1 /*
2 * Copyright (c) 2016, 2021, Red Hat, Inc. 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/shared/tlab_globals.hpp"
27 #include "gc/shenandoah/shenandoahFreeSet.hpp"
28 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
29 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
30 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
31 #include "logging/logStream.hpp"
32 #include "memory/resourceArea.hpp"
33 #include "runtime/orderAccess.hpp"
34
35 ShenandoahFreeSet::ShenandoahFreeSet(ShenandoahHeap* heap, size_t max_regions) :
36 _heap(heap),
37 _mutator_free_bitmap(max_regions, mtGC),
38 _collector_free_bitmap(max_regions, mtGC),
39 _max(max_regions)
40 {
41 clear_internal();
42 }
43
44 void ShenandoahFreeSet::increase_used(size_t num_bytes) {
45 shenandoah_assert_heaplocked();
46 _used += num_bytes;
47
48 assert(_used <= _capacity, "must not use more than we have: used: " SIZE_FORMAT
49 ", capacity: " SIZE_FORMAT ", num_bytes: " SIZE_FORMAT, _used, _capacity, num_bytes);
50 }
51
52 bool ShenandoahFreeSet::is_mutator_free(size_t idx) const {
53 assert (idx < _max, "index is sane: " SIZE_FORMAT " < " SIZE_FORMAT " (left: " SIZE_FORMAT ", right: " SIZE_FORMAT ")",
54 idx, _max, _mutator_leftmost, _mutator_rightmost);
55 return _mutator_free_bitmap.at(idx);
56 }
57
58 bool ShenandoahFreeSet::is_collector_free(size_t idx) const {
59 assert (idx < _max, "index is sane: " SIZE_FORMAT " < " SIZE_FORMAT " (left: " SIZE_FORMAT ", right: " SIZE_FORMAT ")",
60 idx, _max, _collector_leftmost, _collector_rightmost);
61 return _collector_free_bitmap.at(idx);
62 }
63
64 HeapWord* ShenandoahFreeSet::allocate_single(ShenandoahAllocRequest& req, bool& in_new_region) {
65 // Scan the bitmap looking for a first fit.
66 //
67 // Leftmost and rightmost bounds provide enough caching to walk bitmap efficiently. Normally,
68 // we would find the region to allocate at right away.
69 //
70 // Allocations are biased: new application allocs go to beginning of the heap, and GC allocs
71 // go to the end. This makes application allocation faster, because we would clear lots
72 // of regions from the beginning most of the time.
73 //
74 // Free set maintains mutator and collector views, and normally they allocate in their views only,
75 // unless we special cases for stealing and mixed allocations.
76
77 switch (req.type()) {
78 case ShenandoahAllocRequest::_alloc_tlab:
79 case ShenandoahAllocRequest::_alloc_shared: {
80
81 // Try to allocate in the mutator view
82 for (size_t idx = _mutator_leftmost; idx <= _mutator_rightmost; idx++) {
83 if (is_mutator_free(idx)) {
84 HeapWord* result = try_allocate_in(_heap->get_region(idx), req, in_new_region);
85 if (result != nullptr) {
86 return result;
87 }
88 }
89 }
90
91 // There is no recovery. Mutator does not touch collector view at all.
92 break;
93 }
94 case ShenandoahAllocRequest::_alloc_gclab:
95 case ShenandoahAllocRequest::_alloc_shared_gc: {
96 // size_t is unsigned, need to dodge underflow when _leftmost = 0
97
98 // Fast-path: try to allocate in the collector view first
99 for (size_t c = _collector_rightmost + 1; c > _collector_leftmost; c--) {
100 size_t idx = c - 1;
101 if (is_collector_free(idx)) {
102 HeapWord* result = try_allocate_in(_heap->get_region(idx), req, in_new_region);
103 if (result != nullptr) {
104 return result;
105 }
106 }
107 }
108
109 // No dice. Can we borrow space from mutator view?
110 if (!ShenandoahEvacReserveOverflow) {
111 return nullptr;
112 }
113
114 // Try to steal the empty region from the mutator view
115 for (size_t c = _mutator_rightmost + 1; c > _mutator_leftmost; c--) {
116 size_t idx = c - 1;
117 if (is_mutator_free(idx)) {
118 ShenandoahHeapRegion* r = _heap->get_region(idx);
119 if (can_allocate_from(r)) {
120 flip_to_gc(r);
121 HeapWord *result = try_allocate_in(r, req, in_new_region);
122 if (result != nullptr) {
123 return result;
124 }
125 }
126 }
127 }
128
129 // No dice. Do not try to mix mutator and GC allocations, because
130 // URWM moves due to GC allocations would expose unparsable mutator
131 // allocations.
132
133 break;
134 }
135 default:
136 ShouldNotReachHere();
137 }
138
139 return nullptr;
140 }
141
142 HeapWord* ShenandoahFreeSet::try_allocate_in(ShenandoahHeapRegion* r, ShenandoahAllocRequest& req, bool& in_new_region) {
143 assert (!has_no_alloc_capacity(r), "Performance: should avoid full regions on this path: " SIZE_FORMAT, r->index());
144
145 if (_heap->is_concurrent_weak_root_in_progress() &&
146 r->is_trash()) {
147 return nullptr;
148 }
149
150 try_recycle_trashed(r);
151
152 in_new_region = r->is_empty();
153
154 HeapWord* result = nullptr;
155 size_t size = req.size();
156
157 if (req.is_lab_alloc()) {
158 size_t free = align_down(r->free() >> LogHeapWordSize, MinObjAlignment);
159 if (size > free) {
160 size = free;
161 }
162 if (size >= req.min_size()) {
163 result = r->allocate(size, req.type());
164 assert (result != nullptr, "Allocation must succeed: free " SIZE_FORMAT ", actual " SIZE_FORMAT, free, size);
165 }
166 } else {
167 result = r->allocate(size, req.type());
168 }
169
170 if (result != nullptr) {
171 // Allocation successful, bump stats:
172 if (req.is_mutator_alloc()) {
173 increase_used(size * HeapWordSize);
174 }
175
176 // Record actual allocation size
177 req.set_actual_size(size);
178
179 if (req.is_gc_alloc()) {
180 r->set_update_watermark(r->top());
181 }
182 }
183
184 if (result == nullptr || has_no_alloc_capacity(r)) {
185 // Region cannot afford this or future allocations. Retire it.
186 //
187 // While this seems a bit harsh, especially in the case when this large allocation does not
188 // fit, but the next small one would, we are risking to inflate scan times when lots of
189 // almost-full regions precede the fully-empty region where we want allocate the entire TLAB.
190 // TODO: Record first fully-empty region, and use that for large allocations
191
192 // Record the remainder as allocation waste
193 if (req.is_mutator_alloc()) {
194 size_t waste = r->free();
195 if (waste > 0) {
196 increase_used(waste);
197 _heap->notify_mutator_alloc_words(waste >> LogHeapWordSize, true);
198 }
199 }
200
201 size_t num = r->index();
202 _collector_free_bitmap.clear_bit(num);
203 _mutator_free_bitmap.clear_bit(num);
204 // Touched the bounds? Need to update:
205 if (touches_bounds(num)) {
206 adjust_bounds();
207 }
208 assert_bounds();
209 }
210 return result;
211 }
212
213 bool ShenandoahFreeSet::touches_bounds(size_t num) const {
214 return num == _collector_leftmost || num == _collector_rightmost || num == _mutator_leftmost || num == _mutator_rightmost;
215 }
216
217 void ShenandoahFreeSet::recompute_bounds() {
218 // Reset to the most pessimistic case:
219 _mutator_rightmost = _max - 1;
220 _mutator_leftmost = 0;
221 _collector_rightmost = _max - 1;
222 _collector_leftmost = 0;
223
224 // ...and adjust from there
225 adjust_bounds();
226 }
227
228 void ShenandoahFreeSet::adjust_bounds() {
229 // Rewind both mutator bounds until the next bit.
230 while (_mutator_leftmost < _max && !is_mutator_free(_mutator_leftmost)) {
231 _mutator_leftmost++;
232 }
233 while (_mutator_rightmost > 0 && !is_mutator_free(_mutator_rightmost)) {
234 _mutator_rightmost--;
235 }
236 // Rewind both collector bounds until the next bit.
237 while (_collector_leftmost < _max && !is_collector_free(_collector_leftmost)) {
238 _collector_leftmost++;
239 }
240 while (_collector_rightmost > 0 && !is_collector_free(_collector_rightmost)) {
241 _collector_rightmost--;
242 }
243 }
244
245 HeapWord* ShenandoahFreeSet::allocate_contiguous(ShenandoahAllocRequest& req) {
246 shenandoah_assert_heaplocked();
247
248 size_t words_size = req.size();
249 size_t num = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
250
251 // No regions left to satisfy allocation, bye.
252 if (num > mutator_count()) {
253 return nullptr;
254 }
255
256 // Find the continuous interval of $num regions, starting from $beg and ending in $end,
257 // inclusive. Contiguous allocations are biased to the beginning.
258
259 size_t beg = _mutator_leftmost;
260 size_t end = beg;
261
262 while (true) {
263 if (end >= _max) {
264 // Hit the end, goodbye
265 return nullptr;
266 }
267
268 // If regions are not adjacent, then current [beg; end] is useless, and we may fast-forward.
269 // If region is not completely free, the current [beg; end] is useless, and we may fast-forward.
270 if (!is_mutator_free(end) || !can_allocate_from(_heap->get_region(end))) {
271 end++;
272 beg = end;
273 continue;
274 }
275
276 if ((end - beg + 1) == num) {
277 // found the match
278 break;
279 }
280
281 end++;
282 }
283
284 size_t remainder = words_size & ShenandoahHeapRegion::region_size_words_mask();
285
286 // Initialize regions:
287 for (size_t i = beg; i <= end; i++) {
288 ShenandoahHeapRegion* r = _heap->get_region(i);
289 try_recycle_trashed(r);
290
291 assert(i == beg || _heap->get_region(i - 1)->index() + 1 == r->index(), "Should be contiguous");
292 assert(r->is_empty(), "Should be empty");
293
294 if (i == beg) {
295 r->make_humongous_start();
296 } else {
297 r->make_humongous_cont();
298 }
299
300 // Trailing region may be non-full, record the remainder there
301 size_t used_words;
302 if ((i == end) && (remainder != 0)) {
303 used_words = remainder;
304 } else {
305 used_words = ShenandoahHeapRegion::region_size_words();
306 }
307
308 r->set_top(r->bottom() + used_words);
309
310 _mutator_free_bitmap.clear_bit(r->index());
311 }
312
313 // While individual regions report their true use, all humongous regions are
314 // marked used in the free set.
315 increase_used(ShenandoahHeapRegion::region_size_bytes() * num);
316
317 if (remainder != 0) {
318 // Record this remainder as allocation waste
319 _heap->notify_mutator_alloc_words(ShenandoahHeapRegion::region_size_words() - remainder, true);
320 }
321
322 // Allocated at left/rightmost? Move the bounds appropriately.
323 if (beg == _mutator_leftmost || end == _mutator_rightmost) {
324 adjust_bounds();
325 }
326 assert_bounds();
327
328 req.set_actual_size(words_size);
329 return _heap->get_region(beg)->bottom();
330 }
331
332 bool ShenandoahFreeSet::can_allocate_from(ShenandoahHeapRegion *r) {
333 return r->is_empty() || (r->is_trash() && !_heap->is_concurrent_weak_root_in_progress());
334 }
335
336 size_t ShenandoahFreeSet::alloc_capacity(ShenandoahHeapRegion *r) {
337 if (r->is_trash()) {
338 // This would be recycled on allocation path
339 return ShenandoahHeapRegion::region_size_bytes();
340 } else {
341 return r->free();
342 }
343 }
344
345 bool ShenandoahFreeSet::has_no_alloc_capacity(ShenandoahHeapRegion *r) {
346 return alloc_capacity(r) == 0;
347 }
348
349 void ShenandoahFreeSet::try_recycle_trashed(ShenandoahHeapRegion *r) {
350 if (r->is_trash()) {
351 _heap->decrease_used(r->used());
352 r->recycle();
353 }
354 }
355
356 void ShenandoahFreeSet::recycle_trash() {
357 // lock is not reentrable, check we don't have it
358 shenandoah_assert_not_heaplocked();
359
360 for (size_t i = 0; i < _heap->num_regions(); i++) {
361 ShenandoahHeapRegion* r = _heap->get_region(i);
362 if (r->is_trash()) {
363 ShenandoahHeapLocker locker(_heap->lock());
364 try_recycle_trashed(r);
365 }
366 SpinPause(); // allow allocators to take the lock
367 }
368 }
369
370 void ShenandoahFreeSet::flip_to_gc(ShenandoahHeapRegion* r) {
371 size_t idx = r->index();
372
373 assert(_mutator_free_bitmap.at(idx), "Should be in mutator view");
374 assert(can_allocate_from(r), "Should not be allocated");
375
376 _mutator_free_bitmap.clear_bit(idx);
377 _collector_free_bitmap.set_bit(idx);
378 _collector_leftmost = MIN2(idx, _collector_leftmost);
379 _collector_rightmost = MAX2(idx, _collector_rightmost);
380
381 _capacity -= alloc_capacity(r);
382
383 if (touches_bounds(idx)) {
384 adjust_bounds();
385 }
386 assert_bounds();
387 }
388
389 void ShenandoahFreeSet::clear() {
390 shenandoah_assert_heaplocked();
391 clear_internal();
392 }
393
394 void ShenandoahFreeSet::clear_internal() {
395 _mutator_free_bitmap.clear();
396 _collector_free_bitmap.clear();
397 _mutator_leftmost = _max;
398 _mutator_rightmost = 0;
399 _collector_leftmost = _max;
400 _collector_rightmost = 0;
401 _capacity = 0;
402 _used = 0;
403 }
404
405 void ShenandoahFreeSet::rebuild() {
406 shenandoah_assert_heaplocked();
407 clear();
408
409 for (size_t idx = 0; idx < _heap->num_regions(); idx++) {
410 ShenandoahHeapRegion* region = _heap->get_region(idx);
411 if (region->is_alloc_allowed() || region->is_trash()) {
412 assert(!region->is_cset(), "Shouldn't be adding those to the free set");
413
414 // Do not add regions that would surely fail allocation
415 if (has_no_alloc_capacity(region)) continue;
416
417 _capacity += alloc_capacity(region);
418 assert(_used <= _capacity, "must not use more than we have");
419
420 assert(!is_mutator_free(idx), "We are about to add it, it shouldn't be there already");
421 _mutator_free_bitmap.set_bit(idx);
422 }
423 }
424
425 // Evac reserve: reserve trailing space for evacuations
426 size_t to_reserve = _heap->max_capacity() / 100 * ShenandoahEvacReserve;
427 size_t reserved = 0;
428
429 for (size_t idx = _heap->num_regions() - 1; idx > 0; idx--) {
430 if (reserved >= to_reserve) break;
431
432 ShenandoahHeapRegion* region = _heap->get_region(idx);
433 if (_mutator_free_bitmap.at(idx) && can_allocate_from(region)) {
434 _mutator_free_bitmap.clear_bit(idx);
435 _collector_free_bitmap.set_bit(idx);
436 size_t ac = alloc_capacity(region);
437 _capacity -= ac;
438 reserved += ac;
439 }
440 }
441
442 recompute_bounds();
443 assert_bounds();
444 }
445
446 void ShenandoahFreeSet::log_status() {
447 shenandoah_assert_heaplocked();
448
449 LogTarget(Info, gc, ergo) lt;
450 if (lt.is_enabled()) {
451 ResourceMark rm;
452 LogStream ls(lt);
453
454 {
455 size_t last_idx = 0;
456 size_t max = 0;
457 size_t max_contig = 0;
458 size_t empty_contig = 0;
459
460 size_t total_used = 0;
461 size_t total_free = 0;
462 size_t total_free_ext = 0;
463
464 for (size_t idx = _mutator_leftmost; idx <= _mutator_rightmost; idx++) {
465 if (is_mutator_free(idx)) {
466 ShenandoahHeapRegion *r = _heap->get_region(idx);
467 size_t free = alloc_capacity(r);
468
469 max = MAX2(max, free);
470
471 if (r->is_empty()) {
472 total_free_ext += free;
473 if (last_idx + 1 == idx) {
474 empty_contig++;
475 } else {
476 empty_contig = 1;
477 }
478 } else {
479 empty_contig = 0;
480 }
481
482 total_used += r->used();
483 total_free += free;
484
485 max_contig = MAX2(max_contig, empty_contig);
486 last_idx = idx;
487 }
488 }
489
490 size_t max_humongous = max_contig * ShenandoahHeapRegion::region_size_bytes();
491 size_t free = capacity() - used();
492
493 ls.print("Free: " SIZE_FORMAT "%s, Max: " SIZE_FORMAT "%s regular, " SIZE_FORMAT "%s humongous, ",
494 byte_size_in_proper_unit(total_free), proper_unit_for_byte_size(total_free),
495 byte_size_in_proper_unit(max), proper_unit_for_byte_size(max),
496 byte_size_in_proper_unit(max_humongous), proper_unit_for_byte_size(max_humongous)
497 );
498
499 ls.print("Frag: ");
500 size_t frag_ext;
501 if (total_free_ext > 0) {
502 frag_ext = 100 - (100 * max_humongous / total_free_ext);
503 } else {
504 frag_ext = 0;
505 }
506 ls.print(SIZE_FORMAT "%% external, ", frag_ext);
507
508 size_t frag_int;
509 if (mutator_count() > 0) {
510 frag_int = (100 * (total_used / mutator_count()) / ShenandoahHeapRegion::region_size_bytes());
511 } else {
512 frag_int = 0;
513 }
514 ls.print(SIZE_FORMAT "%% internal; ", frag_int);
515 }
516
517 {
518 size_t max = 0;
519 size_t total_free = 0;
520
521 for (size_t idx = _collector_leftmost; idx <= _collector_rightmost; idx++) {
522 if (is_collector_free(idx)) {
523 ShenandoahHeapRegion *r = _heap->get_region(idx);
524 size_t free = alloc_capacity(r);
525 max = MAX2(max, free);
526 total_free += free;
527 }
528 }
529
530 ls.print_cr("Reserve: " SIZE_FORMAT "%s, Max: " SIZE_FORMAT "%s",
531 byte_size_in_proper_unit(total_free), proper_unit_for_byte_size(total_free),
532 byte_size_in_proper_unit(max), proper_unit_for_byte_size(max));
533 }
534 }
535 }
536
537 HeapWord* ShenandoahFreeSet::allocate(ShenandoahAllocRequest& req, bool& in_new_region) {
538 shenandoah_assert_heaplocked();
539 assert_bounds();
540
541 if (req.size() > ShenandoahHeapRegion::humongous_threshold_words()) {
542 switch (req.type()) {
543 case ShenandoahAllocRequest::_alloc_shared:
544 case ShenandoahAllocRequest::_alloc_shared_gc:
545 in_new_region = true;
546 return allocate_contiguous(req);
547 case ShenandoahAllocRequest::_alloc_gclab:
548 case ShenandoahAllocRequest::_alloc_tlab:
549 in_new_region = false;
550 assert(false, "Trying to allocate TLAB larger than the humongous threshold: " SIZE_FORMAT " > " SIZE_FORMAT,
551 req.size(), ShenandoahHeapRegion::humongous_threshold_words());
552 return nullptr;
553 default:
554 ShouldNotReachHere();
555 return nullptr;
556 }
557 } else {
558 return allocate_single(req, in_new_region);
559 }
560 }
561
562 size_t ShenandoahFreeSet::unsafe_peek_free() const {
563 // Deliberately not locked, this method is unsafe when free set is modified.
