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/g1Analytics.hpp"
29 #include "gc/g1/g1CollectedHeap.inline.hpp"
30 #include "gc/g1/g1CollectionSet.hpp"
31 #include "gc/g1/g1CollectorPolicy.hpp"
32 #include "gc/g1/g1ConcurrentMark.hpp"
33 #include "gc/g1/g1IHOPControl.hpp"
34 #include "gc/g1/g1GCPhaseTimes.hpp"
35 #include "gc/g1/g1YoungGenSizer.hpp"
36 #include "gc/g1/heapRegion.inline.hpp"
37 #include "gc/g1/heapRegionRemSet.hpp"
38 #include "gc/shared/gcPolicyCounters.hpp"
39 #include "runtime/arguments.hpp"
40 #include "runtime/java.hpp"
41 #include "runtime/mutexLocker.hpp"
42 #include "utilities/debug.hpp"
43 #include "utilities/pair.hpp"
44
45 G1CollectorPolicy::G1CollectorPolicy() :
46 _predictor(G1ConfidencePercent / 100.0),
47 _analytics(new G1Analytics(&_predictor)),
48 _pause_time_target_ms((double) MaxGCPauseMillis),
49 _rs_lengths_prediction(0),
50 _max_survivor_regions(0),
51 _survivors_age_table(true),
52 _gc_overhead_perc(0.0),
53
54 _bytes_allocated_in_old_since_last_gc(0),
55 _ihop_control(NULL),
56 _initial_mark_to_mixed() {
57
58 // SurvRateGroups below must be initialized after the predictor because they
59 // indirectly use it through this object passed to their constructor.
60 _short_lived_surv_rate_group =
61 new SurvRateGroup(&_predictor, "Short Lived", G1YoungSurvRateNumRegionsSummary);
62 _survivor_surv_rate_group =
63 new SurvRateGroup(&_predictor, "Survivor", G1YoungSurvRateNumRegionsSummary);
64
65 // Set up the region size and associated fields. Given that the
66 // policy is created before the heap, we have to set this up here,
67 // so it's done as soon as possible.
68
69 // It would have been natural to pass initial_heap_byte_size() and
70 // max_heap_byte_size() to setup_heap_region_size() but those have
71 // not been set up at this point since they should be aligned with
72 // the region size. So, there is a circular dependency here. We base
73 // the region size on the heap size, but the heap size should be
74 // aligned with the region size. To get around this we use the
75 // unaligned values for the heap.
76 HeapRegion::setup_heap_region_size(InitialHeapSize, MaxHeapSize);
77 HeapRegionRemSet::setup_remset_size();
78
79 clear_ratio_check_data();
80
81 _phase_times = new G1GCPhaseTimes(ParallelGCThreads);
82
83 // Below, we might need to calculate the pause time target based on
84 // the pause interval. When we do so we are going to give G1 maximum
85 // flexibility and allow it to do pauses when it needs to. So, we'll
86 // arrange that the pause interval to be pause time target + 1 to
87 // ensure that a) the pause time target is maximized with respect to
88 // the pause interval and b) we maintain the invariant that pause
89 // time target < pause interval. If the user does not want this
90 // maximum flexibility, they will have to set the pause interval
91 // explicitly.
92
93 // First make sure that, if either parameter is set, its value is
94 // reasonable.
95 if (!FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
96 if (MaxGCPauseMillis < 1) {
97 vm_exit_during_initialization("MaxGCPauseMillis should be "
98 "greater than 0");
99 }
100 }
101 if (!FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
102 if (GCPauseIntervalMillis < 1) {
103 vm_exit_during_initialization("GCPauseIntervalMillis should be "
104 "greater than 0");
105 }
106 }
107
108 // Then, if the pause time target parameter was not set, set it to
109 // the default value.
110 if (FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
111 if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
112 // The default pause time target in G1 is 200ms
113 FLAG_SET_DEFAULT(MaxGCPauseMillis, 200);
114 } else {
115 // We do not allow the pause interval to be set without the
116 // pause time target
117 vm_exit_during_initialization("GCPauseIntervalMillis cannot be set "
118 "without setting MaxGCPauseMillis");
119 }
120 }
121
122 // Then, if the interval parameter was not set, set it according to
123 // the pause time target (this will also deal with the case when the
124 // pause time target is the default value).
125 if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
126 FLAG_SET_DEFAULT(GCPauseIntervalMillis, MaxGCPauseMillis + 1);
127 }
128
129 // Finally, make sure that the two parameters are consistent.
130 if (MaxGCPauseMillis >= GCPauseIntervalMillis) {
131 char buffer[256];
132 jio_snprintf(buffer, 256,
133 "MaxGCPauseMillis (%u) should be less than "
134 "GCPauseIntervalMillis (%u)",
135 MaxGCPauseMillis, GCPauseIntervalMillis);
136 vm_exit_during_initialization(buffer);
137 }
138
139 double max_gc_time = (double) MaxGCPauseMillis / 1000.0;
140 double time_slice = (double) GCPauseIntervalMillis / 1000.0;
141 _mmu_tracker = new G1MMUTrackerQueue(time_slice, max_gc_time);
142
143 _tenuring_threshold = MaxTenuringThreshold;
144
145 assert(GCTimeRatio > 0,
146 "we should have set it to a default value set_g1_gc_flags() "
147 "if a user set it to 0");
148 _gc_overhead_perc = 100.0 * (1.0 / (1.0 + GCTimeRatio));
149
150 uintx reserve_perc = G1ReservePercent;
151 // Put an artificial ceiling on this so that it's not set to a silly value.
152 if (reserve_perc > 50) {
153 reserve_perc = 50;
154 warning("G1ReservePercent is set to a value that is too large, "
155 "it's been updated to " UINTX_FORMAT, reserve_perc);
156 }
157 _reserve_factor = (double) reserve_perc / 100.0;
158 // This will be set when the heap is expanded
159 // for the first time during initialization.
160 _reserve_regions = 0;
161
162 _ihop_control = create_ihop_control();
163 }
164
165 G1CollectorPolicy::~G1CollectorPolicy() {
166 delete _ihop_control;
167 }
168
169 void G1CollectorPolicy::initialize_alignments() {
170 _space_alignment = HeapRegion::GrainBytes;
171 size_t card_table_alignment = CardTableRS::ct_max_alignment_constraint();
172 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
173 _heap_alignment = MAX3(card_table_alignment, _space_alignment, page_size);
174 }
175
176 G1CollectorState* G1CollectorPolicy::collector_state() const { return _g1->collector_state(); }
177
178 void G1CollectorPolicy::post_heap_initialize() {
179 uintx max_regions = G1CollectedHeap::heap()->max_regions();
180 size_t max_young_size = (size_t)_young_gen_sizer->max_young_length(max_regions) * HeapRegion::GrainBytes;
181 if (max_young_size != MaxNewSize) {
182 FLAG_SET_ERGO(size_t, MaxNewSize, max_young_size);
183 }
184 }
185
186 void G1CollectorPolicy::initialize_flags() {
187 if (G1HeapRegionSize != HeapRegion::GrainBytes) {
188 FLAG_SET_ERGO(size_t, G1HeapRegionSize, HeapRegion::GrainBytes);
189 }
190
191 if (SurvivorRatio < 1) {
192 vm_exit_during_initialization("Invalid survivor ratio specified");
193 }
194 CollectorPolicy::initialize_flags();
195 _young_gen_sizer = new G1YoungGenSizer(); // Must be after call to initialize_flags
196 }
197
198
199 void G1CollectorPolicy::init() {
200 // Set aside an initial future to_space.
