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/g1HotCardCache.hpp"
31 #include "gc/g1/g1ParScanThreadState.hpp"
32 #include "gc/g1/g1Policy.hpp"
33 #include "gc/g1/heapRegion.inline.hpp"
34 #include "gc/g1/heapRegionRemSet.hpp"
35 #include "gc/g1/heapRegionSet.hpp"
36 #include "logging/logStream.hpp"
37 #include "utilities/debug.hpp"
38 #include "utilities/globalDefinitions.hpp"
39 #include "utilities/quickSort.hpp"
40
41 G1CollectorState* G1CollectionSet::collector_state() {
42 return _g1h->collector_state();
43 }
44
45 G1GCPhaseTimes* G1CollectionSet::phase_times() {
46 return _policy->phase_times();
47 }
48
49 double G1CollectionSet::predict_region_elapsed_time_ms(HeapRegion* hr) {
50 return _policy->predict_region_elapsed_time_ms(hr, collector_state()->in_young_only_phase());
51 }
52
53 G1CollectionSet::G1CollectionSet(G1CollectedHeap* g1h, G1Policy* policy) :
54 _g1h(g1h),
55 _policy(policy),
56 _candidates(NULL),
57 _eden_region_length(0),
58 _survivor_region_length(0),
59 _old_region_length(0),
60 _collection_set_regions(NULL),
61 _collection_set_cur_length(0),
62 _collection_set_max_length(0),
63 _num_optional_regions(0),
64 _bytes_used_before(0),
65 _recorded_rs_length(0),
66 _inc_build_state(Inactive),
67 _inc_part_start(0),
68 _inc_bytes_used_before(0),
69 _inc_recorded_rs_length(0),
70 _inc_recorded_rs_length_diff(0),
71 _inc_predicted_elapsed_time_ms(0.0),
72 _inc_predicted_elapsed_time_ms_diff(0.0) {
73 }
74
75 G1CollectionSet::~G1CollectionSet() {
76 FREE_C_HEAP_ARRAY(uint, _collection_set_regions);
77 free_optional_regions();
78 clear_candidates();
79 }
80
81 void G1CollectionSet::init_region_lengths(uint eden_cset_region_length,
82 uint survivor_cset_region_length) {
83 assert_at_safepoint_on_vm_thread();
84
85 _eden_region_length = eden_cset_region_length;
86 _survivor_region_length = survivor_cset_region_length;
87
88 assert((size_t) young_region_length() == _collection_set_cur_length,
89 "Young region length %u should match collection set length " SIZE_FORMAT, young_region_length(), _collection_set_cur_length);
90
91 _old_region_length = 0;
92 free_optional_regions();
93 }
94
95 void G1CollectionSet::initialize(uint max_region_length) {
96 guarantee(_collection_set_regions == NULL, "Must only initialize once.");
97 _collection_set_max_length = max_region_length;
98 _collection_set_regions = NEW_C_HEAP_ARRAY(uint, max_region_length, mtGC);
99 }
100
101 void G1CollectionSet::free_optional_regions() {
102 _num_optional_regions = 0;
103 }
104
105 void G1CollectionSet::clear_candidates() {
106 delete _candidates;
107 _candidates = NULL;
108 }
109
110 void G1CollectionSet::set_recorded_rs_length(size_t rs_length) {
111 _recorded_rs_length = rs_length;
112 }
113
114 // Add the heap region at the head of the non-incremental collection set
115 void G1CollectionSet::add_old_region(HeapRegion* hr) {
116 assert_at_safepoint_on_vm_thread();
117
118 assert(_inc_build_state == Active,
119 "Precondition, actively building cset or adding optional later on");
120 assert(hr->is_old(), "the region should be old");
121
122 assert(!hr->in_collection_set(), "should not already be in the collection set");
123 _g1h->register_old_region_with_region_attr(hr);
124
125 _collection_set_regions[_collection_set_cur_length++] = hr->hrm_index();
126 assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set now larger than maximum size.");
127
128 _bytes_used_before += hr->used();
129 _recorded_rs_length += hr->rem_set()->occupied();
130 _old_region_length++;
131
132 _g1h->old_set_remove(hr);
133 }
134
135 void G1CollectionSet::add_optional_region(HeapRegion* hr) {
136 assert(hr->is_old(), "the region should be old");
137 assert(!hr->in_collection_set(), "should not already be in the CSet");
138
