1 /*
2 * Copyright (c) 2015, 2024, 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 #include "precompiled.hpp"
25 #include "gc/shared/gc_globals.hpp"
26 #include "gc/shared/suspendibleThreadSet.hpp"
27 #include "gc/z/zAbort.inline.hpp"
28 #include "gc/z/zAddress.inline.hpp"
29 #include "gc/z/zAllocator.inline.hpp"
30 #include "gc/z/zBarrier.inline.hpp"
31 #include "gc/z/zCollectedHeap.hpp"
32 #include "gc/z/zForwarding.inline.hpp"
33 #include "gc/z/zGeneration.inline.hpp"
34 #include "gc/z/zHeap.inline.hpp"
35 #include "gc/z/zIndexDistributor.inline.hpp"
36 #include "gc/z/zIterator.inline.hpp"
37 #include "gc/z/zPage.inline.hpp"
38 #include "gc/z/zPageAge.hpp"
39 #include "gc/z/zRelocate.hpp"
40 #include "gc/z/zRelocationSet.inline.hpp"
41 #include "gc/z/zRootsIterator.hpp"
42 #include "gc/z/zStackWatermark.hpp"
43 #include "gc/z/zStat.hpp"
44 #include "gc/z/zTask.hpp"
45 #include "gc/z/zUncoloredRoot.inline.hpp"
46 #include "gc/z/zVerify.hpp"
47 #include "gc/z/zWorkers.hpp"
48 #include "prims/jvmtiTagMap.hpp"
49 #include "runtime/atomic.hpp"
50 #include "utilities/debug.hpp"
51
52 static const ZStatCriticalPhase ZCriticalPhaseRelocationStall("Relocation Stall");
53 static const ZStatSubPhase ZSubPhaseConcurrentRelocateRememberedSetFlipPromotedYoung("Concurrent Relocate Remset FP", ZGenerationId::young);
54
55 ZRelocateQueue::ZRelocateQueue()
56 : _lock(),
57 _queue(),
58 _nworkers(0),
59 _nsynchronized(0),
60 _synchronize(false),
61 _is_active(false),
62 _needs_attention(0) {}
63
64 bool ZRelocateQueue::needs_attention() const {
65 return Atomic::load(&_needs_attention) != 0;
66 }
67
68 void ZRelocateQueue::inc_needs_attention() {
69 const int needs_attention = Atomic::add(&_needs_attention, 1);
70 assert(needs_attention == 1 || needs_attention == 2, "Invalid state");
71 }
72
73 void ZRelocateQueue::dec_needs_attention() {
74 const int needs_attention = Atomic::sub(&_needs_attention, 1);
75 assert(needs_attention == 0 || needs_attention == 1, "Invalid state");
76 }
77
78 void ZRelocateQueue::activate(uint nworkers) {
79 _is_active = true;
80 join(nworkers);
81 }
82
83 void ZRelocateQueue::deactivate() {
84 Atomic::store(&_is_active, false);
85 clear();
86 }
87
88 bool ZRelocateQueue::is_active() const {
89 return Atomic::load(&_is_active);
90 }
91
92 void ZRelocateQueue::join(uint nworkers) {
93 assert(nworkers != 0, "Must request at least one worker");
94 assert(_nworkers == 0, "Invalid state");
95 assert(_nsynchronized == 0, "Invalid state");
96
97 log_debug(gc, reloc)("Joining workers: %u", nworkers);
98
99 _nworkers = nworkers;
100 }
101
102 void ZRelocateQueue::resize_workers(uint nworkers) {
103 assert(nworkers != 0, "Must request at least one worker");
104 assert(_nworkers == 0, "Invalid state");
105 assert(_nsynchronized == 0, "Invalid state");
106
107 log_debug(gc, reloc)("Resize workers: %u", nworkers);
108
109 ZLocker<ZConditionLock> locker(&_lock);
110 _nworkers = nworkers;
111 }
112
113 void ZRelocateQueue::leave() {
114 ZLocker<ZConditionLock> locker(&_lock);
115 _nworkers--;
116
117 assert(_nsynchronized <= _nworkers, "_nsynchronized: %u _nworkers: %u", _nsynchronized, _nworkers);
118
119 log_debug(gc, reloc)("Leaving workers: left: %u _synchronize: %d _nsynchronized: %u", _nworkers, _synchronize, _nsynchronized);
120
121 // Prune done forwardings
122 const bool forwardings_done = prune();
123
124 // Check if all workers synchronized
125 const bool last_synchronized = _synchronize && _nworkers == _nsynchronized;
126
127 if (forwardings_done || last_synchronized) {
128 _lock.notify_all();
129 }
130 }
131
132 void ZRelocateQueue::add_and_wait(ZForwarding* forwarding) {
133 ZStatTimer timer(ZCriticalPhaseRelocationStall);
134 ZLocker<ZConditionLock> locker(&_lock);
135
136 if (forwarding->is_done()) {
137 return;
138 }
139
140 _queue.append(forwarding);
141 if (_queue.length() == 1) {
142 // Queue became non-empty
143 inc_needs_attention();
144 _lock.notify_all();
145 }
146
147 while (!forwarding->is_done()) {
148 _lock.wait();
149 }
150 }
151
152 bool ZRelocateQueue::prune() {
153 if (_queue.is_empty()) {
154 return false;
155 }
156
157 bool done = false;
158
159 for (int i = 0; i < _queue.length();) {
160 const ZForwarding* const forwarding = _queue.at(i);
161 if (forwarding->is_done()) {
162 done = true;
163
164 _queue.delete_at(i);
165 } else {
166 i++;
167 }
168 }
169
170 if (_queue.is_empty()) {
171 dec_needs_attention();
172 }
173
174 return done;
175 }
176
177 ZForwarding* ZRelocateQueue::prune_and_claim() {
178 if (prune()) {
179 _lock.notify_all();
180 }
181
182 for (int i = 0; i < _queue.length(); i++) {
183 ZForwarding* const forwarding = _queue.at(i);
184 if (forwarding->claim()) {
185 return forwarding;
186 }
187 }
188
189 return nullptr;
190 }
191
192 class ZRelocateQueueSynchronizeThread {
193 private:
194 ZRelocateQueue* const _queue;
195
196 public:
197 ZRelocateQueueSynchronizeThread(ZRelocateQueue* queue)
