1 /*
2 * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc/g1/concurrentG1Refine.hpp"
27 #include "gc/g1/concurrentMarkThread.inline.hpp"
28 #include "gc/g1/g1CollectedHeap.inline.hpp"
29 #include "gc/g1/g1CollectorPolicy.hpp"
30 #include "gc/g1/g1ConcurrentMark.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 G1CollectorState* G1CollectorPolicy::collector_state() const { return _g1->collector_state(); }
294
295 // There are three command line options related to the young gen size:
296 // NewSize, MaxNewSize and NewRatio (There is also -Xmn, but that is
297 // just a short form for NewSize==MaxNewSize). G1 will use its internal
298 // heuristics to calculate the actual young gen size, so these options
299 // basically only limit the range within which G1 can pick a young gen
300 // size. Also, these are general options taking byte sizes. G1 will
301 // internally work with a number of regions instead. So, some rounding
302 // will occur.
303 //
304 // If nothing related to the the young gen size is set on the command
305 // line we should allow the young gen to be between G1NewSizePercent
306 // and G1MaxNewSizePercent of the heap size. This means that every time
307 // the heap size changes, the limits for the young gen size will be
308 // recalculated.
309 //
310 // If only -XX:NewSize is set we should use the specified value as the
311 // minimum size for young gen. Still using G1MaxNewSizePercent of the
312 // heap as maximum.
313 //
314 // If only -XX:MaxNewSize is set we should use the specified value as the
315 // maximum size for young gen. Still using G1NewSizePercent of the heap
316 // as minimum.
317 //
318 // If -XX:NewSize and -XX:MaxNewSize are both specified we use these values.
319 // No updates when the heap size changes. There is a special case when
320 // NewSize==MaxNewSize. This is interpreted as "fixed" and will use a
321 // different heuristic for calculating the collection set when we do mixed
322 // collection.
323 //
324 // If only -XX:NewRatio is set we should use the specified ratio of the heap
325 // as both min and max. This will be interpreted as "fixed" just like the
326 // NewSize==MaxNewSize case above. But we will update the min and max
327 // every time the heap size changes.
328 //
329 // NewSize and MaxNewSize override NewRatio. So, NewRatio is ignored if it is
330 // combined with either NewSize or MaxNewSize. (A warning message is printed.)
331 class G1YoungGenSizer : public CHeapObj<mtGC> {
332 private:
333 enum SizerKind {
334 SizerDefaults,
335 SizerNewSizeOnly,
336 SizerMaxNewSizeOnly,
337 SizerMaxAndNewSize,
338 SizerNewRatio
339 };
340 SizerKind _sizer_kind;
341 uint _min_desired_young_length;
342 uint _max_desired_young_length;
343 bool _adaptive_size;
344 uint calculate_default_min_length(uint new_number_of_heap_regions);
345 uint calculate_default_max_length(uint new_number_of_heap_regions);
346
347 // Update the given values for minimum and maximum young gen length in regions
348 // given the number of heap regions depending on the kind of sizing algorithm.
349 void recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length);
350
351 public:
352 G1YoungGenSizer();
353 // Calculate the maximum length of the young gen given the number of regions
354 // depending on the sizing algorithm.
355 uint max_young_length(uint number_of_heap_regions);
356
357 void heap_size_changed(uint new_number_of_heap_regions);
358 uint min_desired_young_length() {
359 return _min_desired_young_length;
360 }
361 uint max_desired_young_length() {
362 return _max_desired_young_length;
363 }
364
365 bool adaptive_young_list_length() const {
366 return _adaptive_size;
367 }
368 };
369
370
371 G1YoungGenSizer::G1YoungGenSizer() : _sizer_kind(SizerDefaults), _adaptive_size(true),
372 _min_desired_young_length(0), _max_desired_young_length(0) {
373 if (FLAG_IS_CMDLINE(NewRatio)) {
374 if (FLAG_IS_CMDLINE(NewSize) || FLAG_IS_CMDLINE(MaxNewSize)) {
375 warning("-XX:NewSize and -XX:MaxNewSize override -XX:NewRatio");
376 } else {
377 _sizer_kind = SizerNewRatio;
378 _adaptive_size = false;
379 return;
380 }
381 }
382
383 if (NewSize > MaxNewSize) {
384 if (FLAG_IS_CMDLINE(MaxNewSize)) {
385 warning("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). "
386 "A new max generation size of " SIZE_FORMAT "k will be used.",
387 NewSize/K, MaxNewSize/K, NewSize/K);
388 }
389 MaxNewSize = NewSize;
390 }
391
392 if (FLAG_IS_CMDLINE(NewSize)) {
393 _min_desired_young_length = MAX2((uint) (NewSize / HeapRegion::GrainBytes),
394 1U);
395 if (FLAG_IS_CMDLINE(MaxNewSize)) {
396 _max_desired_young_length =
397 MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes),
398 1U);
399 _sizer_kind = SizerMaxAndNewSize;
400 _adaptive_size = _min_desired_young_length == _max_desired_young_length;
401 } else {
402 _sizer_kind = SizerNewSizeOnly;
403 }
404 } else if (FLAG_IS_CMDLINE(MaxNewSize)) {
405 _max_desired_young_length =
406 MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes),
407 1U);
408 _sizer_kind = SizerMaxNewSizeOnly;
409 }
410 }
411
412 uint G1YoungGenSizer::calculate_default_min_length(uint new_number_of_heap_regions) {
413 uint default_value = (new_number_of_heap_regions * G1NewSizePercent) / 100;
414 return MAX2(1U, default_value);
415 }
416
417 uint G1YoungGenSizer::calculate_default_max_length(uint new_number_of_heap_regions) {
418 uint default_value = (new_number_of_heap_regions * G1MaxNewSizePercent) / 100;
419 return MAX2(1U, default_value);
420 }
421
422 void G1YoungGenSizer::recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length) {
423 assert(number_of_heap_regions > 0, "Heap must be initialized");
424
425 switch (_sizer_kind) {
426 case SizerDefaults:
427 *min_young_length = calculate_default_min_length(number_of_heap_regions);
428 *max_young_length = calculate_default_max_length(number_of_heap_regions);
429 break;
430 case SizerNewSizeOnly:
431 *max_young_length = calculate_default_max_length(number_of_heap_regions);
432 *max_young_length = MAX2(*min_young_length, *max_young_length);
433 break;
434 case SizerMaxNewSizeOnly:
435 *min_young_length = calculate_default_min_length(number_of_heap_regions);
436 *min_young_length = MIN2(*min_young_length, *max_young_length);
437 break;
438 case SizerMaxAndNewSize:
439 // Do nothing. Values set on the command line, don't update them at runtime.
440 break;
441 case SizerNewRatio:
442 *min_young_length = number_of_heap_regions / (NewRatio + 1);
443 *max_young_length = *min_young_length;
444 break;
445 default:
446 ShouldNotReachHere();
447 }
448
449 assert(*min_young_length <= *max_young_length, "Invalid min/max young gen size values");
450 }
451
452 uint G1YoungGenSizer::max_young_length(uint number_of_heap_regions) {
453 // We need to pass the desired values because recalculation may not update these
454 // values in some cases.
455 uint temp = _min_desired_young_length;
456 uint result = _max_desired_young_length;
457 recalculate_min_max_young_length(number_of_heap_regions, &temp, &result);
458 return result;
459 }
460
461 void G1YoungGenSizer::heap_size_changed(uint new_number_of_heap_regions) {
462 recalculate_min_max_young_length(new_number_of_heap_regions, &_min_desired_young_length,
463 &_max_desired_young_length);
464 }
465
466 void G1CollectorPolicy::post_heap_initialize() {
467 uintx max_regions = G1CollectedHeap::heap()->max_regions();
468 size_t max_young_size = (size_t)_young_gen_sizer->max_young_length(max_regions) * HeapRegion::GrainBytes;
469 if (max_young_size != MaxNewSize) {
470 FLAG_SET_ERGO(size_t, MaxNewSize, max_young_size);
471 }
472
473 _ihop_control = create_ihop_control();
474 }
475
476 void G1CollectorPolicy::initialize_flags() {
477 if (G1HeapRegionSize != HeapRegion::GrainBytes) {
478 FLAG_SET_ERGO(size_t, G1HeapRegionSize, HeapRegion::GrainBytes);
479 }
480
481 if (SurvivorRatio < 1) {
482 vm_exit_during_initialization("Invalid survivor ratio specified");
483 }
484 CollectorPolicy::initialize_flags();
485 _young_gen_sizer = new G1YoungGenSizer(); // Must be after call to initialize_flags
486 }
487
488
489 void G1CollectorPolicy::init() {
490 // Set aside an initial future to_space.
491 _g1 = G1CollectedHeap::heap();
492
493 assert(Heap_lock->owned_by_self(), "Locking discipline.");
494
495 initialize_gc_policy_counters();
496
497 if (adaptive_young_list_length()) {
498 _young_list_fixed_length = 0;
499 } else {
500 _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
501 }
502 _free_regions_at_end_of_collection = _g1->num_free_regions();
503
504 update_young_list_max_and_target_length();
505 // We may immediately start allocating regions and placing them on the
506 // collection set list. Initialize the per-collection set info
507 start_incremental_cset_building();
508 }
509
510 void G1CollectorPolicy::note_gc_start(uint num_active_workers) {
511 phase_times()->note_gc_start(num_active_workers);
512 }
513
514 // Create the jstat counters for the policy.
515 void G1CollectorPolicy::initialize_gc_policy_counters() {
516 _gc_policy_counters = new GCPolicyCounters("GarbageFirst", 1, 3);
517 }
518
519 bool G1CollectorPolicy::predict_will_fit(uint young_length,
520 double base_time_ms,
521 uint base_free_regions,
522 double target_pause_time_ms) const {
523 if (young_length >= base_free_regions) {
524 // end condition 1: not enough space for the young regions
525 return false;
526 }
527
528 double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);
529 size_t bytes_to_copy =
530 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
531 double copy_time_ms = predict_object_copy_time_ms(bytes_to_copy);
532 double young_other_time_ms = predict_young_other_time_ms(young_length);
533 double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;
534 if (pause_time_ms > target_pause_time_ms) {
535 // end condition 2: prediction is over the target pause time
536 return false;
537 }
538
539 size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes;
540
541 // When copying, we will likely need more bytes free than is live in the region.
542 // Add some safety margin to factor in the confidence of our guess, and the
543 // natural expected waste.
