1 /*
   2  * Copyright (c) 2014, 2015, 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/g1/g1Allocator.inline.hpp"
  27 #include "gc/g1/g1CollectedHeap.inline.hpp"
  28 #include "gc/g1/g1OopClosures.inline.hpp"
  29 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  30 #include "gc/g1/g1RootClosures.hpp"
  31 #include "gc/g1/g1StringDedup.hpp"
  32 #include "gc/shared/taskqueue.inline.hpp"
  33 #include "oops/oop.inline.hpp"
  34 #include "runtime/prefetch.inline.hpp"
  35 
  36 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint worker_id, size_t young_cset_length)
  37   : _g1h(g1h),
  38     _refs(g1h->task_queue(worker_id)),
  39     _dcq(&g1h->dirty_card_queue_set()),
  40     _ct_bs(g1h->g1_barrier_set()),
  41     _closures(NULL),
  42     _hash_seed(17),
  43     _worker_id(worker_id),
  44     _tenuring_threshold(g1h->g1_policy()->tenuring_threshold()),
  45     _age_table(false),
  46     _scanner(g1h, this),
  47     _old_gen_is_full(false)
  48 {
  49   // we allocate G1YoungSurvRateNumRegions plus one entries, since
  50   // we "sacrifice" entry 0 to keep track of surviving bytes for
  51   // non-young regions (where the age is -1)
  52   // We also add a few elements at the beginning and at the end in
  53   // an attempt to eliminate cache contention
  54   size_t real_length = 1 + young_cset_length;
  55   size_t array_length = PADDING_ELEM_NUM +
  56                       real_length +
  57                       PADDING_ELEM_NUM;
  58   _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
  59   if (_surviving_young_words_base == NULL)
  60     vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR,
  61                           "Not enough space for young surv histo.");
  62   _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
  63   memset(_surviving_young_words, 0, real_length * sizeof(size_t));
  64 
  65   _plab_allocator = G1PLABAllocator::create_allocator(_g1h->allocator());
  66 
  67   _dest[InCSetState::NotInCSet]    = InCSetState::NotInCSet;
  68   // The dest for Young is used when the objects are aged enough to
  69   // need to be moved to the next space.
  70   _dest[InCSetState::Young]        = InCSetState::Old;
  71   _dest[InCSetState::Old]          = InCSetState::Old;
  72 
  73   _closures = G1EvacuationRootClosures::create_root_closures(this, _g1h);
  74 }
  75 
  76 // Pass locally gathered statistics to global state.
  77 void G1ParScanThreadState::flush(size_t* surviving_young_words) {
  78   _dcq.flush();
  79   // Update allocation statistics.
  80   _plab_allocator->flush_and_retire_stats();
  81   _g1h->g1_policy()->record_age_table(&_age_table);
  82 
  83   uint length = _g1h->g1_policy()->young_cset_region_length();
  84   for (uint region_index = 0; region_index < length; region_index++) {
  85     surviving_young_words[region_index] += _surviving_young_words[region_index];
  86   }
  87 }
  88 
  89 G1ParScanThreadState::~G1ParScanThreadState() {
  90   delete _plab_allocator;
  91   delete _closures;
  92   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base);
  93 }
  94 
  95 void G1ParScanThreadState::waste(size_t& wasted, size_t& undo_wasted) {
  96   _plab_allocator->waste(wasted, undo_wasted);
  97 }
  98 
  99 #ifdef ASSERT
 100 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
 101   assert(ref != NULL, "invariant");
 102   assert(UseCompressedOops, "sanity");
 103   assert(!has_partial_array_mask(ref), "ref=" PTR_FORMAT, p2i(ref));
 104   oop p = oopDesc::load_decode_heap_oop(ref);
 105   assert(_g1h->is_in_g1_reserved(p),
 106          "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
 107   return true;
 108 }
 109 
 110 bool G1ParScanThreadState::verify_ref(oop* ref) const {
 111   assert(ref != NULL, "invariant");
 112   if (has_partial_array_mask(ref)) {
 113     // Must be in the collection set--it's already been copied.
