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.
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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
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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.hpp"
49#include "utilities/debug.hpp"
50#include "utilities/growableArray.hpp"
51#include "utilities/pair.hpp"
52
53G1Policy::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_lengths(0),
72 _rs_lengths_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
88G1Policy::~G1Policy() {
89 delete _ihop_control;
90 delete _young_gen_sizer;
91}
92
93G1Policy* 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
101G1CollectorState* G1Policy::collector_state() const { return _g1h->collector_state(); }
102
103void 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
122void G1Policy::note_gc_start() {
123 phase_times()->note_gc_start();
124}
125
126class 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
185void 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
197uint 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
214uint 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
221uint G1Policy::update_young_list_max_and_target_length() {
222 return update_young_list_max_and_target_length(_analytics->predict_rs_lengths());
223}
224
225uint G1Policy::update_young_list_max_and_target_length(size_t rs_lengths) {
226 uint unbounded_target_length = update_young_list_target_length(rs_lengths);
227 update_max_gc_locker_expansion();
228 return unbounded_target_length;
229}
230
231uint G1Policy::update_young_list_target_length(size_t rs_lengths) {
232 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
233 _young_list_target_length = young_lengths.first;
234
235 return young_lengths.second;
236}
237
238G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_lengths) 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_lengths,
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
303uint
304G1Policy::calculate_young_list_target_length(size_t rs_lengths,
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_lengths = rs_lengths + _analytics->predict_rs_length_diff();
330 const size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, 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
405double 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
417void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
418 guarantee(use_adaptive_young_list_length(), "should not call this otherwise" );
419
420 if (rs_lengths > _rs_lengths_prediction) {
421 // add 10% to avoid having to recalculate often
422 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
423 update_rs_lengths_prediction(rs_lengths_prediction);
424
425 update_young_list_max_and_target_length(rs_lengths_prediction);
426 }
427}
428
429void G1Policy::update_rs_lengths_prediction() {
430 update_rs_lengths_prediction(_analytics->predict_rs_lengths());
431}
432
433void G1Policy::update_rs_lengths_prediction(size_t prediction) {
434 if (collector_state()->in_young_only_phase() && use_adaptive_young_list_length()) {
435 _rs_lengths_prediction = prediction;
436 }
437}
438
439void 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
447void 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_lengths_prediction();
475
476 _bytes_allocated_in_old_since_last_gc = 0;
477
478 record_pause(FullGC, _full_collection_start_sec, end_sec);
479}
480
481void 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
505void 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
510void G1Policy::record_concurrent_mark_remark_start() {
511 _mark_remark_start_sec = os::elapsedTime();
512}
513
514void 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
523void G1Policy::record_concurrent_mark_cleanup_start() {
524 _mark_cleanup_start_sec = os::elapsedTime();
525}
526
527double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
528 return phase_times()->average_time_ms(phase);
529}
530
531double 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
536double 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
541double G1Policy::other_time_ms(double pause_time_ms) const {
542 return pause_time_ms - phase_times()->cur_collection_par_time_ms();
543}
544
545double 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
549bool 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
553bool 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// Anything below that is considered to be zero
576#define MIN_TIMER_GRANULARITY 0.0000001
577
578void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
579 double end_time_sec = os::elapsedTime();
580
581 assert_used_and_recalculate_used_equal(_g1h);
582 size_t cur_used_bytes = _g1h->used();
583 bool this_pause_included_initial_mark = false;
584 bool this_pause_was_young_only = collector_state()->in_young_only_phase();
585
586 bool update_stats = !_g1h->evacuation_failed();
587
588 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
589
590 _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
591
592 this_pause_included_initial_mark = collector_state()->in_initial_mark_gc();
593 if (this_pause_included_initial_mark) {
594 record_concurrent_mark_init_end(0.0);
595 } else {
596 maybe_start_marking();
597 }
598
599 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
600 if (app_time_ms < MIN_TIMER_GRANULARITY) {
601 // This usually happens due to the timer not having the required
602 // granularity. Some Linuxes are the usual culprits.
