1 /*
2 * Copyright (c) 2001, 2016, 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() :
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(ParallelGCThreads)),
67 _tenuring_threshold(MaxTenuringThreshold),
68 _max_survivor_regions(0),
69 _survivors_age_table(true) { }
70
71 G1DefaultPolicy::~G1DefaultPolicy() {
72 delete _ihop_control;
73 }
74
75 G1CollectorState* G1DefaultPolicy::collector_state() const { return _g1->collector_state(); }
76
77 void G1DefaultPolicy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
78 _g1 = g1h;
79 _collection_set = collection_set;
80
81 assert(Heap_lock->owned_by_self(), "Locking discipline.");
82
83 if (!adaptive_young_list_length()) {
84 _young_list_fixed_length = _young_gen_sizer.min_desired_young_length();
85 }
86 _young_gen_sizer.adjust_max_new_size(_g1->max_regions());
87
88 _free_regions_at_end_of_collection = _g1->num_free_regions();
89
90 update_young_list_max_and_target_length();
91 // We may immediately start allocating regions and placing them on the
92 // collection set list. Initialize the per-collection set info
93 _collection_set->start_incremental_building();
94 }
95
96 void G1DefaultPolicy::note_gc_start() {
97 phase_times()->note_gc_start();
98 }
99
100 bool G1DefaultPolicy::predict_will_fit(uint young_length,
101 double base_time_ms,
102 uint base_free_regions,
103 double target_pause_time_ms) const {
104 if (young_length >= base_free_regions) {
105 // end condition 1: not enough space for the young regions
106 return false;
107 }
108
109 double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);
110 size_t bytes_to_copy =
111 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
112 double copy_time_ms = _analytics->predict_object_copy_time_ms(bytes_to_copy,
113 collector_state()->during_concurrent_mark());
114 double young_other_time_ms = _analytics->predict_young_other_time_ms(young_length);
115 double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;
116 if (pause_time_ms > target_pause_time_ms) {
117 // end condition 2: prediction is over the target pause time
118 return false;
119 }
120
121 size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes;
122
123 // When copying, we will likely need more bytes free than is live in the region.
124 // Add some safety margin to factor in the confidence of our guess, and the
125 // natural expected waste.
126 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
127 // of the calculation: the lower the confidence, the more headroom.
128 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
129 // copying due to anticipated waste in the PLABs.
130 double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
131 size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
132
133 if (expected_bytes_to_copy > free_bytes) {
134 // end condition 3: out-of-space
135 return false;
136 }
137
138 // success!
139 return true;
140 }
141
142 void G1DefaultPolicy::record_new_heap_size(uint new_number_of_regions) {
143 // re-calculate the necessary reserve
144 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
145 // We use ceiling so that if reserve_regions_d is > 0.0 (but
146 // smaller than 1.0) we'll get 1.
147 _reserve_regions = (uint) ceil(reserve_regions_d);
148
149 _young_gen_sizer.heap_size_changed(new_number_of_regions);
150
151 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
152 }
153
154 uint G1DefaultPolicy::calculate_young_list_desired_min_length(uint base_min_length) const {
155 uint desired_min_length = 0;
156 if (adaptive_young_list_length()) {
157 if (_analytics->num_alloc_rate_ms() > 3) {
158 double now_sec = os::elapsedTime();
159 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
160 double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
161 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
162 } else {
163 // otherwise we don't have enough info to make the prediction
164 }
165 }
166 desired_min_length += base_min_length;
167 // make sure we don't go below any user-defined minimum bound
168 return MAX2(_young_gen_sizer.min_desired_young_length(), desired_min_length);
169 }
170
171 uint G1DefaultPolicy::calculate_young_list_desired_max_length() const {
172 // Here, we might want to also take into account any additional
173 // constraints (i.e., user-defined minimum bound). Currently, we
174 // effectively don't set this bound.
175 return _young_gen_sizer.max_desired_young_length();
176 }
177
178 uint G1DefaultPolicy::update_young_list_max_and_target_length() {
179 return update_young_list_max_and_target_length(_analytics->predict_rs_lengths());
180 }
181
182 uint G1DefaultPolicy::update_young_list_max_and_target_length(size_t rs_lengths) {
183 uint unbounded_target_length = update_young_list_target_length(rs_lengths);
184 update_max_gc_locker_expansion();
185 return unbounded_target_length;
186 }
187
188 uint G1DefaultPolicy::update_young_list_target_length(size_t rs_lengths) {
189 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
190 _young_list_target_length = young_lengths.first;
191 return young_lengths.second;
192 }
193
194 G1DefaultPolicy::YoungTargetLengths G1DefaultPolicy::young_list_target_lengths(size_t rs_lengths) const {
195 YoungTargetLengths result;
196
197 // Calculate the absolute and desired min bounds first.
198
199 // This is how many young regions we already have (currently: the survivors).
