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/concurrentG1Refine.hpp"
27 #include "gc/g1/concurrentMarkThread.inline.hpp"
28 #include "gc/g1/g1CollectedHeap.inline.hpp"
29 #include "gc/g1/g1CollectionSet.hpp"
30 #include "gc/g1/g1CollectorPolicy.hpp"
31 #include "gc/g1/g1ConcurrentMark.hpp"
32 #include "gc/g1/g1IHOPControl.hpp"
33 #include "gc/g1/g1GCPhaseTimes.hpp"
34 #include "gc/g1/g1YoungGenSizer.hpp"
35 #include "gc/g1/heapRegion.inline.hpp"
36 #include "gc/g1/heapRegionRemSet.hpp"
37 #include "gc/shared/gcPolicyCounters.hpp"
38 #include "runtime/arguments.hpp"
39 #include "runtime/java.hpp"
40 #include "runtime/mutexLocker.hpp"
41 #include "utilities/debug.hpp"
42 #include "utilities/pair.hpp"
43
44 // Different defaults for different number of GC threads
45 // They were chosen by running GCOld and SPECjbb on debris with different
46 // numbers of GC threads and choosing them based on the results
47
48 // all the same
49 static double rs_length_diff_defaults[] = {
50 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0
51 };
52
53 static double cost_per_card_ms_defaults[] = {
54 0.01, 0.005, 0.005, 0.003, 0.003, 0.002, 0.002, 0.0015
55 };
56
57 // all the same
58 static double young_cards_per_entry_ratio_defaults[] = {
59 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0
60 };
61
62 static double cost_per_entry_ms_defaults[] = {
63 0.015, 0.01, 0.01, 0.008, 0.008, 0.0055, 0.0055, 0.005
64 };
65
66 static double cost_per_byte_ms_defaults[] = {
67 0.00006, 0.00003, 0.00003, 0.000015, 0.000015, 0.00001, 0.00001, 0.000009
68 };
69
70 // these should be pretty consistent
71 static double constant_other_time_ms_defaults[] = {
72 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0
73 };
74
75
76 static double young_other_cost_per_region_ms_defaults[] = {
77 0.3, 0.2, 0.2, 0.15, 0.15, 0.12, 0.12, 0.1
78 };
79
80 static double non_young_other_cost_per_region_ms_defaults[] = {
81 1.0, 0.7, 0.7, 0.5, 0.5, 0.42, 0.42, 0.30
82 };
83
84 G1CollectorPolicy::G1CollectorPolicy() :
85 _predictor(G1ConfidencePercent / 100.0),
86
87 _recent_gc_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
88
89 _concurrent_mark_remark_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
90 _concurrent_mark_cleanup_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
91
92 _alloc_rate_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
93 _prev_collection_pause_end_ms(0.0),
94 _rs_length_diff_seq(new TruncatedSeq(TruncatedSeqLength)),
95 _cost_per_card_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
96 _cost_scan_hcc_seq(new TruncatedSeq(TruncatedSeqLength)),
97 _young_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
98 _mixed_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
99 _cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
100 _mixed_cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
101 _cost_per_byte_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
102 _cost_per_byte_ms_during_cm_seq(new TruncatedSeq(TruncatedSeqLength)),
103 _constant_other_time_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
104 _young_other_cost_per_region_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
105 _non_young_other_cost_per_region_ms_seq(
106 new TruncatedSeq(TruncatedSeqLength)),
107
108 _pending_cards_seq(new TruncatedSeq(TruncatedSeqLength)),
109 _rs_lengths_seq(new TruncatedSeq(TruncatedSeqLength)),
110
111 _pause_time_target_ms((double) MaxGCPauseMillis),
112
113 _recent_prev_end_times_for_all_gcs_sec(
114 new TruncatedSeq(NumPrevPausesForHeuristics)),
115
116 _recent_avg_pause_time_ratio(0.0),
117 _rs_lengths_prediction(0),
118 _max_survivor_regions(0),
119
120 // add here any more surv rate groups
121 _survivors_age_table(true),
122
123 _gc_overhead_perc(0.0),
124
125 _bytes_allocated_in_old_since_last_gc(0),
126 _ihop_control(NULL),
127 _initial_mark_to_mixed() {
128
129 // SurvRateGroups below must be initialized after the predictor because they
130 // indirectly use it through this object passed to their constructor.
131 _short_lived_surv_rate_group =
132 new SurvRateGroup(&_predictor, "Short Lived", G1YoungSurvRateNumRegionsSummary);
133 _survivor_surv_rate_group =
134 new SurvRateGroup(&_predictor, "Survivor", G1YoungSurvRateNumRegionsSummary);
135
136 // Set up the region size and associated fields. Given that the
137 // policy is created before the heap, we have to set this up here,
138 // so it's done as soon as possible.
139
140 // It would have been natural to pass initial_heap_byte_size() and
141 // max_heap_byte_size() to setup_heap_region_size() but those have
142 // not been set up at this point since they should be aligned with
143 // the region size. So, there is a circular dependency here. We base
144 // the region size on the heap size, but the heap size should be
145 // aligned with the region size. To get around this we use the
146 // unaligned values for the heap.
147 HeapRegion::setup_heap_region_size(InitialHeapSize, MaxHeapSize);
148 HeapRegionRemSet::setup_remset_size();
149
150 _recent_prev_end_times_for_all_gcs_sec->add(os::elapsedTime());
151 _prev_collection_pause_end_ms = os::elapsedTime() * 1000.0;
152 clear_ratio_check_data();
153
154 _phase_times = new G1GCPhaseTimes(ParallelGCThreads);
155
156 int index = MIN2(ParallelGCThreads - 1, 7u);
157
158 _rs_length_diff_seq->add(rs_length_diff_defaults[index]);
159 _cost_per_card_ms_seq->add(cost_per_card_ms_defaults[index]);
160 _cost_scan_hcc_seq->add(0.0);
161 _young_cards_per_entry_ratio_seq->add(
162 young_cards_per_entry_ratio_defaults[index]);
163 _cost_per_entry_ms_seq->add(cost_per_entry_ms_defaults[index]);
164 _cost_per_byte_ms_seq->add(cost_per_byte_ms_defaults[index]);
165 _constant_other_time_ms_seq->add(constant_other_time_ms_defaults[index]);
166 _young_other_cost_per_region_ms_seq->add(
167 young_other_cost_per_region_ms_defaults[index]);
168 _non_young_other_cost_per_region_ms_seq->add(
169 non_young_other_cost_per_region_ms_defaults[index]);
170
171 // Below, we might need to calculate the pause time target based on
172 // the pause interval. When we do so we are going to give G1 maximum
173 // flexibility and allow it to do pauses when it needs to. So, we'll
174 // arrange that the pause interval to be pause time target + 1 to
175 // ensure that a) the pause time target is maximized with respect to
176 // the pause interval and b) we maintain the invariant that pause
177 // time target < pause interval. If the user does not want this
178 // maximum flexibility, they will have to set the pause interval
179 // explicitly.
180
181 // First make sure that, if either parameter is set, its value is
182 // reasonable.
183 if (!FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
184 if (MaxGCPauseMillis < 1) {
185 vm_exit_during_initialization("MaxGCPauseMillis should be "
186 "greater than 0");
187 }
188 }
189 if (!FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
190 if (GCPauseIntervalMillis < 1) {
211 // the pause time target (this will also deal with the case when the
212 // pause time target is the default value).
213 if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
214 FLAG_SET_DEFAULT(GCPauseIntervalMillis, MaxGCPauseMillis + 1);
215 }
216
217 // Finally, make sure that the two parameters are consistent.
218 if (MaxGCPauseMillis >= GCPauseIntervalMillis) {
219 char buffer[256];
220 jio_snprintf(buffer, 256,
221 "MaxGCPauseMillis (%u) should be less than "
222 "GCPauseIntervalMillis (%u)",
223 MaxGCPauseMillis, GCPauseIntervalMillis);
224 vm_exit_during_initialization(buffer);
225 }
226
227 double max_gc_time = (double) MaxGCPauseMillis / 1000.0;
228 double time_slice = (double) GCPauseIntervalMillis / 1000.0;
229 _mmu_tracker = new G1MMUTrackerQueue(time_slice, max_gc_time);
230
231 // start conservatively (around 50ms is about right)
232 _concurrent_mark_remark_times_ms->add(0.05);
233 _concurrent_mark_cleanup_times_ms->add(0.20);
234 _tenuring_threshold = MaxTenuringThreshold;
235
236 assert(GCTimeRatio > 0,
237 "we should have set it to a default value set_g1_gc_flags() "
238 "if a user set it to 0");
239 _gc_overhead_perc = 100.0 * (1.0 / (1.0 + GCTimeRatio));
240
241 uintx reserve_perc = G1ReservePercent;
242 // Put an artificial ceiling on this so that it's not set to a silly value.