603 // We'll just set it to something (arbitrarily) small.
604 app_time_ms = 1.0;
605 }
606
607 if (update_stats) {
608 // We maintain the invariant that all objects allocated by mutator
609 // threads will be allocated out of eden regions. So, we can use
610 // the eden region number allocated since the previous GC to
611 // calculate the application's allocate rate. The only exception
612 // to that is humongous objects that are allocated separately. But
613 // given that humongous object allocations do not really affect
614 // either the pause's duration nor when the next pause will take
615 // place we can safely ignore them here.
616 uint regions_allocated = _collection_set->eden_region_length();
617 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
618 _analytics->report_alloc_rate_ms(alloc_rate_ms);
619
620 double interval_ms =
621 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;
622 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
623 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);
624 }
625
626 if (collector_state()->in_young_gc_before_mixed()) {
627 assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC");
628 // This has been the young GC before we start doing mixed GCs. We already
629 // decided to start mixed GCs much earlier, so there is nothing to do except
630 // advancing the state.
631 collector_state()->set_in_young_only_phase(false);
632 collector_state()->set_in_young_gc_before_mixed(false);
633 } else if (!this_pause_was_young_only) {
634 // This is a mixed GC. Here we decide whether to continue doing more
635 // mixed GCs or not.
636 if (!next_gc_should_be_mixed("continue mixed GCs",
637 "do not continue mixed GCs")) {
638 collector_state()->set_in_young_only_phase(true);
639
640 clear_collection_set_candidates();
641 maybe_start_marking();
642 }
643 }
644
645 _short_lived_surv_rate_group->start_adding_regions();
646 // Do that for any other surv rate groups
647
648 double scan_hcc_time_ms = G1HotCardCache::default_use_cache() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
649
650 if (update_stats) {
651 double cost_per_card_ms = 0.0;
652 if (_pending_cards > 0) {
653 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS)) / (double) _pending_cards;
654 _analytics->report_cost_per_card_ms(cost_per_card_ms);
655 }
656 _analytics->report_cost_scan_hcc(scan_hcc_time_ms);
657
658 double cost_per_entry_ms = 0.0;
659 if (cards_scanned > 10) {
660 double avg_time_scan_rs = average_time_ms(G1GCPhaseTimes::ScanRS);
661 if (this_pause_was_young_only) {
662 avg_time_scan_rs += average_time_ms(G1GCPhaseTimes::OptScanRS);
663 }
664 cost_per_entry_ms = avg_time_scan_rs / 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) + average_time_ms(G1GCPhaseTimes::OptObjCopy)) / (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
778G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){
779 if (G1UseAdaptiveIHOP) {
780 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
781 predictor,
782 G1ReservePercent,
783 G1HeapWastePercent);
784 } else {
785 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
786 }
787}
788
789void G1Policy::update_ihop_prediction(double mutator_time_s,
790 size_t mutator_alloc_bytes,
791 size_t young_gen_size,
792 bool this_gc_was_young_only) {
793 // Always try to update IHOP prediction. Even evacuation failures give information
794 // about e.g. whether to start IHOP earlier next time.
795
796 // Avoid using really small application times that might create samples with
797 // very high or very low values. They may be caused by e.g. back-to-back gcs.
798 double const min_valid_time = 1e-6;
799
800 bool report = false;
801
802 double marking_to_mixed_time = -1.0;
803 if (!this_gc_was_young_only && _initial_mark_to_mixed.has_result()) {
804 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
805 assert(marking_to_mixed_time > 0.0,
806 "Initial mark to mixed time must be larger than zero but is %.3f",
807 marking_to_mixed_time);
808 if (marking_to_mixed_time > min_valid_time) {
809 _ihop_control->update_marking_length(marking_to_mixed_time);
810 report = true;
811 }
812 }
813
814 // As an approximation for the young gc promotion rates during marking we use
815 // all of them. In many applications there are only a few if any young gcs during
816 // marking, which makes any prediction useless. This increases the accuracy of the
817 // prediction.
