1 /*
2 * Copyright (c) 2001, 2020, 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/g1ConcurrentRefineStats.hpp"
35 #include "gc/g1/g1CollectionSetChooser.hpp"
36 #include "gc/g1/g1HeterogeneousHeapPolicy.hpp"
37 #include "gc/g1/g1HotCardCache.hpp"
38 #include "gc/g1/g1IHOPControl.hpp"
39 #include "gc/g1/g1GCPhaseTimes.hpp"
40 #include "gc/g1/g1Policy.hpp"
41 #include "gc/g1/g1SurvivorRegions.hpp"
42 #include "gc/g1/g1YoungGenSizer.hpp"
43 #include "gc/g1/heapRegion.inline.hpp"
44 #include "gc/g1/heapRegionRemSet.hpp"
45 #include "gc/shared/concurrentGCBreakpoints.hpp"
46 #include "gc/shared/gcPolicyCounters.hpp"
47 #include "logging/log.hpp"
48 #include "runtime/arguments.hpp"
49 #include "runtime/globals.hpp"
50 #include "runtime/java.hpp"
51 #include "runtime/mutexLocker.hpp"
52 #include "utilities/debug.hpp"
53 #include "utilities/growableArray.hpp"
54 #include "utilities/pair.hpp"
55
56 G1Policy::G1Policy(STWGCTimer* gc_timer) :
57 _predictor(G1ConfidencePercent / 100.0),
58 _analytics(new G1Analytics(&_predictor)),
59 _remset_tracker(),
60 _mmu_tracker(new G1MMUTrackerQueue(GCPauseIntervalMillis / 1000.0, MaxGCPauseMillis / 1000.0)),
61 _ihop_control(create_ihop_control(&_predictor)),
62 _policy_counters(new GCPolicyCounters("GarbageFirst", 1, 2)),
63 _full_collection_start_sec(0.0),
64 _collection_pause_end_millis(os::javaTimeNanos() / NANOSECS_PER_MILLISEC),
65 _young_list_target_length(0),
66 _young_list_max_length(0),
67 _eden_surv_rate_group(new G1SurvRateGroup()),
68 _survivor_surv_rate_group(new G1SurvRateGroup()),
69 _reserve_factor((double) G1ReservePercent / 100.0),
70 _reserve_regions(0),
71 _young_gen_sizer(G1YoungGenSizer::create_gen_sizer()),
72 _free_regions_at_end_of_collection(0),
73 _rs_length(0),
74 _rs_length_prediction(0),
75 _pending_cards_at_gc_start(0),
76 _old_gen_alloc_tracker(),
77 _initial_mark_to_mixed(),
78 _collection_set(NULL),
79 _g1h(NULL),
80 _phase_times(new G1GCPhaseTimes(gc_timer, ParallelGCThreads)),
81 _mark_remark_start_sec(0),
82 _mark_cleanup_start_sec(0),
83 _tenuring_threshold(MaxTenuringThreshold),
84 _max_survivor_regions(0),
85 _survivors_age_table(true)
86 {
87 }
88
89 G1Policy::~G1Policy() {
90 delete _ihop_control;
91 delete _young_gen_sizer;
92 }
93
94 G1Policy* G1Policy::create_policy(STWGCTimer* gc_timer_stw) {
95 if (G1Arguments::is_heterogeneous_heap()) {
96 return new G1HeterogeneousHeapPolicy(gc_timer_stw);
97 } else {
98 return new G1Policy(gc_timer_stw);
99 }
100 }
101
102 G1CollectorState* G1Policy::collector_state() const { return _g1h->collector_state(); }
103
104 void G1Policy::init(G1CollectedHeap* g1h, G1CollectionSet* collection_set) {
105 _g1h = g1h;
106 _collection_set = collection_set;
107
108 assert(Heap_lock->owned_by_self(), "Locking discipline.");
109
110 _young_gen_sizer->adjust_max_new_size(_g1h->max_expandable_regions());
111
112 _free_regions_at_end_of_collection = _g1h->num_free_regions();
113
114 update_young_max_and_target_length();
115 // We may immediately start allocating regions and placing them on the
116 // collection set list. Initialize the per-collection set info
117 _collection_set->start_incremental_building();
118 }
119
120 void G1Policy::note_gc_start() {
121 phase_times()->note_gc_start();
122 }
123
124 class G1YoungLengthPredictor {
125 const double _base_time_ms;
126 const double _base_free_regions;
127 const double _target_pause_time_ms;
128 const G1Policy* const _policy;
129
130 public:
131 G1YoungLengthPredictor(double base_time_ms,
132 double base_free_regions,
133 double target_pause_time_ms,
134 const G1Policy* policy) :
135 _base_time_ms(base_time_ms),
136 _base_free_regions(base_free_regions),
137 _target_pause_time_ms(target_pause_time_ms),
138 _policy(policy) {}
139
140 bool will_fit(uint young_length) const {
141 if (young_length >= _base_free_regions) {
142 // end condition 1: not enough space for the young regions
143 return false;
144 }
145
146 size_t bytes_to_copy = 0;
147 const double copy_time_ms = _policy->predict_eden_copy_time_ms(young_length, &bytes_to_copy);
148 const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length);
149 const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms;
150 if (pause_time_ms > _target_pause_time_ms) {
151 // end condition 2: prediction is over the target pause time
152 return false;
153 }
154
155 const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes;
156
157 // When copying, we will likely need more bytes free than is live in the region.
158 // Add some safety margin to factor in the confidence of our guess, and the
159 // natural expected waste.
160 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
161 // of the calculation: the lower the confidence, the more headroom.
162 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
163 // copying due to anticipated waste in the PLABs.
164 const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
165 const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
166
167 if (expected_bytes_to_copy > free_bytes) {
168 // end condition 3: out-of-space
169 return false;
170 }
171
172 // success!
173 return true;
174 }
175 };
176
177 void G1Policy::record_new_heap_size(uint new_number_of_regions) {
178 // re-calculate the necessary reserve
179 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
180 // We use ceiling so that if reserve_regions_d is > 0.0 (but
181 // smaller than 1.0) we'll get 1.
182 _reserve_regions = (uint) ceil(reserve_regions_d);
183
184 _young_gen_sizer->heap_size_changed(new_number_of_regions);
185
186 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
187 }
188
189 uint G1Policy::calculate_desired_eden_length_by_mmu() const {
190 // One could argue that any useful eden length to keep any MMU would be 1, but
191 // in theory this is possible. Other constraints enforce a minimum eden of 1
192 // anyway.
193 uint desired_min_length = 0;
194 if (use_adaptive_young_list_length()) {
195 double now_sec = os::elapsedTime();
196 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
197 double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
198 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
199 }
200 return desired_min_length;
201 }
202
203 uint G1Policy::update_young_max_and_target_length() {
204 return update_young_max_and_target_length(_analytics->predict_rs_length());
205 }
206
207 uint G1Policy::update_young_max_and_target_length(size_t rs_length) {
208 uint unbounded_target_length = update_young_target_length(rs_length);
209 update_max_gc_locker_expansion();
210 return unbounded_target_length;
211 }
212
213 uint G1Policy::update_young_target_length(size_t rs_length) {
214 uint desired_length = calculate_young_desired_length(rs_length);
215 _young_list_target_length = calculate_young_target_length(desired_length);
216
217 log_debug(gc,ergo,heap)("Young target lengths: desired: %u target: %u",
218 desired_length, _young_list_target_length);
219 return desired_length;
220 }
221
222 // Calculates desired young gen length. It is calculated from:
223 //
224 // - sizer min/max bounds on young gen
225 // - pause time goal for whole young gen evacuation
226 // - MMU goal influencing eden to make GCs spaced apart.
227 // - a minimum one eden region length.
228 //
229 uint G1Policy::calculate_young_desired_length(size_t rs_length) const {
230 uint min_young_length_by_sizer = _young_gen_sizer->min_desired_young_length();
231 uint max_young_length_by_sizer = _young_gen_sizer->max_desired_young_length();
232
233 assert(min_young_length_by_sizer >= 1, "invariant");
234 assert(max_young_length_by_sizer >= min_young_length_by_sizer, "invariant");
235
236 // Absolute minimum eden length. See above why.