243 if (reserve_perc > 50) {
244 reserve_perc = 50;
245 warning("G1ReservePercent is set to a value that is too large, "
246 "it's been updated to " UINTX_FORMAT, reserve_perc);
247 }
248 _reserve_factor = (double) reserve_perc / 100.0;
249 // This will be set when the heap is expanded
250 // for the first time during initialization.
251 _reserve_regions = 0;
252
253 _ihop_control = create_ihop_control();
254 }
255
256 G1CollectorPolicy::~G1CollectorPolicy() {
257 delete _ihop_control;
258 }
259
260 double G1CollectorPolicy::get_new_prediction(TruncatedSeq const* seq) const {
261 return _predictor.get_new_prediction(seq);
262 }
263
264 size_t G1CollectorPolicy::get_new_size_prediction(TruncatedSeq const* seq) const {
265 return (size_t)get_new_prediction(seq);
266 }
267
268 void G1CollectorPolicy::initialize_alignments() {
269 _space_alignment = HeapRegion::GrainBytes;
270 size_t card_table_alignment = CardTableRS::ct_max_alignment_constraint();
271 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
272 _heap_alignment = MAX3(card_table_alignment, _space_alignment, page_size);
273 }
274
275 G1CollectorState* G1CollectorPolicy::collector_state() const { return _g1->collector_state(); }
276
277 void G1CollectorPolicy::post_heap_initialize() {
278 uintx max_regions = G1CollectedHeap::heap()->max_regions();
279 size_t max_young_size = (size_t)_young_gen_sizer->max_young_length(max_regions) * HeapRegion::GrainBytes;
280 if (max_young_size != MaxNewSize) {
281 FLAG_SET_ERGO(size_t, MaxNewSize, max_young_size);
282 }
283 }
284
285 void G1CollectorPolicy::initialize_flags() {
286 if (G1HeapRegionSize != HeapRegion::GrainBytes) {
287 FLAG_SET_ERGO(size_t, G1HeapRegionSize, HeapRegion::GrainBytes);
322 phase_times()->note_gc_start(num_active_workers);
323 }
324
325 // Create the jstat counters for the policy.
326 void G1CollectorPolicy::initialize_gc_policy_counters() {
327 _gc_policy_counters = new GCPolicyCounters("GarbageFirst", 1, 3);
328 }
329
330 bool G1CollectorPolicy::predict_will_fit(uint young_length,
331 double base_time_ms,
332 uint base_free_regions,
333 double target_pause_time_ms) const {
334 if (young_length >= base_free_regions) {
335 // end condition 1: not enough space for the young regions
336 return false;
337 }
338
339 double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);
340 size_t bytes_to_copy =
341 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
342 double copy_time_ms = predict_object_copy_time_ms(bytes_to_copy);
343 double young_other_time_ms = predict_young_other_time_ms(young_length);
344 double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;
345 if (pause_time_ms > target_pause_time_ms) {
346 // end condition 2: prediction is over the target pause time
347 return false;
348 }
349
350 size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes;
351
352 // When copying, we will likely need more bytes free than is live in the region.
353 // Add some safety margin to factor in the confidence of our guess, and the
354 // natural expected waste.
355 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
356 // of the calculation: the lower the confidence, the more headroom.
357 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
358 // copying due to anticipated waste in the PLABs.
359 double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
360 size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
361
362 if (expected_bytes_to_copy > free_bytes) {
363 // end condition 3: out-of-space
367 // success!
368 return true;
369 }
370
371 void G1CollectorPolicy::record_new_heap_size(uint new_number_of_regions) {
372 // re-calculate the necessary reserve
373 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
374 // We use ceiling so that if reserve_regions_d is > 0.0 (but
375 // smaller than 1.0) we'll get 1.
376 _reserve_regions = (uint) ceil(reserve_regions_d);
377
378 _young_gen_sizer->heap_size_changed(new_number_of_regions);
379
380 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
381 }
382
383 uint G1CollectorPolicy::calculate_young_list_desired_min_length(
384 uint base_min_length) const {
385 uint desired_min_length = 0;
386 if (adaptive_young_list_length()) {
387 if (_alloc_rate_ms_seq->num() > 3) {
388 double now_sec = os::elapsedTime();
389 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
390 double alloc_rate_ms = predict_alloc_rate_ms();
391 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
392 } else {
393 // otherwise we don't have enough info to make the prediction
394 }
395 }
396 desired_min_length += base_min_length;
397 // make sure we don't go below any user-defined minimum bound
398 return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
399 }
400
401 uint G1CollectorPolicy::calculate_young_list_desired_max_length() const {
402 // Here, we might want to also take into account any additional
403 // constraints (i.e., user-defined minimum bound). Currently, we
404 // effectively don't set this bound.
405 return _young_gen_sizer->max_desired_young_length();
406 }
407
408 uint G1CollectorPolicy::update_young_list_max_and_target_length() {
409 return update_young_list_max_and_target_length(predict_rs_lengths());
410 }
411
412 uint G1CollectorPolicy::update_young_list_max_and_target_length(size_t rs_lengths) {
413 uint unbounded_target_length = update_young_list_target_length(rs_lengths);
414 update_max_gc_locker_expansion();
415 return unbounded_target_length;
416 }
417
418 uint G1CollectorPolicy::update_young_list_target_length(size_t rs_lengths) {
419 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
420 _young_list_target_length = young_lengths.first;
421 return young_lengths.second;
422 }
423
424 G1CollectorPolicy::YoungTargetLengths G1CollectorPolicy::young_list_target_lengths(size_t rs_lengths) const {
425 YoungTargetLengths result;
426
427 // Calculate the absolute and desired min bounds first.
428
429 // This is how many young regions we already have (currently: the survivors).
494 assert(adaptive_young_list_length(), "pre-condition");
495 assert(collector_state()->gcs_are_young(), "only call this for young GCs");
496
497 // In case some edge-condition makes the desired max length too small...
498 if (desired_max_length <= desired_min_length) {
499 return desired_min_length;
500 }
501
502 // We'll adjust min_young_length and max_young_length not to include
503 // the already allocated young regions (i.e., so they reflect the
504 // min and max eden regions we'll allocate). The base_min_length
505 // will be reflected in the predictions by the
506 // survivor_regions_evac_time prediction.
507 assert(desired_min_length > base_min_length, "invariant");
508 uint min_young_length = desired_min_length - base_min_length;
509 assert(desired_max_length > base_min_length, "invariant");
510 uint max_young_length = desired_max_length - base_min_length;
511
512 double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
513 double survivor_regions_evac_time = predict_survivor_regions_evac_time();
514 size_t pending_cards = get_new_size_prediction(_pending_cards_seq);
515 size_t adj_rs_lengths = rs_lengths + predict_rs_length_diff();
516 size_t scanned_cards = predict_young_card_num(adj_rs_lengths);
517 double base_time_ms =
518 predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
519 survivor_regions_evac_time;
520 uint available_free_regions = _free_regions_at_end_of_collection;
521 uint base_free_regions = 0;
522 if (available_free_regions > _reserve_regions) {
523 base_free_regions = available_free_regions - _reserve_regions;
524 }
525
526 // Here, we will make sure that the shortest young length that
527 // makes sense fits within the target pause time.
528
529 if (predict_will_fit(min_young_length, base_time_ms,
530 base_free_regions, target_pause_time_ms)) {
531 // The shortest young length will fit into the target pause time;
532 // we'll now check whether the absolute maximum number of young
533 // regions will fit in the target pause time. If not, we'll do
534 // a binary search between min_young_length and max_young_length.
535 if (predict_will_fit(max_young_length, base_time_ms,
536 base_free_regions, target_pause_time_ms)) {
596 r != NULL && r != _g1->young_list()->last_survivor_region()->get_next_young_region();
597 r = r->get_next_young_region()) {
598 survivor_regions_evac_time += predict_region_elapsed_time_ms(r, collector_state()->gcs_are_young());
599 }
600 return survivor_regions_evac_time;
601 }
602
603 void G1CollectorPolicy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
604 guarantee( adaptive_young_list_length(), "should not call this otherwise" );
605
606 if (rs_lengths > _rs_lengths_prediction) {
607 // add 10% to avoid having to recalculate often
608 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
609 update_rs_lengths_prediction(rs_lengths_prediction);
610
611 update_young_list_max_and_target_length(rs_lengths_prediction);
612 }
613 }
614
615 void G1CollectorPolicy::update_rs_lengths_prediction() {
616 update_rs_lengths_prediction(predict_rs_lengths());
617 }
618
619 void G1CollectorPolicy::update_rs_lengths_prediction(size_t prediction) {
620 if (collector_state()->gcs_are_young() && adaptive_young_list_length()) {
621 _rs_lengths_prediction = prediction;
622 }
623 }
624
625 #ifndef PRODUCT
626 bool G1CollectorPolicy::verify_young_ages() {
627 HeapRegion* head = _g1->young_list()->first_region();
628 return
629 verify_young_ages(head, _short_lived_surv_rate_group);
630 // also call verify_young_ages on any additional surv rate groups
631 }
632
633 bool
634 G1CollectorPolicy::verify_young_ages(HeapRegion* head,
635 SurvRateGroup *surv_rate_group) {
636 guarantee( surv_rate_group != NULL, "pre-condition" );
664 }
665 }
666
667 return ret;
668 }
669 #endif // PRODUCT
670
671 void G1CollectorPolicy::record_full_collection_start() {
672 _full_collection_start_sec = os::elapsedTime();
673 // Release the future to-space so that it is available for compaction into.
