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/g1IHOPControl.hpp"
34 #include "gc/g1/g1GCPhaseTimes.hpp"
35 #include "gc/g1/g1Policy.hpp"
36 #include "gc/g1/g1YoungGenSizer.hpp"
37 #include "gc/g1/heapRegion.inline.hpp"
38 #include "gc/g1/heapRegionRemSet.hpp"
39 #include "gc/shared/gcPolicyCounters.hpp"
40 #include "runtime/arguments.hpp"
41 #include "runtime/java.hpp"
42 #include "runtime/mutexLocker.hpp"
43 #include "utilities/debug.hpp"
44 #include "utilities/pair.hpp"
45
46 G1DefaultPolicy::G1DefaultPolicy() :
47 _predictor(G1ConfidencePercent / 100.0),
48 _analytics(new G1Analytics(&_predictor)),
49 _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)),
50 _ihop_control(create_ihop_control(&_predictor)),
51 _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 3)),
52 _young_list_fixed_length(0),
53 _short_lived_surv_rate_group(new SurvRateGroup(&_predictor, "Short Lived", G1YoungSurvRateNumRegionsSummary)),
54 _survivor_surv_rate_group(new SurvRateGroup(&_predictor, "Survivor", G1YoungSurvRateNumRegionsSummary)),
55 _reserve_factor((double) G1ReservePercent / 100.0),
56 _reserve_regions(0),
57 _rs_lengths_prediction(0),
58 _bytes_allocated_in_old_since_last_gc(0),
59 _initial_mark_to_mixed(),
60 _collection_set(NULL),
61 _g1(NULL),
62 _phase_times(new G1GCPhaseTimes(ParallelGCThreads)),
63 _tenuring_threshold(MaxTenuringThreshold),
64 _max_survivor_regions(0),
65 _survivors_age_table(true) { }
66
67 G1DefaultPolicy::~G1DefaultPolicy() {
68 delete _ihop_control;
69 }
70
71 G1CollectorState* G1DefaultPolicy::collector_state() const { return _g1->collector_state(); }
72
73 void G1DefaultPolicy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
74 _g1 = g1h;
75 _collection_set = collection_set;
76
77 assert(Heap_lock->owned_by_self(), "Locking discipline.");
78
79 if (!adaptive_young_list_length()) {
80 _young_list_fixed_length = _young_gen_sizer.min_desired_young_length();
81 }
82 _young_gen_sizer.adjust_max_new_size(_g1->max_regions());
83
84 _free_regions_at_end_of_collection = _g1->num_free_regions();
85
86 update_young_list_max_and_target_length();
87 // We may immediately start allocating regions and placing them on the
88 // collection set list. Initialize the per-collection set info
89 _collection_set->start_incremental_building();
90 }
91
92 void G1DefaultPolicy::note_gc_start() {
93 phase_times()->note_gc_start();
94 }
95
96 bool G1DefaultPolicy::predict_will_fit(uint young_length,
97 double base_time_ms,
98 uint base_free_regions,
99 double target_pause_time_ms) const {
100 if (young_length >= base_free_regions) {
101 // end condition 1: not enough space for the young regions
102 return false;
103 }
104
105 double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);
106 size_t bytes_to_copy =
107 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
108 double copy_time_ms = _analytics->predict_object_copy_time_ms(bytes_to_copy,
109 collector_state()->during_concurrent_mark());
110 double young_other_time_ms = _analytics->predict_young_other_time_ms(young_length);
111 double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;
112 if (pause_time_ms > target_pause_time_ms) {
113 // end condition 2: prediction is over the target pause time
114 return false;
115 }
116
117 size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes;
118
119 // When copying, we will likely need more bytes free than is live in the region.
120 // Add some safety margin to factor in the confidence of our guess, and the
121 // natural expected waste.
122 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
123 // of the calculation: the lower the confidence, the more headroom.
124 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
125 // copying due to anticipated waste in the PLABs.
126 double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
127 size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
128
129 if (expected_bytes_to_copy > free_bytes) {
130 // end condition 3: out-of-space
131 return false;
132 }
133
134 // success!
135 return true;
136 }
137
138 void G1DefaultPolicy::record_new_heap_size(uint new_number_of_regions) {
139 // re-calculate the necessary reserve
140 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
141 // We use ceiling so that if reserve_regions_d is > 0.0 (but
142 // smaller than 1.0) we'll get 1.
143 _reserve_regions = (uint) ceil(reserve_regions_d);
144
145 _young_gen_sizer.heap_size_changed(new_number_of_regions);
146
147 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
148 }
149
150 uint G1DefaultPolicy::calculate_young_list_desired_min_length(uint base_min_length) const {
151 uint desired_min_length = 0;
152 if (adaptive_young_list_length()) {
153 if (_analytics->num_alloc_rate_ms() > 3) {
154 double now_sec = os::elapsedTime();
155 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
156 double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
157 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
158 } else {
159 // otherwise we don't have enough info to make the prediction
160 }
161 }
162 desired_min_length += base_min_length;
163 // make sure we don't go below any user-defined minimum bound
164 return MAX2(_young_gen_sizer.min_desired_young_length(), desired_min_length);
165 }
166
167 uint G1DefaultPolicy::calculate_young_list_desired_max_length() const {
168 // Here, we might want to also take into account any additional
169 // constraints (i.e., user-defined minimum bound). Currently, we
170 // effectively don't set this bound.
