cur), "Should be in heap"); |
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174 assert(!old_gen()->is_in_reserved(cur), "Should be in young gen"); |
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175 assert(Universe::heap()->is_in_reserved(obj_to_push), "Should be in heap"); |
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176 if (should_be_partially_scanned(obj_to_push, cur)) { |
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177 assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned"); |
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178 obj_to_push = cur; |
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179 } |
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180 bool ok = queue->push(obj_to_push); |
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181 assert(ok, "Should have succeeded"); |
| 0 | 182 } |
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183 assert(young_gen()->overflow_list() == NULL, "Error"); |
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184 return num_take_elems > 0; // was something transferred? |
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185 } |
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186 |
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187 void ParScanThreadState::push_on_overflow_stack(oop p) { |
| 695 | 188 assert(ParGCUseLocalOverflow, "Else should not call"); |
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189 overflow_stack()->push(p); |
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190 assert(young_gen()->overflow_list() == NULL, "Error"); |
| 0 | 191 } |
| 192 | |
| 193 HeapWord* ParScanThreadState::alloc_in_to_space_slow(size_t word_sz) { | |
| 194 | |
| 195 // Otherwise, if the object is small enough, try to reallocate the | |
| 196 // buffer. | |
| 197 HeapWord* obj = NULL; | |
| 198 if (!_to_space_full) { | |
| 199 ParGCAllocBuffer* const plab = to_space_alloc_buffer(); | |
| 200 Space* const sp = to_space(); | |
| 201 if (word_sz * 100 < | |
| 202 ParallelGCBufferWastePct * plab->word_sz()) { | |
| 203 // Is small enough; abandon this buffer and start a new one. | |
| 204 plab->retire(false, false); | |
| 205 size_t buf_size = plab->word_sz(); | |
| 206 HeapWord* buf_space = sp->par_allocate(buf_size); | |
| 207 if (buf_space == NULL) { | |
| 208 const size_t min_bytes = | |
| 209 ParGCAllocBuffer::min_size() << LogHeapWordSize; | |
| 210 size_t free_bytes = sp->free(); | |
| 211 while(buf_space == NULL && free_bytes >= min_bytes) { | |
| 212 buf_size = free_bytes >> LogHeapWordSize; | |
| 213 assert(buf_size == (size_t)align_object_size(buf_size), | |
| 214 "Invariant"); | |
| 215 buf_space = sp->par_allocate(buf_size); | |
| 216 free_bytes = sp->free(); | |
| 217 } | |
| 218 } | |
| 219 if (buf_space != NULL) { | |
| 220 plab->set_word_size(buf_size); | |
| 221 plab->set_buf(buf_space); | |
| 222 record_survivor_plab(buf_space, buf_size); | |
| 223 obj = plab->allocate(word_sz); | |
| 224 // Note that we cannot compare buf_size < word_sz below | |
| 225 // because of AlignmentReserve (see ParGCAllocBuffer::allocate()). | |
| 226 assert(obj != NULL || plab->words_remaining() < word_sz, | |
| 227 "Else should have been able to allocate"); | |
| 228 // It's conceivable that we may be able to use the | |
| 229 // buffer we just grabbed for subsequent small requests | |
| 230 // even if not for this one. | |
| 231 } else { | |
| 232 // We're used up. | |
| 233 _to_space_full = true; | |
| 234 } | |
| 235 | |
| 236 } else { | |
| 237 // Too large; allocate the object individually. | |
| 238 obj = sp->par_allocate(word_sz); | |
| 239 } | |
| 240 } | |
| 241 return obj; | |
| 242 } | |
| 243 | |
| 244 | |
| 245 void ParScanThreadState::undo_alloc_in_to_space(HeapWord* obj, | |
| 246 size_t word_sz) { | |
| 247 // Is the alloc in the current alloc buffer? | |
| 248 if (to_space_alloc_buffer()->contains(obj)) { | |
| 249 assert(to_space_alloc_buffer()->contains(obj + word_sz - 1), | |
| 250 "Should contain whole object."); | |
| 251 to_space_alloc_buffer()->undo_allocation(obj, word_sz); | |
| 252 } else { | |
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253 CollectedHeap::fill_with_object(obj, word_sz); |
| 0 | 254 } |
| 255 } | |
| 256 | |
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257 void ParScanThreadState::print_and_clear_promotion_failure_size() { |
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258 if (_promotion_failure_size != 0) { |
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259 if (PrintPromotionFailure) { |
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260 gclog_or_tty->print(" (%d: promotion failure size = " SIZE_FORMAT ") ", |
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261 _thread_num, _promotion_failure_size); |
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262 } |
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263 _promotion_failure_size = 0; |
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264 } |
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265 } |
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266 |
| 0 | 267 class ParScanThreadStateSet: private ResourceArray { |
| 268 public: | |
| 269 // Initializes states for the specified number of threads; | |
| 270 ParScanThreadStateSet(int num_threads, | |
| 271 Space& to_space, | |
| 272 ParNewGeneration& gen, | |
| 273 Generation& old_gen, | |
| 274 ObjToScanQueueSet& queue_set, | |
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275 Stack<oop>* overflow_stacks_, |
| 0 | 276 size_t desired_plab_sz, |
| 277 ParallelTaskTerminator& term); | |
| 1710 | 278 |
| 279 ~ParScanThreadStateSet() { TASKQUEUE_STATS_ONLY(reset_stats()); } | |
| 280 | |
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281 inline ParScanThreadState& thread_state(int i); |
| 1710 | 282 |
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283 void reset(bool promotion_failed); |
| 0 | 284 void flush(); |
| 1710 | 285 |
| 286 #if TASKQUEUE_STATS | |
| 287 static void | |
| 288 print_termination_stats_hdr(outputStream* const st = gclog_or_tty); | |
| 289 void print_termination_stats(outputStream* const st = gclog_or_tty); | |
| 290 static void | |
| 291 print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty); | |
| 292 void print_taskqueue_stats(outputStream* const st = gclog_or_tty); | |
| 293 void reset_stats(); | |
| 294 #endif // TASKQUEUE_STATS | |
| 295 | |
| 0 | 296 private: |
| 297 ParallelTaskTerminator& _term; | |
| 298 ParNewGeneration& _gen; | |
| 299 Generation& _next_gen; | |
| 300 }; | |
| 301 | |
| 302 | |
| 303 ParScanThreadStateSet::ParScanThreadStateSet( | |
| 304 int num_threads, Space& to_space, ParNewGeneration& gen, | |
| 305 Generation& old_gen, ObjToScanQueueSet& queue_set, | |
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306 Stack<oop>* overflow_stacks, |
| 0 | 307 size_t desired_plab_sz, ParallelTaskTerminator& term) |
| 308 : ResourceArray(sizeof(ParScanThreadState), num_threads), | |
| 1710 | 309 _gen(gen), _next_gen(old_gen), _term(term) |
| 0 | 310 { |
| 311 assert(num_threads > 0, "sanity check!"); | |
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312 assert(ParGCUseLocalOverflow == (overflow_stacks != NULL), |
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313 "overflow_stack allocation mismatch"); |
| 0 | 314 // Initialize states. |
| 315 for (int i = 0; i < num_threads; ++i) { | |
| 316 new ((ParScanThreadState*)_data + i) | |
| 317 ParScanThreadState(&to_space, &gen, &old_gen, i, &queue_set, | |
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318 overflow_stacks, desired_plab_sz, term); |
| 0 | 319 } |
| 320 } | |
| 321 | |
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322 inline ParScanThreadState& ParScanThreadStateSet::thread_state(int i) |
| 0 | 323 { |
| 324 assert(i >= 0 && i < length(), "sanity check!"); | |
| 325 return ((ParScanThreadState*)_data)[i]; | |
| 326 } | |
| 327 | |
| 328 | |
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329 void ParScanThreadStateSet::reset(bool promotion_failed) |
| 0 | 330 { |
| 331 _term.reset_for_reuse(); | |
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332 if (promotion_failed) { |
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333 for (int i = 0; i < length(); ++i) { |
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334 thread_state(i).print_and_clear_promotion_failure_size(); |
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335 } |
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336 } |
| 0 | 337 } |
| 338 | |
| 1710 | 339 #if TASKQUEUE_STATS |
| 340 void | |
| 341 ParScanThreadState::reset_stats() | |
| 342 { | |
| 343 taskqueue_stats().reset(); | |
| 344 _term_attempts = 0; | |
| 345 _overflow_refills = 0; | |
| 346 _overflow_refill_objs = 0; | |
| 347 } | |
| 348 | |
