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 _alloc_bias_weight(0)
733 {
734 clear_internal();
735 }
736
737 void ShenandoahFreeSet::add_promoted_in_place_region_to_old_collector(ShenandoahHeapRegion* region) {
738 shenandoah_assert_heaplocked();
739 size_t plab_min_size_in_bytes = ShenandoahGenerationalHeap::heap()->plab_min_size() * HeapWordSize;
740 size_t idx = region->index();
741 size_t capacity = alloc_capacity(region);
742 assert(_partitions.membership(idx) == ShenandoahFreeSetPartitionId::NotFree,
743 "Regions promoted in place should have been excluded from Mutator partition");
744 if (capacity >= plab_min_size_in_bytes) {
745 _partitions.make_free(idx, ShenandoahFreeSetPartitionId::OldCollector, capacity);
746 _heap->old_generation()->augment_promoted_reserve(capacity);
747 }
748 }
749
750 HeapWord* ShenandoahFreeSet::allocate_from_partition_with_affiliation(ShenandoahAffiliation affiliation,
751 ShenandoahAllocRequest& req, bool& in_new_region) {
752
753 shenandoah_assert_heaplocked();
754 ShenandoahFreeSetPartitionId which_partition = req.is_old()? ShenandoahFreeSetPartitionId::OldCollector: ShenandoahFreeSetPartitionId::Collector;
755 if (_partitions.alloc_from_left_bias(which_partition)) {
756 ShenandoahLeftRightIterator iterator(&_partitions, which_partition, affiliation == ShenandoahAffiliation::FREE);
757 return allocate_with_affiliation(iterator, affiliation, req, in_new_region);
758 } else {
759 ShenandoahRightLeftIterator iterator(&_partitions, which_partition, affiliation == ShenandoahAffiliation::FREE);
760 return allocate_with_affiliation(iterator, affiliation, req, in_new_region);
761 }
762 }
763
764 template<typename Iter>
765 HeapWord* ShenandoahFreeSet::allocate_with_affiliation(Iter& iterator, ShenandoahAffiliation affiliation, ShenandoahAllocRequest& req, bool& in_new_region) {
766 for (idx_t idx = iterator.current(); iterator.has_next(); idx = iterator.next()) {
767 ShenandoahHeapRegion* r = _heap->get_region(idx);
768 if (r->affiliation() == affiliation) {
769 HeapWord* result = try_allocate_in(r, req, in_new_region);
770 if (result != nullptr) {
771 return result;
772 }
773 }
774 }
775 log_debug(gc, free)("Could not allocate collector region with affiliation: %s for request " PTR_FORMAT,
776 shenandoah_affiliation_name(affiliation), p2i(&req));
777 return nullptr;
778 }
779
780 HeapWord* ShenandoahFreeSet::allocate_single(ShenandoahAllocRequest& req, bool& in_new_region) {
781 shenandoah_assert_heaplocked();
782
783 // Scan the bitmap looking for a first fit.
784 //
785 // Leftmost and rightmost bounds provide enough caching to walk bitmap efficiently. Normally,
786 // we would find the region to allocate at right away.
787 //
788 // Allocations are biased: GC allocations are taken from the high end of the heap. Regular (and TLAB)
789 // mutator allocations are taken from the middle of heap, below the memory reserved for Collector.
790 // Humongous mutator allocations are taken from the bottom of the heap.
791 //
792 // Free set maintains mutator and collector partitions. Normally, each allocates only from its partition,
793 // except in special cases when the collector steals regions from the mutator partition.
794
795 // Overwrite with non-zero (non-NULL) values only if necessary for allocation bookkeeping.
796
797 switch (req.type()) {
798 case ShenandoahAllocRequest::_alloc_tlab:
799 case ShenandoahAllocRequest::_alloc_shared:
800 return allocate_for_mutator(req, in_new_region);
801 case ShenandoahAllocRequest::_alloc_gclab:
802 case ShenandoahAllocRequest::_alloc_plab:
803 case ShenandoahAllocRequest::_alloc_shared_gc:
804 return allocate_for_collector(req, in_new_region);
805 default:
806 ShouldNotReachHere();
807 }
808 return nullptr;
809 }
810
811 HeapWord* ShenandoahFreeSet::allocate_for_mutator(ShenandoahAllocRequest &req, bool &in_new_region) {
812 update_allocation_bias();
813
814 if (_partitions.is_empty(ShenandoahFreeSetPartitionId::Mutator)) {
815 // There is no recovery. Mutator does not touch collector view at all.
816 return nullptr;
817 }
818
819 // Try to allocate in the mutator view
820 if (_partitions.alloc_from_left_bias(ShenandoahFreeSetPartitionId::Mutator)) {
821 // Allocate from low to high memory. This keeps the range of fully empty regions more tightly packed.
822 // Note that the most recently allocated regions tend not to be evacuated in a given GC cycle. So this
823 // tends to accumulate "fragmented" uncollected regions in high memory.
824 ShenandoahLeftRightIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator);
825 return allocate_from_regions(iterator, req, in_new_region);
826 }
827
828 // Allocate from high to low memory. This preserves low memory for humongous allocations.
829 ShenandoahRightLeftIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator);
830 return allocate_from_regions(iterator, req, in_new_region);
831 }
832
833 void ShenandoahFreeSet::update_allocation_bias() {
834 if (_alloc_bias_weight-- <= 0) {
835 // We have observed that regions not collected in previous GC cycle tend to congregate at one end or the other
836 // of the heap. Typically, these are the more recently engaged regions and the objects in these regions have not
837 // yet had a chance to die (and/or are treated as floating garbage). If we use the same allocation bias on each
838 // GC pass, these "most recently" engaged regions for GC pass N will also be the "most recently" engaged regions
839 // for GC pass N+1, and the relatively large amount of live data and/or floating garbage introduced
840 // during the most recent GC pass may once again prevent the region from being collected. We have found that
841 // alternating the allocation behavior between GC passes improves evacuation performance by 3-7% on certain
842 // benchmarks. In the best case, this has the effect of consuming these partially consumed regions before
843 // the start of the next mark cycle so all of their garbage can be efficiently reclaimed.
844 //
845 // First, finish consuming regions that are already partially consumed so as to more tightly limit ranges of
846 // available regions. Other potential benefits:
847 // 1. Eventual collection set has fewer regions because we have packed newly allocated objects into fewer regions
848 // 2. We preserve the "empty" regions longer into the GC cycle, reducing likelihood of allocation failures
849 // late in the GC cycle.
850 idx_t non_empty_on_left = (_partitions.leftmost_empty(ShenandoahFreeSetPartitionId::Mutator)
851 - _partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator));
852 idx_t non_empty_on_right = (_partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator)
853 - _partitions.rightmost_empty(ShenandoahFreeSetPartitionId::Mutator));
854 _partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::Mutator, (non_empty_on_right < non_empty_on_left));
855 _alloc_bias_weight = INITIAL_ALLOC_BIAS_WEIGHT;
856 }
857 }
858
859 template<typename Iter>
860 HeapWord* ShenandoahFreeSet::allocate_from_regions(Iter& iterator, ShenandoahAllocRequest &req, bool &in_new_region) {
861 for (idx_t idx = iterator.current(); iterator.has_next(); idx = iterator.next()) {
862 ShenandoahHeapRegion* r = _heap->get_region(idx);
863 size_t min_size = (req.type() == ShenandoahAllocRequest::_alloc_tlab) ? req.min_size() : req.size();
864 if (alloc_capacity(r) >= min_size) {
865 HeapWord* result = try_allocate_in(r, req, in_new_region);
866 if (result != nullptr) {
867 return result;
868 }
869 }
870 }
871 return nullptr;
872 }
873
874 HeapWord* ShenandoahFreeSet::allocate_for_collector(ShenandoahAllocRequest &req, bool &in_new_region) {
875 // Fast-path: try to allocate in the collector view first
876 HeapWord* result;
877 result = allocate_from_partition_with_affiliation(req.affiliation(), req, in_new_region);
878 if (result != nullptr) {
879 return result;
880 }
881
882 bool allow_new_region = can_allocate_in_new_region(req);
883 if (allow_new_region) {
884 // Try a free region that is dedicated to GC allocations.
