1 /*
2 * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc/g1/g1Analytics.hpp"
27 #include "gc/g1/g1Arguments.hpp"
28 #include "gc/g1/g1CollectedHeap.inline.hpp"
29 #include "gc/g1/g1CollectionSet.hpp"
30 #include "gc/g1/g1CollectionSetCandidates.hpp"
31 #include "gc/g1/g1ConcurrentMark.hpp"
32 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
33 #include "gc/g1/g1ConcurrentRefine.hpp"
34 #include "gc/g1/g1CollectionSetChooser.hpp"
35 #include "gc/g1/g1HeterogeneousHeapPolicy.hpp"
36 #include "gc/g1/g1HotCardCache.hpp"
37 #include "gc/g1/g1IHOPControl.hpp"
38 #include "gc/g1/g1GCPhaseTimes.hpp"
39 #include "gc/g1/g1Policy.hpp"
40 #include "gc/g1/g1SurvivorRegions.hpp"
41 #include "gc/g1/g1YoungGenSizer.hpp"
42 #include "gc/g1/heapRegion.inline.hpp"
43 #include "gc/g1/heapRegionRemSet.hpp"
44 #include "gc/shared/gcPolicyCounters.hpp"
45 #include "logging/logStream.hpp"
46 #include "runtime/arguments.hpp"
47 #include "runtime/java.hpp"
48 #include "runtime/mutexLocker.hpp"
49 #include "utilities/debug.hpp"
50 #include "utilities/growableArray.hpp"
51 #include "utilities/pair.hpp"
52
53 G1Policy::G1Policy(STWGCTimer* gc_timer) :
54 _predictor(G1ConfidencePercent / 100.0),
55 _analytics(new G1Analytics(&_predictor)),
56 _remset_tracker(),
57 _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)),
58 _ihop_control(create_ihop_control(&_predictor)),
59 _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 2)),
60 _full_collection_start_sec(0.0),
61 _collection_pause_end_millis(os::javaTimeNanos() / NANOSECS_PER_MILLISEC),
62 _young_list_target_length(0),
63 _young_list_fixed_length(0),
64 _young_list_max_length(0),
65 _eden_surv_rate_group(new G1SurvRateGroup()),
66 _survivor_surv_rate_group(new G1SurvRateGroup()),
67 _reserve_factor((double) G1ReservePercent / 100.0),
68 _reserve_regions(0),
69 _young_gen_sizer(G1YoungGenSizer::create_gen_sizer()),
70 _free_regions_at_end_of_collection(0),
71 _rs_length(0),
72 _rs_length_prediction(0),
73 _pending_cards_at_gc_start(0),
74 _pending_cards_at_prev_gc_end(0),
75 _total_mutator_refined_cards(0),
76 _total_concurrent_refined_cards(0),
77 _total_concurrent_refinement_time(),
78 _bytes_allocated_in_old_since_last_gc(0),
79 _initial_mark_to_mixed(),
80 _collection_set(NULL),
81 _g1h(NULL),
82 _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)),
83 _mark_remark_start_sec(0),
84 _mark_cleanup_start_sec(0),
85 _tenuring_threshold(MaxTenuringThreshold),
86 _max_survivor_regions(0),
87 _survivors_age_table(true)
88 {
89 }
90
91 G1Policy::~G1Policy() {
92 delete _ihop_control;
93 delete _young_gen_sizer;
94 }
95
96 G1Policy* G1Policy::create_policy(STWGCTimer* gc_timer_stw) {
97 if (G1Arguments::is_heterogeneous_heap()) {
98 return new G1HeterogeneousHeapPolicy(gc_timer_stw);
99 } else {
100 return new G1Policy(gc_timer_stw);
101 }
102 }
103
104 G1CollectorState* G1Policy::collector_state() const { return _g1h->collector_state(); }
105
106 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
107 _g1h = g1h;
108 _collection_set = collection_set;
109
110 assert(Heap_lock->owned_by_self(), "Locking discipline.");
111
112 if (!use_adaptive_young_list_length()) {
113 _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
114 }
115 _young_gen_sizer->adjust_max_new_size(_g1h->max_expandable_regions());
116
117 _free_regions_at_end_of_collection = _g1h->num_free_regions();
118
119 update_young_list_max_and_target_length();
120 // We may immediately start allocating regions and placing them on the
121 // collection set list. Initialize the per-collection set info
122 _collection_set->start_incremental_building();
123 }
124
125 void G1Policy::note_gc_start() {
126 phase_times()->note_gc_start();
127 }
128
129 class G1YoungLengthPredictor {
130 const double _base_time_ms;
131 const double _base_free_regions;
132 const double _target_pause_time_ms;
133 const G1Policy* const _policy;
134
135 public:
136 G1YoungLengthPredictor(double base_time_ms,
137 double base_free_regions,
138 double target_pause_time_ms,
139 const G1Policy* policy) :
140 _base_time_ms(base_time_ms),
141 _base_free_regions(base_free_regions),
142 _target_pause_time_ms(target_pause_time_ms),
143 _policy(policy) {}
144
145 bool will_fit(uint young_length) const {
146 if (young_length >= _base_free_regions) {
147 // end condition 1: not enough space for the young regions
148 return false;
149 }
150
151 size_t bytes_to_copy = 0;
152 const double copy_time_ms = _policy->predict_eden_copy_time_ms(young_length, &bytes_to_copy);
153 const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length);
154 const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms;
155 if (pause_time_ms > _target_pause_time_ms) {
156 // end condition 2: prediction is over the target pause time
157 return false;
158 }
159
160 const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes;
161
162 // When copying, we will likely need more bytes free than is live in the region.
163 // Add some safety margin to factor in the confidence of our guess, and the
164 // natural expected waste.
165 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
166 // of the calculation: the lower the confidence, the more headroom.
167 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
168 // copying due to anticipated waste in the PLABs.
169 const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
170 const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
171
172 if (expected_bytes_to_copy > free_bytes) {
173 // end condition 3: out-of-space
174 return false;
175 }
176
177 // success!
178 return true;
179 }
180 };
181
182 void G1Policy::record_new_target_heap_size(uint new_number_of_regions, uint reserve_regions) {
183 _reserve_regions = reserve_regions;
184 _young_gen_sizer->heap_size_changed(new_number_of_regions);
185 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
186 }
187
188 void G1Policy::update_heap_target_size(uint num_regions, uint soft_goal_num_regions) {
189 uint desired_number_of_regions = MIN2(num_regions, soft_goal_num_regions);
190
191 uint regular_reserve_regions = (uint)ceil((double)num_regions * G1ReservePercent / 100);
192 uint reserve_regions = regular_reserve_regions;
193 uint soft_reserve_regions = 0;
194
195 if (soft_goal_num_regions < num_regions) {
196 soft_reserve_regions = num_regions - soft_goal_num_regions +
197 (uint)ceil((double)soft_goal_num_regions * G1ReservePercent / 100);
198 reserve_regions = soft_reserve_regions;
199 }
200
201 // FIXME: this method is called very early during startup during initial heap expansion, so
202 // the _g1h member has not been set yet.
