1 /*
2 * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc/g1/g1Analytics.hpp"
27 #include "gc/g1/g1CollectedHeap.inline.hpp"
28 #include "gc/g1/g1CollectionSet.hpp"
29 #include "gc/g1/g1ConcurrentMark.hpp"
30 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
31 #include "gc/g1/g1ConcurrentRefine.hpp"
32 #include "gc/g1/g1HotCardCache.hpp"
33 #include "gc/g1/g1IHOPControl.hpp"
34 #include "gc/g1/g1GCPhaseTimes.hpp"
35 #include "gc/g1/g1Policy.hpp"
36 #include "gc/g1/g1SurvivorRegions.hpp"
37 #include "gc/g1/g1YoungGenSizer.hpp"
38 #include "gc/g1/heapRegion.inline.hpp"
39 #include "gc/g1/heapRegionRemSet.hpp"
40 #include "gc/shared/gcPolicyCounters.hpp"
41 #include "logging/logStream.hpp"
42 #include "runtime/arguments.hpp"
43 #include "runtime/java.hpp"
44 #include "runtime/mutexLocker.hpp"
45 #include "utilities/debug.hpp"
46 #include "utilities/growableArray.hpp"
47 #include "utilities/pair.hpp"
48
49 G1Policy::G1Policy(STWGCTimer* gc_timer) :
50 _predictor(G1ConfidencePercent / 100.0),
51 _analytics(new G1Analytics(&_predictor)),
52 _remset_tracker(),
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, 2)),
56 _full_collection_start_sec(0.0),
57 _collection_pause_end_millis(os::javaTimeNanos() / NANOSECS_PER_MILLISEC),
58 _young_list_target_length(0),
59 _young_list_fixed_length(0),
60 _young_list_max_length(0),
61 _short_lived_surv_rate_group(new SurvRateGroup()),
62 _survivor_surv_rate_group(new SurvRateGroup()),
63 _reserve_factor((double) G1ReservePercent / 100.0),
64 _reserve_regions(0),
65 _young_gen_sizer(),
66 _free_regions_at_end_of_collection(0),
67 _max_rs_lengths(0),
68 _rs_lengths_prediction(0),
69 _pending_cards(0),
70 _bytes_allocated_in_old_since_last_gc(0),
71 _initial_mark_to_mixed(),
72 _collection_set(NULL),
73 _bytes_copied_during_gc(0),
74 _g1h(NULL),
75 _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)),
76 _mark_remark_start_sec(0),
77 _mark_cleanup_start_sec(0),
78 _tenuring_threshold(MaxTenuringThreshold),
79 _max_survivor_regions(0),
80 _survivors_age_table(true)
81 {
82 }
83
84 G1Policy::~G1Policy() {
85 delete _ihop_control;
86 }
87
88 G1CollectorState* G1Policy::collector_state() const { return _g1h->collector_state(); }
89
90 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
91 _g1h = g1h;
92 _collection_set = collection_set;
93
94 assert(Heap_lock->owned_by_self(), "Locking discipline.");
95
96 if (!adaptive_young_list_length()) {
97 _young_list_fixed_length = _young_gen_sizer.min_desired_young_length();
98 }
99 _young_gen_sizer.adjust_max_new_size(_g1h->max_expandable_regions());
100
101 _free_regions_at_end_of_collection = _g1h->num_free_regions();
102
103 update_young_list_max_and_target_length();
104 // We may immediately start allocating regions and placing them on the
105 // collection set list. Initialize the per-collection set info
106 _collection_set->start_incremental_building();
107 }
108
109 void G1Policy::note_gc_start() {
110 phase_times()->note_gc_start();
111 }
112
113 class G1YoungLengthPredictor {
114 const bool _during_cm;
115 const double _base_time_ms;
116 const double _base_free_regions;
117 const double _target_pause_time_ms;
118 const G1Policy* const _policy;
119
120 public:
121 G1YoungLengthPredictor(bool during_cm,
122 double base_time_ms,
123 double base_free_regions,
124 double target_pause_time_ms,
125 const G1Policy* policy) :
126 _during_cm(during_cm),
127 _base_time_ms(base_time_ms),
128 _base_free_regions(base_free_regions),
129 _target_pause_time_ms(target_pause_time_ms),
130 _policy(policy) {}
131
132 bool will_fit(uint young_length) const {
133 if (young_length >= _base_free_regions) {
134 // end condition 1: not enough space for the young regions
135 return false;
136 }
137
138 const double accum_surv_rate = _policy->accum_yg_surv_rate_pred((int) young_length - 1);
139 const size_t bytes_to_copy =
140 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
141 const double copy_time_ms =
142 _policy->analytics()->predict_object_copy_time_ms(bytes_to_copy, _during_cm);
143 const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length);
144 const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms;
145 if (pause_time_ms > _target_pause_time_ms) {
146 // end condition 2: prediction is over the target pause time
147 return false;
148 }
149
150 const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes;
151
152 // When copying, we will likely need more bytes free than is live in the region.