| 349 void ParScanThreadStateSet::reset_stats() | |
| 350 { | |
| 351 for (int i = 0; i < length(); ++i) { | |
| 352 thread_state(i).reset_stats(); | |
| 353 } | |
| 354 } | |
| 355 | |
| 356 void | |
| 357 ParScanThreadStateSet::print_termination_stats_hdr(outputStream* const st) | |
| 358 { | |
| 359 st->print_raw_cr("GC Termination Stats"); | |
| 360 st->print_raw_cr(" elapsed --strong roots-- " | |
| 361 "-------termination-------"); | |
| 362 st->print_raw_cr("thr ms ms % " | |
| 363 " ms % attempts"); | |
| 364 st->print_raw_cr("--- --------- --------- ------ " | |
| 365 "--------- ------ --------"); | |
| 366 } | |
| 367 | |
| 368 void ParScanThreadStateSet::print_termination_stats(outputStream* const st) | |
| 369 { | |
| 370 print_termination_stats_hdr(st); | |
| 371 | |
| 372 for (int i = 0; i < length(); ++i) { | |
| 373 const ParScanThreadState & pss = thread_state(i); | |
| 374 const double elapsed_ms = pss.elapsed_time() * 1000.0; | |
| 375 const double s_roots_ms = pss.strong_roots_time() * 1000.0; | |
| 376 const double term_ms = pss.term_time() * 1000.0; | |
| 377 st->print_cr("%3d %9.2f %9.2f %6.2f " | |
| 378 "%9.2f %6.2f " SIZE_FORMAT_W(8), | |
| 379 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms, | |
| 380 term_ms, term_ms * 100 / elapsed_ms, pss.term_attempts()); | |
| 381 } | |
| 382 } | |
| 383 | |
| 384 // Print stats related to work queue activity. | |
| 385 void ParScanThreadStateSet::print_taskqueue_stats_hdr(outputStream* const st) | |
| 386 { | |
| 387 st->print_raw_cr("GC Task Stats"); | |
| 388 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr(); | |
| 389 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr(); | |
| 390 } | |
| 391 | |
| 392 void ParScanThreadStateSet::print_taskqueue_stats(outputStream* const st) | |
| 393 { | |
| 394 print_taskqueue_stats_hdr(st); | |
| 395 | |
| 396 TaskQueueStats totals; | |
| 397 for (int i = 0; i < length(); ++i) { | |
| 398 const ParScanThreadState & pss = thread_state(i); | |
| 399 const TaskQueueStats & stats = pss.taskqueue_stats(); | |
| 400 st->print("%3d ", i); stats.print(st); st->cr(); | |
| 401 totals += stats; | |
| 402 | |
| 403 if (pss.overflow_refills() > 0) { | |
| 404 st->print_cr(" " SIZE_FORMAT_W(10) " overflow refills " | |
| 405 SIZE_FORMAT_W(10) " overflow objects", | |
| 406 pss.overflow_refills(), pss.overflow_refill_objs()); | |
| 407 } | |
| 408 } | |
| 409 st->print("tot "); totals.print(st); st->cr(); | |
| 410 | |
| 411 DEBUG_ONLY(totals.verify()); | |
| 412 } | |
| 413 #endif // TASKQUEUE_STATS | |
| 414 | |
| 0 | 415 void ParScanThreadStateSet::flush() |
| 416 { | |
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417 // Work in this loop should be kept as lightweight as |
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418 // possible since this might otherwise become a bottleneck |
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419 // to scaling. Should we add heavy-weight work into this |
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420 // loop, consider parallelizing the loop into the worker threads. |
| 0 | 421 for (int i = 0; i < length(); ++i) { |
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422 ParScanThreadState& par_scan_state = thread_state(i); |
| 0 | 423 |
| 424 // Flush stats related to To-space PLAB activity and | |
| 425 // retire the last buffer. | |
| 426 par_scan_state.to_space_alloc_buffer()-> | |
| 427 flush_stats_and_retire(_gen.plab_stats(), | |
| 428 false /* !retain */); | |
| 429 | |
| 430 // Every thread has its own age table. We need to merge | |
| 431 // them all into one. | |
| 432 ageTable *local_table = par_scan_state.age_table(); | |
| 433 _gen.age_table()->merge(local_table); | |
| 434 | |
| 435 // Inform old gen that we're done. | |
| 436 _next_gen.par_promote_alloc_done(i); | |
| 437 _next_gen.par_oop_since_save_marks_iterate_done(i); | |
| 1710 | 438 } |
| 0 | 439 |
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440 if (UseConcMarkSweepGC && ParallelGCThreads > 0) { |
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441 // We need to call this even when ResizeOldPLAB is disabled |
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442 // so as to avoid breaking some asserts. While we may be able |
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443 // to avoid this by reorganizing the code a bit, I am loathe |
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444 // to do that unless we find cases where ergo leads to bad |
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445 // performance. |
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446 CFLS_LAB::compute_desired_plab_size(); |
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447 } |
| 0 | 448 } |
| 449 | |
| 450 ParScanClosure::ParScanClosure(ParNewGeneration* g, | |
| 451 ParScanThreadState* par_scan_state) : | |
| 452 OopsInGenClosure(g), _par_scan_state(par_scan_state), _g(g) | |
| 453 { | |
| 454 assert(_g->level() == 0, "Optimized for youngest generation"); | |
| 455 _boundary = _g->reserved().end(); | |
| 456 } | |
| 457 | |
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458 void ParScanWithBarrierClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, true, false); } |
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459 void ParScanWithBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, false); } |
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460 |
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461 void ParScanWithoutBarrierClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, false, false); } |
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462 void ParScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, false); } |
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463 |
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464 void ParRootScanWithBarrierTwoGensClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, true, true); } |
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465 void ParRootScanWithBarrierTwoGensClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, true, true); } |
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466 |
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467 void ParRootScanWithoutBarrierClosure::do_oop(oop* p) { ParScanClosure::do_oop_work(p, false, true); } |
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468 void ParRootScanWithoutBarrierClosure::do_oop(narrowOop* p) { ParScanClosure::do_oop_work(p, false, true); } |
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469 |
| 0 | 470 ParScanWeakRefClosure::ParScanWeakRefClosure(ParNewGeneration* g, |
| 471 ParScanThreadState* par_scan_state) | |
| 472 : ScanWeakRefClosure(g), _par_scan_state(par_scan_state) | |
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473 {} |
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474 |
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475 void ParScanWeakRefClosure::do_oop(oop* p) { ParScanWeakRefClosure::do_oop_work(p); } |
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476 void ParScanWeakRefClosure::do_oop(narrowOop* p) { ParScanWeakRefClosure::do_oop_work(p); } |
| 0 | 477 |
| 478 #ifdef WIN32 | |
| 479 #pragma warning(disable: 4786) /* identifier was truncated to '255' characters in the browser information */ | |
| 480 #endif | |
| 481 | |
| 482 ParEvacuateFollowersClosure::ParEvacuateFollowersClosure( | |
| 483 ParScanThreadState* par_scan_state_, | |
| 484 ParScanWithoutBarrierClosure* to_space_closure_, | |
| 485 ParScanWithBarrierClosure* old_gen_closure_, | |
| 486 ParRootScanWithoutBarrierClosure* to_space_root_closure_, | |
| 487 ParNewGeneration* par_gen_, | |
| 488 ParRootScanWithBarrierTwoGensClosure* old_gen_root_closure_, | |
| 489 ObjToScanQueueSet* task_queues_, | |
| 490 ParallelTaskTerminator* terminator_) : | |
| 491 | |
| 492 _par_scan_state(par_scan_state_), | |
| 493 _to_space_closure(to_space_closure_), | |
| 494 _old_gen_closure(old_gen_closure_), | |
| 495 _to_space_root_closure(to_space_root_closure_), | |
| 496 _old_gen_root_closure(old_gen_root_closure_), | |
| 497 _par_gen(par_gen_), | |
| 498 _task_queues(task_queues_), | |
| 499 _terminator(terminator_) | |
| 500 {} | |
| 501 | |
| 502 void ParEvacuateFollowersClosure::do_void() { | |
| 503 ObjToScanQueue* work_q = par_scan_state()->work_queue(); | |
| 504 | |
| 505 while (true) { | |
| 506 | |
| 507 // Scan to-space and old-gen objs until we run out of both. | |
| 508 oop obj_to_scan; | |
| 509 par_scan_state()->trim_queues(0); | |
| 510 | |
| 511 // We have no local work, attempt to steal from other threads. | |
| 512 | |
| 513 // attempt to steal work from promoted. | |
| 514 if (task_queues()->steal(par_scan_state()->thread_num(), | |
| 515 par_scan_state()->hash_seed(), | |
| 516 obj_to_scan)) { | |
| 517 bool res = work_q->push(obj_to_scan); | |
