1 /*
2 * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc/g1/g1Analytics.hpp"
27 #include "gc/g1/g1Arguments.hpp"
28 #include "gc/g1/g1CollectedHeap.inline.hpp"
29 #include "gc/g1/g1CollectionSet.hpp"
30 #include "gc/g1/g1CollectionSetCandidates.hpp"
31 #include "gc/g1/g1ConcurrentMark.hpp"
32 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
33 #include "gc/g1/g1ConcurrentRefine.hpp"
34 #include "gc/g1/g1CollectionSetChooser.hpp"
35 #include "gc/g1/g1HeterogeneousHeapPolicy.hpp"
36 #include "gc/g1/g1HotCardCache.hpp"
37 #include "gc/g1/g1IHOPControl.hpp"
38 #include "gc/g1/g1GCPhaseTimes.hpp"
39 #include "gc/g1/g1Policy.hpp"
40 #include "gc/g1/g1SurvivorRegions.hpp"
41 #include "gc/g1/g1YoungGenSizer.hpp"
42 #include "gc/g1/heapRegion.inline.hpp"
43 #include "gc/g1/heapRegionRemSet.hpp"
44 #include "gc/shared/gcPolicyCounters.hpp"
45 #include "logging/logStream.hpp"
46 #include "runtime/arguments.hpp"
47 #include "runtime/java.hpp"
48 #include "runtime/mutexLocker.hpp"
49 #include "utilities/debug.hpp"
50 #include "utilities/growableArray.hpp"
51 #include "utilities/pair.hpp"
52
53 G1Policy::G1Policy(STWGCTimer* gc_timer) :
54 _predictor(G1ConfidencePercent / 100.0),
55 _analytics(new G1Analytics(&_predictor)),
56 _remset_tracker(),
57 _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)),
58 _ihop_control(create_ihop_control(&_predictor)),
59 _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 2)),
60 _full_collection_start_sec(0.0),
61 _collection_pause_end_millis(os::javaTimeNanos() / NANOSECS_PER_MILLISEC),
62 _young_list_target_length(0),
63 _young_list_fixed_length(0),
64 _young_list_max_length(0),
65 _eden_surv_rate_group(new G1SurvRateGroup()),
66 _survivor_used_bytes_at_start(0),
67 _survivor_used_bytes_at_end(0),
68 _reserve_factor((double) G1ReservePercent / 100.0),
69 _reserve_regions(0),
70 _young_gen_sizer(G1YoungGenSizer::create_gen_sizer()),
71 _free_regions_at_end_of_collection(0),
72 _rs_length(0),
73 _rs_length_prediction(0),
74 _pending_cards_at_gc_start(0),
75 _pending_cards_at_prev_gc_end(0),
76 _total_mutator_refined_cards(0),
77 _total_concurrent_refined_cards(0),
78 _total_concurrent_refinement_time(),
79 _bytes_allocated_in_old_since_last_gc(0),
80 _initial_mark_to_mixed(),
81 _collection_set(NULL),
82 _g1h(NULL),
83 _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)),
84 _mark_remark_start_sec(0),
85 _mark_cleanup_start_sec(0),
86 _tenuring_threshold(MaxTenuringThreshold),
87 _max_survivor_regions(0),
88 _surviving_survivor_words(0)
89 {
90 }
91
92 G1Policy::~G1Policy() {
93 delete _ihop_control;
94 delete _young_gen_sizer;
95 }
96
97 G1Policy* G1Policy::create_policy(STWGCTimer* gc_timer_stw) {
98 if (G1Arguments::is_heterogeneous_heap()) {
99 return new G1HeterogeneousHeapPolicy(gc_timer_stw);
100 } else {
101 return new G1Policy(gc_timer_stw);
102 }
103 }
104
105 G1CollectorState* G1Policy::collector_state() const { return _g1h->collector_state(); }
106
107 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
108 _g1h = g1h;
109 _collection_set = collection_set;
110
111 assert(Heap_lock->owned_by_self(), "Locking discipline.");
112
113 if (!use_adaptive_young_list_length()) {
114 _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
115 }
116 _young_gen_sizer->adjust_max_new_size(_g1h->max_expandable_regions());
117
118 _free_regions_at_end_of_collection = _g1h->num_free_regions();
119
120 update_young_list_max_and_target_length();
121 // We may immediately start allocating regions and placing them on the
122 // collection set list. Initialize the per-collection set info
123 _collection_set->start_incremental_building();
124 }
125
126 void G1Policy::note_gc_start() {
127 phase_times()->note_gc_start();
128 }
129
130 class G1YoungLengthPredictor {
131 const double _base_time_ms;
132 const double _base_free_regions;
133 const double _target_pause_time_ms;
134 const G1Policy* const _policy;
135
136 public:
137 G1YoungLengthPredictor(double base_time_ms,
138 double base_free_regions,
139 double target_pause_time_ms,
140 const G1Policy* policy) :
141 _base_time_ms(base_time_ms),
142 _base_free_regions(base_free_regions),
143 _target_pause_time_ms(target_pause_time_ms),
144 _policy(policy) {}
145
146 bool will_fit(uint young_length) const {
147 if (young_length >= _base_free_regions) {
148 // end condition 1: not enough space for the young regions
149 return false;
150 }
151
152 size_t bytes_to_copy = 0;
153 const double copy_time_ms = _policy->predict_eden_copy_time_ms(young_length, &bytes_to_copy);
154 const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length);
155 const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms;
156 if (pause_time_ms > _target_pause_time_ms) {
157 // end condition 2: prediction is over the target pause time
158 return false;
159 }
160
161 const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes;
162
163 // When copying, we will likely need more bytes free than is live in the region.
164 // Add some safety margin to factor in the confidence of our guess, and the
165 // natural expected waste.
166 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
167 // of the calculation: the lower the confidence, the more headroom.
168 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
169 // copying due to anticipated waste in the PLABs.
170 const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
171 const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
172
173 if (expected_bytes_to_copy > free_bytes) {
174 // end condition 3: out-of-space
175 return false;
176 }
177
178 // success!
179 return true;
180 }
181 };
182
183 void G1Policy::record_new_heap_size(uint new_number_of_regions) {
184 // re-calculate the necessary reserve
185 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
186 // We use ceiling so that if reserve_regions_d is > 0.0 (but
187 // smaller than 1.0) we'll get 1.
188 _reserve_regions = (uint) ceil(reserve_regions_d);
189
190 _young_gen_sizer->heap_size_changed(new_number_of_regions);
191
192 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
193 }
194
195 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const {
196 uint desired_min_length = 0;
197 if (use_adaptive_young_list_length()) {
198 if (_analytics->num_alloc_rate_ms() > 3) {
199 double now_sec = os::elapsedTime();
200 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
201 double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
202 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
203 } else {
204 // otherwise we don't have enough info to make the prediction
205 }
206 }
207 desired_min_length += base_min_length;
208 // make sure we don't go below any user-defined minimum bound
209 return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
210 }
211
212 uint G1Policy::calculate_young_list_desired_max_length() const {
213 // Here, we might want to also take into account any additional
214 // constraints (i.e., user-defined minimum bound). Currently, we
215 // effectively don't set this bound.