818 if (this_gc_was_young_only && mutator_time_s > min_valid_time) {
819 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
820 report = true;
821 }
822
823 if (report) {
824 report_ihop_statistics();
825 }
826}
827
828void G1Policy::report_ihop_statistics() {
829 _ihop_control->print();
830}
831
832void G1Policy::print_phases() {
833 phase_times()->print();
834}
835
836double G1Policy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
837 TruncatedSeq* seq = surv_rate_group->get_seq(age);
838 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
839 double pred = _predictor.get_new_prediction(seq);
840 if (pred > 1.0) {
841 pred = 1.0;
842 }
843 return pred;
844}
845
846double G1Policy::accum_yg_surv_rate_pred(int age) const {
847 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
848}
849
850double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards,
851 size_t scanned_cards) const {
852 return
853 _analytics->predict_rs_update_time_ms(pending_cards) +
854 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->in_young_only_phase()) +
855 _analytics->predict_constant_other_time_ms();
856}
857
858double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const {
859 size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff();
860 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->in_young_only_phase());
861 return predict_base_elapsed_time_ms(pending_cards, card_num);
862}
863
864size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const {
865 size_t bytes_to_copy;
866 if (!hr->is_young()) {
867 bytes_to_copy = hr->max_live_bytes();
868 } else {
869 assert(hr->age_in_surv_rate_group() != -1, "invariant");
870 int age = hr->age_in_surv_rate_group();
871 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
872 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
873 }
874 return bytes_to_copy;
875}
876
877double G1Policy::predict_region_elapsed_time_ms(HeapRegion* hr,
878 bool for_young_gc) const {
879 size_t rs_length = hr->rem_set()->occupied();
880 // Predicting the number of cards is based on which type of GC
881 // we're predicting for.
882 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc);
883 size_t bytes_to_copy = predict_bytes_to_copy(hr);
884
885 double region_elapsed_time_ms =
886 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->in_young_only_phase()) +
887 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress());
888
889 // The prediction of the "other" time for this region is based
890 // upon the region type and NOT the GC type.
891 if (hr->is_young()) {
892 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
893 } else {
894 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
895 }
896 return region_elapsed_time_ms;
897}
898
899bool G1Policy::should_allocate_mutator_region() const {
900 uint young_list_length = _g1h->young_regions_count();
901 uint young_list_target_length = _young_list_target_length;
902 return young_list_length < young_list_target_length;
903}
904
905bool G1Policy::can_expand_young_list() const {
906 uint young_list_length = _g1h->young_regions_count();
907 uint young_list_max_length = _young_list_max_length;
908 return young_list_length < young_list_max_length;
909}
910
911bool G1Policy::use_adaptive_young_list_length() const {
912 return _young_gen_sizer->use_adaptive_young_list_length();
913}
914
915size_t G1Policy::desired_survivor_size(uint max_regions) const {
916 size_t const survivor_capacity = HeapRegion::GrainWords * max_regions;
917 return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
918}
919
920void G1Policy::print_age_table() {
921 _survivors_age_table.print_age_table(_tenuring_threshold);
922}
923
924void G1Policy::update_max_gc_locker_expansion() {
925 uint expansion_region_num = 0;
926 if (GCLockerEdenExpansionPercent > 0) {
927 double perc = (double) GCLockerEdenExpansionPercent / 100.0;
928 double expansion_region_num_d = perc * (double) _young_list_target_length;
929 // We use ceiling so that if expansion_region_num_d is > 0.0 (but
930 // less than 1.0) we'll get 1.
931 expansion_region_num = (uint) ceil(expansion_region_num_d);
932 } else {
933 assert(expansion_region_num == 0, "sanity");
934 }
935 _young_list_max_length = _young_list_target_length + expansion_region_num;
936 assert(_young_list_target_length <= _young_list_max_length, "post-condition");
937}
938
939// Calculates survivor space parameters.
940void G1Policy::update_survivors_policy() {
941 double max_survivor_regions_d =
942 (double) _young_list_target_length / (double) SurvivorRatio;
943
944 // Calculate desired survivor size based on desired max survivor regions (unconstrained
945 // by remaining heap). Otherwise we may cause undesired promotions as we are
946 // already getting close to end of the heap, impacting performance even more.
