1 /*
  2  * Copyright (c) 2016, 2019, 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/g1CollectedHeap.inline.hpp"
 27 #include "gc/g1/g1CollectionSet.hpp"
 28 #include "gc/g1/g1CollectionSetCandidates.hpp"
 29 #include "gc/g1/g1CollectorState.hpp"
 30 #include "gc/g1/g1ParScanThreadState.hpp"
 31 #include "gc/g1/g1Policy.hpp"
 32 #include "gc/g1/heapRegion.inline.hpp"
 33 #include "gc/g1/heapRegionRemSet.hpp"
 34 #include "gc/g1/heapRegionSet.hpp"
 35 #include "logging/logStream.hpp"
 36 #include "utilities/debug.hpp"
 37 #include "utilities/globalDefinitions.hpp"
 38 #include "utilities/quickSort.hpp"
 39 
 40 G1CollectorState* G1CollectionSet::collector_state() {
 41   return _g1h->collector_state();
 42 }
 43 
 44 G1GCPhaseTimes* G1CollectionSet::phase_times() {
 45   return _policy->phase_times();
 46 }
 47 
 48 double G1CollectionSet::predict_region_elapsed_time_ms(HeapRegion* hr) {
 49   return _policy->predict_region_elapsed_time_ms(hr, collector_state()->in_young_only_phase());
 50 }
 51 
 52 G1CollectionSet::G1CollectionSet(G1CollectedHeap* g1h, G1Policy* policy) :
 53   _g1h(g1h),
 54   _policy(policy),
 55   _candidates(NULL),
 56   _eden_region_length(0),
 57   _survivor_region_length(0),
 58   _old_region_length(0),
 59   _collection_set_regions(NULL),
 60   _collection_set_cur_length(0),
 61   _collection_set_max_length(0),
 62   _num_optional_regions(0),
 63   _bytes_used_before(0),
 64   _recorded_rs_length(0),
 65   _inc_build_state(Inactive),
 66   _inc_part_start(0),
 67   _inc_bytes_used_before(0),
 68   _inc_recorded_rs_length(0),
 69   _inc_recorded_rs_length_diff(0),
 70   _inc_predicted_elapsed_time_ms(0.0),
 71   _inc_predicted_elapsed_time_ms_diff(0.0) {
 72 }
 73 
 74 G1CollectionSet::~G1CollectionSet() {
 75   FREE_C_HEAP_ARRAY(uint, _collection_set_regions);


 76   free_optional_regions();
 77   clear_candidates();
 78 }
 79 
 80 void G1CollectionSet::init_region_lengths(uint eden_cset_region_length,
 81                                           uint survivor_cset_region_length) {
 82   assert_at_safepoint_on_vm_thread();
 83 
 84   _eden_region_length     = eden_cset_region_length;
 85   _survivor_region_length = survivor_cset_region_length;
 86 
 87   assert((size_t) young_region_length() == _collection_set_cur_length,
 88          "Young region length %u should match collection set length " SIZE_FORMAT, young_region_length(), _collection_set_cur_length);
 89 
 90   _old_region_length = 0;
 91   free_optional_regions();
 92 }
 93 
 94 void G1CollectionSet::initialize(uint max_region_length) {
 95   guarantee(_collection_set_regions == NULL, "Must only initialize once.");
 96   _collection_set_max_length = max_region_length;
 97   _collection_set_regions = NEW_C_HEAP_ARRAY(uint, max_region_length, mtGC);
 98 }
 99 
100 void G1CollectionSet::free_optional_regions() {
101   _num_optional_regions = 0;
102 }
103 
104 void G1CollectionSet::clear_candidates() {
105   delete _candidates;
106   _candidates = NULL;
107 }
108 
109 void G1CollectionSet::set_recorded_rs_length(size_t rs_length) {
110   _recorded_rs_length = rs_length;
111 }
112 
113 // Add the heap region at the head of the non-incremental collection set
114 void G1CollectionSet::add_old_region(HeapRegion* hr) {
115   assert_at_safepoint_on_vm_thread();
116 
117   assert(_inc_build_state == Active,
118          "Precondition, actively building cset or adding optional later on");
119   assert(hr->is_old(), "the region should be old");
120 
121   assert(!hr->in_collection_set(), "should not already be in the collection set");
122   _g1h->register_old_region_with_region_attr(hr);
123 
124   _collection_set_regions[_collection_set_cur_length++] = hr->hrm_index();
125   assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set now larger than maximum size.");
126 
127   _bytes_used_before += hr->used();
128   _recorded_rs_length += hr->rem_set()->occupied();
129   _old_region_length++;
130 
131   _g1h->old_set_remove(hr);
132 }
133 
134 void G1CollectionSet::add_optional_region(HeapRegion* hr) {
135   assert(hr->is_old(), "the region should be old");
136   assert(!hr->in_collection_set(), "should not already be in the CSet");
137 
138   _g1h->register_optional_region_with_region_attr(hr);
139 
140   hr->set_index_in_opt_cset(_num_optional_regions++);
141 }
142 
143 void G1CollectionSet::start_incremental_building() {
144   assert(_collection_set_cur_length == 0, "Collection set must be empty before starting a new collection set.");