203 G1CollectedHeap* g1h = G1CollectedHeap::heap();
204 uint MBPerRegion = HeapRegion::GrainBytes / (1024 * 1024);
205 log_error(gc)("heap target update: soft-goal %u committed %u goal %u hard-reserve %u soft-reserve %u reserve %u free %u used %u",
206 soft_goal_num_regions * MBPerRegion, num_regions * MBPerRegion,
207 desired_number_of_regions * MBPerRegion,
208 regular_reserve_regions * MBPerRegion, soft_reserve_regions * MBPerRegion, reserve_regions * MBPerRegion,
209 g1h->num_free_regions() * MBPerRegion, g1h->num_used_regions() * MBPerRegion);
210
211 record_new_target_heap_size(desired_number_of_regions, reserve_regions);
212 }
213
214 uint G1Policy::calculate_young_list_desired_min_length(uint base_min_length) const {
215 uint desired_min_length = 0;
216 if (use_adaptive_young_list_length()) {
217 if (_analytics->num_alloc_rate_ms() > 3) {
218 double now_sec = os::elapsedTime();
219 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
220 double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
221 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
222 } else {
223 // otherwise we don't have enough info to make the prediction
224 }
225 }
226 desired_min_length += base_min_length;
227 // make sure we don't go below any user-defined minimum bound
228 return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
229 }
230
231 uint G1Policy::calculate_young_list_desired_max_length() const {
232 // Here, we might want to also take into account any additional
233 // constraints (i.e., user-defined minimum bound). Currently, we
234 // effectively don't set this bound.
235 return _young_gen_sizer->max_desired_young_length();
236 }
237
238 uint G1Policy::update_young_list_max_and_target_length() {
239 return update_young_list_max_and_target_length(_analytics->predict_rs_length());
240 }
241
242 uint G1Policy::update_young_list_max_and_target_length(size_t rs_length) {
243 uint unbounded_target_length = update_young_list_target_length(rs_length);
244 update_max_gc_locker_expansion();
245 return unbounded_target_length;
246 }
247
248 uint G1Policy::update_young_list_target_length(size_t rs_length) {
249 YoungTargetLengths young_lengths = young_list_target_lengths(rs_length);
250 _young_list_target_length = young_lengths.first;
251
252 return young_lengths.second;
253 }
254
255 G1Policy::YoungTargetLengths G1Policy::young_list_target_lengths(size_t rs_length) const {
256 YoungTargetLengths result;
257
258 // Calculate the absolute and desired min bounds first.
259
260 // This is how many young regions we already have (currently: the survivors).
261 const uint base_min_length = _g1h->survivor_regions_count();
262 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
263 // This is the absolute minimum young length. Ensure that we
264 // will at least have one eden region available for allocation.
265 uint absolute_min_length = base_min_length + MAX2(_g1h->eden_regions_count(), (uint)1);
266 // If we shrank the young list target it should not shrink below the current size.
267 desired_min_length = MAX2(desired_min_length, absolute_min_length);
268 // Calculate the absolute and desired max bounds.
269
270 uint desired_max_length = calculate_young_list_desired_max_length();
271
272 uint young_list_target_length = 0;
273 if (use_adaptive_young_list_length()) {
274 if (collector_state()->in_young_only_phase()) {
275 young_list_target_length =
276 calculate_young_list_target_length(rs_length,
277 base_min_length,
278 desired_min_length,
279 desired_max_length);
280 } else {
281 // Don't calculate anything and let the code below bound it to
282 // the desired_min_length, i.e., do the next GC as soon as
283 // possible to maximize how many old regions we can add to it.
284 }
285 } else {
286 // The user asked for a fixed young gen so we'll fix the young gen
287 // whether the next GC is young or mixed.
288 young_list_target_length = _young_list_fixed_length;
289 }
290
291 result.second = young_list_target_length;
292
293 // We will try our best not to "eat" into the reserve.
294 uint absolute_max_length = 0;
295 if (_free_regions_at_end_of_collection > _reserve_regions) {
296 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
297 }
298 if (desired_max_length > absolute_max_length) {
299 desired_max_length = absolute_max_length;
300 }
301
302 // Make sure we don't go over the desired max length, nor under the
303 // desired min length. In case they clash, desired_min_length wins
304 // which is why that test is second.
305 if (young_list_target_length > desired_max_length) {
306 young_list_target_length = desired_max_length;
307 }
308 if (young_list_target_length < desired_min_length) {
309 young_list_target_length = desired_min_length;
310 }
311
312 assert(young_list_target_length > base_min_length,
313 "we should be able to allocate at least one eden region");
314 assert(young_list_target_length >= absolute_min_length, "post-condition");
315
316 result.first = young_list_target_length;
317 return result;
318 }
319
320 uint G1Policy::calculate_young_list_target_length(size_t rs_length,
321 uint base_min_length,
322 uint desired_min_length,
323 uint desired_max_length) const {
324 assert(use_adaptive_young_list_length(), "pre-condition");
325 assert(collector_state()->in_young_only_phase(), "only call this for young GCs");
326
327 // In case some edge-condition makes the desired max length too small...
328 if (desired_max_length <= desired_min_length) {
329 return desired_min_length;
330 }
331
332 // We'll adjust min_young_length and max_young_length not to include
333 // the already allocated young regions (i.e., so they reflect the
334 // min and max eden regions we'll allocate). The base_min_length
335 // will be reflected in the predictions by the
336 // survivor_regions_evac_time prediction.
337 assert(desired_min_length > base_min_length, "invariant");
338 uint min_young_length = desired_min_length - base_min_length;
339 assert(desired_max_length > base_min_length, "invariant");
340 uint max_young_length = desired_max_length - base_min_length;
341
342 const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
343 const size_t pending_cards = _analytics->predict_pending_cards();
344 const double base_time_ms = predict_base_elapsed_time_ms(pending_cards, rs_length);
345 const uint available_free_regions = _free_regions_at_end_of_collection;
346 const uint base_free_regions =
347 available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0;
348
349 // Here, we will make sure that the shortest young length that
350 // makes sense fits within the target pause time.
351
352 G1YoungLengthPredictor p(base_time_ms,
353 base_free_regions,
354 target_pause_time_ms,
355 this);
356 if (p.will_fit(min_young_length)) {
357 // The shortest young length will fit into the target pause time;
358 // we'll now check whether the absolute maximum number of young
359 // regions will fit in the target pause time. If not, we'll do
360 // a binary search between min_young_length and max_young_length.
361 if (p.will_fit(max_young_length)) {
362 // The maximum young length will fit into the target pause time.
363 // We are done so set min young length to the maximum length (as
364 // the result is assumed to be returned in min_young_length).
365 min_young_length = max_young_length;
366 } else {
367 // The maximum possible number of young regions will not fit within
368 // the target pause time so we'll search for the optimal
369 // length. The loop invariants are:
370 //
371 // min_young_length < max_young_length
372 // min_young_length is known to fit into the target pause time
373 // max_young_length is known not to fit into the target pause time
374 //
375 // Going into the loop we know the above hold as we've just
376 // checked them. Every time around the loop we check whether
377 // the middle value between min_young_length and
378 // max_young_length fits into the target pause time. If it
379 // does, it becomes the new min. If it doesn't, it becomes
380 // the new max. This way we maintain the loop invariants.