171 return _young_gen_sizer.max_desired_young_length();
172 }
173
174 uint G1DefaultPolicy::update_young_list_max_and_target_length() {
175 return update_young_list_max_and_target_length(_analytics->predict_rs_lengths());
176 }
177
178 uint G1DefaultPolicy::update_young_list_max_and_target_length(size_t rs_lengths) {
179 uint unbounded_target_length = update_young_list_target_length(rs_lengths);
180 update_max_gc_locker_expansion();
181 return unbounded_target_length;
182 }
183
184 uint G1DefaultPolicy::update_young_list_target_length(size_t rs_lengths) {
185 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
186 _young_list_target_length = young_lengths.first;
187 return young_lengths.second;
188 }
189
190 G1DefaultPolicy::YoungTargetLengths G1DefaultPolicy::young_list_target_lengths(size_t rs_lengths) const {
191 YoungTargetLengths result;
192
193 // Calculate the absolute and desired min bounds first.
194
195 // This is how many young regions we already have (currently: the survivors).
196 const uint base_min_length = _g1->young_list()->survivor_length();
197 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
198 // This is the absolute minimum young length. Ensure that we
199 // will at least have one eden region available for allocation.
200 uint absolute_min_length = base_min_length + MAX2(_g1->young_list()->eden_length(), (uint)1);
201 // If we shrank the young list target it should not shrink below the current size.
202 desired_min_length = MAX2(desired_min_length, absolute_min_length);
203 // Calculate the absolute and desired max bounds.
204
205 uint desired_max_length = calculate_young_list_desired_max_length();
206
207 uint young_list_target_length = 0;
208 if (adaptive_young_list_length()) {
209 if (collector_state()->gcs_are_young()) {
210 young_list_target_length =
211 calculate_young_list_target_length(rs_lengths,
212 base_min_length,
213 desired_min_length,
214 desired_max_length);
215 } else {
216 // Don't calculate anything and let the code below bound it to
217 // the desired_min_length, i.e., do the next GC as soon as
218 // possible to maximize how many old regions we can add to it.
219 }
220 } else {
221 // The user asked for a fixed young gen so we'll fix the young gen
222 // whether the next GC is young or mixed.
223 young_list_target_length = _young_list_fixed_length;
224 }
225
226 result.second = young_list_target_length;
227
228 // We will try our best not to "eat" into the reserve.
229 uint absolute_max_length = 0;
230 if (_free_regions_at_end_of_collection > _reserve_regions) {
231 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
232 }
233 if (desired_max_length > absolute_max_length) {
234 desired_max_length = absolute_max_length;
235 }
236
237 // Make sure we don't go over the desired max length, nor under the
238 // desired min length. In case they clash, desired_min_length wins
239 // which is why that test is second.
240 if (young_list_target_length > desired_max_length) {
241 young_list_target_length = desired_max_length;
242 }
243 if (young_list_target_length < desired_min_length) {
244 young_list_target_length = desired_min_length;
245 }
246
247 assert(young_list_target_length > base_min_length,
248 "we should be able to allocate at least one eden region");
249 assert(young_list_target_length >= absolute_min_length, "post-condition");
250
251 result.first = young_list_target_length;
252 return result;
253 }
254
255 uint
256 G1DefaultPolicy::calculate_young_list_target_length(size_t rs_lengths,
257 uint base_min_length,
258 uint desired_min_length,
259 uint desired_max_length) const {
260 assert(adaptive_young_list_length(), "pre-condition");
261 assert(collector_state()->gcs_are_young(), "only call this for young GCs");
262
263 // In case some edge-condition makes the desired max length too small...
264 if (desired_max_length <= desired_min_length) {
265 return desired_min_length;
266 }
267
268 // We'll adjust min_young_length and max_young_length not to include
269 // the already allocated young regions (i.e., so they reflect the
270 // min and max eden regions we'll allocate). The base_min_length
271 // will be reflected in the predictions by the
272 // survivor_regions_evac_time prediction.
273 assert(desired_min_length > base_min_length, "invariant");
274 uint min_young_length = desired_min_length - base_min_length;
275 assert(desired_max_length > base_min_length, "invariant");
276 uint max_young_length = desired_max_length - base_min_length;
277
278 double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
279 double survivor_regions_evac_time = predict_survivor_regions_evac_time();
280 size_t pending_cards = _analytics->predict_pending_cards();
281 size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff();
282 size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, /* gcs_are_young */ true);
283 double base_time_ms =
284 predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
285 survivor_regions_evac_time;
286 uint available_free_regions = _free_regions_at_end_of_collection;
287 uint base_free_regions = 0;
288 if (available_free_regions > _reserve_regions) {
289 base_free_regions = available_free_regions - _reserve_regions;
290 }
291
292 // Here, we will make sure that the shortest young length that
293 // makes sense fits within the target pause time.
