1 /*
2 * Copyright (c) 2001, 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/g1Analytics.hpp"
27 #include "gc/g1/g1Arguments.hpp"
28 #include "gc/g1/g1CollectedHeap.inline.hpp"
29 #include "gc/g1/g1CollectionSet.hpp"
30 #include "gc/g1/g1CollectionSetCandidates.hpp"
31 #include "gc/g1/g1ConcurrentMark.hpp"
32 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
33 #include "gc/g1/g1ConcurrentRefine.hpp"
34 #include "gc/g1/g1CollectionSetChooser.hpp"
35 #include "gc/g1/g1HeterogeneousHeapPolicy.hpp"
36 #include "gc/g1/g1HotCardCache.hpp"
37 #include "gc/g1/g1IHOPControl.hpp"
38 #include "gc/g1/g1GCPhaseTimes.hpp"
39 #include "gc/g1/g1Policy.hpp"
40 #include "gc/g1/g1SurvivorRegions.hpp"
41 #include "gc/g1/g1YoungGenSizer.hpp"
42 #include "gc/g1/heapRegion.inline.hpp"
43 #include "gc/g1/heapRegionRemSet.hpp"
44 #include "gc/shared/gcPolicyCounters.hpp"
45 #include "logging/logStream.hpp"
46 #include "runtime/arguments.hpp"
47 #include "runtime/java.hpp"
48 #include "runtime/mutexLocker.inline.hpp"
49 #include "utilities/debug.hpp"
50 #include "utilities/growableArray.hpp"
51 #include "utilities/pair.hpp"
52
53 G1Policy::G1Policy(STWGCTimer* gc_timer) :
54 _predictor(G1ConfidencePercent / 100.0),
55 _analytics(new G1Analytics(&_predictor)),
56 _remset_tracker(),
57 _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)),
58 _ihop_control(create_ihop_control(&_predictor)),
59 _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 2)),
60 _full_collection_start_sec(0.0),
61 _collection_pause_end_millis(os::javaTimeNanos() / NANOSECS_PER_MILLISEC),
62 _young_list_target_length(0),
63 _young_list_fixed_length(0),
64 _young_list_max_length(0),
65 _short_lived_surv_rate_group(new SurvRateGroup()),
66 _survivor_surv_rate_group(new SurvRateGroup()),
67 _reserve_factor((double) G1ReservePercent / 100.0),
68 _reserve_regions(0),
69 _young_gen_sizer(G1YoungGenSizer::create_gen_sizer()),
70 _free_regions_at_end_of_collection(0),
71 _max_rs_length(0),
72 _rs_length_prediction(0),
73 _pending_cards(0),
74 _bytes_allocated_in_old_since_last_gc(0),
75 _initial_mark_to_mixed(),
76 _collection_set(NULL),
77 _bytes_copied_during_gc(0),
78 _g1h(NULL),
79 _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)),
80 _mark_remark_start_sec(0),
81 _mark_cleanup_start_sec(0),
82 _tenuring_threshold(MaxTenuringThreshold),
83 _max_survivor_regions(0),
84 _survivors_age_table(true)
85 {
86 }
87
88 G1Policy::~G1Policy() {
89 delete _ihop_control;
90 delete _young_gen_sizer;
91 }
92
93 G1Policy* G1Policy::create_policy(STWGCTimer* gc_timer_stw) {
94 if (G1Arguments::is_heterogeneous_heap()) {
95 return new G1HeterogeneousHeapPolicy(gc_timer_stw);
96 } else {
97 return new G1Policy(gc_timer_stw);
98 }
99 }
100
101 G1CollectorState* G1Policy::collector_state() const { return _g1h->collector_state(); }
102
103 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
104 _g1h = g1h;
105 _collection_set = collection_set;
106
107 assert(Heap_lock->owned_by_self(), "Locking discipline.");
108
109 if (!use_adaptive_young_list_length()) {
110 _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
111 }
112 _young_gen_sizer->adjust_max_new_size(_g1h->max_expandable_regions());
113
114 _free_regions_at_end_of_collection = _g1h->num_free_regions();
115
116 update_young_list_max_and_target_length();
117 // We may immediately start allocating regions and placing them on the
118 // collection set list. Initialize the per-collection set info
119 _collection_set->start_incremental_building();
120 }
121
122 void G1Policy::note_gc_start() {
123 phase_times()->note_gc_start();
124 }
125
126 class G1YoungLengthPredictor {
127 const bool _during_cm;
128 const double _base_time_ms;
129 const double _base_free_regions;
130 const double _target_pause_time_ms;
131 const G1Policy* const _policy;
132
133 public:
134 G1YoungLengthPredictor(bool during_cm,
135 double base_time_ms,
136 double base_free_regions,
137 double target_pause_time_ms,
138 const G1Policy* policy) :
139 _during_cm(during_cm),
140 _base_time_ms(base_time_ms),
141 _base_free_regions(base_free_regions),
142 _target_pause_time_ms(target_pause_time_ms),
143 _policy(policy) {}
144
145 bool will_fit(uint young_length) const {
146 if (young_length >= _base_free_regions) {
147 // end condition 1: not enough space for the young regions
148 return false;
149 }
150
151 const double accum_surv_rate = _policy->accum_yg_surv_rate_pred((int) young_length - 1);
152 const size_t bytes_to_copy =
153 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
154 const double copy_time_ms =
155 _policy->analytics()->predict_object_copy_time_ms(bytes_to_copy, _during_cm);
156 const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length);
157 const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms;
158 if (pause_time_ms > _target_pause_time_ms) {
159 // end condition 2: prediction is over the target pause time
160 return false;
161 }
162
163 const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes;
164
165 // When copying, we will likely need more bytes free than is live in the region.
166 // Add some safety margin to factor in the confidence of our guess, and the
167 // natural expected waste.
168 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
169 // of the calculation: the lower the confidence, the more headroom.
170 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
171 // copying due to anticipated waste in the PLABs.
172 const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
173 const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
174
175 if (expected_bytes_to_copy > free_bytes) {
176 // end condition 3: out-of-space
177 return false;
178 }
179
180 // success!
181 return true;
182 }
183 };
184
185 void G1Policy::record_new_heap_size(uint new_number_of_regions) {
186 // re-calculate the necessary reserve
187 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
188 // We use ceiling so that if reserve_regions_d is > 0.0 (but
189 // smaller than 1.0) we'll get 1.
