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::iterate_optional(HeapRegionClosure* cl) const {
209 assert_at_safepoint();
210
211 for (uint i = 0; i < _num_optional_regions; i++) {
212 HeapRegion* r = _candidates->at(i);
213 bool result = cl->do_heap_region(r);
214 guarantee(!result, "Must not cancel iteration");
215 }
216 }
217
218 void G1CollectionSet::iterate_incremental_part_from(HeapRegionClosure* cl,
219 HeapRegionClaimer* hr_claimer,
220 uint worker_id,
221 uint total_workers) const {
222 assert_at_safepoint();
223
224 size_t len = increment_length();
225 if (len == 0) {
226 return;
227 }
228
229 size_t start_pos = (worker_id * len) / total_workers;
230 size_t cur_pos = start_pos;
231
232 do {
233 uint region_idx = _collection_set_regions[cur_pos + _inc_part_start];
234 if (hr_claimer == NULL || hr_claimer->claim_region(region_idx)) {
235 HeapRegion* r = _g1h->region_at(region_idx);
236 bool result = cl->do_heap_region(r);
237 guarantee(!result, "Must not cancel iteration");
238 }
239
240 cur_pos++;
241 if (cur_pos == len) {
242 cur_pos = 0;
243 }
244 } while (cur_pos != start_pos);
245 }
246
247 void G1CollectionSet::update_young_region_prediction(HeapRegion* hr,
248 size_t new_rs_length) {
249 // Update the CSet information that is dependent on the new RS length
250 assert(hr->is_young(), "Precondition");
251 assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint");
252
253 // We could have updated _inc_recorded_rs_length and
254 // _inc_predicted_elapsed_time_ms directly but we'd need to do
255 // that atomically, as this code is executed by a concurrent
256 // refinement thread, potentially concurrently with a mutator thread
257 // allocating a new region and also updating the same fields. To
258 // avoid the atomic operations we accumulate these updates on two
259 // separate fields (*_diff) and we'll just add them to the "main"
260 // fields at the start of a GC.
261
262 ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length();
263 ssize_t rs_length_diff = (ssize_t) new_rs_length - old_rs_length;
264 _inc_recorded_rs_length_diff += rs_length_diff;
265
266 double old_elapsed_time_ms = hr->predicted_elapsed_time_ms();
267 double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
268 double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms;
269 _inc_predicted_elapsed_time_ms_diff += elapsed_ms_diff;
270
271 hr->set_recorded_rs_length(new_rs_length);
272 hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms);
273 }
274
275 void G1CollectionSet::add_young_region_common(HeapRegion* hr) {
276 assert(hr->is_young(), "invariant");
277 assert(_inc_build_state == Active, "Precondition");
278
279 size_t collection_set_length = _collection_set_cur_length;
280 // We use UINT_MAX as "invalid" marker in verification.
281 assert(collection_set_length < (UINT_MAX - 1),
282 "Collection set is too large with " SIZE_FORMAT " entries", collection_set_length);
283 hr->set_young_index_in_cset((uint)collection_set_length + 1);
284
285 _collection_set_regions[collection_set_length] = hr->hrm_index();
286 // Concurrent readers must observe the store of the value in the array before an
287 // update to the length field.
288 OrderAccess::storestore();
289 _collection_set_cur_length++;
290 assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set larger than maximum allowed.");
291
292 // This routine is used when:
293 // * adding survivor regions to the incremental cset at the end of an
294 // evacuation pause or
295 // * adding the current allocation region to the incremental cset
296 // when it is retired.
297 // Therefore this routine may be called at a safepoint by the
298 // VM thread, or in-between safepoints by mutator threads (when
299 // retiring the current allocation region)
300 // We need to clear and set the cached recorded/cached collection set
301 // information in the heap region here (before the region gets added
302 // to the collection set). An individual heap region's cached values
303 // are calculated, aggregated with the policy collection set info,
304 // and cached in the heap region here (initially) and (subsequently)
305 // by the Young List sampling code.
306 // Ignore calls to this due to retirement during full gc.
