1 /*
2 * Copyright (c) 2001, 2018, 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/g1CollectedHeap.inline.hpp"
28 #include "gc/g1/g1CollectionSet.hpp"
29 #include "gc/g1/g1ConcurrentMark.hpp"
30 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
31 #include "gc/g1/g1ConcurrentRefine.hpp"
32 #include "gc/g1/g1HeterogeneousHeapPolicy.hpp"
33 #include "gc/g1/g1HotCardCache.hpp"
34 #include "gc/g1/g1IHOPControl.hpp"
35 #include "gc/g1/g1GCPhaseTimes.hpp"
36 #include "gc/g1/g1Policy.hpp"
37 #include "gc/g1/g1SurvivorRegions.hpp"
38 #include "gc/g1/g1YoungGenSizer.hpp"
39 #include "gc/g1/heapRegion.inline.hpp"
40 #include "gc/g1/heapRegionRemSet.hpp"
41 #include "gc/shared/gcPolicyCounters.hpp"
42 #include "logging/logStream.hpp"
43 #include "runtime/arguments.hpp"
44 #include "runtime/java.hpp"
45 #include "runtime/mutexLocker.hpp"
46 #include "utilities/debug.hpp"
47 #include "utilities/growableArray.hpp"
48 #include "utilities/pair.hpp"
49
50 G1Policy::G1Policy(G1CollectorPolicy* policy, STWGCTimer* gc_timer) :
51 _predictor(G1ConfidencePercent / 100.0),
52 _analytics(new G1Analytics(&_predictor)),
53 _remset_tracker(),
54 _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)),
55 _ihop_control(create_ihop_control(&_predictor)),
56 _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 2)),
57 _full_collection_start_sec(0.0),
58 _collection_pause_end_millis(os::javaTimeNanos() / NANOSECS_PER_MILLISEC),
59 _young_list_target_length(0),
60 _young_list_fixed_length(0),
61 _young_list_max_length(0),
62 _short_lived_surv_rate_group(new SurvRateGroup()),
63 _survivor_surv_rate_group(new SurvRateGroup()),
64 _reserve_factor((double) G1ReservePercent / 100.0),
65 _reserve_regions(0),
66 _young_gen_sizer(G1YoungGenSizer::create_gen_sizer(policy)),
67 _free_regions_at_end_of_collection(0),
68 _max_rs_lengths(0),
69 _rs_lengths_prediction(0),
70 _pending_cards(0),
71 _bytes_allocated_in_old_since_last_gc(0),
72 _initial_mark_to_mixed(),
73 _collection_set(NULL),
74 _bytes_copied_during_gc(0),
75 _g1h(NULL),
76 _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)),
77 _mark_remark_start_sec(0),
78 _mark_cleanup_start_sec(0),
79 _tenuring_threshold(MaxTenuringThreshold),
80 _max_survivor_regions(0),
81 _survivors_age_table(true)
82 {
83 }
84
85 G1Policy::~G1Policy() {
86 delete _ihop_control;
87 delete _young_gen_sizer;
88 }
89
90 G1Policy* G1Policy::create_policy(G1CollectorPolicy* policy, STWGCTimer* gc_timer_stw) {
91 if (policy->is_hetero_heap()) {
92 return new G1HeterogeneousHeapPolicy(policy, gc_timer_stw);
93 } else {
94 return new G1Policy(policy, gc_timer_stw);
95 }
96 }
97
98 G1CollectorState* G1Policy::collector_state() const { return _g1h->collector_state(); }
99
100 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
101 _g1h = g1h;
102 _collection_set = collection_set;
103
104 assert(Heap_lock->owned_by_self(), "Locking discipline.");
105
106 if (!adaptive_young_list_length()) {
107 _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
108 }
109 _young_gen_sizer->adjust_max_new_size(_g1h->max_expandable_regions());
110
111 _free_regions_at_end_of_collection = _g1h->num_free_regions();
112
113 update_young_list_max_and_target_length();
114 // We may immediately start allocating regions and placing them on the
115 // collection set list. Initialize the per-collection set info
116 _collection_set->start_incremental_building();
117 }
118
119 void G1Policy::note_gc_start() {
120 phase_times()->note_gc_start();
121 }
122
123 class G1YoungLengthPredictor {
124 const bool _during_cm;
125 const double _base_time_ms;
126 const double _base_free_regions;
127 const double _target_pause_time_ms;
128 const G1Policy* const _policy;
129
130 public:
131 G1YoungLengthPredictor(bool during_cm,
132 double base_time_ms,
133 double base_free_regions,
134 double target_pause_time_ms,
135 const G1Policy* policy) :
136 _during_cm(during_cm),
137 _base_time_ms(base_time_ms),
138 _base_free_regions(base_free_regions),
139 _target_pause_time_ms(target_pause_time_ms),
140 _policy(policy) {}
141
142 bool will_fit(uint young_length) const {
143 if (young_length >= _base_free_regions) {
144 // end condition 1: not enough space for the young regions
145 return false;
146 }
147
148 const double accum_surv_rate = _policy->accum_yg_surv_rate_pred((int) young_length - 1);
149 const size_t bytes_to_copy =
150 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
151 const double copy_time_ms =
152 _policy->analytics()->predict_object_copy_time_ms(bytes_to_copy, _during_cm);
153 const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length);
154 const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms;
155 if (pause_time_ms > _target_pause_time_ms) {
156 // end condition 2: prediction is over the target pause time
157 return false;
158 }
159
160 const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes;
161
162 // When copying, we will likely need more bytes free than is live in the region.
