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_bytes_used_before(0),
67 _inc_recorded_rs_lengths(0),
68 _inc_recorded_rs_lengths_diffs(0),
69 _inc_predicted_elapsed_time_ms(0.0),
70 _inc_predicted_elapsed_time_ms_diffs(0.0) {
71 }
72
73 G1CollectionSet::~G1CollectionSet() {
74 if (_collection_set_regions != NULL) {
75 FREE_C_HEAP_ARRAY(uint, _collection_set_regions);
76 }
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 _num_optional_regions = 0;
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_lengths(size_t rs_lengths) {
111 _recorded_rs_lengths = rs_lengths;
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_cset(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_lengths += 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_cset(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_lengths = 0;
151 _inc_recorded_rs_lengths_diffs = 0;
152 _inc_predicted_elapsed_time_ms = 0.0;
153 _inc_predicted_elapsed_time_ms_diffs = 0.0;
154
155 update_incremental_marker();
156 }
157
158 void G1CollectionSet::finalize_young_increment() {
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_lengths 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 *_diffs fields. Here we add the diffs to
167 // the "main" fields.
168
169 if (_inc_recorded_rs_lengths_diffs >= 0) {
170 _inc_recorded_rs_lengths += _inc_recorded_rs_lengths_diffs;
171 } else {
172 // This is defensive. The diff should in theory be always positive
173 // as RSets can only grow between GCs. However, given that we
174 // sample their size concurrently with other threads updating them
175 // it's possible that we might get the wrong size back, which
176 // could make the calculations somewhat inaccurate.
177 size_t diffs = (size_t) (-_inc_recorded_rs_lengths_diffs);
178 if (_inc_recorded_rs_lengths >= diffs) {
179 _inc_recorded_rs_lengths -= diffs;
180 } else {
181 _inc_recorded_rs_lengths = 0;
182 }
183 }
184 _inc_predicted_elapsed_time_ms += _inc_predicted_elapsed_time_ms_diffs;
185
186 _inc_recorded_rs_lengths_diffs = 0;
187 _inc_predicted_elapsed_time_ms_diffs = 0.0;
188 }
189
190 void G1CollectionSet::clear() {
191 assert_at_safepoint_on_vm_thread();
192 _collection_set_cur_length = 0;
193 }
194
195 void G1CollectionSet::iterate(HeapRegionClosure* cl) const {
196 size_t len = _collection_set_cur_length;
197 OrderAccess::loadload();
198
199 for (uint i = 0; i < len; i++) {
200 HeapRegion* r = _g1h->region_at(_collection_set_regions[i]);
201 bool result = cl->do_heap_region(r);
202 if (result) {
203 cl->set_incomplete();
204 return;
205 }
206 }
207 }
208
209 void G1CollectionSet::iterate_optional(HeapRegionClosure* cl) const {
210 assert_at_safepoint();
211
212 for (uint i = 0; i < _num_optional_regions; i++) {
213 HeapRegion* r = _candidates->at(i);
214 bool result = cl->do_heap_region(r);
215 guarantee(!result, "Must not cancel iteration");
216 }
217 }
218
219 void G1CollectionSet::iterate_incremental_part_from(HeapRegionClosure* cl, uint worker_id, uint total_workers) const {
220 assert_at_safepoint();
221
222 size_t len = _collection_set_cur_length - _inc_part_start;
223 if (len == 0) {
224 return;
225 }
226
227 size_t start_pos = (worker_id * len) / total_workers;
228 size_t cur_pos = start_pos;
229
230 do {
231 HeapRegion* r = _g1h->region_at(_collection_set_regions[cur_pos + _inc_part_start]);
232 bool result = cl->do_heap_region(r);
233 guarantee(!result, "Must not cancel iteration");
234
235 cur_pos++;
236 if (cur_pos == len) {
237 cur_pos = 0;
238 }
239 } while (cur_pos != start_pos);
240 }
241
242 void G1CollectionSet::update_young_region_prediction(HeapRegion* hr,
243 size_t new_rs_length) {
244 // Update the CSet information that is dependent on the new RS length
245 assert(hr->is_young(), "Precondition");
246 assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint");
247
248 // We could have updated _inc_recorded_rs_lengths and
249 // _inc_predicted_elapsed_time_ms directly but we'd need to do
250 // that atomically, as this code is executed by a concurrent
251 // refinement thread, potentially concurrently with a mutator thread
252 // allocating a new region and also updating the same fields. To
253 // avoid the atomic operations we accumulate these updates on two
254 // separate fields (*_diffs) and we'll just add them to the "main"
255 // fields at the start of a GC.