674 collector_state()->set_full_collection(true);
675 }
676
677 void G1CollectorPolicy::record_full_collection_end() {
678 // Consider this like a collection pause for the purposes of allocation
679 // since last pause.
680 double end_sec = os::elapsedTime();
681 double full_gc_time_sec = end_sec - _full_collection_start_sec;
682 double full_gc_time_ms = full_gc_time_sec * 1000.0;
683
684 update_recent_gc_times(end_sec, full_gc_time_ms);
685
686 collector_state()->set_full_collection(false);
687
688 // "Nuke" the heuristics that control the young/mixed GC
689 // transitions and make sure we start with young GCs after the Full GC.
690 collector_state()->set_gcs_are_young(true);
691 collector_state()->set_last_young_gc(false);
692 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
693 collector_state()->set_during_initial_mark_pause(false);
694 collector_state()->set_in_marking_window(false);
695 collector_state()->set_in_marking_window_im(false);
696
697 _short_lived_surv_rate_group->start_adding_regions();
698 // also call this on any additional surv rate groups
699
700 _free_regions_at_end_of_collection = _g1->num_free_regions();
701 // Reset survivors SurvRateGroup.
702 _survivor_surv_rate_group->reset();
703 update_young_list_max_and_target_length();
704 update_rs_lengths_prediction();
732 _survivors_age_table.clear();
733
734 assert( verify_young_ages(), "region age verification" );
735 }
736
737 void G1CollectorPolicy::record_concurrent_mark_init_end(double
738 mark_init_elapsed_time_ms) {
739 collector_state()->set_during_marking(true);
740 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
741 collector_state()->set_during_initial_mark_pause(false);
742 }
743
744 void G1CollectorPolicy::record_concurrent_mark_remark_start() {
745 _mark_remark_start_sec = os::elapsedTime();
746 collector_state()->set_during_marking(false);
747 }
748
749 void G1CollectorPolicy::record_concurrent_mark_remark_end() {
750 double end_time_sec = os::elapsedTime();
751 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
752 _concurrent_mark_remark_times_ms->add(elapsed_time_ms);
753 _prev_collection_pause_end_ms += elapsed_time_ms;
754
755 record_pause(Remark, _mark_remark_start_sec, end_time_sec);
756 }
757
758 void G1CollectorPolicy::record_concurrent_mark_cleanup_start() {
759 _mark_cleanup_start_sec = os::elapsedTime();
760 }
761
762 void G1CollectorPolicy::record_concurrent_mark_cleanup_completed() {
763 bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",
764 "skip last young-only gc");
765 collector_state()->set_last_young_gc(should_continue_with_reclaim);
766 // We skip the marking phase.
767 if (!should_continue_with_reclaim) {
768 abort_time_to_mixed_tracking();
769 }
770 collector_state()->set_in_marking_window(false);
771 }
772
773 double G1CollectorPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
832
833 void G1CollectorPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
834 double end_time_sec = os::elapsedTime();
835
836 size_t cur_used_bytes = _g1->used();
837 assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
838 bool last_pause_included_initial_mark = false;
839 bool update_stats = !_g1->evacuation_failed();
840
841 NOT_PRODUCT(_short_lived_surv_rate_group->print());
842
843 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
844
845 last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();
846 if (last_pause_included_initial_mark) {
847 record_concurrent_mark_init_end(0.0);
848 } else {
849 maybe_start_marking();
850 }
851
852 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _prev_collection_pause_end_ms);
853 if (app_time_ms < MIN_TIMER_GRANULARITY) {
854 // This usually happens due to the timer not having the required
855 // granularity. Some Linuxes are the usual culprits.
856 // We'll just set it to something (arbitrarily) small.
857 app_time_ms = 1.0;
858 }
859
860 if (update_stats) {
861 // We maintain the invariant that all objects allocated by mutator
862 // threads will be allocated out of eden regions. So, we can use
863 // the eden region number allocated since the previous GC to
864 // calculate the application's allocate rate. The only exception
865 // to that is humongous objects that are allocated separately. But
866 // given that humongous object allocations do not really affect
867 // either the pause's duration nor when the next pause will take
868 // place we can safely ignore them here.
869 uint regions_allocated = _collection_set->eden_region_length();
870 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
871 _alloc_rate_ms_seq->add(alloc_rate_ms);
872
873 double interval_ms =
874 (end_time_sec - _recent_prev_end_times_for_all_gcs_sec->oldest()) * 1000.0;
875 update_recent_gc_times(end_time_sec, pause_time_ms);
876 _recent_avg_pause_time_ratio = _recent_gc_times_ms->sum()/interval_ms;
877 if (recent_avg_pause_time_ratio() < 0.0 ||
878 (recent_avg_pause_time_ratio() - 1.0 > 0.0)) {
879 // Clip ratio between 0.0 and 1.0, and continue. This will be fixed in
880 // CR 6902692 by redoing the manner in which the ratio is incrementally computed.
881 if (_recent_avg_pause_time_ratio < 0.0) {
882 _recent_avg_pause_time_ratio = 0.0;
883 } else {
884 assert(_recent_avg_pause_time_ratio - 1.0 > 0.0, "Ctl-point invariant");
885 _recent_avg_pause_time_ratio = 1.0;
886 }
887 }
888
889 // Compute the ratio of just this last pause time to the entire time range stored
890 // in the vectors. Comparing this pause to the entire range, rather than only the
891 // most recent interval, has the effect of smoothing over a possible transient 'burst'
892 // of more frequent pauses that don't really reflect a change in heap occupancy.
893 // This reduces the likelihood of a needless heap expansion being triggered.
894 _last_pause_time_ratio =
895 (pause_time_ms * _recent_prev_end_times_for_all_gcs_sec->num()) / interval_ms;
896 }
897
898 bool new_in_marking_window = collector_state()->in_marking_window();
899 bool new_in_marking_window_im = false;
900 if (last_pause_included_initial_mark) {
901 new_in_marking_window = true;
902 new_in_marking_window_im = true;
903 }
904
905 if (collector_state()->last_young_gc()) {
906 // This is supposed to to be the "last young GC" before we start
907 // doing mixed GCs. Here we decide whether to start mixed GCs or not.
908 assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC");
909
910 if (next_gc_should_be_mixed("start mixed GCs",
911 "do not start mixed GCs")) {
912 collector_state()->set_gcs_are_young(false);
913 } else {
914 // We aborted the mixed GC phase early.
915 abort_time_to_mixed_tracking();
921 if (!collector_state()->last_gc_was_young()) {
922 // This is a mixed GC. Here we decide whether to continue doing
923 // mixed GCs or not.
924 if (!next_gc_should_be_mixed("continue mixed GCs",
925 "do not continue mixed GCs")) {
926 collector_state()->set_gcs_are_young(true);
927
928 maybe_start_marking();
929 }
930 }
931
932 _short_lived_surv_rate_group->start_adding_regions();
933 // Do that for any other surv rate groups
934
935 double scan_hcc_time_ms = ConcurrentG1Refine::hot_card_cache_enabled() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
936
937 if (update_stats) {
938 double cost_per_card_ms = 0.0;
939 if (_pending_cards > 0) {
940 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards;
941 _cost_per_card_ms_seq->add(cost_per_card_ms);
942 }
943 _cost_scan_hcc_seq->add(scan_hcc_time_ms);
944
945 double cost_per_entry_ms = 0.0;
946 if (cards_scanned > 10) {
947 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
948 if (collector_state()->last_gc_was_young()) {
949 _cost_per_entry_ms_seq->add(cost_per_entry_ms);
950 } else {
951 _mixed_cost_per_entry_ms_seq->add(cost_per_entry_ms);
952 }
953 }
954
955 if (_max_rs_lengths > 0) {
956 double cards_per_entry_ratio =
957 (double) cards_scanned / (double) _max_rs_lengths;
958 if (collector_state()->last_gc_was_young()) {
959 _young_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
960 } else {
961 _mixed_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
962 }
963 }
964
965 // This is defensive. For a while _max_rs_lengths could get
966 // smaller than _recorded_rs_lengths which was causing
967 // rs_length_diff to get very large and mess up the RSet length
968 // predictions. The reason was unsafe concurrent updates to the
969 // _inc_cset_recorded_rs_lengths field which the code below guards
970 // against (see CR 7118202). This bug has now been fixed (see CR
971 // 7119027). However, I'm still worried that
972 // _inc_cset_recorded_rs_lengths might still end up somewhat
973 // inaccurate. The concurrent refinement thread calculates an
974 // RSet's length concurrently with other CR threads updating it
975 // which might cause it to calculate the length incorrectly (if,
976 // say, it's in mid-coarsening). So I'll leave in the defensive
977 // conditional below just in case.