| 518 assert(res, "Empty queue should have room for a push."); | |
| 519 | |
| 520 // if successful, goto Start. | |
| 521 continue; | |
| 522 | |
| 523 // try global overflow list. | |
| 524 } else if (par_gen()->take_from_overflow_list(par_scan_state())) { | |
| 525 continue; | |
| 526 } | |
| 527 | |
| 528 // Otherwise, offer termination. | |
| 529 par_scan_state()->start_term_time(); | |
| 530 if (terminator()->offer_termination()) break; | |
| 531 par_scan_state()->end_term_time(); | |
| 532 } | |
| 534 | 533 assert(par_gen()->_overflow_list == NULL && par_gen()->_num_par_pushes == 0, |
| 534 "Broken overflow list?"); | |
| 0 | 535 // Finish the last termination pause. |
| 536 par_scan_state()->end_term_time(); | |
| 537 } | |
| 538 | |
| 539 ParNewGenTask::ParNewGenTask(ParNewGeneration* gen, Generation* next_gen, | |
| 540 HeapWord* young_old_boundary, ParScanThreadStateSet* state_set) : | |
| 541 AbstractGangTask("ParNewGeneration collection"), | |
| 542 _gen(gen), _next_gen(next_gen), | |
| 543 _young_old_boundary(young_old_boundary), | |
| 544 _state_set(state_set) | |
| 545 {} | |
| 546 | |
| 547 void ParNewGenTask::work(int i) { | |
| 548 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 549 // Since this is being done in a separate thread, need new resource | |
| 550 // and handle marks. | |
| 551 ResourceMark rm; | |
| 552 HandleMark hm; | |
| 553 // We would need multiple old-gen queues otherwise. | |
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554 assert(gch->n_gens() == 2, "Par young collection currently only works with one older gen."); |
| 0 | 555 |
| 556 Generation* old_gen = gch->next_gen(_gen); | |
| 557 | |
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558 ParScanThreadState& par_scan_state = _state_set->thread_state(i); |
| 0 | 559 par_scan_state.set_young_old_boundary(_young_old_boundary); |
| 560 | |
| 561 par_scan_state.start_strong_roots(); | |
| 562 gch->gen_process_strong_roots(_gen->level(), | |
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563 true, // Process younger gens, if any, |
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564 // as strong roots. |
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565 false, // no scope; this is parallel code |
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566 false, // not collecting perm generation. |
| 0 | 567 SharedHeap::SO_AllClasses, |
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568 &par_scan_state.to_space_root_closure(), |
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569 true, // walk *all* scavengable nmethods |
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570 &par_scan_state.older_gen_closure()); |
| 0 | 571 par_scan_state.end_strong_roots(); |
| 572 | |
| 573 // "evacuate followers". | |
| 574 par_scan_state.evacuate_followers_closure().do_void(); | |
| 575 } | |
| 576 | |
| 577 #ifdef _MSC_VER | |
| 578 #pragma warning( push ) | |
| 579 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list | |
| 580 #endif | |
| 581 ParNewGeneration:: | |
| 582 ParNewGeneration(ReservedSpace rs, size_t initial_byte_size, int level) | |
| 583 : DefNewGeneration(rs, initial_byte_size, level, "PCopy"), | |
| 584 _overflow_list(NULL), | |
| 585 _is_alive_closure(this), | |
| 586 _plab_stats(YoungPLABSize, PLABWeight) | |
| 587 { | |
| 534 | 588 NOT_PRODUCT(_overflow_counter = ParGCWorkQueueOverflowInterval;) |
| 589 NOT_PRODUCT(_num_par_pushes = 0;) | |
| 0 | 590 _task_queues = new ObjToScanQueueSet(ParallelGCThreads); |
| 591 guarantee(_task_queues != NULL, "task_queues allocation failure."); | |
| 592 | |
| 593 for (uint i1 = 0; i1 < ParallelGCThreads; i1++) { | |
| 1665 | 594 ObjToScanQueue *q = new ObjToScanQueue(); |
| 595 guarantee(q != NULL, "work_queue Allocation failure."); | |
| 596 _task_queues->register_queue(i1, q); | |
| 0 | 597 } |
| 598 | |
| 599 for (uint i2 = 0; i2 < ParallelGCThreads; i2++) | |
| 600 _task_queues->queue(i2)->initialize(); | |
| 601 | |
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602 _overflow_stacks = NULL; |
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603 if (ParGCUseLocalOverflow) { |
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604 _overflow_stacks = NEW_C_HEAP_ARRAY(Stack<oop>, ParallelGCThreads); |
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605 for (size_t i = 0; i < ParallelGCThreads; ++i) { |
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606 new (_overflow_stacks + i) Stack<oop>(); |
| 695 | 607 } |
| 608 } | |
| 609 | |
| 0 | 610 if (UsePerfData) { |
| 611 EXCEPTION_MARK; | |
| 612 ResourceMark rm; | |
| 613 | |
| 614 const char* cname = | |
| 615 PerfDataManager::counter_name(_gen_counters->name_space(), "threads"); | |
| 616 PerfDataManager::create_constant(SUN_GC, cname, PerfData::U_None, | |
| 617 ParallelGCThreads, CHECK); | |
| 618 } | |
| 619 } | |
| 620 #ifdef _MSC_VER | |
| 621 #pragma warning( pop ) | |
| 622 #endif | |
| 623 | |
| 624 // ParNewGeneration:: | |
| 625 ParKeepAliveClosure::ParKeepAliveClosure(ParScanWeakRefClosure* cl) : | |
| 626 DefNewGeneration::KeepAliveClosure(cl), _par_cl(cl) {} | |
| 627 | |
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628 template <class T> |
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629 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop_work(T* p) { |
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630 #ifdef ASSERT |
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631 { |
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632 assert(!oopDesc::is_null(*p), "expected non-null ref"); |
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633 oop obj = oopDesc::load_decode_heap_oop_not_null(p); |
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634 // We never expect to see a null reference being processed |
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635 // as a weak reference. |
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636 assert(obj->is_oop(), "expected an oop while scanning weak refs"); |
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637 } |
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638 #endif // ASSERT |
| 0 | 639 |
| 640 _par_cl->do_oop_nv(p); | |
| 641 | |
| 642 if (Universe::heap()->is_in_reserved(p)) { | |
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643 oop obj = oopDesc::load_decode_heap_oop_not_null(p); |
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644 _rs->write_ref_field_gc_par(p, obj); |
| 0 | 645 } |
| 646 } | |
| 647 | |
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648 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(oop* p) { ParKeepAliveClosure::do_oop_work(p); } |
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649 void /*ParNewGeneration::*/ParKeepAliveClosure::do_oop(narrowOop* p) { ParKeepAliveClosure::do_oop_work(p); } |
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650 |
| 0 | 651 // ParNewGeneration:: |
| 652 KeepAliveClosure::KeepAliveClosure(ScanWeakRefClosure* cl) : | |
| 653 DefNewGeneration::KeepAliveClosure(cl) {} | |
| 654 | |
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655 template <class T> |
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656 void /*ParNewGeneration::*/KeepAliveClosure::do_oop_work(T* p) { |
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657 #ifdef ASSERT |
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658 { |
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659 assert(!oopDesc::is_null(*p), "expected non-null ref"); |
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660 oop obj = oopDesc::load_decode_heap_oop_not_null(p); |
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661 // We never expect to see a null reference being processed |
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662 // as a weak reference. |
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663 assert(obj->is_oop(), "expected an oop while scanning weak refs"); |
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664 } |
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665 #endif // ASSERT |
| 0 | 666 |
| 667 _cl->do_oop_nv(p); | |
| 668 | |
| 669 if (Universe::heap()->is_in_reserved(p)) { | |
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670 oop obj = oopDesc::load_decode_heap_oop_not_null(p); |
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671 _rs->write_ref_field_gc_par(p, obj); |
| 0 | 672 } |
| 673 } | |
| 674 | |
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675 void /*ParNewGeneration::*/KeepAliveClosure::do_oop(oop* p) { KeepAliveClosure::do_oop_work(p); } |
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676 void /*ParNewGeneration::*/KeepAliveClosure::do_oop(narrowOop* p) { KeepAliveClosure::do_oop_work(p); } |
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677 |
