1 /*
2 * Copyright (c) 2001, 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/g1Arguments.hpp"
27 #include "gc/g1/g1CollectedHeap.inline.hpp"
28 #include "gc/g1/g1ConcurrentRefine.hpp"
29 #include "gc/g1/g1NUMAStats.hpp"
30 #include "gc/g1/heapRegion.hpp"
31 #include "gc/g1/heapRegionManager.inline.hpp"
32 #include "gc/g1/heapRegionSet.inline.hpp"
33 #include "gc/g1/heterogeneousHeapRegionManager.hpp"
34 #include "logging/logStream.hpp"
35 #include "memory/allocation.hpp"
36 #include "runtime/atomic.hpp"
37 #include "runtime/orderAccess.hpp"
38 #include "utilities/bitMap.inline.hpp"
39
40 class MasterFreeRegionListChecker : public HeapRegionSetChecker {
41 public:
42 void check_mt_safety() {
43 // Master Free List MT safety protocol:
44 // (a) If we're at a safepoint, operations on the master free list
45 // should be invoked by either the VM thread (which will serialize
46 // them) or by the GC workers while holding the
47 // FreeList_lock.
48 // (b) If we're not at a safepoint, operations on the master free
49 // list should be invoked while holding the Heap_lock.
50
51 if (SafepointSynchronize::is_at_safepoint()) {
52 guarantee(Thread::current()->is_VM_thread() ||
53 FreeList_lock->owned_by_self(), "master free list MT safety protocol at a safepoint");
54 } else {
55 guarantee(Heap_lock->owned_by_self(), "master free list MT safety protocol outside a safepoint");
56 }
57 }
58 bool is_correct_type(HeapRegion* hr) { return hr->is_free(); }
59 const char* get_description() { return "Free Regions"; }
60 };
61
62 HeapRegionManager::HeapRegionManager() :
63 _bot_mapper(NULL),
64 _cardtable_mapper(NULL),
65 _card_counts_mapper(NULL),
66 _available_map(mtGC),
67 _num_committed(0),
68 _allocated_heapregions_length(0),
69 _regions(), _heap_mapper(NULL),
70 _prev_bitmap_mapper(NULL),
71 _next_bitmap_mapper(NULL),
72 _free_list("Free list", new MasterFreeRegionListChecker())
73 { }
74
75 HeapRegionManager* HeapRegionManager::create_manager(G1CollectedHeap* heap) {
76 if (G1Arguments::is_heterogeneous_heap()) {
77 return new HeterogeneousHeapRegionManager((uint)(G1Arguments::heap_max_size_bytes() / HeapRegion::GrainBytes) /*heap size as num of regions*/);
78 }
79 return new HeapRegionManager();
80 }
81
82 void HeapRegionManager::initialize(G1RegionToSpaceMapper* heap_storage,
83 G1RegionToSpaceMapper* prev_bitmap,
84 G1RegionToSpaceMapper* next_bitmap,
85 G1RegionToSpaceMapper* bot,
86 G1RegionToSpaceMapper* cardtable,
87 G1RegionToSpaceMapper* card_counts) {
88 _allocated_heapregions_length = 0;
89
90 _heap_mapper = heap_storage;
91
92 _prev_bitmap_mapper = prev_bitmap;
93 _next_bitmap_mapper = next_bitmap;
94
95 _bot_mapper = bot;
96 _cardtable_mapper = cardtable;
97
98 _card_counts_mapper = card_counts;
99
100 MemRegion reserved = heap_storage->reserved();
101 _regions.initialize(reserved.start(), reserved.end(), HeapRegion::GrainBytes);
102
103 _available_map.initialize(_regions.length());
104 }
105
106 bool HeapRegionManager::is_available(uint region) const {
107 return _available_map.at(region);
108 }
109
110 HeapRegion* HeapRegionManager::allocate_free_region(HeapRegionType type, uint requested_node_index) {
111 HeapRegion* hr = NULL;
112 bool from_head = !type.is_young();
113 G1NUMA* numa = G1NUMA::numa();
114
115 if (requested_node_index != G1NUMA::AnyNodeIndex && numa->is_enabled()) {
116 // Try to allocate with requested node index.