216 return _young_gen_sizer->max_desired_young_length();
217 }
218
219 uint G1Policy::update_young_list_max_and_target_length() {
220 return update_young_list_max_and_target_length(_analytics->predict_rs_length());
221 }
222
223 uint G1Policy::update_young_list_max_and_target_length(size_t rs_length) {
224 uint unbounded_target_length = update_young_list_target_length(rs_length);
225 update_max_gc_locker_expansion();
226 return unbounded_target_length;
227 }
228
229 uint G1Policy::update_young_list_target_length(size_t rs_length) {
230 YoungTargetLengths young_lengths = young_list_target_lengths(rs_length);
231 _young_list_target_length = young_lengths.first;
232
233 return young_lengths.second;
234 }
235
236 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_length) const {
237 YoungTargetLengths result;
238
239 // Calculate the absolute and desired min bounds first.
240
241 // This is how many young regions we already have (currently: the survivors).
242 const uint base_min_length = _g1h->survivor_regions_count();
243 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
244 // This is the absolute minimum young length. Ensure that we
245 // will at least have one eden region available for allocation.
246 uint absolute_min_length = base_min_length + MAX2(_g1h->eden_regions_count(), (uint)1);
247 // If we shrank the young list target it should not shrink below the current size.
248 desired_min_length = MAX2(desired_min_length, absolute_min_length);
249 // Calculate the absolute and desired max bounds.
250
251 uint desired_max_length = calculate_young_list_desired_max_length();
252
253 uint young_list_target_length = 0;
254 if (use_adaptive_young_list_length()) {
255 if (collector_state()->in_young_only_phase()) {
256 young_list_target_length =
257 calculate_young_list_target_length(rs_length,
258 base_min_length,
259 desired_min_length,
260 desired_max_length);
261 } else {
262 // Don't calculate anything and let the code below bound it to
263 // the desired_min_length, i.e., do the next GC as soon as
264 // possible to maximize how many old regions we can add to it.
265 }
266 } else {
267 // The user asked for a fixed young gen so we'll fix the young gen
268 // whether the next GC is young or mixed.
269 young_list_target_length = _young_list_fixed_length;
270 }
271
272 result.second = young_list_target_length;
273
274 // We will try our best not to "eat" into the reserve.
275 uint absolute_max_length = 0;
276 if (_free_regions_at_end_of_collection > _reserve_regions) {
277 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
278 }
279 if (desired_max_length > absolute_max_length) {
280 desired_max_length = absolute_max_length;
281 }
282
283 // Make sure we don't go over the desired max length, nor under the
284 // desired min length. In case they clash, desired_min_length wins
285 // which is why that test is second.
286 if (young_list_target_length > desired_max_length) {
287 young_list_target_length = desired_max_length;
288 }
289 if (young_list_target_length < desired_min_length) {
290 young_list_target_length = desired_min_length;
291 }
292
293 assert(young_list_target_length > base_min_length,
294 "we should be able to allocate at least one eden region");
295 assert(young_list_target_length >= absolute_min_length, "post-condition");
296
297 result.first = young_list_target_length;
298 return result;
299 }
300
301 uint G1Policy::calculate_young_list_target_length(size_t rs_length,
302 uint base_min_length,
303 uint desired_min_length,
304 uint desired_max_length) const {
305 assert(use_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 size_t pending_cards = _analytics->predict_pending_cards();
325 const double base_time_ms = predict_base_elapsed_time_ms(pending_cards, rs_length);
326 const uint available_free_regions = _free_regions_at_end_of_collection;
327 const uint base_free_regions =
328 available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0;
329
330 // Here, we will make sure that the shortest young length that
331 // makes sense fits within the target pause time.
332
333 G1YoungLengthPredictor p(base_time_ms,
334 base_free_regions,
335 target_pause_time_ms,
336 this);
337 if (p.will_fit(min_young_length)) {
338 // The shortest young length will fit into the target pause time;
339 // we'll now check whether the absolute maximum number of young
340 // regions will fit in the target pause time. If not, we'll do
341 // a binary search between min_young_length and max_young_length.
342 if (p.will_fit(max_young_length)) {
343 // The maximum young length will fit into the target pause time.
344 // We are done so set min young length to the maximum length (as
345 // the result is assumed to be returned in min_young_length).
346 min_young_length = max_young_length;
347 } else {
348 // The maximum possible number of young regions will not fit within
349 // the target pause time so we'll search for the optimal
350 // length. The loop invariants are:
351 //
352 // min_young_length < max_young_length
353 // min_young_length is known to fit into the target pause time
354 // max_young_length is known not to fit into the target pause time
355 //
356 // Going into the loop we know the above hold as we've just
357 // checked them. Every time around the loop we check whether
358 // the middle value between min_young_length and
359 // max_young_length fits into the target pause time. If it
360 // does, it becomes the new min. If it doesn't, it becomes
361 // the new max. This way we maintain the loop invariants.
362
363 assert(min_young_length < max_young_length, "invariant");
364 uint diff = (max_young_length - min_young_length) / 2;
365 while (diff > 0) {
366 uint young_length = min_young_length + diff;
367 if (p.will_fit(young_length)) {
368 min_young_length = young_length;
369 } else {
370 max_young_length = young_length;
371 }
372 assert(min_young_length < max_young_length, "invariant");
373 diff = (max_young_length - min_young_length) / 2;
374 }
375 // The results is min_young_length which, according to the
376 // loop invariants, should fit within the target pause time.
377
378 // These are the post-conditions of the binary search above:
379 assert(min_young_length < max_young_length,
380 "otherwise we should have discovered that max_young_length "
381 "fits into the pause target and not done the binary search");
382 assert(p.will_fit(min_young_length),
383 "min_young_length, the result of the binary search, should "
384 "fit into the pause target");
385 assert(!p.will_fit(min_young_length + 1),
386 "min_young_length, the result of the binary search, should be "
387 "optimal, so no larger length should fit into the pause target");
388 }
389 } else {
390 // Even the minimum length doesn't fit into the pause time
391 // target, return it as the result nevertheless.
392 }
393 return base_min_length + min_young_length;
394 }
395
396 double G1Policy::predict_survivor_regions_evac_time() const {
397 double survivor_regions_evac_time = 0.0;
398 const GrowableArray<HeapRegion*>* survivor_regions = _g1h->survivor()->regions();
399 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin();
400 it != survivor_regions->end();
401 ++it) {
402 // We could split out copy_time from total time here and calculate it based on
403 // the number of survivor regions. Since we need to iterate over the regions
404 // for the non_copy time anyway, keep it.
