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/g1CollectionSet.hpp"
30 #include "gc/g1/g1CollectorPolicy.hpp"
31 #include "gc/g1/g1ConcurrentMark.hpp"
32 #include "gc/g1/g1IHOPControl.hpp"
33 #include "gc/g1/g1GCPhaseTimes.hpp"
34 #include "gc/g1/heapRegion.inline.hpp"
35 #include "gc/g1/heapRegionRemSet.hpp"
36 #include "gc/shared/gcPolicyCounters.hpp"
37 #include "runtime/arguments.hpp"
38 #include "runtime/java.hpp"
39 #include "runtime/mutexLocker.hpp"
40 #include "utilities/debug.hpp"
41 #include "utilities/pair.hpp"
42
43 // Different defaults for different number of GC threads
44 // They were chosen by running GCOld and SPECjbb on debris with different
45 // numbers of GC threads and choosing them based on the results
46
47 // all the same
48 static double rs_length_diff_defaults[] = {
49 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0
50 };
51
52 static double cost_per_card_ms_defaults[] = {
53 0.01, 0.005, 0.005, 0.003, 0.003, 0.002, 0.002, 0.0015
54 };
55
56 // all the same
57 static double young_cards_per_entry_ratio_defaults[] = {
58 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0
59 };
60
61 static double cost_per_entry_ms_defaults[] = {
62 0.015, 0.01, 0.01, 0.008, 0.008, 0.0055, 0.0055, 0.005
63 };
64
65 static double cost_per_byte_ms_defaults[] = {
66 0.00006, 0.00003, 0.00003, 0.000015, 0.000015, 0.00001, 0.00001, 0.000009
67 };
68
69 // these should be pretty consistent
70 static double constant_other_time_ms_defaults[] = {
71 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0
72 };
73
74
75 static double young_other_cost_per_region_ms_defaults[] = {
76 0.3, 0.2, 0.2, 0.15, 0.15, 0.12, 0.12, 0.1
77 };
78
79 static double non_young_other_cost_per_region_ms_defaults[] = {
80 1.0, 0.7, 0.7, 0.5, 0.5, 0.42, 0.42, 0.30
81 };
82
83 G1CollectorPolicy::G1CollectorPolicy() :
84 _predictor(G1ConfidencePercent / 100.0),
85
86 _recent_gc_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
87
88 _concurrent_mark_remark_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
89 _concurrent_mark_cleanup_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
90
91 _alloc_rate_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
92 _prev_collection_pause_end_ms(0.0),
93 _rs_length_diff_seq(new TruncatedSeq(TruncatedSeqLength)),
94 _cost_per_card_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
95 _cost_scan_hcc_seq(new TruncatedSeq(TruncatedSeqLength)),
96 _young_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
97 _mixed_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
98 _cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
99 _mixed_cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
100 _cost_per_byte_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
101 _cost_per_byte_ms_during_cm_seq(new TruncatedSeq(TruncatedSeqLength)),
102 _constant_other_time_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
103 _young_other_cost_per_region_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
104 _non_young_other_cost_per_region_ms_seq(
105 new TruncatedSeq(TruncatedSeqLength)),
106
107 _pending_cards_seq(new TruncatedSeq(TruncatedSeqLength)),
108 _rs_lengths_seq(new TruncatedSeq(TruncatedSeqLength)),
109
110 _pause_time_target_ms((double) MaxGCPauseMillis),
111
112 _recent_prev_end_times_for_all_gcs_sec(
113 new TruncatedSeq(NumPrevPausesForHeuristics)),
114
115 _recent_avg_pause_time_ratio(0.0),
116 _rs_lengths_prediction(0),
117 _max_survivor_regions(0),
118
119 // add here any more surv rate groups
120 _recorded_survivor_regions(0),
121 _recorded_survivor_head(NULL),
122 _recorded_survivor_tail(NULL),
123 _survivors_age_table(true),
124
125 _gc_overhead_perc(0.0),
126
127 _bytes_allocated_in_old_since_last_gc(0),
128 _ihop_control(NULL),
129 _initial_mark_to_mixed() {
130
131 // SurvRateGroups below must be initialized after the predictor because they
132 // indirectly use it through this object passed to their constructor.
133 _short_lived_surv_rate_group =
134 new SurvRateGroup(&_predictor, "Short Lived", G1YoungSurvRateNumRegionsSummary);
135 _survivor_surv_rate_group =
136 new SurvRateGroup(&_predictor, "Survivor", G1YoungSurvRateNumRegionsSummary);
137
138 // Set up the region size and associated fields. Given that the
139 // policy is created before the heap, we have to set this up here,
140 // so it's done as soon as possible.
141
142 // It would have been natural to pass initial_heap_byte_size() and
143 // max_heap_byte_size() to setup_heap_region_size() but those have
144 // not been set up at this point since they should be aligned with
145 // the region size. So, there is a circular dependency here. We base
146 // the region size on the heap size, but the heap size should be
147 // aligned with the region size. To get around this we use the
148 // unaligned values for the heap.
149 HeapRegion::setup_heap_region_size(InitialHeapSize, MaxHeapSize);
150 HeapRegionRemSet::setup_remset_size();
151
152 _recent_prev_end_times_for_all_gcs_sec->add(os::elapsedTime());
153 _prev_collection_pause_end_ms = os::elapsedTime() * 1000.0;
154 clear_ratio_check_data();
155
156 _phase_times = new G1GCPhaseTimes(ParallelGCThreads);
157
158 int index = MIN2(ParallelGCThreads - 1, 7u);
159
160 _rs_length_diff_seq->add(rs_length_diff_defaults[index]);
161 _cost_per_card_ms_seq->add(cost_per_card_ms_defaults[index]);
162 _cost_scan_hcc_seq->add(0.0);
163 _young_cards_per_entry_ratio_seq->add(
164 young_cards_per_entry_ratio_defaults[index]);
165 _cost_per_entry_ms_seq->add(cost_per_entry_ms_defaults[index]);
166 _cost_per_byte_ms_seq->add(cost_per_byte_ms_defaults[index]);
167 _constant_other_time_ms_seq->add(constant_other_time_ms_defaults[index]);
168 _young_other_cost_per_region_ms_seq->add(
169 young_other_cost_per_region_ms_defaults[index]);
170 _non_young_other_cost_per_region_ms_seq->add(
171 non_young_other_cost_per_region_ms_defaults[index]);
172
173 // Below, we might need to calculate the pause time target based on
174 // the pause interval. When we do so we are going to give G1 maximum
175 // flexibility and allow it to do pauses when it needs to. So, we'll
176 // arrange that the pause interval to be pause time target + 1 to
177 // ensure that a) the pause time target is maximized with respect to
178 // the pause interval and b) we maintain the invariant that pause
179 // time target < pause interval. If the user does not want this
180 // maximum flexibility, they will have to set the pause interval
181 // explicitly.
182
183 // First make sure that, if either parameter is set, its value is
184 // reasonable.
185 if (!FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
186 if (MaxGCPauseMillis < 1) {
187 vm_exit_during_initialization("MaxGCPauseMillis should be "
188 "greater than 0");
189 }
190 }
191 if (!FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
192 if (GCPauseIntervalMillis < 1) {
193 vm_exit_during_initialization("GCPauseIntervalMillis should be "
194 "greater than 0");
195 }
196 }
197
198 // Then, if the pause time target parameter was not set, set it to
199 // the default value.
200 if (FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
201 if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
202 // The default pause time target in G1 is 200ms
203 FLAG_SET_DEFAULT(MaxGCPauseMillis, 200);
204 } else {
205 // We do not allow the pause interval to be set without the
206 // pause time target
207 vm_exit_during_initialization("GCPauseIntervalMillis cannot be set "
208 "without setting MaxGCPauseMillis");
209 }
210 }
211
212 // Then, if the interval parameter was not set, set it according to
213 // the pause time target (this will also deal with the case when the
214 // pause time target is the default value).
215 if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
216 FLAG_SET_DEFAULT(GCPauseIntervalMillis, MaxGCPauseMillis + 1);
217 }
218
219 // Finally, make sure that the two parameters are consistent.
220 if (MaxGCPauseMillis >= GCPauseIntervalMillis) {
221 char buffer[256];
222 jio_snprintf(buffer, 256,
223 "MaxGCPauseMillis (%u) should be less than "
224 "GCPauseIntervalMillis (%u)",
225 MaxGCPauseMillis, GCPauseIntervalMillis);
226 vm_exit_during_initialization(buffer);
227 }
228
229 double max_gc_time = (double) MaxGCPauseMillis / 1000.0;
230 double time_slice = (double) GCPauseIntervalMillis / 1000.0;
231 _mmu_tracker = new G1MMUTrackerQueue(time_slice, max_gc_time);
232
233 // start conservatively (around 50ms is about right)
234 _concurrent_mark_remark_times_ms->add(0.05);
235 _concurrent_mark_cleanup_times_ms->add(0.20);
236 _tenuring_threshold = MaxTenuringThreshold;
237
238 assert(GCTimeRatio > 0,
239 "we should have set it to a default value set_g1_gc_flags() "
240 "if a user set it to 0");
241 _gc_overhead_perc = 100.0 * (1.0 / (1.0 + GCTimeRatio));
242
243 uintx reserve_perc = G1ReservePercent;
244 // Put an artificial ceiling on this so that it's not set to a silly value.
245 if (reserve_perc > 50) {
246 reserve_perc = 50;
247 warning("G1ReservePercent is set to a value that is too large, "
248 "it's been updated to " UINTX_FORMAT, reserve_perc);
249 }
250 _reserve_factor = (double) reserve_perc / 100.0;
251 // This will be set when the heap is expanded
252 // for the first time during initialization.