190 _reserve_regions = (uint) ceil(reserve_regions_d);
191
192 _young_gen_sizer->heap_size_changed(new_number_of_regions);
193
194 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
195 }
196
197 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const {
198 uint desired_min_length = 0;
199 if (use_adaptive_young_list_length()) {
200 if (_analytics->num_alloc_rate_ms() > 3) {
201 double now_sec = os::elapsedTime();
202 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
203 double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
204 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
205 } else {
206 // otherwise we don't have enough info to make the prediction
207 }
208 }
209 desired_min_length += base_min_length;
210 // make sure we don't go below any user-defined minimum bound
211 return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
212 }
213
214 uint G1Policy::calculate_young_list_desired_max_length() const {
215 // Here, we might want to also take into account any additional
216 // constraints (i.e., user-defined minimum bound). Currently, we
217 // effectively don't set this bound.
218 return _young_gen_sizer->max_desired_young_length();
219 }
220
221 uint G1Policy::update_young_list_max_and_target_length() {
222 return update_young_list_max_and_target_length(_analytics->predict_rs_length());
223 }
224
225 uint G1Policy::update_young_list_max_and_target_length(size_t rs_length) {
226 uint unbounded_target_length = update_young_list_target_length(rs_length);
227 update_max_gc_locker_expansion();
228 return unbounded_target_length;
229 }
230
231 uint G1Policy::update_young_list_target_length(size_t rs_length) {
232 YoungTargetLengths young_lengths = young_list_target_lengths(rs_length);
233 _young_list_target_length = young_lengths.first;
234
235 return young_lengths.second;
236 }
237
238 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_length) const {
239 YoungTargetLengths result;
240
241 // Calculate the absolute and desired min bounds first.
242
243 // This is how many young regions we already have (currently: the survivors).
244 const uint base_min_length = _g1h->survivor_regions_count();
245 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
246 // This is the absolute minimum young length. Ensure that we
247 // will at least have one eden region available for allocation.
248 uint absolute_min_length = base_min_length + MAX2(_g1h->eden_regions_count(), (uint)1);
249 // If we shrank the young list target it should not shrink below the current size.
250 desired_min_length = MAX2(desired_min_length, absolute_min_length);
251 // Calculate the absolute and desired max bounds.
252
253 uint desired_max_length = calculate_young_list_desired_max_length();
254
255 uint young_list_target_length = 0;
256 if (use_adaptive_young_list_length()) {
257 if (collector_state()->in_young_only_phase()) {
258 young_list_target_length =
259 calculate_young_list_target_length(rs_length,
260 base_min_length,
261 desired_min_length,
262 desired_max_length);
263 } else {
264 // Don't calculate anything and let the code below bound it to
265 // the desired_min_length, i.e., do the next GC as soon as
266 // possible to maximize how many old regions we can add to it.
267 }
268 } else {
269 // The user asked for a fixed young gen so we'll fix the young gen
270 // whether the next GC is young or mixed.
271 young_list_target_length = _young_list_fixed_length;
272 }
273
274 result.second = young_list_target_length;
275
276 // We will try our best not to "eat" into the reserve.
277 uint absolute_max_length = 0;
278 if (_free_regions_at_end_of_collection > _reserve_regions) {
279 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
280 }
281 if (desired_max_length > absolute_max_length) {
282 desired_max_length = absolute_max_length;
283 }
284
285 // Make sure we don't go over the desired max length, nor under the
286 // desired min length. In case they clash, desired_min_length wins
287 // which is why that test is second.
288 if (young_list_target_length > desired_max_length) {
289 young_list_target_length = desired_max_length;
290 }
291 if (young_list_target_length < desired_min_length) {
292 young_list_target_length = desired_min_length;
293 }
294
295 assert(young_list_target_length > base_min_length,
296 "we should be able to allocate at least one eden region");
297 assert(young_list_target_length >= absolute_min_length, "post-condition");
298
299 result.first = young_list_target_length;
300 return result;
301 }
302
303 uint
304 G1Policy::calculate_young_list_target_length(size_t rs_length,
305 uint base_min_length,
306 uint desired_min_length,
307 uint desired_max_length) const {
308 assert(use_adaptive_young_list_length(), "pre-condition");
309 assert(collector_state()->in_young_only_phase(), "only call this for young GCs");
310
311 // In case some edge-condition makes the desired max length too small...
312 if (desired_max_length <= desired_min_length) {
313 return desired_min_length;
314 }
315
316 // We'll adjust min_young_length and max_young_length not to include
317 // the already allocated young regions (i.e., so they reflect the
318 // min and max eden regions we'll allocate). The base_min_length
319 // will be reflected in the predictions by the
320 // survivor_regions_evac_time prediction.
321 assert(desired_min_length > base_min_length, "invariant");
322 uint min_young_length = desired_min_length - base_min_length;
323 assert(desired_max_length > base_min_length, "invariant");
324 uint max_young_length = desired_max_length - base_min_length;
325
326 const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
327 const double survivor_regions_evac_time = predict_survivor_regions_evac_time();
328 const size_t pending_cards = _analytics->predict_pending_cards();
329 const size_t adj_rs_length = rs_length + _analytics->predict_rs_length_diff();
330 const size_t scanned_cards = _analytics->predict_card_num(adj_rs_length, true /* for_young_gc */);
331 const double base_time_ms =
332 predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
333 survivor_regions_evac_time;
334 const uint available_free_regions = _free_regions_at_end_of_collection;
335 const uint base_free_regions =
336 available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0;
337
338 // Here, we will make sure that the shortest young length that
339 // makes sense fits within the target pause time.
340
341 G1YoungLengthPredictor p(collector_state()->mark_or_rebuild_in_progress(),
342 base_time_ms,
343 base_free_regions,
344 target_pause_time_ms,
345 this);
346 if (p.will_fit(min_young_length)) {
347 // The shortest young length will fit into the target pause time;
348 // we'll now check whether the absolute maximum number of young
349 // regions will fit in the target pause time. If not, we'll do
350 // a binary search between min_young_length and max_young_length.
351 if (p.will_fit(max_young_length)) {
352 // The maximum young length will fit into the target pause time.
353 // We are done so set min young length to the maximum length (as
354 // the result is assumed to be returned in min_young_length).
355 min_young_length = max_young_length;
356 } else {
357 // The maximum possible number of young regions will not fit within
358 // the target pause time so we'll search for the optimal
359 // length. The loop invariants are:
360 //
361 // min_young_length < max_young_length
362 // min_young_length is known to fit into the target pause time
363 // max_young_length is known not to fit into the target pause time
364 //
365 // Going into the loop we know the above hold as we've just
366 // checked them. Every time around the loop we check whether
367 // the middle value between min_young_length and
368 // max_young_length fits into the target pause time. If it
369 // does, it becomes the new min. If it doesn't, it becomes
370 // the new max. This way we maintain the loop invariants.
