1 /*
2 * Copyright (c) 2001, 2017, 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/concurrentG1Refine.hpp"
27 #include "gc/g1/concurrentMarkThread.inline.hpp"
28 #include "gc/g1/g1Analytics.hpp"
29 #include "gc/g1/g1CollectedHeap.inline.hpp"
30 #include "gc/g1/g1CollectionSet.hpp"
31 #include "gc/g1/g1ConcurrentMark.hpp"
32 #include "gc/g1/g1DefaultPolicy.hpp"
33 #include "gc/g1/g1HotCardCache.hpp"
34 #include "gc/g1/g1IHOPControl.hpp"
35 #include "gc/g1/g1GCPhaseTimes.hpp"
36 #include "gc/g1/g1Policy.hpp"
37 #include "gc/g1/g1SurvivorRegions.hpp"
38 #include "gc/g1/g1YoungGenSizer.hpp"
39 #include "gc/g1/heapRegion.inline.hpp"
40 #include "gc/g1/heapRegionRemSet.hpp"
41 #include "gc/shared/gcPolicyCounters.hpp"
42 #include "logging/logStream.hpp"
43 #include "runtime/arguments.hpp"
44 #include "runtime/java.hpp"
45 #include "runtime/mutexLocker.hpp"
46 #include "utilities/debug.hpp"
47 #include "utilities/growableArray.hpp"
48 #include "utilities/pair.hpp"
49
50 G1DefaultPolicy::G1DefaultPolicy(STWGCTimer* gc_timer) :
51 _predictor(G1ConfidencePercent / 100.0),
52 _analytics(new G1Analytics(&_predictor)),
53 _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)),
54 _ihop_control(create_ihop_control(&_predictor)),
55 _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 3)),
56 _young_list_fixed_length(0),
57 _short_lived_surv_rate_group(new SurvRateGroup()),
58 _survivor_surv_rate_group(new SurvRateGroup()),
59 _reserve_factor((double) G1ReservePercent / 100.0),
60 _reserve_regions(0),
61 _rs_lengths_prediction(0),
62 _bytes_allocated_in_old_since_last_gc(0),
63 _initial_mark_to_mixed(),
64 _collection_set(NULL),
65 _g1(NULL),
66 _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)),
67 _tenuring_threshold(MaxTenuringThreshold),
68 _max_survivor_regions(0),
69 _survivors_age_table(true),
70 _collection_pause_end_millis(os::javaTimeNanos() / NANOSECS_PER_MILLISEC) { }
71
72 G1DefaultPolicy::~G1DefaultPolicy() {
73 delete _ihop_control;
74 }
75
76 G1CollectorState* G1DefaultPolicy::collector_state() const { return _g1->collector_state(); }
77
78 void G1DefaultPolicy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
79 _g1 = g1h;
80 _collection_set = collection_set;
81
82 assert(Heap_lock->owned_by_self(), "Locking discipline.");
83
84 if (!adaptive_young_list_length()) {
85 _young_list_fixed_length = _young_gen_sizer.min_desired_young_length();
86 }
87 _young_gen_sizer.adjust_max_new_size(_g1->max_regions());
88
89 _free_regions_at_end_of_collection = _g1->num_free_regions();
90
91 update_young_list_max_and_target_length();
92 // We may immediately start allocating regions and placing them on the
93 // collection set list. Initialize the per-collection set info
94 _collection_set->start_incremental_building();
95 }
96
97 void G1DefaultPolicy::note_gc_start() {
98 phase_times()->note_gc_start();
99 }
100
101 class G1YoungLengthPredictor VALUE_OBJ_CLASS_SPEC {
102 const bool _during_cm;
103 const double _base_time_ms;
104 const double _base_free_regions;
105 const double _target_pause_time_ms;
106 const G1DefaultPolicy* const _policy;
107
108 public:
109 G1YoungLengthPredictor(bool during_cm,
110 double base_time_ms,
111 double base_free_regions,
112 double target_pause_time_ms,
113 const G1DefaultPolicy* policy) :
114 _during_cm(during_cm),
115 _base_time_ms(base_time_ms),
116 _base_free_regions(base_free_regions),
117 _target_pause_time_ms(target_pause_time_ms),
118 _policy(policy) {}
119
120 bool will_fit(uint young_length) const {
121 if (young_length >= _base_free_regions) {
122 // end condition 1: not enough space for the young regions
123 return false;
124 }
125
126 const double accum_surv_rate = _policy->accum_yg_surv_rate_pred((int) young_length - 1);
127 const size_t bytes_to_copy =
128 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
129 const double copy_time_ms =
130 _policy->analytics()->predict_object_copy_time_ms(bytes_to_copy, _during_cm);
131 const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length);
132 const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms;
133 if (pause_time_ms > _target_pause_time_ms) {
134 // end condition 2: prediction is over the target pause time
135 return false;
136 }
137
138 const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes;
139
140 // When copying, we will likely need more bytes free than is live in the region.
141 // Add some safety margin to factor in the confidence of our guess, and the
142 // natural expected waste.
143 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
144 // of the calculation: the lower the confidence, the more headroom.
145 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
146 // copying due to anticipated waste in the PLABs.