405 survivor_regions_evac_time += predict_region_total_time_ms(*it, collector_state()->in_young_only_phase());
406 }
407 return survivor_regions_evac_time;
408 }
409
410 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_length) {
411 guarantee(use_adaptive_young_list_length(), "should not call this otherwise" );
412
413 if (rs_length > _rs_length_prediction) {
414 // add 10% to avoid having to recalculate often
415 size_t rs_length_prediction = rs_length * 1100 / 1000;
416 update_rs_length_prediction(rs_length_prediction);
417
418 update_young_list_max_and_target_length(rs_length_prediction);
419 }
420 }
421
422 void G1Policy::update_rs_length_prediction() {
423 update_rs_length_prediction(_analytics->predict_rs_length());
424 }
425
426 void G1Policy::update_rs_length_prediction(size_t prediction) {
427 if (collector_state()->in_young_only_phase() && use_adaptive_young_list_length()) {
428 _rs_length_prediction = prediction;
429 }
430 }
431
432 void G1Policy::record_full_collection_start() {
433 _full_collection_start_sec = os::elapsedTime();
434 // Release the future to-space so that it is available for compaction into.
435 collector_state()->set_in_young_only_phase(false);
436 collector_state()->set_in_full_gc(true);
437 _collection_set->clear_candidates();
438 record_concurrent_refinement_data(true /* is_full_collection */);
439 }
440
441 void G1Policy::record_full_collection_end() {
442 // Consider this like a collection pause for the purposes of allocation
443 // since last pause.
444 double end_sec = os::elapsedTime();
445 double full_gc_time_sec = end_sec - _full_collection_start_sec;
446 double full_gc_time_ms = full_gc_time_sec * 1000.0;
447
448 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);
449
450 collector_state()->set_in_full_gc(false);
451
452 // "Nuke" the heuristics that control the young/mixed GC
453 // transitions and make sure we start with young GCs after the Full GC.
454 collector_state()->set_in_young_only_phase(true);
455 collector_state()->set_in_young_gc_before_mixed(false);
456 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
457 collector_state()->set_in_initial_mark_gc(false);
458 collector_state()->set_mark_or_rebuild_in_progress(false);
459 collector_state()->set_clearing_next_bitmap(false);
460
461 _eden_surv_rate_group->start_adding_regions();
462
463 _free_regions_at_end_of_collection = _g1h->num_free_regions();
464 update_young_list_max_and_target_length();
465 update_rs_length_prediction();
466 _pending_cards_at_prev_gc_end = _g1h->pending_card_num();
467
468 _bytes_allocated_in_old_since_last_gc = 0;
469
470 record_pause(FullGC, _full_collection_start_sec, end_sec);
471 }
472
473 void G1Policy::record_concurrent_refinement_data(bool is_full_collection) {
474 _pending_cards_at_gc_start = _g1h->pending_card_num();
475
476 // Record info about concurrent refinement thread processing.
477 G1ConcurrentRefine* cr = _g1h->concurrent_refine();
478 G1ConcurrentRefine::RefinementStats cr_stats = cr->total_refinement_stats();
479
480 Tickspan cr_time = cr_stats._time - _total_concurrent_refinement_time;
481 _total_concurrent_refinement_time = cr_stats._time;
482
483 size_t cr_cards = cr_stats._cards - _total_concurrent_refined_cards;
484 _total_concurrent_refined_cards = cr_stats._cards;
485
486 // Don't update rate if full collection. We could be in an implicit full
487 // collection after a non-full collection failure, in which case there
488 // wasn't any mutator/cr-thread activity since last recording. And if
489 // we're in an explicit full collection, the time since the last GC can
490 // be arbitrarily short, so not a very good sample. Similarly, don't
491 // update the rate if the current sample is empty or time is zero.
492 if (!is_full_collection && (cr_cards > 0) && (cr_time > Tickspan())) {
493 double rate = cr_cards / (cr_time.seconds() * MILLIUNITS);
494 _analytics->report_concurrent_refine_rate_ms(rate);
495 }
496
497 // Record info about mutator thread processing.
498 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
499 size_t mut_total_cards = dcqs.total_mutator_refined_cards();
500 size_t mut_cards = mut_total_cards - _total_mutator_refined_cards;
501 _total_mutator_refined_cards = mut_total_cards;
502
503 // Record mutator's card logging rate.
504 // Don't update if full collection; see above.
505 if (!is_full_collection) {
506 size_t total_cards = _pending_cards_at_gc_start + cr_cards + mut_cards;
507 assert(_pending_cards_at_prev_gc_end <= total_cards,
508 "untracked cards: last pending: " SIZE_FORMAT
509 ", pending: " SIZE_FORMAT ", conc refine: " SIZE_FORMAT
510 ", mut refine:" SIZE_FORMAT,
511 _pending_cards_at_prev_gc_end, _pending_cards_at_gc_start,
512 cr_cards, mut_cards);
513 size_t logged_cards = total_cards - _pending_cards_at_prev_gc_end;
514 double logging_start_time = _analytics->prev_collection_pause_end_ms();
515 double logging_end_time = Ticks::now().seconds() * MILLIUNITS;
516 double logging_time = logging_end_time - logging_start_time;
517 // Unlike above for conc-refine rate, here we should not require a
518 // non-empty sample, since an application could go some time with only
519 // young-gen or filtered out writes. But we'll ignore unusually short
520 // sample periods, as they may just pollute the predictions.
521 if (logging_time > 1.0) { // Require > 1ms sample time.
522 _analytics->report_logged_cards_rate_ms(logged_cards / logging_time);
523 }
524 }
525 }
526
527 void G1Policy::record_collection_pause_start(double start_time_sec) {
528 // We only need to do this here as the policy will only be applied
529 // to the GC we're about to start. so, no point is calculating this
530 // every time we calculate / recalculate the target young length.
531 update_survivors_policy();
532 _survivor_used_bytes_at_start = _g1h->survivor()->used_bytes();
533 _survivor_used_bytes_at_end = 0;
534
535 assert(max_survivor_regions() + _g1h->num_used_regions() <= _g1h->max_regions(),
536 "Maximum survivor regions %u plus used regions %u exceeds max regions %u",
537 max_survivor_regions(), _g1h->num_used_regions(), _g1h->max_regions());
538 assert_used_and_recalculate_used_equal(_g1h);
539
540 phase_times()->record_cur_collection_start_sec(start_time_sec);
541
542 record_concurrent_refinement_data(false /* is_full_collection */);
543
544 _collection_set->reset_bytes_used_before();
545
546 // do that for any other surv rate groups
547 _eden_surv_rate_group->stop_adding_regions();
548 _survivors_age_table.clear();
549 _surviving_survivor_words = 0;
550
551 assert(_g1h->collection_set()->verify_young_ages(), "region age verification failed");
552 }
553
554 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {
555 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
556 collector_state()->set_in_initial_mark_gc(false);
557 }
558
559 void G1Policy::record_concurrent_mark_remark_start() {
560 _mark_remark_start_sec = os::elapsedTime();
561 }
562
563 void G1Policy::record_concurrent_mark_remark_end() {
564 double end_time_sec = os::elapsedTime();
565 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
566 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);
567 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
568
569 record_pause(Remark, _mark_remark_start_sec, end_time_sec);
570 }
571
572 void G1Policy::record_concurrent_mark_cleanup_start() {
573 _mark_cleanup_start_sec = os::elapsedTime();
574 }
575
576 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
577 return phase_times()->average_time_ms(phase);
578 }
579
580 double G1Policy::young_other_time_ms() const {
581 return phase_times()->young_cset_choice_time_ms() +
582 phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet);
583 }
584
585 double G1Policy::non_young_other_time_ms() const {
586 return phase_times()->non_young_cset_choice_time_ms() +
587 phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet);
588 }
589
590 double G1Policy::other_time_ms(double pause_time_ms) const {
591 return pause_time_ms - phase_times()->cur_collection_par_time_ms();
592 }
593
594 double G1Policy::constant_other_time_ms(double pause_time_ms) const {
595 return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms();
596 }
597
598 bool G1Policy::about_to_start_mixed_phase() const {
599 return _g1h->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->in_young_gc_before_mixed();
600 }
601
602 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
603 if (about_to_start_mixed_phase()) {
604 return false;
605 }
606
607 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
608
609 size_t cur_used_bytes = _g1h->non_young_capacity_bytes();
610 size_t alloc_byte_size = alloc_word_size * HeapWordSize;
611 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
612
613 bool result = false;
614 if (marking_request_bytes > marking_initiating_used_threshold) {
615 result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed();
616 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
617 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
618 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1h->capacity() * 100, source);
619 }
620
621 return result;
622 }
623
624 double G1Policy::logged_cards_processing_time() const {
625 double all_cards_processing_time = average_time_ms(G1GCPhaseTimes::ScanHR) + average_time_ms(G1GCPhaseTimes::OptScanHR);
626 size_t logged_dirty_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards);
627 size_t scan_heap_roots_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) +
628 phase_times()->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards);
629 // This may happen if there are duplicate cards in different log buffers.
