1 /*
2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc/g1/concurrentG1Refine.hpp"
27 #include "gc/g1/concurrentMark.hpp"
28 #include "gc/g1/concurrentMarkThread.inline.hpp"
29 #include "gc/g1/g1CollectedHeap.inline.hpp"
30 #include "gc/g1/g1CollectorPolicy.hpp"
31 #include "gc/g1/g1IHOPControl.hpp"
32 #include "gc/g1/g1GCPhaseTimes.hpp"
33 #include "gc/g1/heapRegion.inline.hpp"
34 #include "gc/g1/heapRegionRemSet.hpp"
35 #include "gc/shared/gcPolicyCounters.hpp"
36 #include "runtime/arguments.hpp"
37 #include "runtime/java.hpp"
38 #include "runtime/mutexLocker.hpp"
39 #include "utilities/debug.hpp"
40 #include "utilities/pair.hpp"
41
42 // Different defaults for different number of GC threads
43 // They were chosen by running GCOld and SPECjbb on debris with different
44 // numbers of GC threads and choosing them based on the results
45
46 // all the same
47 static double rs_length_diff_defaults[] = {
48 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0
49 };
50
51 static double cost_per_card_ms_defaults[] = {
52 0.01, 0.005, 0.005, 0.003, 0.003, 0.002, 0.002, 0.0015
53 };
54
55 // all the same
56 static double young_cards_per_entry_ratio_defaults[] = {
57 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0
58 };
59
60 static double cost_per_entry_ms_defaults[] = {
61 0.015, 0.01, 0.01, 0.008, 0.008, 0.0055, 0.0055, 0.005
62 };
63
64 static double cost_per_byte_ms_defaults[] = {
65 0.00006, 0.00003, 0.00003, 0.000015, 0.000015, 0.00001, 0.00001, 0.000009
66 };
67
68 // these should be pretty consistent
69 static double constant_other_time_ms_defaults[] = {
70 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0
71 };
72
73
74 static double young_other_cost_per_region_ms_defaults[] = {
75 0.3, 0.2, 0.2, 0.15, 0.15, 0.12, 0.12, 0.1
76 };
77
78 static double non_young_other_cost_per_region_ms_defaults[] = {
79 1.0, 0.7, 0.7, 0.5, 0.5, 0.42, 0.42, 0.30
80 };
81
82 G1CollectorPolicy::G1CollectorPolicy() :
83 _predictor(G1ConfidencePercent / 100.0),
84
85 _recent_gc_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
86
87 _concurrent_mark_remark_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
88 _concurrent_mark_cleanup_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
89
90 _alloc_rate_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
91 _prev_collection_pause_end_ms(0.0),
92 _rs_length_diff_seq(new TruncatedSeq(TruncatedSeqLength)),
93 _cost_per_card_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
94 _cost_scan_hcc_seq(new TruncatedSeq(TruncatedSeqLength)),
95 _young_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
96 _mixed_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
97 _cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
98 _mixed_cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
99 _cost_per_byte_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
100 _cost_per_byte_ms_during_cm_seq(new TruncatedSeq(TruncatedSeqLength)),
101 _constant_other_time_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
102 _young_other_cost_per_region_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
103 _non_young_other_cost_per_region_ms_seq(
104 new TruncatedSeq(TruncatedSeqLength)),
105
106 _pending_cards_seq(new TruncatedSeq(TruncatedSeqLength)),
107 _rs_lengths_seq(new TruncatedSeq(TruncatedSeqLength)),
108
109 _pause_time_target_ms((double) MaxGCPauseMillis),
110
111 _recent_prev_end_times_for_all_gcs_sec(
112 new TruncatedSeq(NumPrevPausesForHeuristics)),
113
114 _recent_avg_pause_time_ratio(0.0),
115 _rs_lengths_prediction(0),
116 _max_survivor_regions(0),
117
118 _eden_cset_region_length(0),
119 _survivor_cset_region_length(0),
120 _old_cset_region_length(0),
121
122 _collection_set(NULL),
123 _collection_set_bytes_used_before(0),
124
125 // Incremental CSet attributes
126 _inc_cset_build_state(Inactive),
127 _inc_cset_head(NULL),
128 _inc_cset_tail(NULL),
129 _inc_cset_bytes_used_before(0),
130 _inc_cset_max_finger(NULL),
131 _inc_cset_recorded_rs_lengths(0),
132 _inc_cset_recorded_rs_lengths_diffs(0),
133 _inc_cset_predicted_elapsed_time_ms(0.0),
134 _inc_cset_predicted_elapsed_time_ms_diffs(0.0),
135
136 // add here any more surv rate groups
137 _recorded_survivor_regions(0),
138 _recorded_survivor_head(NULL),
139 _recorded_survivor_tail(NULL),
140 _survivors_age_table(true),
141
142 _gc_overhead_perc(0.0),
143
144 _bytes_allocated_in_old_since_last_gc(0),
145 _ihop_control(NULL),
146 _initial_mark_to_mixed() {
147
148 // SurvRateGroups below must be initialized after the predictor because they
149 // indirectly use it through this object passed to their constructor.
150 _short_lived_surv_rate_group =
151 new SurvRateGroup(&_predictor, "Short Lived", G1YoungSurvRateNumRegionsSummary);
152 _survivor_surv_rate_group =
153 new SurvRateGroup(&_predictor, "Survivor", G1YoungSurvRateNumRegionsSummary);
154
155 // Set up the region size and associated fields. Given that the
156 // policy is created before the heap, we have to set this up here,
157 // so it's done as soon as possible.
158
159 // It would have been natural to pass initial_heap_byte_size() and
160 // max_heap_byte_size() to setup_heap_region_size() but those have
161 // not been set up at this point since they should be aligned with
162 // the region size. So, there is a circular dependency here. We base
163 // the region size on the heap size, but the heap size should be
164 // aligned with the region size. To get around this we use the
165 // unaligned values for the heap.
166 HeapRegion::setup_heap_region_size(InitialHeapSize, MaxHeapSize);
167 HeapRegionRemSet::setup_remset_size();
168
169 _recent_prev_end_times_for_all_gcs_sec->add(os::elapsedTime());
170 _prev_collection_pause_end_ms = os::elapsedTime() * 1000.0;
171 clear_ratio_check_data();
172
173 _phase_times = new G1GCPhaseTimes(ParallelGCThreads);
174
175 int index = MIN2(ParallelGCThreads - 1, 7u);
176
177 _rs_length_diff_seq->add(rs_length_diff_defaults[index]);
178 _cost_per_card_ms_seq->add(cost_per_card_ms_defaults[index]);
179 _cost_scan_hcc_seq->add(0.0);
180 _young_cards_per_entry_ratio_seq->add(
181 young_cards_per_entry_ratio_defaults[index]);
182 _cost_per_entry_ms_seq->add(cost_per_entry_ms_defaults[index]);
183 _cost_per_byte_ms_seq->add(cost_per_byte_ms_defaults[index]);
184 _constant_other_time_ms_seq->add(constant_other_time_ms_defaults[index]);
185 _young_other_cost_per_region_ms_seq->add(
186 young_other_cost_per_region_ms_defaults[index]);
187 _non_young_other_cost_per_region_ms_seq->add(
188 non_young_other_cost_per_region_ms_defaults[index]);
189
190 // Below, we might need to calculate the pause time target based on
191 // the pause interval. When we do so we are going to give G1 maximum
192 // flexibility and allow it to do pauses when it needs to. So, we'll
193 // arrange that the pause interval to be pause time target + 1 to
194 // ensure that a) the pause time target is maximized with respect to
195 // the pause interval and b) we maintain the invariant that pause
196 // time target < pause interval. If the user does not want this
197 // maximum flexibility, they will have to set the pause interval
198 // explicitly.
199
200 // First make sure that, if either parameter is set, its value is
201 // reasonable.
202 if (!FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
203 if (MaxGCPauseMillis < 1) {
204 vm_exit_during_initialization("MaxGCPauseMillis should be "
205 "greater than 0");
206 }
207 }
208 if (!FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
209 if (GCPauseIntervalMillis < 1) {
210 vm_exit_during_initialization("GCPauseIntervalMillis should be "
211 "greater than 0");
212 }
213 }
214
215 // Then, if the pause time target parameter was not set, set it to
216 // the default value.
217 if (FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
218 if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
219 // The default pause time target in G1 is 200ms
220 FLAG_SET_DEFAULT(MaxGCPauseMillis, 200);
221 } else {
222 // We do not allow the pause interval to be set without the
223 // pause time target
224 vm_exit_during_initialization("GCPauseIntervalMillis cannot be set "
225 "without setting MaxGCPauseMillis");
226 }
227 }
228
229 // Then, if the interval parameter was not set, set it according to
230 // the pause time target (this will also deal with the case when the
231 // pause time target is the default value).
232 if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
233 FLAG_SET_DEFAULT(GCPauseIntervalMillis, MaxGCPauseMillis + 1);
234 }
235
236 // Finally, make sure that the two parameters are consistent.
237 if (MaxGCPauseMillis >= GCPauseIntervalMillis) {
238 char buffer[256];
239 jio_snprintf(buffer, 256,
240 "MaxGCPauseMillis (%u) should be less than "
241 "GCPauseIntervalMillis (%u)",
242 MaxGCPauseMillis, GCPauseIntervalMillis);
243 vm_exit_during_initialization(buffer);
244 }
245
246 double max_gc_time = (double) MaxGCPauseMillis / 1000.0;
247 double time_slice = (double) GCPauseIntervalMillis / 1000.0;
248 _mmu_tracker = new G1MMUTrackerQueue(time_slice, max_gc_time);
249
250 // start conservatively (around 50ms is about right)
251 _concurrent_mark_remark_times_ms->add(0.05);
252 _concurrent_mark_cleanup_times_ms->add(0.20);
253 _tenuring_threshold = MaxTenuringThreshold;
254
255 assert(GCTimeRatio > 0,
256 "we should have set it to a default value set_g1_gc_flags() "
257 "if a user set it to 0");
258 _gc_overhead_perc = 100.0 * (1.0 / (1.0 + GCTimeRatio));
259
260 uintx reserve_perc = G1ReservePercent;
261 // Put an artificial ceiling on this so that it's not set to a silly value.
262 if (reserve_perc > 50) {
263 reserve_perc = 50;
264 warning("G1ReservePercent is set to a value that is too large, "
265 "it's been updated to " UINTX_FORMAT, reserve_perc);
266 }
267 _reserve_factor = (double) reserve_perc / 100.0;
268 // This will be set when the heap is expanded
269 // for the first time during initialization.