564
565 for (size_t index = _mutator_leftmost; index <= _mutator_rightmost; index++) {
566 if (index < _max && is_mutator_free(index)) {
567 ShenandoahHeapRegion* r = _heap->get_region(index);
568 if (r->free() >= MinTLABSize) {
569 return r->free();
570 }
571 }
572 }
573
574 // It appears that no regions left
575 return 0;
576 }
577
578 void ShenandoahFreeSet::print_on(outputStream* out) const {
579 out->print_cr("Mutator Free Set: " SIZE_FORMAT "", mutator_count());
580 for (size_t index = _mutator_leftmost; index <= _mutator_rightmost; index++) {
581 if (is_mutator_free(index)) {
582 _heap->get_region(index)->print_on(out);
583 }
584 }
585 out->print_cr("Collector Free Set: " SIZE_FORMAT "", collector_count());
586 for (size_t index = _collector_leftmost; index <= _collector_rightmost; index++) {
587 if (is_collector_free(index)) {
588 _heap->get_region(index)->print_on(out);
589 }
590 }
591 }
592
593 /*
594 * Internal fragmentation metric: describes how fragmented the heap regions are.
595 *
596 * It is derived as:
597 *
598 * sum(used[i]^2, i=0..k)
599 * IF = 1 - ------------------------------
600 * C * sum(used[i], i=0..k)
601 *
602 * ...where k is the number of regions in computation, C is the region capacity, and
603 * used[i] is the used space in the region.
604 *
605 * The non-linearity causes IF to be lower for the cases where the same total heap
606 * used is densely packed. For example:
607 * a) Heap is completely full => IF = 0
608 * b) Heap is half full, first 50% regions are completely full => IF = 0
609 * c) Heap is half full, each region is 50% full => IF = 1/2
610 * d) Heap is quarter full, first 50% regions are completely full => IF = 0
611 * e) Heap is quarter full, each region is 25% full => IF = 3/4
612 * f) Heap has one small object per each region => IF =~ 1
613 */
614 double ShenandoahFreeSet::internal_fragmentation() {
615 double squared = 0;
616 double linear = 0;
617
618 for (size_t index = _mutator_leftmost; index <= _mutator_rightmost; index++) {
619 if (is_mutator_free(index)) {
620 ShenandoahHeapRegion* r = _heap->get_region(index);
621 size_t used = r->used();
622 squared += used * used;
623 linear += used;
624 }
625 }
626
627 if (linear > 0) {
628 double s = squared / (ShenandoahHeapRegion::region_size_bytes() * linear);
629 return 1 - s;
630 } else {
631 return 0;
632 }
633 }
634
635 /*
636 * External fragmentation metric: describes how fragmented the heap is.
637 *
638 * It is derived as:
639 *
640 * EF = 1 - largest_contiguous_free / total_free
641 *
642 * For example:
643 * a) Heap is completely empty => EF = 0
644 * b) Heap is completely full => EF = 0
645 * c) Heap is first-half full => EF = 1/2
646 * d) Heap is half full, full and empty regions interleave => EF =~ 1
647 */
648 double ShenandoahFreeSet::external_fragmentation() {
649 size_t last_idx = 0;
650 size_t max_contig = 0;
651 size_t empty_contig = 0;
652
653 size_t free = 0;
654
655 for (size_t index = _mutator_leftmost; index <= _mutator_rightmost; index++) {
656 if (is_mutator_free(index)) {
657 ShenandoahHeapRegion* r = _heap->get_region(index);
658 if (r->is_empty()) {
659 free += ShenandoahHeapRegion::region_size_bytes();
660 if (last_idx + 1 == index) {
661 empty_contig++;
662 } else {
663 empty_contig = 1;
664 }
665 } else {
666 empty_contig = 0;
667 }
668
669 max_contig = MAX2(max_contig, empty_contig);
670 last_idx = index;
671 }
672 }
673
674 if (free > 0) {
675 return 1 - (1.0 * max_contig * ShenandoahHeapRegion::region_size_bytes() / free);
676 } else {
677 return 0;
678 }
679 }
680
681 #ifdef ASSERT
682 void ShenandoahFreeSet::assert_bounds() const {
683 // Performance invariants. Failing these would not break the free set, but performance
684 // would suffer.
685 assert (_mutator_leftmost <= _max, "leftmost in bounds: " SIZE_FORMAT " < " SIZE_FORMAT, _mutator_leftmost, _max);
686 assert (_mutator_rightmost < _max, "rightmost in bounds: " SIZE_FORMAT " < " SIZE_FORMAT, _mutator_rightmost, _max);
687
688 assert (_mutator_leftmost == _max || is_mutator_free(_mutator_leftmost), "leftmost region should be free: " SIZE_FORMAT, _mutator_leftmost);
689 assert (_mutator_rightmost == 0 || is_mutator_free(_mutator_rightmost), "rightmost region should be free: " SIZE_FORMAT, _mutator_rightmost);
690
691 size_t beg_off = _mutator_free_bitmap.find_first_set_bit(0);
692 size_t end_off = _mutator_free_bitmap.find_first_set_bit(_mutator_rightmost + 1);
693 assert (beg_off >= _mutator_leftmost, "free regions before the leftmost: " SIZE_FORMAT ", bound " SIZE_FORMAT, beg_off, _mutator_leftmost);
694 assert (end_off == _max, "free regions past the rightmost: " SIZE_FORMAT ", bound " SIZE_FORMAT, end_off, _mutator_rightmost);
695
696 assert (_collector_leftmost <= _max, "leftmost in bounds: " SIZE_FORMAT " < " SIZE_FORMAT, _collector_leftmost, _max);
697 assert (_collector_rightmost < _max, "rightmost in bounds: " SIZE_FORMAT " < " SIZE_FORMAT, _collector_rightmost, _max);
698
699 assert (_collector_leftmost == _max || is_collector_free(_collector_leftmost), "leftmost region should be free: " SIZE_FORMAT, _collector_leftmost);
700 assert (_collector_rightmost == 0 || is_collector_free(_collector_rightmost), "rightmost region should be free: " SIZE_FORMAT, _collector_rightmost);
701
702 beg_off = _collector_free_bitmap.find_first_set_bit(0);
703 end_off = _collector_free_bitmap.find_first_set_bit(_collector_rightmost + 1);
704 assert (beg_off >= _collector_leftmost, "free regions before the leftmost: " SIZE_FORMAT ", bound " SIZE_FORMAT, beg_off, _collector_leftmost);
705 assert (end_off == _max, "free regions past the rightmost: " SIZE_FORMAT ", bound " SIZE_FORMAT, end_off, _collector_rightmost);
706 }
707 #endif
|
1 /*
2 * Copyright (c) 2016, 2021, Red Hat, Inc. All rights reserved.
3 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "precompiled.hpp"
27 #include "gc/shared/tlab_globals.hpp"
28 #include "gc/shenandoah/shenandoahAffiliation.hpp"
29 #include "gc/shenandoah/shenandoahFreeSet.hpp"
30 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
31 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp"
32 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
33 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
34 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
35 #include "gc/shenandoah/shenandoahSimpleBitMap.hpp"
36 #include "gc/shenandoah/shenandoahSimpleBitMap.inline.hpp"
37 #include "logging/logStream.hpp"
38 #include "memory/resourceArea.hpp"
39 #include "runtime/orderAccess.hpp"
40
41 static const char* partition_name(ShenandoahFreeSetPartitionId t) {
42 switch (t) {
43 case ShenandoahFreeSetPartitionId::NotFree: return "NotFree";
44 case ShenandoahFreeSetPartitionId::Mutator: return "Mutator";
45 case ShenandoahFreeSetPartitionId::Collector: return "Collector";
46 case ShenandoahFreeSetPartitionId::OldCollector: return "OldCollector";
47 default:
48 ShouldNotReachHere();
49 return "Unrecognized";
50 }
51 }
52
53 class ShenandoahLeftRightIterator {
54 private:
55 idx_t _idx;
56 idx_t _end;
57 ShenandoahRegionPartitions* _partitions;
58 ShenandoahFreeSetPartitionId _partition;
59 public:
60 explicit ShenandoahLeftRightIterator(ShenandoahRegionPartitions* partitions, ShenandoahFreeSetPartitionId partition, bool use_empty = false)
61 : _idx(0), _end(0), _partitions(partitions), _partition(partition) {
62 _idx = use_empty ? _partitions->leftmost_empty(_partition) : _partitions->leftmost(_partition);
63 _end = use_empty ? _partitions->rightmost_empty(_partition) : _partitions->rightmost(_partition);
64 }
65
66 bool has_next() const {
67 if (_idx <= _end) {
68 assert(_partitions->in_free_set(_partition, _idx), "Boundaries or find_last_set_bit failed: " SSIZE_FORMAT, _idx);
69 return true;
70 }
71 return false;
72 }
73
74 idx_t current() const {
75 return _idx;
76 }
77
78 idx_t next() {
79 _idx = _partitions->find_index_of_next_available_region(_partition, _idx + 1);
80 return current();
81 }
82 };
83
84 class ShenandoahRightLeftIterator {
85 private:
86 idx_t _idx;
87 idx_t _end;
88 ShenandoahRegionPartitions* _partitions;
89 ShenandoahFreeSetPartitionId _partition;
90 public:
91 explicit ShenandoahRightLeftIterator(ShenandoahRegionPartitions* partitions, ShenandoahFreeSetPartitionId partition, bool use_empty = false)
92 : _idx(0), _end(0), _partitions(partitions), _partition(partition) {
93 _idx = use_empty ? _partitions->rightmost_empty(_partition) : _partitions->rightmost(_partition);
94 _end = use_empty ? _partitions->leftmost_empty(_partition) : _partitions->leftmost(_partition);
95 }
96
97 bool has_next() const {
98 if (_idx >= _end) {
99 assert(_partitions->in_free_set(_partition, _idx), "Boundaries or find_last_set_bit failed: " SSIZE_FORMAT, _idx);
100 return true;
101 }
102 return false;
103 }
104
105 idx_t current() const {
106 return _idx;
107 }
108
109 idx_t next() {
110 _idx = _partitions->find_index_of_previous_available_region(_partition, _idx - 1);
111 return current();
112 }
113 };
114
115 #ifndef PRODUCT
116 void ShenandoahRegionPartitions::dump_bitmap() const {
117 log_debug(gc)("Mutator range [" SSIZE_FORMAT ", " SSIZE_FORMAT "], Collector range [" SSIZE_FORMAT ", " SSIZE_FORMAT
118 "], Old Collector range [" SSIZE_FORMAT ", " SSIZE_FORMAT "]",
119 _leftmosts[int(ShenandoahFreeSetPartitionId::Mutator)],
120 _rightmosts[int(ShenandoahFreeSetPartitionId::Mutator)],
121 _leftmosts[int(ShenandoahFreeSetPartitionId::Collector)],
122 _rightmosts[int(ShenandoahFreeSetPartitionId::Collector)],
123 _leftmosts[int(ShenandoahFreeSetPartitionId::OldCollector)],
124 _rightmosts[int(ShenandoahFreeSetPartitionId::OldCollector)]);
125 log_debug(gc)("Empty Mutator range [" SSIZE_FORMAT ", " SSIZE_FORMAT
126 "], Empty Collector range [" SSIZE_FORMAT ", " SSIZE_FORMAT
127 "], Empty Old Collecto range [" SSIZE_FORMAT ", " SSIZE_FORMAT "]",
128 _leftmosts_empty[int(ShenandoahFreeSetPartitionId::Mutator)],
129 _rightmosts_empty[int(ShenandoahFreeSetPartitionId::Mutator)],
130 _leftmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)],
131 _rightmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)],
132 _leftmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)],
133 _rightmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)]);
134
135 log_debug(gc)("%6s: %18s %18s %18s %18s", "index", "Mutator Bits", "Collector Bits", "Old Collector Bits", "NotFree Bits");
136 dump_bitmap_range(0, _max-1);
137 }
138
139 void ShenandoahRegionPartitions::dump_bitmap_range(idx_t start_region_idx, idx_t end_region_idx) const {
140 assert((start_region_idx >= 0) && (start_region_idx < (idx_t) _max), "precondition");
141 assert((end_region_idx >= 0) && (end_region_idx < (idx_t) _max), "precondition");
142 idx_t aligned_start = _membership[int(ShenandoahFreeSetPartitionId::Mutator)].aligned_index(start_region_idx);
143 idx_t aligned_end = _membership[int(ShenandoahFreeSetPartitionId::Mutator)].aligned_index(end_region_idx);
144 idx_t alignment = _membership[int(ShenandoahFreeSetPartitionId::Mutator)].alignment();
145 while (aligned_start <= aligned_end) {
146 dump_bitmap_row(aligned_start);
147 aligned_start += alignment;
148 }
149 }
150
151 void ShenandoahRegionPartitions::dump_bitmap_row(idx_t region_idx) const {
152 assert((region_idx >= 0) && (region_idx < (idx_t) _max), "precondition");
153 idx_t aligned_idx = _membership[int(ShenandoahFreeSetPartitionId::Mutator)].aligned_index(region_idx);
154 uintx mutator_bits = _membership[int(ShenandoahFreeSetPartitionId::Mutator)].bits_at(aligned_idx);
155 uintx collector_bits = _membership[int(ShenandoahFreeSetPartitionId::Collector)].bits_at(aligned_idx);
156 uintx old_collector_bits = _membership[int(ShenandoahFreeSetPartitionId::OldCollector)].bits_at(aligned_idx);
157 uintx free_bits = mutator_bits | collector_bits | old_collector_bits;
158 uintx notfree_bits = ~free_bits;
159 log_debug(gc)(SSIZE_FORMAT_W(6) ": " SIZE_FORMAT_X_0 " 0x" SIZE_FORMAT_X_0 " 0x" SIZE_FORMAT_X_0 " 0x" SIZE_FORMAT_X_0,
160 aligned_idx, mutator_bits, collector_bits, old_collector_bits, notfree_bits);
161 }
162 #endif
163
164 ShenandoahRegionPartitions::ShenandoahRegionPartitions(size_t max_regions, ShenandoahFreeSet* free_set) :
165 _max(max_regions),
166 _region_size_bytes(ShenandoahHeapRegion::region_size_bytes()),
167 _free_set(free_set),
168 _membership{ ShenandoahSimpleBitMap(max_regions), ShenandoahSimpleBitMap(max_regions) , ShenandoahSimpleBitMap(max_regions) }
169 {
170 make_all_regions_unavailable();
171 }
172
173 inline bool ShenandoahFreeSet::can_allocate_from(ShenandoahHeapRegion *r) const {
174 return r->is_empty() || (r->is_trash() && !_heap->is_concurrent_weak_root_in_progress());
175 }
176
177 inline bool ShenandoahFreeSet::can_allocate_from(size_t idx) const {
178 ShenandoahHeapRegion* r = _heap->get_region(idx);
179 return can_allocate_from(r);
180 }
181
182 inline size_t ShenandoahFreeSet::alloc_capacity(ShenandoahHeapRegion *r) const {
183 if (r->is_trash()) {
184 // This would be recycled on allocation path
185 return ShenandoahHeapRegion::region_size_bytes();
186 } else {
187 return r->free();
188 }
189 }
190
191 inline size_t ShenandoahFreeSet::alloc_capacity(size_t idx) const {
192 ShenandoahHeapRegion* r = _heap->get_region(idx);
193 return alloc_capacity(r);
194 }
195
196 inline bool ShenandoahFreeSet::has_alloc_capacity(ShenandoahHeapRegion *r) const {
197 return alloc_capacity(r) > 0;
198 }
199
200 inline idx_t ShenandoahRegionPartitions::leftmost(ShenandoahFreeSetPartitionId which_partition) const {
201 assert (which_partition < NumPartitions, "selected free partition must be valid");
202 idx_t idx = _leftmosts[int(which_partition)];
203 if (idx >= _max) {
204 return _max;
205 } else {
206 // Cannot assert that membership[which_partition.is_set(idx) because this helper method may be used
207 // to query the original value of leftmost when leftmost must be adjusted because the interval representing
208 // which_partition is shrinking after the region that used to be leftmost is retired.