153 // Add some safety margin to factor in the confidence of our guess, and the
154 // natural expected waste.
155 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
156 // of the calculation: the lower the confidence, the more headroom.
157 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
158 // copying due to anticipated waste in the PLABs.
159 const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
160 const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
161
162 if (expected_bytes_to_copy > free_bytes) {
163 // end condition 3: out-of-space
164 return false;
165 }
166
167 // success!
168 return true;
169 }
170 };
171
172 void G1Policy::record_new_heap_size(uint new_number_of_regions) {
173 // re-calculate the necessary reserve
174 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
175 // We use ceiling so that if reserve_regions_d is > 0.0 (but
176 // smaller than 1.0) we'll get 1.
177 _reserve_regions = (uint) ceil(reserve_regions_d);
178
179 _young_gen_sizer.heap_size_changed(new_number_of_regions);
180
181 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
182 }
183
184 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const {
185 uint desired_min_length = 0;
186 if (adaptive_young_list_length()) {
187 if (_analytics->num_alloc_rate_ms() > 3) {
188 double now_sec = os::elapsedTime();
189 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
190 double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
191 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
192 } else {
193 // otherwise we don't have enough info to make the prediction
194 }
195 }
196 desired_min_length += base_min_length;
197 // make sure we don't go below any user-defined minimum bound
198 return MAX2(_young_gen_sizer.min_desired_young_length(), desired_min_length);
199 }
200
201 uint G1Policy::calculate_young_list_desired_max_length() const {
202 // Here, we might want to also take into account any additional
203 // constraints (i.e., user-defined minimum bound). Currently, we
204 // effectively don't set this bound.
205 return _young_gen_sizer.max_desired_young_length();
206 }
207
208 uint G1Policy::update_young_list_max_and_target_length() {
209 return update_young_list_max_and_target_length(_analytics->predict_rs_lengths());
210 }
211
212 uint G1Policy::update_young_list_max_and_target_length(size_t rs_lengths) {
213 uint unbounded_target_length = update_young_list_target_length(rs_lengths);
214 update_max_gc_locker_expansion();
215 return unbounded_target_length;
216 }
217
218 uint G1Policy::update_young_list_target_length(size_t rs_lengths) {
219 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
220 _young_list_target_length = young_lengths.first;
221
222 // Resize dram regions set if called after full collection end.
223 if(_g1h->is_hetero_heap() && (Thread::current()->is_VM_thread() || Heap_lock->owned_by_self())) {
224 static_cast <HeapRegionManagerForHeteroHeap*>(_g1h->hrm())->resize_dram_regions(_young_list_target_length, _g1h->workers());
225 }
226 return young_lengths.second;
227 }
228
229 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_lengths) const {
230 YoungTargetLengths result;
231
232 // Calculate the absolute and desired min bounds first.
233
234 // This is how many young regions we already have (currently: the survivors).
235 const uint base_min_length = _g1h->survivor_regions_count();
236 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
237 // This is the absolute minimum young length. Ensure that we
238 // will at least have one eden region available for allocation.
239 uint absolute_min_length = base_min_length + MAX2(_g1h->eden_regions_count(), (uint)1);
240 // If we shrank the young list target it should not shrink below the current size.
241 desired_min_length = MAX2(desired_min_length, absolute_min_length);
242 // Calculate the absolute and desired max bounds.
243
244 uint desired_max_length = calculate_young_list_desired_max_length();
245
246 uint young_list_target_length = 0;
247 if (adaptive_young_list_length()) {
248 if (collector_state()->in_young_only_phase()) {
249 young_list_target_length =
250 calculate_young_list_target_length(rs_lengths,
251 base_min_length,
252 desired_min_length,
253 desired_max_length);
254 } else {
255 // Don't calculate anything and let the code below bound it to
256 // the desired_min_length, i.e., do the next GC as soon as
257 // possible to maximize how many old regions we can add to it.
258 }
259 } else {
260 // The user asked for a fixed young gen so we'll fix the young gen
261 // whether the next GC is young or mixed.
262 young_list_target_length = _young_list_fixed_length;
263 }
264
265 result.second = young_list_target_length;
266
267 // We will try our best not to "eat" into the reserve.
268 uint absolute_max_length = 0;
269 if (_free_regions_at_end_of_collection > _reserve_regions) {
270 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
271 }
272 if (desired_max_length > absolute_max_length) {
273 desired_max_length = absolute_max_length;
274 }
275
276 // Make sure we don't go over the desired max length, nor under the
277 // desired min length. In case they clash, desired_min_length wins
278 // which is why that test is second.
