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