270 _reserve_regions = 0;
271
272 _cset_chooser = new CollectionSetChooser();
273 }
274
275 G1CollectorPolicy::~G1CollectorPolicy() {
276 delete _ihop_control;
277 }
278
279 double G1CollectorPolicy::get_new_prediction(TruncatedSeq const* seq) const {
280 return _predictor.get_new_prediction(seq);
281 }
282
283 size_t G1CollectorPolicy::get_new_size_prediction(TruncatedSeq const* seq) const {
284 return (size_t)get_new_prediction(seq);
285 }
286
287 void G1CollectorPolicy::initialize_alignments() {
288 _space_alignment = HeapRegion::GrainBytes;
289 size_t card_table_alignment = CardTableRS::ct_max_alignment_constraint();
290 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
291 _heap_alignment = MAX3(card_table_alignment, _space_alignment, page_size);
292 }
293
294 void G1CollectorPolicy::initialize_flags() {
295 if (G1HeapRegionSize != HeapRegion::GrainBytes) {
296 FLAG_SET_ERGO(size_t, G1HeapRegionSize, HeapRegion::GrainBytes);
297 }
298
299 if (SurvivorRatio < 1) {
300 vm_exit_during_initialization("Invalid survivor ratio specified");
301 }
302 CollectorPolicy::initialize_flags();
303 _young_gen_sizer = new G1YoungGenSizer(); // Must be after call to initialize_flags
304 }
305
306 void G1CollectorPolicy::post_heap_initialize() {
307 uintx max_regions = G1CollectedHeap::heap()->max_regions();
308 size_t max_young_size = (size_t)_young_gen_sizer->max_young_length(max_regions) * HeapRegion::GrainBytes;
309 if (max_young_size != MaxNewSize) {
310 FLAG_SET_ERGO(size_t, MaxNewSize, max_young_size);
311 }
312
313 _ihop_control = create_ihop_control();
314 }
315
316 G1CollectorState* G1CollectorPolicy::collector_state() const { return _g1->collector_state(); }
317
318 G1YoungGenSizer::G1YoungGenSizer() : _sizer_kind(SizerDefaults), _adaptive_size(true),
319 _min_desired_young_length(0), _max_desired_young_length(0) {
320 if (FLAG_IS_CMDLINE(NewRatio)) {
321 if (FLAG_IS_CMDLINE(NewSize) || FLAG_IS_CMDLINE(MaxNewSize)) {
322 warning("-XX:NewSize and -XX:MaxNewSize override -XX:NewRatio");
323 } else {
324 _sizer_kind = SizerNewRatio;
325 _adaptive_size = false;
326 return;
327 }
328 }
329
330 if (NewSize > MaxNewSize) {
331 if (FLAG_IS_CMDLINE(MaxNewSize)) {
332 warning("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). "
333 "A new max generation size of " SIZE_FORMAT "k will be used.",
334 NewSize/K, MaxNewSize/K, NewSize/K);
335 }
336 MaxNewSize = NewSize;
337 }
338
339 if (FLAG_IS_CMDLINE(NewSize)) {
340 _min_desired_young_length = MAX2((uint) (NewSize / HeapRegion::GrainBytes),
341 1U);
342 if (FLAG_IS_CMDLINE(MaxNewSize)) {
343 _max_desired_young_length =
344 MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes),
345 1U);
346 _sizer_kind = SizerMaxAndNewSize;
347 _adaptive_size = _min_desired_young_length == _max_desired_young_length;
348 } else {
349 _sizer_kind = SizerNewSizeOnly;
350 }
351 } else if (FLAG_IS_CMDLINE(MaxNewSize)) {
352 _max_desired_young_length =
353 MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes),
354 1U);
355 _sizer_kind = SizerMaxNewSizeOnly;
356 }
357 }
358
359 uint G1YoungGenSizer::calculate_default_min_length(uint new_number_of_heap_regions) {
360 uint default_value = (new_number_of_heap_regions * G1NewSizePercent) / 100;
361 return MAX2(1U, default_value);
362 }
363
364 uint G1YoungGenSizer::calculate_default_max_length(uint new_number_of_heap_regions) {
365 uint default_value = (new_number_of_heap_regions * G1MaxNewSizePercent) / 100;
366 return MAX2(1U, default_value);
367 }
368
369 void G1YoungGenSizer::recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length) {
370 assert(number_of_heap_regions > 0, "Heap must be initialized");
371
372 switch (_sizer_kind) {
373 case SizerDefaults:
374 *min_young_length = calculate_default_min_length(number_of_heap_regions);
375 *max_young_length = calculate_default_max_length(number_of_heap_regions);
376 break;
377 case SizerNewSizeOnly:
378 *max_young_length = calculate_default_max_length(number_of_heap_regions);
379 *max_young_length = MAX2(*min_young_length, *max_young_length);
380 break;
381 case SizerMaxNewSizeOnly:
382 *min_young_length = calculate_default_min_length(number_of_heap_regions);
383 *min_young_length = MIN2(*min_young_length, *max_young_length);
384 break;
385 case SizerMaxAndNewSize:
386 // Do nothing. Values set on the command line, don't update them at runtime.
387 break;
388 case SizerNewRatio:
389 *min_young_length = number_of_heap_regions / (NewRatio + 1);
390 *max_young_length = *min_young_length;
391 break;
392 default:
393 ShouldNotReachHere();
394 }
395
396 assert(*min_young_length <= *max_young_length, "Invalid min/max young gen size values");
397 }
398
399 uint G1YoungGenSizer::max_young_length(uint number_of_heap_regions) {
400 // We need to pass the desired values because recalculation may not update these
401 // values in some cases.
402 uint temp = _min_desired_young_length;
403 uint result = _max_desired_young_length;
404 recalculate_min_max_young_length(number_of_heap_regions, &temp, &result);
405 return result;
406 }
407
408 void G1YoungGenSizer::heap_size_changed(uint new_number_of_heap_regions) {
409 recalculate_min_max_young_length(new_number_of_heap_regions, &_min_desired_young_length,
410 &_max_desired_young_length);
411 }
412
413 void G1CollectorPolicy::init() {
414 // Set aside an initial future to_space.
415 _g1 = G1CollectedHeap::heap();
416
417 assert(Heap_lock->owned_by_self(), "Locking discipline.");
418
419 initialize_gc_policy_counters();
420
421 if (adaptive_young_list_length()) {
422 _young_list_fixed_length = 0;
423 } else {
424 _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
425 }
426 _free_regions_at_end_of_collection = _g1->num_free_regions();
427
428 update_young_list_max_and_target_length();
429 // We may immediately start allocating regions and placing them on the
430 // collection set list. Initialize the per-collection set info
431 start_incremental_cset_building();
432 }
433
434 void G1CollectorPolicy::note_gc_start(uint num_active_workers) {
435 phase_times()->note_gc_start(num_active_workers);
436 }
437
438 // Create the jstat counters for the policy.
439 void G1CollectorPolicy::initialize_gc_policy_counters() {
440 _gc_policy_counters = new GCPolicyCounters("GarbageFirst", 1, 3);
441 }
442
443 bool G1CollectorPolicy::predict_will_fit(uint young_length,
444 double base_time_ms,
445 uint base_free_regions,
446 double target_pause_time_ms) const {
447 if (young_length >= base_free_regions) {
448 // end condition 1: not enough space for the young regions
449 return false;
450 }
451
452 double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);
453 size_t bytes_to_copy =
454 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
455 double copy_time_ms = predict_object_copy_time_ms(bytes_to_copy);
456 double young_other_time_ms = predict_young_other_time_ms(young_length);
457 double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;
458 if (pause_time_ms > target_pause_time_ms) {
459 // end condition 2: prediction is over the target pause time
460 return false;
461 }
462
463 size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes;
464
465 // When copying, we will likely need more bytes free than is live in the region.
466 // Add some safety margin to factor in the confidence of our guess, and the
467 // natural expected waste.
468 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
469 // of the calculation: the lower the confidence, the more headroom.
470 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
471 // copying due to anticipated waste in the PLABs.
472 double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
473 size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
474
475 if (expected_bytes_to_copy > free_bytes) {
476 // end condition 3: out-of-space
477 return false;
478 }
479
480 // success!
481 return true;
482 }
483
484 void G1CollectorPolicy::record_new_heap_size(uint new_number_of_regions) {
485 // re-calculate the necessary reserve
486 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
487 // We use ceiling so that if reserve_regions_d is > 0.0 (but
488 // smaller than 1.0) we'll get 1.
489 _reserve_regions = (uint) ceil(reserve_regions_d);
490
491 _young_gen_sizer->heap_size_changed(new_number_of_regions);
492 }
493
494 uint G1CollectorPolicy::calculate_young_list_desired_min_length(
495 uint base_min_length) const {
496 uint desired_min_length = 0;
497 if (adaptive_young_list_length()) {
498 if (_alloc_rate_ms_seq->num() > 3) {
499 double now_sec = os::elapsedTime();
500 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
501 double alloc_rate_ms = predict_alloc_rate_ms();
502 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
503 } else {
504 // otherwise we don't have enough info to make the prediction
505 }
506 }
507 desired_min_length += base_min_length;
508 // make sure we don't go below any user-defined minimum bound
509 return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
510 }
511
512 uint G1CollectorPolicy::calculate_young_list_desired_max_length() const {
513 // Here, we might want to also take into account any additional
514 // constraints (i.e., user-defined minimum bound). Currently, we
515 // effectively don't set this bound.
516 return _young_gen_sizer->max_desired_young_length();
517 }
518
519 uint G1CollectorPolicy::update_young_list_max_and_target_length() {
520 return update_young_list_max_and_target_length(get_new_size_prediction(_rs_lengths_seq));
521 }
522
523 uint G1CollectorPolicy::update_young_list_max_and_target_length(size_t rs_lengths) {
524 uint unbounded_target_length = update_young_list_target_length(rs_lengths);
525 update_max_gc_locker_expansion();
526 return unbounded_target_length;
527 }
528
529 uint G1CollectorPolicy::update_young_list_target_length(size_t rs_lengths) {
530 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
531 _young_list_target_length = young_lengths.first;
532 return young_lengths.second;
533 }
534
535 G1CollectorPolicy::YoungTargetLengths G1CollectorPolicy::young_list_target_lengths(size_t rs_lengths) const {
536 YoungTargetLengths result;
537
538 // Calculate the absolute and desired min bounds first.
539
540 // This is how many young regions we already have (currently: the survivors).
541 uint base_min_length = recorded_survivor_regions();
542 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
543 // This is the absolute minimum young length. Ensure that we
544 // will at least have one eden region available for allocation.
545 uint absolute_min_length = base_min_length + MAX2(_g1->young_list()->eden_length(), (uint)1);
546 // If we shrank the young list target it should not shrink below the current size.
547 desired_min_length = MAX2(desired_min_length, absolute_min_length);
548 // Calculate the absolute and desired max bounds.
549
550 uint desired_max_length = calculate_young_list_desired_max_length();
551
552 uint young_list_target_length = 0;
553 if (adaptive_young_list_length()) {
554 if (collector_state()->gcs_are_young()) {
555 young_list_target_length =
556 calculate_young_list_target_length(rs_lengths,
557 base_min_length,
558 desired_min_length,
559 desired_max_length);
560 } else {
561 // Don't calculate anything and let the code below bound it to
562 // the desired_min_length, i.e., do the next GC as soon as
563 // possible to maximize how many old regions we can add to it.
564 }
565 } else {
566 // The user asked for a fixed young gen so we'll fix the young gen
567 // whether the next GC is young or mixed.
568 young_list_target_length = _young_list_fixed_length;
569 }
570
571 result.second = young_list_target_length;
572
573 // We will try our best not to "eat" into the reserve.
574 uint absolute_max_length = 0;
575 if (_free_regions_at_end_of_collection > _reserve_regions) {
576 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
577 }
578 if (desired_max_length > absolute_max_length) {
579 desired_max_length = absolute_max_length;
580 }
581
582 // Make sure we don't go over the desired max length, nor under the
583 // desired min length. In case they clash, desired_min_length wins
584 // which is why that test is second.