371
372 assert(min_young_length < max_young_length, "invariant");
373 uint diff = (max_young_length - min_young_length) / 2;
374 while (diff > 0) {
375 uint young_length = min_young_length + diff;
376 if (p.will_fit(young_length)) {
377 min_young_length = young_length;
378 } else {
379 max_young_length = young_length;
380 }
381 assert(min_young_length < max_young_length, "invariant");
382 diff = (max_young_length - min_young_length) / 2;
383 }
384 // The results is min_young_length which, according to the
385 // loop invariants, should fit within the target pause time.
386
387 // These are the post-conditions of the binary search above:
388 assert(min_young_length < max_young_length,
389 "otherwise we should have discovered that max_young_length "
390 "fits into the pause target and not done the binary search");
391 assert(p.will_fit(min_young_length),
392 "min_young_length, the result of the binary search, should "
393 "fit into the pause target");
394 assert(!p.will_fit(min_young_length + 1),
395 "min_young_length, the result of the binary search, should be "
396 "optimal, so no larger length should fit into the pause target");
397 }
398 } else {
399 // Even the minimum length doesn't fit into the pause time
400 // target, return it as the result nevertheless.
401 }
402 return base_min_length + min_young_length;
403 }
404
405 double G1Policy::predict_survivor_regions_evac_time() const {
406 double survivor_regions_evac_time = 0.0;
407 const GrowableArray<HeapRegion*>* survivor_regions = _g1h->survivor()->regions();
408
409 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin();
410 it != survivor_regions->end();
411 ++it) {
412 survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->in_young_only_phase());
413 }
414 return survivor_regions_evac_time;
415 }
416
417 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_length) {
418 guarantee(use_adaptive_young_list_length(), "should not call this otherwise" );
419
420 if (rs_length > _rs_length_prediction) {
421 // add 10% to avoid having to recalculate often
422 size_t rs_length_prediction = rs_length * 1100 / 1000;
423 update_rs_length_prediction(rs_length_prediction);
424
425 update_young_list_max_and_target_length(rs_length_prediction);
426 }
427 }
428
429 void G1Policy::update_rs_length_prediction() {
430 update_rs_length_prediction(_analytics->predict_rs_length());
431 }
432
433 void G1Policy::update_rs_length_prediction(size_t prediction) {
434 if (collector_state()->in_young_only_phase() && use_adaptive_young_list_length()) {
435 _rs_length_prediction = prediction;
436 }
437 }
438
439 void G1Policy::record_full_collection_start() {
440 _full_collection_start_sec = os::elapsedTime();
441 // Release the future to-space so that it is available for compaction into.
442 collector_state()->set_in_young_only_phase(false);
443 collector_state()->set_in_full_gc(true);
444 _collection_set->clear_candidates();
445 }
446
447 void G1Policy::record_full_collection_end() {
448 // Consider this like a collection pause for the purposes of allocation
449 // since last pause.
450 double end_sec = os::elapsedTime();
451 double full_gc_time_sec = end_sec - _full_collection_start_sec;
452 double full_gc_time_ms = full_gc_time_sec * 1000.0;
453
454 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);
455
456 collector_state()->set_in_full_gc(false);
457
458 // "Nuke" the heuristics that control the young/mixed GC
459 // transitions and make sure we start with young GCs after the Full GC.
460 collector_state()->set_in_young_only_phase(true);
461 collector_state()->set_in_young_gc_before_mixed(false);
462 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
463 collector_state()->set_in_initial_mark_gc(false);
464 collector_state()->set_mark_or_rebuild_in_progress(false);
465 collector_state()->set_clearing_next_bitmap(false);
466
467 _short_lived_surv_rate_group->start_adding_regions();
468 // also call this on any additional surv rate groups
469
470 _free_regions_at_end_of_collection = _g1h->num_free_regions();
471 // Reset survivors SurvRateGroup.
472 _survivor_surv_rate_group->reset();
473 update_young_list_max_and_target_length();
474 update_rs_length_prediction();
475
476 _bytes_allocated_in_old_since_last_gc = 0;
477
478 record_pause(FullGC, _full_collection_start_sec, end_sec);
479 }
480
481 void G1Policy::record_collection_pause_start(double start_time_sec) {
482 // We only need to do this here as the policy will only be applied
483 // to the GC we're about to start. so, no point is calculating this
484 // every time we calculate / recalculate the target young length.
485 update_survivors_policy();
486
487 assert(max_survivor_regions() + _g1h->num_used_regions() <= _g1h->max_regions(),
488 "Maximum survivor regions %u plus used regions %u exceeds max regions %u",
489 max_survivor_regions(), _g1h->num_used_regions(), _g1h->max_regions());
490 assert_used_and_recalculate_used_equal(_g1h);
491
492 phase_times()->record_cur_collection_start_sec(start_time_sec);
493 _pending_cards = _g1h->pending_card_num();
494
495 _collection_set->reset_bytes_used_before();
496 _bytes_copied_during_gc = 0;
497
498 // do that for any other surv rate groups
499 _short_lived_surv_rate_group->stop_adding_regions();
500 _survivors_age_table.clear();
501
502 assert(_g1h->collection_set()->verify_young_ages(), "region age verification failed");
503 }
504
505 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {
506 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
507 collector_state()->set_in_initial_mark_gc(false);
508 }
509
510 void G1Policy::record_concurrent_mark_remark_start() {
511 _mark_remark_start_sec = os::elapsedTime();
512 }
513
514 void G1Policy::record_concurrent_mark_remark_end() {
515 double end_time_sec = os::elapsedTime();
516 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
517 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);
518 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
519
520 record_pause(Remark, _mark_remark_start_sec, end_time_sec);
521 }
522
523 void G1Policy::record_concurrent_mark_cleanup_start() {
524 _mark_cleanup_start_sec = os::elapsedTime();
525 }
526
527 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
528 return phase_times()->average_time_ms(phase);
529 }
530
531 double G1Policy::young_other_time_ms() const {
532 return phase_times()->young_cset_choice_time_ms() +
533 phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet);
534 }
535
536 double G1Policy::non_young_other_time_ms() const {
537 return phase_times()->non_young_cset_choice_time_ms() +
538 phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet);
539 }
540
541 double G1Policy::other_time_ms(double pause_time_ms) const {
542 return pause_time_ms - phase_times()->cur_collection_par_time_ms();
543 }
544
545 double G1Policy::constant_other_time_ms(double pause_time_ms) const {
546 return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms();
547 }
548
549 bool G1Policy::about_to_start_mixed_phase() const {
550 return _g1h->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->in_young_gc_before_mixed();
551 }
552
553 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
554 if (about_to_start_mixed_phase()) {
555 return false;
556 }
557
558 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
559
560 size_t cur_used_bytes = _g1h->non_young_capacity_bytes();
561 size_t alloc_byte_size = alloc_word_size * HeapWordSize;
562 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
563
564 bool result = false;
565 if (marking_request_bytes > marking_initiating_used_threshold) {
566 result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed();
567 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
568 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
569 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1h->capacity() * 100, source);
570 }
571
572 return result;
573 }
574
575 double G1Policy::logged_cards_processing_time() const {
576 double all_cards_processing_time = average_time_ms(G1GCPhaseTimes::ScanHR) + average_time_ms(G1GCPhaseTimes::OptScanHR);
577 size_t logged_dirty_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards);
578 size_t scan_heap_roots_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) +
579 phase_times()->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards);
580 // This may happen if there are duplicate cards in different log buffers.
