1 /*
   2  * Copyright (c) 2014, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/g1/g1Allocator.inline.hpp"
  27 #include "gc/g1/g1CollectedHeap.inline.hpp"
  28 #include "gc/g1/g1CollectionSet.hpp"
  29 #include "gc/g1/g1OopClosures.inline.hpp"
  30 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  31 #include "gc/g1/g1RootClosures.hpp"
  32 #include "gc/g1/g1StringDedup.hpp"
  33 #include "gc/shared/gcTrace.hpp"
  34 #include "gc/shared/taskqueue.inline.hpp"
  35 #include "memory/allocation.inline.hpp"
  36 #include "oops/access.inline.hpp"
  37 #include "oops/oop.inline.hpp"
  38 #include "runtime/prefetch.inline.hpp"
  39 
  40 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint worker_id, size_t young_cset_length)
  41   : _g1h(g1h),
  42     _refs(g1h->task_queue(worker_id)),
  43     _dcq(&g1h->dirty_card_queue_set()),
  44     _ct(g1h->card_table()),
  45     _closures(NULL),
  46     _hash_seed(17),
  47     _worker_id(worker_id),
  48     _tenuring_threshold(g1h->g1_policy()->tenuring_threshold()),
  49     _age_table(false),
  50     _scanner(g1h, this),
  51     _old_gen_is_full(false)
  52 {
  53   // we allocate G1YoungSurvRateNumRegions plus one entries, since
  54   // we "sacrifice" entry 0 to keep track of surviving bytes for
  55   // non-young regions (where the age is -1)
  56   // We also add a few elements at the beginning and at the end in
  57   // an attempt to eliminate cache contention
  58   size_t real_length = 1 + young_cset_length;
  59   size_t array_length = PADDING_ELEM_NUM +
  60                       real_length +
  61                       PADDING_ELEM_NUM;
  62   _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
  63   if (_surviving_young_words_base == NULL)
  64     vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR,
  65                           "Not enough space for young surv histo.");
  66   _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
  67   memset(_surviving_young_words, 0, real_length * sizeof(size_t));
  68 
  69   _plab_allocator = new G1PLABAllocator(_g1h->allocator());
  70 
  71   _dest[InCSetState::NotInCSet]    = InCSetState::NotInCSet;
  72   // The dest for Young is used when the objects are aged enough to
  73   // need to be moved to the next space.
  74   _dest[InCSetState::Young]        = InCSetState::Old;
  75   _dest[InCSetState::Old]          = InCSetState::Old;
  76 
  77   _closures = G1EvacuationRootClosures::create_root_closures(this, _g1h);
  78 }
  79 
  80 // Pass locally gathered statistics to global state.
  81 void G1ParScanThreadState::flush(size_t* surviving_young_words) {
  82   _dcq.flush();
  83   // Update allocation statistics.
  84   _plab_allocator->flush_and_retire_stats();
  85   _g1h->g1_policy()->record_age_table(&_age_table);
  86 
  87   uint length = _g1h->collection_set()->young_region_length();
  88   for (uint region_index = 0; region_index < length; region_index++) {
  89     surviving_young_words[region_index] += _surviving_young_words[region_index];
  90   }
  91 }
  92 
  93 G1ParScanThreadState::~G1ParScanThreadState() {
  94   delete _plab_allocator;
  95   delete _closures;
  96   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base);
  97 }
  98 
  99 void G1ParScanThreadState::waste(size_t& wasted, size_t& undo_wasted) {
 100   _plab_allocator->waste(wasted, undo_wasted);
 101 }
 102 
 103 #ifdef ASSERT
 104 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
 105   assert(ref != NULL, "invariant");
 106   assert(UseCompressedOops, "sanity");
 107   assert(!has_partial_array_mask(ref), "ref=" PTR_FORMAT, p2i(ref));
 108   oop p = RawAccess<>::oop_load(ref);
 109   assert(_g1h->is_in_g1_reserved(p),
 110          "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
 111   return true;
 112 }
 113 
 114 bool G1ParScanThreadState::verify_ref(oop* ref) const {
 115   assert(ref != NULL, "invariant");
 116   if (has_partial_array_mask(ref)) {
 117     // Must be in the collection set--it's already been copied.