237 // Enforcing a minimum eden length helps at startup when the predictors are not
238 // yet trained on the application to avoid unnecessary (but very short) full gcs
239 // on very small (initial) heaps.
240 uint const MinDesiredEdenLength = 1;
241
242 // Calculate the absolute and desired min bounds first.
243
244 // This is how many survivor regions we already have.
245 const uint survivor_length = _g1h->survivor_regions_count();
246 // Size of the already allocated young gen.
247 const uint allocated_young_length = _g1h->young_regions_count();
248 // This is the absolute minimum young length that we can return. Ensure that we
249 // don't go below any user-defined minimum bound; but we might have already
250 // allocated more than that for reasons. In this case, use that.
251 uint absolute_min_young_length = MAX2(allocated_young_length, min_young_length_by_sizer);
252 // Calculate the absolute max bounds. After evac failure or when revising the
253 // young length we might have exceeded absolute min length or absolute_max_length,
254 // so adjust the result accordingly.
255 uint absolute_max_young_length = MAX2(max_young_length_by_sizer, absolute_min_young_length);
256
257 uint desired_eden_length_by_mmu = 0;
258 uint desired_eden_length_by_pause = 0;
259 uint desired_eden_length_before_mixed = 0;
260
261 uint desired_young_length = 0;
262 if (use_adaptive_young_list_length()) {
263 desired_eden_length_by_mmu = calculate_desired_eden_length_by_mmu();
264
265 const size_t pending_cards = _analytics->predict_pending_cards();
266 double survivor_base_time_ms = predict_base_elapsed_time_ms(pending_cards, rs_length);
267
268 if (!next_gc_should_be_mixed(NULL, NULL)) {
269 desired_eden_length_by_pause =
270 calculate_desired_eden_length_by_pause(survivor_base_time_ms,
271 absolute_min_young_length - survivor_length,
272 absolute_max_young_length - survivor_length);
273 } else {
274 desired_eden_length_before_mixed =
275 calculate_desired_eden_length_before_mixed(survivor_base_time_ms,
276 absolute_min_young_length - survivor_length,
277 absolute_max_young_length - survivor_length);
278 }
279 // Above either sets desired_eden_length_by_pause or desired_eden_length_before_mixed,
280 // the other is zero. Use the one that has been set below.
281 uint desired_eden_length = MAX2(desired_eden_length_by_pause,
282 desired_eden_length_before_mixed);
283
284 // Finally incorporate MMU concerns; assume that it overrides the pause time
285 // goal, as the default value has been chosen to effectively disable it.
286 // Also request at least one eden region, see above for reasons.
287 desired_eden_length = MAX3(desired_eden_length,
288 desired_eden_length_by_mmu,
289 MinDesiredEdenLength);
290
291 desired_young_length = desired_eden_length + survivor_length;
292 } else {
293 // The user asked for a fixed young gen so we'll fix the young gen
294 // whether the next GC is young or mixed.
295 desired_young_length = min_young_length_by_sizer;
296 }
297 // Clamp to absolute min/max after we determined desired lengths.
298 desired_young_length = clamp(desired_young_length, absolute_min_young_length, absolute_max_young_length);
299
300 log_trace(gc, ergo, heap)("Young desired length %u "
301 "survivor length %u "
302 "allocated young length %u "
303 "absolute min young length %u "
304 "absolute max young length %u "
305 "desired eden length by mmu %u "
306 "desired eden length by pause %u "
307 "desired eden length before mixed %u"
308 "desired eden length by default %u",
309 desired_young_length, survivor_length,
310 allocated_young_length, absolute_min_young_length,
311 absolute_max_young_length, desired_eden_length_by_mmu,
312 desired_eden_length_by_pause,
313 desired_eden_length_before_mixed,
314 MinDesiredEdenLength);
315
316 assert(desired_young_length >= allocated_young_length, "must be");
317 return desired_young_length;
318 }
319
320 // Limit the desired (wished) young length by current free regions. If the request
321 // can be satisfied without using up reserve regions, do so, otherwise eat into
322 // the reserve, giving away at most what the heap sizer allows.
323 uint G1Policy::calculate_young_target_length(uint desired_young_length) const {
324 uint allocated_young_length = _g1h->young_regions_count();
325
326 uint receiving_additional_eden;
327 if (allocated_young_length >= desired_young_length) {
328 // Already used up all we actually want (may happen as G1 revises the
329 // young list length concurrently, or caused by gclocker). Do not allow more,
330 // potentially resulting in GC.
331 receiving_additional_eden = 0;
332 log_trace(gc, ergo, heap)("Young target length: Already used up desired young %u allocated %u",
333 desired_young_length,
334 allocated_young_length);
335 } else {
336 // Now look at how many free regions are there currently, and the heap reserve.
337 // We will try our best not to "eat" into the reserve as long as we can. If we
338 // do, we at most eat the sizer's minimum regions into the reserve or half the
339 // reserve rounded up (if possible; this is an arbitrary value).
340
341 uint max_to_eat_into_reserve = MIN2(_young_gen_sizer->min_desired_young_length(),
342 (_reserve_regions + 1) / 2);
343
344 log_trace(gc, ergo, heap)("Young target length: Common "
345 "free regions at end of collection %u "
346 "desired young length %u "
347 "reserve region %u "
348 "max to eat into reserve %u",
349 _free_regions_at_end_of_collection,
350 desired_young_length,
351 _reserve_regions,
352 max_to_eat_into_reserve);
353
354 if (_free_regions_at_end_of_collection <= _reserve_regions) {
355 // Fully eat (or already eating) into the reserve, hand back at most absolute_min_length regions.
356 uint receiving_young = MIN3(_free_regions_at_end_of_collection,
357 desired_young_length,
358 max_to_eat_into_reserve);
359 // We could already have allocated more regions than what we could get
360 // above.
361 receiving_additional_eden = allocated_young_length < receiving_young ?
362 receiving_young - allocated_young_length : 0;
363
364 log_trace(gc, ergo, heap)("Young target length: Fully eat into reserve "
365 "receiving young %u receiving additional eden %u",
366 receiving_young,
367 receiving_additional_eden);
368 } else if (_free_regions_at_end_of_collection < (desired_young_length + _reserve_regions)) {
369 // Partially eat into the reserve, at most max_to_eat_into_reserve regions.
370 uint free_outside_reserve = _free_regions_at_end_of_collection - _reserve_regions;
371 assert(free_outside_reserve < desired_young_length,
372 "must be %u %u",
373 free_outside_reserve, desired_young_length);
374
375 uint receiving_within_reserve = MIN2(desired_young_length - free_outside_reserve,
376 max_to_eat_into_reserve);
377 uint receiving_young = free_outside_reserve + receiving_within_reserve;
378 // Again, we could have already allocated more than we could get.
379 receiving_additional_eden = allocated_young_length < receiving_young ?
380 receiving_young - allocated_young_length : 0;
381
382 log_trace(gc, ergo, heap)("Young target length: Partially eat into reserve "
383 "free outside reserve %u "
384 "receiving within reserve %u "
385 "receiving young %u "
386 "receiving additional eden %u",
387 free_outside_reserve, receiving_within_reserve,
388 receiving_young, receiving_additional_eden);
389 } else {
390 // No need to use the reserve.
391 receiving_additional_eden = desired_young_length - allocated_young_length;
392 log_trace(gc, ergo, heap)("Young target length: No need to use reserve "
393 "receiving additional eden %u",
394 receiving_additional_eden);
395 }
396 }
397
398 uint target_young_length = allocated_young_length + receiving_additional_eden;
399
400 assert(target_young_length >= allocated_young_length, "must be");
401
402 log_trace(gc, ergo, heap)("Young target length: "
403 "young target length %u "
404 "allocated young length %u "
405 "received additional eden %u",
406 target_young_length, allocated_young_length,
407 receiving_additional_eden);
408 return target_young_length;
409 }
410
411 uint G1Policy::calculate_desired_eden_length_by_pause(double base_time_ms,
412 uint min_eden_length,
413 uint max_eden_length) const {
414 assert(use_adaptive_young_list_length(), "pre-condition");
415
416 assert(min_eden_length <= max_eden_length, "must be %u %u", min_eden_length, max_eden_length);
417
418 // Here, we will make sure that the shortest young length that
419 // makes sense fits within the target pause time.