198 : _queue(queue) {
199 _queue->synchronize_thread();
200 }
201
202 ~ZRelocateQueueSynchronizeThread() {
203 _queue->desynchronize_thread();
204 }
205 };
206
207 void ZRelocateQueue::synchronize_thread() {
208 _nsynchronized++;
209
210 log_debug(gc, reloc)("Synchronize worker _nsynchronized %u", _nsynchronized);
211
212 assert(_nsynchronized <= _nworkers, "_nsynchronized: %u _nworkers: %u", _nsynchronized, _nworkers);
213 if (_nsynchronized == _nworkers) {
214 // All workers synchronized
215 _lock.notify_all();
216 }
217 }
218
219 void ZRelocateQueue::desynchronize_thread() {
220 _nsynchronized--;
221
222 log_debug(gc, reloc)("Desynchronize worker _nsynchronized %u", _nsynchronized);
223
224 assert(_nsynchronized < _nworkers, "_nsynchronized: %u _nworkers: %u", _nsynchronized, _nworkers);
225 }
226
227 ZForwarding* ZRelocateQueue::synchronize_poll() {
228 // Fast path avoids locking
229 if (!needs_attention()) {
230 return nullptr;
231 }
232
233 // Slow path to get the next forwarding and/or synchronize
234 ZLocker<ZConditionLock> locker(&_lock);
235
236 {
237 ZForwarding* const forwarding = prune_and_claim();
238 if (forwarding != nullptr) {
239 // Don't become synchronized while there are elements in the queue
240 return forwarding;
241 }
242 }
243
244 if (!_synchronize) {
245 return nullptr;
246 }
247
248 ZRelocateQueueSynchronizeThread rqst(this);
249
250 do {
251 _lock.wait();
252
253 ZForwarding* const forwarding = prune_and_claim();
254 if (forwarding != nullptr) {
255 return forwarding;
256 }
257 } while (_synchronize);
258
259 return nullptr;
260 }
261
262 void ZRelocateQueue::clear() {
263 assert(_nworkers == 0, "Invalid state");
264
265 if (_queue.is_empty()) {
266 return;
267 }
268
269 ZArrayIterator<ZForwarding*> iter(&_queue);
270 for (ZForwarding* forwarding; iter.next(&forwarding);) {
271 assert(forwarding->is_done(), "All should be done");
272 }
273
274 assert(false, "Clear was not empty");
275
276 _queue.clear();
277 dec_needs_attention();
278 }
279
280 void ZRelocateQueue::synchronize() {
281 ZLocker<ZConditionLock> locker(&_lock);
282 _synchronize = true;
283
284 inc_needs_attention();
285
286 log_debug(gc, reloc)("Synchronize all workers 1 _nworkers: %u _nsynchronized: %u", _nworkers, _nsynchronized);
287
288 while (_nworkers != _nsynchronized) {
289 _lock.wait();
290 log_debug(gc, reloc)("Synchronize all workers 2 _nworkers: %u _nsynchronized: %u", _nworkers, _nsynchronized);
291 }
292 }
293
294 void ZRelocateQueue::desynchronize() {
295 ZLocker<ZConditionLock> locker(&_lock);
296 _synchronize = false;
297
298 log_debug(gc, reloc)("Desynchronize all workers _nworkers: %u _nsynchronized: %u", _nworkers, _nsynchronized);
299
300 assert(_nsynchronized <= _nworkers, "_nsynchronized: %u _nworkers: %u", _nsynchronized, _nworkers);
301
302 dec_needs_attention();
303
304 _lock.notify_all();
305 }
306
307 ZRelocate::ZRelocate(ZGeneration* generation)
308 : _generation(generation),
309 _queue() {}
310
311 ZWorkers* ZRelocate::workers() const {
312 return _generation->workers();
313 }
314
315 void ZRelocate::start() {
316 _queue.activate(workers()->active_workers());
317 }
318
319 void ZRelocate::add_remset(volatile zpointer* p) {
320 ZGeneration::young()->remember(p);
321 }
322
323 static zaddress relocate_object_inner(ZForwarding* forwarding, zaddress from_addr, ZForwardingCursor* cursor) {
324 assert(ZHeap::heap()->is_object_live(from_addr), "Should be live");
325
326 // Allocate object
327 const size_t size = ZUtils::object_size(from_addr);
328
329 ZAllocatorForRelocation* allocator = ZAllocator::relocation(forwarding->to_age());
330
331 const zaddress to_addr = allocator->alloc_object(size);
332
333 if (is_null(to_addr)) {
334 // Allocation failed
335 return zaddress::null;
336 }
337
338 // Copy object
339 ZUtils::object_copy_disjoint(from_addr, to_addr, size);
340
341 // Insert forwarding
342 const zaddress to_addr_final = forwarding->insert(from_addr, to_addr, cursor);
343
344 if (to_addr_final != to_addr) {
345 // Already relocated, try undo allocation
346 allocator->undo_alloc_object(to_addr, size);
347 }
348
349 return to_addr_final;
350 }
351
352 zaddress ZRelocate::relocate_object(ZForwarding* forwarding, zaddress_unsafe from_addr) {
353 ZForwardingCursor cursor;
354
355 // Lookup forwarding
356 zaddress to_addr = forwarding->find(from_addr, &cursor);
357 if (!is_null(to_addr)) {
358 // Already relocated
359 return to_addr;
360 }
361
362 // Relocate object
363 if (forwarding->retain_page(&_queue)) {
364 assert(_generation->is_phase_relocate(), "Must be");
365 to_addr = relocate_object_inner(forwarding, safe(from_addr), &cursor);
366 forwarding->release_page();
367
368 if (!is_null(to_addr)) {
369 // Success
370 return to_addr;
371 }
372
373 // Failed to relocate object. Signal and wait for a worker thread to
374 // complete relocation of this page, and then forward the object.
