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/growableArray.hpp"
45 #include "utilities/pair.hpp"
46
47 G1DefaultPolicy::G1DefaultPolicy() :
48 _predictor(G1ConfidencePercent / 100.0),
49 _analytics(new G1Analytics(&_predictor)),
50 _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)),
51 _ihop_control(create_ihop_control(&_predictor)),
52 _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 3)),
53 _young_list_fixed_length(0),
54 _short_lived_surv_rate_group(new SurvRateGroup(&_predictor, "Short Lived", G1YoungSurvRateNumRegionsSummary)),
55 _survivor_surv_rate_group(new SurvRateGroup(&_predictor, "Survivor", G1YoungSurvRateNumRegionsSummary)),
56 _reserve_factor((double) G1ReservePercent / 100.0),
57 _reserve_regions(0),
58 _rs_lengths_prediction(0),
59 _bytes_allocated_in_old_since_last_gc(0),
60 _initial_mark_to_mixed(),
61 _collection_set(NULL),
62 _g1(NULL),
63 _phase_times(new G1GCPhaseTimes(ParallelGCThreads)),
64 _tenuring_threshold(MaxTenuringThreshold),
65 _max_survivor_regions(0),
66 _survivors_age_table(true) { }
67
68 G1DefaultPolicy::~G1DefaultPolicy() {
69 delete _ihop_control;
70 }
71
72 G1CollectorState* G1DefaultPolicy::collector_state() const { return _g1->collector_state(); }
73
74 void G1DefaultPolicy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
75 _g1 = g1h;
76 _collection_set = collection_set;
77
78 assert(Heap_lock->owned_by_self(), "Locking discipline.");
79
80 if (!adaptive_young_list_length()) {
81 _young_list_fixed_length = _young_gen_sizer.min_desired_young_length();
82 }
83 _young_gen_sizer.adjust_max_new_size(_g1->max_regions());
84
85 _free_regions_at_end_of_collection = _g1->num_free_regions();
86
87 update_young_list_max_and_target_length();
88 // We may immediately start allocating regions and placing them on the
89 // collection set list. Initialize the per-collection set info
90 _collection_set->start_incremental_building();
91 }
92
93 void G1DefaultPolicy::note_gc_start() {
94 phase_times()->note_gc_start();
95 }
96
97 bool G1DefaultPolicy::predict_will_fit(uint young_length,
98 double base_time_ms,
99 uint base_free_regions,
100 double target_pause_time_ms) const {
101 if (young_length >= base_free_regions) {
102 // end condition 1: not enough space for the young regions
103 return false;
104 }
105
106 double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);
107 size_t bytes_to_copy =
108 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
109 double copy_time_ms = _analytics->predict_object_copy_time_ms(bytes_to_copy,
110 collector_state()->during_concurrent_mark());
111 double young_other_time_ms = _analytics->predict_young_other_time_ms(young_length);
112 double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;
113 if (pause_time_ms > target_pause_time_ms) {
114 // end condition 2: prediction is over the target pause time
115 return false;
116 }
117
118 size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes;
119
120 // When copying, we will likely need more bytes free than is live in the region.
121 // Add some safety margin to factor in the confidence of our guess, and the
122 // natural expected waste.
123 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
124 // of the calculation: the lower the confidence, the more headroom.
125 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
126 // copying due to anticipated waste in the PLABs.
127 double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
128 size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
129
130 if (expected_bytes_to_copy > free_bytes) {
131 // end condition 3: out-of-space
132 return false;
133 }
134
135 // success!
136 return true;
137 }
138
139 void G1DefaultPolicy::record_new_heap_size(uint new_number_of_regions) {
140 // re-calculate the necessary reserve
141 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
142 // We use ceiling so that if reserve_regions_d is > 0.0 (but
143 // smaller than 1.0) we'll get 1.
144 _reserve_regions = (uint) ceil(reserve_regions_d);
145
146 _young_gen_sizer.heap_size_changed(new_number_of_regions);
147
148 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
149 }
150
151 uint G1DefaultPolicy::calculate_young_list_desired_min_length(uint base_min_length) const {
152 uint desired_min_length = 0;
153 if (adaptive_young_list_length()) {
154 if (_analytics->num_alloc_rate_ms() > 3) {
155 double now_sec = os::elapsedTime();
156 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
157 double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
158 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
159 } else {
160 // otherwise we don't have enough info to make the prediction
161 }
162 }
163 desired_min_length += base_min_length;
164 // make sure we don't go below any user-defined minimum bound
165 return MAX2(_young_gen_sizer.min_desired_young_length(), desired_min_length);
166 }
167
168 uint G1DefaultPolicy::calculate_young_list_desired_max_length() const {
169 // Here, we might want to also take into account any additional
170 // constraints (i.e., user-defined minimum bound). Currently, we
171 // effectively don't set this bound.