139 _g1h->register_optional_region_with_region_attr(hr);
140
141 hr->set_index_in_opt_cset(_num_optional_regions++);
142 }
143
144 void G1CollectionSet::start_incremental_building() {
145 assert(_collection_set_cur_length == 0, "Collection set must be empty before starting a new collection set.");
146 assert(_inc_build_state == Inactive, "Precondition");
147
148 _inc_bytes_used_before = 0;
149
150 _inc_recorded_rs_length = 0;
151 _inc_recorded_rs_length_diff = 0;
152 _inc_predicted_elapsed_time_ms = 0.0;
153 _inc_predicted_elapsed_time_ms_diff = 0.0;
154
155 update_incremental_marker();
156 }
157
158 void G1CollectionSet::finalize_incremental_building() {
159 assert(_inc_build_state == Active, "Precondition");
160 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
161
162 // The two "main" fields, _inc_recorded_rs_length and
163 // _inc_predicted_elapsed_time_ms, are updated by the thread
164 // that adds a new region to the CSet. Further updates by the
165 // concurrent refinement thread that samples the young RSet lengths
166 // are accumulated in the *_diff fields. Here we add the diffs to
167 // the "main" fields.
168
169 _inc_recorded_rs_length += _inc_recorded_rs_length_diff;
170 _inc_predicted_elapsed_time_ms += _inc_predicted_elapsed_time_ms_diff;
171
172 _inc_recorded_rs_length_diff = 0;
173 _inc_predicted_elapsed_time_ms_diff = 0.0;
174 }
175
176 void G1CollectionSet::clear() {
177 assert_at_safepoint_on_vm_thread();
178 _collection_set_cur_length = 0;
179 }
180
181 void G1CollectionSet::iterate(HeapRegionClosure* cl) const {
182 size_t len = _collection_set_cur_length;
183 OrderAccess::loadload();
184
185 for (uint i = 0; i < len; i++) {
186 HeapRegion* r = _g1h->region_at(_collection_set_regions[i]);
187 bool result = cl->do_heap_region(r);
188 if (result) {
189 cl->set_incomplete();
190 return;
191 }
192 }
193 }
194
195 void G1CollectionSet::iterate_optional(HeapRegionClosure* cl) const {
196 assert_at_safepoint();
197
198 for (uint i = 0; i < _num_optional_regions; i++) {
199 HeapRegion* r = _candidates->at(i);
200 bool result = cl->do_heap_region(r);
201 guarantee(!result, "Must not cancel iteration");
202 }
203 }
204
205 void G1CollectionSet::iterate_incremental_part_from(HeapRegionClosure* cl,
206 HeapRegionClaimer* hr_claimer,
207 uint worker_id,
208 uint total_workers) const {
209 assert_at_safepoint();
210
211 size_t len = increment_length();
212 if (len == 0) {
213 return;
214 }
215
216 size_t start_pos = (worker_id * len) / total_workers;
217 size_t cur_pos = start_pos;
218
219 do {
220 uint region_idx = _collection_set_regions[cur_pos + _inc_part_start];
221 if (hr_claimer == NULL || hr_claimer->claim_region(region_idx)) {
222 HeapRegion* r = _g1h->region_at(region_idx);
223 bool result = cl->do_heap_region(r);
224 guarantee(!result, "Must not cancel iteration");
225 }
226
227 cur_pos++;
228 if (cur_pos == len) {
229 cur_pos = 0;
230 }
231 } while (cur_pos != start_pos);
232 }
233
234 void G1CollectionSet::update_young_region_prediction(HeapRegion* hr,
235 size_t new_rs_length) {
236 // Update the CSet information that is dependent on the new RS length
237 assert(hr->is_young(), "Precondition");
238 assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint");
239
240 // We could have updated _inc_recorded_rs_length and
241 // _inc_predicted_elapsed_time_ms directly but we'd need to do
242 // that atomically, as this code is executed by a concurrent
243 // refinement thread, potentially concurrently with a mutator thread
244 // allocating a new region and also updating the same fields. To
245 // avoid the atomic operations we accumulate these updates on two
246 // separate fields (*_diff) and we'll just add them to the "main"
247 // fields at the start of a GC.