209 return idx;
210 }
211 }
212
213 inline idx_t ShenandoahRegionPartitions::rightmost(ShenandoahFreeSetPartitionId which_partition) const {
214 assert (which_partition < NumPartitions, "selected free partition must be valid");
215 idx_t idx = _rightmosts[int(which_partition)];
216 // Cannot assert that membership[which_partition.is_set(idx) because this helper method may be used
217 // to query the original value of leftmost when leftmost must be adjusted because the interval representing
218 // which_partition is shrinking after the region that used to be leftmost is retired.
219 return idx;
220 }
221
222 void ShenandoahRegionPartitions::make_all_regions_unavailable() {
223 for (size_t partition_id = 0; partition_id < IntNumPartitions; partition_id++) {
224 _membership[partition_id].clear_all();
225 _leftmosts[partition_id] = _max;
226 _rightmosts[partition_id] = -1;
227 _leftmosts_empty[partition_id] = _max;
228 _rightmosts_empty[partition_id] = -1;;
229 _capacity[partition_id] = 0;
230 _used[partition_id] = 0;
231 }
232 _region_counts[int(ShenandoahFreeSetPartitionId::Mutator)] = _region_counts[int(ShenandoahFreeSetPartitionId::Collector)] = 0;
233 }
234
235 void ShenandoahRegionPartitions::establish_mutator_intervals(idx_t mutator_leftmost, idx_t mutator_rightmost,
236 idx_t mutator_leftmost_empty, idx_t mutator_rightmost_empty,
237 size_t mutator_region_count, size_t mutator_used) {
238 _leftmosts[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_leftmost;
239 _rightmosts[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_rightmost;
240 _leftmosts_empty[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_leftmost_empty;
241 _rightmosts_empty[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_rightmost_empty;
242
243 _region_counts[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_region_count;
244 _used[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_used;
245 _capacity[int(ShenandoahFreeSetPartitionId::Mutator)] = mutator_region_count * _region_size_bytes;
246
247 _leftmosts[int(ShenandoahFreeSetPartitionId::Collector)] = _max;
248 _rightmosts[int(ShenandoahFreeSetPartitionId::Collector)] = -1;
249 _leftmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)] = _max;
250 _rightmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)] = -1;
251
252 _region_counts[int(ShenandoahFreeSetPartitionId::Collector)] = 0;
253 _used[int(ShenandoahFreeSetPartitionId::Collector)] = 0;
254 _capacity[int(ShenandoahFreeSetPartitionId::Collector)] = 0;
255 }
256
257 void ShenandoahRegionPartitions::establish_old_collector_intervals(idx_t old_collector_leftmost, idx_t old_collector_rightmost,
258 idx_t old_collector_leftmost_empty,
259 idx_t old_collector_rightmost_empty,
260 size_t old_collector_region_count, size_t old_collector_used) {
261 _leftmosts[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_leftmost;
262 _rightmosts[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_rightmost;
263 _leftmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_leftmost_empty;
264 _rightmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_rightmost_empty;
265
266 _region_counts[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_region_count;
267 _used[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_used;
268 _capacity[int(ShenandoahFreeSetPartitionId::OldCollector)] = old_collector_region_count * _region_size_bytes;
269 }
270
271 void ShenandoahRegionPartitions::increase_used(ShenandoahFreeSetPartitionId which_partition, size_t bytes) {
272 assert (which_partition < NumPartitions, "Partition must be valid");
273 _used[int(which_partition)] += bytes;
274 assert (_used[int(which_partition)] <= _capacity[int(which_partition)],
275 "Must not use (" SIZE_FORMAT ") more than capacity (" SIZE_FORMAT ") after increase by " SIZE_FORMAT,
276 _used[int(which_partition)], _capacity[int(which_partition)], bytes);
277 }
278
279 inline void ShenandoahRegionPartitions::shrink_interval_if_range_modifies_either_boundary(
280 ShenandoahFreeSetPartitionId partition, idx_t low_idx, idx_t high_idx) {
281 assert((low_idx <= high_idx) && (low_idx >= 0) && (high_idx < _max), "Range must span legal index values");
282 if (low_idx == leftmost(partition)) {
283 assert (!_membership[int(partition)].is_set(low_idx), "Do not shrink interval if region not removed");
284 if (high_idx + 1 == _max) {
285 _leftmosts[int(partition)] = _max;
286 } else {
287 _leftmosts[int(partition)] = find_index_of_next_available_region(partition, high_idx + 1);
288 }
289 if (_leftmosts_empty[int(partition)] < _leftmosts[int(partition)]) {
290 // This gets us closer to where we need to be; we'll scan further when leftmosts_empty is requested.
291 _leftmosts_empty[int(partition)] = _leftmosts[int(partition)];
292 }
293 }
294 if (high_idx == _rightmosts[int(partition)]) {
295 assert (!_membership[int(partition)].is_set(high_idx), "Do not shrink interval if region not removed");
296 if (low_idx == 0) {
297 _rightmosts[int(partition)] = -1;
298 } else {
299 _rightmosts[int(partition)] = find_index_of_previous_available_region(partition, low_idx - 1);
300 }
301 if (_rightmosts_empty[int(partition)] > _rightmosts[int(partition)]) {
302 // This gets us closer to where we need to be; we'll scan further when rightmosts_empty is requested.
303 _rightmosts_empty[int(partition)] = _rightmosts[int(partition)];
304 }
305 }
306 if (_leftmosts[int(partition)] > _rightmosts[int(partition)]) {
307 _leftmosts[int(partition)] = _max;
308 _rightmosts[int(partition)] = -1;
309 _leftmosts_empty[int(partition)] = _max;
310 _rightmosts_empty[int(partition)] = -1;
311 }
312 }
313
314 inline void ShenandoahRegionPartitions::shrink_interval_if_boundary_modified(ShenandoahFreeSetPartitionId partition, idx_t idx) {
315 shrink_interval_if_range_modifies_either_boundary(partition, idx, idx);
316 }
317
318 inline void ShenandoahRegionPartitions::expand_interval_if_boundary_modified(ShenandoahFreeSetPartitionId partition,
319 idx_t idx, size_t region_available) {
320 if (_leftmosts[int(partition)] > idx) {
321 _leftmosts[int(partition)] = idx;
322 }
323 if (_rightmosts[int(partition)] < idx) {
324 _rightmosts[int(partition)] = idx;
325 }
326 if (region_available == _region_size_bytes) {
327 if (_leftmosts_empty[int(partition)] > idx) {
328 _leftmosts_empty[int(partition)] = idx;
329 }
330 if (_rightmosts_empty[int(partition)] < idx) {
331 _rightmosts_empty[int(partition)] = idx;
332 }
333 }
334 }
335
336 void ShenandoahRegionPartitions::retire_range_from_partition(
337 ShenandoahFreeSetPartitionId partition, idx_t low_idx, idx_t high_idx) {
338
339 // Note: we may remove from free partition even if region is not entirely full, such as when available < PLAB::min_size()
340 assert ((low_idx < _max) && (high_idx < _max), "Both indices are sane: " SIZE_FORMAT " and " SIZE_FORMAT " < " SIZE_FORMAT,
341 low_idx, high_idx, _max);
342 assert (partition < NumPartitions, "Cannot remove from free partitions if not already free");
343
344 for (idx_t idx = low_idx; idx <= high_idx; idx++) {
345 assert (in_free_set(partition, idx), "Must be in partition to remove from partition");
346 _membership[int(partition)].clear_bit(idx);
347 }
348 _region_counts[int(partition)] -= high_idx + 1 - low_idx;
349 shrink_interval_if_range_modifies_either_boundary(partition, low_idx, high_idx);
350 }
351
352 void ShenandoahRegionPartitions::retire_from_partition(ShenandoahFreeSetPartitionId partition, idx_t idx, size_t used_bytes) {
353
354 // Note: we may remove from free partition even if region is not entirely full, such as when available < PLAB::min_size()
355 assert (idx < _max, "index is sane: " SIZE_FORMAT " < " SIZE_FORMAT, idx, _max);
356 assert (partition < NumPartitions, "Cannot remove from free partitions if not already free");
357 assert (in_free_set(partition, idx), "Must be in partition to remove from partition");
358
359 if (used_bytes < _region_size_bytes) {
360 // Count the alignment pad remnant of memory as used when we retire this region
361 increase_used(partition, _region_size_bytes - used_bytes);
362 }
363 _membership[int(partition)].clear_bit(idx);
364 shrink_interval_if_boundary_modified(partition, idx);
365 _region_counts[int(partition)]--;
366 }
367
368 void ShenandoahRegionPartitions::make_free(idx_t idx, ShenandoahFreeSetPartitionId which_partition, size_t available) {
369 assert (idx < _max, "index is sane: " SIZE_FORMAT " < " SIZE_FORMAT, idx, _max);
370 assert (membership(idx) == ShenandoahFreeSetPartitionId::NotFree, "Cannot make free if already free");
371 assert (which_partition < NumPartitions, "selected free partition must be valid");
372 assert (available <= _region_size_bytes, "Available cannot exceed region size");
373
374 _membership[int(which_partition)].set_bit(idx);
375 _capacity[int(which_partition)] += _region_size_bytes;
376 _used[int(which_partition)] += _region_size_bytes - available;
377 expand_interval_if_boundary_modified(which_partition, idx, available);
378 _region_counts[int(which_partition)]++;
379 }
380
381 bool ShenandoahRegionPartitions::is_mutator_partition(ShenandoahFreeSetPartitionId p) {
382 return (p == ShenandoahFreeSetPartitionId::Mutator);
383 }
384
385 bool ShenandoahRegionPartitions::is_young_collector_partition(ShenandoahFreeSetPartitionId p) {
386 return (p == ShenandoahFreeSetPartitionId::Collector);
387 }
388
389 bool ShenandoahRegionPartitions::is_old_collector_partition(ShenandoahFreeSetPartitionId p) {
390 return (p == ShenandoahFreeSetPartitionId::OldCollector);
391 }
392
393 bool ShenandoahRegionPartitions::available_implies_empty(size_t available_in_region) {
394 return (available_in_region == _region_size_bytes);
395 }
396
397
398 void ShenandoahRegionPartitions::move_from_partition_to_partition(idx_t idx, ShenandoahFreeSetPartitionId orig_partition,
399 ShenandoahFreeSetPartitionId new_partition, size_t available) {
400 ShenandoahHeapRegion* r = ShenandoahHeap::heap()->get_region(idx);
401 assert (idx < _max, "index is sane: " SIZE_FORMAT " < " SIZE_FORMAT, idx, _max);
402 assert (orig_partition < NumPartitions, "Original partition must be valid");
403 assert (new_partition < NumPartitions, "New partition must be valid");
404 assert (available <= _region_size_bytes, "Available cannot exceed region size");
405 assert (_membership[int(orig_partition)].is_set(idx), "Cannot move from partition unless in partition");
406 assert ((r != nullptr) && ((r->is_trash() && (available == _region_size_bytes)) ||
407 (r->used() + available == _region_size_bytes)),
408 "Used: " SIZE_FORMAT " + available: " SIZE_FORMAT " should equal region size: " SIZE_FORMAT,
409 ShenandoahHeap::heap()->get_region(idx)->used(), available, _region_size_bytes);
410
411 // Expected transitions:
412 // During rebuild: Mutator => Collector
413 // Mutator empty => Collector
414 // Mutator empty => OldCollector
415 // During flip_to_gc: Mutator empty => Collector
416 // Mutator empty => OldCollector
417 // At start of update refs: Collector => Mutator
418 // OldCollector Empty => Mutator
419 assert ((is_mutator_partition(orig_partition) && is_young_collector_partition(new_partition)) ||
420 (is_mutator_partition(orig_partition) &&
421 available_implies_empty(available) && is_old_collector_partition(new_partition)) ||
422 (is_young_collector_partition(orig_partition) && is_mutator_partition(new_partition)) ||
423 (is_old_collector_partition(orig_partition)
424 && available_implies_empty(available) && is_mutator_partition(new_partition)),
425 "Unexpected movement between partitions, available: " SIZE_FORMAT ", _region_size_bytes: " SIZE_FORMAT
426 ", orig_partition: %s, new_partition: %s",
427 available, _region_size_bytes, partition_name(orig_partition), partition_name(new_partition));
428
429 size_t used = _region_size_bytes - available;
430 assert (_used[int(orig_partition)] >= used,
431 "Orig partition used: " SIZE_FORMAT " must exceed moved used: " SIZE_FORMAT " within region " SSIZE_FORMAT,
432 _used[int(orig_partition)], used, idx);
433
434 _membership[int(orig_partition)].clear_bit(idx);
435 _membership[int(new_partition)].set_bit(idx);
436
437 _capacity[int(orig_partition)] -= _region_size_bytes;
438 _used[int(orig_partition)] -= used;
439 shrink_interval_if_boundary_modified(orig_partition, idx);
440
441 _capacity[int(new_partition)] += _region_size_bytes;;
442 _used[int(new_partition)] += used;
443 expand_interval_if_boundary_modified(new_partition, idx, available);
444
445 _region_counts[int(orig_partition)]--;
446 _region_counts[int(new_partition)]++;
447 }
448
449 const char* ShenandoahRegionPartitions::partition_membership_name(idx_t idx) const {
450 return partition_name(membership(idx));
451 }
452
453 inline ShenandoahFreeSetPartitionId ShenandoahRegionPartitions::membership(idx_t idx) const {
454 assert (idx < _max, "index is sane: " SIZE_FORMAT " < " SIZE_FORMAT, idx, _max);
455 ShenandoahFreeSetPartitionId result = ShenandoahFreeSetPartitionId::NotFree;
456 for (uint partition_id = 0; partition_id < UIntNumPartitions; partition_id++) {
457 if (_membership[partition_id].is_set(idx)) {
458 assert(result == ShenandoahFreeSetPartitionId::NotFree, "Region should reside in only one partition");
459 result = (ShenandoahFreeSetPartitionId) partition_id;
460 }
461 }
462 return result;
463 }
464
465 #ifdef ASSERT
466 inline bool ShenandoahRegionPartitions::partition_id_matches(idx_t idx, ShenandoahFreeSetPartitionId test_partition) const {
467 assert (idx < _max, "index is sane: " SIZE_FORMAT " < " SIZE_FORMAT, idx, _max);
468 assert (test_partition < ShenandoahFreeSetPartitionId::NotFree, "must be a valid partition");
469
470 return membership(idx) == test_partition;
471 }
472 #endif
473
474 inline bool ShenandoahRegionPartitions::is_empty(ShenandoahFreeSetPartitionId which_partition) const {
475 assert (which_partition < NumPartitions, "selected free partition must be valid");
476 return (leftmost(which_partition) > rightmost(which_partition));
477 }
478
479 inline idx_t ShenandoahRegionPartitions::find_index_of_next_available_region(
480 ShenandoahFreeSetPartitionId which_partition, idx_t start_index) const {
481 idx_t rightmost_idx = rightmost(which_partition);
482 idx_t leftmost_idx = leftmost(which_partition);
483 if ((rightmost_idx < leftmost_idx) || (start_index > rightmost_idx)) return _max;
484 if (start_index < leftmost_idx) {
485 start_index = leftmost_idx;
486 }
487 idx_t result = _membership[int(which_partition)].find_first_set_bit(start_index, rightmost_idx + 1);
488 if (result > rightmost_idx) {
489 result = _max;
490 }
491 assert (result >= start_index, "Requires progress");
492 return result;
493 }
494
495 inline idx_t ShenandoahRegionPartitions::find_index_of_previous_available_region(
496 ShenandoahFreeSetPartitionId which_partition, idx_t last_index) const {
497 idx_t rightmost_idx = rightmost(which_partition);
498 idx_t leftmost_idx = leftmost(which_partition);
499 // if (leftmost_idx == max) then (last_index < leftmost_idx)