375 _queue.add_and_wait(forwarding);
376 }
377
378 // Forward object
379 return forward_object(forwarding, from_addr);
380 }
381
382 zaddress ZRelocate::forward_object(ZForwarding* forwarding, zaddress_unsafe from_addr) {
383 const zaddress to_addr = forwarding->find(from_addr);
384 assert(!is_null(to_addr), "Should be forwarded: " PTR_FORMAT, untype(from_addr));
385 return to_addr;
386 }
387
388 static ZPage* alloc_page(ZAllocatorForRelocation* allocator, ZPageType type, size_t size) {
389 if (ZStressRelocateInPlace) {
390 // Simulate failure to allocate a new page. This will
391 // cause the page being relocated to be relocated in-place.
392 return nullptr;
393 }
394
395 ZAllocationFlags flags;
396 flags.set_non_blocking();
397 flags.set_gc_relocation();
398
399 return allocator->alloc_page_for_relocation(type, size, flags);
400 }
401
402 static void retire_target_page(ZGeneration* generation, ZPage* page) {
403 if (generation->is_young() && page->is_old()) {
404 generation->increase_promoted(page->used());
405 } else {
406 generation->increase_compacted(page->used());
407 }
408
409 // Free target page if it is empty. We can end up with an empty target
410 // page if we allocated a new target page, and then lost the race to
411 // relocate the remaining objects, leaving the target page empty when
412 // relocation completed.
413 if (page->used() == 0) {
414 ZHeap::heap()->free_page(page);
415 }
416 }
417
418 class ZRelocateSmallAllocator {
419 private:
420 ZGeneration* const _generation;
421 volatile size_t _in_place_count;
422
423 public:
424 ZRelocateSmallAllocator(ZGeneration* generation)
425 : _generation(generation),
426 _in_place_count(0) {}
427
428 ZPage* alloc_and_retire_target_page(ZForwarding* forwarding, ZPage* target) {
429 ZAllocatorForRelocation* const allocator = ZAllocator::relocation(forwarding->to_age());
430 ZPage* const page = alloc_page(allocator, forwarding->type(), forwarding->size());
431 if (page == nullptr) {
432 Atomic::inc(&_in_place_count);
433 }
434
435 if (target != nullptr) {
436 // Retire the old target page
437 retire_target_page(_generation, target);
438 }
439
440 return page;
441 }
442
443 void share_target_page(ZPage* page) {
444 // Does nothing
445 }
446
447 void free_target_page(ZPage* page) {
448 if (page != nullptr) {
449 retire_target_page(_generation, page);
450 }
451 }
452
453 zaddress alloc_object(ZPage* page, size_t size) const {
454 return (page != nullptr) ? page->alloc_object(size) : zaddress::null;
455 }
456
457 void undo_alloc_object(ZPage* page, zaddress addr, size_t size) const {
458 page->undo_alloc_object(addr, size);
459 }
460
461 size_t in_place_count() const {
462 return _in_place_count;
463 }
464 };
465
466 class ZRelocateMediumAllocator {
467 private:
468 ZGeneration* const _generation;
469 ZConditionLock _lock;
470 ZPage* _shared[ZAllocator::_relocation_allocators];
471 bool _in_place;
472 volatile size_t _in_place_count;
473
474 public:
475 ZRelocateMediumAllocator(ZGeneration* generation)
476 : _generation(generation),
477 _lock(),
478 _shared(),
479 _in_place(false),
480 _in_place_count(0) {}
481
482 ~ZRelocateMediumAllocator() {
483 for (uint i = 0; i < ZAllocator::_relocation_allocators; ++i) {
484 if (_shared[i] != nullptr) {
485 retire_target_page(_generation, _shared[i]);
486 }
487 }
488 }
489
490 ZPage* shared(ZPageAge age) {
491 return _shared[static_cast<uint>(age) - 1];
492 }
493
494 void set_shared(ZPageAge age, ZPage* page) {
495 _shared[static_cast<uint>(age) - 1] = page;
496 }
497
498 ZPage* alloc_and_retire_target_page(ZForwarding* forwarding, ZPage* target) {
499 ZLocker<ZConditionLock> locker(&_lock);
500
501 // Wait for any ongoing in-place relocation to complete
502 while (_in_place) {
503 _lock.wait();
504 }
505
506 // Allocate a new page only if the shared page is the same as the
507 // current target page. The shared page will be different from the
508 // current target page if another thread shared a page, or allocated
509 // a new page.