172 return _young_gen_sizer.max_desired_young_length();
173 }
174
175 uint G1DefaultPolicy::update_young_list_max_and_target_length() {
176 return update_young_list_max_and_target_length(_analytics->predict_rs_lengths());
177 }
178
179 uint G1DefaultPolicy::update_young_list_max_and_target_length(size_t rs_lengths) {
180 uint unbounded_target_length = update_young_list_target_length(rs_lengths);
181 update_max_gc_locker_expansion();
182 return unbounded_target_length;
183 }
184
185 uint G1DefaultPolicy::update_young_list_target_length(size_t rs_lengths) {
186 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
187 _young_list_target_length = young_lengths.first;
188 return young_lengths.second;
189 }
190
191 G1DefaultPolicy::YoungTargetLengths G1DefaultPolicy::young_list_target_lengths(size_t rs_lengths) const {
192 YoungTargetLengths result;
193
194 // Calculate the absolute and desired min bounds first.
195
196 // This is how many young regions we already have (currently: the survivors).
197 const uint base_min_length = _g1->young_list()->survivor_length();
198 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
199 // This is the absolute minimum young length. Ensure that we
200 // will at least have one eden region available for allocation.
201 uint absolute_min_length = base_min_length + MAX2(_g1->young_list()->eden_length(), (uint)1);
202 // If we shrank the young list target it should not shrink below the current size.
203 desired_min_length = MAX2(desired_min_length, absolute_min_length);
204 // Calculate the absolute and desired max bounds.
205
206 uint desired_max_length = calculate_young_list_desired_max_length();
207
208 uint young_list_target_length = 0;
209 if (adaptive_young_list_length()) {
210 if (collector_state()->gcs_are_young()) {
211 young_list_target_length =
212 calculate_young_list_target_length(rs_lengths,
213 base_min_length,
214 desired_min_length,
215 desired_max_length);
216 } else {
217 // Don't calculate anything and let the code below bound it to
218 // the desired_min_length, i.e., do the next GC as soon as
219 // possible to maximize how many old regions we can add to it.
220 }
221 } else {
222 // The user asked for a fixed young gen so we'll fix the young gen
223 // whether the next GC is young or mixed.
224 young_list_target_length = _young_list_fixed_length;
225 }
226
227 result.second = young_list_target_length;
228
229 // We will try our best not to "eat" into the reserve.
230 uint absolute_max_length = 0;
231 if (_free_regions_at_end_of_collection > _reserve_regions) {
232 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
233 }
234 if (desired_max_length > absolute_max_length) {
235 desired_max_length = absolute_max_length;
236 }
237
238 // Make sure we don't go over the desired max length, nor under the
239 // desired min length. In case they clash, desired_min_length wins
240 // which is why that test is second.
241 if (young_list_target_length > desired_max_length) {
242 young_list_target_length = desired_max_length;
243 }
244 if (young_list_target_length < desired_min_length) {
245 young_list_target_length = desired_min_length;
246 }
247
248 assert(young_list_target_length > base_min_length,
249 "we should be able to allocate at least one eden region");
250 assert(young_list_target_length >= absolute_min_length, "post-condition");
251
252 result.first = young_list_target_length;
253 return result;
254 }
255
256 uint
257 G1DefaultPolicy::calculate_young_list_target_length(size_t rs_lengths,
258 uint base_min_length,
259 uint desired_min_length,
260 uint desired_max_length) const {
261 assert(adaptive_young_list_length(), "pre-condition");
262 assert(collector_state()->gcs_are_young(), "only call this for young GCs");
263
264 // In case some edge-condition makes the desired max length too small...
265 if (desired_max_length <= desired_min_length) {
266 return desired_min_length;
267 }
268
269 // We'll adjust min_young_length and max_young_length not to include
270 // the already allocated young regions (i.e., so they reflect the
271 // min and max eden regions we'll allocate). The base_min_length
272 // will be reflected in the predictions by the
273 // survivor_regions_evac_time prediction.
274 assert(desired_min_length > base_min_length, "invariant");
275 uint min_young_length = desired_min_length - base_min_length;
276 assert(desired_max_length > base_min_length, "invariant");
277 uint max_young_length = desired_max_length - base_min_length;
278
279 double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
280 double survivor_regions_evac_time = predict_survivor_regions_evac_time();
281 size_t pending_cards = _analytics->predict_pending_cards();
282 size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff();
283 size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, /* gcs_are_young */ true);
284 double base_time_ms =
285 predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
286 survivor_regions_evac_time;
287 uint available_free_regions = _free_regions_at_end_of_collection;
288 uint base_free_regions = 0;
289 if (available_free_regions > _reserve_regions) {
290 base_free_regions = available_free_regions - _reserve_regions;
291 }
292
293 // Here, we will make sure that the shortest young length that
294 // makes sense fits within the target pause time.
295
296 if (predict_will_fit(min_young_length, base_time_ms,
297 base_free_regions, target_pause_time_ms)) {
298 // The shortest young length will fit into the target pause time;
299 // we'll now check whether the absolute maximum number of young
300 // regions will fit in the target pause time. If not, we'll do
301 // a binary search between min_young_length and max_young_length.
302 if (predict_will_fit(max_young_length, base_time_ms,
303 base_free_regions, target_pause_time_ms)) {
304 // The maximum young length will fit into the target pause time.
305 // We are done so set min young length to the maximum length (as
306 // the result is assumed to be returned in min_young_length).