117 hr = _free_list.remove_region_with_node_index(from_head, requested_node_index);
118 }
119
120 if (hr == NULL) {
121 // If there's a single active node or we did not get a region from our requested node,
122 // try without requested node index.
123 hr = _free_list.remove_region(from_head);
124 }
125
126 if (hr != NULL) {
127 assert(hr->next() == NULL, "Single region should not have next");
128 assert(is_available(hr->hrm_index()), "Must be committed");
129
130 if (numa->is_enabled() && hr->node_index() < numa->num_active_nodes()) {
131 numa->update_statistics(G1NUMAStats::NewRegionAlloc, requested_node_index, hr->node_index());
132 }
133 }
134
135 return hr;
136 }
137
138 #ifdef ASSERT
139 bool HeapRegionManager::is_free(HeapRegion* hr) const {
140 return _free_list.contains(hr);
141 }
142 #endif
143
144 HeapRegion* HeapRegionManager::new_heap_region(uint hrm_index) {
145 G1CollectedHeap* g1h = G1CollectedHeap::heap();
146 HeapWord* bottom = g1h->bottom_addr_for_region(hrm_index);
147 MemRegion mr(bottom, bottom + HeapRegion::GrainWords);
148 assert(reserved().contains(mr), "invariant");
149 return g1h->new_heap_region(hrm_index, mr);
150 }
151
152 void HeapRegionManager::commit_regions(uint index, size_t num_regions, WorkGang* pretouch_gang) {
153 guarantee(num_regions > 0, "Must commit more than zero regions");
154 guarantee(_num_committed + num_regions <= max_length(), "Cannot commit more than the maximum amount of regions");
155
156 _num_committed += (uint)num_regions;
157
158 _heap_mapper->commit_regions(index, num_regions, pretouch_gang);
159
160 // Also commit auxiliary data
161 _prev_bitmap_mapper->commit_regions(index, num_regions, pretouch_gang);
162 _next_bitmap_mapper->commit_regions(index, num_regions, pretouch_gang);
163
164 _bot_mapper->commit_regions(index, num_regions, pretouch_gang);
165 _cardtable_mapper->commit_regions(index, num_regions, pretouch_gang);
166
167 _card_counts_mapper->commit_regions(index, num_regions, pretouch_gang);
168 }
169
170 void HeapRegionManager::uncommit_regions(uint start, size_t num_regions) {
171 guarantee(num_regions >= 1, "Need to specify at least one region to uncommit, tried to uncommit zero regions at %u", start);
172 guarantee(_num_committed >= num_regions, "pre-condition");
173
174 // Reset node index to distinguish with committed regions.
175 for (uint i = start; i < start + num_regions; i++) {
176 at(i)->set_node_index(G1NUMA::UnknownNodeIndex);
177 }
178
179 // Print before uncommitting.