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678 template <class T> void ScanClosureWithParBarrier::do_oop_work(T* p) { |
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679 T heap_oop = oopDesc::load_heap_oop(p); |
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680 if (!oopDesc::is_null(heap_oop)) { |
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681 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop); |
| 0 | 682 if ((HeapWord*)obj < _boundary) { |
| 683 assert(!_g->to()->is_in_reserved(obj), "Scanning field twice?"); | |
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684 oop new_obj = obj->is_forwarded() |
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685 ? obj->forwardee() |
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686 : _g->DefNewGeneration::copy_to_survivor_space(obj); |
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687 oopDesc::encode_store_heap_oop_not_null(p, new_obj); |
| 0 | 688 } |
| 689 if (_gc_barrier) { | |
| 690 // If p points to a younger generation, mark the card. | |
| 691 if ((HeapWord*)obj < _gen_boundary) { | |
| 692 _rs->write_ref_field_gc_par(p, obj); | |
| 693 } | |
| 694 } | |
| 695 } | |
| 696 } | |
| 697 | |
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698 void ScanClosureWithParBarrier::do_oop(oop* p) { ScanClosureWithParBarrier::do_oop_work(p); } |
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699 void ScanClosureWithParBarrier::do_oop(narrowOop* p) { ScanClosureWithParBarrier::do_oop_work(p); } |
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700 |
| 0 | 701 class ParNewRefProcTaskProxy: public AbstractGangTask { |
| 702 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask; | |
| 703 public: | |
| 704 ParNewRefProcTaskProxy(ProcessTask& task, ParNewGeneration& gen, | |
| 705 Generation& next_gen, | |
| 706 HeapWord* young_old_boundary, | |
| 707 ParScanThreadStateSet& state_set); | |
| 708 | |
| 709 private: | |
| 710 virtual void work(int i); | |
| 711 | |
| 712 private: | |
| 713 ParNewGeneration& _gen; | |
| 714 ProcessTask& _task; | |
| 715 Generation& _next_gen; | |
| 716 HeapWord* _young_old_boundary; | |
| 717 ParScanThreadStateSet& _state_set; | |
| 718 }; | |
| 719 | |
| 720 ParNewRefProcTaskProxy::ParNewRefProcTaskProxy( | |
| 721 ProcessTask& task, ParNewGeneration& gen, | |
| 722 Generation& next_gen, | |
| 723 HeapWord* young_old_boundary, | |
| 724 ParScanThreadStateSet& state_set) | |
| 725 : AbstractGangTask("ParNewGeneration parallel reference processing"), | |
| 726 _gen(gen), | |
| 727 _task(task), | |
| 728 _next_gen(next_gen), | |
| 729 _young_old_boundary(young_old_boundary), | |
| 730 _state_set(state_set) | |
| 731 { | |
| 732 } | |
| 733 | |
| 734 void ParNewRefProcTaskProxy::work(int i) | |
| 735 { | |
| 736 ResourceMark rm; | |
| 737 HandleMark hm; | |
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738 ParScanThreadState& par_scan_state = _state_set.thread_state(i); |
| 0 | 739 par_scan_state.set_young_old_boundary(_young_old_boundary); |
| 740 _task.work(i, par_scan_state.is_alive_closure(), | |
| 741 par_scan_state.keep_alive_closure(), | |
| 742 par_scan_state.evacuate_followers_closure()); | |
| 743 } | |
| 744 | |
| 745 class ParNewRefEnqueueTaskProxy: public AbstractGangTask { | |
| 746 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask; | |
| 747 EnqueueTask& _task; | |
| 748 | |
| 749 public: | |
| 750 ParNewRefEnqueueTaskProxy(EnqueueTask& task) | |
| 751 : AbstractGangTask("ParNewGeneration parallel reference enqueue"), | |
| 752 _task(task) | |
| 753 { } | |
| 754 | |
| 755 virtual void work(int i) | |
| 756 { | |
| 757 _task.work(i); | |
| 758 } | |
| 759 }; | |
| 760 | |
| 761 | |
| 762 void ParNewRefProcTaskExecutor::execute(ProcessTask& task) | |
| 763 { | |
| 764 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 765 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
| 766 "not a generational heap"); | |
| 767 WorkGang* workers = gch->workers(); | |
| 768 assert(workers != NULL, "Need parallel worker threads."); | |
| 769 ParNewRefProcTaskProxy rp_task(task, _generation, *_generation.next_gen(), | |
| 770 _generation.reserved().end(), _state_set); | |
| 771 workers->run_task(&rp_task); | |
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772 _state_set.reset(_generation.promotion_failed()); |
| 0 | 773 } |
| 774 | |
| 775 void ParNewRefProcTaskExecutor::execute(EnqueueTask& task) | |
| 776 { | |
| 777 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 778 WorkGang* workers = gch->workers(); | |
| 779 assert(workers != NULL, "Need parallel worker threads."); | |
| 780 ParNewRefEnqueueTaskProxy enq_task(task); | |
| 781 workers->run_task(&enq_task); | |
| 782 } | |
| 783 | |
| 784 void ParNewRefProcTaskExecutor::set_single_threaded_mode() | |
| 785 { | |
| 786 _state_set.flush(); | |
| 787 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 788 gch->set_par_threads(0); // 0 ==> non-parallel. | |
| 789 gch->save_marks(); | |
| 790 } | |
| 791 | |
| 792 ScanClosureWithParBarrier:: | |
| 793 ScanClosureWithParBarrier(ParNewGeneration* g, bool gc_barrier) : | |
| 794 ScanClosure(g, gc_barrier) {} | |
| 795 | |
| 796 EvacuateFollowersClosureGeneral:: | |
| 797 EvacuateFollowersClosureGeneral(GenCollectedHeap* gch, int level, | |
| 798 OopsInGenClosure* cur, | |
| 799 OopsInGenClosure* older) : | |
| 800 _gch(gch), _level(level), | |
| 801 _scan_cur_or_nonheap(cur), _scan_older(older) | |
| 802 {} | |
| 803 | |
| 804 void EvacuateFollowersClosureGeneral::do_void() { | |
| 805 do { | |
| 806 // Beware: this call will lead to closure applications via virtual | |
| 807 // calls. | |
| 808 _gch->oop_since_save_marks_iterate(_level, | |
| 809 _scan_cur_or_nonheap, | |
| 810 _scan_older); | |
| 811 } while (!_gch->no_allocs_since_save_marks(_level)); | |
| 812 } | |
| 813 | |
| 814 | |
| 815 bool ParNewGeneration::_avoid_promotion_undo = false; | |
| 816 | |
| 817 void ParNewGeneration::adjust_desired_tenuring_threshold() { | |
| 818 // Set the desired survivor size to half the real survivor space | |
| 819 _tenuring_threshold = | |
| 820 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize); | |
| 821 } | |
| 822 | |
| 823 // A Generation that does parallel young-gen collection. | |
| 824 | |
| 825 void ParNewGeneration::collect(bool full, | |
| 826 bool clear_all_soft_refs, | |
| 827 size_t size, | |
| 828 bool is_tlab) { | |
| 829 assert(full || size > 0, "otherwise we don't want to collect"); | |
| 830 GenCollectedHeap* gch = GenCollectedHeap::heap(); | |
| 831 assert(gch->kind() == CollectedHeap::GenCollectedHeap, | |
| 832 "not a CMS generational heap"); | |
| 833 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy(); | |
| 834 WorkGang* workers = gch->workers(); | |
| 835 _next_gen = gch->next_gen(this); | |
| 836 assert(_next_gen != NULL, | |
| 837 "This must be the youngest gen, and not the only gen"); | |
| 838 assert(gch->n_gens() == 2, | |
| 839 "Par collection currently only works with single older gen."); | |
| 840 // Do we have to avoid promotion_undo? | |
| 841 if (gch->collector_policy()->is_concurrent_mark_sweep_policy()) { | |
| 842 set_avoid_promotion_undo(true); | |
| 843 } | |
| 844 | |
| 845 // If the next generation is too full to accomodate worst-case promotion | |
| 846 // from this generation, pass on collection; let the next generation | |
| 847 // do it. | |
| 848 if (!collection_attempt_is_safe()) { | |
| 849 gch->set_incremental_collection_will_fail(); | |
| 850 return; | |
| 851 } | |
| 852 assert(to()->is_empty(), "Else not collection_attempt_is_safe"); | |
| 853 | |
| 854 init_assuming_no_promotion_failure(); | |
| 855 | |
| 856 if (UseAdaptiveSizePolicy) { | |
| 857 set_survivor_overflow(false); | |
| 858 size_policy->minor_collection_begin(); | |
| 859 } | |
| 860 | |
| 861 TraceTime t1("GC", PrintGC && !PrintGCDetails, true, gclog_or_tty); | |
| 862 // Capture heap used before collection (for printing). | |
| 863 size_t gch_prev_used = gch->used(); | |
| 864 | |
| 865 SpecializationStats::clear(); | |
| 866 | |
| 867 age_table()->clear(); | |
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868 to()->clear(SpaceDecorator::Mangle); |
| 0 | 869 |
| 870 gch->save_marks(); | |
| 871 assert(workers != NULL, "Need parallel worker threads."); | |
| 872 ParallelTaskTerminator _term(workers->total_workers(), task_queues()); | |
| 873 ParScanThreadStateSet thread_state_set(workers->total_workers(), | |
| 874 *to(), *this, *_next_gen, *task_queues(), | |
| 695 | 875 _overflow_stacks, desired_plab_sz(), _term); |
| 0 | 876 |
| 877 ParNewGenTask tsk(this, _next_gen, reserved().end(), &thread_state_set); | |
| 878 int n_workers = workers->total_workers(); | |
| 879 gch->set_par_threads(n_workers); | |
| 880 gch->rem_set()->prepare_for_younger_refs_iterate(true); | |
| 881 // It turns out that even when we're using 1 thread, doing the work in a | |