256
257 ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length();
258 ssize_t rs_lengths_diff = (ssize_t) new_rs_length - old_rs_length;
259 _inc_recorded_rs_lengths_diffs += rs_lengths_diff;
260
261 double old_elapsed_time_ms = hr->predicted_elapsed_time_ms();
262 double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
263 double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms;
264 _inc_predicted_elapsed_time_ms_diffs += elapsed_ms_diff;
265
266 hr->set_recorded_rs_length(new_rs_length);
267 hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms);
268 }
269
270 void G1CollectionSet::add_young_region_common(HeapRegion* hr) {
271 assert(hr->is_young(), "invariant");
272 assert(_inc_build_state == Active, "Precondition");
273
274 size_t collection_set_length = _collection_set_cur_length;
275 assert(collection_set_length <= INT_MAX, "Collection set is too large with %d entries", (int)collection_set_length);
276 hr->set_young_index_in_cset((int)collection_set_length);
277
278 _collection_set_regions[collection_set_length] = hr->hrm_index();
279 // Concurrent readers must observe the store of the value in the array before an
280 // update to the length field.
281 OrderAccess::storestore();
282 _collection_set_cur_length++;
283 assert(_collection_set_cur_length <= _collection_set_max_length, "Collection set larger than maximum allowed.");
284
285 // This routine is used when:
286 // * adding survivor regions to the incremental cset at the end of an
287 // evacuation pause or
288 // * adding the current allocation region to the incremental cset
289 // when it is retired.
290 // Therefore this routine may be called at a safepoint by the
291 // VM thread, or in-between safepoints by mutator threads (when
292 // retiring the current allocation region)
293 // We need to clear and set the cached recorded/cached collection set
294 // information in the heap region here (before the region gets added
295 // to the collection set). An individual heap region's cached values
296 // are calculated, aggregated with the policy collection set info,
297 // and cached in the heap region here (initially) and (subsequently)
298 // by the Young List sampling code.
299 // Ignore calls to this due to retirement during full gc.
300
301 if (!_g1h->collector_state()->in_full_gc()) {
302 size_t rs_length = hr->rem_set()->occupied();
303 double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
304
305 // Cache the values we have added to the aggregated information
306 // in the heap region in case we have to remove this region from
307 // the incremental collection set, or it is updated by the
308 // rset sampling code
309 hr->set_recorded_rs_length(rs_length);
310 hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms);
311
312 _inc_recorded_rs_lengths += rs_length;
313 _inc_predicted_elapsed_time_ms += region_elapsed_time_ms;
314 _inc_bytes_used_before += hr->used();
315 }
316
317 assert(!hr->in_collection_set(), "invariant");
318 _g1h->register_young_region_with_cset(hr);
319 }
320
321 void G1CollectionSet::add_survivor_regions(HeapRegion* hr) {
322 assert(hr->is_survivor(), "Must only add survivor regions, but is %s", hr->get_type_str());
323 add_young_region_common(hr);
324 }
325
326 void G1CollectionSet::add_eden_region(HeapRegion* hr) {
327 assert(hr->is_eden(), "Must only add eden regions, but is %s", hr->get_type_str());
328 add_young_region_common(hr);
329 }
330
331 #ifndef PRODUCT
332 class G1VerifyYoungAgesClosure : public HeapRegionClosure {
333 public:
334 bool _valid;
335 public:
336 G1VerifyYoungAgesClosure() : HeapRegionClosure(), _valid(true) { }
337
338 virtual bool do_heap_region(HeapRegion* r) {
339 guarantee(r->is_young(), "Region must be young but is %s", r->get_type_str());
340
341 SurvRateGroup* group = r->surv_rate_group();
342
343 if (group == NULL) {