163 // Add some safety margin to factor in the confidence of our guess, and the
164 // natural expected waste.
165 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
166 // of the calculation: the lower the confidence, the more headroom.
167 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
168 // copying due to anticipated waste in the PLABs.
169 const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
170 const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
171
172 if (expected_bytes_to_copy > free_bytes) {
173 // end condition 3: out-of-space
174 return false;
175 }
176
177 // success!
178 return true;
179 }
180 };
181
182 void G1Policy::record_new_heap_size(uint new_number_of_regions) {
183 // re-calculate the necessary reserve
184 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
185 // We use ceiling so that if reserve_regions_d is > 0.0 (but
186 // smaller than 1.0) we'll get 1.
187 _reserve_regions = (uint) ceil(reserve_regions_d);
188
189 _young_gen_sizer->heap_size_changed(new_number_of_regions);
190
191 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
192 }
193
194 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const {
195 uint desired_min_length = 0;
196 if (adaptive_young_list_length()) {
197 if (_analytics->num_alloc_rate_ms() > 3) {
198 double now_sec = os::elapsedTime();
199 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
200 double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
201 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
202 } else {
203 // otherwise we don't have enough info to make the prediction
204 }
205 }
206 desired_min_length += base_min_length;
207 // make sure we don't go below any user-defined minimum bound
208 return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
209 }
210
211 uint G1Policy::calculate_young_list_desired_max_length() const {
212 // Here, we might want to also take into account any additional
213 // constraints (i.e., user-defined minimum bound). Currently, we
214 // effectively don't set this bound.
215 return _young_gen_sizer->max_desired_young_length();
216 }
217
218 uint G1Policy::update_young_list_max_and_target_length() {
219 return update_young_list_max_and_target_length(_analytics->predict_rs_lengths());
220 }
221
222 uint G1Policy::update_young_list_max_and_target_length(size_t rs_lengths) {
223 uint unbounded_target_length = update_young_list_target_length(rs_lengths);
224 update_max_gc_locker_expansion();
225 return unbounded_target_length;
226 }
227
228 uint G1Policy::update_young_list_target_length(size_t rs_lengths) {
229 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
230 _young_list_target_length = young_lengths.first;
231
232 return young_lengths.second;
233 }
234
235 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_lengths) const {
236 YoungTargetLengths result;
237
238 // Calculate the absolute and desired min bounds first.
239
240 // This is how many young regions we already have (currently: the survivors).
241 const uint base_min_length = _g1h->survivor_regions_count();
242 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
243 // This is the absolute minimum young length. Ensure that we
244 // will at least have one eden region available for allocation.
245 uint absolute_min_length = base_min_length + MAX2(_g1h->eden_regions_count(), (uint)1);
246 // If we shrank the young list target it should not shrink below the current size.
247 desired_min_length = MAX2(desired_min_length, absolute_min_length);
248 // Calculate the absolute and desired max bounds.
249
250 uint desired_max_length = calculate_young_list_desired_max_length();
251
252 uint young_list_target_length = 0;
253 if (adaptive_young_list_length()) {
254 if (collector_state()->in_young_only_phase()) {
255 young_list_target_length =
256 calculate_young_list_target_length(rs_lengths,
257 base_min_length,
258 desired_min_length,
259 desired_max_length);
260 } else {
261 // Don't calculate anything and let the code below bound it to
262 // the desired_min_length, i.e., do the next GC as soon as
263 // possible to maximize how many old regions we can add to it.
264 }
265 } else {
266 // The user asked for a fixed young gen so we'll fix the young gen
267 // whether the next GC is young or mixed.
268 young_list_target_length = _young_list_fixed_length;
269 }
270
271 result.second = young_list_target_length;
272
273 // We will try our best not to "eat" into the reserve.
274 uint absolute_max_length = 0;
275 if (_free_regions_at_end_of_collection > _reserve_regions) {
276 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
277 }
278 if (desired_max_length > absolute_max_length) {
279 desired_max_length = absolute_max_length;
280 }
281
282 // Make sure we don't go over the desired max length, nor under the
283 // desired min length. In case they clash, desired_min_length wins
284 // which is why that test is second.
285 if (young_list_target_length > desired_max_length) {
286 young_list_target_length = desired_max_length;
287 }
288 if (young_list_target_length < desired_min_length) {
289 young_list_target_length = desired_min_length;
290 }
291
292 assert(young_list_target_length > base_min_length,
293 "we should be able to allocate at least one eden region");
294 assert(young_list_target_length >= absolute_min_length, "post-condition");
295
296 result.first = young_list_target_length;
297 return result;
298 }
299
300 uint
301 G1Policy::calculate_young_list_target_length(size_t rs_lengths,
302 uint base_min_length,
303 uint desired_min_length,
304 uint desired_max_length) const {
305 assert(adaptive_young_list_length(), "pre-condition");
306 assert(collector_state()->in_young_only_phase(), "only call this for young GCs");
307
308 // In case some edge-condition makes the desired max length too small...