279 if (young_list_target_length > desired_max_length) {
280 young_list_target_length = desired_max_length;
281 }
282 if (young_list_target_length < desired_min_length) {
283 young_list_target_length = desired_min_length;
284 }
285
286 assert(young_list_target_length > base_min_length,
287 "we should be able to allocate at least one eden region");
288 assert(young_list_target_length >= absolute_min_length, "post-condition");
289
290 result.first = young_list_target_length;
291 return result;
292 }
293
294 uint
295 G1Policy::calculate_young_list_target_length(size_t rs_lengths,
296 uint base_min_length,
297 uint desired_min_length,
298 uint desired_max_length) const {
299 assert(adaptive_young_list_length(), "pre-condition");
300 assert(collector_state()->in_young_only_phase(), "only call this for young GCs");
301
302 // In case some edge-condition makes the desired max length too small...
303 if (desired_max_length <= desired_min_length) {
304 return desired_min_length;
305 }
306
307 // We'll adjust min_young_length and max_young_length not to include
308 // the already allocated young regions (i.e., so they reflect the
309 // min and max eden regions we'll allocate). The base_min_length
310 // will be reflected in the predictions by the
311 // survivor_regions_evac_time prediction.
312 assert(desired_min_length > base_min_length, "invariant");
313 uint min_young_length = desired_min_length - base_min_length;
314 assert(desired_max_length > base_min_length, "invariant");
315 uint max_young_length = desired_max_length - base_min_length;
316
317 const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
318 const double survivor_regions_evac_time = predict_survivor_regions_evac_time();
319 const size_t pending_cards = _analytics->predict_pending_cards();
320 const size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff();
321 const size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, true /* for_young_gc */);
322 const double base_time_ms =
323 predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
324 survivor_regions_evac_time;
325 const uint available_free_regions = _free_regions_at_end_of_collection;
326 const uint base_free_regions =
327 available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0;
328
329 // Here, we will make sure that the shortest young length that
330 // makes sense fits within the target pause time.
331
332 G1YoungLengthPredictor p(collector_state()->mark_or_rebuild_in_progress(),
333 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
400 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin();
401 it != survivor_regions->end();
402 ++it) {
403 survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->in_young_only_phase());
404 }
405 return survivor_regions_evac_time;
406 }
407
408 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
409 guarantee( adaptive_young_list_length(), "should not call this otherwise" );
410
411 if (rs_lengths > _rs_lengths_prediction) {
412 // add 10% to avoid having to recalculate often
413 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
414 update_rs_lengths_prediction(rs_lengths_prediction);
415
416 update_young_list_max_and_target_length(rs_lengths_prediction);
417 }
418 }
419
420 void G1Policy::update_rs_lengths_prediction() {
421 update_rs_lengths_prediction(_analytics->predict_rs_lengths());
422 }
423
424 void G1Policy::update_rs_lengths_prediction(size_t prediction) {
425 if (collector_state()->in_young_only_phase() && adaptive_young_list_length()) {
426 _rs_lengths_prediction = prediction;
427 }
428 }
429
430 void G1Policy::record_full_collection_start() {
431 _full_collection_start_sec = os::elapsedTime();
432 // Release the future to-space so that it is available for compaction into.
433 collector_state()->set_in_young_only_phase(false);
434 collector_state()->set_in_full_gc(true);
435 cset_chooser()->clear();
436 }
437
438 void G1Policy::record_full_collection_end() {
439 // Consider this like a collection pause for the purposes of allocation
440 // since last pause.
441 double end_sec = os::elapsedTime();
442 double full_gc_time_sec = end_sec - _full_collection_start_sec;
443 double full_gc_time_ms = full_gc_time_sec * 1000.0;
444
445 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);
446
447 collector_state()->set_in_full_gc(false);
448
449 // "Nuke" the heuristics that control the young/mixed GC
450 // transitions and make sure we start with young GCs after the Full GC.
451 collector_state()->set_in_young_only_phase(true);
452 collector_state()->set_in_young_gc_before_mixed(false);
453 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
454 collector_state()->set_in_initial_mark_gc(false);
455 collector_state()->set_mark_or_rebuild_in_progress(false);
456 collector_state()->set_clearing_next_bitmap(false);
457
458 _short_lived_surv_rate_group->start_adding_regions();
459 // also call this on any additional surv rate groups
460
461 _free_regions_at_end_of_collection = _g1h->num_free_regions();
462 // Reset survivors SurvRateGroup.
463 _survivor_surv_rate_group->reset();
464 update_young_list_max_and_target_length();
465 update_rs_lengths_prediction();
466
467 _bytes_allocated_in_old_since_last_gc = 0;
468
469 record_pause(FullGC, _full_collection_start_sec, end_sec);
470 }
471
472 void G1Policy::record_collection_pause_start(double start_time_sec) {
473 // We only need to do this here as the policy will only be applied
474 // to the GC we're about to start. so, no point is calculating this
475 // every time we calculate / recalculate the target young length.