885 result = allocate_from_partition_with_affiliation(ShenandoahAffiliation::FREE, req, in_new_region);
886 if (result != nullptr) {
887 return result;
888 }
889 }
890
891 // No dice. Can we borrow space from mutator view?
892 if (!ShenandoahEvacReserveOverflow) {
893 return nullptr;
894 }
895
896 if (!allow_new_region && req.is_old() && (_heap->young_generation()->free_unaffiliated_regions() > 0)) {
897 // This allows us to flip a mutator region to old_collector
898 allow_new_region = true;
899 }
900
901 // We should expand old-gen if this can prevent an old-gen evacuation failure. We don't care so much about
902 // promotion failures since they can be mitigated in a subsequent GC pass. Would be nice to know if this
903 // allocation request is for evacuation or promotion. Individual threads limit their use of PLAB memory for
904 // promotions, so we already have an assurance that any additional memory set aside for old-gen will be used
905 // only for old-gen evacuations.
906 if (allow_new_region) {
907 // Try to steal an empty region from the mutator view.
908 result = try_allocate_from_mutator(req, in_new_region);
909 }
910
911 // This is it. Do not try to mix mutator and GC allocations, because adjusting region UWM
912 // due to GC allocations would expose unparsable mutator allocations.
913 return result;
914 }
915
916 bool ShenandoahFreeSet::can_allocate_in_new_region(const ShenandoahAllocRequest& req) {
917 if (!_heap->mode()->is_generational()) {
918 return true;
919 }
920
921 assert(req.is_old() || req.is_young(), "Should request affiliation");
922 return (req.is_old() && _heap->old_generation()->free_unaffiliated_regions() > 0)
923 || (req.is_young() && _heap->young_generation()->free_unaffiliated_regions() > 0);
924 }
925
926 HeapWord* ShenandoahFreeSet::try_allocate_from_mutator(ShenandoahAllocRequest& req, bool& in_new_region) {
927 // The collector prefers to keep longer lived regions toward the right side of the heap, so it always
928 // searches for regions from right to left here.
929 ShenandoahRightLeftIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator, true);
930 for (idx_t idx = iterator.current(); iterator.has_next(); idx = iterator.next()) {
931 ShenandoahHeapRegion* r = _heap->get_region(idx);
932 if (can_allocate_from(r)) {
933 if (req.is_old()) {
934 flip_to_old_gc(r);
935 } else {
936 flip_to_gc(r);
937 }
938 // Region r is entirely empty. If try_allocate_in fails on region r, something else is really wrong.
939 // Don't bother to retry with other regions.
940 log_debug(gc, free)("Flipped region " SIZE_FORMAT " to gc for request: " PTR_FORMAT, idx, p2i(&req));
941 return try_allocate_in(r, req, in_new_region);
942 }
943 }
944
945 return nullptr;
946 }
947
948 // This work method takes an argument corresponding to the number of bytes
949 // free in a region, and returns the largest amount in heapwords that can be allocated
950 // such that both of the following conditions are satisfied:
951 //
952 // 1. it is a multiple of card size
953 // 2. any remaining shard may be filled with a filler object
954 //
955 // The idea is that the allocation starts and ends at card boundaries. Because
956 // a region ('s end) is card-aligned, the remainder shard that must be filled is
957 // at the start of the free space.
958 //
959 // This is merely a helper method to use for the purpose of such a calculation.
960 size_t ShenandoahFreeSet::get_usable_free_words(size_t free_bytes) const {
961 // e.g. card_size is 512, card_shift is 9, min_fill_size() is 8
962 // free is 514
963 // usable_free is 512, which is decreased to 0
964 size_t usable_free = (free_bytes / CardTable::card_size()) << CardTable::card_shift();
965 assert(usable_free <= free_bytes, "Sanity check");
966 if ((free_bytes != usable_free) && (free_bytes - usable_free < ShenandoahHeap::min_fill_size() * HeapWordSize)) {
967 // After aligning to card multiples, the remainder would be smaller than
968 // the minimum filler object, so we'll need to take away another card's
969 // worth to construct a filler object.
970 if (usable_free >= CardTable::card_size()) {
971 usable_free -= CardTable::card_size();
972 } else {
973 assert(usable_free == 0, "usable_free is a multiple of card_size and card_size > min_fill_size");
974 }
975 }
976
977 return usable_free / HeapWordSize;
978 }
979
980 // Given a size argument, which is a multiple of card size, a request struct
981 // for a PLAB, and an old region, return a pointer to the allocated space for
982 // a PLAB which is card-aligned and where any remaining shard in the region
983 // has been suitably filled by a filler object.
984 // It is assumed (and assertion-checked) that such an allocation is always possible.
985 HeapWord* ShenandoahFreeSet::allocate_aligned_plab(size_t size, ShenandoahAllocRequest& req, ShenandoahHeapRegion* r) {
986 assert(_heap->mode()->is_generational(), "PLABs are only for generational mode");
987 assert(r->is_old(), "All PLABs reside in old-gen");
988 assert(!req.is_mutator_alloc(), "PLABs should not be allocated by mutators.");
989 assert(is_aligned(size, CardTable::card_size_in_words()), "Align by design");
990
991 HeapWord* result = r->allocate_aligned(size, req, CardTable::card_size());
992 assert(result != nullptr, "Allocation cannot fail");
993 assert(r->top() <= r->end(), "Allocation cannot span end of region");
994 assert(is_aligned(result, CardTable::card_size_in_words()), "Align by design");
995 return result;
996 }
997
998 HeapWord* ShenandoahFreeSet::try_allocate_in(ShenandoahHeapRegion* r, ShenandoahAllocRequest& req, bool& in_new_region) {
999 assert (has_alloc_capacity(r), "Performance: should avoid full regions on this path: " SIZE_FORMAT, r->index());
1000 if (_heap->is_concurrent_weak_root_in_progress() && r->is_trash()) {
1001 // We cannot use this region for allocation when weak roots are in progress because the collector may need
1002 // to reference unmarked oops during concurrent classunloading. The collector also needs accurate marking
1003 // information to determine which weak handles need to be null'd out. If the region is recycled before weak
1004 // roots processing has finished, weak root processing may fail to null out a handle into a trashed region.
1005 // This turns the handle into a dangling pointer and will crash or corrupt the heap.
1006 return nullptr;
1007 }
1008 HeapWord* result = nullptr;
1009 r->try_recycle_under_lock();
1010 in_new_region = r->is_empty();
1011
1012 if (in_new_region) {
1013 log_debug(gc, free)("Using new region (" SIZE_FORMAT ") for %s (" PTR_FORMAT ").",
1014 r->index(), ShenandoahAllocRequest::alloc_type_to_string(req.type()), p2i(&req));
1015 assert(!r->is_affiliated(), "New region " SIZE_FORMAT " should be unaffiliated", r->index());
1016 r->set_affiliation(req.affiliation());
1017 if (r->is_old()) {
1018 // Any OLD region allocated during concurrent coalesce-and-fill does not need to be coalesced and filled because
1019 // all objects allocated within this region are above TAMS (and thus are implicitly marked). In case this is an
1020 // OLD region and concurrent preparation for mixed evacuations visits this region before the start of the next
1021 // old-gen concurrent mark (i.e. this region is allocated following the start of old-gen concurrent mark but before
1022 // concurrent preparations for mixed evacuations are completed), we mark this region as not requiring any
1023 // coalesce-and-fill processing.