180 if (G1CollectedHeap::heap()->hr_printer()->is_active()) {
181 for (uint i = start; i < start + num_regions; i++) {
182 HeapRegion* hr = at(i);
183 G1CollectedHeap::heap()->hr_printer()->uncommit(hr);
184 }
185 }
186
187 _num_committed -= (uint)num_regions;
188
189 _available_map.par_clear_range(start, start + num_regions, BitMap::unknown_range);
190 _heap_mapper->uncommit_regions(start, num_regions);
191
192 // Also uncommit auxiliary data
193 _prev_bitmap_mapper->uncommit_regions(start, num_regions);
194 _next_bitmap_mapper->uncommit_regions(start, num_regions);
195
196 _bot_mapper->uncommit_regions(start, num_regions);
197 _cardtable_mapper->uncommit_regions(start, num_regions);
198
199 _card_counts_mapper->uncommit_regions(start, num_regions);
200 }
201
202 void HeapRegionManager::make_regions_available(uint start, uint num_regions, WorkGang* pretouch_gang) {
203 guarantee(num_regions > 0, "No point in calling this for zero regions");
204 commit_regions(start, num_regions, pretouch_gang);
205 for (uint i = start; i < start + num_regions; i++) {
206 if (_regions.get_by_index(i) == NULL) {
207 HeapRegion* new_hr = new_heap_region(i);
208 OrderAccess::storestore();
209 _regions.set_by_index(i, new_hr);
210 _allocated_heapregions_length = MAX2(_allocated_heapregions_length, i + 1);
211 }
212 }
213
214 _available_map.par_set_range(start, start + num_regions, BitMap::unknown_range);
215
216 for (uint i = start; i < start + num_regions; i++) {
217 assert(is_available(i), "Just made region %u available but is apparently not.", i);
218 HeapRegion* hr = at(i);
219 if (G1CollectedHeap::heap()->hr_printer()->is_active()) {
220 G1CollectedHeap::heap()->hr_printer()->commit(hr);
221 }
222
223 hr->initialize();
224 hr->set_node_index(G1NUMA::numa()->index_for_region(hr));
225 insert_into_free_list(at(i));
226 }
227 }
228
229 MemoryUsage HeapRegionManager::get_auxiliary_data_memory_usage() const {
230 size_t used_sz =
231 _prev_bitmap_mapper->committed_size() +
232 _next_bitmap_mapper->committed_size() +
233 _bot_mapper->committed_size() +
234 _cardtable_mapper->committed_size() +
235 _card_counts_mapper->committed_size();
236
237 size_t committed_sz =
238 _prev_bitmap_mapper->reserved_size() +
239 _next_bitmap_mapper->reserved_size() +
240 _bot_mapper->reserved_size() +
241 _cardtable_mapper->reserved_size() +
242 _card_counts_mapper->reserved_size();
243
244 return MemoryUsage(0, used_sz, committed_sz, committed_sz);
245 }
246
247 uint HeapRegionManager::expand_by(uint num_regions, WorkGang* pretouch_workers) {
248 return expand_at(0, num_regions, pretouch_workers);
249 }
250
251 uint HeapRegionManager::expand_at(uint start, uint num_regions, WorkGang* pretouch_workers) {
252 if (num_regions == 0) {
253 return 0;
254 }
255
256 uint cur = start;
257 uint idx_last_found = 0;
258 uint num_last_found = 0;
259
260 uint expanded = 0;
261
262 while (expanded < num_regions &&
263 (num_last_found = find_unavailable_from_idx(cur, &idx_last_found)) > 0) {
264 uint to_expand = MIN2(num_regions - expanded, num_last_found);
265 make_regions_available(idx_last_found, to_expand, pretouch_workers);
266 expanded += to_expand;
267 cur = idx_last_found + num_last_found + 1;
268 }
269
270 verify_optional();
271 return expanded;
272 }
273
274 uint HeapRegionManager::expand_on_preferred_node(uint preferred_index) {
275 uint expand_candidate = UINT_MAX;
276 for (uint i = 0; i < max_length(); i++) {
277 if (is_available(i)) {
278 // Already in use continue
279 continue;
280 }
281 // Always save the candidate so we can expand later on.
282 expand_candidate = i;
283 if (is_on_preferred_index(expand_candidate, preferred_index)) {
284 // We have found a candidate on the preffered node, break.
285 break;
286 }
287 }
288
289 if (expand_candidate == UINT_MAX) {
290 // No regions left, expand failed.