947 uint const desired_max_survivor_regions = ceil(max_survivor_regions_d);
948 size_t const survivor_size = desired_survivor_size(desired_max_survivor_regions);
949
950 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(survivor_size);
951 if (UsePerfData) {
952 _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold);
953 _policy_counters->desired_survivor_size()->set_value(survivor_size * oopSize);
954 }
955 // The real maximum survivor size is bounded by the number of regions that can
956 // be allocated into.
957 _max_survivor_regions = MIN2(desired_max_survivor_regions,
958 _g1h->num_free_or_available_regions());
959}
960
961bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
962 // We actually check whether we are marking here and not if we are in a
963 // reclamation phase. This means that we will schedule a concurrent mark
964 // even while we are still in the process of reclaiming memory.
965 bool during_cycle = _g1h->concurrent_mark()->cm_thread()->during_cycle();
966 if (!during_cycle) {
967 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
968 collector_state()->set_initiate_conc_mark_if_possible(true);
969 return true;
970 } else {
971 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
972 return false;
973 }
974}
975
976void G1Policy::initiate_conc_mark() {
977 collector_state()->set_in_initial_mark_gc(true);
978 collector_state()->set_initiate_conc_mark_if_possible(false);
979}
980
981void G1Policy::decide_on_conc_mark_initiation() {
982 // We are about to decide on whether this pause will be an
983 // initial-mark pause.
984
985 // First, collector_state()->in_initial_mark_gc() should not be already set. We
986 // will set it here if we have to. However, it should be cleared by
987 // the end of the pause (it's only set for the duration of an
988 // initial-mark pause).
989 assert(!collector_state()->in_initial_mark_gc(), "pre-condition");
990
991 if (collector_state()->initiate_conc_mark_if_possible()) {
992 // We had noticed on a previous pause that the heap occupancy has
993 // gone over the initiating threshold and we should start a
994 // concurrent marking cycle. So we might initiate one.
995
996 if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) {
997 // Initiate a new initial mark if there is no marking or reclamation going on.
998 initiate_conc_mark();
999 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
1000 } else if (_g1h->is_user_requested_concurrent_full_gc(_g1h->gc_cause())) {
1001 // Initiate a user requested initial mark. An initial mark must be young only
1002 // GC, so the collector state must be updated to reflect this.
1003 collector_state()->set_in_young_only_phase(true);
1004 collector_state()->set_in_young_gc_before_mixed(false);
1005
1006 // We might have ended up coming here about to start a mixed phase with a collection set
1007 // active. The following remark might change the change the "evacuation efficiency" of
1008 // the regions in this set, leading to failing asserts later.
1009 // Since the concurrent cycle will recreate the collection set anyway, simply drop it here.
1010 clear_collection_set_candidates();
1011 abort_time_to_mixed_tracking();
1012 initiate_conc_mark();
1013 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1014 } else {
1015 // The concurrent marking thread is still finishing up the
1016 // previous cycle. If we start one right now the two cycles
1017 // overlap. In particular, the concurrent marking thread might
1018 // be in the process of clearing the next marking bitmap (which
1019 // we will use for the next cycle if we start one). Starting a
1020 // cycle now will be bad given that parts of the marking
1021 // information might get cleared by the marking thread. And we
1022 // cannot wait for the marking thread to finish the cycle as it
1023 // periodically yields while clearing the next marking bitmap
1024 // and, if it's in a yield point, it's waiting for us to
1025 // finish. So, at this point we will not start a cycle and we'll
1026 // let the concurrent marking thread complete the last one.