500 if (last_index < leftmost_idx) return -1;
501 if (last_index > rightmost_idx) {
502 last_index = rightmost_idx;
503 }
504 idx_t result = _membership[int(which_partition)].find_last_set_bit(-1, last_index);
505 if (result < leftmost_idx) {
506 result = -1;
507 }
508 assert (result <= last_index, "Requires progress");
509 return result;
510 }
511
512 inline idx_t ShenandoahRegionPartitions::find_index_of_next_available_cluster_of_regions(
513 ShenandoahFreeSetPartitionId which_partition, idx_t start_index, size_t cluster_size) const {
514 idx_t rightmost_idx = rightmost(which_partition);
515 idx_t leftmost_idx = leftmost(which_partition);
516 if ((rightmost_idx < leftmost_idx) || (start_index > rightmost_idx)) return _max;
517 idx_t result = _membership[int(which_partition)].find_first_consecutive_set_bits(start_index, rightmost_idx + 1, cluster_size);
518 if (result > rightmost_idx) {
519 result = _max;
520 }
521 assert (result >= start_index, "Requires progress");
522 return result;
523 }
524
525 inline idx_t ShenandoahRegionPartitions::find_index_of_previous_available_cluster_of_regions(
526 ShenandoahFreeSetPartitionId which_partition, idx_t last_index, size_t cluster_size) const {
527 idx_t leftmost_idx = leftmost(which_partition);
528 // if (leftmost_idx == max) then (last_index < leftmost_idx)
529 if (last_index < leftmost_idx) return -1;
530 idx_t result = _membership[int(which_partition)].find_last_consecutive_set_bits(leftmost_idx - 1, last_index, cluster_size);
531 if (result <= leftmost_idx) {
532 result = -1;
533 }
534 assert (result <= last_index, "Requires progress");
535 return result;
536 }
537
538 idx_t ShenandoahRegionPartitions::leftmost_empty(ShenandoahFreeSetPartitionId which_partition) {
539 assert (which_partition < NumPartitions, "selected free partition must be valid");
540 idx_t max_regions = _max;
541 if (_leftmosts_empty[int(which_partition)] == _max) {
542 return _max;
543 }
544 for (idx_t idx = find_index_of_next_available_region(which_partition, _leftmosts_empty[int(which_partition)]);
545 idx < max_regions; ) {
546 assert(in_free_set(which_partition, idx), "Boundaries or find_last_set_bit failed: " SSIZE_FORMAT, idx);
547 if (_free_set->alloc_capacity(idx) == _region_size_bytes) {
548 _leftmosts_empty[int(which_partition)] = idx;
549 return idx;
550 }
551 idx = find_index_of_next_available_region(which_partition, idx + 1);
552 }
553 _leftmosts_empty[int(which_partition)] = _max;
554 _rightmosts_empty[int(which_partition)] = -1;
555 return _max;
556 }
557
558 idx_t ShenandoahRegionPartitions::rightmost_empty(ShenandoahFreeSetPartitionId which_partition) {
559 assert (which_partition < NumPartitions, "selected free partition must be valid");
560 if (_rightmosts_empty[int(which_partition)] < 0) {
561 return -1;
562 }
563 for (idx_t idx = find_index_of_previous_available_region(which_partition, _rightmosts_empty[int(which_partition)]);
564 idx >= 0; ) {
565 assert(in_free_set(which_partition, idx), "Boundaries or find_last_set_bit failed: " SSIZE_FORMAT, idx);
566 if (_free_set->alloc_capacity(idx) == _region_size_bytes) {
567 _rightmosts_empty[int(which_partition)] = idx;
568 return idx;
569 }
570 idx = find_index_of_previous_available_region(which_partition, idx - 1);
571 }
572 _leftmosts_empty[int(which_partition)] = _max;
573 _rightmosts_empty[int(which_partition)] = -1;
574 return -1;
575 }
576
577
578 #ifdef ASSERT
579 void ShenandoahRegionPartitions::assert_bounds() {
580
581 idx_t leftmosts[UIntNumPartitions];
582 idx_t rightmosts[UIntNumPartitions];
583 idx_t empty_leftmosts[UIntNumPartitions];
584 idx_t empty_rightmosts[UIntNumPartitions];
585
586 for (uint i = 0; i < UIntNumPartitions; i++) {
587 leftmosts[i] = _max;
588 empty_leftmosts[i] = _max;
589 rightmosts[i] = -1;
590 empty_rightmosts[i] = -1;
591 }
592
593 for (idx_t i = 0; i < _max; i++) {
594 ShenandoahFreeSetPartitionId partition = membership(i);
595 switch (partition) {
596 case ShenandoahFreeSetPartitionId::NotFree:
597 break;
598
599 case ShenandoahFreeSetPartitionId::Mutator:
600 case ShenandoahFreeSetPartitionId::Collector:
601 case ShenandoahFreeSetPartitionId::OldCollector:
602 {
603 size_t capacity = _free_set->alloc_capacity(i);
604 bool is_empty = (capacity == _region_size_bytes);
605 assert(capacity > 0, "free regions must have allocation capacity");
606 if (i < leftmosts[int(partition)]) {
607 leftmosts[int(partition)] = i;
608 }
609 if (is_empty && (i < empty_leftmosts[int(partition)])) {
610 empty_leftmosts[int(partition)] = i;
611 }
612 if (i > rightmosts[int(partition)]) {
613 rightmosts[int(partition)] = i;
614 }
615 if (is_empty && (i > empty_rightmosts[int(partition)])) {
616 empty_rightmosts[int(partition)] = i;
617 }
618 break;
619 }
620
621 default:
622 ShouldNotReachHere();
623 }
624 }
625
626 // Performance invariants. Failing these would not break the free partition, but performance would suffer.
627 assert (leftmost(ShenandoahFreeSetPartitionId::Mutator) <= _max,
628 "leftmost in bounds: " SSIZE_FORMAT " < " SSIZE_FORMAT, leftmost(ShenandoahFreeSetPartitionId::Mutator), _max);
629 assert (rightmost(ShenandoahFreeSetPartitionId::Mutator) < _max,
630 "rightmost in bounds: " SSIZE_FORMAT " < " SSIZE_FORMAT, rightmost(ShenandoahFreeSetPartitionId::Mutator), _max);
631
632 assert (leftmost(ShenandoahFreeSetPartitionId::Mutator) == _max
633 || partition_id_matches(leftmost(ShenandoahFreeSetPartitionId::Mutator), ShenandoahFreeSetPartitionId::Mutator),
634 "leftmost region should be free: " SSIZE_FORMAT, leftmost(ShenandoahFreeSetPartitionId::Mutator));
635 assert (leftmost(ShenandoahFreeSetPartitionId::Mutator) == _max
636 || partition_id_matches(rightmost(ShenandoahFreeSetPartitionId::Mutator), ShenandoahFreeSetPartitionId::Mutator),
637 "rightmost region should be free: " SSIZE_FORMAT, rightmost(ShenandoahFreeSetPartitionId::Mutator));
638
639 // If Mutator partition is empty, leftmosts will both equal max, rightmosts will both equal zero.
640 // Likewise for empty region partitions.
641 idx_t beg_off = leftmosts[int(ShenandoahFreeSetPartitionId::Mutator)];
642 idx_t end_off = rightmosts[int(ShenandoahFreeSetPartitionId::Mutator)];
643 assert (beg_off >= leftmost(ShenandoahFreeSetPartitionId::Mutator),
644 "free regions before the leftmost: " SSIZE_FORMAT ", bound " SSIZE_FORMAT,
645 beg_off, leftmost(ShenandoahFreeSetPartitionId::Mutator));
646 assert (end_off <= rightmost(ShenandoahFreeSetPartitionId::Mutator),
647 "free regions past the rightmost: " SSIZE_FORMAT ", bound " SSIZE_FORMAT,
648 end_off, rightmost(ShenandoahFreeSetPartitionId::Mutator));
649
650 beg_off = empty_leftmosts[int(ShenandoahFreeSetPartitionId::Mutator)];
651 end_off = empty_rightmosts[int(ShenandoahFreeSetPartitionId::Mutator)];
652 assert (beg_off >= leftmost_empty(ShenandoahFreeSetPartitionId::Mutator),
653 "free empty regions before the leftmost: " SSIZE_FORMAT ", bound " SSIZE_FORMAT,
654 beg_off, leftmost_empty(ShenandoahFreeSetPartitionId::Mutator));
655 assert (end_off <= rightmost_empty(ShenandoahFreeSetPartitionId::Mutator),
656 "free empty regions past the rightmost: " SSIZE_FORMAT ", bound " SSIZE_FORMAT,
657 end_off, rightmost_empty(ShenandoahFreeSetPartitionId::Mutator));
658
659 // Performance invariants. Failing these would not break the free partition, but performance would suffer.
660 assert (leftmost(ShenandoahFreeSetPartitionId::Collector) <= _max, "leftmost in bounds: " SSIZE_FORMAT " < " SSIZE_FORMAT,
661 leftmost(ShenandoahFreeSetPartitionId::Collector), _max);
662 assert (rightmost(ShenandoahFreeSetPartitionId::Collector) < _max, "rightmost in bounds: " SSIZE_FORMAT " < " SSIZE_FORMAT,
663 rightmost(ShenandoahFreeSetPartitionId::Collector), _max);
664
665 assert (leftmost(ShenandoahFreeSetPartitionId::Collector) == _max
666 || partition_id_matches(leftmost(ShenandoahFreeSetPartitionId::Collector), ShenandoahFreeSetPartitionId::Collector),
667 "leftmost region should be free: " SSIZE_FORMAT, leftmost(ShenandoahFreeSetPartitionId::Collector));
668 assert (leftmost(ShenandoahFreeSetPartitionId::Collector) == _max
669 || partition_id_matches(rightmost(ShenandoahFreeSetPartitionId::Collector), ShenandoahFreeSetPartitionId::Collector),
670 "rightmost region should be free: " SSIZE_FORMAT, rightmost(ShenandoahFreeSetPartitionId::Collector));
671
672 // If Collector partition is empty, leftmosts will both equal max, rightmosts will both equal zero.
673 // Likewise for empty region partitions.
674 beg_off = leftmosts[int(ShenandoahFreeSetPartitionId::Collector)];
675 end_off = rightmosts[int(ShenandoahFreeSetPartitionId::Collector)];
676 assert (beg_off >= leftmost(ShenandoahFreeSetPartitionId::Collector),
677 "free regions before the leftmost: " SSIZE_FORMAT ", bound " SSIZE_FORMAT,
678 beg_off, leftmost(ShenandoahFreeSetPartitionId::Collector));
679 assert (end_off <= rightmost(ShenandoahFreeSetPartitionId::Collector),
680 "free regions past the rightmost: " SSIZE_FORMAT ", bound " SSIZE_FORMAT,
681 end_off, rightmost(ShenandoahFreeSetPartitionId::Collector));
682
683 beg_off = empty_leftmosts[int(ShenandoahFreeSetPartitionId::Collector)];
684 end_off = empty_rightmosts[int(ShenandoahFreeSetPartitionId::Collector)];
685 assert (beg_off >= _leftmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)],
686 "free empty regions before the leftmost: " SSIZE_FORMAT ", bound " SSIZE_FORMAT,
687 beg_off, leftmost_empty(ShenandoahFreeSetPartitionId::Collector));
688 assert (end_off <= _rightmosts_empty[int(ShenandoahFreeSetPartitionId::Collector)],
689 "free empty regions past the rightmost: " SSIZE_FORMAT ", bound " SSIZE_FORMAT,
690 end_off, rightmost_empty(ShenandoahFreeSetPartitionId::Collector));
691
692 // Performance invariants. Failing these would not break the free partition, but performance would suffer.
693 assert (leftmost(ShenandoahFreeSetPartitionId::OldCollector) <= _max, "leftmost in bounds: " SSIZE_FORMAT " < " SSIZE_FORMAT,
694 leftmost(ShenandoahFreeSetPartitionId::OldCollector), _max);
695 assert (rightmost(ShenandoahFreeSetPartitionId::OldCollector) < _max, "rightmost in bounds: " SSIZE_FORMAT " < " SSIZE_FORMAT,
696 rightmost(ShenandoahFreeSetPartitionId::OldCollector), _max);
697
698 assert (leftmost(ShenandoahFreeSetPartitionId::OldCollector) == _max
699 || partition_id_matches(leftmost(ShenandoahFreeSetPartitionId::OldCollector),
700 ShenandoahFreeSetPartitionId::OldCollector),
701 "leftmost region should be free: " SSIZE_FORMAT, leftmost(ShenandoahFreeSetPartitionId::OldCollector));
702 assert (leftmost(ShenandoahFreeSetPartitionId::OldCollector) == _max
703 || partition_id_matches(rightmost(ShenandoahFreeSetPartitionId::OldCollector),
704 ShenandoahFreeSetPartitionId::OldCollector),
705 "rightmost region should be free: " SSIZE_FORMAT, rightmost(ShenandoahFreeSetPartitionId::OldCollector));
706
707 // If OldCollector partition is empty, leftmosts will both equal max, rightmosts will both equal zero.
708 // Likewise for empty region partitions.
709 beg_off = leftmosts[int(ShenandoahFreeSetPartitionId::OldCollector)];
710 end_off = rightmosts[int(ShenandoahFreeSetPartitionId::OldCollector)];
711 assert (beg_off >= leftmost(ShenandoahFreeSetPartitionId::OldCollector),
712 "free regions before the leftmost: " SSIZE_FORMAT ", bound " SSIZE_FORMAT,
713 beg_off, leftmost(ShenandoahFreeSetPartitionId::OldCollector));
714 assert (end_off <= rightmost(ShenandoahFreeSetPartitionId::OldCollector),
715 "free regions past the rightmost: " SSIZE_FORMAT ", bound " SSIZE_FORMAT,
716 end_off, rightmost(ShenandoahFreeSetPartitionId::OldCollector));
717
718 beg_off = empty_leftmosts[int(ShenandoahFreeSetPartitionId::OldCollector)];
719 end_off = empty_rightmosts[int(ShenandoahFreeSetPartitionId::OldCollector)];
720 assert (beg_off >= _leftmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)],
721 "free empty regions before the leftmost: " SSIZE_FORMAT ", bound " SSIZE_FORMAT,
722 beg_off, leftmost_empty(ShenandoahFreeSetPartitionId::OldCollector));
723 assert (end_off <= _rightmosts_empty[int(ShenandoahFreeSetPartitionId::OldCollector)],
724 "free empty regions past the rightmost: " SSIZE_FORMAT ", bound " SSIZE_FORMAT,
725 end_off, rightmost_empty(ShenandoahFreeSetPartitionId::OldCollector));
726 }
727 #endif
728
729 ShenandoahFreeSet::ShenandoahFreeSet(ShenandoahHeap* heap, size_t max_regions) :
730 _heap(heap),
731 _partitions(max_regions, this),
732 _trash_regions(NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, max_regions, mtGC)),
733 _alloc_bias_weight(0)
734 {
735 clear_internal();
736 }
737
738 void ShenandoahFreeSet::add_promoted_in_place_region_to_old_collector(ShenandoahHeapRegion* region) {
739 shenandoah_assert_heaplocked();
740 size_t plab_min_size_in_bytes = ShenandoahGenerationalHeap::heap()->plab_min_size() * HeapWordSize;
741 size_t idx = region->index();
742 size_t capacity = alloc_capacity(region);
743 assert(_partitions.membership(idx) == ShenandoahFreeSetPartitionId::NotFree,
744 "Regions promoted in place should have been excluded from Mutator partition");
745 if (capacity >= plab_min_size_in_bytes) {
746 _partitions.make_free(idx, ShenandoahFreeSetPartitionId::OldCollector, capacity);
747 _heap->old_generation()->augment_promoted_reserve(capacity);
748 }
749 }
750
751 HeapWord* ShenandoahFreeSet::allocate_from_partition_with_affiliation(ShenandoahAffiliation affiliation,
752 ShenandoahAllocRequest& req, bool& in_new_region) {
753
754 shenandoah_assert_heaplocked();
755 ShenandoahFreeSetPartitionId which_partition = req.is_old()? ShenandoahFreeSetPartitionId::OldCollector: ShenandoahFreeSetPartitionId::Collector;
756 if (_partitions.alloc_from_left_bias(which_partition)) {
757 ShenandoahLeftRightIterator iterator(&_partitions, which_partition, affiliation == ShenandoahAffiliation::FREE);
758 return allocate_with_affiliation(iterator, affiliation, req, in_new_region);
759 } else {
760 ShenandoahRightLeftIterator iterator(&_partitions, which_partition, affiliation == ShenandoahAffiliation::FREE);
761 return allocate_with_affiliation(iterator, affiliation, req, in_new_region);
762 }
763 }
764
765 template<typename Iter>
766 HeapWord* ShenandoahFreeSet::allocate_with_affiliation(Iter& iterator, ShenandoahAffiliation affiliation, ShenandoahAllocRequest& req, bool& in_new_region) {
767 for (idx_t idx = iterator.current(); iterator.has_next(); idx = iterator.next()) {
768 ShenandoahHeapRegion* r = _heap->get_region(idx);
769 if (r->affiliation() == affiliation) {
770 HeapWord* result = try_allocate_in(r, req, in_new_region);
771 if (result != nullptr) {
772 return result;
773 }
774 }
775 }
776 log_debug(gc, free)("Could not allocate collector region with affiliation: %s for request " PTR_FORMAT,
777 shenandoah_affiliation_name(affiliation), p2i(&req));
778 return nullptr;
779 }
780
781 HeapWord* ShenandoahFreeSet::allocate_single(ShenandoahAllocRequest& req, bool& in_new_region) {
782 shenandoah_assert_heaplocked();
783
784 // Scan the bitmap looking for a first fit.