309 if (desired_max_length <= desired_min_length) {
310 return desired_min_length;
311 }
312
313 // We'll adjust min_young_length and max_young_length not to include
314 // the already allocated young regions (i.e., so they reflect the
315 // min and max eden regions we'll allocate). The base_min_length
316 // will be reflected in the predictions by the
317 // survivor_regions_evac_time prediction.
318 assert(desired_min_length > base_min_length, "invariant");
319 uint min_young_length = desired_min_length - base_min_length;
320 assert(desired_max_length > base_min_length, "invariant");
321 uint max_young_length = desired_max_length - base_min_length;
322
323 const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
324 const double survivor_regions_evac_time = predict_survivor_regions_evac_time();
325 const size_t pending_cards = _analytics->predict_pending_cards();
326 const size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff();
327 const size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, true /* for_young_gc */);
328 const double base_time_ms =
329 predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
330 survivor_regions_evac_time;
331 const uint available_free_regions = _free_regions_at_end_of_collection;
332 const uint base_free_regions =
333 available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0;
334
335 // Here, we will make sure that the shortest young length that
336 // makes sense fits within the target pause time.
337
338 G1YoungLengthPredictor p(collector_state()->mark_or_rebuild_in_progress(),
339 base_time_ms,
340 base_free_regions,
341 target_pause_time_ms,
342 this);
343 if (p.will_fit(min_young_length)) {
344 // The shortest young length will fit into the target pause time;
345 // we'll now check whether the absolute maximum number of young
346 // regions will fit in the target pause time. If not, we'll do
347 // a binary search between min_young_length and max_young_length.
348 if (p.will_fit(max_young_length)) {
349 // The maximum young length will fit into the target pause time.
350 // We are done so set min young length to the maximum length (as
351 // the result is assumed to be returned in min_young_length).
352 min_young_length = max_young_length;
353 } else {
354 // The maximum possible number of young regions will not fit within
355 // the target pause time so we'll search for the optimal
356 // length. The loop invariants are:
357 //
358 // min_young_length < max_young_length
359 // min_young_length is known to fit into the target pause time
360 // max_young_length is known not to fit into the target pause time
361 //
362 // Going into the loop we know the above hold as we've just
363 // checked them. Every time around the loop we check whether
364 // the middle value between min_young_length and
365 // max_young_length fits into the target pause time. If it
366 // does, it becomes the new min. If it doesn't, it becomes
367 // the new max. This way we maintain the loop invariants.
368
369 assert(min_young_length < max_young_length, "invariant");
370 uint diff = (max_young_length - min_young_length) / 2;
371 while (diff > 0) {
372 uint young_length = min_young_length + diff;
373 if (p.will_fit(young_length)) {
374 min_young_length = young_length;
375 } else {
376 max_young_length = young_length;
377 }
378 assert(min_young_length < max_young_length, "invariant");
379 diff = (max_young_length - min_young_length) / 2;
380 }
381 // The results is min_young_length which, according to the
382 // loop invariants, should fit within the target pause time.
383
384 // These are the post-conditions of the binary search above:
385 assert(min_young_length < max_young_length,
386 "otherwise we should have discovered that max_young_length "
387 "fits into the pause target and not done the binary search");
388 assert(p.will_fit(min_young_length),
389 "min_young_length, the result of the binary search, should "
390 "fit into the pause target");
391 assert(!p.will_fit(min_young_length + 1),
392 "min_young_length, the result of the binary search, should be "
393 "optimal, so no larger length should fit into the pause target");
394 }
395 } else {
396 // Even the minimum length doesn't fit into the pause time
397 // target, return it as the result nevertheless.
398 }
399 return base_min_length + min_young_length;
400 }
401
402 double G1Policy::predict_survivor_regions_evac_time() const {
403 double survivor_regions_evac_time = 0.0;
404 const GrowableArray<HeapRegion*>* survivor_regions = _g1h->survivor()->regions();
405
406 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin();
407 it != survivor_regions->end();
408 ++it) {
409 survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->in_young_only_phase());
410 }
411 return survivor_regions_evac_time;
412 }
413
414 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
415 guarantee( adaptive_young_list_length(), "should not call this otherwise" );
416
417 if (rs_lengths > _rs_lengths_prediction) {
418 // add 10% to avoid having to recalculate often
419 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
420 update_rs_lengths_prediction(rs_lengths_prediction);
421
422 update_young_list_max_and_target_length(rs_lengths_prediction);
423 }
424 }
425
426 void G1Policy::update_rs_lengths_prediction() {
427 update_rs_lengths_prediction(_analytics->predict_rs_lengths());
428 }
429
430 void G1Policy::update_rs_lengths_prediction(size_t prediction) {
431 if (collector_state()->in_young_only_phase() && adaptive_young_list_length()) {
432 _rs_lengths_prediction = prediction;
433 }
434 }
435
436 void G1Policy::record_full_collection_start() {
437 _full_collection_start_sec = os::elapsedTime();
438 // Release the future to-space so that it is available for compaction into.