630 if (logged_dirty_cards > scan_heap_roots_cards) {
631 return all_cards_processing_time + average_time_ms(G1GCPhaseTimes::MergeLB);
632 }
633 return (all_cards_processing_time * logged_dirty_cards / scan_heap_roots_cards) + average_time_ms(G1GCPhaseTimes::MergeLB);
634 }
635
636 // Anything below that is considered to be zero
637 #define MIN_TIMER_GRANULARITY 0.0000001
638
639 void G1Policy::record_collection_pause_end(double pause_time_ms) {
640 G1GCPhaseTimes* p = phase_times();
641
642 double end_time_sec = os::elapsedTime();
643
644 bool this_pause_included_initial_mark = false;
645 bool this_pause_was_young_only = collector_state()->in_young_only_phase();
646
647 bool update_stats = !_g1h->evacuation_failed();
648
649 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
650
651 _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
652
653 this_pause_included_initial_mark = collector_state()->in_initial_mark_gc();
654 if (this_pause_included_initial_mark) {
655 record_concurrent_mark_init_end(0.0);
656 } else {
657 maybe_start_marking();
658 }
659
660 size_t survived = _surviving_survivor_words * HeapWordSize;
661
662 if (_survivor_used_bytes_at_start != 0) {
663 double ratio = (double)survived / _survivor_used_bytes_at_start;
664 guarantee(ratio >= 0.0 && ratio <= 1.0, "ratio %.3lf", ratio);
665 _analytics->report_survivor_ratio(ratio);
666 } else {
667 _analytics->report_survivor_ratio(0.0f);
668 }
669 _survivor_used_bytes_at_end = survived;
670
671 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
672 if (app_time_ms < MIN_TIMER_GRANULARITY) {
673 // This usually happens due to the timer not having the required
674 // granularity. Some Linuxes are the usual culprits.
675 // We'll just set it to something (arbitrarily) small.
676 app_time_ms = 1.0;
677 }
678
679 if (update_stats) {
680 // We maintain the invariant that all objects allocated by mutator
681 // threads will be allocated out of eden regions. So, we can use
682 // the eden region number allocated since the previous GC to
683 // calculate the application's allocate rate. The only exception
684 // to that is humongous objects that are allocated separately. But
685 // given that humongous object allocations do not really affect
686 // either the pause's duration nor when the next pause will take
687 // place we can safely ignore them here.
688 uint regions_allocated = _collection_set->eden_region_length();
689 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
690 _analytics->report_alloc_rate_ms(alloc_rate_ms);
691
692 double interval_ms =
693 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;
694 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
695 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);
696 }
697
698 if (collector_state()->in_young_gc_before_mixed()) {
699 assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC");
700 // This has been the young GC before we start doing mixed GCs. We already
701 // decided to start mixed GCs much earlier, so there is nothing to do except
702 // advancing the state.
703 collector_state()->set_in_young_only_phase(false);
704 collector_state()->set_in_young_gc_before_mixed(false);
705 } else if (!this_pause_was_young_only) {
706 // This is a mixed GC. Here we decide whether to continue doing more
707 // mixed GCs or not.
708 if (!next_gc_should_be_mixed("continue mixed GCs",
709 "do not continue mixed GCs")) {
710 collector_state()->set_in_young_only_phase(true);
711
712 clear_collection_set_candidates();
713 maybe_start_marking();
714 }
715 }
716
717 _eden_surv_rate_group->start_adding_regions();
718
719 double merge_hcc_time_ms = average_time_ms(G1GCPhaseTimes::MergeHCC);
720 if (update_stats) {
721 size_t const total_log_buffer_cards = p->sum_thread_work_items(G1GCPhaseTimes::MergeHCC, G1GCPhaseTimes::MergeHCCDirtyCards) +
722 p->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards);
723 // Update prediction for card merge; MergeRSDirtyCards includes the cards from the Eager Reclaim phase.
724 size_t const total_cards_merged = p->sum_thread_work_items(G1GCPhaseTimes::MergeRS, G1GCPhaseTimes::MergeRSDirtyCards) +
725 p->sum_thread_work_items(G1GCPhaseTimes::OptMergeRS, G1GCPhaseTimes::MergeRSDirtyCards) +
726 total_log_buffer_cards;
727
728 // The threshold for the number of cards in a given sampling which we consider
729 // large enough so that the impact from setup and other costs is negligible.
730 size_t const CardsNumSamplingThreshold = 10;
731
732 if (total_cards_merged > CardsNumSamplingThreshold) {
733 double avg_time_merge_cards = average_time_ms(G1GCPhaseTimes::MergeER) +
734 average_time_ms(G1GCPhaseTimes::MergeRS) +
735 average_time_ms(G1GCPhaseTimes::MergeHCC) +
736 average_time_ms(G1GCPhaseTimes::MergeLB) +
737 average_time_ms(G1GCPhaseTimes::OptMergeRS);
738 _analytics->report_cost_per_card_merge_ms(avg_time_merge_cards / total_cards_merged, this_pause_was_young_only);
739 }
740
741 // Update prediction for card scan
742 size_t const total_cards_scanned = p->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) +
743 p->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards);
744
745 if (total_cards_scanned > CardsNumSamplingThreshold) {
746 double avg_time_dirty_card_scan = average_time_ms(G1GCPhaseTimes::ScanHR) +
747 average_time_ms(G1GCPhaseTimes::OptScanHR);
748
749 _analytics->report_cost_per_card_scan_ms(avg_time_dirty_card_scan / total_cards_scanned, this_pause_was_young_only);
750 }
751
752 // Update prediction for the ratio between cards from the remembered
753 // sets and actually scanned cards from the remembered sets.