291 return 0;
292 }
293
294 make_regions_available(expand_candidate, 1, NULL);
295 return 1;
296 }
297
298 bool HeapRegionManager::is_on_preferred_index(uint region_index, uint preferred_node_index) {
299 uint region_node_index = G1NUMA::numa()->preferred_node_index_for_index(region_index);
300 return region_node_index == preferred_node_index;
301 }
302
303 uint HeapRegionManager::find_contiguous(size_t num, bool empty_only) {
304 uint found = 0;
305 size_t length_found = 0;
306 uint cur = 0;
307
308 while (length_found < num && cur < max_length()) {
309 HeapRegion* hr = _regions.get_by_index(cur);
310 if ((!empty_only && !is_available(cur)) || (is_available(cur) && hr != NULL && hr->is_empty())) {
311 // This region is a potential candidate for allocation into.
312 length_found++;
313 } else {
314 // This region is not a candidate. The next region is the next possible one.
315 found = cur + 1;
316 length_found = 0;
317 }
318 cur++;
319 }
320
321 if (length_found == num) {
322 for (uint i = found; i < (found + num); i++) {
323 HeapRegion* hr = _regions.get_by_index(i);
324 // sanity check
325 guarantee((!empty_only && !is_available(i)) || (is_available(i) && hr != NULL && hr->is_empty()),
326 "Found region sequence starting at " UINT32_FORMAT ", length " SIZE_FORMAT
327 " that is not empty at " UINT32_FORMAT ". Hr is " PTR_FORMAT, found, num, i, p2i(hr));
328 }
329 return found;
330 } else {
331 return G1_NO_HRM_INDEX;
332 }
333 }
334
335 HeapRegion* HeapRegionManager::next_region_in_heap(const HeapRegion* r) const {
336 guarantee(r != NULL, "Start region must be a valid region");
337 guarantee(is_available(r->hrm_index()), "Trying to iterate starting from region %u which is not in the heap", r->hrm_index());
338 for (uint i = r->hrm_index() + 1; i < _allocated_heapregions_length; i++) {
339 HeapRegion* hr = _regions.get_by_index(i);
340 if (is_available(i)) {
341 return hr;
342 }
343 }
344 return NULL;
345 }
346
347 void HeapRegionManager::iterate(HeapRegionClosure* blk) const {
348 uint len = max_length();
349
350 for (uint i = 0; i < len; i++) {
351 if (!is_available(i)) {
352 continue;
353 }
354 guarantee(at(i) != NULL, "Tried to access region %u that has a NULL HeapRegion*", i);
355 bool res = blk->do_heap_region(at(i));
356 if (res) {
357 blk->set_incomplete();
358 return;
359 }
360 }
361 }
362
363 uint HeapRegionManager::find_unavailable_from_idx(uint start_idx, uint* res_idx) const {
364 guarantee(res_idx != NULL, "checking");
365 guarantee(start_idx <= (max_length() + 1), "checking");
366
367 uint num_regions = 0;
368
369 uint cur = start_idx;
370 while (cur < max_length() && is_available(cur)) {
371 cur++;
372 }
373 if (cur == max_length()) {
374 return num_regions;
375 }
376 *res_idx = cur;
377 while (cur < max_length() && !is_available(cur)) {
378 cur++;
379 }
380 num_regions = cur - *res_idx;
381 #ifdef ASSERT
382 for (uint i = *res_idx; i < (*res_idx + num_regions); i++) {
383 assert(!is_available(i), "just checking");
384 }
385 assert(cur == max_length() || num_regions == 0 || is_available(cur),
386 "The region at the current position %u must be available or at the end of the heap.", cur);
387 #endif
388 return num_regions;
389 }
390
391 uint HeapRegionManager::find_highest_free(bool* expanded) {
392 // Loop downwards from the highest region index, looking for an
393 // entry which is either free or not yet committed. If not yet
394 // committed, expand_at that index.