201 _g1 = G1CollectedHeap::heap();
202 _collection_set = _g1->collection_set();
203 _collection_set->set_policy(this);
204
205 assert(Heap_lock->owned_by_self(), "Locking discipline.");
206
207 initialize_gc_policy_counters();
208
209 if (adaptive_young_list_length()) {
210 _young_list_fixed_length = 0;
211 } else {
212 _young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
213 }
214 _free_regions_at_end_of_collection = _g1->num_free_regions();
215
216 update_young_list_max_and_target_length();
217 // We may immediately start allocating regions and placing them on the
218 // collection set list. Initialize the per-collection set info
219 _collection_set->start_incremental_building();
220 }
221
222 void G1CollectorPolicy::note_gc_start(uint num_active_workers) {
223 phase_times()->note_gc_start(num_active_workers);
224 }
225
226 // Create the jstat counters for the policy.
227 void G1CollectorPolicy::initialize_gc_policy_counters() {
228 _gc_policy_counters = new GCPolicyCounters("GarbageFirst", 1, 3);
229 }
230
231 bool G1CollectorPolicy::predict_will_fit(uint young_length,
232 double base_time_ms,
233 uint base_free_regions,
234 double target_pause_time_ms) const {
235 if (young_length >= base_free_regions) {
236 // end condition 1: not enough space for the young regions
237 return false;
238 }
239
240 double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);
241 size_t bytes_to_copy =
242 (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
243 double copy_time_ms = _analytics->predict_object_copy_time_ms(bytes_to_copy,
244 collector_state()->during_concurrent_mark());
245 double young_other_time_ms = _analytics->predict_young_other_time_ms(young_length);
246 double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;
247 if (pause_time_ms > target_pause_time_ms) {
248 // end condition 2: prediction is over the target pause time
249 return false;
250 }
251
252 size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes;
253
254 // When copying, we will likely need more bytes free than is live in the region.
255 // Add some safety margin to factor in the confidence of our guess, and the
256 // natural expected waste.
257 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
258 // of the calculation: the lower the confidence, the more headroom.
259 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
260 // copying due to anticipated waste in the PLABs.
261 double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
262 size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
263
264 if (expected_bytes_to_copy > free_bytes) {
265 // end condition 3: out-of-space
266 return false;
267 }
268
269 // success!
270 return true;
271 }
272
273 void G1CollectorPolicy::record_new_heap_size(uint new_number_of_regions) {
274 // re-calculate the necessary reserve
275 double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
276 // We use ceiling so that if reserve_regions_d is > 0.0 (but
277 // smaller than 1.0) we'll get 1.
278 _reserve_regions = (uint) ceil(reserve_regions_d);
279
280 _young_gen_sizer->heap_size_changed(new_number_of_regions);
281
282 _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes);
283 }
284
285 uint G1CollectorPolicy::calculate_young_list_desired_min_length(
286 uint base_min_length) const {
287 uint desired_min_length = 0;
288 if (adaptive_young_list_length()) {
289 if (_analytics->num_alloc_rate_ms() > 3) {
290 double now_sec = os::elapsedTime();
291 double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
292 double alloc_rate_ms = _analytics->predict_alloc_rate_ms();
293 desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
294 } else {
295 // otherwise we don't have enough info to make the prediction
296 }
297 }
298 desired_min_length += base_min_length;
299 // make sure we don't go below any user-defined minimum bound
300 return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
301 }
302
303 uint G1CollectorPolicy::calculate_young_list_desired_max_length() const {
304 // Here, we might want to also take into account any additional
305 // constraints (i.e., user-defined minimum bound). Currently, we
306 // effectively don't set this bound.
307 return _young_gen_sizer->max_desired_young_length();
308 }
309
310 uint G1CollectorPolicy::update_young_list_max_and_target_length() {
311 return update_young_list_max_and_target_length(_analytics->predict_rs_lengths());
312 }
313
314 uint G1CollectorPolicy::update_young_list_max_and_target_length(size_t rs_lengths) {
315 uint unbounded_target_length = update_young_list_target_length(rs_lengths);
316 update_max_gc_locker_expansion();
317 return unbounded_target_length;
318 }
319
320 uint G1CollectorPolicy::update_young_list_target_length(size_t rs_lengths) {
321 YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths);
322 _young_list_target_length = young_lengths.first;
323 return young_lengths.second;
324 }
325
326 G1CollectorPolicy::YoungTargetLengths G1CollectorPolicy::young_list_target_lengths(size_t rs_lengths) const {
327 YoungTargetLengths result;
328
329 // Calculate the absolute and desired min bounds first.
330
331 // This is how many young regions we already have (currently: the survivors).
332 const uint base_min_length = _g1->young_list()->survivor_length();
333 uint desired_min_length = calculate_young_list_desired_min_length(base_min_length);
334 // This is the absolute minimum young length. Ensure that we
335 // will at least have one eden region available for allocation.
336 uint absolute_min_length = base_min_length + MAX2(_g1->young_list()->eden_length(), (uint)1);
337 // If we shrank the young list target it should not shrink below the current size.
338 desired_min_length = MAX2(desired_min_length, absolute_min_length);
339 // Calculate the absolute and desired max bounds.
340
341 uint desired_max_length = calculate_young_list_desired_max_length();
342
343 uint young_list_target_length = 0;
344 if (adaptive_young_list_length()) {
345 if (collector_state()->gcs_are_young()) {
346 young_list_target_length =
347 calculate_young_list_target_length(rs_lengths,
348 base_min_length,
349 desired_min_length,
350 desired_max_length);
351 } else {
352 // Don't calculate anything and let the code below bound it to
353 // the desired_min_length, i.e., do the next GC as soon as
354 // possible to maximize how many old regions we can add to it.
355 }
356 } else {
357 // The user asked for a fixed young gen so we'll fix the young gen
358 // whether the next GC is young or mixed.
359 young_list_target_length = _young_list_fixed_length;
360 }
361
362 result.second = young_list_target_length;
363
364 // We will try our best not to "eat" into the reserve.
365 uint absolute_max_length = 0;
366 if (_free_regions_at_end_of_collection > _reserve_regions) {
367 absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
368 }
369 if (desired_max_length > absolute_max_length) {
370 desired_max_length = absolute_max_length;
371 }
372
373 // Make sure we don't go over the desired max length, nor under the
374 // desired min length. In case they clash, desired_min_length wins
375 // which is why that test is second.
376 if (young_list_target_length > desired_max_length) {
377 young_list_target_length = desired_max_length;
378 }
379 if (young_list_target_length < desired_min_length) {
380 young_list_target_length = desired_min_length;
381 }
382
383 assert(young_list_target_length > base_min_length,
384 "we should be able to allocate at least one eden region");
385 assert(young_list_target_length >= absolute_min_length, "post-condition");
386
387 result.first = young_list_target_length;
388 return result;
389 }
390
391 uint
392 G1CollectorPolicy::calculate_young_list_target_length(size_t rs_lengths,
393 uint base_min_length,
394 uint desired_min_length,
395 uint desired_max_length) const {
396 assert(adaptive_young_list_length(), "pre-condition");
397 assert(collector_state()->gcs_are_young(), "only call this for young GCs");
398
399 // In case some edge-condition makes the desired max length too small...