581 if (logged_dirty_cards > scan_heap_roots_cards) {
582 return all_cards_processing_time + average_time_ms(G1GCPhaseTimes::MergeLB);
583 }
584 return (all_cards_processing_time * logged_dirty_cards / scan_heap_roots_cards) + average_time_ms(G1GCPhaseTimes::MergeLB);
585 }
586
587 // Anything below that is considered to be zero
588 #define MIN_TIMER_GRANULARITY 0.0000001
589
590 void G1Policy::record_collection_pause_end(double pause_time_ms, size_t heap_used_bytes_before_gc) {
591 G1GCPhaseTimes* p = phase_times();
592
593 double end_time_sec = os::elapsedTime();
594
595 assert_used_and_recalculate_used_equal(_g1h);
596 size_t cur_used_bytes = _g1h->used();
597 bool this_pause_included_initial_mark = false;
598 bool this_pause_was_young_only = collector_state()->in_young_only_phase();
599
600 bool update_stats = !_g1h->evacuation_failed();
601
602 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
603
604 _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
605
606 this_pause_included_initial_mark = collector_state()->in_initial_mark_gc();
607 if (this_pause_included_initial_mark) {
608 record_concurrent_mark_init_end(0.0);
609 } else {
610 maybe_start_marking();
611 }
612
613 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
614 if (app_time_ms < MIN_TIMER_GRANULARITY) {
615 // This usually happens due to the timer not having the required
616 // granularity. Some Linuxes are the usual culprits.
617 // We'll just set it to something (arbitrarily) small.
618 app_time_ms = 1.0;
619 }
620
621 if (update_stats) {
622 // We maintain the invariant that all objects allocated by mutator
623 // threads will be allocated out of eden regions. So, we can use
624 // the eden region number allocated since the previous GC to
625 // calculate the application's allocate rate. The only exception
626 // to that is humongous objects that are allocated separately. But
627 // given that humongous object allocations do not really affect
628 // either the pause's duration nor when the next pause will take
629 // place we can safely ignore them here.
630 uint regions_allocated = _collection_set->eden_region_length();
631 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
632 _analytics->report_alloc_rate_ms(alloc_rate_ms);
633
634 double interval_ms =
635 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;
636 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
637 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);
638 }
639
640 if (collector_state()->in_young_gc_before_mixed()) {
641 assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC");
642 // This has been the young GC before we start doing mixed GCs. We already
643 // decided to start mixed GCs much earlier, so there is nothing to do except
644 // advancing the state.
645 collector_state()->set_in_young_only_phase(false);
646 collector_state()->set_in_young_gc_before_mixed(false);
647 } else if (!this_pause_was_young_only) {
648 // This is a mixed GC. Here we decide whether to continue doing more
649 // mixed GCs or not.
650 if (!next_gc_should_be_mixed("continue mixed GCs",
651 "do not continue mixed GCs")) {
652 collector_state()->set_in_young_only_phase(true);
653
654 clear_collection_set_candidates();
655 maybe_start_marking();
656 }
657 }
658
659 _short_lived_surv_rate_group->start_adding_regions();
660 // Do that for any other surv rate groups
661
662 double scan_hcc_time_ms = G1HotCardCache::default_use_cache() ? average_time_ms(G1GCPhaseTimes::MergeHCC) : 0.0;
663
664 if (update_stats) {
665 double cost_per_logged_card = 0.0;
666 size_t const pending_logged_cards = p->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards);
667 if (pending_logged_cards > 0) {
668 cost_per_logged_card = logged_cards_processing_time() / pending_logged_cards;
669 _analytics->report_cost_per_logged_card_ms(cost_per_logged_card);
670 }
671 _analytics->report_cost_scan_hcc(scan_hcc_time_ms);
672
673 size_t const total_cards_scanned = p->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) +
674 p->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards);
675 size_t remset_cards_scanned = 0;
676 // There might have been duplicate log buffer entries in the queues which could
677 // increase this value beyond the cards scanned. In this case attribute all cards
678 // to the log buffers.
679 if (pending_logged_cards <= total_cards_scanned) {
680 remset_cards_scanned = total_cards_scanned - pending_logged_cards;
681 }
682
683 double cost_per_remset_card_ms = 0.0;
684 if (remset_cards_scanned > 10) {
685 double avg_time_remset_scan = ((average_time_ms(G1GCPhaseTimes::ScanHR) + average_time_ms(G1GCPhaseTimes::OptScanHR)) *
686 remset_cards_scanned / total_cards_scanned) +
687 average_time_ms(G1GCPhaseTimes::MergeER) +
688 average_time_ms(G1GCPhaseTimes::MergeRS) +
689 average_time_ms(G1GCPhaseTimes::OptMergeRS);
690
691 cost_per_remset_card_ms = avg_time_remset_scan / remset_cards_scanned;
692 _analytics->report_cost_per_remset_card_ms(cost_per_remset_card_ms, this_pause_was_young_only);
693 }
694
695 if (_max_rs_length > 0) {
696 double cards_per_entry_ratio =
697 (double) remset_cards_scanned / (double) _max_rs_length;
698 _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, this_pause_was_young_only);
699 }
700
701 // This is defensive. For a while _max_rs_length could get
702 // smaller than _recorded_rs_length which was causing
703 // rs_length_diff to get very large and mess up the RSet length
704 // predictions. The reason was unsafe concurrent updates to the
705 // _inc_cset_recorded_rs_length field which the code below guards
706 // against (see CR 7118202). This bug has now been fixed (see CR
707 // 7119027). However, I'm still worried that
708 // _inc_cset_recorded_rs_length might still end up somewhat
709 // inaccurate. The concurrent refinement thread calculates an
710 // RSet's length concurrently with other CR threads updating it
711 // which might cause it to calculate the length incorrectly (if,
712 // say, it's in mid-coarsening). So I'll leave in the defensive
713 // conditional below just in case.