585 if (young_list_target_length > desired_max_length) {
586 young_list_target_length = desired_max_length;
587 }
588 if (young_list_target_length < desired_min_length) {
589 young_list_target_length = desired_min_length;
590 }
591
592 assert(young_list_target_length > recorded_survivor_regions(),
593 "we should be able to allocate at least one eden region");
594 assert(young_list_target_length >= absolute_min_length, "post-condition");
595
596 result.first = young_list_target_length;
597 return result;
598 }
599
600 uint
601 G1CollectorPolicy::calculate_young_list_target_length(size_t rs_lengths,
602 uint base_min_length,
603 uint desired_min_length,
604 uint desired_max_length) const {
605 assert(adaptive_young_list_length(), "pre-condition");
606 assert(collector_state()->gcs_are_young(), "only call this for young GCs");
607
608 // In case some edge-condition makes the desired max length too small...
609 if (desired_max_length <= desired_min_length) {
610 return desired_min_length;
611 }
612
613 // We'll adjust min_young_length and max_young_length not to include
614 // the already allocated young regions (i.e., so they reflect the
615 // min and max eden regions we'll allocate). The base_min_length
616 // will be reflected in the predictions by the
617 // survivor_regions_evac_time prediction.
618 assert(desired_min_length > base_min_length, "invariant");
619 uint min_young_length = desired_min_length - base_min_length;
620 assert(desired_max_length > base_min_length, "invariant");
621 uint max_young_length = desired_max_length - base_min_length;
622
623 double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
624 double survivor_regions_evac_time = predict_survivor_regions_evac_time();
625 size_t pending_cards = get_new_size_prediction(_pending_cards_seq);
626 size_t adj_rs_lengths = rs_lengths + predict_rs_length_diff();
627 size_t scanned_cards = predict_young_card_num(adj_rs_lengths);
628 double base_time_ms =
629 predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
630 survivor_regions_evac_time;
631 uint available_free_regions = _free_regions_at_end_of_collection;
632 uint base_free_regions = 0;
633 if (available_free_regions > _reserve_regions) {
634 base_free_regions = available_free_regions - _reserve_regions;
635 }
636
637 // Here, we will make sure that the shortest young length that
638 // makes sense fits within the target pause time.
639
640 if (predict_will_fit(min_young_length, base_time_ms,
641 base_free_regions, target_pause_time_ms)) {
642 // The shortest young length will fit into the target pause time;
643 // we'll now check whether the absolute maximum number of young
644 // regions will fit in the target pause time. If not, we'll do
645 // a binary search between min_young_length and max_young_length.
646 if (predict_will_fit(max_young_length, base_time_ms,
647 base_free_regions, target_pause_time_ms)) {
648 // The maximum young length will fit into the target pause time.
649 // We are done so set min young length to the maximum length (as
650 // the result is assumed to be returned in min_young_length).
651 min_young_length = max_young_length;
652 } else {
653 // The maximum possible number of young regions will not fit within
654 // the target pause time so we'll search for the optimal
655 // length. The loop invariants are:
656 //
657 // min_young_length < max_young_length
658 // min_young_length is known to fit into the target pause time
659 // max_young_length is known not to fit into the target pause time
660 //
661 // Going into the loop we know the above hold as we've just
662 // checked them. Every time around the loop we check whether
663 // the middle value between min_young_length and
664 // max_young_length fits into the target pause time. If it
665 // does, it becomes the new min. If it doesn't, it becomes
666 // the new max. This way we maintain the loop invariants.
667
668 assert(min_young_length < max_young_length, "invariant");
669 uint diff = (max_young_length - min_young_length) / 2;
670 while (diff > 0) {
671 uint young_length = min_young_length + diff;
672 if (predict_will_fit(young_length, base_time_ms,
673 base_free_regions, target_pause_time_ms)) {
674 min_young_length = young_length;
675 } else {
676 max_young_length = young_length;
677 }
678 assert(min_young_length < max_young_length, "invariant");
679 diff = (max_young_length - min_young_length) / 2;
680 }
681 // The results is min_young_length which, according to the
682 // loop invariants, should fit within the target pause time.
683
684 // These are the post-conditions of the binary search above:
685 assert(min_young_length < max_young_length,
686 "otherwise we should have discovered that max_young_length "
687 "fits into the pause target and not done the binary search");
688 assert(predict_will_fit(min_young_length, base_time_ms,
689 base_free_regions, target_pause_time_ms),
690 "min_young_length, the result of the binary search, should "
691 "fit into the pause target");
692 assert(!predict_will_fit(min_young_length + 1, base_time_ms,
693 base_free_regions, target_pause_time_ms),
694 "min_young_length, the result of the binary search, should be "
695 "optimal, so no larger length should fit into the pause target");
696 }
697 } else {
698 // Even the minimum length doesn't fit into the pause time
699 // target, return it as the result nevertheless.
700 }
701 return base_min_length + min_young_length;
702 }
703
704 double G1CollectorPolicy::predict_survivor_regions_evac_time() const {
705 double survivor_regions_evac_time = 0.0;
706 for (HeapRegion * r = _recorded_survivor_head;
707 r != NULL && r != _recorded_survivor_tail->get_next_young_region();
708 r = r->get_next_young_region()) {
709 survivor_regions_evac_time += predict_region_elapsed_time_ms(r, collector_state()->gcs_are_young());
710 }
711 return survivor_regions_evac_time;
712 }
713
714 void G1CollectorPolicy::revise_young_list_target_length_if_necessary() {
715 guarantee( adaptive_young_list_length(), "should not call this otherwise" );
716
717 size_t rs_lengths = _g1->young_list()->sampled_rs_lengths();
718 if (rs_lengths > _rs_lengths_prediction) {
719 // add 10% to avoid having to recalculate often
720 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
721 update_rs_lengths_prediction(rs_lengths_prediction);
722
723 update_young_list_max_and_target_length(rs_lengths_prediction);
724 }
725 }
726
727 void G1CollectorPolicy::update_rs_lengths_prediction() {
728 update_rs_lengths_prediction(get_new_size_prediction(_rs_lengths_seq));
729 }
730
731 void G1CollectorPolicy::update_rs_lengths_prediction(size_t prediction) {
732 if (collector_state()->gcs_are_young() && adaptive_young_list_length()) {
733 _rs_lengths_prediction = prediction;
734 }
735 }
736
737 HeapWord* G1CollectorPolicy::mem_allocate_work(size_t size,
738 bool is_tlab,
739 bool* gc_overhead_limit_was_exceeded) {
740 guarantee(false, "Not using this policy feature yet.");
741 return NULL;
742 }
743
744 // This method controls how a collector handles one or more
745 // of its generations being fully allocated.
746 HeapWord* G1CollectorPolicy::satisfy_failed_allocation(size_t size,
747 bool is_tlab) {
748 guarantee(false, "Not using this policy feature yet.");
749 return NULL;
750 }
751
752
753 #ifndef PRODUCT
754 bool G1CollectorPolicy::verify_young_ages() {
755 HeapRegion* head = _g1->young_list()->first_region();
756 return
757 verify_young_ages(head, _short_lived_surv_rate_group);
758 // also call verify_young_ages on any additional surv rate groups
759 }
760
761 bool
762 G1CollectorPolicy::verify_young_ages(HeapRegion* head,
763 SurvRateGroup *surv_rate_group) {
764 guarantee( surv_rate_group != NULL, "pre-condition" );
765
766 const char* name = surv_rate_group->name();
767 bool ret = true;
768 int prev_age = -1;
769
770 for (HeapRegion* curr = head;
771 curr != NULL;
772 curr = curr->get_next_young_region()) {
773 SurvRateGroup* group = curr->surv_rate_group();
774 if (group == NULL && !curr->is_survivor()) {
775 log_info(gc, verify)("## %s: encountered NULL surv_rate_group", name);
776 ret = false;
777 }
778
779 if (surv_rate_group == group) {
780 int age = curr->age_in_surv_rate_group();
781
782 if (age < 0) {
783 log_info(gc, verify)("## %s: encountered negative age", name);
784 ret = false;
785 }
786
787 if (age <= prev_age) {
788 log_info(gc, verify)("## %s: region ages are not strictly increasing (%d, %d)", name, age, prev_age);
789 ret = false;
790 }
791 prev_age = age;
792 }
793 }
794
795 return ret;
796 }
797 #endif // PRODUCT
798
799 void G1CollectorPolicy::record_full_collection_start() {
800 _full_collection_start_sec = os::elapsedTime();
801 // Release the future to-space so that it is available for compaction into.
802 collector_state()->set_full_collection(true);
803 }
804
805 void G1CollectorPolicy::record_full_collection_end() {
806 // Consider this like a collection pause for the purposes of allocation
807 // since last pause.
808 double end_sec = os::elapsedTime();
809 double full_gc_time_sec = end_sec - _full_collection_start_sec;
810 double full_gc_time_ms = full_gc_time_sec * 1000.0;
811
812 update_recent_gc_times(end_sec, full_gc_time_ms);
813
814 collector_state()->set_full_collection(false);
815
816 // "Nuke" the heuristics that control the young/mixed GC
817 // transitions and make sure we start with young GCs after the Full GC.
818 collector_state()->set_gcs_are_young(true);
819 collector_state()->set_last_young_gc(false);
820 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
821 collector_state()->set_during_initial_mark_pause(false);
822 collector_state()->set_in_marking_window(false);
823 collector_state()->set_in_marking_window_im(false);
824
825 _short_lived_surv_rate_group->start_adding_regions();
826 // also call this on any additional surv rate groups
827
828 record_survivor_regions(0, NULL, NULL);
829
830 _free_regions_at_end_of_collection = _g1->num_free_regions();
831 // Reset survivors SurvRateGroup.
832 _survivor_surv_rate_group->reset();
833 update_young_list_max_and_target_length();
834 update_rs_lengths_prediction();
835 cset_chooser()->clear();
836
837 _bytes_allocated_in_old_since_last_gc = 0;
838
839 record_pause(FullGC, _full_collection_start_sec, end_sec);
840 }
841
842 void G1CollectorPolicy::record_collection_pause_start(double start_time_sec) {
843 // We only need to do this here as the policy will only be applied
844 // to the GC we're about to start. so, no point is calculating this
845 // every time we calculate / recalculate the target young length.
846 update_survivors_policy();
847
848 assert(_g1->used() == _g1->recalculate_used(),
849 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
850 _g1->used(), _g1->recalculate_used());
851
852 phase_times()->record_cur_collection_start_sec(start_time_sec);
853 _pending_cards = _g1->pending_card_num();
854
855 _collection_set_bytes_used_before = 0;
856 _bytes_copied_during_gc = 0;
857
858 collector_state()->set_last_gc_was_young(false);
859
860 // do that for any other surv rate groups
861 _short_lived_surv_rate_group->stop_adding_regions();
862 _survivors_age_table.clear();
863
864 assert( verify_young_ages(), "region age verification" );
865 }
866
867 void G1CollectorPolicy::record_concurrent_mark_init_end(double
868 mark_init_elapsed_time_ms) {
869 collector_state()->set_during_marking(true);
870 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
871 collector_state()->set_during_initial_mark_pause(false);
872 }
873
874 void G1CollectorPolicy::record_concurrent_mark_remark_start() {
875 _mark_remark_start_sec = os::elapsedTime();
876 collector_state()->set_during_marking(false);
877 }
878
879 void G1CollectorPolicy::record_concurrent_mark_remark_end() {
880 double end_time_sec = os::elapsedTime();
881 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
882 _concurrent_mark_remark_times_ms->add(elapsed_time_ms);
883 _prev_collection_pause_end_ms += elapsed_time_ms;
884
885 record_pause(Remark, _mark_remark_start_sec, end_time_sec);
886 }
887
888 void G1CollectorPolicy::record_concurrent_mark_cleanup_start() {
889 _mark_cleanup_start_sec = os::elapsedTime();
890 }
891
892 void G1CollectorPolicy::record_concurrent_mark_cleanup_completed() {
893 bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",
894 "skip last young-only gc");
895 collector_state()->set_last_young_gc(should_continue_with_reclaim);
896 // We skip the marking phase.