1024 r->end_preemptible_coalesce_and_fill();
1025 _heap->old_generation()->clear_cards_for(r);
1026 }
1027 _heap->generation_for(r->affiliation())->increment_affiliated_region_count();
1028
1029 #ifdef ASSERT
1030 ShenandoahMarkingContext* const ctx = _heap->complete_marking_context();
1031 assert(ctx->top_at_mark_start(r) == r->bottom(), "Newly established allocation region starts with TAMS equal to bottom");
1032 assert(ctx->is_bitmap_range_within_region_clear(ctx->top_bitmap(r), r->end()), "Bitmap above top_bitmap() must be clear");
1033 #endif
1034 log_debug(gc, free)("Using new region (" SIZE_FORMAT ") for %s (" PTR_FORMAT ").",
1035 r->index(), ShenandoahAllocRequest::alloc_type_to_string(req.type()), p2i(&req));
1036 } else {
1037 assert(r->is_affiliated(), "Region " SIZE_FORMAT " that is not new should be affiliated", r->index());
1038 if (r->affiliation() != req.affiliation()) {
1039 assert(_heap->mode()->is_generational(), "Request for %s from %s region should only happen in generational mode.",
1040 req.affiliation_name(), r->affiliation_name());
1041 return nullptr;
1042 }
1043 }
1044
1045 // req.size() is in words, r->free() is in bytes.
1046 if (req.is_lab_alloc()) {
1047 size_t adjusted_size = req.size();
1048 size_t free = r->free(); // free represents bytes available within region r
1049 if (req.type() == ShenandoahAllocRequest::_alloc_plab) {
1050 // This is a PLAB allocation
1051 assert(_heap->mode()->is_generational(), "PLABs are only for generational mode");
1052 assert(_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, r->index()),
1053 "PLABS must be allocated in old_collector_free regions");
1054
1055 // Need to assure that plabs are aligned on multiple of card region
1056 // Convert free from unaligned bytes to aligned number of words
1057 size_t usable_free = get_usable_free_words(free);
1058 if (adjusted_size > usable_free) {
1059 adjusted_size = usable_free;
1060 }
1061 adjusted_size = align_down(adjusted_size, CardTable::card_size_in_words());
1062 if (adjusted_size >= req.min_size()) {
1063 result = allocate_aligned_plab(adjusted_size, req, r);
1064 assert(result != nullptr, "allocate must succeed");
1065 req.set_actual_size(adjusted_size);
1066 } else {
1067 // Otherwise, leave result == nullptr because the adjusted size is smaller than min size.
1068 log_trace(gc, free)("Failed to shrink PLAB request (" SIZE_FORMAT ") in region " SIZE_FORMAT " to " SIZE_FORMAT
1069 " because min_size() is " SIZE_FORMAT, req.size(), r->index(), adjusted_size, req.min_size());
1070 }
1071 } else {
1072 // This is a GCLAB or a TLAB allocation
1073 // Convert free from unaligned bytes to aligned number of words
1074 free = align_down(free >> LogHeapWordSize, MinObjAlignment);
1075 if (adjusted_size > free) {
1076 adjusted_size = free;
1077 }
1078 if (adjusted_size >= req.min_size()) {
1079 result = r->allocate(adjusted_size, req);
1080 assert (result != nullptr, "Allocation must succeed: free " SIZE_FORMAT ", actual " SIZE_FORMAT, free, adjusted_size);
1081 req.set_actual_size(adjusted_size);
1082 } else {
1083 log_trace(gc, free)("Failed to shrink TLAB or GCLAB request (" SIZE_FORMAT ") in region " SIZE_FORMAT " to " SIZE_FORMAT
1084 " because min_size() is " SIZE_FORMAT, req.size(), r->index(), adjusted_size, req.min_size());
1085 }
1086 }
1087 } else {
1088 size_t size = req.size();
1089 result = r->allocate(size, req);
1090 if (result != nullptr) {
1091 // Record actual allocation size
1092 req.set_actual_size(size);
1093 }
1094 }
1095
1096 if (result != nullptr) {
1097 // Allocation successful, bump stats:
1098 if (req.is_mutator_alloc()) {
1099 assert(req.is_young(), "Mutator allocations always come from young generation.");
1100 _partitions.increase_used(ShenandoahFreeSetPartitionId::Mutator, req.actual_size() * HeapWordSize);
1101 } else {
1102 assert(req.is_gc_alloc(), "Should be gc_alloc since req wasn't mutator alloc");
1103
1104 // For GC allocations, we advance update_watermark because the objects relocated into this memory during
1105 // evacuation are not updated during evacuation. For both young and old regions r, it is essential that all
1106 // PLABs be made parsable at the end of evacuation. This is enabled by retiring all plabs at end of evacuation.
1107 r->set_update_watermark(r->top());
1108 if (r->is_old()) {
1109 _partitions.increase_used(ShenandoahFreeSetPartitionId::OldCollector, req.actual_size() * HeapWordSize);
1110 assert(req.type() != ShenandoahAllocRequest::_alloc_gclab, "old-gen allocations use PLAB or shared allocation");
1111 // for plabs, we'll sort the difference between evac and promotion usage when we retire the plab
1112 } else {
1113 _partitions.increase_used(ShenandoahFreeSetPartitionId::Collector, req.actual_size() * HeapWordSize);
1114 }
1115 }
1116 }
1117
1118 static const size_t min_capacity = (size_t) (ShenandoahHeapRegion::region_size_bytes() * (1.0 - 1.0 / ShenandoahEvacWaste));
1119 size_t ac = alloc_capacity(r);
1120
1121 if (((result == nullptr) && (ac < min_capacity)) || (alloc_capacity(r) < PLAB::min_size() * HeapWordSize)) {
1122 // Regardless of whether this allocation succeeded, if the remaining memory is less than PLAB:min_size(), retire this region.
1123 // Note that retire_from_partition() increases used to account for waste.
1124
1125 // Also, if this allocation request failed and the consumed within this region * ShenandoahEvacWaste > region size,
1126 // then retire the region so that subsequent searches can find available memory more quickly.
1127
1128 size_t idx = r->index();
1129 ShenandoahFreeSetPartitionId orig_partition;
1130 if (req.is_mutator_alloc()) {
1131 orig_partition = ShenandoahFreeSetPartitionId::Mutator;
1132 } else if (req.type() == ShenandoahAllocRequest::_alloc_gclab) {
1133 orig_partition = ShenandoahFreeSetPartitionId::Collector;
1134 } else if (req.type() == ShenandoahAllocRequest::_alloc_plab) {
1135 orig_partition = ShenandoahFreeSetPartitionId::OldCollector;
1136 } else {
1137 assert(req.type() == ShenandoahAllocRequest::_alloc_shared_gc, "Unexpected allocation type");
1138 if (req.is_old()) {
1139 orig_partition = ShenandoahFreeSetPartitionId::OldCollector;
1140 } else {
1141 orig_partition = ShenandoahFreeSetPartitionId::Collector;
1142 }
1143 }
1144 _partitions.retire_from_partition(orig_partition, idx, r->used());
1145 _partitions.assert_bounds();
1146 }
1147 return result;
1148 }
1149
1150 HeapWord* ShenandoahFreeSet::allocate_contiguous(ShenandoahAllocRequest& req) {
1151 assert(req.is_mutator_alloc(), "All humongous allocations are performed by mutator");
1152 shenandoah_assert_heaplocked();
1153
1154 size_t words_size = req.size();
1155 idx_t num = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize);
1156
1157 assert(req.is_young(), "Humongous regions always allocated in YOUNG");
1158 ShenandoahGeneration* generation = _heap->generation_for(req.affiliation());
1159
1160 // Check if there are enough regions left to satisfy allocation.
1161 if (num > (idx_t) _partitions.count(ShenandoahFreeSetPartitionId::Mutator)) {
1162 return nullptr;
1163 }
1164
1165 idx_t start_range = _partitions.leftmost_empty(ShenandoahFreeSetPartitionId::Mutator);
1166 idx_t end_range = _partitions.rightmost_empty(ShenandoahFreeSetPartitionId::Mutator) + 1;
1167 idx_t last_possible_start = end_range - num;
1168
1169 // Find the continuous interval of $num regions, starting from $beg and ending in $end,
1170 // inclusive. Contiguous allocations are biased to the beginning.