400 if (desired_max_length <= desired_min_length) {
401 return desired_min_length;
402 }
403
404 // We'll adjust min_young_length and max_young_length not to include
405 // the already allocated young regions (i.e., so they reflect the
406 // min and max eden regions we'll allocate). The base_min_length
407 // will be reflected in the predictions by the
408 // survivor_regions_evac_time prediction.
409 assert(desired_min_length > base_min_length, "invariant");
410 uint min_young_length = desired_min_length - base_min_length;
411 assert(desired_max_length > base_min_length, "invariant");
412 uint max_young_length = desired_max_length - base_min_length;
413
414 double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
415 double survivor_regions_evac_time = predict_survivor_regions_evac_time();
416 size_t pending_cards = _analytics->predict_pending_cards();
417 size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff();
418 size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, /* gcs_are_young */ true);
419 double base_time_ms =
420 predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
421 survivor_regions_evac_time;
422 uint available_free_regions = _free_regions_at_end_of_collection;
423 uint base_free_regions = 0;
424 if (available_free_regions > _reserve_regions) {
425 base_free_regions = available_free_regions - _reserve_regions;
426 }
427
428 // Here, we will make sure that the shortest young length that
429 // makes sense fits within the target pause time.
430
431 if (predict_will_fit(min_young_length, base_time_ms,
432 base_free_regions, target_pause_time_ms)) {
433 // The shortest young length will fit into the target pause time;
434 // we'll now check whether the absolute maximum number of young
435 // regions will fit in the target pause time. If not, we'll do
436 // a binary search between min_young_length and max_young_length.
437 if (predict_will_fit(max_young_length, base_time_ms,
438 base_free_regions, target_pause_time_ms)) {
439 // The maximum young length will fit into the target pause time.
440 // We are done so set min young length to the maximum length (as
441 // the result is assumed to be returned in min_young_length).
442 min_young_length = max_young_length;
443 } else {
444 // The maximum possible number of young regions will not fit within
445 // the target pause time so we'll search for the optimal
446 // length. The loop invariants are:
447 //
448 // min_young_length < max_young_length
449 // min_young_length is known to fit into the target pause time
450 // max_young_length is known not to fit into the target pause time
451 //
452 // Going into the loop we know the above hold as we've just
453 // checked them. Every time around the loop we check whether
454 // the middle value between min_young_length and
455 // max_young_length fits into the target pause time. If it
456 // does, it becomes the new min. If it doesn't, it becomes
457 // the new max. This way we maintain the loop invariants.
458
459 assert(min_young_length < max_young_length, "invariant");
460 uint diff = (max_young_length - min_young_length) / 2;
461 while (diff > 0) {
462 uint young_length = min_young_length + diff;
463 if (predict_will_fit(young_length, base_time_ms,
464 base_free_regions, target_pause_time_ms)) {
465 min_young_length = young_length;
466 } else {
467 max_young_length = young_length;
468 }
469 assert(min_young_length < max_young_length, "invariant");
470 diff = (max_young_length - min_young_length) / 2;
471 }
472 // The results is min_young_length which, according to the
473 // loop invariants, should fit within the target pause time.
474
475 // These are the post-conditions of the binary search above:
476 assert(min_young_length < max_young_length,
477 "otherwise we should have discovered that max_young_length "
478 "fits into the pause target and not done the binary search");
479 assert(predict_will_fit(min_young_length, base_time_ms,
480 base_free_regions, target_pause_time_ms),
481 "min_young_length, the result of the binary search, should "
482 "fit into the pause target");
483 assert(!predict_will_fit(min_young_length + 1, base_time_ms,
484 base_free_regions, target_pause_time_ms),
485 "min_young_length, the result of the binary search, should be "
486 "optimal, so no larger length should fit into the pause target");
487 }
488 } else {
489 // Even the minimum length doesn't fit into the pause time
490 // target, return it as the result nevertheless.
491 }
492 return base_min_length + min_young_length;
493 }
494
495 double G1CollectorPolicy::predict_survivor_regions_evac_time() const {
496 double survivor_regions_evac_time = 0.0;
497 for (HeapRegion * r = _g1->young_list()->first_survivor_region();
498 r != NULL && r != _g1->young_list()->last_survivor_region()->get_next_young_region();
499 r = r->get_next_young_region()) {
500 survivor_regions_evac_time += predict_region_elapsed_time_ms(r, collector_state()->gcs_are_young());
501 }
502 return survivor_regions_evac_time;
503 }
504
505 void G1CollectorPolicy::revise_young_list_target_length_if_necessary(size_t rs_lengths) {
506 guarantee( adaptive_young_list_length(), "should not call this otherwise" );
507
508 if (rs_lengths > _rs_lengths_prediction) {
509 // add 10% to avoid having to recalculate often
510 size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
511 update_rs_lengths_prediction(rs_lengths_prediction);
512
513 update_young_list_max_and_target_length(rs_lengths_prediction);
514 }
515 }
516
517 void G1CollectorPolicy::update_rs_lengths_prediction() {
518 update_rs_lengths_prediction(_analytics->predict_rs_lengths());
519 }
520
521 void G1CollectorPolicy::update_rs_lengths_prediction(size_t prediction) {
522 if (collector_state()->gcs_are_young() && adaptive_young_list_length()) {
523 _rs_lengths_prediction = prediction;
524 }
525 }
526
527 #ifndef PRODUCT
528 bool G1CollectorPolicy::verify_young_ages() {
529 HeapRegion* head = _g1->young_list()->first_region();
530 return
531 verify_young_ages(head, _short_lived_surv_rate_group);
532 // also call verify_young_ages on any additional surv rate groups
533 }
534
535 bool
536 G1CollectorPolicy::verify_young_ages(HeapRegion* head,
537 SurvRateGroup *surv_rate_group) {
538 guarantee( surv_rate_group != NULL, "pre-condition" );
539
540 const char* name = surv_rate_group->name();
541 bool ret = true;
542 int prev_age = -1;
543
544 for (HeapRegion* curr = head;
545 curr != NULL;
546 curr = curr->get_next_young_region()) {
547 SurvRateGroup* group = curr->surv_rate_group();
548 if (group == NULL && !curr->is_survivor()) {
549 log_error(gc, verify)("## %s: encountered NULL surv_rate_group", name);
550 ret = false;
551 }
552
553 if (surv_rate_group == group) {
554 int age = curr->age_in_surv_rate_group();
555
556 if (age < 0) {
557 log_error(gc, verify)("## %s: encountered negative age", name);
558 ret = false;
559 }
560
561 if (age <= prev_age) {
562 log_error(gc, verify)("## %s: region ages are not strictly increasing (%d, %d)", name, age, prev_age);
563 ret = false;
564 }
565 prev_age = age;
566 }
567 }
568
569 return ret;
570 }
571 #endif // PRODUCT
572
573 void G1CollectorPolicy::record_full_collection_start() {
574 _full_collection_start_sec = os::elapsedTime();
575 // Release the future to-space so that it is available for compaction into.