294
295 if (predict_will_fit(min_young_length, base_time_ms,
296 base_free_regions, target_pause_time_ms)) {
297 // The shortest young length will fit into the target pause time;
298 // we'll now check whether the absolute maximum number of young
299 // regions will fit in the target pause time. If not, we'll do
300 // a binary search between min_young_length and max_young_length.
301 if (predict_will_fit(max_young_length, base_time_ms,
302 base_free_regions, target_pause_time_ms)) {
303 // The maximum young length will fit into the target pause time.
304 // We are done so set min young length to the maximum length (as
305 // the result is assumed to be returned in min_young_length).
306 min_young_length = max_young_length;
307 } else {
308 // The maximum possible number of young regions will not fit within
309 // the target pause time so we'll search for the optimal
310 // length. The loop invariants are:
311 //
312 // min_young_length < max_young_length
313 // min_young_length is known to fit into the target pause time
314 // max_young_length is known not to fit into the target pause time
315 //
316 // Going into the loop we know the above hold as we've just
317 // checked them. Every time around the loop we check whether
318 // the middle value between min_young_length and
319 // max_young_length fits into the target pause time. If it
320 // does, it becomes the new min. If it doesn't, it becomes
321 // the new max. This way we maintain the loop invariants.
322
323 assert(min_young_length < max_young_length, "invariant");
324 uint diff = (max_young_length - min_young_length) / 2;
325 while (diff > 0) {
326 uint young_length = min_young_length + diff;
327 if (predict_will_fit(young_length, base_time_ms,
328 base_free_regions, target_pause_time_ms)) {
329 min_young_length = young_length;
330 } else {
331 max_young_length = young_length;
332 }
333 assert(min_young_length < max_young_length, "invariant");
334 diff = (max_young_length - min_young_length) / 2;
335 }
336 // The results is min_young_length which, according to the
337 // loop invariants, should fit within the target pause time.
338
339 // These are the post-conditions of the binary search above:
340 assert(min_young_length < max_young_length,
341 "otherwise we should have discovered that max_young_length "
342 "fits into the pause target and not done the binary search");
343 assert(predict_will_fit(min_young_length, base_time_ms,
344 base_free_regions, target_pause_time_ms),
345 "min_young_length, the result of the binary search, should "
346 "fit into the pause target");
347 assert(!predict_will_fit(min_young_length + 1, base_time_ms,
348 base_free_regions, target_pause_time_ms),
349 "min_young_length, the result of the binary search, should be "
350 "optimal, so no larger length should fit into the pause target");
351 }
352 } else {
353 // Even the minimum length doesn't fit into the pause time
354 // target, return it as the result nevertheless.
355 }
356 return base_min_length + min_young_length;
357 }
358
359 double G1DefaultPolicy::predict_survivor_regions_evac_time() const {
360 double survivor_regions_evac_time = 0.0;
361 for (HeapRegion * r = _g1->young_list()->first_survivor_region();
362 r != NULL && r != _g1->young_list()->last_survivor_region()->get_next_young_region();
363 r = r->get_next_young_region()) {
364 survivor_regions_evac_time += predict_region_elapsed_time_ms(r, collector_state()->gcs_are_young());
365 }
366 return survivor_regions_evac_time;
367 }
368
369 void G1DefaultPolicy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
370 guarantee( adaptive_young_list_length(), "should not call this otherwise" );
371
372 if (rs_lengths > _rs_lengths_prediction) {
373 // add 10% to avoid having to recalculate often
374 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
375 update_rs_lengths_prediction(rs_lengths_prediction);
376
377 update_young_list_max_and_target_length(rs_lengths_prediction);
378 }
379 }
380
381 void G1DefaultPolicy::update_rs_lengths_prediction() {
382 update_rs_lengths_prediction(_analytics->predict_rs_lengths());
383 }
384
385 void G1DefaultPolicy::update_rs_lengths_prediction(size_t prediction) {
386 if (collector_state()->gcs_are_young() && adaptive_young_list_length()) {
387 _rs_lengths_prediction = prediction;
388 }
389 }
390
391 #ifndef PRODUCT
392 bool G1DefaultPolicy::verify_young_ages() {
393 HeapRegion* head = _g1->young_list()->first_region();
394 return
395 verify_young_ages(head, _short_lived_surv_rate_group);
396 // also call verify_young_ages on any additional surv rate groups
397 }
398
399 bool G1DefaultPolicy::verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group) {
400 guarantee( surv_rate_group != NULL, "pre-condition" );
401
402 const char* name = surv_rate_group->name();
403 bool ret = true;
404 int prev_age = -1;
405
406 for (HeapRegion* curr = head;
407 curr != NULL;
408 curr = curr->get_next_young_region()) {
409 SurvRateGroup* group = curr->surv_rate_group();
410 if (group == NULL && !curr->is_survivor()) {
411 log_error(gc, verify)("## %s: encountered NULL surv_rate_group", name);
412 ret = false;
413 }
414
415 if (surv_rate_group == group) {
416 int age = curr->age_in_surv_rate_group();
417
418 if (age < 0) {
419 log_error(gc, verify)("## %s: encountered negative age", name);
420 ret = false;
421 }
422
423 if (age <= prev_age) {
424 log_error(gc, verify)("## %s: region ages are not strictly increasing (%d, %d)", name, age, prev_age);
425 ret = false;
426 }
427 prev_age = age;
428 }
429 }
430
431 return ret;
432 }
433 #endif // PRODUCT
434
435 void G1DefaultPolicy::record_full_collection_start() {
436 _full_collection_start_sec = os::elapsedTime();
437 // Release the future to-space so that it is available for compaction into.