| 882 // separate thread causes wide variance in run times. We can't help this | |
| 883 // in the multi-threaded case, but we special-case n=1 here to get | |
| 884 // repeatable measurements of the 1-thread overhead of the parallel code. | |
| 885 if (n_workers > 1) { | |
|
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886 GenCollectedHeap::StrongRootsScope srs(gch); |
| 0 | 887 workers->run_task(&tsk); |
| 888 } else { | |
|
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889 GenCollectedHeap::StrongRootsScope srs(gch); |
| 0 | 890 tsk.work(0); |
| 891 } | |
|
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892 thread_state_set.reset(promotion_failed()); |
| 0 | 893 |
| 894 // Process (weak) reference objects found during scavenge. | |
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895 ReferenceProcessor* rp = ref_processor(); |
| 0 | 896 IsAliveClosure is_alive(this); |
| 897 ScanWeakRefClosure scan_weak_ref(this); | |
| 898 KeepAliveClosure keep_alive(&scan_weak_ref); | |
| 899 ScanClosure scan_without_gc_barrier(this, false); | |
| 900 ScanClosureWithParBarrier scan_with_gc_barrier(this, true); | |
| 901 set_promo_failure_scan_stack_closure(&scan_without_gc_barrier); | |
| 902 EvacuateFollowersClosureGeneral evacuate_followers(gch, _level, | |
| 903 &scan_without_gc_barrier, &scan_with_gc_barrier); | |
|
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904 rp->setup_policy(clear_all_soft_refs); |
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905 if (rp->processing_is_mt()) { |
| 0 | 906 ParNewRefProcTaskExecutor task_executor(*this, thread_state_set); |
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907 rp->process_discovered_references(&is_alive, &keep_alive, |
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908 &evacuate_followers, &task_executor); |
| 0 | 909 } else { |
| 910 thread_state_set.flush(); | |
| 911 gch->set_par_threads(0); // 0 ==> non-parallel. | |
| 912 gch->save_marks(); | |
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913 rp->process_discovered_references(&is_alive, &keep_alive, |
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914 &evacuate_followers, NULL); |
| 0 | 915 } |
| 916 if (!promotion_failed()) { | |
| 917 // Swap the survivor spaces. | |
|
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918 eden()->clear(SpaceDecorator::Mangle); |
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919 from()->clear(SpaceDecorator::Mangle); |
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920 if (ZapUnusedHeapArea) { |
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921 // This is now done here because of the piece-meal mangling which |
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922 // can check for valid mangling at intermediate points in the |
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923 // collection(s). When a minor collection fails to collect |
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924 // sufficient space resizing of the young generation can occur |
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925 // an redistribute the spaces in the young generation. Mangle |
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926 // here so that unzapped regions don't get distributed to |
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927 // other spaces. |
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928 to()->mangle_unused_area(); |
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929 } |
| 0 | 930 swap_spaces(); |
| 931 | |
|
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932 // A successful scavenge should restart the GC time limit count which is |
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933 // for full GC's. |
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934 size_policy->reset_gc_overhead_limit_count(); |
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935 |
| 0 | 936 assert(to()->is_empty(), "to space should be empty now"); |
| 937 } else { | |
| 938 assert(HandlePromotionFailure, | |
| 939 "Should only be here if promotion failure handling is on"); | |
|
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940 assert(_promo_failure_scan_stack.is_empty(), "post condition"); |
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941 _promo_failure_scan_stack.clear(true); // Clear cached segments. |
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942 |
| 0 | 943 remove_forwarding_pointers(); |
| 944 if (PrintGCDetails) { | |
| 945 gclog_or_tty->print(" (promotion failed)"); | |
| 946 } | |
| 947 // All the spaces are in play for mark-sweep. | |
| 948 swap_spaces(); // Make life simpler for CMS || rescan; see 6483690. | |
| 949 from()->set_next_compaction_space(to()); | |
| 950 gch->set_incremental_collection_will_fail(); | |
|
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951 // Inform the next generation that a promotion failure occurred. |
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952 _next_gen->promotion_failure_occurred(); |
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953 |
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954 // Reset the PromotionFailureALot counters. |
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955 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();) |
| 0 | 956 } |
| 957 // set new iteration safe limit for the survivor spaces | |
| 958 from()->set_concurrent_iteration_safe_limit(from()->top()); | |
| 959 to()->set_concurrent_iteration_safe_limit(to()->top()); | |
| 960 | |
| 961 adjust_desired_tenuring_threshold(); | |
| 962 if (ResizePLAB) { | |
| 963 plab_stats()->adjust_desired_plab_sz(); | |
| 964 } | |
| 965 | |
| 966 if (PrintGC && !PrintGCDetails) { | |
| 967 gch->print_heap_change(gch_prev_used); | |
| 968 } | |
| 969 | |
|
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970 if (PrintGCDetails && ParallelGCVerbose) { |
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971 TASKQUEUE_STATS_ONLY(thread_state_set.print_termination_stats()); |
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972 TASKQUEUE_STATS_ONLY(thread_state_set.print_taskqueue_stats()); |
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973 } |
| 1710 | 974 |
| 0 | 975 if (UseAdaptiveSizePolicy) { |
| 976 size_policy->minor_collection_end(gch->gc_cause()); | |
| 977 size_policy->avg_survived()->sample(from()->used()); | |
| 978 } | |
| 979 | |
| 980 update_time_of_last_gc(os::javaTimeMillis()); | |
| 981 | |
| 982 SpecializationStats::print(); | |
| 983 | |
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984 rp->set_enqueuing_is_done(true); |
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985 if (rp->processing_is_mt()) { |
| 0 | 986 ParNewRefProcTaskExecutor task_executor(*this, thread_state_set); |
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987 rp->enqueue_discovered_references(&task_executor); |
| 0 | 988 } else { |
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989 rp->enqueue_discovered_references(NULL); |
| 0 | 990 } |
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991 rp->verify_no_references_recorded(); |
| 0 | 992 } |
| 993 | |
| 994 static int sum; | |
| 995 void ParNewGeneration::waste_some_time() { | |
| 996 for (int i = 0; i < 100; i++) { | |
| 997 sum += i; | |
| 998 } | |
| 999 } | |
| 1000 | |
| 1001 static const oop ClaimedForwardPtr = oop(0x4); | |
| 1002 | |
| 1003 // Because of concurrency, there are times where an object for which | |
| 1004 // "is_forwarded()" is true contains an "interim" forwarding pointer | |
| 1005 // value. Such a value will soon be overwritten with a real value. | |
| 1006 // This method requires "obj" to have a forwarding pointer, and waits, if | |
| 1007 // necessary for a real one to be inserted, and returns it. | |
| 1008 | |
| 1009 oop ParNewGeneration::real_forwardee(oop obj) { | |
| 1010 oop forward_ptr = obj->forwardee(); | |
| 1011 if (forward_ptr != ClaimedForwardPtr) { | |
| 1012 return forward_ptr; | |
| 1013 } else { | |
| 1014 return real_forwardee_slow(obj); | |
| 1015 } | |
| 1016 } | |
| 1017 | |
| 1018 oop ParNewGeneration::real_forwardee_slow(oop obj) { | |
| 1019 // Spin-read if it is claimed but not yet written by another thread. | |
| 1020 oop forward_ptr = obj->forwardee(); | |
| 1021 while (forward_ptr == ClaimedForwardPtr) { | |
| 1022 waste_some_time(); | |
| 1023 assert(obj->is_forwarded(), "precondition"); | |
| 1024 forward_ptr = obj->forwardee(); | |
| 1025 } | |
| 1026 return forward_ptr; | |
| 1027 } | |
| 1028 | |
| 1029 #ifdef ASSERT | |
| 1030 bool ParNewGeneration::is_legal_forward_ptr(oop p) { | |
| 1031 return | |
| 1032 (_avoid_promotion_undo && p == ClaimedForwardPtr) | |
| 1033 || Universe::heap()->is_in_reserved(p); | |
| 1034 } | |
| 1035 #endif | |
| 1036 | |
| 1037 void ParNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) { | |