307 min_young_length = max_young_length;
308 } else {
309 // The maximum possible number of young regions will not fit within
310 // the target pause time so we'll search for the optimal
311 // length. The loop invariants are:
312 //
313 // min_young_length < max_young_length
314 // min_young_length is known to fit into the target pause time
315 // max_young_length is known not to fit into the target pause time
316 //
317 // Going into the loop we know the above hold as we've just
318 // checked them. Every time around the loop we check whether
319 // the middle value between min_young_length and
320 // max_young_length fits into the target pause time. If it
321 // does, it becomes the new min. If it doesn't, it becomes
322 // the new max. This way we maintain the loop invariants.
323
324 assert(min_young_length < max_young_length, "invariant");
325 uint diff = (max_young_length - min_young_length) / 2;
326 while (diff > 0) {
327 uint young_length = min_young_length + diff;
328 if (predict_will_fit(young_length, base_time_ms,
329 base_free_regions, target_pause_time_ms)) {
330 min_young_length = young_length;
331 } else {
332 max_young_length = young_length;
333 }
334 assert(min_young_length < max_young_length, "invariant");
335 diff = (max_young_length - min_young_length) / 2;
336 }
337 // The results is min_young_length which, according to the
338 // loop invariants, should fit within the target pause time.
339
340 // These are the post-conditions of the binary search above:
341 assert(min_young_length < max_young_length,
342 "otherwise we should have discovered that max_young_length "
343 "fits into the pause target and not done the binary search");
344 assert(predict_will_fit(min_young_length, base_time_ms,
345 base_free_regions, target_pause_time_ms),
346 "min_young_length, the result of the binary search, should "
347 "fit into the pause target");
348 assert(!predict_will_fit(min_young_length + 1, base_time_ms,
349 base_free_regions, target_pause_time_ms),
350 "min_young_length, the result of the binary search, should be "
351 "optimal, so no larger length should fit into the pause target");
352 }
353 } else {
354 // Even the minimum length doesn't fit into the pause time
355 // target, return it as the result nevertheless.
356 }
357 return base_min_length + min_young_length;
358 }
359
360 double G1DefaultPolicy::predict_survivor_regions_evac_time() const {
361 double survivor_regions_evac_time = 0.0;
362 const GrowableArray<HeapRegion*>* survivor_regions = _g1->young_list()->survivor_regions();
363
364 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin();
365 it != survivor_regions->end();
366 ++it) {
367 survivor_regions_evac_time += predict_region_elapsed_time_ms(*it, collector_state()->gcs_are_young());
368 }
369 return survivor_regions_evac_time;
370 }
371
372 void G1DefaultPolicy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
373 guarantee( adaptive_young_list_length(), "should not call this otherwise" );
374
375 if (rs_lengths > _rs_lengths_prediction) {
376 // add 10% to avoid having to recalculate often
377 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
378 update_rs_lengths_prediction(rs_lengths_prediction);
379
380 update_young_list_max_and_target_length(rs_lengths_prediction);
381 }
382 }
383
384 void G1DefaultPolicy::update_rs_lengths_prediction() {
385 update_rs_lengths_prediction(_analytics->predict_rs_lengths());
386 }
387
388 void G1DefaultPolicy::update_rs_lengths_prediction(size_t prediction) {
389 if (collector_state()->gcs_are_young() && adaptive_young_list_length()) {
390 _rs_lengths_prediction = prediction;
391 }
392 }
393
394 #ifndef PRODUCT
395 bool G1DefaultPolicy::verify_young_ages() {
396 HeapRegion* head = _g1->young_list()->first_region();
397 return
398 verify_young_ages(head, _short_lived_surv_rate_group);
399 // also call verify_young_ages on any additional surv rate groups
400 }
401
402 bool G1DefaultPolicy::verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group) {
403 guarantee( surv_rate_group != NULL, "pre-condition" );
404
405 const char* name = surv_rate_group->name();
406 bool ret = true;
407 int prev_age = -1;
408
409 for (HeapRegion* curr = head;
410 curr != NULL;
411 curr = curr->get_next_young_region()) {
412 SurvRateGroup* group = curr->surv_rate_group();
413 if (group == NULL && !curr->is_survivor()) {
414 log_error(gc, verify)("## %s: encountered NULL surv_rate_group", name);
415 ret = false;
416 }
417
418 if (surv_rate_group == group) {
419 int age = curr->age_in_surv_rate_group();
420
421 if (age < 0) {
422 log_error(gc, verify)("## %s: encountered negative age", name);
423 ret = false;
424 }
425
426 if (age <= prev_age) {
427 log_error(gc, verify)("## %s: region ages are not strictly increasing (%d, %d)", name, age, prev_age);
428 ret = false;
429 }
430 prev_age = age;
431 }
432 }
433
434 return ret;
435 }
436 #endif // PRODUCT
437
438 void G1DefaultPolicy::record_full_collection_start() {
439 _full_collection_start_sec = os::elapsedTime();
440 // Release the future to-space so that it is available for compaction into.
441 collector_state()->set_full_collection(true);
442 }
443
444 void G1DefaultPolicy::record_full_collection_end() {
445 // Consider this like a collection pause for the purposes of allocation
446 // since last pause.