147 const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
148 const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
149
150 if (expected_bytes_to_copy > free_bytes) {
151 // end condition 3: out-of-space
152 return false;
153 }
154
155 // success!
156 return true;
157 }
158 };
159
160 void G1DefaultPolicy::record_new_heap_size(uint new_number_of_regions) {
161 // re-calculate the necessary reserve
162 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
163 // We use ceiling so that if reserve_regions_d is > 0.0 (but
164 // smaller than 1.0) we'll get 1.
165 _reserve_regions = (uint) ceil(reserve_regions_d);
166
167 _young_gen_sizer.heap_size_changed(new_number_of_regions);
168
169 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
170 }
171
172 uint G1DefaultPolicy::calculate_young_list_desired_min_length(uint base_min_length) const {
173 uint desired_min_length = 0;
174 if (adaptive_young_list_length()) {
175 if (_analytics->num_alloc_rate_ms() > 3) {
176 double now_sec = os::elapsedTime();
177 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
178 double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
179 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
180 } else {
181 // otherwise we don't have enough info to make the prediction
182 }
183 }
184 desired_min_length += base_min_length;
185 // make sure we don't go below any user-defined minimum bound
186 return MAX2(_young_gen_sizer.min_desired_young_length(), desired_min_length);
187 }
188
189 uint G1DefaultPolicy::calculate_young_list_desired_max_length() const {
190 // Here, we might want to also take into account any additional
191 // constraints (i.e., user-defined minimum bound). Currently, we
192 // effectively don't set this bound.
193 return _young_gen_sizer.max_desired_young_length();
194 }
195
196 uint G1DefaultPolicy::update_young_list_max_and_target_length() {
197 return update_young_list_max_and_target_length(_analytics->predict_rs_lengths());
198 }
199
200 uint G1DefaultPolicy::update_young_list_max_and_target_length(size_t rs_lengths) {
201 uint unbounded_target_length = update_young_list_target_length(rs_lengths);
202 update_max_gc_locker_expansion();
203 return unbounded_target_length;
204 }
205
206 uint G1DefaultPolicy::update_young_list_target_length(size_t rs_lengths) {
207 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
208 _young_list_target_length = young_lengths.first;
209 return young_lengths.second;
210 }
211
212 G1DefaultPolicy::YoungTargetLengths G1DefaultPolicy::young_list_target_lengths(size_t rs_lengths) const {
213 YoungTargetLengths result;
214
215 // Calculate the absolute and desired min bounds first.
216
217 // This is how many young regions we already have (currently: the survivors).
218 const uint base_min_length = _g1->survivor_regions_count();
219 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
220 // This is the absolute minimum young length. Ensure that we
221 // will at least have one eden region available for allocation.
222 uint absolute_min_length = base_min_length + MAX2(_g1->eden_regions_count(), (uint)1);
223 // If we shrank the young list target it should not shrink below the current size.
224 desired_min_length = MAX2(desired_min_length, absolute_min_length);
225 // Calculate the absolute and desired max bounds.
226
227 uint desired_max_length = calculate_young_list_desired_max_length();
228
229 uint young_list_target_length = 0;
230 if (adaptive_young_list_length()) {
231 if (collector_state()->gcs_are_young()) {
232 young_list_target_length =
233 calculate_young_list_target_length(rs_lengths,
234 base_min_length,
235 desired_min_length,
236 desired_max_length);
237 } else {
238 // Don't calculate anything and let the code below bound it to
239 // the desired_min_length, i.e., do the next GC as soon as
240 // possible to maximize how many old regions we can add to it.
241 }
242 } else {
243 // The user asked for a fixed young gen so we'll fix the young gen
244 // whether the next GC is young or mixed.
245 young_list_target_length = _young_list_fixed_length;
246 }
247
248 result.second = young_list_target_length;
249
250 // We will try our best not to "eat" into the reserve.
251 uint absolute_max_length = 0;
252 if (_free_regions_at_end_of_collection > _reserve_regions) {
253 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
254 }
255 if (desired_max_length > absolute_max_length) {
256 desired_max_length = absolute_max_length;
257 }
258
259 // Make sure we don't go over the desired max length, nor under the
260 // desired min length. In case they clash, desired_min_length wins
261 // which is why that test is second.
262 if (young_list_target_length > desired_max_length) {
263 young_list_target_length = desired_max_length;
264 }
265 if (young_list_target_length < desired_min_length) {
266 young_list_target_length = desired_min_length;
267 }
268
269 assert(young_list_target_length > base_min_length,
270 "we should be able to allocate at least one eden region");
271 assert(young_list_target_length >= absolute_min_length, "post-condition");
272
273 result.first = young_list_target_length;
274 return result;
275 }
276
277 uint
278 G1DefaultPolicy::calculate_young_list_target_length(size_t rs_lengths,
279 uint base_min_length,
280 uint desired_min_length,
281 uint desired_max_length) const {
282 assert(adaptive_young_list_length(), "pre-condition");
283 assert(collector_state()->gcs_are_young(), "only call this for young GCs");
284
285 // In case some edge-condition makes the desired max length too small...