253 _reserve_regions = 0;
254 }
255
256 G1CollectorPolicy::~G1CollectorPolicy() {
257 delete _ihop_control;
258 }
259
260 double G1CollectorPolicy::get_new_prediction(TruncatedSeq const* seq) const {
261 return _predictor.get_new_prediction(seq);
262 }
263
264 size_t G1CollectorPolicy::get_new_size_prediction(TruncatedSeq const* seq) const {
265 return (size_t)get_new_prediction(seq);
266 }
267
268 void G1CollectorPolicy::initialize_alignments() {
269 _space_alignment = HeapRegion::GrainBytes;
270 size_t card_table_alignment = CardTableRS::ct_max_alignment_constraint();
271 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
272 _heap_alignment = MAX3(card_table_alignment, _space_alignment, page_size);
273 }
274
275 G1CollectorState* G1CollectorPolicy::collector_state() const { return _g1->collector_state(); }
276
277 // There are three command line options related to the young gen size:
278 // NewSize, MaxNewSize and NewRatio (There is also -Xmn, but that is
279 // just a short form for NewSize==MaxNewSize). G1 will use its internal
280 // heuristics to calculate the actual young gen size, so these options
281 // basically only limit the range within which G1 can pick a young gen
282 // size. Also, these are general options taking byte sizes. G1 will
283 // internally work with a number of regions instead. So, some rounding
284 // will occur.
285 //
286 // If nothing related to the the young gen size is set on the command
287 // line we should allow the young gen to be between G1NewSizePercent
288 // and G1MaxNewSizePercent of the heap size. This means that every time
289 // the heap size changes, the limits for the young gen size will be
290 // recalculated.
291 //
292 // If only -XX:NewSize is set we should use the specified value as the
293 // minimum size for young gen. Still using G1MaxNewSizePercent of the
294 // heap as maximum.
295 //
296 // If only -XX:MaxNewSize is set we should use the specified value as the
297 // maximum size for young gen. Still using G1NewSizePercent of the heap
298 // as minimum.
299 //
300 // If -XX:NewSize and -XX:MaxNewSize are both specified we use these values.
301 // No updates when the heap size changes. There is a special case when
302 // NewSize==MaxNewSize. This is interpreted as "fixed" and will use a
303 // different heuristic for calculating the collection set when we do mixed
304 // collection.
305 //
306 // If only -XX:NewRatio is set we should use the specified ratio of the heap
307 // as both min and max. This will be interpreted as "fixed" just like the
308 // NewSize==MaxNewSize case above. But we will update the min and max
309 // every time the heap size changes.
310 //
311 // NewSize and MaxNewSize override NewRatio. So, NewRatio is ignored if it is
312 // combined with either NewSize or MaxNewSize. (A warning message is printed.)
313 class G1YoungGenSizer : public CHeapObj<mtGC> {
314 private:
315 enum SizerKind {
316 SizerDefaults,
317 SizerNewSizeOnly,
318 SizerMaxNewSizeOnly,
319 SizerMaxAndNewSize,
320 SizerNewRatio
321 };
322 SizerKind _sizer_kind;
323 uint _min_desired_young_length;
324 uint _max_desired_young_length;
325 bool _adaptive_size;
326 uint calculate_default_min_length(uint new_number_of_heap_regions);
327 uint calculate_default_max_length(uint new_number_of_heap_regions);
328
329 // Update the given values for minimum and maximum young gen length in regions
330 // given the number of heap regions depending on the kind of sizing algorithm.
331 void recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length);
332
333 public:
334 G1YoungGenSizer();
335 // Calculate the maximum length of the young gen given the number of regions
336 // depending on the sizing algorithm.
337 uint max_young_length(uint number_of_heap_regions);
338
339 void heap_size_changed(uint new_number_of_heap_regions);
340 uint min_desired_young_length() {
341 return _min_desired_young_length;
342 }
343 uint max_desired_young_length() {
344 return _max_desired_young_length;
345 }
346
347 bool adaptive_young_list_length() const {
348 return _adaptive_size;
349 }
350 };
351
352
353 G1YoungGenSizer::G1YoungGenSizer() : _sizer_kind(SizerDefaults), _adaptive_size(true),
354 _min_desired_young_length(0), _max_desired_young_length(0) {
355 if (FLAG_IS_CMDLINE(NewRatio)) {
356 if (FLAG_IS_CMDLINE(NewSize) || FLAG_IS_CMDLINE(MaxNewSize)) {
357 warning("-XX:NewSize and -XX:MaxNewSize override -XX:NewRatio");
358 } else {
359 _sizer_kind = SizerNewRatio;
360 _adaptive_size = false;
361 return;
362 }
363 }
364
365 if (NewSize > MaxNewSize) {
366 if (FLAG_IS_CMDLINE(MaxNewSize)) {
367 warning("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). "
368 "A new max generation size of " SIZE_FORMAT "k will be used.",
369 NewSize/K, MaxNewSize/K, NewSize/K);
370 }
371 MaxNewSize = NewSize;
372 }
373
374 if (FLAG_IS_CMDLINE(NewSize)) {
375 _min_desired_young_length = MAX2((uint) (NewSize / HeapRegion::GrainBytes),
376 1U);
377 if (FLAG_IS_CMDLINE(MaxNewSize)) {
378 _max_desired_young_length =
379 MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes),
380 1U);
381 _sizer_kind = SizerMaxAndNewSize;
382 _adaptive_size = _min_desired_young_length == _max_desired_young_length;
383 } else {
384 _sizer_kind = SizerNewSizeOnly;
385 }
386 } else if (FLAG_IS_CMDLINE(MaxNewSize)) {
387 _max_desired_young_length =
388 MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes),
389 1U);
390 _sizer_kind = SizerMaxNewSizeOnly;
391 }
392 }
393
394 uint G1YoungGenSizer::calculate_default_min_length(uint new_number_of_heap_regions) {
395 uint default_value = (new_number_of_heap_regions * G1NewSizePercent) / 100;
396 return MAX2(1U, default_value);
397 }
398
399 uint G1YoungGenSizer::calculate_default_max_length(uint new_number_of_heap_regions) {
400 uint default_value = (new_number_of_heap_regions * G1MaxNewSizePercent) / 100;
401 return MAX2(1U, default_value);
402 }
403
404 void G1YoungGenSizer::recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length) {
405 assert(number_of_heap_regions > 0, "Heap must be initialized");
406
407 switch (_sizer_kind) {
408 case SizerDefaults:
409 *min_young_length = calculate_default_min_length(number_of_heap_regions);
410 *max_young_length = calculate_default_max_length(number_of_heap_regions);
411 break;
412 case SizerNewSizeOnly:
413 *max_young_length = calculate_default_max_length(number_of_heap_regions);
414 *max_young_length = MAX2(*min_young_length, *max_young_length);
415 break;
416 case SizerMaxNewSizeOnly:
417 *min_young_length = calculate_default_min_length(number_of_heap_regions);
418 *min_young_length = MIN2(*min_young_length, *max_young_length);
419 break;
420 case SizerMaxAndNewSize:
421 // Do nothing. Values set on the command line, don't update them at runtime.
422 break;
423 case SizerNewRatio:
424 *min_young_length = number_of_heap_regions / (NewRatio + 1);
425 *max_young_length = *min_young_length;
426 break;
427 default:
428 ShouldNotReachHere();
429 }
430
431 assert(*min_young_length <= *max_young_length, "Invalid min/max young gen size values");
432 }
433
434 uint G1YoungGenSizer::max_young_length(uint number_of_heap_regions) {
435 // We need to pass the desired values because recalculation may not update these
436 // values in some cases.
437 uint temp = _min_desired_young_length;
438 uint result = _max_desired_young_length;
439 recalculate_min_max_young_length(number_of_heap_regions, &temp, &result);
440 return result;
441 }
442
443 void G1YoungGenSizer::heap_size_changed(uint new_number_of_heap_regions) {
444 recalculate_min_max_young_length(new_number_of_heap_regions, &_min_desired_young_length,
445 &_max_desired_young_length);
446 }
447
448 void G1CollectorPolicy::post_heap_initialize() {
449 uintx max_regions = G1CollectedHeap::heap()->max_regions();
450 size_t max_young_size = (size_t)_young_gen_sizer->max_young_length(max_regions) * HeapRegion::GrainBytes;
451 if (max_young_size != MaxNewSize) {
452 FLAG_SET_ERGO(size_t, MaxNewSize, max_young_size);
453 }
454
455 _ihop_control = create_ihop_control();
456 }
457
458 void G1CollectorPolicy::initialize_flags() {
459 if (G1HeapRegionSize != HeapRegion::GrainBytes) {
460 FLAG_SET_ERGO(size_t, G1HeapRegionSize, HeapRegion::GrainBytes);
461 }
462
463 if (SurvivorRatio < 1) {
464 vm_exit_during_initialization("Invalid survivor ratio specified");
465 }
466 CollectorPolicy::initialize_flags();
467 _young_gen_sizer = new G1YoungGenSizer(); // Must be after call to initialize_flags
468 }
469
470
471 void G1CollectorPolicy::init() {
472 // Set aside an initial future to_space.
473 _g1 = G1CollectedHeap::heap();
474 _collection_set = _g1->collection_set();
475
476 assert(Heap_lock->owned_by_self(), "Locking discipline.");
477
478 initialize_gc_policy_counters();
479
480 if (adaptive_young_list_length()) {
481 _young_list_fixed_length = 0;
482 } else {
483 _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
484 }
485 _free_regions_at_end_of_collection = _g1->num_free_regions();
486
487 update_young_list_max_and_target_length();
488 // We may immediately start allocating regions and placing them on the
489 // collection set list. Initialize the per-collection set info
490 _collection_set->start_incremental_building();
491 }
492
493 void G1CollectorPolicy::note_gc_start(uint num_active_workers) {
494 phase_times()->note_gc_start(num_active_workers);
495 }
496
497 // Create the jstat counters for the policy.