248
249 size_t old_rs_length = hr->recorded_rs_length();
250 assert(old_rs_length <= new_rs_length,
251 "Remembered set sizes must increase (changed from " SIZE_FORMAT " to " SIZE_FORMAT " region %u type %s)",
252 old_rs_length, new_rs_length, hr->hrm_index(), hr->get_short_type_str());
253 size_t rs_length_diff = new_rs_length - old_rs_length;
254 _inc_recorded_rs_length_diff += rs_length_diff;
255
256 double old_elapsed_time_ms = hr->predicted_elapsed_time_ms();
257 double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
258 double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms;
259 _inc_predicted_elapsed_time_ms_diff += elapsed_ms_diff;
260
261 hr->set_recorded_rs_length(new_rs_length);
262 hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms);
263 }
264
265 void G1CollectionSet::add_young_region_common(HeapRegion* hr) {
266 assert(hr->is_young(), "invariant");
267 assert(_inc_build_state == Active, "Precondition");
268
269 // This routine is used when:
270 // * adding survivor regions to the incremental cset at the end of an
271 // evacuation pause or
272 // * adding the current allocation region to the incremental cset
273 // when it is retired.
274 // Therefore this routine may be called at a safepoint by the
275 // VM thread, or in-between safepoints by mutator threads (when
276 // retiring the current allocation region)
277 // We need to clear and set the cached recorded/cached collection set
278 // information in the heap region here (before the region gets added
279 // to the collection set). An individual heap region's cached values
280 // are calculated, aggregated with the policy collection set info,
281 // and cached in the heap region here (initially) and (subsequently)
282 // by the Young List sampling code.
283 // Ignore calls to this due to retirement during full gc.
284
285 if (!_g1h->collector_state()->in_full_gc()) {
286 size_t rs_length = hr->rem_set()->occupied();
287 double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
288
289 // Cache the values we have added to the aggregated information
290 // in the heap region in case we have to remove this region from
291 // the incremental collection set, or it is updated by the
292 // rset sampling code
293 hr->set_recorded_rs_length(rs_length);
294 hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms);
295
296 _inc_recorded_rs_length += rs_length;
297 _inc_predicted_elapsed_time_ms += region_elapsed_time_ms;
298 _inc_bytes_used_before += hr->used();
299 }
300
301 assert(!hr->in_collection_set(), "invariant");
302 _g1h->register_young_region_with_region_attr(hr);
303
304 size_t collection_set_length = _collection_set_cur_length;
305 // We use UINT_MAX as "invalid" marker in verification.
306 assert(collection_set_length < (UINT_MAX - 1),
307 "Collection set is too large with " SIZE_FORMAT " entries", collection_set_length);
308 hr->set_young_index_in_cset((uint)collection_set_length + 1);
309
310 _collection_set_regions[collection_set_length] = hr->hrm_index();
311 // Concurrent readers must observe the store of the value in the array before an
312 // update to the length field.