544 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
545 // of the calculation: the lower the confidence, the more headroom.
546 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
547 // copying due to anticipated waste in the PLABs.
548 double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
549 size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
550
551 if (expected_bytes_to_copy > free_bytes) {
552 // end condition 3: out-of-space
553 return false;
554 }
555
556 // success!
557 return true;
558 }
559
560 void G1CollectorPolicy::record_new_heap_size(uint new_number_of_regions) {
561 // re-calculate the necessary reserve
562 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
563 // We use ceiling so that if reserve_regions_d is > 0.0 (but
564 // smaller than 1.0) we'll get 1.
565 _reserve_regions = (uint) ceil(reserve_regions_d);
566
567 _young_gen_sizer->heap_size_changed(new_number_of_regions);
568 }
569
570 uint G1CollectorPolicy::calculate_young_list_desired_min_length(
571 uint base_min_length) const {
572 uint desired_min_length = 0;
573 if (adaptive_young_list_length()) {
574 if (_alloc_rate_ms_seq->num() > 3) {
575 double now_sec = os::elapsedTime();
576 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
577 double alloc_rate_ms = predict_alloc_rate_ms();
578 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
579 } else {
580 // otherwise we don't have enough info to make the prediction
581 }
582 }
583 desired_min_length += base_min_length;
584 // make sure we don't go below any user-defined minimum bound
585 return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
586 }
587
588 uint G1CollectorPolicy::calculate_young_list_desired_max_length() const {
589 // Here, we might want to also take into account any additional
590 // constraints (i.e., user-defined minimum bound). Currently, we
591 // effectively don't set this bound.
592 return _young_gen_sizer->max_desired_young_length();
593 }
594
595 uint G1CollectorPolicy::update_young_list_max_and_target_length() {
596 return update_young_list_max_and_target_length(get_new_size_prediction(_rs_lengths_seq));
597 }
598
599 uint G1CollectorPolicy::update_young_list_max_and_target_length(size_t rs_lengths) {
600 uint unbounded_target_length = update_young_list_target_length(rs_lengths);
601 update_max_gc_locker_expansion();
602 return unbounded_target_length;
603 }
604
605 uint G1CollectorPolicy::update_young_list_target_length(size_t rs_lengths) {
606 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
607 _young_list_target_length = young_lengths.first;
608 return young_lengths.second;
609 }
610
611 G1CollectorPolicy::YoungTargetLengths G1CollectorPolicy::young_list_target_lengths(size_t rs_lengths) const {
612 YoungTargetLengths result;
613
614 // Calculate the absolute and desired min bounds first.
615
616 // This is how many young regions we already have (currently: the survivors).
617 uint base_min_length = recorded_survivor_regions();
618 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
619 // This is the absolute minimum young length. Ensure that we
620 // will at least have one eden region available for allocation.
621 uint absolute_min_length = base_min_length + MAX2(_g1->young_list()->eden_length(), (uint)1);
622 // If we shrank the young list target it should not shrink below the current size.
623 desired_min_length = MAX2(desired_min_length, absolute_min_length);
624 // Calculate the absolute and desired max bounds.
625
626 uint desired_max_length = calculate_young_list_desired_max_length();
627
628 uint young_list_target_length = 0;
629 if (adaptive_young_list_length()) {
630 if (collector_state()->gcs_are_young()) {
631 young_list_target_length =
632 calculate_young_list_target_length(rs_lengths,
633 base_min_length,
634 desired_min_length,
635 desired_max_length);
636 } else {
637 // Don't calculate anything and let the code below bound it to
638 // the desired_min_length, i.e., do the next GC as soon as
639 // possible to maximize how many old regions we can add to it.
640 }
641 } else {
642 // The user asked for a fixed young gen so we'll fix the young gen
643 // whether the next GC is young or mixed.
644 young_list_target_length = _young_list_fixed_length;
645 }
646
647 result.second = young_list_target_length;
648
649 // We will try our best not to "eat" into the reserve.
650 uint absolute_max_length = 0;
651 if (_free_regions_at_end_of_collection > _reserve_regions) {
652 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
653 }
654 if (desired_max_length > absolute_max_length) {
655 desired_max_length = absolute_max_length;
656 }
657
658 // Make sure we don't go over the desired max length, nor under the
659 // desired min length. In case they clash, desired_min_length wins
660 // which is why that test is second.
661 if (young_list_target_length > desired_max_length) {
662 young_list_target_length = desired_max_length;
663 }
664 if (young_list_target_length < desired_min_length) {
665 young_list_target_length = desired_min_length;
666 }
667
668 assert(young_list_target_length > recorded_survivor_regions(),
669 "we should be able to allocate at least one eden region");
670 assert(young_list_target_length >= absolute_min_length, "post-condition");
671
672 result.first = young_list_target_length;
673 return result;
674 }
675
676 uint
677 G1CollectorPolicy::calculate_young_list_target_length(size_t rs_lengths,
678 uint base_min_length,
679 uint desired_min_length,
680 uint desired_max_length) const {
681 assert(adaptive_young_list_length(), "pre-condition");
682 assert(collector_state()->gcs_are_young(), "only call this for young GCs");
683
684 // In case some edge-condition makes the desired max length too small...
685 if (desired_max_length <= desired_min_length) {
686 return desired_min_length;
687 }
688
689 // We'll adjust min_young_length and max_young_length not to include
690 // the already allocated young regions (i.e., so they reflect the
691 // min and max eden regions we'll allocate). The base_min_length
692 // will be reflected in the predictions by the
693 // survivor_regions_evac_time prediction.
694 assert(desired_min_length > base_min_length, "invariant");
695 uint min_young_length = desired_min_length - base_min_length;
696 assert(desired_max_length > base_min_length, "invariant");
697 uint max_young_length = desired_max_length - base_min_length;
698
699 double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
700 double survivor_regions_evac_time = predict_survivor_regions_evac_time();
701 size_t pending_cards = get_new_size_prediction(_pending_cards_seq);
702 size_t adj_rs_lengths = rs_lengths + predict_rs_length_diff();
703 size_t scanned_cards = predict_young_card_num(adj_rs_lengths);
704 double base_time_ms =
705 predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
706 survivor_regions_evac_time;
707 uint available_free_regions = _free_regions_at_end_of_collection;
708 uint base_free_regions = 0;
709 if (available_free_regions > _reserve_regions) {
710 base_free_regions = available_free_regions - _reserve_regions;
711 }
712
713 // Here, we will make sure that the shortest young length that
714 // makes sense fits within the target pause time.
715
716 if (predict_will_fit(min_young_length, base_time_ms,
717 base_free_regions, target_pause_time_ms)) {
718 // The shortest young length will fit into the target pause time;
719 // we'll now check whether the absolute maximum number of young
720 // regions will fit in the target pause time. If not, we'll do
721 // a binary search between min_young_length and max_young_length.
722 if (predict_will_fit(max_young_length, base_time_ms,
723 base_free_regions, target_pause_time_ms)) {
724 // The maximum young length will fit into the target pause time.
725 // We are done so set min young length to the maximum length (as
726 // the result is assumed to be returned in min_young_length).
727 min_young_length = max_young_length;
728 } else {
729 // The maximum possible number of young regions will not fit within
730 // the target pause time so we'll search for the optimal
731 // length. The loop invariants are:
732 //
733 // min_young_length < max_young_length
734 // min_young_length is known to fit into the target pause time
735 // max_young_length is known not to fit into the target pause time
736 //
737 // Going into the loop we know the above hold as we've just
738 // checked them. Every time around the loop we check whether
739 // the middle value between min_young_length and
740 // max_young_length fits into the target pause time. If it
741 // does, it becomes the new min. If it doesn't, it becomes
742 // the new max. This way we maintain the loop invariants.
743
744 assert(min_young_length < max_young_length, "invariant");
745 uint diff = (max_young_length - min_young_length) / 2;
746 while (diff > 0) {
747 uint young_length = min_young_length + diff;
748 if (predict_will_fit(young_length, base_time_ms,
749 base_free_regions, target_pause_time_ms)) {
750 min_young_length = young_length;
751 } else {
752 max_young_length = young_length;
753 }
754 assert(min_young_length < max_young_length, "invariant");
755 diff = (max_young_length - min_young_length) / 2;
756 }
757 // The results is min_young_length which, according to the
758 // loop invariants, should fit within the target pause time.
759
760 // These are the post-conditions of the binary search above:
761 assert(min_young_length < max_young_length,
762 "otherwise we should have discovered that max_young_length "
763 "fits into the pause target and not done the binary search");
764 assert(predict_will_fit(min_young_length, base_time_ms,
765 base_free_regions, target_pause_time_ms),
766 "min_young_length, the result of the binary search, should "
767 "fit into the pause target");
768 assert(!predict_will_fit(min_young_length + 1, base_time_ms,
769 base_free_regions, target_pause_time_ms),
770 "min_young_length, the result of the binary search, should be "
771 "optimal, so no larger length should fit into the pause target");
772 }
773 } else {
774 // Even the minimum length doesn't fit into the pause time
775 // target, return it as the result nevertheless.