381
382 assert(min_young_length < max_young_length, "invariant");
383 uint diff = (max_young_length - min_young_length) / 2;
384 while (diff > 0) {
385 uint young_length = min_young_length + diff;
386 if (p.will_fit(young_length)) {
387 min_young_length = young_length;
388 } else {
389 max_young_length = young_length;
390 }
391 assert(min_young_length < max_young_length, "invariant");
392 diff = (max_young_length - min_young_length) / 2;
393 }
394 // The results is min_young_length which, according to the
395 // loop invariants, should fit within the target pause time.
396
397 // These are the post-conditions of the binary search above:
398 assert(min_young_length < max_young_length,
399 "otherwise we should have discovered that max_young_length "
400 "fits into the pause target and not done the binary search");
401 assert(p.will_fit(min_young_length),
402 "min_young_length, the result of the binary search, should "
403 "fit into the pause target");
404 assert(!p.will_fit(min_young_length + 1),
405 "min_young_length, the result of the binary search, should be "
406 "optimal, so no larger length should fit into the pause target");
407 }
408 } else {
409 // Even the minimum length doesn't fit into the pause time
410 // target, return it as the result nevertheless.
411 }
412 return base_min_length + min_young_length;
413 }
414
415 double G1Policy::predict_survivor_regions_evac_time() const {
416 double survivor_regions_evac_time = 0.0;
417 const GrowableArray<HeapRegion*>* survivor_regions = _g1h->survivor()->regions();
418 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin();
419 it != survivor_regions->end();
420 ++it) {
421 survivor_regions_evac_time += predict_region_total_time_ms(*it, collector_state()->in_young_only_phase());
422 }
423 return survivor_regions_evac_time;
424 }
425
426 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_length) {
427 guarantee(use_adaptive_young_list_length(), "should not call this otherwise" );
428
429 if (rs_length > _rs_length_prediction) {
430 // add 10% to avoid having to recalculate often
431 size_t rs_length_prediction = rs_length * 1100 / 1000;
432 update_rs_length_prediction(rs_length_prediction);
433
434 update_young_list_max_and_target_length(rs_length_prediction);
435 }
436 }
437
438 void G1Policy::update_rs_length_prediction() {
439 update_rs_length_prediction(_analytics->predict_rs_length());
440 }
441
442 void G1Policy::update_rs_length_prediction(size_t prediction) {
443 if (collector_state()->in_young_only_phase() && use_adaptive_young_list_length()) {
444 _rs_length_prediction = prediction;
445 }
446 }
447
448 void G1Policy::record_full_collection_start() {
449 _full_collection_start_sec = os::elapsedTime();
450 // Release the future to-space so that it is available for compaction into.
451 collector_state()->set_in_young_only_phase(false);
452 collector_state()->set_in_full_gc(true);
453 _collection_set->clear_candidates();
454 record_concurrent_refinement_data(true /* is_full_collection */);
455 }
456
457 void G1Policy::record_full_collection_end() {
458 // Consider this like a collection pause for the purposes of allocation
459 // since last pause.
460 double end_sec = os::elapsedTime();
461 double full_gc_time_sec = end_sec - _full_collection_start_sec;
462 double full_gc_time_ms = full_gc_time_sec * 1000.0;
463
464 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);
465
466 collector_state()->set_in_full_gc(false);
467
468 // "Nuke" the heuristics that control the young/mixed GC
469 // transitions and make sure we start with young GCs after the Full GC.
470 collector_state()->set_in_young_only_phase(true);
471 collector_state()->set_in_young_gc_before_mixed(false);
472 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
473 collector_state()->set_in_initial_mark_gc(false);
474 collector_state()->set_mark_or_rebuild_in_progress(false);
475 collector_state()->set_clearing_next_bitmap(false);
476
477 _eden_surv_rate_group->start_adding_regions();
478 // also call this on any additional surv rate groups
479
480 _free_regions_at_end_of_collection = _g1h->num_free_regions();
481 _survivor_surv_rate_group->reset();
482 update_young_list_max_and_target_length();
483 update_rs_length_prediction();
484 _pending_cards_at_prev_gc_end = _g1h->pending_card_num();
485
486 _bytes_allocated_in_old_since_last_gc = 0;
487
488 record_pause(FullGC, _full_collection_start_sec, end_sec);
489 }
490
491 void G1Policy::record_concurrent_refinement_data(bool is_full_collection) {
492 _pending_cards_at_gc_start = _g1h->pending_card_num();
493
494 // Record info about concurrent refinement thread processing.
495 G1ConcurrentRefine* cr = _g1h->concurrent_refine();
496 G1ConcurrentRefine::RefinementStats cr_stats = cr->total_refinement_stats();
497
498 Tickspan cr_time = cr_stats._time - _total_concurrent_refinement_time;
499 _total_concurrent_refinement_time = cr_stats._time;
500
501 size_t cr_cards = cr_stats._cards - _total_concurrent_refined_cards;
502 _total_concurrent_refined_cards = cr_stats._cards;
503
504 // Don't update rate if full collection. We could be in an implicit full
505 // collection after a non-full collection failure, in which case there
506 // wasn't any mutator/cr-thread activity since last recording. And if
507 // we're in an explicit full collection, the time since the last GC can
508 // be arbitrarily short, so not a very good sample. Similarly, don't
509 // update the rate if the current sample is empty or time is zero.
510 if (!is_full_collection && (cr_cards > 0) && (cr_time > Tickspan())) {
511 double rate = cr_cards / (cr_time.seconds() * MILLIUNITS);
512 _analytics->report_concurrent_refine_rate_ms(rate);
513 }
514
515 // Record info about mutator thread processing.
516 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
517 size_t mut_total_cards = dcqs.total_mutator_refined_cards();
518 size_t mut_cards = mut_total_cards - _total_mutator_refined_cards;
519 _total_mutator_refined_cards = mut_total_cards;
520
521 // Record mutator's card logging rate.
522 // Don't update if full collection; see above.
523 if (!is_full_collection) {
524 size_t total_cards = _pending_cards_at_gc_start + cr_cards + mut_cards;
525 assert(_pending_cards_at_prev_gc_end <= total_cards,
526 "untracked cards: last pending: " SIZE_FORMAT
527 ", pending: " SIZE_FORMAT ", conc refine: " SIZE_FORMAT
528 ", mut refine:" SIZE_FORMAT,
529 _pending_cards_at_prev_gc_end, _pending_cards_at_gc_start,
530 cr_cards, mut_cards);
531 size_t logged_cards = total_cards - _pending_cards_at_prev_gc_end;
532 double logging_start_time = _analytics->prev_collection_pause_end_ms();
533 double logging_end_time = Ticks::now().seconds() * MILLIUNITS;
534 double logging_time = logging_end_time - logging_start_time;
535 // Unlike above for conc-refine rate, here we should not require a
536 // non-empty sample, since an application could go some time with only
537 // young-gen or filtered out writes. But we'll ignore unusually short
538 // sample periods, as they may just pollute the predictions.
539 if (logging_time > 1.0) { // Require > 1ms sample time.