498 void G1CollectorPolicy::initialize_gc_policy_counters() {
499 _gc_policy_counters = new GCPolicyCounters("GarbageFirst", 1, 3);
500 }
501
502 bool G1CollectorPolicy::predict_will_fit(uint young_length,
503 double base_time_ms,
504 uint base_free_regions,
505 double target_pause_time_ms) const {
506 if (young_length >= base_free_regions) {
507 // end condition 1: not enough space for the young regions
508 return false;
509 }
510
511 double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);
512 size_t bytes_to_copy =
513 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
514 double copy_time_ms = predict_object_copy_time_ms(bytes_to_copy);
515 double young_other_time_ms = predict_young_other_time_ms(young_length);
516 double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;
517 if (pause_time_ms > target_pause_time_ms) {
518 // end condition 2: prediction is over the target pause time
519 return false;
520 }
521
522 size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes;
523
524 // When copying, we will likely need more bytes free than is live in the region.
525 // Add some safety margin to factor in the confidence of our guess, and the
526 // natural expected waste.
527 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
528 // of the calculation: the lower the confidence, the more headroom.
529 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
530 // copying due to anticipated waste in the PLABs.
531 double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
532 size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
533
534 if (expected_bytes_to_copy > free_bytes) {
535 // end condition 3: out-of-space
536 return false;
537 }
538
539 // success!
540 return true;
541 }
542
543 void G1CollectorPolicy::record_new_heap_size(uint new_number_of_regions) {
544 // re-calculate the necessary reserve
545 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
546 // We use ceiling so that if reserve_regions_d is > 0.0 (but
547 // smaller than 1.0) we'll get 1.
548 _reserve_regions = (uint) ceil(reserve_regions_d);
549
550 _young_gen_sizer->heap_size_changed(new_number_of_regions);
551 }
552
553 uint G1CollectorPolicy::calculate_young_list_desired_min_length(
554 uint base_min_length) const {
555 uint desired_min_length = 0;
556 if (adaptive_young_list_length()) {
557 if (_alloc_rate_ms_seq->num() > 3) {
558 double now_sec = os::elapsedTime();
559 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
560 double alloc_rate_ms = predict_alloc_rate_ms();
561 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
562 } else {
563 // otherwise we don't have enough info to make the prediction
564 }
565 }
566 desired_min_length += base_min_length;
567 // make sure we don't go below any user-defined minimum bound
568 return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
569 }
570
571 uint G1CollectorPolicy::calculate_young_list_desired_max_length() const {
572 // Here, we might want to also take into account any additional
573 // constraints (i.e., user-defined minimum bound). Currently, we
574 // effectively don't set this bound.
575 return _young_gen_sizer->max_desired_young_length();
576 }
577
578 uint G1CollectorPolicy::update_young_list_max_and_target_length() {
579 return update_young_list_max_and_target_length(get_new_size_prediction(_rs_lengths_seq));
580 }
581
582 uint G1CollectorPolicy::update_young_list_max_and_target_length(size_t rs_lengths) {
583 uint unbounded_target_length = update_young_list_target_length(rs_lengths);
584 update_max_gc_locker_expansion();
585 return unbounded_target_length;
586 }
587
588 uint G1CollectorPolicy::update_young_list_target_length(size_t rs_lengths) {
589 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
590 _young_list_target_length = young_lengths.first;
591 return young_lengths.second;
592 }
593
594 G1CollectorPolicy::YoungTargetLengths G1CollectorPolicy::young_list_target_lengths(size_t rs_lengths) const {
595 YoungTargetLengths result;
596
597 // Calculate the absolute and desired min bounds first.
598
599 // This is how many young regions we already have (currently: the survivors).
600 uint base_min_length = recorded_survivor_regions();
601 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
602 // This is the absolute minimum young length. Ensure that we
603 // will at least have one eden region available for allocation.
604 uint absolute_min_length = base_min_length + MAX2(_g1->young_list()->eden_length(), (uint)1);
605 // If we shrank the young list target it should not shrink below the current size.
606 desired_min_length = MAX2(desired_min_length, absolute_min_length);
607 // Calculate the absolute and desired max bounds.
608
609 uint desired_max_length = calculate_young_list_desired_max_length();
610
611 uint young_list_target_length = 0;
612 if (adaptive_young_list_length()) {
613 if (collector_state()->gcs_are_young()) {
614 young_list_target_length =
615 calculate_young_list_target_length(rs_lengths,
616 base_min_length,
617 desired_min_length,
618 desired_max_length);
619 } else {
620 // Don't calculate anything and let the code below bound it to
621 // the desired_min_length, i.e., do the next GC as soon as
622 // possible to maximize how many old regions we can add to it.
623 }
624 } else {
625 // The user asked for a fixed young gen so we'll fix the young gen
626 // whether the next GC is young or mixed.
627 young_list_target_length = _young_list_fixed_length;
628 }
629
630 result.second = young_list_target_length;
631
632 // We will try our best not to "eat" into the reserve.
633 uint absolute_max_length = 0;
634 if (_free_regions_at_end_of_collection > _reserve_regions) {
635 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
636 }
637 if (desired_max_length > absolute_max_length) {
638 desired_max_length = absolute_max_length;
639 }
640
641 // Make sure we don't go over the desired max length, nor under the
642 // desired min length. In case they clash, desired_min_length wins
643 // which is why that test is second.
644 if (young_list_target_length > desired_max_length) {
645 young_list_target_length = desired_max_length;
646 }
647 if (young_list_target_length < desired_min_length) {
648 young_list_target_length = desired_min_length;
649 }
650
651 assert(young_list_target_length > recorded_survivor_regions(),
652 "we should be able to allocate at least one eden region");
653 assert(young_list_target_length >= absolute_min_length, "post-condition");
654
655 result.first = young_list_target_length;
656 return result;
657 }
658
659 uint
660 G1CollectorPolicy::calculate_young_list_target_length(size_t rs_lengths,
661 uint base_min_length,
662 uint desired_min_length,
663 uint desired_max_length) const {
664 assert(adaptive_young_list_length(), "pre-condition");
665 assert(collector_state()->gcs_are_young(), "only call this for young GCs");
666
667 // In case some edge-condition makes the desired max length too small...
668 if (desired_max_length <= desired_min_length) {
669 return desired_min_length;
670 }
671
672 // We'll adjust min_young_length and max_young_length not to include
673 // the already allocated young regions (i.e., so they reflect the
674 // min and max eden regions we'll allocate). The base_min_length
675 // will be reflected in the predictions by the
676 // survivor_regions_evac_time prediction.
677 assert(desired_min_length > base_min_length, "invariant");
678 uint min_young_length = desired_min_length - base_min_length;
679 assert(desired_max_length > base_min_length, "invariant");
680 uint max_young_length = desired_max_length - base_min_length;
681
682 double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
683 double survivor_regions_evac_time = predict_survivor_regions_evac_time();
684 size_t pending_cards = get_new_size_prediction(_pending_cards_seq);
685 size_t adj_rs_lengths = rs_lengths + predict_rs_length_diff();
686 size_t scanned_cards = predict_young_card_num(adj_rs_lengths);
687 double base_time_ms =
688 predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
689 survivor_regions_evac_time;
690 uint available_free_regions = _free_regions_at_end_of_collection;
691 uint base_free_regions = 0;
692 if (available_free_regions > _reserve_regions) {
693 base_free_regions = available_free_regions - _reserve_regions;
694 }
695
696 // Here, we will make sure that the shortest young length that
697 // makes sense fits within the target pause time.
698
699 if (predict_will_fit(min_young_length, base_time_ms,
700 base_free_regions, target_pause_time_ms)) {
701 // The shortest young length will fit into the target pause time;
702 // we'll now check whether the absolute maximum number of young
703 // regions will fit in the target pause time. If not, we'll do
704 // a binary search between min_young_length and max_young_length.
705 if (predict_will_fit(max_young_length, base_time_ms,
706 base_free_regions, target_pause_time_ms)) {
707 // The maximum young length will fit into the target pause time.
708 // We are done so set min young length to the maximum length (as
709 // the result is assumed to be returned in min_young_length).
710 min_young_length = max_young_length;
711 } else {
712 // The maximum possible number of young regions will not fit within
713 // the target pause time so we'll search for the optimal
714 // length. The loop invariants are:
715 //
716 // min_young_length < max_young_length
717 // min_young_length is known to fit into the target pause time
718 // max_young_length is known not to fit into the target pause time
719 //
720 // Going into the loop we know the above hold as we've just
721 // checked them. Every time around the loop we check whether
722 // the middle value between min_young_length and
723 // max_young_length fits into the target pause time. If it
724 // does, it becomes the new min. If it doesn't, it becomes
725 // the new max. This way we maintain the loop invariants.
726
727 assert(min_young_length < max_young_length, "invariant");
728 uint diff = (max_young_length - min_young_length) / 2;
729 while (diff > 0) {
730 uint young_length = min_young_length + diff;
731 if (predict_will_fit(young_length, base_time_ms,
732 base_free_regions, target_pause_time_ms)) {
733 min_young_length = young_length;
734 } else {
735 max_young_length = young_length;
736 }
737 assert(min_young_length < max_young_length, "invariant");
738 diff = (max_young_length - min_young_length) / 2;
739 }
740 // The results is min_young_length which, according to the
741 // loop invariants, should fit within the target pause time.