776 }
777 return base_min_length + min_young_length;
778 }
779
780 double G1CollectorPolicy::predict_survivor_regions_evac_time() const {
781 double survivor_regions_evac_time = 0.0;
782 for (HeapRegion * r = _recorded_survivor_head;
783 r != NULL && r != _recorded_survivor_tail->get_next_young_region();
784 r = r->get_next_young_region()) {
785 survivor_regions_evac_time += predict_region_elapsed_time_ms(r, collector_state()->gcs_are_young());
786 }
787 return survivor_regions_evac_time;
788 }
789
790 void G1CollectorPolicy::revise_young_list_target_length_if_necessary() {
791 guarantee( adaptive_young_list_length(), "should not call this otherwise" );
792
793 size_t rs_lengths = _g1->young_list()->sampled_rs_lengths();
794 if (rs_lengths > _rs_lengths_prediction) {
795 // add 10% to avoid having to recalculate often
796 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
797 update_rs_lengths_prediction(rs_lengths_prediction);
798
799 update_young_list_max_and_target_length(rs_lengths_prediction);
800 }
801 }
802
803 void G1CollectorPolicy::update_rs_lengths_prediction() {
804 update_rs_lengths_prediction(get_new_size_prediction(_rs_lengths_seq));
805 }
806
807 void G1CollectorPolicy::update_rs_lengths_prediction(size_t prediction) {
808 if (collector_state()->gcs_are_young() && adaptive_young_list_length()) {
809 _rs_lengths_prediction = prediction;
810 }
811 }
812
813 #ifndef PRODUCT
814 bool G1CollectorPolicy::verify_young_ages() {
815 HeapRegion* head = _g1->young_list()->first_region();
816 return
817 verify_young_ages(head, _short_lived_surv_rate_group);
818 // also call verify_young_ages on any additional surv rate groups
819 }
820
821 bool
822 G1CollectorPolicy::verify_young_ages(HeapRegion* head,
823 SurvRateGroup *surv_rate_group) {
824 guarantee( surv_rate_group != NULL, "pre-condition" );
825
826 const char* name = surv_rate_group->name();
827 bool ret = true;
828 int prev_age = -1;
829
830 for (HeapRegion* curr = head;
831 curr != NULL;
832 curr = curr->get_next_young_region()) {
833 SurvRateGroup* group = curr->surv_rate_group();
834 if (group == NULL && !curr->is_survivor()) {
835 log_error(gc, verify)("## %s: encountered NULL surv_rate_group", name);
836 ret = false;
837 }
838
839 if (surv_rate_group == group) {
840 int age = curr->age_in_surv_rate_group();
841
842 if (age < 0) {
843 log_error(gc, verify)("## %s: encountered negative age", name);
844 ret = false;
845 }
846
847 if (age <= prev_age) {
848 log_error(gc, verify)("## %s: region ages are not strictly increasing (%d, %d)", name, age, prev_age);
849 ret = false;
850 }
851 prev_age = age;
852 }
853 }
854
855 return ret;
856 }
857 #endif // PRODUCT
858
859 void G1CollectorPolicy::record_full_collection_start() {
860 _full_collection_start_sec = os::elapsedTime();
861 // Release the future to-space so that it is available for compaction into.
862 collector_state()->set_full_collection(true);
863 }
864
865 void G1CollectorPolicy::record_full_collection_end() {
866 // Consider this like a collection pause for the purposes of allocation
867 // since last pause.
868 double end_sec = os::elapsedTime();
869 double full_gc_time_sec = end_sec - _full_collection_start_sec;
870 double full_gc_time_ms = full_gc_time_sec * 1000.0;
871
872 update_recent_gc_times(end_sec, full_gc_time_ms);
873
874 collector_state()->set_full_collection(false);
875
876 // "Nuke" the heuristics that control the young/mixed GC
877 // transitions and make sure we start with young GCs after the Full GC.
878 collector_state()->set_gcs_are_young(true);
879 collector_state()->set_last_young_gc(false);
880 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
881 collector_state()->set_during_initial_mark_pause(false);
882 collector_state()->set_in_marking_window(false);
883 collector_state()->set_in_marking_window_im(false);
884
885 _short_lived_surv_rate_group->start_adding_regions();
886 // also call this on any additional surv rate groups
887
888 record_survivor_regions(0, NULL, NULL);
889
890 _free_regions_at_end_of_collection = _g1->num_free_regions();
891 // Reset survivors SurvRateGroup.
892 _survivor_surv_rate_group->reset();
893 update_young_list_max_and_target_length();
894 update_rs_lengths_prediction();
895 cset_chooser()->clear();
896
897 _bytes_allocated_in_old_since_last_gc = 0;
898
899 record_pause(FullGC, _full_collection_start_sec, end_sec);
900 }
901
902 void G1CollectorPolicy::record_collection_pause_start(double start_time_sec) {
903 // We only need to do this here as the policy will only be applied
904 // to the GC we're about to start. so, no point is calculating this
905 // every time we calculate / recalculate the target young length.
906 update_survivors_policy();
907
908 assert(_g1->used() == _g1->recalculate_used(),
909 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
910 _g1->used(), _g1->recalculate_used());
911
912 phase_times()->record_cur_collection_start_sec(start_time_sec);
913 _pending_cards = _g1->pending_card_num();
914
915 _collection_set_bytes_used_before = 0;
916 _bytes_copied_during_gc = 0;
917
918 collector_state()->set_last_gc_was_young(false);
919
920 // do that for any other surv rate groups
921 _short_lived_surv_rate_group->stop_adding_regions();
922 _survivors_age_table.clear();
923
924 assert( verify_young_ages(), "region age verification" );
925 }
926
927 void G1CollectorPolicy::record_concurrent_mark_init_end(double
928 mark_init_elapsed_time_ms) {
929 collector_state()->set_during_marking(true);
930 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
931 collector_state()->set_during_initial_mark_pause(false);
932 }
933
934 void G1CollectorPolicy::record_concurrent_mark_remark_start() {
935 _mark_remark_start_sec = os::elapsedTime();
936 collector_state()->set_during_marking(false);
937 }
938
939 void G1CollectorPolicy::record_concurrent_mark_remark_end() {
940 double end_time_sec = os::elapsedTime();
941 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
942 _concurrent_mark_remark_times_ms->add(elapsed_time_ms);
943 _prev_collection_pause_end_ms += elapsed_time_ms;
944
945 record_pause(Remark, _mark_remark_start_sec, end_time_sec);
946 }
947
948 void G1CollectorPolicy::record_concurrent_mark_cleanup_start() {
949 _mark_cleanup_start_sec = os::elapsedTime();
950 }
951
952 void G1CollectorPolicy::record_concurrent_mark_cleanup_completed() {
953 bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",
954 "skip last young-only gc");
955 collector_state()->set_last_young_gc(should_continue_with_reclaim);
956 // We skip the marking phase.
957 if (!should_continue_with_reclaim) {
958 abort_time_to_mixed_tracking();
959 }
960 collector_state()->set_in_marking_window(false);
961 }
962
963 double G1CollectorPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
964 return phase_times()->average_time_ms(phase);
965 }
966
967 double G1CollectorPolicy::young_other_time_ms() const {
968 return phase_times()->young_cset_choice_time_ms() +
969 phase_times()->young_free_cset_time_ms();
970 }
971
972 double G1CollectorPolicy::non_young_other_time_ms() const {
973 return phase_times()->non_young_cset_choice_time_ms() +
974 phase_times()->non_young_free_cset_time_ms();
975
976 }
977
978 double G1CollectorPolicy::other_time_ms(double pause_time_ms) const {
979 return pause_time_ms -
980 average_time_ms(G1GCPhaseTimes::UpdateRS) -
981 average_time_ms(G1GCPhaseTimes::ScanRS) -
982 average_time_ms(G1GCPhaseTimes::ObjCopy) -
983 average_time_ms(G1GCPhaseTimes::Termination);
984 }
985
986 double G1CollectorPolicy::constant_other_time_ms(double pause_time_ms) const {
987 return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms();
988 }
989
990 bool G1CollectorPolicy::about_to_start_mixed_phase() const {
991 return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc();
992 }
993
994 bool G1CollectorPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
995 if (about_to_start_mixed_phase()) {
996 return false;
997 }
998
999 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
1000
1001 size_t cur_used_bytes = _g1->non_young_capacity_bytes();
1002 size_t alloc_byte_size = alloc_word_size * HeapWordSize;
1003 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
1004
1005 bool result = false;
1006 if (marking_request_bytes > marking_initiating_used_threshold) {
1007 result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc();
1008 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
1009 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
1010 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source);
1011 }
1012
1013 return result;
1014 }
1015
1016 // Anything below that is considered to be zero
1017 #define MIN_TIMER_GRANULARITY 0.0000001
1018
1019 void G1CollectorPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
1020 double end_time_sec = os::elapsedTime();
1021
1022 size_t cur_used_bytes = _g1->used();
1023 assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
1024 bool last_pause_included_initial_mark = false;
1025 bool update_stats = !_g1->evacuation_failed();
1026
1027 NOT_PRODUCT(_short_lived_surv_rate_group->print());
1028
1029 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
1030
1031 last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();
1032 if (last_pause_included_initial_mark) {
1033 record_concurrent_mark_init_end(0.0);
1034 } else {
1035 maybe_start_marking();
1036 }
1037
1038 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _prev_collection_pause_end_ms);
1039 if (app_time_ms < MIN_TIMER_GRANULARITY) {
1040 // This usually happens due to the timer not having the required
1041 // granularity. Some Linuxes are the usual culprits.
1042 // We'll just set it to something (arbitrarily) small.
1043 app_time_ms = 1.0;
1044 }
1045
1046 if (update_stats) {
1047 // We maintain the invariant that all objects allocated by mutator
1048 // threads will be allocated out of eden regions. So, we can use
1049 // the eden region number allocated since the previous GC to
1050 // calculate the application's allocate rate. The only exception
1051 // to that is humongous objects that are allocated separately. But
1052 // given that humongous object allocations do not really affect
1053 // either the pause's duration nor when the next pause will take
1054 // place we can safely ignore them here.
1055 uint regions_allocated = eden_cset_region_length();
1056 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
1057 _alloc_rate_ms_seq->add(alloc_rate_ms);
1058
1059 double interval_ms =
1060 (end_time_sec - _recent_prev_end_times_for_all_gcs_sec->oldest()) * 1000.0;
1061 update_recent_gc_times(end_time_sec, pause_time_ms);
1062 _recent_avg_pause_time_ratio = _recent_gc_times_ms->sum()/interval_ms;
1063 if (recent_avg_pause_time_ratio() < 0.0 ||
1064 (recent_avg_pause_time_ratio() - 1.0 > 0.0)) {
1065 // Clip ratio between 0.0 and 1.0, and continue. This will be fixed in
1066 // CR 6902692 by redoing the manner in which the ratio is incrementally computed.
1067 if (_recent_avg_pause_time_ratio < 0.0) {
1068 _recent_avg_pause_time_ratio = 0.0;
1069 } else {
1070 assert(_recent_avg_pause_time_ratio - 1.0 > 0.0, "Ctl-point invariant");
1071 _recent_avg_pause_time_ratio = 1.0;
1072 }
1073 }
1074
1075 // Compute the ratio of just this last pause time to the entire time range stored
1076 // in the vectors. Comparing this pause to the entire range, rather than only the
1077 // most recent interval, has the effect of smoothing over a possible transient 'burst'
1078 // of more frequent pauses that don't really reflect a change in heap occupancy.
1079 // This reduces the likelihood of a needless heap expansion being triggered.