200 const uint base_min_length = _g1->survivor_regions_count();
201 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
202 // This is the absolute minimum young length. Ensure that we
203 // will at least have one eden region available for allocation.
204 uint absolute_min_length = base_min_length + MAX2(_g1->eden_regions_count(), (uint)1);
205 // If we shrank the young list target it should not shrink below the current size.
206 desired_min_length = MAX2(desired_min_length, absolute_min_length);
207 // Calculate the absolute and desired max bounds.
208
209 uint desired_max_length = calculate_young_list_desired_max_length();
210
211 uint young_list_target_length = 0;
212 if (adaptive_young_list_length()) {
213 if (collector_state()->gcs_are_young()) {
214 young_list_target_length =
215 calculate_young_list_target_length(rs_lengths,
216 base_min_length,
217 desired_min_length,
218 desired_max_length);
219 } else {
220 // Don't calculate anything and let the code below bound it to
221 // the desired_min_length, i.e., do the next GC as soon as
222 // possible to maximize how many old regions we can add to it.
223 }
224 } else {
225 // The user asked for a fixed young gen so we'll fix the young gen
226 // whether the next GC is young or mixed.
227 young_list_target_length = _young_list_fixed_length;
228 }
229
230 result.second = young_list_target_length;
231
232 // We will try our best not to "eat" into the reserve.
233 uint absolute_max_length = 0;
234 if (_free_regions_at_end_of_collection > _reserve_regions) {
235 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
236 }
237 if (desired_max_length > absolute_max_length) {
238 desired_max_length = absolute_max_length;
239 }
240
241 // Make sure we don't go over the desired max length, nor under the
242 // desired min length. In case they clash, desired_min_length wins
243 // which is why that test is second.
244 if (young_list_target_length > desired_max_length) {
245 young_list_target_length = desired_max_length;
246 }
247 if (young_list_target_length < desired_min_length) {
248 young_list_target_length = desired_min_length;
249 }
250
251 assert(young_list_target_length > base_min_length,
252 "we should be able to allocate at least one eden region");
253 assert(young_list_target_length >= absolute_min_length, "post-condition");
254
255 result.first = young_list_target_length;
256 return result;
257 }
258
259 uint
260 G1DefaultPolicy::calculate_young_list_target_length(size_t rs_lengths,
261 uint base_min_length,
262 uint desired_min_length,
263 uint desired_max_length) const {
264 assert(adaptive_young_list_length(), "pre-condition");
265 assert(collector_state()->gcs_are_young(), "only call this for young GCs");
266
267 // In case some edge-condition makes the desired max length too small...
268 if (desired_max_length <= desired_min_length) {
269 return desired_min_length;
270 }
271
272 // We'll adjust min_young_length and max_young_length not to include
273 // the already allocated young regions (i.e., so they reflect the
274 // min and max eden regions we'll allocate). The base_min_length
275 // will be reflected in the predictions by the
276 // survivor_regions_evac_time prediction.
277 assert(desired_min_length > base_min_length, "invariant");
278 uint min_young_length = desired_min_length - base_min_length;
279 assert(desired_max_length > base_min_length, "invariant");
280 uint max_young_length = desired_max_length - base_min_length;
281
282 double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
283 double survivor_regions_evac_time = predict_survivor_regions_evac_time();
284 size_t pending_cards = _analytics->predict_pending_cards();
285 size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff();
286 size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, /* gcs_are_young */ true);
287 double base_time_ms =
288 predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
289 survivor_regions_evac_time;
290 uint available_free_regions = _free_regions_at_end_of_collection;
291 uint base_free_regions = 0;
292 if (available_free_regions > _reserve_regions) {
293 base_free_regions = available_free_regions - _reserve_regions;
294 }
295
296 // Here, we will make sure that the shortest young length that
297 // makes sense fits within the target pause time.
298
299 if (predict_will_fit(min_young_length, base_time_ms,
300 base_free_regions, target_pause_time_ms)) {
301 // The shortest young length will fit into the target pause time;
302 // we'll now check whether the absolute maximum number of young
303 // regions will fit in the target pause time. If not, we'll do
304 // a binary search between min_young_length and max_young_length.
305 if (predict_will_fit(max_young_length, base_time_ms,
306 base_free_regions, target_pause_time_ms)) {
307 // The maximum young length will fit into the target pause time.
308 // We are done so set min young length to the maximum length (as
309 // the result is assumed to be returned in min_young_length).
310 min_young_length = max_young_length;
311 } else {
312 // The maximum possible number of young regions will not fit within
313 // the target pause time so we'll search for the optimal
314 // length. The loop invariants are:
315 //
316 // min_young_length < max_young_length
317 // min_young_length is known to fit into the target pause time
318 // max_young_length is known not to fit into the target pause time
319 //
320 // Going into the loop we know the above hold as we've just
321 // checked them. Every time around the loop we check whether
322 // the middle value between min_young_length and
323 // max_young_length fits into the target pause time. If it
324 // does, it becomes the new min. If it doesn't, it becomes
325 // the new max. This way we maintain the loop invariants.