420
421 G1YoungLengthPredictor p(base_time_ms,
422 _free_regions_at_end_of_collection,
423 _mmu_tracker->max_gc_time() * 1000.0,
424 this);
425 if (p.will_fit(min_eden_length)) {
426 // The shortest young length will fit into the target pause time;
427 // we'll now check whether the absolute maximum number of young
428 // regions will fit in the target pause time. If not, we'll do
429 // a binary search between min_young_length and max_young_length.
430 if (p.will_fit(max_eden_length)) {
431 // The maximum young length will fit into the target pause time.
432 // We are done so set min young length to the maximum length (as
433 // the result is assumed to be returned in min_young_length).
434 min_eden_length = max_eden_length;
435 } else {
436 // The maximum possible number of young regions will not fit within
437 // the target pause time so we'll search for the optimal
438 // length. The loop invariants are:
439 //
440 // min_young_length < max_young_length
441 // min_young_length is known to fit into the target pause time
442 // max_young_length is known not to fit into the target pause time
443 //
444 // Going into the loop we know the above hold as we've just
445 // checked them. Every time around the loop we check whether
446 // the middle value between min_young_length and
447 // max_young_length fits into the target pause time. If it
448 // does, it becomes the new min. If it doesn't, it becomes
449 // the new max. This way we maintain the loop invariants.
450
451 assert(min_eden_length < max_eden_length, "invariant");
452 uint diff = (max_eden_length - min_eden_length) / 2;
453 while (diff > 0) {
454 uint eden_length = min_eden_length + diff;
455 if (p.will_fit(eden_length)) {
456 min_eden_length = eden_length;
457 } else {
458 max_eden_length = eden_length;
459 }
460 assert(min_eden_length < max_eden_length, "invariant");
461 diff = (max_eden_length - min_eden_length) / 2;
462 }
463 // The results is min_young_length which, according to the
464 // loop invariants, should fit within the target pause time.
465
466 // These are the post-conditions of the binary search above:
467 assert(min_eden_length < max_eden_length,
468 "otherwise we should have discovered that max_eden_length "
469 "fits into the pause target and not done the binary search");
470 assert(p.will_fit(min_eden_length),
471 "min_eden_length, the result of the binary search, should "
472 "fit into the pause target");
473 assert(!p.will_fit(min_eden_length + 1),
474 "min_eden_length, the result of the binary search, should be "
475 "optimal, so no larger length should fit into the pause target");
476 }
477 } else {
478 // Even the minimum length doesn't fit into the pause time
479 // target, return it as the result nevertheless.
480 }
481 return min_eden_length;
482 }
483
484 uint G1Policy::calculate_desired_eden_length_before_mixed(double survivor_base_time_ms,
485 uint min_eden_length,
486 uint max_eden_length) const {
487 G1CollectionSetCandidates* candidates = _collection_set->candidates();
488
489 uint min_old_regions_end = MIN2(candidates->cur_idx() + calc_min_old_cset_length(), candidates->num_regions());
490 double predicted_region_evac_time_ms = survivor_base_time_ms;
491 for (uint i = candidates->cur_idx(); i < min_old_regions_end; i++) {
492 HeapRegion* r = candidates->at(i);
493 predicted_region_evac_time_ms += predict_region_total_time_ms(r, false);
494 }
495 uint desired_eden_length_by_min_cset_length =
496 calculate_desired_eden_length_by_pause(predicted_region_evac_time_ms,
497 min_eden_length,
498 max_eden_length);
499
500 return desired_eden_length_by_min_cset_length;
501 }
502
503 double G1Policy::predict_survivor_regions_evac_time() const {
504 double survivor_regions_evac_time = 0.0;
505 const GrowableArray<HeapRegion*>* survivor_regions = _g1h->survivor()->regions();
506 for (GrowableArrayIterator<HeapRegion*> it = survivor_regions->begin();
507 it != survivor_regions->end();
508 ++it) {
509 survivor_regions_evac_time += predict_region_total_time_ms(*it, collector_state()->in_young_only_phase());
510 }
511 return survivor_regions_evac_time;
512 }
513
514 void G1Policy::revise_young_list_target_length_if_necessary(size_t rs_length) {
515 guarantee(use_adaptive_young_list_length(), "should not call this otherwise" );
516
517 if (rs_length > _rs_length_prediction) {
518 // add 10% to avoid having to recalculate often
519 size_t rs_length_prediction = rs_length * 1100 / 1000;
520 update_rs_length_prediction(rs_length_prediction);
521
522 update_young_max_and_target_length(rs_length_prediction);
523 }
524 }
525
526 void G1Policy::update_rs_length_prediction() {
527 update_rs_length_prediction(_analytics->predict_rs_length());
528 }
529
530 void G1Policy::update_rs_length_prediction(size_t prediction) {
531 if (collector_state()->in_young_only_phase() && use_adaptive_young_list_length()) {
532 _rs_length_prediction = prediction;
533 }
534 }
535
536 void G1Policy::record_full_collection_start() {
537 _full_collection_start_sec = os::elapsedTime();
538 // Release the future to-space so that it is available for compaction into.
539 collector_state()->set_in_young_only_phase(false);
540 collector_state()->set_in_full_gc(true);
541 _collection_set->clear_candidates();
542 _pending_cards_at_gc_start = 0;
543 }
544
545 void G1Policy::record_full_collection_end() {
546 // Consider this like a collection pause for the purposes of allocation
547 // since last pause.
548 double end_sec = os::elapsedTime();
549 double full_gc_time_sec = end_sec - _full_collection_start_sec;
550 double full_gc_time_ms = full_gc_time_sec * 1000.0;
551
552 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);
553
554 collector_state()->set_in_full_gc(false);
555
556 // "Nuke" the heuristics that control the young/mixed GC
557 // transitions and make sure we start with young GCs after the Full GC.
558 collector_state()->set_in_young_only_phase(true);
559 collector_state()->set_in_young_gc_before_mixed(false);
560 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
561 collector_state()->set_in_initial_mark_gc(false);
562 collector_state()->set_mark_or_rebuild_in_progress(false);
563 collector_state()->set_clearing_next_bitmap(false);
564
565 _eden_surv_rate_group->start_adding_regions();
566 // also call this on any additional surv rate groups
567
568 _free_regions_at_end_of_collection = _g1h->num_free_regions();
569 _survivor_surv_rate_group->reset();
570 update_young_max_and_target_length();
571 update_rs_length_prediction();
572
573 _old_gen_alloc_tracker.reset_after_full_gc();
574
575 record_pause(FullGC, _full_collection_start_sec, end_sec);
576 }
577
578 static void log_refinement_stats(const char* kind, const G1ConcurrentRefineStats& stats) {
579 log_debug(gc, refine, stats)
580 ("%s refinement: %.2fms, refined: " SIZE_FORMAT
581 ", precleaned: " SIZE_FORMAT ", dirtied: " SIZE_FORMAT,
582 kind,
583 stats.refinement_time().seconds() * MILLIUNITS,
584 stats.refined_cards(),
585 stats.precleaned_cards(),
586 stats.dirtied_cards());
587 }
588
589 void G1Policy::record_concurrent_refinement_stats() {
590 G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
591 _pending_cards_at_gc_start = dcqs.num_cards();
592
593 // Collect per-thread stats, mostly from mutator activity.
594 G1ConcurrentRefineStats mut_stats = dcqs.get_and_reset_refinement_stats();
595
596 // Collect specialized concurrent refinement thread stats.
597 G1ConcurrentRefine* cr = _g1h->concurrent_refine();
598 G1ConcurrentRefineStats cr_stats = cr->get_and_reset_refinement_stats();
599
600 G1ConcurrentRefineStats total_stats = mut_stats + cr_stats;
601
602 log_refinement_stats("Mutator", mut_stats);
603 log_refinement_stats("Concurrent", cr_stats);
604 log_refinement_stats("Total", total_stats);
605
606 // Record the rate at which cards were refined.