576 collector_state()->set_full_collection(true);
577 }
578
579 void G1CollectorPolicy::record_full_collection_end() {
580 // Consider this like a collection pause for the purposes of allocation
581 // since last pause.
582 double end_sec = os::elapsedTime();
583 double full_gc_time_sec = end_sec - _full_collection_start_sec;
584 double full_gc_time_ms = full_gc_time_sec * 1000.0;
585
586 _analytics->update_recent_gc_times(end_sec, full_gc_time_ms);
587
588 collector_state()->set_full_collection(false);
589
590 // "Nuke" the heuristics that control the young/mixed GC
591 // transitions and make sure we start with young GCs after the Full GC.
592 collector_state()->set_gcs_are_young(true);
593 collector_state()->set_last_young_gc(false);
594 collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0));
595 collector_state()->set_during_initial_mark_pause(false);
596 collector_state()->set_in_marking_window(false);
597 collector_state()->set_in_marking_window_im(false);
598
599 _short_lived_surv_rate_group->start_adding_regions();
600 // also call this on any additional surv rate groups
601
602 _free_regions_at_end_of_collection = _g1->num_free_regions();
603 // Reset survivors SurvRateGroup.
604 _survivor_surv_rate_group->reset();
605 update_young_list_max_and_target_length();
606 update_rs_lengths_prediction();
607 cset_chooser()->clear();
608
609 _bytes_allocated_in_old_since_last_gc = 0;
610
611 record_pause(FullGC, _full_collection_start_sec, end_sec);
612 }
613
614 void G1CollectorPolicy::record_collection_pause_start(double start_time_sec) {
615 // We only need to do this here as the policy will only be applied
616 // to the GC we're about to start. so, no point is calculating this
617 // every time we calculate / recalculate the target young length.
618 update_survivors_policy();
619
620 assert(_g1->used() == _g1->recalculate_used(),
621 "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT,
622 _g1->used(), _g1->recalculate_used());
623
624 phase_times()->record_cur_collection_start_sec(start_time_sec);
625 _pending_cards = _g1->pending_card_num();
626
627 _collection_set->reset_bytes_used_before();
628 _bytes_copied_during_gc = 0;
629
630 collector_state()->set_last_gc_was_young(false);
631
632 // do that for any other surv rate groups
633 _short_lived_surv_rate_group->stop_adding_regions();
634 _survivors_age_table.clear();
635
636 assert( verify_young_ages(), "region age verification" );
637 }
638
639 void G1CollectorPolicy::record_concurrent_mark_init_end(double
640 mark_init_elapsed_time_ms) {
641 collector_state()->set_during_marking(true);
642 assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now");
643 collector_state()->set_during_initial_mark_pause(false);
644 }
645
646 void G1CollectorPolicy::record_concurrent_mark_remark_start() {
647 _mark_remark_start_sec = os::elapsedTime();
648 collector_state()->set_during_marking(false);
649 }
650
651 void G1CollectorPolicy::record_concurrent_mark_remark_end() {
652 double end_time_sec = os::elapsedTime();
653 double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
654 _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms);
655 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
656
657 record_pause(Remark, _mark_remark_start_sec, end_time_sec);
658 }
659
660 void G1CollectorPolicy::record_concurrent_mark_cleanup_start() {
661 _mark_cleanup_start_sec = os::elapsedTime();
662 }
663
664 void G1CollectorPolicy::record_concurrent_mark_cleanup_completed() {
665 bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc",
666 "skip last young-only gc");
667 collector_state()->set_last_young_gc(should_continue_with_reclaim);
668 // We skip the marking phase.
669 if (!should_continue_with_reclaim) {
670 abort_time_to_mixed_tracking();
671 }
672 collector_state()->set_in_marking_window(false);
673 }
674
675 double G1CollectorPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const {
676 return phase_times()->average_time_ms(phase);
677 }
678
679 double G1CollectorPolicy::young_other_time_ms() const {
680 return phase_times()->young_cset_choice_time_ms() +
681 phase_times()->young_free_cset_time_ms();
682 }
683
684 double G1CollectorPolicy::non_young_other_time_ms() const {
685 return phase_times()->non_young_cset_choice_time_ms() +
686 phase_times()->non_young_free_cset_time_ms();
687
688 }
689
690 double G1CollectorPolicy::other_time_ms(double pause_time_ms) const {
691 return pause_time_ms -
692 average_time_ms(G1GCPhaseTimes::UpdateRS) -
693 average_time_ms(G1GCPhaseTimes::ScanRS) -
694 average_time_ms(G1GCPhaseTimes::ObjCopy) -
695 average_time_ms(G1GCPhaseTimes::Termination);
696 }
697
698 double G1CollectorPolicy::constant_other_time_ms(double pause_time_ms) const {
699 return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms();
700 }
701
702 CollectionSetChooser* G1CollectorPolicy::cset_chooser() const {
703 return _collection_set->cset_chooser();
704 }
705
706 bool G1CollectorPolicy::about_to_start_mixed_phase() const {
707 return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc();
708 }
709
710 bool G1CollectorPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
711 if (about_to_start_mixed_phase()) {
712 return false;
713 }
714
715 size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold();
716
717 size_t cur_used_bytes = _g1->non_young_capacity_bytes();
718 size_t alloc_byte_size = alloc_word_size * HeapWordSize;
719 size_t marking_request_bytes = cur_used_bytes + alloc_byte_size;
720
721 bool result = false;
722 if (marking_request_bytes > marking_initiating_used_threshold) {
723 result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc();
724 log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s",
725 result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)",
726 cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source);
727 }
728
729 return result;
730 }
731
732 // Anything below that is considered to be zero
733 #define MIN_TIMER_GRANULARITY 0.0000001
734
735 void G1CollectorPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) {
736 double end_time_sec = os::elapsedTime();
737
738 size_t cur_used_bytes = _g1->used();
739 assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
740 bool last_pause_included_initial_mark = false;
741 bool update_stats = !_g1->evacuation_failed();
742
743 NOT_PRODUCT(_short_lived_surv_rate_group->print());
744
745 record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec);
746
747 last_pause_included_initial_mark = collector_state()->during_initial_mark_pause();
748 if (last_pause_included_initial_mark) {
749 record_concurrent_mark_init_end(0.0);
750 } else {
751 maybe_start_marking();
752 }
753
754 double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _analytics->prev_collection_pause_end_ms());
755 if (app_time_ms < MIN_TIMER_GRANULARITY) {
756 // This usually happens due to the timer not having the required
757 // granularity. Some Linuxes are the usual culprits.
758 // We'll just set it to something (arbitrarily) small.
759 app_time_ms = 1.0;
760 }
761
762 if (update_stats) {
763 // We maintain the invariant that all objects allocated by mutator
764 // threads will be allocated out of eden regions. So, we can use
765 // the eden region number allocated since the previous GC to
766 // calculate the application's allocate rate. The only exception
767 // to that is humongous objects that are allocated separately. But
768 // given that humongous object allocations do not really affect
769 // either the pause's duration nor when the next pause will take
770 // place we can safely ignore them here.