145   assert(_inc_build_state == Inactive, "Precondition");
146 
147   _inc_bytes_used_before = 0;
148 
149   _inc_recorded_rs_length = 0;
150   _inc_recorded_rs_length_diff = 0;
151   _inc_predicted_elapsed_time_ms = 0.0;
152   _inc_predicted_elapsed_time_ms_diff = 0.0;
153 
154   update_incremental_marker();
155 }
156 
157 void G1CollectionSet::finalize_incremental_building() {
158   assert(_inc_build_state == Active, "Precondition");
159   assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
160 
161   // The two "main" fields, _inc_recorded_rs_length and
162   // _inc_predicted_elapsed_time_ms, are updated by the thread
163   // that adds a new region to the CSet. Further updates by the
164   // concurrent refinement thread that samples the young RSet lengths
165   // are accumulated in the *_diff fields. Here we add the diffs to
166   // the "main" fields.
167 
168   if (_inc_recorded_rs_length_diff >= 0) {
169     _inc_recorded_rs_length += _inc_recorded_rs_length_diff;
170   } else {
171     // This is defensive. The diff should in theory be always positive
172     // as RSets can only grow between GCs. However, given that we
173     // sample their size concurrently with other threads updating them
174     // it's possible that we might get the wrong size back, which
175     // could make the calculations somewhat inaccurate.
176     size_t diffs = (size_t) (-_inc_recorded_rs_length_diff);
177     if (_inc_recorded_rs_length >= diffs) {
178       _inc_recorded_rs_length -= diffs;
179     } else {
180       _inc_recorded_rs_length = 0;
181     }
182   }
183   _inc_predicted_elapsed_time_ms += _inc_predicted_elapsed_time_ms_diff;
184 
185   _inc_recorded_rs_length_diff = 0;
186   _inc_predicted_elapsed_time_ms_diff = 0.0;
187 }
188 
189 void G1CollectionSet::clear() {
190   assert_at_safepoint_on_vm_thread();
191   _collection_set_cur_length = 0;
192 }
193 
194 void G1CollectionSet::iterate(HeapRegionClosure* cl) const {
195   size_t len = _collection_set_cur_length;
196   OrderAccess::loadload();
197 
198   for (uint i = 0; i < len; i++) {
199     HeapRegion* r = _g1h->region_at(_collection_set_regions[i]);
200     bool result = cl->do_heap_region(r);
201     if (result) {
202       cl->set_incomplete();
203       return;
204     }
205   }
206 }
207 
208 void G1CollectionSet::iterate_optional(HeapRegionClosure* cl) const {
209   assert_at_safepoint();
210 
211   for (uint i = 0; i < _num_optional_regions; i++) {
212     HeapRegion* r = _candidates->at(i);
213     bool result = cl->do_heap_region(r);
214     guarantee(!result, "Must not cancel iteration");
215   }
216 }
217 
218 void G1CollectionSet::iterate_incremental_part_from(HeapRegionClosure* cl,
219                                                     HeapRegionClaimer* hr_claimer,
220                                                     uint worker_id,
221                                                     uint total_workers) const {
222   assert_at_safepoint();
223 
224   size_t len = increment_length();
225   if (len == 0) {
226     return;
227   }
228 
229   size_t start_pos = (worker_id * len) / total_workers;
230   size_t cur_pos = start_pos;
231 
232   do {
233     uint region_idx = _collection_set_regions[cur_pos + _inc_part_start];
234     if (hr_claimer == NULL || hr_claimer->claim_region(region_idx)) {
235       HeapRegion* r = _g1h->region_at(region_idx);
236       bool result = cl->do_heap_region(r);
237       guarantee(!result, "Must not cancel iteration");
238     }
239 
240     cur_pos++;
241     if (cur_pos == len) {
242       cur_pos = 0;
243     }
244   } while (cur_pos != start_pos);
245 }
246 
247 void G1CollectionSet::update_young_region_prediction(HeapRegion* hr,
248                                                      size_t new_rs_length) {
249   // Update the CSet information that is dependent on the new RS length
250   assert(hr->is_young(), "Precondition");
251   assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint");
252 
253   // We could have updated _inc_recorded_rs_length and
254   // _inc_predicted_elapsed_time_ms directly but we'd need to do
255   // that atomically, as this code is executed by a concurrent
256   // refinement thread, potentially concurrently with a mutator thread
257   // allocating a new region and also updating the same fields. To
258   // avoid the atomic operations we accumulate these updates on two
259   // separate fields (*_diff) and we'll just add them to the "main"
260   // fields at the start of a GC.