286 if (desired_max_length <= desired_min_length) {
287 return desired_min_length;
288 }
289
290 // We'll adjust min_young_length and max_young_length not to include
291 // the already allocated young regions (i.e., so they reflect the
292 // min and max eden regions we'll allocate). The base_min_length
293 // will be reflected in the predictions by the
294 // survivor_regions_evac_time prediction.
295 assert(desired_min_length > base_min_length, "invariant");
296 uint min_young_length = desired_min_length - base_min_length;
297 assert(desired_max_length > base_min_length, "invariant");
298 uint max_young_length = desired_max_length - base_min_length;
299
300 const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
301 const double survivor_regions_evac_time = predict_survivor_regions_evac_time();
302 const size_t pending_cards = _analytics->predict_pending_cards();
303 const size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff();
304 const size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, /* gcs_are_young */ true);
305 const double base_time_ms =
306 predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
307 survivor_regions_evac_time;
308 const uint available_free_regions = _free_regions_at_end_of_collection;
309 const uint base_free_regions =
310 available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0;
311
312 // Here, we will make sure that the shortest young length that
313 // makes sense fits within the target pause time.
314
315 G1YoungLengthPredictor p(collector_state()->during_concurrent_mark(),
316 base_time_ms,
317 base_free_regions,
318 target_pause_time_ms,
319 this);
320 if (p.will_fit(min_young_length)) {
321 // The shortest young length will fit into the target pause time;
322 // we'll now check whether the absolute maximum number of young
323 // regions will fit in the target pause time. If not, we'll do
324 // a binary search between min_young_length and max_young_length.
325 if (p.will_fit(max_young_length)) {
326 // The maximum young length will fit into the target pause time.
327 // We are done so set min young length to the maximum length (as
328 // the result is assumed to be returned in min_young_length).
329 min_young_length = max_young_length;
330 } else {
331 // The maximum possible number of young regions will not fit within
332 // the target pause time so we'll search for the optimal
333 // length. The loop invariants are:
334 //
335 // min_young_length < max_young_length
336 // min_young_length is known to fit into the target pause time
337 // max_young_length is known not to fit into the target pause time
338 //
339 // Going into the loop we know the above hold as we've just
340 // checked them. Every time around the loop we check whether
341 // the middle value between min_young_length and
342 // max_young_length fits into the target pause time. If it
343 // does, it becomes the new min. If it doesn't, it becomes
344 // the new max. This way we maintain the loop invariants.
345
346 assert(min_young_length < max_young_length, "invariant");
347 uint diff = (max_young_length - min_young_length) / 2;
348 while (diff > 0) {
349 uint young_length = min_young_length + diff;
350 if (p.will_fit(young_length)) {
351 min_young_length = young_length;
352 } else {
353 max_young_length = young_length;
354 }
355 assert(min_young_length < max_young_length, "invariant");
356 diff = (max_young_length - min_young_length) / 2;
357 }
358 // The results is min_young_length which, according to the
359 // loop invariants, should fit within the target pause time.
360
361 // These are the post-conditions of the binary search above:
362 assert(min_young_length < max_young_length,
363 "otherwise we should have discovered that max_young_length "
364 "fits into the pause target and not done the binary search");
365 assert(p.will_fit(min_young_length),
366 "min_young_length, the result of the binary search, should "
367 "fit into the pause target");
368 assert(!p.will_fit(min_young_length + 1),
369 "min_young_length, the result of the binary search, should be "
370 "optimal, so no larger length should fit into the pause target");
371 }
372 } else {
373 // Even the minimum length doesn't fit into the pause time
374 // target, return it as the result nevertheless.
375 }
376 return base_min_length + min_young_length;
377 }
378
379 double G1DefaultPolicy::predict_survivor_regions_evac_time() const {
380 double survivor_regions_evac_time = 0.0;
381 const GrowableArray<HeapRegion*>* survivor_regions = _g1->survivor()->regions();
382
383 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin();
384 it != survivor_regions->end();
385 ++it) {
386 survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->gcs_are_young());
387 }
388 return survivor_regions_evac_time;
389 }
390
391 void G1DefaultPolicy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
392 guarantee( adaptive_young_list_length(), "should not call this otherwise" );
393
394 if (rs_lengths > _rs_lengths_prediction) {
395 // add 10% to avoid having to recalculate often
396 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
397 update_rs_lengths_prediction(rs_lengths_prediction);
398
399 update_young_list_max_and_target_length(rs_lengths_prediction);
400 }
401 }
402
403 void G1DefaultPolicy::update_rs_lengths_prediction() {
404 update_rs_lengths_prediction(_analytics->predict_rs_lengths());
405 }
406
407 void G1DefaultPolicy::update_rs_lengths_prediction(size_t prediction) {
408 if (collector_state()->gcs_are_young() && adaptive_young_list_length()) {
409 _rs_lengths_prediction = prediction;
410 }
411 }
412
413 void G1DefaultPolicy::record_full_collection_start() {
414 _full_collection_start_sec = os::elapsedTime();
415 // Release the future to-space so that it is available for compaction into.
416 collector_state()->set_full_collection(true);
417 }
418
419 void G1DefaultPolicy::record_full_collection_end() {
420 // Consider this like a collection pause for the purposes of allocation
421 // since last pause.
