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/g1YoungGenSizer.hpp"
35 #include "gc/g1/heapRegion.inline.hpp"
36 #include "gc/g1/heapRegionRemSet.hpp"
37 #include "gc/shared/gcPolicyCounters.hpp"
38 #include "runtime/arguments.hpp"
39 #include "runtime/java.hpp"
40 #include "runtime/mutexLocker.hpp"
41 #include "utilities/debug.hpp"
42 #include "utilities/pair.hpp"
43
44 // Different defaults for different number of GC threads
45 // They were chosen by running GCOld and SPECjbb on debris with different
46 // numbers of GC threads and choosing them based on the results
47
48 // all the same
49 static double rs_length_diff_defaults[] = {
50 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0
51 };
52
53 static double cost_per_card_ms_defaults[] = {
54 0.01, 0.005, 0.005, 0.003, 0.003, 0.002, 0.002, 0.0015
55 };
56
57 // all the same
58 static double young_cards_per_entry_ratio_defaults[] = {
59 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0
60 };
61
62 static double cost_per_entry_ms_defaults[] = {
63 0.015, 0.01, 0.01, 0.008, 0.008, 0.0055, 0.0055, 0.005
64 };
65
66 static double cost_per_byte_ms_defaults[] = {
67 0.00006, 0.00003, 0.00003, 0.000015, 0.000015, 0.00001, 0.00001, 0.000009
68 };
69
70 // these should be pretty consistent
71 static double constant_other_time_ms_defaults[] = {
72 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0
73 };
74
75
76 static double young_other_cost_per_region_ms_defaults[] = {
77 0.3, 0.2, 0.2, 0.15, 0.15, 0.12, 0.12, 0.1
78 };
79
80 static double non_young_other_cost_per_region_ms_defaults[] = {
81 1.0, 0.7, 0.7, 0.5, 0.5, 0.42, 0.42, 0.30
82 };
83
84 G1CollectorPolicy::G1CollectorPolicy() :
85 _predictor(G1ConfidencePercent / 100.0),
86
87 _recent_gc_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
88
89 _concurrent_mark_remark_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
90 _concurrent_mark_cleanup_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
91
92 _alloc_rate_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
93 _prev_collection_pause_end_ms(0.0),
94 _rs_length_diff_seq(new TruncatedSeq(TruncatedSeqLength)),
95 _cost_per_card_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
96 _cost_scan_hcc_seq(new TruncatedSeq(TruncatedSeqLength)),
97 _young_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
98 _mixed_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
99 _cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
100 _mixed_cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
101 _cost_per_byte_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
102 _cost_per_byte_ms_during_cm_seq(new TruncatedSeq(TruncatedSeqLength)),
103 _constant_other_time_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
104 _young_other_cost_per_region_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
105 _non_young_other_cost_per_region_ms_seq(
106 new TruncatedSeq(TruncatedSeqLength)),
107
108 _pending_cards_seq(new TruncatedSeq(TruncatedSeqLength)),
109 _rs_lengths_seq(new TruncatedSeq(TruncatedSeqLength)),
110
111 _pause_time_target_ms((double) MaxGCPauseMillis),
112
113 _recent_prev_end_times_for_all_gcs_sec(
114 new TruncatedSeq(NumPrevPausesForHeuristics)),
115
116 _recent_avg_pause_time_ratio(0.0),
117 _rs_lengths_prediction(0),
118 _max_survivor_regions(0),
119
120 // add here any more surv rate groups
121 _survivors_age_table(true),
122
123 _gc_overhead_perc(0.0),
124
125 _bytes_allocated_in_old_since_last_gc(0),
126 _ihop_control(NULL),
127 _initial_mark_to_mixed() {
128
129 // SurvRateGroups below must be initialized after the predictor because they
130 // indirectly use it through this object passed to their constructor.
131 _short_lived_surv_rate_group =
132 new SurvRateGroup(&_predictor, "Short Lived", G1YoungSurvRateNumRegionsSummary);
133 _survivor_surv_rate_group =
134 new SurvRateGroup(&_predictor, "Survivor", G1YoungSurvRateNumRegionsSummary);
135
136 // Set up the region size and associated fields. Given that the
137 // policy is created before the heap, we have to set this up here,
138 // so it's done as soon as possible.
139
140 // It would have been natural to pass initial_heap_byte_size() and
141 // max_heap_byte_size() to setup_heap_region_size() but those have
142 // not been set up at this point since they should be aligned with
143 // the region size. So, there is a circular dependency here. We base
144 // the region size on the heap size, but the heap size should be
145 // aligned with the region size. To get around this we use the
146 // unaligned values for the heap.
147 HeapRegion::setup_heap_region_size(InitialHeapSize, MaxHeapSize);
148 HeapRegionRemSet::setup_remset_size();
149
150 _recent_prev_end_times_for_all_gcs_sec->add(os::elapsedTime());
151 _prev_collection_pause_end_ms = os::elapsedTime() * 1000.0;
152 clear_ratio_check_data();
153
154 _phase_times = new G1GCPhaseTimes(ParallelGCThreads);
155
156 int index = MIN2(ParallelGCThreads - 1, 7u);
157
158 _rs_length_diff_seq->add(rs_length_diff_defaults[index]);
159 _cost_per_card_ms_seq->add(cost_per_card_ms_defaults[index]);
160 _cost_scan_hcc_seq->add(0.0);
161 _young_cards_per_entry_ratio_seq->add(
162 young_cards_per_entry_ratio_defaults[index]);
163 _cost_per_entry_ms_seq->add(cost_per_entry_ms_defaults[index]);
164 _cost_per_byte_ms_seq->add(cost_per_byte_ms_defaults[index]);
165 _constant_other_time_ms_seq->add(constant_other_time_ms_defaults[index]);
166 _young_other_cost_per_region_ms_seq->add(
167 young_other_cost_per_region_ms_defaults[index]);
168 _non_young_other_cost_per_region_ms_seq->add(
169 non_young_other_cost_per_region_ms_defaults[index]);
170
171 // Below, we might need to calculate the pause time target based on
172 // the pause interval. When we do so we are going to give G1 maximum
173 // flexibility and allow it to do pauses when it needs to. So, we'll
174 // arrange that the pause interval to be pause time target + 1 to
175 // ensure that a) the pause time target is maximized with respect to
176 // the pause interval and b) we maintain the invariant that pause
177 // time target < pause interval. If the user does not want this
178 // maximum flexibility, they will have to set the pause interval
179 // explicitly.
180
181 // First make sure that, if either parameter is set, its value is
182 // reasonable.
183 guarantee(MaxGCPauseMillis >= 1, "Range checking for MaxGCPauseMillis should guarantee that value is >= 1");
184
185 // Then, if the pause time target parameter was not set, set it to
186 // the default value.
187 if (FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
188 if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
189 // The default pause time target in G1 is 200ms
190 FLAG_SET_DEFAULT(MaxGCPauseMillis, 200);
191 } else {
192 // We do not allow the pause interval to be set without the
193 // pause time target
194 vm_exit_during_initialization("GCPauseIntervalMillis cannot be set "
195 "without setting MaxGCPauseMillis");
196 }
197 }
198
199 // Then, if the interval parameter was not set, set it according to
200 // the pause time target (this will also deal with the case when the
201 // pause time target is the default value).
202 if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
203 FLAG_SET_DEFAULT(GCPauseIntervalMillis, MaxGCPauseMillis + 1);
204 }
205 guarantee(GCPauseIntervalMillis >= 1, "Constraint for GCPauseIntervalMillis should guarantee that value is >= 1");
206 guarantee(GCPauseIntervalMillis > MaxGCPauseMillis, "Constraint for GCPauseIntervalMillis should guarantee that GCPauseIntervalMillis > MaxGCPauseMillis");
207
208 double max_gc_time = (double) MaxGCPauseMillis / 1000.0;
209 double time_slice = (double) GCPauseIntervalMillis / 1000.0;
210 _mmu_tracker = new G1MMUTrackerQueue(time_slice, max_gc_time);
211
212 // start conservatively (around 50ms is about right)
213 _concurrent_mark_remark_times_ms->add(0.05);
214 _concurrent_mark_cleanup_times_ms->add(0.20);
215 _tenuring_threshold = MaxTenuringThreshold;
216
217 assert(GCTimeRatio > 0,
218 "we should have set it to a default value set_g1_gc_flags() "
219 "if a user set it to 0");
220 _gc_overhead_perc = 100.0 * (1.0 / (1.0 + GCTimeRatio));
221
222 guarantee(G1ReservePercent <= 50, "Range checking should not allow values over 50.");
223 _reserve_factor = (double) G1ReservePercent / 100.0;
224 // This will be set when the heap is expanded
225 // for the first time during initialization.