742
743 // These are the post-conditions of the binary search above:
744 assert(min_young_length < max_young_length,
745 "otherwise we should have discovered that max_young_length "
746 "fits into the pause target and not done the binary search");
747 assert(predict_will_fit(min_young_length, base_time_ms,
748 base_free_regions, target_pause_time_ms),
749 "min_young_length, the result of the binary search, should "
750 "fit into the pause target");
751 assert(!predict_will_fit(min_young_length + 1, base_time_ms,
752 base_free_regions, target_pause_time_ms),
753 "min_young_length, the result of the binary search, should be "
754 "optimal, so no larger length should fit into the pause target");
755 }
756 } else {
757 // Even the minimum length doesn't fit into the pause time
758 // target, return it as the result nevertheless.
759 }
760 return base_min_length + min_young_length;
761 }
762
763 double G1CollectorPolicy::predict_survivor_regions_evac_time() const {
764 double survivor_regions_evac_time = 0.0;
765 for (HeapRegion * r = _recorded_survivor_head;
766 r != NULL && r != _recorded_survivor_tail->get_next_young_region();
767 r = r->get_next_young_region()) {
768 survivor_regions_evac_time += predict_region_elapsed_time_ms(r, collector_state()->gcs_are_young());
769 }
770 return survivor_regions_evac_time;
771 }
772
773 void G1CollectorPolicy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
774 guarantee( adaptive_young_list_length(), "should not call this otherwise" );
775
776 if (rs_lengths > _rs_lengths_prediction) {
777 // add 10% to avoid having to recalculate often
778 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
779 update_rs_lengths_prediction(rs_lengths_prediction);
780
781 update_young_list_max_and_target_length(rs_lengths_prediction);
782 }
783 }
784
785 void G1CollectorPolicy::update_rs_lengths_prediction() {
786 update_rs_lengths_prediction(get_new_size_prediction(_rs_lengths_seq));
787 }
788
789 void G1CollectorPolicy::update_rs_lengths_prediction(size_t prediction) {
790 if (collector_state()->gcs_are_young() && adaptive_young_list_length()) {
791 _rs_lengths_prediction = prediction;
792 }
793 }
794
795 #ifndef PRODUCT
796 bool G1CollectorPolicy::verify_young_ages() {
797 HeapRegion* head = _g1->young_list()->first_region();
798 return
799 verify_young_ages(head, _short_lived_surv_rate_group);
800 // also call verify_young_ages on any additional surv rate groups
801 }
802
803 bool
804 G1CollectorPolicy::verify_young_ages(HeapRegion* head,
805 SurvRateGroup *surv_rate_group) {
806 guarantee( surv_rate_group != NULL, "pre-condition" );
807
808 const char* name = surv_rate_group->name();
809 bool ret = true;
810 int prev_age = -1;
811
812 for (HeapRegion* curr = head;
813 curr != NULL;
814 curr = curr->get_next_young_region()) {
815 SurvRateGroup* group = curr->surv_rate_group();
816 if (group == NULL && !curr->is_survivor()) {
817 log_error(gc, verify)("## %s: encountered NULL surv_rate_group", name);
818 ret = false;
819 }
820
821 if (surv_rate_group == group) {
822 int age = curr->age_in_surv_rate_group();
823
824 if (age < 0) {
825 log_error(gc, verify)("## %s: encountered negative age", name);
826 ret = false;
827 }
828
829 if (age <= prev_age) {
830 log_error(gc, verify)("## %s: region ages are not strictly increasing (%d, %d)", name, age, prev_age);
831 ret = false;
832 }
833 prev_age = age;
834 }
835 }
836
837 return ret;
838 }
839 #endif // PRODUCT
840
841 void G1CollectorPolicy::record_full_collection_start() {
842 _full_collection_start_sec = os::elapsedTime();
843 // Release the future to-space so that it is available for compaction into.
844 collector_state()->set_full_collection(true);
845 }
846
847 void G1CollectorPolicy::record_full_collection_end() {
848 // Consider this like a collection pause for the purposes of allocation
849 // since last pause.
850 double end_sec = os::elapsedTime();
851 double full_gc_time_sec = end_sec - _full_collection_start_sec;
852 double full_gc_time_ms = full_gc_time_sec * 1000.0;
853
854 update_recent_gc_times(end_sec, full_gc_time_ms);
855
856 collector_state()->set_full_collection(false);
857
858 // "Nuke" the heuristics that control the young/mixed GC
859 // transitions and make sure we start with young GCs after the Full GC.
860 collector_state()->set_gcs_are_young(true);
861 collector_state()->set_last_young_gc(false);
862 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
863 collector_state()->set_during_initial_mark_pause(false);
864 collector_state()->set_in_marking_window(false);
865 collector_state()->set_in_marking_window_im(false);
866
867 _short_lived_surv_rate_group->start_adding_regions();
868 // also call this on any additional surv rate groups
869
870 record_survivor_regions(0, NULL, NULL);
871
872 _free_regions_at_end_of_collection = _g1->num_free_regions();
873 // Reset survivors SurvRateGroup.
874 _survivor_surv_rate_group->reset();
875 update_young_list_max_and_target_length();
876 update_rs_lengths_prediction();
877 cset_chooser()->clear();
878
879 _bytes_allocated_in_old_since_last_gc = 0;
880
881 record_pause(FullGC, _full_collection_start_sec, end_sec);
882 }
883
884 void G1CollectorPolicy::record_collection_pause_start(double start_time_sec) {
885 // We only need to do this here as the policy will only be applied
886 // to the GC we're about to start. so, no point is calculating this
887 // every time we calculate / recalculate the target young length.
888 update_survivors_policy();
889
890 assert(_g1->used() == _g1->recalculate_used(),
891 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
892 _g1->used(), _g1->recalculate_used());
893
894 phase_times()->record_cur_collection_start_sec(start_time_sec);
895 _pending_cards = _g1->pending_card_num();
896
897 _collection_set->reset_bytes_used_before();
898 _bytes_copied_during_gc = 0;
899
900 collector_state()->set_last_gc_was_young(false);
901
902 // do that for any other surv rate groups
903 _short_lived_surv_rate_group->stop_adding_regions();
904 _survivors_age_table.clear();
905
906 assert( verify_young_ages(), "region age verification" );
907 }
908
909 void G1CollectorPolicy::record_concurrent_mark_init_end(double
910 mark_init_elapsed_time_ms) {
911 collector_state()->set_during_marking(true);
912 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
913 collector_state()->set_during_initial_mark_pause(false);
914 }
915
916 void G1CollectorPolicy::record_concurrent_mark_remark_start() {
917 _mark_remark_start_sec = os::elapsedTime();
918 collector_state()->set_during_marking(false);
919 }
920
921 void G1CollectorPolicy::record_concurrent_mark_remark_end() {
922 double end_time_sec = os::elapsedTime();
923 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
924 _concurrent_mark_remark_times_ms->add(elapsed_time_ms);
925 _prev_collection_pause_end_ms += elapsed_time_ms;
926
927 record_pause(Remark, _mark_remark_start_sec, end_time_sec);
928 }
929
930 void G1CollectorPolicy::record_concurrent_mark_cleanup_start() {
931 _mark_cleanup_start_sec = os::elapsedTime();
932 }
933
934 void G1CollectorPolicy::record_concurrent_mark_cleanup_completed() {
935 bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",
936 "skip last young-only gc");
937 collector_state()->set_last_young_gc(should_continue_with_reclaim);
938 // We skip the marking phase.
939 if (!should_continue_with_reclaim) {
940 abort_time_to_mixed_tracking();
941 }
942 collector_state()->set_in_marking_window(false);
943 }
944
945 double G1CollectorPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
946 return phase_times()->average_time_ms(phase);
947 }
948
949 double G1CollectorPolicy::young_other_time_ms() const {
950 return phase_times()->young_cset_choice_time_ms() +
951 phase_times()->young_free_cset_time_ms();
952 }
953
954 double G1CollectorPolicy::non_young_other_time_ms() const {
955 return phase_times()->non_young_cset_choice_time_ms() +
956 phase_times()->non_young_free_cset_time_ms();
957
958 }
959
960 double G1CollectorPolicy::other_time_ms(double pause_time_ms) const {
961 return pause_time_ms -
962 average_time_ms(G1GCPhaseTimes::UpdateRS) -
963 average_time_ms(G1GCPhaseTimes::ScanRS) -
964 average_time_ms(G1GCPhaseTimes::ObjCopy) -
965 average_time_ms(G1GCPhaseTimes::Termination);
966 }
967
968 double G1CollectorPolicy::constant_other_time_ms(double pause_time_ms) const {
969 return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms();
970 }
971
972 CollectionSetChooser* G1CollectorPolicy::cset_chooser() const {
973 return _collection_set->cset_chooser();
974 }
975
976
977 bool G1CollectorPolicy::about_to_start_mixed_phase() const {
978 return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc();
979 }
980
981 bool G1CollectorPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
982 if (about_to_start_mixed_phase()) {
983 return false;
984 }
985
986 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
987
988 size_t cur_used_bytes = _g1->non_young_capacity_bytes();
989 size_t alloc_byte_size = alloc_word_size * HeapWordSize;
990 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
991
992 bool result = false;
993 if (marking_request_bytes > marking_initiating_used_threshold) {
994 result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc();
995 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
996 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
997 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source);
998 }
999
1000 return result;
1001 }
1002
1003 // Anything below that is considered to be zero
1004 #define MIN_TIMER_GRANULARITY 0.0000001
1005
1006 void G1CollectorPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
1007 double end_time_sec = os::elapsedTime();
1008
1009 size_t cur_used_bytes = _g1->used();
1010 assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
1011 bool last_pause_included_initial_mark = false;
1012 bool update_stats = !_g1->evacuation_failed();
1013
1014 NOT_PRODUCT(_short_lived_surv_rate_group->print());
1015
1016 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
1017
1018 last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();
1019 if (last_pause_included_initial_mark) {
1020 record_concurrent_mark_init_end(0.0);
1021 } else {
1022 maybe_start_marking();
1023 }
1024
1025 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _prev_collection_pause_end_ms);
1026 if (app_time_ms < MIN_TIMER_GRANULARITY) {
1027 // This usually happens due to the timer not having the required
1028 // granularity. Some Linuxes are the usual culprits.