897 if (!should_continue_with_reclaim) {
898 abort_time_to_mixed_tracking();
899 }
900 collector_state()->set_in_marking_window(false);
901 }
902
903 double G1CollectorPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
904 return phase_times()->average_time_ms(phase);
905 }
906
907 double G1CollectorPolicy::young_other_time_ms() const {
908 return phase_times()->young_cset_choice_time_ms() +
909 phase_times()->young_free_cset_time_ms();
910 }
911
912 double G1CollectorPolicy::non_young_other_time_ms() const {
913 return phase_times()->non_young_cset_choice_time_ms() +
914 phase_times()->non_young_free_cset_time_ms();
915
916 }
917
918 double G1CollectorPolicy::other_time_ms(double pause_time_ms) const {
919 return pause_time_ms -
920 average_time_ms(G1GCPhaseTimes::UpdateRS) -
921 average_time_ms(G1GCPhaseTimes::ScanRS) -
922 average_time_ms(G1GCPhaseTimes::ObjCopy) -
923 average_time_ms(G1GCPhaseTimes::Termination);
924 }
925
926 double G1CollectorPolicy::constant_other_time_ms(double pause_time_ms) const {
927 return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms();
928 }
929
930 bool G1CollectorPolicy::about_to_start_mixed_phase() const {
931 return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc();
932 }
933
934 bool G1CollectorPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
935 if (about_to_start_mixed_phase()) {
936 return false;
937 }
938
939 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
940
941 size_t cur_used_bytes = _g1->non_young_capacity_bytes();
942 size_t alloc_byte_size = alloc_word_size * HeapWordSize;
943 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
944
945 bool result = false;
946 if (marking_request_bytes > marking_initiating_used_threshold) {
947 result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc();
948 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
949 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
950 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source);
951 }
952
953 return result;
954 }
955
956 // Anything below that is considered to be zero
957 #define MIN_TIMER_GRANULARITY 0.0000001
958
959 void G1CollectorPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
960 double end_time_sec = os::elapsedTime();
961
962 size_t cur_used_bytes = _g1->used();
963 assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
964 bool last_pause_included_initial_mark = false;
965 bool update_stats = !_g1->evacuation_failed();
966
967 NOT_PRODUCT(_short_lived_surv_rate_group->print());
968
969 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
970
971 last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();
972 if (last_pause_included_initial_mark) {
973 record_concurrent_mark_init_end(0.0);
974 } else {
975 maybe_start_marking();
976 }
977
978 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _prev_collection_pause_end_ms);
979 if (app_time_ms < MIN_TIMER_GRANULARITY) {
980 // This usually happens due to the timer not having the required
981 // granularity. Some Linuxes are the usual culprits.
982 // We'll just set it to something (arbitrarily) small.
983 app_time_ms = 1.0;
984 }
985
986 if (update_stats) {
987 // We maintain the invariant that all objects allocated by mutator
988 // threads will be allocated out of eden regions. So, we can use
989 // the eden region number allocated since the previous GC to
990 // calculate the application's allocate rate. The only exception
991 // to that is humongous objects that are allocated separately. But
992 // given that humongous object allocations do not really affect
993 // either the pause's duration nor when the next pause will take
994 // place we can safely ignore them here.
995 uint regions_allocated = eden_cset_region_length();
996 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
997 _alloc_rate_ms_seq->add(alloc_rate_ms);
998
999 double interval_ms =
1000 (end_time_sec - _recent_prev_end_times_for_all_gcs_sec->oldest()) * 1000.0;
1001 update_recent_gc_times(end_time_sec, pause_time_ms);
1002 _recent_avg_pause_time_ratio = _recent_gc_times_ms->sum()/interval_ms;
1003 if (recent_avg_pause_time_ratio() < 0.0 ||
1004 (recent_avg_pause_time_ratio() - 1.0 > 0.0)) {
1005 // Clip ratio between 0.0 and 1.0, and continue. This will be fixed in
1006 // CR 6902692 by redoing the manner in which the ratio is incrementally computed.
1007 if (_recent_avg_pause_time_ratio < 0.0) {
1008 _recent_avg_pause_time_ratio = 0.0;
1009 } else {
1010 assert(_recent_avg_pause_time_ratio - 1.0 > 0.0, "Ctl-point invariant");
1011 _recent_avg_pause_time_ratio = 1.0;
1012 }
1013 }
1014
1015 // Compute the ratio of just this last pause time to the entire time range stored
1016 // in the vectors. Comparing this pause to the entire range, rather than only the
1017 // most recent interval, has the effect of smoothing over a possible transient 'burst'
1018 // of more frequent pauses that don't really reflect a change in heap occupancy.
1019 // This reduces the likelihood of a needless heap expansion being triggered.
1020 _last_pause_time_ratio =
1021 (pause_time_ms * _recent_prev_end_times_for_all_gcs_sec->num()) / interval_ms;
1022 }
1023
1024 bool new_in_marking_window = collector_state()->in_marking_window();
1025 bool new_in_marking_window_im = false;
1026 if (last_pause_included_initial_mark) {
1027 new_in_marking_window = true;
1028 new_in_marking_window_im = true;
1029 }
1030
1031 if (collector_state()->last_young_gc()) {
1032 // This is supposed to to be the "last young GC" before we start
1033 // doing mixed GCs. Here we decide whether to start mixed GCs or not.
1034 assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC");
1035
1036 if (next_gc_should_be_mixed("start mixed GCs",
1037 "do not start mixed GCs")) {
1038 collector_state()->set_gcs_are_young(false);
1039 } else {
1040 // We aborted the mixed GC phase early.
1041 abort_time_to_mixed_tracking();
1042 }
1043
1044 collector_state()->set_last_young_gc(false);
1045 }
1046
1047 if (!collector_state()->last_gc_was_young()) {
1048 // This is a mixed GC. Here we decide whether to continue doing
1049 // mixed GCs or not.
1050 if (!next_gc_should_be_mixed("continue mixed GCs",
1051 "do not continue mixed GCs")) {
1052 collector_state()->set_gcs_are_young(true);
1053
1054 maybe_start_marking();
1055 }
1056 }
1057
1058 _short_lived_surv_rate_group->start_adding_regions();
1059 // Do that for any other surv rate groups
1060
1061 if (update_stats) {
1062 double cost_per_card_ms = 0.0;
1063 double cost_scan_hcc = average_time_ms(G1GCPhaseTimes::ScanHCC);
1064 if (_pending_cards > 0) {
1065 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - cost_scan_hcc) / (double) _pending_cards;
1066 _cost_per_card_ms_seq->add(cost_per_card_ms);
1067 }
1068 _cost_scan_hcc_seq->add(cost_scan_hcc);
1069
1070 double cost_per_entry_ms = 0.0;
1071 if (cards_scanned > 10) {
1072 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
1073 if (collector_state()->last_gc_was_young()) {
1074 _cost_per_entry_ms_seq->add(cost_per_entry_ms);
1075 } else {
1076 _mixed_cost_per_entry_ms_seq->add(cost_per_entry_ms);
1077 }
1078 }
1079
1080 if (_max_rs_lengths > 0) {
1081 double cards_per_entry_ratio =
1082 (double) cards_scanned / (double) _max_rs_lengths;
1083 if (collector_state()->last_gc_was_young()) {
1084 _young_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
1085 } else {
1086 _mixed_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
1087 }
1088 }
1089
1090 // This is defensive. For a while _max_rs_lengths could get
1091 // smaller than _recorded_rs_lengths which was causing
1092 // rs_length_diff to get very large and mess up the RSet length
1093 // predictions. The reason was unsafe concurrent updates to the
1094 // _inc_cset_recorded_rs_lengths field which the code below guards
1095 // against (see CR 7118202). This bug has now been fixed (see CR
1096 // 7119027). However, I'm still worried that
1097 // _inc_cset_recorded_rs_lengths might still end up somewhat
1098 // inaccurate. The concurrent refinement thread calculates an
1099 // RSet's length concurrently with other CR threads updating it
1100 // which might cause it to calculate the length incorrectly (if,
1101 // say, it's in mid-coarsening). So I'll leave in the defensive
1102 // conditional below just in case.
1103 size_t rs_length_diff = 0;
1104 if (_max_rs_lengths > _recorded_rs_lengths) {
1105 rs_length_diff = _max_rs_lengths - _recorded_rs_lengths;
1106 }
1107 _rs_length_diff_seq->add((double) rs_length_diff);
1108
1109 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
1110 size_t copied_bytes = _collection_set_bytes_used_before - freed_bytes;
1111 double cost_per_byte_ms = 0.0;
1112
1113 if (copied_bytes > 0) {
1114 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
1115 if (collector_state()->in_marking_window()) {
1116 _cost_per_byte_ms_during_cm_seq->add(cost_per_byte_ms);
1117 } else {
1118 _cost_per_byte_ms_seq->add(cost_per_byte_ms);
1119 }
1120 }
1121
1122 if (young_cset_region_length() > 0) {
1123 _young_other_cost_per_region_ms_seq->add(young_other_time_ms() /
1124 young_cset_region_length());
1125 }
1126
1127 if (old_cset_region_length() > 0) {
1128 _non_young_other_cost_per_region_ms_seq->add(non_young_other_time_ms() /
1129 old_cset_region_length());
1130 }
1131
1132 _constant_other_time_ms_seq->add(constant_other_time_ms(pause_time_ms));
1133
1134 _pending_cards_seq->add((double) _pending_cards);
1135 _rs_lengths_seq->add((double) _max_rs_lengths);
1136 }
1137
1138 collector_state()->set_in_marking_window(new_in_marking_window);
1139 collector_state()->set_in_marking_window_im(new_in_marking_window_im);
1140 _free_regions_at_end_of_collection = _g1->num_free_regions();
1141 // IHOP control wants to know the expected young gen length if it were not
1142 // restrained by the heap reserve. Using the actual length would make the
1143 // prediction too small and the limit the young gen every time we get to the
1144 // predicted target occupancy.
1145 size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
1146 update_rs_lengths_prediction();
1147
1148 update_ihop_prediction(app_time_ms / 1000.0,
1149 _bytes_allocated_in_old_since_last_gc,
1150 last_unrestrained_young_length * HeapRegion::GrainBytes);
1151 _bytes_allocated_in_old_since_last_gc = 0;
1152
1153 _ihop_control->send_trace_event(_g1->gc_tracer_stw());
1154
1155 // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
1156 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
1157
1158 double scan_hcc_time_ms = average_time_ms(G1GCPhaseTimes::ScanHCC);
1159
1160 if (update_rs_time_goal_ms < scan_hcc_time_ms) {
1161 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
1162 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",
1163 update_rs_time_goal_ms, scan_hcc_time_ms);
1164
1165 update_rs_time_goal_ms = 0;
1166 } else {
1167 update_rs_time_goal_ms -= scan_hcc_time_ms;
1168 }
1169 adjust_concurrent_refinement(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms,
1170 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
1171 update_rs_time_goal_ms);
1172
1173 cset_chooser()->verify();
1174 }
1175
1176 G1IHOPControl* G1CollectorPolicy::create_ihop_control() const {
1177 if (G1UseAdaptiveIHOP) {
1178 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
1179 G1CollectedHeap::heap()->max_capacity(),
1180 &_predictor,
1181 G1ReservePercent,
1182 G1HeapWastePercent);
1183 } else {
1184 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent,
1185 G1CollectedHeap::heap()->max_capacity());
1186 }
1187 }
1188
1189 void G1CollectorPolicy::update_ihop_prediction(double mutator_time_s,
1190 size_t mutator_alloc_bytes,
1191 size_t young_gen_size) {
1192 // Always try to update IHOP prediction. Even evacuation failures give information
1193 // about e.g. whether to start IHOP earlier next time.