1027 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1028 }
1029 }
1030}
1031
1032void G1Policy::record_concurrent_mark_cleanup_end() {
1033 G1CollectionSetCandidates* candidates = G1CollectionSetChooser::build(_g1h->workers(), _g1h->num_regions());
1034 _collection_set->set_candidates(candidates);
1035
1036 bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs");
1037 if (!mixed_gc_pending) {
1038 clear_collection_set_candidates();
1039 abort_time_to_mixed_tracking();
1040 }
1041 collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending);
1042 collector_state()->set_mark_or_rebuild_in_progress(false);
1043
1044 double end_sec = os::elapsedTime();
1045 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1046 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
1047 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
1048
1049 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1050}
1051
1052double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const {
1053 return percent_of(reclaimable_bytes, _g1h->capacity());
1054}
1055
1056class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure {
1057 virtual bool do_heap_region(HeapRegion* r) {
1058 r->rem_set()->clear_locked(true /* only_cardset */);
1059 return false;
1060 }
1061};
1062
1063void G1Policy::clear_collection_set_candidates() {
1064 // Clear remembered sets of remaining candidate regions and the actual candidate
1065 // set.
1066 G1ClearCollectionSetCandidateRemSets cl;
1067 _collection_set->candidates()->iterate(&cl);
1068 _collection_set->clear_candidates();
1069}
1070
1071void G1Policy::maybe_start_marking() {
1072 if (need_to_start_conc_mark("end of GC")) {
1073 // Note: this might have already been set, if during the last
1074 // pause we decided to start a cycle but at the beginning of
1075 // this pause we decided to postpone it. That's OK.
1076 collector_state()->set_initiate_conc_mark_if_possible(true);
1077 }
1078}
1079
1080G1Policy::PauseKind G1Policy::young_gc_pause_kind() const {
1081 assert(!collector_state()->in_full_gc(), "must be");
1082 if (collector_state()->in_initial_mark_gc()) {
1083 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1084 return InitialMarkGC;
1085 } else if (collector_state()->in_young_gc_before_mixed()) {
1086 assert(!collector_state()->in_initial_mark_gc(), "must be");
1087 return LastYoungGC;
1088 } else if (collector_state()->in_mixed_phase()) {
1089 assert(!collector_state()->in_initial_mark_gc(), "must be");
1090 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1091 return MixedGC;
1092 } else {
1093 assert(!collector_state()->in_initial_mark_gc(), "must be");
1094 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1095 return YoungOnlyGC;
1096 }
1097}
1098
1099void G1Policy::record_pause(PauseKind kind, double start, double end) {
1100 // Manage the MMU tracker. For some reason it ignores Full GCs.
1101 if (kind != FullGC) {
1102 _mmu_tracker->add_pause(start, end);
1103 }
1104 // Manage the mutator time tracking from initial mark to first mixed gc.
1105 switch (kind) {
1106 case FullGC:
1107 abort_time_to_mixed_tracking();
1108 break;
1109 case Cleanup:
1110 case Remark:
1111 case YoungOnlyGC:
1112 case LastYoungGC:
1113 _initial_mark_to_mixed.add_pause(end - start);
1114 break;
1115 case InitialMarkGC:
1116 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) {
1117 _initial_mark_to_mixed.record_initial_mark_end(end);
1118 }
1119 break;
1120 case MixedGC:
1121 _initial_mark_to_mixed.record_mixed_gc_start(start);
1122 break;
1123 default:
1124 ShouldNotReachHere();
1125 }
1126}
1127
1128void G1Policy::abort_time_to_mixed_tracking() {
1129 _initial_mark_to_mixed.reset();
1130}
1131
1132bool G1Policy::next_gc_should_be_mixed(const char* true_action_str,
1133 const char* false_action_str) const {
1134 G1CollectionSetCandidates* candidates = _collection_set->candidates();
1135
1136 if (candidates->is_empty()) {
1137 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1138 return false;
1139 }
1140
1141 // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1142 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes();
1143 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1144 double threshold = (double) G1HeapWastePercent;
1145 if (reclaimable_percent <= threshold) {
1146 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1147 false_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1148 return false;
1149 }
1150 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1151 true_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1152 return true;
1153}
1154
1155uint G1Policy::calc_min_old_cset_length() const {
1156 // The min old CSet region bound is based on the maximum desired
1157 // number of mixed GCs after a cycle. I.e., even if some old regions
1158 // look expensive, we should add them to the CSet anyway to make
1159 // sure we go through the available old regions in no more than the
1160 // maximum desired number of mixed GCs.