326
327 assert(min_young_length < max_young_length, "invariant");
328 uint diff = (max_young_length - min_young_length) / 2;
329 while (diff > 0) {
330 uint young_length = min_young_length + diff;
331 if (predict_will_fit(young_length, base_time_ms,
332 base_free_regions, target_pause_time_ms)) {
333 min_young_length = young_length;
334 } else {
335 max_young_length = young_length;
336 }
337 assert(min_young_length < max_young_length, "invariant");
338 diff = (max_young_length - min_young_length) / 2;
339 }
340 // The results is min_young_length which, according to the
341 // loop invariants, should fit within the target pause time.
342
343 // These are the post-conditions of the binary search above:
344 assert(min_young_length < max_young_length,
345 "otherwise we should have discovered that max_young_length "
346 "fits into the pause target and not done the binary search");
347 assert(predict_will_fit(min_young_length, base_time_ms,
348 base_free_regions, target_pause_time_ms),
349 "min_young_length, the result of the binary search, should "
350 "fit into the pause target");
351 assert(!predict_will_fit(min_young_length + 1, base_time_ms,
352 base_free_regions, target_pause_time_ms),
353 "min_young_length, the result of the binary search, should be "
354 "optimal, so no larger length should fit into the pause target");
355 }
356 } else {
357 // Even the minimum length doesn't fit into the pause time
358 // target, return it as the result nevertheless.
359 }
360 return base_min_length + min_young_length;
361 }
362
363 double G1DefaultPolicy::predict_survivor_regions_evac_time() const {
364 double survivor_regions_evac_time = 0.0;
365 const GrowableArray<HeapRegion*>* survivor_regions = _g1->survivor()->regions();
366
367 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin();
368 it != survivor_regions->end();
369 ++it) {
370 survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->gcs_are_young());
371 }
372 return survivor_regions_evac_time;
373 }
374
375 void G1DefaultPolicy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
376 guarantee( adaptive_young_list_length(), "should not call this otherwise" );
377
378 if (rs_lengths > _rs_lengths_prediction) {
379 // add 10% to avoid having to recalculate often
380 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
381 update_rs_lengths_prediction(rs_lengths_prediction);
382
383 update_young_list_max_and_target_length(rs_lengths_prediction);
384 }
385 }
386
387 void G1DefaultPolicy::update_rs_lengths_prediction() {
388 update_rs_lengths_prediction(_analytics->predict_rs_lengths());
389 }
390
391 void G1DefaultPolicy::update_rs_lengths_prediction(size_t prediction) {
392 if (collector_state()->gcs_are_young() && adaptive_young_list_length()) {
393 _rs_lengths_prediction = prediction;
394 }
395 }
396
397 void G1DefaultPolicy::record_full_collection_start() {
398 _full_collection_start_sec = os::elapsedTime();
399 // Release the future to-space so that it is available for compaction into.
400 collector_state()->set_full_collection(true);
401 }
402
403 void G1DefaultPolicy::record_full_collection_end() {
404 // Consider this like a collection pause for the purposes of allocation
405 // since last pause.
406 double end_sec = os::elapsedTime();
407 double full_gc_time_sec = end_sec - _full_collection_start_sec;
408 double full_gc_time_ms = full_gc_time_sec * 1000.0;
409
410 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);
411
412 collector_state()->set_full_collection(false);
413
414 // "Nuke" the heuristics that control the young/mixed GC
415 // transitions and make sure we start with young GCs after the Full GC.
416 collector_state()->set_gcs_are_young(true);
417 collector_state()->set_last_young_gc(false);
418 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
419 collector_state()->set_during_initial_mark_pause(false);
420 collector_state()->set_in_marking_window(false);
421 collector_state()->set_in_marking_window_im(false);
422
423 _short_lived_surv_rate_group->start_adding_regions();
424 // also call this on any additional surv rate groups
425
426 _free_regions_at_end_of_collection = _g1->num_free_regions();
427 // Reset survivors SurvRateGroup.
428 _survivor_surv_rate_group->reset();
429 update_young_list_max_and_target_length();
430 update_rs_lengths_prediction();
431 cset_chooser()->clear();
432
433 _bytes_allocated_in_old_since_last_gc = 0;
434
435 record_pause(FullGC, _full_collection_start_sec, end_sec);
436 }
437
438 void G1DefaultPolicy::record_collection_pause_start(double start_time_sec) {
439 // We only need to do this here as the policy will only be applied
440 // to the GC we're about to start. so, no point is calculating this
441 // every time we calculate / recalculate the target young length.