226 _reserve_regions = 0;
227
228 _ihop_control = create_ihop_control();
229 }
230
231 G1CollectorPolicy::~G1CollectorPolicy() {
232 delete _ihop_control;
233 }
234
235 double G1CollectorPolicy::get_new_prediction(TruncatedSeq const* seq) const {
236 return _predictor.get_new_prediction(seq);
237 }
238
239 size_t G1CollectorPolicy::get_new_size_prediction(TruncatedSeq const* seq) const {
240 return (size_t)get_new_prediction(seq);
241 }
242
243 void G1CollectorPolicy::initialize_alignments() {
244 _space_alignment = HeapRegion::GrainBytes;
245 size_t card_table_alignment = CardTableRS::ct_max_alignment_constraint();
246 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
247 _heap_alignment = MAX3(card_table_alignment, _space_alignment, page_size);
248 }
249
250 G1CollectorState* G1CollectorPolicy::collector_state() const { return _g1->collector_state(); }
251
252 void G1CollectorPolicy::post_heap_initialize() {
253 uintx max_regions = G1CollectedHeap::heap()->max_regions();
254 size_t max_young_size = (size_t)_young_gen_sizer->max_young_length(max_regions) * HeapRegion::GrainBytes;
255 if (max_young_size != MaxNewSize) {
256 FLAG_SET_ERGO(size_t, MaxNewSize, max_young_size);
257 }
258 }
259
260 void G1CollectorPolicy::initialize_flags() {
261 if (G1HeapRegionSize != HeapRegion::GrainBytes) {
262 FLAG_SET_ERGO(size_t, G1HeapRegionSize, HeapRegion::GrainBytes);
263 }
264
265 guarantee(SurvivorRatio >= 1, "Range checking for SurvivorRatio should guarantee that value is >= 1");
266
267 CollectorPolicy::initialize_flags();
268 _young_gen_sizer = new G1YoungGenSizer(); // Must be after call to initialize_flags
269 }
270
271
272 void G1CollectorPolicy::init() {
273 // Set aside an initial future to_space.
274 _g1 = G1CollectedHeap::heap();
275 _collection_set = _g1->collection_set();
276 _collection_set->set_policy(this);
277
278 assert(Heap_lock->owned_by_self(), "Locking discipline.");
279
280 initialize_gc_policy_counters();
281
282 if (adaptive_young_list_length()) {
283 _young_list_fixed_length = 0;
284 } else {
285 _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
286 }
287 _free_regions_at_end_of_collection = _g1->num_free_regions();
288
289 update_young_list_max_and_target_length();
290 // We may immediately start allocating regions and placing them on the
291 // collection set list. Initialize the per-collection set info
292 _collection_set->start_incremental_building();
293 }
294
295 void G1CollectorPolicy::note_gc_start(uint num_active_workers) {
296 phase_times()->note_gc_start(num_active_workers);
297 }
298
299 // Create the jstat counters for the policy.
300 void G1CollectorPolicy::initialize_gc_policy_counters() {
301 _gc_policy_counters = new GCPolicyCounters("GarbageFirst", 1, 3);
302 }
303
304 bool G1CollectorPolicy::predict_will_fit(uint young_length,
305 double base_time_ms,
306 uint base_free_regions,
307 double target_pause_time_ms) const {
308 if (young_length >= base_free_regions) {
309 // end condition 1: not enough space for the young regions
310 return false;
311 }
312
313 double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);
314 size_t bytes_to_copy =
315 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
316 double copy_time_ms = predict_object_copy_time_ms(bytes_to_copy);
317 double young_other_time_ms = predict_young_other_time_ms(young_length);
318 double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;
319 if (pause_time_ms > target_pause_time_ms) {
320 // end condition 2: prediction is over the target pause time
321 return false;
322 }
323
324 size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes;
325
326 // When copying, we will likely need more bytes free than is live in the region.
327 // Add some safety margin to factor in the confidence of our guess, and the
328 // natural expected waste.
329 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
330 // of the calculation: the lower the confidence, the more headroom.
331 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
332 // copying due to anticipated waste in the PLABs.
333 double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
334 size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
335
336 if (expected_bytes_to_copy > free_bytes) {
337 // end condition 3: out-of-space
338 return false;
339 }
340
341 // success!
342 return true;
343 }
344
345 void G1CollectorPolicy::record_new_heap_size(uint new_number_of_regions) {
346 // re-calculate the necessary reserve
347 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
348 // We use ceiling so that if reserve_regions_d is > 0.0 (but
349 // smaller than 1.0) we'll get 1.
350 _reserve_regions = (uint) ceil(reserve_regions_d);
351
352 _young_gen_sizer->heap_size_changed(new_number_of_regions);
353
354 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
355 }
356
357 uint G1CollectorPolicy::calculate_young_list_desired_min_length(
358 uint base_min_length) const {
359 uint desired_min_length = 0;
360 if (adaptive_young_list_length()) {
361 if (_alloc_rate_ms_seq->num() > 3) {
362 double now_sec = os::elapsedTime();
363 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
364 double alloc_rate_ms = predict_alloc_rate_ms();
365 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
366 } else {
367 // otherwise we don't have enough info to make the prediction
368 }
369 }
370 desired_min_length += base_min_length;
371 // make sure we don't go below any user-defined minimum bound
372 return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
373 }
374
375 uint G1CollectorPolicy::calculate_young_list_desired_max_length() const {
376 // Here, we might want to also take into account any additional
377 // constraints (i.e., user-defined minimum bound). Currently, we
378 // effectively don't set this bound.
379 return _young_gen_sizer->max_desired_young_length();
380 }
381
382 uint G1CollectorPolicy::update_young_list_max_and_target_length() {
383 return update_young_list_max_and_target_length(predict_rs_lengths());
384 }
385
386 uint G1CollectorPolicy::update_young_list_max_and_target_length(size_t rs_lengths) {
387 uint unbounded_target_length = update_young_list_target_length(rs_lengths);
388 update_max_gc_locker_expansion();
389 return unbounded_target_length;
390 }
391
392 uint G1CollectorPolicy::update_young_list_target_length(size_t rs_lengths) {
393 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
394 _young_list_target_length = young_lengths.first;
395 return young_lengths.second;
396 }
397
398 G1CollectorPolicy::YoungTargetLengths G1CollectorPolicy::young_list_target_lengths(size_t rs_lengths) const {
399 YoungTargetLengths result;
400
401 // Calculate the absolute and desired min bounds first.
402
403 // This is how many young regions we already have (currently: the survivors).
404 const uint base_min_length = _g1->young_list()->survivor_length();
405 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
406 // This is the absolute minimum young length. Ensure that we
407 // will at least have one eden region available for allocation.
408 uint absolute_min_length = base_min_length + MAX2(_g1->young_list()->eden_length(), (uint)1);
409 // If we shrank the young list target it should not shrink below the current size.
410 desired_min_length = MAX2(desired_min_length, absolute_min_length);
411 // Calculate the absolute and desired max bounds.
412
413 uint desired_max_length = calculate_young_list_desired_max_length();
414
415 uint young_list_target_length = 0;
416 if (adaptive_young_list_length()) {
417 if (collector_state()->gcs_are_young()) {
418 young_list_target_length =
419 calculate_young_list_target_length(rs_lengths,
420 base_min_length,
421 desired_min_length,
422 desired_max_length);
423 } else {
424 // Don't calculate anything and let the code below bound it to
425 // the desired_min_length, i.e., do the next GC as soon as
426 // possible to maximize how many old regions we can add to it.
427 }
428 } else {
429 // The user asked for a fixed young gen so we'll fix the young gen
430 // whether the next GC is young or mixed.
431 young_list_target_length = _young_list_fixed_length;
432 }
433
434 result.second = young_list_target_length;
435
436 // We will try our best not to "eat" into the reserve.
437 uint absolute_max_length = 0;
438 if (_free_regions_at_end_of_collection > _reserve_regions) {
439 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
440 }
441 if (desired_max_length > absolute_max_length) {
442 desired_max_length = absolute_max_length;
443 }
444
445 // Make sure we don't go over the desired max length, nor under the
446 // desired min length. In case they clash, desired_min_length wins
447 // which is why that test is second.
448 if (young_list_target_length > desired_max_length) {
449 young_list_target_length = desired_max_length;
450 }
451 if (young_list_target_length < desired_min_length) {
452 young_list_target_length = desired_min_length;
453 }
454
455 assert(young_list_target_length > base_min_length,
456 "we should be able to allocate at least one eden region");
457 assert(young_list_target_length >= absolute_min_length, "post-condition");
458
459 result.first = young_list_target_length;
460 return result;
461 }
462
463 uint
464 G1CollectorPolicy::calculate_young_list_target_length(size_t rs_lengths,
465 uint base_min_length,
466 uint desired_min_length,
467 uint desired_max_length) const {
468 assert(adaptive_young_list_length(), "pre-condition");
469 assert(collector_state()->gcs_are_young(), "only call this for young GCs");
470
471 // In case some edge-condition makes the desired max length too small...