307
308 if (!_g1h->collector_state()->in_full_gc()) {
309 size_t rs_length = hr->rem_set()->occupied();
310 double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
311
312 // Cache the values we have added to the aggregated information
313 // in the heap region in case we have to remove this region from
314 // the incremental collection set, or it is updated by the
315 // rset sampling code
316 hr->set_recorded_rs_length(rs_length);
317 hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms);
318
319 _inc_recorded_rs_length += rs_length;
320 _inc_predicted_elapsed_time_ms += region_elapsed_time_ms;
321 _inc_bytes_used_before += hr->used();
322 }
323
324 assert(!hr->in_collection_set(), "invariant");
325 _g1h->register_young_region_with_region_attr(hr);
326 }
327
328 void G1CollectionSet::add_survivor_regions(HeapRegion* hr) {
329 assert(hr->is_survivor(), "Must only add survivor regions, but is %s", hr->get_type_str());
330 add_young_region_common(hr);
331 }
332
333 void G1CollectionSet::add_eden_region(HeapRegion* hr) {
334 assert(hr->is_eden(), "Must only add eden regions, but is %s", hr->get_type_str());
335 add_young_region_common(hr);
336 }
337
338 #ifndef PRODUCT
339 class G1VerifyYoungAgesClosure : public HeapRegionClosure {
340 public:
341 bool _valid;
342 public:
343 G1VerifyYoungAgesClosure() : HeapRegionClosure(), _valid(true) { }
344
345 virtual bool do_heap_region(HeapRegion* r) {
346 guarantee(r->is_young(), "Region must be young but is %s", r->get_type_str());
347
348 SurvRateGroup* group = r->surv_rate_group();
349
350 if (group == NULL) {
351 log_error(gc, verify)("## encountered NULL surv_rate_group in young region");
352 _valid = false;
353 }
354
355 if (r->age_in_surv_rate_group() < 0) {
356 log_error(gc, verify)("## encountered negative age in young region");
357 _valid = false;
358 }
359
360 return false;
361 }
362
363 bool valid() const { return _valid; }
364 };
365
366 bool G1CollectionSet::verify_young_ages() {
367 assert_at_safepoint_on_vm_thread();
368
369 G1VerifyYoungAgesClosure cl;
370 iterate(&cl);
371
372 if (!cl.valid()) {
373 LogStreamHandle(Error, gc, verify) log;
374 print(&log);
375 }
376
377 return cl.valid();
378 }
379
380 class G1PrintCollectionSetDetailClosure : public HeapRegionClosure {
381 outputStream* _st;
382 public:
383 G1PrintCollectionSetDetailClosure(outputStream* st) : HeapRegionClosure(), _st(st) { }
384
385 virtual bool do_heap_region(HeapRegion* r) {
386 assert(r->in_collection_set(), "Region %u should be in collection set", r->hrm_index());
387 _st->print_cr(" " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d",
388 HR_FORMAT_PARAMS(r),
389 p2i(r->prev_top_at_mark_start()),
390 p2i(r->next_top_at_mark_start()),
391 r->age_in_surv_rate_group_cond());
392 return false;
393 }
394 };
395
396 void G1CollectionSet::print(outputStream* st) {
397 st->print_cr("\nCollection_set:");
398
399 G1PrintCollectionSetDetailClosure cl(st);
400 iterate(&cl);
401 }
402 #endif // !PRODUCT
403
404 double G1CollectionSet::finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors) {
405 double young_start_time_sec = os::elapsedTime();
406
407 finalize_incremental_building();
408
409 guarantee(target_pause_time_ms > 0.0,
410 "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms);
411
412 size_t pending_cards = _policy->pending_cards_at_gc_start();
413 double base_time_ms = _policy->predict_base_elapsed_time_ms(pending_cards);
414 double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0);
415
416 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",
417 pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms);
418
419 // The young list is laid with the survivor regions from the previous
420 // pause are appended to the RHS of the young list, i.e.
421 // [Newly Young Regions ++ Survivors from last pause].
422
423 uint survivor_region_length = survivors->length();
424 uint eden_region_length = _g1h->eden_regions_count();
425 init_region_lengths(eden_region_length, survivor_region_length);
426
427 verify_young_cset_indices();
428
429 // Clear the fields that point to the survivor list - they are all young now.
430 survivors->convert_to_eden();
431
432 _bytes_used_before = _inc_bytes_used_before;
433 time_remaining_ms = MAX2(time_remaining_ms - _inc_predicted_elapsed_time_ms, 0.0);
434
435 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",
436 eden_region_length, survivor_region_length, _inc_predicted_elapsed_time_ms, target_pause_time_ms);
437
438 // The number of recorded young regions is the incremental
439 // collection set's current size
440 set_recorded_rs_length(_inc_recorded_rs_length);
441
442 double young_end_time_sec = os::elapsedTime();
443 phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0);
444
445 return time_remaining_ms;
446 }
447
448 static int compare_region_idx(const uint a, const uint b) {
449 if (a > b) {
450 return 1;
451 } else if (a == b) {
452 return 0;
453 } else {
454 return -1;
455 }
456 }
457
458 void G1CollectionSet::finalize_old_part(double time_remaining_ms) {
459 double non_young_start_time_sec = os::elapsedTime();
460
461 if (collector_state()->in_mixed_phase()) {
462 candidates()->verify();
463
464 uint num_initial_old_regions;
465 uint num_optional_old_regions;
466
467 _policy->calculate_old_collection_set_regions(candidates(),
468 time_remaining_ms,
469 num_initial_old_regions,
470 num_optional_old_regions);
471
472 // Prepare initial old regions.