313 OrderAccess::storestore();
314 _collection_set_cur_length++;
315 assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set larger than maximum allowed.");
316 }
317
318 void G1CollectionSet::add_survivor_regions(HeapRegion* hr) {
319 assert(hr->is_survivor(), "Must only add survivor regions, but is %s", hr->get_type_str());
320 add_young_region_common(hr);
321 }
322
323 void G1CollectionSet::add_eden_region(HeapRegion* hr) {
324 assert(hr->is_eden(), "Must only add eden regions, but is %s", hr->get_type_str());
325 add_young_region_common(hr);
326 }
327
328 #ifndef PRODUCT
329 class G1VerifyYoungAgesClosure : public HeapRegionClosure {
330 public:
331 bool _valid;
332 public:
333 G1VerifyYoungAgesClosure() : HeapRegionClosure(), _valid(true) { }
334
335 virtual bool do_heap_region(HeapRegion* r) {
336 guarantee(r->is_young(), "Region must be young but is %s", r->get_type_str());
337
338 SurvRateGroup* group = r->surv_rate_group();
339
340 if (group == NULL) {
341 log_error(gc, verify)("## encountered NULL surv_rate_group in young region");
342 _valid = false;
343 }
344
345 if (r->age_in_surv_rate_group() < 0) {
346 log_error(gc, verify)("## encountered negative age in young region");
347 _valid = false;
348 }
349
350 return false;
351 }
352
353 bool valid() const { return _valid; }
354 };
355
356 bool G1CollectionSet::verify_young_ages() {
357 assert_at_safepoint_on_vm_thread();
358
359 G1VerifyYoungAgesClosure cl;
360 iterate(&cl);
361
362 if (!cl.valid()) {
363 LogStreamHandle(Error, gc, verify) log;
364 print(&log);
365 }
366
367 return cl.valid();
368 }
369
370 class G1PrintCollectionSetDetailClosure : public HeapRegionClosure {
371 outputStream* _st;
372 public:
373 G1PrintCollectionSetDetailClosure(outputStream* st) : HeapRegionClosure(), _st(st) { }
374
375 virtual bool do_heap_region(HeapRegion* r) {
376 assert(r->in_collection_set(), "Region %u should be in collection set", r->hrm_index());
377 _st->print_cr(" " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d",
378 HR_FORMAT_PARAMS(r),
379 p2i(r->prev_top_at_mark_start()),
380 p2i(r->next_top_at_mark_start()),
381 r->age_in_surv_rate_group_cond());
382 return false;
383 }
384 };
385
386 void G1CollectionSet::print(outputStream* st) {
387 st->print_cr("\nCollection_set:");
388
389 G1PrintCollectionSetDetailClosure cl(st);
390 iterate(&cl);
391 }
392 #endif // !PRODUCT
393
394 double G1CollectionSet::finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors) {
395 double young_start_time_sec = os::elapsedTime();
396
397 finalize_incremental_building();
398
399 guarantee(target_pause_time_ms > 0.0,
400 "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms);
401
402 size_t pending_cards = _policy->pending_cards_at_gc_start() + _g1h->hot_card_cache()->num_entries();
403 double base_time_ms = _policy->predict_base_elapsed_time_ms(pending_cards);
404 double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0);
405
406 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",
407 pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms);
408
409 // The young list is laid with the survivor regions from the previous
410 // pause are appended to the RHS of the young list, i.e.
411 // [Newly Young Regions ++ Survivors from last pause].
412
413 uint survivor_region_length = survivors->length();
414 uint eden_region_length = _g1h->eden_regions_count();
415 init_region_lengths(eden_region_length, survivor_region_length);
416
417 verify_young_cset_indices();
418
419 // Clear the fields that point to the survivor list - they are all young now.
420 survivors->convert_to_eden();
421
422 _bytes_used_before = _inc_bytes_used_before;
423 time_remaining_ms = MAX2(time_remaining_ms - _inc_predicted_elapsed_time_ms, 0.0);
424
425 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",
426 eden_region_length, survivor_region_length, _inc_predicted_elapsed_time_ms, target_pause_time_ms);
427
428 // The number of recorded young regions is the incremental
429 // collection set's current size
430 set_recorded_rs_length(_inc_recorded_rs_length);
431
432 double young_end_time_sec = os::elapsedTime();
433 phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0);
434
435 return time_remaining_ms;
436 }
437
438 static int compare_region_idx(const uint a, const uint b) {
439 if (a > b) {
440 return 1;
441 } else if (a == b) {
442 return 0;
443 } else {
444 return -1;
445 }
446 }
447
448 void G1CollectionSet::finalize_old_part(double time_remaining_ms) {
449 double non_young_start_time_sec = os::elapsedTime();
450
451 if (collector_state()->in_mixed_phase()) {
452 candidates()->verify();
453
454 uint num_initial_old_regions;
455 uint num_optional_old_regions;
456
457 _policy->calculate_old_collection_set_regions(candidates(),
458 time_remaining_ms,
459 num_initial_old_regions,
460 num_optional_old_regions);
461
462 // Prepare initial old regions.
463 move_candidates_to_collection_set(num_initial_old_regions);
464
465 // Prepare optional old regions for evacuation.
