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     _plab_allocator(NULL),
  47     _age_table(false),
  48     _tenuring_threshold(g1h->g1_policy()->tenuring_threshold()),
  49     _scanner(g1h, this),
  50     _worker_id(worker_id),
  51     _stack_trim_upper_threshold(GCDrainStackTargetSize * 2 + 1),
  52     _stack_trim_lower_threshold(GCDrainStackTargetSize),
  53     _trim_ticks(),
  54     _old_gen_is_full(false)
  55 {
  56   // we allocate G1YoungSurvRateNumRegions plus one entries, since
  57   // we "sacrifice" entry 0 to keep track of surviving bytes for
  58   // non-young regions (where the age is -1)
  59   // We also add a few elements at the beginning and at the end in
  60   // an attempt to eliminate cache contention
  61   size_t real_length = 1 + young_cset_length;
  62   size_t array_length = PADDING_ELEM_NUM +
  63                       real_length +
  64                       PADDING_ELEM_NUM;
  65   _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
  66   if (_surviving_young_words_base == NULL)
  67     vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR,
  68                           "Not enough space for young surv histo.");
  69   _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
  70   memset(_surviving_young_words, 0, real_length * sizeof(size_t));
  71 
  72   _plab_allocator = new G1PLABAllocator(_g1h->allocator());
  73 
  74   _dest[InCSetState::NotInCSet]    = InCSetState::NotInCSet;
  75   // The dest for Young is used when the objects are aged enough to
  76   // need to be moved to the next space.
  77   _dest[InCSetState::Young]        = InCSetState::Old;
  78   _dest[InCSetState::Old]          = InCSetState::Old;
  79 
  80   _closures = G1EvacuationRootClosures::create_root_closures(this, _g1h);
  81 }
  82 
  83 // Pass locally gathered statistics to global state.
  84 void G1ParScanThreadState::flush(size_t* surviving_young_words) {
  85   _dcq.flush();
  86   // Update allocation statistics.
  87   _plab_allocator->flush_and_retire_stats();
  88   _g1h->g1_policy()->record_age_table(&_age_table);
  89 
  90   uint length = _g1h->collection_set()->young_region_length();
  91   for (uint region_index = 0; region_index < length; region_index++) {
  92     surviving_young_words[region_index] += _surviving_young_words[region_index];
  93   }
  94 }
  95 
  96 G1ParScanThreadState::~G1ParScanThreadState() {
  97   delete _plab_allocator;
  98   delete _closures;
  99   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base);
 100 }
 101 
 102 void G1ParScanThreadState::waste(size_t& wasted, size_t& undo_wasted) {
 103   _plab_allocator->waste(wasted, undo_wasted);
 104 }
 105 
 106 #ifdef ASSERT
 107 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
 108   assert(ref != NULL, "invariant");
 109   assert(UseCompressedOops, "sanity");
 110   assert(!has_partial_array_mask(ref), "ref=" PTR_FORMAT, p2i(ref));
 111   oop p = RawAccess<>::oop_load(ref);
 112   assert(_g1h->is_in_g1_reserved(p),
 113          "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
 114   return true;
 115 }
 116 
 117 bool G1ParScanThreadState::verify_ref(oop* ref) const {
 118   assert(ref != NULL, "invariant");
 119   if (has_partial_array_mask(ref)) {
 120     // Must be in the collection set--it's already been copied.
 121     oop p = clear_partial_array_mask(ref);
 122     assert(_g1h->is_in_cset(p),
 123            "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
 124   } else {
 125     oop p = RawAccess<>::oop_load(ref);
 126     assert(_g1h->is_in_g1_reserved(p),
 127            "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
 128   }
 129   return true;
 130 }
 131 
 132 bool G1ParScanThreadState::verify_task(StarTask ref) const {
 133   if (ref.is_narrow()) {
 134     return verify_ref((narrowOop*) ref);
 135   } else {
 136     return verify_ref((oop*) ref);
 137   }
 138 }
 139 #endif // ASSERT
 140 
 141 void G1ParScanThreadState::trim_queue() {
 142   StarTask ref;
 143   do {
 144     // Fully drain the queue.
 145     trim_queue_to_threshold(0);
 146   } while (!_refs->is_empty());
 147 }
 148 
 149 HeapWord* G1ParScanThreadState::allocate_in_next_plab(InCSetState const state,
 150                                                       InCSetState* dest,
 151                                                       size_t word_sz,
 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                                                         &plab_refill_in_old_failed);
 163     // Make sure that we won't attempt to copy any other objects out
 164     // of a survivor region (given that apparently we cannot allocate
 165     // any new ones) to avoid coming into this slow path again and again.
 166     // Only consider failed PLAB refill here: failed inline allocations are
 167     // typically large, so not indicative of remaining space.
 168     if (previous_plab_refill_failed) {
 169       _tenuring_threshold = 0;
 170     }
 171 
 172     if (obj_ptr != NULL) {
 173       dest->set_old();
 174     } else {
 175       // We just failed to allocate in old gen. The same idea as explained above
 176       // for making survivor gen unavailable for allocation applies for old gen.