| 1038 if ((m != markOopDesc::prototype()) && | |
| 1039 (!UseBiasedLocking || (m != markOopDesc::biased_locking_prototype()))) { | |
| 1040 MutexLocker ml(ParGCRareEvent_lock); | |
| 1041 DefNewGeneration::preserve_mark_if_necessary(obj, m); | |
| 1042 } | |
| 1043 } | |
| 1044 | |
| 1045 // Multiple GC threads may try to promote an object. If the object | |
| 1046 // is successfully promoted, a forwarding pointer will be installed in | |
| 1047 // the object in the young generation. This method claims the right | |
| 1048 // to install the forwarding pointer before it copies the object, | |
| 1049 // thus avoiding the need to undo the copy as in | |
| 1050 // copy_to_survivor_space_avoiding_with_undo. | |
| 1051 | |
| 1052 oop ParNewGeneration::copy_to_survivor_space_avoiding_promotion_undo( | |
| 1053 ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) { | |
| 1054 // In the sequential version, this assert also says that the object is | |
| 1055 // not forwarded. That might not be the case here. It is the case that | |
| 1056 // the caller observed it to be not forwarded at some time in the past. | |
| 1057 assert(is_in_reserved(old), "shouldn't be scavenging this oop"); | |
| 1058 | |
| 1059 // The sequential code read "old->age()" below. That doesn't work here, | |
| 1060 // since the age is in the mark word, and that might be overwritten with | |
| 1061 // a forwarding pointer by a parallel thread. So we must save the mark | |
| 1062 // word in a local and then analyze it. | |
| 1063 oopDesc dummyOld; | |
| 1064 dummyOld.set_mark(m); | |
| 1065 assert(!dummyOld.is_forwarded(), | |
| 1066 "should not be called with forwarding pointer mark word."); | |
| 1067 | |
| 1068 oop new_obj = NULL; | |
| 1069 oop forward_ptr; | |
| 1070 | |
| 1071 // Try allocating obj in to-space (unless too old) | |
| 1072 if (dummyOld.age() < tenuring_threshold()) { | |
| 1073 new_obj = (oop)par_scan_state->alloc_in_to_space(sz); | |
| 1074 if (new_obj == NULL) { | |
| 1075 set_survivor_overflow(true); | |
| 1076 } | |
| 1077 } | |
| 1078 | |
| 1079 if (new_obj == NULL) { | |
| 1080 // Either to-space is full or we decided to promote | |
| 1081 // try allocating obj tenured | |
| 1082 | |
| 1083 // Attempt to install a null forwarding pointer (atomically), | |
| 1084 // to claim the right to install the real forwarding pointer. | |
| 1085 forward_ptr = old->forward_to_atomic(ClaimedForwardPtr); | |
| 1086 if (forward_ptr != NULL) { | |
| 1087 // someone else beat us to it. | |
| 1088 return real_forwardee(old); | |
| 1089 } | |
| 1090 | |
| 1091 new_obj = _next_gen->par_promote(par_scan_state->thread_num(), | |
| 1092 old, m, sz); | |
| 1093 | |
| 1094 if (new_obj == NULL) { | |
| 1095 if (!HandlePromotionFailure) { | |
| 1096 // A failed promotion likely means the MaxLiveObjectEvacuationRatio flag | |
| 1097 // is incorrectly set. In any case, its seriously wrong to be here! | |
| 1098 vm_exit_out_of_memory(sz*wordSize, "promotion"); | |
| 1099 } | |
| 1100 // promotion failed, forward to self | |
| 1101 _promotion_failed = true; | |
| 1102 new_obj = old; | |
| 1103 | |
| 1104 preserve_mark_if_necessary(old, m); | |
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1105 // Log the size of the maiden promotion failure |
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1106 par_scan_state->log_promotion_failure(sz); |
| 0 | 1107 } |
| 1108 | |
| 1109 old->forward_to(new_obj); | |
| 1110 forward_ptr = NULL; | |
| 1111 } else { | |
| 1112 // Is in to-space; do copying ourselves. | |
| 1113 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz); | |
| 1114 forward_ptr = old->forward_to_atomic(new_obj); | |
| 1115 // Restore the mark word copied above. | |
| 1116 new_obj->set_mark(m); | |
| 1117 // Increment age if obj still in new generation | |
| 1118 new_obj->incr_age(); | |
| 1119 par_scan_state->age_table()->add(new_obj, sz); | |
| 1120 } | |
| 1121 assert(new_obj != NULL, "just checking"); | |
| 1122 | |
| 1123 if (forward_ptr == NULL) { | |
| 1124 oop obj_to_push = new_obj; | |
| 1125 if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) { | |
| 1126 // Length field used as index of next element to be scanned. | |
| 1127 // Real length can be obtained from real_forwardee() | |
| 1128 arrayOop(old)->set_length(0); | |
| 1129 obj_to_push = old; | |
| 1130 assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push, | |
| 1131 "push forwarded object"); | |
| 1132 } | |
| 1133 // Push it on one of the queues of to-be-scanned objects. | |
| 534 | 1134 bool simulate_overflow = false; |
| 1135 NOT_PRODUCT( | |
| 1136 if (ParGCWorkQueueOverflowALot && should_simulate_overflow()) { | |
| 1137 // simulate a stack overflow | |
| 1138 simulate_overflow = true; | |
| 1139 } | |
| 1140 ) | |
| 1141 if (simulate_overflow || !par_scan_state->work_queue()->push(obj_to_push)) { | |
| 0 | 1142 // Add stats for overflow pushes. |
| 1143 if (Verbose && PrintGCDetails) { | |
| 1144 gclog_or_tty->print("queue overflow!\n"); | |
| 1145 } | |
| 534 | 1146 push_on_overflow_list(old, par_scan_state); |
| 1710 | 1147 TASKQUEUE_STATS_ONLY(par_scan_state->taskqueue_stats().record_overflow(0)); |
| 0 | 1148 } |
| 1149 | |
| 1150 return new_obj; | |
| 1151 } | |
| 1152 | |
| 1153 // Oops. Someone beat us to it. Undo the allocation. Where did we | |
| 1154 // allocate it? | |
| 1155 if (is_in_reserved(new_obj)) { | |
| 1156 // Must be in to_space. | |
| 1157 assert(to()->is_in_reserved(new_obj), "Checking"); | |
| 1158 if (forward_ptr == ClaimedForwardPtr) { | |
| 1159 // Wait to get the real forwarding pointer value. | |
| 1160 forward_ptr = real_forwardee(old); | |
| 1161 } | |
| 1162 par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz); | |
| 1163 } | |
| 1164 | |
| 1165 return forward_ptr; | |
| 1166 } | |
| 1167 | |
| 1168 | |
| 1169 // Multiple GC threads may try to promote the same object. If two | |
| 1170 // or more GC threads copy the object, only one wins the race to install | |
| 1171 // the forwarding pointer. The other threads have to undo their copy. | |
| 1172 | |
| 1173 oop ParNewGeneration::copy_to_survivor_space_with_undo( | |
| 1174 ParScanThreadState* par_scan_state, oop old, size_t sz, markOop m) { | |
| 1175 | |
| 1176 // In the sequential version, this assert also says that the object is | |
| 1177 // not forwarded. That might not be the case here. It is the case that | |
| 1178 // the caller observed it to be not forwarded at some time in the past. | |
| 1179 assert(is_in_reserved(old), "shouldn't be scavenging this oop"); | |
| 1180 | |
| 1181 // The sequential code read "old->age()" below. That doesn't work here, | |
| 1182 // since the age is in the mark word, and that might be overwritten with | |
| 1183 // a forwarding pointer by a parallel thread. So we must save the mark | |
| 1184 // word here, install it in a local oopDesc, and then analyze it. | |
| 1185 oopDesc dummyOld; | |
| 1186 dummyOld.set_mark(m); | |
| 1187 assert(!dummyOld.is_forwarded(), | |
| 1188 "should not be called with forwarding pointer mark word."); | |
| 1189 | |
| 1190 bool failed_to_promote = false; | |
| 1191 oop new_obj = NULL; | |
| 1192 oop forward_ptr; | |
| 1193 | |
| 1194 // Try allocating obj in to-space (unless too old) | |
| 1195 if (dummyOld.age() < tenuring_threshold()) { | |
| 1196 new_obj = (oop)par_scan_state->alloc_in_to_space(sz); | |
| 1197 if (new_obj == NULL) { | |
| 1198 set_survivor_overflow(true); | |
| 1199 } | |
| 1200 } | |
| 1201 | |
| 1202 if (new_obj == NULL) { | |
| 1203 // Either to-space is full or we decided to promote | |
| 1204 // try allocating obj tenured | |
| 1205 new_obj = _next_gen->par_promote(par_scan_state->thread_num(), | |
| 1206 old, m, sz); | |
| 1207 | |
| 1208 if (new_obj == NULL) { | |
| 1209 if (!HandlePromotionFailure) { | |
| 1210 // A failed promotion likely means the MaxLiveObjectEvacuationRatio | |
| 1211 // flag is incorrectly set. In any case, its seriously wrong to be | |
| 1212 // here! | |
| 1213 vm_exit_out_of_memory(sz*wordSize, "promotion"); | |
| 1214 } | |
| 1215 // promotion failed, forward to self | |
| 1216 forward_ptr = old->forward_to_atomic(old); | |
| 1217 new_obj = old; | |
| 1218 | |
| 1219 if (forward_ptr != NULL) { | |
| 1220 return forward_ptr; // someone else succeeded | |
| 1221 } | |
| 1222 | |
| 1223 _promotion_failed = true; | |
| 1224 failed_to_promote = true; | |
| 1225 | |
| 1226 preserve_mark_if_necessary(old, m); | |
|
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1227 // Log the size of the maiden promotion failure |
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1228 par_scan_state->log_promotion_failure(sz); |
| 0 | 1229 } |
| 1230 } else { | |
| 1231 // Is in to-space; do copying ourselves. | |
| 1232 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)new_obj, sz); | |
| 1233 // Restore the mark word copied above. | |