472 if (desired_max_length <= desired_min_length) {
473 return desired_min_length;
474 }
475
476 // We'll adjust min_young_length and max_young_length not to include
477 // the already allocated young regions (i.e., so they reflect the
478 // min and max eden regions we'll allocate). The base_min_length
479 // will be reflected in the predictions by the
480 // survivor_regions_evac_time prediction.
481 assert(desired_min_length > base_min_length, "invariant");
482 uint min_young_length = desired_min_length - base_min_length;
483 assert(desired_max_length > base_min_length, "invariant");
484 uint max_young_length = desired_max_length - base_min_length;
485
486 double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
487 double survivor_regions_evac_time = predict_survivor_regions_evac_time();
488 size_t pending_cards = get_new_size_prediction(_pending_cards_seq);
489 size_t adj_rs_lengths = rs_lengths + predict_rs_length_diff();
490 size_t scanned_cards = predict_young_card_num(adj_rs_lengths);
491 double base_time_ms =
492 predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
493 survivor_regions_evac_time;
494 uint available_free_regions = _free_regions_at_end_of_collection;
495 uint base_free_regions = 0;
496 if (available_free_regions > _reserve_regions) {
497 base_free_regions = available_free_regions - _reserve_regions;
498 }
499
500 // Here, we will make sure that the shortest young length that
501 // makes sense fits within the target pause time.
502
503 if (predict_will_fit(min_young_length, base_time_ms,
504 base_free_regions, target_pause_time_ms)) {
505 // The shortest young length will fit into the target pause time;
506 // we'll now check whether the absolute maximum number of young
507 // regions will fit in the target pause time. If not, we'll do
508 // a binary search between min_young_length and max_young_length.
509 if (predict_will_fit(max_young_length, base_time_ms,
510 base_free_regions, target_pause_time_ms)) {
511 // The maximum young length will fit into the target pause time.
512 // We are done so set min young length to the maximum length (as
513 // the result is assumed to be returned in min_young_length).
514 min_young_length = max_young_length;
515 } else {
516 // The maximum possible number of young regions will not fit within
517 // the target pause time so we'll search for the optimal
518 // length. The loop invariants are:
519 //
520 // min_young_length < max_young_length
521 // min_young_length is known to fit into the target pause time
522 // max_young_length is known not to fit into the target pause time
523 //
524 // Going into the loop we know the above hold as we've just
525 // checked them. Every time around the loop we check whether
526 // the middle value between min_young_length and
527 // max_young_length fits into the target pause time. If it
528 // does, it becomes the new min. If it doesn't, it becomes
529 // the new max. This way we maintain the loop invariants.
530
531 assert(min_young_length < max_young_length, "invariant");
532 uint diff = (max_young_length - min_young_length) / 2;
533 while (diff > 0) {
534 uint young_length = min_young_length + diff;
535 if (predict_will_fit(young_length, base_time_ms,
536 base_free_regions, target_pause_time_ms)) {
537 min_young_length = young_length;
538 } else {
539 max_young_length = young_length;
540 }
541 assert(min_young_length < max_young_length, "invariant");
542 diff = (max_young_length - min_young_length) / 2;
543 }
544 // The results is min_young_length which, according to the
545 // loop invariants, should fit within the target pause time.
546
547 // These are the post-conditions of the binary search above:
548 assert(min_young_length < max_young_length,
549 "otherwise we should have discovered that max_young_length "
550 "fits into the pause target and not done the binary search");
551 assert(predict_will_fit(min_young_length, base_time_ms,
552 base_free_regions, target_pause_time_ms),
553 "min_young_length, the result of the binary search, should "
554 "fit into the pause target");
555 assert(!predict_will_fit(min_young_length + 1, base_time_ms,
556 base_free_regions, target_pause_time_ms),
557 "min_young_length, the result of the binary search, should be "
558 "optimal, so no larger length should fit into the pause target");
559 }
560 } else {
561 // Even the minimum length doesn't fit into the pause time
562 // target, return it as the result nevertheless.
563 }
564 return base_min_length + min_young_length;
565 }
566
567 double G1CollectorPolicy::predict_survivor_regions_evac_time() const {
568 double survivor_regions_evac_time = 0.0;
569 for (HeapRegion * r = _g1->young_list()->first_survivor_region();
570 r != NULL && r != _g1->young_list()->last_survivor_region()->get_next_young_region();
571 r = r->get_next_young_region()) {
572 survivor_regions_evac_time += predict_region_elapsed_time_ms(r, collector_state()->gcs_are_young());
573 }
574 return survivor_regions_evac_time;
575 }
576
577 void G1CollectorPolicy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
578 guarantee( adaptive_young_list_length(), "should not call this otherwise" );
579
580 if (rs_lengths > _rs_lengths_prediction) {
581 // add 10% to avoid having to recalculate often
582 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
583 update_rs_lengths_prediction(rs_lengths_prediction);
584
585 update_young_list_max_and_target_length(rs_lengths_prediction);
586 }
587 }
588
589 void G1CollectorPolicy::update_rs_lengths_prediction() {
590 update_rs_lengths_prediction(predict_rs_lengths());
591 }
592
593 void G1CollectorPolicy::update_rs_lengths_prediction(size_t prediction) {
594 if (collector_state()->gcs_are_young() && adaptive_young_list_length()) {
595 _rs_lengths_prediction = prediction;
596 }
597 }
598
599 #ifndef PRODUCT
600 bool G1CollectorPolicy::verify_young_ages() {
601 HeapRegion* head = _g1->young_list()->first_region();
602 return
603 verify_young_ages(head, _short_lived_surv_rate_group);
604 // also call verify_young_ages on any additional surv rate groups
605 }
606
607 bool
608 G1CollectorPolicy::verify_young_ages(HeapRegion* head,
609 SurvRateGroup *surv_rate_group) {
610 guarantee( surv_rate_group != NULL, "pre-condition" );
611
612 const char* name = surv_rate_group->name();
613 bool ret = true;
614 int prev_age = -1;
615
616 for (HeapRegion* curr = head;
617 curr != NULL;
618 curr = curr->get_next_young_region()) {
619 SurvRateGroup* group = curr->surv_rate_group();
620 if (group == NULL && !curr->is_survivor()) {
621 log_error(gc, verify)("## %s: encountered NULL surv_rate_group", name);
622 ret = false;
623 }
624
625 if (surv_rate_group == group) {
626 int age = curr->age_in_surv_rate_group();
627
628 if (age < 0) {
629 log_error(gc, verify)("## %s: encountered negative age", name);
630 ret = false;
631 }
632
633 if (age <= prev_age) {
634 log_error(gc, verify)("## %s: region ages are not strictly increasing (%d, %d)", name, age, prev_age);
635 ret = false;
636 }
637 prev_age = age;
638 }
639 }
640
641 return ret;
642 }
643 #endif // PRODUCT
644
645 void G1CollectorPolicy::record_full_collection_start() {
646 _full_collection_start_sec = os::elapsedTime();
647 // Release the future to-space so that it is available for compaction into.
648 collector_state()->set_full_collection(true);
649 }
650
651 void G1CollectorPolicy::record_full_collection_end() {
652 // Consider this like a collection pause for the purposes of allocation
653 // since last pause.
654 double end_sec = os::elapsedTime();
655 double full_gc_time_sec = end_sec - _full_collection_start_sec;
656 double full_gc_time_ms = full_gc_time_sec * 1000.0;
657
658 update_recent_gc_times(end_sec, full_gc_time_ms);
659
660 collector_state()->set_full_collection(false);
661
662 // "Nuke" the heuristics that control the young/mixed GC
663 // transitions and make sure we start with young GCs after the Full GC.
664 collector_state()->set_gcs_are_young(true);
665 collector_state()->set_last_young_gc(false);
666 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
667 collector_state()->set_during_initial_mark_pause(false);
668 collector_state()->set_in_marking_window(false);
669 collector_state()->set_in_marking_window_im(false);
670
671 _short_lived_surv_rate_group->start_adding_regions();
672 // also call this on any additional surv rate groups
673
674 _free_regions_at_end_of_collection = _g1->num_free_regions();
675 // Reset survivors SurvRateGroup.