395 uint curr = max_length() - 1;
396 while (true) {
397 HeapRegion *hr = _regions.get_by_index(curr);
398 if (hr == NULL || !is_available(curr)) {
399 uint res = expand_at(curr, 1, NULL);
400 if (res == 1) {
401 *expanded = true;
402 return curr;
403 }
404 } else {
405 if (hr->is_free()) {
406 *expanded = false;
407 return curr;
408 }
409 }
410 if (curr == 0) {
411 return G1_NO_HRM_INDEX;
412 }
413 curr--;
414 }
415 }
416
417 bool HeapRegionManager::allocate_containing_regions(MemRegion range, size_t* commit_count, WorkGang* pretouch_workers) {
418 size_t commits = 0;
419 uint start_index = (uint)_regions.get_index_by_address(range.start());
420 uint last_index = (uint)_regions.get_index_by_address(range.last());
421
422 // Ensure that each G1 region in the range is free, returning false if not.
423 // Commit those that are not yet available, and keep count.
424 for (uint curr_index = start_index; curr_index <= last_index; curr_index++) {
425 if (!is_available(curr_index)) {
426 commits++;
427 expand_at(curr_index, 1, pretouch_workers);
428 }
429 HeapRegion* curr_region = _regions.get_by_index(curr_index);
430 if (!curr_region->is_free()) {
431 return false;
432 }
433 }
434
435 allocate_free_regions_starting_at(start_index, (last_index - start_index) + 1);
436 *commit_count = commits;
437 return true;
438 }
439
440 void HeapRegionManager::par_iterate(HeapRegionClosure* blk, HeapRegionClaimer* hrclaimer, const uint start_index) const {
441 // Every worker will actually look at all regions, skipping over regions that
442 // are currently not committed.
443 // This also (potentially) iterates over regions newly allocated during GC. This
444 // is no problem except for some extra work.
445 const uint n_regions = hrclaimer->n_regions();
446 for (uint count = 0; count < n_regions; count++) {
447 const uint index = (start_index + count) % n_regions;
448 assert(index < n_regions, "sanity");
449 // Skip over unavailable regions
450 if (!is_available(index)) {
451 continue;
452 }
453 HeapRegion* r = _regions.get_by_index(index);
454 // We'll ignore regions already claimed.
455 // However, if the iteration is specified as concurrent, the values for
456 // is_starts_humongous and is_continues_humongous can not be trusted,
457 // and we should just blindly iterate over regions regardless of their
458 // humongous status.
459 if (hrclaimer->is_region_claimed(index)) {
460 continue;
461 }
462 // OK, try to claim it
463 if (!hrclaimer->claim_region(index)) {
464 continue;
465 }
466 bool res = blk->do_heap_region(r);
467 if (res) {
468 return;
469 }
470 }
471 }
472
473 uint HeapRegionManager::shrink_by(uint num_regions_to_remove) {
474 assert(length() > 0, "the region sequence should not be empty");
475 assert(length() <= _allocated_heapregions_length, "invariant");
476 assert(_allocated_heapregions_length > 0, "we should have at least one region committed");
477 assert(num_regions_to_remove < length(), "We should never remove all regions");
478
479 if (num_regions_to_remove == 0) {
480 return 0;
481 }
482
483 uint removed = 0;
484 uint cur = _allocated_heapregions_length - 1;
485 uint idx_last_found = 0;
486 uint num_last_found = 0;
487
488 while ((removed < num_regions_to_remove) &&
489 (num_last_found = find_empty_from_idx_reverse(cur, &idx_last_found)) > 0) {
490 uint to_remove = MIN2(num_regions_to_remove - removed, num_last_found);
491
492 shrink_at(idx_last_found + num_last_found - to_remove, to_remove);
493
494 cur = idx_last_found;
495 removed += to_remove;
496 }
497
498 verify_optional();
499