771 uint regions_allocated = _collection_set->eden_region_length();
772 double alloc_rate_ms = (double) regions_allocated / app_time_ms;
773 _analytics->report_alloc_rate_ms(alloc_rate_ms);
774
775 double interval_ms =
776 (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;
777 _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
778 _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);
779 }
780
781 bool new_in_marking_window = collector_state()->in_marking_window();
782 bool new_in_marking_window_im = false;
783 if (last_pause_included_initial_mark) {
784 new_in_marking_window = true;
785 new_in_marking_window_im = true;
786 }
787
788 if (collector_state()->last_young_gc()) {
789 // This is supposed to to be the "last young GC" before we start
790 // doing mixed GCs. Here we decide whether to start mixed GCs or not.
791 assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC");
792
793 if (next_gc_should_be_mixed("start mixed GCs",
794 "do not start mixed GCs")) {
795 collector_state()->set_gcs_are_young(false);
796 } else {
797 // We aborted the mixed GC phase early.
798 abort_time_to_mixed_tracking();
799 }
800
801 collector_state()->set_last_young_gc(false);
802 }
803
804 if (!collector_state()->last_gc_was_young()) {
805 // This is a mixed GC. Here we decide whether to continue doing
806 // mixed GCs or not.
807 if (!next_gc_should_be_mixed("continue mixed GCs",
808 "do not continue mixed GCs")) {
809 collector_state()->set_gcs_are_young(true);
810
811 maybe_start_marking();
812 }
813 }
814
815 _short_lived_surv_rate_group->start_adding_regions();
816 // Do that for any other surv rate groups
817
818 double scan_hcc_time_ms = ConcurrentG1Refine::hot_card_cache_enabled() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0;
819
820 if (update_stats) {
821 double cost_per_card_ms = 0.0;
822 if (_pending_cards > 0) {
823 cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards;
824 _analytics->report_cost_per_card_ms(cost_per_card_ms);
825 }
826 _analytics->report_cost_scan_hcc(scan_hcc_time_ms);
827
828 double cost_per_entry_ms = 0.0;
829 if (cards_scanned > 10) {
830 cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned;
831 _analytics->report_cost_per_entry_ms(cost_per_entry_ms, collector_state()->last_gc_was_young());
832 }
833
834 if (_max_rs_lengths > 0) {
835 double cards_per_entry_ratio =
836 (double) cards_scanned / (double) _max_rs_lengths;
837 _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, collector_state()->last_gc_was_young());
838 }
839
840 // This is defensive. For a while _max_rs_lengths could get
841 // smaller than _recorded_rs_lengths which was causing
842 // rs_length_diff to get very large and mess up the RSet length
843 // predictions. The reason was unsafe concurrent updates to the
844 // _inc_cset_recorded_rs_lengths field which the code below guards
845 // against (see CR 7118202). This bug has now been fixed (see CR
846 // 7119027). However, I'm still worried that
847 // _inc_cset_recorded_rs_lengths might still end up somewhat
848 // inaccurate. The concurrent refinement thread calculates an
849 // RSet's length concurrently with other CR threads updating it
850 // which might cause it to calculate the length incorrectly (if,
851 // say, it's in mid-coarsening). So I'll leave in the defensive
852 // conditional below just in case.
853 size_t rs_length_diff = 0;
854 size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths();
855 if (_max_rs_lengths > recorded_rs_lengths) {
856 rs_length_diff = _max_rs_lengths - recorded_rs_lengths;
857 }
858 _analytics->report_rs_length_diff((double) rs_length_diff);
859
860 size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes;
861 size_t copied_bytes = _collection_set->bytes_used_before() - freed_bytes;
862 double cost_per_byte_ms = 0.0;
863
864 if (copied_bytes > 0) {
865 cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes;
866 _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->in_marking_window());
867 }
868
869 if (_collection_set->young_region_length() > 0) {
870 _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() /
871 _collection_set->young_region_length());
872 }
873
874 if (_collection_set->old_region_length() > 0) {
875 _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() /
876 _collection_set->old_region_length());
877 }
878
879 _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms));
880
881 _analytics->report_pending_cards((double) _pending_cards);
882 _analytics->report_rs_lengths((double) _max_rs_lengths);
883 }
884
885 collector_state()->set_in_marking_window(new_in_marking_window);
886 collector_state()->set_in_marking_window_im(new_in_marking_window_im);
887 _free_regions_at_end_of_collection = _g1->num_free_regions();
888 // IHOP control wants to know the expected young gen length if it were not
889 // restrained by the heap reserve. Using the actual length would make the
890 // prediction too small and the limit the young gen every time we get to the
891 // predicted target occupancy.
892 size_t last_unrestrained_young_length = update_young_list_max_and_target_length();
893 update_rs_lengths_prediction();
894
895 update_ihop_prediction(app_time_ms / 1000.0,
896 _bytes_allocated_in_old_since_last_gc,
897 last_unrestrained_young_length * HeapRegion::GrainBytes);
898 _bytes_allocated_in_old_since_last_gc = 0;
899
900 _ihop_control->send_trace_event(_g1->gc_tracer_stw());
901
902 // Note that _mmu_tracker->max_gc_time() returns the time in seconds.
903 double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
904
905 if (update_rs_time_goal_ms < scan_hcc_time_ms) {
906 log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)."
907 "Update RS time goal: %1.2fms Scan HCC time: %1.2fms",
908 update_rs_time_goal_ms, scan_hcc_time_ms);
909
910 update_rs_time_goal_ms = 0;
911 } else {
912 update_rs_time_goal_ms -= scan_hcc_time_ms;
913 }
914 adjust_concurrent_refinement(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms,
915 phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS),
916 update_rs_time_goal_ms);
917
918 cset_chooser()->verify();
919 }
920
921 G1IHOPControl* G1CollectorPolicy::create_ihop_control() const {
922 if (G1UseAdaptiveIHOP) {
923 return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent,
924 &_predictor,
925 G1ReservePercent,
926 G1HeapWastePercent);
927 } else {
928 return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent);
929 }
930 }
931
932 void G1CollectorPolicy::update_ihop_prediction(double mutator_time_s,
933 size_t mutator_alloc_bytes,
934 size_t young_gen_size) {
935 // Always try to update IHOP prediction. Even evacuation failures give information
936 // about e.g. whether to start IHOP earlier next time.
937
938 // Avoid using really small application times that might create samples with
939 // very high or very low values. They may be caused by e.g. back-to-back gcs.
940 double const min_valid_time = 1e-6;
941
942 bool report = false;
943
944 double marking_to_mixed_time = -1.0;
945 if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) {
946 marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time();
947 assert(marking_to_mixed_time > 0.0,
948 "Initial mark to mixed time must be larger than zero but is %.3f",
949 marking_to_mixed_time);
950 if (marking_to_mixed_time > min_valid_time) {
951 _ihop_control->update_marking_length(marking_to_mixed_time);
952 report = true;
953 }
954 }
955
956 // As an approximation for the young gc promotion rates during marking we use
957 // all of them. In many applications there are only a few if any young gcs during
958 // marking, which makes any prediction useless. This increases the accuracy of the
959 // prediction.