439 collector_state()->set_in_young_only_phase(false);
440 collector_state()->set_in_full_gc(true);
441 cset_chooser()->clear();
442 }
443
444 void G1Policy::record_full_collection_end() {
445 // Consider this like a collection pause for the purposes of allocation
446 // since last pause.
447 double end_sec = os::elapsedTime();
448 double full_gc_time_sec = end_sec - _full_collection_start_sec;
449 double full_gc_time_ms = full_gc_time_sec * 1000.0;
450
451 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);
452
453 collector_state()->set_in_full_gc(false);
454
455 // "Nuke" the heuristics that control the young/mixed GC
456 // transitions and make sure we start with young GCs after the Full GC.
457 collector_state()->set_in_young_only_phase(true);
458 collector_state()->set_in_young_gc_before_mixed(false);
459 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
460 collector_state()->set_in_initial_mark_gc(false);
461 collector_state()->set_mark_or_rebuild_in_progress(false);
462 collector_state()->set_clearing_next_bitmap(false);
463
464 _short_lived_surv_rate_group->start_adding_regions();
465 // also call this on any additional surv rate groups
466
467 _free_regions_at_end_of_collection = _g1h->num_free_regions();
468 // Reset survivors SurvRateGroup.
469 _survivor_surv_rate_group->reset();
470 update_young_list_max_and_target_length();
471 update_rs_lengths_prediction();
472
473 _bytes_allocated_in_old_since_last_gc = 0;
474
475 record_pause(FullGC, _full_collection_start_sec, end_sec);
476 }
477
478 void G1Policy::record_collection_pause_start(double start_time_sec) {
479 // We only need to do this here as the policy will only be applied
480 // to the GC we're about to start. so, no point is calculating this
481 // every time we calculate / recalculate the target young length.
482 update_survivors_policy();
483
484 assert(max_survivor_regions() + _g1h->num_used_regions() <= _g1h->max_regions(),
485 "Maximum survivor regions %u plus used regions %u exceeds max regions %u",
486 max_survivor_regions(), _g1h->num_used_regions(), _g1h->max_regions());
487
488 assert(_g1h->used() == _g1h->recalculate_used(),
489 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
490 _g1h->used(), _g1h->recalculate_used());
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 CollectionSetChooser* G1Policy::cset_chooser() const {
550 return _collection_set->cset_chooser();
551 }
552
553 bool G1Policy::about_to_start_mixed_phase() const {
554 return _g1h->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->in_young_gc_before_mixed();
555 }
556
557 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
558 if (about_to_start_mixed_phase()) {
559 return false;
560 }
561
562 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
563
564 size_t cur_used_bytes = _g1h->non_young_capacity_bytes();
565 size_t alloc_byte_size = alloc_word_size * HeapWordSize;
566 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
567
568 bool result = false;
569 if (marking_request_bytes > marking_initiating_used_threshold) {
570 result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed();
571 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
572 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
573 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1h->capacity() * 100, source);
574 }
575
576 return result;
577 }
578
579 // Anything below that is considered to be zero
580 #define MIN_TIMER_GRANULARITY 0.0000001
581
582 void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
583 double end_time_sec = os::elapsedTime();
584
585 size_t cur_used_bytes = _g1h->used();
586 assert(cur_used_bytes == _g1h->recalculate_used(), "It should!");
587 bool this_pause_included_initial_mark = false;
588 bool this_pause_was_young_only = collector_state()->in_young_only_phase();
589
590 bool update_stats = !_g1h->evacuation_failed();
591
592 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
593
594 _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
595
596 this_pause_included_initial_mark = collector_state()->in_initial_mark_gc();
597 if (this_pause_included_initial_mark) {
598 record_concurrent_mark_init_end(0.0);
599 } else {
600 maybe_start_marking();
601 }
602
603 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
604 if (app_time_ms < MIN_TIMER_GRANULARITY) {
605 // This usually happens due to the timer not having the required
606 // granularity. Some Linuxes are the usual culprits.
607 // We'll just set it to something (arbitrarily) small.
608 app_time_ms = 1.0;
609 }
610
611 if (update_stats) {
612 // We maintain the invariant that all objects allocated by mutator
613 // threads will be allocated out of eden regions. So, we can use
614 // the eden region number allocated since the previous GC to
615 // calculate the application's allocate rate. The only exception
616 // to that is humongous objects that are allocated separately. But
617 // given that humongous object allocations do not really affect
618 // either the pause's duration nor when the next pause will take
619 // place we can safely ignore them here.
620 uint regions_allocated = _collection_set->eden_region_length();
621 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
622 _analytics->report_alloc_rate_ms(alloc_rate_ms);
623
624 double interval_ms =
625 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;
626 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
627 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);
628 }
629
630 if (collector_state()->in_young_gc_before_mixed()) {
631 assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC");
632 // This has been the young GC before we start doing mixed GCs. We already
633 // decided to start mixed GCs much earlier, so there is nothing to do except
634 // advancing the state.
635 collector_state()->set_in_young_only_phase(false);
636 collector_state()->set_in_young_gc_before_mixed(false);
637 } else if (!this_pause_was_young_only) {
638 // This is a mixed GC. Here we decide whether to continue doing more
639 // mixed GCs or not.
