1 /*
2 * Copyright (c) 2016, 2019, 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/g1CollectedHeap.inline.hpp"
27 #include "gc/g1/g1CollectionSet.hpp"
28 #include "gc/g1/g1CollectionSetCandidates.hpp"
29 #include "gc/g1/g1CollectorState.hpp"
30 #include "gc/g1/g1ParScanThreadState.hpp"
31 #include "gc/g1/g1Policy.hpp"
32 #include "gc/g1/heapRegion.inline.hpp"
33 #include "gc/g1/heapRegionRemSet.hpp"
34 #include "gc/g1/heapRegionSet.hpp"
35 #include "logging/logStream.hpp"
36 #include "utilities/debug.hpp"
37 #include "utilities/globalDefinitions.hpp"
38 #include "utilities/quickSort.hpp"
39
40 G1CollectorState* G1CollectionSet::collector_state() {
41 return _g1h->collector_state();
42 }
43
44 G1GCPhaseTimes* G1CollectionSet::phase_times() {
45 return _policy->phase_times();
46 }
47
48 double G1CollectionSet::predict_region_elapsed_time_ms(HeapRegion* hr) {
49 return _policy->predict_region_elapsed_time_ms(hr, collector_state()->in_young_only_phase());
50 }
51
52 G1CollectionSet::G1CollectionSet(G1CollectedHeap* g1h, G1Policy* policy) :
53 _g1h(g1h),
54 _policy(policy),
55 _candidates(NULL),
56 _eden_region_length(0),
57 _survivor_region_length(0),
58 _old_region_length(0),
59 _collection_set_regions(NULL),
60 _collection_set_cur_length(0),
61 _collection_set_max_length(0),
62 _num_optional_regions(0),
63 _bytes_used_before(0),
64 _recorded_rs_length(0),
65 _inc_build_state(Inactive),
66 _inc_part_start(0),
67 _inc_bytes_used_before(0),
68 _inc_recorded_rs_length(0),
69 _inc_recorded_rs_length_diff(0),
70 _inc_predicted_elapsed_time_ms(0.0),
71 _inc_predicted_elapsed_time_ms_diff(0.0) {
72 }
73
74 G1CollectionSet::~G1CollectionSet() {
75 FREE_C_HEAP_ARRAY(uint, _collection_set_regions);
76 free_optional_regions();
77 clear_candidates();
78 }
79
80 void G1CollectionSet::init_region_lengths(uint eden_cset_region_length,
81 uint survivor_cset_region_length) {
82 assert_at_safepoint_on_vm_thread();
83
84 _eden_region_length = eden_cset_region_length;
85 _survivor_region_length = survivor_cset_region_length;
86
87 assert((size_t) young_region_length() == _collection_set_cur_length,
88 "Young region length %u should match collection set length " SIZE_FORMAT, young_region_length(), _collection_set_cur_length);
89
90 _old_region_length = 0;
91 free_optional_regions();
92 }
93
94 void G1CollectionSet::initialize(uint max_region_length) {
95 guarantee(_collection_set_regions == NULL, "Must only initialize once.");
96 _collection_set_max_length = max_region_length;
97 _collection_set_regions = NEW_C_HEAP_ARRAY(uint, max_region_length, mtGC);
98 }
99
100 void G1CollectionSet::free_optional_regions() {
101 _num_optional_regions = 0;
102 }
103
104 void G1CollectionSet::clear_candidates() {
105 delete _candidates;
106 _candidates = NULL;
107 }
108
109 void G1CollectionSet::set_recorded_rs_length(size_t rs_length) {
110 _recorded_rs_length = rs_length;
111 }
112
113 // Add the heap region at the head of the non-incremental collection set
114 void G1CollectionSet::add_old_region(HeapRegion* hr) {
115 assert_at_safepoint_on_vm_thread();
116
117 assert(_inc_build_state == Active,
118 "Precondition, actively building cset or adding optional later on");
119 assert(hr->is_old(), "the region should be old");
120
121 assert(!hr->in_collection_set(), "should not already be in the collection set");
122 _g1h->register_old_region_with_region_attr(hr);
123
124 _collection_set_regions[_collection_set_cur_length++] = hr->hrm_index();
125 assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set now larger than maximum size.");
126
127 _bytes_used_before += hr->used();
128 _recorded_rs_length += hr->rem_set()->occupied();
129 _old_region_length++;
130
131 _g1h->old_set_remove(hr);
132 }
133
134 void G1CollectionSet::add_optional_region(HeapRegion* hr) {
135 assert(hr->is_old(), "the region should be old");
136 assert(!hr->in_collection_set(), "should not already be in the CSet");
137
138 _g1h->register_optional_region_with_region_attr(hr);
139
140 hr->set_index_in_opt_cset(_num_optional_regions++);
141 }
142
143 void G1CollectionSet::start_incremental_building() {
144 assert(_collection_set_cur_length == 0, "Collection set must be empty before starting a new collection set.");
145 assert(_inc_build_state == Inactive, "Precondition");
146
147 _inc_bytes_used_before = 0;
148
149 _inc_recorded_rs_length = 0;
150 _inc_recorded_rs_length_diff = 0;
151 _inc_predicted_elapsed_time_ms = 0.0;
152 _inc_predicted_elapsed_time_ms_diff = 0.0;
153
154 update_incremental_marker();
155 }
156
157 void G1CollectionSet::finalize_incremental_building() {
158 assert(_inc_build_state == Active, "Precondition");
159 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
160
161 // The two "main" fields, _inc_recorded_rs_length and
162 // _inc_predicted_elapsed_time_ms, are updated by the thread
163 // that adds a new region to the CSet. Further updates by the
164 // concurrent refinement thread that samples the young RSet lengths
165 // are accumulated in the *_diff fields. Here we add the diffs to
166 // the "main" fields.