466 uint candidate_idx = candidates()->cur_idx();
467 for (uint i = 0; i < num_optional_old_regions; i++) {
468 add_optional_region(candidates()->at(candidate_idx + i));
469 }
470
471 candidates()->verify();
472 }
473
474 stop_incremental_building();
475
476 double non_young_end_time_sec = os::elapsedTime();
477 phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);
478
479 QuickSort::sort(_collection_set_regions, _collection_set_cur_length, compare_region_idx, true);
480 }
481
482 void G1CollectionSet::move_candidates_to_collection_set(uint num_old_candidate_regions) {
483 if (num_old_candidate_regions == 0) {
484 return;
485 }
486 uint candidate_idx = candidates()->cur_idx();
487 for (uint i = 0; i < num_old_candidate_regions; i++) {
488 HeapRegion* r = candidates()->at(candidate_idx + i);
489 // This potentially optional candidate region is going to be an actual collection
490 // set region. Clear cset marker.
491 _g1h->clear_region_attr(r);
492 add_old_region(r);
493 }
494 candidates()->remove(num_old_candidate_regions);
495
496 candidates()->verify();
497 }
498
499 void G1CollectionSet::finalize_initial_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {
500 double time_remaining_ms = finalize_young_part(target_pause_time_ms, survivor);
501 finalize_old_part(time_remaining_ms);
502 }
503
504 bool G1CollectionSet::finalize_optional_for_evacuation(double remaining_pause_time) {
505 update_incremental_marker();
506
507 uint num_selected_regions;
508 _policy->calculate_optional_collection_set_regions(candidates(),
509 _num_optional_regions,
510 remaining_pause_time,
511 num_selected_regions);
512
513 move_candidates_to_collection_set(num_selected_regions);
514
515 _num_optional_regions -= num_selected_regions;
516
517 stop_incremental_building();
518
519 _g1h->verify_region_attr_remset_update();
520
521 return num_selected_regions > 0;
522 }
523
524 void G1CollectionSet::abandon_optional_collection_set(G1ParScanThreadStateSet* pss) {
525 for (uint i = 0; i < _num_optional_regions; i++) {
526 HeapRegion* r = candidates()->at(candidates()->cur_idx() + i);
527 pss->record_unused_optional_region(r);
528 // Clear collection set marker and make sure that the remembered set information
529 // is correct as we still need it later.
530 _g1h->clear_region_attr(r);
531 _g1h->register_region_with_region_attr(r);
532 r->clear_index_in_opt_cset();
533 }
534 free_optional_regions();
535
536 _g1h->verify_region_attr_remset_update();
537 }
538
539 #ifdef ASSERT
540 class G1VerifyYoungCSetIndicesClosure : public HeapRegionClosure {
541 private:
542 size_t _young_length;
543 uint* _heap_region_indices;
544 public:
545 G1VerifyYoungCSetIndicesClosure(size_t young_length) : HeapRegionClosure(), _young_length(young_length) {
546 _heap_region_indices = NEW_C_HEAP_ARRAY(uint, young_length + 1, mtGC);
547 for (size_t i = 0; i < young_length + 1; i++) {
548 _heap_region_indices[i] = UINT_MAX;
549 }
550 }
551 ~G1VerifyYoungCSetIndicesClosure() {
552 FREE_C_HEAP_ARRAY(int, _heap_region_indices);
553 }
554
555 virtual bool do_heap_region(HeapRegion* r) {
556 const uint idx = r->young_index_in_cset();
557
558 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());
559 assert(idx <= _young_length, "Young cset index %u too large for region %u", idx, r->hrm_index());
560
561 assert(_heap_region_indices[idx] == UINT_MAX,
562 "Index %d used by multiple regions, first use by region %u, second by region %u",
563 idx, _heap_region_indices[idx], r->hrm_index());
564
565 _heap_region_indices[idx] = r->hrm_index();
566
567 return false;
568 }
569 };
570
571 void G1CollectionSet::verify_young_cset_indices() const {
572 assert_at_safepoint_on_vm_thread();
573
574 G1VerifyYoungCSetIndicesClosure cl(_collection_set_cur_length);
575 iterate(&cl);
576 }
577 #endif