500 return removed;
501 }
502
503 void HeapRegionManager::shrink_at(uint index, size_t num_regions) {
504 #ifdef ASSERT
505 for (uint i = index; i < (index + num_regions); i++) {
506 assert(is_available(i), "Expected available region at index %u", i);
507 assert(at(i)->is_empty(), "Expected empty region at index %u", i);
508 assert(at(i)->is_free(), "Expected free region at index %u", i);
509 }
510 #endif
511 uncommit_regions(index, num_regions);
512 }
513
514 uint HeapRegionManager::find_empty_from_idx_reverse(uint start_idx, uint* res_idx) const {
515 guarantee(start_idx < _allocated_heapregions_length, "checking");
516 guarantee(res_idx != NULL, "checking");
517
518 uint num_regions_found = 0;
519
520 jlong cur = start_idx;
521 while (cur != -1 && !(is_available(cur) && at(cur)->is_empty())) {
522 cur--;
523 }
524 if (cur == -1) {
525 return num_regions_found;
526 }
527 jlong old_cur = cur;
528 // cur indexes the first empty region
529 while (cur != -1 && is_available(cur) && at(cur)->is_empty()) {
530 cur--;
531 }
532 *res_idx = cur + 1;
533 num_regions_found = old_cur - cur;
534
535 #ifdef ASSERT
536 for (uint i = *res_idx; i < (*res_idx + num_regions_found); i++) {
537 assert(at(i)->is_empty(), "just checking");
538 }
539 #endif
540 return num_regions_found;
541 }
542
543 void HeapRegionManager::verify() {
544 guarantee(length() <= _allocated_heapregions_length,
545 "invariant: _length: %u _allocated_length: %u",
546 length(), _allocated_heapregions_length);
547 guarantee(_allocated_heapregions_length <= max_length(),
548 "invariant: _allocated_length: %u _max_length: %u",
549 _allocated_heapregions_length, max_length());
550
551 bool prev_committed = true;
552 uint num_committed = 0;
553 HeapWord* prev_end = heap_bottom();
554 for (uint i = 0; i < _allocated_heapregions_length; i++) {
555 if (!is_available(i)) {
556 prev_committed = false;
557 continue;
558 }
559 num_committed++;
560 HeapRegion* hr = _regions.get_by_index(i);
561 guarantee(hr != NULL, "invariant: i: %u", i);
562 guarantee(!prev_committed || hr->bottom() == prev_end,
563 "invariant i: %u " HR_FORMAT " prev_end: " PTR_FORMAT,
564 i, HR_FORMAT_PARAMS(hr), p2i(prev_end));
565 guarantee(hr->hrm_index() == i,
566 "invariant: i: %u hrm_index(): %u", i, hr->hrm_index());
567 // Asserts will fire if i is >= _length
568 HeapWord* addr = hr->bottom();
569 guarantee(addr_to_region(addr) == hr, "sanity");
570 // We cannot check whether the region is part of a particular set: at the time
571 // this method may be called, we have only completed allocation of the regions,
572 // but not put into a region set.
573 prev_committed = true;
574 prev_end = hr->end();
575 }
576 for (uint i = _allocated_heapregions_length; i < max_length(); i++) {
577 guarantee(_regions.get_by_index(i) == NULL, "invariant i: %u", i);
578 }
579
580 guarantee(num_committed == _num_committed, "Found %u committed regions, but should be %u", num_committed, _num_committed);
581 _free_list.verify();
582 }
583
584 #ifndef PRODUCT
585 void HeapRegionManager::verify_optional() {
586 verify();
587 }
588 #endif // PRODUCT
589
590 HeapRegionClaimer::HeapRegionClaimer(uint n_workers) :
591 _n_workers(n_workers), _n_regions(G1CollectedHeap::heap()->_hrm->_allocated_heapregions_length), _claims(NULL) {
592 assert(n_workers > 0, "Need at least one worker.");
593 uint* new_claims = NEW_C_HEAP_ARRAY(uint, _n_regions, mtGC);
594 memset(new_claims, Unclaimed, sizeof(*_claims) * _n_regions);
595 _claims = new_claims;
596 }
597
598 HeapRegionClaimer::~HeapRegionClaimer() {