640 if (!next_gc_should_be_mixed("continue mixed GCs",
641 "do not continue mixed GCs")) {
642 collector_state()->set_in_young_only_phase(true);
643
644 clear_collection_set_candidates();
645 maybe_start_marking();
646 }
647 }
648
649 _short_lived_surv_rate_group->start_adding_regions();
650 // Do that for any other surv rate groups
651
652 double scan_hcc_time_ms = G1HotCardCache::default_use_cache() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
653
654 if (update_stats) {
655 double cost_per_card_ms = 0.0;
656 if (_pending_cards > 0) {
657 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS)) / (double) _pending_cards;
658 _analytics->report_cost_per_card_ms(cost_per_card_ms);
659 }
660 _analytics->report_cost_scan_hcc(scan_hcc_time_ms);
661
662 double cost_per_entry_ms = 0.0;
663 if (cards_scanned > 10) {
664 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
665 _analytics->report_cost_per_entry_ms(cost_per_entry_ms, this_pause_was_young_only);
666 }
667
668 if (_max_rs_lengths > 0) {
669 double cards_per_entry_ratio =
670 (double) cards_scanned / (double) _max_rs_lengths;
671 _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, this_pause_was_young_only);
672 }
673
674 // This is defensive. For a while _max_rs_lengths could get
675 // smaller than _recorded_rs_lengths which was causing
676 // rs_length_diff to get very large and mess up the RSet length
677 // predictions. The reason was unsafe concurrent updates to the
678 // _inc_cset_recorded_rs_lengths field which the code below guards
679 // against (see CR 7118202). This bug has now been fixed (see CR
680 // 7119027). However, I'm still worried that
681 // _inc_cset_recorded_rs_lengths might still end up somewhat
682 // inaccurate. The concurrent refinement thread calculates an
683 // RSet's length concurrently with other CR threads updating it
684 // which might cause it to calculate the length incorrectly (if,
685 // say, it's in mid-coarsening). So I'll leave in the defensive
686 // conditional below just in case.
687 size_t rs_length_diff = 0;
688 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();
689 if (_max_rs_lengths > recorded_rs_lengths) {
690 rs_length_diff = _max_rs_lengths - recorded_rs_lengths;
691 }
692 _analytics->report_rs_length_diff((double) rs_length_diff);
693
694 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
695 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
696 double cost_per_byte_ms = 0.0;
697
698 if (copied_bytes > 0) {
699 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
700 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress());
701 }
702
703 if (_collection_set->young_region_length() > 0) {
704 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
705 _collection_set->young_region_length());
706 }
707
708 if (_collection_set->old_region_length() > 0) {
709 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
710 _collection_set->old_region_length());
711 }
712
713 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
714
715 // Do not update RS lengths and the number of pending cards with information from mixed gc:
716 // these are is wildly different to during young only gc and mess up young gen sizing right
717 // after the mixed gc phase.
718 // During mixed gc we do not use them for young gen sizing.
719 if (this_pause_was_young_only) {
720 _analytics->report_pending_cards((double) _pending_cards);
721 _analytics->report_rs_lengths((double) _max_rs_lengths);
722 }
723 }
724
725 assert(!(this_pause_included_initial_mark && collector_state()->mark_or_rebuild_in_progress()),
726 "If the last pause has been an initial mark, we should not have been in the marking window");
727 if (this_pause_included_initial_mark) {
728 collector_state()->set_mark_or_rebuild_in_progress(true);
729 }
730
731 _free_regions_at_end_of_collection = _g1h->num_free_regions();
732
733 update_rs_lengths_prediction();
734
735 // Do not update dynamic IHOP due to G1 periodic collection as it is highly likely
736 // that in this case we are not running in a "normal" operating mode.
737 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) {
738 // IHOP control wants to know the expected young gen length if it were not
739 // restrained by the heap reserve. Using the actual length would make the
740 // prediction too small and the limit the young gen every time we get to the
741 // predicted target occupancy.
742 size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
743
744 update_ihop_prediction(app_time_ms / 1000.0,
745 _bytes_allocated_in_old_since_last_gc,
746 last_unrestrained_young_length * HeapRegion::GrainBytes,
747 this_pause_was_young_only);
748 _bytes_allocated_in_old_since_last_gc = 0;
749
750 _ihop_control->send_trace_event(_g1h->gc_tracer_stw());
751 } else {
752 // Any garbage collection triggered as periodic collection resets the time-to-mixed
753 // measurement. Periodic collection typically means that the application is "inactive", i.e.
754 // the marking threads may have received an uncharacterisic amount of cpu time
755 // for completing the marking, i.e. are faster than expected.
756 // This skews the predicted marking length towards smaller values which might cause
757 // the mark start being too late.
758 _initial_mark_to_mixed.reset();
759 }
760
761 // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
762 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
763
764 if (update_rs_time_goal_ms < scan_hcc_time_ms) {
765 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
766 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",
767 update_rs_time_goal_ms, scan_hcc_time_ms);
768
769 update_rs_time_goal_ms = 0;
770 } else {
771 update_rs_time_goal_ms -= scan_hcc_time_ms;
772 }
773 _g1h->concurrent_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS),
774 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
775 update_rs_time_goal_ms);
776
777 cset_chooser()->verify();
778 }
779
780 G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){
781 if (G1UseAdaptiveIHOP) {
782 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
783 predictor,
784 G1ReservePercent,
785 G1HeapWastePercent);
786 } else {
787 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
788 }
789 }
790
791 void G1Policy::update_ihop_prediction(double mutator_time_s,
792 size_t mutator_alloc_bytes,
793 size_t young_gen_size,
794 bool this_gc_was_young_only) {
795 // Always try to update IHOP prediction. Even evacuation failures give information
796 // about e.g. whether to start IHOP earlier next time.