754 // Cards from the remembered sets are all cards not duplicated by cards from
755 // the logs.
756 // Due to duplicates in the log buffers, the number of actually scanned cards
757 // can be smaller than the cards in the log buffers.
758 const size_t from_rs_length_cards = (total_cards_scanned > total_log_buffer_cards) ? total_cards_scanned - total_log_buffer_cards : 0;
759 double merge_to_scan_ratio = 0.0;
760 if (total_cards_scanned > 0) {
761 merge_to_scan_ratio = (double) from_rs_length_cards / total_cards_scanned;
762 }
763 _analytics->report_card_merge_to_scan_ratio(merge_to_scan_ratio, this_pause_was_young_only);
764
765 const size_t recorded_rs_length = _collection_set->recorded_rs_length();
766 const size_t rs_length_diff = _rs_length > recorded_rs_length ? _rs_length - recorded_rs_length : 0;
767 _analytics->report_rs_length_diff(rs_length_diff);
768
769 // Update prediction for copy cost per byte
770 size_t copied_bytes = p->sum_thread_work_items(G1GCPhaseTimes::MergePSS, G1GCPhaseTimes::MergePSSCopiedBytes);
771
772 if (copied_bytes > 0) {
773 double cost_per_byte_ms = (average_time_ms(G1GCPhaseTimes::ObjCopy) + average_time_ms(G1GCPhaseTimes::OptObjCopy)) / copied_bytes;
774 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress());
775 }
776
777 if (_collection_set->young_region_length() > 0) {
778 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
779 _collection_set->young_region_length());
780 }
781
782 if (_collection_set->old_region_length() > 0) {
783 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
784 _collection_set->old_region_length());
785 }
786
787 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
788
789 // Do not update RS lengths and the number of pending cards with information from mixed gc:
790 // these are is wildly different to during young only gc and mess up young gen sizing right
791 // after the mixed gc phase.
792 // During mixed gc we do not use them for young gen sizing.
793 if (this_pause_was_young_only) {
794 _analytics->report_pending_cards((double) _pending_cards_at_gc_start);
795 _analytics->report_rs_length((double) _rs_length);
796 }
797 }
798
799 assert(!(this_pause_included_initial_mark && collector_state()->mark_or_rebuild_in_progress()),
800 "If the last pause has been an initial mark, we should not have been in the marking window");
801 if (this_pause_included_initial_mark) {
802 collector_state()->set_mark_or_rebuild_in_progress(true);
803 }
804
805 _free_regions_at_end_of_collection = _g1h->num_free_regions();
806
807 update_rs_length_prediction();
808
809 // Do not update dynamic IHOP due to G1 periodic collection as it is highly likely
810 // that in this case we are not running in a "normal" operating mode.
811 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) {
812 // IHOP control wants to know the expected young gen length if it were not
813 // restrained by the heap reserve. Using the actual length would make the
814 // prediction too small and the limit the young gen every time we get to the
815 // predicted target occupancy.
816 size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
817
818 update_ihop_prediction(app_time_ms / 1000.0,
819 _bytes_allocated_in_old_since_last_gc,
820 last_unrestrained_young_length * HeapRegion::GrainBytes,
821 this_pause_was_young_only);
822 _bytes_allocated_in_old_since_last_gc = 0;
823
824 _ihop_control->send_trace_event(_g1h->gc_tracer_stw());
825 } else {
826 // Any garbage collection triggered as periodic collection resets the time-to-mixed
827 // measurement. Periodic collection typically means that the application is "inactive", i.e.
828 // the marking threads may have received an uncharacterisic amount of cpu time
829 // for completing the marking, i.e. are faster than expected.
830 // This skews the predicted marking length towards smaller values which might cause
831 // the mark start being too late.
832 _initial_mark_to_mixed.reset();
833 }
834
835 // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
836 double scan_logged_cards_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
837
838 if (scan_logged_cards_time_goal_ms < merge_hcc_time_ms) {
839 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
840 "Logged Cards Scan time goal: %1.2fms Scan HCC time: %1.2fms",
841 scan_logged_cards_time_goal_ms, merge_hcc_time_ms);
842
843 scan_logged_cards_time_goal_ms = 0;
844 } else {
845 scan_logged_cards_time_goal_ms -= merge_hcc_time_ms;
846 }
847
848 _pending_cards_at_prev_gc_end = _g1h->pending_card_num();
849 double const logged_cards_time = logged_cards_processing_time();
850
851 log_debug(gc, ergo, refine)("Concurrent refinement times: Logged Cards Scan time goal: %1.2fms Logged Cards Scan time: %1.2fms HCC time: %1.2fms",
852 scan_logged_cards_time_goal_ms, logged_cards_time, merge_hcc_time_ms);
853
854 _g1h->concurrent_refine()->adjust(logged_cards_time,
855 phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards),
856 scan_logged_cards_time_goal_ms);
857 }
858
859 G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){
860 if (G1UseAdaptiveIHOP) {
861 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
862 predictor,
863 G1ReservePercent,
864 G1HeapWastePercent);
865 } else {
866 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
867 }
868 }
869
870 void G1Policy::update_ihop_prediction(double mutator_time_s,
871 size_t mutator_alloc_bytes,
872 size_t young_gen_size,
873 bool this_gc_was_young_only) {
874 // Always try to update IHOP prediction. Even evacuation failures give information
875 // about e.g. whether to start IHOP earlier next time.
876
877 // Avoid using really small application times that might create samples with
878 // very high or very low values. They may be caused by e.g. back-to-back gcs.
879 double const min_valid_time = 1e-6;
880
881 bool report = false;
882
883 double marking_to_mixed_time = -1.0;
884 if (!this_gc_was_young_only && _initial_mark_to_mixed.has_result()) {
885 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
886 assert(marking_to_mixed_time > 0.0,
887 "Initial mark to mixed time must be larger than zero but is %.3f",
888 marking_to_mixed_time);
889 if (marking_to_mixed_time > min_valid_time) {
890 _ihop_control->update_marking_length(marking_to_mixed_time);
891 report = true;
892 }
893 }
894
895 // As an approximation for the young gc promotion rates during marking we use
896 // all of them. In many applications there are only a few if any young gcs during
897 // marking, which makes any prediction useless. This increases the accuracy of the
898 // prediction.