1080 _last_pause_time_ratio =
1081 (pause_time_ms * _recent_prev_end_times_for_all_gcs_sec->num()) / interval_ms;
1082 }
1083
1084 bool new_in_marking_window = collector_state()->in_marking_window();
1085 bool new_in_marking_window_im = false;
1086 if (last_pause_included_initial_mark) {
1087 new_in_marking_window = true;
1088 new_in_marking_window_im = true;
1089 }
1090
1091 if (collector_state()->last_young_gc()) {
1092 // This is supposed to to be the "last young GC" before we start
1093 // doing mixed GCs. Here we decide whether to start mixed GCs or not.
1094 assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC");
1095
1096 if (next_gc_should_be_mixed("start mixed GCs",
1097 "do not start mixed GCs")) {
1098 collector_state()->set_gcs_are_young(false);
1099 } else {
1100 // We aborted the mixed GC phase early.
1101 abort_time_to_mixed_tracking();
1102 }
1103
1104 collector_state()->set_last_young_gc(false);
1105 }
1106
1107 if (!collector_state()->last_gc_was_young()) {
1108 // This is a mixed GC. Here we decide whether to continue doing
1109 // mixed GCs or not.
1110 if (!next_gc_should_be_mixed("continue mixed GCs",
1111 "do not continue mixed GCs")) {
1112 collector_state()->set_gcs_are_young(true);
1113
1114 maybe_start_marking();
1115 }
1116 }
1117
1118 _short_lived_surv_rate_group->start_adding_regions();
1119 // Do that for any other surv rate groups
1120
1121 double scan_hcc_time_ms = ConcurrentG1Refine::hot_card_cache_enabled() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
1122
1123 if (update_stats) {
1124 double cost_per_card_ms = 0.0;
1125 if (_pending_cards > 0) {
1126 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards;
1127 _cost_per_card_ms_seq->add(cost_per_card_ms);
1128 }
1129 _cost_scan_hcc_seq->add(scan_hcc_time_ms);
1130
1131 double cost_per_entry_ms = 0.0;
1132 if (cards_scanned > 10) {
1133 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
1134 if (collector_state()->last_gc_was_young()) {
1135 _cost_per_entry_ms_seq->add(cost_per_entry_ms);
1136 } else {
1137 _mixed_cost_per_entry_ms_seq->add(cost_per_entry_ms);
1138 }
1139 }
1140
1141 if (_max_rs_lengths > 0) {
1142 double cards_per_entry_ratio =
1143 (double) cards_scanned / (double) _max_rs_lengths;
1144 if (collector_state()->last_gc_was_young()) {
1145 _young_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
1146 } else {
1147 _mixed_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
1148 }
1149 }
1150
1151 // This is defensive. For a while _max_rs_lengths could get
1152 // smaller than _recorded_rs_lengths which was causing
1153 // rs_length_diff to get very large and mess up the RSet length
1154 // predictions. The reason was unsafe concurrent updates to the
1155 // _inc_cset_recorded_rs_lengths field which the code below guards
1156 // against (see CR 7118202). This bug has now been fixed (see CR
1157 // 7119027). However, I'm still worried that
1158 // _inc_cset_recorded_rs_lengths might still end up somewhat
1159 // inaccurate. The concurrent refinement thread calculates an
1160 // RSet's length concurrently with other CR threads updating it
1161 // which might cause it to calculate the length incorrectly (if,
1162 // say, it's in mid-coarsening). So I'll leave in the defensive
1163 // conditional below just in case.
1164 size_t rs_length_diff = 0;
1165 if (_max_rs_lengths > _recorded_rs_lengths) {
1166 rs_length_diff = _max_rs_lengths - _recorded_rs_lengths;
1167 }
1168 _rs_length_diff_seq->add((double) rs_length_diff);
1169
1170 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
1171 size_t copied_bytes = _collection_set_bytes_used_before - freed_bytes;
1172 double cost_per_byte_ms = 0.0;
1173
1174 if (copied_bytes > 0) {
1175 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
1176 if (collector_state()->in_marking_window()) {
1177 _cost_per_byte_ms_during_cm_seq->add(cost_per_byte_ms);
1178 } else {
1179 _cost_per_byte_ms_seq->add(cost_per_byte_ms);
1180 }
1181 }
1182
1183 if (young_cset_region_length() > 0) {
1184 _young_other_cost_per_region_ms_seq->add(young_other_time_ms() /
1185 young_cset_region_length());
1186 }
1187
1188 if (old_cset_region_length() > 0) {
1189 _non_young_other_cost_per_region_ms_seq->add(non_young_other_time_ms() /
1190 old_cset_region_length());
1191 }
1192
1193 _constant_other_time_ms_seq->add(constant_other_time_ms(pause_time_ms));
1194
1195 _pending_cards_seq->add((double) _pending_cards);
1196 _rs_lengths_seq->add((double) _max_rs_lengths);
1197 }
1198
1199 collector_state()->set_in_marking_window(new_in_marking_window);
1200 collector_state()->set_in_marking_window_im(new_in_marking_window_im);
1201 _free_regions_at_end_of_collection = _g1->num_free_regions();
1202 // IHOP control wants to know the expected young gen length if it were not
1203 // restrained by the heap reserve. Using the actual length would make the
1204 // prediction too small and the limit the young gen every time we get to the
1205 // predicted target occupancy.
1206 size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
1207 update_rs_lengths_prediction();
1208
1209 update_ihop_prediction(app_time_ms / 1000.0,
1210 _bytes_allocated_in_old_since_last_gc,
1211 last_unrestrained_young_length * HeapRegion::GrainBytes);
1212 _bytes_allocated_in_old_since_last_gc = 0;
1213
1214 _ihop_control->send_trace_event(_g1->gc_tracer_stw());
1215
1216 // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
1217 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
1218
1219 if (update_rs_time_goal_ms < scan_hcc_time_ms) {
1220 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
1221 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",
1222 update_rs_time_goal_ms, scan_hcc_time_ms);
1223
1224 update_rs_time_goal_ms = 0;
1225 } else {
1226 update_rs_time_goal_ms -= scan_hcc_time_ms;
1227 }
1228 adjust_concurrent_refinement(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms,
1229 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
1230 update_rs_time_goal_ms);
1231
1232 cset_chooser()->verify();
1233 }
1234
1235 G1IHOPControl* G1CollectorPolicy::create_ihop_control() const {
1236 if (G1UseAdaptiveIHOP) {
1237 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
1238 G1CollectedHeap::heap()->max_capacity(),
1239 &_predictor,
1240 G1ReservePercent,
1241 G1HeapWastePercent);
1242 } else {
1243 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent,
1244 G1CollectedHeap::heap()->max_capacity());
1245 }
1246 }
1247
1248 void G1CollectorPolicy::update_ihop_prediction(double mutator_time_s,
1249 size_t mutator_alloc_bytes,
1250 size_t young_gen_size) {
1251 // Always try to update IHOP prediction. Even evacuation failures give information
1252 // about e.g. whether to start IHOP earlier next time.
1253
1254 // Avoid using really small application times that might create samples with
1255 // very high or very low values. They may be caused by e.g. back-to-back gcs.
1256 double const min_valid_time = 1e-6;
1257
1258 bool report = false;
1259
1260 double marking_to_mixed_time = -1.0;
1261 if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) {
1262 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
1263 assert(marking_to_mixed_time > 0.0,
1264 "Initial mark to mixed time must be larger than zero but is %.3f",
1265 marking_to_mixed_time);
1266 if (marking_to_mixed_time > min_valid_time) {
1267 _ihop_control->update_marking_length(marking_to_mixed_time);
1268 report = true;
1269 }
1270 }
1271
1272 // As an approximation for the young gc promotion rates during marking we use
1273 // all of them. In many applications there are only a few if any young gcs during
1274 // marking, which makes any prediction useless. This increases the accuracy of the
1275 // prediction.
1276 if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) {
1277 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
1278 report = true;
1279 }
1280
1281 if (report) {
1282 report_ihop_statistics();
1283 }
1284 }
1285
1286 void G1CollectorPolicy::report_ihop_statistics() {
1287 _ihop_control->print();
1288 }
1289
1290 void G1CollectorPolicy::print_phases() {
1291 phase_times()->print();
1292 }
1293
1294 void G1CollectorPolicy::adjust_concurrent_refinement(double update_rs_time,
1295 double update_rs_processed_buffers,
1296 double goal_ms) {
1297 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1298 ConcurrentG1Refine *cg1r = G1CollectedHeap::heap()->concurrent_g1_refine();
1299
1300 if (G1UseAdaptiveConcRefinement) {
1301 const int k_gy = 3, k_gr = 6;
1302 const double inc_k = 1.1, dec_k = 0.9;
1303
1304 int g = cg1r->green_zone();
1305 if (update_rs_time > goal_ms) {
1306 g = (int)(g * dec_k); // Can become 0, that's OK. That would mean a mutator-only processing.