785 //
786 // Leftmost and rightmost bounds provide enough caching to walk bitmap efficiently. Normally,
787 // we would find the region to allocate at right away.
788 //
789 // Allocations are biased: GC allocations are taken from the high end of the heap. Regular (and TLAB)
790 // mutator allocations are taken from the middle of heap, below the memory reserved for Collector.
791 // Humongous mutator allocations are taken from the bottom of the heap.
792 //
793 // Free set maintains mutator and collector partitions. Normally, each allocates only from its partition,
794 // except in special cases when the collector steals regions from the mutator partition.
795
796 // Overwrite with non-zero (non-NULL) values only if necessary for allocation bookkeeping.
797
798 switch (req.type()) {
799 case ShenandoahAllocRequest::_alloc_tlab:
800 case ShenandoahAllocRequest::_alloc_shared:
801 return allocate_for_mutator(req, in_new_region);
802 case ShenandoahAllocRequest::_alloc_gclab:
803 case ShenandoahAllocRequest::_alloc_plab:
804 case ShenandoahAllocRequest::_alloc_shared_gc:
805 return allocate_for_collector(req, in_new_region);
806 default:
807 ShouldNotReachHere();
808 }
809 return nullptr;
810 }
811
812 HeapWord* ShenandoahFreeSet::allocate_for_mutator(ShenandoahAllocRequest &req, bool &in_new_region) {
813 update_allocation_bias();
814
815 if (_partitions.is_empty(ShenandoahFreeSetPartitionId::Mutator)) {
816 // There is no recovery. Mutator does not touch collector view at all.
817 return nullptr;
818 }
819
820 // Try to allocate in the mutator view
821 if (_partitions.alloc_from_left_bias(ShenandoahFreeSetPartitionId::Mutator)) {
822 // Allocate from low to high memory. This keeps the range of fully empty regions more tightly packed.
823 // Note that the most recently allocated regions tend not to be evacuated in a given GC cycle. So this
824 // tends to accumulate "fragmented" uncollected regions in high memory.
825 ShenandoahLeftRightIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator);
826 return allocate_from_regions(iterator, req, in_new_region);
827 }
828
829 // Allocate from high to low memory. This preserves low memory for humongous allocations.
830 ShenandoahRightLeftIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator);
831 return allocate_from_regions(iterator, req, in_new_region);
832 }
833
834 void ShenandoahFreeSet::update_allocation_bias() {
835 if (_alloc_bias_weight-- <= 0) {
836 // We have observed that regions not collected in previous GC cycle tend to congregate at one end or the other
837 // of the heap. Typically, these are the more recently engaged regions and the objects in these regions have not
838 // yet had a chance to die (and/or are treated as floating garbage). If we use the same allocation bias on each
839 // GC pass, these "most recently" engaged regions for GC pass N will also be the "most recently" engaged regions
840 // for GC pass N+1, and the relatively large amount of live data and/or floating garbage introduced
841 // during the most recent GC pass may once again prevent the region from being collected. We have found that
842 // alternating the allocation behavior between GC passes improves evacuation performance by 3-7% on certain
843 // benchmarks. In the best case, this has the effect of consuming these partially consumed regions before
844 // the start of the next mark cycle so all of their garbage can be efficiently reclaimed.
845 //
846 // First, finish consuming regions that are already partially consumed so as to more tightly limit ranges of
847 // available regions. Other potential benefits:
848 // 1. Eventual collection set has fewer regions because we have packed newly allocated objects into fewer regions
849 // 2. We preserve the "empty" regions longer into the GC cycle, reducing likelihood of allocation failures
850 // late in the GC cycle.
851 idx_t non_empty_on_left = (_partitions.leftmost_empty(ShenandoahFreeSetPartitionId::Mutator)
852 - _partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator));
853 idx_t non_empty_on_right = (_partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator)
854 - _partitions.rightmost_empty(ShenandoahFreeSetPartitionId::Mutator));
855 _partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::Mutator, (non_empty_on_right < non_empty_on_left));
856 _alloc_bias_weight = INITIAL_ALLOC_BIAS_WEIGHT;
857 }
858 }
859
860 template<typename Iter>
861 HeapWord* ShenandoahFreeSet::allocate_from_regions(Iter& iterator, ShenandoahAllocRequest &req, bool &in_new_region) {
862 for (idx_t idx = iterator.current(); iterator.has_next(); idx = iterator.next()) {
863 ShenandoahHeapRegion* r = _heap->get_region(idx);
864 size_t min_size = (req.type() == ShenandoahAllocRequest::_alloc_tlab) ? req.min_size() : req.size();
865 if (alloc_capacity(r) >= min_size) {
866 HeapWord* result = try_allocate_in(r, req, in_new_region);
867 if (result != nullptr) {
868 return result;
869 }
870 }
871 }
872 return nullptr;
873 }
874
875 HeapWord* ShenandoahFreeSet::allocate_for_collector(ShenandoahAllocRequest &req, bool &in_new_region) {
876 // Fast-path: try to allocate in the collector view first
877 HeapWord* result;
878 result = allocate_from_partition_with_affiliation(req.affiliation(), req, in_new_region);
879 if (result != nullptr) {
880 return result;
881 }
882
883 bool allow_new_region = can_allocate_in_new_region(req);
884 if (allow_new_region) {
885 // Try a free region that is dedicated to GC allocations.
886 result = allocate_from_partition_with_affiliation(ShenandoahAffiliation::FREE, req, in_new_region);
887 if (result != nullptr) {
888 return result;
889 }
890 }
891
892 // No dice. Can we borrow space from mutator view?
893 if (!ShenandoahEvacReserveOverflow) {
894 return nullptr;
895 }
896
897 if (!allow_new_region && req.is_old() && (_heap->young_generation()->free_unaffiliated_regions() > 0)) {
898 // This allows us to flip a mutator region to old_collector
899 allow_new_region = true;
900 }
901
902 // We should expand old-gen if this can prevent an old-gen evacuation failure. We don't care so much about
903 // promotion failures since they can be mitigated in a subsequent GC pass. Would be nice to know if this
904 // allocation request is for evacuation or promotion. Individual threads limit their use of PLAB memory for
905 // promotions, so we already have an assurance that any additional memory set aside for old-gen will be used
906 // only for old-gen evacuations.
907 if (allow_new_region) {
908 // Try to steal an empty region from the mutator view.
909 result = try_allocate_from_mutator(req, in_new_region);
910 }
911
912 // This is it. Do not try to mix mutator and GC allocations, because adjusting region UWM
913 // due to GC allocations would expose unparsable mutator allocations.
914 return result;
915 }
916
917 bool ShenandoahFreeSet::can_allocate_in_new_region(const ShenandoahAllocRequest& req) {
918 if (!_heap->mode()->is_generational()) {
919 return true;
920 }
921
922 assert(req.is_old() || req.is_young(), "Should request affiliation");
923 return (req.is_old() && _heap->old_generation()->free_unaffiliated_regions() > 0)
924 || (req.is_young() && _heap->young_generation()->free_unaffiliated_regions() > 0);
925 }
926
927 HeapWord* ShenandoahFreeSet::try_allocate_from_mutator(ShenandoahAllocRequest& req, bool& in_new_region) {
928 // The collector prefers to keep longer lived regions toward the right side of the heap, so it always
929 // searches for regions from right to left here.
930 ShenandoahRightLeftIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator, true);
931 for (idx_t idx = iterator.current(); iterator.has_next(); idx = iterator.next()) {
932 ShenandoahHeapRegion* r = _heap->get_region(idx);
933 if (can_allocate_from(r)) {
934 if (req.is_old()) {
935 flip_to_old_gc(r);
936 } else {
937 flip_to_gc(r);
938 }
939 // Region r is entirely empty. If try_allocate_in fails on region r, something else is really wrong.
940 // Don't bother to retry with other regions.
941 log_debug(gc, free)("Flipped region " SIZE_FORMAT " to gc for request: " PTR_FORMAT, idx, p2i(&req));
942 return try_allocate_in(r, req, in_new_region);
943 }
944 }
945
946 return nullptr;
947 }
948
949 // This work method takes an argument corresponding to the number of bytes
950 // free in a region, and returns the largest amount in heapwords that can be allocated
951 // such that both of the following conditions are satisfied:
952 //
953 // 1. it is a multiple of card size
954 // 2. any remaining shard may be filled with a filler object
955 //
956 // The idea is that the allocation starts and ends at card boundaries. Because
957 // a region ('s end) is card-aligned, the remainder shard that must be filled is
958 // at the start of the free space.
959 //
960 // This is merely a helper method to use for the purpose of such a calculation.
961 size_t ShenandoahFreeSet::get_usable_free_words(size_t free_bytes) const {
962 // e.g. card_size is 512, card_shift is 9, min_fill_size() is 8
963 // free is 514
964 // usable_free is 512, which is decreased to 0
965 size_t usable_free = (free_bytes / CardTable::card_size()) << CardTable::card_shift();
966 assert(usable_free <= free_bytes, "Sanity check");
967 if ((free_bytes != usable_free) && (free_bytes - usable_free < ShenandoahHeap::min_fill_size() * HeapWordSize)) {
968 // After aligning to card multiples, the remainder would be smaller than
969 // the minimum filler object, so we'll need to take away another card's
970 // worth to construct a filler object.
971 if (usable_free >= CardTable::card_size()) {
972 usable_free -= CardTable::card_size();
973 } else {
974 assert(usable_free == 0, "usable_free is a multiple of card_size and card_size > min_fill_size");
975 }
976 }
977
978 return usable_free / HeapWordSize;
979 }
980
981 // Given a size argument, which is a multiple of card size, a request struct
982 // for a PLAB, and an old region, return a pointer to the allocated space for
983 // a PLAB which is card-aligned and where any remaining shard in the region
984 // has been suitably filled by a filler object.
985 // It is assumed (and assertion-checked) that such an allocation is always possible.
986 HeapWord* ShenandoahFreeSet::allocate_aligned_plab(size_t size, ShenandoahAllocRequest& req, ShenandoahHeapRegion* r) {
987 assert(_heap->mode()->is_generational(), "PLABs are only for generational mode");
988 assert(r->is_old(), "All PLABs reside in old-gen");
989 assert(!req.is_mutator_alloc(), "PLABs should not be allocated by mutators.");
990 assert(is_aligned(size, CardTable::card_size_in_words()), "Align by design");
991
992 HeapWord* result = r->allocate_aligned(size, req, CardTable::card_size());
993 assert(result != nullptr, "Allocation cannot fail");
994 assert(r->top() <= r->end(), "Allocation cannot span end of region");
995 assert(is_aligned(result, CardTable::card_size_in_words()), "Align by design");
996 return result;
997 }
998
999 HeapWord* ShenandoahFreeSet::try_allocate_in(ShenandoahHeapRegion* r, ShenandoahAllocRequest& req, bool& in_new_region) {
1000 assert (has_alloc_capacity(r), "Performance: should avoid full regions on this path: " SIZE_FORMAT, r->index());
1001 if (_heap->is_concurrent_weak_root_in_progress() && r->is_trash()) {
1002 return nullptr;
1003 }
1004 HeapWord* result = nullptr;
1005 try_recycle_trashed(r);
1006 in_new_region = r->is_empty();
1007
1008 if (in_new_region) {
1009 log_debug(gc)("Using new region (" SIZE_FORMAT ") for %s (" PTR_FORMAT ").",
1010 r->index(), ShenandoahAllocRequest::alloc_type_to_string(req.type()), p2i(&req));
1011 assert(!r->is_affiliated(), "New region " SIZE_FORMAT " should be unaffiliated", r->index());
1012 r->set_affiliation(req.affiliation());
1013 if (r->is_old()) {
1014 // Any OLD region allocated during concurrent coalesce-and-fill does not need to be coalesced and filled because
1015 // all objects allocated within this region are above TAMS (and thus are implicitly marked). In case this is an
1016 // OLD region and concurrent preparation for mixed evacuations visits this region before the start of the next
1017 // old-gen concurrent mark (i.e. this region is allocated following the start of old-gen concurrent mark but before
1018 // concurrent preparations for mixed evacuations are completed), we mark this region as not requiring any
1019 // coalesce-and-fill processing.
1020 r->end_preemptible_coalesce_and_fill();
1021 _heap->old_generation()->clear_cards_for(r);
1022 }
1023 _heap->generation_for(r->affiliation())->increment_affiliated_region_count();
1024
1025 #ifdef ASSERT
1026 ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
1027 assert(ctx->top_at_mark_start(r) == r->bottom(), "Newly established allocation region starts with TAMS equal to bottom");
1028 assert(ctx->is_bitmap_range_within_region_clear(ctx->top_bitmap(r), r->end()), "Bitmap above top_bitmap() must be clear");
1029 #endif
1030 log_debug(gc)("Using new region (" SIZE_FORMAT ") for %s (" PTR_FORMAT ").",
1031 r->index(), ShenandoahAllocRequest::alloc_type_to_string(req.type()), p2i(&req));
1032 } else {
1033 assert(r->is_affiliated(), "Region " SIZE_FORMAT " that is not new should be affiliated", r->index());
1034 if (r->affiliation() != req.affiliation()) {
1035 assert(_heap->mode()->is_generational(), "Request for %s from %s region should only happen in generational mode.",
1036 req.affiliation_name(), r->affiliation_name());
1037 return nullptr;
1038 }
1039 }
1040
1041 // req.size() is in words, r->free() is in bytes.
1042 if (req.is_lab_alloc()) {
1043 size_t adjusted_size = req.size();
1044 size_t free = r->free(); // free represents bytes available within region r
1045 if (req.type() == ShenandoahAllocRequest::_alloc_plab) {
1046 // This is a PLAB allocation
1047 assert(_heap->mode()->is_generational(), "PLABs are only for generational mode");
1048 assert(_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, r->index()),
1049 "PLABS must be allocated in old_collector_free regions");
1050
1051 // Need to assure that plabs are aligned on multiple of card region
1052 // Convert free from unaligned bytes to aligned number of words
1053 size_t usable_free = get_usable_free_words(free);
1054 if (adjusted_size > usable_free) {
1055 adjusted_size = usable_free;
1056 }
1057 adjusted_size = align_down(adjusted_size, CardTable::card_size_in_words());
1058 if (adjusted_size >= req.min_size()) {
1059 result = allocate_aligned_plab(adjusted_size, req, r);
1060 assert(result != nullptr, "allocate must succeed");
1061 req.set_actual_size(adjusted_size);
1062 } else {
1063 // Otherwise, leave result == nullptr because the adjusted size is smaller than min size.
1064 log_trace(gc, free)("Failed to shrink PLAB request (" SIZE_FORMAT ") in region " SIZE_FORMAT " to " SIZE_FORMAT
1065 " because min_size() is " SIZE_FORMAT, req.size(), r->index(), adjusted_size, req.min_size());
1066 }
1067 } else {
1068 // This is a GCLAB or a TLAB allocation
1069 // Convert free from unaligned bytes to aligned number of words
1070 free = align_down(free >> LogHeapWordSize, MinObjAlignment);
1071 if (adjusted_size > free) {
1072 adjusted_size = free;
1073 }
1074 if (adjusted_size >= req.min_size()) {
1075 result = r->allocate(adjusted_size, req);
1076 assert (result != nullptr, "Allocation must succeed: free " SIZE_FORMAT ", actual " SIZE_FORMAT, free, adjusted_size);
1077 req.set_actual_size(adjusted_size);
1078 } else {
1079 log_trace(gc, free)("Failed to shrink TLAB or GCLAB request (" SIZE_FORMAT ") in region " SIZE_FORMAT " to " SIZE_FORMAT
1080 " because min_size() is " SIZE_FORMAT, req.size(), r->index(), adjusted_size, req.min_size());
1081 }
1082 }
1083 } else {
1084 size_t size = req.size();
1085 result = r->allocate(size, req);
1086 if (result != nullptr) {
1087 // Record actual allocation size
1088 req.set_actual_size(size);
1089 }
1090 }
1091
1092 if (result != nullptr) {
1093 // Allocation successful, bump stats:
1094 if (req.is_mutator_alloc()) {
1095 assert(req.is_young(), "Mutator allocations always come from young generation.");
1096 _partitions.increase_used(ShenandoahFreeSetPartitionId::Mutator, req.actual_size() * HeapWordSize);
1097 } else {
1098 assert(req.is_gc_alloc(), "Should be gc_alloc since req wasn't mutator alloc");
1099
1100 // For GC allocations, we advance update_watermark because the objects relocated into this memory during
1101 // evacuation are not updated during evacuation. For both young and old regions r, it is essential that all
1102 // PLABs be made parsable at the end of evacuation. This is enabled by retiring all plabs at end of evacuation.