978 size_t rs_length_diff = 0;
979 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();
980 if (_max_rs_lengths > recorded_rs_lengths) {
981 rs_length_diff = _max_rs_lengths - recorded_rs_lengths;
982 }
983 _rs_length_diff_seq->add((double) rs_length_diff);
984
985 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
986 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
987 double cost_per_byte_ms = 0.0;
988
989 if (copied_bytes > 0) {
990 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
991 if (collector_state()->in_marking_window()) {
992 _cost_per_byte_ms_during_cm_seq->add(cost_per_byte_ms);
993 } else {
994 _cost_per_byte_ms_seq->add(cost_per_byte_ms);
995 }
996 }
997
998 if (_collection_set->young_region_length() > 0) {
999 _young_other_cost_per_region_ms_seq->add(young_other_time_ms() /
1000 _collection_set->young_region_length());
1001 }
1002
1003 if (_collection_set->old_region_length() > 0) {
1004 _non_young_other_cost_per_region_ms_seq->add(non_young_other_time_ms() /
1005 _collection_set->old_region_length());
1006 }
1007
1008 _constant_other_time_ms_seq->add(constant_other_time_ms(pause_time_ms));
1009
1010 _pending_cards_seq->add((double) _pending_cards);
1011 _rs_lengths_seq->add((double) _max_rs_lengths);
1012 }
1013
1014 collector_state()->set_in_marking_window(new_in_marking_window);
1015 collector_state()->set_in_marking_window_im(new_in_marking_window_im);
1016 _free_regions_at_end_of_collection = _g1->num_free_regions();
1017 // IHOP control wants to know the expected young gen length if it were not
1018 // restrained by the heap reserve. Using the actual length would make the
1019 // prediction too small and the limit the young gen every time we get to the
1020 // predicted target occupancy.
1021 size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
1022 update_rs_lengths_prediction();
1023
1024 update_ihop_prediction(app_time_ms / 1000.0,
1025 _bytes_allocated_in_old_since_last_gc,
1026 last_unrestrained_young_length * HeapRegion::GrainBytes);
1027 _bytes_allocated_in_old_since_last_gc = 0;
1028
1029 _ihop_control->send_trace_event(_g1->gc_tracer_stw());
1030
1031 // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
1128 cg1r->set_red_zone(g * k_gr);
1129 cg1r->reinitialize_threads();
1130
1131 size_t processing_threshold_delta = MAX2<size_t>(cg1r->green_zone() * _predictor.sigma(), 1);
1132 size_t processing_threshold = MIN2(cg1r->green_zone() + processing_threshold_delta,
1133 cg1r->yellow_zone());
1134 // Change the barrier params
1135 dcqs.set_process_completed_threshold((int)processing_threshold);
1136 dcqs.set_max_completed_queue((int)cg1r->red_zone());
1137 }
1138
1139 size_t curr_queue_size = dcqs.completed_buffers_num();
1140 if (curr_queue_size >= cg1r->yellow_zone()) {
1141 dcqs.set_completed_queue_padding(curr_queue_size);
1142 } else {
1143 dcqs.set_completed_queue_padding(0);
1144 }
1145 dcqs.notify_if_necessary();
1146 }
1147
1148 size_t G1CollectorPolicy::predict_rs_lengths() const {
1149 return get_new_size_prediction(_rs_lengths_seq);
1150 }
1151
1152 size_t G1CollectorPolicy::predict_rs_length_diff() const {
1153 return get_new_size_prediction(_rs_length_diff_seq);
1154 }
1155
1156 double G1CollectorPolicy::predict_alloc_rate_ms() const {
1157 return get_new_prediction(_alloc_rate_ms_seq);
1158 }
1159
1160 double G1CollectorPolicy::predict_cost_per_card_ms() const {
1161 return get_new_prediction(_cost_per_card_ms_seq);
1162 }
1163
1164 double G1CollectorPolicy::predict_scan_hcc_ms() const {
1165 return get_new_prediction(_cost_scan_hcc_seq);
1166 }
1167
1168 double G1CollectorPolicy::predict_rs_update_time_ms(size_t pending_cards) const {
1169 return pending_cards * predict_cost_per_card_ms() + predict_scan_hcc_ms();
1170 }
1171
1172 double G1CollectorPolicy::predict_young_cards_per_entry_ratio() const {
1173 return get_new_prediction(_young_cards_per_entry_ratio_seq);
1174 }
1175
1176 double G1CollectorPolicy::predict_mixed_cards_per_entry_ratio() const {
1177 if (_mixed_cards_per_entry_ratio_seq->num() < 2) {
1178 return predict_young_cards_per_entry_ratio();
1179 } else {
1180 return get_new_prediction(_mixed_cards_per_entry_ratio_seq);
1181 }
1182 }
1183
1184 size_t G1CollectorPolicy::predict_young_card_num(size_t rs_length) const {
1185 return (size_t) (rs_length * predict_young_cards_per_entry_ratio());
1186 }
1187
1188 size_t G1CollectorPolicy::predict_non_young_card_num(size_t rs_length) const {
1189 return (size_t)(rs_length * predict_mixed_cards_per_entry_ratio());
1190 }
1191
1192 double G1CollectorPolicy::predict_rs_scan_time_ms(size_t card_num) const {
1193 if (collector_state()->gcs_are_young()) {
1194 return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1195 } else {
1196 return predict_mixed_rs_scan_time_ms(card_num);
1197 }
1198 }
1199
1200 double G1CollectorPolicy::predict_mixed_rs_scan_time_ms(size_t card_num) const {
1201 if (_mixed_cost_per_entry_ms_seq->num() < 3) {
1202 return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1203 } else {
1204 return card_num * get_new_prediction(_mixed_cost_per_entry_ms_seq);
1205 }
1206 }
1207
1208 double G1CollectorPolicy::predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) const {
1209 if (_cost_per_byte_ms_during_cm_seq->num() < 3) {
1210 return (1.1 * bytes_to_copy) * get_new_prediction(_cost_per_byte_ms_seq);
1211 } else {
1212 return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_during_cm_seq);
1213 }
1214 }
1215
1216 double G1CollectorPolicy::predict_object_copy_time_ms(size_t bytes_to_copy) const {
1217 if (collector_state()->during_concurrent_mark()) {
1218 return predict_object_copy_time_ms_during_cm(bytes_to_copy);
1219 } else {
1220 return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_seq);
1221 }
1222 }
1223
1224 double G1CollectorPolicy::predict_constant_other_time_ms() const {
1225 return get_new_prediction(_constant_other_time_ms_seq);
1226 }
1227
1228 double G1CollectorPolicy::predict_young_other_time_ms(size_t young_num) const {
1229 return young_num * get_new_prediction(_young_other_cost_per_region_ms_seq);
1230 }
1231
1232 double G1CollectorPolicy::predict_non_young_other_time_ms(size_t non_young_num) const {
1233 return non_young_num * get_new_prediction(_non_young_other_cost_per_region_ms_seq);
1234 }
1235
1236 double G1CollectorPolicy::predict_remark_time_ms() const {
1237 return get_new_prediction(_concurrent_mark_remark_times_ms);
1238 }
1239
1240 double G1CollectorPolicy::predict_cleanup_time_ms() const {
1241 return get_new_prediction(_concurrent_mark_cleanup_times_ms);
1242 }
1243
1244 double G1CollectorPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
1245 TruncatedSeq* seq = surv_rate_group->get_seq(age);
1246 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
1247 double pred = get_new_prediction(seq);
1248 if (pred > 1.0) {
1249 pred = 1.0;
1250 }
1251 return pred;
1252 }
1253
1254 double G1CollectorPolicy::predict_yg_surv_rate(int age) const {
1255 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
1256 }
1257
1258 double G1CollectorPolicy::accum_yg_surv_rate_pred(int age) const {
1259 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
1260 }
1261
1262 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards,
1263 size_t scanned_cards) const {
1264 return
1265 predict_rs_update_time_ms(pending_cards) +
1266 predict_rs_scan_time_ms(scanned_cards) +
1267 predict_constant_other_time_ms();
1268 }
1269
1270 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const {
1271 size_t rs_length = predict_rs_lengths() + predict_rs_length_diff();
1272 size_t card_num;
1273 if (collector_state()->gcs_are_young()) {
1274 card_num = predict_young_card_num(rs_length);
1275 } else {
1276 card_num = predict_non_young_card_num(rs_length);
1277 }
1278 return predict_base_elapsed_time_ms(pending_cards, card_num);
1279 }
1280
1281 size_t G1CollectorPolicy::predict_bytes_to_copy(HeapRegion* hr) const {
1282 size_t bytes_to_copy;
1283 if (hr->is_marked())
1284 bytes_to_copy = hr->max_live_bytes();
1285 else {
1286 assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
1287 int age = hr->age_in_surv_rate_group();
1288 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
1289 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
1290 }
1291 return bytes_to_copy;
1292 }
1293
1294 double G1CollectorPolicy::predict_region_elapsed_time_ms(HeapRegion* hr,
1295 bool for_young_gc) const {
1296 size_t rs_length = hr->rem_set()->occupied();
1297 size_t card_num;
1298
1299 // Predicting the number of cards is based on which type of GC
1300 // we're predicting for.
