1/*
2 * Copyright (c) 2014, 2017, 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 "oops/oop.inline.hpp"
36#include "runtime/prefetch.inline.hpp"
37
38G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint worker_id, size_t young_cset_length)
39  : _g1h(g1h),
40    _refs(g1h->task_queue(worker_id)),
41    _dcq(&g1h->dirty_card_queue_set()),
42    _ct_bs(g1h->g1_barrier_set()),
43    _closures(NULL),
44    _hash_seed(17),
45    _worker_id(worker_id),
46    _tenuring_threshold(g1h->g1_policy()->tenuring_threshold()),
47    _age_table(false),
48    _scanner(g1h, this),
49    _old_gen_is_full(false)
50{
51  // we allocate G1YoungSurvRateNumRegions plus one entries, since
52  // we "sacrifice" entry 0 to keep track of surviving bytes for
53  // non-young regions (where the age is -1)
54  // We also add a few elements at the beginning and at the end in
55  // an attempt to eliminate cache contention
56  size_t real_length = 1 + young_cset_length;
57  size_t array_length = PADDING_ELEM_NUM +
58                      real_length +
59                      PADDING_ELEM_NUM;
60  _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
61  if (_surviving_young_words_base == NULL)
62    vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR,
63                          "Not enough space for young surv histo.");
64  _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
65  memset(_surviving_young_words, 0, real_length * sizeof(size_t));
66
67  _plab_allocator = G1PLABAllocator::create_allocator(_g1h->allocator());
68
69  _dest[InCSetState::NotInCSet]    = InCSetState::NotInCSet;
70  // The dest for Young is used when the objects are aged enough to
71  // need to be moved to the next space.
72  _dest[InCSetState::Young]        = InCSetState::Old;
73  _dest[InCSetState::Old]          = InCSetState::Old;
74
75  _closures = G1EvacuationRootClosures::create_root_closures(this, _g1h);
76}
77
78// Pass locally gathered statistics to global state.
79void G1ParScanThreadState::flush(size_t* surviving_young_words) {
80  _dcq.flush();
81  // Update allocation statistics.
82  _plab_allocator->flush_and_retire_stats();
83  _g1h->g1_policy()->record_age_table(&_age_table);
84
85  uint length = _g1h->collection_set()->young_region_length();
86  for (uint region_index = 0; region_index < length; region_index++) {
87    surviving_young_words[region_index] += _surviving_young_words[region_index];
88  }
89}
90
91G1ParScanThreadState::~G1ParScanThreadState() {
92  delete _plab_allocator;
93  delete _closures;
94  FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base);
95}
96
97void G1ParScanThreadState::waste(size_t& wasted, size_t& undo_wasted) {
98  _plab_allocator->waste(wasted, undo_wasted);
99}
100
101#ifdef ASSERT
102bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
103  assert(ref != NULL, "invariant");
104  assert(UseCompressedOops, "sanity");
105  assert(!has_partial_array_mask(ref), "ref=" PTR_FORMAT, p2i(ref));
106  oop p = oopDesc::load_decode_heap_oop(ref);
107  assert(_g1h->is_in_g1_reserved(p),
108         "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
109  return true;
110}
111
112bool G1ParScanThreadState::verify_ref(oop* ref) const {
113  assert(ref != NULL, "invariant");
114  if (has_partial_array_mask(ref)) {
115    // Must be in the collection set--it's already been copied.
116    oop p = clear_partial_array_mask(ref);
117    assert(_g1h->is_in_cset(p),
118           "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
119  } else {
120    oop p = oopDesc::load_decode_heap_oop(ref);
121    assert(_g1h->is_in_g1_reserved(p),
122           "ref=" PTR_FORMAT " p=" PTR_FORMAT, p2i(ref), p2i(p));
123  }
124  return true;
125}
126
127bool G1ParScanThreadState::verify_task(StarTask ref) const {
128  if (ref.is_narrow()) {
129    return verify_ref((narrowOop*) ref);
130  } else {
131    return verify_ref((oop*) ref);
132  }
133}
134#endif // ASSERT
135
136void G1ParScanThreadState::trim_queue() {
137  StarTask ref;
138  do {
139    // Drain the overflow stack first, so other threads can steal.