899 if (this_gc_was_young_only && mutator_time_s > min_valid_time) {
900 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
901 report = true;
902 }
903
904 if (report) {
905 report_ihop_statistics();
906 }
907 }
908
909 void G1Policy::report_ihop_statistics() {
910 _ihop_control->print();
911 }
912
913 void G1Policy::print_phases() {
914 phase_times()->print();
915 }
916
917 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards,
918 size_t rs_length) const {
919 size_t effective_scanned_cards = _analytics->predict_scan_card_num(rs_length, collector_state()->in_young_only_phase());
920 return
921 _analytics->predict_card_merge_time_ms(pending_cards + rs_length, collector_state()->in_young_only_phase()) +
922 _analytics->predict_card_scan_time_ms(effective_scanned_cards, collector_state()->in_young_only_phase()) +
923 _analytics->predict_constant_other_time_ms() +
924 predict_survivor_regions_evac_time();
925 }
926
927 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const {
928 size_t rs_length = _analytics->predict_rs_length();
929 return predict_base_elapsed_time_ms(pending_cards, rs_length);
930 }
931
932 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const {
933 size_t bytes_to_copy = 0;
934 if (!hr->is_young()) {
935 bytes_to_copy = hr->max_live_bytes();
936 } else {
937 size_t survived = hr->survivor_bytes();
938
939 guarantee(hr->used() >= survived, "Used " SIZE_FORMAT " >= survived " SIZE_FORMAT, hr->used(), survived);
940
941 if (survived > 0) {
942 bytes_to_copy += survived * _analytics->predict_survivor_ratio();
943 }
944
945 if (hr->used() > survived) {
946 bytes_to_copy += (size_t) ((hr->used() - survived) * hr->surv_rate_prediction(_predictor));
947 }
948 /*
949 log_debug(gc)("straggler region %u type %s old survived " SIZE_FORMAT " exp survived " SIZE_FORMAT " eden used " SIZE_FORMAT " exp eden survived " SIZE_FORMAT " total " SIZE_FORMAT,
950 hr->hrm_index(), hr->get_short_type_str(), survived, (size_t)(survived * _analytics->predict_survivor_ratio()), hr->used() - survived,
951 ((hr->used() - survived) > 0) ? (size_t)((hr->used() - survived) * hr->surv_rate_prediction(_predictor)) : 0, bytes_to_copy);
952 */
953 }
954 return bytes_to_copy;
955 }
956
957 double G1Policy::predict_eden_copy_time_ms(uint count, size_t* bytes_to_copy) const {
958 if (count == 0) {
959 return 0.0;
960 }
961 size_t const expected_bytes = _eden_surv_rate_group->accum_surv_rate_pred(count) * HeapRegion::GrainBytes;
962 if (bytes_to_copy != NULL) {
963 *bytes_to_copy = expected_bytes;
964 }
965 return _analytics->predict_object_copy_time_ms(expected_bytes, collector_state()->mark_or_rebuild_in_progress());
966 }
967
968 double G1Policy::predict_region_copy_time_ms(HeapRegion* hr) const {
969 size_t const bytes_to_copy = predict_bytes_to_copy(hr);
970 return _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress());
971 }
972
973 double G1Policy::predict_region_non_copy_time_ms(HeapRegion* hr,
974 bool for_young_gc) const {
975 size_t rs_length = hr->rem_set()->occupied();
976 size_t scan_card_num = _analytics->predict_scan_card_num(rs_length, for_young_gc);
977
978 double region_elapsed_time_ms =
979 _analytics->predict_card_merge_time_ms(rs_length, collector_state()->in_young_only_phase()) +
980 _analytics->predict_card_scan_time_ms(scan_card_num, collector_state()->in_young_only_phase());
981
982 // The prediction of the "other" time for this region is based
983 // upon the region type and NOT the GC type.
984 if (hr->is_young()) {
985 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
986 } else {
987 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
988 }
989 return region_elapsed_time_ms;
990 }
991
992 double G1Policy::predict_region_total_time_ms(HeapRegion* hr, bool for_young_gc) const {
993 return predict_region_non_copy_time_ms(hr, for_young_gc) + predict_region_copy_time_ms(hr);
994 }
995
996 bool G1Policy::should_allocate_mutator_region() const {
997 uint young_list_length = _g1h->young_regions_count();
998 uint young_list_target_length = _young_list_target_length;
999 return young_list_length < young_list_target_length;
1000 }
1001
1002 bool G1Policy::can_expand_young_list() const {
1003 uint young_list_length = _g1h->young_regions_count();
1004 uint young_list_max_length = _young_list_max_length;
1005 return young_list_length < young_list_max_length;
1006 }
1007
1008 bool G1Policy::use_adaptive_young_list_length() const {
1009 return _young_gen_sizer->use_adaptive_young_list_length();
1010 }
1011
1012 size_t G1Policy::desired_survivor_size(uint max_regions) const {
1013 size_t const survivor_capacity = HeapRegion::GrainWords * max_regions;
1014 return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
1015 }
1016
1017 void G1Policy::print_age_table() {
1018 _survivors_age_table.print_age_table(_tenuring_threshold);
1019 }
1020
1021 void G1Policy::update_max_gc_locker_expansion() {
1022 uint expansion_region_num = 0;
1023 if (GCLockerEdenExpansionPercent > 0) {
1024 double perc = (double) GCLockerEdenExpansionPercent / 100.0;
1025 double expansion_region_num_d = perc * (double) _young_list_target_length;
1026 // We use ceiling so that if expansion_region_num_d is > 0.0 (but
1027 // less than 1.0) we'll get 1.
1028 expansion_region_num = (uint) ceil(expansion_region_num_d);
1029 } else {
1030 assert(expansion_region_num == 0, "sanity");
1031 }
1032 _young_list_max_length = _young_list_target_length + expansion_region_num;
1033 assert(_young_list_target_length <= _young_list_max_length, "post-condition");
1034 }
1035
1036 // Calculates survivor space parameters.
1037 void G1Policy::update_survivors_policy() {
1038 double max_survivor_regions_d =
1039 (double) _young_list_target_length / (double) SurvivorRatio;
1040
1041 // Calculate desired survivor size based on desired max survivor regions (unconstrained
1042 // by remaining heap). Otherwise we may cause undesired promotions as we are
1043 // already getting close to end of the heap, impacting performance even more.
1044 uint const desired_max_survivor_regions = ceil(max_survivor_regions_d);
1045 size_t const survivor_size = desired_survivor_size(desired_max_survivor_regions);
1046
1047 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(survivor_size);
1048 if (UsePerfData) {
1049 _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold);
1050 _policy_counters->desired_survivor_size()->set_value(survivor_size * oopSize);
1051 }
1052 // The real maximum survivor size is bounded by the number of regions that can
1053 // be allocated into.
1054 _max_survivor_regions = MIN2(desired_max_survivor_regions,
1055 _g1h->num_free_or_available_regions());
1056 }
1057
1058 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
1059 // We actually check whether we are marking here and not if we are in a
1060 // reclamation phase. This means that we will schedule a concurrent mark
1061 // even while we are still in the process of reclaiming memory.
1062 bool during_cycle = _g1h->concurrent_mark()->cm_thread()->during_cycle();
1063 if (!during_cycle) {
1064 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
1065 collector_state()->set_initiate_conc_mark_if_possible(true);
1066 return true;
1067 } else {
1068 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
1069 return false;
1070 }
1071 }
1072
1073 void G1Policy::initiate_conc_mark() {
1074 collector_state()->set_in_initial_mark_gc(true);
1075 collector_state()->set_initiate_conc_mark_if_possible(false);
1076 }
1077
1078 void G1Policy::decide_on_conc_mark_initiation() {
1079 // We are about to decide on whether this pause will be an
1080 // initial-mark pause.