797
798 // Avoid using really small application times that might create samples with
799 // very high or very low values. They may be caused by e.g. back-to-back gcs.
800 double const min_valid_time = 1e-6;
801
802 bool report = false;
803
804 double marking_to_mixed_time = -1.0;
805 if (!this_gc_was_young_only && _initial_mark_to_mixed.has_result()) {
806 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
807 assert(marking_to_mixed_time > 0.0,
808 "Initial mark to mixed time must be larger than zero but is %.3f",
809 marking_to_mixed_time);
810 if (marking_to_mixed_time > min_valid_time) {
811 _ihop_control->update_marking_length(marking_to_mixed_time);
812 report = true;
813 }
814 }
815
816 // As an approximation for the young gc promotion rates during marking we use
817 // all of them. In many applications there are only a few if any young gcs during
818 // marking, which makes any prediction useless. This increases the accuracy of the
819 // prediction.
820 if (this_gc_was_young_only && mutator_time_s > min_valid_time) {
821 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
822 report = true;
823 }
824
825 if (report) {
826 report_ihop_statistics();
827 }
828 }
829
830 void G1Policy::report_ihop_statistics() {
831 _ihop_control->print();
832 }
833
834 void G1Policy::print_phases() {
835 phase_times()->print();
836 }
837
838 double G1Policy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
839 TruncatedSeq* seq = surv_rate_group->get_seq(age);
840 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
841 double pred = _predictor.get_new_prediction(seq);
842 if (pred > 1.0) {
843 pred = 1.0;
844 }
845 return pred;
846 }
847
848 double G1Policy::accum_yg_surv_rate_pred(int age) const {
849 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
850 }
851
852 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards,
853 size_t scanned_cards) const {
854 return
855 _analytics->predict_rs_update_time_ms(pending_cards) +
856 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->in_young_only_phase()) +
857 _analytics->predict_constant_other_time_ms();
858 }
859
860 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const {
861 size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff();
862 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->in_young_only_phase());
863 return predict_base_elapsed_time_ms(pending_cards, card_num);
864 }
865
866 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const {
867 size_t bytes_to_copy;
868 if (!hr->is_young()) {
869 bytes_to_copy = hr->max_live_bytes();
870 } else {
871 assert(hr->age_in_surv_rate_group() != -1, "invariant");
872 int age = hr->age_in_surv_rate_group();
873 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
874 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
875 }
876 return bytes_to_copy;
877 }
878
879 double G1Policy::predict_region_elapsed_time_ms(HeapRegion* hr,
880 bool for_young_gc) const {
881 size_t rs_length = hr->rem_set()->occupied();
882 // Predicting the number of cards is based on which type of GC
883 // we're predicting for.
884 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc);
885 size_t bytes_to_copy = predict_bytes_to_copy(hr);
886
887 double region_elapsed_time_ms =
888 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->in_young_only_phase()) +
889 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress());
890
891 // The prediction of the "other" time for this region is based
892 // upon the region type and NOT the GC type.
893 if (hr->is_young()) {
894 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
895 } else {
896 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
897 }
898 return region_elapsed_time_ms;
899 }
900
901 bool G1Policy::should_allocate_mutator_region() const {
902 uint young_list_length = _g1h->young_regions_count();
903 uint young_list_target_length = _young_list_target_length;
904 return young_list_length < young_list_target_length;
905 }
906
907 bool G1Policy::can_expand_young_list() const {
908 uint young_list_length = _g1h->young_regions_count();
909 uint young_list_max_length = _young_list_max_length;
910 return young_list_length < young_list_max_length;
911 }
912
913 bool G1Policy::adaptive_young_list_length() const {
914 return _young_gen_sizer->adaptive_young_list_length();
915 }
916
917 size_t G1Policy::desired_survivor_size(uint max_regions) const {
918 size_t const survivor_capacity = HeapRegion::GrainWords * max_regions;
919 return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
920 }
921
922 void G1Policy::print_age_table() {
923 _survivors_age_table.print_age_table(_tenuring_threshold);
924 }
925
926 void G1Policy::update_max_gc_locker_expansion() {
927 uint expansion_region_num = 0;
928 if (GCLockerEdenExpansionPercent > 0) {
929 double perc = (double) GCLockerEdenExpansionPercent / 100.0;
930 double expansion_region_num_d = perc * (double) _young_list_target_length;
931 // We use ceiling so that if expansion_region_num_d is > 0.0 (but
932 // less than 1.0) we'll get 1.
933 expansion_region_num = (uint) ceil(expansion_region_num_d);
934 } else {
935 assert(expansion_region_num == 0, "sanity");
936 }
937 _young_list_max_length = _young_list_target_length + expansion_region_num;
938 assert(_young_list_target_length <= _young_list_max_length, "post-condition");
939 }
940
941 // Calculates survivor space parameters.