140    while (_refs->pop_overflow(ref)) {
141      if (!_refs->try_push_to_taskqueue(ref)) {
142        dispatch_reference(ref);
143      }
144    }
145
146    while (_refs->pop_local(ref)) {
147      dispatch_reference(ref);
148    }
149  } while (!_refs->is_empty());
150}
151
152HeapWord* G1ParScanThreadState::allocate_in_next_plab(InCSetState const state,
153                                                      InCSetState* dest,
154                                                      size_t word_sz,
155                                                      AllocationContext_t const context,
156                                                      bool previous_plab_refill_failed) {
157  assert(state.is_in_cset_or_humongous(), "Unexpected state: " CSETSTATE_FORMAT, state.value());
158  assert(dest->is_in_cset_or_humongous(), "Unexpected dest: " CSETSTATE_FORMAT, dest->value());
159
160  // Right now we only have two types of regions (young / old) so
161  // let's keep the logic here simple. We can generalize it when necessary.
162  if (dest->is_young()) {
163    bool plab_refill_in_old_failed = false;
164    HeapWord* const obj_ptr = _plab_allocator->allocate(InCSetState::Old,
165                                                        word_sz,
166                                                        context,
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
193InCSetState 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
204void G1ParScanThreadState::report_promotion_event(InCSetState const dest_state,
205                                                  oop const old, size_t word_sz, uint age,
206                                                  HeapWord * const obj_ptr,
207                                                  const AllocationContext_t context) const {
208  G1PLAB* alloc_buf = _plab_allocator->alloc_buffer(dest_state, context);
209  if (alloc_buf->contains(obj_ptr)) {
210    _g1h->_gc_tracer_stw->report_promotion_in_new_plab_event(old->klass(), word_sz, age,
211                                                             dest_state.value() == InCSetState::Old,
212                                                             alloc_buf->word_sz());
213  } else {
214    _g1h->_gc_tracer_stw->report_promotion_outside_plab_event(old->klass(), word_sz, age,
215                                                              dest_state.value() == InCSetState::Old);
216  }
217}
218
219oop G1ParScanThreadState::copy_to_survivor_space(InCSetState const state,
220                                                 oop const old,
221                                                 markOop const old_mark) {
222  const size_t word_sz = old->size();
223  HeapRegion* const from_region = _g1h->heap_region_containing(old);
224  // +1 to make the -1 indexes valid...
225  const int young_index = from_region->young_index_in_cset()+1;
226  assert( (from_region->is_young() && young_index >  0) ||
227         (!from_region->is_young() && young_index == 0), "invariant" );
228  const AllocationContext_t context = from_region->allocation_context();
229
230  uint age = 0;
231  InCSetState dest_state = next_state(state, old_mark, age);
232  // The second clause is to prevent premature evacuation failure in case there
233  // is still space in survivor, but old gen is full.
234  if (_old_gen_is_full && dest_state.is_old()) {
235    return handle_evacuation_failure_par(old, old_mark);
236  }
237  HeapWord* obj_ptr = _plab_allocator->plab_allocate(dest_state, word_sz, context);
238
239  // PLAB allocations should succeed most of the time, so we'll
240  // normally check against NULL once and that's it.
241  if (obj_ptr == NULL) {
242    bool plab_refill_failed = false;
243    obj_ptr = _plab_allocator->allocate_direct_or_new_plab(dest_state, word_sz, context, &plab_refill_failed);
244    if (obj_ptr == NULL) {
245      obj_ptr = allocate_in_next_plab(state, &dest_state, word_sz, context, plab_refill_failed);
246      if (obj_ptr == NULL) {
247        // This will either forward-to-self, or detect that someone else has
248        // installed a forwarding pointer.
249        return handle_evacuation_failure_par(old, old_mark);
250      }
251    }
252    if (_g1h->_gc_tracer_stw->should_report_promotion_events()) {
253      // The events are checked individually as part of the actual commit
254      report_promotion_event(dest_state, old, word_sz, age, obj_ptr, context);
255    }
256  }
257
258  assert(obj_ptr != NULL, "when we get here, allocation should have succeeded");
259  assert(_g1h->is_in_reserved(obj_ptr), "Allocated memory should be in the heap");
260
261#ifndef PRODUCT
262  // Should this evacuation fail?
263  if (_g1h->evacuation_should_fail()) {
264    // Doing this after all the allocation attempts also tests the
265    // undo_allocation() method too.
266    _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
267    return handle_evacuation_failure_par(old, old_mark);
268  }
269#endif // !PRODUCT
270
271  // We're going to allocate linearly, so might as well prefetch ahead.