261 
262   ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length();
263   ssize_t rs_length_diff = (ssize_t) new_rs_length - old_rs_length;
264   _inc_recorded_rs_length_diff += rs_length_diff;
265 
266   double old_elapsed_time_ms = hr->predicted_elapsed_time_ms();
267   double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
268   double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms;
269   _inc_predicted_elapsed_time_ms_diff += elapsed_ms_diff;
270 
271   hr->set_recorded_rs_length(new_rs_length);
272   hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms);
273 }
274 
275 void G1CollectionSet::add_young_region_common(HeapRegion* hr) {
276   assert(hr->is_young(), "invariant");
277   assert(_inc_build_state == Active, "Precondition");
278 
279   size_t collection_set_length = _collection_set_cur_length;
280   // We use UINT_MAX as "invalid" marker in verification.
281   assert(collection_set_length < (UINT_MAX - 1),
282          "Collection set is too large with " SIZE_FORMAT " entries", collection_set_length);
283   hr->set_young_index_in_cset((uint)collection_set_length + 1);
284 
285   _collection_set_regions[collection_set_length] = hr->hrm_index();
286   // Concurrent readers must observe the store of the value in the array before an
287   // update to the length field.
288   OrderAccess::storestore();
289   _collection_set_cur_length++;
290   assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set larger than maximum allowed.");
291 
292   // This routine is used when:
293   // * adding survivor regions to the incremental cset at the end of an
294   //   evacuation pause or
295   // * adding the current allocation region to the incremental cset
296   //   when it is retired.
297   // Therefore this routine may be called at a safepoint by the
298   // VM thread, or in-between safepoints by mutator threads (when
299   // retiring the current allocation region)
300   // We need to clear and set the cached recorded/cached collection set
301   // information in the heap region here (before the region gets added
302   // to the collection set). An individual heap region's cached values
303   // are calculated, aggregated with the policy collection set info,
304   // and cached in the heap region here (initially) and (subsequently)
305   // by the Young List sampling code.
306   // Ignore calls to this due to retirement during full gc.
307 
308   if (!_g1h->collector_state()->in_full_gc()) {
309     size_t rs_length = hr->rem_set()->occupied();
310     double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
311 
312     // Cache the values we have added to the aggregated information
313     // in the heap region in case we have to remove this region from
314     // the incremental collection set, or it is updated by the
315     // rset sampling code
316     hr->set_recorded_rs_length(rs_length);
317     hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms);
318 
319     _inc_recorded_rs_length += rs_length;
320     _inc_predicted_elapsed_time_ms += region_elapsed_time_ms;
321     _inc_bytes_used_before += hr->used();
322   }
323 
324   assert(!hr->in_collection_set(), "invariant");
325   _g1h->register_young_region_with_region_attr(hr);
326 }
327 
328 void G1CollectionSet::add_survivor_regions(HeapRegion* hr) {
329   assert(hr->is_survivor(), "Must only add survivor regions, but is %s", hr->get_type_str());
330   add_young_region_common(hr);
331 }
332 
333 void G1CollectionSet::add_eden_region(HeapRegion* hr) {
334   assert(hr->is_eden(), "Must only add eden regions, but is %s", hr->get_type_str());
335   add_young_region_common(hr);
336 }
337 
338 #ifndef PRODUCT
339 class G1VerifyYoungAgesClosure : public HeapRegionClosure {
340 public:
341   bool _valid;
342 public:
343   G1VerifyYoungAgesClosure() : HeapRegionClosure(), _valid(true) { }
344 
345   virtual bool do_heap_region(HeapRegion* r) {
346     guarantee(r->is_young(), "Region must be young but is %s", r->get_type_str());
347 
348     SurvRateGroup* group = r->surv_rate_group();
349 
350     if (group == NULL) {
351       log_error(gc, verify)("## encountered NULL surv_rate_group in young region");
352       _valid = false;
353     }
354 
355     if (r->age_in_surv_rate_group() < 0) {
356       log_error(gc, verify)("## encountered negative age in young region");
