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