1171 idx_t beg = _partitions.find_index_of_next_available_cluster_of_regions(ShenandoahFreeSetPartitionId::Mutator,
1172 start_range, num);
1173 if (beg > last_possible_start) {
1174 // Hit the end, goodbye
1175 return nullptr;
1176 }
1177 idx_t end = beg;
1178
1179 while (true) {
1180 // We've confirmed num contiguous regions belonging to Mutator partition, so no need to confirm membership.
1181 // If region is not completely free, the current [beg; end] is useless, and we may fast-forward. If we can extend
1182 // the existing range, we can exploit that certain regions are already known to be in the Mutator free set.
1183 while (!can_allocate_from(_heap->get_region(end))) {
1184 // region[end] is not empty, so we restart our search after region[end]
1185 idx_t slide_delta = end + 1 - beg;
1186 if (beg + slide_delta > last_possible_start) {
1187 // no room to slide
1188 return nullptr;
1189 }
1190 for (idx_t span_end = beg + num; slide_delta > 0; slide_delta--) {
1191 if (!_partitions.in_free_set(ShenandoahFreeSetPartitionId::Mutator, span_end)) {
1192 beg = _partitions.find_index_of_next_available_cluster_of_regions(ShenandoahFreeSetPartitionId::Mutator,
1193 span_end + 1, num);
1194 break;
1195 } else {
1196 beg++;
1197 span_end++;
1198 }
1199 }
1200 // Here, either beg identifies a range of num regions all of which are in the Mutator free set, or beg > last_possible_start
1201 if (beg > last_possible_start) {
1202 // Hit the end, goodbye
1203 return nullptr;
1204 }
1205 end = beg;
1206 }
1207
1208 if ((end - beg + 1) == num) {
1209 // found the match
1210 break;
1211 }
1212
1213 end++;
1214 }
1215
1216 size_t remainder = words_size & ShenandoahHeapRegion::region_size_words_mask();
1217 // Initialize regions:
1218 for (idx_t i = beg; i <= end; i++) {
1219 ShenandoahHeapRegion* r = _heap->get_region(i);
1220 r->try_recycle_under_lock();
1221
1222 assert(i == beg || _heap->get_region(i - 1)->index() + 1 == r->index(), "Should be contiguous");
1223 assert(r->is_empty(), "Should be empty");
1224
1225 if (i == beg) {
1226 r->make_humongous_start();
1227 } else {
1228 r->make_humongous_cont();
1229 }
1230
1231 // Trailing region may be non-full, record the remainder there
1232 size_t used_words;
1233 if ((i == end) && (remainder != 0)) {
1234 used_words = remainder;
1235 } else {
1236 used_words = ShenandoahHeapRegion::region_size_words();
1237 }
1238
1239 r->set_affiliation(req.affiliation());
1240 r->set_update_watermark(r->bottom());
1241 r->set_top(r->bottom() + used_words);
1242 }
1243 generation->increase_affiliated_region_count(num);
1244 if (remainder != 0) {
1245 // Record this remainder as allocation waste
1246 _heap->notify_mutator_alloc_words(ShenandoahHeapRegion::region_size_words() - remainder, true);
1247 }
1248
1249 // retire_range_from_partition() will adjust bounds on Mutator free set if appropriate
1250 _partitions.retire_range_from_partition(ShenandoahFreeSetPartitionId::Mutator, beg, end);
1251
1252 size_t total_humongous_size = ShenandoahHeapRegion::region_size_bytes() * num;
1253 _partitions.increase_used(ShenandoahFreeSetPartitionId::Mutator, total_humongous_size);
1254 _partitions.assert_bounds();
1255 req.set_actual_size(words_size);
1256 if (remainder != 0) {
1257 req.set_waste(ShenandoahHeapRegion::region_size_words() - remainder);
1258 }
1259 return _heap->get_region(beg)->bottom();
1260 }
1261
1262 class ShenandoahRecycleTrashedRegionClosure final : public ShenandoahHeapRegionClosure {
1263 public:
1264 ShenandoahRecycleTrashedRegionClosure(): ShenandoahHeapRegionClosure() {}
1265
1266 void heap_region_do(ShenandoahHeapRegion* r) {
1267 r->try_recycle();
1268 }
1269
1270 bool is_thread_safe() {
1271 return true;
1272 }
1273 };
1274
1275 void ShenandoahFreeSet::recycle_trash() {
1276 // lock is not non-reentrant, check we don't have it
1277 shenandoah_assert_not_heaplocked();
1278
1279 ShenandoahHeap* heap = ShenandoahHeap::heap();
1280 heap->assert_gc_workers(heap->workers()->active_workers());
1281
1282 ShenandoahRecycleTrashedRegionClosure closure;
1283 heap->parallel_heap_region_iterate(&closure);
1284 }
1285
1286 void ShenandoahFreeSet::flip_to_old_gc(ShenandoahHeapRegion* r) {
1287 size_t idx = r->index();
1288
1289 assert(_partitions.partition_id_matches(idx, ShenandoahFreeSetPartitionId::Mutator), "Should be in mutator view");
1290 assert(can_allocate_from(r), "Should not be allocated");
1291
1292 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::heap();
1293 size_t region_capacity = alloc_capacity(r);
1294 _partitions.move_from_partition_to_partition(idx, ShenandoahFreeSetPartitionId::Mutator,
1295 ShenandoahFreeSetPartitionId::OldCollector, region_capacity);
1296 _partitions.assert_bounds();
1297 _heap->old_generation()->augment_evacuation_reserve(region_capacity);
1298 bool transferred = gen_heap->generation_sizer()->transfer_to_old(1);
1299 if (!transferred) {
1300 log_warning(gc, free)("Forcing transfer of " SIZE_FORMAT " to old reserve.", idx);
1301 gen_heap->generation_sizer()->force_transfer_to_old(1);
1302 }
1303 // We do not ensure that the region is no longer trash, relying on try_allocate_in(), which always comes next,
1304 // to recycle trash before attempting to allocate anything in the region.
1305 }
1306
1307 void ShenandoahFreeSet::flip_to_gc(ShenandoahHeapRegion* r) {
1308 size_t idx = r->index();
1309
1310 assert(_partitions.partition_id_matches(idx, ShenandoahFreeSetPartitionId::Mutator), "Should be in mutator view");
1311 assert(can_allocate_from(r), "Should not be allocated");
1312
1313 size_t ac = alloc_capacity(r);
1314 _partitions.move_from_partition_to_partition(idx, ShenandoahFreeSetPartitionId::Mutator,
1315 ShenandoahFreeSetPartitionId::Collector, ac);
1316 _partitions.assert_bounds();
1317
1318 // We do not ensure that the region is no longer trash, relying on try_allocate_in(), which always comes next,
1319 // to recycle trash before attempting to allocate anything in the region.
1320 }
1321
1322 void ShenandoahFreeSet::clear() {
1323 shenandoah_assert_heaplocked();
1324 clear_internal();
1325 }
1326
1327 void ShenandoahFreeSet::clear_internal() {
1328 _partitions.make_all_regions_unavailable();
1329
1330 _alloc_bias_weight = 0;
1331 _partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::Mutator, true);
1332 _partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::Collector, false);
1333 _partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::OldCollector, false);
1334 }
1335
1336 void ShenandoahFreeSet::find_regions_with_alloc_capacity(size_t &young_cset_regions, size_t &old_cset_regions,
1337 size_t &first_old_region, size_t &last_old_region,
1338 size_t &old_region_count) {
1339 clear_internal();
1340
1341 first_old_region = _heap->num_regions();
1342 last_old_region = 0;
1343 old_region_count = 0;
1344 old_cset_regions = 0;
1345 young_cset_regions = 0;
1346
1347 size_t region_size_bytes = _partitions.region_size_bytes();
1348 size_t max_regions = _partitions.max_regions();
1349
1350 size_t mutator_leftmost = max_regions;
1351 size_t mutator_rightmost = 0;
1352 size_t mutator_leftmost_empty = max_regions;
1353 size_t mutator_rightmost_empty = 0;
1354 size_t mutator_regions = 0;
1355 size_t mutator_used = 0;
1356
1357 size_t old_collector_leftmost = max_regions;
1358 size_t old_collector_rightmost = 0;
1359 size_t old_collector_leftmost_empty = max_regions;
1360 size_t old_collector_rightmost_empty = 0;
1361 size_t old_collector_regions = 0;
1362 size_t old_collector_used = 0;
1363
1364 size_t num_regions = _heap->num_regions();
1365 for (size_t idx = 0; idx < num_regions; idx++) {
1366 ShenandoahHeapRegion* region = _heap->get_region(idx);
1367 if (region->is_trash()) {
1368 // Trashed regions represent regions that had been in the collection partition but have not yet been "cleaned up".