476 update_survivors_policy();
477
478 assert(_g1h->used() == _g1h->recalculate_used(),
479 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
480 _g1h->used(), _g1h->recalculate_used());
481
482 phase_times()->record_cur_collection_start_sec(start_time_sec);
483 _pending_cards = _g1h->pending_card_num();
484
485 _collection_set->reset_bytes_used_before();
486 _bytes_copied_during_gc = 0;
487
488 // do that for any other surv rate groups
489 _short_lived_surv_rate_group->stop_adding_regions();
490 _survivors_age_table.clear();
491
492 assert(_g1h->collection_set()->verify_young_ages(), "region age verification failed");
493 }
494
495 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {
496 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
497 collector_state()->set_in_initial_mark_gc(false);
498 }
499
500 void G1Policy::record_concurrent_mark_remark_start() {
501 _mark_remark_start_sec = os::elapsedTime();
502 }
503
504 void G1Policy::record_concurrent_mark_remark_end() {
505 double end_time_sec = os::elapsedTime();
506 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
507 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);
508 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
509
510 record_pause(Remark, _mark_remark_start_sec, end_time_sec);
511 }
512
513 void G1Policy::record_concurrent_mark_cleanup_start() {
514 _mark_cleanup_start_sec = os::elapsedTime();
515 }
516
517 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
518 return phase_times()->average_time_ms(phase);
519 }
520
521 double G1Policy::young_other_time_ms() const {
522 return phase_times()->young_cset_choice_time_ms() +
523 phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet);
524 }
525
526 double G1Policy::non_young_other_time_ms() const {
527 return phase_times()->non_young_cset_choice_time_ms() +
528 phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet);
529 }
530
531 double G1Policy::other_time_ms(double pause_time_ms) const {
532 return pause_time_ms - phase_times()->cur_collection_par_time_ms();
533 }
534
535 double G1Policy::constant_other_time_ms(double pause_time_ms) const {
536 return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms();
537 }
538
539 CollectionSetChooser* G1Policy::cset_chooser() const {
540 return _collection_set->cset_chooser();
541 }
542
543 bool G1Policy::about_to_start_mixed_phase() const {
544 return _g1h->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->in_young_gc_before_mixed();
545 }
546
547 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
548 if (about_to_start_mixed_phase()) {
549 return false;
550 }
551
552 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
553
554 size_t cur_used_bytes = _g1h->non_young_capacity_bytes();
555 size_t alloc_byte_size = alloc_word_size * HeapWordSize;
556 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
557
558 bool result = false;
559 if (marking_request_bytes > marking_initiating_used_threshold) {
560 result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed();
561 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
562 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
563 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1h->capacity() * 100, source);
564 }
565
566 return result;
567 }
568
569 // Anything below that is considered to be zero
570 #define MIN_TIMER_GRANULARITY 0.0000001
571
572 void G1Policy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
573 double end_time_sec = os::elapsedTime();
574
575 size_t cur_used_bytes = _g1h->used();
576 assert(cur_used_bytes == _g1h->recalculate_used(), "It should!");
577 bool this_pause_included_initial_mark = false;
578 bool this_pause_was_young_only = collector_state()->in_young_only_phase();
579
580 bool update_stats = !_g1h->evacuation_failed();
581
582 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
583
584 _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
585
586 this_pause_included_initial_mark = collector_state()->in_initial_mark_gc();
587 if (this_pause_included_initial_mark) {
588 record_concurrent_mark_init_end(0.0);
589 } else {
590 maybe_start_marking();
591 }
592
593 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
594 if (app_time_ms < MIN_TIMER_GRANULARITY) {
595 // This usually happens due to the timer not having the required
596 // granularity. Some Linuxes are the usual culprits.
597 // We'll just set it to something (arbitrarily) small.
598 app_time_ms = 1.0;
599 }
600
601 if (update_stats) {
602 // We maintain the invariant that all objects allocated by mutator
603 // threads will be allocated out of eden regions. So, we can use
604 // the eden region number allocated since the previous GC to
605 // calculate the application's allocate rate. The only exception
606 // to that is humongous objects that are allocated separately. But
607 // given that humongous object allocations do not really affect
608 // either the pause's duration nor when the next pause will take
609 // place we can safely ignore them here.
610 uint regions_allocated = _collection_set->eden_region_length();
611 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
612 _analytics->report_alloc_rate_ms(alloc_rate_ms);
613
614 double interval_ms =
615 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;
616 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
617 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);
618 }
619
620 if (collector_state()->in_young_gc_before_mixed()) {
621 assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC");
622 // This has been the young GC before we start doing mixed GCs. We already
623 // decided to start mixed GCs much earlier, so there is nothing to do except
624 // advancing the state.
625 collector_state()->set_in_young_only_phase(false);
626 collector_state()->set_in_young_gc_before_mixed(false);
627 } else if (!this_pause_was_young_only) {
628 // This is a mixed GC. Here we decide whether to continue doing more
629 // mixed GCs or not.