676 _survivor_surv_rate_group->reset();
677 update_young_list_max_and_target_length();
678 update_rs_lengths_prediction();
679 cset_chooser()->clear();
680
681 _bytes_allocated_in_old_since_last_gc = 0;
682
683 record_pause(FullGC, _full_collection_start_sec, end_sec);
684 }
685
686 void G1CollectorPolicy::record_collection_pause_start(double start_time_sec) {
687 // We only need to do this here as the policy will only be applied
688 // to the GC we're about to start. so, no point is calculating this
689 // every time we calculate / recalculate the target young length.
690 update_survivors_policy();
691
692 assert(_g1->used() == _g1->recalculate_used(),
693 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
694 _g1->used(), _g1->recalculate_used());
695
696 phase_times()->record_cur_collection_start_sec(start_time_sec);
697 _pending_cards = _g1->pending_card_num();
698
699 _collection_set->reset_bytes_used_before();
700 _bytes_copied_during_gc = 0;
701
702 collector_state()->set_last_gc_was_young(false);
703
704 // do that for any other surv rate groups
705 _short_lived_surv_rate_group->stop_adding_regions();
706 _survivors_age_table.clear();
707
708 assert( verify_young_ages(), "region age verification" );
709 }
710
711 void G1CollectorPolicy::record_concurrent_mark_init_end(double
712 mark_init_elapsed_time_ms) {
713 collector_state()->set_during_marking(true);
714 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
715 collector_state()->set_during_initial_mark_pause(false);
716 }
717
718 void G1CollectorPolicy::record_concurrent_mark_remark_start() {
719 _mark_remark_start_sec = os::elapsedTime();
720 collector_state()->set_during_marking(false);
721 }
722
723 void G1CollectorPolicy::record_concurrent_mark_remark_end() {
724 double end_time_sec = os::elapsedTime();
725 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
726 _concurrent_mark_remark_times_ms->add(elapsed_time_ms);
727 _prev_collection_pause_end_ms += elapsed_time_ms;
728
729 record_pause(Remark, _mark_remark_start_sec, end_time_sec);
730 }
731
732 void G1CollectorPolicy::record_concurrent_mark_cleanup_start() {
733 _mark_cleanup_start_sec = os::elapsedTime();
734 }
735
736 void G1CollectorPolicy::record_concurrent_mark_cleanup_completed() {
737 bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",
738 "skip last young-only gc");
739 collector_state()->set_last_young_gc(should_continue_with_reclaim);
740 // We skip the marking phase.
741 if (!should_continue_with_reclaim) {
742 abort_time_to_mixed_tracking();
743 }
744 collector_state()->set_in_marking_window(false);
745 }
746
747 double G1CollectorPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
748 return phase_times()->average_time_ms(phase);
749 }
750
751 double G1CollectorPolicy::young_other_time_ms() const {
752 return phase_times()->young_cset_choice_time_ms() +
753 phase_times()->young_free_cset_time_ms();
754 }
755
756 double G1CollectorPolicy::non_young_other_time_ms() const {
757 return phase_times()->non_young_cset_choice_time_ms() +
758 phase_times()->non_young_free_cset_time_ms();
759
760 }
761
762 double G1CollectorPolicy::other_time_ms(double pause_time_ms) const {
763 return pause_time_ms -
764 average_time_ms(G1GCPhaseTimes::UpdateRS) -
765 average_time_ms(G1GCPhaseTimes::ScanRS) -
766 average_time_ms(G1GCPhaseTimes::ObjCopy) -
767 average_time_ms(G1GCPhaseTimes::Termination);
768 }
769
770 double G1CollectorPolicy::constant_other_time_ms(double pause_time_ms) const {
771 return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms();
772 }
773
774 CollectionSetChooser* G1CollectorPolicy::cset_chooser() const {
775 return _collection_set->cset_chooser();
776 }
777
778 bool G1CollectorPolicy::about_to_start_mixed_phase() const {
779 return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc();
780 }
781
782 bool G1CollectorPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
783 if (about_to_start_mixed_phase()) {
784 return false;
785 }
786
787 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
788
789 size_t cur_used_bytes = _g1->non_young_capacity_bytes();
790 size_t alloc_byte_size = alloc_word_size * HeapWordSize;
791 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
792
793 bool result = false;
794 if (marking_request_bytes > marking_initiating_used_threshold) {
795 result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc();
796 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
797 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
798 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source);
799 }
800
801 return result;
802 }
803
804 // Anything below that is considered to be zero
805 #define MIN_TIMER_GRANULARITY 0.0000001
806
807 void G1CollectorPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
808 double end_time_sec = os::elapsedTime();
809
810 size_t cur_used_bytes = _g1->used();
811 assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
812 bool last_pause_included_initial_mark = false;
813 bool update_stats = !_g1->evacuation_failed();
814
815 NOT_PRODUCT(_short_lived_surv_rate_group->print());
816
817 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
818
819 last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();
820 if (last_pause_included_initial_mark) {
821 record_concurrent_mark_init_end(0.0);
822 } else {
823 maybe_start_marking();
824 }
825
826 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _prev_collection_pause_end_ms);
827 if (app_time_ms < MIN_TIMER_GRANULARITY) {
828 // This usually happens due to the timer not having the required
829 // granularity. Some Linuxes are the usual culprits.
830 // We'll just set it to something (arbitrarily) small.
831 app_time_ms = 1.0;
832 }
833
834 if (update_stats) {
835 // We maintain the invariant that all objects allocated by mutator
836 // threads will be allocated out of eden regions. So, we can use
837 // the eden region number allocated since the previous GC to
838 // calculate the application's allocate rate. The only exception
839 // to that is humongous objects that are allocated separately. But
840 // given that humongous object allocations do not really affect
841 // either the pause's duration nor when the next pause will take
842 // place we can safely ignore them here.
843 uint regions_allocated = _collection_set->eden_region_length();
844 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
845 _alloc_rate_ms_seq->add(alloc_rate_ms);
846
847 double interval_ms =
848 (end_time_sec - _recent_prev_end_times_for_all_gcs_sec->oldest()) * 1000.0;
849 update_recent_gc_times(end_time_sec, pause_time_ms);
850 _recent_avg_pause_time_ratio = _recent_gc_times_ms->sum()/interval_ms;
851 if (recent_avg_pause_time_ratio() < 0.0 ||
852 (recent_avg_pause_time_ratio() - 1.0 > 0.0)) {
853 // Clip ratio between 0.0 and 1.0, and continue. This will be fixed in
854 // CR 6902692 by redoing the manner in which the ratio is incrementally computed.
855 if (_recent_avg_pause_time_ratio < 0.0) {
856 _recent_avg_pause_time_ratio = 0.0;
857 } else {
858 assert(_recent_avg_pause_time_ratio - 1.0 > 0.0, "Ctl-point invariant");
859 _recent_avg_pause_time_ratio = 1.0;
860 }
861 }
862
863 // Compute the ratio of just this last pause time to the entire time range stored
864 // in the vectors. Comparing this pause to the entire range, rather than only the
865 // most recent interval, has the effect of smoothing over a possible transient 'burst'
866 // of more frequent pauses that don't really reflect a change in heap occupancy.
867 // This reduces the likelihood of a needless heap expansion being triggered.
868 _last_pause_time_ratio =
869 (pause_time_ms * _recent_prev_end_times_for_all_gcs_sec->num()) / interval_ms;
870 }
871
872 bool new_in_marking_window = collector_state()->in_marking_window();
873 bool new_in_marking_window_im = false;
874 if (last_pause_included_initial_mark) {
875 new_in_marking_window = true;
876 new_in_marking_window_im = true;
877 }
878
879 if (collector_state()->last_young_gc()) {
880 // This is supposed to to be the "last young GC" before we start
881 // doing mixed GCs. Here we decide whether to start mixed GCs or not.
882 assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC");
883
884 if (next_gc_should_be_mixed("start mixed GCs",
885 "do not start mixed GCs")) {
886 collector_state()->set_gcs_are_young(false);
887 } else {
888 // We aborted the mixed GC phase early.
889 abort_time_to_mixed_tracking();
890 }
891
892 collector_state()->set_last_young_gc(false);
893 }
894
895 if (!collector_state()->last_gc_was_young()) {
896 // This is a mixed GC. Here we decide whether to continue doing
897 // mixed GCs or not.