1194
1195 // Avoid using really small application times that might create samples with
1196 // very high or very low values. They may be caused by e.g. back-to-back gcs.
1197 double const min_valid_time = 1e-6;
1198
1199 bool report = false;
1200
1201 double marking_to_mixed_time = -1.0;
1202 if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) {
1203 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
1204 assert(marking_to_mixed_time > 0.0,
1205 "Initial mark to mixed time must be larger than zero but is %.3f",
1206 marking_to_mixed_time);
1207 if (marking_to_mixed_time > min_valid_time) {
1208 _ihop_control->update_marking_length(marking_to_mixed_time);
1209 report = true;
1210 }
1211 }
1212
1213 // As an approximation for the young gc promotion rates during marking we use
1214 // all of them. In many applications there are only a few if any young gcs during
1215 // marking, which makes any prediction useless. This increases the accuracy of the
1216 // prediction.
1217 if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) {
1218 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
1219 report = true;
1220 }
1221
1222 if (report) {
1223 report_ihop_statistics();
1224 }
1225 }
1226
1227 void G1CollectorPolicy::report_ihop_statistics() {
1228 _ihop_control->print();
1229 }
1230
1231 void G1CollectorPolicy::print_phases() {
1232 phase_times()->print();
1233 }
1234
1235 void G1CollectorPolicy::adjust_concurrent_refinement(double update_rs_time,
1236 double update_rs_processed_buffers,
1237 double goal_ms) {
1238 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1239 ConcurrentG1Refine *cg1r = G1CollectedHeap::heap()->concurrent_g1_refine();
1240
1241 if (G1UseAdaptiveConcRefinement) {
1242 const int k_gy = 3, k_gr = 6;
1243 const double inc_k = 1.1, dec_k = 0.9;
1244
1245 int g = cg1r->green_zone();
1246 if (update_rs_time > goal_ms) {
1247 g = (int)(g * dec_k); // Can become 0, that's OK. That would mean a mutator-only processing.
1248 } else {
1249 if (update_rs_time < goal_ms && update_rs_processed_buffers > g) {
1250 g = (int)MAX2(g * inc_k, g + 1.0);
1251 }
1252 }
1253 // Change the refinement threads params
1254 cg1r->set_green_zone(g);
1255 cg1r->set_yellow_zone(g * k_gy);
1256 cg1r->set_red_zone(g * k_gr);
1257 cg1r->reinitialize_threads();
1258
1259 int processing_threshold_delta = MAX2((int)(cg1r->green_zone() * _predictor.sigma()), 1);
1260 int processing_threshold = MIN2(cg1r->green_zone() + processing_threshold_delta,
1261 cg1r->yellow_zone());
1262 // Change the barrier params
1263 dcqs.set_process_completed_threshold(processing_threshold);
1264 dcqs.set_max_completed_queue(cg1r->red_zone());
1265 }
1266
1267 int curr_queue_size = dcqs.completed_buffers_num();
1268 if (curr_queue_size >= cg1r->yellow_zone()) {
1269 dcqs.set_completed_queue_padding(curr_queue_size);
1270 } else {
1271 dcqs.set_completed_queue_padding(0);
1272 }
1273 dcqs.notify_if_necessary();
1274 }
1275
1276 size_t G1CollectorPolicy::predict_rs_length_diff() const {
1277 return get_new_size_prediction(_rs_length_diff_seq);
1278 }
1279
1280 double G1CollectorPolicy::predict_alloc_rate_ms() const {
1281 return get_new_prediction(_alloc_rate_ms_seq);
1282 }
1283
1284 double G1CollectorPolicy::predict_cost_per_card_ms() const {
1285 return get_new_prediction(_cost_per_card_ms_seq);
1286 }
1287
1288 double G1CollectorPolicy::predict_scan_hcc_ms() const {
1289 return get_new_prediction(_cost_scan_hcc_seq);
1290 }
1291
1292 double G1CollectorPolicy::predict_rs_update_time_ms(size_t pending_cards) const {
1293 return pending_cards * predict_cost_per_card_ms() + predict_scan_hcc_ms();
1294 }
1295
1296 double G1CollectorPolicy::predict_young_cards_per_entry_ratio() const {
1297 return get_new_prediction(_young_cards_per_entry_ratio_seq);
1298 }
1299
1300 double G1CollectorPolicy::predict_mixed_cards_per_entry_ratio() const {
1301 if (_mixed_cards_per_entry_ratio_seq->num() < 2) {
1302 return predict_young_cards_per_entry_ratio();
1303 } else {
1304 return get_new_prediction(_mixed_cards_per_entry_ratio_seq);
1305 }
1306 }
1307
1308 size_t G1CollectorPolicy::predict_young_card_num(size_t rs_length) const {
1309 return (size_t) (rs_length * predict_young_cards_per_entry_ratio());
1310 }
1311
1312 size_t G1CollectorPolicy::predict_non_young_card_num(size_t rs_length) const {
1313 return (size_t)(rs_length * predict_mixed_cards_per_entry_ratio());
1314 }
1315
1316 double G1CollectorPolicy::predict_rs_scan_time_ms(size_t card_num) const {
1317 if (collector_state()->gcs_are_young()) {
1318 return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1319 } else {
1320 return predict_mixed_rs_scan_time_ms(card_num);
1321 }
1322 }
1323
1324 double G1CollectorPolicy::predict_mixed_rs_scan_time_ms(size_t card_num) const {
1325 if (_mixed_cost_per_entry_ms_seq->num() < 3) {
1326 return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1327 } else {
1328 return card_num * get_new_prediction(_mixed_cost_per_entry_ms_seq);
1329 }
1330 }
1331
1332 double G1CollectorPolicy::predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) const {
1333 if (_cost_per_byte_ms_during_cm_seq->num() < 3) {
1334 return (1.1 * bytes_to_copy) * get_new_prediction(_cost_per_byte_ms_seq);
1335 } else {
1336 return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_during_cm_seq);
1337 }
1338 }
1339
1340 double G1CollectorPolicy::predict_object_copy_time_ms(size_t bytes_to_copy) const {
1341 if (collector_state()->during_concurrent_mark()) {
1342 return predict_object_copy_time_ms_during_cm(bytes_to_copy);
1343 } else {
1344 return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_seq);
1345 }
1346 }
1347
1348 double G1CollectorPolicy::predict_constant_other_time_ms() const {
1349 return get_new_prediction(_constant_other_time_ms_seq);
1350 }
1351
1352 double G1CollectorPolicy::predict_young_other_time_ms(size_t young_num) const {
1353 return young_num * get_new_prediction(_young_other_cost_per_region_ms_seq);
1354 }
1355
1356 double G1CollectorPolicy::predict_non_young_other_time_ms(size_t non_young_num) const {
1357 return non_young_num * get_new_prediction(_non_young_other_cost_per_region_ms_seq);
1358 }
1359
1360 double G1CollectorPolicy::predict_remark_time_ms() const {
1361 return get_new_prediction(_concurrent_mark_remark_times_ms);
1362 }
1363
1364 double G1CollectorPolicy::predict_cleanup_time_ms() const {
1365 return get_new_prediction(_concurrent_mark_cleanup_times_ms);
1366 }
1367
1368 double G1CollectorPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
1369 TruncatedSeq* seq = surv_rate_group->get_seq(age);
1370 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
1371 double pred = get_new_prediction(seq);
1372 if (pred > 1.0) {
1373 pred = 1.0;
1374 }
1375 return pred;
1376 }
1377
1378 double G1CollectorPolicy::predict_yg_surv_rate(int age) const {
1379 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
1380 }
1381
1382 double G1CollectorPolicy::accum_yg_surv_rate_pred(int age) const {
1383 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
1384 }
1385
1386 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards,
1387 size_t scanned_cards) const {
1388 return
1389 predict_rs_update_time_ms(pending_cards) +
1390 predict_rs_scan_time_ms(scanned_cards) +
1391 predict_constant_other_time_ms();
1392 }
1393
1394 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const {
1395 size_t rs_length = predict_rs_length_diff();
1396 size_t card_num;
1397 if (collector_state()->gcs_are_young()) {
1398 card_num = predict_young_card_num(rs_length);
1399 } else {
1400 card_num = predict_non_young_card_num(rs_length);
1401 }
1402 return predict_base_elapsed_time_ms(pending_cards, card_num);
1403 }
1404
1405 size_t G1CollectorPolicy::predict_bytes_to_copy(HeapRegion* hr) const {
1406 size_t bytes_to_copy;
1407 if (hr->is_marked())
1408 bytes_to_copy = hr->max_live_bytes();
1409 else {
1410 assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
1411 int age = hr->age_in_surv_rate_group();
1412 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
1413 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
1414 }
1415 return bytes_to_copy;
1416 }
1417
1418 double G1CollectorPolicy::predict_region_elapsed_time_ms(HeapRegion* hr,
1419 bool for_young_gc) const {
1420 size_t rs_length = hr->rem_set()->occupied();
1421 size_t card_num;
1422
1423 // Predicting the number of cards is based on which type of GC
1424 // we're predicting for.
1425 if (for_young_gc) {
1426 card_num = predict_young_card_num(rs_length);
1427 } else {
1428 card_num = predict_non_young_card_num(rs_length);
1429 }
1430 size_t bytes_to_copy = predict_bytes_to_copy(hr);
1431
1432 double region_elapsed_time_ms =
1433 predict_rs_scan_time_ms(card_num) +
1434 predict_object_copy_time_ms(bytes_to_copy);
1435
1436 // The prediction of the "other" time for this region is based
1437 // upon the region type and NOT the GC type.
1438 if (hr->is_young()) {
1439 region_elapsed_time_ms += predict_young_other_time_ms(1);
1440 } else {
1441 region_elapsed_time_ms += predict_non_young_other_time_ms(1);
1442 }
1443 return region_elapsed_time_ms;
1444 }
1445
1446 void G1CollectorPolicy::init_cset_region_lengths(uint eden_cset_region_length,
1447 uint survivor_cset_region_length) {
1448 _eden_cset_region_length = eden_cset_region_length;
1449 _survivor_cset_region_length = survivor_cset_region_length;
1450 _old_cset_region_length = 0;
1451 }
1452
1453 void G1CollectorPolicy::set_recorded_rs_lengths(size_t rs_lengths) {
1454 _recorded_rs_lengths = rs_lengths;
1455 }
1456
1457 void G1CollectorPolicy::update_recent_gc_times(double end_time_sec,
1458 double elapsed_ms) {
1459 _recent_gc_times_ms->add(elapsed_ms);
1460 _recent_prev_end_times_for_all_gcs_sec->add(end_time_sec);
1461 _prev_collection_pause_end_ms = end_time_sec * 1000.0;
1462 }
1463
1464 void G1CollectorPolicy::clear_ratio_check_data() {
1465 _ratio_over_threshold_count = 0;
1466 _ratio_over_threshold_sum = 0.0;
1467 _pauses_since_start = 0;
1468 }
1469
1470 size_t G1CollectorPolicy::expansion_amount() {
1471 double recent_gc_overhead = recent_avg_pause_time_ratio() * 100.0;
1472 double last_gc_overhead = _last_pause_time_ratio * 100.0;
1473 double threshold = _gc_overhead_perc;
1474 size_t expand_bytes = 0;
1475
1476 // If the heap is at less than half its maximum size, scale the threshold down,
1477 // to a limit of 1. Thus the smaller the heap is, the more likely it is to expand,
1478 // though the scaling code will likely keep the increase small.