714 size_t rs_length_diff = 0;
715 size_t recorded_rs_length = _collection_set->recorded_rs_length();
716 if (_max_rs_length > recorded_rs_length) {
717 rs_length_diff = _max_rs_length - recorded_rs_length;
718 }
719 _analytics->report_rs_length_diff((double) rs_length_diff);
720
721 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
722 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
723 double cost_per_byte_ms = 0.0;
724
725 if (copied_bytes > 0) {
726 cost_per_byte_ms = (average_time_ms(G1GCPhaseTimes::ObjCopy) + average_time_ms(G1GCPhaseTimes::OptObjCopy)) / (double) copied_bytes;
727 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress());
728 }
729
730 if (_collection_set->young_region_length() > 0) {
731 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
732 _collection_set->young_region_length());
733 }
734
735 if (_collection_set->old_region_length() > 0) {
736 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
737 _collection_set->old_region_length());
738 }
739
740 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
741
742 // Do not update RS lengths and the number of pending cards with information from mixed gc:
743 // these are is wildly different to during young only gc and mess up young gen sizing right
744 // after the mixed gc phase.
745 // During mixed gc we do not use them for young gen sizing.
746 if (this_pause_was_young_only) {
747 _analytics->report_pending_cards((double) _pending_cards);
748 _analytics->report_rs_length((double) _max_rs_length);
749 }
750 }
751
752 assert(!(this_pause_included_initial_mark && collector_state()->mark_or_rebuild_in_progress()),
753 "If the last pause has been an initial mark, we should not have been in the marking window");
754 if (this_pause_included_initial_mark) {
755 collector_state()->set_mark_or_rebuild_in_progress(true);
756 }
757
758 _free_regions_at_end_of_collection = _g1h->num_free_regions();
759
760 update_rs_length_prediction();
761
762 // Do not update dynamic IHOP due to G1 periodic collection as it is highly likely
763 // that in this case we are not running in a "normal" operating mode.
764 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) {
765 // IHOP control wants to know the expected young gen length if it were not
766 // restrained by the heap reserve. Using the actual length would make the
767 // prediction too small and the limit the young gen every time we get to the
768 // predicted target occupancy.
769 size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
770
771 update_ihop_prediction(app_time_ms / 1000.0,
772 _bytes_allocated_in_old_since_last_gc,
773 last_unrestrained_young_length * HeapRegion::GrainBytes,
774 this_pause_was_young_only);
775 _bytes_allocated_in_old_since_last_gc = 0;
776
777 _ihop_control->send_trace_event(_g1h->gc_tracer_stw());
778 } else {
779 // Any garbage collection triggered as periodic collection resets the time-to-mixed
780 // measurement. Periodic collection typically means that the application is "inactive", i.e.
781 // the marking threads may have received an uncharacterisic amount of cpu time
782 // for completing the marking, i.e. are faster than expected.
783 // This skews the predicted marking length towards smaller values which might cause
784 // the mark start being too late.
785 _initial_mark_to_mixed.reset();
786 }
787
788 // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
789 double scan_logged_cards_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
790
791 if (scan_logged_cards_time_goal_ms < scan_hcc_time_ms) {
792 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
793 "Logged Cards Scan time goal: %1.2fms Scan HCC time: %1.2fms",
794 scan_logged_cards_time_goal_ms, scan_hcc_time_ms);
795
796 scan_logged_cards_time_goal_ms = 0;
797 } else {
798 scan_logged_cards_time_goal_ms -= scan_hcc_time_ms;
799 }
800
801 double const logged_cards_time = logged_cards_processing_time();
802
803 log_debug(gc, ergo, refine)("Concurrent refinement times: Logged Cards Scan time goal: %1.2fms Logged Cards Scan time: %1.2fms HCC time: %1.2fms",
804 scan_logged_cards_time_goal_ms, logged_cards_time, scan_hcc_time_ms);
805
806 _g1h->concurrent_refine()->adjust(logged_cards_time,
807 phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards),
808 scan_logged_cards_time_goal_ms);
809 }
810
811 G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){
812 if (G1UseAdaptiveIHOP) {
813 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
814 predictor,
815 G1ReservePercent,
816 G1HeapWastePercent);
817 } else {
818 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
819 }
820 }
821
822 void G1Policy::update_ihop_prediction(double mutator_time_s,
823 size_t mutator_alloc_bytes,
824 size_t young_gen_size,
825 bool this_gc_was_young_only) {
826 // Always try to update IHOP prediction. Even evacuation failures give information
827 // about e.g. whether to start IHOP earlier next time.
828
829 // Avoid using really small application times that might create samples with
830 // very high or very low values. They may be caused by e.g. back-to-back gcs.
831 double const min_valid_time = 1e-6;
832
833 bool report = false;
834
835 double marking_to_mixed_time = -1.0;
836 if (!this_gc_was_young_only && _initial_mark_to_mixed.has_result()) {
837 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
838 assert(marking_to_mixed_time > 0.0,
839 "Initial mark to mixed time must be larger than zero but is %.3f",
840 marking_to_mixed_time);
841 if (marking_to_mixed_time > min_valid_time) {
842 _ihop_control->update_marking_length(marking_to_mixed_time);
843 report = true;
844 }
845 }
846
847 // As an approximation for the young gc promotion rates during marking we use
848 // all of them. In many applications there are only a few if any young gcs during
849 // marking, which makes any prediction useless. This increases the accuracy of the
850 // prediction.