540 _analytics->report_logged_cards_rate_ms(logged_cards / logging_time);
541 }
542 }
543 }
544
545 void G1Policy::record_collection_pause_start(double start_time_sec) {
546 // We only need to do this here as the policy will only be applied
547 // to the GC we're about to start. so, no point is calculating this
548 // every time we calculate / recalculate the target young length.
549 update_survivors_policy();
550
551 assert(max_survivor_regions() + _g1h->num_used_regions() <= _g1h->max_regions(),
552 "Maximum survivor regions %u plus used regions %u exceeds max regions %u",
553 max_survivor_regions(), _g1h->num_used_regions(), _g1h->max_regions());
554 assert_used_and_recalculate_used_equal(_g1h);
555
556 phase_times()->record_cur_collection_start_sec(start_time_sec);
557
558 record_concurrent_refinement_data(false /* is_full_collection */);
559
560 _collection_set->reset_bytes_used_before();
561
562 // do that for any other surv rate groups
563 _eden_surv_rate_group->stop_adding_regions();
564 _survivors_age_table.clear();
565
566 assert(_g1h->collection_set()->verify_young_ages(), "region age verification failed");
567 }
568
569 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {
570 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
571 collector_state()->set_in_initial_mark_gc(false);
572 }
573
574 void G1Policy::record_concurrent_mark_remark_start() {
575 _mark_remark_start_sec = os::elapsedTime();
576 }
577
578 void G1Policy::record_concurrent_mark_remark_end() {
579 double end_time_sec = os::elapsedTime();
580 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
581 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);
582 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
583
584 record_pause(Remark, _mark_remark_start_sec, end_time_sec);
585 }
586
587 void G1Policy::record_concurrent_mark_cleanup_start() {
588 _mark_cleanup_start_sec = os::elapsedTime();
589 }
590
591 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
592 return phase_times()->average_time_ms(phase);
593 }
594
595 double G1Policy::young_other_time_ms() const {
596 return phase_times()->young_cset_choice_time_ms() +
597 phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet);
598 }
599
600 double G1Policy::non_young_other_time_ms() const {
601 return phase_times()->non_young_cset_choice_time_ms() +
602 phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet);
603 }
604
605 double G1Policy::other_time_ms(double pause_time_ms) const {
606 return pause_time_ms - phase_times()->cur_collection_par_time_ms();
607 }
608
609 double G1Policy::constant_other_time_ms(double pause_time_ms) const {
610 return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms() - phase_times()->total_rebuild_freelist_time_ms();
611 }
612
613 bool G1Policy::about_to_start_mixed_phase() const {
614 return _g1h->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->in_young_gc_before_mixed();
615 }
616
617 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
618 if (about_to_start_mixed_phase()) {
619 return false;
620 }
621
622 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
623
624 size_t cur_used_bytes = _g1h->non_young_capacity_bytes();
625 size_t alloc_byte_size = alloc_word_size * HeapWordSize;
626 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
627
628 bool result = false;
629 if (marking_request_bytes > marking_initiating_used_threshold) {
630 result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed();
631 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
632 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
633 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1h->capacity() * 100, source);
634 }
635
636 return result;
637 }
638
639 double G1Policy::logged_cards_processing_time() const {
640 double all_cards_processing_time = average_time_ms(G1GCPhaseTimes::ScanHR) + average_time_ms(G1GCPhaseTimes::OptScanHR);
641 size_t logged_dirty_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards);
642 size_t scan_heap_roots_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) +
643 phase_times()->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards);
644 // This may happen if there are duplicate cards in different log buffers.
645 if (logged_dirty_cards > scan_heap_roots_cards) {
646 return all_cards_processing_time + average_time_ms(G1GCPhaseTimes::MergeLB);
647 }
648 return (all_cards_processing_time * logged_dirty_cards / scan_heap_roots_cards) + average_time_ms(G1GCPhaseTimes::MergeLB);
649 }
650
651 // Anything below that is considered to be zero
652 #define MIN_TIMER_GRANULARITY 0.0000001
653
654 void G1Policy::record_collection_pause_end(double pause_time_ms) {
655 G1GCPhaseTimes* p = phase_times();
656
657 double end_time_sec = os::elapsedTime();
658
659 bool this_pause_included_initial_mark = false;
660 bool this_pause_was_young_only = collector_state()->in_young_only_phase();
661
662 bool update_stats = !_g1h->evacuation_failed();
663
664 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
665
666 _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
667
668 this_pause_included_initial_mark = collector_state()->in_initial_mark_gc();
669 if (this_pause_included_initial_mark) {
670 record_concurrent_mark_init_end(0.0);
671 } else {
672 maybe_start_marking();
673 }
674
675 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
676 if (app_time_ms < MIN_TIMER_GRANULARITY) {
677 // This usually happens due to the timer not having the required
678 // granularity. Some Linuxes are the usual culprits.
679 // We'll just set it to something (arbitrarily) small.
680 app_time_ms = 1.0;
681 }
682
683 if (update_stats) {
684 // We maintain the invariant that all objects allocated by mutator
685 // threads will be allocated out of eden regions. So, we can use
686 // the eden region number allocated since the previous GC to
687 // calculate the application's allocate rate. The only exception
688 // to that is humongous objects that are allocated separately. But
689 // given that humongous object allocations do not really affect
690 // either the pause's duration nor when the next pause will take
691 // place we can safely ignore them here.
692 uint regions_allocated = _collection_set->eden_region_length();
693 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
694 _analytics->report_alloc_rate_ms(alloc_rate_ms);
695
696 double interval_ms =
697 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;
698 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
699 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);
700 }
701
702 if (collector_state()->in_young_gc_before_mixed()) {
703 assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC");
704 // This has been the young GC before we start doing mixed GCs. We already
705 // decided to start mixed GCs much earlier, so there is nothing to do except
706 // advancing the state.
707 collector_state()->set_in_young_only_phase(false);
708 collector_state()->set_in_young_gc_before_mixed(false);
709 } else if (!this_pause_was_young_only) {
710 // This is a mixed GC. Here we decide whether to continue doing more
711 // mixed GCs or not.
712 if (!next_gc_should_be_mixed("continue mixed GCs",
713 "do not continue mixed GCs")) {
714 collector_state()->set_in_young_only_phase(true);
715
716 clear_collection_set_candidates();
717 maybe_start_marking();
718 }
719 }
720
721 _eden_surv_rate_group->start_adding_regions();
722
723 double merge_hcc_time_ms = average_time_ms(G1GCPhaseTimes::MergeHCC);
724 if (update_stats) {
725 size_t const total_log_buffer_cards = p->sum_thread_work_items(G1GCPhaseTimes::MergeHCC, G1GCPhaseTimes::MergeHCCDirtyCards) +
726 p->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards);
727 // Update prediction for card merge; MergeRSDirtyCards includes the cards from the Eager Reclaim phase.
728 size_t const total_cards_merged = p->sum_thread_work_items(G1GCPhaseTimes::MergeRS, G1GCPhaseTimes::MergeRSDirtyCards) +
729 p->sum_thread_work_items(G1GCPhaseTimes::OptMergeRS, G1GCPhaseTimes::MergeRSDirtyCards) +
730 total_log_buffer_cards;
731
732 // The threshold for the number of cards in a given sampling which we consider
733 // large enough so that the impact from setup and other costs is negligible.