510 const ZPageAge to_age = forwarding->to_age();
511 if (shared(to_age) == target) {
512 ZAllocatorForRelocation* const allocator = ZAllocator::relocation(forwarding->to_age());
513 ZPage* const to_page = alloc_page(allocator, forwarding->type(), forwarding->size());
514 set_shared(to_age, to_page);
515 if (to_page == nullptr) {
516 Atomic::inc(&_in_place_count);
517 _in_place = true;
518 }
519
520 // This thread is responsible for retiring the shared target page
521 if (target != nullptr) {
522 retire_target_page(_generation, target);
523 }
524 }
525
526 return shared(to_age);
527 }
528
529 void share_target_page(ZPage* page) {
530 const ZPageAge age = page->age();
531
532 ZLocker<ZConditionLock> locker(&_lock);
533 assert(_in_place, "Invalid state");
534 assert(shared(age) == nullptr, "Invalid state");
535 assert(page != nullptr, "Invalid page");
536
537 set_shared(age, page);
538 _in_place = false;
539
540 _lock.notify_all();
541 }
542
543 void free_target_page(ZPage* page) {
544 // Does nothing
545 }
546
547 zaddress alloc_object(ZPage* page, size_t size) const {
548 return (page != nullptr) ? page->alloc_object_atomic(size) : zaddress::null;
549 }
550
551 void undo_alloc_object(ZPage* page, zaddress addr, size_t size) const {
552 page->undo_alloc_object_atomic(addr, size);
553 }
554
555 size_t in_place_count() const {
556 return _in_place_count;
557 }
558 };
559
560 template <typename Allocator>
561 class ZRelocateWork : public StackObj {
562 private:
563 Allocator* const _allocator;
564 ZForwarding* _forwarding;
565 ZPage* _target[ZAllocator::_relocation_allocators];
566 ZGeneration* const _generation;
567 size_t _other_promoted;
568 size_t _other_compacted;
569
570 ZPage* target(ZPageAge age) {
571 return _target[static_cast<uint>(age) - 1];
572 }
573
574 void set_target(ZPageAge age, ZPage* page) {
575 _target[static_cast<uint>(age) - 1] = page;
576 }
577
578 size_t object_alignment() const {
579 return (size_t)1 << _forwarding->object_alignment_shift();
580 }
581
582 void increase_other_forwarded(size_t unaligned_object_size) {
583 const size_t aligned_size = align_up(unaligned_object_size, object_alignment());
584 if (_forwarding->is_promotion()) {
585 _other_promoted += aligned_size;
586 } else {
587 _other_compacted += aligned_size;
588 }
589 }
590
591 zaddress try_relocate_object_inner(zaddress from_addr) {
592 ZForwardingCursor cursor;
593
594 const size_t size = ZUtils::object_size(from_addr);
595 ZPage* const to_page = target(_forwarding->to_age());
596
597 // Lookup forwarding
598 {
599 const zaddress to_addr = _forwarding->find(from_addr, &cursor);
600 if (!is_null(to_addr)) {
601 // Already relocated
602 increase_other_forwarded(size);
603 return to_addr;
604 }
605 }
606
607 // Allocate object
608 const zaddress allocated_addr = _allocator->alloc_object(to_page, size);
609 if (is_null(allocated_addr)) {
610 // Allocation failed
611 return zaddress::null;
612 }
613
614 // Copy object. Use conjoint copying if we are relocating
615 // in-place and the new object overlaps with the old object.
616 if (_forwarding->in_place_relocation() && allocated_addr + size > from_addr) {
617 ZUtils::object_copy_conjoint(from_addr, allocated_addr, size);
618 } else {
619 ZUtils::object_copy_disjoint(from_addr, allocated_addr, size);
620 }
621
622 // Insert forwarding
623 const zaddress to_addr = _forwarding->insert(from_addr, allocated_addr, &cursor);
624 if (to_addr != allocated_addr) {
625 // Already relocated, undo allocation
626 _allocator->undo_alloc_object(to_page, to_addr, size);
627 increase_other_forwarded(size);
628 }
629
630 return to_addr;
631 }
632
633 void update_remset_old_to_old(zaddress from_addr, zaddress to_addr) const {
634 // Old-to-old relocation - move existing remset bits
635
636 // If this is called for an in-place relocated page, then this code has the
637 // responsibility to clear the old remset bits. Extra care is needed because:
638 //
639 // 1) The to-object copy can overlap with the from-object copy
640 // 2) Remset bits of old objects need to be cleared
641 //
642 // A watermark is used to keep track of how far the old remset bits have been removed.
643
644 const bool in_place = _forwarding->in_place_relocation();
645 ZPage* const from_page = _forwarding->page();
646 const uintptr_t from_local_offset = from_page->local_offset(from_addr);
647
648 // Note: even with in-place relocation, the to_page could be another page
649 ZPage* const to_page = ZHeap::heap()->page(to_addr);
650
651 // Uses _relaxed version to handle that in-place relocation resets _top
652 assert(ZHeap::heap()->is_in_page_relaxed(from_page, from_addr), "Must be");
653 assert(to_page->is_in(to_addr), "Must be");
654
655
656 // Read the size from the to-object, since the from-object
657 // could have been overwritten during in-place relocation.
658 const size_t size = ZUtils::object_size(to_addr);
659
660 // If a young generation collection started while the old generation
661 // relocated objects, the remember set bits were flipped from "current"
662 // to "previous".
663 //
664 // We need to select the correct remembered sets bitmap to ensure that the
665 // old remset bits are found.
666 //
667 // Note that if the young generation marking (remset scanning) finishes
668 // before the old generation relocation has relocated this page, then the
669 // young generation will visit this page's previous remembered set bits and
670 // moved them over to the current bitmap.
671 //
672 // If the young generation runs multiple cycles while the old generation is
673 // relocating, then the first cycle will have consume the the old remset,
674 // bits and moved associated objects to a new old page. The old relocation
675 // could find either the the two bitmaps. So, either it will find the original
676 // remset bits for the page, or it will find an empty bitmap for the page. It
677 // doesn't matter for correctness, because the young generation marking has
678 // already taken care of the bits.
679
680 const bool active_remset_is_current = ZGeneration::old()->active_remset_is_current();
681
682 // When in-place relocation is done and the old remset bits are located in
683 // the bitmap that is going to be used for the new remset bits, then we
684 // need to clear the old bits before the new bits are inserted.