851 if (this_gc_was_young_only && mutator_time_s > min_valid_time) {
852 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
853 report = true;
854 }
855
856 if (report) {
857 report_ihop_statistics();
858 }
859 }
860
861 void G1Policy::report_ihop_statistics() {
862 _ihop_control->print();
863 }
864
865 void G1Policy::print_phases() {
866 phase_times()->print();
867 }
868
869 double G1Policy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
870 TruncatedSeq* seq = surv_rate_group->get_seq(age);
871 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
872 double pred = _predictor.get_new_prediction(seq);
873 if (pred > 1.0) {
874 pred = 1.0;
875 }
876 return pred;
877 }
878
879 double G1Policy::accum_yg_surv_rate_pred(int age) const {
880 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
881 }
882
883 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards,
884 size_t scanned_cards) const {
885 return
886 _analytics->predict_rs_update_time_ms(pending_cards) +
887 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->in_young_only_phase()) +
888 _analytics->predict_constant_other_time_ms();
889 }
890
891 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const {
892 size_t rs_length = _analytics->predict_rs_length() + _analytics->predict_rs_length_diff();
893 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->in_young_only_phase());
894 return predict_base_elapsed_time_ms(pending_cards, card_num);
895 }
896
897 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const {
898 size_t bytes_to_copy;
899 if (!hr->is_young()) {
900 bytes_to_copy = hr->max_live_bytes();
901 } else {
902 assert(hr->age_in_surv_rate_group() != -1, "invariant");
903 int age = hr->age_in_surv_rate_group();
904 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
905 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
906 }
907 return bytes_to_copy;
908 }
909
910 double G1Policy::predict_region_elapsed_time_ms(HeapRegion* hr,
911 bool for_young_gc) const {
912 size_t rs_length = hr->rem_set()->occupied();
913 // Predicting the number of cards is based on which type of GC
914 // we're predicting for.
915 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc);
916 size_t bytes_to_copy = predict_bytes_to_copy(hr);
917
918 double region_elapsed_time_ms =
919 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->in_young_only_phase()) +
920 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress());
921
922 // The prediction of the "other" time for this region is based
923 // upon the region type and NOT the GC type.
924 if (hr->is_young()) {
925 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
926 } else {
927 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
928 }
929 return region_elapsed_time_ms;
930 }
931
932 bool G1Policy::should_allocate_mutator_region() const {
933 uint young_list_length = _g1h->young_regions_count();
934 uint young_list_target_length = _young_list_target_length;
935 return young_list_length < young_list_target_length;
936 }
937
938 bool G1Policy::can_expand_young_list() const {
939 uint young_list_length = _g1h->young_regions_count();
940 uint young_list_max_length = _young_list_max_length;
941 return young_list_length < young_list_max_length;
942 }
943
944 bool G1Policy::use_adaptive_young_list_length() const {
945 return _young_gen_sizer->use_adaptive_young_list_length();
946 }
947
948 size_t G1Policy::desired_survivor_size(uint max_regions) const {
949 size_t const survivor_capacity = HeapRegion::GrainWords * max_regions;
950 return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
951 }
952
953 void G1Policy::print_age_table() {
954 _survivors_age_table.print_age_table(_tenuring_threshold);
955 }
956
957 void G1Policy::update_max_gc_locker_expansion() {
958 uint expansion_region_num = 0;
959 if (GCLockerEdenExpansionPercent > 0) {
960 double perc = (double) GCLockerEdenExpansionPercent / 100.0;
961 double expansion_region_num_d = perc * (double) _young_list_target_length;
962 // We use ceiling so that if expansion_region_num_d is > 0.0 (but
963 // less than 1.0) we'll get 1.
964 expansion_region_num = (uint) ceil(expansion_region_num_d);
965 } else {
966 assert(expansion_region_num == 0, "sanity");
967 }
968 _young_list_max_length = _young_list_target_length + expansion_region_num;
969 assert(_young_list_target_length <= _young_list_max_length, "post-condition");
970 }
971
972 // Calculates survivor space parameters.
973 void G1Policy::update_survivors_policy() {
974 double max_survivor_regions_d =
975 (double) _young_list_target_length / (double) SurvivorRatio;
976
977 // Calculate desired survivor size based on desired max survivor regions (unconstrained
978 // by remaining heap). Otherwise we may cause undesired promotions as we are
979 // already getting close to end of the heap, impacting performance even more.
980 uint const desired_max_survivor_regions = ceil(max_survivor_regions_d);
981 size_t const survivor_size = desired_survivor_size(desired_max_survivor_regions);
982
983 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(survivor_size);
984 if (UsePerfData) {
985 _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold);
986 _policy_counters->desired_survivor_size()->set_value(survivor_size * oopSize);
987 }
988 // The real maximum survivor size is bounded by the number of regions that can
989 // be allocated into.
990 _max_survivor_regions = MIN2(desired_max_survivor_regions,
991 _g1h->num_free_or_available_regions());
992 }
993
994 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
995 // We actually check whether we are marking here and not if we are in a
996 // reclamation phase. This means that we will schedule a concurrent mark
997 // even while we are still in the process of reclaiming memory.
998 bool during_cycle = _g1h->concurrent_mark()->cm_thread()->during_cycle();
999 if (!during_cycle) {
1000 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
1001 collector_state()->set_initiate_conc_mark_if_possible(true);
1002 return true;
1003 } else {
1004 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
1005 return false;
1006 }
1007 }
1008
1009 void G1Policy::initiate_conc_mark() {
1010 collector_state()->set_in_initial_mark_gc(true);
1011 collector_state()->set_initiate_conc_mark_if_possible(false);
1012 }
1013
1014 void G1Policy::decide_on_conc_mark_initiation() {
1015 // We are about to decide on whether this pause will be an
1016 // initial-mark pause.
1017
1018 // First, collector_state()->in_initial_mark_gc() should not be already set. We
1019 // will set it here if we have to. However, it should be cleared by
1020 // the end of the pause (it's only set for the duration of an
1021 // initial-mark pause).
1022 assert(!collector_state()->in_initial_mark_gc(), "pre-condition");
1023
1024 if (collector_state()->initiate_conc_mark_if_possible()) {
1025 // We had noticed on a previous pause that the heap occupancy has
1026 // gone over the initiating threshold and we should start a
1027 // concurrent marking cycle. So we might initiate one.
1028
1029 if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) {
1030 // Initiate a new initial mark if there is no marking or reclamation going on.
1031 initiate_conc_mark();
1032 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
1033 } else if (_g1h->is_user_requested_concurrent_full_gc(_g1h->gc_cause())) {
1034 // Initiate a user requested initial mark. An initial mark must be young only
1035 // GC, so the collector state must be updated to reflect this.
1036 collector_state()->set_in_young_only_phase(true);
1037 collector_state()->set_in_young_gc_before_mixed(false);
1038
1039 // We might have ended up coming here about to start a mixed phase with a collection set
1040 // active. The following remark might change the change the "evacuation efficiency" of
1041 // the regions in this set, leading to failing asserts later.
1042 // Since the concurrent cycle will recreate the collection set anyway, simply drop it here.