1029 // We'll just set it to something (arbitrarily) small.
1030 app_time_ms = 1.0;
1031 }
1032
1033 if (update_stats) {
1034 // We maintain the invariant that all objects allocated by mutator
1035 // threads will be allocated out of eden regions. So, we can use
1036 // the eden region number allocated since the previous GC to
1037 // calculate the application's allocate rate. The only exception
1038 // to that is humongous objects that are allocated separately. But
1039 // given that humongous object allocations do not really affect
1040 // either the pause's duration nor when the next pause will take
1041 // place we can safely ignore them here.
1042 uint regions_allocated = _collection_set->eden_region_length();
1043 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
1044 _alloc_rate_ms_seq->add(alloc_rate_ms);
1045
1046 double interval_ms =
1047 (end_time_sec - _recent_prev_end_times_for_all_gcs_sec->oldest()) * 1000.0;
1048 update_recent_gc_times(end_time_sec, pause_time_ms);
1049 _recent_avg_pause_time_ratio = _recent_gc_times_ms->sum()/interval_ms;
1050 if (recent_avg_pause_time_ratio() < 0.0 ||
1051 (recent_avg_pause_time_ratio() - 1.0 > 0.0)) {
1052 // Clip ratio between 0.0 and 1.0, and continue. This will be fixed in
1053 // CR 6902692 by redoing the manner in which the ratio is incrementally computed.
1054 if (_recent_avg_pause_time_ratio < 0.0) {
1055 _recent_avg_pause_time_ratio = 0.0;
1056 } else {
1057 assert(_recent_avg_pause_time_ratio - 1.0 > 0.0, "Ctl-point invariant");
1058 _recent_avg_pause_time_ratio = 1.0;
1059 }
1060 }
1061
1062 // Compute the ratio of just this last pause time to the entire time range stored
1063 // in the vectors. Comparing this pause to the entire range, rather than only the
1064 // most recent interval, has the effect of smoothing over a possible transient 'burst'
1065 // of more frequent pauses that don't really reflect a change in heap occupancy.
1066 // This reduces the likelihood of a needless heap expansion being triggered.
1067 _last_pause_time_ratio =
1068 (pause_time_ms * _recent_prev_end_times_for_all_gcs_sec->num()) / interval_ms;
1069 }
1070
1071 bool new_in_marking_window = collector_state()->in_marking_window();
1072 bool new_in_marking_window_im = false;
1073 if (last_pause_included_initial_mark) {
1074 new_in_marking_window = true;
1075 new_in_marking_window_im = true;
1076 }
1077
1078 if (collector_state()->last_young_gc()) {
1079 // This is supposed to to be the "last young GC" before we start
1080 // doing mixed GCs. Here we decide whether to start mixed GCs or not.
1081 assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC");
1082
1083 if (next_gc_should_be_mixed("start mixed GCs",
1084 "do not start mixed GCs")) {
1085 collector_state()->set_gcs_are_young(false);
1086 } else {
1087 // We aborted the mixed GC phase early.
1088 abort_time_to_mixed_tracking();
1089 }
1090
1091 collector_state()->set_last_young_gc(false);
1092 }
1093
1094 if (!collector_state()->last_gc_was_young()) {
1095 // This is a mixed GC. Here we decide whether to continue doing
1096 // mixed GCs or not.
1097 if (!next_gc_should_be_mixed("continue mixed GCs",
1098 "do not continue mixed GCs")) {
1099 collector_state()->set_gcs_are_young(true);
1100
1101 maybe_start_marking();
1102 }
1103 }
1104
1105 _short_lived_surv_rate_group->start_adding_regions();
1106 // Do that for any other surv rate groups
1107
1108 if (update_stats) {
1109 double cost_per_card_ms = 0.0;
1110 double cost_scan_hcc = average_time_ms(G1GCPhaseTimes::ScanHCC);
1111 if (_pending_cards > 0) {
1112 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - cost_scan_hcc) / (double) _pending_cards;
1113 _cost_per_card_ms_seq->add(cost_per_card_ms);
1114 }
1115 _cost_scan_hcc_seq->add(cost_scan_hcc);
1116
1117 double cost_per_entry_ms = 0.0;
1118 if (cards_scanned > 10) {
1119 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
1120 if (collector_state()->last_gc_was_young()) {
1121 _cost_per_entry_ms_seq->add(cost_per_entry_ms);
1122 } else {
1123 _mixed_cost_per_entry_ms_seq->add(cost_per_entry_ms);
1124 }
1125 }
1126
1127 if (_max_rs_lengths > 0) {
1128 double cards_per_entry_ratio =
1129 (double) cards_scanned / (double) _max_rs_lengths;
1130 if (collector_state()->last_gc_was_young()) {
1131 _young_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
1132 } else {
1133 _mixed_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
1134 }
1135 }
1136
1137 // This is defensive. For a while _max_rs_lengths could get
1138 // smaller than _recorded_rs_lengths which was causing
1139 // rs_length_diff to get very large and mess up the RSet length
1140 // predictions. The reason was unsafe concurrent updates to the
1141 // _inc_cset_recorded_rs_lengths field which the code below guards
1142 // against (see CR 7118202). This bug has now been fixed (see CR
1143 // 7119027). However, I'm still worried that
1144 // _inc_cset_recorded_rs_lengths might still end up somewhat
1145 // inaccurate. The concurrent refinement thread calculates an
1146 // RSet's length concurrently with other CR threads updating it
1147 // which might cause it to calculate the length incorrectly (if,
1148 // say, it's in mid-coarsening). So I'll leave in the defensive
1149 // conditional below just in case.
1150 size_t rs_length_diff = 0;
1151 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();
1152 if (_max_rs_lengths > recorded_rs_lengths) {
1153 rs_length_diff = _max_rs_lengths - recorded_rs_lengths;
1154 }
1155 _rs_length_diff_seq->add((double) rs_length_diff);
1156
1157 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
1158 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
1159 double cost_per_byte_ms = 0.0;
1160
1161 if (copied_bytes > 0) {
1162 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
1163 if (collector_state()->in_marking_window()) {
1164 _cost_per_byte_ms_during_cm_seq->add(cost_per_byte_ms);
1165 } else {
1166 _cost_per_byte_ms_seq->add(cost_per_byte_ms);
1167 }
1168 }
1169
1170 if (_collection_set->young_region_length() > 0) {
1171 _young_other_cost_per_region_ms_seq->add(young_other_time_ms() /
1172 _collection_set->young_region_length());
1173 }
1174
1175 if (_collection_set->old_region_length() > 0) {
1176 _non_young_other_cost_per_region_ms_seq->add(non_young_other_time_ms() /
1177 _collection_set->old_region_length());
1178 }
1179
1180 _constant_other_time_ms_seq->add(constant_other_time_ms(pause_time_ms));
1181
1182 _pending_cards_seq->add((double) _pending_cards);
1183 _rs_lengths_seq->add((double) _max_rs_lengths);
1184 }
1185
1186 collector_state()->set_in_marking_window(new_in_marking_window);
1187 collector_state()->set_in_marking_window_im(new_in_marking_window_im);
1188 _free_regions_at_end_of_collection = _g1->num_free_regions();
1189 // IHOP control wants to know the expected young gen length if it were not
1190 // restrained by the heap reserve. Using the actual length would make the
1191 // prediction too small and the limit the young gen every time we get to the
1192 // predicted target occupancy.
1193 size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
1194 update_rs_lengths_prediction();
1195
1196 update_ihop_prediction(app_time_ms / 1000.0,
1197 _bytes_allocated_in_old_since_last_gc,
1198 last_unrestrained_young_length * HeapRegion::GrainBytes);
1199 _bytes_allocated_in_old_since_last_gc = 0;
1200
1201 _ihop_control->send_trace_event(_g1->gc_tracer_stw());
1202
1203 // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
1204 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
1205
1206 double scan_hcc_time_ms = average_time_ms(G1GCPhaseTimes::ScanHCC);
1207
1208 if (update_rs_time_goal_ms < scan_hcc_time_ms) {
1209 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
1210 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",
1211 update_rs_time_goal_ms, scan_hcc_time_ms);
1212
1213 update_rs_time_goal_ms = 0;
1214 } else {
1215 update_rs_time_goal_ms -= scan_hcc_time_ms;
1216 }
1217 adjust_concurrent_refinement(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms,
1218 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
1219 update_rs_time_goal_ms);
1220
1221 cset_chooser()->verify();
1222 }
1223
1224 G1IHOPControl* G1CollectorPolicy::create_ihop_control() const {
1225 if (G1UseAdaptiveIHOP) {
1226 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
1227 G1CollectedHeap::heap()->max_capacity(),
1228 &_predictor,
1229 G1ReservePercent,
1230 G1HeapWastePercent);
1231 } else {
1232 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent,
1233 G1CollectedHeap::heap()->max_capacity());
1234 }
1235 }
1236
1237 void G1CollectorPolicy::update_ihop_prediction(double mutator_time_s,
1238 size_t mutator_alloc_bytes,
1239 size_t young_gen_size) {
1240 // Always try to update IHOP prediction. Even evacuation failures give information
1241 // about e.g. whether to start IHOP earlier next time.
1242
1243 // Avoid using really small application times that might create samples with
1244 // very high or very low values. They may be caused by e.g. back-to-back gcs.