 177       _old_gen_is_full = plab_refill_in_old_failed;
 178     }
 179     return obj_ptr;
 180   } else {
 181     _old_gen_is_full = previous_plab_refill_failed;
 182     assert(dest->is_old(), "Unexpected dest: " CSETSTATE_FORMAT, dest->value());
 183     // no other space to try.
 184     return NULL;
 185   }
 186 }
 187 
 188 InCSetState G1ParScanThreadState::next_state(InCSetState const state, markOop const m, uint& age) {
 189   if (state.is_young()) {
 190     age = !m->has_displaced_mark_helper() ? m->age()
 191                                           : m->displaced_mark_helper()->age();
 192     if (age < _tenuring_threshold) {
 193       return state;
 194     }
 195   }
 196   return dest(state);
 197 }
 198 
 199 void G1ParScanThreadState::report_promotion_event(InCSetState const dest_state,
 200                                                   oop const old, size_t word_sz, uint age,
 201                                                   HeapWord * const obj_ptr) const {
 202   PLAB* alloc_buf = _plab_allocator->alloc_buffer(dest_state);
 203   if (alloc_buf->contains(obj_ptr)) {
 204     _g1h->_gc_tracer_stw->report_promotion_in_new_plab_event(old->klass(), word_sz * HeapWordSize, age,
 205                                                              dest_state.value() == InCSetState::Old,
 206                                                              alloc_buf->word_sz() * HeapWordSize);
 207   } else {
 208     _g1h->_gc_tracer_stw->report_promotion_outside_plab_event(old->klass(), word_sz * HeapWordSize, age,
 209                                                               dest_state.value() == InCSetState::Old);
 210   }
 211 }
 212 
 213 oop G1ParScanThreadState::copy_to_survivor_space(InCSetState const state,
 214                                                  oop const old,
 215                                                  markOop const old_mark) {
 216   const size_t word_sz = old->size();
 217   HeapRegion* const from_region = _g1h->heap_region_containing(old);
 218   // +1 to make the -1 indexes valid...
 219   const int young_index = from_region->young_index_in_cset()+1;
 220   assert( (from_region->is_young() && young_index >  0) ||
 221          (!from_region->is_young() && young_index == 0), "invariant" );
 222 
 223   uint age = 0;
 224   InCSetState dest_state = next_state(state, old_mark, age);
 225   // The second clause is to prevent premature evacuation failure in case there
 226   // is still space in survivor, but old gen is full.
 227   if (_old_gen_is_full && dest_state.is_old()) {
 228     return handle_evacuation_failure_par(old, old_mark);
 229   }
 230   HeapWord* obj_ptr = _plab_allocator->plab_allocate(dest_state, word_sz);
 231 
 232   // PLAB allocations should succeed most of the time, so we'll
 233   // normally check against NULL once and that's it.
 234   if (obj_ptr == NULL) {
 235     bool plab_refill_failed = false;
 236     obj_ptr = _plab_allocator->allocate_direct_or_new_plab(dest_state, word_sz, &plab_refill_failed);
 237     if (obj_ptr == NULL) {
 238       obj_ptr = allocate_in_next_plab(state, &dest_state, word_sz, plab_refill_failed);
 239       if (obj_ptr == NULL) {
 240         // This will either forward-to-self, or detect that someone else has
 241         // installed a forwarding pointer.
 242         return handle_evacuation_failure_par(old, old_mark);
 243       }
 244     }
 245     if (_g1h->_gc_tracer_stw->should_report_promotion_events()) {
 246       // The events are checked individually as part of the actual commit
 247       report_promotion_event(dest_state, old, word_sz, age, obj_ptr);
 248     }
 249   }
 250 
 251   assert(obj_ptr != NULL, "when we get here, allocation should have succeeded");
 252   assert(_g1h->is_in_reserved(obj_ptr), "Allocated memory should be in the heap");
 253 
 254 #ifndef PRODUCT
 255   // Should this evacuation fail?
 256   if (_g1h->evacuation_should_fail()) {
 257     // Doing this after all the allocation attempts also tests the
 258     // undo_allocation() method too.
 259     _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz);
 260     return handle_evacuation_failure_par(old, old_mark);
 261   }
 262 #endif // !PRODUCT
 263 
 264   // We're going to allocate linearly, so might as well prefetch ahead.