447 double end_sec = os::elapsedTime();
448 double full_gc_time_sec = end_sec - _full_collection_start_sec;
449 double full_gc_time_ms = full_gc_time_sec * 1000.0;
450
451 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);
452
453 collector_state()->set_full_collection(false);
454
455 // "Nuke" the heuristics that control the young/mixed GC
456 // transitions and make sure we start with young GCs after the Full GC.
457 collector_state()->set_gcs_are_young(true);
458 collector_state()->set_last_young_gc(false);
459 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
460 collector_state()->set_during_initial_mark_pause(false);
461 collector_state()->set_in_marking_window(false);
462 collector_state()->set_in_marking_window_im(false);
463
464 _short_lived_surv_rate_group->start_adding_regions();
465 // also call this on any additional surv rate groups
466
467 _free_regions_at_end_of_collection = _g1->num_free_regions();
468 // Reset survivors SurvRateGroup.
469 _survivor_surv_rate_group->reset();
470 update_young_list_max_and_target_length();
471 update_rs_lengths_prediction();
472 cset_chooser()->clear();
473
474 _bytes_allocated_in_old_since_last_gc = 0;
475
476 record_pause(FullGC, _full_collection_start_sec, end_sec);
477 }
478
479 void G1DefaultPolicy::record_collection_pause_start(double start_time_sec) {
480 // We only need to do this here as the policy will only be applied
481 // to the GC we're about to start. so, no point is calculating this
482 // every time we calculate / recalculate the target young length.
483 update_survivors_policy();
484
485 assert(_g1->used() == _g1->recalculate_used(),
486 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
487 _g1->used(), _g1->recalculate_used());
488
489 phase_times()->record_cur_collection_start_sec(start_time_sec);
490 _pending_cards = _g1->pending_card_num();
491
492 _collection_set->reset_bytes_used_before();
493 _bytes_copied_during_gc = 0;
494
495 collector_state()->set_last_gc_was_young(false);
496
497 // do that for any other surv rate groups
498 _short_lived_surv_rate_group->stop_adding_regions();
499 _survivors_age_table.clear();
500
501 assert( verify_young_ages(), "region age verification" );
502 }
503
504 void G1DefaultPolicy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {
505 collector_state()->set_during_marking(true);
506 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
507 collector_state()->set_during_initial_mark_pause(false);
508 }
509
510 void G1DefaultPolicy::record_concurrent_mark_remark_start() {
511 _mark_remark_start_sec = os::elapsedTime();
512 collector_state()->set_during_marking(false);
513 }
514
515 void G1DefaultPolicy::record_concurrent_mark_remark_end() {
516 double end_time_sec = os::elapsedTime();
517 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
518 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);
519 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
520
521 record_pause(Remark, _mark_remark_start_sec, end_time_sec);
522 }
523
524 void G1DefaultPolicy::record_concurrent_mark_cleanup_start() {
525 _mark_cleanup_start_sec = os::elapsedTime();
526 }
527
528 void G1DefaultPolicy::record_concurrent_mark_cleanup_completed() {
529 bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",
530 "skip last young-only gc");
531 collector_state()->set_last_young_gc(should_continue_with_reclaim);
532 // We skip the marking phase.
533 if (!should_continue_with_reclaim) {
534 abort_time_to_mixed_tracking();
535 }
536 collector_state()->set_in_marking_window(false);
537 }
538
539 double G1DefaultPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
540 return phase_times()->average_time_ms(phase);
541 }
542
543 double G1DefaultPolicy::young_other_time_ms() const {
544 return phase_times()->young_cset_choice_time_ms() +
545 phase_times()->young_free_cset_time_ms();
546 }
547
548 double G1DefaultPolicy::non_young_other_time_ms() const {
549 return phase_times()->non_young_cset_choice_time_ms() +
550 phase_times()->non_young_free_cset_time_ms();
551
552 }
553
554 double G1DefaultPolicy::other_time_ms(double pause_time_ms) const {
555 return pause_time_ms - phase_times()->cur_collection_par_time_ms();
556 }
557
558 double G1DefaultPolicy::constant_other_time_ms(double pause_time_ms) const {
559 return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms();
560 }
561
562 CollectionSetChooser* G1DefaultPolicy::cset_chooser() const {
563 return _collection_set->cset_chooser();
564 }
565
566 bool G1DefaultPolicy::about_to_start_mixed_phase() const {
567 return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc();
568 }
569
570 bool G1DefaultPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
571 if (about_to_start_mixed_phase()) {
572 return false;
573 }
574
575 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
576
577 size_t cur_used_bytes = _g1->non_young_capacity_bytes();
578 size_t alloc_byte_size = alloc_word_size * HeapWordSize;
579 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
580
581 bool result = false;
582 if (marking_request_bytes > marking_initiating_used_threshold) {
583 result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc();
584 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
585 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
586 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source);
587 }
588
589 return result;
590 }
591
592 // Anything below that is considered to be zero
593 #define MIN_TIMER_GRANULARITY 0.0000001
594
595 void G1DefaultPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
596 double end_time_sec = os::elapsedTime();
597
598 size_t cur_used_bytes = _g1->used();
599 assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
600 bool last_pause_included_initial_mark = false;
601 bool update_stats = !_g1->evacuation_failed();
602
603 NOT_PRODUCT(_short_lived_surv_rate_group->print());
604
605 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
606
607 last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();
608 if (last_pause_included_initial_mark) {
609 record_concurrent_mark_init_end(0.0);
610 } else {
611 maybe_start_marking();
612 }
613
614 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
615 if (app_time_ms < MIN_TIMER_GRANULARITY) {
616 // This usually happens due to the timer not having the required
617 // granularity. Some Linuxes are the usual culprits.