1081
1082 // First, collector_state()->in_initial_mark_gc() should not be already set. We
1083 // will set it here if we have to. However, it should be cleared by
1084 // the end of the pause (it's only set for the duration of an
1085 // initial-mark pause).
1086 assert(!collector_state()->in_initial_mark_gc(), "pre-condition");
1087
1088 if (collector_state()->initiate_conc_mark_if_possible()) {
1089 // We had noticed on a previous pause that the heap occupancy has
1090 // gone over the initiating threshold and we should start a
1091 // concurrent marking cycle. So we might initiate one.
1092
1093 if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) {
1094 // Initiate a new initial mark if there is no marking or reclamation going on.
1095 initiate_conc_mark();
1096 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
1097 } else if (_g1h->is_user_requested_concurrent_full_gc(_g1h->gc_cause())) {
1098 // Initiate a user requested initial mark. An initial mark must be young only
1099 // GC, so the collector state must be updated to reflect this.
1100 collector_state()->set_in_young_only_phase(true);
1101 collector_state()->set_in_young_gc_before_mixed(false);
1102
1103 // We might have ended up coming here about to start a mixed phase with a collection set
1104 // active. The following remark might change the change the "evacuation efficiency" of
1105 // the regions in this set, leading to failing asserts later.
1106 // Since the concurrent cycle will recreate the collection set anyway, simply drop it here.
1107 clear_collection_set_candidates();
1108 abort_time_to_mixed_tracking();
1109 initiate_conc_mark();
1110 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1111 } else {
1112 // The concurrent marking thread is still finishing up the
1113 // previous cycle. If we start one right now the two cycles
1114 // overlap. In particular, the concurrent marking thread might
1115 // be in the process of clearing the next marking bitmap (which
1116 // we will use for the next cycle if we start one). Starting a
1117 // cycle now will be bad given that parts of the marking
1118 // information might get cleared by the marking thread. And we
1119 // cannot wait for the marking thread to finish the cycle as it
1120 // periodically yields while clearing the next marking bitmap
1121 // and, if it's in a yield point, it's waiting for us to
1122 // finish. So, at this point we will not start a cycle and we'll
1123 // let the concurrent marking thread complete the last one.
1124 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1125 }
1126 }
1127 }
1128
1129 void G1Policy::record_concurrent_mark_cleanup_end() {
1130 G1CollectionSetCandidates* candidates = G1CollectionSetChooser::build(_g1h->workers(), _g1h->num_regions());
1131 _collection_set->set_candidates(candidates);
1132
1133 bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs");
1134 if (!mixed_gc_pending) {
1135 clear_collection_set_candidates();
1136 abort_time_to_mixed_tracking();
1137 }
1138 collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending);
1139 collector_state()->set_mark_or_rebuild_in_progress(false);
1140
1141 double end_sec = os::elapsedTime();
1142 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1143 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
1144 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
1145
1146 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1147 }
1148
1149 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const {
1150 return percent_of(reclaimable_bytes, _g1h->capacity());
1151 }
1152
1153 class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure {
1154 virtual bool do_heap_region(HeapRegion* r) {
1155 r->rem_set()->clear_locked(true /* only_cardset */);
1156 return false;
1157 }
1158 };
1159
1160 void G1Policy::clear_collection_set_candidates() {
1161 // Clear remembered sets of remaining candidate regions and the actual candidate
1162 // set.
1163 G1ClearCollectionSetCandidateRemSets cl;
1164 _collection_set->candidates()->iterate(&cl);
1165 _collection_set->clear_candidates();
1166 }
1167
1168 void G1Policy::maybe_start_marking() {
1169 if (need_to_start_conc_mark("end of GC")) {
1170 // Note: this might have already been set, if during the last
1171 // pause we decided to start a cycle but at the beginning of
1172 // this pause we decided to postpone it. That's OK.
1173 collector_state()->set_initiate_conc_mark_if_possible(true);
1174 }
1175 }
1176
1177 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const {
1178 assert(!collector_state()->in_full_gc(), "must be");
1179 if (collector_state()->in_initial_mark_gc()) {
1180 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1181 return InitialMarkGC;
1182 } else if (collector_state()->in_young_gc_before_mixed()) {
1183 assert(!collector_state()->in_initial_mark_gc(), "must be");
1184 return LastYoungGC;
1185 } else if (collector_state()->in_mixed_phase()) {
1186 assert(!collector_state()->in_initial_mark_gc(), "must be");
1187 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1188 return MixedGC;
1189 } else {
1190 assert(!collector_state()->in_initial_mark_gc(), "must be");
1191 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1192 return YoungOnlyGC;
1193 }
1194 }
1195
1196 void G1Policy::record_pause(PauseKind kind, double start, double end) {
1197 // Manage the MMU tracker. For some reason it ignores Full GCs.
1198 if (kind != FullGC) {
1199 _mmu_tracker->add_pause(start, end);
1200 }
1201 // Manage the mutator time tracking from initial mark to first mixed gc.
1202 switch (kind) {
1203 case FullGC:
1204 abort_time_to_mixed_tracking();
1205 break;
1206 case Cleanup:
1207 case Remark:
1208 case YoungOnlyGC:
1209 case LastYoungGC:
1210 _initial_mark_to_mixed.add_pause(end - start);
1211 break;
1212 case InitialMarkGC:
1213 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) {
1214 _initial_mark_to_mixed.record_initial_mark_end(end);
1215 }
1216 break;
1217 case MixedGC:
1218 _initial_mark_to_mixed.record_mixed_gc_start(start);
1219 break;
1220 default:
1221 ShouldNotReachHere();
1222 }
1223 }
1224
1225 void G1Policy::abort_time_to_mixed_tracking() {
1226 _initial_mark_to_mixed.reset();
1227 }
1228
1229 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str,
1230 const char* false_action_str) const {
1231 G1CollectionSetCandidates* candidates = _collection_set->candidates();
1232
1233 if (candidates->is_empty()) {
1234 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1235 return false;
1236 }
1237
1238 // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1239 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes();
1240 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1241 double threshold = (double) G1HeapWastePercent;
1242 if (reclaimable_percent <= threshold) {
1243 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1244 false_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1245 return false;
1246 }
1247 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1248 true_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1249 return true;
1250 }
1251
1252 uint G1Policy::calc_min_old_cset_length() const {
1253 // The min old CSet region bound is based on the maximum desired
1254 // number of mixed GCs after a cycle. I.e., even if some old regions
1255 // look expensive, we should add them to the CSet anyway to make
1256 // sure we go through the available old regions in no more than the
1257 // maximum desired number of mixed GCs.
1258 //
1259 // The calculation is based on the number of marked regions we added
1260 // to the CSet candidates in the first place, not how many remain, so
1261 // that the result is the same during all mixed GCs that follow a cycle.