607 // Don't update the rate if the current sample is empty or time is zero.
608 Tickspan refinement_time = total_stats.refinement_time();
609 size_t refined_cards = total_stats.refined_cards();
610 if ((refined_cards > 0) && (refinement_time > Tickspan())) {
611 double rate = refined_cards / (refinement_time.seconds() * MILLIUNITS);
612 _analytics->report_concurrent_refine_rate_ms(rate);
613 log_debug(gc, refine, stats)("Concurrent refinement rate: %.2f cards/ms", rate);
614 }
615
616 // Record mutator's card logging rate.
617 double mut_start_time = _analytics->prev_collection_pause_end_ms();
618 double mut_end_time = phase_times()->cur_collection_start_sec() * MILLIUNITS;
619 double mut_time = mut_end_time - mut_start_time;
620 // Unlike above for conc-refine rate, here we should not require a
621 // non-empty sample, since an application could go some time with only
622 // young-gen or filtered out writes. But we'll ignore unusually short
623 // sample periods, as they may just pollute the predictions.
624 if (mut_time > 1.0) { // Require > 1ms sample time.
625 double dirtied_rate = total_stats.dirtied_cards() / mut_time;
626 _analytics->report_dirtied_cards_rate_ms(dirtied_rate);
627 log_debug(gc, refine, stats)("Generate dirty cards rate: %.2f cards/ms", dirtied_rate);
628 }
629 }
630
631 void G1Policy::record_collection_pause_start(double start_time_sec) {
632 // We only need to do this here as the policy will only be applied
633 // to the GC we're about to start. so, no point is calculating this
634 // every time we calculate / recalculate the target young length.
635 update_survivors_policy();
636
637 assert(max_survivor_regions() + _g1h->num_used_regions() <= _g1h->max_regions(),
638 "Maximum survivor regions %u plus used regions %u exceeds max regions %u",
639 max_survivor_regions(), _g1h->num_used_regions(), _g1h->max_regions());
640 assert_used_and_recalculate_used_equal(_g1h);
641
642 phase_times()->record_cur_collection_start_sec(start_time_sec);
643
644 record_concurrent_refinement_stats();
645
646 _collection_set->reset_bytes_used_before();
647
648 // do that for any other surv rate groups
649 _eden_surv_rate_group->stop_adding_regions();
650 _survivors_age_table.clear();
651
652 assert(_g1h->collection_set()->verify_young_ages(), "region age verification failed");
653 }
654
655 void G1Policy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) {
656 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
657 collector_state()->set_in_initial_mark_gc(false);
658 }
659
660 void G1Policy::record_concurrent_mark_remark_start() {
661 _mark_remark_start_sec = os::elapsedTime();
662 }
663
664 void G1Policy::record_concurrent_mark_remark_end() {
665 double end_time_sec = os::elapsedTime();
666 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
667 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);
668 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
669
670 record_pause(Remark, _mark_remark_start_sec, end_time_sec);
671 }
672
673 void G1Policy::record_concurrent_mark_cleanup_start() {
674 _mark_cleanup_start_sec = os::elapsedTime();
675 }
676
677 double G1Policy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
678 return phase_times()->average_time_ms(phase);
679 }
680
681 double G1Policy::young_other_time_ms() const {
682 return phase_times()->young_cset_choice_time_ms() +
683 phase_times()->average_time_ms(G1GCPhaseTimes::YoungFreeCSet);
684 }
685
686 double G1Policy::non_young_other_time_ms() const {
687 return phase_times()->non_young_cset_choice_time_ms() +
688 phase_times()->average_time_ms(G1GCPhaseTimes::NonYoungFreeCSet);
689 }
690
691 double G1Policy::other_time_ms(double pause_time_ms) const {
692 return pause_time_ms - phase_times()->cur_collection_par_time_ms();
693 }
694
695 double G1Policy::constant_other_time_ms(double pause_time_ms) const {
696 return other_time_ms(pause_time_ms) - phase_times()->total_free_cset_time_ms() - phase_times()->total_rebuild_freelist_time_ms();
697 }
698
699 bool G1Policy::about_to_start_mixed_phase() const {
700 return _g1h->concurrent_mark()->cm_thread()->during_cycle() || collector_state()->in_young_gc_before_mixed();
701 }
702
703 bool G1Policy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
704 if (about_to_start_mixed_phase()) {
705 return false;
706 }
707
708 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
709
710 size_t cur_used_bytes = _g1h->non_young_capacity_bytes();
711 size_t alloc_byte_size = alloc_word_size * HeapWordSize;
712 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
713
714 bool result = false;
715 if (marking_request_bytes > marking_initiating_used_threshold) {
716 result = collector_state()->in_young_only_phase() && !collector_state()->in_young_gc_before_mixed();
717 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
718 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
719 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1h->capacity() * 100, source);
720 }
721
722 return result;
723 }
724
725 double G1Policy::logged_cards_processing_time() const {
726 double all_cards_processing_time = average_time_ms(G1GCPhaseTimes::ScanHR) + average_time_ms(G1GCPhaseTimes::OptScanHR);
727 size_t logged_dirty_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards);
728 size_t scan_heap_roots_cards = phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) +
729 phase_times()->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards);
730 // This may happen if there are duplicate cards in different log buffers.
731 if (logged_dirty_cards > scan_heap_roots_cards) {
732 return all_cards_processing_time + average_time_ms(G1GCPhaseTimes::MergeLB);
733 }
734 return (all_cards_processing_time * logged_dirty_cards / scan_heap_roots_cards) + average_time_ms(G1GCPhaseTimes::MergeLB);
735 }
736
737 // Anything below that is considered to be zero
738 #define MIN_TIMER_GRANULARITY 0.0000001
739
740 void G1Policy::record_collection_pause_end(double pause_time_ms) {
741 G1GCPhaseTimes* p = phase_times();
742
743 double end_time_sec = os::elapsedTime();
744
745 bool this_pause_included_initial_mark = false;
746 bool this_pause_was_young_only = collector_state()->in_young_only_phase();
747
748 bool update_stats = !_g1h->evacuation_failed();
749
750 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
751
752 _collection_pause_end_millis = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
753
754 this_pause_included_initial_mark = collector_state()->in_initial_mark_gc();
755 if (this_pause_included_initial_mark) {
756 record_concurrent_mark_init_end(0.0);
757 } else {
758 maybe_start_marking();
759 }
760
761 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
762 if (app_time_ms < MIN_TIMER_GRANULARITY) {
763 // This usually happens due to the timer not having the required
764 // granularity. Some Linuxes are the usual culprits.
765 // We'll just set it to something (arbitrarily) small.
766 app_time_ms = 1.0;
767 }
768
769 if (update_stats) {
770 // We maintain the invariant that all objects allocated by mutator
771 // threads will be allocated out of eden regions. So, we can use
772 // the eden region number allocated since the previous GC to
773 // calculate the application's allocate rate. The only exception
774 // to that is humongous objects that are allocated separately. But
775 // given that humongous object allocations do not really affect
776 // either the pause's duration nor when the next pause will take
777 // place we can safely ignore them here.
778 uint regions_allocated = _collection_set->eden_region_length();
779 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
780 _analytics->report_alloc_rate_ms(alloc_rate_ms);
781
782 _analytics->compute_pause_time_ratios(end_time_sec, pause_time_ms);
783 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
784 }
785
786 if (collector_state()->in_young_gc_before_mixed()) {
787 assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC");
788 // This has been the young GC before we start doing mixed GCs. We already
789 // decided to start mixed GCs much earlier, so there is nothing to do except
790 // advancing the state.
791 collector_state()->set_in_young_only_phase(false);
792 collector_state()->set_in_young_gc_before_mixed(false);
793 } else if (!this_pause_was_young_only) {
794 // This is a mixed GC. Here we decide whether to continue doing more
795 // mixed GCs or not.