422 double end_sec = os::elapsedTime();
423 double full_gc_time_sec = end_sec - _full_collection_start_sec;
424 double full_gc_time_ms = full_gc_time_sec * 1000.0;
425
426 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);
427
428 collector_state()->set_full_collection(false);
429
430 // "Nuke" the heuristics that control the young/mixed GC
431 // transitions and make sure we start with young GCs after the Full GC.
432 collector_state()->set_gcs_are_young(true);
433 collector_state()->set_last_young_gc(false);
434 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
435 collector_state()->set_during_initial_mark_pause(false);
436 collector_state()->set_in_marking_window(false);
437 collector_state()->set_in_marking_window_im(false);
438
439 _short_lived_surv_rate_group->start_adding_regions();
440 // also call this on any additional surv rate groups
441
442 _free_regions_at_end_of_collection = _g1->num_free_regions();
443 // Reset survivors SurvRateGroup.
444 _survivor_surv_rate_group->reset();
445 update_young_list_max_and_target_length();
446 update_rs_lengths_prediction();
447 cset_chooser()->clear();
448
449 _bytes_allocated_in_old_since_last_gc = 0;
450
451 record_pause(FullGC, _full_collection_start_sec, end_sec);
452 }
453
454 void G1DefaultPolicy::record_collection_pause_start(double start_time_sec) {
455 // We only need to do this here as the policy will only be applied
456 // to the GC we're about to start. so, no point is calculating this
457 // every time we calculate / recalculate the target young length.
458 update_survivors_policy();
459
460 assert(_g1->used() == _g1->recalculate_used(),
461 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
462 _g1->used(), _g1->recalculate_used());
463
464 phase_times()->record_cur_collection_start_sec(start_time_sec);
465 _pending_cards = _g1->pending_card_num();
466
467 _collection_set->reset_bytes_used_before();
468 _bytes_copied_during_gc = 0;
469
470 collector_state()->set_last_gc_was_young(false);
471
472 // do that for any other surv rate groups
473 _short_lived_surv_rate_group->stop_adding_regions();
474 _survivors_age_table.clear();
475
476 assert(_g1->collection_set()->verify_young_ages(), "region age verification failed");
477 }
478
479 void G1DefaultPolicy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {
480 collector_state()->set_during_marking(true);
481 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
482 collector_state()->set_during_initial_mark_pause(false);
483 }
484
485 void G1DefaultPolicy::record_concurrent_mark_remark_start() {
486 _mark_remark_start_sec = os::elapsedTime();
487 collector_state()->set_during_marking(false);
488 }
489
490 void G1DefaultPolicy::record_concurrent_mark_remark_end() {
491 double end_time_sec = os::elapsedTime();
492 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
493 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);
494 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
495
496 record_pause(Remark, _mark_remark_start_sec, end_time_sec);
497 }
498
499 void G1DefaultPolicy::record_concurrent_mark_cleanup_start() {
500 _mark_cleanup_start_sec = os::elapsedTime();
501 }
502
503 void G1DefaultPolicy::record_concurrent_mark_cleanup_completed() {
504 bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",
505 "skip last young-only gc");
506 collector_state()->set_last_young_gc(should_continue_with_reclaim);
507 // We skip the marking phase.
508 if (!should_continue_with_reclaim) {
509 abort_time_to_mixed_tracking();
510 }
511 collector_state()->set_in_marking_window(false);
512 }
513
514 double G1DefaultPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
515 return phase_times()->average_time_ms(phase);
516 }
517
518 double G1DefaultPolicy::young_other_time_ms() const {
519 return phase_times()->young_cset_choice_time_ms() +
520 phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet);
521 }
522
523 double G1DefaultPolicy::non_young_other_time_ms() const {
524 return phase_times()->non_young_cset_choice_time_ms() +
525 phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet);
526 }
527
528 double G1DefaultPolicy::other_time_ms(double pause_time_ms) const {
529 return pause_time_ms - phase_times()->cur_collection_par_time_ms();
530 }
531
532 double G1DefaultPolicy::constant_other_time_ms(double pause_time_ms) const {
533 return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms();
534 }
535
536 CollectionSetChooser* G1DefaultPolicy::cset_chooser() const {
537 return _collection_set->cset_chooser();
538 }
539
540 bool G1DefaultPolicy::about_to_start_mixed_phase() const {
541 return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc();
542 }
543
544 bool G1DefaultPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
545 if (about_to_start_mixed_phase()) {
546 return false;
547 }
548
549 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
550
551 size_t cur_used_bytes = _g1->non_young_capacity_bytes();
552 size_t alloc_byte_size = alloc_word_size * HeapWordSize;
553 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
554
555 bool result = false;
556 if (marking_request_bytes > marking_initiating_used_threshold) {
557 result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc();
558 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
559 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
560 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source);
561 }
562
563 return result;
564 }
565
566 // Anything below that is considered to be zero
567 #define MIN_TIMER_GRANULARITY 0.0000001
568
569 void G1DefaultPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
570 double end_time_sec = os::elapsedTime();
571
572 size_t cur_used_bytes = _g1->used();
573 assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
574 bool last_pause_included_initial_mark = false;
575 bool update_stats = !_g1->evacuation_failed();
576
577 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
578
579 _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
580
581 last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();
582 if (last_pause_included_initial_mark) {
583 record_concurrent_mark_init_end(0.0);
584 } else {
585 maybe_start_marking();
586 }
587
588 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
589 if (app_time_ms < MIN_TIMER_GRANULARITY) {
590 // This usually happens due to the timer not having the required
591 // granularity. Some Linuxes are the usual culprits.