1301 if (for_young_gc) {
1302 card_num = predict_young_card_num(rs_length);
1303 } else {
1304 card_num = predict_non_young_card_num(rs_length);
1305 }
1306 size_t bytes_to_copy = predict_bytes_to_copy(hr);
1307
1308 double region_elapsed_time_ms =
1309 predict_rs_scan_time_ms(card_num) +
1310 predict_object_copy_time_ms(bytes_to_copy);
1311
1312 // The prediction of the "other" time for this region is based
1313 // upon the region type and NOT the GC type.
1314 if (hr->is_young()) {
1315 region_elapsed_time_ms += predict_young_other_time_ms(1);
1316 } else {
1317 region_elapsed_time_ms += predict_non_young_other_time_ms(1);
1318 }
1319 return region_elapsed_time_ms;
1320 }
1321
1322 void G1CollectorPolicy::update_recent_gc_times(double end_time_sec,
1323 double elapsed_ms) {
1324 _recent_gc_times_ms->add(elapsed_ms);
1325 _recent_prev_end_times_for_all_gcs_sec->add(end_time_sec);
1326 _prev_collection_pause_end_ms = end_time_sec * 1000.0;
1327 }
1328
1329 void G1CollectorPolicy::clear_ratio_check_data() {
1330 _ratio_over_threshold_count = 0;
1331 _ratio_over_threshold_sum = 0.0;
1332 _pauses_since_start = 0;
1333 }
1334
1335 size_t G1CollectorPolicy::expansion_amount() {
1336 double recent_gc_overhead = recent_avg_pause_time_ratio() * 100.0;
1337 double last_gc_overhead = _last_pause_time_ratio * 100.0;
1338 double threshold = _gc_overhead_perc;
1339 size_t expand_bytes = 0;
1340
1341 // If the heap is at less than half its maximum size, scale the threshold down,
1342 // to a limit of 1. Thus the smaller the heap is, the more likely it is to expand,
1343 // though the scaling code will likely keep the increase small.
1344 if (_g1->capacity() <= _g1->max_capacity() / 2) {
1345 threshold *= (double)_g1->capacity() / (double)(_g1->max_capacity() / 2);
1346 threshold = MAX2(threshold, 1.0);
1347 }
1348
1349 // If the last GC time ratio is over the threshold, increment the count of
1350 // times it has been exceeded, and add this ratio to the sum of exceeded
1351 // ratios.
1352 if (last_gc_overhead > threshold) {
1353 _ratio_over_threshold_count++;
1354 _ratio_over_threshold_sum += last_gc_overhead;
1355 }
1356
1357 // Check if we've had enough GC time ratio checks that were over the
1602 const uint min_chunk_size = MAX2(n_regions / n_workers, 1U);
1603 return MAX2(n_regions / (n_workers * overpartition_factor), min_chunk_size);
1604 }
1605
1606 void G1CollectorPolicy::record_concurrent_mark_cleanup_end() {
1607 cset_chooser()->clear();
1608
1609 WorkGang* workers = _g1->workers();
1610 uint n_workers = workers->active_workers();
1611
1612 uint n_regions = _g1->num_regions();
1613 uint chunk_size = calculate_parallel_work_chunk_size(n_workers, n_regions);
1614 cset_chooser()->prepare_for_par_region_addition(n_workers, n_regions, chunk_size);
1615 ParKnownGarbageTask par_known_garbage_task(cset_chooser(), chunk_size, n_workers);
1616 workers->run_task(&par_known_garbage_task);
1617
1618 cset_chooser()->sort_regions();
1619
1620 double end_sec = os::elapsedTime();
1621 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1622 _concurrent_mark_cleanup_times_ms->add(elapsed_time_ms);
1623 _prev_collection_pause_end_ms += elapsed_time_ms;
1624
1625 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1626 }
1627
1628 double G1CollectorPolicy::reclaimable_bytes_perc(size_t reclaimable_bytes) const {
1629 // Returns the given amount of reclaimable bytes (that represents
1630 // the amount of reclaimable space still to be collected) as a
1631 // percentage of the current heap capacity.
1632 size_t capacity_bytes = _g1->capacity();
1633 return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
1634 }
1635
1636 void G1CollectorPolicy::maybe_start_marking() {
1637 if (need_to_start_conc_mark("end of GC")) {
1638 // Note: this might have already been set, if during the last
1639 // pause we decided to start a cycle but at the beginning of
1640 // this pause we decided to postpone it. That's OK.
1641 collector_state()->set_initiate_conc_mark_if_possible(true);
1642 }
1643 }
1741 // The max old CSet region bound is based on the threshold expressed
1742 // as a percentage of the heap size. I.e., it should bound the
1743 // number of old regions added to the CSet irrespective of how many
1744 // of them are available.
1745
1746 const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1747 const size_t region_num = g1h->num_regions();
1748 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1749 size_t result = region_num * perc / 100;
1750 // emulate ceiling
1751 if (100 * result < region_num * perc) {
1752 result += 1;
1753 }
1754 return (uint) result;
1755 }
1756
1757 void G1CollectorPolicy::finalize_collection_set(double target_pause_time_ms) {
1758 double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms);
1759 _collection_set->finalize_old_part(time_remaining_ms);
1760 }
1761
|
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/concurrentG1Refine.hpp"
27 #include "gc/g1/concurrentMarkThread.inline.hpp"
28 #include "gc/g1/g1Analytics.hpp"
29 #include "gc/g1/g1CollectedHeap.inline.hpp"
30 #include "gc/g1/g1CollectionSet.hpp"
31 #include "gc/g1/g1CollectorPolicy.hpp"
32 #include "gc/g1/g1ConcurrentMark.hpp"
33 #include "gc/g1/g1IHOPControl.hpp"
34 #include "gc/g1/g1GCPhaseTimes.hpp"
35 #include "gc/g1/g1YoungGenSizer.hpp"
36 #include "gc/g1/heapRegion.inline.hpp"
37 #include "gc/g1/heapRegionRemSet.hpp"
38 #include "gc/shared/gcPolicyCounters.hpp"
39 #include "runtime/arguments.hpp"
40 #include "runtime/java.hpp"
41 #include "runtime/mutexLocker.hpp"
42 #include "utilities/debug.hpp"
43 #include "utilities/pair.hpp"
44
45 G1CollectorPolicy::G1CollectorPolicy() :
46 _predictor(G1ConfidencePercent / 100.0),
47 _analytics(new G1Analytics(&_predictor)),
48 _pause_time_target_ms((double) MaxGCPauseMillis),
49 _rs_lengths_prediction(0),
50 _max_survivor_regions(0),
51 _survivors_age_table(true),
52 _gc_overhead_perc(0.0),
53
54 _bytes_allocated_in_old_since_last_gc(0),
55 _ihop_control(NULL),
56 _initial_mark_to_mixed() {
57
58 // SurvRateGroups below must be initialized after the predictor because they
59 // indirectly use it through this object passed to their constructor.
60 _short_lived_surv_rate_group =
61 new SurvRateGroup(&_predictor, "Short Lived", G1YoungSurvRateNumRegionsSummary);
62 _survivor_surv_rate_group =
63 new SurvRateGroup(&_predictor, "Survivor", G1YoungSurvRateNumRegionsSummary);
64
65 // Set up the region size and associated fields. Given that the
66 // policy is created before the heap, we have to set this up here,
67 // so it's done as soon as possible.
68
69 // It would have been natural to pass initial_heap_byte_size() and
70 // max_heap_byte_size() to setup_heap_region_size() but those have
71 // not been set up at this point since they should be aligned with
72 // the region size. So, there is a circular dependency here. We base
73 // the region size on the heap size, but the heap size should be
74 // aligned with the region size. To get around this we use the
75 // unaligned values for the heap.
76 HeapRegion::setup_heap_region_size(InitialHeapSize, MaxHeapSize);
77 HeapRegionRemSet::setup_remset_size();
78
79 clear_ratio_check_data();
80
81 _phase_times = new G1GCPhaseTimes(ParallelGCThreads);
82
83 // Below, we might need to calculate the pause time target based on
84 // the pause interval. When we do so we are going to give G1 maximum
85 // flexibility and allow it to do pauses when it needs to. So, we'll
86 // arrange that the pause interval to be pause time target + 1 to
87 // ensure that a) the pause time target is maximized with respect to
88 // the pause interval and b) we maintain the invariant that pause
89 // time target < pause interval. If the user does not want this
90 // maximum flexibility, they will have to set the pause interval
91 // explicitly.