438 collector_state()->set_full_collection(true);
439 }
440
441 void G1DefaultPolicy::record_full_collection_end() {
442 // Consider this like a collection pause for the purposes of allocation
443 // since last pause.
444 double end_sec = os::elapsedTime();
445 double full_gc_time_sec = end_sec - _full_collection_start_sec;
446 double full_gc_time_ms = full_gc_time_sec * 1000.0;
447
448 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);
449
450 collector_state()->set_full_collection(false);
451
452 // "Nuke" the heuristics that control the young/mixed GC
453 // transitions and make sure we start with young GCs after the Full GC.
454 collector_state()->set_gcs_are_young(true);
455 collector_state()->set_last_young_gc(false);
456 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
457 collector_state()->set_during_initial_mark_pause(false);
458 collector_state()->set_in_marking_window(false);
459 collector_state()->set_in_marking_window_im(false);
460
461 _short_lived_surv_rate_group->start_adding_regions();
462 // also call this on any additional surv rate groups
463
464 _free_regions_at_end_of_collection = _g1->num_free_regions();
465 // Reset survivors SurvRateGroup.
466 _survivor_surv_rate_group->reset();
467 update_young_list_max_and_target_length();
468 update_rs_lengths_prediction();
469 cset_chooser()->clear();
470
471 _bytes_allocated_in_old_since_last_gc = 0;
472
473 record_pause(FullGC, _full_collection_start_sec, end_sec);
474 }
475
476 void G1DefaultPolicy::record_collection_pause_start(double start_time_sec) {
477 // We only need to do this here as the policy will only be applied
478 // to the GC we're about to start. so, no point is calculating this
479 // every time we calculate / recalculate the target young length.
480 update_survivors_policy();
481
482 assert(_g1->used() == _g1->recalculate_used(),
483 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
484 _g1->used(), _g1->recalculate_used());
485
486 phase_times()->record_cur_collection_start_sec(start_time_sec);
487 _pending_cards = _g1->pending_card_num();
488
489 _collection_set->reset_bytes_used_before();
490 _bytes_copied_during_gc = 0;
491
492 collector_state()->set_last_gc_was_young(false);
493
494 // do that for any other surv rate groups
495 _short_lived_surv_rate_group->stop_adding_regions();
496 _survivors_age_table.clear();
497
498 assert( verify_young_ages(), "region age verification" );
499 }
500
501 void G1DefaultPolicy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {
502 collector_state()->set_during_marking(true);
503 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
504 collector_state()->set_during_initial_mark_pause(false);
505 }
506
507 void G1DefaultPolicy::record_concurrent_mark_remark_start() {
508 _mark_remark_start_sec = os::elapsedTime();
509 collector_state()->set_during_marking(false);
510 }
511
512 void G1DefaultPolicy::record_concurrent_mark_remark_end() {
513 double end_time_sec = os::elapsedTime();
514 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
515 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);
516 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
517
518 record_pause(Remark, _mark_remark_start_sec, end_time_sec);
519 }
520
521 void G1DefaultPolicy::record_concurrent_mark_cleanup_start() {
522 _mark_cleanup_start_sec = os::elapsedTime();
523 }
524
525 void G1DefaultPolicy::record_concurrent_mark_cleanup_completed() {
526 bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",
527 "skip last young-only gc");
528 collector_state()->set_last_young_gc(should_continue_with_reclaim);
529 // We skip the marking phase.