1479 if (_g1->capacity() <= _g1->max_capacity() / 2) {
1480 threshold *= (double)_g1->capacity() / (double)(_g1->max_capacity() / 2);
1481 threshold = MAX2(threshold, 1.0);
1482 }
1483
1484 // If the last GC time ratio is over the threshold, increment the count of
1485 // times it has been exceeded, and add this ratio to the sum of exceeded
1486 // ratios.
1487 if (last_gc_overhead > threshold) {
1488 _ratio_over_threshold_count++;
1489 _ratio_over_threshold_sum += last_gc_overhead;
1490 }
1491
1492 // Check if we've had enough GC time ratio checks that were over the
1493 // threshold to trigger an expansion. We'll also expand if we've
1494 // reached the end of the history buffer and the average of all entries
1495 // is still over the threshold. This indicates a smaller number of GCs were
1496 // long enough to make the average exceed the threshold.
1497 bool filled_history_buffer = _pauses_since_start == NumPrevPausesForHeuristics;
1498 if ((_ratio_over_threshold_count == MinOverThresholdForGrowth) ||
1499 (filled_history_buffer && (recent_gc_overhead > threshold))) {
1500 size_t min_expand_bytes = HeapRegion::GrainBytes;
1501 size_t reserved_bytes = _g1->max_capacity();
1502 size_t committed_bytes = _g1->capacity();
1503 size_t uncommitted_bytes = reserved_bytes - committed_bytes;
1504 size_t expand_bytes_via_pct =
1505 uncommitted_bytes * G1ExpandByPercentOfAvailable / 100;
1506 double scale_factor = 1.0;
1507
1508 // If the current size is less than 1/4 of the Initial heap size, expand
1509 // by half of the delta between the current and Initial sizes. IE, grow
1510 // back quickly.
1511 //
1512 // Otherwise, take the current size, or G1ExpandByPercentOfAvailable % of
1513 // the available expansion space, whichever is smaller, as the base
1514 // expansion size. Then possibly scale this size according to how much the
1515 // threshold has (on average) been exceeded by. If the delta is small
1516 // (less than the StartScaleDownAt value), scale the size down linearly, but
1517 // not by less than MinScaleDownFactor. If the delta is large (greater than
1518 // the StartScaleUpAt value), scale up, but adding no more than MaxScaleUpFactor
1519 // times the base size. The scaling will be linear in the range from
1520 // StartScaleUpAt to (StartScaleUpAt + ScaleUpRange). In other words,
1521 // ScaleUpRange sets the rate of scaling up.
1522 if (committed_bytes < InitialHeapSize / 4) {
1523 expand_bytes = (InitialHeapSize - committed_bytes) / 2;
1524 } else {
1525 double const MinScaleDownFactor = 0.2;
1526 double const MaxScaleUpFactor = 2;
1527 double const StartScaleDownAt = _gc_overhead_perc;
1528 double const StartScaleUpAt = _gc_overhead_perc * 1.5;
1529 double const ScaleUpRange = _gc_overhead_perc * 2.0;
1530
1531 double ratio_delta;
1532 if (filled_history_buffer) {
1533 ratio_delta = recent_gc_overhead - threshold;
1534 } else {
1535 ratio_delta = (_ratio_over_threshold_sum/_ratio_over_threshold_count) - threshold;
1536 }
1537
1538 expand_bytes = MIN2(expand_bytes_via_pct, committed_bytes);
1539 if (ratio_delta < StartScaleDownAt) {
1540 scale_factor = ratio_delta / StartScaleDownAt;
1541 scale_factor = MAX2(scale_factor, MinScaleDownFactor);
1542 } else if (ratio_delta > StartScaleUpAt) {
1543 scale_factor = 1 + ((ratio_delta - StartScaleUpAt) / ScaleUpRange);
1544 scale_factor = MIN2(scale_factor, MaxScaleUpFactor);
1545 }
1546 }
1547
1548 log_debug(gc, ergo, heap)("Attempt heap expansion (recent GC overhead higher than threshold after GC) "
1549 "recent GC overhead: %1.2f %% threshold: %1.2f %% uncommitted: " SIZE_FORMAT "B base expansion amount and scale: " SIZE_FORMAT "B (%1.2f%%)",
1550 recent_gc_overhead, threshold, uncommitted_bytes, expand_bytes, scale_factor * 100);
1551
1552 expand_bytes = static_cast<size_t>(expand_bytes * scale_factor);
1553
1554 // Ensure the expansion size is at least the minimum growth amount
1555 // and at most the remaining uncommitted byte size.
1556 expand_bytes = MAX2(expand_bytes, min_expand_bytes);
1557 expand_bytes = MIN2(expand_bytes, uncommitted_bytes);
1558
1559 clear_ratio_check_data();
1560 } else {
1561 // An expansion was not triggered. If we've started counting, increment
1562 // the number of checks we've made in the current window. If we've
1563 // reached the end of the window without resizing, clear the counters to
1564 // start again the next time we see a ratio above the threshold.
1565 if (_ratio_over_threshold_count > 0) {
1566 _pauses_since_start++;
1567 if (_pauses_since_start > NumPrevPausesForHeuristics) {
1568 clear_ratio_check_data();
1569 }
1570 }
1571 }
1572
1573 return expand_bytes;
1574 }
1575
1576 void G1CollectorPolicy::print_yg_surv_rate_info() const {
1577 #ifndef PRODUCT
1578 _short_lived_surv_rate_group->print_surv_rate_summary();
1579 // add this call for any other surv rate groups
1580 #endif // PRODUCT
1581 }
1582
1583 bool G1CollectorPolicy::is_young_list_full() const {
1584 uint young_list_length = _g1->young_list()->length();
1585 uint young_list_target_length = _young_list_target_length;
1586 return young_list_length >= young_list_target_length;
1587 }
1588
1589 bool G1CollectorPolicy::can_expand_young_list() const {
1590 uint young_list_length = _g1->young_list()->length();
1591 uint young_list_max_length = _young_list_max_length;
1592 return young_list_length < young_list_max_length;
1593 }
1594
1595 void G1CollectorPolicy::update_max_gc_locker_expansion() {
1596 uint expansion_region_num = 0;
1597 if (GCLockerEdenExpansionPercent > 0) {
1598 double perc = (double) GCLockerEdenExpansionPercent / 100.0;
1599 double expansion_region_num_d = perc * (double) _young_list_target_length;
1600 // We use ceiling so that if expansion_region_num_d is > 0.0 (but
1601 // less than 1.0) we'll get 1.
1602 expansion_region_num = (uint) ceil(expansion_region_num_d);
1603 } else {
1604 assert(expansion_region_num == 0, "sanity");
1605 }
1606 _young_list_max_length = _young_list_target_length + expansion_region_num;
1607 assert(_young_list_target_length <= _young_list_max_length, "post-condition");
1608 }
1609
1610 // Calculates survivor space parameters.
1611 void G1CollectorPolicy::update_survivors_policy() {
1612 double max_survivor_regions_d =
1613 (double) _young_list_target_length / (double) SurvivorRatio;
1614 // We use ceiling so that if max_survivor_regions_d is > 0.0 (but
1615 // smaller than 1.0) we'll get 1.
1616 _max_survivor_regions = (uint) ceil(max_survivor_regions_d);
1617
1618 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(
1619 HeapRegion::GrainWords * _max_survivor_regions, counters());
1620 }
1621
1622 bool G1CollectorPolicy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
1623 // We actually check whether we are marking here and not if we are in a
1624 // reclamation phase. This means that we will schedule a concurrent mark
1625 // even while we are still in the process of reclaiming memory.
1626 bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
1627 if (!during_cycle) {
1628 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
1629 collector_state()->set_initiate_conc_mark_if_possible(true);
1630 return true;
1631 } else {
1632 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
1633 return false;
1634 }
1635 }
1636
1637 void G1CollectorPolicy::initiate_conc_mark() {
1638 collector_state()->set_during_initial_mark_pause(true);
1639 collector_state()->set_initiate_conc_mark_if_possible(false);
1640 }
1641
1642 void G1CollectorPolicy::decide_on_conc_mark_initiation() {
1643 // We are about to decide on whether this pause will be an
1644 // initial-mark pause.
1645
1646 // First, collector_state()->during_initial_mark_pause() should not be already set. We
1647 // will set it here if we have to. However, it should be cleared by
1648 // the end of the pause (it's only set for the duration of an
1649 // initial-mark pause).
1650 assert(!collector_state()->during_initial_mark_pause(), "pre-condition");
1651
1652 if (collector_state()->initiate_conc_mark_if_possible()) {
1653 // We had noticed on a previous pause that the heap occupancy has
1654 // gone over the initiating threshold and we should start a
1655 // concurrent marking cycle. So we might initiate one.
1656
1657 if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) {
1658 // Initiate a new initial mark if there is no marking or reclamation going on.
1659 initiate_conc_mark();
1660 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
1661 } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) {
1662 // Initiate a user requested initial mark. An initial mark must be young only
1663 // GC, so the collector state must be updated to reflect this.
1664 collector_state()->set_gcs_are_young(true);
1665 collector_state()->set_last_young_gc(false);
1666
1667 abort_time_to_mixed_tracking();
1668 initiate_conc_mark();
1669 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1670 } else {
1671 // The concurrent marking thread is still finishing up the
1672 // previous cycle. If we start one right now the two cycles
1673 // overlap. In particular, the concurrent marking thread might
1674 // be in the process of clearing the next marking bitmap (which
1675 // we will use for the next cycle if we start one). Starting a
1676 // cycle now will be bad given that parts of the marking
1677 // information might get cleared by the marking thread. And we
1678 // cannot wait for the marking thread to finish the cycle as it
1679 // periodically yields while clearing the next marking bitmap
1680 // and, if it's in a yield point, it's waiting for us to
1681 // finish. So, at this point we will not start a cycle and we'll
1682 // let the concurrent marking thread complete the last one.
1683 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1684 }
1685 }
1686 }
1687
1688 class ParKnownGarbageHRClosure: public HeapRegionClosure {
1689 G1CollectedHeap* _g1h;
1690 CSetChooserParUpdater _cset_updater;
1691
1692 public:
1693 ParKnownGarbageHRClosure(CollectionSetChooser* hrSorted,
1694 uint chunk_size) :
1695 _g1h(G1CollectedHeap::heap()),
1696 _cset_updater(hrSorted, true /* parallel */, chunk_size) { }
1697
1698 bool doHeapRegion(HeapRegion* r) {
1699 // Do we have any marking information for this region?
1700 if (r->is_marked()) {
1701 // We will skip any region that's currently used as an old GC
1702 // alloc region (we should not consider those for collection
1703 // before we fill them up).