 265   Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
 266 
 267   const oop obj = oop(obj_ptr);
 268   const oop forward_ptr = old->forward_to_atomic(obj, old_mark, memory_order_relaxed);
 269   if (forward_ptr == NULL) {
 270     Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
 271 
 272     if (dest_state.is_young()) {
 273       if (age < markOopDesc::max_age) {
 274         age++;
 275       }
 276       if (old_mark->has_displaced_mark_helper()) {
 277         // In this case, we have to install the mark word first,
 278         // otherwise obj looks to be forwarded (the old mark word,
 279         // which contains the forward pointer, was copied)
 280         obj->set_mark_raw(old_mark);
 281         markOop new_mark = old_mark->displaced_mark_helper()->set_age(age);
 282         old_mark->set_displaced_mark_helper(new_mark);
 283       } else {
 284         obj->set_mark_raw(old_mark->set_age(age));
 285       }
 286       _age_table.add(age, word_sz);
 287     } else {
 288       obj->set_mark_raw(old_mark);
 289     }
 290 
 291     if (G1StringDedup::is_enabled()) {
 292       const bool is_from_young = state.is_young();
 293       const bool is_to_young = dest_state.is_young();
 294       assert(is_from_young == _g1h->heap_region_containing(old)->is_young(),
 295              "sanity");
 296       assert(is_to_young == _g1h->heap_region_containing(obj)->is_young(),
 297              "sanity");
 298       G1StringDedup::enqueue_from_evacuation(is_from_young,
 299                                              is_to_young,
 300                                              _worker_id,
 301                                              obj);
 302     }
 303 
 304     _surviving_young_words[young_index] += word_sz;
 305 
 306     if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
 307       // We keep track of the next start index in the length field of
 308       // the to-space object. The actual length can be found in the
 309       // length field of the from-space object.
 310       arrayOop(obj)->set_length(0);
 311       oop* old_p = set_partial_array_mask(old);
 312       do_oop_partial_array(old_p);
 313     } else {
 314       HeapRegion* const to_region = _g1h->heap_region_containing(obj_ptr);
 315       _scanner.set_region(to_region);
 316       obj->oop_iterate_backwards(&_scanner);
 317     }
 318     return obj;
 319   } else {
 320     _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz);
 321     return forward_ptr;
 322   }
 323 }
 324 
 325 G1ParScanThreadState* G1ParScanThreadStateSet::state_for_worker(uint worker_id) {
 326   assert(worker_id < _n_workers, "out of bounds access");
 327   if (_states[worker_id] == NULL) {
 328     _states[worker_id] = new G1ParScanThreadState(_g1h, worker_id, _young_cset_length);
 329   }
 330   return _states[worker_id];
 331 }
 332 
 333 const size_t* G1ParScanThreadStateSet::surviving_young_words() const {
 334   assert(_flushed, "thread local state from the per thread states should have been flushed");
 335   return _surviving_young_words_total;
 336 }
 337 
 338 void G1ParScanThreadStateSet::flush() {
 339   assert(!_flushed, "thread local state from the per thread states should be flushed once");
 340 
 341   for (uint worker_index = 0; worker_index < _n_workers; ++worker_index) {
 342     G1ParScanThreadState* pss = _states[worker_index];
 343 
 344     if (pss == NULL) {
 345       continue;
 346     }
 347 
 348     pss->flush(_surviving_young_words_total);
 349     delete pss;
 350     _states[worker_index] = NULL;
 351   }
 352   _flushed = true;
 353 }
 354 
 355 oop G1ParScanThreadState::handle_evacuation_failure_par(oop old, markOop m) {
 356   assert(_g1h->is_in_cset(old), "Object " PTR_FORMAT " should be in the CSet", p2i(old));
 357 
 358   oop forward_ptr = old->forward_to_atomic(old, m, memory_order_relaxed);
 359   if (forward_ptr == NULL) {
 360     // Forward-to-self succeeded. We are the "owner" of the object.
 361     HeapRegion* r = _g1h->heap_region_containing(old);
 362 
 363     if (!r->evacuation_failed()) {
 364       r->set_evacuation_failed(true);
 365      _g1h->hr_printer()->evac_failure(r);
 366     }
 367 
 368     _g1h->preserve_mark_during_evac_failure(_worker_id, old, m);
 369 
 370     _scanner.set_region(r);
 371     old->oop_iterate_backwards(&_scanner);
 372 
 373     return old;
 374   } else {
 375     // Forward-to-self failed. Either someone else managed to allocate
 376     // space for this object (old != forward_ptr) or they beat us in
 377     // self-forwarding it (old == forward_ptr).
 378     assert(old == forward_ptr || !_g1h->is_in_cset(forward_ptr),
 379            "Object " PTR_FORMAT " forwarded to: " PTR_FORMAT " "
 380            "should not be in the CSet",
 381            p2i(old), p2i(forward_ptr));
 382     return forward_ptr;
 383   }
 384 }
 385 G1ParScanThreadStateSet::G1ParScanThreadStateSet(G1CollectedHeap* g1h, uint n_workers, size_t young_cset_length) :
 386     _g1h(g1h),
 387     _states(NEW_C_HEAP_ARRAY(G1ParScanThreadState*, n_workers, mtGC)),
 388     _surviving_young_words_total(NEW_C_HEAP_ARRAY(size_t, young_cset_length, mtGC)),
 389     _young_cset_length(young_cset_length),
 390     _n_workers(n_workers),
 391     _flushed(false) {
 392   for (uint i = 0; i < n_workers; ++i) {
 393     _states[i] = NULL;
 394   }
 395   memset(_surviving_young_words_total, 0, young_cset_length * sizeof(size_t));
 396 }
 397 
 398 G1ParScanThreadStateSet::~G1ParScanThreadStateSet() {
 399   assert(_flushed, "thread local state from the per thread states should have been flushed");
 400   FREE_C_HEAP_ARRAY(G1ParScanThreadState*, _states);
 401   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_total);
 402 }