 114     oop p = clear_partial_array_mask(ref);
 115     assert(_g1h->obj_in_cs(p),
 116            "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
 117   } else {
 118     oop p = oopDesc::load_decode_heap_oop(ref);
 119     assert(_g1h->is_in_g1_reserved(p),
 120            "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
 121   }
 122   return true;
 123 }
 124 
 125 bool G1ParScanThreadState::verify_task(StarTask ref) const {
 126   if (ref.is_narrow()) {
 127     return verify_ref((narrowOop*) ref);
 128   } else {
 129     return verify_ref((oop*) ref);
 130   }
 131 }
 132 #endif // ASSERT
 133 
 134 void G1ParScanThreadState::trim_queue() {
 135   StarTask ref;
 136   do {
 137     // Drain the overflow stack first, so other threads can steal.
 138     while (_refs->pop_overflow(ref)) {
 139       dispatch_reference(ref);
 140     }
 141 
 142     while (_refs->pop_local(ref)) {
 143       dispatch_reference(ref);
 144     }
 145   } while (!_refs->is_empty());
 146 }
 147 
 148 HeapWord* G1ParScanThreadState::allocate_in_next_plab(InCSetState const state,
 149                                                       InCSetState* dest,
 150                                                       size_t word_sz,
 151                                                       AllocationContext_t const context,
 152                                                       bool previous_plab_refill_failed) {
 153   assert(state.is_in_cset_or_humongous(), "Unexpected state: " CSETSTATE_FORMAT, state.value());
 154   assert(dest->is_in_cset_or_humongous(), "Unexpected dest: " CSETSTATE_FORMAT, dest->value());
 155 
 156   // Right now we only have two types of regions (young / old) so
 157   // let's keep the logic here simple. We can generalize it when necessary.
 158   if (dest->is_young()) {
 159     bool plab_refill_in_old_failed = false;
 160     HeapWord* const obj_ptr = _plab_allocator->allocate(InCSetState::Old,
 161                                                         word_sz,
 162                                                         context,
 163                                                         &plab_refill_in_old_failed);
 164     // Make sure that we won't attempt to copy any other objects out
 165     // of a survivor region (given that apparently we cannot allocate
 166     // any new ones) to avoid coming into this slow path again and again.
 167     // Only consider failed PLAB refill here: failed inline allocations are
 168     // typically large, so not indicative of remaining space.
 169     if (previous_plab_refill_failed) {
 170       _tenuring_threshold = 0;
 171     }
 172 
 173     if (obj_ptr != NULL) {
 174       dest->set_old();
 175     } else {
 176       // We just failed to allocate in old gen. The same idea as explained above
 177       // for making survivor gen unavailable for allocation applies for old gen.
 178       _old_gen_is_full = plab_refill_in_old_failed;
 179     }
 180     return obj_ptr;
 181   } else {
 182     _old_gen_is_full = previous_plab_refill_failed;
 183     assert(dest->is_old(), "Unexpected dest: " CSETSTATE_FORMAT, dest->value());
 184     // no other space to try.
 185     return NULL;
 186   }
 187 }
 188 
 189 InCSetState G1ParScanThreadState::next_state(InCSetState const state, markOop const m, uint& age) {
 190   if (state.is_young()) {
 191     age = !m->has_displaced_mark_helper() ? m->age()
 192                                           : m->displaced_mark_helper()->age();
 193     if (age < _tenuring_threshold) {
 194       return state;
 195     }
 196   }
 197   return dest(state);
 198 }
 199 
 200 void G1ParScanThreadState::report_promotion_event(InCSetState const dest_state,
 201                                                   oop const old, size_t word_sz, uint age,
 202                                                   HeapWord * const obj_ptr,
 203                                                   const AllocationContext_t context) const {
 204   G1PLAB* alloc_buf = _plab_allocator->alloc_buffer(dest_state, context);
 205   if (alloc_buf->contains(obj_ptr)) {
 206     _g1h->_gc_tracer_stw->report_promotion_in_new_plab_event(old->klass(), word_sz, age,
 207                                                              dest_state.value() == InCSetState::Old,
 208                                                              alloc_buf->word_sz());
 209   } else {
 210     _g1h->_gc_tracer_stw->report_promotion_outside_plab_event(old->klass(), word_sz, age,
 211                                                               dest_state.value() == InCSetState::Old);
 212   }
 213 }
 214 
 215 oop G1ParScanThreadState::copy_to_survivor_space(InCSetState const state,
 216                                                  oop const old,
 217                                                  markOop const old_mark) {
 218   const size_t word_sz = old->size();
 219   HeapRegion* const from_region = _g1h->heap_region_containing(old);
 220   // +1 to make the -1 indexes valid...