92
93 // First make sure that, if either parameter is set, its value is
94 // reasonable.
95 if (!FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
96 if (MaxGCPauseMillis < 1) {
97 vm_exit_during_initialization("MaxGCPauseMillis should be "
98 "greater than 0");
99 }
100 }
101 if (!FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
102 if (GCPauseIntervalMillis < 1) {
123 // the pause time target (this will also deal with the case when the
124 // pause time target is the default value).
125 if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
126 FLAG_SET_DEFAULT(GCPauseIntervalMillis, MaxGCPauseMillis + 1);
127 }
128
129 // Finally, make sure that the two parameters are consistent.
130 if (MaxGCPauseMillis >= GCPauseIntervalMillis) {
131 char buffer[256];
132 jio_snprintf(buffer, 256,
133 "MaxGCPauseMillis (%u) should be less than "
134 "GCPauseIntervalMillis (%u)",
135 MaxGCPauseMillis, GCPauseIntervalMillis);
136 vm_exit_during_initialization(buffer);
137 }
138
139 double max_gc_time = (double) MaxGCPauseMillis / 1000.0;
140 double time_slice = (double) GCPauseIntervalMillis / 1000.0;
141 _mmu_tracker = new G1MMUTrackerQueue(time_slice, max_gc_time);
142
143 _tenuring_threshold = MaxTenuringThreshold;
144
145 assert(GCTimeRatio > 0,
146 "we should have set it to a default value set_g1_gc_flags() "
147 "if a user set it to 0");
148 _gc_overhead_perc = 100.0 * (1.0 / (1.0 + GCTimeRatio));
149
150 uintx reserve_perc = G1ReservePercent;
151 // Put an artificial ceiling on this so that it's not set to a silly value.
152 if (reserve_perc > 50) {
153 reserve_perc = 50;
154 warning("G1ReservePercent is set to a value that is too large, "
155 "it's been updated to " UINTX_FORMAT, reserve_perc);
156 }
157 _reserve_factor = (double) reserve_perc / 100.0;
158 // This will be set when the heap is expanded
159 // for the first time during initialization.
160 _reserve_regions = 0;
161
162 _ihop_control = create_ihop_control();
163 }
164
165 G1CollectorPolicy::~G1CollectorPolicy() {
166 delete _ihop_control;
167 }
168
169 void G1CollectorPolicy::initialize_alignments() {
170 _space_alignment = HeapRegion::GrainBytes;
171 size_t card_table_alignment = CardTableRS::ct_max_alignment_constraint();
172 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
173 _heap_alignment = MAX3(card_table_alignment, _space_alignment, page_size);
174 }
175
176 G1CollectorState* G1CollectorPolicy::collector_state() const { return _g1->collector_state(); }
177
178 void G1CollectorPolicy::post_heap_initialize() {
179 uintx max_regions = G1CollectedHeap::heap()->max_regions();
180 size_t max_young_size = (size_t)_young_gen_sizer->max_young_length(max_regions) * HeapRegion::GrainBytes;
181 if (max_young_size != MaxNewSize) {
182 FLAG_SET_ERGO(size_t, MaxNewSize, max_young_size);
183 }
184 }
185
186 void G1CollectorPolicy::initialize_flags() {
187 if (G1HeapRegionSize != HeapRegion::GrainBytes) {
188 FLAG_SET_ERGO(size_t, G1HeapRegionSize, HeapRegion::GrainBytes);
223 phase_times()->note_gc_start(num_active_workers);
224 }
225
226 // Create the jstat counters for the policy.
227 void G1CollectorPolicy::initialize_gc_policy_counters() {
228 _gc_policy_counters = new GCPolicyCounters("GarbageFirst", 1, 3);
229 }
230
231 bool G1CollectorPolicy::predict_will_fit(uint young_length,
232 double base_time_ms,
233 uint base_free_regions,
234 double target_pause_time_ms) const {
235 if (young_length >= base_free_regions) {
236 // end condition 1: not enough space for the young regions
237 return false;
238 }
239
240 double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);
241 size_t bytes_to_copy =
242 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
243 double copy_time_ms = _analytics->predict_object_copy_time_ms(bytes_to_copy,
244 collector_state()->during_concurrent_mark());
245 double young_other_time_ms = _analytics->predict_young_other_time_ms(young_length);
246 double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;
247 if (pause_time_ms > target_pause_time_ms) {
248 // end condition 2: prediction is over the target pause time
249 return false;
250 }
251
252 size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes;
253
254 // When copying, we will likely need more bytes free than is live in the region.
255 // Add some safety margin to factor in the confidence of our guess, and the
256 // natural expected waste.
257 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
258 // of the calculation: the lower the confidence, the more headroom.
259 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
260 // copying due to anticipated waste in the PLABs.
261 double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
262 size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
263
264 if (expected_bytes_to_copy > free_bytes) {
265 // end condition 3: out-of-space
269 // success!
270 return true;
271 }
272
273 void G1CollectorPolicy::record_new_heap_size(uint new_number_of_regions) {
274 // re-calculate the necessary reserve
275 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
276 // We use ceiling so that if reserve_regions_d is > 0.0 (but
277 // smaller than 1.0) we'll get 1.
278 _reserve_regions = (uint) ceil(reserve_regions_d);
279
280 _young_gen_sizer->heap_size_changed(new_number_of_regions);
281
282 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
283 }
284
285 uint G1CollectorPolicy::calculate_young_list_desired_min_length(
286 uint base_min_length) const {
287 uint desired_min_length = 0;
288 if (adaptive_young_list_length()) {
289 if (_analytics->num_alloc_rate_ms() > 3) {
290 double now_sec = os::elapsedTime();
291 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
292 double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
293 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
294 } else {
295 // otherwise we don't have enough info to make the prediction
296 }
297 }
298 desired_min_length += base_min_length;
299 // make sure we don't go below any user-defined minimum bound
300 return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
301 }
302
303 uint G1CollectorPolicy::calculate_young_list_desired_max_length() const {
304 // Here, we might want to also take into account any additional
305 // constraints (i.e., user-defined minimum bound). Currently, we
306 // effectively don't set this bound.
307 return _young_gen_sizer->max_desired_young_length();
308 }
309
310 uint G1CollectorPolicy::update_young_list_max_and_target_length() {
311 return update_young_list_max_and_target_length(_analytics->predict_rs_lengths());
312 }
313
314 uint G1CollectorPolicy::update_young_list_max_and_target_length(size_t rs_lengths) {
315 uint unbounded_target_length = update_young_list_target_length(rs_lengths);
316 update_max_gc_locker_expansion();
317 return unbounded_target_length;
318 }
319
320 uint G1CollectorPolicy::update_young_list_target_length(size_t rs_lengths) {
321 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
322 _young_list_target_length = young_lengths.first;
323 return young_lengths.second;
324 }
325
326 G1CollectorPolicy::YoungTargetLengths G1CollectorPolicy::young_list_target_lengths(size_t rs_lengths) const {
327 YoungTargetLengths result;
328
329 // Calculate the absolute and desired min bounds first.
330
331 // This is how many young regions we already have (currently: the survivors).
396 assert(adaptive_young_list_length(), "pre-condition");
397 assert(collector_state()->gcs_are_young(), "only call this for young GCs");
398
399 // In case some edge-condition makes the desired max length too small...
400 if (desired_max_length <= desired_min_length) {
401 return desired_min_length;
402 }
403
404 // We'll adjust min_young_length and max_young_length not to include
405 // the already allocated young regions (i.e., so they reflect the
406 // min and max eden regions we'll allocate). The base_min_length
407 // will be reflected in the predictions by the
408 // survivor_regions_evac_time prediction.
409 assert(desired_min_length > base_min_length, "invariant");
410 uint min_young_length = desired_min_length - base_min_length;
411 assert(desired_max_length > base_min_length, "invariant");
412 uint max_young_length = desired_max_length - base_min_length;
413
414 double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
415 double survivor_regions_evac_time = predict_survivor_regions_evac_time();
416 size_t pending_cards = _analytics->predict_pending_cards();
417 size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff();
418 size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, /* gcs_are_young */ true);
419 double base_time_ms =
420 predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
421 survivor_regions_evac_time;
422 uint available_free_regions = _free_regions_at_end_of_collection;
423 uint base_free_regions = 0;
424 if (available_free_regions > _reserve_regions) {
425 base_free_regions = available_free_regions - _reserve_regions;
426 }
427
428 // Here, we will make sure that the shortest young length that
429 // makes sense fits within the target pause time.
430
431 if (predict_will_fit(min_young_length, base_time_ms,
432 base_free_regions, target_pause_time_ms)) {
433 // The shortest young length will fit into the target pause time;
434 // we'll now check whether the absolute maximum number of young
435 // regions will fit in the target pause time. If not, we'll do
436 // a binary search between min_young_length and max_young_length.