618 // We'll just set it to something (arbitrarily) small.
619 app_time_ms = 1.0;
620 }
621
622 if (update_stats) {
623 // We maintain the invariant that all objects allocated by mutator
624 // threads will be allocated out of eden regions. So, we can use
625 // the eden region number allocated since the previous GC to
626 // calculate the application's allocate rate. The only exception
627 // to that is humongous objects that are allocated separately. But
628 // given that humongous object allocations do not really affect
629 // either the pause's duration nor when the next pause will take
630 // place we can safely ignore them here.
631 uint regions_allocated = _collection_set->eden_region_length();
632 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
633 _analytics->report_alloc_rate_ms(alloc_rate_ms);
634
635 double interval_ms =
636 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;
637 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
638 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);
639 }
640
641 bool new_in_marking_window = collector_state()->in_marking_window();
642 bool new_in_marking_window_im = false;
643 if (last_pause_included_initial_mark) {
644 new_in_marking_window = true;
645 new_in_marking_window_im = true;
646 }
647
648 if (collector_state()->last_young_gc()) {
649 // This is supposed to to be the "last young GC" before we start
650 // doing mixed GCs. Here we decide whether to start mixed GCs or not.
651 assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC");
652
653 if (next_gc_should_be_mixed("start mixed GCs",
654 "do not start mixed GCs")) {
655 collector_state()->set_gcs_are_young(false);
656 } else {
657 // We aborted the mixed GC phase early.
658 abort_time_to_mixed_tracking();
659 }
660
661 collector_state()->set_last_young_gc(false);
662 }
663
664 if (!collector_state()->last_gc_was_young()) {
665 // This is a mixed GC. Here we decide whether to continue doing
666 // mixed GCs or not.
667 if (!next_gc_should_be_mixed("continue mixed GCs",
668 "do not continue mixed GCs")) {
669 collector_state()->set_gcs_are_young(true);
670
671 maybe_start_marking();
672 }
673 }
674
675 _short_lived_surv_rate_group->start_adding_regions();
676 // Do that for any other surv rate groups
677
678 double scan_hcc_time_ms = ConcurrentG1Refine::hot_card_cache_enabled() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
679
680 if (update_stats) {
681 double cost_per_card_ms = 0.0;
682 if (_pending_cards > 0) {
683 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards;
684 _analytics->report_cost_per_card_ms(cost_per_card_ms);
685 }
686 _analytics->report_cost_scan_hcc(scan_hcc_time_ms);
687
688 double cost_per_entry_ms = 0.0;
689 if (cards_scanned > 10) {
690 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
691 _analytics->report_cost_per_entry_ms(cost_per_entry_ms, collector_state()->last_gc_was_young());
692 }
693
694 if (_max_rs_lengths > 0) {
695 double cards_per_entry_ratio =
696 (double) cards_scanned / (double) _max_rs_lengths;
697 _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, collector_state()->last_gc_was_young());
698 }
699
700 // This is defensive. For a while _max_rs_lengths could get
701 // smaller than _recorded_rs_lengths which was causing
702 // rs_length_diff to get very large and mess up the RSet length
703 // predictions. The reason was unsafe concurrent updates to the
704 // _inc_cset_recorded_rs_lengths field which the code below guards
705 // against (see CR 7118202). This bug has now been fixed (see CR
706 // 7119027). However, I'm still worried that
707 // _inc_cset_recorded_rs_lengths might still end up somewhat
708 // inaccurate. The concurrent refinement thread calculates an
709 // RSet's length concurrently with other CR threads updating it
710 // which might cause it to calculate the length incorrectly (if,
711 // say, it's in mid-coarsening). So I'll leave in the defensive
712 // conditional below just in case.
713 size_t rs_length_diff = 0;
714 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();
715 if (_max_rs_lengths > recorded_rs_lengths) {
716 rs_length_diff = _max_rs_lengths - recorded_rs_lengths;
717 }
718 _analytics->report_rs_length_diff((double) rs_length_diff);
719
720 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
721 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
722 double cost_per_byte_ms = 0.0;
723
724 if (copied_bytes > 0) {
725 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
726 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->in_marking_window());
727 }
728
729 if (_collection_set->young_region_length() > 0) {
730 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
731 _collection_set->young_region_length());
732 }
733
734 if (_collection_set->old_region_length() > 0) {
735 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
736 _collection_set->old_region_length());
737 }
738
739 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
740
741 _analytics->report_pending_cards((double) _pending_cards);
742 _analytics->report_rs_lengths((double) _max_rs_lengths);
743 }
744
745 collector_state()->set_in_marking_window(new_in_marking_window);
746 collector_state()->set_in_marking_window_im(new_in_marking_window_im);
747 _free_regions_at_end_of_collection = _g1->num_free_regions();
748 // IHOP control wants to know the expected young gen length if it were not
749 // restrained by the heap reserve. Using the actual length would make the
750 // prediction too small and the limit the young gen every time we get to the
751 // predicted target occupancy.