 221   const int young_index = from_region->young_index_in_cset()+1;
 222   assert( (from_region->is_young() && young_index >  0) ||
 223          (!from_region->is_young() && young_index == 0), "invariant" );
 224   const AllocationContext_t context = from_region->allocation_context();
 225 
 226   uint age = 0;
 227   InCSetState dest_state = next_state(state, old_mark, age);
 228   // The second clause is to prevent premature evacuation failure in case there
 229   // is still space in survivor, but old gen is full.
 230   if (_old_gen_is_full && dest_state.is_old()) {
 231     return handle_evacuation_failure_par(old, old_mark);
 232   }
 233   HeapWord* obj_ptr = _plab_allocator->plab_allocate(dest_state, word_sz, context);
 234 
 235   // PLAB allocations should succeed most of the time, so we'll
 236   // normally check against NULL once and that's it.
 237   if (obj_ptr == NULL) {
 238     bool plab_refill_failed = false;
 239     obj_ptr = _plab_allocator->allocate_direct_or_new_plab(dest_state, word_sz, context, &plab_refill_failed);
 240     if (obj_ptr == NULL) {
 241       obj_ptr = allocate_in_next_plab(state, &dest_state, word_sz, context, plab_refill_failed);
 242       if (obj_ptr == NULL) {
 243         // This will either forward-to-self, or detect that someone else has
 244         // installed a forwarding pointer.
 245         return handle_evacuation_failure_par(old, old_mark);
 246       }
 247     }
 248     if (_g1h->_gc_tracer_stw->should_report_promotion_events()) {
 249       // The events are checked individually as part of the actual commit
 250       report_promotion_event(dest_state, old, word_sz, age, obj_ptr, context);
 251     }
 252   }
 253 
 254   assert(obj_ptr != NULL, "when we get here, allocation should have succeeded");
 255   assert(_g1h->is_in_reserved(obj_ptr), "Allocated memory should be in the heap");
 256 
 257 #ifndef PRODUCT
 258   // Should this evacuation fail?
 259   if (_g1h->evacuation_should_fail()) {
 260     // Doing this after all the allocation attempts also tests the
 261     // undo_allocation() method too.
 262     _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
 263     return handle_evacuation_failure_par(old, old_mark);
 264   }
 265 #endif // !PRODUCT
 266 
 267   // We're going to allocate linearly, so might as well prefetch ahead.
 268   Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
 269 
 270   const oop obj = oop(obj_ptr);
 271   const oop forward_ptr = old->forward_to_atomic(obj);
 272   if (forward_ptr == NULL) {
 273     Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
 274 
 275     if (dest_state.is_young()) {
 276       if (age < markOopDesc::max_age) {
 277         age++;
 278       }
 279       if (old_mark->has_displaced_mark_helper()) {
 280         // In this case, we have to install the mark word first,
 281         // otherwise obj looks to be forwarded (the old mark word,
 282         // which contains the forward pointer, was copied)
 283         obj->set_mark(old_mark);
 284         markOop new_mark = old_mark->displaced_mark_helper()->set_age(age);
 285         old_mark->set_displaced_mark_helper(new_mark);
 286       } else {
 287         obj->set_mark(old_mark->set_age(age));
 288       }
 289       _age_table.add(age, word_sz);
 290     } else {
 291       obj->set_mark(old_mark);
 292     }
 293 
 294     if (G1StringDedup::is_enabled()) {
 295       const bool is_from_young = state.is_young();
 296       const bool is_to_young = dest_state.is_young();
 297       assert(is_from_young == _g1h->heap_region_containing(old)->is_young(),
 298              "sanity");
 299       assert(is_to_young == _g1h->heap_region_containing(obj)->is_young(),
 300              "sanity");
 301       G1StringDedup::enqueue_from_evacuation(is_from_young,
 302                                              is_to_young,
 303                                              _worker_id,
 304                                              obj);
 305     }
 306 
 307     _surviving_young_words[young_index] += word_sz;
 308 
 309     if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
 310       // We keep track of the next start index in the length field of
 311       // the to-space object. The actual length can be found in the
 312       // length field of the from-space object.