1369 // The cset regions are not "trashed" until we have finished update refs.
1370 if (region->is_old()) {
1371 old_cset_regions++;
1372 } else {
1373 assert(region->is_young(), "Trashed region should be old or young");
1374 young_cset_regions++;
1375 }
1376 } else if (region->is_old()) {
1377 // count both humongous and regular regions, but don't count trash (cset) regions.
1378 old_region_count++;
1379 if (first_old_region > idx) {
1380 first_old_region = idx;
1381 }
1382 last_old_region = idx;
1383 }
1384 if (region->is_alloc_allowed() || region->is_trash()) {
1385 assert(!region->is_cset(), "Shouldn't be adding cset regions to the free set");
1386
1387 // Do not add regions that would almost surely fail allocation
1388 size_t ac = alloc_capacity(region);
1389 if (ac > PLAB::min_size() * HeapWordSize) {
1390 if (region->is_trash() || !region->is_old()) {
1391 // Both young and old collected regions (trashed) are placed into the Mutator set
1392 _partitions.raw_assign_membership(idx, ShenandoahFreeSetPartitionId::Mutator);
1393 if (idx < mutator_leftmost) {
1394 mutator_leftmost = idx;
1395 }
1396 if (idx > mutator_rightmost) {
1397 mutator_rightmost = idx;
1398 }
1399 if (ac == region_size_bytes) {
1400 if (idx < mutator_leftmost_empty) {
1401 mutator_leftmost_empty = idx;
1402 }
1403 if (idx > mutator_rightmost_empty) {
1404 mutator_rightmost_empty = idx;
1405 }
1406 }
1407 mutator_regions++;
1408 mutator_used += (region_size_bytes - ac);
1409 } else {
1410 // !region->is_trash() && region is_old()
1411 _partitions.raw_assign_membership(idx, ShenandoahFreeSetPartitionId::OldCollector);
1412 if (idx < old_collector_leftmost) {
1413 old_collector_leftmost = idx;
1414 }
1415 if (idx > old_collector_rightmost) {
1416 old_collector_rightmost = idx;
1417 }
1418 if (ac == region_size_bytes) {
1419 if (idx < old_collector_leftmost_empty) {
1420 old_collector_leftmost_empty = idx;
1421 }
1422 if (idx > old_collector_rightmost_empty) {
1423 old_collector_rightmost_empty = idx;
1424 }
1425 }
1426 old_collector_regions++;
1427 old_collector_used += (region_size_bytes - ac);
1428 }
1429 }
1430 }
1431 }
1432 log_debug(gc, free)(" At end of prep_to_rebuild, mutator_leftmost: " SIZE_FORMAT
1433 ", mutator_rightmost: " SIZE_FORMAT
1434 ", mutator_leftmost_empty: " SIZE_FORMAT
1435 ", mutator_rightmost_empty: " SIZE_FORMAT
1436 ", mutator_regions: " SIZE_FORMAT
1437 ", mutator_used: " SIZE_FORMAT,
1438 mutator_leftmost, mutator_rightmost, mutator_leftmost_empty, mutator_rightmost_empty,
1439 mutator_regions, mutator_used);
1440
1441 log_debug(gc, free)(" old_collector_leftmost: " SIZE_FORMAT
1442 ", old_collector_rightmost: " SIZE_FORMAT
1443 ", old_collector_leftmost_empty: " SIZE_FORMAT
1444 ", old_collector_rightmost_empty: " SIZE_FORMAT
1445 ", old_collector_regions: " SIZE_FORMAT
1446 ", old_collector_used: " SIZE_FORMAT,
1447 old_collector_leftmost, old_collector_rightmost, old_collector_leftmost_empty, old_collector_rightmost_empty,
1448 old_collector_regions, old_collector_used);
1449
1450 idx_t rightmost_idx = (mutator_leftmost == max_regions)? -1: (idx_t) mutator_rightmost;
1451 idx_t rightmost_empty_idx = (mutator_leftmost_empty == max_regions)? -1: (idx_t) mutator_rightmost_empty;
1452 _partitions.establish_mutator_intervals(mutator_leftmost, rightmost_idx, mutator_leftmost_empty, rightmost_empty_idx,
1453 mutator_regions, mutator_used);
1454 rightmost_idx = (old_collector_leftmost == max_regions)? -1: (idx_t) old_collector_rightmost;
1455 rightmost_empty_idx = (old_collector_leftmost_empty == max_regions)? -1: (idx_t) old_collector_rightmost_empty;
1456 _partitions.establish_old_collector_intervals(old_collector_leftmost, rightmost_idx, old_collector_leftmost_empty,
1457 rightmost_empty_idx, old_collector_regions, old_collector_used);
1458 log_debug(gc, free)(" After find_regions_with_alloc_capacity(), Mutator range [%zd, %zd],"
1459 " Old Collector range [%zd, %zd]",
1460 _partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator),
1461 _partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator),
1462 _partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector),
1463 _partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector));
1464 }
1465
1466 // Returns number of regions transferred, adds transferred bytes to var argument bytes_transferred
1467 size_t ShenandoahFreeSet::transfer_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId which_collector,
1468 size_t max_xfer_regions,
1469 size_t& bytes_transferred) {
1470 shenandoah_assert_heaplocked();
1471 const size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
1472 size_t transferred_regions = 0;
1473 ShenandoahLeftRightIterator iterator(&_partitions, which_collector, true);
1474 for (idx_t idx = iterator.current(); transferred_regions < max_xfer_regions && iterator.has_next(); idx = iterator.next()) {
1475 // Note: can_allocate_from() denotes that region is entirely empty
1476 if (can_allocate_from(idx)) {
1477 _partitions.move_from_partition_to_partition(idx, which_collector, ShenandoahFreeSetPartitionId::Mutator, region_size_bytes);
1478 transferred_regions++;
1479 bytes_transferred += region_size_bytes;
1480 }
1481 }
1482 return transferred_regions;
1483 }
1484
1485 // Returns number of regions transferred, adds transferred bytes to var argument bytes_transferred
1486 size_t ShenandoahFreeSet::transfer_non_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId which_collector,
1487 size_t max_xfer_regions,
1488 size_t& bytes_transferred) {
1489 shenandoah_assert_heaplocked();
1490 size_t transferred_regions = 0;
1491 ShenandoahLeftRightIterator iterator(&_partitions, which_collector, false);
1492 for (idx_t idx = iterator.current(); transferred_regions < max_xfer_regions && iterator.has_next(); idx = iterator.next()) {
1493 size_t ac = alloc_capacity(idx);
1494 if (ac > 0) {
1495 _partitions.move_from_partition_to_partition(idx, which_collector, ShenandoahFreeSetPartitionId::Mutator, ac);
1496 transferred_regions++;
1497 bytes_transferred += ac;
1498 }
1499 }
1500 return transferred_regions;
1501 }
1502
1503 void ShenandoahFreeSet::move_regions_from_collector_to_mutator(size_t max_xfer_regions) {
1504 size_t collector_xfer = 0;
1505 size_t old_collector_xfer = 0;
1506
1507 // Process empty regions within the Collector free partition
1508 if ((max_xfer_regions > 0) &&
1509 (_partitions.leftmost_empty(ShenandoahFreeSetPartitionId::Collector)
1510 <= _partitions.rightmost_empty(ShenandoahFreeSetPartitionId::Collector))) {
1511 ShenandoahHeapLocker locker(_heap->lock());
1512 max_xfer_regions -=