752 size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
753 update_rs_lengths_prediction();
754
755 update_ihop_prediction(app_time_ms / 1000.0,
756 _bytes_allocated_in_old_since_last_gc,
757 last_unrestrained_young_length * HeapRegion::GrainBytes);
758 _bytes_allocated_in_old_since_last_gc = 0;
759
760 _ihop_control->send_trace_event(_g1->gc_tracer_stw());
761
762 // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
763 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
764
765 if (update_rs_time_goal_ms < scan_hcc_time_ms) {
766 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
767 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",
768 update_rs_time_goal_ms, scan_hcc_time_ms);
769
770 update_rs_time_goal_ms = 0;
771 } else {
772 update_rs_time_goal_ms -= scan_hcc_time_ms;
773 }
774 _g1->concurrent_g1_refine()->adjust(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms,
775 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
776 update_rs_time_goal_ms);
777
778 cset_chooser()->verify();
779 }
780
781 G1IHOPControl* G1DefaultPolicy::create_ihop_control(const G1Predictions* predictor){
782 if (G1UseAdaptiveIHOP) {
783 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
784 predictor,
785 G1ReservePercent,
786 G1HeapWastePercent);
787 } else {
788 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
789 }
790 }
791
792 void G1DefaultPolicy::update_ihop_prediction(double mutator_time_s,
793 size_t mutator_alloc_bytes,
794 size_t young_gen_size) {
795 // Always try to update IHOP prediction. Even evacuation failures give information
796 // about e.g. whether to start IHOP earlier next time.
797
798 // Avoid using really small application times that might create samples with
799 // very high or very low values. They may be caused by e.g. back-to-back gcs.
800 double const min_valid_time = 1e-6;
801
802 bool report = false;
803
804 double marking_to_mixed_time = -1.0;
805 if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) {
806 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
807 assert(marking_to_mixed_time > 0.0,
808 "Initial mark to mixed time must be larger than zero but is %.3f",
809 marking_to_mixed_time);
810 if (marking_to_mixed_time > min_valid_time) {
811 _ihop_control->update_marking_length(marking_to_mixed_time);
812 report = true;
813 }
814 }
815
816 // As an approximation for the young gc promotion rates during marking we use
817 // all of them. In many applications there are only a few if any young gcs during
818 // marking, which makes any prediction useless. This increases the accuracy of the
819 // prediction.
820 if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) {
821 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
822 report = true;
823 }
824
825 if (report) {
826 report_ihop_statistics();
827 }
828 }
829
830 void G1DefaultPolicy::report_ihop_statistics() {
831 _ihop_control->print();
832 }
833
834 void G1DefaultPolicy::print_phases() {
835 phase_times()->print();
836 }
837
838 double G1DefaultPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
839 TruncatedSeq* seq = surv_rate_group->get_seq(age);
840 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
841 double pred = _predictor.get_new_prediction(seq);
842 if (pred > 1.0) {
843 pred = 1.0;
844 }
845 return pred;
846 }
847
848 double G1DefaultPolicy::predict_yg_surv_rate(int age) const {
849 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
850 }
851
852 double G1DefaultPolicy::accum_yg_surv_rate_pred(int age) const {
853 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
854 }
855
856 double G1DefaultPolicy::predict_base_elapsed_time_ms(size_t pending_cards,
857 size_t scanned_cards) const {
858 return
859 _analytics->predict_rs_update_time_ms(pending_cards) +
860 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->gcs_are_young()) +
861 _analytics->predict_constant_other_time_ms();
862 }
863
864 double G1DefaultPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const {
865 size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff();
866 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->gcs_are_young());
867 return predict_base_elapsed_time_ms(pending_cards, card_num);
868 }
869
870 size_t G1DefaultPolicy::predict_bytes_to_copy(HeapRegion* hr) const {
871 size_t bytes_to_copy;
872 if (hr->is_marked())
873 bytes_to_copy = hr->max_live_bytes();
874 else {
875 assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
876 int age = hr->age_in_surv_rate_group();
877 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
878 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
879 }
880 return bytes_to_copy;
881 }
882
883 double G1DefaultPolicy::predict_region_elapsed_time_ms(HeapRegion* hr,
884 bool for_young_gc) const {
885 size_t rs_length = hr->rem_set()->occupied();
886 // Predicting the number of cards is based on which type of GC
887 // we're predicting for.
888 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc);
889 size_t bytes_to_copy = predict_bytes_to_copy(hr);
890
891 double region_elapsed_time_ms =
892 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->gcs_are_young()) +
893 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->during_concurrent_mark());
894
895 // The prediction of the "other" time for this region is based
896 // upon the region type and NOT the GC type.