685 const bool iterate_current_remset = active_remset_is_current && !in_place;
686
687 BitMap::Iterator iter = iterate_current_remset
688 ? from_page->remset_iterator_limited_current(from_local_offset, size)
689 : from_page->remset_iterator_limited_previous(from_local_offset, size);
690
691 for (BitMap::idx_t field_bit : iter) {
692 const uintptr_t field_local_offset = ZRememberedSet::to_offset(field_bit);
693
694 // Add remset entry in the to-page
695 const uintptr_t offset = field_local_offset - from_local_offset;
696 const zaddress to_field = to_addr + offset;
697 log_trace(gc, reloc)("Remember: from: " PTR_FORMAT " to: " PTR_FORMAT " current: %d marking: %d page: " PTR_FORMAT " remset: " PTR_FORMAT,
698 untype(from_page->start() + field_local_offset), untype(to_field), active_remset_is_current, ZGeneration::young()->is_phase_mark(), p2i(to_page), p2i(to_page->remset_current()));
699
700 volatile zpointer* const p = (volatile zpointer*)to_field;
701
702 if (ZGeneration::young()->is_phase_mark()) {
703 // Young generation remembered set scanning needs to know about this
704 // field. It will take responsibility to add a new remember set entry if needed.
705 _forwarding->relocated_remembered_fields_register(p);
706 } else {
707 to_page->remember(p);
708 if (in_place) {
709 assert(to_page->is_remembered(p), "p: " PTR_FORMAT, p2i(p));
710 }
711 }
712 }
713 }
714
715 static bool add_remset_if_young(volatile zpointer* p, zaddress addr) {
716 if (ZHeap::heap()->is_young(addr)) {
717 ZRelocate::add_remset(p);
718 return true;
719 }
720
721 return false;
722 }
723
724 static void update_remset_promoted_filter_and_remap_per_field(volatile zpointer* p) {
725 const zpointer ptr = Atomic::load(p);
726
727 assert(ZPointer::is_old_load_good(ptr), "Should be at least old load good: " PTR_FORMAT, untype(ptr));
728
729 if (ZPointer::is_store_good(ptr)) {
730 // Already has a remset entry
731 return;
732 }
733
734 if (ZPointer::is_load_good(ptr)) {
735 if (!is_null_any(ptr)) {
736 const zaddress addr = ZPointer::uncolor(ptr);
737 add_remset_if_young(p, addr);
738 }
739 // No need to remap it is already load good
740 return;
741 }
742
743 if (is_null_any(ptr)) {
744 // Eagerly remap to skip adding a remset entry just to get deferred remapping
745 ZBarrier::remap_young_relocated(p, ptr);
746 return;
747 }
748
749 const zaddress_unsafe addr_unsafe = ZPointer::uncolor_unsafe(ptr);
750 ZForwarding* const forwarding = ZGeneration::young()->forwarding(addr_unsafe);
751
752 if (forwarding == nullptr) {
753 // Object isn't being relocated
754 const zaddress addr = safe(addr_unsafe);
755 if (!add_remset_if_young(p, addr)) {
756 // Not young - eagerly remap to skip adding a remset entry just to get deferred remapping
757 ZBarrier::remap_young_relocated(p, ptr);
758 }
759 return;
760 }
761
762 const zaddress addr = forwarding->find(addr_unsafe);
763
764 if (!is_null(addr)) {
765 // Object has already been relocated
766 if (!add_remset_if_young(p, addr)) {
767 // Not young - eagerly remap to skip adding a remset entry just to get deferred remapping
768 ZBarrier::remap_young_relocated(p, ptr);
769 }
770 return;
771 }
772
773 // Object has not been relocated yet
774 // Don't want to eagerly relocate objects, so just add a remset
775 ZRelocate::add_remset(p);
776 return;
777 }
778
779 void update_remset_promoted(zaddress to_addr) const {
780 ZIterator::basic_oop_iterate(to_oop(to_addr), update_remset_promoted_filter_and_remap_per_field);
781 }
782
783 void update_remset_for_fields(zaddress from_addr, zaddress to_addr) const {
784 if (_forwarding->to_age() != ZPageAge::old) {
785 // No remembered set in young pages
786 return;
787 }
788
789 // Need to deal with remset when moving objects to the old generation
790 if (_forwarding->from_age() == ZPageAge::old) {
791 update_remset_old_to_old(from_addr, to_addr);
792 return;
793 }
794
795 // Normal promotion
796 update_remset_promoted(to_addr);
797 }
798
799 bool try_relocate_object(zaddress from_addr) {
800 const zaddress to_addr = try_relocate_object_inner(from_addr);
801
802 if (is_null(to_addr)) {
803 return false;
804 }
805
806 update_remset_for_fields(from_addr, to_addr);
807
808 return true;
809 }
810
811 void start_in_place_relocation_prepare_remset(ZPage* from_page) {
812 if (_forwarding->from_age() != ZPageAge::old) {
813 // Only old pages have use remset bits
814 return;
815 }
816
817 if (ZGeneration::old()->active_remset_is_current()) {
818 // We want to iterate over and clear the remset bits of the from-space page,
819 // and insert current bits in the to-space page. However, with in-place
820 // relocation, the from-space and to-space pages are the same. Clearing
821 // is destructive, and is difficult to perform before or during the iteration.
822 // However, clearing of the current bits has to be done before exposing the
823 // to-space objects in the forwarding table.
824 //
825 // To solve this tricky dependency problem, we start by stashing away the
826 // current bits in the previous bits, and clearing the current bits
827 // (implemented by swapping the bits). This way, the current bits are
828 // cleared before copying the objects (like a normal to-space page),
829 // and the previous bits are representing a copy of the current bits
830 // of the from-space page, and are used for iteration.