437 if (predict_will_fit(max_young_length, base_time_ms,
438 base_free_regions, target_pause_time_ms)) {
498 r != NULL && r != _g1->young_list()->last_survivor_region()->get_next_young_region();
499 r = r->get_next_young_region()) {
500 survivor_regions_evac_time += predict_region_elapsed_time_ms(r, collector_state()->gcs_are_young());
501 }
502 return survivor_regions_evac_time;
503 }
504
505 void G1CollectorPolicy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
506 guarantee( adaptive_young_list_length(), "should not call this otherwise" );
507
508 if (rs_lengths > _rs_lengths_prediction) {
509 // add 10% to avoid having to recalculate often
510 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
511 update_rs_lengths_prediction(rs_lengths_prediction);
512
513 update_young_list_max_and_target_length(rs_lengths_prediction);
514 }
515 }
516
517 void G1CollectorPolicy::update_rs_lengths_prediction() {
518 update_rs_lengths_prediction(_analytics->predict_rs_lengths());
519 }
520
521 void G1CollectorPolicy::update_rs_lengths_prediction(size_t prediction) {
522 if (collector_state()->gcs_are_young() && adaptive_young_list_length()) {
523 _rs_lengths_prediction = prediction;
524 }
525 }
526
527 #ifndef PRODUCT
528 bool G1CollectorPolicy::verify_young_ages() {
529 HeapRegion* head = _g1->young_list()->first_region();
530 return
531 verify_young_ages(head, _short_lived_surv_rate_group);
532 // also call verify_young_ages on any additional surv rate groups
533 }
534
535 bool
536 G1CollectorPolicy::verify_young_ages(HeapRegion* head,
537 SurvRateGroup *surv_rate_group) {
538 guarantee( surv_rate_group != NULL, "pre-condition" );
566 }
567 }
568
569 return ret;
570 }
571 #endif // PRODUCT
572
573 void G1CollectorPolicy::record_full_collection_start() {
574 _full_collection_start_sec = os::elapsedTime();
575 // Release the future to-space so that it is available for compaction into.
576 collector_state()->set_full_collection(true);
577 }
578
579 void G1CollectorPolicy::record_full_collection_end() {
580 // Consider this like a collection pause for the purposes of allocation
581 // since last pause.
582 double end_sec = os::elapsedTime();
583 double full_gc_time_sec = end_sec - _full_collection_start_sec;
584 double full_gc_time_ms = full_gc_time_sec * 1000.0;
585
586 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);
587
588 collector_state()->set_full_collection(false);
589
590 // "Nuke" the heuristics that control the young/mixed GC
591 // transitions and make sure we start with young GCs after the Full GC.
592 collector_state()->set_gcs_are_young(true);
593 collector_state()->set_last_young_gc(false);
594 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
595 collector_state()->set_during_initial_mark_pause(false);
596 collector_state()->set_in_marking_window(false);
597 collector_state()->set_in_marking_window_im(false);
598
599 _short_lived_surv_rate_group->start_adding_regions();
600 // also call this on any additional surv rate groups
601
602 _free_regions_at_end_of_collection = _g1->num_free_regions();
603 // Reset survivors SurvRateGroup.
604 _survivor_surv_rate_group->reset();
605 update_young_list_max_and_target_length();
606 update_rs_lengths_prediction();
634 _survivors_age_table.clear();
635
636 assert( verify_young_ages(), "region age verification" );
637 }
638
639 void G1CollectorPolicy::record_concurrent_mark_init_end(double
640 mark_init_elapsed_time_ms) {
641 collector_state()->set_during_marking(true);
642 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
643 collector_state()->set_during_initial_mark_pause(false);
644 }
645
646 void G1CollectorPolicy::record_concurrent_mark_remark_start() {
647 _mark_remark_start_sec = os::elapsedTime();
648 collector_state()->set_during_marking(false);
649 }
650
651 void G1CollectorPolicy::record_concurrent_mark_remark_end() {
652 double end_time_sec = os::elapsedTime();
653 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
654 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);
655 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
656
657 record_pause(Remark, _mark_remark_start_sec, end_time_sec);
658 }
659
660 void G1CollectorPolicy::record_concurrent_mark_cleanup_start() {
661 _mark_cleanup_start_sec = os::elapsedTime();
662 }
663
664 void G1CollectorPolicy::record_concurrent_mark_cleanup_completed() {
665 bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",
666 "skip last young-only gc");
667 collector_state()->set_last_young_gc(should_continue_with_reclaim);
668 // We skip the marking phase.
669 if (!should_continue_with_reclaim) {
670 abort_time_to_mixed_tracking();
671 }
672 collector_state()->set_in_marking_window(false);
673 }
674
675 double G1CollectorPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
734
735 void G1CollectorPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
736 double end_time_sec = os::elapsedTime();
737
738 size_t cur_used_bytes = _g1->used();
739 assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
740 bool last_pause_included_initial_mark = false;
741 bool update_stats = !_g1->evacuation_failed();
742
743 NOT_PRODUCT(_short_lived_surv_rate_group->print());
744
745 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
746
747 last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();
748 if (last_pause_included_initial_mark) {
749 record_concurrent_mark_init_end(0.0);
750 } else {
751 maybe_start_marking();
752 }
753
754 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
755 if (app_time_ms < MIN_TIMER_GRANULARITY) {
756 // This usually happens due to the timer not having the required
757 // granularity. Some Linuxes are the usual culprits.
758 // We'll just set it to something (arbitrarily) small.
759 app_time_ms = 1.0;
760 }
761
762 if (update_stats) {
763 // We maintain the invariant that all objects allocated by mutator
764 // threads will be allocated out of eden regions. So, we can use
765 // the eden region number allocated since the previous GC to
766 // calculate the application's allocate rate. The only exception
767 // to that is humongous objects that are allocated separately. But
768 // given that humongous object allocations do not really affect
769 // either the pause's duration nor when the next pause will take
770 // place we can safely ignore them here.
771 uint regions_allocated = _collection_set->eden_region_length();
772 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
773 _analytics->report_alloc_rate_ms(alloc_rate_ms);
774
775 double interval_ms =
776 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;
777 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
778 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);
779 }
780
781 bool new_in_marking_window = collector_state()->in_marking_window();
782 bool new_in_marking_window_im = false;
783 if (last_pause_included_initial_mark) {
784 new_in_marking_window = true;
785 new_in_marking_window_im = true;
786 }
787
788 if (collector_state()->last_young_gc()) {
789 // This is supposed to to be the "last young GC" before we start
790 // doing mixed GCs. Here we decide whether to start mixed GCs or not.
791 assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC");
792
793 if (next_gc_should_be_mixed("start mixed GCs",
794 "do not start mixed GCs")) {
795 collector_state()->set_gcs_are_young(false);
796 } else {
797 // We aborted the mixed GC phase early.
798 abort_time_to_mixed_tracking();
804 if (!collector_state()->last_gc_was_young()) {
805 // This is a mixed GC. Here we decide whether to continue doing
806 // mixed GCs or not.
807 if (!next_gc_should_be_mixed("continue mixed GCs",
808 "do not continue mixed GCs")) {
809 collector_state()->set_gcs_are_young(true);
810
811 maybe_start_marking();
812 }
813 }
814
815 _short_lived_surv_rate_group->start_adding_regions();
816 // Do that for any other surv rate groups
817
818 double scan_hcc_time_ms = ConcurrentG1Refine::hot_card_cache_enabled() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
819
820 if (update_stats) {
821 double cost_per_card_ms = 0.0;
822 if (_pending_cards > 0) {
823 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards;
824 _analytics->report_cost_per_card_ms(cost_per_card_ms);
825 }
826 _analytics->report_cost_scan_hcc(scan_hcc_time_ms);
827
828 double cost_per_entry_ms = 0.0;
829 if (cards_scanned > 10) {
830 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
831 _analytics->report_cost_per_entry_ms(cost_per_entry_ms, collector_state()->last_gc_was_young());
832 }
833
834 if (_max_rs_lengths > 0) {
835 double cards_per_entry_ratio =
836 (double) cards_scanned / (double) _max_rs_lengths;
837 _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, collector_state()->last_gc_was_young());
838 }
839
840 // This is defensive. For a while _max_rs_lengths could get
841 // smaller than _recorded_rs_lengths which was causing
842 // rs_length_diff to get very large and mess up the RSet length
843 // predictions. The reason was unsafe concurrent updates to the
844 // _inc_cset_recorded_rs_lengths field which the code below guards
845 // against (see CR 7118202). This bug has now been fixed (see CR
846 // 7119027). However, I'm still worried that
847 // _inc_cset_recorded_rs_lengths might still end up somewhat
848 // inaccurate. The concurrent refinement thread calculates an
849 // RSet's length concurrently with other CR threads updating it
850 // which might cause it to calculate the length incorrectly (if,
851 // say, it's in mid-coarsening). So I'll leave in the defensive
852 // conditional below just in case.
