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   if (_collection_set_regions != NULL) {
 76     FREE_C_HEAP_ARRAY(uint, _collection_set_regions);
 77   }
 78   free_optional_regions();
 79   clear_candidates();
 80 }
 81 
 82 void G1CollectionSet::init_region_lengths(uint eden_cset_region_length,
 83                                           uint survivor_cset_region_length) {
 84   assert_at_safepoint_on_vm_thread();
 85 
 86   _eden_region_length     = eden_cset_region_length;
 87   _survivor_region_length = survivor_cset_region_length;
 88 
 89   assert((size_t) young_region_length() == _collection_set_cur_length,
 90          "Young region length %u should match collection set length " SIZE_FORMAT, young_region_length(), _collection_set_cur_length);
 91 
 92   _old_region_length = 0;
 93   free_optional_regions();
 94 }
 95 
 96 void G1CollectionSet::initialize(uint max_region_length) {
 97   guarantee(_collection_set_regions == NULL, "Must only initialize once.");
 98   _collection_set_max_length = max_region_length;
 99   _collection_set_regions = NEW_C_HEAP_ARRAY(uint, max_region_length, mtGC);
100 }
101 
102 void G1CollectionSet::free_optional_regions() {
103   _num_optional_regions = 0;
104 }
105 
106 void G1CollectionSet::clear_candidates() {
107   delete _candidates;
108   _candidates = NULL;
109 }
110 
111 void G1CollectionSet::set_recorded_rs_length(size_t rs_length) {
112   _recorded_rs_length = rs_length;
113 }
114 
115 // Add the heap region at the head of the non-incremental collection set
116 void G1CollectionSet::add_old_region(HeapRegion* hr) {
117   assert_at_safepoint_on_vm_thread();
118 
119   assert(_inc_build_state == Active,
120          "Precondition, actively building cset or adding optional later on");
121   assert(hr->is_old(), "the region should be old");
122 
123   assert(!hr->in_collection_set(), "should not already be in the collection set");
124   _g1h->register_old_region_with_region_attr(hr);
125 
126   _collection_set_regions[_collection_set_cur_length++] = hr->hrm_index();
127   assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set now larger than maximum size.");
128 
129   _bytes_used_before += hr->used();
130   _recorded_rs_length += hr->rem_set()->occupied();
131   _old_region_length++;
132 
133   _g1h->old_set_remove(hr);
134 }
135 
136 void G1CollectionSet::add_optional_region(HeapRegion* hr) {
137   assert(hr->is_old(), "the region should be old");
138   assert(!hr->in_collection_set(), "should not already be in the CSet");
139 
140   _g1h->register_optional_region_with_region_attr(hr);
141 
142   hr->set_index_in_opt_cset(_num_optional_regions++);
143 }
144 
145 void G1CollectionSet::start_incremental_building() {
146   assert(_collection_set_cur_length == 0, "Collection set must be empty before starting a new collection set.");
147   assert(_inc_build_state == Inactive, "Precondition");
148 
149   _inc_bytes_used_before = 0;
150 
151   _inc_recorded_rs_length = 0;
152   _inc_recorded_rs_length_diff = 0;
153   _inc_predicted_elapsed_time_ms = 0.0;
154   _inc_predicted_elapsed_time_ms_diff = 0.0;
155 
156   update_incremental_marker();
157 }
158 
159 void G1CollectionSet::finalize_incremental_building() {
160   assert(_inc_build_state == Active, "Precondition");
161   assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
162 
163   // The two "main" fields, _inc_recorded_rs_length and
164   // _inc_predicted_elapsed_time_ms, are updated by the thread
165   // that adds a new region to the CSet. Further updates by the
166   // concurrent refinement thread that samples the young RSet lengths
167   // are accumulated in the *_diff fields. Here we add the diffs to
168   // the "main" fields.