473 move_candidates_to_collection_set(num_initial_old_regions);
474
475 // Prepare optional old regions for evacuation.
476 uint candidate_idx = candidates()->cur_idx();
477 for (uint i = 0; i < num_optional_old_regions; i++) {
478 add_optional_region(candidates()->at(candidate_idx + i));
479 }
480
481 candidates()->verify();
482 }
483
484 stop_incremental_building();
485
486 double non_young_end_time_sec = os::elapsedTime();
487 phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);
488
489 QuickSort::sort(_collection_set_regions, _collection_set_cur_length, compare_region_idx, true);
490 }
491
492 void G1CollectionSet::move_candidates_to_collection_set(uint num_old_candidate_regions) {
493 if (num_old_candidate_regions == 0) {
494 return;
495 }
496 uint candidate_idx = candidates()->cur_idx();
497 for (uint i = 0; i < num_old_candidate_regions; i++) {
498 HeapRegion* r = candidates()->at(candidate_idx + i);
499 // This potentially optional candidate region is going to be an actual collection
500 // set region. Clear cset marker.
501 _g1h->clear_region_attr(r);
502 add_old_region(r);
503 }
504 candidates()->remove(num_old_candidate_regions);
505
506 candidates()->verify();
507 }
508
509 void G1CollectionSet::finalize_initial_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {
510 double time_remaining_ms = finalize_young_part(target_pause_time_ms, survivor);
511 finalize_old_part(time_remaining_ms);
512 }
513
514 bool G1CollectionSet::finalize_optional_for_evacuation(double remaining_pause_time) {
515 update_incremental_marker();
516
517 uint num_selected_regions;
518 _policy->calculate_optional_collection_set_regions(candidates(),
519 _num_optional_regions,
520 remaining_pause_time,
521 num_selected_regions);
522
523 move_candidates_to_collection_set(num_selected_regions);
524
525 _num_optional_regions -= num_selected_regions;
526
527 stop_incremental_building();
528
529 _g1h->verify_region_attr_remset_update();
530
531 return num_selected_regions > 0;
532 }
533
534 void G1CollectionSet::abandon_optional_collection_set(G1ParScanThreadStateSet* pss) {
535 for (uint i = 0; i < _num_optional_regions; i++) {
536 HeapRegion* r = candidates()->at(candidates()->cur_idx() + i);
537 pss->record_unused_optional_region(r);
538 // Clear collection set marker and make sure that the remembered set information
539 // is correct as we still need it later.
540 _g1h->clear_region_attr(r);
541 _g1h->register_region_with_region_attr(r);
542 r->clear_index_in_opt_cset();
543 }
544 free_optional_regions();
545
546 _g1h->verify_region_attr_remset_update();
547 }
548
549 #ifdef ASSERT
550 class G1VerifyYoungCSetIndicesClosure : public HeapRegionClosure {
551 private:
552 size_t _young_length;
553 uint* _heap_region_indices;
554 public:
555 G1VerifyYoungCSetIndicesClosure(size_t young_length) : HeapRegionClosure(), _young_length(young_length) {
556 _heap_region_indices = NEW_C_HEAP_ARRAY(uint, young_length + 1, mtGC);
557 for (size_t i = 0; i < young_length + 1; i++) {
558 _heap_region_indices[i] = UINT_MAX;
559 }
560 }
561 ~G1VerifyYoungCSetIndicesClosure() {
562 FREE_C_HEAP_ARRAY(int, _heap_region_indices);
563 }
564
565 virtual bool do_heap_region(HeapRegion* r) {
566 const uint idx = r->young_index_in_cset();
567
568 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());
569 assert(idx <= _young_length, "Young cset index %u too large for region %u", idx, r->hrm_index());
570
571 assert(_heap_region_indices[idx] == UINT_MAX,
572 "Index %d used by multiple regions, first use by region %u, second by region %u",
573 idx, _heap_region_indices[idx], r->hrm_index());
574
575 _heap_region_indices[idx] = r->hrm_index();
576
577 return false;
578 }
579 };
580
581 void G1CollectionSet::verify_young_cset_indices() const {
582 assert_at_safepoint_on_vm_thread();
583
584 G1VerifyYoungCSetIndicesClosure cl(_collection_set_cur_length);
585 iterate(&cl);
586 }
587 #endif