167
168 if (_inc_recorded_rs_length_diff >= 0) {
169 _inc_recorded_rs_length += _inc_recorded_rs_length_diff;
170 } else {
171 // This is defensive. The diff should in theory be always positive
172 // as RSets can only grow between GCs. However, given that we
173 // sample their size concurrently with other threads updating them
174 // it's possible that we might get the wrong size back, which
175 // could make the calculations somewhat inaccurate.
176 size_t diffs = (size_t) (-_inc_recorded_rs_length_diff);
177 if (_inc_recorded_rs_length >= diffs) {
178 _inc_recorded_rs_length -= diffs;
179 } else {
180 _inc_recorded_rs_length = 0;
181 }
182 }
183 _inc_predicted_elapsed_time_ms += _inc_predicted_elapsed_time_ms_diff;
184
185 _inc_recorded_rs_length_diff = 0;
186 _inc_predicted_elapsed_time_ms_diff = 0.0;
187 }
188
189 void G1CollectionSet::clear() {
190 assert_at_safepoint_on_vm_thread();
191 _collection_set_cur_length = 0;
192 }
193
194 void G1CollectionSet::iterate(HeapRegionClosure* cl) const {
195 size_t len = _collection_set_cur_length;
196 OrderAccess::loadload();
197
198 for (uint i = 0; i < len; i++) {
199 HeapRegion* r = _g1h->region_at(_collection_set_regions[i]);
200 bool result = cl->do_heap_region(r);
201 if (result) {
202 cl->set_incomplete();
203 return;
204 }
205 }
206 }
207
208 void G1CollectionSet::par_iterate(HeapRegionClosure* cl,
209 HeapRegionClaimer* hr_claimer,
210 uint worker_id,
211 uint total_workers) const {
212 iterate_part_from(cl, hr_claimer, 0, cur_length(), worker_id, total_workers);
213 }
214
215 void G1CollectionSet::iterate_optional(HeapRegionClosure* cl) const {
216 assert_at_safepoint();
217
218 for (uint i = 0; i < _num_optional_regions; i++) {
219 HeapRegion* r = _candidates->at(i);
220 bool result = cl->do_heap_region(r);
221 guarantee(!result, "Must not cancel iteration");
222 }
223 }
224
225 void G1CollectionSet::iterate_incremental_part_from(HeapRegionClosure* cl,
226 HeapRegionClaimer* hr_claimer,
227 uint worker_id,
228 uint total_workers) const {
229 iterate_part_from(cl, hr_claimer, _inc_part_start, increment_length(), worker_id, total_workers);
230 }
231
232 void G1CollectionSet::iterate_part_from(HeapRegionClosure* cl,
233 HeapRegionClaimer* hr_claimer,
234 size_t offset,
235 size_t lenght,
236 uint worker_id,
237 uint total_workers) const {
238 assert_at_safepoint();
239 if (lenght == 0) {
240 return;
241 }
242
243 size_t start_pos = (worker_id * lenght) / total_workers;
244 size_t cur_pos = start_pos;
245
246 do {
247 uint region_idx = _collection_set_regions[cur_pos + offset];
248 if (hr_claimer == NULL || hr_claimer->claim_region(region_idx)) {
249 HeapRegion* r = _g1h->region_at(region_idx);
250 bool result = cl->do_heap_region(r);
251 guarantee(!result, "Must not cancel iteration");
252 }
253
254 cur_pos++;
255 if (cur_pos == lenght) {
256 cur_pos = 0;
257 }
258 } while (cur_pos != start_pos);
259 }
260
261 void G1CollectionSet::update_young_region_prediction(HeapRegion* hr,
262 size_t new_rs_length) {
263 // Update the CSet information that is dependent on the new RS length
264 assert(hr->is_young(), "Precondition");
265 assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint");
266
267 // We could have updated _inc_recorded_rs_length and
268 // _inc_predicted_elapsed_time_ms directly but we'd need to do
269 // that atomically, as this code is executed by a concurrent
270 // refinement thread, potentially concurrently with a mutator thread
271 // allocating a new region and also updating the same fields. To
272 // avoid the atomic operations we accumulate these updates on two
273 // separate fields (*_diff) and we'll just add them to the "main"
274 // fields at the start of a GC.