898 if (!next_gc_should_be_mixed("continue mixed GCs",
899 "do not continue mixed GCs")) {
900 collector_state()->set_gcs_are_young(true);
901
902 maybe_start_marking();
903 }
904 }
905
906 _short_lived_surv_rate_group->start_adding_regions();
907 // Do that for any other surv rate groups
908
909 double scan_hcc_time_ms = ConcurrentG1Refine::hot_card_cache_enabled() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
910
911 if (update_stats) {
912 double cost_per_card_ms = 0.0;
913 if (_pending_cards > 0) {
914 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards;
915 _cost_per_card_ms_seq->add(cost_per_card_ms);
916 }
917 _cost_scan_hcc_seq->add(scan_hcc_time_ms);
918
919 double cost_per_entry_ms = 0.0;
920 if (cards_scanned > 10) {
921 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
922 if (collector_state()->last_gc_was_young()) {
923 _cost_per_entry_ms_seq->add(cost_per_entry_ms);
924 } else {
925 _mixed_cost_per_entry_ms_seq->add(cost_per_entry_ms);
926 }
927 }
928
929 if (_max_rs_lengths > 0) {
930 double cards_per_entry_ratio =
931 (double) cards_scanned / (double) _max_rs_lengths;
932 if (collector_state()->last_gc_was_young()) {
933 _young_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
934 } else {
935 _mixed_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
936 }
937 }
938
939 // This is defensive. For a while _max_rs_lengths could get
940 // smaller than _recorded_rs_lengths which was causing
941 // rs_length_diff to get very large and mess up the RSet length
942 // predictions. The reason was unsafe concurrent updates to the
943 // _inc_cset_recorded_rs_lengths field which the code below guards
944 // against (see CR 7118202). This bug has now been fixed (see CR
945 // 7119027). However, I'm still worried that
946 // _inc_cset_recorded_rs_lengths might still end up somewhat
947 // inaccurate. The concurrent refinement thread calculates an
948 // RSet's length concurrently with other CR threads updating it
949 // which might cause it to calculate the length incorrectly (if,
950 // say, it's in mid-coarsening). So I'll leave in the defensive
951 // conditional below just in case.
952 size_t rs_length_diff = 0;
953 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();
954 if (_max_rs_lengths > recorded_rs_lengths) {
955 rs_length_diff = _max_rs_lengths - recorded_rs_lengths;
956 }
957 _rs_length_diff_seq->add((double) rs_length_diff);
958
959 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
960 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
961 double cost_per_byte_ms = 0.0;
962
963 if (copied_bytes > 0) {
964 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
965 if (collector_state()->in_marking_window()) {
966 _cost_per_byte_ms_during_cm_seq->add(cost_per_byte_ms);
967 } else {
968 _cost_per_byte_ms_seq->add(cost_per_byte_ms);
969 }
970 }
971
972 if (_collection_set->young_region_length() > 0) {
973 _young_other_cost_per_region_ms_seq->add(young_other_time_ms() /
974 _collection_set->young_region_length());
975 }
976
977 if (_collection_set->old_region_length() > 0) {
978 _non_young_other_cost_per_region_ms_seq->add(non_young_other_time_ms() /
979 _collection_set->old_region_length());
980 }
981
982 _constant_other_time_ms_seq->add(constant_other_time_ms(pause_time_ms));
983
984 _pending_cards_seq->add((double) _pending_cards);
985 _rs_lengths_seq->add((double) _max_rs_lengths);
986 }
987
988 collector_state()->set_in_marking_window(new_in_marking_window);
989 collector_state()->set_in_marking_window_im(new_in_marking_window_im);
990 _free_regions_at_end_of_collection = _g1->num_free_regions();
991 // IHOP control wants to know the expected young gen length if it were not
992 // restrained by the heap reserve. Using the actual length would make the
993 // prediction too small and the limit the young gen every time we get to the
994 // predicted target occupancy.
995 size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
996 update_rs_lengths_prediction();
997
998 update_ihop_prediction(app_time_ms / 1000.0,
999 _bytes_allocated_in_old_since_last_gc,
1000 last_unrestrained_young_length * HeapRegion::GrainBytes);
1001 _bytes_allocated_in_old_since_last_gc = 0;
1002
1003 _ihop_control->send_trace_event(_g1->gc_tracer_stw());
1004
1005 // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
1006 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
1007
1008 if (update_rs_time_goal_ms < scan_hcc_time_ms) {
1009 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
1010 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",
1011 update_rs_time_goal_ms, scan_hcc_time_ms);
1012
1013 update_rs_time_goal_ms = 0;
1014 } else {
1015 update_rs_time_goal_ms -= scan_hcc_time_ms;
1016 }
1017 adjust_concurrent_refinement(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms,
1018 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
1019 update_rs_time_goal_ms);
1020
1021 cset_chooser()->verify();
1022 }
1023
1024 G1IHOPControl* G1CollectorPolicy::create_ihop_control() const {
1025 if (G1UseAdaptiveIHOP) {
1026 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
1027 &_predictor,
1028 G1ReservePercent,
1029 G1HeapWastePercent);
1030 } else {
1031 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
1032 }
1033 }
1034
1035 void G1CollectorPolicy::update_ihop_prediction(double mutator_time_s,
1036 size_t mutator_alloc_bytes,
1037 size_t young_gen_size) {
1038 // Always try to update IHOP prediction. Even evacuation failures give information
1039 // about e.g. whether to start IHOP earlier next time.
1040
1041 // Avoid using really small application times that might create samples with
1042 // very high or very low values. They may be caused by e.g. back-to-back gcs.
1043 double const min_valid_time = 1e-6;
1044
1045 bool report = false;
1046
1047 double marking_to_mixed_time = -1.0;
1048 if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) {
1049 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
1050 assert(marking_to_mixed_time > 0.0,
1051 "Initial mark to mixed time must be larger than zero but is %.3f",
1052 marking_to_mixed_time);
1053 if (marking_to_mixed_time > min_valid_time) {
1054 _ihop_control->update_marking_length(marking_to_mixed_time);
1055 report = true;
1056 }
1057 }
1058
1059 // As an approximation for the young gc promotion rates during marking we use
1060 // all of them. In many applications there are only a few if any young gcs during
1061 // marking, which makes any prediction useless. This increases the accuracy of the
1062 // prediction.
1063 if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) {
1064 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
1065 report = true;
1066 }
1067
1068 if (report) {
1069 report_ihop_statistics();
1070 }
1071 }
1072
1073 void G1CollectorPolicy::report_ihop_statistics() {
1074 _ihop_control->print();
1075 }
1076
1077 void G1CollectorPolicy::print_phases() {
1078 phase_times()->print();
1079 }
1080
1081 void G1CollectorPolicy::adjust_concurrent_refinement(double update_rs_time,
1082 double update_rs_processed_buffers,
1083 double goal_ms) {
1084 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
1085 ConcurrentG1Refine *cg1r = G1CollectedHeap::heap()->concurrent_g1_refine();
1086
1087 if (G1UseAdaptiveConcRefinement) {
1088 const int k_gy = 3, k_gr = 6;
1089 const double inc_k = 1.1, dec_k = 0.9;
1090
1091 size_t g = cg1r->green_zone();
1092 if (update_rs_time > goal_ms) {
1093 g = (size_t)(g * dec_k); // Can become 0, that's OK. That would mean a mutator-only processing.