| 1234 new_obj->set_mark(m); | |
| 1235 // Increment age if new_obj still in new generation | |
| 1236 new_obj->incr_age(); | |
| 1237 par_scan_state->age_table()->add(new_obj, sz); | |
| 1238 } | |
| 1239 assert(new_obj != NULL, "just checking"); | |
| 1240 | |
| 1241 // Now attempt to install the forwarding pointer (atomically). | |
| 1242 // We have to copy the mark word before overwriting with forwarding | |
| 1243 // ptr, so we can restore it below in the copy. | |
| 1244 if (!failed_to_promote) { | |
| 1245 forward_ptr = old->forward_to_atomic(new_obj); | |
| 1246 } | |
| 1247 | |
| 1248 if (forward_ptr == NULL) { | |
| 1249 oop obj_to_push = new_obj; | |
| 1250 if (par_scan_state->should_be_partially_scanned(obj_to_push, old)) { | |
| 1251 // Length field used as index of next element to be scanned. | |
| 1252 // Real length can be obtained from real_forwardee() | |
| 1253 arrayOop(old)->set_length(0); | |
| 1254 obj_to_push = old; | |
| 1255 assert(obj_to_push->is_forwarded() && obj_to_push->forwardee() != obj_to_push, | |
| 1256 "push forwarded object"); | |
| 1257 } | |
| 1258 // Push it on one of the queues of to-be-scanned objects. | |
| 534 | 1259 bool simulate_overflow = false; |
| 1260 NOT_PRODUCT( | |
| 1261 if (ParGCWorkQueueOverflowALot && should_simulate_overflow()) { | |
| 1262 // simulate a stack overflow | |
| 1263 simulate_overflow = true; | |
| 1264 } | |
| 1265 ) | |
| 1266 if (simulate_overflow || !par_scan_state->work_queue()->push(obj_to_push)) { | |
| 0 | 1267 // Add stats for overflow pushes. |
| 534 | 1268 push_on_overflow_list(old, par_scan_state); |
| 1710 | 1269 TASKQUEUE_STATS_ONLY(par_scan_state->taskqueue_stats().record_overflow(0)); |
| 0 | 1270 } |
| 1271 | |
| 1272 return new_obj; | |
| 1273 } | |
| 1274 | |
| 1275 // Oops. Someone beat us to it. Undo the allocation. Where did we | |
| 1276 // allocate it? | |
| 1277 if (is_in_reserved(new_obj)) { | |
| 1278 // Must be in to_space. | |
| 1279 assert(to()->is_in_reserved(new_obj), "Checking"); | |
| 1280 par_scan_state->undo_alloc_in_to_space((HeapWord*)new_obj, sz); | |
| 1281 } else { | |
| 1282 assert(!_avoid_promotion_undo, "Should not be here if avoiding."); | |
| 1283 _next_gen->par_promote_alloc_undo(par_scan_state->thread_num(), | |
| 1284 (HeapWord*)new_obj, sz); | |
| 1285 } | |
| 1286 | |
| 1287 return forward_ptr; | |
| 1288 } | |
| 1289 | |
| 534 | 1290 #ifndef PRODUCT |
| 1291 // It's OK to call this multi-threaded; the worst thing | |
| 1292 // that can happen is that we'll get a bunch of closely | |
| 1293 // spaced simulated oveflows, but that's OK, in fact | |
| 1294 // probably good as it would exercise the overflow code | |
| 1295 // under contention. | |
| 1296 bool ParNewGeneration::should_simulate_overflow() { | |
| 1297 if (_overflow_counter-- <= 0) { // just being defensive | |
| 1298 _overflow_counter = ParGCWorkQueueOverflowInterval; | |
| 1299 return true; | |
| 1300 } else { | |
| 1301 return false; | |
| 1302 } | |
| 1303 } | |
| 1304 #endif | |
| 1305 | |
|
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1306 // In case we are using compressed oops, we need to be careful. |
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1307 // If the object being pushed is an object array, then its length |
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1308 // field keeps track of the "grey boundary" at which the next |
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1309 // incremental scan will be done (see ParGCArrayScanChunk). |
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1310 // When using compressed oops, this length field is kept in the |
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1311 // lower 32 bits of the erstwhile klass word and cannot be used |
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1312 // for the overflow chaining pointer (OCP below). As such the OCP |
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1313 // would itself need to be compressed into the top 32-bits in this |
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1314 // case. Unfortunately, see below, in the event that we have a |
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1315 // promotion failure, the node to be pushed on the list can be |
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1316 // outside of the Java heap, so the heap-based pointer compression |
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1317 // would not work (we would have potential aliasing between C-heap |
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1318 // and Java-heap pointers). For this reason, when using compressed |
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1319 // oops, we simply use a worker-thread-local, non-shared overflow |
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1320 // list in the form of a growable array, with a slightly different |
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1321 // overflow stack draining strategy. If/when we start using fat |
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1322 // stacks here, we can go back to using (fat) pointer chains |
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1323 // (although some performance comparisons would be useful since |
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1324 // single global lists have their own performance disadvantages |
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1325 // as we were made painfully aware not long ago, see 6786503). |
| 534 | 1326 #define BUSY (oop(0x1aff1aff)) |
| 1327 void ParNewGeneration::push_on_overflow_list(oop from_space_obj, ParScanThreadState* par_scan_state) { | |
|
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1328 assert(is_in_reserved(from_space_obj), "Should be from this generation"); |
| 695 | 1329 if (ParGCUseLocalOverflow) { |
|
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1330 // In the case of compressed oops, we use a private, not-shared |
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1331 // overflow stack. |
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1332 par_scan_state->push_on_overflow_stack(from_space_obj); |
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1333 } else { |
| 695 | 1334 assert(!UseCompressedOops, "Error"); |
|
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1335 // if the object has been forwarded to itself, then we cannot |
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1336 // use the klass pointer for the linked list. Instead we have |
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1337 // to allocate an oopDesc in the C-Heap and use that for the linked list. |
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1338 // XXX This is horribly inefficient when a promotion failure occurs |
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1339 // and should be fixed. XXX FIX ME !!! |
| 534 | 1340 #ifndef PRODUCT |
|
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1341 Atomic::inc_ptr(&_num_par_pushes); |
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1342 assert(_num_par_pushes > 0, "Tautology"); |
| 534 | 1343 #endif |
|
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1344 if (from_space_obj->forwardee() == from_space_obj) { |
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1345 oopDesc* listhead = NEW_C_HEAP_ARRAY(oopDesc, 1); |
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1346 listhead->forward_to(from_space_obj); |
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1347 from_space_obj = listhead; |
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1348 } |
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1349 oop observed_overflow_list = _overflow_list; |
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1350 oop cur_overflow_list; |
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1351 do { |
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1352 cur_overflow_list = observed_overflow_list; |
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1353 if (cur_overflow_list != BUSY) { |
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1354 from_space_obj->set_klass_to_list_ptr(cur_overflow_list); |
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1355 } else { |
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1356 from_space_obj->set_klass_to_list_ptr(NULL); |
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1357 } |
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1358 observed_overflow_list = |
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1359 (oop)Atomic::cmpxchg_ptr(from_space_obj, &_overflow_list, cur_overflow_list); |
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1360 } while (cur_overflow_list != observed_overflow_list); |
| 0 | 1361 } |
| 1362 } | |
| 1363 | |