275
276 ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length();
277 ssize_t rs_length_diff = (ssize_t) new_rs_length - old_rs_length;
278 _inc_recorded_rs_length_diff += rs_length_diff;
279
280 double old_elapsed_time_ms = hr->predicted_elapsed_time_ms();
281 double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
282 double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms;
283 _inc_predicted_elapsed_time_ms_diff += elapsed_ms_diff;
284
285 hr->set_recorded_rs_length(new_rs_length);
286 hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms);
287 }
288
289 void G1CollectionSet::add_young_region_common(HeapRegion* hr) {
290 assert(hr->is_young(), "invariant");
291 assert(_inc_build_state == Active, "Precondition");
292
293 size_t collection_set_length = _collection_set_cur_length;
294 // We use UINT_MAX as "invalid" marker in verification.
295 assert(collection_set_length < (UINT_MAX - 1),
296 "Collection set is too large with " SIZE_FORMAT " entries", collection_set_length);
297 hr->set_young_index_in_cset((uint)collection_set_length + 1);
298
299 _collection_set_regions[collection_set_length] = hr->hrm_index();
300 // Concurrent readers must observe the store of the value in the array before an
301 // update to the length field.
302 OrderAccess::storestore();
303 _collection_set_cur_length++;
304 assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set larger than maximum allowed.");
305
306 // This routine is used when:
307 // * adding survivor regions to the incremental cset at the end of an
308 // evacuation pause or
309 // * adding the current allocation region to the incremental cset
310 // when it is retired.
311 // Therefore this routine may be called at a safepoint by the
312 // VM thread, or in-between safepoints by mutator threads (when
313 // retiring the current allocation region)
314 // We need to clear and set the cached recorded/cached collection set
315 // information in the heap region here (before the region gets added
316 // to the collection set). An individual heap region's cached values
317 // are calculated, aggregated with the policy collection set info,
318 // and cached in the heap region here (initially) and (subsequently)
319 // by the Young List sampling code.
320 // Ignore calls to this due to retirement during full gc.
321
322 if (!_g1h->collector_state()->in_full_gc()) {
323 size_t rs_length = hr->rem_set()->occupied();
324 double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
325
326 // Cache the values we have added to the aggregated information
327 // in the heap region in case we have to remove this region from
328 // the incremental collection set, or it is updated by the
329 // rset sampling code
330 hr->set_recorded_rs_length(rs_length);
331 hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms);
332
333 _inc_recorded_rs_length += rs_length;
334 _inc_predicted_elapsed_time_ms += region_elapsed_time_ms;
335 _inc_bytes_used_before += hr->used();
336 }
337
338 assert(!hr->in_collection_set(), "invariant");
339 _g1h->register_young_region_with_region_attr(hr);
340 }
341
342 void G1CollectionSet::add_survivor_regions(HeapRegion* hr) {
343 assert(hr->is_survivor(), "Must only add survivor regions, but is %s", hr->get_type_str());
344 add_young_region_common(hr);
345 }
346
347 void G1CollectionSet::add_eden_region(HeapRegion* hr) {
348 assert(hr->is_eden(), "Must only add eden regions, but is %s", hr->get_type_str());
349 add_young_region_common(hr);
350 }
351
352 #ifndef PRODUCT
353 class G1VerifyYoungAgesClosure : public HeapRegionClosure {
354 public:
355 bool _valid;
356 public:
357 G1VerifyYoungAgesClosure() : HeapRegionClosure(), _valid(true) { }
358
359 virtual bool do_heap_region(HeapRegion* r) {
360 guarantee(r->is_young(), "Region must be young but is %s", r->get_type_str());
361
362 SurvRateGroup* group = r->surv_rate_group();
363
364 if (group == NULL) {
365 log_error(gc, verify)("## encountered NULL surv_rate_group in young region");