169 
170   if (_inc_recorded_rs_length_diff >= 0) {
171     _inc_recorded_rs_length += _inc_recorded_rs_length_diff;
172   } else {
173     // This is defensive. The diff should in theory be always positive
174     // as RSets can only grow between GCs. However, given that we
175     // sample their size concurrently with other threads updating them
176     // it's possible that we might get the wrong size back, which
177     // could make the calculations somewhat inaccurate.
178     size_t diffs = (size_t) (-_inc_recorded_rs_length_diff);
179     if (_inc_recorded_rs_length >= diffs) {
180       _inc_recorded_rs_length -= diffs;
181     } else {
182       _inc_recorded_rs_length = 0;
183     }
184   }
185   _inc_predicted_elapsed_time_ms += _inc_predicted_elapsed_time_ms_diff;
186 
187   _inc_recorded_rs_length_diff = 0;
188   _inc_predicted_elapsed_time_ms_diff = 0.0;
189 }
190 
191 void G1CollectionSet::clear() {
192   assert_at_safepoint_on_vm_thread();
193   _collection_set_cur_length = 0;
194 }
195 
196 void G1CollectionSet::iterate(HeapRegionClosure* cl) const {
197   size_t len = _collection_set_cur_length;
198   OrderAccess::loadload();
199 
200   for (uint i = 0; i < len; i++) {
201     HeapRegion* r = _g1h->region_at(_collection_set_regions[i]);
202     bool result = cl->do_heap_region(r);
203     if (result) {
204       cl->set_incomplete();
205       return;
206     }
207   }
208 }
209 
210 void G1CollectionSet::iterate_optional(HeapRegionClosure* cl) const {
211   assert_at_safepoint();
212 
213   for (uint i = 0; i < _num_optional_regions; i++) {
214     HeapRegion* r = _candidates->at(i);
215     bool result = cl->do_heap_region(r);
216     guarantee(!result, "Must not cancel iteration");
217   }
218 }
219 
220 void G1CollectionSet::iterate_incremental_part_from(HeapRegionClosure* cl,
221                                                     HeapRegionClaimer* hr_claimer,
222                                                     uint worker_id,
223                                                     uint total_workers) const {
224   assert_at_safepoint();
225 
226   size_t len = increment_length();
227   if (len == 0) {
228     return;
229   }
230 
231   size_t start_pos = (worker_id * len) / total_workers;
232   size_t cur_pos = start_pos;
233 
234   do {
235     uint region_idx = _collection_set_regions[cur_pos + _inc_part_start];
236     if (hr_claimer == NULL || hr_claimer->claim_region(region_idx)) {
237       HeapRegion* r = _g1h->region_at(region_idx);
238       bool result = cl->do_heap_region(r);
239       guarantee(!result, "Must not cancel iteration");
240     }
241 
242     cur_pos++;
243     if (cur_pos == len) {
244       cur_pos = 0;
245     }
246   } while (cur_pos != start_pos);
247 }
248 
249 void G1CollectionSet::update_young_region_prediction(HeapRegion* hr,
250                                                      size_t new_rs_length) {
251   // Update the CSet information that is dependent on the new RS length
252   assert(hr->is_young(), "Precondition");
253   assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint");
254 
255   // We could have updated _inc_recorded_rs_length and
256   // _inc_predicted_elapsed_time_ms directly but we'd need to do
257   // that atomically, as this code is executed by a concurrent
258   // refinement thread, potentially concurrently with a mutator thread
259   // allocating a new region and also updating the same fields. To
260   // avoid the atomic operations we accumulate these updates on two
261   // separate fields (*_diff) and we'll just add them to the "main"
262   // fields at the start of a GC.