1307 } else {
1308 if (update_rs_time < goal_ms && update_rs_processed_buffers > g) {
1309 g = (int)MAX2(g * inc_k, g + 1.0);
1310 }
1311 }
1312 // Change the refinement threads params
1313 cg1r->set_green_zone(g);
1314 cg1r->set_yellow_zone(g * k_gy);
1315 cg1r->set_red_zone(g * k_gr);
1316 cg1r->reinitialize_threads();
1317
1318 int processing_threshold_delta = MAX2((int)(cg1r->green_zone() * _predictor.sigma()), 1);
1319 int processing_threshold = MIN2(cg1r->green_zone() + processing_threshold_delta,
1320 cg1r->yellow_zone());
1321 // Change the barrier params
1322 dcqs.set_process_completed_threshold(processing_threshold);
1323 dcqs.set_max_completed_queue(cg1r->red_zone());
1324 }
1325
1326 int curr_queue_size = dcqs.completed_buffers_num();
1327 if (curr_queue_size >= cg1r->yellow_zone()) {
1328 dcqs.set_completed_queue_padding(curr_queue_size);
1329 } else {
1330 dcqs.set_completed_queue_padding(0);
1331 }
1332 dcqs.notify_if_necessary();
1333 }
1334
1335 size_t G1CollectorPolicy::predict_rs_length_diff() const {
1336 return get_new_size_prediction(_rs_length_diff_seq);
1337 }
1338
1339 double G1CollectorPolicy::predict_alloc_rate_ms() const {
1340 return get_new_prediction(_alloc_rate_ms_seq);
1341 }
1342
1343 double G1CollectorPolicy::predict_cost_per_card_ms() const {
1344 return get_new_prediction(_cost_per_card_ms_seq);
1345 }
1346
1347 double G1CollectorPolicy::predict_scan_hcc_ms() const {
1348 return get_new_prediction(_cost_scan_hcc_seq);
1349 }
1350
1351 double G1CollectorPolicy::predict_rs_update_time_ms(size_t pending_cards) const {
1352 return pending_cards * predict_cost_per_card_ms() + predict_scan_hcc_ms();
1353 }
1354
1355 double G1CollectorPolicy::predict_young_cards_per_entry_ratio() const {
1356 return get_new_prediction(_young_cards_per_entry_ratio_seq);
1357 }
1358
1359 double G1CollectorPolicy::predict_mixed_cards_per_entry_ratio() const {
1360 if (_mixed_cards_per_entry_ratio_seq->num() < 2) {
1361 return predict_young_cards_per_entry_ratio();
1362 } else {
1363 return get_new_prediction(_mixed_cards_per_entry_ratio_seq);
1364 }
1365 }
1366
1367 size_t G1CollectorPolicy::predict_young_card_num(size_t rs_length) const {
1368 return (size_t) (rs_length * predict_young_cards_per_entry_ratio());
1369 }
1370
1371 size_t G1CollectorPolicy::predict_non_young_card_num(size_t rs_length) const {
1372 return (size_t)(rs_length * predict_mixed_cards_per_entry_ratio());
1373 }
1374
1375 double G1CollectorPolicy::predict_rs_scan_time_ms(size_t card_num) const {
1376 if (collector_state()->gcs_are_young()) {
1377 return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1378 } else {
1379 return predict_mixed_rs_scan_time_ms(card_num);
1380 }
1381 }
1382
1383 double G1CollectorPolicy::predict_mixed_rs_scan_time_ms(size_t card_num) const {
1384 if (_mixed_cost_per_entry_ms_seq->num() < 3) {
1385 return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1386 } else {
1387 return card_num * get_new_prediction(_mixed_cost_per_entry_ms_seq);
1388 }
1389 }
1390
1391 double G1CollectorPolicy::predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) const {
1392 if (_cost_per_byte_ms_during_cm_seq->num() < 3) {
1393 return (1.1 * bytes_to_copy) * get_new_prediction(_cost_per_byte_ms_seq);
1394 } else {
1395 return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_during_cm_seq);
1396 }
1397 }
1398
1399 double G1CollectorPolicy::predict_object_copy_time_ms(size_t bytes_to_copy) const {
1400 if (collector_state()->during_concurrent_mark()) {
1401 return predict_object_copy_time_ms_during_cm(bytes_to_copy);
1402 } else {
1403 return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_seq);
1404 }
1405 }
1406
1407 double G1CollectorPolicy::predict_constant_other_time_ms() const {
1408 return get_new_prediction(_constant_other_time_ms_seq);
1409 }
1410
1411 double G1CollectorPolicy::predict_young_other_time_ms(size_t young_num) const {
1412 return young_num * get_new_prediction(_young_other_cost_per_region_ms_seq);
1413 }
1414
1415 double G1CollectorPolicy::predict_non_young_other_time_ms(size_t non_young_num) const {
1416 return non_young_num * get_new_prediction(_non_young_other_cost_per_region_ms_seq);
1417 }
1418
1419 double G1CollectorPolicy::predict_remark_time_ms() const {
1420 return get_new_prediction(_concurrent_mark_remark_times_ms);
1421 }
1422
1423 double G1CollectorPolicy::predict_cleanup_time_ms() const {
1424 return get_new_prediction(_concurrent_mark_cleanup_times_ms);
1425 }
1426
1427 double G1CollectorPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
1428 TruncatedSeq* seq = surv_rate_group->get_seq(age);
1429 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
1430 double pred = get_new_prediction(seq);
1431 if (pred > 1.0) {
1432 pred = 1.0;
1433 }
1434 return pred;
1435 }
1436
1437 double G1CollectorPolicy::predict_yg_surv_rate(int age) const {
1438 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
1439 }
1440
1441 double G1CollectorPolicy::accum_yg_surv_rate_pred(int age) const {
1442 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
1443 }
1444
1445 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards,
1446 size_t scanned_cards) const {
1447 return
1448 predict_rs_update_time_ms(pending_cards) +
1449 predict_rs_scan_time_ms(scanned_cards) +
1450 predict_constant_other_time_ms();
1451 }
1452
1453 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const {
1454 size_t rs_length = predict_rs_length_diff();
1455 size_t card_num;
1456 if (collector_state()->gcs_are_young()) {
1457 card_num = predict_young_card_num(rs_length);
1458 } else {
1459 card_num = predict_non_young_card_num(rs_length);
1460 }
1461 return predict_base_elapsed_time_ms(pending_cards, card_num);
1462 }
1463
1464 size_t G1CollectorPolicy::predict_bytes_to_copy(HeapRegion* hr) const {
1465 size_t bytes_to_copy;
1466 if (hr->is_marked())
1467 bytes_to_copy = hr->max_live_bytes();
1468 else {
1469 assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
1470 int age = hr->age_in_surv_rate_group();
1471 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
1472 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
1473 }
1474 return bytes_to_copy;
1475 }
1476
1477 double G1CollectorPolicy::predict_region_elapsed_time_ms(HeapRegion* hr,
1478 bool for_young_gc) const {
1479 size_t rs_length = hr->rem_set()->occupied();
1480 size_t card_num;
1481
1482 // Predicting the number of cards is based on which type of GC
1483 // we're predicting for.
1484 if (for_young_gc) {
1485 card_num = predict_young_card_num(rs_length);
1486 } else {
1487 card_num = predict_non_young_card_num(rs_length);
1488 }
1489 size_t bytes_to_copy = predict_bytes_to_copy(hr);
1490
1491 double region_elapsed_time_ms =
1492 predict_rs_scan_time_ms(card_num) +
1493 predict_object_copy_time_ms(bytes_to_copy);
1494
1495 // The prediction of the "other" time for this region is based
1496 // upon the region type and NOT the GC type.
1497 if (hr->is_young()) {
1498 region_elapsed_time_ms += predict_young_other_time_ms(1);
1499 } else {
1500 region_elapsed_time_ms += predict_non_young_other_time_ms(1);
1501 }
1502 return region_elapsed_time_ms;
1503 }
1504
1505 void G1CollectorPolicy::init_cset_region_lengths(uint eden_cset_region_length,
1506 uint survivor_cset_region_length) {
1507 _eden_cset_region_length = eden_cset_region_length;
1508 _survivor_cset_region_length = survivor_cset_region_length;
1509 _old_cset_region_length = 0;
1510 }
1511
1512 void G1CollectorPolicy::set_recorded_rs_lengths(size_t rs_lengths) {
1513 _recorded_rs_lengths = rs_lengths;
1514 }
1515
1516 void G1CollectorPolicy::update_recent_gc_times(double end_time_sec,
1517 double elapsed_ms) {
1518 _recent_gc_times_ms->add(elapsed_ms);
1519 _recent_prev_end_times_for_all_gcs_sec->add(end_time_sec);
1520 _prev_collection_pause_end_ms = end_time_sec * 1000.0;
1521 }
1522
1523 void G1CollectorPolicy::clear_ratio_check_data() {
1524 _ratio_over_threshold_count = 0;
1525 _ratio_over_threshold_sum = 0.0;
1526 _pauses_since_start = 0;
1527 }
1528
1529 size_t G1CollectorPolicy::expansion_amount() {
1530 double recent_gc_overhead = recent_avg_pause_time_ratio() * 100.0;
1531 double last_gc_overhead = _last_pause_time_ratio * 100.0;
1532 double threshold = _gc_overhead_perc;
1533 size_t expand_bytes = 0;
1534
1535 // If the heap is at less than half its maximum size, scale the threshold down,
1536 // to a limit of 1. Thus the smaller the heap is, the more likely it is to expand,
1537 // though the scaling code will likely keep the increase small.
1538 if (_g1->capacity() <= _g1->max_capacity() / 2) {
1539 threshold *= (double)_g1->capacity() / (double)(_g1->max_capacity() / 2);
1540 threshold = MAX2(threshold, 1.0);
1541 }
1542
1543 // If the last GC time ratio is over the threshold, increment the count of
1544 // times it has been exceeded, and add this ratio to the sum of exceeded
1545 // ratios.
1546 if (last_gc_overhead > threshold) {
1547 _ratio_over_threshold_count++;
1548 _ratio_over_threshold_sum += last_gc_overhead;
1549 }
1550
1551 // Check if we've had enough GC time ratio checks that were over the
1552 // threshold to trigger an expansion. We'll also expand if we've
1553 // reached the end of the history buffer and the average of all entries
1554 // is still over the threshold. This indicates a smaller number of GCs were
1555 // long enough to make the average exceed the threshold.
1556 bool filled_history_buffer = _pauses_since_start == NumPrevPausesForHeuristics;
1557 if ((_ratio_over_threshold_count == MinOverThresholdForGrowth) ||
1558 (filled_history_buffer && (recent_gc_overhead > threshold))) {
1559 size_t min_expand_bytes = HeapRegion::GrainBytes;
1560 size_t reserved_bytes = _g1->max_capacity();
1561 size_t committed_bytes = _g1->capacity();
1562 size_t uncommitted_bytes = reserved_bytes - committed_bytes;
1563 size_t expand_bytes_via_pct =
1564 uncommitted_bytes * G1ExpandByPercentOfAvailable / 100;
1565 double scale_factor = 1.0;
1566
1567 // If the current size is less than 1/4 of the Initial heap size, expand
1568 // by half of the delta between the current and Initial sizes. IE, grow
1569 // back quickly.
1570 //
1571 // Otherwise, take the current size, or G1ExpandByPercentOfAvailable % of
1572 // the available expansion space, whichever is smaller, as the base
1573 // expansion size. Then possibly scale this size according to how much the
1574 // threshold has (on average) been exceeded by. If the delta is small
1575 // (less than the StartScaleDownAt value), scale the size down linearly, but
1576 // not by less than MinScaleDownFactor. If the delta is large (greater than
1577 // the StartScaleUpAt value), scale up, but adding no more than MaxScaleUpFactor
1578 // times the base size. The scaling will be linear in the range from
1579 // StartScaleUpAt to (StartScaleUpAt + ScaleUpRange). In other words,
1580 // ScaleUpRange sets the rate of scaling up.