796 if (!next_gc_should_be_mixed("continue mixed GCs",
797 "do not continue mixed GCs")) {
798 collector_state()->set_in_young_only_phase(true);
799
800 clear_collection_set_candidates();
801 maybe_start_marking();
802 }
803 }
804
805 _eden_surv_rate_group->start_adding_regions();
806
807 double merge_hcc_time_ms = average_time_ms(G1GCPhaseTimes::MergeHCC);
808 if (update_stats) {
809 size_t const total_log_buffer_cards = p->sum_thread_work_items(G1GCPhaseTimes::MergeHCC, G1GCPhaseTimes::MergeHCCDirtyCards) +
810 p->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards);
811 // Update prediction for card merge; MergeRSDirtyCards includes the cards from the Eager Reclaim phase.
812 size_t const total_cards_merged = p->sum_thread_work_items(G1GCPhaseTimes::MergeRS, G1GCPhaseTimes::MergeRSDirtyCards) +
813 p->sum_thread_work_items(G1GCPhaseTimes::OptMergeRS, G1GCPhaseTimes::MergeRSDirtyCards) +
814 total_log_buffer_cards;
815
816 // The threshold for the number of cards in a given sampling which we consider
817 // large enough so that the impact from setup and other costs is negligible.
818 size_t const CardsNumSamplingThreshold = 10;
819
820 if (total_cards_merged > CardsNumSamplingThreshold) {
821 double avg_time_merge_cards = average_time_ms(G1GCPhaseTimes::MergeER) +
822 average_time_ms(G1GCPhaseTimes::MergeRS) +
823 average_time_ms(G1GCPhaseTimes::MergeHCC) +
824 average_time_ms(G1GCPhaseTimes::MergeLB) +
825 average_time_ms(G1GCPhaseTimes::OptMergeRS);
826 _analytics->report_cost_per_card_merge_ms(avg_time_merge_cards / total_cards_merged, this_pause_was_young_only);
827 }
828
829 // Update prediction for card scan
830 size_t const total_cards_scanned = p->sum_thread_work_items(G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ScanHRScannedCards) +
831 p->sum_thread_work_items(G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::ScanHRScannedCards);
832
833 if (total_cards_scanned > CardsNumSamplingThreshold) {
834 double avg_time_dirty_card_scan = average_time_ms(G1GCPhaseTimes::ScanHR) +
835 average_time_ms(G1GCPhaseTimes::OptScanHR);
836
837 _analytics->report_cost_per_card_scan_ms(avg_time_dirty_card_scan / total_cards_scanned, this_pause_was_young_only);
838 }
839
840 // Update prediction for the ratio between cards from the remembered
841 // sets and actually scanned cards from the remembered sets.
842 // Cards from the remembered sets are all cards not duplicated by cards from
843 // the logs.
844 // Due to duplicates in the log buffers, the number of actually scanned cards
845 // can be smaller than the cards in the log buffers.
846 const size_t from_rs_length_cards = (total_cards_scanned > total_log_buffer_cards) ? total_cards_scanned - total_log_buffer_cards : 0;
847 double merge_to_scan_ratio = 0.0;
848 if (total_cards_scanned > 0) {
849 merge_to_scan_ratio = (double) from_rs_length_cards / total_cards_scanned;
850 }
851 _analytics->report_card_merge_to_scan_ratio(merge_to_scan_ratio, this_pause_was_young_only);
852
853 const size_t recorded_rs_length = _collection_set->recorded_rs_length();
854 const size_t rs_length_diff = _rs_length > recorded_rs_length ? _rs_length - recorded_rs_length : 0;
855 _analytics->report_rs_length_diff(rs_length_diff);
856
857 // Update prediction for copy cost per byte
858 size_t copied_bytes = p->sum_thread_work_items(G1GCPhaseTimes::MergePSS, G1GCPhaseTimes::MergePSSCopiedBytes);
859
860 if (copied_bytes > 0) {
861 double cost_per_byte_ms = (average_time_ms(G1GCPhaseTimes::ObjCopy) + average_time_ms(G1GCPhaseTimes::OptObjCopy)) / copied_bytes;
862 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->mark_or_rebuild_in_progress());
863 }
864
865 if (_collection_set->young_region_length() > 0) {
866 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
867 _collection_set->young_region_length());
868 }
869
870 if (_collection_set->old_region_length() > 0) {
871 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
872 _collection_set->old_region_length());
873 }
874
875 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
876
877 // Do not update RS lengths and the number of pending cards with information from mixed gc:
878 // these are is wildly different to during young only gc and mess up young gen sizing right
879 // after the mixed gc phase.
880 // During mixed gc we do not use them for young gen sizing.
881 if (this_pause_was_young_only) {
882 _analytics->report_pending_cards((double) _pending_cards_at_gc_start);
883 _analytics->report_rs_length((double) _rs_length);
884 }
885 }
886
887 assert(!(this_pause_included_initial_mark && collector_state()->mark_or_rebuild_in_progress()),
888 "If the last pause has been an initial mark, we should not have been in the marking window");
889 if (this_pause_included_initial_mark) {
890 collector_state()->set_mark_or_rebuild_in_progress(true);
891 }
892
893 _free_regions_at_end_of_collection = _g1h->num_free_regions();
894
895 update_rs_length_prediction();
896
897 // Do not update dynamic IHOP due to G1 periodic collection as it is highly likely
898 // that in this case we are not running in a "normal" operating mode.
899 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) {
900 // IHOP control wants to know the expected young gen length if it were not
901 // restrained by the heap reserve. Using the actual length would make the
902 // prediction too small and the limit the young gen every time we get to the
903 // predicted target occupancy.
904 size_t last_unrestrained_young_length = update_young_max_and_target_length();
905
906 _old_gen_alloc_tracker.reset_after_young_gc(app_time_ms / 1000.0);
907 update_ihop_prediction(_old_gen_alloc_tracker.last_cycle_duration(),
908 _old_gen_alloc_tracker.last_cycle_old_bytes(),
909 last_unrestrained_young_length * HeapRegion::GrainBytes,
910 this_pause_was_young_only);
911
912 _ihop_control->send_trace_event(_g1h->gc_tracer_stw());
913 } else {
914 // Any garbage collection triggered as periodic collection resets the time-to-mixed
915 // measurement. Periodic collection typically means that the application is "inactive", i.e.
916 // the marking threads may have received an uncharacterisic amount of cpu time
917 // for completing the marking, i.e. are faster than expected.
918 // This skews the predicted marking length towards smaller values which might cause
919 // the mark start being too late.
920 _initial_mark_to_mixed.reset();
921 }
922
923 // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
924 double scan_logged_cards_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
925
926 if (scan_logged_cards_time_goal_ms < merge_hcc_time_ms) {
927 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
928 "Logged Cards Scan time goal: %1.2fms Scan HCC time: %1.2fms",
929 scan_logged_cards_time_goal_ms, merge_hcc_time_ms);
930
931 scan_logged_cards_time_goal_ms = 0;
932 } else {
933 scan_logged_cards_time_goal_ms -= merge_hcc_time_ms;
934 }
935
936 double const logged_cards_time = logged_cards_processing_time();
937
938 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",
939 scan_logged_cards_time_goal_ms, logged_cards_time, merge_hcc_time_ms);
940
941 _g1h->concurrent_refine()->adjust(logged_cards_time,
942 phase_times()->sum_thread_work_items(G1GCPhaseTimes::MergeLB, G1GCPhaseTimes::MergeLBDirtyCards),
943 scan_logged_cards_time_goal_ms);
944 }
945
946 G1IHOPControl* G1Policy::create_ihop_control(const G1Predictions* predictor){
947 if (G1UseAdaptiveIHOP) {
948 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
949 predictor,
950 G1ReservePercent,
951 G1HeapWastePercent);
952 } else {
953 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
954 }
955 }
956
957 void G1Policy::update_ihop_prediction(double mutator_time_s,
958 size_t mutator_alloc_bytes,
959 size_t young_gen_size,
960 bool this_gc_was_young_only) {
961 // Always try to update IHOP prediction. Even evacuation failures give information
962 // about e.g. whether to start IHOP earlier next time.
963
964 // Avoid using really small application times that might create samples with
965 // very high or very low values. They may be caused by e.g. back-to-back gcs.