599 FREE_C_HEAP_ARRAY(uint, _claims);
600 }
601
602 uint HeapRegionClaimer::offset_for_worker(uint worker_id) const {
603 assert(worker_id < _n_workers, "Invalid worker_id.");
604 return _n_regions * worker_id / _n_workers;
605 }
606
607 bool HeapRegionClaimer::is_region_claimed(uint region_index) const {
608 assert(region_index < _n_regions, "Invalid index.");
609 return _claims[region_index] == Claimed;
610 }
611
612 bool HeapRegionClaimer::claim_region(uint region_index) {
613 assert(region_index < _n_regions, "Invalid index.");
614 uint old_val = Atomic::cmpxchg(&_claims[region_index], Unclaimed, Claimed);
615 return old_val == Unclaimed;
616 }
617
618 class G1RebuildFreeListTask : public AbstractGangTask {
619 HeapRegionManager* _hrm;
620 FreeRegionList* _worker_freelists;
621 uint _worker_chunk_size;
622 uint _num_workers;
623
624 public:
625 G1RebuildFreeListTask(HeapRegionManager* hrm, uint num_workers) :
626 AbstractGangTask("G1 Rebuild Free List Task"),
627 _hrm(hrm),
628 _worker_freelists(NEW_C_HEAP_ARRAY(FreeRegionList, num_workers, mtGC)),
629 _worker_chunk_size((_hrm->max_length() + num_workers - 1) / num_workers),
630 _num_workers(num_workers) {
631 for (uint worker = 0; worker < _num_workers; worker++) {
632 ::new (&_worker_freelists[worker]) FreeRegionList("Appendable Worker Free List");
633 }
634 }
635
636 ~G1RebuildFreeListTask() {
637 for (uint worker = 0; worker < _num_workers; worker++) {
638 _worker_freelists[worker].~FreeRegionList();
639 }
640 FREE_C_HEAP_ARRAY(FreeRegionList, _worker_freelists);
641 }
642
643 FreeRegionList* worker_freelist(uint worker) {
644 return &_worker_freelists[worker];
645 }
646
647 // Each worker creates a free list for a chunk of the heap. The chunks won't
648 // be overlapping so we don't need to do any claiming.
649 void work(uint worker_id) {
650 Ticks start_time = Ticks::now();
651 EventGCPhaseParallel event;
652
653 uint start = worker_id * _worker_chunk_size;
654 uint end = MIN2(start + _worker_chunk_size, _hrm->max_length());
655
656 // If start is outside the heap, this worker has nothing to do.
657 if (start > end) {
658 return;
659 }
660
661 FreeRegionList *free_list = worker_freelist(worker_id);
662 for (uint i = start; i < end; i++) {
663 HeapRegion *region = _hrm->at_or_null(i);
664 if (region != NULL && region->is_free()) {
665 // Need to clear old links to allow to be added to new freelist.
666 region->unlink_from_list();
667 free_list->add_to_tail(region);
668 }
669 }
670
671 event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::RebuildFreeList));
672 G1CollectedHeap::heap()->phase_times()->record_time_secs(G1GCPhaseTimes::RebuildFreeList, worker_id, (Ticks::now() - start_time).seconds());
673 }
674 };
675
676 void HeapRegionManager::rebuild_free_list(WorkGang* workers) {
677 // Abandon current free list to allow a rebuild.
678 _free_list.abandon();
679
680 uint const num_workers = clamp(max_length(), 1u, workers->active_workers());
681 G1RebuildFreeListTask task(this, num_workers);
682
683 log_debug(gc, ergo)("Running %s using %u workers for rebuilding free list of %u (%u) regions",
684 task.name(), num_workers, num_free_regions(), max_length());
685 workers->run_task(&task, num_workers);
686
687 // Link the partial free lists together.
688 Ticks serial_time = Ticks::now();
689 for (uint worker = 0; worker < num_workers; worker++) {
690 _free_list.append_ordered(task.worker_freelist(worker));
691 }
692 G1CollectedHeap::heap()->phase_times()->record_serial_rebuild_freelist_time_ms((Ticks::now() - serial_time).seconds() * 1000.0);
693 }