263 
264   ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length();
265   ssize_t rs_length_diff = (ssize_t) new_rs_length - old_rs_length;
266   _inc_recorded_rs_length_diff += rs_length_diff;
267 
268   double old_elapsed_time_ms = hr->predicted_elapsed_time_ms();
269   double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
270   double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms;
271   _inc_predicted_elapsed_time_ms_diff += elapsed_ms_diff;
272 
273   hr->set_recorded_rs_length(new_rs_length);
274   hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms);
275 }
276 
277 void G1CollectionSet::add_young_region_common(HeapRegion* hr) {
278   assert(hr->is_young(), "invariant");
279   assert(_inc_build_state == Active, "Precondition");
280 
281   size_t collection_set_length = _collection_set_cur_length;
282   // We use UINT_MAX as "invalid" marker in verification.
283   assert(collection_set_length < (UINT_MAX - 1),
284          "Collection set is too large with " SIZE_FORMAT " entries", collection_set_length);
285   hr->set_young_index_in_cset((uint)collection_set_length + 1);
286 
287   _collection_set_regions[collection_set_length] = hr->hrm_index();
288   // Concurrent readers must observe the store of the value in the array before an
289   // update to the length field.
290   OrderAccess::storestore();
291   _collection_set_cur_length++;
292   assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set larger than maximum allowed.");
293 
294   // This routine is used when:
295   // * adding survivor regions to the incremental cset at the end of an
296   //   evacuation pause or
297   // * adding the current allocation region to the incremental cset
298   //   when it is retired.
299   // Therefore this routine may be called at a safepoint by the
300   // VM thread, or in-between safepoints by mutator threads (when
301   // retiring the current allocation region)
302   // We need to clear and set the cached recorded/cached collection set
303   // information in the heap region here (before the region gets added
304   // to the collection set). An individual heap region's cached values
305   // are calculated, aggregated with the policy collection set info,
306   // and cached in the heap region here (initially) and (subsequently)
307   // by the Young List sampling code.
308   // Ignore calls to this due to retirement during full gc.
309 
310   if (!_g1h->collector_state()->in_full_gc()) {
311     size_t rs_length = hr->rem_set()->occupied();
312     double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
313 
314     // Cache the values we have added to the aggregated information
315     // in the heap region in case we have to remove this region from
316     // the incremental collection set, or it is updated by the
317     // rset sampling code
318     hr->set_recorded_rs_length(rs_length);
319     hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms);
320 
321     _inc_recorded_rs_length += rs_length;
322     _inc_predicted_elapsed_time_ms += region_elapsed_time_ms;
323     _inc_bytes_used_before += hr->used();
324   }
325 
326   assert(!hr->in_collection_set(), "invariant");
327   _g1h->register_young_region_with_region_attr(hr);
328 }
329 
330 void G1CollectionSet::add_survivor_regions(HeapRegion* hr) {
331   assert(hr->is_survivor(), "Must only add survivor regions, but is %s", hr->get_type_str());
332   add_young_region_common(hr);
333 }
334 
335 void G1CollectionSet::add_eden_region(HeapRegion* hr) {
336   assert(hr->is_eden(), "Must only add eden regions, but is %s", hr->get_type_str());
337   add_young_region_common(hr);
338 }
339 
340 #ifndef PRODUCT
341 class G1VerifyYoungAgesClosure : public HeapRegionClosure {
342 public:
343   bool _valid;
344 public:
345   G1VerifyYoungAgesClosure() : HeapRegionClosure(), _valid(true) { }
346 
347   virtual bool do_heap_region(HeapRegion* r) {
348     guarantee(r->is_young(), "Region must be young but is %s", r->get_type_str());
349 
350     SurvRateGroup* group = r->surv_rate_group();
351 
352     if (group == NULL) {
353       log_error(gc, verify)("## encountered NULL surv_rate_group in young region");
354       _valid = false;
355     }
356 
357     if (r->age_in_surv_rate_group() < 0) {