960 if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) {
961 _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size);
962 report = true;
963 }
964
965 if (report) {
966 report_ihop_statistics();
967 }
968 }
969
970 void G1CollectorPolicy::report_ihop_statistics() {
971 _ihop_control->print();
972 }
973
974 void G1CollectorPolicy::print_phases() {
975 phase_times()->print();
976 }
977
978 void G1CollectorPolicy::adjust_concurrent_refinement(double update_rs_time,
979 double update_rs_processed_buffers,
980 double goal_ms) {
981 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
982 ConcurrentG1Refine *cg1r = G1CollectedHeap::heap()->concurrent_g1_refine();
983
984 if (G1UseAdaptiveConcRefinement) {
985 const int k_gy = 3, k_gr = 6;
986 const double inc_k = 1.1, dec_k = 0.9;
987
988 size_t g = cg1r->green_zone();
989 if (update_rs_time > goal_ms) {
990 g = (size_t)(g * dec_k); // Can become 0, that's OK. That would mean a mutator-only processing.
991 } else {
992 if (update_rs_time < goal_ms && update_rs_processed_buffers > g) {
993 g = (size_t)MAX2(g * inc_k, g + 1.0);
994 }
995 }
996 // Change the refinement threads params
997 cg1r->set_green_zone(g);
998 cg1r->set_yellow_zone(g * k_gy);
999 cg1r->set_red_zone(g * k_gr);
1000 cg1r->reinitialize_threads();
1001
1002 size_t processing_threshold_delta = MAX2<size_t>(cg1r->green_zone() * _predictor.sigma(), 1);
1003 size_t processing_threshold = MIN2(cg1r->green_zone() + processing_threshold_delta,
1004 cg1r->yellow_zone());
1005 // Change the barrier params
1006 dcqs.set_process_completed_threshold((int)processing_threshold);
1007 dcqs.set_max_completed_queue((int)cg1r->red_zone());
1008 }
1009
1010 size_t curr_queue_size = dcqs.completed_buffers_num();
1011 if (curr_queue_size >= cg1r->yellow_zone()) {
1012 dcqs.set_completed_queue_padding(curr_queue_size);
1013 } else {
1014 dcqs.set_completed_queue_padding(0);
1015 }
1016 dcqs.notify_if_necessary();
1017 }
1018
1019 double G1CollectorPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const {
1020 TruncatedSeq* seq = surv_rate_group->get_seq(age);
1021 guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age);
1022 double pred = _predictor.get_new_prediction(seq);
1023 if (pred > 1.0) {
1024 pred = 1.0;
1025 }
1026 return pred;
1027 }
1028
1029 double G1CollectorPolicy::predict_yg_surv_rate(int age) const {
1030 return predict_yg_surv_rate(age, _short_lived_surv_rate_group);
1031 }
1032
1033 double G1CollectorPolicy::accum_yg_surv_rate_pred(int age) const {
1034 return _short_lived_surv_rate_group->accum_surv_rate_pred(age);
1035 }
1036
1037 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards,
1038 size_t scanned_cards) const {
1039 return
1040 _analytics->predict_rs_update_time_ms(pending_cards) +
1041 _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->gcs_are_young()) +
1042 _analytics->predict_constant_other_time_ms();
1043 }
1044
1045 double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const {
1046 size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff();
1047 size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->gcs_are_young());
1048 return predict_base_elapsed_time_ms(pending_cards, card_num);
1049 }
1050
1051 size_t G1CollectorPolicy::predict_bytes_to_copy(HeapRegion* hr) const {
1052 size_t bytes_to_copy;
1053 if (hr->is_marked())
1054 bytes_to_copy = hr->max_live_bytes();
1055 else {
1056 assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
1057 int age = hr->age_in_surv_rate_group();
1058 double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
1059 bytes_to_copy = (size_t) (hr->used() * yg_surv_rate);
1060 }
1061 return bytes_to_copy;
1062 }
1063
1064 double G1CollectorPolicy::predict_region_elapsed_time_ms(HeapRegion* hr,
1065 bool for_young_gc) const {
1066 size_t rs_length = hr->rem_set()->occupied();
1067 // Predicting the number of cards is based on which type of GC
1068 // we're predicting for.
1069 size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc);
1070 size_t bytes_to_copy = predict_bytes_to_copy(hr);
1071
1072 double region_elapsed_time_ms =
1073 _analytics->predict_rs_scan_time_ms(card_num, collector_state()->gcs_are_young()) +
1074 _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->during_concurrent_mark());
1075
1076 // The prediction of the "other" time for this region is based
1077 // upon the region type and NOT the GC type.
1078 if (hr->is_young()) {
1079 region_elapsed_time_ms += _analytics->predict_young_other_time_ms(1);
1080 } else {
1081 region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1);
1082 }
1083 return region_elapsed_time_ms;
1084 }
1085
1086 void G1CollectorPolicy::clear_ratio_check_data() {
1087 _ratio_over_threshold_count = 0;
1088 _ratio_over_threshold_sum = 0.0;
1089 _pauses_since_start = 0;
1090 }
1091
1092 size_t G1CollectorPolicy::expansion_amount() {
1093 double recent_gc_overhead = _analytics->recent_avg_pause_time_ratio() * 100.0;
1094 double last_gc_overhead = _analytics->last_pause_time_ratio() * 100.0;
1095 double threshold = _gc_overhead_perc;
1096 size_t expand_bytes = 0;
1097
1098 // If the heap is at less than half its maximum size, scale the threshold down,
1099 // to a limit of 1. Thus the smaller the heap is, the more likely it is to expand,
1100 // though the scaling code will likely keep the increase small.
1101 if (_g1->capacity() <= _g1->max_capacity() / 2) {
1102 threshold *= (double)_g1->capacity() / (double)(_g1->max_capacity() / 2);
1103 threshold = MAX2(threshold, 1.0);
1104 }
1105
1106 // If the last GC time ratio is over the threshold, increment the count of
1107 // times it has been exceeded, and add this ratio to the sum of exceeded
1108 // ratios.
1109 if (last_gc_overhead > threshold) {
1110 _ratio_over_threshold_count++;
1111 _ratio_over_threshold_sum += last_gc_overhead;
1112 }
1113
1114 // Check if we've had enough GC time ratio checks that were over the
1115 // threshold to trigger an expansion. We'll also expand if we've
1116 // reached the end of the history buffer and the average of all entries
1117 // is still over the threshold. This indicates a smaller number of GCs were
1118 // long enough to make the average exceed the threshold.
1119 bool filled_history_buffer = _pauses_since_start == NumPrevPausesForHeuristics;
1120 if ((_ratio_over_threshold_count == MinOverThresholdForGrowth) ||
1121 (filled_history_buffer && (recent_gc_overhead > threshold))) {
1122 size_t min_expand_bytes = HeapRegion::GrainBytes;
1123 size_t reserved_bytes = _g1->max_capacity();
1124 size_t committed_bytes = _g1->capacity();
1125 size_t uncommitted_bytes = reserved_bytes - committed_bytes;
1126 size_t expand_bytes_via_pct =
1127 uncommitted_bytes * G1ExpandByPercentOfAvailable / 100;
1128 double scale_factor = 1.0;
1129
1130 // If the current size is less than 1/4 of the Initial heap size, expand
1131 // by half of the delta between the current and Initial sizes. IE, grow
1132 // back quickly.