1704 if (_cset_updater.should_add(r) && !_g1h->is_old_gc_alloc_region(r)) {
1705 _cset_updater.add_region(r);
1706 }
1707 }
1708 return false;
1709 }
1710 };
1711
1712 class ParKnownGarbageTask: public AbstractGangTask {
1713 CollectionSetChooser* _hrSorted;
1714 uint _chunk_size;
1715 G1CollectedHeap* _g1;
1716 HeapRegionClaimer _hrclaimer;
1717
1718 public:
1719 ParKnownGarbageTask(CollectionSetChooser* hrSorted, uint chunk_size, uint n_workers) :
1720 AbstractGangTask("ParKnownGarbageTask"),
1721 _hrSorted(hrSorted), _chunk_size(chunk_size),
1722 _g1(G1CollectedHeap::heap()), _hrclaimer(n_workers) {}
1723
1724 void work(uint worker_id) {
1725 ParKnownGarbageHRClosure parKnownGarbageCl(_hrSorted, _chunk_size);
1726 _g1->heap_region_par_iterate(&parKnownGarbageCl, worker_id, &_hrclaimer);
1727 }
1728 };
1729
1730 uint G1CollectorPolicy::calculate_parallel_work_chunk_size(uint n_workers, uint n_regions) const {
1731 assert(n_workers > 0, "Active gc workers should be greater than 0");
1732 const uint overpartition_factor = 4;
1733 const uint min_chunk_size = MAX2(n_regions / n_workers, 1U);
1734 return MAX2(n_regions / (n_workers * overpartition_factor), min_chunk_size);
1735 }
1736
1737 void G1CollectorPolicy::record_concurrent_mark_cleanup_end() {
1738 cset_chooser()->clear();
1739
1740 WorkGang* workers = _g1->workers();
1741 uint n_workers = workers->active_workers();
1742
1743 uint n_regions = _g1->num_regions();
1744 uint chunk_size = calculate_parallel_work_chunk_size(n_workers, n_regions);
1745 cset_chooser()->prepare_for_par_region_addition(n_workers, n_regions, chunk_size);
1746 ParKnownGarbageTask par_known_garbage_task(cset_chooser(), chunk_size, n_workers);
1747 workers->run_task(&par_known_garbage_task);
1748
1749 cset_chooser()->sort_regions();
1750
1751 double end_sec = os::elapsedTime();
1752 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1753 _concurrent_mark_cleanup_times_ms->add(elapsed_time_ms);
1754 _prev_collection_pause_end_ms += elapsed_time_ms;
1755
1756 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1757 }
1758
1759 // Add the heap region at the head of the non-incremental collection set
1760 void G1CollectorPolicy::add_old_region_to_cset(HeapRegion* hr) {
1761 assert(_inc_cset_build_state == Active, "Precondition");
1762 assert(hr->is_old(), "the region should be old");
1763
1764 assert(!hr->in_collection_set(), "should not already be in the CSet");
1765 _g1->register_old_region_with_cset(hr);
1766 hr->set_next_in_collection_set(_collection_set);
1767 _collection_set = hr;
1768 _collection_set_bytes_used_before += hr->used();
1769 size_t rs_length = hr->rem_set()->occupied();
1770 _recorded_rs_lengths += rs_length;
1771 _old_cset_region_length += 1;
1772 }
1773
1774 // Initialize the per-collection-set information
1775 void G1CollectorPolicy::start_incremental_cset_building() {
1776 assert(_inc_cset_build_state == Inactive, "Precondition");
1777
1778 _inc_cset_head = NULL;
1779 _inc_cset_tail = NULL;
1780 _inc_cset_bytes_used_before = 0;
1781
1782 _inc_cset_max_finger = 0;
1783 _inc_cset_recorded_rs_lengths = 0;
1784 _inc_cset_recorded_rs_lengths_diffs = 0;
1785 _inc_cset_predicted_elapsed_time_ms = 0.0;
1786 _inc_cset_predicted_elapsed_time_ms_diffs = 0.0;
1787 _inc_cset_build_state = Active;
1788 }
1789
1790 void G1CollectorPolicy::finalize_incremental_cset_building() {
1791 assert(_inc_cset_build_state == Active, "Precondition");
1792 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
1793
1794 // The two "main" fields, _inc_cset_recorded_rs_lengths and
1795 // _inc_cset_predicted_elapsed_time_ms, are updated by the thread
1796 // that adds a new region to the CSet. Further updates by the
1797 // concurrent refinement thread that samples the young RSet lengths
1798 // are accumulated in the *_diffs fields. Here we add the diffs to
1799 // the "main" fields.
1800
1801 if (_inc_cset_recorded_rs_lengths_diffs >= 0) {
1802 _inc_cset_recorded_rs_lengths += _inc_cset_recorded_rs_lengths_diffs;
1803 } else {
1804 // This is defensive. The diff should in theory be always positive
1805 // as RSets can only grow between GCs. However, given that we
1806 // sample their size concurrently with other threads updating them
1807 // it's possible that we might get the wrong size back, which
1808 // could make the calculations somewhat inaccurate.
1809 size_t diffs = (size_t) (-_inc_cset_recorded_rs_lengths_diffs);
1810 if (_inc_cset_recorded_rs_lengths >= diffs) {
1811 _inc_cset_recorded_rs_lengths -= diffs;
1812 } else {
1813 _inc_cset_recorded_rs_lengths = 0;
1814 }
1815 }
1816 _inc_cset_predicted_elapsed_time_ms +=
1817 _inc_cset_predicted_elapsed_time_ms_diffs;
1818
1819 _inc_cset_recorded_rs_lengths_diffs = 0;
1820 _inc_cset_predicted_elapsed_time_ms_diffs = 0.0;
1821 }
1822
1823 void G1CollectorPolicy::add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length) {
1824 // This routine is used when:
1825 // * adding survivor regions to the incremental cset at the end of an
1826 // evacuation pause,
1827 // * adding the current allocation region to the incremental cset
1828 // when it is retired, and
1829 // * updating existing policy information for a region in the
1830 // incremental cset via young list RSet sampling.
1831 // Therefore this routine may be called at a safepoint by the
1832 // VM thread, or in-between safepoints by mutator threads (when
1833 // retiring the current allocation region) or a concurrent
1834 // refine thread (RSet sampling).
1835
1836 double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young());
1837 size_t used_bytes = hr->used();
1838 _inc_cset_recorded_rs_lengths += rs_length;
1839 _inc_cset_predicted_elapsed_time_ms += region_elapsed_time_ms;
1840 _inc_cset_bytes_used_before += used_bytes;
1841
1842 // Cache the values we have added to the aggregated information
1843 // in the heap region in case we have to remove this region from
1844 // the incremental collection set, or it is updated by the
1845 // rset sampling code
1846 hr->set_recorded_rs_length(rs_length);
1847 hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms);
1848 }
1849
1850 void G1CollectorPolicy::update_incremental_cset_info(HeapRegion* hr,
1851 size_t new_rs_length) {
1852 // Update the CSet information that is dependent on the new RS length
1853 assert(hr->is_young(), "Precondition");
1854 assert(!SafepointSynchronize::is_at_safepoint(),
1855 "should not be at a safepoint");
1856
1857 // We could have updated _inc_cset_recorded_rs_lengths and
1858 // _inc_cset_predicted_elapsed_time_ms directly but we'd need to do
1859 // that atomically, as this code is executed by a concurrent
1860 // refinement thread, potentially concurrently with a mutator thread
1861 // allocating a new region and also updating the same fields. To
1862 // avoid the atomic operations we accumulate these updates on two
1863 // separate fields (*_diffs) and we'll just add them to the "main"
1864 // fields at the start of a GC.
1865
1866 ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length();
1867 ssize_t rs_lengths_diff = (ssize_t) new_rs_length - old_rs_length;
1868 _inc_cset_recorded_rs_lengths_diffs += rs_lengths_diff;
1869
1870 double old_elapsed_time_ms = hr->predicted_elapsed_time_ms();
1871 double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young());
1872 double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms;
1873 _inc_cset_predicted_elapsed_time_ms_diffs += elapsed_ms_diff;
1874
1875 hr->set_recorded_rs_length(new_rs_length);
1876 hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms);
1877 }
1878
1879 void G1CollectorPolicy::add_region_to_incremental_cset_common(HeapRegion* hr) {
1880 assert(hr->is_young(), "invariant");
1881 assert(hr->young_index_in_cset() > -1, "should have already been set");
1882 assert(_inc_cset_build_state == Active, "Precondition");
1883
1884 // We need to clear and set the cached recorded/cached collection set
1885 // information in the heap region here (before the region gets added
1886 // to the collection set). An individual heap region's cached values
1887 // are calculated, aggregated with the policy collection set info,
1888 // and cached in the heap region here (initially) and (subsequently)
1889 // by the Young List sampling code.
1890
1891 size_t rs_length = hr->rem_set()->occupied();
1892 add_to_incremental_cset_info(hr, rs_length);
1893
1894 HeapWord* hr_end = hr->end();
1895 _inc_cset_max_finger = MAX2(_inc_cset_max_finger, hr_end);
1896
1897 assert(!hr->in_collection_set(), "invariant");
1898 _g1->register_young_region_with_cset(hr);
1899 assert(hr->next_in_collection_set() == NULL, "invariant");
1900 }
1901
1902 // Add the region at the RHS of the incremental cset
1903 void G1CollectorPolicy::add_region_to_incremental_cset_rhs(HeapRegion* hr) {
1904 // We should only ever be appending survivors at the end of a pause
1905 assert(hr->is_survivor(), "Logic");
1906
1907 // Do the 'common' stuff
1908 add_region_to_incremental_cset_common(hr);
1909
1910 // Now add the region at the right hand side
1911 if (_inc_cset_tail == NULL) {
1912 assert(_inc_cset_head == NULL, "invariant");
1913 _inc_cset_head = hr;
1914 } else {
1915 _inc_cset_tail->set_next_in_collection_set(hr);
1916 }
1917 _inc_cset_tail = hr;
1918 }
1919
1920 // Add the region to the LHS of the incremental cset
1921 void G1CollectorPolicy::add_region_to_incremental_cset_lhs(HeapRegion* hr) {
1922 // Survivors should be added to the RHS at the end of a pause
1923 assert(hr->is_eden(), "Logic");
1924
1925 // Do the 'common' stuff
1926 add_region_to_incremental_cset_common(hr);
1927
1928 // Add the region at the left hand side
1929 hr->set_next_in_collection_set(_inc_cset_head);
1930 if (_inc_cset_head == NULL) {
1931 assert(_inc_cset_tail == NULL, "Invariant");
1932 _inc_cset_tail = hr;
1933 }
1934 _inc_cset_head = hr;
1935 }
1936
1937 #ifndef PRODUCT
1938 void G1CollectorPolicy::print_collection_set(HeapRegion* list_head, outputStream* st) {
1939 assert(list_head == inc_cset_head() || list_head == collection_set(), "must be");
1940
1941 st->print_cr("\nCollection_set:");
1942 HeapRegion* csr = list_head;
1943 while (csr != NULL) {
1944 HeapRegion* next = csr->next_in_collection_set();
1945 assert(csr->in_collection_set(), "bad CS");
1946 st->print_cr(" " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d",
1947 HR_FORMAT_PARAMS(csr),
1948 p2i(csr->prev_top_at_mark_start()), p2i(csr->next_top_at_mark_start()),
1949 csr->age_in_surv_rate_group_cond());
1950 csr = next;
1951 }
1952 }
1953 #endif // !PRODUCT
1954
1955 double G1CollectorPolicy::reclaimable_bytes_perc(size_t reclaimable_bytes) const {
1956 // Returns the given amount of reclaimable bytes (that represents
1957 // the amount of reclaimable space still to be collected) as a
1958 // percentage of the current heap capacity.