442 update_survivors_policy();
443
444 assert(_g1->used() == _g1->recalculate_used(),
445 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
446 _g1->used(), _g1->recalculate_used());
447
448 phase_times()->record_cur_collection_start_sec(start_time_sec);
449 _pending_cards = _g1->pending_card_num();
450
451 _collection_set->reset_bytes_used_before();
452 _bytes_copied_during_gc = 0;
453
454 collector_state()->set_last_gc_was_young(false);
455
456 // do that for any other surv rate groups
457 _short_lived_surv_rate_group->stop_adding_regions();
458 _survivors_age_table.clear();
459
460 assert(_g1->collection_set()->verify_young_ages(), "region age verification failed");
461 }
462
463 void G1DefaultPolicy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {
464 collector_state()->set_during_marking(true);
465 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
466 collector_state()->set_during_initial_mark_pause(false);
467 }
468
469 void G1DefaultPolicy::record_concurrent_mark_remark_start() {
470 _mark_remark_start_sec = os::elapsedTime();
471 collector_state()->set_during_marking(false);
472 }
473
474 void G1DefaultPolicy::record_concurrent_mark_remark_end() {
475 double end_time_sec = os::elapsedTime();
476 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
477 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);
478 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
479
480 record_pause(Remark, _mark_remark_start_sec, end_time_sec);
481 }
482
483 void G1DefaultPolicy::record_concurrent_mark_cleanup_start() {
484 _mark_cleanup_start_sec = os::elapsedTime();
485 }
486
487 void G1DefaultPolicy::record_concurrent_mark_cleanup_completed() {
488 bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",
489 "skip last young-only gc");
490 collector_state()->set_last_young_gc(should_continue_with_reclaim);
491 // We skip the marking phase.
492 if (!should_continue_with_reclaim) {
493 abort_time_to_mixed_tracking();
494 }
495 collector_state()->set_in_marking_window(false);
496 }
497
498 double G1DefaultPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
499 return phase_times()->average_time_ms(phase);
500 }
501
502 double G1DefaultPolicy::young_other_time_ms() const {
503 return phase_times()->young_cset_choice_time_ms() +
504 phase_times()->young_free_cset_time_ms();
505 }
506
507 double G1DefaultPolicy::non_young_other_time_ms() const {
508 return phase_times()->non_young_cset_choice_time_ms() +
509 phase_times()->non_young_free_cset_time_ms();
510
511 }
512
513 double G1DefaultPolicy::other_time_ms(double pause_time_ms) const {
514 return pause_time_ms - phase_times()->cur_collection_par_time_ms();
515 }
516
517 double G1DefaultPolicy::constant_other_time_ms(double pause_time_ms) const {
518 return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms();
519 }
520
521 CollectionSetChooser* G1DefaultPolicy::cset_chooser() const {
522 return _collection_set->cset_chooser();
523 }
524
525 bool G1DefaultPolicy::about_to_start_mixed_phase() const {
526 return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc();
527 }
528
529 bool G1DefaultPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
530 if (about_to_start_mixed_phase()) {
531 return false;
532 }
533
534 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
535
536 size_t cur_used_bytes = _g1->non_young_capacity_bytes();
537 size_t alloc_byte_size = alloc_word_size * HeapWordSize;
538 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
539
540 bool result = false;
541 if (marking_request_bytes > marking_initiating_used_threshold) {
542 result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc();
543 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
544 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
545 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source);
546 }
547
548 return result;
549 }
550
551 // Anything below that is considered to be zero
552 #define MIN_TIMER_GRANULARITY 0.0000001
553
554 void G1DefaultPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
555 double end_time_sec = os::elapsedTime();
556
557 size_t cur_used_bytes = _g1->used();
558 assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
559 bool last_pause_included_initial_mark = false;
560 bool update_stats = !_g1->evacuation_failed();
561
562 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
563
564 last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();
565 if (last_pause_included_initial_mark) {
566 record_concurrent_mark_init_end(0.0);
567 } else {
568 maybe_start_marking();
569 }
570
571 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
572 if (app_time_ms < MIN_TIMER_GRANULARITY) {
573 // This usually happens due to the timer not having the required
574 // granularity. Some Linuxes are the usual culprits.
575 // We'll just set it to something (arbitrarily) small.
576 app_time_ms = 1.0;
577 }
578
579 if (update_stats) {
580 // We maintain the invariant that all objects allocated by mutator
581 // threads will be allocated out of eden regions. So, we can use
582 // the eden region number allocated since the previous GC to
583 // calculate the application's allocate rate. The only exception
584 // to that is humongous objects that are allocated separately. But
585 // given that humongous object allocations do not really affect
586 // either the pause's duration nor when the next pause will take
587 // place we can safely ignore them here.
588 uint regions_allocated = _collection_set->eden_region_length();
589 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
590 _analytics->report_alloc_rate_ms(alloc_rate_ms);
591
592 double interval_ms =
593 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;
594 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
595 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);
596 }
597
598 bool new_in_marking_window = collector_state()->in_marking_window();
599 bool new_in_marking_window_im = false;
600 if (last_pause_included_initial_mark) {
601 new_in_marking_window = true;
602 new_in_marking_window_im = true;
603 }
604
605 if (collector_state()->last_young_gc()) {
606 // This is supposed to to be the "last young GC" before we start
607 // doing mixed GCs. Here we decide whether to start mixed GCs or not.