831 from_page->swap_remset_bitmaps();
832 }
833 }
834
835 ZPage* start_in_place_relocation(zoffset relocated_watermark) {
836 _forwarding->in_place_relocation_claim_page();
837 _forwarding->in_place_relocation_start(relocated_watermark);
838
839 ZPage* const from_page = _forwarding->page();
840
841 const ZPageAge to_age = _forwarding->to_age();
842 const bool promotion = _forwarding->is_promotion();
843
844 // Promotions happen through a new cloned page
845 ZPage* const to_page = promotion ? from_page->clone_limited() : from_page;
846 to_page->reset(to_age, ZPageResetType::InPlaceRelocation);
847
848 // Clear remset bits for all objects that were relocated
849 // before this page became an in-place relocated page.
850 start_in_place_relocation_prepare_remset(from_page);
851
852 if (promotion) {
853 // Register the the promotion
854 ZGeneration::young()->in_place_relocate_promote(from_page, to_page);
855 ZGeneration::young()->register_in_place_relocate_promoted(from_page);
856 }
857
858 return to_page;
859 }
860
861 void relocate_object(oop obj) {
862 const zaddress addr = to_zaddress(obj);
863 assert(ZHeap::heap()->is_object_live(addr), "Should be live");
864
865 while (!try_relocate_object(addr)) {
866 // Allocate a new target page, or if that fails, use the page being
867 // relocated as the new target, which will cause it to be relocated
868 // in-place.
869 const ZPageAge to_age = _forwarding->to_age();
870 ZPage* to_page = _allocator->alloc_and_retire_target_page(_forwarding, target(to_age));
871 set_target(to_age, to_page);
872 if (to_page != nullptr) {
873 continue;
874 }
875
876 // Start in-place relocation to block other threads from accessing
877 // the page, or its forwarding table, until it has been released
878 // (relocation completed).
879 to_page = start_in_place_relocation(ZAddress::offset(addr));
880 set_target(to_age, to_page);
881 }
882 }
883
884 public:
885 ZRelocateWork(Allocator* allocator, ZGeneration* generation)
886 : _allocator(allocator),
887 _forwarding(nullptr),
888 _target(),
889 _generation(generation),
890 _other_promoted(0),
891 _other_compacted(0) {}
892
893 ~ZRelocateWork() {
894 for (uint i = 0; i < ZAllocator::_relocation_allocators; ++i) {
895 _allocator->free_target_page(_target[i]);
896 }
897 // Report statistics on-behalf of non-worker threads
898 _generation->increase_promoted(_other_promoted);
899 _generation->increase_compacted(_other_compacted);
900 }
901
902 bool active_remset_is_current() const {
903 // Normal old-to-old relocation can treat the from-page remset as a
904 // read-only copy, and then copy over the appropriate remset bits to the
905 // cleared to-page's 'current' remset bitmap.
906 //
907 // In-place relocation is more complicated. Since, the same page is both
908 // a from-page and a to-page, we need to remove the old remset bits, and
909 // add remset bits that corresponds to the new locations of the relocated
910 // objects.
911 //
912 // Depending on how long ago (in terms of number of young GC's and the
913 // current young GC's phase), the page was allocated, the active
914 // remembered set will be in either the 'current' or 'previous' bitmap.
915 //
916 // If the active bits are in the 'previous' bitmap, we know that the
917 // 'current' bitmap was cleared at some earlier point in time, and we can
918 // simply set new bits in 'current' bitmap, and later when relocation has
919 // read all the old remset bits, we could just clear the 'previous' remset
920 // bitmap.
921 //
922 // If, on the other hand, the active bits are in the 'current' bitmap, then
923 // that bitmap will be used to both read the old remset bits, and the
924 // destination for the remset bits that we copy when an object is copied
925 // to it's new location within the page. We need to *carefully* remove all
926 // all old remset bits, without clearing out the newly set bits.
927 return ZGeneration::old()->active_remset_is_current();
928 }
929
930 void clear_remset_before_reuse(ZPage* page, bool in_place) {
931 if (_forwarding->from_age() != ZPageAge::old) {
932 // No remset bits
933 return;
934 }
935
936 if (in_place) {
937 // Clear 'previous' remset bits. For in-place relocated pages, the previous
938 // remset bits are always used, even when active_remset_is_current().
939 page->clear_remset_previous();
940
941 return;
942 }
943
944 // Normal relocate
945
946 // Clear active remset bits
947 if (active_remset_is_current()) {
948 page->clear_remset_current();
949 } else {
950 page->clear_remset_previous();
951 }
952
953 // Verify that inactive remset bits are all cleared
954 if (active_remset_is_current()) {
955 page->verify_remset_cleared_previous();
956 } else {
957 page->verify_remset_cleared_current();
958 }
959 }
960
961 void finish_in_place_relocation() {
962 // We are done with the from_space copy of the page
963 _forwarding->in_place_relocation_finish();
964 }
965
966 void do_forwarding(ZForwarding* forwarding) {
967 _forwarding = forwarding;
968
969 _forwarding->page()->log_msg(" (relocate page)");
970
971 ZVerify::before_relocation(_forwarding);
972
973 // Relocate objects
974 _forwarding->object_iterate([&](oop obj) { relocate_object(obj); });
975
976 ZVerify::after_relocation(_forwarding);
977
978 // Verify
979 if (ZVerifyForwarding) {
980 _forwarding->verify();
981 }
982
983 _generation->increase_freed(_forwarding->page()->size());
984
985 // Deal with in-place relocation
986 const bool in_place = _forwarding->in_place_relocation();
987 if (in_place) {
988 finish_in_place_relocation();
989 }
990
991 // Old from-space pages need to deal with remset bits
992 if (_forwarding->from_age() == ZPageAge::old) {
993 _forwarding->relocated_remembered_fields_after_relocate();
994 }
995
996 // Release relocated page
997 _forwarding->release_page();
998
999 if (in_place) {
1000 // Wait for all other threads to call release_page
1001 ZPage* const page = _forwarding->detach_page();
1002
1003 // Ensure that previous remset bits are cleared
1004 clear_remset_before_reuse(page, true /* in_place */);
1005
1006 page->log_msg(" (relocate page done in-place)");
1007
1008 // Different pages when promoting
1009 ZPage* const target_page = target(_forwarding->to_age());
1010 _allocator->share_target_page(target_page);
1011
1012 } else {
1013 // Wait for all other threads to call release_page
1014 ZPage* const page = _forwarding->detach_page();
1015
1016 // Ensure that all remset bits are cleared
1017 // Note: cleared after detach_page, when we know that
1018 // the young generation isn't scanning the remset.