1513 transfer_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId::Collector, max_xfer_regions,
1514 collector_xfer);
1515 }
1516
1517 // Process empty regions within the OldCollector free partition
1518 if ((max_xfer_regions > 0) &&
1519 (_partitions.leftmost_empty(ShenandoahFreeSetPartitionId::OldCollector)
1520 <= _partitions.rightmost_empty(ShenandoahFreeSetPartitionId::OldCollector))) {
1521 ShenandoahHeapLocker locker(_heap->lock());
1522 size_t old_collector_regions =
1523 transfer_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId::OldCollector, max_xfer_regions,
1524 old_collector_xfer);
1525 max_xfer_regions -= old_collector_regions;
1526 if (old_collector_regions > 0) {
1527 ShenandoahGenerationalHeap::cast(_heap)->generation_sizer()->transfer_to_young(old_collector_regions);
1528 }
1529 }
1530
1531 // If there are any non-empty regions within Collector partition, we can also move them to the Mutator free partition
1532 if ((max_xfer_regions > 0) && (_partitions.leftmost(ShenandoahFreeSetPartitionId::Collector)
1533 <= _partitions.rightmost(ShenandoahFreeSetPartitionId::Collector))) {
1534 ShenandoahHeapLocker locker(_heap->lock());
1535 max_xfer_regions -=
1536 transfer_non_empty_regions_from_collector_set_to_mutator_set(ShenandoahFreeSetPartitionId::Collector, max_xfer_regions,
1537 collector_xfer);
1538 }
1539
1540 size_t total_xfer = collector_xfer + old_collector_xfer;
1541 log_info(gc, ergo)("At start of update refs, moving " SIZE_FORMAT "%s to Mutator free set from Collector Reserve ("
1542 SIZE_FORMAT "%s) and from Old Collector Reserve (" SIZE_FORMAT "%s)",
1543 byte_size_in_proper_unit(total_xfer), proper_unit_for_byte_size(total_xfer),
1544 byte_size_in_proper_unit(collector_xfer), proper_unit_for_byte_size(collector_xfer),
1545 byte_size_in_proper_unit(old_collector_xfer), proper_unit_for_byte_size(old_collector_xfer));
1546 }
1547
1548
1549 // Overwrite arguments to represent the amount of memory in each generation that is about to be recycled
1550 void ShenandoahFreeSet::prepare_to_rebuild(size_t &young_cset_regions, size_t &old_cset_regions,
1551 size_t &first_old_region, size_t &last_old_region, size_t &old_region_count) {
1552 shenandoah_assert_heaplocked();
1553 // This resets all state information, removing all regions from all sets.
1554 clear();
1555 log_debug(gc, free)("Rebuilding FreeSet");
1556
1557 // This places regions that have alloc_capacity into the old_collector set if they identify as is_old() or the
1558 // mutator set otherwise. All trashed (cset) regions are affiliated young and placed in mutator set.
1559 find_regions_with_alloc_capacity(young_cset_regions, old_cset_regions, first_old_region, last_old_region, old_region_count);
1560 }
1561
1562 void ShenandoahFreeSet::establish_generation_sizes(size_t young_region_count, size_t old_region_count) {
1563 assert(young_region_count + old_region_count == ShenandoahHeap::heap()->num_regions(), "Sanity");
1564 if (ShenandoahHeap::heap()->mode()->is_generational()) {
1565 ShenandoahGenerationalHeap* heap = ShenandoahGenerationalHeap::heap();
1566 ShenandoahOldGeneration* old_gen = heap->old_generation();
1567 ShenandoahYoungGeneration* young_gen = heap->young_generation();
1568 size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
1569
1570 size_t original_old_capacity = old_gen->max_capacity();
1571 size_t new_old_capacity = old_region_count * region_size_bytes;
1572 size_t new_young_capacity = young_region_count * region_size_bytes;
1573 old_gen->set_capacity(new_old_capacity);
1574 young_gen->set_capacity(new_young_capacity);
1575
1576 if (new_old_capacity > original_old_capacity) {
1577 size_t region_count = (new_old_capacity - original_old_capacity) / region_size_bytes;
1578 log_info(gc, ergo)("Transfer " SIZE_FORMAT " region(s) from %s to %s, yielding increased size: " PROPERFMT,
1579 region_count, young_gen->name(), old_gen->name(), PROPERFMTARGS(new_old_capacity));
1580 } else if (new_old_capacity < original_old_capacity) {
1581 size_t region_count = (original_old_capacity - new_old_capacity) / region_size_bytes;
1582 log_info(gc, ergo)("Transfer " SIZE_FORMAT " region(s) from %s to %s, yielding increased size: " PROPERFMT,
1583 region_count, old_gen->name(), young_gen->name(), PROPERFMTARGS(new_young_capacity));
1584 }
1585 // This balances generations, so clear any pending request to balance.
1586 old_gen->set_region_balance(0);
1587 }
1588 }
1589
1590 void ShenandoahFreeSet::finish_rebuild(size_t young_cset_regions, size_t old_cset_regions, size_t old_region_count,
1591 bool have_evacuation_reserves) {
1592 shenandoah_assert_heaplocked();
1593 size_t young_reserve(0), old_reserve(0);
1594
1595 if (_heap->mode()->is_generational()) {
1596 compute_young_and_old_reserves(young_cset_regions, old_cset_regions, have_evacuation_reserves,
1597 young_reserve, old_reserve);
1598 } else {
1599 young_reserve = (_heap->max_capacity() / 100) * ShenandoahEvacReserve;
1600 old_reserve = 0;
1601 }
1602
1603 // Move some of the mutator regions in the Collector and OldCollector partitions in order to satisfy
1604 // young_reserve and old_reserve.
1605 reserve_regions(young_reserve, old_reserve, old_region_count);
1606 size_t young_region_count = _heap->num_regions() - old_region_count;
1607 establish_generation_sizes(young_region_count, old_region_count);
1608 establish_old_collector_alloc_bias();
1609 _partitions.assert_bounds();
1610 log_status();
1611 }
1612
1613 void ShenandoahFreeSet::compute_young_and_old_reserves(size_t young_cset_regions, size_t old_cset_regions,
1614 bool have_evacuation_reserves,
1615 size_t& young_reserve_result, size_t& old_reserve_result) const {
1616 shenandoah_assert_generational();
1617 const size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes();
1618
1619 ShenandoahOldGeneration* const old_generation = _heap->old_generation();
1620 size_t old_available = old_generation->available();
1621 size_t old_unaffiliated_regions = old_generation->free_unaffiliated_regions();
1622 ShenandoahYoungGeneration* const young_generation = _heap->young_generation();
1623 size_t young_capacity = young_generation->max_capacity();
1624 size_t young_unaffiliated_regions = young_generation->free_unaffiliated_regions();
1625
1626 // Add in the regions we anticipate to be freed by evacuation of the collection set
1627 old_unaffiliated_regions += old_cset_regions;
1628 young_unaffiliated_regions += young_cset_regions;
1629
1630 // Consult old-region balance to make adjustments to current generation capacities and availability.
1631 // The generation region transfers take place after we rebuild.