357       _valid = false;
358     }
359 
360     return false;
361   }
362 
363   bool valid() const { return _valid; }
364 };
365 
366 bool G1CollectionSet::verify_young_ages() {
367   assert_at_safepoint_on_vm_thread();
368 
369   G1VerifyYoungAgesClosure cl;
370   iterate(&cl);
371 
372   if (!cl.valid()) {
373     LogStreamHandle(Error, gc, verify) log;
374     print(&log);
375   }
376 
377   return cl.valid();
378 }
379 
380 class G1PrintCollectionSetDetailClosure : public HeapRegionClosure {
381   outputStream* _st;
382 public:
383   G1PrintCollectionSetDetailClosure(outputStream* st) : HeapRegionClosure(), _st(st) { }
384 
385   virtual bool do_heap_region(HeapRegion* r) {
386     assert(r->in_collection_set(), "Region %u should be in collection set", r->hrm_index());
387     _st->print_cr("  " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d",
388                   HR_FORMAT_PARAMS(r),
389                   p2i(r->prev_top_at_mark_start()),
390                   p2i(r->next_top_at_mark_start()),
391                   r->age_in_surv_rate_group_cond());
392     return false;
393   }
394 };
395 
396 void G1CollectionSet::print(outputStream* st) {
397   st->print_cr("\nCollection_set:");
398 
399   G1PrintCollectionSetDetailClosure cl(st);
400   iterate(&cl);
401 }
402 #endif // !PRODUCT
403 
404 double G1CollectionSet::finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors) {
405   double young_start_time_sec = os::elapsedTime();
406 
407   finalize_incremental_building();
408 
409   guarantee(target_pause_time_ms > 0.0,
410             "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms);
411 
412   size_t pending_cards = _policy->pending_cards();
413   double base_time_ms = _policy->predict_base_elapsed_time_ms(pending_cards);
414   double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0);
415 
416   log_trace(gc, ergo, cset)("Start choosing CSet. pending cards: " SIZE_FORMAT " predicted base time: %1.2fms remaining time: %1.2fms target pause time: %1.2fms",
417                             pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms);
418 
419   // The young list is laid with the survivor regions from the previous
420   // pause are appended to the RHS of the young list, i.e.
421   //   [Newly Young Regions ++ Survivors from last pause].
422 
423   uint survivor_region_length = survivors->length();
424   uint eden_region_length = _g1h->eden_regions_count();
425   init_region_lengths(eden_region_length, survivor_region_length);
426 
427   verify_young_cset_indices();
428 
429   // Clear the fields that point to the survivor list - they are all young now.
430   survivors->convert_to_eden();
431 
432   _bytes_used_before = _inc_bytes_used_before;
433   time_remaining_ms = MAX2(time_remaining_ms - _inc_predicted_elapsed_time_ms, 0.0);
434 
435   log_trace(gc, ergo, cset)("Add young regions to CSet. eden: %u regions, survivors: %u regions, predicted young region time: %1.2fms, target pause time: %1.2fms",
436                             eden_region_length, survivor_region_length, _inc_predicted_elapsed_time_ms, target_pause_time_ms);
437 
438   // The number of recorded young regions is the incremental
439   // collection set's current size
440   set_recorded_rs_length(_inc_recorded_rs_length);
441 
442   double young_end_time_sec = os::elapsedTime();
443   phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0);
444 
445   return time_remaining_ms;
446 }
447 
448 static int compare_region_idx(const uint a, const uint b) {
449   if (a > b) {
450     return 1;
451   } else if (a == b) {
452     return 0;
453   } else {
454     return -1;
455   }
456 }
457 
458 void G1CollectionSet::finalize_old_part(double time_remaining_ms) {
459   double non_young_start_time_sec = os::elapsedTime();
460 
461   if (collector_state()->in_mixed_phase()) {
462     candidates()->verify();
463 
464     uint num_initial_old_regions;
465     uint num_optional_old_regions;
466 
467     _policy->calculate_old_collection_set_regions(candidates(),
468                                                   time_remaining_ms,
469                                                   num_initial_old_regions,
470                                                   num_optional_old_regions);
471 
472     // Prepare initial old regions.