272  Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
273
274  const oop obj = oop(obj_ptr);
275  const oop forward_ptr = old->forward_to_atomic(obj);
276  if (forward_ptr == NULL) {
277    Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
278
279    if (dest_state.is_young()) {
280      if (age < markOopDesc::max_age) {
281        age++;
282      }
283      if (old_mark->has_displaced_mark_helper()) {
284        // In this case, we have to install the mark word first,
285        // otherwise obj looks to be forwarded (the old mark word,
286        // which contains the forward pointer, was copied)
287        obj->set_mark(old_mark);
288        markOop new_mark = old_mark->displaced_mark_helper()->set_age(age);
289        old_mark->set_displaced_mark_helper(new_mark);
290      } else {
291        obj->set_mark(old_mark->set_age(age));
292      }
293      _age_table.add(age, word_sz);
294    } else {
295      obj->set_mark(old_mark);
296    }
297
298    if (G1StringDedup::is_enabled()) {
299      const bool is_from_young = state.is_young();
300      const bool is_to_young = dest_state.is_young();
301      assert(is_from_young == _g1h->heap_region_containing(old)->is_young(),
302             "sanity");
303      assert(is_to_young == _g1h->heap_region_containing(obj)->is_young(),
304             "sanity");
305      G1StringDedup::enqueue_from_evacuation(is_from_young,
306                                             is_to_young,
307                                             _worker_id,
308                                             obj);
309    }
310
311    _surviving_young_words[young_index] += word_sz;
312
313    if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
314      // We keep track of the next start index in the length field of
315      // the to-space object. The actual length can be found in the
316      // length field of the from-space object.
317      arrayOop(obj)->set_length(0);
318      oop* old_p = set_partial_array_mask(old);
319      push_on_queue(old_p);
320    } else {
321      HeapRegion* const to_region = _g1h->heap_region_containing(obj_ptr);
322      _scanner.set_region(to_region);
323      obj->oop_iterate_backwards(&_scanner);
324    }
325    return obj;
326  } else {
327    _plab_allocator->undo_allocation(dest_state, obj_ptr, word_sz, context);
328    return forward_ptr;
329  }
330}
331
332G1ParScanThreadState* G1ParScanThreadStateSet::state_for_worker(uint worker_id) {
333  assert(worker_id < _n_workers, "out of bounds access");
334  if (_states[worker_id] == NULL) {
335    _states[worker_id] = new_par_scan_state(worker_id, _young_cset_length);
336  }
337  return _states[worker_id];
338}
339
340const size_t* G1ParScanThreadStateSet::surviving_young_words() const {
341  assert(_flushed, "thread local state from the per thread states should have been flushed");
342  return _surviving_young_words_total;
343}
344
345void G1ParScanThreadStateSet::flush() {
346  assert(!_flushed, "thread local state from the per thread states should be flushed once");
347
348  for (uint worker_index = 0; worker_index < _n_workers; ++worker_index) {
349    G1ParScanThreadState* pss = _states[worker_index];
350
351    if (pss == NULL) {
352      continue;
353    }
354
355    pss->flush(_surviving_young_words_total);
356    delete pss;
357    _states[worker_index] = NULL;
358  }
359  _flushed = true;
360}
361
362oop G1ParScanThreadState::handle_evacuation_failure_par(oop old, markOop m) {
363  assert(_g1h->is_in_cset(old), "Object " PTR_FORMAT " should be in the CSet", p2i(old));
364
365  oop forward_ptr = old->forward_to_atomic(old);
366  if (forward_ptr == NULL) {
367    // Forward-to-self succeeded. We are the "owner" of the object.
368    HeapRegion* r = _g1h->heap_region_containing(old);
369
370    if (!r->evacuation_failed()) {
371      r->set_evacuation_failed(true);
372     _g1h->hr_printer()->evac_failure(r);
373    }
374
375    _g1h->preserve_mark_during_evac_failure(_worker_id, old, m);
376
377    _scanner.set_region(r);
378    old->oop_iterate_backwards(&_scanner);
379
380    return old;
381  } else {
382    // Forward-to-self failed. Either someone else managed to allocate
383    // space for this object (old != forward_ptr) or they beat us in
384    // self-forwarding it (old == forward_ptr).
385    assert(old == forward_ptr || !_g1h->is_in_cset(forward_ptr),
386           "Object " PTR_FORMAT " forwarded to: " PTR_FORMAT " "
387           "should not be in the CSet",
388           p2i(old), p2i(forward_ptr));
389    return forward_ptr;
390  }
391}
392
393