942 void G1Policy::update_survivors_policy() {
943 double max_survivor_regions_d =
944 (double) _young_list_target_length / (double) SurvivorRatio;
945
946 // Calculate desired survivor size based on desired max survivor regions (unconstrained
947 // by remaining heap). Otherwise we may cause undesired promotions as we are
948 // already getting close to end of the heap, impacting performance even more.
949 uint const desired_max_survivor_regions = ceil(max_survivor_regions_d);
950 size_t const survivor_size = desired_survivor_size(desired_max_survivor_regions);
951
952 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(survivor_size);
953 if (UsePerfData) {
954 _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold);
955 _policy_counters->desired_survivor_size()->set_value(survivor_size * oopSize);
956 }
957 // The real maximum survivor size is bounded by the number of regions that can
958 // be allocated into.
959 _max_survivor_regions = MIN2(desired_max_survivor_regions,
960 _g1h->num_free_or_available_regions());
961 }
962
963 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
964 // We actually check whether we are marking here and not if we are in a
965 // reclamation phase. This means that we will schedule a concurrent mark
966 // even while we are still in the process of reclaiming memory.
967 bool during_cycle = _g1h->concurrent_mark()->cm_thread()->during_cycle();
968 if (!during_cycle) {
969 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
970 collector_state()->set_initiate_conc_mark_if_possible(true);
971 return true;
972 } else {
973 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
974 return false;
975 }
976 }
977
978 void G1Policy::initiate_conc_mark() {
979 collector_state()->set_in_initial_mark_gc(true);
980 collector_state()->set_initiate_conc_mark_if_possible(false);
981 }
982
983 void G1Policy::decide_on_conc_mark_initiation() {
984 // We are about to decide on whether this pause will be an
985 // initial-mark pause.
986
987 // First, collector_state()->in_initial_mark_gc() should not be already set. We
988 // will set it here if we have to. However, it should be cleared by
989 // the end of the pause (it's only set for the duration of an
990 // initial-mark pause).
991 assert(!collector_state()->in_initial_mark_gc(), "pre-condition");
992
993 if (collector_state()->initiate_conc_mark_if_possible()) {
994 // We had noticed on a previous pause that the heap occupancy has
995 // gone over the initiating threshold and we should start a
996 // concurrent marking cycle. So we might initiate one.
997
998 if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) {
999 // Initiate a new initial mark if there is no marking or reclamation going on.
1000 initiate_conc_mark();
1001 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
1002 } else if (_g1h->is_user_requested_concurrent_full_gc(_g1h->gc_cause())) {
1003 // Initiate a user requested initial mark. An initial mark must be young only
1004 // GC, so the collector state must be updated to reflect this.
1005 collector_state()->set_in_young_only_phase(true);
1006 collector_state()->set_in_young_gc_before_mixed(false);
1007
1008 // We might have ended up coming here about to start a mixed phase with a collection set
1009 // active. The following remark might change the change the "evacuation efficiency" of
1010 // the regions in this set, leading to failing asserts later.
1011 // Since the concurrent cycle will recreate the collection set anyway, simply drop it here.
1012 clear_collection_set_candidates();
1013 abort_time_to_mixed_tracking();
1014 initiate_conc_mark();
1015 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1016 } else {
1017 // The concurrent marking thread is still finishing up the
1018 // previous cycle. If we start one right now the two cycles
1019 // overlap. In particular, the concurrent marking thread might
1020 // be in the process of clearing the next marking bitmap (which
1021 // we will use for the next cycle if we start one). Starting a
1022 // cycle now will be bad given that parts of the marking
1023 // information might get cleared by the marking thread. And we
1024 // cannot wait for the marking thread to finish the cycle as it
1025 // periodically yields while clearing the next marking bitmap
1026 // and, if it's in a yield point, it's waiting for us to
1027 // finish. So, at this point we will not start a cycle and we'll
1028 // let the concurrent marking thread complete the last one.
1029 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1030 }
1031 }
1032 }
1033
1034 void G1Policy::record_concurrent_mark_cleanup_end() {
1035 cset_chooser()->rebuild(_g1h->workers(), _g1h->num_regions());
1036
1037 bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs");
1038 if (!mixed_gc_pending) {
1039 clear_collection_set_candidates();
1040 abort_time_to_mixed_tracking();
1041 }
1042 collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending);
1043 collector_state()->set_mark_or_rebuild_in_progress(false);
1044
1045 double end_sec = os::elapsedTime();
1046 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1047 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
1048 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
1049
1050 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1051 }
1052
1053 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const {
1054 return percent_of(reclaimable_bytes, _g1h->capacity());
1055 }
1056
1057 class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure {
1058 virtual bool do_heap_region(HeapRegion* r) {
1059 r->rem_set()->clear_locked(true /* only_cardset */);
1060 return false;
1061 }
1062 };
1063
1064 void G1Policy::clear_collection_set_candidates() {
1065 // Clear remembered sets of remaining candidate regions and the actual candidate
1066 // list.