366 _valid = false;
367 }
368
369 if (r->age_in_surv_rate_group() < 0) {
370 log_error(gc, verify)("## encountered negative age in young region");
371 _valid = false;
372 }
373
374 return false;
375 }
376
377 bool valid() const { return _valid; }
378 };
379
380 bool G1CollectionSet::verify_young_ages() {
381 assert_at_safepoint_on_vm_thread();
382
383 G1VerifyYoungAgesClosure cl;
384 iterate(&cl);
385
386 if (!cl.valid()) {
387 LogStreamHandle(Error, gc, verify) log;
388 print(&log);
389 }
390
391 return cl.valid();
392 }
393
394 class G1PrintCollectionSetDetailClosure : public HeapRegionClosure {
395 outputStream* _st;
396 public:
397 G1PrintCollectionSetDetailClosure(outputStream* st) : HeapRegionClosure(), _st(st) { }
398
399 virtual bool do_heap_region(HeapRegion* r) {
400 assert(r->in_collection_set(), "Region %u should be in collection set", r->hrm_index());
401 _st->print_cr(" " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d",
402 HR_FORMAT_PARAMS(r),
403 p2i(r->prev_top_at_mark_start()),
404 p2i(r->next_top_at_mark_start()),
405 r->age_in_surv_rate_group_cond());
406 return false;
407 }
408 };
409
410 void G1CollectionSet::print(outputStream* st) {
411 st->print_cr("\nCollection_set:");
412
413 G1PrintCollectionSetDetailClosure cl(st);
414 iterate(&cl);
415 }
416 #endif // !PRODUCT
417
418 double G1CollectionSet::finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors) {
419 double young_start_time_sec = os::elapsedTime();
420
421 finalize_incremental_building();
422
423 guarantee(target_pause_time_ms > 0.0,
424 "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms);
425
426 size_t pending_cards = _policy->pending_cards_at_gc_start();
427 double base_time_ms = _policy->predict_base_elapsed_time_ms(pending_cards);
428 double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0);
429
430 log_trace(gc, ergo, cset)("Start choosing CSet. pending cards: " SIZE_FORMAT " predicted base time: %1.2fms remaining time: %1.2fms target pause time: %1.2fms",
431 pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms);
432
433 // The young list is laid with the survivor regions from the previous
434 // pause are appended to the RHS of the young list, i.e.
435 // [Newly Young Regions ++ Survivors from last pause].
436
437 uint survivor_region_length = survivors->length();
438 uint eden_region_length = _g1h->eden_regions_count();
439 init_region_lengths(eden_region_length, survivor_region_length);
440
441 verify_young_cset_indices();
442
443 // Clear the fields that point to the survivor list - they are all young now.
444 survivors->convert_to_eden();
445
446 _bytes_used_before = _inc_bytes_used_before;
447 time_remaining_ms = MAX2(time_remaining_ms - _inc_predicted_elapsed_time_ms, 0.0);
448
449 log_trace(gc, ergo, cset)("Add young regions to CSet. eden: %u regions, survivors: %u regions, predicted young region time: %1.2fms, target pause time: %1.2fms",
450 eden_region_length, survivor_region_length, _inc_predicted_elapsed_time_ms, target_pause_time_ms);
451
452 // The number of recorded young regions is the incremental
453 // collection set's current size
454 set_recorded_rs_length(_inc_recorded_rs_length);
455
456 double young_end_time_sec = os::elapsedTime();
457 phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0);
458
459 return time_remaining_ms;
460 }
461
462 static int compare_region_idx(const uint a, const uint b) {
463 if (a > b) {
464 return 1;
465 } else if (a == b) {
466 return 0;
467 } else {
468 return -1;
469 }
470 }
471
472 void G1CollectionSet::finalize_old_part(double time_remaining_ms) {
473 double non_young_start_time_sec = os::elapsedTime();
474
475 if (collector_state()->in_mixed_phase()) {
476 candidates()->verify();
477
478 uint num_initial_old_regions;
479 uint num_optional_old_regions;
480
481 _policy->calculate_old_collection_set_regions(candidates(),
482 time_remaining_ms,
483 num_initial_old_regions,
484 num_optional_old_regions);
485
486 // Prepare initial old regions.