630 if (!next_gc_should_be_mixed("continue mixed GCs",
631 "do not continue mixed GCs")) {
632 collector_state()->set_in_young_only_phase(true);
633
634 clear_collection_set_candidates();
635 maybe_start_marking();
636 }
637 }
638
639 _short_lived_surv_rate_group->start_adding_regions();
640 // Do that for any other surv rate groups
641
642 double scan_hcc_time_ms = G1HotCardCache::default_use_cache() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
643
644 if (update_stats) {
645 double cost_per_card_ms = 0.0;
646 if (_pending_cards > 0) {
647 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS)) / (double) _pending_cards;
648 _analytics->report_cost_per_card_ms(cost_per_card_ms);
649 }
650 _analytics->report_cost_scan_hcc(scan_hcc_time_ms);
651
652 double cost_per_entry_ms = 0.0;
653 if (cards_scanned > 10) {
654 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
655 _analytics->report_cost_per_entry_ms(cost_per_entry_ms, this_pause_was_young_only);
656 }
657
658 if (_max_rs_lengths > 0) {
659 double cards_per_entry_ratio =
660 (double) cards_scanned / (double) _max_rs_lengths;
661 _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, this_pause_was_young_only);
662 }
663
664 // This is defensive. For a while _max_rs_lengths could get
665 // smaller than _recorded_rs_lengths which was causing
666 // rs_length_diff to get very large and mess up the RSet length
667 // predictions. The reason was unsafe concurrent updates to the
668 // _inc_cset_recorded_rs_lengths field which the code below guards
669 // against (see CR 7118202). This bug has now been fixed (see CR
670 // 7119027). However, I'm still worried that
671 // _inc_cset_recorded_rs_lengths might still end up somewhat
672 // inaccurate. The concurrent refinement thread calculates an
673 // RSet's length concurrently with other CR threads updating it
674 // which might cause it to calculate the length incorrectly (if,
675 // say, it's in mid-coarsening). So I'll leave in the defensive
676 // conditional below just in case.
677 size_t rs_length_diff = 0;
678 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();
679 if (_max_rs_lengths > recorded_rs_lengths) {
680 rs_length_diff = _max_rs_lengths - recorded_rs_lengths;
681 }
682 _analytics->report_rs_length_diff((double) rs_length_diff);
683
684 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
685 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
686 double cost_per_byte_ms = 0.0;
687
688 if (copied_bytes > 0) {
689 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
690 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress());
691 }
692
693 if (_collection_set->young_region_length() > 0) {
694 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
695 _collection_set->young_region_length());
696 }
697
698 if (_collection_set->old_region_length() > 0) {
699 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
700 _collection_set->old_region_length());
701 }
702
703 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
704
705 // Do not update RS lengths and the number of pending cards with information from mixed gc:
706 // these are is wildly different to during young only gc and mess up young gen sizing right
707 // after the mixed gc phase.
708 // During mixed gc we do not use them for young gen sizing.
709 if (this_pause_was_young_only) {
710 _analytics->report_pending_cards((double) _pending_cards);
711 _analytics->report_rs_lengths((double) _max_rs_lengths);
712 }
713 }
714
715 assert(!(this_pause_included_initial_mark && collector_state()->mark_or_rebuild_in_progress()),
716 "If the last pause has been an initial mark, we should not have been in the marking window");
717 if (this_pause_included_initial_mark) {
718 collector_state()->set_mark_or_rebuild_in_progress(true);
719 }
720
721 _free_regions_at_end_of_collection = _g1h->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 this_pause_was_young_only);
733 _bytes_allocated_in_old_since_last_gc = 0;
734
735 _ihop_control->send_trace_event(_g1h->gc_tracer_stw());
736
737 // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
738 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
739
740 if (update_rs_time_goal_ms < scan_hcc_time_ms) {
741 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
742 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",
743 update_rs_time_goal_ms, scan_hcc_time_ms);
744
745 update_rs_time_goal_ms = 0;
746 } else {
747 update_rs_time_goal_ms -= scan_hcc_time_ms;
748 }
749 _g1h->concurrent_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS),
750 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
751 update_rs_time_goal_ms);
752
753 cset_chooser()->verify();
754 }
755
756 G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){
757 if (G1UseAdaptiveIHOP) {
758 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
759 predictor,
760 G1ReservePercent,
761 G1HeapWastePercent);
762 } else {
763 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
764 }
765 }
766
767 void G1Policy::update_ihop_prediction(double mutator_time_s,
768 size_t mutator_alloc_bytes,
769 size_t young_gen_size,
770 bool this_gc_was_young_only) {
771 // Always try to update IHOP prediction. Even evacuation failures give information
772 // about e.g. whether to start IHOP earlier next time.
773
774 // Avoid using really small application times that might create samples with
775 // very high or very low values. They may be caused by e.g. back-to-back gcs.