734 size_t const CardsNumSamplingThreshold = 10;
735
736 if (total_cards_merged > CardsNumSamplingThreshold) {
737 double avg_time_merge_cards = average_time_ms(G1GCPhaseTimes::MergeER) +
738 average_time_ms(G1GCPhaseTimes::MergeRS) +
739 average_time_ms(G1GCPhaseTimes::MergeHCC) +
740 average_time_ms(G1GCPhaseTimes::MergeLB) +
741 average_time_ms(G1GCPhaseTimes::OptMergeRS);
742 _analytics->report_cost_per_card_merge_ms(avg_time_merge_cards / total_cards_merged, this_pause_was_young_only);
743 }
744
745 // Update prediction for card scan
746 size_t const total_cards_scanned = p->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) +
747 p->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards);
748
749 if (total_cards_scanned > CardsNumSamplingThreshold) {
750 double avg_time_dirty_card_scan = average_time_ms(G1GCPhaseTimes::ScanHR) +
751 average_time_ms(G1GCPhaseTimes::OptScanHR);
752
753 _analytics->report_cost_per_card_scan_ms(avg_time_dirty_card_scan / total_cards_scanned, this_pause_was_young_only);
754 }
755
756 // Update prediction for the ratio between cards from the remembered
757 // sets and actually scanned cards from the remembered sets.
758 // Cards from the remembered sets are all cards not duplicated by cards from
759 // the logs.
760 // Due to duplicates in the log buffers, the number of actually scanned cards
761 // can be smaller than the cards in the log buffers.
762 const size_t from_rs_length_cards = (total_cards_scanned > total_log_buffer_cards) ? total_cards_scanned - total_log_buffer_cards : 0;
763 double merge_to_scan_ratio = 0.0;
764 if (total_cards_scanned > 0) {
765 merge_to_scan_ratio = (double) from_rs_length_cards / total_cards_scanned;
766 }
767 _analytics->report_card_merge_to_scan_ratio(merge_to_scan_ratio, this_pause_was_young_only);
768
769 const size_t recorded_rs_length = _collection_set->recorded_rs_length();
770 const size_t rs_length_diff = _rs_length > recorded_rs_length ? _rs_length - recorded_rs_length : 0;
771 _analytics->report_rs_length_diff(rs_length_diff);
772
773 // Update prediction for copy cost per byte
774 size_t copied_bytes = p->sum_thread_work_items(G1GCPhaseTimes::MergePSS, G1GCPhaseTimes::MergePSSCopiedBytes);
775
776 if (copied_bytes > 0) {
777 double cost_per_byte_ms = (average_time_ms(G1GCPhaseTimes::ObjCopy) + average_time_ms(G1GCPhaseTimes::OptObjCopy)) / copied_bytes;
778 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress());
779 }
780
781 if (_collection_set->young_region_length() > 0) {
782 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
783 _collection_set->young_region_length());
784 }
785
786 if (_collection_set->old_region_length() > 0) {
787 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
788 _collection_set->old_region_length());
789 }
790
791 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
792
793 // Do not update RS lengths and the number of pending cards with information from mixed gc:
794 // these are is wildly different to during young only gc and mess up young gen sizing right
795 // after the mixed gc phase.
796 // During mixed gc we do not use them for young gen sizing.
797 if (this_pause_was_young_only) {
798 _analytics->report_pending_cards((double) _pending_cards_at_gc_start);
799 _analytics->report_rs_length((double) _rs_length);
800 }
801 }
802
803 assert(!(this_pause_included_initial_mark && collector_state()->mark_or_rebuild_in_progress()),
804 "If the last pause has been an initial mark, we should not have been in the marking window");
805 if (this_pause_included_initial_mark) {
806 collector_state()->set_mark_or_rebuild_in_progress(true);
807 }
808
809 _free_regions_at_end_of_collection = _g1h->num_free_regions();
810
811 update_rs_length_prediction();
812
813 // Do not update dynamic IHOP due to G1 periodic collection as it is highly likely
814 // that in this case we are not running in a "normal" operating mode.
815 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) {
816 // IHOP control wants to know the expected young gen length if it were not
817 // restrained by the heap reserve. Using the actual length would make the
818 // prediction too small and the limit the young gen every time we get to the
819 // predicted target occupancy.
820 size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
821
822 update_ihop_prediction(app_time_ms / 1000.0,
823 _bytes_allocated_in_old_since_last_gc,
824 last_unrestrained_young_length * HeapRegion::GrainBytes,
825 this_pause_was_young_only);
826 _bytes_allocated_in_old_since_last_gc = 0;
827
828 _ihop_control->send_trace_event(_g1h->gc_tracer_stw());
829 } else {
830 // Any garbage collection triggered as periodic collection resets the time-to-mixed
831 // measurement. Periodic collection typically means that the application is "inactive", i.e.
832 // the marking threads may have received an uncharacterisic amount of cpu time
833 // for completing the marking, i.e. are faster than expected.
834 // This skews the predicted marking length towards smaller values which might cause
835 // the mark start being too late.
836 _initial_mark_to_mixed.reset();
837 }
838
839 // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
840 double scan_logged_cards_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
841
842 if (scan_logged_cards_time_goal_ms < merge_hcc_time_ms) {
843 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
844 "Logged Cards Scan time goal: %1.2fms Scan HCC time: %1.2fms",
845 scan_logged_cards_time_goal_ms, merge_hcc_time_ms);
846
847 scan_logged_cards_time_goal_ms = 0;
848 } else {
849 scan_logged_cards_time_goal_ms -= merge_hcc_time_ms;
850 }
851
852 _pending_cards_at_prev_gc_end = _g1h->pending_card_num();
853 double const logged_cards_time = logged_cards_processing_time();
854
855 log_debug(gc, ergo, refine)("Concurrent refinement times: Logged Cards Scan time goal: %1.2fms Logged Cards Scan time: %1.2fms HCC time: %1.2fms",
856 scan_logged_cards_time_goal_ms, logged_cards_time, merge_hcc_time_ms);
857
858 _g1h->concurrent_refine()->adjust(logged_cards_time,
859 phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards),
860 scan_logged_cards_time_goal_ms);
861 }
862
863 G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){
864 if (G1UseAdaptiveIHOP) {
865 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
866 predictor,
867 G1ReservePercent,
868 G1HeapWastePercent);
869 } else {
870 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
871 }
872 }
873
874 void G1Policy::update_ihop_prediction(double mutator_time_s,
875 size_t mutator_alloc_bytes,
876 size_t young_gen_size,
877 bool this_gc_was_young_only) {
878 // Always try to update IHOP prediction. Even evacuation failures give information
879 // about e.g. whether to start IHOP earlier next time.
880
881 // Avoid using really small application times that might create samples with
882 // very high or very low values. They may be caused by e.g. back-to-back gcs.