1161 //
1162 // The calculation is based on the number of marked regions we added
1163 // to the CSet candidates in the first place, not how many remain, so
1164 // that the result is the same during all mixed GCs that follow a cycle.
1165
1166 const size_t region_num = _collection_set->candidates()->num_regions();
1167 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1168 size_t result = region_num / gc_num;
1169 // emulate ceiling
1170 if (result * gc_num < region_num) {
1171 result += 1;
1172 }
1173 return (uint) result;
1174}
1175
1176uint G1Policy::calc_max_old_cset_length() const {
1177 // The max old CSet region bound is based on the threshold expressed
1178 // as a percentage of the heap size. I.e., it should bound the
1179 // number of old regions added to the CSet irrespective of how many
1180 // of them are available.
1181
1182 const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1183 const size_t region_num = g1h->num_regions();
1184 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1185 size_t result = region_num * perc / 100;
1186 // emulate ceiling
1187 if (100 * result < region_num * perc) {
1188 result += 1;
1189 }
1190 return (uint) result;
1191}
1192
1193void G1Policy::calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
1194 double time_remaining_ms,
1195 uint& num_initial_regions,
1196 uint& num_optional_regions) {
1197 assert(candidates != NULL, "Must be");
1198
1199 num_initial_regions = 0;
1200 num_optional_regions = 0;
1201 uint num_expensive_regions = 0;
1202
1203 double predicted_old_time_ms = 0.0;
1204 double predicted_initial_time_ms = 0.0;
1205 double predicted_optional_time_ms = 0.0;
1206
1207 double optional_threshold_ms = time_remaining_ms * optional_prediction_fraction();
1208
1209 const uint min_old_cset_length = calc_min_old_cset_length();
1210 const uint max_old_cset_length = MAX2(min_old_cset_length, calc_max_old_cset_length());
1211 const uint max_optional_regions = max_old_cset_length - min_old_cset_length;
1212 bool check_time_remaining = use_adaptive_young_list_length();
1213
1214 uint candidate_idx = candidates->cur_idx();
1215
1216 log_debug(gc, ergo, cset)("Start adding old regions to collection set. Min %u regions, max %u regions, "
1217 "time remaining %1.2fms, optional threshold %1.2fms",
1218 min_old_cset_length, max_old_cset_length, time_remaining_ms, optional_threshold_ms);
1219
1220 HeapRegion* hr = candidates->at(candidate_idx);
1221 while (hr != NULL) {
1222 if (num_initial_regions + num_optional_regions >= max_old_cset_length) {
1223 // Added maximum number of old regions to the CSet.
1224 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Maximum number of regions). "
1225 "Initial %u regions, optional %u regions",
1226 num_initial_regions, num_optional_regions);
1227 break;
1228 }
1229
1230 // Stop adding regions if the remaining reclaimable space is
1231 // not above G1HeapWastePercent.
1232 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes();
1233 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1234 double threshold = (double) G1HeapWastePercent;
1235 if (reclaimable_percent <= threshold) {
1236 // We've added enough old regions that the amount of uncollected
1237 // reclaimable space is at or below the waste threshold. Stop
1238 // adding old regions to the CSet.
1239 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Reclaimable percentage below threshold). "
1240 "Reclaimable: " SIZE_FORMAT "%s (%1.2f%%) threshold: " UINTX_FORMAT "%%",
1241 byte_size_in_proper_unit(reclaimable_bytes), proper_unit_for_byte_size(reclaimable_bytes),
1242 reclaimable_percent, G1HeapWastePercent);
1243 break;
1244 }
1245
1246 double predicted_time_ms = predict_region_elapsed_time_ms(hr, false);
1247 time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0);
1248 // Add regions to old set until we reach the minimum amount
1249 if (num_initial_regions < min_old_cset_length) {
1250 predicted_old_time_ms += predicted_time_ms;
1251 num_initial_regions++;
1252 // Record the number of regions added with no time remaining
1253 if (time_remaining_ms == 0.0) {
1254 num_expensive_regions++;
1255 }
1256 } else if (!check_time_remaining) {
1257 // In the non-auto-tuning case, we'll finish adding regions
1258 // to the CSet if we reach the minimum.