608 assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC");
609
610 if (next_gc_should_be_mixed("start mixed GCs",
611 "do not start mixed GCs")) {
612 collector_state()->set_gcs_are_young(false);
613 } else {
614 // We aborted the mixed GC phase early.
615 abort_time_to_mixed_tracking();
616 }
617
618 collector_state()->set_last_young_gc(false);
619 }
620
621 if (!collector_state()->last_gc_was_young()) {
622 // This is a mixed GC. Here we decide whether to continue doing
623 // mixed GCs or not.
624 if (!next_gc_should_be_mixed("continue mixed GCs",
625 "do not continue mixed GCs")) {
626 collector_state()->set_gcs_are_young(true);
627
628 maybe_start_marking();
629 }
630 }
631
632 _short_lived_surv_rate_group->start_adding_regions();
633 // Do that for any other surv rate groups
634
635 double scan_hcc_time_ms = G1HotCardCache::default_use_cache() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
636
637 if (update_stats) {
638 double cost_per_card_ms = 0.0;
639 if (_pending_cards > 0) {
640 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards;
641 _analytics->report_cost_per_card_ms(cost_per_card_ms);
642 }
643 _analytics->report_cost_scan_hcc(scan_hcc_time_ms);
644
645 double cost_per_entry_ms = 0.0;
646 if (cards_scanned > 10) {
647 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
648 _analytics->report_cost_per_entry_ms(cost_per_entry_ms, collector_state()->last_gc_was_young());
649 }
650
651 if (_max_rs_lengths > 0) {
652 double cards_per_entry_ratio =
653 (double) cards_scanned / (double) _max_rs_lengths;
654 _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, collector_state()->last_gc_was_young());
655 }
656
657 // This is defensive. For a while _max_rs_lengths could get
658 // smaller than _recorded_rs_lengths which was causing
659 // rs_length_diff to get very large and mess up the RSet length
660 // predictions. The reason was unsafe concurrent updates to the
661 // _inc_cset_recorded_rs_lengths field which the code below guards
662 // against (see CR 7118202). This bug has now been fixed (see CR
663 // 7119027). However, I'm still worried that
664 // _inc_cset_recorded_rs_lengths might still end up somewhat
665 // inaccurate. The concurrent refinement thread calculates an
666 // RSet's length concurrently with other CR threads updating it
667 // which might cause it to calculate the length incorrectly (if,
668 // say, it's in mid-coarsening). So I'll leave in the defensive
669 // conditional below just in case.
670 size_t rs_length_diff = 0;
671 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();
672 if (_max_rs_lengths > recorded_rs_lengths) {
673 rs_length_diff = _max_rs_lengths - recorded_rs_lengths;
674 }
675 _analytics->report_rs_length_diff((double) rs_length_diff);
676
677 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
678 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
679 double cost_per_byte_ms = 0.0;
680
681 if (copied_bytes > 0) {
682 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
683 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->in_marking_window());
684 }
685
686 if (_collection_set->young_region_length() > 0) {
687 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
688 _collection_set->young_region_length());
689 }
690
691 if (_collection_set->old_region_length() > 0) {
692 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
693 _collection_set->old_region_length());
694 }
695
696 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
697
698 _analytics->report_pending_cards((double) _pending_cards);
699 _analytics->report_rs_lengths((double) _max_rs_lengths);
700 }
701
702 collector_state()->set_in_marking_window(new_in_marking_window);
703 collector_state()->set_in_marking_window_im(new_in_marking_window_im);
704 _free_regions_at_end_of_collection = _g1->num_free_regions();
705 // IHOP control wants to know the expected young gen length if it were not
706 // restrained by the heap reserve. Using the actual length would make the
707 // prediction too small and the limit the young gen every time we get to the
708 // predicted target occupancy.
709 size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
710 update_rs_lengths_prediction();
711
712 update_ihop_prediction(app_time_ms / 1000.0,
713 _bytes_allocated_in_old_since_last_gc,
714 last_unrestrained_young_length * HeapRegion::GrainBytes);
715 _bytes_allocated_in_old_since_last_gc = 0;
716
717 _ihop_control->send_trace_event(_g1->gc_tracer_stw());
718
719 // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
720 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
721
722 if (update_rs_time_goal_ms < scan_hcc_time_ms) {
723 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
724 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",
725 update_rs_time_goal_ms, scan_hcc_time_ms);
726
727 update_rs_time_goal_ms = 0;
728 } else {
729 update_rs_time_goal_ms -= scan_hcc_time_ms;
730 }
731 _g1->concurrent_g1_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms,
732 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
733 update_rs_time_goal_ms);
734
735 cset_chooser()->verify();
736 }
737
738 G1IHOPControl* G1DefaultPolicy::create_ihop_control(const G1Predictions* predictor){
739 if (G1UseAdaptiveIHOP) {
740 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
741 predictor,
742 G1ReservePercent,
743 G1HeapWastePercent);
744 } else {
745 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
746 }
747 }
748
749 void G1DefaultPolicy::update_ihop_prediction(double mutator_time_s,
750 size_t mutator_alloc_bytes,
751 size_t young_gen_size) {
752 // Always try to update IHOP prediction. Even evacuation failures give information
753 // about e.g. whether to start IHOP earlier next time.