1043 clear_collection_set_candidates();
1044 abort_time_to_mixed_tracking();
1045 initiate_conc_mark();
1046 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1047 } else {
1048 // The concurrent marking thread is still finishing up the
1049 // previous cycle. If we start one right now the two cycles
1050 // overlap. In particular, the concurrent marking thread might
1051 // be in the process of clearing the next marking bitmap (which
1052 // we will use for the next cycle if we start one). Starting a
1053 // cycle now will be bad given that parts of the marking
1054 // information might get cleared by the marking thread. And we
1055 // cannot wait for the marking thread to finish the cycle as it
1056 // periodically yields while clearing the next marking bitmap
1057 // and, if it's in a yield point, it's waiting for us to
1058 // finish. So, at this point we will not start a cycle and we'll
1059 // let the concurrent marking thread complete the last one.
1060 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1061 }
1062 }
1063 }
1064
1065 void G1Policy::record_concurrent_mark_cleanup_end() {
1066 G1CollectionSetCandidates* candidates = G1CollectionSetChooser::build(_g1h->workers(), _g1h->num_regions());
1067 _collection_set->set_candidates(candidates);
1068
1069 bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs");
1070 if (!mixed_gc_pending) {
1071 clear_collection_set_candidates();
1072 abort_time_to_mixed_tracking();
1073 }
1074 collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending);
1075 collector_state()->set_mark_or_rebuild_in_progress(false);
1076
1077 double end_sec = os::elapsedTime();
1078 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1079 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
1080 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
1081
1082 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1083 }
1084
1085 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const {
1086 return percent_of(reclaimable_bytes, _g1h->capacity());
1087 }
1088
1089 class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure {
1090 virtual bool do_heap_region(HeapRegion* r) {
1091 r->rem_set()->clear_locked(true /* only_cardset */);
1092 return false;
1093 }
1094 };
1095
1096 void G1Policy::clear_collection_set_candidates() {
1097 // Clear remembered sets of remaining candidate regions and the actual candidate
1098 // set.
1099 G1ClearCollectionSetCandidateRemSets cl;
1100 _collection_set->candidates()->iterate(&cl);
1101 _collection_set->clear_candidates();
1102 }
1103
1104 void G1Policy::maybe_start_marking() {
1105 if (need_to_start_conc_mark("end of GC")) {
1106 // Note: this might have already been set, if during the last
1107 // pause we decided to start a cycle but at the beginning of
1108 // this pause we decided to postpone it. That's OK.
1109 collector_state()->set_initiate_conc_mark_if_possible(true);
1110 }
1111 }
1112
1113 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const {
1114 assert(!collector_state()->in_full_gc(), "must be");
1115 if (collector_state()->in_initial_mark_gc()) {
1116 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1117 return InitialMarkGC;
1118 } else if (collector_state()->in_young_gc_before_mixed()) {
1119 assert(!collector_state()->in_initial_mark_gc(), "must be");
1120 return LastYoungGC;
1121 } else if (collector_state()->in_mixed_phase()) {
1122 assert(!collector_state()->in_initial_mark_gc(), "must be");
1123 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1124 return MixedGC;
1125 } else {
1126 assert(!collector_state()->in_initial_mark_gc(), "must be");
1127 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1128 return YoungOnlyGC;
1129 }
1130 }
1131
1132 void G1Policy::record_pause(PauseKind kind, double start, double end) {
1133 // Manage the MMU tracker. For some reason it ignores Full GCs.
1134 if (kind != FullGC) {
1135 _mmu_tracker->add_pause(start, end);
1136 }
1137 // Manage the mutator time tracking from initial mark to first mixed gc.
1138 switch (kind) {
1139 case FullGC:
1140 abort_time_to_mixed_tracking();
1141 break;
1142 case Cleanup:
1143 case Remark:
1144 case YoungOnlyGC:
1145 case LastYoungGC:
1146 _initial_mark_to_mixed.add_pause(end - start);
1147 break;
1148 case InitialMarkGC:
1149 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) {
1150 _initial_mark_to_mixed.record_initial_mark_end(end);
1151 }
1152 break;
1153 case MixedGC:
1154 _initial_mark_to_mixed.record_mixed_gc_start(start);
1155 break;
1156 default:
1157 ShouldNotReachHere();
1158 }
1159 }
1160
1161 void G1Policy::abort_time_to_mixed_tracking() {
1162 _initial_mark_to_mixed.reset();
1163 }
1164
1165 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str,
1166 const char* false_action_str) const {
1167 G1CollectionSetCandidates* candidates = _collection_set->candidates();
1168
1169 if (candidates->is_empty()) {
1170 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1171 return false;
1172 }
1173
1174 // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1175 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes();
1176 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1177 double threshold = (double) G1HeapWastePercent;
1178 if (reclaimable_percent <= threshold) {
1179 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1180 false_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1181 return false;
1182 }
1183 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1184 true_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1185 return true;
1186 }
1187
1188 uint G1Policy::calc_min_old_cset_length() const {
1189 // The min old CSet region bound is based on the maximum desired
1190 // number of mixed GCs after a cycle. I.e., even if some old regions
1191 // look expensive, we should add them to the CSet anyway to make
1192 // sure we go through the available old regions in no more than the
1193 // maximum desired number of mixed GCs.
1194 //
1195 // The calculation is based on the number of marked regions we added
1196 // to the CSet candidates in the first place, not how many remain, so
1197 // that the result is the same during all mixed GCs that follow a cycle.
1198
1199 const size_t region_num = _collection_set->candidates()->num_regions();
1200 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1201 size_t result = region_num / gc_num;
1202 // emulate ceiling
1203 if (result * gc_num < region_num) {
1204 result += 1;
1205 }
1206 return (uint) result;
1207 }
1208
1209 uint G1Policy::calc_max_old_cset_length() const {
1210 // The max old CSet region bound is based on the threshold expressed
1211 // as a percentage of the heap size. I.e., it should bound the
1212 // number of old regions added to the CSet irrespective of how many
1213 // of them are available.