883 double const min_valid_time = 1e-6;
884
885 bool report = false;
886
887 double marking_to_mixed_time = -1.0;
888 if (!this_gc_was_young_only && _initial_mark_to_mixed.has_result()) {
889 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
890 assert(marking_to_mixed_time > 0.0,
891 "Initial mark to mixed time must be larger than zero but is %.3f",
892 marking_to_mixed_time);
893 if (marking_to_mixed_time > min_valid_time) {
894 _ihop_control->update_marking_length(marking_to_mixed_time);
895 report = true;
896 }
897 }
898
899 // As an approximation for the young gc promotion rates during marking we use
900 // all of them. In many applications there are only a few if any young gcs during
901 // marking, which makes any prediction useless. This increases the accuracy of the
902 // prediction.
903 if (this_gc_was_young_only && mutator_time_s > min_valid_time) {
904 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
905 report = true;
906 }
907
908 if (report) {
909 report_ihop_statistics();
910 }
911 }
912
913 void G1Policy::report_ihop_statistics() {
914 _ihop_control->print();
915 }
916
917 void G1Policy::print_phases() {
918 phase_times()->print();
919 }
920
921 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards,
922 size_t rs_length) const {
923 size_t effective_scanned_cards = _analytics->predict_scan_card_num(rs_length, collector_state()->in_young_only_phase());
924 return
925 _analytics->predict_card_merge_time_ms(pending_cards + rs_length, collector_state()->in_young_only_phase()) +
926 _analytics->predict_card_scan_time_ms(effective_scanned_cards, collector_state()->in_young_only_phase()) +
927 _analytics->predict_constant_other_time_ms() +
928 predict_survivor_regions_evac_time();
929 }
930
931 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const {
932 size_t rs_length = _analytics->predict_rs_length();
933 return predict_base_elapsed_time_ms(pending_cards, rs_length);
934 }
935
936 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const {
937 size_t bytes_to_copy;
938 if (!hr->is_young()) {
939 bytes_to_copy = hr->max_live_bytes();
940 } else {
941 bytes_to_copy = (size_t) (hr->used() * hr->surv_rate_prediction(_predictor));
942 }
943 return bytes_to_copy;
944 }
945
946 double G1Policy::predict_eden_copy_time_ms(uint count, size_t* bytes_to_copy) const {
947 if (count == 0) {
948 return 0.0;
949 }
950 size_t const expected_bytes = _eden_surv_rate_group->accum_surv_rate_pred(count) * HeapRegion::GrainBytes;
951 if (bytes_to_copy != NULL) {
952 *bytes_to_copy = expected_bytes;
953 }
954 return _analytics->predict_object_copy_time_ms(expected_bytes, collector_state()->mark_or_rebuild_in_progress());
955 }
956
957 double G1Policy::predict_region_copy_time_ms(HeapRegion* hr) const {
958 size_t const bytes_to_copy = predict_bytes_to_copy(hr);
959 return _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress());
960 }
961
962 double G1Policy::predict_region_non_copy_time_ms(HeapRegion* hr,
963 bool for_young_gc) const {
964 size_t rs_length = hr->rem_set()->occupied();
965 size_t scan_card_num = _analytics->predict_scan_card_num(rs_length, for_young_gc);
966
967 double region_elapsed_time_ms =
968 _analytics->predict_card_merge_time_ms(rs_length, collector_state()->in_young_only_phase()) +
969 _analytics->predict_card_scan_time_ms(scan_card_num, collector_state()->in_young_only_phase());
970
971 // The prediction of the "other" time for this region is based
972 // upon the region type and NOT the GC type.
973 if (hr->is_young()) {
974 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
975 } else {
976 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
977 }
978 return region_elapsed_time_ms;
979 }
980
981 double G1Policy::predict_region_total_time_ms(HeapRegion* hr, bool for_young_gc) const {
982 return predict_region_non_copy_time_ms(hr, for_young_gc) + predict_region_copy_time_ms(hr);
983 }
984
985 bool G1Policy::should_allocate_mutator_region() const {
986 uint young_list_length = _g1h->young_regions_count();
987 uint young_list_target_length = _young_list_target_length;
988 return young_list_length < young_list_target_length;
989 }
990
991 bool G1Policy::can_expand_young_list() const {
992 uint young_list_length = _g1h->young_regions_count();
993 uint young_list_max_length = _young_list_max_length;
994 return young_list_length < young_list_max_length;
995 }
996
997 bool G1Policy::use_adaptive_young_list_length() const {
998 return _young_gen_sizer->use_adaptive_young_list_length();
999 }
1000
1001 size_t G1Policy::desired_survivor_size(uint max_regions) const {
1002 size_t const survivor_capacity = HeapRegion::GrainWords * max_regions;
1003 return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
1004 }
1005
1006 void G1Policy::print_age_table() {
1007 _survivors_age_table.print_age_table(_tenuring_threshold);
1008 }
1009
1010 void G1Policy::update_max_gc_locker_expansion() {
1011 uint expansion_region_num = 0;
1012 if (GCLockerEdenExpansionPercent > 0) {
1013 double perc = (double) GCLockerEdenExpansionPercent / 100.0;
1014 double expansion_region_num_d = perc * (double) _young_list_target_length;
1015 // We use ceiling so that if expansion_region_num_d is > 0.0 (but
1016 // less than 1.0) we'll get 1.
1017 expansion_region_num = (uint) ceil(expansion_region_num_d);
1018 } else {
1019 assert(expansion_region_num == 0, "sanity");
1020 }
1021 _young_list_max_length = _young_list_target_length + expansion_region_num;
1022 assert(_young_list_target_length <= _young_list_max_length, "post-condition");
1023 }
1024
1025 // Calculates survivor space parameters.
1026 void G1Policy::update_survivors_policy() {
1027 double max_survivor_regions_d =
1028 (double) _young_list_target_length / (double) SurvivorRatio;
1029
1030 // Calculate desired survivor size based on desired max survivor regions (unconstrained
1031 // by remaining heap). Otherwise we may cause undesired promotions as we are
1032 // already getting close to end of the heap, impacting performance even more.
1033 uint const desired_max_survivor_regions = ceil(max_survivor_regions_d);
1034 size_t const survivor_size = desired_survivor_size(desired_max_survivor_regions);
1035
1036 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(survivor_size);
1037 if (UsePerfData) {
1038 _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold);
1039 _policy_counters->desired_survivor_size()->set_value(survivor_size * oopSize);
1040 }
1041 // The real maximum survivor size is bounded by the number of regions that can
1042 // be allocated into.
1043 _max_survivor_regions = MIN2(desired_max_survivor_regions,
1044 _g1h->num_free_or_available_regions());
1045 }
1046
1047 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
1048 // We actually check whether we are marking here and not if we are in a
1049 // reclamation phase. This means that we will schedule a concurrent mark
1050 // even while we are still in the process of reclaiming memory.
1051 bool during_cycle = _g1h->concurrent_mark()->cm_thread()->during_cycle();
1052 if (!during_cycle) {
1053 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
1054 collector_state()->set_initiate_conc_mark_if_possible(true);
1055 return true;
1056 } else {
1057 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
1058 return false;
1059 }
1060 }
1061
1062 void G1Policy::initiate_conc_mark() {
1063 collector_state()->set_in_initial_mark_gc(true);
1064 collector_state()->set_initiate_conc_mark_if_possible(false);
1065 }
1066
1067 void G1Policy::decide_on_conc_mark_initiation() {
1068 // We are about to decide on whether this pause will be an
1069 // initial-mark pause.