 313       arrayOop(obj)->set_length(0);
 314       oop* old_p = set_partial_array_mask(old);
 315       push_on_queue(old_p);
 316     } else {
 317       HeapRegion* const to_region = _g1h->heap_region_containing(obj_ptr);
 318       _scanner.set_region(to_region);
 319       obj->oop_iterate_backwards(&_scanner);
 320     }
 321     return obj;
 322   } else {
 323     _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
 324     return forward_ptr;
 325   }
 326 }
 327 
 328 G1ParScanThreadState* G1ParScanThreadStateSet::state_for_worker(uint worker_id) {
 329   assert(worker_id < _n_workers, "out of bounds access");
 330   return _states[worker_id];
 331 }
 332 
 333 void G1ParScanThreadStateSet::add_cards_scanned(uint worker_id, size_t cards_scanned) {
 334   assert(worker_id < _n_workers, "out of bounds access");
 335   _cards_scanned[worker_id] += cards_scanned;
 336 }
 337 
 338 size_t G1ParScanThreadStateSet::total_cards_scanned() const {
 339   assert(_flushed, "thread local state from the per thread states should have been flushed");
 340   return _total_cards_scanned;
 341 }
 342 
 343 const size_t* G1ParScanThreadStateSet::surviving_young_words() const {
 344   assert(_flushed, "thread local state from the per thread states should have been flushed");
 345   return _surviving_young_words_total;
 346 }
 347 
 348 void G1ParScanThreadStateSet::flush() {
 349   assert(!_flushed, "thread local state from the per thread states should be flushed once");
 350   assert(_total_cards_scanned == 0, "should have been cleared");
 351 
 352   for (uint worker_index = 0; worker_index < _n_workers; ++worker_index) {
 353     G1ParScanThreadState* pss = _states[worker_index];
 354 
 355     _total_cards_scanned += _cards_scanned[worker_index];
 356 
 357     pss->flush(_surviving_young_words_total);
 358     delete pss;
 359     _states[worker_index] = NULL;
 360   }
 361   _flushed = true;
 362 }
 363 
 364 oop G1ParScanThreadState::handle_evacuation_failure_par(oop old, markOop m) {
 365   assert(_g1h->obj_in_cs(old), "Object " PTR_FORMAT " should be in the CSet", p2i(old));
 366 
 367   oop forward_ptr = old->forward_to_atomic(old);
 368   if (forward_ptr == NULL) {
 369     // Forward-to-self succeeded. We are the "owner" of the object.
 370     HeapRegion* r = _g1h->heap_region_containing(old);
 371 
 372     if (!r->evacuation_failed()) {
 373       r->set_evacuation_failed(true);
 374      _g1h->hr_printer()->evac_failure(r);
 375     }
 376 
 377     _g1h->preserve_mark_during_evac_failure(_worker_id, old, m);
 378 
 379     _scanner.set_region(r);
 380     old->oop_iterate_backwards(&_scanner);
 381 
 382     return old;
 383   } else {
 384     // Forward-to-self failed. Either someone else managed to allocate
 385     // space for this object (old != forward_ptr) or they beat us in
 386     // self-forwarding it (old == forward_ptr).
 387     assert(old == forward_ptr || !_g1h->obj_in_cs(forward_ptr),
 388            "Object " PTR_FORMAT " forwarded to: " PTR_FORMAT " "
 389            "should not be in the CSet",
 390            p2i(old), p2i(forward_ptr));
 391     return forward_ptr;
 392   }
 393 }
 394