897 if (hr->is_young()) {
898 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
899 } else {
900 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
901 }
902 return region_elapsed_time_ms;
903 }
904
905
906 void G1DefaultPolicy::print_yg_surv_rate_info() const {
907 #ifndef PRODUCT
908 _short_lived_surv_rate_group->print_surv_rate_summary();
909 // add this call for any other surv rate groups
910 #endif // PRODUCT
911 }
912
913 bool G1DefaultPolicy::should_allocate_mutator_region() const {
914 uint young_list_length = _g1->young_list()->length();
915 uint young_list_target_length = _young_list_target_length;
916 return young_list_length < young_list_target_length;
917 }
918
919 bool G1DefaultPolicy::can_expand_young_list() const {
920 uint young_list_length = _g1->young_list()->length();
921 uint young_list_max_length = _young_list_max_length;
922 return young_list_length < young_list_max_length;
923 }
924
925 bool G1DefaultPolicy::adaptive_young_list_length() const {
926 return _young_gen_sizer.adaptive_young_list_length();
927 }
928
929 void G1DefaultPolicy::update_max_gc_locker_expansion() {
930 uint expansion_region_num = 0;
931 if (GCLockerEdenExpansionPercent > 0) {
932 double perc = (double) GCLockerEdenExpansionPercent / 100.0;
933 double expansion_region_num_d = perc * (double) _young_list_target_length;
934 // We use ceiling so that if expansion_region_num_d is > 0.0 (but
935 // less than 1.0) we'll get 1.
936 expansion_region_num = (uint) ceil(expansion_region_num_d);
937 } else {
938 assert(expansion_region_num == 0, "sanity");
939 }
940 _young_list_max_length = _young_list_target_length + expansion_region_num;
941 assert(_young_list_target_length <= _young_list_max_length, "post-condition");
942 }
943
944 // Calculates survivor space parameters.
945 void G1DefaultPolicy::update_survivors_policy() {
946 double max_survivor_regions_d =
947 (double) _young_list_target_length / (double) SurvivorRatio;
948 // We use ceiling so that if max_survivor_regions_d is > 0.0 (but
949 // smaller than 1.0) we'll get 1.
950 _max_survivor_regions = (uint) ceil(max_survivor_regions_d);
951
952 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(
953 HeapRegion::GrainWords * _max_survivor_regions, _policy_counters);
954 }
955
956 bool G1DefaultPolicy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
957 // We actually check whether we are marking here and not if we are in a
958 // reclamation phase. This means that we will schedule a concurrent mark
959 // even while we are still in the process of reclaiming memory.
960 bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
961 if (!during_cycle) {
962 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
963 collector_state()->set_initiate_conc_mark_if_possible(true);
964 return true;
965 } else {
966 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
967 return false;
968 }
969 }
970
971 void G1DefaultPolicy::initiate_conc_mark() {
972 collector_state()->set_during_initial_mark_pause(true);
973 collector_state()->set_initiate_conc_mark_if_possible(false);
974 }
975
976 void G1DefaultPolicy::decide_on_conc_mark_initiation() {
977 // We are about to decide on whether this pause will be an
978 // initial-mark pause.
979
980 // First, collector_state()->during_initial_mark_pause() should not be already set. We
981 // will set it here if we have to. However, it should be cleared by
982 // the end of the pause (it's only set for the duration of an
983 // initial-mark pause).
984 assert(!collector_state()->during_initial_mark_pause(), "pre-condition");
985
986 if (collector_state()->initiate_conc_mark_if_possible()) {
987 // We had noticed on a previous pause that the heap occupancy has
988 // gone over the initiating threshold and we should start a
989 // concurrent marking cycle. So we might initiate one.
990
991 if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) {
992 // Initiate a new initial mark if there is no marking or reclamation going on.
993 initiate_conc_mark();
994 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
995 } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) {
996 // Initiate a user requested initial mark. An initial mark must be young only
997 // GC, so the collector state must be updated to reflect this.
998 collector_state()->set_gcs_are_young(true);
999 collector_state()->set_last_young_gc(false);
1000
1001 abort_time_to_mixed_tracking();
1002 initiate_conc_mark();
1003 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1004 } else {
1005 // The concurrent marking thread is still finishing up the
1006 // previous cycle. If we start one right now the two cycles
1007 // overlap. In particular, the concurrent marking thread might
1008 // be in the process of clearing the next marking bitmap (which
1009 // we will use for the next cycle if we start one). Starting a
1010 // cycle now will be bad given that parts of the marking
1011 // information might get cleared by the marking thread. And we
1012 // cannot wait for the marking thread to finish the cycle as it
1013 // periodically yields while clearing the next marking bitmap
1014 // and, if it's in a yield point, it's waiting for us to
1015 // finish. So, at this point we will not start a cycle and we'll
1016 // let the concurrent marking thread complete the last one.
1017 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1018 }
1019 }
1020 }
1021
1022 void G1DefaultPolicy::record_concurrent_mark_cleanup_end() {
1023 cset_chooser()->rebuild(_g1->workers(), _g1->num_regions());
1024
1025 double end_sec = os::elapsedTime();
1026 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1027 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
1028 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
1029
1030 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1031 }
1032
1033 double G1DefaultPolicy::reclaimable_bytes_perc(size_t reclaimable_bytes) const {
1034 // Returns the given amount of reclaimable bytes (that represents
1035 // the amount of reclaimable space still to be collected) as a
1036 // percentage of the current heap capacity.