966 double const min_valid_time = 1e-6;
967
968 bool report = false;
969
970 double marking_to_mixed_time = -1.0;
971 if (!this_gc_was_young_only && _initial_mark_to_mixed.has_result()) {
972 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
973 assert(marking_to_mixed_time > 0.0,
974 "Initial mark to mixed time must be larger than zero but is %.3f",
975 marking_to_mixed_time);
976 if (marking_to_mixed_time > min_valid_time) {
977 _ihop_control->update_marking_length(marking_to_mixed_time);
978 report = true;
979 }
980 }
981
982 // As an approximation for the young gc promotion rates during marking we use
983 // all of them. In many applications there are only a few if any young gcs during
984 // marking, which makes any prediction useless. This increases the accuracy of the
985 // prediction.
986 if (this_gc_was_young_only && mutator_time_s > min_valid_time) {
987 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
988 report = true;
989 }
990
991 if (report) {
992 report_ihop_statistics();
993 }
994 }
995
996 void G1Policy::report_ihop_statistics() {
997 _ihop_control->print();
998 }
999
1000 void G1Policy::print_phases() {
1001 phase_times()->print();
1002 }
1003
1004 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards,
1005 size_t rs_length) const {
1006 size_t effective_scanned_cards = _analytics->predict_scan_card_num(rs_length, collector_state()->in_young_only_phase());
1007 return
1008 _analytics->predict_card_merge_time_ms(pending_cards + rs_length, collector_state()->in_young_only_phase()) +
1009 _analytics->predict_card_scan_time_ms(effective_scanned_cards, collector_state()->in_young_only_phase()) +
1010 _analytics->predict_constant_other_time_ms() +
1011 predict_survivor_regions_evac_time();
1012 }
1013
1014 double G1Policy::predict_base_elapsed_time_ms(size_t pending_cards) const {
1015 size_t rs_length = _analytics->predict_rs_length();
1016 return predict_base_elapsed_time_ms(pending_cards, rs_length);
1017 }
1018
1019 size_t G1Policy::predict_bytes_to_copy(HeapRegion* hr) const {
1020 size_t bytes_to_copy;
1021 if (!hr->is_young()) {
1022 bytes_to_copy = hr->max_live_bytes();
1023 } else {
1024 bytes_to_copy = (size_t) (hr->used() * hr->surv_rate_prediction(_predictor));
1025 }
1026 return bytes_to_copy;
1027 }
1028
1029 double G1Policy::predict_eden_copy_time_ms(uint count, size_t* bytes_to_copy) const {
1030 if (count == 0) {
1031 return 0.0;
1032 }
1033 size_t const expected_bytes = _eden_surv_rate_group->accum_surv_rate_pred(count) * HeapRegion::GrainBytes;
1034 if (bytes_to_copy != NULL) {
1035 *bytes_to_copy = expected_bytes;
1036 }
1037 return _analytics->predict_object_copy_time_ms(expected_bytes, collector_state()->mark_or_rebuild_in_progress());
1038 }
1039
1040 double G1Policy::predict_region_copy_time_ms(HeapRegion* hr) const {
1041 size_t const bytes_to_copy = predict_bytes_to_copy(hr);
1042 return _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->mark_or_rebuild_in_progress());
1043 }
1044
1045 double G1Policy::predict_region_non_copy_time_ms(HeapRegion* hr,
1046 bool for_young_gc) const {
1047 size_t rs_length = hr->rem_set()->occupied();
1048 size_t scan_card_num = _analytics->predict_scan_card_num(rs_length, for_young_gc);
1049
1050 double region_elapsed_time_ms =
1051 _analytics->predict_card_merge_time_ms(rs_length, collector_state()->in_young_only_phase()) +
1052 _analytics->predict_card_scan_time_ms(scan_card_num, collector_state()->in_young_only_phase());
1053
1054 // The prediction of the "other" time for this region is based
1055 // upon the region type and NOT the GC type.
1056 if (hr->is_young()) {
1057 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
1058 } else {
1059 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
1060 }
1061 return region_elapsed_time_ms;
1062 }
1063
1064 double G1Policy::predict_region_total_time_ms(HeapRegion* hr, bool for_young_gc) const {
1065 return predict_region_non_copy_time_ms(hr, for_young_gc) + predict_region_copy_time_ms(hr);
1066 }
1067
1068 bool G1Policy::should_allocate_mutator_region() const {
1069 uint young_list_length = _g1h->young_regions_count();
1070 uint young_list_target_length = _young_list_target_length;
1071 return young_list_length < young_list_target_length;
1072 }
1073
1074 bool G1Policy::can_expand_young_list() const {
1075 uint young_list_length = _g1h->young_regions_count();
1076 uint young_list_max_length = _young_list_max_length;
1077 return young_list_length < young_list_max_length;
1078 }
1079
1080 bool G1Policy::use_adaptive_young_list_length() const {
1081 return _young_gen_sizer->use_adaptive_young_list_length();
1082 }
1083
1084 size_t G1Policy::desired_survivor_size(uint max_regions) const {
1085 size_t const survivor_capacity = HeapRegion::GrainWords * max_regions;
1086 return (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
1087 }
1088
1089 void G1Policy::print_age_table() {
1090 _survivors_age_table.print_age_table(_tenuring_threshold);
1091 }
1092
1093 void G1Policy::update_max_gc_locker_expansion() {
1094 uint expansion_region_num = 0;
1095 if (GCLockerEdenExpansionPercent > 0) {
1096 double perc = (double) GCLockerEdenExpansionPercent / 100.0;
1097 double expansion_region_num_d = perc * (double) _young_list_target_length;
1098 // We use ceiling so that if expansion_region_num_d is > 0.0 (but
1099 // less than 1.0) we'll get 1.
1100 expansion_region_num = (uint) ceil(expansion_region_num_d);
1101 } else {
1102 assert(expansion_region_num == 0, "sanity");
1103 }
1104 _young_list_max_length = _young_list_target_length + expansion_region_num;
1105 assert(_young_list_target_length <= _young_list_max_length, "post-condition");
1106 }
1107
1108 // Calculates survivor space parameters.
1109 void G1Policy::update_survivors_policy() {
1110 double max_survivor_regions_d =
1111 (double) _young_list_target_length / (double) SurvivorRatio;
1112
1113 // Calculate desired survivor size based on desired max survivor regions (unconstrained
1114 // by remaining heap). Otherwise we may cause undesired promotions as we are
1115 // already getting close to end of the heap, impacting performance even more.
1116 uint const desired_max_survivor_regions = ceil(max_survivor_regions_d);
1117 size_t const survivor_size = desired_survivor_size(desired_max_survivor_regions);
1118
1119 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(survivor_size);
1120 if (UsePerfData) {
1121 _policy_counters->tenuring_threshold()->set_value(_tenuring_threshold);
1122 _policy_counters->desired_survivor_size()->set_value(survivor_size * oopSize);
1123 }
1124 // The real maximum survivor size is bounded by the number of regions that can
1125 // be allocated into.
1126 _max_survivor_regions = MIN2(desired_max_survivor_regions,
1127 _g1h->num_free_or_available_regions());
1128 }
1129
1130 bool G1Policy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
1131 // We actually check whether we are marking here and not if we are in a
1132 // reclamation phase. This means that we will schedule a concurrent mark
1133 // even while we are still in the process of reclaiming memory.
1134 bool during_cycle = _g1h->concurrent_mark()->cm_thread()->during_cycle();
1135 if (!during_cycle) {
1136 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
1137 collector_state()->set_initiate_conc_mark_if_possible(true);
1138 return true;
1139 } else {
1140 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
1141 return false;
1142 }
1143 }
1144
1145 void G1Policy::initiate_conc_mark() {
1146 collector_state()->set_in_initial_mark_gc(true);
1147 collector_state()->set_initiate_conc_mark_if_possible(false);
1148 }
1149
1150 void G1Policy::decide_on_conc_mark_initiation() {
1151 // We are about to decide on whether this pause will be an
1152 // initial-mark pause.