754
755 // Avoid using really small application times that might create samples with
756 // very high or very low values. They may be caused by e.g. back-to-back gcs.
757 double const min_valid_time = 1e-6;
758
759 bool report = false;
760
761 double marking_to_mixed_time = -1.0;
762 if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) {
763 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
764 assert(marking_to_mixed_time > 0.0,
765 "Initial mark to mixed time must be larger than zero but is %.3f",
766 marking_to_mixed_time);
767 if (marking_to_mixed_time > min_valid_time) {
768 _ihop_control->update_marking_length(marking_to_mixed_time);
769 report = true;
770 }
771 }
772
773 // As an approximation for the young gc promotion rates during marking we use
774 // all of them. In many applications there are only a few if any young gcs during
775 // marking, which makes any prediction useless. This increases the accuracy of the
776 // prediction.
777 if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) {
778 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
779 report = true;
780 }
781
782 if (report) {
783 report_ihop_statistics();
784 }
785 }
786
787 void G1DefaultPolicy::report_ihop_statistics() {
788 _ihop_control->print();
789 }
790
791 void G1DefaultPolicy::print_phases() {
792 phase_times()->print();
793 }
794
795 double G1DefaultPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
796 TruncatedSeq* seq = surv_rate_group->get_seq(age);
797 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
798 double pred = _predictor.get_new_prediction(seq);
799 if (pred > 1.0) {
800 pred = 1.0;
801 }
802 return pred;
803 }
804
805 double G1DefaultPolicy::accum_yg_surv_rate_pred(int age) const {
806 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
807 }
808
809 double G1DefaultPolicy::predict_base_elapsed_time_ms(size_t pending_cards,
810 size_t scanned_cards) const {
811 return
812 _analytics->predict_rs_update_time_ms(pending_cards) +
813 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->gcs_are_young()) +
814 _analytics->predict_constant_other_time_ms();
815 }
816
817 double G1DefaultPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const {
818 size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff();
819 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->gcs_are_young());
820 return predict_base_elapsed_time_ms(pending_cards, card_num);
821 }
822
823 size_t G1DefaultPolicy::predict_bytes_to_copy(HeapRegion* hr) const {
824 size_t bytes_to_copy;
825 if (hr->is_marked())
826 bytes_to_copy = hr->max_live_bytes();
827 else {
828 assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
829 int age = hr->age_in_surv_rate_group();
830 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
831 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
832 }
833 return bytes_to_copy;
834 }
835
836 double G1DefaultPolicy::predict_region_elapsed_time_ms(HeapRegion* hr,
837 bool for_young_gc) const {
838 size_t rs_length = hr->rem_set()->occupied();
839 // Predicting the number of cards is based on which type of GC
840 // we're predicting for.
841 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc);
842 size_t bytes_to_copy = predict_bytes_to_copy(hr);
843
844 double region_elapsed_time_ms =
845 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->gcs_are_young()) +
846 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->during_concurrent_mark());
847
848 // The prediction of the "other" time for this region is based
849 // upon the region type and NOT the GC type.
850 if (hr->is_young()) {
851 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
852 } else {
853 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
854 }
855 return region_elapsed_time_ms;
856 }
857
858 bool G1DefaultPolicy::should_allocate_mutator_region() const {
859 uint young_list_length = _g1->young_regions_count();
860 uint young_list_target_length = _young_list_target_length;
861 return young_list_length < young_list_target_length;
862 }
863
864 bool G1DefaultPolicy::can_expand_young_list() const {
865 uint young_list_length = _g1->young_regions_count();
866 uint young_list_max_length = _young_list_max_length;
867 return young_list_length < young_list_max_length;
868 }
869
870 bool G1DefaultPolicy::adaptive_young_list_length() const {
871 return _young_gen_sizer.adaptive_young_list_length();
872 }
873
874 void G1DefaultPolicy::update_max_gc_locker_expansion() {
875 uint expansion_region_num = 0;
876 if (GCLockerEdenExpansionPercent > 0) {
877 double perc = (double) GCLockerEdenExpansionPercent / 100.0;
878 double expansion_region_num_d = perc * (double) _young_list_target_length;
879 // We use ceiling so that if expansion_region_num_d is > 0.0 (but
880 // less than 1.0) we'll get 1.