344 log_error(gc, verify)("## encountered NULL surv_rate_group in young region");
345 _valid = false;
346 }
347
348 if (r->age_in_surv_rate_group() < 0) {
349 log_error(gc, verify)("## encountered negative age in young region");
350 _valid = false;
351 }
352
353 return false;
354 }
355
356 bool valid() const { return _valid; }
357 };
358
359 bool G1CollectionSet::verify_young_ages() {
360 assert_at_safepoint_on_vm_thread();
361
362 G1VerifyYoungAgesClosure cl;
363 iterate(&cl);
364
365 if (!cl.valid()) {
366 LogStreamHandle(Error, gc, verify) log;
367 print(&log);
368 }
369
370 return cl.valid();
371 }
372
373 class G1PrintCollectionSetDetailClosure : public HeapRegionClosure {
374 outputStream* _st;
375 public:
376 G1PrintCollectionSetDetailClosure(outputStream* st) : HeapRegionClosure(), _st(st) { }
377
378 virtual bool do_heap_region(HeapRegion* r) {
379 assert(r->in_collection_set(), "Region %u should be in collection set", r->hrm_index());
380 _st->print_cr(" " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d",
381 HR_FORMAT_PARAMS(r),
382 p2i(r->prev_top_at_mark_start()),
383 p2i(r->next_top_at_mark_start()),
384 r->age_in_surv_rate_group_cond());
385 return false;
386 }
387 };
388
389 void G1CollectionSet::print(outputStream* st) {
390 st->print_cr("\nCollection_set:");
391
392 G1PrintCollectionSetDetailClosure cl(st);
393 iterate(&cl);
394 }
395 #endif // !PRODUCT
396
397 double G1CollectionSet::finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors) {
398 double young_start_time_sec = os::elapsedTime();
399
400 finalize_young_increment();
401
402 guarantee(target_pause_time_ms > 0.0,
403 "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms);
404
405 size_t pending_cards = _policy->pending_cards();
406 double base_time_ms = _policy->predict_base_elapsed_time_ms(pending_cards);
407 double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0);
408
409 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",
410 pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms);
411
412 // The young list is laid with the survivor regions from the previous
413 // pause are appended to the RHS of the young list, i.e.
414 // [Newly Young Regions ++ Survivors from last pause].
415
416 uint survivor_region_length = survivors->length();
417 uint eden_region_length = _g1h->eden_regions_count();
418 init_region_lengths(eden_region_length, survivor_region_length);
419
420 verify_young_cset_indices();
421
422 // Clear the fields that point to the survivor list - they are all young now.
423 survivors->convert_to_eden();
424
425 _bytes_used_before = _inc_bytes_used_before;
426 time_remaining_ms = MAX2(time_remaining_ms - _inc_predicted_elapsed_time_ms, 0.0);
427
428 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",
429 eden_region_length, survivor_region_length, _inc_predicted_elapsed_time_ms, target_pause_time_ms);
430
431 // The number of recorded young regions is the incremental
432 // collection set's current size
433 set_recorded_rs_lengths(_inc_recorded_rs_lengths);
434
435 double young_end_time_sec = os::elapsedTime();
436 phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0);
437
438 return time_remaining_ms;
439 }
440
441 static int compare_region_idx(const uint a, const uint b) {
442 if (a > b) {
443 return 1;
444 } else if (a == b) {
445 return 0;
446 } else {
447 return -1;
448 }
449 }
450
451 void G1CollectionSet::finalize_old_part(double time_remaining_ms) {
452 double non_young_start_time_sec = os::elapsedTime();
453
454 uint num_expensive_regions = 0;
455
456 if (collector_state()->in_mixed_phase()) {
457 candidates()->verify();
458
459 uint num_initial_regions;
460 uint num_optional_regions;
461
462 _policy->select_old_collection_set_regions(candidates(),
463 time_remaining_ms,
464 num_expensive_regions,
465 num_initial_regions,
466 num_optional_regions);
467
468 // Prepare initial old regions.