1259 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Region amount reached min).");
1260 break;
1261 } else {
1262 // Keep adding regions to old set until we reach the optional threshold
1263 if (time_remaining_ms > optional_threshold_ms) {
1264 predicted_old_time_ms += predicted_time_ms;
1265 num_initial_regions++;
1266 } else if (time_remaining_ms > 0) {
1267 // Keep adding optional regions until time is up.
1268 assert(num_optional_regions < max_optional_regions, "Should not be possible.");
1269 predicted_optional_time_ms += predicted_time_ms;
1270 num_optional_regions++;
1271 } else {
1272 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Predicted time too high).");
1273 break;
1274 }
1275 }
1276 hr = candidates->at(++candidate_idx);
1277 }
1278 if (hr == NULL) {
1279 log_debug(gc, ergo, cset)("Old candidate collection set empty.");
1280 }
1281
1282 if (num_expensive_regions > 0) {
1283 log_debug(gc, ergo, cset)("Added %u initial old regions to collection set although the predicted time was too high.",
1284 num_expensive_regions);
1285 }
1286
1287 log_debug(gc, ergo, cset)("Finish choosing collection set old regions. Initial: %u, optional: %u, "
1288 "predicted old time: %1.2fms, predicted optional time: %1.2fms, time remaining: %1.2f",
1289 num_initial_regions, num_optional_regions,
1290 predicted_initial_time_ms, predicted_optional_time_ms, time_remaining_ms);
1291}
1292
1293void G1Policy::calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
1294 uint const max_optional_regions,
1295 double time_remaining_ms,
1296 uint& num_optional_regions) {
1297 assert(_g1h->collector_state()->in_mixed_phase(), "Should only be called in mixed phase");
1298
1299 num_optional_regions = 0;
1300 double prediction_ms = 0;
1301 uint candidate_idx = candidates->cur_idx();
1302
1303 HeapRegion* r = candidates->at(candidate_idx);
1304 while (num_optional_regions < max_optional_regions) {
1305 assert(r != NULL, "Region must exist");
1306 prediction_ms += predict_region_elapsed_time_ms(r, false);
1307
1308 if (prediction_ms > time_remaining_ms) {
1309 log_debug(gc, ergo, cset)("Prediction %.3fms for region %u does not fit remaining time: %.3fms.",
1310 prediction_ms, r->hrm_index(), time_remaining_ms);
1311 break;
1312 }
1313 // This region will be included in the next optional evacuation.
1314
1315 time_remaining_ms -= prediction_ms;
1316 num_optional_regions++;
1317 r = candidates->at(++candidate_idx);
1318 }
1319
1320 log_debug(gc, ergo, cset)("Prepared %u regions out of %u for optional evacuation. Predicted time: %.3fms",
1321 num_optional_regions, max_optional_regions, prediction_ms);
1322}
1323
1324void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) {
1325
1326 // Add survivor regions to SurvRateGroup.
1327 note_start_adding_survivor_regions();
1328 finished_recalculating_age_indexes(true /* is_survivors */);
1329
1330 HeapRegion* last = NULL;
1331 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin();
1332 it != survivors->regions()->end();
1333 ++it) {
1334 HeapRegion* curr = *it;
1335 set_region_survivor(curr);
1336
1337 // The region is a non-empty survivor so let's add it to
1338 // the incremental collection set for the next evacuation
1339 // pause.
1340 _collection_set->add_survivor_regions(curr);
1341
1342 last = curr;
1343 }
1344 note_stop_adding_survivor_regions();
1345
1346 // Don't clear the survivor list handles until the start of
1347 // the next evacuation pause - we need it in order to re-tag
1348 // the survivor regions from this evacuation pause as 'young'
1349 // at the start of the next.
1350
1351 finished_recalculating_age_indexes(false /* is_survivors */);
1352}
1353