1103 r->set_update_watermark(r->top());
1104 if (r->is_old()) {
1105 _partitions.increase_used(ShenandoahFreeSetPartitionId::OldCollector, req.actual_size() * HeapWordSize);
1106 assert(req.type() != ShenandoahAllocRequest::_alloc_gclab, "old-gen allocations use PLAB or shared allocation");
1107 // for plabs, we'll sort the difference between evac and promotion usage when we retire the plab
1108 } else {
1109 _partitions.increase_used(ShenandoahFreeSetPartitionId::Collector, req.actual_size() * HeapWordSize);
1110 }
1111 }
1112 }
1113
1114 static const size_t min_capacity = (size_t) (ShenandoahHeapRegion::region_size_bytes() * (1.0 - 1.0 / ShenandoahEvacWaste));
1115 size_t ac = alloc_capacity(r);
1116
1117 if (((result == nullptr) && (ac < min_capacity)) || (alloc_capacity(r) < PLAB::min_size() * HeapWordSize)) {
1118 // Regardless of whether this allocation succeeded, if the remaining memory is less than PLAB:min_size(), retire this region.
1119 // Note that retire_from_partition() increases used to account for waste.
1120
1121 // Also, if this allocation request failed and the consumed within this region * ShenandoahEvacWaste > region size,
1122 // then retire the region so that subsequent searches can find available memory more quickly.
1123
1124 size_t idx = r->index();
1125 ShenandoahFreeSetPartitionId orig_partition;
1126 if (req.is_mutator_alloc()) {
1127 orig_partition = ShenandoahFreeSetPartitionId::Mutator;
1128 } else if (req.type() == ShenandoahAllocRequest::_alloc_gclab) {
1129 orig_partition = ShenandoahFreeSetPartitionId::Collector;
1130 } else if (req.type() == ShenandoahAllocRequest::_alloc_plab) {
1131 orig_partition = ShenandoahFreeSetPartitionId::OldCollector;
1132 } else {
1133 assert(req.type() == ShenandoahAllocRequest::_alloc_shared_gc, "Unexpected allocation type");
1134 if (req.is_old()) {
1135 orig_partition = ShenandoahFreeSetPartitionId::OldCollector;
1136 } else {
1137 orig_partition = ShenandoahFreeSetPartitionId::Collector;
1138 }
1139 }
1140 _partitions.retire_from_partition(orig_partition, idx, r->used());
1141 _partitions.assert_bounds();
1142 }
1143 return result;
1144 }
1145
1146 HeapWord* ShenandoahFreeSet::allocate_contiguous(ShenandoahAllocRequest& req) {
1147 assert(req.is_mutator_alloc(), "All humongous allocations are performed by mutator");
1148 shenandoah_assert_heaplocked();
1149
1150 size_t words_size = req.size();
1151 idx_t num = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
1152
1153 assert(req.is_young(), "Humongous regions always allocated in YOUNG");
1154 ShenandoahGeneration* generation = _heap->generation_for(req.affiliation());
1155
1156 // Check if there are enough regions left to satisfy allocation.
1157 if (num > (idx_t) _partitions.count(ShenandoahFreeSetPartitionId::Mutator)) {
1158 return nullptr;
1159 }
1160
1161 idx_t start_range = _partitions.leftmost_empty(ShenandoahFreeSetPartitionId::Mutator);
1162 idx_t end_range = _partitions.rightmost_empty(ShenandoahFreeSetPartitionId::Mutator) + 1;
1163 idx_t last_possible_start = end_range - num;
1164
1165 // Find the continuous interval of $num regions, starting from $beg and ending in $end,
1166 // inclusive. Contiguous allocations are biased to the beginning.
1167 idx_t beg = _partitions.find_index_of_next_available_cluster_of_regions(ShenandoahFreeSetPartitionId::Mutator,
1168 start_range, num);
1169 if (beg > last_possible_start) {
1170 // Hit the end, goodbye
1171 return nullptr;
1172 }
1173 idx_t end = beg;
1174
1175 while (true) {
1176 // We've confirmed num contiguous regions belonging to Mutator partition, so no need to confirm membership.
1177 // If region is not completely free, the current [beg; end] is useless, and we may fast-forward. If we can extend
1178 // the existing range, we can exploit that certain regions are already known to be in the Mutator free set.
1179 while (!can_allocate_from(_heap->get_region(end))) {
1180 // region[end] is not empty, so we restart our search after region[end]
1181 idx_t slide_delta = end + 1 - beg;
1182 if (beg + slide_delta > last_possible_start) {
1183 // no room to slide
1184 return nullptr;
1185 }
1186 for (idx_t span_end = beg + num; slide_delta > 0; slide_delta--) {
1187 if (!_partitions.in_free_set(ShenandoahFreeSetPartitionId::Mutator, span_end)) {
1188 beg = _partitions.find_index_of_next_available_cluster_of_regions(ShenandoahFreeSetPartitionId::Mutator,
1189 span_end + 1, num);
1190 break;
1191 } else {
1192 beg++;
1193 span_end++;
1194 }
1195 }
1196 // Here, either beg identifies a range of num regions all of which are in the Mutator free set, or beg > last_possible_start
1197 if (beg > last_possible_start) {
1198 // Hit the end, goodbye
1199 return nullptr;
1200 }
1201 end = beg;
1202 }
1203
1204 if ((end - beg + 1) == num) {
1205 // found the match
1206 break;
1207 }
1208
1209 end++;
1210 }
1211
1212 size_t remainder = words_size & ShenandoahHeapRegion::region_size_words_mask();
1213 // Initialize regions:
1214 for (idx_t i = beg; i <= end; i++) {
1215 ShenandoahHeapRegion* r = _heap->get_region(i);
1216 try_recycle_trashed(r);
1217
1218 assert(i == beg || _heap->get_region(i - 1)->index() + 1 == r->index(), "Should be contiguous");
1219 assert(r->is_empty(), "Should be empty");
1220
1221 if (i == beg) {
1222 r->make_humongous_start();
1223 } else {
1224 r->make_humongous_cont();
1225 }
1226
1227 // Trailing region may be non-full, record the remainder there
1228 size_t used_words;
1229 if ((i == end) && (remainder != 0)) {
1230 used_words = remainder;
1231 } else {
1232 used_words = ShenandoahHeapRegion::region_size_words();
1233 }
1234
1235 r->set_affiliation(req.affiliation());
1236 r->set_update_watermark(r->bottom());
1237 r->set_top(r->bottom() + used_words);
1238 }
1239 generation->increase_affiliated_region_count(num);
1240 if (remainder != 0) {
1241 // Record this remainder as allocation waste
1242 _heap->notify_mutator_alloc_words(ShenandoahHeapRegion::region_size_words() - remainder, true);
1243 }
1244
1245 // retire_range_from_partition() will adjust bounds on Mutator free set if appropriate
1246 _partitions.retire_range_from_partition(ShenandoahFreeSetPartitionId::Mutator, beg, end);
1247
1248 size_t total_humongous_size = ShenandoahHeapRegion::region_size_bytes() * num;
1249 _partitions.increase_used(ShenandoahFreeSetPartitionId::Mutator, total_humongous_size);
1250 _partitions.assert_bounds();
1251 req.set_actual_size(words_size);
1252 if (remainder != 0) {
1253 req.set_waste(ShenandoahHeapRegion::region_size_words() - remainder);
1254 }
1255 return _heap->get_region(beg)->bottom();
1256 }
1257
1258 void ShenandoahFreeSet::try_recycle_trashed(ShenandoahHeapRegion* r) {
1259 if (r->is_trash()) {
1260 r->recycle();
1261 }
1262 }
1263
1264 void ShenandoahFreeSet::recycle_trash() {
1265 // lock is not reentrable, check we don't have it
1266 shenandoah_assert_not_heaplocked();
1267 size_t count = 0;
1268 for (size_t i = 0; i < _heap->num_regions(); i++) {
1269 ShenandoahHeapRegion* r = _heap->get_region(i);
1270 if (r->is_trash()) {
1271 _trash_regions[count++] = r;
1272 }
1273 }
1274
1275 size_t total_batches = 0;
1276 jlong batch_start_time = 0;
1277 jlong recycle_trash_start_time = os::javaTimeNanos(); // This value will be treated as the initial batch_start_time
1278 jlong batch_end_time = recycle_trash_start_time;
1279 // Process as many batches as can be processed within 10 us.
1280 static constexpr jlong deadline_ns = 10000; // 10 us
1281 size_t idx = 0;
1282 jlong predicted_next_batch_end_time;
1283 jlong batch_process_time_estimate = 0;
1284 while (idx < count) {
1285 if (idx > 0) {
1286 os::naked_yield(); // Yield to allow allocators to take the lock, except on the first iteration
1287 }
1288 // Avoid another call to javaTimeNanos() if we already know time at which last batch ended
1289 batch_start_time = batch_end_time;
1290 const jlong deadline = batch_start_time + deadline_ns;
1291
1292 ShenandoahHeapLocker locker(_heap->lock());
1293 do {
1294 // Measurements on typical 2024 hardware suggest it typically requires between 1400 and 2000 ns to process a batch of
1295 // 32 regions, assuming low contention with other threads. Sometimes this goes higher, when mutator threads
1296 // are contending for CPU cores and/or the heap lock. On this hardware with a 10 us deadline, we expect 3-6 batches
1297 // to be processed between yields most of the time.
1298 //
1299 // Note that deadline is enforced since the end of previous batch. In the case that yield() or acquisition of heap lock
1300 // takes a "long time", we will have less time to process regions, but we will always process at least one batch between
1301 // yields. Yielding more frequently when there is heavy contention for the heap lock or for CPU cores is considered the
1302 // right thing to do.
1303 const size_t REGIONS_PER_BATCH = 32;
1304 size_t max_idx = MIN2(count, idx + REGIONS_PER_BATCH);
1305 while (idx < max_idx) {
1306 try_recycle_trashed(_trash_regions[idx++]);
1307 }
1308 total_batches++;
1309 batch_end_time = os::javaTimeNanos();
1310 // Estimate includes historic combination of yield times and heap lock acquisition times.
1311 batch_process_time_estimate = (batch_end_time - recycle_trash_start_time) / total_batches;
1312 predicted_next_batch_end_time = batch_end_time + batch_process_time_estimate;
1313 } while ((idx < count) && (predicted_next_batch_end_time < deadline));
1314 }
1315 }
1316
1317 void ShenandoahFreeSet::flip_to_old_gc(ShenandoahHeapRegion* r) {
1318 size_t idx = r->index();
1319
1320 assert(_partitions.partition_id_matches(idx, ShenandoahFreeSetPartitionId::Mutator), "Should be in mutator view");
1321 assert(can_allocate_from(r), "Should not be allocated");
1322
1323 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
1324 size_t region_capacity = alloc_capacity(r);
1325 _partitions.move_from_partition_to_partition(idx, ShenandoahFreeSetPartitionId::Mutator,
1326 ShenandoahFreeSetPartitionId::OldCollector, region_capacity);
1327 _partitions.assert_bounds();
1328 _heap->old_generation()->augment_evacuation_reserve(region_capacity);
1329 bool transferred = gen_heap->generation_sizer()->transfer_to_old(1);
1330 if (!transferred) {
1331 log_warning(gc, free)("Forcing transfer of " SIZE_FORMAT " to old reserve.", idx);
1332 gen_heap->generation_sizer()->force_transfer_to_old(1);
1333 }
1334 // We do not ensure that the region is no longer trash, relying on try_allocate_in(), which always comes next,
1335 // to recycle trash before attempting to allocate anything in the region.
1336 }
1337
1338 void ShenandoahFreeSet::flip_to_gc(ShenandoahHeapRegion* r) {
1339 size_t idx = r->index();
1340
1341 assert(_partitions.partition_id_matches(idx, ShenandoahFreeSetPartitionId::Mutator), "Should be in mutator view");
1342 assert(can_allocate_from(r), "Should not be allocated");
1343
1344 size_t ac = alloc_capacity(r);
1345 _partitions.move_from_partition_to_partition(idx, ShenandoahFreeSetPartitionId::Mutator,
1346 ShenandoahFreeSetPartitionId::Collector, ac);
1347 _partitions.assert_bounds();
1348
1349 // We do not ensure that the region is no longer trash, relying on try_allocate_in(), which always comes next,
1350 // to recycle trash before attempting to allocate anything in the region.
1351 }
1352
1353 void ShenandoahFreeSet::clear() {
1354 shenandoah_assert_heaplocked();
1355 clear_internal();
1356 }
1357
1358 void ShenandoahFreeSet::clear_internal() {
1359 _partitions.make_all_regions_unavailable();
1360
1361 _alloc_bias_weight = 0;
1362 _partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::Mutator, true);
1363 _partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::Collector, false);
1364 _partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::OldCollector, false);
1365 }
1366
1367 void ShenandoahFreeSet::find_regions_with_alloc_capacity(size_t &young_cset_regions, size_t &old_cset_regions,
1368 size_t &first_old_region, size_t &last_old_region,
1369 size_t &old_region_count) {
1370 clear_internal();
1371
1372 first_old_region = _heap->num_regions();
1373 last_old_region = 0;
1374 old_region_count = 0;
1375 old_cset_regions = 0;
1376 young_cset_regions = 0;
1377
1378 size_t region_size_bytes = _partitions.region_size_bytes();
1379 size_t max_regions = _partitions.max_regions();
1380
1381 size_t mutator_leftmost = max_regions;
1382 size_t mutator_rightmost = 0;
1383 size_t mutator_leftmost_empty = max_regions;
1384 size_t mutator_rightmost_empty = 0;
1385 size_t mutator_regions = 0;
1386 size_t mutator_used = 0;
1387
1388 size_t old_collector_leftmost = max_regions;
1389 size_t old_collector_rightmost = 0;
1390 size_t old_collector_leftmost_empty = max_regions;
1391 size_t old_collector_rightmost_empty = 0;
1392 size_t old_collector_regions = 0;
1393 size_t old_collector_used = 0;
1394
1395 size_t num_regions = _heap->num_regions();
1396 for (size_t idx = 0; idx < num_regions; idx++) {
1397 ShenandoahHeapRegion* region = _heap->get_region(idx);
1398 if (region->is_trash()) {
1399 // Trashed regions represent regions that had been in the collection partition but have not yet been "cleaned up".
1400 // The cset regions are not "trashed" until we have finished update refs.
1401 if (region->is_old()) {
1402 old_cset_regions++;
1403 } else {
1404 assert(region->is_young(), "Trashed region should be old or young");
1405 young_cset_regions++;
1406 }
1407 } else if (region->is_old()) {
1408 // count both humongous and regular regions, but don't count trash (cset) regions.