473     move_candidates_to_collection_set(num_initial_old_regions);
474 
475     // Prepare optional old regions for evacuation.
476     uint candidate_idx = candidates()->cur_idx();
477     for (uint i = 0; i < num_optional_old_regions; i++) {
478       add_optional_region(candidates()->at(candidate_idx + i));
479     }
480 
481     candidates()->verify();
482   }
483 
484   stop_incremental_building();
485 
486   double non_young_end_time_sec = os::elapsedTime();
487   phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);
488 
489   QuickSort::sort(_collection_set_regions, _collection_set_cur_length, compare_region_idx, true);
490 }
491 
492 void G1CollectionSet::move_candidates_to_collection_set(uint num_old_candidate_regions) {
493   if (num_old_candidate_regions == 0) {
494     return;
495   }
496   uint candidate_idx = candidates()->cur_idx();
497   for (uint i = 0; i < num_old_candidate_regions; i++) {
498     HeapRegion* r = candidates()->at(candidate_idx + i);
499     // This potentially optional candidate region is going to be an actual collection
500     // set region. Clear cset marker.
501     _g1h->clear_region_attr(r);
502     add_old_region(r);
503   }
504   candidates()->remove(num_old_candidate_regions);
505 
506   candidates()->verify();
507 }
508 
509 void G1CollectionSet::finalize_initial_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {
510   double time_remaining_ms = finalize_young_part(target_pause_time_ms, survivor);
511   finalize_old_part(time_remaining_ms);
512 }
513 
514 bool G1CollectionSet::finalize_optional_for_evacuation(double remaining_pause_time) {
515   update_incremental_marker();
516 
517   uint num_selected_regions;
518   _policy->calculate_optional_collection_set_regions(candidates(),
519                                                      _num_optional_regions,
520                                                      remaining_pause_time,
521                                                      num_selected_regions);
522 
523   move_candidates_to_collection_set(num_selected_regions);
524 
525   _num_optional_regions -= num_selected_regions;
526 
527   stop_incremental_building();
528 
529   _g1h->verify_region_attr_remset_update();
530 
531   return num_selected_regions > 0;
532 }
533 
534 void G1CollectionSet::abandon_optional_collection_set(G1ParScanThreadStateSet* pss) {
535   for (uint i = 0; i < _num_optional_regions; i++) {
536     HeapRegion* r = candidates()->at(candidates()->cur_idx() + i);
537     pss->record_unused_optional_region(r);
538     // Clear collection set marker and make sure that the remembered set information
539     // is correct as we still need it later.
540     _g1h->clear_region_attr(r);
541     _g1h->register_region_with_region_attr(r);
542     r->clear_index_in_opt_cset();
543   }
544   free_optional_regions();
545 
546   _g1h->verify_region_attr_remset_update();
547 }
548 
549 #ifdef ASSERT
550 class G1VerifyYoungCSetIndicesClosure : public HeapRegionClosure {
551 private:
552   size_t _young_length;
553   uint* _heap_region_indices;
554 public:
555   G1VerifyYoungCSetIndicesClosure(size_t young_length) : HeapRegionClosure(), _young_length(young_length) {
556     _heap_region_indices = NEW_C_HEAP_ARRAY(uint, young_length + 1, mtGC);
557     for (size_t i = 0; i < young_length + 1; i++) {
558       _heap_region_indices[i] = UINT_MAX;
559     }
560   }
561   ~G1VerifyYoungCSetIndicesClosure() {
562     FREE_C_HEAP_ARRAY(int, _heap_region_indices);
563   }
564 
565   virtual bool do_heap_region(HeapRegion* r) {
566     const uint idx = r->young_index_in_cset();
567 
568     assert(idx > 0, "Young index must be set for all regions in the incremental collection set but is not for region %u.", r->hrm_index());
569     assert(idx <= _young_length, "Young cset index %u too large for region %u", idx, r->hrm_index());
570 
571     assert(_heap_region_indices[idx] == UINT_MAX,
572            "Index %d used by multiple regions, first use by region %u, second by region %u",
573            idx, _heap_region_indices[idx], r->hrm_index());
574 
575     _heap_region_indices[idx] = r->hrm_index();
576 
577     return false;
578   }
579 };
580 
581 void G1CollectionSet::verify_young_cset_indices() const {
582   assert_at_safepoint_on_vm_thread();
583 
584   G1VerifyYoungCSetIndicesClosure cl(_collection_set_cur_length);
585   iterate(&cl);
586 }
587 #endif
--- EOF ---