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1364 bool ParNewGeneration::take_from_overflow_list(ParScanThreadState* par_scan_state) { |
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1365 bool res; |
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1366 |
| 695 | 1367 if (ParGCUseLocalOverflow) { |
|
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1368 res = par_scan_state->take_from_overflow_stack(); |
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1369 } else { |
| 695 | 1370 assert(!UseCompressedOops, "Error"); |
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1371 res = take_from_overflow_list_work(par_scan_state); |
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1372 } |
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1373 return res; |
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1374 } |
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1375 |
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1376 |
| 534 | 1377 // *NOTE*: The overflow list manipulation code here and |
| 1378 // in CMSCollector:: are very similar in shape, | |
| 1379 // except that in the CMS case we thread the objects | |
| 1380 // directly into the list via their mark word, and do | |
| 1381 // not need to deal with special cases below related | |
| 1382 // to chunking of object arrays and promotion failure | |
| 1383 // handling. | |
| 1384 // CR 6797058 has been filed to attempt consolidation of | |
| 1385 // the common code. | |
| 1386 // Because of the common code, if you make any changes in | |
| 1387 // the code below, please check the CMS version to see if | |
| 1388 // similar changes might be needed. | |
| 1389 // See CMSCollector::par_take_from_overflow_list() for | |
| 1390 // more extensive documentation comments. | |
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1391 bool ParNewGeneration::take_from_overflow_list_work(ParScanThreadState* par_scan_state) { |
| 0 | 1392 ObjToScanQueue* work_q = par_scan_state->work_queue(); |
| 1393 // How many to take? | |
|
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1394 size_t objsFromOverflow = MIN2((size_t)(work_q->max_elems() - work_q->size())/4, |
| 534 | 1395 (size_t)ParGCDesiredObjsFromOverflowList); |
| 0 | 1396 |
|
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1397 assert(!UseCompressedOops, "Error"); |
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1398 assert(par_scan_state->overflow_stack() == NULL, "Error"); |
| 0 | 1399 if (_overflow_list == NULL) return false; |
| 1400 | |
| 1401 // Otherwise, there was something there; try claiming the list. | |
| 534 | 1402 oop prefix = (oop)Atomic::xchg_ptr(BUSY, &_overflow_list); |
| 1403 // Trim off a prefix of at most objsFromOverflow items | |
| 1404 Thread* tid = Thread::current(); | |
| 1405 size_t spin_count = (size_t)ParallelGCThreads; | |
| 1406 size_t sleep_time_millis = MAX2((size_t)1, objsFromOverflow/100); | |
| 1407 for (size_t spin = 0; prefix == BUSY && spin < spin_count; spin++) { | |
| 1408 // someone grabbed it before we did ... | |
| 1409 // ... we spin for a short while... | |
| 1410 os::sleep(tid, sleep_time_millis, false); | |
| 1411 if (_overflow_list == NULL) { | |
| 1412 // nothing left to take | |
| 1413 return false; | |
| 1414 } else if (_overflow_list != BUSY) { | |
| 1415 // try and grab the prefix | |
| 1416 prefix = (oop)Atomic::xchg_ptr(BUSY, &_overflow_list); | |
| 1417 } | |
| 0 | 1418 } |
| 534 | 1419 if (prefix == NULL || prefix == BUSY) { |
| 1420 // Nothing to take or waited long enough | |
| 1421 if (prefix == NULL) { | |
| 1422 // Write back the NULL in case we overwrote it with BUSY above | |
| 1423 // and it is still the same value. | |
| 1424 (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); | |
| 1425 } | |
| 1426 return false; | |
| 1427 } | |
| 1428 assert(prefix != NULL && prefix != BUSY, "Error"); | |
| 1429 size_t i = 1; | |
| 0 | 1430 oop cur = prefix; |
|
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1431 while (i < objsFromOverflow && cur->klass_or_null() != NULL) { |
| 0 | 1432 i++; cur = oop(cur->klass()); |
| 1433 } | |
| 1434 | |
| 1435 // Reattach remaining (suffix) to overflow list | |
| 534 | 1436 if (cur->klass_or_null() == NULL) { |
| 1437 // Write back the NULL in lieu of the BUSY we wrote | |
| 1438 // above and it is still the same value. | |
| 1439 if (_overflow_list == BUSY) { | |
| 1440 (void) Atomic::cmpxchg_ptr(NULL, &_overflow_list, BUSY); | |
| 0 | 1441 } |
| 534 | 1442 } else { |
| 1443 assert(cur->klass_or_null() != BUSY, "Error"); | |
| 1444 oop suffix = oop(cur->klass()); // suffix will be put back on global list | |
| 1445 cur->set_klass_to_list_ptr(NULL); // break off suffix | |
| 1446 // It's possible that the list is still in the empty(busy) state | |
| 1447 // we left it in a short while ago; in that case we may be | |
| 1448 // able to place back the suffix. | |
| 1449 oop observed_overflow_list = _overflow_list; | |
| 1450 oop cur_overflow_list = observed_overflow_list; | |
| 1451 bool attached = false; | |
| 1452 while (observed_overflow_list == BUSY || observed_overflow_list == NULL) { | |
| 1453 observed_overflow_list = | |
| 1454 (oop) Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list); | |
| 1455 if (cur_overflow_list == observed_overflow_list) { | |
| 1456 attached = true; | |
| 1457 break; | |
| 1458 } else cur_overflow_list = observed_overflow_list; | |
| 1459 } | |
| 1460 if (!attached) { | |
| 1461 // Too bad, someone else got in in between; we'll need to do a splice. | |
| 1462 // Find the last item of suffix list | |
| 1463 oop last = suffix; | |
| 1464 while (last->klass_or_null() != NULL) { | |
| 1465 last = oop(last->klass()); | |
| 1466 } | |
| 1467 // Atomically prepend suffix to current overflow list | |
| 1468 observed_overflow_list = _overflow_list; | |
| 1469 do { | |
| 1470 cur_overflow_list = observed_overflow_list; | |
| 1471 if (cur_overflow_list != BUSY) { | |
| 1472 // Do the splice ... | |
| 1473 last->set_klass_to_list_ptr(cur_overflow_list); | |
| 1474 } else { // cur_overflow_list == BUSY | |
| 1475 last->set_klass_to_list_ptr(NULL); | |
| 1476 } | |
| 1477 observed_overflow_list = | |
| 1478 (oop)Atomic::cmpxchg_ptr(suffix, &_overflow_list, cur_overflow_list); | |
| 1479 } while (cur_overflow_list != observed_overflow_list); | |
| 0 | 1480 } |
| 1481 } | |
| 1482 | |
| 1483 // Push objects on prefix list onto this thread's work queue | |
| 534 | 1484 assert(prefix != NULL && prefix != BUSY, "program logic"); |
| 0 | 1485 cur = prefix; |
| 534 | 1486 ssize_t n = 0; |
| 0 | 1487 while (cur != NULL) { |
| 1488 oop obj_to_push = cur->forwardee(); | |
|
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1489 oop next = oop(cur->klass_or_null()); |
| 0 | 1490 cur->set_klass(obj_to_push->klass()); |
| 534 | 1491 // This may be an array object that is self-forwarded. In that case, the list pointer |
| 1492 // space, cur, is not in the Java heap, but rather in the C-heap and should be freed. | |
| 1493 if (!is_in_reserved(cur)) { | |
| 1494 // This can become a scaling bottleneck when there is work queue overflow coincident | |
| 1495 // with promotion failure. | |
| 1496 oopDesc* f = cur; | |
| 1497 FREE_C_HEAP_ARRAY(oopDesc, f); | |
| 1498 } else if (par_scan_state->should_be_partially_scanned(obj_to_push, cur)) { | |
| 0 | 1499 assert(arrayOop(cur)->length() == 0, "entire array remaining to be scanned"); |
| 534 | 1500 obj_to_push = cur; |
| 0 | 1501 } |
| 534 | 1502 bool ok = work_q->push(obj_to_push); |
| 1503 assert(ok, "Should have succeeded"); | |
| 0 | 1504 cur = next; |
| 1505 n++; | |
| 1506 } | |
| 1710 | 1507 TASKQUEUE_STATS_ONLY(par_scan_state->note_overflow_refill(n)); |
| 534 | 1508 #ifndef PRODUCT |
| 1509 assert(_num_par_pushes >= n, "Too many pops?"); | |
| 1510 Atomic::add_ptr(-(intptr_t)n, &_num_par_pushes); | |
| 1511 #endif | |
| 0 | 1512 return true; |
| 1513 } | |
| 534 | 1514 #undef BUSY |
| 0 | 1515 |
| 1516 void ParNewGeneration::ref_processor_init() | |
| 1517 { | |
| 1518 if (_ref_processor == NULL) { | |
| 1519 // Allocate and initialize a reference processor | |
| 1520 _ref_processor = ReferenceProcessor::create_ref_processor( | |
| 1521 _reserved, // span | |
| 1522 refs_discovery_is_atomic(), // atomic_discovery | |
| 1523 refs_discovery_is_mt(), // mt_discovery | |
| 1524 NULL, // is_alive_non_header | |
| 1525 ParallelGCThreads, | |
| 1526 ParallelRefProcEnabled); | |
| 1527 } | |
| 1528 } | |
| 1529 | |
| 1530 const char* ParNewGeneration::name() const { | |
| 1531 return "par new generation"; | |
| 1532 } | |
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1533 |
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1534 bool ParNewGeneration::in_use() { |
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1535 return UseParNewGC && ParallelGCThreads > 0; |
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1536 } |