592 // We'll just set it to something (arbitrarily) small.
593 app_time_ms = 1.0;
594 }
595
596 if (update_stats) {
597 // We maintain the invariant that all objects allocated by mutator
598 // threads will be allocated out of eden regions. So, we can use
599 // the eden region number allocated since the previous GC to
600 // calculate the application's allocate rate. The only exception
601 // to that is humongous objects that are allocated separately. But
602 // given that humongous object allocations do not really affect
603 // either the pause's duration nor when the next pause will take
604 // place we can safely ignore them here.
605 uint regions_allocated = _collection_set->eden_region_length();
606 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
607 _analytics->report_alloc_rate_ms(alloc_rate_ms);
608
609 double interval_ms =
610 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;
611 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
612 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);
613 }
614
615 bool new_in_marking_window = collector_state()->in_marking_window();
616 bool new_in_marking_window_im = false;
617 if (last_pause_included_initial_mark) {
618 new_in_marking_window = true;
619 new_in_marking_window_im = true;
620 }
621
622 if (collector_state()->last_young_gc()) {
623 // This is supposed to to be the "last young GC" before we start
624 // doing mixed GCs. Here we decide whether to start mixed GCs or not.
625 assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC");
626
627 if (next_gc_should_be_mixed("start mixed GCs",
628 "do not start mixed GCs")) {
629 collector_state()->set_gcs_are_young(false);
630 } else {
631 // We aborted the mixed GC phase early.
632 abort_time_to_mixed_tracking();
633 }
634
635 collector_state()->set_last_young_gc(false);
636 }
637
638 if (!collector_state()->last_gc_was_young()) {
639 // This is a mixed GC. Here we decide whether to continue doing
640 // mixed GCs or not.
641 if (!next_gc_should_be_mixed("continue mixed GCs",
642 "do not continue mixed GCs")) {
643 collector_state()->set_gcs_are_young(true);
644
645 maybe_start_marking();
646 }
647 }
648
649 _short_lived_surv_rate_group->start_adding_regions();
650 // Do that for any other surv rate groups
651
652 double scan_hcc_time_ms = G1HotCardCache::default_use_cache() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
653
654 if (update_stats) {
655 double cost_per_card_ms = 0.0;
656 if (_pending_cards > 0) {
657 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards;
658 _analytics->report_cost_per_card_ms(cost_per_card_ms);
659 }
660 _analytics->report_cost_scan_hcc(scan_hcc_time_ms);
661
662 double cost_per_entry_ms = 0.0;
663 if (cards_scanned > 10) {
664 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
665 _analytics->report_cost_per_entry_ms(cost_per_entry_ms, collector_state()->last_gc_was_young());
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, collector_state()->last_gc_was_young());
672 }
673
674 // This is defensive. For a while _max_rs_lengths could get
675 // smaller than _recorded_rs_lengths which was causing
676 // rs_length_diff to get very large and mess up the RSet length
677 // predictions. The reason was unsafe concurrent updates to the
678 // _inc_cset_recorded_rs_lengths field which the code below guards
679 // against (see CR 7118202). This bug has now been fixed (see CR
680 // 7119027). However, I'm still worried that
681 // _inc_cset_recorded_rs_lengths might still end up somewhat
682 // inaccurate. The concurrent refinement thread calculates an
683 // RSet's length concurrently with other CR threads updating it
684 // which might cause it to calculate the length incorrectly (if,
685 // say, it's in mid-coarsening). So I'll leave in the defensive
686 // conditional below just in case.
687 size_t rs_length_diff = 0;
688 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();
689 if (_max_rs_lengths > recorded_rs_lengths) {
690 rs_length_diff = _max_rs_lengths - recorded_rs_lengths;
691 }
692 _analytics->report_rs_length_diff((double) rs_length_diff);
693
694 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
695 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
696 double cost_per_byte_ms = 0.0;
697
698 if (copied_bytes > 0) {
699 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
700 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->in_marking_window());
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 _analytics->report_pending_cards((double) _pending_cards);
716 _analytics->report_rs_lengths((double) _max_rs_lengths);
717 }
718
719 collector_state()->set_in_marking_window(new_in_marking_window);
720 collector_state()->set_in_marking_window_im(new_in_marking_window_im);
721 _free_regions_at_end_of_collection = _g1->num_free_regions();
722 // IHOP control wants to know the expected young gen length if it were not
723 // restrained by the heap reserve. Using the actual length would make the
724 // prediction too small and the limit the young gen every time we get to the
725 // predicted target occupancy.