 118     oop p = clear_partial_array_mask(ref);
 119     assert(_g1h->is_in_cset(p),
 120            "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
 121   } else {
 122     oop p = RawAccess<>::oop_load(ref);
 123     assert(_g1h->is_in_g1_reserved(p),
 124            "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
 125   }
 126   return true;
 127 }
 128 
 129 bool G1ParScanThreadState::verify_task(StarTask ref) const {
 130   if (ref.is_narrow()) {
 131     return verify_ref((narrowOop*) ref);
 132   } else {
 133     return verify_ref((oop*) ref);
 134   }
 135 }
 136 #endif // ASSERT
 137 
 138 void G1ParScanThreadState::trim_queue() {
 139   StarTask ref;
 140   do {
 141     // Drain the overflow stack first, so other threads can steal.
 142     while (_refs->pop_overflow(ref)) {
 143       if (!_refs->try_push_to_taskqueue(ref)) {
 144         dispatch_reference(ref);
 145       }
 146     }
 147 
 148     while (_refs->pop_local(ref)) {
 149       dispatch_reference(ref);
 150     }
 151   } while (!_refs->is_empty());
 152 }
 153 
 154 HeapWord* G1ParScanThreadState::allocate_in_next_plab(InCSetState const state,
 155                                                       InCSetState* dest,
 156                                                       size_t word_sz,
 157                                                       bool previous_plab_refill_failed) {
 158   assert(state.is_in_cset_or_humongous(), "Unexpected state: " CSETSTATE_FORMAT, state.value());
 159   assert(dest->is_in_cset_or_humongous(), "Unexpected dest: " CSETSTATE_FORMAT, dest->value());
 160 
 161   // Right now we only have two types of regions (young / old) so
 162   // let's keep the logic here simple. We can generalize it when necessary.
 163   if (dest->is_young()) {
 164     bool plab_refill_in_old_failed = false;
 165     HeapWord* const obj_ptr = _plab_allocator->allocate(InCSetState::Old,
 166                                                         word_sz,
 167                                                         &plab_refill_in_old_failed);
 168     // Make sure that we won't attempt to copy any other objects out
 169     // of a survivor region (given that apparently we cannot allocate
 170     // any new ones) to avoid coming into this slow path again and again.
 171     // Only consider failed PLAB refill here: failed inline allocations are
 172     // typically large, so not indicative of remaining space.
 173     if (previous_plab_refill_failed) {
 174       _tenuring_threshold = 0;
 175     }
 176 
 177     if (obj_ptr != NULL) {
 178       dest->set_old();
 179     } else {
 180       // We just failed to allocate in old gen. The same idea as explained above
 181       // for making survivor gen unavailable for allocation applies for old gen.
 182       _old_gen_is_full = plab_refill_in_old_failed;
 183     }
 184     return obj_ptr;
 185   } else {
 186     _old_gen_is_full = previous_plab_refill_failed;
 187     assert(dest->is_old(), "Unexpected dest: " CSETSTATE_FORMAT, dest->value());
 188     // no other space to try.
 189     return NULL;
 190   }
 191 }
 192 
 193 InCSetState G1ParScanThreadState::next_state(InCSetState const state, markOop const m, uint& age) {
 194   if (state.is_young()) {
 195     age = !m->has_displaced_mark_helper() ? m->age()
 196                                           : m->displaced_mark_helper()->age();
 197     if (age < _tenuring_threshold) {
 198       return state;
 199     }
 200   }
 201   return dest(state);
 202 }
 203 
 204 void G1ParScanThreadState::report_promotion_event(InCSetState const dest_state,
 205                                                   oop const old, size_t word_sz, uint age,
 206                                                   HeapWord * const obj_ptr) const {
 207   PLAB* alloc_buf = _plab_allocator->alloc_buffer(dest_state);
 208   if (alloc_buf->contains(obj_ptr)) {
 209     _g1h->_gc_tracer_stw->report_promotion_in_new_plab_event(old->klass(), word_sz, age,
 210                                                              dest_state.value() == InCSetState::Old,
 211                                                              alloc_buf->word_sz());
 212   } else {
 213     _g1h->_gc_tracer_stw->report_promotion_outside_plab_event(old->klass(), word_sz, age,
 214                                                               dest_state.value() == InCSetState::Old);
 215   }
 216 }
 217 
 218 oop G1ParScanThreadState::copy_to_survivor_space(InCSetState const state,
 219                                                  oop const old,
 220                                                  markOop const old_mark) {
 221   const size_t word_sz = old->size();
 222   HeapRegion* const from_region = _g1h->heap_region_containing(old);
 223   // +1 to make the -1 indexes valid...