530 if (!should_continue_with_reclaim) {
531 abort_time_to_mixed_tracking();
532 }
533 collector_state()->set_in_marking_window(false);
534 }
535
536 double G1DefaultPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
537 return phase_times()->average_time_ms(phase);
538 }
539
540 double G1DefaultPolicy::young_other_time_ms() const {
541 return phase_times()->young_cset_choice_time_ms() +
542 phase_times()->young_free_cset_time_ms();
543 }
544
545 double G1DefaultPolicy::non_young_other_time_ms() const {
546 return phase_times()->non_young_cset_choice_time_ms() +
547 phase_times()->non_young_free_cset_time_ms();
548
549 }
550
551 double G1DefaultPolicy::other_time_ms(double pause_time_ms) const {
552 return pause_time_ms - phase_times()->cur_collection_par_time_ms();
553 }
554
555 double G1DefaultPolicy::constant_other_time_ms(double pause_time_ms) const {
556 return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms();
557 }
558
559 CollectionSetChooser* G1DefaultPolicy::cset_chooser() const {
560 return _collection_set->cset_chooser();
561 }
562
563 bool G1DefaultPolicy::about_to_start_mixed_phase() const {
564 return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc();
565 }
566
567 bool G1DefaultPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
568 if (about_to_start_mixed_phase()) {
569 return false;
570 }
571
572 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
573
574 size_t cur_used_bytes = _g1->non_young_capacity_bytes();
575 size_t alloc_byte_size = alloc_word_size * HeapWordSize;
576 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
577
578 bool result = false;
579 if (marking_request_bytes > marking_initiating_used_threshold) {
580 result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc();
581 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
582 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
583 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source);
584 }
585
586 return result;
587 }
588
589 // Anything below that is considered to be zero
590 #define MIN_TIMER_GRANULARITY 0.0000001
591
592 void G1DefaultPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
593 double end_time_sec = os::elapsedTime();
594
595 size_t cur_used_bytes = _g1->used();
596 assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
597 bool last_pause_included_initial_mark = false;
598 bool update_stats = !_g1->evacuation_failed();
599
600 NOT_PRODUCT(_short_lived_surv_rate_group->print());
601
602 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
603
604 last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();
605 if (last_pause_included_initial_mark) {
606 record_concurrent_mark_init_end(0.0);
607 } else {
608 maybe_start_marking();
609 }
610
611 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
612 if (app_time_ms < MIN_TIMER_GRANULARITY) {
613 // This usually happens due to the timer not having the required
614 // granularity. Some Linuxes are the usual culprits.
615 // We'll just set it to something (arbitrarily) small.
616 app_time_ms = 1.0;
617 }
618
619 if (update_stats) {
620 // We maintain the invariant that all objects allocated by mutator
621 // threads will be allocated out of eden regions. So, we can use
622 // the eden region number allocated since the previous GC to
623 // calculate the application's allocate rate. The only exception
624 // to that is humongous objects that are allocated separately. But
625 // given that humongous object allocations do not really affect
626 // either the pause's duration nor when the next pause will take
627 // place we can safely ignore them here.
628 uint regions_allocated = _collection_set->eden_region_length();
629 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
630 _analytics->report_alloc_rate_ms(alloc_rate_ms);
631
632 double interval_ms =
633 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;
634 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
635 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);
636 }
637
638 bool new_in_marking_window = collector_state()->in_marking_window();
639 bool new_in_marking_window_im = false;
640 if (last_pause_included_initial_mark) {
641 new_in_marking_window = true;
642 new_in_marking_window_im = true;
643 }
644
645 if (collector_state()->last_young_gc()) {
646 // This is supposed to to be the "last young GC" before we start
647 // doing mixed GCs. Here we decide whether to start mixed GCs or not.
648 assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC");
649
650 if (next_gc_should_be_mixed("start mixed GCs",
651 "do not start mixed GCs")) {
652 collector_state()->set_gcs_are_young(false);
653 } else {
654 // We aborted the mixed GC phase early.
655 abort_time_to_mixed_tracking();
656 }
657
658 collector_state()->set_last_young_gc(false);
659 }
660
661 if (!collector_state()->last_gc_was_young()) {
662 // This is a mixed GC. Here we decide whether to continue doing
663 // mixed GCs or not.
664 if (!next_gc_should_be_mixed("continue mixed GCs",
665 "do not continue mixed GCs")) {
666 collector_state()->set_gcs_are_young(true);
667
668 maybe_start_marking();
669 }
670 }
671
672 _short_lived_surv_rate_group->start_adding_regions();
673 // Do that for any other surv rate groups
674
675 double scan_hcc_time_ms = ConcurrentG1Refine::hot_card_cache_enabled() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
676
677 if (update_stats) {
678 double cost_per_card_ms = 0.0;
679 if (_pending_cards > 0) {
680 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards;
681 _analytics->report_cost_per_card_ms(cost_per_card_ms);
682 }
683 _analytics->report_cost_scan_hcc(scan_hcc_time_ms);
684
685 double cost_per_entry_ms = 0.0;
686 if (cards_scanned > 10) {
687 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
688 _analytics->report_cost_per_entry_ms(cost_per_entry_ms, collector_state()->last_gc_was_young());
689 }
690
691 if (_max_rs_lengths > 0) {
692 double cards_per_entry_ratio =
693 (double) cards_scanned / (double) _max_rs_lengths;
694 _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, collector_state()->last_gc_was_young());
695 }
696
697 // This is defensive. For a while _max_rs_lengths could get
698 // smaller than _recorded_rs_lengths which was causing
699 // rs_length_diff to get very large and mess up the RSet length
700 // predictions. The reason was unsafe concurrent updates to the
701 // _inc_cset_recorded_rs_lengths field which the code below guards
702 // against (see CR 7118202). This bug has now been fixed (see CR
703 // 7119027). However, I'm still worried that
704 // _inc_cset_recorded_rs_lengths might still end up somewhat
705 // inaccurate. The concurrent refinement thread calculates an
706 // RSet's length concurrently with other CR threads updating it
707 // which might cause it to calculate the length incorrectly (if,
708 // say, it's in mid-coarsening). So I'll leave in the defensive
709 // conditional below just in case.