1070
1071 // First, collector_state()->in_initial_mark_gc() should not be already set. We
1072 // will set it here if we have to. However, it should be cleared by
1073 // the end of the pause (it's only set for the duration of an
1074 // initial-mark pause).
1075 assert(!collector_state()->in_initial_mark_gc(), "pre-condition");
1076
1077 if (collector_state()->initiate_conc_mark_if_possible()) {
1078 // We had noticed on a previous pause that the heap occupancy has
1079 // gone over the initiating threshold and we should start a
1080 // concurrent marking cycle. So we might initiate one.
1081
1082 if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) {
1083 // Initiate a new initial mark if there is no marking or reclamation going on.
1084 initiate_conc_mark();
1085 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
1086 } else if (_g1h->is_user_requested_concurrent_full_gc(_g1h->gc_cause())) {
1087 // Initiate a user requested initial mark. An initial mark must be young only
1088 // GC, so the collector state must be updated to reflect this.
1089 collector_state()->set_in_young_only_phase(true);
1090 collector_state()->set_in_young_gc_before_mixed(false);
1091
1092 // We might have ended up coming here about to start a mixed phase with a collection set
1093 // active. The following remark might change the change the "evacuation efficiency" of
1094 // the regions in this set, leading to failing asserts later.
1095 // Since the concurrent cycle will recreate the collection set anyway, simply drop it here.
1096 clear_collection_set_candidates();
1097 abort_time_to_mixed_tracking();
1098 initiate_conc_mark();
1099 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1100 } else {
1101 // The concurrent marking thread is still finishing up the
1102 // previous cycle. If we start one right now the two cycles
1103 // overlap. In particular, the concurrent marking thread might
1104 // be in the process of clearing the next marking bitmap (which
1105 // we will use for the next cycle if we start one). Starting a
1106 // cycle now will be bad given that parts of the marking
1107 // information might get cleared by the marking thread. And we
1108 // cannot wait for the marking thread to finish the cycle as it
1109 // periodically yields while clearing the next marking bitmap
1110 // and, if it's in a yield point, it's waiting for us to
1111 // finish. So, at this point we will not start a cycle and we'll
1112 // let the concurrent marking thread complete the last one.
1113 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1114 }
1115 }
1116 }
1117
1118 void G1Policy::record_concurrent_mark_cleanup_end() {
1119 G1CollectionSetCandidates* candidates = G1CollectionSetChooser::build(_g1h->workers(), _g1h->num_regions());
1120 _collection_set->set_candidates(candidates);
1121
1122 bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs");
1123 if (!mixed_gc_pending) {
1124 clear_collection_set_candidates();
1125 abort_time_to_mixed_tracking();
1126 }
1127 collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending);
1128 collector_state()->set_mark_or_rebuild_in_progress(false);
1129
1130 double end_sec = os::elapsedTime();
1131 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1132 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
1133 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
1134
1135 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1136 }
1137
1138 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const {
1139 return percent_of(reclaimable_bytes, _g1h->capacity());
1140 }
1141
1142 class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure {
1143 virtual bool do_heap_region(HeapRegion* r) {
1144 r->rem_set()->clear_locked(true /* only_cardset */);
1145 return false;
1146 }
1147 };
1148
1149 void G1Policy::clear_collection_set_candidates() {
1150 // Clear remembered sets of remaining candidate regions and the actual candidate
1151 // set.
1152 G1ClearCollectionSetCandidateRemSets cl;
1153 _collection_set->candidates()->iterate(&cl);
1154 _collection_set->clear_candidates();
1155 }
1156
1157 void G1Policy::maybe_start_marking() {
1158 if (need_to_start_conc_mark("end of GC")) {
1159 // Note: this might have already been set, if during the last
1160 // pause we decided to start a cycle but at the beginning of
1161 // this pause we decided to postpone it. That's OK.
1162 collector_state()->set_initiate_conc_mark_if_possible(true);
1163 }
1164 }
1165
1166 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const {
1167 assert(!collector_state()->in_full_gc(), "must be");
1168 if (collector_state()->in_initial_mark_gc()) {
1169 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1170 return InitialMarkGC;
1171 } else if (collector_state()->in_young_gc_before_mixed()) {
1172 assert(!collector_state()->in_initial_mark_gc(), "must be");
1173 return LastYoungGC;
1174 } else if (collector_state()->in_mixed_phase()) {
1175 assert(!collector_state()->in_initial_mark_gc(), "must be");
1176 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1177 return MixedGC;
1178 } else {
1179 assert(!collector_state()->in_initial_mark_gc(), "must be");
1180 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1181 return YoungOnlyGC;
1182 }
1183 }
1184
1185 void G1Policy::record_pause(PauseKind kind, double start, double end) {
1186 // Manage the MMU tracker. For some reason it ignores Full GCs.
1187 if (kind != FullGC) {
1188 _mmu_tracker->add_pause(start, end);
1189 }
1190 // Manage the mutator time tracking from initial mark to first mixed gc.
1191 switch (kind) {
1192 case FullGC:
1193 abort_time_to_mixed_tracking();
1194 break;
1195 case Cleanup:
1196 case Remark:
1197 case YoungOnlyGC:
1198 case LastYoungGC:
1199 _initial_mark_to_mixed.add_pause(end - start);
1200 break;
1201 case InitialMarkGC:
1202 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) {
1203 _initial_mark_to_mixed.record_initial_mark_end(end);
1204 }
1205 break;
1206 case MixedGC:
1207 _initial_mark_to_mixed.record_mixed_gc_start(start);
1208 break;
1209 default:
1210 ShouldNotReachHere();
1211 }
1212 }
1213
1214 void G1Policy::abort_time_to_mixed_tracking() {
1215 _initial_mark_to_mixed.reset();
1216 }
1217
1218 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str,
1219 const char* false_action_str) const {
1220 G1CollectionSetCandidates* candidates = _collection_set->candidates();
1221
1222 if (candidates->is_empty()) {
1223 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1224 return false;
1225 }
1226
1227 // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1228 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes();
1229 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1230 double threshold = (double) G1HeapWastePercent;
1231 if (reclaimable_percent <= threshold) {
1232 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1233 false_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1234 return false;
1235 }
1236 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1237 true_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1238 return true;
1239 }
1240
1241 uint G1Policy::calc_min_old_cset_length() const {
1242 // The min old CSet region bound is based on the maximum desired
1243 // number of mixed GCs after a cycle. I.e., even if some old regions
1244 // look expensive, we should add them to the CSet anyway to make
1245 // sure we go through the available old regions in no more than the
1246 // maximum desired number of mixed GCs.
1247 //
1248 // The calculation is based on the number of marked regions we added
1249 // to the CSet candidates in the first place, not how many remain, so
1250 // that the result is the same during all mixed GCs that follow a cycle.
1251
1252 const size_t region_num = _collection_set->candidates()->num_regions();
1253 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1254 size_t result = region_num / gc_num;
1255 // emulate ceiling
1256 if (result * gc_num < region_num) {
1257 result += 1;
1258 }
1259 return (uint) result;
1260 }
1261
1262 uint G1Policy::calc_max_old_cset_length() const {
1263 // The max old CSet region bound is based on the threshold expressed
1264 // as a percentage of the heap size. I.e., it should bound the
1265 // number of old regions added to the CSet irrespective of how many
1266 // of them are available.