776 double const min_valid_time = 1e-6;
777
778 bool report = false;
779
780 double marking_to_mixed_time = -1.0;
781 if (!this_gc_was_young_only && _initial_mark_to_mixed.has_result()) {
782 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
783 assert(marking_to_mixed_time > 0.0,
784 "Initial mark to mixed time must be larger than zero but is %.3f",
785 marking_to_mixed_time);
786 if (marking_to_mixed_time > min_valid_time) {
787 _ihop_control->update_marking_length(marking_to_mixed_time);
788 report = true;
789 }
790 }
791
792 // As an approximation for the young gc promotion rates during marking we use
793 // all of them. In many applications there are only a few if any young gcs during
794 // marking, which makes any prediction useless. This increases the accuracy of the
795 // prediction.
796 if (this_gc_was_young_only && mutator_time_s > min_valid_time) {
797 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
798 report = true;
799 }
800
801 if (report) {
802 report_ihop_statistics();
803 }
804 }
805
806 void G1Policy::report_ihop_statistics() {
807 _ihop_control->print();
808 }
809
810 void G1Policy::print_phases() {
811 phase_times()->print();
812 }
813
814 double G1Policy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
815 TruncatedSeq* seq = surv_rate_group->get_seq(age);
816 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
817 double pred = _predictor.get_new_prediction(seq);
818 if (pred > 1.0) {
819 pred = 1.0;
820 }
821 return pred;
822 }
823
824 double G1Policy::accum_yg_surv_rate_pred(int age) const {
825 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
826 }
827
828 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards,
829 size_t scanned_cards) const {
830 return
831 _analytics->predict_rs_update_time_ms(pending_cards) +
832 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->in_young_only_phase()) +
833 _analytics->predict_constant_other_time_ms();
834 }
835
836 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const {
837 size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff();
838 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->in_young_only_phase());
839 return predict_base_elapsed_time_ms(pending_cards, card_num);
840 }
841
842 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const {
843 size_t bytes_to_copy;
844 if (!hr->is_young()) {
845 bytes_to_copy = hr->max_live_bytes();
846 } else {
847 assert(hr->age_in_surv_rate_group() != -1, "invariant");
848 int age = hr->age_in_surv_rate_group();
849 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
850 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
851 }
852 return bytes_to_copy;
853 }
854
855 double G1Policy::predict_region_elapsed_time_ms(HeapRegion* hr,
856 bool for_young_gc) const {
857 size_t rs_length = hr->rem_set()->occupied();
858 // Predicting the number of cards is based on which type of GC
859 // we're predicting for.
860 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc);
861 size_t bytes_to_copy = predict_bytes_to_copy(hr);
862
863 double region_elapsed_time_ms =
864 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->in_young_only_phase()) +
865 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress());
866
867 // The prediction of the "other" time for this region is based
868 // upon the region type and NOT the GC type.
869 if (hr->is_young()) {
870 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
871 } else {
872 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
873 }
874 return region_elapsed_time_ms;
875 }
876
877 bool G1Policy::should_allocate_mutator_region() const {
878 uint young_list_length = _g1h->young_regions_count();
879 uint young_list_target_length = _young_list_target_length;
880 return young_list_length < young_list_target_length;
881 }
882
883 bool G1Policy::can_expand_young_list() const {
884 uint young_list_length = _g1h->young_regions_count();
885 uint young_list_max_length = _young_list_max_length;
886 return young_list_length < young_list_max_length;
887 }
888
889 bool G1Policy::adaptive_young_list_length() const {
890 return _young_gen_sizer.adaptive_young_list_length();
891 }
892
893 size_t G1Policy::desired_survivor_size() const {
894 size_t const survivor_capacity = HeapRegion::GrainWords * _max_survivor_regions;
895 return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
896 }
897
898 void G1Policy::print_age_table() {
899 _survivors_age_table.print_age_table(_tenuring_threshold);
900 }
901
902 void G1Policy::update_max_gc_locker_expansion() {
903 uint expansion_region_num = 0;
904 if (GCLockerEdenExpansionPercent > 0) {
905 double perc = (double) GCLockerEdenExpansionPercent / 100.0;
906 double expansion_region_num_d = perc * (double) _young_list_target_length;
907 // We use ceiling so that if expansion_region_num_d is > 0.0 (but
908 // less than 1.0) we'll get 1.
909 expansion_region_num = (uint) ceil(expansion_region_num_d);
910 } else {
911 assert(expansion_region_num == 0, "sanity");
912 }
913 _young_list_max_length = _young_list_target_length + expansion_region_num;
914 assert(_young_list_target_length <= _young_list_max_length, "post-condition");
915 }
916
917 // Calculates survivor space parameters.
918 void G1Policy::update_survivors_policy() {
919 double max_survivor_regions_d =
920 (double) _young_list_target_length / (double) SurvivorRatio;
921 // We use ceiling so that if max_survivor_regions_d is > 0.0 (but
922 // smaller than 1.0) we'll get 1.