726 size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
727 update_rs_lengths_prediction();
728
729 update_ihop_prediction(app_time_ms / 1000.0,
730 _bytes_allocated_in_old_since_last_gc,
731 last_unrestrained_young_length * HeapRegion::GrainBytes);
732 _bytes_allocated_in_old_since_last_gc = 0;
733
734 _ihop_control->send_trace_event(_g1->gc_tracer_stw());
735
736 // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
737 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
738
739 if (update_rs_time_goal_ms < scan_hcc_time_ms) {
740 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
741 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",
742 update_rs_time_goal_ms, scan_hcc_time_ms);
743
744 update_rs_time_goal_ms = 0;
745 } else {
746 update_rs_time_goal_ms -= scan_hcc_time_ms;
747 }
748 _g1->concurrent_g1_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms,
749 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
750 update_rs_time_goal_ms);
751
752 cset_chooser()->verify();
753 }
754
755 G1IHOPControl* G1DefaultPolicy::create_ihop_control(const G1Predictions* predictor){
756 if (G1UseAdaptiveIHOP) {
757 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
758 predictor,
759 G1ReservePercent,
760 G1HeapWastePercent);
761 } else {
762 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
763 }
764 }
765
766 void G1DefaultPolicy::update_ihop_prediction(double mutator_time_s,
767 size_t mutator_alloc_bytes,
768 size_t young_gen_size) {
769 // Always try to update IHOP prediction. Even evacuation failures give information
770 // about e.g. whether to start IHOP earlier next time.
771
772 // Avoid using really small application times that might create samples with
773 // very high or very low values. They may be caused by e.g. back-to-back gcs.
774 double const min_valid_time = 1e-6;
775
776 bool report = false;
777
778 double marking_to_mixed_time = -1.0;
779 if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) {
780 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
781 assert(marking_to_mixed_time > 0.0,
782 "Initial mark to mixed time must be larger than zero but is %.3f",
783 marking_to_mixed_time);
784 if (marking_to_mixed_time > min_valid_time) {
785 _ihop_control->update_marking_length(marking_to_mixed_time);
786 report = true;
787 }
788 }
789
790 // As an approximation for the young gc promotion rates during marking we use
791 // all of them. In many applications there are only a few if any young gcs during
792 // marking, which makes any prediction useless. This increases the accuracy of the
793 // prediction.
794 if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) {
795 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
796 report = true;
797 }
798
799 if (report) {
800 report_ihop_statistics();
801 }
802 }
803
804 void G1DefaultPolicy::report_ihop_statistics() {
805 _ihop_control->print();
806 }
807
808 void G1DefaultPolicy::print_phases() {
809 phase_times()->print();
810 }
811
812 double G1DefaultPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
813 TruncatedSeq* seq = surv_rate_group->get_seq(age);
814 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
815 double pred = _predictor.get_new_prediction(seq);
816 if (pred > 1.0) {
817 pred = 1.0;
818 }
819 return pred;
820 }
821
822 double G1DefaultPolicy::accum_yg_surv_rate_pred(int age) const {
823 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
824 }
825
826 double G1DefaultPolicy::predict_base_elapsed_time_ms(size_t pending_cards,
827 size_t scanned_cards) const {
828 return
829 _analytics->predict_rs_update_time_ms(pending_cards) +
830 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->gcs_are_young()) +
831 _analytics->predict_constant_other_time_ms();
832 }
833
834 double G1DefaultPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const {
835 size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff();
836 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->gcs_are_young());
837 return predict_base_elapsed_time_ms(pending_cards, card_num);
838 }
839
840 size_t G1DefaultPolicy::predict_bytes_to_copy(HeapRegion* hr) const {
841 size_t bytes_to_copy;
842 if (hr->is_marked())
843 bytes_to_copy = hr->max_live_bytes();
844 else {
845 assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
846 int age = hr->age_in_surv_rate_group();
847 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
848 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
849 }
850 return bytes_to_copy;
851 }
852
853 double G1DefaultPolicy::predict_region_elapsed_time_ms(HeapRegion* hr,
854 bool for_young_gc) const {
855 size_t rs_length = hr->rem_set()->occupied();
856 // Predicting the number of cards is based on which type of GC
857 // we're predicting for.
858 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc);
859 size_t bytes_to_copy = predict_bytes_to_copy(hr);
860
861 double region_elapsed_time_ms =
862 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->gcs_are_young()) +
863 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->during_concurrent_mark());
864
865 // The prediction of the "other" time for this region is based
866 // upon the region type and NOT the GC type.
867 if (hr->is_young()) {
868 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
869 } else {
870 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
871 }
872 return region_elapsed_time_ms;
873 }
874
875 bool G1DefaultPolicy::should_allocate_mutator_region() const {
876 uint young_list_length = _g1->young_regions_count();
877 uint young_list_target_length = _young_list_target_length;
878 return young_list_length < young_list_target_length;
879 }
880
881 bool G1DefaultPolicy::can_expand_young_list() const {
882 uint young_list_length = _g1->young_regions_count();
883 uint young_list_max_length = _young_list_max_length;
884 return young_list_length < young_list_max_length;
885 }
886
887 bool G1DefaultPolicy::adaptive_young_list_length() const {
888 return _young_gen_sizer.adaptive_young_list_length();
889 }
890
891 size_t G1DefaultPolicy::desired_survivor_size() const {
892 size_t const survivor_capacity = HeapRegion::GrainWords * _max_survivor_regions;
893 return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
894 }
895
896 void G1DefaultPolicy::print_age_table() {
897 _survivors_age_table.print_age_table(_tenuring_threshold);
898 }
899
900 void G1DefaultPolicy::update_max_gc_locker_expansion() {
901 uint expansion_region_num = 0;
902 if (GCLockerEdenExpansionPercent > 0) {
903 double perc = (double) GCLockerEdenExpansionPercent / 100.0;
904 double expansion_region_num_d = perc * (double) _young_list_target_length;
905 // We use ceiling so that if expansion_region_num_d is > 0.0 (but
906 // less than 1.0) we'll get 1.