1632 const ssize_t old_region_balance = old_generation->get_region_balance();
1633 if (old_region_balance != 0) {
1634 #ifdef ASSERT
1635 if (old_region_balance > 0) {
1636 assert(old_region_balance <= checked_cast<ssize_t>(old_unaffiliated_regions), "Cannot transfer regions that are affiliated");
1637 } else {
1638 assert(0 - old_region_balance <= checked_cast<ssize_t>(young_unaffiliated_regions), "Cannot transfer regions that are affiliated");
1639 }
1640 #endif
1641
1642 ssize_t xfer_bytes = old_region_balance * checked_cast<ssize_t>(region_size_bytes);
1643 old_available -= xfer_bytes;
1644 old_unaffiliated_regions -= old_region_balance;
1645 young_capacity += xfer_bytes;
1646 young_unaffiliated_regions += old_region_balance;
1647 }
1648
1649 // All allocations taken from the old collector set are performed by GC, generally using PLABs for both
1650 // promotions and evacuations. The partition between which old memory is reserved for evacuation and
1651 // which is reserved for promotion is enforced using thread-local variables that prescribe intentions for
1652 // each PLAB's available memory.
1653 if (have_evacuation_reserves) {
1654 // We are rebuilding at the end of final mark, having already established evacuation budgets for this GC pass.
1655 const size_t promoted_reserve = old_generation->get_promoted_reserve();
1656 const size_t old_evac_reserve = old_generation->get_evacuation_reserve();
1657 young_reserve_result = young_generation->get_evacuation_reserve();
1658 old_reserve_result = promoted_reserve + old_evac_reserve;
1659 assert(old_reserve_result <= old_available,
1660 "Cannot reserve (" SIZE_FORMAT " + " SIZE_FORMAT") more OLD than is available: " SIZE_FORMAT,
1661 promoted_reserve, old_evac_reserve, old_available);
1662 } else {
1663 // We are rebuilding at end of GC, so we set aside budgets specified on command line (or defaults)
1664 young_reserve_result = (young_capacity * ShenandoahEvacReserve) / 100;
1665 // The auto-sizer has already made old-gen large enough to hold all anticipated evacuations and promotions.
1666 // Affiliated old-gen regions are already in the OldCollector free set. Add in the relevant number of
1667 // unaffiliated regions.
1668 old_reserve_result = old_available;
1669 }
1670
1671 // Old available regions that have less than PLAB::min_size() of available memory are not placed into the OldCollector
1672 // free set. Because of this, old_available may not have enough memory to represent the intended reserve. Adjust
1673 // the reserve downward to account for this possibility. This loss is part of the reason why the original budget
1674 // was adjusted with ShenandoahOldEvacWaste and ShenandoahOldPromoWaste multipliers.
1675 if (old_reserve_result >
1676 _partitions.capacity_of(ShenandoahFreeSetPartitionId::OldCollector) + old_unaffiliated_regions * region_size_bytes) {
1677 old_reserve_result =
1678 _partitions.capacity_of(ShenandoahFreeSetPartitionId::OldCollector) + old_unaffiliated_regions * region_size_bytes;
1679 }
1680
1681 if (young_reserve_result > young_unaffiliated_regions * region_size_bytes) {
1682 young_reserve_result = young_unaffiliated_regions * region_size_bytes;
1683 }
1684 }
1685
1686 // Having placed all regions that have allocation capacity into the mutator set if they identify as is_young()
1687 // or into the old collector set if they identify as is_old(), move some of these regions from the mutator set
1688 // into the collector set or old collector set in order to assure that the memory available for allocations within
1689 // the collector set is at least to_reserve and the memory available for allocations within the old collector set
1690 // is at least to_reserve_old.
1691 void ShenandoahFreeSet::reserve_regions(size_t to_reserve, size_t to_reserve_old, size_t &old_region_count) {
1692 for (size_t i = _heap->num_regions(); i > 0; i--) {
1693 size_t idx = i - 1;
1694 ShenandoahHeapRegion* r = _heap->get_region(idx);
1695 if (!_partitions.in_free_set(ShenandoahFreeSetPartitionId::Mutator, idx)) {
1696 continue;
1697 }
1698
1699 size_t ac = alloc_capacity(r);
1700 assert (ac > 0, "Membership in free set implies has capacity");
1701 assert (!r->is_old() || r->is_trash(), "Except for trash, mutator_is_free regions should not be affiliated OLD");
1702
1703 bool move_to_old_collector = _partitions.available_in(ShenandoahFreeSetPartitionId::OldCollector) < to_reserve_old;
1704 bool move_to_collector = _partitions.available_in(ShenandoahFreeSetPartitionId::Collector) < to_reserve;
1705
1706 if (!move_to_collector && !move_to_old_collector) {
1707 // We've satisfied both to_reserve and to_reserved_old
1708 break;
1709 }
1710
1711 if (move_to_old_collector) {
1712 // We give priority to OldCollector partition because we desire to pack OldCollector regions into higher
1713 // addresses than Collector regions. Presumably, OldCollector regions are more "stable" and less likely to
1714 // be collected in the near future.
1715 if (r->is_trash() || !r->is_affiliated()) {
1716 // OLD regions that have available memory are already in the old_collector free set.
1717 _partitions.move_from_partition_to_partition(idx, ShenandoahFreeSetPartitionId::Mutator,
1718 ShenandoahFreeSetPartitionId::OldCollector, ac);
1719 log_trace(gc, free)(" Shifting region " SIZE_FORMAT " from mutator_free to old_collector_free", idx);
1720 log_trace(gc, free)(" Shifted Mutator range [%zd, %zd],"
1721 " Old Collector range [%zd, %zd]",
1722 _partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator),
1723 _partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator),
1724 _partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector),
1725 _partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector));
1726 old_region_count++;
1727 continue;
1728 }
1729 }
1730
1731 if (move_to_collector) {
1732 // Note: In a previous implementation, regions were only placed into the survivor space (collector_is_free) if
1733 // they were entirely empty. This has the effect of causing new Mutator allocation to reside next to objects
1734 // that have already survived at least one GC, mixing ephemeral with longer-lived objects in the same region.
1735 // Any objects that have survived a GC are less likely to immediately become garbage, so a region that contains
1736 // survivor objects is less likely to be selected for the collection set. This alternative implementation allows
1737 // survivor regions to continue accumulating other survivor objects, and makes it more likely that ephemeral objects
1738 // occupy regions comprised entirely of ephemeral objects. These regions are highly likely to be included in the next
1739 // collection set, and they are easily evacuated because they have low density of live objects.
1740 _partitions.move_from_partition_to_partition(idx, ShenandoahFreeSetPartitionId::Mutator,
1741 ShenandoahFreeSetPartitionId::Collector, ac);
1742 log_trace(gc, free)(" Shifting region " SIZE_FORMAT " from mutator_free to collector_free", idx);
1743 log_trace(gc, free)(" Shifted Mutator range [%zd, %zd],"
1744 " Collector range [%zd, %zd]",
1745 _partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator),
1746 _partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator),
1747 _partitions.leftmost(ShenandoahFreeSetPartitionId::Collector),
1748 _partitions.rightmost(ShenandoahFreeSetPartitionId::Collector));
1749 }
1750 }
1751
1752 if (LogTarget(Info, gc, free)::is_enabled()) {
1753 size_t old_reserve = _partitions.available_in(ShenandoahFreeSetPartitionId::OldCollector);
1754 if (old_reserve < to_reserve_old) {
1755 log_info(gc, free)("Wanted " PROPERFMT " for old reserve, but only reserved: " PROPERFMT,
1756 PROPERFMTARGS(to_reserve_old), PROPERFMTARGS(old_reserve));
1757 }
1758 size_t reserve = _partitions.available_in(ShenandoahFreeSetPartitionId::Collector);
1759 if (reserve < to_reserve) {
1760 log_info(gc, free)("Wanted " PROPERFMT " for young reserve, but only reserved: " PROPERFMT,
1761 PROPERFMTARGS(to_reserve), PROPERFMTARGS(reserve));
1762 }
1763 }
1764 }
1765
1766 void ShenandoahFreeSet::establish_old_collector_alloc_bias() {
1767 ShenandoahHeap* heap = ShenandoahHeap::heap();
1768 shenandoah_assert_heaplocked();
1769
1770 idx_t left_idx = _partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector);
1771 idx_t right_idx = _partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector);
1772 idx_t middle = (left_idx + right_idx) / 2;
1773 size_t available_in_first_half = 0;
1774 size_t available_in_second_half = 0;
1775
1776 for (idx_t index = left_idx; index < middle; index++) {
1777 if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, index)) {
1778 ShenandoahHeapRegion* r = heap->get_region((size_t) index);
1779 available_in_first_half += r->free();
1780 }
1781 }
1782 for (idx_t index = middle; index <= right_idx; index++) {
1783 if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, index)) {
1784 ShenandoahHeapRegion* r = heap->get_region(index);
1785 available_in_second_half += r->free();
1786 }
1787 }
1788
1789 // We desire to first consume the sparsely distributed regions in order that the remaining regions are densely packed.