1267
1268 const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1269 const size_t region_num = g1h->num_regions();
1270 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1271 size_t result = region_num * perc / 100;
1272 // emulate ceiling
1273 if (100 * result < region_num * perc) {
1274 result += 1;
1275 }
1276 return (uint) result;
1277 }
1278
1279 void G1Policy::calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
1280 double time_remaining_ms,
1281 uint& num_initial_regions,
1282 uint& num_optional_regions) {
1283 assert(candidates != NULL, "Must be");
1284
1285 num_initial_regions = 0;
1286 num_optional_regions = 0;
1287 uint num_expensive_regions = 0;
1288
1289 double predicted_old_time_ms = 0.0;
1290 double predicted_initial_time_ms = 0.0;
1291 double predicted_optional_time_ms = 0.0;
1292
1293 double optional_threshold_ms = time_remaining_ms * optional_prediction_fraction();
1294
1295 const uint min_old_cset_length = calc_min_old_cset_length();
1296 const uint max_old_cset_length = MAX2(min_old_cset_length, calc_max_old_cset_length());
1297 const uint max_optional_regions = max_old_cset_length - min_old_cset_length;
1298 bool check_time_remaining = use_adaptive_young_list_length();
1299
1300 uint candidate_idx = candidates->cur_idx();
1301
1302 log_debug(gc, ergo, cset)("Start adding old regions to collection set. Min %u regions, max %u regions, "
1303 "time remaining %1.2fms, optional threshold %1.2fms",
1304 min_old_cset_length, max_old_cset_length, time_remaining_ms, optional_threshold_ms);
1305
1306 HeapRegion* hr = candidates->at(candidate_idx);
1307 while (hr != NULL) {
1308 if (num_initial_regions + num_optional_regions >= max_old_cset_length) {
1309 // Added maximum number of old regions to the CSet.
1310 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Maximum number of regions). "
1311 "Initial %u regions, optional %u regions",
1312 num_initial_regions, num_optional_regions);
1313 break;
1314 }
1315
1316 // Stop adding regions if the remaining reclaimable space is
1317 // not above G1HeapWastePercent.
1318 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes();
1319 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1320 double threshold = (double) G1HeapWastePercent;
1321 if (reclaimable_percent <= threshold) {
1322 // We've added enough old regions that the amount of uncollected
1323 // reclaimable space is at or below the waste threshold. Stop
1324 // adding old regions to the CSet.
1325 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Reclaimable percentage below threshold). "
1326 "Reclaimable: " SIZE_FORMAT "%s (%1.2f%%) threshold: " UINTX_FORMAT "%%",
1327 byte_size_in_proper_unit(reclaimable_bytes), proper_unit_for_byte_size(reclaimable_bytes),
1328 reclaimable_percent, G1HeapWastePercent);
1329 break;
1330 }
1331
1332 double predicted_time_ms = predict_region_total_time_ms(hr, false);
1333 time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0);
1334 // Add regions to old set until we reach the minimum amount
1335 if (num_initial_regions < min_old_cset_length) {
1336 predicted_old_time_ms += predicted_time_ms;
1337 num_initial_regions++;
1338 // Record the number of regions added with no time remaining
1339 if (time_remaining_ms == 0.0) {
1340 num_expensive_regions++;
1341 }
1342 } else if (!check_time_remaining) {
1343 // In the non-auto-tuning case, we'll finish adding regions
1344 // to the CSet if we reach the minimum.
1345 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Region amount reached min).");
1346 break;
1347 } else {
1348 // Keep adding regions to old set until we reach the optional threshold
1349 if (time_remaining_ms > optional_threshold_ms) {
1350 predicted_old_time_ms += predicted_time_ms;
1351 num_initial_regions++;
1352 } else if (time_remaining_ms > 0) {
1353 // Keep adding optional regions until time is up.
1354 assert(num_optional_regions < max_optional_regions, "Should not be possible.");
1355 predicted_optional_time_ms += predicted_time_ms;
1356 num_optional_regions++;
1357 } else {
1358 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Predicted time too high).");
1359 break;
1360 }
1361 }
1362 hr = candidates->at(++candidate_idx);
1363 }
1364 if (hr == NULL) {
1365 log_debug(gc, ergo, cset)("Old candidate collection set empty.");
1366 }
1367
1368 if (num_expensive_regions > 0) {
1369 log_debug(gc, ergo, cset)("Added %u initial old regions to collection set although the predicted time was too high.",
1370 num_expensive_regions);
1371 }
1372
1373 log_debug(gc, ergo, cset)("Finish choosing collection set old regions. Initial: %u, optional: %u, "
1374 "predicted old time: %1.2fms, predicted optional time: %1.2fms, time remaining: %1.2f",
1375 num_initial_regions, num_optional_regions,
1376 predicted_initial_time_ms, predicted_optional_time_ms, time_remaining_ms);
1377 }
1378
1379 void G1Policy::calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
1380 uint const max_optional_regions,
1381 double time_remaining_ms,
1382 uint& num_optional_regions) {
1383 assert(_g1h->collector_state()->in_mixed_phase(), "Should only be called in mixed phase");
1384
1385 num_optional_regions = 0;
1386 double prediction_ms = 0;
1387 uint candidate_idx = candidates->cur_idx();
1388
1389 HeapRegion* r = candidates->at(candidate_idx);
1390 while (num_optional_regions < max_optional_regions) {
1391 assert(r != NULL, "Region must exist");
1392 prediction_ms += predict_region_total_time_ms(r, false);
1393
1394 if (prediction_ms > time_remaining_ms) {
1395 log_debug(gc, ergo, cset)("Prediction %.3fms for region %u does not fit remaining time: %.3fms.",
1396 prediction_ms, r->hrm_index(), time_remaining_ms);
1397 break;
1398 }
1399 // This region will be included in the next optional evacuation.
1400
1401 time_remaining_ms -= prediction_ms;
1402 num_optional_regions++;
1403 r = candidates->at(++candidate_idx);
1404 }
1405
1406 log_debug(gc, ergo, cset)("Prepared %u regions out of %u for optional evacuation. Predicted time: %.3fms",
1407 num_optional_regions, max_optional_regions, prediction_ms);
1408 }
1409
1410 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) {
1411 note_start_adding_survivor_regions();
1412
1413 HeapRegion* last = NULL;
1414 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin();
1415 it != survivors->regions()->end();
1416 ++it) {
1417 HeapRegion* curr = *it;
1418 set_region_survivor(curr);
1419
1420 // The region is a non-empty survivor so let's add it to
1421 // the incremental collection set for the next evacuation
1422 // pause.
1423 _collection_set->add_survivor_regions(curr);
1424
1425 last = curr;
1426 }
1427 note_stop_adding_survivor_regions();
1428
1429 // Don't clear the survivor list handles until the start of
1430 // the next evacuation pause - we need it in order to re-tag
1431 // the survivor regions from this evacuation pause as 'young'
1432 // at the start of the next.
1433 }