923 _max_survivor_regions = (uint) ceil(max_survivor_regions_d);
924
925 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(desired_survivor_size());
926 if (UsePerfData) {
927 _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold);
928 _policy_counters->desired_survivor_size()->set_value(desired_survivor_size() * oopSize);
929 }
930 }
931
932 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
933 // We actually check whether we are marking here and not if we are in a
934 // reclamation phase. This means that we will schedule a concurrent mark
935 // even while we are still in the process of reclaiming memory.
936 bool during_cycle = _g1h->concurrent_mark()->cm_thread()->during_cycle();
937 if (!during_cycle) {
938 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
939 collector_state()->set_initiate_conc_mark_if_possible(true);
940 return true;
941 } else {
942 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
943 return false;
944 }
945 }
946
947 void G1Policy::initiate_conc_mark() {
948 collector_state()->set_in_initial_mark_gc(true);
949 collector_state()->set_initiate_conc_mark_if_possible(false);
950 }
951
952 void G1Policy::decide_on_conc_mark_initiation() {
953 // We are about to decide on whether this pause will be an
954 // initial-mark pause.
955
956 // First, collector_state()->in_initial_mark_gc() should not be already set. We
957 // will set it here if we have to. However, it should be cleared by
958 // the end of the pause (it's only set for the duration of an
959 // initial-mark pause).
960 assert(!collector_state()->in_initial_mark_gc(), "pre-condition");
961
962 if (collector_state()->initiate_conc_mark_if_possible()) {
963 // We had noticed on a previous pause that the heap occupancy has
964 // gone over the initiating threshold and we should start a
965 // concurrent marking cycle. So we might initiate one.
966
967 if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) {
968 // Initiate a new initial mark if there is no marking or reclamation going on.
969 initiate_conc_mark();
970 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
971 } else if (_g1h->is_user_requested_concurrent_full_gc(_g1h->gc_cause())) {
972 // Initiate a user requested initial mark. An initial mark must be young only
973 // GC, so the collector state must be updated to reflect this.
974 collector_state()->set_in_young_only_phase(true);
975 collector_state()->set_in_young_gc_before_mixed(false);
976
977 // We might have ended up coming here about to start a mixed phase with a collection set
978 // active. The following remark might change the change the "evacuation efficiency" of
979 // the regions in this set, leading to failing asserts later.
980 // Since the concurrent cycle will recreate the collection set anyway, simply drop it here.
981 clear_collection_set_candidates();
982 abort_time_to_mixed_tracking();
983 initiate_conc_mark();
984 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
985 } else {
986 // The concurrent marking thread is still finishing up the
987 // previous cycle. If we start one right now the two cycles
988 // overlap. In particular, the concurrent marking thread might
989 // be in the process of clearing the next marking bitmap (which
990 // we will use for the next cycle if we start one). Starting a
991 // cycle now will be bad given that parts of the marking
992 // information might get cleared by the marking thread. And we
993 // cannot wait for the marking thread to finish the cycle as it
994 // periodically yields while clearing the next marking bitmap
995 // and, if it's in a yield point, it's waiting for us to
996 // finish. So, at this point we will not start a cycle and we'll
997 // let the concurrent marking thread complete the last one.
998 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
999 }
1000 }
1001 }
1002
1003 void G1Policy::record_concurrent_mark_cleanup_end() {
1004 cset_chooser()->rebuild(_g1h->workers(), _g1h->num_regions());
1005
1006 bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs");
1007 if (!mixed_gc_pending) {
1008 clear_collection_set_candidates();
1009 abort_time_to_mixed_tracking();
1010 }
1011 collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending);
1012 collector_state()->set_mark_or_rebuild_in_progress(false);
1013
1014 double end_sec = os::elapsedTime();
1015 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1016 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
1017 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
1018
1019 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1020 }
1021
1022 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const {
1023 return percent_of(reclaimable_bytes, _g1h->capacity());
1024 }
1025
1026 class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure {
1027 virtual bool do_heap_region(HeapRegion* r) {
1028 r->rem_set()->clear_locked(true /* only_cardset */);
1029 return false;
1030 }
1031 };
1032
1033 void G1Policy::clear_collection_set_candidates() {
1034 // Clear remembered sets of remaining candidate regions and the actual candidate
1035 // list.
1036 G1ClearCollectionSetCandidateRemSets cl;
1037 cset_chooser()->iterate(&cl);
1038 cset_chooser()->clear();
1039 }
1040
1041 void G1Policy::maybe_start_marking() {
1042 if (need_to_start_conc_mark("end of GC")) {
1043 // Note: this might have already been set, if during the last
1044 // pause we decided to start a cycle but at the beginning of
1045 // this pause we decided to postpone it. That's OK.