 224   const int young_index = from_region->young_index_in_cset()+1;
 225   assert( (from_region->is_young() && young_index >  0) ||
 226          (!from_region->is_young() && young_index == 0), "invariant" );
 227 
 228   uint age = 0;
 229   InCSetState dest_state = next_state(state, old_mark, age);
 230   // The second clause is to prevent premature evacuation failure in case there
 231   // is still space in survivor, but old gen is full.
 232   if (_old_gen_is_full && dest_state.is_old()) {
 233     return handle_evacuation_failure_par(old, old_mark);
 234   }
 235   HeapWord* obj_ptr = _plab_allocator->plab_allocate(dest_state, word_sz);
 236 
 237   // PLAB allocations should succeed most of the time, so we'll
 238   // normally check against NULL once and that's it.
 239   if (obj_ptr == NULL) {
 240     bool plab_refill_failed = false;
 241     obj_ptr = _plab_allocator->allocate_direct_or_new_plab(dest_state, word_sz, &plab_refill_failed);
 242     if (obj_ptr == NULL) {
 243       obj_ptr = allocate_in_next_plab(state, &dest_state, word_sz, plab_refill_failed);
 244       if (obj_ptr == NULL) {
 245         // This will either forward-to-self, or detect that someone else has
 246         // installed a forwarding pointer.
 247         return handle_evacuation_failure_par(old, old_mark);
 248       }
 249     }
 250     if (_g1h->_gc_tracer_stw->should_report_promotion_events()) {
 251       // The events are checked individually as part of the actual commit
 252       report_promotion_event(dest_state, old, word_sz, age, obj_ptr);
 253     }
 254   }
 255 
 256   assert(obj_ptr != NULL, "when we get here, allocation should have succeeded");
 257   assert(_g1h->is_in_reserved(obj_ptr), "Allocated memory should be in the heap");
 258 
 259 #ifndef PRODUCT
 260   // Should this evacuation fail?
 261   if (_g1h->evacuation_should_fail()) {
 262     // Doing this after all the allocation attempts also tests the
 263     // undo_allocation() method too.
 264     _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz);
 265     return handle_evacuation_failure_par(old, old_mark);
 266   }
 267 #endif // !PRODUCT
 268 
 269   // We're going to allocate linearly, so might as well prefetch ahead.
 270   Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
 271 
 272   const oop obj = oop(obj_ptr);
 273   const oop forward_ptr = old->forward_to_atomic(obj);
 274   if (forward_ptr == NULL) {
 275     Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
 276 
 277     if (dest_state.is_young()) {
 278       if (age < markOopDesc::max_age) {
 279         age++;
 280       }
 281       if (old_mark->has_displaced_mark_helper()) {
 282         // In this case, we have to install the mark word first,
 283         // otherwise obj looks to be forwarded (the old mark word,
 284         // which contains the forward pointer, was copied)
 285         obj->set_mark_raw(old_mark);
 286         markOop new_mark = old_mark->displaced_mark_helper()->set_age(age);
 287         old_mark->set_displaced_mark_helper(new_mark);
 288       } else {
 289         obj->set_mark_raw(old_mark->set_age(age));
 290       }
 291       _age_table.add(age, word_sz);
 292     } else {
 293       obj->set_mark_raw(old_mark);
 294     }
 295 
 296     if (G1StringDedup::is_enabled()) {
 297       const bool is_from_young = state.is_young();
 298       const bool is_to_young = dest_state.is_young();
 299       assert(is_from_young == _g1h->heap_region_containing(old)->is_young(),
 300              "sanity");
 301       assert(is_to_young == _g1h->heap_region_containing(obj)->is_young(),
 302              "sanity");
 303       G1StringDedup::enqueue_from_evacuation(is_from_young,
 304                                              is_to_young,
 305                                              _worker_id,
 306                                              obj);
 307     }
 308 
 309     _surviving_young_words[young_index] += word_sz;
 310 
 311     if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
 312       // We keep track of the next start index in the length field of
 313       // the to-space object. The actual length can be found in the
 314       // length field of the from-space object.