1067 G1ClearCollectionSetCandidateRemSets cl;
1068 cset_chooser()->iterate(&cl);
1069 cset_chooser()->clear();
1070 }
1071
1072 void G1Policy::maybe_start_marking() {
1073 if (need_to_start_conc_mark("end of GC")) {
1074 // Note: this might have already been set, if during the last
1075 // pause we decided to start a cycle but at the beginning of
1076 // this pause we decided to postpone it. That's OK.
1077 collector_state()->set_initiate_conc_mark_if_possible(true);
1078 }
1079 }
1080
1081 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const {
1082 assert(!collector_state()->in_full_gc(), "must be");
1083 if (collector_state()->in_initial_mark_gc()) {
1084 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1085 return InitialMarkGC;
1086 } else if (collector_state()->in_young_gc_before_mixed()) {
1087 assert(!collector_state()->in_initial_mark_gc(), "must be");
1088 return LastYoungGC;
1089 } else if (collector_state()->in_mixed_phase()) {
1090 assert(!collector_state()->in_initial_mark_gc(), "must be");
1091 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1092 return MixedGC;
1093 } else {
1094 assert(!collector_state()->in_initial_mark_gc(), "must be");
1095 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1096 return YoungOnlyGC;
1097 }
1098 }
1099
1100 void G1Policy::record_pause(PauseKind kind, double start, double end) {
1101 // Manage the MMU tracker. For some reason it ignores Full GCs.
1102 if (kind != FullGC) {
1103 _mmu_tracker->add_pause(start, end);
1104 }
1105 // Manage the mutator time tracking from initial mark to first mixed gc.
1106 switch (kind) {
1107 case FullGC:
1108 abort_time_to_mixed_tracking();
1109 break;
1110 case Cleanup:
1111 case Remark:
1112 case YoungOnlyGC:
1113 case LastYoungGC:
1114 _initial_mark_to_mixed.add_pause(end - start);
1115 break;
1116 case InitialMarkGC:
1117 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) {
1118 _initial_mark_to_mixed.record_initial_mark_end(end);
1119 }
1120 break;
1121 case MixedGC:
1122 _initial_mark_to_mixed.record_mixed_gc_start(start);
1123 break;
1124 default:
1125 ShouldNotReachHere();
1126 }
1127 }
1128
1129 void G1Policy::abort_time_to_mixed_tracking() {
1130 _initial_mark_to_mixed.reset();
1131 }
1132
1133 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str,
1134 const char* false_action_str) const {
1135 if (cset_chooser()->is_empty()) {
1136 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1137 return false;
1138 }
1139
1140 // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1141 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
1142 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1143 double threshold = (double) G1HeapWastePercent;
1144 if (reclaimable_percent <= threshold) {
1145 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1146 false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1147 return false;
1148 }
1149 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1150 true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1151 return true;
1152 }
1153
1154 uint G1Policy::calc_min_old_cset_length() const {
1155 // The min old CSet region bound is based on the maximum desired
1156 // number of mixed GCs after a cycle. I.e., even if some old regions
1157 // look expensive, we should add them to the CSet anyway to make
1158 // sure we go through the available old regions in no more than the
1159 // maximum desired number of mixed GCs.
1160 //
1161 // The calculation is based on the number of marked regions we added
1162 // to the CSet chooser in the first place, not how many remain, so
1163 // that the result is the same during all mixed GCs that follow a cycle.
1164
1165 const size_t region_num = (size_t) cset_chooser()->length();
1166 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1167 size_t result = region_num / gc_num;
1168 // emulate ceiling
1169 if (result * gc_num < region_num) {
1170 result += 1;
1171 }
1172 return (uint) result;
1173 }
1174
1175 uint G1Policy::calc_max_old_cset_length() const {
1176 // The max old CSet region bound is based on the threshold expressed
1177 // as a percentage of the heap size. I.e., it should bound the
1178 // number of old regions added to the CSet irrespective of how many
1179 // of them are available.
1180
1181 const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1182 const size_t region_num = g1h->num_regions();
1183 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1184 size_t result = region_num * perc / 100;
1185 // emulate ceiling
1186 if (100 * result < region_num * perc) {
1187 result += 1;
1188 }
1189 return (uint) result;
1190 }
1191
1192 void G1Policy::finalize_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {
1193 double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms, survivor);
1194 _collection_set->finalize_old_part(time_remaining_ms);
1195 }
1196
1197 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) {
1198
1199 // Add survivor regions to SurvRateGroup.
1200 note_start_adding_survivor_regions();
1201 finished_recalculating_age_indexes(true /* is_survivors */);
1202
1203 HeapRegion* last = NULL;
1204 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin();
1205 it != survivors->regions()->end();
1206 ++it) {
1207 HeapRegion* curr = *it;
1208 set_region_survivor(curr);
1209
1210 // The region is a non-empty survivor so let's add it to
1211 // the incremental collection set for the next evacuation
1212 // pause.
1213 _collection_set->add_survivor_regions(curr);
1214
1215 last = curr;
1216 }
1217 note_stop_adding_survivor_regions();
1218
1219 // Don't clear the survivor list handles until the start of
1220 // the next evacuation pause - we need it in order to re-tag
1221 // the survivor regions from this evacuation pause as 'young'
1222 // at the start of the next.
1223
1224 finished_recalculating_age_indexes(false /* is_survivors */);
1225 }