1959 size_t capacity_bytes = _g1->capacity();
1960 return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
1961 }
1962
1963 void G1CollectorPolicy::maybe_start_marking() {
1964 if (need_to_start_conc_mark("end of GC")) {
1965 // Note: this might have already been set, if during the last
1966 // pause we decided to start a cycle but at the beginning of
1967 // this pause we decided to postpone it. That's OK.
1968 collector_state()->set_initiate_conc_mark_if_possible(true);
1969 }
1970 }
1971
1972 G1CollectorPolicy::PauseKind G1CollectorPolicy::young_gc_pause_kind() const {
1973 assert(!collector_state()->full_collection(), "must be");
1974 if (collector_state()->during_initial_mark_pause()) {
1975 assert(collector_state()->last_gc_was_young(), "must be");
1976 assert(!collector_state()->last_young_gc(), "must be");
1977 return InitialMarkGC;
1978 } else if (collector_state()->last_young_gc()) {
1979 assert(!collector_state()->during_initial_mark_pause(), "must be");
1980 assert(collector_state()->last_gc_was_young(), "must be");
1981 return LastYoungGC;
1982 } else if (!collector_state()->last_gc_was_young()) {
1983 assert(!collector_state()->during_initial_mark_pause(), "must be");
1984 assert(!collector_state()->last_young_gc(), "must be");
1985 return MixedGC;
1986 } else {
1987 assert(collector_state()->last_gc_was_young(), "must be");
1988 assert(!collector_state()->during_initial_mark_pause(), "must be");
1989 assert(!collector_state()->last_young_gc(), "must be");
1990 return YoungOnlyGC;
1991 }
1992 }
1993
1994 void G1CollectorPolicy::record_pause(PauseKind kind, double start, double end) {
1995 // Manage the MMU tracker. For some reason it ignores Full GCs.
1996 if (kind != FullGC) {
1997 _mmu_tracker->add_pause(start, end);
1998 }
1999 // Manage the mutator time tracking from initial mark to first mixed gc.
2000 switch (kind) {
2001 case FullGC:
2002 abort_time_to_mixed_tracking();
2003 break;
2004 case Cleanup:
2005 case Remark:
2006 case YoungOnlyGC:
2007 case LastYoungGC:
2008 _initial_mark_to_mixed.add_pause(end - start);
2009 break;
2010 case InitialMarkGC:
2011 _initial_mark_to_mixed.record_initial_mark_end(end);
2012 break;
2013 case MixedGC:
2014 _initial_mark_to_mixed.record_mixed_gc_start(start);
2015 break;
2016 default:
2017 ShouldNotReachHere();
2018 }
2019 }
2020
2021 void G1CollectorPolicy::abort_time_to_mixed_tracking() {
2022 _initial_mark_to_mixed.reset();
2023 }
2024
2025 bool G1CollectorPolicy::next_gc_should_be_mixed(const char* true_action_str,
2026 const char* false_action_str) const {
2027 if (cset_chooser()->is_empty()) {
2028 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
2029 return false;
2030 }
2031
2032 // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
2033 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
2034 double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
2035 double threshold = (double) G1HeapWastePercent;
2036 if (reclaimable_perc <= threshold) {
2037 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
2038 false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
2039 return false;
2040 }
2041 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
2042 true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
2043 return true;
2044 }
2045
2046 uint G1CollectorPolicy::calc_min_old_cset_length() const {
2047 // The min old CSet region bound is based on the maximum desired
2048 // number of mixed GCs after a cycle. I.e., even if some old regions
2049 // look expensive, we should add them to the CSet anyway to make
2050 // sure we go through the available old regions in no more than the
2051 // maximum desired number of mixed GCs.
2052 //
2053 // The calculation is based on the number of marked regions we added
2054 // to the CSet chooser in the first place, not how many remain, so
2055 // that the result is the same during all mixed GCs that follow a cycle.
2056
2057 const size_t region_num = (size_t) cset_chooser()->length();
2058 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
2059 size_t result = region_num / gc_num;
2060 // emulate ceiling
2061 if (result * gc_num < region_num) {
2062 result += 1;
2063 }
2064 return (uint) result;
2065 }
2066
2067 uint G1CollectorPolicy::calc_max_old_cset_length() const {
2068 // The max old CSet region bound is based on the threshold expressed
2069 // as a percentage of the heap size. I.e., it should bound the
2070 // number of old regions added to the CSet irrespective of how many
2071 // of them are available.
2072
2073 const G1CollectedHeap* g1h = G1CollectedHeap::heap();
2074 const size_t region_num = g1h->num_regions();
2075 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
2076 size_t result = region_num * perc / 100;
2077 // emulate ceiling
2078 if (100 * result < region_num * perc) {
2079 result += 1;
2080 }
2081 return (uint) result;
2082 }
2083
2084
2085 double G1CollectorPolicy::finalize_young_cset_part(double target_pause_time_ms) {
2086 double young_start_time_sec = os::elapsedTime();
2087
2088 YoungList* young_list = _g1->young_list();
2089 finalize_incremental_cset_building();
2090
2091 guarantee(target_pause_time_ms > 0.0,
2092 "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms);
2093 guarantee(_collection_set == NULL, "Precondition");
2094
2095 double base_time_ms = predict_base_elapsed_time_ms(_pending_cards);
2096 double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0);
2097
2098 log_trace(gc, ergo, cset)("Start choosing CSet. pending cards: " SIZE_FORMAT " predicted base time: %1.2fms remaining time: %1.2fms target pause time: %1.2fms",
2099 _pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms);
2100
2101 collector_state()->set_last_gc_was_young(collector_state()->gcs_are_young());
2102
2103 // The young list is laid with the survivor regions from the previous
2104 // pause are appended to the RHS of the young list, i.e.
2105 // [Newly Young Regions ++ Survivors from last pause].
2106
2107 uint survivor_region_length = young_list->survivor_length();
2108 uint eden_region_length = young_list->eden_length();
2109 init_cset_region_lengths(eden_region_length, survivor_region_length);
2110
2111 HeapRegion* hr = young_list->first_survivor_region();
2112 while (hr != NULL) {
2113 assert(hr->is_survivor(), "badly formed young list");
2114 // There is a convention that all the young regions in the CSet
2115 // are tagged as "eden", so we do this for the survivors here. We
2116 // use the special set_eden_pre_gc() as it doesn't check that the
2117 // region is free (which is not the case here).
2118 hr->set_eden_pre_gc();
2119 hr = hr->get_next_young_region();
2120 }
2121
2122 // Clear the fields that point to the survivor list - they are all young now.
2123 young_list->clear_survivors();
2124
2125 _collection_set = _inc_cset_head;
2126 _collection_set_bytes_used_before = _inc_cset_bytes_used_before;
2127 time_remaining_ms = MAX2(time_remaining_ms - _inc_cset_predicted_elapsed_time_ms, 0.0);
2128
2129 log_trace(gc, ergo, cset)("Add young regions to CSet. eden: %u regions, survivors: %u regions, predicted young region time: %1.2fms, target pause time: %1.2fms",
2130 eden_region_length, survivor_region_length, _inc_cset_predicted_elapsed_time_ms, target_pause_time_ms);
2131
2132 // The number of recorded young regions is the incremental
2133 // collection set's current size
2134 set_recorded_rs_lengths(_inc_cset_recorded_rs_lengths);
2135
2136 double young_end_time_sec = os::elapsedTime();
2137 phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0);
2138
2139 return time_remaining_ms;
2140 }
2141
2142 void G1CollectorPolicy::finalize_old_cset_part(double time_remaining_ms) {
2143 double non_young_start_time_sec = os::elapsedTime();
2144 double predicted_old_time_ms = 0.0;
2145
2146
2147 if (!collector_state()->gcs_are_young()) {
2148 cset_chooser()->verify();
2149 const uint min_old_cset_length = calc_min_old_cset_length();
2150 const uint max_old_cset_length = calc_max_old_cset_length();
2151
2152 uint expensive_region_num = 0;
2153 bool check_time_remaining = adaptive_young_list_length();
2154
2155 HeapRegion* hr = cset_chooser()->peek();
2156 while (hr != NULL) {
2157 if (old_cset_region_length() >= max_old_cset_length) {
2158 // Added maximum number of old regions to the CSet.
2159 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached max). old %u regions, max %u regions",
2160 old_cset_region_length(), max_old_cset_length);
2161 break;
2162 }
2163
2164
2165 // Stop adding regions if the remaining reclaimable space is
2166 // not above G1HeapWastePercent.
2167 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
2168 double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
2169 double threshold = (double) G1HeapWastePercent;
2170 if (reclaimable_perc <= threshold) {
2171 // We've added enough old regions that the amount of uncollected
2172 // reclaimable space is at or below the waste threshold. Stop
2173 // adding old regions to the CSet.
2174 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (reclaimable percentage not over threshold). "
2175 "old %u regions, max %u regions, reclaimable: " SIZE_FORMAT "B (%1.2f%%) threshold: " UINTX_FORMAT "%%",
2176 old_cset_region_length(), max_old_cset_length, reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
2177 break;
2178 }
2179
2180 double predicted_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young());
2181 if (check_time_remaining) {
2182 if (predicted_time_ms > time_remaining_ms) {
2183 // Too expensive for the current CSet.
2184
2185 if (old_cset_region_length() >= min_old_cset_length) {
2186 // We have added the minimum number of old regions to the CSet,
2187 // we are done with this CSet.
2188 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (predicted time is too high). "
2189 "predicted time: %1.2fms, remaining time: %1.2fms old %u regions, min %u regions",
2190 predicted_time_ms, time_remaining_ms, old_cset_region_length(), min_old_cset_length);
2191 break;
2192 }
2193
2194 // We'll add it anyway given that we haven't reached the
2195 // minimum number of old regions.
2196 expensive_region_num += 1;
2197 }
2198 } else {
2199 if (old_cset_region_length() >= min_old_cset_length) {
2200 // In the non-auto-tuning case, we'll finish adding regions
2201 // to the CSet if we reach the minimum.
2202
2203 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached min). old %u regions, min %u regions",
2204 old_cset_region_length(), min_old_cset_length);
2205 break;
2206 }
2207 }
2208
2209 // We will add this region to the CSet.
2210 time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0);
2211 predicted_old_time_ms += predicted_time_ms;
2212 cset_chooser()->pop(); // already have region via peek()
2213 _g1->old_set_remove(hr);
2214 add_old_region_to_cset(hr);
2215
2216 hr = cset_chooser()->peek();
2217 }
2218 if (hr == NULL) {
2219 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (candidate old regions not available)");
2220 }
2221
2222 if (expensive_region_num > 0) {
2223 // We print the information once here at the end, predicated on
2224 // whether we added any apparently expensive regions or not, to
2225 // avoid generating output per region.
2226 log_debug(gc, ergo, cset)("Added expensive regions to CSet (old CSet region num not reached min)."
2227 "old: %u regions, expensive: %u regions, min: %u regions, remaining time: %1.2fms",
2228 old_cset_region_length(), expensive_region_num, min_old_cset_length, time_remaining_ms);
2229 }
2230
2231 cset_chooser()->verify();
2232 }
2233
2234 stop_incremental_cset_building();
2235
2236 log_debug(gc, ergo, cset)("Finish choosing CSet. old: %u regions, predicted old region time: %1.2fms, time remaining: %1.2f",
2237 old_cset_region_length(), predicted_old_time_ms, time_remaining_ms);
2238
2239 double non_young_end_time_sec = os::elapsedTime();
2240 phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);
2241 }