358       log_error(gc, verify)("## encountered negative age in young region");
359       _valid = false;
360     }
361 
362     return false;
363   }
364 
365   bool valid() const { return _valid; }
366 };
367 
368 bool G1CollectionSet::verify_young_ages() {
369   assert_at_safepoint_on_vm_thread();
370 
371   G1VerifyYoungAgesClosure cl;
372   iterate(&cl);
373 
374   if (!cl.valid()) {
375     LogStreamHandle(Error, gc, verify) log;
376     print(&log);
377   }
378 
379   return cl.valid();
380 }
381 
382 class G1PrintCollectionSetDetailClosure : public HeapRegionClosure {
383   outputStream* _st;
384 public:
385   G1PrintCollectionSetDetailClosure(outputStream* st) : HeapRegionClosure(), _st(st) { }
386 
387   virtual bool do_heap_region(HeapRegion* r) {
388     assert(r->in_collection_set(), "Region %u should be in collection set", r->hrm_index());
389     _st->print_cr("  " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d",
390                   HR_FORMAT_PARAMS(r),
391                   p2i(r->prev_top_at_mark_start()),
392                   p2i(r->next_top_at_mark_start()),
393                   r->age_in_surv_rate_group_cond());
394     return false;
395   }
396 };
397 
398 void G1CollectionSet::print(outputStream* st) {
399   st->print_cr("\nCollection_set:");
400 
401   G1PrintCollectionSetDetailClosure cl(st);
402   iterate(&cl);
403 }
404 #endif // !PRODUCT
405 
406 double G1CollectionSet::finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors) {
407   double young_start_time_sec = os::elapsedTime();
408 
409   finalize_incremental_building();
410 
411   guarantee(target_pause_time_ms > 0.0,
412             "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms);
413 
414   size_t pending_cards = _policy->pending_cards();
415   double base_time_ms = _policy->predict_base_elapsed_time_ms(pending_cards);
416   double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0);
417 
418   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",
419                             pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms);
420 
421   // The young list is laid with the survivor regions from the previous
422   // pause are appended to the RHS of the young list, i.e.
423   //   [Newly Young Regions ++ Survivors from last pause].
424 
425   uint survivor_region_length = survivors->length();
426   uint eden_region_length = _g1h->eden_regions_count();
427   init_region_lengths(eden_region_length, survivor_region_length);
428 
429   verify_young_cset_indices();
430 
431   // Clear the fields that point to the survivor list - they are all young now.
432   survivors->convert_to_eden();
433 
434   _bytes_used_before = _inc_bytes_used_before;
435   time_remaining_ms = MAX2(time_remaining_ms - _inc_predicted_elapsed_time_ms, 0.0);
436 
437   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",
438                             eden_region_length, survivor_region_length, _inc_predicted_elapsed_time_ms, target_pause_time_ms);
439 
440   // The number of recorded young regions is the incremental
441   // collection set's current size
442   set_recorded_rs_length(_inc_recorded_rs_length);
443 
444   double young_end_time_sec = os::elapsedTime();
445   phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0);
446 
447   return time_remaining_ms;
448 }
449 
450 static int compare_region_idx(const uint a, const uint b) {
451   if (a > b) {
452     return 1;
453   } else if (a == b) {
454     return 0;
455   } else {
456     return -1;
457   }
458 }
459 
460 void G1CollectionSet::finalize_old_part(double time_remaining_ms) {
461   double non_young_start_time_sec = os::elapsedTime();
462 
463   if (collector_state()->in_mixed_phase()) {
464     candidates()->verify();
465 
466     uint num_initial_old_regions;
467     uint num_optional_old_regions;
468 
469     _policy->calculate_old_collection_set_regions(candidates(),
470                                                   time_remaining_ms,
471                                                   num_initial_old_regions,
472                                                   num_optional_old_regions);
473 
474     // Prepare initial old regions.
475     move_candidates_to_collection_set(num_initial_old_regions);
476 
477     // Prepare optional old regions for evacuation.