1245 double const min_valid_time = 1e-6;
1246
1247 bool report = false;
1248
1249 double marking_to_mixed_time = -1.0;
1250 if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) {
1251 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
1252 assert(marking_to_mixed_time > 0.0,
1253 "Initial mark to mixed time must be larger than zero but is %.3f",
1254 marking_to_mixed_time);
1255 if (marking_to_mixed_time > min_valid_time) {
1256 _ihop_control->update_marking_length(marking_to_mixed_time);
1257 report = true;
1258 }
1259 }
1260
1261 // As an approximation for the young gc promotion rates during marking we use
1262 // all of them. In many applications there are only a few if any young gcs during
1263 // marking, which makes any prediction useless. This increases the accuracy of the
1264 // prediction.
1265 if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) {
1266 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
1267 report = true;
1268 }
1269
1270 if (report) {
1271 report_ihop_statistics();
1272 }
1273 }
1274
1275 void G1CollectorPolicy::report_ihop_statistics() {
1276 _ihop_control->print();
1277 }
1278
1279 void G1CollectorPolicy::print_phases() {
1280 phase_times()->print();
1281 }
1282
1283 void G1CollectorPolicy::adjust_concurrent_refinement(double update_rs_time,
1284 double update_rs_processed_buffers,
1285 double goal_ms) {
1286 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1287 ConcurrentG1Refine *cg1r = G1CollectedHeap::heap()->concurrent_g1_refine();
1288
1289 if (G1UseAdaptiveConcRefinement) {
1290 const int k_gy = 3, k_gr = 6;
1291 const double inc_k = 1.1, dec_k = 0.9;
1292
1293 int g = cg1r->green_zone();
1294 if (update_rs_time > goal_ms) {
1295 g = (int)(g * dec_k); // Can become 0, that's OK. That would mean a mutator-only processing.
1296 } else {
1297 if (update_rs_time < goal_ms && update_rs_processed_buffers > g) {
1298 g = (int)MAX2(g * inc_k, g + 1.0);
1299 }
1300 }
1301 // Change the refinement threads params
1302 cg1r->set_green_zone(g);
1303 cg1r->set_yellow_zone(g * k_gy);
1304 cg1r->set_red_zone(g * k_gr);
1305 cg1r->reinitialize_threads();
1306
1307 int processing_threshold_delta = MAX2((int)(cg1r->green_zone() * _predictor.sigma()), 1);
1308 int processing_threshold = MIN2(cg1r->green_zone() + processing_threshold_delta,
1309 cg1r->yellow_zone());
1310 // Change the barrier params
1311 dcqs.set_process_completed_threshold(processing_threshold);
1312 dcqs.set_max_completed_queue(cg1r->red_zone());
1313 }
1314
1315 int curr_queue_size = dcqs.completed_buffers_num();
1316 if (curr_queue_size >= cg1r->yellow_zone()) {
1317 dcqs.set_completed_queue_padding(curr_queue_size);
1318 } else {
1319 dcqs.set_completed_queue_padding(0);
1320 }
1321 dcqs.notify_if_necessary();
1322 }
1323
1324 size_t G1CollectorPolicy::predict_rs_length_diff() const {
1325 return get_new_size_prediction(_rs_length_diff_seq);
1326 }
1327
1328 double G1CollectorPolicy::predict_alloc_rate_ms() const {
1329 return get_new_prediction(_alloc_rate_ms_seq);
1330 }
1331
1332 double G1CollectorPolicy::predict_cost_per_card_ms() const {
1333 return get_new_prediction(_cost_per_card_ms_seq);
1334 }
1335
1336 double G1CollectorPolicy::predict_scan_hcc_ms() const {
1337 return get_new_prediction(_cost_scan_hcc_seq);
1338 }
1339
1340 double G1CollectorPolicy::predict_rs_update_time_ms(size_t pending_cards) const {
1341 return pending_cards * predict_cost_per_card_ms() + predict_scan_hcc_ms();
1342 }
1343
1344 double G1CollectorPolicy::predict_young_cards_per_entry_ratio() const {
1345 return get_new_prediction(_young_cards_per_entry_ratio_seq);
1346 }
1347
1348 double G1CollectorPolicy::predict_mixed_cards_per_entry_ratio() const {
1349 if (_mixed_cards_per_entry_ratio_seq->num() < 2) {
1350 return predict_young_cards_per_entry_ratio();
1351 } else {
1352 return get_new_prediction(_mixed_cards_per_entry_ratio_seq);
1353 }
1354 }
1355
1356 size_t G1CollectorPolicy::predict_young_card_num(size_t rs_length) const {
1357 return (size_t) (rs_length * predict_young_cards_per_entry_ratio());
1358 }
1359
1360 size_t G1CollectorPolicy::predict_non_young_card_num(size_t rs_length) const {
1361 return (size_t)(rs_length * predict_mixed_cards_per_entry_ratio());
1362 }
1363
1364 double G1CollectorPolicy::predict_rs_scan_time_ms(size_t card_num) const {
1365 if (collector_state()->gcs_are_young()) {
1366 return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1367 } else {
1368 return predict_mixed_rs_scan_time_ms(card_num);
1369 }
1370 }
1371
1372 double G1CollectorPolicy::predict_mixed_rs_scan_time_ms(size_t card_num) const {
1373 if (_mixed_cost_per_entry_ms_seq->num() < 3) {
1374 return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1375 } else {
1376 return card_num * get_new_prediction(_mixed_cost_per_entry_ms_seq);
1377 }
1378 }
1379
1380 double G1CollectorPolicy::predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) const {
1381 if (_cost_per_byte_ms_during_cm_seq->num() < 3) {
1382 return (1.1 * bytes_to_copy) * get_new_prediction(_cost_per_byte_ms_seq);
1383 } else {
1384 return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_during_cm_seq);
1385 }
1386 }
1387
1388 double G1CollectorPolicy::predict_object_copy_time_ms(size_t bytes_to_copy) const {
1389 if (collector_state()->during_concurrent_mark()) {
1390 return predict_object_copy_time_ms_during_cm(bytes_to_copy);
1391 } else {
1392 return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_seq);
1393 }
1394 }
1395
1396 double G1CollectorPolicy::predict_constant_other_time_ms() const {
1397 return get_new_prediction(_constant_other_time_ms_seq);
1398 }
1399
1400 double G1CollectorPolicy::predict_young_other_time_ms(size_t young_num) const {
1401 return young_num * get_new_prediction(_young_other_cost_per_region_ms_seq);
1402 }
1403
1404 double G1CollectorPolicy::predict_non_young_other_time_ms(size_t non_young_num) const {
1405 return non_young_num * get_new_prediction(_non_young_other_cost_per_region_ms_seq);
1406 }
1407
1408 double G1CollectorPolicy::predict_remark_time_ms() const {
1409 return get_new_prediction(_concurrent_mark_remark_times_ms);
1410 }
1411
1412 double G1CollectorPolicy::predict_cleanup_time_ms() const {
1413 return get_new_prediction(_concurrent_mark_cleanup_times_ms);
1414 }
1415
1416 double G1CollectorPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
1417 TruncatedSeq* seq = surv_rate_group->get_seq(age);
1418 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
1419 double pred = get_new_prediction(seq);
1420 if (pred > 1.0) {
1421 pred = 1.0;
1422 }
1423 return pred;
1424 }
1425
1426 double G1CollectorPolicy::predict_yg_surv_rate(int age) const {
1427 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
1428 }
1429
1430 double G1CollectorPolicy::accum_yg_surv_rate_pred(int age) const {
1431 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
1432 }
1433
1434 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards,
1435 size_t scanned_cards) const {
1436 return
1437 predict_rs_update_time_ms(pending_cards) +
1438 predict_rs_scan_time_ms(scanned_cards) +
1439 predict_constant_other_time_ms();
1440 }
1441
1442 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const {
1443 size_t rs_length = predict_rs_length_diff();
1444 size_t card_num;
1445 if (collector_state()->gcs_are_young()) {
1446 card_num = predict_young_card_num(rs_length);
1447 } else {
1448 card_num = predict_non_young_card_num(rs_length);
1449 }
1450 return predict_base_elapsed_time_ms(pending_cards, card_num);
1451 }
1452
1453 size_t G1CollectorPolicy::predict_bytes_to_copy(HeapRegion* hr) const {
1454 size_t bytes_to_copy;
1455 if (hr->is_marked())
1456 bytes_to_copy = hr->max_live_bytes();
1457 else {
1458 assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
1459 int age = hr->age_in_surv_rate_group();
1460 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
1461 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
1462 }
1463 return bytes_to_copy;
1464 }
1465
1466 double G1CollectorPolicy::predict_region_elapsed_time_ms(HeapRegion* hr,
1467 bool for_young_gc) const {
1468 size_t rs_length = hr->rem_set()->occupied();
1469 size_t card_num;
1470
1471 // Predicting the number of cards is based on which type of GC
1472 // we're predicting for.
1473 if (for_young_gc) {
1474 card_num = predict_young_card_num(rs_length);
1475 } else {
1476 card_num = predict_non_young_card_num(rs_length);
1477 }
1478 size_t bytes_to_copy = predict_bytes_to_copy(hr);
1479
1480 double region_elapsed_time_ms =
1481 predict_rs_scan_time_ms(card_num) +
1482 predict_object_copy_time_ms(bytes_to_copy);
1483
1484 // The prediction of the "other" time for this region is based
1485 // upon the region type and NOT the GC type.