1037 size_t capacity_bytes = _g1->capacity();
1038 return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
1039 }
1040
1041 void G1DefaultPolicy::maybe_start_marking() {
1042 if (need_to_start_conc_mark("end of GC")) {
1043 // Note: this might have already been set, if during the last
1044 // pause we decided to start a cycle but at the beginning of
1045 // this pause we decided to postpone it. That's OK.
1046 collector_state()->set_initiate_conc_mark_if_possible(true);
1047 }
1048 }
1049
1050 G1DefaultPolicy::PauseKind G1DefaultPolicy::young_gc_pause_kind() const {
1051 assert(!collector_state()->full_collection(), "must be");
1052 if (collector_state()->during_initial_mark_pause()) {
1053 assert(collector_state()->last_gc_was_young(), "must be");
1054 assert(!collector_state()->last_young_gc(), "must be");
1055 return InitialMarkGC;
1056 } else if (collector_state()->last_young_gc()) {
1057 assert(!collector_state()->during_initial_mark_pause(), "must be");
1058 assert(collector_state()->last_gc_was_young(), "must be");
1059 return LastYoungGC;
1060 } else if (!collector_state()->last_gc_was_young()) {
1061 assert(!collector_state()->during_initial_mark_pause(), "must be");
1062 assert(!collector_state()->last_young_gc(), "must be");
1063 return MixedGC;
1064 } else {
1065 assert(collector_state()->last_gc_was_young(), "must be");
1066 assert(!collector_state()->during_initial_mark_pause(), "must be");
1067 assert(!collector_state()->last_young_gc(), "must be");
1068 return YoungOnlyGC;
1069 }
1070 }
1071
1072 void G1DefaultPolicy::record_pause(PauseKind kind, double start, double end) {
1073 // Manage the MMU tracker. For some reason it ignores Full GCs.
1074 if (kind != FullGC) {
1075 _mmu_tracker->add_pause(start, end);
1076 }
1077 // Manage the mutator time tracking from initial mark to first mixed gc.
1078 switch (kind) {
1079 case FullGC:
1080 abort_time_to_mixed_tracking();
1081 break;
1082 case Cleanup:
1083 case Remark:
1084 case YoungOnlyGC:
1085 case LastYoungGC:
1086 _initial_mark_to_mixed.add_pause(end - start);
1087 break;
1088 case InitialMarkGC:
1089 _initial_mark_to_mixed.record_initial_mark_end(end);
1090 break;
1091 case MixedGC:
1092 _initial_mark_to_mixed.record_mixed_gc_start(start);
1093 break;
1094 default:
1095 ShouldNotReachHere();
1096 }
1097 }
1098
1099 void G1DefaultPolicy::abort_time_to_mixed_tracking() {
1100 _initial_mark_to_mixed.reset();
1101 }
1102
1103 bool G1DefaultPolicy::next_gc_should_be_mixed(const char* true_action_str,
1104 const char* false_action_str) const {
1105 if (cset_chooser()->is_empty()) {
1106 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1107 return false;
1108 }
1109
1110 // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1111 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
1112 double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
1113 double threshold = (double) G1HeapWastePercent;
1114 if (reclaimable_perc <= threshold) {
1115 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1116 false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
1117 return false;
1118 }
1119 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1120 true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
1121 return true;
1122 }
1123
1124 uint G1DefaultPolicy::calc_min_old_cset_length() const {
1125 // The min old CSet region bound is based on the maximum desired
1126 // number of mixed GCs after a cycle. I.e., even if some old regions
1127 // look expensive, we should add them to the CSet anyway to make
1128 // sure we go through the available old regions in no more than the
1129 // maximum desired number of mixed GCs.
1130 //
1131 // The calculation is based on the number of marked regions we added
1132 // to the CSet chooser in the first place, not how many remain, so
1133 // that the result is the same during all mixed GCs that follow a cycle.
1134
1135 const size_t region_num = (size_t) cset_chooser()->length();
1136 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1137 size_t result = region_num / gc_num;
1138 // emulate ceiling
1139 if (result * gc_num < region_num) {
1140 result += 1;
1141 }
1142 return (uint) result;
1143 }
1144
1145 uint G1DefaultPolicy::calc_max_old_cset_length() const {
1146 // The max old CSet region bound is based on the threshold expressed
1147 // as a percentage of the heap size. I.e., it should bound the
1148 // number of old regions added to the CSet irrespective of how many
1149 // of them are available.
1150
1151 const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1152 const size_t region_num = g1h->num_regions();
1153 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1154 size_t result = region_num * perc / 100;
1155 // emulate ceiling
1156 if (100 * result < region_num * perc) {
1157 result += 1;
1158 }
1159 return (uint) result;
1160 }
1161
1162 void G1DefaultPolicy::finalize_collection_set(double target_pause_time_ms) {
1163 double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms);
1164 _collection_set->finalize_old_part(time_remaining_ms);
1165 }