1262
1263 const size_t region_num = _collection_set->candidates()->num_regions();
1264 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1265 size_t result = region_num / gc_num;
1266 // emulate ceiling
1267 if (result * gc_num < region_num) {
1268 result += 1;
1269 }
1270 return (uint) result;
1271 }
1272
1273 uint G1Policy::calc_max_old_cset_length() const {
1274 // The max old CSet region bound is based on the threshold expressed
1275 // as a percentage of the heap size. I.e., it should bound the
1276 // number of old regions added to the CSet irrespective of how many
1277 // of them are available.
1278
1279 const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1280 const size_t region_num = g1h->num_regions();
1281 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1282 size_t result = region_num * perc / 100;
1283 // emulate ceiling
1284 if (100 * result < region_num * perc) {
1285 result += 1;
1286 }
1287 return (uint) result;
1288 }
1289
1290 void G1Policy::calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
1291 double time_remaining_ms,
1292 uint& num_initial_regions,
1293 uint& num_optional_regions) {
1294 assert(candidates != NULL, "Must be");
1295
1296 num_initial_regions = 0;
1297 num_optional_regions = 0;
1298 uint num_expensive_regions = 0;
1299
1300 double predicted_old_time_ms = 0.0;
1301 double predicted_initial_time_ms = 0.0;
1302 double predicted_optional_time_ms = 0.0;
1303
1304 double optional_threshold_ms = time_remaining_ms * optional_prediction_fraction();
1305
1306 const uint min_old_cset_length = calc_min_old_cset_length();
1307 const uint max_old_cset_length = MAX2(min_old_cset_length, calc_max_old_cset_length());
1308 const uint max_optional_regions = max_old_cset_length - min_old_cset_length;
1309 bool check_time_remaining = use_adaptive_young_list_length();
1310
1311 uint candidate_idx = candidates->cur_idx();
1312
1313 log_debug(gc, ergo, cset)("Start adding old regions to collection set. Min %u regions, max %u regions, "
1314 "time remaining %1.2fms, optional threshold %1.2fms",
1315 min_old_cset_length, max_old_cset_length, time_remaining_ms, optional_threshold_ms);
1316
1317 HeapRegion* hr = candidates->at(candidate_idx);
1318 while (hr != NULL) {
1319 if (num_initial_regions + num_optional_regions >= max_old_cset_length) {
1320 // Added maximum number of old regions to the CSet.
1321 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Maximum number of regions). "
1322 "Initial %u regions, optional %u regions",
1323 num_initial_regions, num_optional_regions);
1324 break;
1325 }
1326
1327 // Stop adding regions if the remaining reclaimable space is
1328 // not above G1HeapWastePercent.
1329 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes();
1330 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1331 double threshold = (double) G1HeapWastePercent;
1332 if (reclaimable_percent <= threshold) {
1333 // We've added enough old regions that the amount of uncollected
1334 // reclaimable space is at or below the waste threshold. Stop
1335 // adding old regions to the CSet.
1336 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Reclaimable percentage below threshold). "
1337 "Reclaimable: " SIZE_FORMAT "%s (%1.2f%%) threshold: " UINTX_FORMAT "%%",
1338 byte_size_in_proper_unit(reclaimable_bytes), proper_unit_for_byte_size(reclaimable_bytes),
1339 reclaimable_percent, G1HeapWastePercent);
1340 break;
1341 }
1342
1343 double predicted_time_ms = predict_region_total_time_ms(hr, false);
1344 time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0);
1345 // Add regions to old set until we reach the minimum amount
1346 if (num_initial_regions < min_old_cset_length) {
1347 predicted_old_time_ms += predicted_time_ms;
1348 num_initial_regions++;
1349 // Record the number of regions added with no time remaining
1350 if (time_remaining_ms == 0.0) {
1351 num_expensive_regions++;
1352 }
1353 } else if (!check_time_remaining) {
1354 // In the non-auto-tuning case, we'll finish adding regions
1355 // to the CSet if we reach the minimum.
1356 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Region amount reached min).");
1357 break;
1358 } else {
1359 // Keep adding regions to old set until we reach the optional threshold
1360 if (time_remaining_ms > optional_threshold_ms) {
1361 predicted_old_time_ms += predicted_time_ms;
1362 num_initial_regions++;
1363 } else if (time_remaining_ms > 0) {
1364 // Keep adding optional regions until time is up.
1365 assert(num_optional_regions < max_optional_regions, "Should not be possible.");
1366 predicted_optional_time_ms += predicted_time_ms;
1367 num_optional_regions++;
1368 } else {
1369 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Predicted time too high).");
1370 break;
1371 }
1372 }
1373 hr = candidates->at(++candidate_idx);
1374 }
1375 if (hr == NULL) {
1376 log_debug(gc, ergo, cset)("Old candidate collection set empty.");
1377 }
1378
1379 if (num_expensive_regions > 0) {
1380 log_debug(gc, ergo, cset)("Added %u initial old regions to collection set although the predicted time was too high.",
1381 num_expensive_regions);
1382 }
1383
1384 log_debug(gc, ergo, cset)("Finish choosing collection set old regions. Initial: %u, optional: %u, "
1385 "predicted old time: %1.2fms, predicted optional time: %1.2fms, time remaining: %1.2f",
1386 num_initial_regions, num_optional_regions,
1387 predicted_initial_time_ms, predicted_optional_time_ms, time_remaining_ms);
1388 }
1389
1390 void G1Policy::calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
1391 uint const max_optional_regions,
1392 double time_remaining_ms,
1393 uint& num_optional_regions) {
1394 assert(_g1h->collector_state()->in_mixed_phase(), "Should only be called in mixed phase");
1395
1396 num_optional_regions = 0;
1397 double prediction_ms = 0;
1398 uint candidate_idx = candidates->cur_idx();
1399
1400 HeapRegion* r = candidates->at(candidate_idx);
1401 while (num_optional_regions < max_optional_regions) {
1402 assert(r != NULL, "Region must exist");
1403 prediction_ms += predict_region_total_time_ms(r, false);
1404
1405 if (prediction_ms > time_remaining_ms) {
1406 log_debug(gc, ergo, cset)("Prediction %.3fms for region %u does not fit remaining time: %.3fms.",
1407 prediction_ms, r->hrm_index(), time_remaining_ms);
1408 break;
1409 }
1410 // This region will be included in the next optional evacuation.
1411
1412 time_remaining_ms -= prediction_ms;
1413 num_optional_regions++;
1414 r = candidates->at(++candidate_idx);
1415 }
1416
1417 log_debug(gc, ergo, cset)("Prepared %u regions out of %u for optional evacuation. Predicted time: %.3fms",
1418 num_optional_regions, max_optional_regions, prediction_ms);
1419 }
1420
1421 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) {
1422 HeapRegion* last = NULL;
1423 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin();
1424 it != survivors->regions()->end();
1425 ++it) {
1426 HeapRegion* curr = *it;
1427
1428 // The region is a non-empty survivor so let's add it to
1429 // the incremental collection set for the next evacuation
1430 // pause.
1431 _collection_set->add_survivor_regions(curr);
1432
1433 last = curr;
1434 }
1435
1436 // Don't clear the survivor list handles until the start of
1437 // the next evacuation pause - we need it in order to re-tag
1438 // the survivor regions from this evacuation pause as 'young'
1439 // at the start of the next.
1440 }