1153
1154 // First, collector_state()->in_initial_mark_gc() should not be already set. We
1155 // will set it here if we have to. However, it should be cleared by
1156 // the end of the pause (it's only set for the duration of an
1157 // initial-mark pause).
1158 assert(!collector_state()->in_initial_mark_gc(), "pre-condition");
1159
1160 if (collector_state()->initiate_conc_mark_if_possible()) {
1161 // We had noticed on a previous pause that the heap occupancy has
1162 // gone over the initiating threshold and we should start a
1163 // concurrent marking cycle. Or we've been explicitly requested
1164 // to start a concurrent marking cycle. Either way, we initiate
1165 // one if not inhibited for some reason.
1166
1167 GCCause::Cause cause = _g1h->gc_cause();
1168 if ((cause != GCCause::_wb_breakpoint) &&
1169 ConcurrentGCBreakpoints::is_controlled()) {
1170 log_debug(gc, ergo)("Do not initiate concurrent cycle (whitebox controlled)");
1171 } else if (!about_to_start_mixed_phase() && collector_state()->in_young_only_phase()) {
1172 // Initiate a new initial mark if there is no marking or reclamation going on.
1173 initiate_conc_mark();
1174 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
1175 } else if (_g1h->is_user_requested_concurrent_full_gc(cause) ||
1176 (cause == GCCause::_wb_breakpoint)) {
1177 // Initiate a user requested initial mark or run_to a breakpoint.
1178 // An initial mark must be young only GC, so the collector state
1179 // must be updated to reflect this.
1180 collector_state()->set_in_young_only_phase(true);
1181 collector_state()->set_in_young_gc_before_mixed(false);
1182
1183 // We might have ended up coming here about to start a mixed phase with a collection set
1184 // active. The following remark might change the change the "evacuation efficiency" of
1185 // the regions in this set, leading to failing asserts later.
1186 // Since the concurrent cycle will recreate the collection set anyway, simply drop it here.
1187 clear_collection_set_candidates();
1188 abort_time_to_mixed_tracking();
1189 initiate_conc_mark();
1190 log_debug(gc, ergo)("Initiate concurrent cycle (%s requested concurrent cycle)",
1191 (cause == GCCause::_wb_breakpoint) ? "run_to breakpoint" : "user");
1192 } else {
1193 // The concurrent marking thread is still finishing up the
1194 // previous cycle. If we start one right now the two cycles
1195 // overlap. In particular, the concurrent marking thread might
1196 // be in the process of clearing the next marking bitmap (which
1197 // we will use for the next cycle if we start one). Starting a
1198 // cycle now will be bad given that parts of the marking
1199 // information might get cleared by the marking thread. And we
1200 // cannot wait for the marking thread to finish the cycle as it
1201 // periodically yields while clearing the next marking bitmap
1202 // and, if it's in a yield point, it's waiting for us to
1203 // finish. So, at this point we will not start a cycle and we'll
1204 // let the concurrent marking thread complete the last one.
1205 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1206 }
1207 }
1208 }
1209
1210 void G1Policy::record_concurrent_mark_cleanup_end() {
1211 G1CollectionSetCandidates* candidates = G1CollectionSetChooser::build(_g1h->workers(), _g1h->num_regions());
1212 _collection_set->set_candidates(candidates);
1213
1214 bool mixed_gc_pending = next_gc_should_be_mixed("request mixed gcs", "request young-only gcs");
1215 if (!mixed_gc_pending) {
1216 clear_collection_set_candidates();
1217 abort_time_to_mixed_tracking();
1218 }
1219 collector_state()->set_in_young_gc_before_mixed(mixed_gc_pending);
1220 collector_state()->set_mark_or_rebuild_in_progress(false);
1221
1222 double end_sec = os::elapsedTime();
1223 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1224 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
1225 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
1226
1227 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1228 }
1229
1230 double G1Policy::reclaimable_bytes_percent(size_t reclaimable_bytes) const {
1231 return percent_of(reclaimable_bytes, _g1h->capacity());
1232 }
1233
1234 class G1ClearCollectionSetCandidateRemSets : public HeapRegionClosure {
1235 virtual bool do_heap_region(HeapRegion* r) {
1236 r->rem_set()->clear_locked(true /* only_cardset */);
1237 return false;
1238 }
1239 };
1240
1241 void G1Policy::clear_collection_set_candidates() {
1242 // Clear remembered sets of remaining candidate regions and the actual candidate
1243 // set.
1244 G1ClearCollectionSetCandidateRemSets cl;
1245 _collection_set->candidates()->iterate(&cl);
1246 _collection_set->clear_candidates();
1247 }
1248
1249 void G1Policy::maybe_start_marking() {
1250 if (need_to_start_conc_mark("end of GC")) {
1251 // Note: this might have already been set, if during the last
1252 // pause we decided to start a cycle but at the beginning of
1253 // this pause we decided to postpone it. That's OK.
1254 collector_state()->set_initiate_conc_mark_if_possible(true);
1255 }
1256 }
1257
1258 G1Policy::PauseKind G1Policy::young_gc_pause_kind() const {
1259 assert(!collector_state()->in_full_gc(), "must be");
1260 if (collector_state()->in_initial_mark_gc()) {
1261 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1262 return InitialMarkGC;
1263 } else if (collector_state()->in_young_gc_before_mixed()) {
1264 assert(!collector_state()->in_initial_mark_gc(), "must be");
1265 return LastYoungGC;
1266 } else if (collector_state()->in_mixed_phase()) {
1267 assert(!collector_state()->in_initial_mark_gc(), "must be");
1268 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1269 return MixedGC;
1270 } else {
1271 assert(!collector_state()->in_initial_mark_gc(), "must be");
1272 assert(!collector_state()->in_young_gc_before_mixed(), "must be");
1273 return YoungOnlyGC;
1274 }
1275 }
1276
1277 void G1Policy::record_pause(PauseKind kind, double start, double end) {
1278 // Manage the MMU tracker. For some reason it ignores Full GCs.
1279 if (kind != FullGC) {
1280 _mmu_tracker->add_pause(start, end);
1281 }
1282 // Manage the mutator time tracking from initial mark to first mixed gc.
1283 switch (kind) {
1284 case FullGC:
1285 abort_time_to_mixed_tracking();
1286 break;
1287 case Cleanup:
1288 case Remark:
1289 case YoungOnlyGC:
1290 case LastYoungGC:
1291 _initial_mark_to_mixed.add_pause(end - start);
1292 break;
1293 case InitialMarkGC:
1294 if (_g1h->gc_cause() != GCCause::_g1_periodic_collection) {
1295 _initial_mark_to_mixed.record_initial_mark_end(end);
1296 }
1297 break;
1298 case MixedGC:
1299 _initial_mark_to_mixed.record_mixed_gc_start(start);
1300 break;
1301 default:
1302 ShouldNotReachHere();
1303 }
1304 }
1305
1306 void G1Policy::abort_time_to_mixed_tracking() {
1307 _initial_mark_to_mixed.reset();
1308 }
1309
1310 bool G1Policy::next_gc_should_be_mixed(const char* true_action_str,
1311 const char* false_action_str) const {
1312 G1CollectionSetCandidates* candidates = _collection_set->candidates();
1313
1314 if (candidates == NULL || candidates->is_empty()) {
1315 if (false_action_str != NULL) {
1316 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1317 }
1318 return false;
1319 }
1320
1321 // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1322 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes();
1323 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1324 double threshold = (double) G1HeapWastePercent;
1325 if (reclaimable_percent <= threshold) {
1326 if (false_action_str != NULL) {
1327 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1328 false_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1329 }
1330 return false;
1331 }
1332 if (true_action_str != NULL) {
1333 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1334 true_action_str, candidates->num_remaining(), reclaimable_bytes, reclaimable_percent, G1HeapWastePercent);
1335 }
1336 return true;
1337 }
1338
1339 uint G1Policy::calc_min_old_cset_length() const {
1340 // The min old CSet region bound is based on the maximum desired
1341 // number of mixed GCs after a cycle. I.e., even if some old regions
1342 // look expensive, we should add them to the CSet anyway to make
1343 // sure we go through the available old regions in no more than the
1344 // maximum desired number of mixed GCs.