853 size_t rs_length_diff = 0;
854 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();
855 if (_max_rs_lengths > recorded_rs_lengths) {
856 rs_length_diff = _max_rs_lengths - recorded_rs_lengths;
857 }
858 _analytics->report_rs_length_diff((double) rs_length_diff);
859
860 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
861 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
862 double cost_per_byte_ms = 0.0;
863
864 if (copied_bytes > 0) {
865 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
866 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->in_marking_window());
867 }
868
869 if (_collection_set->young_region_length() > 0) {
870 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
871 _collection_set->young_region_length());
872 }
873
874 if (_collection_set->old_region_length() > 0) {
875 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
876 _collection_set->old_region_length());
877 }
878
879 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
880
881 _analytics->report_pending_cards((double) _pending_cards);
882 _analytics->report_rs_lengths((double) _max_rs_lengths);
883 }
884
885 collector_state()->set_in_marking_window(new_in_marking_window);
886 collector_state()->set_in_marking_window_im(new_in_marking_window_im);
887 _free_regions_at_end_of_collection = _g1->num_free_regions();
888 // IHOP control wants to know the expected young gen length if it were not
889 // restrained by the heap reserve. Using the actual length would make the
890 // prediction too small and the limit the young gen every time we get to the
891 // predicted target occupancy.
892 size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
893 update_rs_lengths_prediction();
894
895 update_ihop_prediction(app_time_ms / 1000.0,
896 _bytes_allocated_in_old_since_last_gc,
897 last_unrestrained_young_length * HeapRegion::GrainBytes);
898 _bytes_allocated_in_old_since_last_gc = 0;
899
900 _ihop_control->send_trace_event(_g1->gc_tracer_stw());
901
902 // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
999 cg1r->set_red_zone(g * k_gr);
1000 cg1r->reinitialize_threads();
1001
1002 size_t processing_threshold_delta = MAX2<size_t>(cg1r->green_zone() * _predictor.sigma(), 1);
1003 size_t processing_threshold = MIN2(cg1r->green_zone() + processing_threshold_delta,
1004 cg1r->yellow_zone());
1005 // Change the barrier params
1006 dcqs.set_process_completed_threshold((int)processing_threshold);
1007 dcqs.set_max_completed_queue((int)cg1r->red_zone());
1008 }
1009
1010 size_t curr_queue_size = dcqs.completed_buffers_num();
1011 if (curr_queue_size >= cg1r->yellow_zone()) {
1012 dcqs.set_completed_queue_padding(curr_queue_size);
1013 } else {
1014 dcqs.set_completed_queue_padding(0);
1015 }
1016 dcqs.notify_if_necessary();
1017 }
1018
1019 double G1CollectorPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
1020 TruncatedSeq* seq = surv_rate_group->get_seq(age);
1021 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
1022 double pred = _predictor.get_new_prediction(seq);
1023 if (pred > 1.0) {
1024 pred = 1.0;
1025 }
1026 return pred;
1027 }
1028
1029 double G1CollectorPolicy::predict_yg_surv_rate(int age) const {
1030 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
1031 }
1032
1033 double G1CollectorPolicy::accum_yg_surv_rate_pred(int age) const {
1034 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
1035 }
1036
1037 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards,
1038 size_t scanned_cards) const {
1039 return
1040 _analytics->predict_rs_update_time_ms(pending_cards) +
1041 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->gcs_are_young()) +
1042 _analytics->predict_constant_other_time_ms();
1043 }
1044
1045 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const {
1046 size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff();
1047 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->gcs_are_young());
1048 return predict_base_elapsed_time_ms(pending_cards, card_num);
1049 }
1050
1051 size_t G1CollectorPolicy::predict_bytes_to_copy(HeapRegion* hr) const {
1052 size_t bytes_to_copy;
1053 if (hr->is_marked())
1054 bytes_to_copy = hr->max_live_bytes();
1055 else {
1056 assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
1057 int age = hr->age_in_surv_rate_group();
1058 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
1059 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
1060 }
1061 return bytes_to_copy;
1062 }
1063
1064 double G1CollectorPolicy::predict_region_elapsed_time_ms(HeapRegion* hr,
1065 bool for_young_gc) const {
1066 size_t rs_length = hr->rem_set()->occupied();
1067 // Predicting the number of cards is based on which type of GC
1068 // we're predicting for.
1069 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc);
1070 size_t bytes_to_copy = predict_bytes_to_copy(hr);
1071
1072 double region_elapsed_time_ms =
1073 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->gcs_are_young()) +
1074 _analytics->predict_object_copy_time_ms(bytes_to_copy ,collector_state()->during_concurrent_mark());
1075
1076 // The prediction of the "other" time for this region is based
1077 // upon the region type and NOT the GC type.
1078 if (hr->is_young()) {
1079 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
1080 } else {
1081 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
1082 }
1083 return region_elapsed_time_ms;
1084 }
1085
1086 void G1CollectorPolicy::clear_ratio_check_data() {
1087 _ratio_over_threshold_count = 0;
1088 _ratio_over_threshold_sum = 0.0;
1089 _pauses_since_start = 0;
1090 }
1091
1092 size_t G1CollectorPolicy::expansion_amount() {
1093 double recent_gc_overhead = _analytics->recent_avg_pause_time_ratio() * 100.0;
1094 double last_gc_overhead = _analytics->last_pause_time_ratio() * 100.0;
1095 double threshold = _gc_overhead_perc;
1096 size_t expand_bytes = 0;
1097
1098 // If the heap is at less than half its maximum size, scale the threshold down,
1099 // to a limit of 1. Thus the smaller the heap is, the more likely it is to expand,
1100 // though the scaling code will likely keep the increase small.
1101 if (_g1->capacity() <= _g1->max_capacity() / 2) {
1102 threshold *= (double)_g1->capacity() / (double)(_g1->max_capacity() / 2);
1103 threshold = MAX2(threshold, 1.0);
1104 }
1105
1106 // If the last GC time ratio is over the threshold, increment the count of
1107 // times it has been exceeded, and add this ratio to the sum of exceeded
1108 // ratios.
1109 if (last_gc_overhead > threshold) {
1110 _ratio_over_threshold_count++;
1111 _ratio_over_threshold_sum += last_gc_overhead;
1112 }
1113
1114 // Check if we've had enough GC time ratio checks that were over the
1359 const uint min_chunk_size = MAX2(n_regions / n_workers, 1U);
1360 return MAX2(n_regions / (n_workers * overpartition_factor), min_chunk_size);
1361 }
1362
1363 void G1CollectorPolicy::record_concurrent_mark_cleanup_end() {
1364 cset_chooser()->clear();
1365
1366 WorkGang* workers = _g1->workers();
1367 uint n_workers = workers->active_workers();
1368
1369 uint n_regions = _g1->num_regions();
1370 uint chunk_size = calculate_parallel_work_chunk_size(n_workers, n_regions);
1371 cset_chooser()->prepare_for_par_region_addition(n_workers, n_regions, chunk_size);
1372 ParKnownGarbageTask par_known_garbage_task(cset_chooser(), chunk_size, n_workers);
1373 workers->run_task(&par_known_garbage_task);
1374
1375 cset_chooser()->sort_regions();
1376
1377 double end_sec = os::elapsedTime();
1378 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1379 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
1380 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
1381
1382 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1383 }
1384
1385 double G1CollectorPolicy::reclaimable_bytes_perc(size_t reclaimable_bytes) const {
1386 // Returns the given amount of reclaimable bytes (that represents
1387 // the amount of reclaimable space still to be collected) as a
1388 // percentage of the current heap capacity.
1389 size_t capacity_bytes = _g1->capacity();
1390 return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
1391 }
1392
1393 void G1CollectorPolicy::maybe_start_marking() {
1394 if (need_to_start_conc_mark("end of GC")) {
1395 // Note: this might have already been set, if during the last
1396 // pause we decided to start a cycle but at the beginning of
1397 // this pause we decided to postpone it. That's OK.
1398 collector_state()->set_initiate_conc_mark_if_possible(true);
1399 }
1400 }
1498 // The max old CSet region bound is based on the threshold expressed
1499 // as a percentage of the heap size. I.e., it should bound the
1500 // number of old regions added to the CSet irrespective of how many
1501 // of them are available.
1502
1503 const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1504 const size_t region_num = g1h->num_regions();
1505 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1506 size_t result = region_num * perc / 100;
1507 // emulate ceiling
1508 if (100 * result < region_num * perc) {
1509 result += 1;
1510 }
1511 return (uint) result;
1512 }
1513
1514 void G1CollectorPolicy::finalize_collection_set(double target_pause_time_ms) {
1515 double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms);
1516 _collection_set->finalize_old_part(time_remaining_ms);
1517 }
|