907 expansion_region_num = (uint) ceil(expansion_region_num_d);
908 } else {
909 assert(expansion_region_num == 0, "sanity");
910 }
911 _young_list_max_length = _young_list_target_length + expansion_region_num;
912 assert(_young_list_target_length <= _young_list_max_length, "post-condition");
913 }
914
915 // Calculates survivor space parameters.
916 void G1DefaultPolicy::update_survivors_policy() {
917 double max_survivor_regions_d =
918 (double) _young_list_target_length / (double) SurvivorRatio;
919 // We use ceiling so that if max_survivor_regions_d is > 0.0 (but
920 // smaller than 1.0) we'll get 1.
921 _max_survivor_regions = (uint) ceil(max_survivor_regions_d);
922
923 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(desired_survivor_size());
924 if (UsePerfData) {
925 _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold);
926 _policy_counters->desired_survivor_size()->set_value(desired_survivor_size() * oopSize);
927 }
928 }
929
930 bool G1DefaultPolicy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
931 // We actually check whether we are marking here and not if we are in a
932 // reclamation phase. This means that we will schedule a concurrent mark
933 // even while we are still in the process of reclaiming memory.
934 bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
935 if (!during_cycle) {
936 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
937 collector_state()->set_initiate_conc_mark_if_possible(true);
938 return true;
939 } else {
940 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
941 return false;
942 }
943 }
944
945 void G1DefaultPolicy::initiate_conc_mark() {
946 collector_state()->set_during_initial_mark_pause(true);
947 collector_state()->set_initiate_conc_mark_if_possible(false);
948 }
949
950 void G1DefaultPolicy::decide_on_conc_mark_initiation() {
951 // We are about to decide on whether this pause will be an
952 // initial-mark pause.
953
954 // First, collector_state()->during_initial_mark_pause() should not be already set. We
955 // will set it here if we have to. However, it should be cleared by
956 // the end of the pause (it's only set for the duration of an
957 // initial-mark pause).
958 assert(!collector_state()->during_initial_mark_pause(), "pre-condition");
959
960 if (collector_state()->initiate_conc_mark_if_possible()) {
961 // We had noticed on a previous pause that the heap occupancy has
962 // gone over the initiating threshold and we should start a
963 // concurrent marking cycle. So we might initiate one.
964
965 if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) {
966 // Initiate a new initial mark if there is no marking or reclamation going on.
967 initiate_conc_mark();
968 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
969 } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) {
970 // Initiate a user requested initial mark. An initial mark must be young only
971 // GC, so the collector state must be updated to reflect this.
972 collector_state()->set_gcs_are_young(true);
973 collector_state()->set_last_young_gc(false);
974
975 abort_time_to_mixed_tracking();
976 initiate_conc_mark();
977 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
978 } else {
979 // The concurrent marking thread is still finishing up the
980 // previous cycle. If we start one right now the two cycles
981 // overlap. In particular, the concurrent marking thread might
982 // be in the process of clearing the next marking bitmap (which
983 // we will use for the next cycle if we start one). Starting a
984 // cycle now will be bad given that parts of the marking
985 // information might get cleared by the marking thread. And we
986 // cannot wait for the marking thread to finish the cycle as it
987 // periodically yields while clearing the next marking bitmap
988 // and, if it's in a yield point, it's waiting for us to
989 // finish. So, at this point we will not start a cycle and we'll
990 // let the concurrent marking thread complete the last one.
991 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
992 }
993 }
994 }
995
996 void G1DefaultPolicy::record_concurrent_mark_cleanup_end() {
997 cset_chooser()->rebuild(_g1->workers(), _g1->num_regions());
998
999 double end_sec = os::elapsedTime();
1000 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1001 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
1002 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
1003
1004 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1005 }
1006
1007 double G1DefaultPolicy::reclaimable_bytes_perc(size_t reclaimable_bytes) const {
1008 // Returns the given amount of reclaimable bytes (that represents
1009 // the amount of reclaimable space still to be collected) as a
1010 // percentage of the current heap capacity.
1011 size_t capacity_bytes = _g1->capacity();
1012 return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
1013 }
1014
1015 void G1DefaultPolicy::maybe_start_marking() {
1016 if (need_to_start_conc_mark("end of GC")) {
1017 // Note: this might have already been set, if during the last
1018 // pause we decided to start a cycle but at the beginning of
1019 // this pause we decided to postpone it. That's OK.