1094 } else {
1095 if (update_rs_time < goal_ms && update_rs_processed_buffers > g) {
1096 g = (size_t)MAX2(g * inc_k, g + 1.0);
1097 }
1098 }
1099 // Change the refinement threads params
1100 cg1r->set_green_zone(g);
1101 cg1r->set_yellow_zone(g * k_gy);
1102 cg1r->set_red_zone(g * k_gr);
1103 cg1r->reinitialize_threads();
1104
1105 size_t processing_threshold_delta = MAX2<size_t>(cg1r->green_zone() * _predictor.sigma(), 1);
1106 size_t processing_threshold = MIN2(cg1r->green_zone() + processing_threshold_delta,
1107 cg1r->yellow_zone());
1108 // Change the barrier params
1109 dcqs.set_process_completed_threshold((int)processing_threshold);
1110 dcqs.set_max_completed_queue((int)cg1r->red_zone());
1111 }
1112
1113 size_t curr_queue_size = dcqs.completed_buffers_num();
1114 if (curr_queue_size >= cg1r->yellow_zone()) {
1115 dcqs.set_completed_queue_padding(curr_queue_size);
1116 } else {
1117 dcqs.set_completed_queue_padding(0);
1118 }
1119 dcqs.notify_if_necessary();
1120 }
1121
1122 size_t G1CollectorPolicy::predict_rs_lengths() const {
1123 return get_new_size_prediction(_rs_lengths_seq);
1124 }
1125
1126 size_t G1CollectorPolicy::predict_rs_length_diff() const {
1127 return get_new_size_prediction(_rs_length_diff_seq);
1128 }
1129
1130 double G1CollectorPolicy::predict_alloc_rate_ms() const {
1131 return get_new_prediction(_alloc_rate_ms_seq);
1132 }
1133
1134 double G1CollectorPolicy::predict_cost_per_card_ms() const {
1135 return get_new_prediction(_cost_per_card_ms_seq);
1136 }
1137
1138 double G1CollectorPolicy::predict_scan_hcc_ms() const {
1139 return get_new_prediction(_cost_scan_hcc_seq);
1140 }
1141
1142 double G1CollectorPolicy::predict_rs_update_time_ms(size_t pending_cards) const {
1143 return pending_cards * predict_cost_per_card_ms() + predict_scan_hcc_ms();
1144 }
1145
1146 double G1CollectorPolicy::predict_young_cards_per_entry_ratio() const {
1147 return get_new_prediction(_young_cards_per_entry_ratio_seq);
1148 }
1149
1150 double G1CollectorPolicy::predict_mixed_cards_per_entry_ratio() const {
1151 if (_mixed_cards_per_entry_ratio_seq->num() < 2) {
1152 return predict_young_cards_per_entry_ratio();
1153 } else {
1154 return get_new_prediction(_mixed_cards_per_entry_ratio_seq);
1155 }
1156 }
1157
1158 size_t G1CollectorPolicy::predict_young_card_num(size_t rs_length) const {
1159 return (size_t) (rs_length * predict_young_cards_per_entry_ratio());
1160 }
1161
1162 size_t G1CollectorPolicy::predict_non_young_card_num(size_t rs_length) const {
1163 return (size_t)(rs_length * predict_mixed_cards_per_entry_ratio());
1164 }
1165
1166 double G1CollectorPolicy::predict_rs_scan_time_ms(size_t card_num) const {
1167 if (collector_state()->gcs_are_young()) {
1168 return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1169 } else {
1170 return predict_mixed_rs_scan_time_ms(card_num);
1171 }
1172 }
1173
1174 double G1CollectorPolicy::predict_mixed_rs_scan_time_ms(size_t card_num) const {
1175 if (_mixed_cost_per_entry_ms_seq->num() < 3) {
1176 return card_num * get_new_prediction(_cost_per_entry_ms_seq);
1177 } else {
1178 return card_num * get_new_prediction(_mixed_cost_per_entry_ms_seq);
1179 }
1180 }
1181
1182 double G1CollectorPolicy::predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) const {
1183 if (_cost_per_byte_ms_during_cm_seq->num() < 3) {
1184 return (1.1 * bytes_to_copy) * get_new_prediction(_cost_per_byte_ms_seq);
1185 } else {
1186 return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_during_cm_seq);
1187 }
1188 }
1189
1190 double G1CollectorPolicy::predict_object_copy_time_ms(size_t bytes_to_copy) const {
1191 if (collector_state()->during_concurrent_mark()) {
1192 return predict_object_copy_time_ms_during_cm(bytes_to_copy);
1193 } else {
1194 return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_seq);
1195 }
1196 }
1197
1198 double G1CollectorPolicy::predict_constant_other_time_ms() const {
1199 return get_new_prediction(_constant_other_time_ms_seq);
1200 }
1201
1202 double G1CollectorPolicy::predict_young_other_time_ms(size_t young_num) const {
1203 return young_num * get_new_prediction(_young_other_cost_per_region_ms_seq);
1204 }
1205
1206 double G1CollectorPolicy::predict_non_young_other_time_ms(size_t non_young_num) const {
1207 return non_young_num * get_new_prediction(_non_young_other_cost_per_region_ms_seq);
1208 }
1209
1210 double G1CollectorPolicy::predict_remark_time_ms() const {
1211 return get_new_prediction(_concurrent_mark_remark_times_ms);
1212 }
1213
1214 double G1CollectorPolicy::predict_cleanup_time_ms() const {
1215 return get_new_prediction(_concurrent_mark_cleanup_times_ms);
1216 }
1217
1218 double G1CollectorPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
1219 TruncatedSeq* seq = surv_rate_group->get_seq(age);
1220 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
1221 double pred = get_new_prediction(seq);
1222 if (pred > 1.0) {
1223 pred = 1.0;
1224 }
1225 return pred;
1226 }
1227
1228 double G1CollectorPolicy::predict_yg_surv_rate(int age) const {
1229 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
1230 }
1231
1232 double G1CollectorPolicy::accum_yg_surv_rate_pred(int age) const {
1233 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
1234 }
1235
1236 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards,
1237 size_t scanned_cards) const {
1238 return
1239 predict_rs_update_time_ms(pending_cards) +
1240 predict_rs_scan_time_ms(scanned_cards) +
1241 predict_constant_other_time_ms();
1242 }
1243
1244 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const {
1245 size_t rs_length = predict_rs_lengths() + predict_rs_length_diff();
1246 size_t card_num;
1247 if (collector_state()->gcs_are_young()) {
1248 card_num = predict_young_card_num(rs_length);
1249 } else {
1250 card_num = predict_non_young_card_num(rs_length);
1251 }
1252 return predict_base_elapsed_time_ms(pending_cards, card_num);
1253 }
1254
1255 size_t G1CollectorPolicy::predict_bytes_to_copy(HeapRegion* hr) const {
1256 size_t bytes_to_copy;
1257 if (hr->is_marked())
1258 bytes_to_copy = hr->max_live_bytes();
1259 else {
1260 assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
1261 int age = hr->age_in_surv_rate_group();
1262 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
1263 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
1264 }
1265 return bytes_to_copy;
1266 }
1267
1268 double G1CollectorPolicy::predict_region_elapsed_time_ms(HeapRegion* hr,
1269 bool for_young_gc) const {
1270 size_t rs_length = hr->rem_set()->occupied();
1271 size_t card_num;
1272
1273 // Predicting the number of cards is based on which type of GC
1274 // we're predicting for.
1275 if (for_young_gc) {
1276 card_num = predict_young_card_num(rs_length);
1277 } else {
1278 card_num = predict_non_young_card_num(rs_length);
1279 }
1280 size_t bytes_to_copy = predict_bytes_to_copy(hr);
1281
1282 double region_elapsed_time_ms =
1283 predict_rs_scan_time_ms(card_num) +
1284 predict_object_copy_time_ms(bytes_to_copy);
1285
1286 // The prediction of the "other" time for this region is based
1287 // upon the region type and NOT the GC type.
1288 if (hr->is_young()) {
1289 region_elapsed_time_ms += predict_young_other_time_ms(1);
1290 } else {
1291 region_elapsed_time_ms += predict_non_young_other_time_ms(1);
1292 }
1293 return region_elapsed_time_ms;
1294 }
1295
1296 void G1CollectorPolicy::update_recent_gc_times(double end_time_sec,
1297 double elapsed_ms) {
1298 _recent_gc_times_ms->add(elapsed_ms);
1299 _recent_prev_end_times_for_all_gcs_sec->add(end_time_sec);
1300 _prev_collection_pause_end_ms = end_time_sec * 1000.0;
1301 }
1302
1303 void G1CollectorPolicy::clear_ratio_check_data() {
1304 _ratio_over_threshold_count = 0;
1305 _ratio_over_threshold_sum = 0.0;
1306 _pauses_since_start = 0;
1307 }
1308
1309 size_t G1CollectorPolicy::expansion_amount() {
1310 double recent_gc_overhead = recent_avg_pause_time_ratio() * 100.0;
1311 double last_gc_overhead = _last_pause_time_ratio * 100.0;
1312 double threshold = _gc_overhead_perc;
1313 size_t expand_bytes = 0;
1314
1315 // If the heap is at less than half its maximum size, scale the threshold down,
1316 // to a limit of 1. Thus the smaller the heap is, the more likely it is to expand,
1317 // though the scaling code will likely keep the increase small.
1318 if (_g1->capacity() <= _g1->max_capacity() / 2) {
1319 threshold *= (double)_g1->capacity() / (double)(_g1->max_capacity() / 2);
1320 threshold = MAX2(threshold, 1.0);
1321 }
1322
1323 // If the last GC time ratio is over the threshold, increment the count of
1324 // times it has been exceeded, and add this ratio to the sum of exceeded
1325 // ratios.
1326 if (last_gc_overhead > threshold) {
1327 _ratio_over_threshold_count++;
1328 _ratio_over_threshold_sum += last_gc_overhead;
1329 }
1330
1331 // Check if we've had enough GC time ratio checks that were over the
1332 // threshold to trigger an expansion. We'll also expand if we've
1333 // reached the end of the history buffer and the average of all entries
1334 // is still over the threshold. This indicates a smaller number of GCs were
1335 // long enough to make the average exceed the threshold.