1019 clear_remset_before_reuse(page, false /* in_place */);
1020
1021 page->log_msg(" (relocate page done normal)");
1022
1023 // Free page
1024 ZHeap::heap()->free_page(page);
1025 }
1026 }
1027 };
1028
1029 class ZRelocateStoreBufferInstallBasePointersThreadClosure : public ThreadClosure {
1030 public:
1031 virtual void do_thread(Thread* thread) {
1032 JavaThread* const jt = JavaThread::cast(thread);
1033 ZStoreBarrierBuffer* buffer = ZThreadLocalData::store_barrier_buffer(jt);
1034 buffer->install_base_pointers();
1035 }
1036 };
1037
1038 // Installs the object base pointers (object starts), for the fields written
1039 // in the store buffer. The code that searches for the object start uses that
1040 // liveness information stored in the pages. That information is lost when the
1041 // pages have been relocated and then destroyed.
1042 class ZRelocateStoreBufferInstallBasePointersTask : public ZTask {
1043 private:
1044 ZJavaThreadsIterator _threads_iter;
1045
1046 public:
1047 ZRelocateStoreBufferInstallBasePointersTask(ZGeneration* generation)
1048 : ZTask("ZRelocateStoreBufferInstallBasePointersTask"),
1049 _threads_iter(generation->id_optional()) {}
1050
1051 virtual void work() {
1052 ZRelocateStoreBufferInstallBasePointersThreadClosure fix_store_buffer_cl;
1053 _threads_iter.apply(&fix_store_buffer_cl);
1054 }
1055 };
1056
1057 class ZRelocateTask : public ZRestartableTask {
1058 private:
1059 ZRelocationSetParallelIterator _iter;
1060 ZGeneration* const _generation;
1061 ZRelocateQueue* const _queue;
1062 ZRelocateSmallAllocator _small_allocator;
1063 ZRelocateMediumAllocator _medium_allocator;
1064
1065 public:
1066 ZRelocateTask(ZRelocationSet* relocation_set, ZRelocateQueue* queue)
1067 : ZRestartableTask("ZRelocateTask"),
1068 _iter(relocation_set),
1069 _generation(relocation_set->generation()),
1070 _queue(queue),
1071 _small_allocator(_generation),
1072 _medium_allocator(_generation) {}
1073
1074 ~ZRelocateTask() {
1075 _generation->stat_relocation()->at_relocate_end(_small_allocator.in_place_count(), _medium_allocator.in_place_count());
1076
1077 // Signal that we're not using the queue anymore. Used mostly for asserts.
1078 _queue->deactivate();
1079 }
1080
1081 virtual void work() {
1082 ZRelocateWork<ZRelocateSmallAllocator> small(&_small_allocator, _generation);
1083 ZRelocateWork<ZRelocateMediumAllocator> medium(&_medium_allocator, _generation);
1084
1085 const auto do_forwarding = [&](ZForwarding* forwarding) {
1086 ZPage* const page = forwarding->page();
1087 if (page->is_small()) {
1088 small.do_forwarding(forwarding);
1089 } else {
1090 medium.do_forwarding(forwarding);
1091 }
1092
1093 // Absolute last thing done while relocating a page.
1094 //
1095 // We don't use the SuspendibleThreadSet when relocating pages.
1096 // Instead the ZRelocateQueue is used as a pseudo STS joiner/leaver.
1097 //
1098 // After the mark_done call a safepointing could be completed and a
1099 // new GC phase could be entered.
1100 forwarding->mark_done();
1101 };
1102
1103 const auto claim_and_do_forwarding = [&](ZForwarding* forwarding) {
1104 if (forwarding->claim()) {
1105 do_forwarding(forwarding);
1106 }
1107 };
1108
1109 const auto do_forwarding_one_from_iter = [&]() {
1110 ZForwarding* forwarding;
1111
1112 if (_iter.next(&forwarding)) {
1113 claim_and_do_forwarding(forwarding);
1114 return true;
1115 }
1116
1117 return false;
1118 };
1119
1120 for (;;) {
1121 // As long as there are requests in the relocate queue, there are threads
1122 // waiting in a VM state that does not allow them to be blocked. The
1123 // worker thread needs to finish relocate these pages, and allow the
1124 // other threads to continue and proceed to a blocking state. After that,
1125 // the worker threads are allowed to safepoint synchronize.
1126 for (ZForwarding* forwarding; (forwarding = _queue->synchronize_poll()) != nullptr;) {
1127 do_forwarding(forwarding);
1128 }
1129
1130 if (!do_forwarding_one_from_iter()) {
1131 // No more work
1132 break;
1133 }
1134
1135 if (_generation->should_worker_resize()) {
1136 break;
1137 }
1138 }
1139
1140 _queue->leave();
1141 }
1142
1143 virtual void resize_workers(uint nworkers) {
1144 _queue->resize_workers(nworkers);
1145 }
1146 };
1147
1148 static void remap_and_maybe_add_remset(volatile zpointer* p) {
1149 const zpointer ptr = Atomic::load(p);
1150
1151 if (ZPointer::is_store_good(ptr)) {
1152 // Already has a remset entry
1153 return;
1154 }
1155
1156 // Remset entries are used for two reasons:
1157 // 1) Young marking old-to-young pointer roots
1158 // 2) Deferred remapping of stale old-to-young pointers
1159 //
1160 // This load barrier will up-front perform the remapping of (2),
1161 // and the code below only has to make sure we register up-to-date
1162 // old-to-young pointers for (1).