469 move_candidates_to_collection_set(num_initial_regions);
470
471 // Prepare optional regions for evacuation.
472 uint candidate_idx = candidates()->cur_idx();
473 for (uint i = 0; i < num_optional_regions; i++) {
474 add_optional_region(candidates()->at(candidate_idx + i));
475 }
476
477 candidates()->verify();
478 }
479
480 stop_incremental_building();
481
482 double non_young_end_time_sec = os::elapsedTime();
483 phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);
484
485 QuickSort::sort(_collection_set_regions, _collection_set_cur_length, compare_region_idx, true);
486 }
487
488 void G1CollectionSet::move_candidates_to_collection_set(uint num_old_candidate_regions) {
489 if (num_old_candidate_regions == 0) {
490 return;
491 }
492 uint candidate_idx = candidates()->cur_idx();
493 for (uint i = 0; i < num_old_candidate_regions; i++) {
494 HeapRegion* r = candidates()->at(candidate_idx + i);
495 // This potentially optional candidate region is going to be an actual collection
496 // set region. Clear cset marker.
497 _g1h->clear_in_cset(r);
498 add_old_region(r);
499 }
500 candidates()->remove(num_old_candidate_regions);
501
502 candidates()->verify();
503 }
504
505 void G1CollectionSet::finalize_initial_collection_set(double target_pause_time_ms, G1SurvivorRegions* survivor) {
506 double time_remaining_ms = finalize_young_part(target_pause_time_ms, survivor);
507 finalize_old_part(time_remaining_ms);
508 }
509
510 bool G1CollectionSet::finalize_optional_for_evacuation(double remaining_pause_time) {
511 update_incremental_marker();
512
513 uint num_selected_regions;
514 _policy->select_optional_collection_set_regions(candidates(),
515 _num_optional_regions,
516 remaining_pause_time,
517 num_selected_regions);
518
519 move_candidates_to_collection_set(num_selected_regions);
520
521 _num_optional_regions -= num_selected_regions;
522
523 stop_incremental_building();
524 return num_selected_regions > 0;
525 }
526
527 void G1CollectionSet::abandon_optional_collection_set(G1ParScanThreadStateSet* pss) {
528 for (uint i = 0; i < _num_optional_regions; i++) {
529 HeapRegion* r = candidates()->at(candidates()->cur_idx() + i);
530 pss->record_unused_optional_region(r);
531 _g1h->clear_in_cset(r);
532 r->clear_index_in_opt_cset();
533 }
534 _num_optional_regions = 0;
535 }
536
537 #ifdef ASSERT
538 class G1VerifyYoungCSetIndicesClosure : public HeapRegionClosure {
539 private:
540 size_t _young_length;
541 int* _heap_region_indices;
542 public:
543 G1VerifyYoungCSetIndicesClosure(size_t young_length) : HeapRegionClosure(), _young_length(young_length) {
544 _heap_region_indices = NEW_C_HEAP_ARRAY(int, young_length, mtGC);
545 for (size_t i = 0; i < young_length; i++) {
546 _heap_region_indices[i] = -1;
547 }
548 }
549 ~G1VerifyYoungCSetIndicesClosure() {
550 FREE_C_HEAP_ARRAY(int, _heap_region_indices);
551 }
552
553 virtual bool do_heap_region(HeapRegion* r) {
554 const int idx = r->young_index_in_cset();
555
556 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());
557 assert((size_t)idx < _young_length, "Young cset index too large for region %u", r->hrm_index());
558
559 assert(_heap_region_indices[idx] == -1,
560 "Index %d used by multiple regions, first use by region %u, second by region %u",
561 idx, _heap_region_indices[idx], r->hrm_index());
562
563 _heap_region_indices[idx] = r->hrm_index();
564
565 return false;
566 }
567 };
568
569 void G1CollectionSet::verify_young_cset_indices() const {
570 assert_at_safepoint_on_vm_thread();
571
572 G1VerifyYoungCSetIndicesClosure cl(_collection_set_cur_length);
573 iterate(&cl);
574 }
575 #endif