1581 if (committed_bytes < InitialHeapSize / 4) {
1582 expand_bytes = (InitialHeapSize - committed_bytes) / 2;
1583 } else {
1584 double const MinScaleDownFactor = 0.2;
1585 double const MaxScaleUpFactor = 2;
1586 double const StartScaleDownAt = _gc_overhead_perc;
1587 double const StartScaleUpAt = _gc_overhead_perc * 1.5;
1588 double const ScaleUpRange = _gc_overhead_perc * 2.0;
1589
1590 double ratio_delta;
1591 if (filled_history_buffer) {
1592 ratio_delta = recent_gc_overhead - threshold;
1593 } else {
1594 ratio_delta = (_ratio_over_threshold_sum/_ratio_over_threshold_count) - threshold;
1595 }
1596
1597 expand_bytes = MIN2(expand_bytes_via_pct, committed_bytes);
1598 if (ratio_delta < StartScaleDownAt) {
1599 scale_factor = ratio_delta / StartScaleDownAt;
1600 scale_factor = MAX2(scale_factor, MinScaleDownFactor);
1601 } else if (ratio_delta > StartScaleUpAt) {
1602 scale_factor = 1 + ((ratio_delta - StartScaleUpAt) / ScaleUpRange);
1603 scale_factor = MIN2(scale_factor, MaxScaleUpFactor);
1604 }
1605 }
1606
1607 log_debug(gc, ergo, heap)("Attempt heap expansion (recent GC overhead higher than threshold after GC) "
1608 "recent GC overhead: %1.2f %% threshold: %1.2f %% uncommitted: " SIZE_FORMAT "B base expansion amount and scale: " SIZE_FORMAT "B (%1.2f%%)",
1609 recent_gc_overhead, threshold, uncommitted_bytes, expand_bytes, scale_factor * 100);
1610
1611 expand_bytes = static_cast<size_t>(expand_bytes * scale_factor);
1612
1613 // Ensure the expansion size is at least the minimum growth amount
1614 // and at most the remaining uncommitted byte size.
1615 expand_bytes = MAX2(expand_bytes, min_expand_bytes);
1616 expand_bytes = MIN2(expand_bytes, uncommitted_bytes);
1617
1618 clear_ratio_check_data();
1619 } else {
1620 // An expansion was not triggered. If we've started counting, increment
1621 // the number of checks we've made in the current window. If we've
1622 // reached the end of the window without resizing, clear the counters to
1623 // start again the next time we see a ratio above the threshold.
1624 if (_ratio_over_threshold_count > 0) {
1625 _pauses_since_start++;
1626 if (_pauses_since_start > NumPrevPausesForHeuristics) {
1627 clear_ratio_check_data();
1628 }
1629 }
1630 }
1631
1632 return expand_bytes;
1633 }
1634
1635 void G1CollectorPolicy::print_yg_surv_rate_info() const {
1636 #ifndef PRODUCT
1637 _short_lived_surv_rate_group->print_surv_rate_summary();
1638 // add this call for any other surv rate groups
1639 #endif // PRODUCT
1640 }
1641
1642 bool G1CollectorPolicy::is_young_list_full() const {
1643 uint young_list_length = _g1->young_list()->length();
1644 uint young_list_target_length = _young_list_target_length;
1645 return young_list_length >= young_list_target_length;
1646 }
1647
1648 bool G1CollectorPolicy::can_expand_young_list() const {
1649 uint young_list_length = _g1->young_list()->length();
1650 uint young_list_max_length = _young_list_max_length;
1651 return young_list_length < young_list_max_length;
1652 }
1653
1654 bool G1CollectorPolicy::adaptive_young_list_length() const {
1655 return _young_gen_sizer->adaptive_young_list_length();
1656 }
1657
1658 void G1CollectorPolicy::update_max_gc_locker_expansion() {
1659 uint expansion_region_num = 0;
1660 if (GCLockerEdenExpansionPercent > 0) {
1661 double perc = (double) GCLockerEdenExpansionPercent / 100.0;
1662 double expansion_region_num_d = perc * (double) _young_list_target_length;
1663 // We use ceiling so that if expansion_region_num_d is > 0.0 (but
1664 // less than 1.0) we'll get 1.
1665 expansion_region_num = (uint) ceil(expansion_region_num_d);
1666 } else {
1667 assert(expansion_region_num == 0, "sanity");
1668 }
1669 _young_list_max_length = _young_list_target_length + expansion_region_num;
1670 assert(_young_list_target_length <= _young_list_max_length, "post-condition");
1671 }
1672
1673 // Calculates survivor space parameters.
1674 void G1CollectorPolicy::update_survivors_policy() {
1675 double max_survivor_regions_d =
1676 (double) _young_list_target_length / (double) SurvivorRatio;
1677 // We use ceiling so that if max_survivor_regions_d is > 0.0 (but
1678 // smaller than 1.0) we'll get 1.
1679 _max_survivor_regions = (uint) ceil(max_survivor_regions_d);
1680
1681 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(
1682 HeapRegion::GrainWords * _max_survivor_regions, counters());
1683 }
1684
1685 bool G1CollectorPolicy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
1686 // We actually check whether we are marking here and not if we are in a
1687 // reclamation phase. This means that we will schedule a concurrent mark
1688 // even while we are still in the process of reclaiming memory.
1689 bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
1690 if (!during_cycle) {
1691 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
1692 collector_state()->set_initiate_conc_mark_if_possible(true);
1693 return true;
1694 } else {
1695 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
1696 return false;
1697 }
1698 }
1699
1700 void G1CollectorPolicy::initiate_conc_mark() {
1701 collector_state()->set_during_initial_mark_pause(true);
1702 collector_state()->set_initiate_conc_mark_if_possible(false);
1703 }
1704
1705 void G1CollectorPolicy::decide_on_conc_mark_initiation() {
1706 // We are about to decide on whether this pause will be an
1707 // initial-mark pause.
1708
1709 // First, collector_state()->during_initial_mark_pause() should not be already set. We
1710 // will set it here if we have to. However, it should be cleared by
1711 // the end of the pause (it's only set for the duration of an
1712 // initial-mark pause).
1713 assert(!collector_state()->during_initial_mark_pause(), "pre-condition");
1714
1715 if (collector_state()->initiate_conc_mark_if_possible()) {
1716 // We had noticed on a previous pause that the heap occupancy has
1717 // gone over the initiating threshold and we should start a
1718 // concurrent marking cycle. So we might initiate one.
1719
1720 if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) {
1721 // Initiate a new initial mark if there is no marking or reclamation going on.
1722 initiate_conc_mark();
1723 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
1724 } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) {
1725 // Initiate a user requested initial mark. An initial mark must be young only
1726 // GC, so the collector state must be updated to reflect this.
1727 collector_state()->set_gcs_are_young(true);
1728 collector_state()->set_last_young_gc(false);
1729
1730 abort_time_to_mixed_tracking();
1731 initiate_conc_mark();
1732 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1733 } else {
1734 // The concurrent marking thread is still finishing up the
1735 // previous cycle. If we start one right now the two cycles
1736 // overlap. In particular, the concurrent marking thread might
1737 // be in the process of clearing the next marking bitmap (which
1738 // we will use for the next cycle if we start one). Starting a
1739 // cycle now will be bad given that parts of the marking
1740 // information might get cleared by the marking thread. And we
1741 // cannot wait for the marking thread to finish the cycle as it
1742 // periodically yields while clearing the next marking bitmap
1743 // and, if it's in a yield point, it's waiting for us to
1744 // finish. So, at this point we will not start a cycle and we'll
1745 // let the concurrent marking thread complete the last one.
1746 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1747 }
1748 }
1749 }
1750
1751 class ParKnownGarbageHRClosure: public HeapRegionClosure {
1752 G1CollectedHeap* _g1h;
1753 CSetChooserParUpdater _cset_updater;
1754
1755 public:
1756 ParKnownGarbageHRClosure(CollectionSetChooser* hrSorted,
1757 uint chunk_size) :
1758 _g1h(G1CollectedHeap::heap()),
1759 _cset_updater(hrSorted, true /* parallel */, chunk_size) { }
1760
1761 bool doHeapRegion(HeapRegion* r) {
1762 // Do we have any marking information for this region?
1763 if (r->is_marked()) {
1764 // We will skip any region that's currently used as an old GC
1765 // alloc region (we should not consider those for collection
1766 // before we fill them up).