1486 if (hr->is_young()) {
1487 region_elapsed_time_ms += predict_young_other_time_ms(1);
1488 } else {
1489 region_elapsed_time_ms += predict_non_young_other_time_ms(1);
1490 }
1491 return region_elapsed_time_ms;
1492 }
1493
1494 void G1CollectorPolicy::update_recent_gc_times(double end_time_sec,
1495 double elapsed_ms) {
1496 _recent_gc_times_ms->add(elapsed_ms);
1497 _recent_prev_end_times_for_all_gcs_sec->add(end_time_sec);
1498 _prev_collection_pause_end_ms = end_time_sec * 1000.0;
1499 }
1500
1501 void G1CollectorPolicy::clear_ratio_check_data() {
1502 _ratio_over_threshold_count = 0;
1503 _ratio_over_threshold_sum = 0.0;
1504 _pauses_since_start = 0;
1505 }
1506
1507 size_t G1CollectorPolicy::expansion_amount() {
1508 double recent_gc_overhead = recent_avg_pause_time_ratio() * 100.0;
1509 double last_gc_overhead = _last_pause_time_ratio * 100.0;
1510 double threshold = _gc_overhead_perc;
1511 size_t expand_bytes = 0;
1512
1513 // If the heap is at less than half its maximum size, scale the threshold down,
1514 // to a limit of 1. Thus the smaller the heap is, the more likely it is to expand,
1515 // though the scaling code will likely keep the increase small.
1516 if (_g1->capacity() <= _g1->max_capacity() / 2) {
1517 threshold *= (double)_g1->capacity() / (double)(_g1->max_capacity() / 2);
1518 threshold = MAX2(threshold, 1.0);
1519 }
1520
1521 // If the last GC time ratio is over the threshold, increment the count of
1522 // times it has been exceeded, and add this ratio to the sum of exceeded
1523 // ratios.
1524 if (last_gc_overhead > threshold) {
1525 _ratio_over_threshold_count++;
1526 _ratio_over_threshold_sum += last_gc_overhead;
1527 }
1528
1529 // Check if we've had enough GC time ratio checks that were over the
1530 // threshold to trigger an expansion. We'll also expand if we've
1531 // reached the end of the history buffer and the average of all entries
1532 // is still over the threshold. This indicates a smaller number of GCs were
1533 // long enough to make the average exceed the threshold.
1534 bool filled_history_buffer = _pauses_since_start == NumPrevPausesForHeuristics;
1535 if ((_ratio_over_threshold_count == MinOverThresholdForGrowth) ||
1536 (filled_history_buffer && (recent_gc_overhead > threshold))) {
1537 size_t min_expand_bytes = HeapRegion::GrainBytes;
1538 size_t reserved_bytes = _g1->max_capacity();
1539 size_t committed_bytes = _g1->capacity();
1540 size_t uncommitted_bytes = reserved_bytes - committed_bytes;
1541 size_t expand_bytes_via_pct =
1542 uncommitted_bytes * G1ExpandByPercentOfAvailable / 100;
1543 double scale_factor = 1.0;
1544
1545 // If the current size is less than 1/4 of the Initial heap size, expand
1546 // by half of the delta between the current and Initial sizes. IE, grow
1547 // back quickly.
1548 //
1549 // Otherwise, take the current size, or G1ExpandByPercentOfAvailable % of
1550 // the available expansion space, whichever is smaller, as the base
1551 // expansion size. Then possibly scale this size according to how much the
1552 // threshold has (on average) been exceeded by. If the delta is small
1553 // (less than the StartScaleDownAt value), scale the size down linearly, but
1554 // not by less than MinScaleDownFactor. If the delta is large (greater than
1555 // the StartScaleUpAt value), scale up, but adding no more than MaxScaleUpFactor
1556 // times the base size. The scaling will be linear in the range from
1557 // StartScaleUpAt to (StartScaleUpAt + ScaleUpRange). In other words,
1558 // ScaleUpRange sets the rate of scaling up.
1559 if (committed_bytes < InitialHeapSize / 4) {
1560 expand_bytes = (InitialHeapSize - committed_bytes) / 2;
1561 } else {
1562 double const MinScaleDownFactor = 0.2;
1563 double const MaxScaleUpFactor = 2;
1564 double const StartScaleDownAt = _gc_overhead_perc;
1565 double const StartScaleUpAt = _gc_overhead_perc * 1.5;
1566 double const ScaleUpRange = _gc_overhead_perc * 2.0;
1567
1568 double ratio_delta;
1569 if (filled_history_buffer) {
1570 ratio_delta = recent_gc_overhead - threshold;
1571 } else {
1572 ratio_delta = (_ratio_over_threshold_sum/_ratio_over_threshold_count) - threshold;
1573 }
1574
1575 expand_bytes = MIN2(expand_bytes_via_pct, committed_bytes);
1576 if (ratio_delta < StartScaleDownAt) {
1577 scale_factor = ratio_delta / StartScaleDownAt;
1578 scale_factor = MAX2(scale_factor, MinScaleDownFactor);
1579 } else if (ratio_delta > StartScaleUpAt) {
1580 scale_factor = 1 + ((ratio_delta - StartScaleUpAt) / ScaleUpRange);
1581 scale_factor = MIN2(scale_factor, MaxScaleUpFactor);
1582 }
1583 }
1584
1585 log_debug(gc, ergo, heap)("Attempt heap expansion (recent GC overhead higher than threshold after GC) "
1586 "recent GC overhead: %1.2f %% threshold: %1.2f %% uncommitted: " SIZE_FORMAT "B base expansion amount and scale: " SIZE_FORMAT "B (%1.2f%%)",
1587 recent_gc_overhead, threshold, uncommitted_bytes, expand_bytes, scale_factor * 100);
1588
1589 expand_bytes = static_cast<size_t>(expand_bytes * scale_factor);
1590
1591 // Ensure the expansion size is at least the minimum growth amount
1592 // and at most the remaining uncommitted byte size.
1593 expand_bytes = MAX2(expand_bytes, min_expand_bytes);
1594 expand_bytes = MIN2(expand_bytes, uncommitted_bytes);
1595
1596 clear_ratio_check_data();
1597 } else {
1598 // An expansion was not triggered. If we've started counting, increment
1599 // the number of checks we've made in the current window. If we've
1600 // reached the end of the window without resizing, clear the counters to
1601 // start again the next time we see a ratio above the threshold.
1602 if (_ratio_over_threshold_count > 0) {
1603 _pauses_since_start++;
1604 if (_pauses_since_start > NumPrevPausesForHeuristics) {
1605 clear_ratio_check_data();
1606 }
1607 }
1608 }
1609
1610 return expand_bytes;
1611 }
1612
1613 void G1CollectorPolicy::print_yg_surv_rate_info() const {
1614 #ifndef PRODUCT
1615 _short_lived_surv_rate_group->print_surv_rate_summary();
1616 // add this call for any other surv rate groups
1617 #endif // PRODUCT
1618 }
1619
1620 bool G1CollectorPolicy::is_young_list_full() const {
1621 uint young_list_length = _g1->young_list()->length();
1622 uint young_list_target_length = _young_list_target_length;
1623 return young_list_length >= young_list_target_length;
1624 }
1625
1626 bool G1CollectorPolicy::can_expand_young_list() const {
1627 uint young_list_length = _g1->young_list()->length();
1628 uint young_list_max_length = _young_list_max_length;
1629 return young_list_length < young_list_max_length;
1630 }
1631
1632 bool G1CollectorPolicy::adaptive_young_list_length() const {
1633 return _young_gen_sizer->adaptive_young_list_length();
1634 }
1635
1636 void G1CollectorPolicy::update_max_gc_locker_expansion() {
1637 uint expansion_region_num = 0;
1638 if (GCLockerEdenExpansionPercent > 0) {
1639 double perc = (double) GCLockerEdenExpansionPercent / 100.0;
1640 double expansion_region_num_d = perc * (double) _young_list_target_length;
1641 // We use ceiling so that if expansion_region_num_d is > 0.0 (but
1642 // less than 1.0) we'll get 1.
1643 expansion_region_num = (uint) ceil(expansion_region_num_d);
1644 } else {
1645 assert(expansion_region_num == 0, "sanity");
1646 }
1647 _young_list_max_length = _young_list_target_length + expansion_region_num;
1648 assert(_young_list_target_length <= _young_list_max_length, "post-condition");
1649 }
1650
1651 // Calculates survivor space parameters.
1652 void G1CollectorPolicy::update_survivors_policy() {
1653 double max_survivor_regions_d =
1654 (double) _young_list_target_length / (double) SurvivorRatio;
1655 // We use ceiling so that if max_survivor_regions_d is > 0.0 (but
1656 // smaller than 1.0) we'll get 1.
1657 _max_survivor_regions = (uint) ceil(max_survivor_regions_d);
1658
1659 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(
1660 HeapRegion::GrainWords * _max_survivor_regions, counters());
1661 }
1662
1663 bool G1CollectorPolicy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
1664 // We actually check whether we are marking here and not if we are in a
1665 // reclamation phase. This means that we will schedule a concurrent mark
1666 // even while we are still in the process of reclaiming memory.
1667 bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
1668 if (!during_cycle) {
1669 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
1670 collector_state()->set_initiate_conc_mark_if_possible(true);
1671 return true;
1672 } else {
1673 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
1674 return false;
1675 }
1676 }
1677
1678 void G1CollectorPolicy::initiate_conc_mark() {
1679 collector_state()->set_during_initial_mark_pause(true);
1680 collector_state()->set_initiate_conc_mark_if_possible(false);
1681 }
1682
1683 void G1CollectorPolicy::decide_on_conc_mark_initiation() {
1684 // We are about to decide on whether this pause will be an
1685 // initial-mark pause.
1686
1687 // First, collector_state()->during_initial_mark_pause() should not be already set. We
1688 // will set it here if we have to. However, it should be cleared by
1689 // the end of the pause (it's only set for the duration of an
1690 // initial-mark pause).
1691 assert(!collector_state()->during_initial_mark_pause(), "pre-condition");
1692
1693 if (collector_state()->initiate_conc_mark_if_possible()) {
1694 // We had noticed on a previous pause that the heap occupancy has
1695 // gone over the initiating threshold and we should start a
1696 // concurrent marking cycle. So we might initiate one.