710 size_t rs_length_diff = 0;
711 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();
712 if (_max_rs_lengths > recorded_rs_lengths) {
713 rs_length_diff = _max_rs_lengths - recorded_rs_lengths;
714 }
715 _analytics->report_rs_length_diff((double) rs_length_diff);
716
717 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
718 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
719 double cost_per_byte_ms = 0.0;
720
721 if (copied_bytes > 0) {
722 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
723 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->in_marking_window());
724 }
725
726 if (_collection_set->young_region_length() > 0) {
727 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
728 _collection_set->young_region_length());
729 }
730
731 if (_collection_set->old_region_length() > 0) {
732 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
733 _collection_set->old_region_length());
734 }
735
736 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
737
738 _analytics->report_pending_cards((double) _pending_cards);
739 _analytics->report_rs_lengths((double) _max_rs_lengths);
740 }
741
742 collector_state()->set_in_marking_window(new_in_marking_window);
743 collector_state()->set_in_marking_window_im(new_in_marking_window_im);
744 _free_regions_at_end_of_collection = _g1->num_free_regions();
745 // IHOP control wants to know the expected young gen length if it were not
746 // restrained by the heap reserve. Using the actual length would make the
747 // prediction too small and the limit the young gen every time we get to the
748 // predicted target occupancy.
749 size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
750 update_rs_lengths_prediction();
751
752 update_ihop_prediction(app_time_ms / 1000.0,
753 _bytes_allocated_in_old_since_last_gc,
754 last_unrestrained_young_length * HeapRegion::GrainBytes);
755 _bytes_allocated_in_old_since_last_gc = 0;
756
757 _ihop_control->send_trace_event(_g1->gc_tracer_stw());
758
759 // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
760 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
761
762 if (update_rs_time_goal_ms < scan_hcc_time_ms) {
763 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
764 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",
765 update_rs_time_goal_ms, scan_hcc_time_ms);
766
767 update_rs_time_goal_ms = 0;
768 } else {
769 update_rs_time_goal_ms -= scan_hcc_time_ms;
770 }
771 _g1->concurrent_g1_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms,
772 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
773 update_rs_time_goal_ms);
774
775 cset_chooser()->verify();
776 }
777
778 G1IHOPControl* G1DefaultPolicy::create_ihop_control(const G1Predictions* predictor){
779 if (G1UseAdaptiveIHOP) {
780 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
781 predictor,
782 G1ReservePercent,
783 G1HeapWastePercent);
784 } else {
785 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
786 }
787 }
788
789 void G1DefaultPolicy::update_ihop_prediction(double mutator_time_s,
790 size_t mutator_alloc_bytes,
791 size_t young_gen_size) {
792 // Always try to update IHOP prediction. Even evacuation failures give information
793 // about e.g. whether to start IHOP earlier next time.
794
795 // Avoid using really small application times that might create samples with
796 // very high or very low values. They may be caused by e.g. back-to-back gcs.
797 double const min_valid_time = 1e-6;
798
799 bool report = false;
800
801 double marking_to_mixed_time = -1.0;
802 if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) {
803 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
804 assert(marking_to_mixed_time > 0.0,
805 "Initial mark to mixed time must be larger than zero but is %.3f",
806 marking_to_mixed_time);
807 if (marking_to_mixed_time > min_valid_time) {
808 _ihop_control->update_marking_length(marking_to_mixed_time);
809 report = true;
810 }
811 }
812
813 // As an approximation for the young gc promotion rates during marking we use
814 // all of them. In many applications there are only a few if any young gcs during
815 // marking, which makes any prediction useless. This increases the accuracy of the
816 // prediction.