487 move_candidates_to_collection_set(num_initial_old_regions);
488
489 // Prepare optional old regions for evacuation.
490 uint candidate_idx = candidates()->cur_idx();
491 for (uint i = 0; i < num_optional_old_regions; i++) {
492 add_optional_region(candidates()->at(candidate_idx + i));
493 }
494
495 candidates()->verify();
496 }
497
498 stop_incremental_building();
499
500 double non_young_end_time_sec = os::elapsedTime();
501 phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);
502
503 QuickSort::sort(_collection_set_regions, _collection_set_cur_length, compare_region_idx, true);
504 }
505
506 void G1CollectionSet::move_candidates_to_collection_set(uint num_old_candidate_regions) {
507 if (num_old_candidate_regions == 0) {
508 return;
509 }
510 uint candidate_idx = candidates()->cur_idx();
511 for (uint i = 0; i < num_old_candidate_regions; i++) {
512 HeapRegion* r = candidates()->at(candidate_idx + i);
513 // This potentially optional candidate region is going to be an actual collection
514 // set region. Clear cset marker.
515 _g1h->clear_region_attr(r);
516 add_old_region(r);
517 }
518 candidates()->remove(num_old_candidate_regions);
519
520 candidates()->verify();
521 }
522
523 void G1CollectionSet::finalize_initial_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {
524 double time_remaining_ms = finalize_young_part(target_pause_time_ms, survivor);
525 finalize_old_part(time_remaining_ms);
526 }
527
528 bool G1CollectionSet::finalize_optional_for_evacuation(double remaining_pause_time) {
529 update_incremental_marker();
530
531 uint num_selected_regions;
532 _policy->calculate_optional_collection_set_regions(candidates(),
533 _num_optional_regions,
534 remaining_pause_time,
535 num_selected_regions);
536
537 move_candidates_to_collection_set(num_selected_regions);
538
539 _num_optional_regions -= num_selected_regions;
540
541 stop_incremental_building();
542
543 _g1h->verify_region_attr_remset_update();
544
545 return num_selected_regions > 0;
546 }
547
548 void G1CollectionSet::abandon_optional_collection_set(G1ParScanThreadStateSet* pss) {
549 for (uint i = 0; i < _num_optional_regions; i++) {
550 HeapRegion* r = candidates()->at(candidates()->cur_idx() + i);
551 pss->record_unused_optional_region(r);
552 // Clear collection set marker and make sure that the remembered set information
553 // is correct as we still need it later.
554 _g1h->clear_region_attr(r);
555 _g1h->register_region_with_region_attr(r);
556 r->clear_index_in_opt_cset();
557 }
558 free_optional_regions();
559
560 _g1h->verify_region_attr_remset_update();
561 }
562
563 #ifdef ASSERT
564 class G1VerifyYoungCSetIndicesClosure : public HeapRegionClosure {
565 private:
566 size_t _young_length;
567 uint* _heap_region_indices;
568 public:
569 G1VerifyYoungCSetIndicesClosure(size_t young_length) : HeapRegionClosure(), _young_length(young_length) {
570 _heap_region_indices = NEW_C_HEAP_ARRAY(uint, young_length + 1, mtGC);
571 for (size_t i = 0; i < young_length + 1; i++) {
572 _heap_region_indices[i] = UINT_MAX;
573 }
574 }
575 ~G1VerifyYoungCSetIndicesClosure() {
576 FREE_C_HEAP_ARRAY(int, _heap_region_indices);
577 }
578
579 virtual bool do_heap_region(HeapRegion* r) {
580 const uint idx = r->young_index_in_cset();
581
582 assert(idx > 0, "Young index must be set for all regions in the incremental collection set but is not for region %u.", r->hrm_index());
583 assert(idx <= _young_length, "Young cset index %u too large for region %u", idx, r->hrm_index());
584
585 assert(_heap_region_indices[idx] == UINT_MAX,
586 "Index %d used by multiple regions, first use by region %u, second by region %u",
587 idx, _heap_region_indices[idx], r->hrm_index());
588
589 _heap_region_indices[idx] = r->hrm_index();
590
591 return false;
592 }
593 };
594
595 void G1CollectionSet::verify_young_cset_indices() const {
596 assert_at_safepoint_on_vm_thread();
597
598 G1VerifyYoungCSetIndicesClosure cl(_collection_set_cur_length);
599 iterate(&cl);
600 }
601 #endif