1697
1698 if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) {
1699 // Initiate a new initial mark if there is no marking or reclamation going on.
1700 initiate_conc_mark();
1701 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
1702 } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) {
1703 // Initiate a user requested initial mark. An initial mark must be young only
1704 // GC, so the collector state must be updated to reflect this.
1705 collector_state()->set_gcs_are_young(true);
1706 collector_state()->set_last_young_gc(false);
1707
1708 abort_time_to_mixed_tracking();
1709 initiate_conc_mark();
1710 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1711 } else {
1712 // The concurrent marking thread is still finishing up the
1713 // previous cycle. If we start one right now the two cycles
1714 // overlap. In particular, the concurrent marking thread might
1715 // be in the process of clearing the next marking bitmap (which
1716 // we will use for the next cycle if we start one). Starting a
1717 // cycle now will be bad given that parts of the marking
1718 // information might get cleared by the marking thread. And we
1719 // cannot wait for the marking thread to finish the cycle as it
1720 // periodically yields while clearing the next marking bitmap
1721 // and, if it's in a yield point, it's waiting for us to
1722 // finish. So, at this point we will not start a cycle and we'll
1723 // let the concurrent marking thread complete the last one.
1724 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1725 }
1726 }
1727 }
1728
1729 class ParKnownGarbageHRClosure: public HeapRegionClosure {
1730 G1CollectedHeap* _g1h;
1731 CSetChooserParUpdater _cset_updater;
1732
1733 public:
1734 ParKnownGarbageHRClosure(CollectionSetChooser* hrSorted,
1735 uint chunk_size) :
1736 _g1h(G1CollectedHeap::heap()),
1737 _cset_updater(hrSorted, true /* parallel */, chunk_size) { }
1738
1739 bool doHeapRegion(HeapRegion* r) {
1740 // Do we have any marking information for this region?
1741 if (r->is_marked()) {
1742 // We will skip any region that's currently used as an old GC
1743 // alloc region (we should not consider those for collection
1744 // before we fill them up).
1745 if (_cset_updater.should_add(r) && !_g1h->is_old_gc_alloc_region(r)) {
1746 _cset_updater.add_region(r);
1747 }
1748 }
1749 return false;
1750 }
1751 };
1752
1753 class ParKnownGarbageTask: public AbstractGangTask {
1754 CollectionSetChooser* _hrSorted;
1755 uint _chunk_size;
1756 G1CollectedHeap* _g1;
1757 HeapRegionClaimer _hrclaimer;
1758
1759 public:
1760 ParKnownGarbageTask(CollectionSetChooser* hrSorted, uint chunk_size, uint n_workers) :
1761 AbstractGangTask("ParKnownGarbageTask"),
1762 _hrSorted(hrSorted), _chunk_size(chunk_size),
1763 _g1(G1CollectedHeap::heap()), _hrclaimer(n_workers) {}
1764
1765 void work(uint worker_id) {
1766 ParKnownGarbageHRClosure parKnownGarbageCl(_hrSorted, _chunk_size);
1767 _g1->heap_region_par_iterate(&parKnownGarbageCl, worker_id, &_hrclaimer);
1768 }
1769 };
1770
1771 uint G1CollectorPolicy::calculate_parallel_work_chunk_size(uint n_workers, uint n_regions) const {
1772 assert(n_workers > 0, "Active gc workers should be greater than 0");
1773 const uint overpartition_factor = 4;
1774 const uint min_chunk_size = MAX2(n_regions / n_workers, 1U);
1775 return MAX2(n_regions / (n_workers * overpartition_factor), min_chunk_size);
1776 }
1777
1778 void G1CollectorPolicy::record_concurrent_mark_cleanup_end() {
1779 cset_chooser()->clear();
1780
1781 WorkGang* workers = _g1->workers();
1782 uint n_workers = workers->active_workers();
1783
1784 uint n_regions = _g1->num_regions();
1785 uint chunk_size = calculate_parallel_work_chunk_size(n_workers, n_regions);
1786 cset_chooser()->prepare_for_par_region_addition(n_workers, n_regions, chunk_size);
1787 ParKnownGarbageTask par_known_garbage_task(cset_chooser(), chunk_size, n_workers);
1788 workers->run_task(&par_known_garbage_task);
1789
1790 cset_chooser()->sort_regions();
1791
1792 double end_sec = os::elapsedTime();
1793 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1794 _concurrent_mark_cleanup_times_ms->add(elapsed_time_ms);
1795 _prev_collection_pause_end_ms += elapsed_time_ms;
1796
1797 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1798 }
1799
1800 double G1CollectorPolicy::reclaimable_bytes_perc(size_t reclaimable_bytes) const {
1801 // Returns the given amount of reclaimable bytes (that represents
1802 // the amount of reclaimable space still to be collected) as a
1803 // percentage of the current heap capacity.
1804 size_t capacity_bytes = _g1->capacity();
1805 return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
1806 }
1807
1808 void G1CollectorPolicy::maybe_start_marking() {
1809 if (need_to_start_conc_mark("end of GC")) {
1810 // Note: this might have already been set, if during the last
1811 // pause we decided to start a cycle but at the beginning of
1812 // this pause we decided to postpone it. That's OK.
1813 collector_state()->set_initiate_conc_mark_if_possible(true);
1814 }
1815 }
1816
1817 G1CollectorPolicy::PauseKind G1CollectorPolicy::young_gc_pause_kind() const {
1818 assert(!collector_state()->full_collection(), "must be");
1819 if (collector_state()->during_initial_mark_pause()) {
1820 assert(collector_state()->last_gc_was_young(), "must be");
1821 assert(!collector_state()->last_young_gc(), "must be");
1822 return InitialMarkGC;
1823 } else if (collector_state()->last_young_gc()) {
1824 assert(!collector_state()->during_initial_mark_pause(), "must be");
1825 assert(collector_state()->last_gc_was_young(), "must be");
1826 return LastYoungGC;
1827 } else if (!collector_state()->last_gc_was_young()) {
1828 assert(!collector_state()->during_initial_mark_pause(), "must be");
1829 assert(!collector_state()->last_young_gc(), "must be");
1830 return MixedGC;
1831 } else {
1832 assert(collector_state()->last_gc_was_young(), "must be");
1833 assert(!collector_state()->during_initial_mark_pause(), "must be");
1834 assert(!collector_state()->last_young_gc(), "must be");
1835 return YoungOnlyGC;
1836 }
1837 }
1838
1839 void G1CollectorPolicy::record_pause(PauseKind kind, double start, double end) {
1840 // Manage the MMU tracker. For some reason it ignores Full GCs.
1841 if (kind != FullGC) {
1842 _mmu_tracker->add_pause(start, end);
1843 }
1844 // Manage the mutator time tracking from initial mark to first mixed gc.
1845 switch (kind) {
1846 case FullGC:
1847 abort_time_to_mixed_tracking();
1848 break;
1849 case Cleanup:
1850 case Remark:
1851 case YoungOnlyGC:
1852 case LastYoungGC:
1853 _initial_mark_to_mixed.add_pause(end - start);
1854 break;
1855 case InitialMarkGC:
1856 _initial_mark_to_mixed.record_initial_mark_end(end);
1857 break;
1858 case MixedGC:
1859 _initial_mark_to_mixed.record_mixed_gc_start(start);
1860 break;
1861 default:
1862 ShouldNotReachHere();
1863 }
1864 }
1865
1866 void G1CollectorPolicy::abort_time_to_mixed_tracking() {
1867 _initial_mark_to_mixed.reset();
1868 }
1869
1870 bool G1CollectorPolicy::next_gc_should_be_mixed(const char* true_action_str,
1871 const char* false_action_str) const {
1872 if (cset_chooser()->is_empty()) {
1873 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1874 return false;
1875 }
1876
1877 // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1878 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
1879 double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
1880 double threshold = (double) G1HeapWastePercent;
1881 if (reclaimable_perc <= threshold) {
1882 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1883 false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
1884 return false;
1885 }
1886 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1887 true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
1888 return true;
1889 }
1890
1891 uint G1CollectorPolicy::calc_min_old_cset_length() const {
1892 // The min old CSet region bound is based on the maximum desired
1893 // number of mixed GCs after a cycle. I.e., even if some old regions
1894 // look expensive, we should add them to the CSet anyway to make
1895 // sure we go through the available old regions in no more than the
1896 // maximum desired number of mixed GCs.
1897 //
1898 // The calculation is based on the number of marked regions we added
1899 // to the CSet chooser in the first place, not how many remain, so
1900 // that the result is the same during all mixed GCs that follow a cycle.
1901
1902 const size_t region_num = (size_t) cset_chooser()->length();
1903 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1904 size_t result = region_num / gc_num;
1905 // emulate ceiling
1906 if (result * gc_num < region_num) {
1907 result += 1;
1908 }
1909 return (uint) result;
1910 }
1911
1912 uint G1CollectorPolicy::calc_max_old_cset_length() const {
1913 // The max old CSet region bound is based on the threshold expressed
1914 // as a percentage of the heap size. I.e., it should bound the
1915 // number of old regions added to the CSet irrespective of how many
1916 // of them are available.
1917
1918 const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1919 const size_t region_num = g1h->num_regions();
1920 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1921 size_t result = region_num * perc / 100;
1922 // emulate ceiling
1923 if (100 * result < region_num * perc) {
1924 result += 1;
1925 }
1926 return (uint) result;
1927 }
1928
1929 void G1CollectorPolicy::finalize_collection_set(double target_pause_time_ms) {
1930 double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms);
1931 _collection_set->finalize_old_part(time_remaining_ms);
1932 }
1933