1336 bool filled_history_buffer = _pauses_since_start == NumPrevPausesForHeuristics;
1337 if ((_ratio_over_threshold_count == MinOverThresholdForGrowth) ||
1338 (filled_history_buffer && (recent_gc_overhead > threshold))) {
1339 size_t min_expand_bytes = HeapRegion::GrainBytes;
1340 size_t reserved_bytes = _g1->max_capacity();
1341 size_t committed_bytes = _g1->capacity();
1342 size_t uncommitted_bytes = reserved_bytes - committed_bytes;
1343 size_t expand_bytes_via_pct =
1344 uncommitted_bytes * G1ExpandByPercentOfAvailable / 100;
1345 double scale_factor = 1.0;
1346
1347 // If the current size is less than 1/4 of the Initial heap size, expand
1348 // by half of the delta between the current and Initial sizes. IE, grow
1349 // back quickly.
1350 //
1351 // Otherwise, take the current size, or G1ExpandByPercentOfAvailable % of
1352 // the available expansion space, whichever is smaller, as the base
1353 // expansion size. Then possibly scale this size according to how much the
1354 // threshold has (on average) been exceeded by. If the delta is small
1355 // (less than the StartScaleDownAt value), scale the size down linearly, but
1356 // not by less than MinScaleDownFactor. If the delta is large (greater than
1357 // the StartScaleUpAt value), scale up, but adding no more than MaxScaleUpFactor
1358 // times the base size. The scaling will be linear in the range from
1359 // StartScaleUpAt to (StartScaleUpAt + ScaleUpRange). In other words,
1360 // ScaleUpRange sets the rate of scaling up.
1361 if (committed_bytes < InitialHeapSize / 4) {
1362 expand_bytes = (InitialHeapSize - committed_bytes) / 2;
1363 } else {
1364 double const MinScaleDownFactor = 0.2;
1365 double const MaxScaleUpFactor = 2;
1366 double const StartScaleDownAt = _gc_overhead_perc;
1367 double const StartScaleUpAt = _gc_overhead_perc * 1.5;
1368 double const ScaleUpRange = _gc_overhead_perc * 2.0;
1369
1370 double ratio_delta;
1371 if (filled_history_buffer) {
1372 ratio_delta = recent_gc_overhead - threshold;
1373 } else {
1374 ratio_delta = (_ratio_over_threshold_sum/_ratio_over_threshold_count) - threshold;
1375 }
1376
1377 expand_bytes = MIN2(expand_bytes_via_pct, committed_bytes);
1378 if (ratio_delta < StartScaleDownAt) {
1379 scale_factor = ratio_delta / StartScaleDownAt;
1380 scale_factor = MAX2(scale_factor, MinScaleDownFactor);
1381 } else if (ratio_delta > StartScaleUpAt) {
1382 scale_factor = 1 + ((ratio_delta - StartScaleUpAt) / ScaleUpRange);
1383 scale_factor = MIN2(scale_factor, MaxScaleUpFactor);
1384 }
1385 }
1386
1387 log_debug(gc, ergo, heap)("Attempt heap expansion (recent GC overhead higher than threshold after GC) "
1388 "recent GC overhead: %1.2f %% threshold: %1.2f %% uncommitted: " SIZE_FORMAT "B base expansion amount and scale: " SIZE_FORMAT "B (%1.2f%%)",
1389 recent_gc_overhead, threshold, uncommitted_bytes, expand_bytes, scale_factor * 100);
1390
1391 expand_bytes = static_cast<size_t>(expand_bytes * scale_factor);
1392
1393 // Ensure the expansion size is at least the minimum growth amount
1394 // and at most the remaining uncommitted byte size.
1395 expand_bytes = MAX2(expand_bytes, min_expand_bytes);
1396 expand_bytes = MIN2(expand_bytes, uncommitted_bytes);
1397
1398 clear_ratio_check_data();
1399 } else {
1400 // An expansion was not triggered. If we've started counting, increment
1401 // the number of checks we've made in the current window. If we've
1402 // reached the end of the window without resizing, clear the counters to
1403 // start again the next time we see a ratio above the threshold.
1404 if (_ratio_over_threshold_count > 0) {
1405 _pauses_since_start++;
1406 if (_pauses_since_start > NumPrevPausesForHeuristics) {
1407 clear_ratio_check_data();
1408 }
1409 }
1410 }
1411
1412 return expand_bytes;
1413 }
1414
1415 void G1CollectorPolicy::print_yg_surv_rate_info() const {
1416 #ifndef PRODUCT
1417 _short_lived_surv_rate_group->print_surv_rate_summary();
1418 // add this call for any other surv rate groups
1419 #endif // PRODUCT
1420 }
1421
1422 bool G1CollectorPolicy::is_young_list_full() const {
1423 uint young_list_length = _g1->young_list()->length();
1424 uint young_list_target_length = _young_list_target_length;
1425 return young_list_length >= young_list_target_length;
1426 }
1427
1428 bool G1CollectorPolicy::can_expand_young_list() const {
1429 uint young_list_length = _g1->young_list()->length();
1430 uint young_list_max_length = _young_list_max_length;
1431 return young_list_length < young_list_max_length;
1432 }
1433
1434 bool G1CollectorPolicy::adaptive_young_list_length() const {
1435 return _young_gen_sizer->adaptive_young_list_length();
1436 }
1437
1438 void G1CollectorPolicy::update_max_gc_locker_expansion() {
1439 uint expansion_region_num = 0;
1440 if (GCLockerEdenExpansionPercent > 0) {
1441 double perc = (double) GCLockerEdenExpansionPercent / 100.0;
1442 double expansion_region_num_d = perc * (double) _young_list_target_length;
1443 // We use ceiling so that if expansion_region_num_d is > 0.0 (but
1444 // less than 1.0) we'll get 1.
1445 expansion_region_num = (uint) ceil(expansion_region_num_d);
1446 } else {
1447 assert(expansion_region_num == 0, "sanity");
1448 }
1449 _young_list_max_length = _young_list_target_length + expansion_region_num;
1450 assert(_young_list_target_length <= _young_list_max_length, "post-condition");
1451 }
1452
1453 // Calculates survivor space parameters.
1454 void G1CollectorPolicy::update_survivors_policy() {
1455 double max_survivor_regions_d =
1456 (double) _young_list_target_length / (double) SurvivorRatio;
1457 // We use ceiling so that if max_survivor_regions_d is > 0.0 (but
1458 // smaller than 1.0) we'll get 1.
1459 _max_survivor_regions = (uint) ceil(max_survivor_regions_d);
1460
1461 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(
1462 HeapRegion::GrainWords * _max_survivor_regions, counters());
1463 }
1464
1465 bool G1CollectorPolicy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
1466 // We actually check whether we are marking here and not if we are in a
1467 // reclamation phase. This means that we will schedule a concurrent mark
1468 // even while we are still in the process of reclaiming memory.
1469 bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
1470 if (!during_cycle) {
1471 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
1472 collector_state()->set_initiate_conc_mark_if_possible(true);
1473 return true;
1474 } else {
1475 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
1476 return false;
1477 }
1478 }
1479
1480 void G1CollectorPolicy::initiate_conc_mark() {
1481 collector_state()->set_during_initial_mark_pause(true);
1482 collector_state()->set_initiate_conc_mark_if_possible(false);
1483 }
1484
1485 void G1CollectorPolicy::decide_on_conc_mark_initiation() {
1486 // We are about to decide on whether this pause will be an
1487 // initial-mark pause.
1488
1489 // First, collector_state()->during_initial_mark_pause() should not be already set. We
1490 // will set it here if we have to. However, it should be cleared by
1491 // the end of the pause (it's only set for the duration of an
1492 // initial-mark pause).
1493 assert(!collector_state()->during_initial_mark_pause(), "pre-condition");
1494
1495 if (collector_state()->initiate_conc_mark_if_possible()) {
1496 // We had noticed on a previous pause that the heap occupancy has
1497 // gone over the initiating threshold and we should start a
1498 // concurrent marking cycle. So we might initiate one.
1499
1500 if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) {
1501 // Initiate a new initial mark if there is no marking or reclamation going on.
1502 initiate_conc_mark();
1503 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
1504 } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) {
1505 // Initiate a user requested initial mark. An initial mark must be young only
1506 // GC, so the collector state must be updated to reflect this.
1507 collector_state()->set_gcs_are_young(true);
1508 collector_state()->set_last_young_gc(false);
1509
1510 abort_time_to_mixed_tracking();
1511 initiate_conc_mark();
1512 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1513 } else {
1514 // The concurrent marking thread is still finishing up the
1515 // previous cycle. If we start one right now the two cycles
1516 // overlap. In particular, the concurrent marking thread might
1517 // be in the process of clearing the next marking bitmap (which
1518 // we will use for the next cycle if we start one). Starting a
1519 // cycle now will be bad given that parts of the marking
1520 // information might get cleared by the marking thread. And we
1521 // cannot wait for the marking thread to finish the cycle as it
1522 // periodically yields while clearing the next marking bitmap
1523 // and, if it's in a yield point, it's waiting for us to
1524 // finish. So, at this point we will not start a cycle and we'll
1525 // let the concurrent marking thread complete the last one.