817 if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) {
818 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
819 report = true;
820 }
821
822 if (report) {
823 report_ihop_statistics();
824 }
825 }
826
827 void G1DefaultPolicy::report_ihop_statistics() {
828 _ihop_control->print();
829 }
830
831 void G1DefaultPolicy::print_phases() {
832 phase_times()->print();
833 }
834
835 double G1DefaultPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
836 TruncatedSeq* seq = surv_rate_group->get_seq(age);
837 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
838 double pred = _predictor.get_new_prediction(seq);
839 if (pred > 1.0) {
840 pred = 1.0;
841 }
842 return pred;
843 }
844
845 double G1DefaultPolicy::predict_yg_surv_rate(int age) const {
846 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
847 }
848
849 double G1DefaultPolicy::accum_yg_surv_rate_pred(int age) const {
850 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
851 }
852
853 double G1DefaultPolicy::predict_base_elapsed_time_ms(size_t pending_cards,
854 size_t scanned_cards) const {
855 return
856 _analytics->predict_rs_update_time_ms(pending_cards) +
857 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->gcs_are_young()) +
858 _analytics->predict_constant_other_time_ms();
859 }
860
861 double G1DefaultPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const {
862 size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff();
863 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->gcs_are_young());
864 return predict_base_elapsed_time_ms(pending_cards, card_num);
865 }
866
867 size_t G1DefaultPolicy::predict_bytes_to_copy(HeapRegion* hr) const {
868 size_t bytes_to_copy;
869 if (hr->is_marked())
870 bytes_to_copy = hr->max_live_bytes();
871 else {
872 assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
873 int age = hr->age_in_surv_rate_group();
874 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
875 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
876 }
877 return bytes_to_copy;
878 }
879
880 double G1DefaultPolicy::predict_region_elapsed_time_ms(HeapRegion* hr,
881 bool for_young_gc) const {
882 size_t rs_length = hr->rem_set()->occupied();
883 // Predicting the number of cards is based on which type of GC
884 // we're predicting for.
885 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc);
886 size_t bytes_to_copy = predict_bytes_to_copy(hr);
887
888 double region_elapsed_time_ms =
889 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->gcs_are_young()) +
890 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->during_concurrent_mark());
891
892 // The prediction of the "other" time for this region is based
893 // upon the region type and NOT the GC type.
894 if (hr->is_young()) {
895 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
896 } else {
897 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
898 }
899 return region_elapsed_time_ms;
900 }
901
902
903 void G1DefaultPolicy::print_yg_surv_rate_info() const {
904 #ifndef PRODUCT
905 _short_lived_surv_rate_group->print_surv_rate_summary();
906 // add this call for any other surv rate groups
907 #endif // PRODUCT
908 }
909
910 bool G1DefaultPolicy::should_allocate_mutator_region() const {
911 uint young_list_length = _g1->young_list()->length();
912 uint young_list_target_length = _young_list_target_length;
913 return young_list_length < young_list_target_length;
914 }
915
916 bool G1DefaultPolicy::can_expand_young_list() const {
917 uint young_list_length = _g1->young_list()->length();
918 uint young_list_max_length = _young_list_max_length;
919 return young_list_length < young_list_max_length;
920 }
921
922 bool G1DefaultPolicy::adaptive_young_list_length() const {
923 return _young_gen_sizer.adaptive_young_list_length();
924 }
925
926 void G1DefaultPolicy::update_max_gc_locker_expansion() {
927 uint expansion_region_num = 0;
928 if (GCLockerEdenExpansionPercent > 0) {
929 double perc = (double) GCLockerEdenExpansionPercent / 100.0;
930 double expansion_region_num_d = perc * (double) _young_list_target_length;
931 // We use ceiling so that if expansion_region_num_d is > 0.0 (but
932 // less than 1.0) we'll get 1.
933 expansion_region_num = (uint) ceil(expansion_region_num_d);
934 } else {
935 assert(expansion_region_num == 0, "sanity");
936 }
937 _young_list_max_length = _young_list_target_length + expansion_region_num;
938 assert(_young_list_target_length <= _young_list_max_length, "post-condition");
939 }
940
941 // Calculates survivor space parameters.
942 void G1DefaultPolicy::update_survivors_policy() {
943 double max_survivor_regions_d =
944 (double) _young_list_target_length / (double) SurvivorRatio;
945 // We use ceiling so that if max_survivor_regions_d is > 0.0 (but
946 // smaller than 1.0) we'll get 1.
947 _max_survivor_regions = (uint) ceil(max_survivor_regions_d);
948
949 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(
950 HeapRegion::GrainWords * _max_survivor_regions, _policy_counters);
951 }
952
953 bool G1DefaultPolicy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
954 // We actually check whether we are marking here and not if we are in a
955 // reclamation phase. This means that we will schedule a concurrent mark
956 // even while we are still in the process of reclaiming memory.
957 bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
958 if (!during_cycle) {
959 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
960 collector_state()->set_initiate_conc_mark_if_possible(true);
961 return true;
962 } else {
963 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
964 return false;
965 }
966 }
967
968 void G1DefaultPolicy::initiate_conc_mark() {
969 collector_state()->set_during_initial_mark_pause(true);
970 collector_state()->set_initiate_conc_mark_if_possible(false);
971 }
972
973 void G1DefaultPolicy::decide_on_conc_mark_initiation() {
974 // We are about to decide on whether this pause will be an
975 // initial-mark pause.