1409 old_region_count++;
1410 if (first_old_region > idx) {
1411 first_old_region = idx;
1412 }
1413 last_old_region = idx;
1414 }
1415 if (region->is_alloc_allowed() || region->is_trash()) {
1416 assert(!region->is_cset(), "Shouldn't be adding cset regions to the free set");
1417
1418 // Do not add regions that would almost surely fail allocation
1419 size_t ac = alloc_capacity(region);
1420 if (ac > PLAB::min_size() * HeapWordSize) {
1421 if (region->is_trash() || !region->is_old()) {
1422 // Both young and old collected regions (trashed) are placed into the Mutator set
1423 _partitions.raw_assign_membership(idx, ShenandoahFreeSetPartitionId::Mutator);
1424 if (idx < mutator_leftmost) {
1425 mutator_leftmost = idx;
1426 }
1427 if (idx > mutator_rightmost) {
1428 mutator_rightmost = idx;
1429 }
1430 if (ac == region_size_bytes) {
1431 if (idx < mutator_leftmost_empty) {
1432 mutator_leftmost_empty = idx;
1433 }
1434 if (idx > mutator_rightmost_empty) {
1435 mutator_rightmost_empty = idx;
1436 }
1437 }
1438 mutator_regions++;
1439 mutator_used += (region_size_bytes - ac);
1440 } else {
1441 // !region->is_trash() && region is_old()
1442 _partitions.raw_assign_membership(idx, ShenandoahFreeSetPartitionId::OldCollector);
1443 if (idx < old_collector_leftmost) {
1444 old_collector_leftmost = idx;
1445 }
1446 if (idx > old_collector_rightmost) {
1447 old_collector_rightmost = idx;
1448 }
1449 if (ac == region_size_bytes) {
1450 if (idx < old_collector_leftmost_empty) {
1451 old_collector_leftmost_empty = idx;
1452 }
1453 if (idx > old_collector_rightmost_empty) {
1454 old_collector_rightmost_empty = idx;
1455 }
1456 }
1457 old_collector_regions++;
1458 old_collector_used += (region_size_bytes - ac);
1459 }
1460 }
1461 }
1462 }
1463 log_debug(gc)(" At end of prep_to_rebuild, mutator_leftmost: " SIZE_FORMAT
1464 ", mutator_rightmost: " SIZE_FORMAT
1465 ", mutator_leftmost_empty: " SIZE_FORMAT
1466 ", mutator_rightmost_empty: " SIZE_FORMAT
1467 ", mutator_regions: " SIZE_FORMAT
1468 ", mutator_used: " SIZE_FORMAT,
1469 mutator_leftmost, mutator_rightmost, mutator_leftmost_empty, mutator_rightmost_empty,
1470 mutator_regions, mutator_used);
1471
1472 log_debug(gc)(" old_collector_leftmost: " SIZE_FORMAT
1473 ", old_collector_rightmost: " SIZE_FORMAT
1474 ", old_collector_leftmost_empty: " SIZE_FORMAT
1475 ", old_collector_rightmost_empty: " SIZE_FORMAT
1476 ", old_collector_regions: " SIZE_FORMAT
1477 ", old_collector_used: " SIZE_FORMAT,
1478 old_collector_leftmost, old_collector_rightmost, old_collector_leftmost_empty, old_collector_rightmost_empty,
1479 old_collector_regions, old_collector_used);
1480
1481 idx_t rightmost_idx = (mutator_leftmost == max_regions)? -1: (idx_t) mutator_rightmost;
1482 idx_t rightmost_empty_idx = (mutator_leftmost_empty == max_regions)? -1: (idx_t) mutator_rightmost_empty;
1483 _partitions.establish_mutator_intervals(mutator_leftmost, rightmost_idx, mutator_leftmost_empty, rightmost_empty_idx,
1484 mutator_regions, mutator_used);
1485 rightmost_idx = (old_collector_leftmost == max_regions)? -1: (idx_t) old_collector_rightmost;
1486 rightmost_empty_idx = (old_collector_leftmost_empty == max_regions)? -1: (idx_t) old_collector_rightmost_empty;
1487 _partitions.establish_old_collector_intervals(old_collector_leftmost, rightmost_idx, old_collector_leftmost_empty,
1488 rightmost_empty_idx, old_collector_regions, old_collector_used);
1489 log_debug(gc)(" After find_regions_with_alloc_capacity(), Mutator range [" SSIZE_FORMAT ", " SSIZE_FORMAT "],"
1490 " Old Collector range [" SSIZE_FORMAT ", " SSIZE_FORMAT "]",
1491 _partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator),
1492 _partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator),
1493 _partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector),
1494 _partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector));
1495 }
1496
1497 // Returns number of regions transferred, adds transferred bytes to var argument bytes_transferred
1498 size_t ShenandoahFreeSet::transfer_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId which_collector,
1499 size_t max_xfer_regions,
1500 size_t& bytes_transferred) {
1501 shenandoah_assert_heaplocked();
1502 const size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
1503 size_t transferred_regions = 0;
1504 ShenandoahLeftRightIterator iterator(&_partitions, which_collector, true);
1505 idx_t rightmost = _partitions.rightmost_empty(which_collector);
1506 for (idx_t idx = iterator.current(); transferred_regions < max_xfer_regions && iterator.has_next(); idx = iterator.next()) {
1507 // Note: can_allocate_from() denotes that region is entirely empty
1508 if (can_allocate_from(idx)) {
1509 _partitions.move_from_partition_to_partition(idx, which_collector, ShenandoahFreeSetPartitionId::Mutator, region_size_bytes);
1510 transferred_regions++;
1511 bytes_transferred += region_size_bytes;
1512 }
1513 }
1514 return transferred_regions;
1515 }
1516
1517 // Returns number of regions transferred, adds transferred bytes to var argument bytes_transferred
1518 size_t ShenandoahFreeSet::transfer_non_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId which_collector,
1519 size_t max_xfer_regions,
1520 size_t& bytes_transferred) {
1521 shenandoah_assert_heaplocked();
1522 size_t transferred_regions = 0;
1523 ShenandoahLeftRightIterator iterator(&_partitions, which_collector, false);
1524 for (idx_t idx = iterator.current(); transferred_regions < max_xfer_regions && iterator.has_next(); idx = iterator.next()) {
1525 size_t ac = alloc_capacity(idx);
1526 if (ac > 0) {
1527 _partitions.move_from_partition_to_partition(idx, which_collector, ShenandoahFreeSetPartitionId::Mutator, ac);
1528 transferred_regions++;
1529 bytes_transferred += ac;
1530 }
1531 }
1532 return transferred_regions;
1533 }
1534
1535 void ShenandoahFreeSet::move_regions_from_collector_to_mutator(size_t max_xfer_regions) {
1536 size_t collector_xfer = 0;
1537 size_t old_collector_xfer = 0;
1538
1539 // Process empty regions within the Collector free partition
1540 if ((max_xfer_regions > 0) &&
1541 (_partitions.leftmost_empty(ShenandoahFreeSetPartitionId::Collector)
1542 <= _partitions.rightmost_empty(ShenandoahFreeSetPartitionId::Collector))) {
1543 ShenandoahHeapLocker locker(_heap->lock());
1544 max_xfer_regions -=
1545 transfer_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId::Collector, max_xfer_regions,
1546 collector_xfer);
1547 }
1548
1549 // Process empty regions within the OldCollector free partition
1550 if ((max_xfer_regions > 0) &&
1551 (_partitions.leftmost_empty(ShenandoahFreeSetPartitionId::OldCollector)
1552 <= _partitions.rightmost_empty(ShenandoahFreeSetPartitionId::OldCollector))) {
1553 ShenandoahHeapLocker locker(_heap->lock());
1554 size_t old_collector_regions =
1555 transfer_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId::OldCollector, max_xfer_regions,
1556 old_collector_xfer);
1557 max_xfer_regions -= old_collector_regions;
1558 if (old_collector_regions > 0) {
1559 ShenandoahGenerationalHeap::cast(_heap)->generation_sizer()->transfer_to_young(old_collector_regions);
1560 }
1561 }
1562
1563 // If there are any non-empty regions within Collector partition, we can also move them to the Mutator free partition
1564 if ((max_xfer_regions > 0) && (_partitions.leftmost(ShenandoahFreeSetPartitionId::Collector)
1565 <= _partitions.rightmost(ShenandoahFreeSetPartitionId::Collector))) {
1566 ShenandoahHeapLocker locker(_heap->lock());
1567 max_xfer_regions -=
1568 transfer_non_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId::Collector, max_xfer_regions,
1569 collector_xfer);
1570 }
1571
1572 size_t total_xfer = collector_xfer + old_collector_xfer;
1573 log_info(gc, ergo)("At start of update refs, moving " SIZE_FORMAT "%s to Mutator free set from Collector Reserve ("
1574 SIZE_FORMAT "%s) and from Old Collector Reserve (" SIZE_FORMAT "%s)",
1575 byte_size_in_proper_unit(total_xfer), proper_unit_for_byte_size(total_xfer),
1576 byte_size_in_proper_unit(collector_xfer), proper_unit_for_byte_size(collector_xfer),
1577 byte_size_in_proper_unit(old_collector_xfer), proper_unit_for_byte_size(old_collector_xfer));
1578 }
1579
1580
1581 // Overwrite arguments to represent the amount of memory in each generation that is about to be recycled
1582 void ShenandoahFreeSet::prepare_to_rebuild(size_t &young_cset_regions, size_t &old_cset_regions,
1583 size_t &first_old_region, size_t &last_old_region, size_t &old_region_count) {
1584 shenandoah_assert_heaplocked();
1585 // This resets all state information, removing all regions from all sets.
1586 clear();
1587 log_debug(gc, free)("Rebuilding FreeSet");
1588
1589 // This places regions that have alloc_capacity into the old_collector set if they identify as is_old() or the
1590 // mutator set otherwise. All trashed (cset) regions are affiliated young and placed in mutator set.
1591 find_regions_with_alloc_capacity(young_cset_regions, old_cset_regions, first_old_region, last_old_region, old_region_count);
1592 }
1593
1594 void ShenandoahFreeSet::establish_generation_sizes(size_t young_region_count, size_t old_region_count) {
1595 assert(young_region_count + old_region_count == ShenandoahHeap::heap()->num_regions(), "Sanity");
1596 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1597 ShenandoahGenerationalHeap* heap = ShenandoahGenerationalHeap::heap();
1598 ShenandoahOldGeneration* old_gen = heap->old_generation();
1599 ShenandoahYoungGeneration* young_gen = heap->young_generation();
1600 size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
1601
1602 size_t original_old_capacity = old_gen->max_capacity();
1603 size_t new_old_capacity = old_region_count * region_size_bytes;
1604 size_t new_young_capacity = young_region_count * region_size_bytes;
1605 old_gen->set_capacity(new_old_capacity);
1606 young_gen->set_capacity(new_young_capacity);
1607
1608 if (new_old_capacity > original_old_capacity) {
1609 size_t region_count = (new_old_capacity - original_old_capacity) / region_size_bytes;
1610 log_info(gc, ergo)("Transfer " SIZE_FORMAT " region(s) from %s to %s, yielding increased size: " PROPERFMT,
1611 region_count, young_gen->name(), old_gen->name(), PROPERFMTARGS(new_old_capacity));
1612 } else if (new_old_capacity < original_old_capacity) {
1613 size_t region_count = (original_old_capacity - new_old_capacity) / region_size_bytes;
1614 log_info(gc, ergo)("Transfer " SIZE_FORMAT " region(s) from %s to %s, yielding increased size: " PROPERFMT,
1615 region_count, old_gen->name(), young_gen->name(), PROPERFMTARGS(new_young_capacity));
1616 }
1617 // This balances generations, so clear any pending request to balance.
1618 old_gen->set_region_balance(0);
1619 }
1620 }
1621
1622 void ShenandoahFreeSet::finish_rebuild(size_t young_cset_regions, size_t old_cset_regions, size_t old_region_count,
1623 bool have_evacuation_reserves) {
1624 shenandoah_assert_heaplocked();
1625 size_t young_reserve(0), old_reserve(0);
1626
1627 if (_heap->mode()->is_generational()) {
1628 compute_young_and_old_reserves(young_cset_regions, old_cset_regions, have_evacuation_reserves,
1629 young_reserve, old_reserve);
1630 } else {
1631 young_reserve = (_heap->max_capacity() / 100) * ShenandoahEvacReserve;
1632 old_reserve = 0;
1633 }
1634
1635 // Move some of the mutator regions in the Collector and OldCollector partitions in order to satisfy
1636 // young_reserve and old_reserve.
1637 reserve_regions(young_reserve, old_reserve, old_region_count);
1638 size_t young_region_count = _heap->num_regions() - old_region_count;
1639 establish_generation_sizes(young_region_count, old_region_count);
1640 establish_old_collector_alloc_bias();
1641 _partitions.assert_bounds();
1642 log_status();
1643 }
1644
1645 void ShenandoahFreeSet::compute_young_and_old_reserves(size_t young_cset_regions, size_t old_cset_regions,
1646 bool have_evacuation_reserves,
1647 size_t& young_reserve_result, size_t& old_reserve_result) const {
1648 shenandoah_assert_generational();
1649 const size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
1650
1651 ShenandoahOldGeneration* const old_generation = _heap->old_generation();
1652 size_t old_available = old_generation->available();
1653 size_t old_unaffiliated_regions = old_generation->free_unaffiliated_regions();
1654 ShenandoahYoungGeneration* const young_generation = _heap->young_generation();
1655 size_t young_capacity = young_generation->max_capacity();
1656 size_t young_unaffiliated_regions = young_generation->free_unaffiliated_regions();
1657
1658 // Add in the regions we anticipate to be freed by evacuation of the collection set
1659 old_unaffiliated_regions += old_cset_regions;
1660 young_unaffiliated_regions += young_cset_regions;
1661
1662 // Consult old-region balance to make adjustments to current generation capacities and availability.
1663 // The generation region transfers take place after we rebuild.
1664 const ssize_t old_region_balance = old_generation->get_region_balance();
1665 if (old_region_balance != 0) {
1666 #ifdef ASSERT
1667 if (old_region_balance > 0) {
1668 assert(old_region_balance <= checked_cast<ssize_t>(old_unaffiliated_regions), "Cannot transfer regions that are affiliated");
1669 } else {
1670 assert(0 - old_region_balance <= checked_cast<ssize_t>(young_unaffiliated_regions), "Cannot transfer regions that are affiliated");
1671 }
1672 #endif
1673
1674 ssize_t xfer_bytes = old_region_balance * checked_cast<ssize_t>(region_size_bytes);
1675 old_available -= xfer_bytes;
1676 old_unaffiliated_regions -= old_region_balance;
1677 young_capacity += xfer_bytes;
1678 young_unaffiliated_regions += old_region_balance;
1679 }
1680
1681 // All allocations taken from the old collector set are performed by GC, generally using PLABs for both
1682 // promotions and evacuations. The partition between which old memory is reserved for evacuation and
1683 // which is reserved for promotion is enforced using thread-local variables that prescribe intentions for
1684 // each PLAB's available memory.
1685 if (have_evacuation_reserves) {
1686 // We are rebuilding at the end of final mark, having already established evacuation budgets for this GC pass.
1687 const size_t promoted_reserve = old_generation->get_promoted_reserve();
1688 const size_t old_evac_reserve = old_generation->get_evacuation_reserve();
1689 young_reserve_result = young_generation->get_evacuation_reserve();
1690 old_reserve_result = promoted_reserve + old_evac_reserve;
1691 assert(old_reserve_result <= old_available,
1692 "Cannot reserve (" SIZE_FORMAT " + " SIZE_FORMAT") more OLD than is available: " SIZE_FORMAT,
1693 promoted_reserve, old_evac_reserve, old_available);
1694 } else {
1695 // We are rebuilding at end of GC, so we set aside budgets specified on command line (or defaults)
1696 young_reserve_result = (young_capacity * ShenandoahEvacReserve) / 100;
1697 // The auto-sizer has already made old-gen large enough to hold all anticipated evacuations and promotions.
1698 // Affiliated old-gen regions are already in the OldCollector free set. Add in the relevant number of
1699 // unaffiliated regions.
1700 old_reserve_result = old_available;
1701 }
1702
1703 // Old available regions that have less than PLAB::min_size() of available memory are not placed into the OldCollector
1704 // free set. Because of this, old_available may not have enough memory to represent the intended reserve. Adjust
1705 // the reserve downward to account for this possibility. This loss is part of the reason why the original budget
1706 // was adjusted with ShenandoahOldEvacWaste and ShenandoahOldPromoWaste multipliers.
1707 if (old_reserve_result >
1708 _partitions.capacity_of(ShenandoahFreeSetPartitionId::OldCollector) + old_unaffiliated_regions * region_size_bytes) {
1709 old_reserve_result =
1710 _partitions.capacity_of(ShenandoahFreeSetPartitionId::OldCollector) + old_unaffiliated_regions * region_size_bytes;
1711 }
1712
1713 if (young_reserve_result > young_unaffiliated_regions * region_size_bytes) {
1714 young_reserve_result = young_unaffiliated_regions * region_size_bytes;
1715 }
1716 }
1717
1718 // Having placed all regions that have allocation capacity into the mutator set if they identify as is_young()
1719 // or into the old collector set if they identify as is_old(), move some of these regions from the mutator set
1720 // into the collector set or old collector set in order to assure that the memory available for allocations within
1721 // the collector set is at least to_reserve and the memory available for allocations within the old collector set
1722 // is at least to_reserve_old.
1723 void ShenandoahFreeSet::reserve_regions(size_t to_reserve, size_t to_reserve_old, size_t &old_region_count) {
1724 for (size_t i = _heap->num_regions(); i > 0; i--) {
1725 size_t idx = i - 1;
1726 ShenandoahHeapRegion* r = _heap->get_region(idx);
1727 if (!_partitions.in_free_set(ShenandoahFreeSetPartitionId::Mutator, idx)) {
1728 continue;
1729 }
1730
1731 size_t ac = alloc_capacity(r);
1732 assert (ac > 0, "Membership in free set implies has capacity");
1733 assert (!r->is_old() || r->is_trash(), "Except for trash, mutator_is_free regions should not be affiliated OLD");
1734
1735 bool move_to_old_collector = _partitions.available_in(ShenandoahFreeSetPartitionId::OldCollector) < to_reserve_old;
1736 bool move_to_collector = _partitions.available_in(ShenandoahFreeSetPartitionId::Collector) < to_reserve;
1737
1738 if (!move_to_collector && !move_to_old_collector) {
1739 // We've satisfied both to_reserve and to_reserved_old
1740 break;
1741 }
1742
1743 if (move_to_old_collector) {
1744 // We give priority to OldCollector partition because we desire to pack OldCollector regions into higher
1745 // addresses than Collector regions. Presumably, OldCollector regions are more "stable" and less likely to
1746 // be collected in the near future.
1747 if (r->is_trash() || !r->is_affiliated()) {
1748 // OLD regions that have available memory are already in the old_collector free set.
1749 _partitions.move_from_partition_to_partition(idx, ShenandoahFreeSetPartitionId::Mutator,
1750 ShenandoahFreeSetPartitionId::OldCollector, ac);
1751 log_debug(gc)(" Shifting region " SIZE_FORMAT " from mutator_free to old_collector_free", idx);
1752 log_debug(gc)(" Shifted Mutator range [" SSIZE_FORMAT ", " SSIZE_FORMAT "],"
1753 " Old Collector range [" SSIZE_FORMAT ", " SSIZE_FORMAT "]",
1754 _partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator),
1755 _partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator),
1756 _partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector),
1757 _partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector));
1758 old_region_count++;
1759 continue;
1760 }
1761 }
1762
1763 if (move_to_collector) {
1764 // Note: In a previous implementation, regions were only placed into the survivor space (collector_is_free) if
1765 // they were entirely empty. This has the effect of causing new Mutator allocation to reside next to objects
1766 // that have already survived at least one GC, mixing ephemeral with longer-lived objects in the same region.