881 expansion_region_num = (uint) ceil(expansion_region_num_d);
882 } else {
883 assert(expansion_region_num == 0, "sanity");
884 }
885 _young_list_max_length = _young_list_target_length + expansion_region_num;
886 assert(_young_list_target_length <= _young_list_max_length, "post-condition");
887 }
888
889 // Calculates survivor space parameters.
890 void G1DefaultPolicy::update_survivors_policy() {
891 double max_survivor_regions_d =
892 (double) _young_list_target_length / (double) SurvivorRatio;
893 // We use ceiling so that if max_survivor_regions_d is > 0.0 (but
894 // smaller than 1.0) we'll get 1.
895 _max_survivor_regions = (uint) ceil(max_survivor_regions_d);
896
897 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(
898 HeapRegion::GrainWords * _max_survivor_regions, _policy_counters);
899 }
900
901 bool G1DefaultPolicy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
902 // We actually check whether we are marking here and not if we are in a
903 // reclamation phase. This means that we will schedule a concurrent mark
904 // even while we are still in the process of reclaiming memory.
905 bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
906 if (!during_cycle) {
907 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
908 collector_state()->set_initiate_conc_mark_if_possible(true);
909 return true;
910 } else {
911 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
912 return false;
913 }
914 }
915
916 void G1DefaultPolicy::initiate_conc_mark() {
917 collector_state()->set_during_initial_mark_pause(true);
918 collector_state()->set_initiate_conc_mark_if_possible(false);
919 }
920
921 void G1DefaultPolicy::decide_on_conc_mark_initiation() {
922 // We are about to decide on whether this pause will be an
923 // initial-mark pause.
924
925 // First, collector_state()->during_initial_mark_pause() should not be already set. We
926 // will set it here if we have to. However, it should be cleared by
927 // the end of the pause (it's only set for the duration of an
928 // initial-mark pause).
929 assert(!collector_state()->during_initial_mark_pause(), "pre-condition");
930
931 if (collector_state()->initiate_conc_mark_if_possible()) {
932 // We had noticed on a previous pause that the heap occupancy has
933 // gone over the initiating threshold and we should start a
934 // concurrent marking cycle. So we might initiate one.
935
936 if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) {
937 // Initiate a new initial mark if there is no marking or reclamation going on.
938 initiate_conc_mark();
939 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
940 } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) {
941 // Initiate a user requested initial mark. An initial mark must be young only
942 // GC, so the collector state must be updated to reflect this.
943 collector_state()->set_gcs_are_young(true);
944 collector_state()->set_last_young_gc(false);
945
946 abort_time_to_mixed_tracking();
947 initiate_conc_mark();
948 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
949 } else {
950 // The concurrent marking thread is still finishing up the
951 // previous cycle. If we start one right now the two cycles
952 // overlap. In particular, the concurrent marking thread might
953 // be in the process of clearing the next marking bitmap (which
954 // we will use for the next cycle if we start one). Starting a
955 // cycle now will be bad given that parts of the marking
956 // information might get cleared by the marking thread. And we
957 // cannot wait for the marking thread to finish the cycle as it
958 // periodically yields while clearing the next marking bitmap
959 // and, if it's in a yield point, it's waiting for us to
960 // finish. So, at this point we will not start a cycle and we'll
961 // let the concurrent marking thread complete the last one.
962 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
963 }
964 }
965 }
966
967 void G1DefaultPolicy::record_concurrent_mark_cleanup_end() {
968 cset_chooser()->rebuild(_g1->workers(), _g1->num_regions());
969
970 double end_sec = os::elapsedTime();
971 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
972 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
973 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
974
975 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
976 }
977
978 double G1DefaultPolicy::reclaimable_bytes_perc(size_t reclaimable_bytes) const {
979 // Returns the given amount of reclaimable bytes (that represents
980 // the amount of reclaimable space still to be collected) as a
981 // percentage of the current heap capacity.
982 size_t capacity_bytes = _g1->capacity();
983 return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
984 }
985
986 void G1DefaultPolicy::maybe_start_marking() {
987 if (need_to_start_conc_mark("end of GC")) {
988 // Note: this might have already been set, if during the last
989 // pause we decided to start a cycle but at the beginning of
990 // this pause we decided to postpone it. That's OK.