1767 if (_cset_updater.should_add(r) && !_g1h->is_old_gc_alloc_region(r)) {
1768 _cset_updater.add_region(r);
1769 }
1770 }
1771 return false;
1772 }
1773 };
1774
1775 class ParKnownGarbageTask: public AbstractGangTask {
1776 CollectionSetChooser* _hrSorted;
1777 uint _chunk_size;
1778 G1CollectedHeap* _g1;
1779 HeapRegionClaimer _hrclaimer;
1780
1781 public:
1782 ParKnownGarbageTask(CollectionSetChooser* hrSorted, uint chunk_size, uint n_workers) :
1783 AbstractGangTask("ParKnownGarbageTask"),
1784 _hrSorted(hrSorted), _chunk_size(chunk_size),
1785 _g1(G1CollectedHeap::heap()), _hrclaimer(n_workers) {}
1786
1787 void work(uint worker_id) {
1788 ParKnownGarbageHRClosure parKnownGarbageCl(_hrSorted, _chunk_size);
1789 _g1->heap_region_par_iterate(&parKnownGarbageCl, worker_id, &_hrclaimer);
1790 }
1791 };
1792
1793 uint G1CollectorPolicy::calculate_parallel_work_chunk_size(uint n_workers, uint n_regions) const {
1794 assert(n_workers > 0, "Active gc workers should be greater than 0");
1795 const uint overpartition_factor = 4;
1796 const uint min_chunk_size = MAX2(n_regions / n_workers, 1U);
1797 return MAX2(n_regions / (n_workers * overpartition_factor), min_chunk_size);
1798 }
1799
1800 void G1CollectorPolicy::record_concurrent_mark_cleanup_end() {
1801 cset_chooser()->clear();
1802
1803 WorkGang* workers = _g1->workers();
1804 uint n_workers = workers->active_workers();
1805
1806 uint n_regions = _g1->num_regions();
1807 uint chunk_size = calculate_parallel_work_chunk_size(n_workers, n_regions);
1808 cset_chooser()->prepare_for_par_region_addition(n_workers, n_regions, chunk_size);
1809 ParKnownGarbageTask par_known_garbage_task(cset_chooser(), chunk_size, n_workers);
1810 workers->run_task(&par_known_garbage_task);
1811
1812 cset_chooser()->sort_regions();
1813
1814 double end_sec = os::elapsedTime();
1815 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1816 _concurrent_mark_cleanup_times_ms->add(elapsed_time_ms);
1817 _prev_collection_pause_end_ms += elapsed_time_ms;
1818
1819 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1820 }
1821
1822 // Add the heap region at the head of the non-incremental collection set
1823 void G1CollectorPolicy::add_old_region_to_cset(HeapRegion* hr) {
1824 assert(_inc_cset_build_state == Active, "Precondition");
1825 assert(hr->is_old(), "the region should be old");
1826
1827 assert(!hr->in_collection_set(), "should not already be in the CSet");
1828 _g1->register_old_region_with_cset(hr);
1829 hr->set_next_in_collection_set(_collection_set);
1830 _collection_set = hr;
1831 _collection_set_bytes_used_before += hr->used();
1832 size_t rs_length = hr->rem_set()->occupied();
1833 _recorded_rs_lengths += rs_length;
1834 _old_cset_region_length += 1;
1835 }
1836
1837 // Initialize the per-collection-set information
1838 void G1CollectorPolicy::start_incremental_cset_building() {
1839 assert(_inc_cset_build_state == Inactive, "Precondition");
1840
1841 _inc_cset_head = NULL;
1842 _inc_cset_tail = NULL;
1843 _inc_cset_bytes_used_before = 0;
1844
1845 _inc_cset_recorded_rs_lengths = 0;
1846 _inc_cset_recorded_rs_lengths_diffs = 0;
1847 _inc_cset_predicted_elapsed_time_ms = 0.0;
1848 _inc_cset_predicted_elapsed_time_ms_diffs = 0.0;
1849 _inc_cset_build_state = Active;
1850 }
1851
1852 void G1CollectorPolicy::finalize_incremental_cset_building() {
1853 assert(_inc_cset_build_state == Active, "Precondition");
1854 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
1855
1856 // The two "main" fields, _inc_cset_recorded_rs_lengths and
1857 // _inc_cset_predicted_elapsed_time_ms, are updated by the thread
1858 // that adds a new region to the CSet. Further updates by the
1859 // concurrent refinement thread that samples the young RSet lengths
1860 // are accumulated in the *_diffs fields. Here we add the diffs to
1861 // the "main" fields.
1862
1863 if (_inc_cset_recorded_rs_lengths_diffs >= 0) {
1864 _inc_cset_recorded_rs_lengths += _inc_cset_recorded_rs_lengths_diffs;
1865 } else {
1866 // This is defensive. The diff should in theory be always positive
1867 // as RSets can only grow between GCs. However, given that we
1868 // sample their size concurrently with other threads updating them
1869 // it's possible that we might get the wrong size back, which
1870 // could make the calculations somewhat inaccurate.
1871 size_t diffs = (size_t) (-_inc_cset_recorded_rs_lengths_diffs);
1872 if (_inc_cset_recorded_rs_lengths >= diffs) {
1873 _inc_cset_recorded_rs_lengths -= diffs;
1874 } else {
1875 _inc_cset_recorded_rs_lengths = 0;
1876 }
1877 }
1878 _inc_cset_predicted_elapsed_time_ms +=
1879 _inc_cset_predicted_elapsed_time_ms_diffs;
1880
1881 _inc_cset_recorded_rs_lengths_diffs = 0;
1882 _inc_cset_predicted_elapsed_time_ms_diffs = 0.0;
1883 }
1884
1885 void G1CollectorPolicy::add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length) {
1886 // This routine is used when:
1887 // * adding survivor regions to the incremental cset at the end of an
1888 // evacuation pause,
1889 // * adding the current allocation region to the incremental cset
1890 // when it is retired, and
1891 // * updating existing policy information for a region in the
1892 // incremental cset via young list RSet sampling.
1893 // Therefore this routine may be called at a safepoint by the
1894 // VM thread, or in-between safepoints by mutator threads (when
1895 // retiring the current allocation region) or a concurrent
1896 // refine thread (RSet sampling).
1897
1898 double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young());
1899 size_t used_bytes = hr->used();
1900 _inc_cset_recorded_rs_lengths += rs_length;
1901 _inc_cset_predicted_elapsed_time_ms += region_elapsed_time_ms;
1902 _inc_cset_bytes_used_before += used_bytes;
1903
1904 // Cache the values we have added to the aggregated information
1905 // in the heap region in case we have to remove this region from
1906 // the incremental collection set, or it is updated by the
1907 // rset sampling code
1908 hr->set_recorded_rs_length(rs_length);
1909 hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms);
1910 }
1911
1912 void G1CollectorPolicy::update_incremental_cset_info(HeapRegion* hr,
1913 size_t new_rs_length) {
1914 // Update the CSet information that is dependent on the new RS length
1915 assert(hr->is_young(), "Precondition");
1916 assert(!SafepointSynchronize::is_at_safepoint(),
1917 "should not be at a safepoint");
1918
1919 // We could have updated _inc_cset_recorded_rs_lengths and
1920 // _inc_cset_predicted_elapsed_time_ms directly but we'd need to do
1921 // that atomically, as this code is executed by a concurrent
1922 // refinement thread, potentially concurrently with a mutator thread
1923 // allocating a new region and also updating the same fields. To
1924 // avoid the atomic operations we accumulate these updates on two
1925 // separate fields (*_diffs) and we'll just add them to the "main"
1926 // fields at the start of a GC.
1927
1928 ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length();
1929 ssize_t rs_lengths_diff = (ssize_t) new_rs_length - old_rs_length;
1930 _inc_cset_recorded_rs_lengths_diffs += rs_lengths_diff;
1931
1932 double old_elapsed_time_ms = hr->predicted_elapsed_time_ms();
1933 double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young());
1934 double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms;
1935 _inc_cset_predicted_elapsed_time_ms_diffs += elapsed_ms_diff;
1936
1937 hr->set_recorded_rs_length(new_rs_length);
1938 hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms);
1939 }
1940
1941 void G1CollectorPolicy::add_region_to_incremental_cset_common(HeapRegion* hr) {
1942 assert(hr->is_young(), "invariant");
1943 assert(hr->young_index_in_cset() > -1, "should have already been set");
1944 assert(_inc_cset_build_state == Active, "Precondition");
1945
1946 // We need to clear and set the cached recorded/cached collection set
1947 // information in the heap region here (before the region gets added
1948 // to the collection set). An individual heap region's cached values
1949 // are calculated, aggregated with the policy collection set info,
1950 // and cached in the heap region here (initially) and (subsequently)
1951 // by the Young List sampling code.
1952
1953 size_t rs_length = hr->rem_set()->occupied();
1954 add_to_incremental_cset_info(hr, rs_length);
1955
1956 assert(!hr->in_collection_set(), "invariant");
1957 _g1->register_young_region_with_cset(hr);
1958 assert(hr->next_in_collection_set() == NULL, "invariant");
1959 }
1960
1961 // Add the region at the RHS of the incremental cset
1962 void G1CollectorPolicy::add_region_to_incremental_cset_rhs(HeapRegion* hr) {
1963 // We should only ever be appending survivors at the end of a pause
1964 assert(hr->is_survivor(), "Logic");
1965
1966 // Do the 'common' stuff
1967 add_region_to_incremental_cset_common(hr);
1968
1969 // Now add the region at the right hand side
1970 if (_inc_cset_tail == NULL) {
1971 assert(_inc_cset_head == NULL, "invariant");
1972 _inc_cset_head = hr;
1973 } else {
1974 _inc_cset_tail->set_next_in_collection_set(hr);
1975 }
1976 _inc_cset_tail = hr;
1977 }
1978
1979 // Add the region to the LHS of the incremental cset
1980 void G1CollectorPolicy::add_region_to_incremental_cset_lhs(HeapRegion* hr) {
1981 // Survivors should be added to the RHS at the end of a pause
1982 assert(hr->is_eden(), "Logic");
1983
1984 // Do the 'common' stuff
1985 add_region_to_incremental_cset_common(hr);
1986
1987 // Add the region at the left hand side
1988 hr->set_next_in_collection_set(_inc_cset_head);
1989 if (_inc_cset_head == NULL) {
1990 assert(_inc_cset_tail == NULL, "Invariant");
1991 _inc_cset_tail = hr;
1992 }
1993 _inc_cset_head = hr;
1994 }
1995
1996 #ifndef PRODUCT
1997 void G1CollectorPolicy::print_collection_set(HeapRegion* list_head, outputStream* st) {
1998 assert(list_head == inc_cset_head() || list_head == collection_set(), "must be");
1999
2000 st->print_cr("\nCollection_set:");
2001 HeapRegion* csr = list_head;
2002 while (csr != NULL) {
2003 HeapRegion* next = csr->next_in_collection_set();
2004 assert(csr->in_collection_set(), "bad CS");
2005 st->print_cr(" " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d",
2006 HR_FORMAT_PARAMS(csr),
2007 p2i(csr->prev_top_at_mark_start()), p2i(csr->next_top_at_mark_start()),
2008 csr->age_in_surv_rate_group_cond());
2009 csr = next;
2010 }
2011 }
2012 #endif // !PRODUCT
2013
2014 double G1CollectorPolicy::reclaimable_bytes_perc(size_t reclaimable_bytes) const {
2015 // Returns the given amount of reclaimable bytes (that represents
2016 // the amount of reclaimable space still to be collected) as a
2017 // percentage of the current heap capacity.
2018 size_t capacity_bytes = _g1->capacity();
2019 return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
2020 }
2021
2022 void G1CollectorPolicy::maybe_start_marking() {
2023 if (need_to_start_conc_mark("end of GC")) {
2024 // Note: this might have already been set, if during the last
2025 // pause we decided to start a cycle but at the beginning of
2026 // this pause we decided to postpone it. That's OK.