1163 const zaddress addr = ZBarrier::load_barrier_on_oop_field_preloaded(p, ptr);
1164
1165 if (is_null(addr)) {
1166 // No need for remset entries for null pointers
1167 return;
1168 }
1169
1170 if (ZHeap::heap()->is_old(addr)) {
1171 // No need for remset entries for pointers to old gen
1172 return;
1173 }
1174
1175 ZRelocate::add_remset(p);
1176 }
1177
1178 class ZRelocateAddRemsetForFlipPromoted : public ZRestartableTask {
1179 private:
1180 ZStatTimerYoung _timer;
1181 ZArrayParallelIterator<ZPage*> _iter;
1182
1183 public:
1184 ZRelocateAddRemsetForFlipPromoted(ZArray<ZPage*>* pages)
1185 : ZRestartableTask("ZRelocateAddRemsetForFlipPromoted"),
1186 _timer(ZSubPhaseConcurrentRelocateRememberedSetFlipPromotedYoung),
1187 _iter(pages) {}
1188
1189 virtual void work() {
1190 SuspendibleThreadSetJoiner sts_joiner;
1191
1192 for (ZPage* page; _iter.next(&page);) {
1193 page->object_iterate([&](oop obj) {
1194 ZIterator::basic_oop_iterate_safe(obj, remap_and_maybe_add_remset);
1195 });
1196
1197 SuspendibleThreadSet::yield();
1198 if (ZGeneration::young()->should_worker_resize()) {
1199 return;
1200 }
1201 }
1202 }
1203 };
1204
1205 void ZRelocate::relocate(ZRelocationSet* relocation_set) {
1206 {
1207 // Install the store buffer's base pointers before the
1208 // relocate task destroys the liveness information in
1209 // the relocated pages.
1210 ZRelocateStoreBufferInstallBasePointersTask buffer_task(_generation);
1211 workers()->run(&buffer_task);
1212 }
1213
1214 {
1215 ZRelocateTask relocate_task(relocation_set, &_queue);
1216 workers()->run(&relocate_task);
1217 }
1218
1219 if (relocation_set->generation()->is_young()) {
1220 ZRelocateAddRemsetForFlipPromoted task(relocation_set->flip_promoted_pages());
1221 workers()->run(&task);
1222 }
1223 }
1224
1225 ZPageAge ZRelocate::compute_to_age(ZPageAge from_age) {
1226 if (from_age == ZPageAge::old) {
1227 return ZPageAge::old;
1228 }
1229
1230 const uint age = static_cast<uint>(from_age);
1231 if (age >= ZGeneration::young()->tenuring_threshold()) {
1232 return ZPageAge::old;
1233 }
1234
1235 return static_cast<ZPageAge>(age + 1);
1236 }
1237
1238 class ZFlipAgePagesTask : public ZTask {
1239 private:
1240 ZArrayParallelIterator<ZPage*> _iter;
1241
1242 public:
1243 ZFlipAgePagesTask(const ZArray<ZPage*>* pages)
1244 : ZTask("ZPromotePagesTask"),
1245 _iter(pages) {}
1246
1247 virtual void work() {
1248 SuspendibleThreadSetJoiner sts_joiner;
1249 ZArray<ZPage*> promoted_pages;
1250
1251 for (ZPage* prev_page; _iter.next(&prev_page);) {
1252 const ZPageAge from_age = prev_page->age();
1253 const ZPageAge to_age = ZRelocate::compute_to_age(from_age);
1254 assert(from_age != ZPageAge::old, "invalid age for a young collection");
1255
1256 // Figure out if this is proper promotion
1257 const bool promotion = to_age == ZPageAge::old;
1258
1259 if (promotion) {
1260 // Before promoting an object (and before relocate start), we must ensure that all
1261 // contained zpointers are store good. The marking code ensures that for non-null
1262 // pointers, but null pointers are ignored. This code ensures that even null pointers
1263 // are made store good, for the promoted objects.
1264 prev_page->object_iterate([&](oop obj) {
1265 ZIterator::basic_oop_iterate_safe(obj, ZBarrier::promote_barrier_on_young_oop_field);
1266 });
1267 }
1268
1269 // Logging
1270 prev_page->log_msg(promotion ? " (flip promoted)" : " (flip survived)");
1271
1272 // Setup to-space page
1273 ZPage* const new_page = promotion ? prev_page->clone_limited_promote_flipped() : prev_page;
1274 new_page->reset(to_age, ZPageResetType::FlipAging);
1275
1276 if (promotion) {
1277 ZGeneration::young()->flip_promote(prev_page, new_page);
1278 // Defer promoted page registration times the lock is taken
1279 promoted_pages.push(prev_page);
1280 }
1281
1282 SuspendibleThreadSet::yield();
1283 }
1284
1285 ZGeneration::young()->register_flip_promoted(promoted_pages);
1286 }
1287 };
1288
1289 void ZRelocate::flip_age_pages(const ZArray<ZPage*>* pages) {
1290 ZFlipAgePagesTask flip_age_task(pages);
1291 workers()->run(&flip_age_task);
1292 }
1293
1294 void ZRelocate::synchronize() {
1295 _queue.synchronize();
1296 }
1297
1298 void ZRelocate::desynchronize() {
1299 _queue.desynchronize();
1300 }
1301
1302 ZRelocateQueue* ZRelocate::queue() {
1303 return &_queue;
1304 }
1305
1306 bool ZRelocate::is_queue_active() const {
1307 return _queue.is_active();
1308 }