 315       arrayOop(obj)->set_length(0);
 316       oop* old_p = set_partial_array_mask(old);
 317       push_on_queue(old_p);
 318     } else {
 319       HeapRegion* const to_region = _g1h->heap_region_containing(obj_ptr);
 320       _scanner.set_region(to_region);
 321       obj->oop_iterate_backwards(&_scanner);
 322     }
 323     return obj;
 324   } else {
 325     _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz);
 326     return forward_ptr;
 327   }
 328 }
 329 
 330 G1ParScanThreadState* G1ParScanThreadStateSet::state_for_worker(uint worker_id) {
 331   assert(worker_id < _n_workers, "out of bounds access");
 332   if (_states[worker_id] == NULL) {
 333     _states[worker_id] = new G1ParScanThreadState(_g1h, worker_id, _young_cset_length);
 334   }
 335   return _states[worker_id];
 336 }
 337 
 338 const size_t* G1ParScanThreadStateSet::surviving_young_words() const {
 339   assert(_flushed, "thread local state from the per thread states should have been flushed");
 340   return _surviving_young_words_total;
 341 }
 342 
 343 void G1ParScanThreadStateSet::flush() {
 344   assert(!_flushed, "thread local state from the per thread states should be flushed once");
 345 
 346   for (uint worker_index = 0; worker_index < _n_workers; ++worker_index) {
 347     G1ParScanThreadState* pss = _states[worker_index];
 348 
 349     if (pss == NULL) {
 350       continue;
 351     }
 352 
 353     pss->flush(_surviving_young_words_total);
 354     delete pss;
 355     _states[worker_index] = NULL;
 356   }
 357   _flushed = true;
 358 }
 359 
 360 oop G1ParScanThreadState::handle_evacuation_failure_par(oop old, markOop m) {
 361   assert(_g1h->is_in_cset(old), "Object " PTR_FORMAT " should be in the CSet", p2i(old));
 362 
 363   oop forward_ptr = old->forward_to_atomic(old);
 364   if (forward_ptr == NULL) {
 365     // Forward-to-self succeeded. We are the "owner" of the object.
 366     HeapRegion* r = _g1h->heap_region_containing(old);
 367 
 368     if (!r->evacuation_failed()) {
 369       r->set_evacuation_failed(true);
 370      _g1h->hr_printer()->evac_failure(r);
 371     }
 372 
 373     _g1h->preserve_mark_during_evac_failure(_worker_id, old, m);
 374 
 375     _scanner.set_region(r);
 376     old->oop_iterate_backwards(&_scanner);
 377 
 378     return old;
 379   } else {
 380     // Forward-to-self failed. Either someone else managed to allocate
 381     // space for this object (old != forward_ptr) or they beat us in
 382     // self-forwarding it (old == forward_ptr).
 383     assert(old == forward_ptr || !_g1h->is_in_cset(forward_ptr),
 384            "Object " PTR_FORMAT " forwarded to: " PTR_FORMAT " "
 385            "should not be in the CSet",
 386            p2i(old), p2i(forward_ptr));
 387     return forward_ptr;
 388   }
 389 }
 390 G1ParScanThreadStateSet::G1ParScanThreadStateSet(G1CollectedHeap* g1h, uint n_workers, size_t young_cset_length) :
 391     _g1h(g1h),
 392     _states(NEW_C_HEAP_ARRAY(G1ParScanThreadState*, n_workers, mtGC)),
 393     _surviving_young_words_total(NEW_C_HEAP_ARRAY(size_t, young_cset_length, mtGC)),
 394     _young_cset_length(young_cset_length),
 395     _n_workers(n_workers),
 396     _flushed(false) {
 397   for (uint i = 0; i < n_workers; ++i) {
 398     _states[i] = NULL;
 399   }
 400   memset(_surviving_young_words_total, 0, young_cset_length * sizeof(size_t));
 401 }
 402 
 403 G1ParScanThreadStateSet::~G1ParScanThreadStateSet() {
 404   assert(_flushed, "thread local state from the per thread states should have been flushed");
 405   FREE_C_HEAP_ARRAY(G1ParScanThreadState*, _states);
 406   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_total);
 407 }