2027 collector_state()->set_initiate_conc_mark_if_possible(true);
2028 }
2029 }
2030
2031 G1CollectorPolicy::PauseKind G1CollectorPolicy::young_gc_pause_kind() const {
2032 assert(!collector_state()->full_collection(), "must be");
2033 if (collector_state()->during_initial_mark_pause()) {
2034 assert(collector_state()->last_gc_was_young(), "must be");
2035 assert(!collector_state()->last_young_gc(), "must be");
2036 return InitialMarkGC;
2037 } else if (collector_state()->last_young_gc()) {
2038 assert(!collector_state()->during_initial_mark_pause(), "must be");
2039 assert(collector_state()->last_gc_was_young(), "must be");
2040 return LastYoungGC;
2041 } else if (!collector_state()->last_gc_was_young()) {
2042 assert(!collector_state()->during_initial_mark_pause(), "must be");
2043 assert(!collector_state()->last_young_gc(), "must be");
2044 return MixedGC;
2045 } else {
2046 assert(collector_state()->last_gc_was_young(), "must be");
2047 assert(!collector_state()->during_initial_mark_pause(), "must be");
2048 assert(!collector_state()->last_young_gc(), "must be");
2049 return YoungOnlyGC;
2050 }
2051 }
2052
2053 void G1CollectorPolicy::record_pause(PauseKind kind, double start, double end) {
2054 // Manage the MMU tracker. For some reason it ignores Full GCs.
2055 if (kind != FullGC) {
2056 _mmu_tracker->add_pause(start, end);
2057 }
2058 // Manage the mutator time tracking from initial mark to first mixed gc.
2059 switch (kind) {
2060 case FullGC:
2061 abort_time_to_mixed_tracking();
2062 break;
2063 case Cleanup:
2064 case Remark:
2065 case YoungOnlyGC:
2066 case LastYoungGC:
2067 _initial_mark_to_mixed.add_pause(end - start);
2068 break;
2069 case InitialMarkGC:
2070 _initial_mark_to_mixed.record_initial_mark_end(end);
2071 break;
2072 case MixedGC:
2073 _initial_mark_to_mixed.record_mixed_gc_start(start);
2074 break;
2075 default:
2076 ShouldNotReachHere();
2077 }
2078 }
2079
2080 void G1CollectorPolicy::abort_time_to_mixed_tracking() {
2081 _initial_mark_to_mixed.reset();
2082 }
2083
2084 bool G1CollectorPolicy::next_gc_should_be_mixed(const char* true_action_str,
2085 const char* false_action_str) const {
2086 if (cset_chooser()->is_empty()) {
2087 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
2088 return false;
2089 }
2090
2091 // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
2092 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
2093 double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
2094 double threshold = (double) G1HeapWastePercent;
2095 if (reclaimable_perc <= threshold) {
2096 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
2097 false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
2098 return false;
2099 }
2100 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
2101 true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
2102 return true;
2103 }
2104
2105 uint G1CollectorPolicy::calc_min_old_cset_length() const {
2106 // The min old CSet region bound is based on the maximum desired
2107 // number of mixed GCs after a cycle. I.e., even if some old regions
2108 // look expensive, we should add them to the CSet anyway to make
2109 // sure we go through the available old regions in no more than the
2110 // maximum desired number of mixed GCs.
2111 //
2112 // The calculation is based on the number of marked regions we added
2113 // to the CSet chooser in the first place, not how many remain, so
2114 // that the result is the same during all mixed GCs that follow a cycle.
2115
2116 const size_t region_num = (size_t) cset_chooser()->length();
2117 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
2118 size_t result = region_num / gc_num;
2119 // emulate ceiling
2120 if (result * gc_num < region_num) {
2121 result += 1;
2122 }
2123 return (uint) result;
2124 }
2125
2126 uint G1CollectorPolicy::calc_max_old_cset_length() const {
2127 // The max old CSet region bound is based on the threshold expressed
2128 // as a percentage of the heap size. I.e., it should bound the
2129 // number of old regions added to the CSet irrespective of how many
2130 // of them are available.
2131
2132 const G1CollectedHeap* g1h = G1CollectedHeap::heap();
2133 const size_t region_num = g1h->num_regions();
2134 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
2135 size_t result = region_num * perc / 100;
2136 // emulate ceiling
2137 if (100 * result < region_num * perc) {
2138 result += 1;
2139 }
2140 return (uint) result;
2141 }
2142
2143
2144 double G1CollectorPolicy::finalize_young_cset_part(double target_pause_time_ms) {
2145 double young_start_time_sec = os::elapsedTime();
2146
2147 YoungList* young_list = _g1->young_list();
2148 finalize_incremental_cset_building();
2149
2150 guarantee(target_pause_time_ms > 0.0,
2151 "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms);
2152 guarantee(_collection_set == NULL, "Precondition");
2153
2154 double base_time_ms = predict_base_elapsed_time_ms(_pending_cards);
2155 double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0);
2156
2157 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",
2158 _pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms);
2159
2160 collector_state()->set_last_gc_was_young(collector_state()->gcs_are_young());
2161
2162 // The young list is laid with the survivor regions from the previous
2163 // pause are appended to the RHS of the young list, i.e.
2164 // [Newly Young Regions ++ Survivors from last pause].
2165
2166 uint survivor_region_length = young_list->survivor_length();
2167 uint eden_region_length = young_list->eden_length();
2168 init_cset_region_lengths(eden_region_length, survivor_region_length);
2169
2170 HeapRegion* hr = young_list->first_survivor_region();
2171 while (hr != NULL) {
2172 assert(hr->is_survivor(), "badly formed young list");
2173 // There is a convention that all the young regions in the CSet
2174 // are tagged as "eden", so we do this for the survivors here. We
2175 // use the special set_eden_pre_gc() as it doesn't check that the
2176 // region is free (which is not the case here).
2177 hr->set_eden_pre_gc();
2178 hr = hr->get_next_young_region();
2179 }
2180
2181 // Clear the fields that point to the survivor list - they are all young now.
2182 young_list->clear_survivors();
2183
2184 _collection_set = _inc_cset_head;
2185 _collection_set_bytes_used_before = _inc_cset_bytes_used_before;
2186 time_remaining_ms = MAX2(time_remaining_ms - _inc_cset_predicted_elapsed_time_ms, 0.0);
2187
2188 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",
2189 eden_region_length, survivor_region_length, _inc_cset_predicted_elapsed_time_ms, target_pause_time_ms);
2190
2191 // The number of recorded young regions is the incremental
2192 // collection set's current size
2193 set_recorded_rs_lengths(_inc_cset_recorded_rs_lengths);
2194
2195 double young_end_time_sec = os::elapsedTime();
2196 phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0);
2197
2198 return time_remaining_ms;
2199 }
2200
2201 void G1CollectorPolicy::finalize_old_cset_part(double time_remaining_ms) {
2202 double non_young_start_time_sec = os::elapsedTime();
2203 double predicted_old_time_ms = 0.0;
2204
2205
2206 if (!collector_state()->gcs_are_young()) {
2207 cset_chooser()->verify();
2208 const uint min_old_cset_length = calc_min_old_cset_length();
2209 const uint max_old_cset_length = calc_max_old_cset_length();
2210
2211 uint expensive_region_num = 0;
2212 bool check_time_remaining = adaptive_young_list_length();
2213
2214 HeapRegion* hr = cset_chooser()->peek();
2215 while (hr != NULL) {
2216 if (old_cset_region_length() >= max_old_cset_length) {
2217 // Added maximum number of old regions to the CSet.
2218 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached max). old %u regions, max %u regions",
2219 old_cset_region_length(), max_old_cset_length);
2220 break;
2221 }
2222
2223
2224 // Stop adding regions if the remaining reclaimable space is
2225 // not above G1HeapWastePercent.
2226 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
2227 double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
2228 double threshold = (double) G1HeapWastePercent;
2229 if (reclaimable_perc <= threshold) {
2230 // We've added enough old regions that the amount of uncollected
2231 // reclaimable space is at or below the waste threshold. Stop
2232 // adding old regions to the CSet.
2233 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (reclaimable percentage not over threshold). "
2234 "old %u regions, max %u regions, reclaimable: " SIZE_FORMAT "B (%1.2f%%) threshold: " UINTX_FORMAT "%%",
2235 old_cset_region_length(), max_old_cset_length, reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
2236 break;
2237 }
2238
2239 double predicted_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young());
2240 if (check_time_remaining) {
2241 if (predicted_time_ms > time_remaining_ms) {
2242 // Too expensive for the current CSet.
2243
2244 if (old_cset_region_length() >= min_old_cset_length) {
2245 // We have added the minimum number of old regions to the CSet,
2246 // we are done with this CSet.
2247 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (predicted time is too high). "
2248 "predicted time: %1.2fms, remaining time: %1.2fms old %u regions, min %u regions",
2249 predicted_time_ms, time_remaining_ms, old_cset_region_length(), min_old_cset_length);
2250 break;
2251 }
2252
2253 // We'll add it anyway given that we haven't reached the
2254 // minimum number of old regions.
2255 expensive_region_num += 1;
2256 }
2257 } else {
2258 if (old_cset_region_length() >= min_old_cset_length) {
2259 // In the non-auto-tuning case, we'll finish adding regions
2260 // to the CSet if we reach the minimum.
2261
2262 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached min). old %u regions, min %u regions",
2263 old_cset_region_length(), min_old_cset_length);
2264 break;
2265 }
2266 }
2267
2268 // We will add this region to the CSet.
2269 time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0);
2270 predicted_old_time_ms += predicted_time_ms;
2271 cset_chooser()->pop(); // already have region via peek()
2272 _g1->old_set_remove(hr);
2273 add_old_region_to_cset(hr);
2274
2275 hr = cset_chooser()->peek();
2276 }
2277 if (hr == NULL) {
2278 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (candidate old regions not available)");
2279 }
2280
2281 if (expensive_region_num > 0) {
2282 // We print the information once here at the end, predicated on
2283 // whether we added any apparently expensive regions or not, to
2284 // avoid generating output per region.
2285 log_debug(gc, ergo, cset)("Added expensive regions to CSet (old CSet region num not reached min)."
2286 "old: %u regions, expensive: %u regions, min: %u regions, remaining time: %1.2fms",
2287 old_cset_region_length(), expensive_region_num, min_old_cset_length, time_remaining_ms);
2288 }
2289
2290 cset_chooser()->verify();
2291 }
2292
2293 stop_incremental_cset_building();
2294
2295 log_debug(gc, ergo, cset)("Finish choosing CSet. old: %u regions, predicted old region time: %1.2fms, time remaining: %1.2f",
2296 old_cset_region_length(), predicted_old_time_ms, time_remaining_ms);
2297
2298 double non_young_end_time_sec = os::elapsedTime();
2299 phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);
2300 }