1767 // Any objects that have survived a GC are less likely to immediately become garbage, so a region that contains
1768 // survivor objects is less likely to be selected for the collection set. This alternative implementation allows
1769 // survivor regions to continue accumulating other survivor objects, and makes it more likely that ephemeral objects
1770 // occupy regions comprised entirely of ephemeral objects. These regions are highly likely to be included in the next
1771 // collection set, and they are easily evacuated because they have low density of live objects.
1772 _partitions.move_from_partition_to_partition(idx, ShenandoahFreeSetPartitionId::Mutator,
1773 ShenandoahFreeSetPartitionId::Collector, ac);
1774 log_debug(gc)(" Shifting region " SIZE_FORMAT " from mutator_free to collector_free", idx);
1775 log_debug(gc)(" Shifted Mutator range [" SSIZE_FORMAT ", " SSIZE_FORMAT "],"
1776 " Collector range [" SSIZE_FORMAT ", " SSIZE_FORMAT "]",
1777 _partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator),
1778 _partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator),
1779 _partitions.leftmost(ShenandoahFreeSetPartitionId::Collector),
1780 _partitions.rightmost(ShenandoahFreeSetPartitionId::Collector));
1781 }
1782 }
1783
1784 if (LogTarget(Info, gc, free)::is_enabled()) {
1785 size_t old_reserve = _partitions.available_in(ShenandoahFreeSetPartitionId::OldCollector);
1786 if (old_reserve < to_reserve_old) {
1787 log_info(gc, free)("Wanted " PROPERFMT " for old reserve, but only reserved: " PROPERFMT,
1788 PROPERFMTARGS(to_reserve_old), PROPERFMTARGS(old_reserve));
1789 }
1790 size_t reserve = _partitions.available_in(ShenandoahFreeSetPartitionId::Collector);
1791 if (reserve < to_reserve) {
1792 log_debug(gc)("Wanted " PROPERFMT " for young reserve, but only reserved: " PROPERFMT,
1793 PROPERFMTARGS(to_reserve), PROPERFMTARGS(reserve));
1794 }
1795 }
1796 }
1797
1798 void ShenandoahFreeSet::establish_old_collector_alloc_bias() {
1799 ShenandoahHeap* heap = ShenandoahHeap::heap();
1800 shenandoah_assert_heaplocked();
1801
1802 idx_t left_idx = _partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector);
1803 idx_t right_idx = _partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector);
1804 idx_t middle = (left_idx + right_idx) / 2;
1805 size_t available_in_first_half = 0;
1806 size_t available_in_second_half = 0;
1807
1808 for (idx_t index = left_idx; index < middle; index++) {
1809 if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, index)) {
1810 ShenandoahHeapRegion* r = heap->get_region((size_t) index);
1811 available_in_first_half += r->free();
1812 }
1813 }
1814 for (idx_t index = middle; index <= right_idx; index++) {
1815 if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, index)) {
1816 ShenandoahHeapRegion* r = heap->get_region(index);
1817 available_in_second_half += r->free();
1818 }
1819 }
1820
1821 // We desire to first consume the sparsely distributed regions in order that the remaining regions are densely packed.
1822 // Densely packing regions reduces the effort to search for a region that has sufficient memory to satisfy a new allocation
1823 // request. Regions become sparsely distributed following a Full GC, which tends to slide all regions to the front of the
1824 // heap rather than allowing survivor regions to remain at the high end of the heap where we intend for them to congregate.
1825 _partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::OldCollector,
1826 (available_in_second_half > available_in_first_half));
1827 }
1828
1829 void ShenandoahFreeSet::log_status_under_lock() {
1830 // Must not be heap locked, it acquires heap lock only when log is enabled
1831 shenandoah_assert_not_heaplocked();
1832 if (LogTarget(Info, gc, free)::is_enabled()
1833 DEBUG_ONLY(|| LogTarget(Debug, gc, free)::is_enabled())) {
1834 ShenandoahHeapLocker locker(_heap->lock());
1835 log_status();
1836 }
1837 }
1838
1839 void ShenandoahFreeSet::log_status() {
1840 shenandoah_assert_heaplocked();
1841
1842 #ifdef ASSERT
1843 // Dump of the FreeSet details is only enabled if assertions are enabled
1844 if (LogTarget(Debug, gc, free)::is_enabled()) {
1845 #define BUFFER_SIZE 80
1846
1847 char buffer[BUFFER_SIZE];
1848 for (uint i = 0; i < BUFFER_SIZE; i++) {
1849 buffer[i] = '\0';
1850 }
1851
1852 log_debug(gc)("FreeSet map legend:"
1853 " M:mutator_free C:collector_free O:old_collector_free"
1854 " H:humongous ~:retired old _:retired young");
1855 log_debug(gc)(" mutator free range [" SIZE_FORMAT ".." SIZE_FORMAT "] allocating from %s, "
1856 " collector free range [" SIZE_FORMAT ".." SIZE_FORMAT "], "
1857 "old collector free range [" SIZE_FORMAT ".." SIZE_FORMAT "] allocates from %s",
1858 _partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator),
1859 _partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator),
1860 _partitions.alloc_from_left_bias(ShenandoahFreeSetPartitionId::Mutator)? "left to right": "right to left",
1861 _partitions.leftmost(ShenandoahFreeSetPartitionId::Collector),
1862 _partitions.rightmost(ShenandoahFreeSetPartitionId::Collector),
1863 _partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector),
1864 _partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector),
1865 _partitions.alloc_from_left_bias(ShenandoahFreeSetPartitionId::OldCollector)? "left to right": "right to left");
1866
1867 for (uint i = 0; i < _heap->num_regions(); i++) {
1868 ShenandoahHeapRegion *r = _heap->get_region(i);
1869 uint idx = i % 64;
1870 if ((i != 0) && (idx == 0)) {
1871 log_debug(gc)(" %6u: %s", i-64, buffer);
1872 }
1873 if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::Mutator, i)) {
1874 size_t capacity = alloc_capacity(r);
1875 assert(!r->is_old() || r->is_trash(), "Old regions except trash regions should not be in mutator_free set");
1876 buffer[idx] = (capacity == ShenandoahHeapRegion::region_size_bytes()) ? 'M' : 'm';
1877 } else if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::Collector, i)) {
1878 size_t capacity = alloc_capacity(r);
1879 assert(!r->is_old() || r->is_trash(), "Old regions except trash regions should not be in collector_free set");
1880 buffer[idx] = (capacity == ShenandoahHeapRegion::region_size_bytes()) ? 'C' : 'c';
1881 } else if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, i)) {
1882 size_t capacity = alloc_capacity(r);
1883 buffer[idx] = (capacity == ShenandoahHeapRegion::region_size_bytes()) ? 'O' : 'o';
1884 } else if (r->is_humongous()) {
1885 if (r->is_old()) {
1886 buffer[idx] = 'H';
1887 } else {
1888 buffer[idx] = 'h';
1889 }
1890 } else {
1891 if (r->is_old()) {
1892 buffer[idx] = '~';
1893 } else {
1894 buffer[idx] = '_';
1895 }
1896 }
1897 }
1898 uint remnant = _heap->num_regions() % 64;
1899 if (remnant > 0) {
1900 buffer[remnant] = '\0';
1901 } else {
1902 remnant = 64;
1903 }
1904 log_debug(gc)(" %6u: %s", (uint) (_heap->num_regions() - remnant), buffer);
1905 }
1906 #endif
1907
1908 LogTarget(Info, gc, free) lt;
1909 if (lt.is_enabled()) {
1910 ResourceMark rm;
1911 LogStream ls(lt);
1912
1913 {
1914 idx_t last_idx = 0;
1915 size_t max = 0;
1916 size_t max_contig = 0;
1917 size_t empty_contig = 0;
1918
1919 size_t total_used = 0;
1920 size_t total_free = 0;
1921 size_t total_free_ext = 0;
1922
1923 for (idx_t idx = _partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator);
1924 idx <= _partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator); idx++) {
1925 if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::Mutator, idx)) {
1926 ShenandoahHeapRegion *r = _heap->get_region(idx);
1927 size_t free = alloc_capacity(r);
1928 max = MAX2(max, free);
1929 if (r->is_empty()) {
1930 total_free_ext += free;
1931 if (last_idx + 1 == idx) {
1932 empty_contig++;
1933 } else {
1934 empty_contig = 1;
1935 }
1936 } else {
1937 empty_contig = 0;
1938 }
1939 total_used += r->used();
1940 total_free += free;
1941 max_contig = MAX2(max_contig, empty_contig);
1942 last_idx = idx;
1943 }
1944 }
1945
1946 size_t max_humongous = max_contig * ShenandoahHeapRegion::region_size_bytes();
1947 size_t free = capacity() - used();
1948
1949 // Since certain regions that belonged to the Mutator free partition at the time of most recent rebuild may have been
1950 // retired, the sum of used and capacities within regions that are still in the Mutator free partition may not match
1951 // my internally tracked values of used() and free().
1952 assert(free == total_free, "Free memory should match");
1953 ls.print("Free: " SIZE_FORMAT "%s, Max: " SIZE_FORMAT "%s regular, " SIZE_FORMAT "%s humongous, ",
1954 byte_size_in_proper_unit(total_free), proper_unit_for_byte_size(total_free),
1955 byte_size_in_proper_unit(max), proper_unit_for_byte_size(max),
1956 byte_size_in_proper_unit(max_humongous), proper_unit_for_byte_size(max_humongous)
1957 );
1958
1959 ls.print("Frag: ");
1960 size_t frag_ext;
1961 if (total_free_ext > 0) {
1962 frag_ext = 100 - (100 * max_humongous / total_free_ext);
1963 } else {
1964 frag_ext = 0;
1965 }
1966 ls.print(SIZE_FORMAT "%% external, ", frag_ext);
1967
1968 size_t frag_int;
1969 if (_partitions.count(ShenandoahFreeSetPartitionId::Mutator) > 0) {
1970 frag_int = (100 * (total_used / _partitions.count(ShenandoahFreeSetPartitionId::Mutator))
1971 / ShenandoahHeapRegion::region_size_bytes());
1972 } else {
1973 frag_int = 0;
1974 }
1975 ls.print(SIZE_FORMAT "%% internal; ", frag_int);
1976 ls.print("Used: " SIZE_FORMAT "%s, Mutator Free: " SIZE_FORMAT,
1977 byte_size_in_proper_unit(total_used), proper_unit_for_byte_size(total_used),
1978 _partitions.count(ShenandoahFreeSetPartitionId::Mutator));
1979 }
1980
1981 {
1982 size_t max = 0;
1983 size_t total_free = 0;
1984 size_t total_used = 0;
1985
1986 for (idx_t idx = _partitions.leftmost(ShenandoahFreeSetPartitionId::Collector);
1987 idx <= _partitions.rightmost(ShenandoahFreeSetPartitionId::Collector); idx++) {
1988 if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::Collector, idx)) {
1989 ShenandoahHeapRegion *r = _heap->get_region(idx);
1990 size_t free = alloc_capacity(r);
1991 max = MAX2(max, free);
1992 total_free += free;
1993 total_used += r->used();
1994 }
1995 }
1996 ls.print(" Collector Reserve: " SIZE_FORMAT "%s, Max: " SIZE_FORMAT "%s; Used: " SIZE_FORMAT "%s",
1997 byte_size_in_proper_unit(total_free), proper_unit_for_byte_size(total_free),
1998 byte_size_in_proper_unit(max), proper_unit_for_byte_size(max),
1999 byte_size_in_proper_unit(total_used), proper_unit_for_byte_size(total_used));
2000 }
2001
2002 if (_heap->mode()->is_generational()) {
2003 size_t max = 0;
2004 size_t total_free = 0;
2005 size_t total_used = 0;
2006
2007 for (idx_t idx = _partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector);
2008 idx <= _partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector); idx++) {
2009 if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, idx)) {
2010 ShenandoahHeapRegion *r = _heap->get_region(idx);
2011 size_t free = alloc_capacity(r);
2012 max = MAX2(max, free);
2013 total_free += free;
2014 total_used += r->used();
2015 }
2016 }
2017 ls.print_cr(" Old Collector Reserve: " SIZE_FORMAT "%s, Max: " SIZE_FORMAT "%s; Used: " SIZE_FORMAT "%s",
2018 byte_size_in_proper_unit(total_free), proper_unit_for_byte_size(total_free),
2019 byte_size_in_proper_unit(max), proper_unit_for_byte_size(max),
2020 byte_size_in_proper_unit(total_used), proper_unit_for_byte_size(total_used));
2021 }
2022 }
2023 }
2024
2025 HeapWord* ShenandoahFreeSet::allocate(ShenandoahAllocRequest& req, bool& in_new_region) {
2026 shenandoah_assert_heaplocked();
2027 if (ShenandoahHeapRegion::requires_humongous(req.size())) {
2028 switch (req.type()) {
2029 case ShenandoahAllocRequest::_alloc_shared:
2030 case ShenandoahAllocRequest::_alloc_shared_gc:
2031 in_new_region = true;
2032 return allocate_contiguous(req);
2033 case ShenandoahAllocRequest::_alloc_plab:
2034 case ShenandoahAllocRequest::_alloc_gclab:
2035 case ShenandoahAllocRequest::_alloc_tlab:
2036 in_new_region = false;
2037 assert(false, "Trying to allocate TLAB in humongous region: " SIZE_FORMAT, req.size());
2038 return nullptr;
2039 default:
2040 ShouldNotReachHere();
2041 return nullptr;
2042 }
2043 } else {
2044 return allocate_single(req, in_new_region);
2045 }
2046 }
2047
2048 void ShenandoahFreeSet::print_on(outputStream* out) const {
2049 out->print_cr("Mutator Free Set: " SIZE_FORMAT "", _partitions.count(ShenandoahFreeSetPartitionId::Mutator));
2050 ShenandoahLeftRightIterator mutator(const_cast<ShenandoahRegionPartitions*>(&_partitions), ShenandoahFreeSetPartitionId::Mutator);
2051 for (idx_t index = mutator.current(); mutator.has_next(); index = mutator.next()) {
2052 _heap->get_region(index)->print_on(out);
2053 }
2054
2055 out->print_cr("Collector Free Set: " SIZE_FORMAT "", _partitions.count(ShenandoahFreeSetPartitionId::Collector));
2056 ShenandoahLeftRightIterator collector(const_cast<ShenandoahRegionPartitions*>(&_partitions), ShenandoahFreeSetPartitionId::Collector);
2057 for (idx_t index = collector.current(); collector.has_next(); index = collector.next()) {
2058 _heap->get_region(index)->print_on(out);
2059 }
2060
2061 if (_heap->mode()->is_generational()) {
2062 out->print_cr("Old Collector Free Set: " SIZE_FORMAT "", _partitions.count(ShenandoahFreeSetPartitionId::OldCollector));
2063 for (idx_t index = _partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector);
2064 index <= _partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector); index++) {
2065 if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, index)) {
2066 _heap->get_region(index)->print_on(out);
2067 }
2068 }
2069 }
2070 }
2071
2072 double ShenandoahFreeSet::internal_fragmentation() {
2073 double squared = 0;
2074 double linear = 0;
2075
2076 ShenandoahLeftRightIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator);
2077 for (idx_t index = iterator.current(); iterator.has_next(); index = iterator.next()) {
2078 ShenandoahHeapRegion* r = _heap->get_region(index);
2079 size_t used = r->used();
2080 squared += used * used;
2081 linear += used;
2082 }
2083
2084 if (linear > 0) {
2085 double s = squared / (ShenandoahHeapRegion::region_size_bytes() * linear);
2086 return 1 - s;
2087 } else {
2088 return 0;
2089 }
2090 }
2091
2092 double ShenandoahFreeSet::external_fragmentation() {
2093 idx_t last_idx = 0;
2094 size_t max_contig = 0;
2095 size_t empty_contig = 0;
2096 size_t free = 0;
2097
2098 ShenandoahLeftRightIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator);
2099 for (idx_t index = iterator.current(); iterator.has_next(); index = iterator.next()) {
2100 ShenandoahHeapRegion* r = _heap->get_region(index);
2101 if (r->is_empty()) {
2102 free += ShenandoahHeapRegion::region_size_bytes();
2103 if (last_idx + 1 == index) {
2104 empty_contig++;
2105 } else {
2106 empty_contig = 1;
2107 }
2108 } else {
2109 empty_contig = 0;
2110 }
2111 max_contig = MAX2(max_contig, empty_contig);
2112 last_idx = index;
2113 }
2114
2115 if (free > 0) {
2116 return 1 - (1.0 * max_contig * ShenandoahHeapRegion::region_size_bytes() / free);
2117 } else {
2118 return 0;
2119 }
2120 }
2121
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