1526 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1527 }
1528 }
1529 }
1530
1531 class ParKnownGarbageHRClosure: public HeapRegionClosure {
1532 G1CollectedHeap* _g1h;
1533 CSetChooserParUpdater _cset_updater;
1534
1535 public:
1536 ParKnownGarbageHRClosure(CollectionSetChooser* hrSorted,
1537 uint chunk_size) :
1538 _g1h(G1CollectedHeap::heap()),
1539 _cset_updater(hrSorted, true /* parallel */, chunk_size) { }
1540
1541 bool doHeapRegion(HeapRegion* r) {
1542 // Do we have any marking information for this region?
1543 if (r->is_marked()) {
1544 // We will skip any region that's currently used as an old GC
1545 // alloc region (we should not consider those for collection
1546 // before we fill them up).
1547 if (_cset_updater.should_add(r) && !_g1h->is_old_gc_alloc_region(r)) {
1548 _cset_updater.add_region(r);
1549 }
1550 }
1551 return false;
1552 }
1553 };
1554
1555 class ParKnownGarbageTask: public AbstractGangTask {
1556 CollectionSetChooser* _hrSorted;
1557 uint _chunk_size;
1558 G1CollectedHeap* _g1;
1559 HeapRegionClaimer _hrclaimer;
1560
1561 public:
1562 ParKnownGarbageTask(CollectionSetChooser* hrSorted, uint chunk_size, uint n_workers) :
1563 AbstractGangTask("ParKnownGarbageTask"),
1564 _hrSorted(hrSorted), _chunk_size(chunk_size),
1565 _g1(G1CollectedHeap::heap()), _hrclaimer(n_workers) {}
1566
1567 void work(uint worker_id) {
1568 ParKnownGarbageHRClosure parKnownGarbageCl(_hrSorted, _chunk_size);
1569 _g1->heap_region_par_iterate(&parKnownGarbageCl, worker_id, &_hrclaimer);
1570 }
1571 };
1572
1573 uint G1CollectorPolicy::calculate_parallel_work_chunk_size(uint n_workers, uint n_regions) const {
1574 assert(n_workers > 0, "Active gc workers should be greater than 0");
1575 const uint overpartition_factor = 4;
1576 const uint min_chunk_size = MAX2(n_regions / n_workers, 1U);
1577 return MAX2(n_regions / (n_workers * overpartition_factor), min_chunk_size);
1578 }
1579
1580 void G1CollectorPolicy::record_concurrent_mark_cleanup_end() {
1581 cset_chooser()->clear();
1582
1583 WorkGang* workers = _g1->workers();
1584 uint n_workers = workers->active_workers();
1585
1586 uint n_regions = _g1->num_regions();
1587 uint chunk_size = calculate_parallel_work_chunk_size(n_workers, n_regions);
1588 cset_chooser()->prepare_for_par_region_addition(n_workers, n_regions, chunk_size);
1589 ParKnownGarbageTask par_known_garbage_task(cset_chooser(), chunk_size, n_workers);
1590 workers->run_task(&par_known_garbage_task);
1591
1592 cset_chooser()->sort_regions();
1593
1594 double end_sec = os::elapsedTime();
1595 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1596 _concurrent_mark_cleanup_times_ms->add(elapsed_time_ms);
1597 _prev_collection_pause_end_ms += elapsed_time_ms;
1598
1599 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1600 }
1601
1602 double G1CollectorPolicy::reclaimable_bytes_perc(size_t reclaimable_bytes) const {
1603 // Returns the given amount of reclaimable bytes (that represents
1604 // the amount of reclaimable space still to be collected) as a
1605 // percentage of the current heap capacity.
1606 size_t capacity_bytes = _g1->capacity();
1607 return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
1608 }
1609
1610 void G1CollectorPolicy::maybe_start_marking() {
1611 if (need_to_start_conc_mark("end of GC")) {
1612 // Note: this might have already been set, if during the last
1613 // pause we decided to start a cycle but at the beginning of
1614 // this pause we decided to postpone it. That's OK.
1615 collector_state()->set_initiate_conc_mark_if_possible(true);
1616 }
1617 }
1618
1619 G1CollectorPolicy::PauseKind G1CollectorPolicy::young_gc_pause_kind() const {
1620 assert(!collector_state()->full_collection(), "must be");
1621 if (collector_state()->during_initial_mark_pause()) {
1622 assert(collector_state()->last_gc_was_young(), "must be");
1623 assert(!collector_state()->last_young_gc(), "must be");
1624 return InitialMarkGC;
1625 } else if (collector_state()->last_young_gc()) {
1626 assert(!collector_state()->during_initial_mark_pause(), "must be");
1627 assert(collector_state()->last_gc_was_young(), "must be");
1628 return LastYoungGC;
1629 } else if (!collector_state()->last_gc_was_young()) {
1630 assert(!collector_state()->during_initial_mark_pause(), "must be");
1631 assert(!collector_state()->last_young_gc(), "must be");
1632 return MixedGC;
1633 } else {
1634 assert(collector_state()->last_gc_was_young(), "must be");
1635 assert(!collector_state()->during_initial_mark_pause(), "must be");
1636 assert(!collector_state()->last_young_gc(), "must be");
1637 return YoungOnlyGC;
1638 }
1639 }
1640
1641 void G1CollectorPolicy::record_pause(PauseKind kind, double start, double end) {
1642 // Manage the MMU tracker. For some reason it ignores Full GCs.
1643 if (kind != FullGC) {
1644 _mmu_tracker->add_pause(start, end);
1645 }
1646 // Manage the mutator time tracking from initial mark to first mixed gc.
1647 switch (kind) {
1648 case FullGC:
1649 abort_time_to_mixed_tracking();
1650 break;
1651 case Cleanup:
1652 case Remark:
1653 case YoungOnlyGC:
1654 case LastYoungGC:
1655 _initial_mark_to_mixed.add_pause(end - start);
1656 break;
1657 case InitialMarkGC:
1658 _initial_mark_to_mixed.record_initial_mark_end(end);
1659 break;
1660 case MixedGC:
1661 _initial_mark_to_mixed.record_mixed_gc_start(start);
1662 break;
1663 default:
1664 ShouldNotReachHere();
1665 }
1666 }
1667
1668 void G1CollectorPolicy::abort_time_to_mixed_tracking() {
1669 _initial_mark_to_mixed.reset();
1670 }
1671
1672 bool G1CollectorPolicy::next_gc_should_be_mixed(const char* true_action_str,
1673 const char* false_action_str) const {
1674 if (cset_chooser()->is_empty()) {
1675 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1676 return false;
1677 }
1678
1679 // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1680 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
1681 double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
1682 double threshold = (double) G1HeapWastePercent;
1683 if (reclaimable_perc <= threshold) {
1684 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1685 false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
1686 return false;
1687 }
1688 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1689 true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
1690 return true;
1691 }
1692
1693 uint G1CollectorPolicy::calc_min_old_cset_length() const {
1694 // The min old CSet region bound is based on the maximum desired
1695 // number of mixed GCs after a cycle. I.e., even if some old regions
1696 // look expensive, we should add them to the CSet anyway to make
1697 // sure we go through the available old regions in no more than the
1698 // maximum desired number of mixed GCs.
1699 //
1700 // The calculation is based on the number of marked regions we added
1701 // to the CSet chooser in the first place, not how many remain, so
1702 // that the result is the same during all mixed GCs that follow a cycle.
1703
1704 const size_t region_num = (size_t) cset_chooser()->length();
1705 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1706 size_t result = region_num / gc_num;
1707 // emulate ceiling
1708 if (result * gc_num < region_num) {
1709 result += 1;
1710 }
1711 return (uint) result;
1712 }
1713
1714 uint G1CollectorPolicy::calc_max_old_cset_length() const {
1715 // The max old CSet region bound is based on the threshold expressed
1716 // as a percentage of the heap size. I.e., it should bound the
1717 // number of old regions added to the CSet irrespective of how many
1718 // of them are available.
1719
1720 const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1721 const size_t region_num = g1h->num_regions();
1722 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1723 size_t result = region_num * perc / 100;
1724 // emulate ceiling
1725 if (100 * result < region_num * perc) {
1726 result += 1;
1727 }
1728 return (uint) result;
1729 }
1730
1731 void G1CollectorPolicy::finalize_collection_set(double target_pause_time_ms) {
1732 double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms);
1733 _collection_set->finalize_old_part(time_remaining_ms);
1734 }
1735