991 collector_state()->set_initiate_conc_mark_if_possible(true);
992 }
993 }
994
995 G1DefaultPolicy::PauseKind G1DefaultPolicy::young_gc_pause_kind() const {
996 assert(!collector_state()->full_collection(), "must be");
997 if (collector_state()->during_initial_mark_pause()) {
998 assert(collector_state()->last_gc_was_young(), "must be");
999 assert(!collector_state()->last_young_gc(), "must be");
1000 return InitialMarkGC;
1001 } else if (collector_state()->last_young_gc()) {
1002 assert(!collector_state()->during_initial_mark_pause(), "must be");
1003 assert(collector_state()->last_gc_was_young(), "must be");
1004 return LastYoungGC;
1005 } else if (!collector_state()->last_gc_was_young()) {
1006 assert(!collector_state()->during_initial_mark_pause(), "must be");
1007 assert(!collector_state()->last_young_gc(), "must be");
1008 return MixedGC;
1009 } else {
1010 assert(collector_state()->last_gc_was_young(), "must be");
1011 assert(!collector_state()->during_initial_mark_pause(), "must be");
1012 assert(!collector_state()->last_young_gc(), "must be");
1013 return YoungOnlyGC;
1014 }
1015 }
1016
1017 void G1DefaultPolicy::record_pause(PauseKind kind, double start, double end) {
1018 // Manage the MMU tracker. For some reason it ignores Full GCs.
1019 if (kind != FullGC) {
1020 _mmu_tracker->add_pause(start, end);
1021 }
1022 // Manage the mutator time tracking from initial mark to first mixed gc.
1023 switch (kind) {
1024 case FullGC:
1025 abort_time_to_mixed_tracking();
1026 break;
1027 case Cleanup:
1028 case Remark:
1029 case YoungOnlyGC:
1030 case LastYoungGC:
1031 _initial_mark_to_mixed.add_pause(end - start);
1032 break;
1033 case InitialMarkGC:
1034 _initial_mark_to_mixed.record_initial_mark_end(end);
1035 break;
1036 case MixedGC:
1037 _initial_mark_to_mixed.record_mixed_gc_start(start);
1038 break;
1039 default:
1040 ShouldNotReachHere();
1041 }
1042 }
1043
1044 void G1DefaultPolicy::abort_time_to_mixed_tracking() {
1045 _initial_mark_to_mixed.reset();
1046 }
1047
1048 bool G1DefaultPolicy::next_gc_should_be_mixed(const char* true_action_str,
1049 const char* false_action_str) const {
1050 if (cset_chooser()->is_empty()) {
1051 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1052 return false;
1053 }
1054
1055 // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1056 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
1057 double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
1058 double threshold = (double) G1HeapWastePercent;
1059 if (reclaimable_perc <= threshold) {
1060 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1061 false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
1062 return false;
1063 }
1064 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1065 true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
1066 return true;
1067 }
1068
1069 uint G1DefaultPolicy::calc_min_old_cset_length() const {
1070 // The min old CSet region bound is based on the maximum desired
1071 // number of mixed GCs after a cycle. I.e., even if some old regions
1072 // look expensive, we should add them to the CSet anyway to make
1073 // sure we go through the available old regions in no more than the
1074 // maximum desired number of mixed GCs.
1075 //
1076 // The calculation is based on the number of marked regions we added
1077 // to the CSet chooser in the first place, not how many remain, so
1078 // that the result is the same during all mixed GCs that follow a cycle.
1079
1080 const size_t region_num = (size_t) cset_chooser()->length();
1081 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1082 size_t result = region_num / gc_num;
1083 // emulate ceiling
1084 if (result * gc_num < region_num) {
1085 result += 1;
1086 }
1087 return (uint) result;
1088 }
1089
1090 uint G1DefaultPolicy::calc_max_old_cset_length() const {
1091 // The max old CSet region bound is based on the threshold expressed
1092 // as a percentage of the heap size. I.e., it should bound the
1093 // number of old regions added to the CSet irrespective of how many
1094 // of them are available.
1095
1096 const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1097 const size_t region_num = g1h->num_regions();
1098 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1099 size_t result = region_num * perc / 100;
1100 // emulate ceiling
1101 if (100 * result < region_num * perc) {
1102 result += 1;
1103 }
1104 return (uint) result;
1105 }
1106
1107 void G1DefaultPolicy::finalize_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {
1108 double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms, survivor);
1109 _collection_set->finalize_old_part(time_remaining_ms);
1110 }
1111
1112 void G1DefaultPolicy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) {
1113
1114 // Add survivor regions to SurvRateGroup.
1115 note_start_adding_survivor_regions();
1116 finished_recalculating_age_indexes(true /* is_survivors */);
1117
1118 HeapRegion* last = NULL;
1119 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin();
1120 it != survivors->regions()->end();
1121 ++it) {
1122 HeapRegion* curr = *it;
1123 set_region_survivor(curr);
1124
1125 // The region is a non-empty survivor so let's add it to
1126 // the incremental collection set for the next evacuation
1127 // pause.
1128 _collection_set->add_survivor_regions(curr);
1129
1130 last = curr;
1131 }
1132 note_stop_adding_survivor_regions();
1133
1134 // Don't clear the survivor list handles until the start of
1135 // the next evacuation pause - we need it in order to re-tag
1136 // the survivor regions from this evacuation pause as 'young'
1137 // at the start of the next.
1138
1139 finished_recalculating_age_indexes(false /* is_survivors */);
1140 }