478     uint candidate_idx = candidates()->cur_idx();
479     for (uint i = 0; i < num_optional_old_regions; i++) {
480       add_optional_region(candidates()->at(candidate_idx + i));
481     }
482 
483     candidates()->verify();
484   }
485 
486   stop_incremental_building();
487 
488   double non_young_end_time_sec = os::elapsedTime();
489   phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);
490 
491   QuickSort::sort(_collection_set_regions, _collection_set_cur_length, compare_region_idx, true);
492 }
493 
494 void G1CollectionSet::move_candidates_to_collection_set(uint num_old_candidate_regions) {
495   if (num_old_candidate_regions == 0) {
496     return;
497   }
498   uint candidate_idx = candidates()->cur_idx();
499   for (uint i = 0; i < num_old_candidate_regions; i++) {
500     HeapRegion* r = candidates()->at(candidate_idx + i);
501     // This potentially optional candidate region is going to be an actual collection
502     // set region. Clear cset marker.
503     _g1h->clear_region_attr(r);
504     add_old_region(r);
505   }
506   candidates()->remove(num_old_candidate_regions);
507 
508   candidates()->verify();
509 }
510 
511 void G1CollectionSet::finalize_initial_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {
512   double time_remaining_ms = finalize_young_part(target_pause_time_ms, survivor);
513   finalize_old_part(time_remaining_ms);
514 }
515 
516 bool G1CollectionSet::finalize_optional_for_evacuation(double remaining_pause_time) {
517   update_incremental_marker();
518 
519   uint num_selected_regions;
520   _policy->calculate_optional_collection_set_regions(candidates(),
521                                                      _num_optional_regions,
522                                                      remaining_pause_time,
523                                                      num_selected_regions);
524 
525   move_candidates_to_collection_set(num_selected_regions);
526 
527   _num_optional_regions -= num_selected_regions;
528 
529   stop_incremental_building();
530 
531   _g1h->verify_region_attr_remset_update();
532 
533   return num_selected_regions > 0;
534 }
535 
536 void G1CollectionSet::abandon_optional_collection_set(G1ParScanThreadStateSet* pss) {
537   for (uint i = 0; i < _num_optional_regions; i++) {
538     HeapRegion* r = candidates()->at(candidates()->cur_idx() + i);
539     pss->record_unused_optional_region(r);
540     // Clear collection set marker and make sure that the remembered set information
541     // is correct as we still need it later.
542     _g1h->clear_region_attr(r);
543     _g1h->register_region_with_region_attr(r);
544     r->clear_index_in_opt_cset();
545   }
546   free_optional_regions();
547 
548   _g1h->verify_region_attr_remset_update();
549 }
550 
551 #ifdef ASSERT
552 class G1VerifyYoungCSetIndicesClosure : public HeapRegionClosure {
553 private:
554   size_t _young_length;
555   uint* _heap_region_indices;
556 public:
557   G1VerifyYoungCSetIndicesClosure(size_t young_length) : HeapRegionClosure(), _young_length(young_length) {
558     _heap_region_indices = NEW_C_HEAP_ARRAY(uint, young_length + 1, mtGC);
559     for (size_t i = 0; i < young_length + 1; i++) {
560       _heap_region_indices[i] = UINT_MAX;
561     }
562   }
563   ~G1VerifyYoungCSetIndicesClosure() {
564     FREE_C_HEAP_ARRAY(int, _heap_region_indices);
565   }
566 
567   virtual bool do_heap_region(HeapRegion* r) {
568     const uint idx = r->young_index_in_cset();
569 
570     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());
571     assert(idx <= _young_length, "Young cset index %u too large for region %u", idx, r->hrm_index());
572 
573     assert(_heap_region_indices[idx] == UINT_MAX,
574            "Index %d used by multiple regions, first use by region %u, second by region %u",
575            idx, _heap_region_indices[idx], r->hrm_index());
576 
577     _heap_region_indices[idx] = r->hrm_index();
578 
579     return false;
580   }
581 };
582 
583 void G1CollectionSet::verify_young_cset_indices() const {
584   assert_at_safepoint_on_vm_thread();
585 
586   G1VerifyYoungCSetIndicesClosure cl(_collection_set_cur_length);
587   iterate(&cl);
588 }
589 #endif
--- EOF ---