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