1133 //
1134 // Otherwise, take the current size, or G1ExpandByPercentOfAvailable % of
1135 // the available expansion space, whichever is smaller, as the base
1136 // expansion size. Then possibly scale this size according to how much the
1137 // threshold has (on average) been exceeded by. If the delta is small
1138 // (less than the StartScaleDownAt value), scale the size down linearly, but
1139 // not by less than MinScaleDownFactor. If the delta is large (greater than
1140 // the StartScaleUpAt value), scale up, but adding no more than MaxScaleUpFactor
1141 // times the base size. The scaling will be linear in the range from
1142 // StartScaleUpAt to (StartScaleUpAt + ScaleUpRange). In other words,
1143 // ScaleUpRange sets the rate of scaling up.
1144 if (committed_bytes < InitialHeapSize / 4) {
1145 expand_bytes = (InitialHeapSize - committed_bytes) / 2;
1146 } else {
1147 double const MinScaleDownFactor = 0.2;
1148 double const MaxScaleUpFactor = 2;
1149 double const StartScaleDownAt = _gc_overhead_perc;
1150 double const StartScaleUpAt = _gc_overhead_perc * 1.5;
1151 double const ScaleUpRange = _gc_overhead_perc * 2.0;
1152
1153 double ratio_delta;
1154 if (filled_history_buffer) {
1155 ratio_delta = recent_gc_overhead - threshold;
1156 } else {
1157 ratio_delta = (_ratio_over_threshold_sum/_ratio_over_threshold_count) - threshold;
1158 }
1159
1160 expand_bytes = MIN2(expand_bytes_via_pct, committed_bytes);
1161 if (ratio_delta < StartScaleDownAt) {
1162 scale_factor = ratio_delta / StartScaleDownAt;
1163 scale_factor = MAX2(scale_factor, MinScaleDownFactor);
1164 } else if (ratio_delta > StartScaleUpAt) {
1165 scale_factor = 1 + ((ratio_delta - StartScaleUpAt) / ScaleUpRange);
1166 scale_factor = MIN2(scale_factor, MaxScaleUpFactor);
1167 }
1168 }
1169
1170 log_debug(gc, ergo, heap)("Attempt heap expansion (recent GC overhead higher than threshold after GC) "
1171 "recent GC overhead: %1.2f %% threshold: %1.2f %% uncommitted: " SIZE_FORMAT "B base expansion amount and scale: " SIZE_FORMAT "B (%1.2f%%)",
1172 recent_gc_overhead, threshold, uncommitted_bytes, expand_bytes, scale_factor * 100);
1173
1174 expand_bytes = static_cast<size_t>(expand_bytes * scale_factor);
1175
1176 // Ensure the expansion size is at least the minimum growth amount
1177 // and at most the remaining uncommitted byte size.
1178 expand_bytes = MAX2(expand_bytes, min_expand_bytes);
1179 expand_bytes = MIN2(expand_bytes, uncommitted_bytes);
1180
1181 clear_ratio_check_data();
1182 } else {
1183 // An expansion was not triggered. If we've started counting, increment
1184 // the number of checks we've made in the current window. If we've
1185 // reached the end of the window without resizing, clear the counters to
1186 // start again the next time we see a ratio above the threshold.
1187 if (_ratio_over_threshold_count > 0) {
1188 _pauses_since_start++;
1189 if (_pauses_since_start > NumPrevPausesForHeuristics) {
1190 clear_ratio_check_data();
1191 }
1192 }
1193 }
1194
1195 return expand_bytes;
1196 }
1197
1198 void G1CollectorPolicy::print_yg_surv_rate_info() const {
1199 #ifndef PRODUCT
1200 _short_lived_surv_rate_group->print_surv_rate_summary();
1201 // add this call for any other surv rate groups
1202 #endif // PRODUCT
1203 }
1204
1205 bool G1CollectorPolicy::is_young_list_full() const {
1206 uint young_list_length = _g1->young_list()->length();
1207 uint young_list_target_length = _young_list_target_length;
1208 return young_list_length >= young_list_target_length;
1209 }
1210
1211 bool G1CollectorPolicy::can_expand_young_list() const {
1212 uint young_list_length = _g1->young_list()->length();
1213 uint young_list_max_length = _young_list_max_length;
1214 return young_list_length < young_list_max_length;
1215 }
1216
1217 bool G1CollectorPolicy::adaptive_young_list_length() const {
1218 return _young_gen_sizer->adaptive_young_list_length();
1219 }
1220
1221 void G1CollectorPolicy::update_max_gc_locker_expansion() {
1222 uint expansion_region_num = 0;
1223 if (GCLockerEdenExpansionPercent > 0) {
1224 double perc = (double) GCLockerEdenExpansionPercent / 100.0;
1225 double expansion_region_num_d = perc * (double) _young_list_target_length;
1226 // We use ceiling so that if expansion_region_num_d is > 0.0 (but
1227 // less than 1.0) we'll get 1.
1228 expansion_region_num = (uint) ceil(expansion_region_num_d);
1229 } else {
1230 assert(expansion_region_num == 0, "sanity");
1231 }
1232 _young_list_max_length = _young_list_target_length + expansion_region_num;
1233 assert(_young_list_target_length <= _young_list_max_length, "post-condition");
1234 }
1235
1236 // Calculates survivor space parameters.
1237 void G1CollectorPolicy::update_survivors_policy() {
1238 double max_survivor_regions_d =
1239 (double) _young_list_target_length / (double) SurvivorRatio;
1240 // We use ceiling so that if max_survivor_regions_d is > 0.0 (but
1241 // smaller than 1.0) we'll get 1.
1242 _max_survivor_regions = (uint) ceil(max_survivor_regions_d);
1243
1244 _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(
1245 HeapRegion::GrainWords * _max_survivor_regions, counters());
1246 }
1247
1248 bool G1CollectorPolicy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) {
1249 // We actually check whether we are marking here and not if we are in a
1250 // reclamation phase. This means that we will schedule a concurrent mark
1251 // even while we are still in the process of reclaiming memory.
1252 bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
1253 if (!during_cycle) {
1254 log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause));
1255 collector_state()->set_initiate_conc_mark_if_possible(true);
1256 return true;
1257 } else {
1258 log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause));
1259 return false;
1260 }
1261 }
1262
1263 void G1CollectorPolicy::initiate_conc_mark() {
1264 collector_state()->set_during_initial_mark_pause(true);
1265 collector_state()->set_initiate_conc_mark_if_possible(false);
1266 }
1267
1268 void G1CollectorPolicy::decide_on_conc_mark_initiation() {
1269 // We are about to decide on whether this pause will be an
1270 // initial-mark pause.
1271
1272 // First, collector_state()->during_initial_mark_pause() should not be already set. We
1273 // will set it here if we have to. However, it should be cleared by
1274 // the end of the pause (it's only set for the duration of an
1275 // initial-mark pause).
1276 assert(!collector_state()->during_initial_mark_pause(), "pre-condition");
1277
1278 if (collector_state()->initiate_conc_mark_if_possible()) {
1279 // We had noticed on a previous pause that the heap occupancy has
1280 // gone over the initiating threshold and we should start a
1281 // concurrent marking cycle. So we might initiate one.