976
977 // First, collector_state()->during_initial_mark_pause() should not be already set. We
978 // will set it here if we have to. However, it should be cleared by
979 // the end of the pause (it's only set for the duration of an
980 // initial-mark pause).
981 assert(!collector_state()->during_initial_mark_pause(), "pre-condition");
982
983 if (collector_state()->initiate_conc_mark_if_possible()) {
984 // We had noticed on a previous pause that the heap occupancy has
985 // gone over the initiating threshold and we should start a
986 // concurrent marking cycle. So we might initiate one.
987
988 if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) {
989 // Initiate a new initial mark if there is no marking or reclamation going on.
990 initiate_conc_mark();
991 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
992 } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) {
993 // Initiate a user requested initial mark. An initial mark must be young only
994 // GC, so the collector state must be updated to reflect this.
995 collector_state()->set_gcs_are_young(true);
996 collector_state()->set_last_young_gc(false);
997
998 abort_time_to_mixed_tracking();
999 initiate_conc_mark();
1000 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1001 } else {
1002 // The concurrent marking thread is still finishing up the
1003 // previous cycle. If we start one right now the two cycles
1004 // overlap. In particular, the concurrent marking thread might
1005 // be in the process of clearing the next marking bitmap (which
1006 // we will use for the next cycle if we start one). Starting a
1007 // cycle now will be bad given that parts of the marking
1008 // information might get cleared by the marking thread. And we
1009 // cannot wait for the marking thread to finish the cycle as it
1010 // periodically yields while clearing the next marking bitmap
1011 // and, if it's in a yield point, it's waiting for us to
1012 // finish. So, at this point we will not start a cycle and we'll
1013 // let the concurrent marking thread complete the last one.
1014 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1015 }
1016 }
1017 }
1018
1019 void G1DefaultPolicy::record_concurrent_mark_cleanup_end() {
1020 cset_chooser()->rebuild(_g1->workers(), _g1->num_regions());
1021
1022 double end_sec = os::elapsedTime();
1023 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1024 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
1025 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
1026
1027 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1028 }
1029
1030 double G1DefaultPolicy::reclaimable_bytes_perc(size_t reclaimable_bytes) const {
1031 // Returns the given amount of reclaimable bytes (that represents
1032 // the amount of reclaimable space still to be collected) as a
1033 // percentage of the current heap capacity.
1034 size_t capacity_bytes = _g1->capacity();
1035 return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
1036 }
1037
1038 void G1DefaultPolicy::maybe_start_marking() {
1039 if (need_to_start_conc_mark("end of GC")) {
1040 // Note: this might have already been set, if during the last
1041 // pause we decided to start a cycle but at the beginning of
1042 // this pause we decided to postpone it. That's OK.
1043 collector_state()->set_initiate_conc_mark_if_possible(true);
1044 }
1045 }
1046
1047 G1DefaultPolicy::PauseKind G1DefaultPolicy::young_gc_pause_kind() const {
1048 assert(!collector_state()->full_collection(), "must be");
1049 if (collector_state()->during_initial_mark_pause()) {
1050 assert(collector_state()->last_gc_was_young(), "must be");
1051 assert(!collector_state()->last_young_gc(), "must be");
1052 return InitialMarkGC;
1053 } else if (collector_state()->last_young_gc()) {
1054 assert(!collector_state()->during_initial_mark_pause(), "must be");
1055 assert(collector_state()->last_gc_was_young(), "must be");
1056 return LastYoungGC;
1057 } else if (!collector_state()->last_gc_was_young()) {
1058 assert(!collector_state()->during_initial_mark_pause(), "must be");
1059 assert(!collector_state()->last_young_gc(), "must be");
1060 return MixedGC;
1061 } else {
1062 assert(collector_state()->last_gc_was_young(), "must be");
1063 assert(!collector_state()->during_initial_mark_pause(), "must be");
1064 assert(!collector_state()->last_young_gc(), "must be");
1065 return YoungOnlyGC;
1066 }
1067 }
1068
1069 void G1DefaultPolicy::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 G1DefaultPolicy::abort_time_to_mixed_tracking() {
1097 _initial_mark_to_mixed.reset();
1098 }
1099
1100 bool G1DefaultPolicy::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_perc = reclaimable_bytes_perc(reclaimable_bytes);
1110 double threshold = (double) G1HeapWastePercent;
1111 if (reclaimable_perc <= 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_perc, 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_perc, G1HeapWastePercent);
1118 return true;
1119 }
1120
1121 uint G1DefaultPolicy::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 G1DefaultPolicy::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 G1DefaultPolicy::finalize_collection_set(double target_pause_time_ms) {
1160 double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms);
1161 _collection_set->finalize_old_part(time_remaining_ms);
1162 }