1345 //
1346 // The calculation is based on the number of marked regions we added
1347 // to the CSet candidates in the first place, not how many remain, so
1348 // that the result is the same during all mixed GCs that follow a cycle.
1349
1350 const size_t region_num = _collection_set->candidates()->num_regions();
1351 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1352 size_t result = region_num / gc_num;
1353 // emulate ceiling
1354 if (result * gc_num < region_num) {
1355 result += 1;
1356 }
1357 return (uint) result;
1358 }
1359
1360 uint G1Policy::calc_max_old_cset_length() const {
1361 // The max old CSet region bound is based on the threshold expressed
1362 // as a percentage of the heap size. I.e., it should bound the
1363 // number of old regions added to the CSet irrespective of how many
1364 // of them are available.
1365
1366 const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1367 const size_t region_num = g1h->num_regions();
1368 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1369 size_t result = region_num * perc / 100;
1370 // emulate ceiling
1371 if (100 * result < region_num * perc) {
1372 result += 1;
1373 }
1374 return (uint) result;
1375 }
1376
1377 void G1Policy::calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
1378 double time_remaining_ms,
1379 uint& num_initial_regions,
1380 uint& num_optional_regions) {
1381 assert(candidates != NULL, "Must be");
1382
1383 num_initial_regions = 0;
1384 num_optional_regions = 0;
1385 uint num_expensive_regions = 0;
1386
1387 double predicted_old_time_ms = 0.0;
1388 double predicted_initial_time_ms = 0.0;
1389 double predicted_optional_time_ms = 0.0;
1390
1391 double optional_threshold_ms = time_remaining_ms * optional_prediction_fraction();
1392
1393 const uint min_old_cset_length = calc_min_old_cset_length();
1394 const uint max_old_cset_length = MAX2(min_old_cset_length, calc_max_old_cset_length());
1395 const uint max_optional_regions = max_old_cset_length - min_old_cset_length;
1396 bool check_time_remaining = use_adaptive_young_list_length();
1397
1398 uint candidate_idx = candidates->cur_idx();
1399
1400 log_debug(gc, ergo, cset)("Start adding old regions to collection set. Min %u regions, max %u regions, "
1401 "time remaining %1.2fms, optional threshold %1.2fms",
1402 min_old_cset_length, max_old_cset_length, time_remaining_ms, optional_threshold_ms);
1403
1404 HeapRegion* hr = candidates->at(candidate_idx);
1405 while (hr != NULL) {
1406 if (num_initial_regions + num_optional_regions >= max_old_cset_length) {
1407 // Added maximum number of old regions to the CSet.
1408 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Maximum number of regions). "
1409 "Initial %u regions, optional %u regions",
1410 num_initial_regions, num_optional_regions);
1411 break;
1412 }
1413
1414 // Stop adding regions if the remaining reclaimable space is
1415 // not above G1HeapWastePercent.
1416 size_t reclaimable_bytes = candidates->remaining_reclaimable_bytes();
1417 double reclaimable_percent = reclaimable_bytes_percent(reclaimable_bytes);
1418 double threshold = (double) G1HeapWastePercent;
1419 if (reclaimable_percent <= threshold) {
1420 // We've added enough old regions that the amount of uncollected
1421 // reclaimable space is at or below the waste threshold. Stop
1422 // adding old regions to the CSet.
1423 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Reclaimable percentage below threshold). "
1424 "Reclaimable: " SIZE_FORMAT "%s (%1.2f%%) threshold: " UINTX_FORMAT "%%",
1425 byte_size_in_proper_unit(reclaimable_bytes), proper_unit_for_byte_size(reclaimable_bytes),
1426 reclaimable_percent, G1HeapWastePercent);
1427 break;
1428 }
1429
1430 double predicted_time_ms = predict_region_total_time_ms(hr, false);
1431 time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0);
1432 // Add regions to old set until we reach the minimum amount
1433 if (num_initial_regions < min_old_cset_length) {
1434 predicted_old_time_ms += predicted_time_ms;
1435 num_initial_regions++;
1436 // Record the number of regions added with no time remaining
1437 if (time_remaining_ms == 0.0) {
1438 num_expensive_regions++;
1439 }
1440 } else if (!check_time_remaining) {
1441 // In the non-auto-tuning case, we'll finish adding regions
1442 // to the CSet if we reach the minimum.
1443 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Region amount reached min).");
1444 break;
1445 } else {
1446 // Keep adding regions to old set until we reach the optional threshold
1447 if (time_remaining_ms > optional_threshold_ms) {
1448 predicted_old_time_ms += predicted_time_ms;
1449 num_initial_regions++;
1450 } else if (time_remaining_ms > 0) {
1451 // Keep adding optional regions until time is up.
1452 assert(num_optional_regions < max_optional_regions, "Should not be possible.");
1453 predicted_optional_time_ms += predicted_time_ms;
1454 num_optional_regions++;
1455 } else {
1456 log_debug(gc, ergo, cset)("Finish adding old regions to collection set (Predicted time too high).");
1457 break;
1458 }
1459 }
1460 hr = candidates->at(++candidate_idx);
1461 }
1462 if (hr == NULL) {
1463 log_debug(gc, ergo, cset)("Old candidate collection set empty.");
1464 }
1465
1466 if (num_expensive_regions > 0) {
1467 log_debug(gc, ergo, cset)("Added %u initial old regions to collection set although the predicted time was too high.",
1468 num_expensive_regions);
1469 }
1470
1471 log_debug(gc, ergo, cset)("Finish choosing collection set old regions. Initial: %u, optional: %u, "
1472 "predicted old time: %1.2fms, predicted optional time: %1.2fms, time remaining: %1.2f",
1473 num_initial_regions, num_optional_regions,
1474 predicted_initial_time_ms, predicted_optional_time_ms, time_remaining_ms);
1475 }
1476
1477 void G1Policy::calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
1478 uint const max_optional_regions,
1479 double time_remaining_ms,
1480 uint& num_optional_regions) {
1481 assert(_g1h->collector_state()->in_mixed_phase(), "Should only be called in mixed phase");
1482
1483 num_optional_regions = 0;
1484 double prediction_ms = 0;
1485 uint candidate_idx = candidates->cur_idx();
1486
1487 HeapRegion* r = candidates->at(candidate_idx);
1488 while (num_optional_regions < max_optional_regions) {
1489 assert(r != NULL, "Region must exist");
1490 prediction_ms += predict_region_total_time_ms(r, false);
1491
1492 if (prediction_ms > time_remaining_ms) {
1493 log_debug(gc, ergo, cset)("Prediction %.3fms for region %u does not fit remaining time: %.3fms.",
1494 prediction_ms, r->hrm_index(), time_remaining_ms);
1495 break;
1496 }
1497 // This region will be included in the next optional evacuation.
1498
1499 time_remaining_ms -= prediction_ms;
1500 num_optional_regions++;
1501 r = candidates->at(++candidate_idx);
1502 }
1503
1504 log_debug(gc, ergo, cset)("Prepared %u regions out of %u for optional evacuation. Predicted time: %.3fms",
1505 num_optional_regions, max_optional_regions, prediction_ms);
1506 }
1507
1508 void G1Policy::transfer_survivors_to_cset(const G1SurvivorRegions* survivors) {
1509 note_start_adding_survivor_regions();
1510
1511 HeapRegion* last = NULL;
1512 for (GrowableArrayIterator<HeapRegion*> it = survivors->regions()->begin();
1513 it != survivors->regions()->end();
1514 ++it) {
1515 HeapRegion* curr = *it;
1516 set_region_survivor(curr);
1517
1518 // The region is a non-empty survivor so let's add it to
1519 // the incremental collection set for the next evacuation
1520 // pause.
1521 _collection_set->add_survivor_regions(curr);
1522
1523 last = curr;
1524 }
1525 note_stop_adding_survivor_regions();
1526
1527 // Don't clear the survivor list handles until the start of
1528 // the next evacuation pause - we need it in order to re-tag
1529 // the survivor regions from this evacuation pause as 'young'
1530 // at the start of the next.
1531 }