1282
1283 if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) {
1284 // Initiate a new initial mark if there is no marking or reclamation going on.
1285 initiate_conc_mark();
1286 log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)");
1287 } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) {
1288 // Initiate a user requested initial mark. An initial mark must be young only
1289 // GC, so the collector state must be updated to reflect this.
1290 collector_state()->set_gcs_are_young(true);
1291 collector_state()->set_last_young_gc(false);
1292
1293 abort_time_to_mixed_tracking();
1294 initiate_conc_mark();
1295 log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)");
1296 } else {
1297 // The concurrent marking thread is still finishing up the
1298 // previous cycle. If we start one right now the two cycles
1299 // overlap. In particular, the concurrent marking thread might
1300 // be in the process of clearing the next marking bitmap (which
1301 // we will use for the next cycle if we start one). Starting a
1302 // cycle now will be bad given that parts of the marking
1303 // information might get cleared by the marking thread. And we
1304 // cannot wait for the marking thread to finish the cycle as it
1305 // periodically yields while clearing the next marking bitmap
1306 // and, if it's in a yield point, it's waiting for us to
1307 // finish. So, at this point we will not start a cycle and we'll
1308 // let the concurrent marking thread complete the last one.
1309 log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)");
1310 }
1311 }
1312 }
1313
1314 void G1CollectorPolicy::record_concurrent_mark_cleanup_end() {
1315 cset_chooser()->rebuild(_g1->workers(), _g1->num_regions());
1316
1317 double end_sec = os::elapsedTime();
1318 double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
1319 _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms);
1320 _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms);
1321
1322 record_pause(Cleanup, _mark_cleanup_start_sec, end_sec);
1323 }
1324
1325 double G1CollectorPolicy::reclaimable_bytes_perc(size_t reclaimable_bytes) const {
1326 // Returns the given amount of reclaimable bytes (that represents
1327 // the amount of reclaimable space still to be collected) as a
1328 // percentage of the current heap capacity.
1329 size_t capacity_bytes = _g1->capacity();
1330 return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
1331 }
1332
1333 void G1CollectorPolicy::maybe_start_marking() {
1334 if (need_to_start_conc_mark("end of GC")) {
1335 // Note: this might have already been set, if during the last
1336 // pause we decided to start a cycle but at the beginning of
1337 // this pause we decided to postpone it. That's OK.
1338 collector_state()->set_initiate_conc_mark_if_possible(true);
1339 }
1340 }
1341
1342 G1CollectorPolicy::PauseKind G1CollectorPolicy::young_gc_pause_kind() const {
1343 assert(!collector_state()->full_collection(), "must be");
1344 if (collector_state()->during_initial_mark_pause()) {
1345 assert(collector_state()->last_gc_was_young(), "must be");
1346 assert(!collector_state()->last_young_gc(), "must be");
1347 return InitialMarkGC;
1348 } else if (collector_state()->last_young_gc()) {
1349 assert(!collector_state()->during_initial_mark_pause(), "must be");
1350 assert(collector_state()->last_gc_was_young(), "must be");
1351 return LastYoungGC;
1352 } else if (!collector_state()->last_gc_was_young()) {
1353 assert(!collector_state()->during_initial_mark_pause(), "must be");
1354 assert(!collector_state()->last_young_gc(), "must be");
1355 return MixedGC;
1356 } else {
1357 assert(collector_state()->last_gc_was_young(), "must be");
1358 assert(!collector_state()->during_initial_mark_pause(), "must be");
1359 assert(!collector_state()->last_young_gc(), "must be");
1360 return YoungOnlyGC;
1361 }
1362 }
1363
1364 void G1CollectorPolicy::record_pause(PauseKind kind, double start, double end) {
1365 // Manage the MMU tracker. For some reason it ignores Full GCs.
1366 if (kind != FullGC) {
1367 _mmu_tracker->add_pause(start, end);
1368 }
1369 // Manage the mutator time tracking from initial mark to first mixed gc.
1370 switch (kind) {
1371 case FullGC:
1372 abort_time_to_mixed_tracking();
1373 break;
1374 case Cleanup:
1375 case Remark:
1376 case YoungOnlyGC:
1377 case LastYoungGC:
1378 _initial_mark_to_mixed.add_pause(end - start);
1379 break;
1380 case InitialMarkGC:
1381 _initial_mark_to_mixed.record_initial_mark_end(end);
1382 break;
1383 case MixedGC:
1384 _initial_mark_to_mixed.record_mixed_gc_start(start);
1385 break;
1386 default:
1387 ShouldNotReachHere();
1388 }
1389 }
1390
1391 void G1CollectorPolicy::abort_time_to_mixed_tracking() {
1392 _initial_mark_to_mixed.reset();
1393 }
1394
1395 bool G1CollectorPolicy::next_gc_should_be_mixed(const char* true_action_str,
1396 const char* false_action_str) const {
1397 if (cset_chooser()->is_empty()) {
1398 log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str);
1399 return false;
1400 }
1401
1402 // Is the amount of uncollected reclaimable space above G1HeapWastePercent?
1403 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
1404 double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes);
1405 double threshold = (double) G1HeapWastePercent;
1406 if (reclaimable_perc <= threshold) {
1407 log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1408 false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
1409 return false;
1410 }
1411 log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT,
1412 true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
1413 return true;
1414 }
1415
1416 uint G1CollectorPolicy::calc_min_old_cset_length() const {
1417 // The min old CSet region bound is based on the maximum desired
1418 // number of mixed GCs after a cycle. I.e., even if some old regions
1419 // look expensive, we should add them to the CSet anyway to make
1420 // sure we go through the available old regions in no more than the
1421 // maximum desired number of mixed GCs.
1422 //
1423 // The calculation is based on the number of marked regions we added
1424 // to the CSet chooser in the first place, not how many remain, so
1425 // that the result is the same during all mixed GCs that follow a cycle.
1426
1427 const size_t region_num = (size_t) cset_chooser()->length();
1428 const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1);
1429 size_t result = region_num / gc_num;
1430 // emulate ceiling
1431 if (result * gc_num < region_num) {
1432 result += 1;
1433 }
1434 return (uint) result;
1435 }
1436
1437 uint G1CollectorPolicy::calc_max_old_cset_length() const {
1438 // The max old CSet region bound is based on the threshold expressed
1439 // as a percentage of the heap size. I.e., it should bound the
1440 // number of old regions added to the CSet irrespective of how many
1441 // of them are available.
1442
1443 const G1CollectedHeap* g1h = G1CollectedHeap::heap();
1444 const size_t region_num = g1h->num_regions();
1445 const size_t perc = (size_t) G1OldCSetRegionThresholdPercent;
1446 size_t result = region_num * perc / 100;
1447 // emulate ceiling
1448 if (100 * result < region_num * perc) {
1449 result += 1;
1450 }
1451 return (uint) result;
1452 }
1453
1454 void G1CollectorPolicy::finalize_collection_set(double target_pause_time_ms) {
1455 double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms);
1456 _collection_set->finalize_old_part(time_remaining_ms);
1457 }