1020 collector_state()->set_initiate_conc_mark_if_possible(true);
1021 }
1022 }
1023
1024 G1DefaultPolicy::PauseKind G1DefaultPolicy::young_gc_pause_kind() const {
1025 assert(!collector_state()->full_collection(), "must be");
1026 if (collector_state()->during_initial_mark_pause()) {
1027 assert(collector_state()->last_gc_was_young(), "must be");
1028 assert(!collector_state()->last_young_gc(), "must be");
1029 return InitialMarkGC;
1030 } else if (collector_state()->last_young_gc()) {
1031 assert(!collector_state()->during_initial_mark_pause(), "must be");
1032 assert(collector_state()->last_gc_was_young(), "must be");
1033 return LastYoungGC;
1034 } else if (!collector_state()->last_gc_was_young()) {
1035 assert(!collector_state()->during_initial_mark_pause(), "must be");
1036 assert(!collector_state()->last_young_gc(), "must be");
1037 return MixedGC;
1038 } else {
1039 assert(collector_state()->last_gc_was_young(), "must be");
1040 assert(!collector_state()->during_initial_mark_pause(), "must be");
1041 assert(!collector_state()->last_young_gc(), "must be");
1042 return YoungOnlyGC;
1043 }
1044 }
1045
1046 void G1DefaultPolicy::record_pause(PauseKind kind, double start, double end) {
1047 // Manage the MMU tracker. For some reason it ignores Full GCs.
1048 if (kind != FullGC) {
1049 _mmu_tracker->add_pause(start, end);
1050 }
1051 // Manage the mutator time tracking from initial mark to first mixed gc.
1052 switch (kind) {
1053 case FullGC:
1054 abort_time_to_mixed_tracking();
1055 break;
1056 case Cleanup:
1057 case Remark:
1058 case YoungOnlyGC:
1059 case LastYoungGC:
1060 _initial_mark_to_mixed.add_pause(end - start);
1061 break;
1062 case InitialMarkGC:
1063 _initial_mark_to_mixed.record_initial_mark_end(end);
1064 break;
1065 case MixedGC:
1066 _initial_mark_to_mixed.record_mixed_gc_start(start);
1067 break;
1068 default:
1069 ShouldNotReachHere();
1070 }
1071 }
1072
1073 void G1DefaultPolicy::abort_time_to_mixed_tracking() {
1074 _initial_mark_to_mixed.reset();
1075 }
1076
1077 bool G1DefaultPolicy::next_gc_should_be_mixed(const char* true_action_str,
1078 const char* false_action_str) const {
1079 if (cset_chooser()->is_empty()) {
1080 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1081 return false;
1082 }
1083
1084 // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1085 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
1086 double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
1087 double threshold = (double) G1HeapWastePercent;
1088 if (reclaimable_perc <= threshold) {
1089 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1090 false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
1091 return false;
1092 }
1093 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1094 true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
1095 return true;
1096 }
1097
1098 uint G1DefaultPolicy::calc_min_old_cset_length() const {
1099 // The min old CSet region bound is based on the maximum desired
1100 // number of mixed GCs after a cycle. I.e., even if some old regions
1101 // look expensive, we should add them to the CSet anyway to make
1102 // sure we go through the available old regions in no more than the
1103 // maximum desired number of mixed GCs.
1104 //
1105 // The calculation is based on the number of marked regions we added
1106 // to the CSet chooser in the first place, not how many remain, so
1107 // that the result is the same during all mixed GCs that follow a cycle.
1108
1109 const size_t region_num = (size_t) cset_chooser()->length();
1110 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1111 size_t result = region_num / gc_num;
1112 // emulate ceiling
1113 if (result * gc_num < region_num) {
1114 result += 1;
1115 }
1116 return (uint) result;
1117 }
1118
1119 uint G1DefaultPolicy::calc_max_old_cset_length() const {
1120 // The max old CSet region bound is based on the threshold expressed
1121 // as a percentage of the heap size. I.e., it should bound the
1122 // number of old regions added to the CSet irrespective of how many
1123 // of them are available.
1124
1125 const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1126 const size_t region_num = g1h->num_regions();
1127 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1128 size_t result = region_num * perc / 100;
1129 // emulate ceiling
1130 if (100 * result < region_num * perc) {
1131 result += 1;
1132 }
1133 return (uint) result;
1134 }
1135
1136 void G1DefaultPolicy::finalize_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {
1137 double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms, survivor);
1138 _collection_set->finalize_old_part(time_remaining_ms);
1139 }
1140
1141 void G1DefaultPolicy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) {
1142
1143 // Add survivor regions to SurvRateGroup.
1144 note_start_adding_survivor_regions();
1145 finished_recalculating_age_indexes(true /* is_survivors */);
1146
1147 HeapRegion* last = NULL;
1148 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin();
1149 it != survivors->regions()->end();
1150 ++it) {
1151 HeapRegion* curr = *it;
1152 set_region_survivor(curr);
1153
1154 // The region is a non-empty survivor so let's add it to
1155 // the incremental collection set for the next evacuation
1156 // pause.
1157 _collection_set->add_survivor_regions(curr);
1158
1159 last = curr;
1160 }
1161 note_stop_adding_survivor_regions();
1162
1163 // Don't clear the survivor list handles until the start of
1164 // the next evacuation pause - we need it in order to re-tag
1165 // the survivor regions from this evacuation pause as 'young'
1166 // at the start of the next.
1167
1168 finished_recalculating_age_indexes(false /* is_survivors */);
1169 }