1046 collector_state()->set_initiate_conc_mark_if_possible(true);
1047 }
1048 }
1049
1050 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const {
1051 assert(!collector_state()->in_full_gc(), "must be");
1052 if (collector_state()->in_initial_mark_gc()) {
1053 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1054 return InitialMarkGC;
1055 } else if (collector_state()->in_young_gc_before_mixed()) {
1056 assert(!collector_state()->in_initial_mark_gc(), "must be");
1057 return LastYoungGC;
1058 } else if (collector_state()->in_mixed_phase()) {
1059 assert(!collector_state()->in_initial_mark_gc(), "must be");
1060 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1061 return MixedGC;
1062 } else {
1063 assert(!collector_state()->in_initial_mark_gc(), "must be");
1064 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1065 return YoungOnlyGC;
1066 }
1067 }
1068
1069 void G1Policy::record_pause(PauseKind kind, double start, double end) {
1070 // Manage the MMU tracker. For some reason it ignores Full GCs.
1071 if (kind != FullGC) {
1072 _mmu_tracker->add_pause(start, end);
1073 }
1074 // Manage the mutator time tracking from initial mark to first mixed gc.
1075 switch (kind) {
1076 case FullGC:
1077 abort_time_to_mixed_tracking();
1078 break;
1079 case Cleanup:
1080 case Remark:
1081 case YoungOnlyGC:
1082 case LastYoungGC:
1083 _initial_mark_to_mixed.add_pause(end - start);
1084 break;
1085 case InitialMarkGC:
1086 _initial_mark_to_mixed.record_initial_mark_end(end);
1087 break;
1088 case MixedGC:
1089 _initial_mark_to_mixed.record_mixed_gc_start(start);
1090 break;
1091 default:
1092 ShouldNotReachHere();
1093 }
1094 }
1095
1096 void G1Policy::abort_time_to_mixed_tracking() {
1097 _initial_mark_to_mixed.reset();
1098 }
1099
1100 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str,
1101 const char* false_action_str) const {
1102 if (cset_chooser()->is_empty()) {
1103 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1104 return false;
1105 }
1106
1107 // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1108 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
1109 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1110 double threshold = (double) G1HeapWastePercent;
1111 if (reclaimable_percent <= threshold) {
1112 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1113 false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1114 return false;
1115 }
1116 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1117 true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1118 return true;
1119 }
1120
1121 uint G1Policy::calc_min_old_cset_length() const {
1122 // The min old CSet region bound is based on the maximum desired
1123 // number of mixed GCs after a cycle. I.e., even if some old regions
1124 // look expensive, we should add them to the CSet anyway to make
1125 // sure we go through the available old regions in no more than the
1126 // maximum desired number of mixed GCs.
1127 //
1128 // The calculation is based on the number of marked regions we added
1129 // to the CSet chooser in the first place, not how many remain, so
1130 // that the result is the same during all mixed GCs that follow a cycle.
1131
1132 const size_t region_num = (size_t) cset_chooser()->length();
1133 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1134 size_t result = region_num / gc_num;
1135 // emulate ceiling
1136 if (result * gc_num < region_num) {
1137 result += 1;
1138 }
1139 return (uint) result;
1140 }
1141
1142 uint G1Policy::calc_max_old_cset_length() const {
1143 // The max old CSet region bound is based on the threshold expressed
1144 // as a percentage of the heap size. I.e., it should bound the
1145 // number of old regions added to the CSet irrespective of how many
1146 // of them are available.
1147
1148 const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1149 const size_t region_num = g1h->num_regions();
1150 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1151 size_t result = region_num * perc / 100;
1152 // emulate ceiling
1153 if (100 * result < region_num * perc) {
1154 result += 1;
1155 }
1156 return (uint) result;
1157 }
1158
1159 void G1Policy::finalize_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {
1160 double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms, survivor);
1161 _collection_set->finalize_old_part(time_remaining_ms);
1162 }
1163
1164 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) {
1165
1166 // Add survivor regions to SurvRateGroup.
1167 note_start_adding_survivor_regions();
1168 finished_recalculating_age_indexes(true /* is_survivors */);
1169
1170 HeapRegion* last = NULL;
1171 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin();
1172 it != survivors->regions()->end();
1173 ++it) {
1174 HeapRegion* curr = *it;
1175 set_region_survivor(curr);
1176
1177 // The region is a non-empty survivor so let's add it to
1178 // the incremental collection set for the next evacuation
1179 // pause.
1180 _collection_set->add_survivor_regions(curr);
1181
1182 last = curr;
1183 }
1184 note_stop_adding_survivor_regions();
1185
1186 // Don't clear the survivor list handles until the start of
1187 // the next evacuation pause - we need it in order to re-tag
1188 // the survivor regions from this evacuation pause as 'young'
1189 // at the start of the next.
1190
1191 finished_recalculating_age_indexes(false /* is_survivors */);
1192 }