1214
1215 const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1216 const size_t region_num = g1h->num_regions();
1217 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1218 size_t result = region_num * perc / 100;
1219 // emulate ceiling
1220 if (100 * result < region_num * perc) {
1221 result += 1;
1222 }
1223 return (uint) result;
1224 }
1225
1226 void G1Policy::calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
1227 double time_remaining_ms,
1228 uint& num_initial_regions,
1229 uint& num_optional_regions) {
1230 assert(candidates != NULL, "Must be");
1231
1232 num_initial_regions = 0;
1233 num_optional_regions = 0;
1234 uint num_expensive_regions = 0;
1235
1236 double predicted_old_time_ms = 0.0;
1237 double predicted_initial_time_ms = 0.0;
1238 double predicted_optional_time_ms = 0.0;
1239
1240 double optional_threshold_ms = time_remaining_ms * optional_prediction_fraction();
1241
1242 const uint min_old_cset_length = calc_min_old_cset_length();
1243 const uint max_old_cset_length = MAX2(min_old_cset_length, calc_max_old_cset_length());
1244 const uint max_optional_regions = max_old_cset_length - min_old_cset_length;
1245 bool check_time_remaining = use_adaptive_young_list_length();
1246
1247 uint candidate_idx = candidates->cur_idx();
1248
1249 log_debug(gc, ergo, cset)("Start adding old regions to collection set. Min %u regions, max %u regions, "
1250 "time remaining %1.2fms, optional threshold %1.2fms",
1251 min_old_cset_length, max_old_cset_length, time_remaining_ms, optional_threshold_ms);
1252
1253 HeapRegion* hr = candidates->at(candidate_idx);
1254 while (hr != NULL) {
1255 if (num_initial_regions + num_optional_regions >= max_old_cset_length) {
1256 // Added maximum number of old regions to the CSet.
1257 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Maximum number of regions). "
1258 "Initial %u regions, optional %u regions",
1259 num_initial_regions, num_optional_regions);
1260 break;
1261 }
1262
1263 // Stop adding regions if the remaining reclaimable space is
1264 // not above G1HeapWastePercent.
1265 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes();
1266 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1267 double threshold = (double) G1HeapWastePercent;
1268 if (reclaimable_percent <= threshold) {
1269 // We've added enough old regions that the amount of uncollected
1270 // reclaimable space is at or below the waste threshold. Stop
1271 // adding old regions to the CSet.
1272 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Reclaimable percentage below threshold). "
1273 "Reclaimable: " SIZE_FORMAT "%s (%1.2f%%) threshold: " UINTX_FORMAT "%%",
1274 byte_size_in_proper_unit(reclaimable_bytes), proper_unit_for_byte_size(reclaimable_bytes),
1275 reclaimable_percent, G1HeapWastePercent);
1276 break;
1277 }
1278
1279 double predicted_time_ms = predict_region_elapsed_time_ms(hr, false);
1280 time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0);
1281 // Add regions to old set until we reach the minimum amount
1282 if (num_initial_regions < min_old_cset_length) {
1283 predicted_old_time_ms += predicted_time_ms;
1284 num_initial_regions++;
1285 // Record the number of regions added with no time remaining
1286 if (time_remaining_ms == 0.0) {
1287 num_expensive_regions++;
1288 }
1289 } else if (!check_time_remaining) {
1290 // In the non-auto-tuning case, we'll finish adding regions
1291 // to the CSet if we reach the minimum.
1292 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Region amount reached min).");
1293 break;
1294 } else {
1295 // Keep adding regions to old set until we reach the optional threshold
1296 if (time_remaining_ms > optional_threshold_ms) {
1297 predicted_old_time_ms += predicted_time_ms;
1298 num_initial_regions++;
1299 } else if (time_remaining_ms > 0) {
1300 // Keep adding optional regions until time is up.
1301 assert(num_optional_regions < max_optional_regions, "Should not be possible.");
1302 predicted_optional_time_ms += predicted_time_ms;
1303 num_optional_regions++;
1304 } else {
1305 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Predicted time too high).");
1306 break;
1307 }
1308 }
1309 hr = candidates->at(++candidate_idx);
1310 }
1311 if (hr == NULL) {
1312 log_debug(gc, ergo, cset)("Old candidate collection set empty.");
1313 }
1314
1315 if (num_expensive_regions > 0) {
1316 log_debug(gc, ergo, cset)("Added %u initial old regions to collection set although the predicted time was too high.",
1317 num_expensive_regions);
1318 }
1319
1320 log_debug(gc, ergo, cset)("Finish choosing collection set old regions. Initial: %u, optional: %u, "
1321 "predicted old time: %1.2fms, predicted optional time: %1.2fms, time remaining: %1.2f",
1322 num_initial_regions, num_optional_regions,
1323 predicted_initial_time_ms, predicted_optional_time_ms, time_remaining_ms);
1324 }
1325
1326 void G1Policy::calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
1327 uint const max_optional_regions,
1328 double time_remaining_ms,
1329 uint& num_optional_regions) {
1330 assert(_g1h->collector_state()->in_mixed_phase(), "Should only be called in mixed phase");
1331
1332 num_optional_regions = 0;
1333 double prediction_ms = 0;
1334 uint candidate_idx = candidates->cur_idx();
1335
1336 HeapRegion* r = candidates->at(candidate_idx);
1337 while (num_optional_regions < max_optional_regions) {
1338 assert(r != NULL, "Region must exist");
1339 prediction_ms += predict_region_elapsed_time_ms(r, false);
1340
1341 if (prediction_ms > time_remaining_ms) {
1342 log_debug(gc, ergo, cset)("Prediction %.3fms for region %u does not fit remaining time: %.3fms.",
1343 prediction_ms, r->hrm_index(), time_remaining_ms);
1344 break;
1345 }
1346 // This region will be included in the next optional evacuation.
1347
1348 time_remaining_ms -= prediction_ms;
1349 num_optional_regions++;
1350 r = candidates->at(++candidate_idx);
1351 }
1352
1353 log_debug(gc, ergo, cset)("Prepared %u regions out of %u for optional evacuation. Predicted time: %.3fms",
1354 num_optional_regions, max_optional_regions, prediction_ms);
1355 }
1356
1357 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) {
1358
1359 // Add survivor regions to SurvRateGroup.
1360 note_start_adding_survivor_regions();
1361 finished_recalculating_age_indexes(true /* is_survivors */);
1362
1363 HeapRegion* last = NULL;
1364 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin();
1365 it != survivors->regions()->end();
1366 ++it) {
1367 HeapRegion* curr = *it;
1368 set_region_survivor(curr);
1369
1370 // The region is a non-empty survivor so let's add it to
1371 // the incremental collection set for the next evacuation
1372 // pause.
1373 _collection_set->add_survivor_regions(curr);
1374
1375 last = curr;
1376 }
1377 note_stop_adding_survivor_regions();
1378
1379 // Don't clear the survivor list handles until the start of
1380 // the next evacuation pause - we need it in order to re-tag
1381 // the survivor regions from this evacuation pause as 'young'
1382 // at the start of the next.
1383
1384 finished_recalculating_age_indexes(false /* is_survivors */);
1385 }