1790 // Densely packing regions reduces the effort to search for a region that has sufficient memory to satisfy a new allocation
1791 // request. Regions become sparsely distributed following a Full GC, which tends to slide all regions to the front of the
1792 // heap rather than allowing survivor regions to remain at the high end of the heap where we intend for them to congregate.
1793 _partitions.set_bias_from_left_to_right(ShenandoahFreeSetPartitionId::OldCollector,
1794 (available_in_second_half > available_in_first_half));
1795 }
1796
1797 void ShenandoahFreeSet::log_status_under_lock() {
1798 // Must not be heap locked, it acquires heap lock only when log is enabled
1799 shenandoah_assert_not_heaplocked();
1800 if (LogTarget(Info, gc, free)::is_enabled()
1801 DEBUG_ONLY(|| LogTarget(Debug, gc, free)::is_enabled())) {
1802 ShenandoahHeapLocker locker(_heap->lock());
1803 log_status();
1804 }
1805 }
1806
1807 void ShenandoahFreeSet::log_status() {
1808 shenandoah_assert_heaplocked();
1809
1810 #ifdef ASSERT
1811 // Dump of the FreeSet details is only enabled if assertions are enabled
1812 LogTarget(Debug, gc, free) debug_free;
1813 if (debug_free.is_enabled()) {
1814 #define BUFFER_SIZE 80
1815 LogStream ls(debug_free);
1816
1817 char buffer[BUFFER_SIZE];
1818 for (uint i = 0; i < BUFFER_SIZE; i++) {
1819 buffer[i] = '\0';
1820 }
1821
1822 ls.cr();
1823 ls.print_cr("Mutator free range [%zd..%zd] allocating from %s",
1824 _partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator),
1825 _partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator),
1826 _partitions.alloc_from_left_bias(ShenandoahFreeSetPartitionId::Mutator)? "left to right": "right to left");
1827
1828 ls.print_cr("Collector free range [%zd..%zd] allocating from %s",
1829 _partitions.leftmost(ShenandoahFreeSetPartitionId::Collector),
1830 _partitions.rightmost(ShenandoahFreeSetPartitionId::Collector),
1831 _partitions.alloc_from_left_bias(ShenandoahFreeSetPartitionId::Collector)? "left to right": "right to left");
1832
1833 ls.print_cr("Old collector free range [%zd..%zd] allocates from %s",
1834 _partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector),
1835 _partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector),
1836 _partitions.alloc_from_left_bias(ShenandoahFreeSetPartitionId::OldCollector)? "left to right": "right to left");
1837 ls.cr();
1838 ls.print_cr("FreeSet map legend:");
1839 ls.print_cr(" M/m:mutator, C/c:collector O/o:old_collector (Empty/Occupied)");
1840 ls.print_cr(" H/h:humongous, X/x:no alloc capacity, ~/_:retired (Old/Young)");
1841
1842 for (uint i = 0; i < _heap->num_regions(); i++) {
1843 ShenandoahHeapRegion *r = _heap->get_region(i);
1844 uint idx = i % 64;
1845 if ((i != 0) && (idx == 0)) {
1846 ls.print_cr(" %6u: %s", i-64, buffer);
1847 }
1848 if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::Mutator, i)) {
1849 size_t capacity = alloc_capacity(r);
1850 assert(!r->is_old() || r->is_trash(), "Old regions except trash regions should not be in mutator_free set");
1851 buffer[idx] = (capacity == ShenandoahHeapRegion::region_size_bytes()) ? 'M' : 'm';
1852 } else if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::Collector, i)) {
1853 size_t capacity = alloc_capacity(r);
1854 assert(!r->is_old() || r->is_trash(), "Old regions except trash regions should not be in collector_free set");
1855 buffer[idx] = (capacity == ShenandoahHeapRegion::region_size_bytes()) ? 'C' : 'c';
1856 } else if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, i)) {
1857 size_t capacity = alloc_capacity(r);
1858 buffer[idx] = (capacity == ShenandoahHeapRegion::region_size_bytes()) ? 'O' : 'o';
1859 } else if (r->is_humongous()) {
1860 buffer[idx] = (r->is_old() ? 'H' : 'h');
1861 } else if (alloc_capacity(r) == 0) {
1862 buffer[idx] = (r->is_old() ? 'X' : 'x');
1863 } else {
1864 buffer[idx] = (r->is_old() ? '~' : '_');
1865 }
1866 }
1867 uint remnant = _heap->num_regions() % 64;
1868 if (remnant > 0) {
1869 buffer[remnant] = '\0';
1870 } else {
1871 remnant = 64;
1872 }
1873 ls.print_cr(" %6u: %s", (uint) (_heap->num_regions() - remnant), buffer);
1874 }
1875 #endif
1876
1877 LogTarget(Info, gc, free) lt;
1878 if (lt.is_enabled()) {
1879 ResourceMark rm;
1880 LogStream ls(lt);
1881
1882 {
1883 idx_t last_idx = 0;
1884 size_t max = 0;
1885 size_t max_contig = 0;
1886 size_t empty_contig = 0;
1887
1888 size_t total_used = 0;
1889 size_t total_free = 0;
1890 size_t total_free_ext = 0;
1891
1892 for (idx_t idx = _partitions.leftmost(ShenandoahFreeSetPartitionId::Mutator);
1893 idx <= _partitions.rightmost(ShenandoahFreeSetPartitionId::Mutator); idx++) {
1894 if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::Mutator, idx)) {
1895 ShenandoahHeapRegion *r = _heap->get_region(idx);
1896 size_t free = alloc_capacity(r);
1897 max = MAX2(max, free);
1898 if (r->is_empty()) {
1899 total_free_ext += free;
1900 if (last_idx + 1 == idx) {
1901 empty_contig++;
1902 } else {
1903 empty_contig = 1;
1904 }
1905 } else {
1906 empty_contig = 0;
1907 }
1908 total_used += r->used();
1909 total_free += free;
1910 max_contig = MAX2(max_contig, empty_contig);
1911 last_idx = idx;
1912 }
1913 }
1914
1915 size_t max_humongous = max_contig * ShenandoahHeapRegion::region_size_bytes();
1916 size_t free = capacity() - used();
1917
1918 // Since certain regions that belonged to the Mutator free partition at the time of most recent rebuild may have been
1919 // retired, the sum of used and capacities within regions that are still in the Mutator free partition may not match
1920 // my internally tracked values of used() and free().
1921 assert(free == total_free, "Free memory should match");
1922 ls.print("Free: " SIZE_FORMAT "%s, Max: " SIZE_FORMAT "%s regular, " SIZE_FORMAT "%s humongous, ",
1923 byte_size_in_proper_unit(total_free), proper_unit_for_byte_size(total_free),
1924 byte_size_in_proper_unit(max), proper_unit_for_byte_size(max),
1925 byte_size_in_proper_unit(max_humongous), proper_unit_for_byte_size(max_humongous)
1926 );
1927
1928 ls.print("Frag: ");
1929 size_t frag_ext;
1930 if (total_free_ext > 0) {
1931 frag_ext = 100 - (100 * max_humongous / total_free_ext);
1932 } else {
1933 frag_ext = 0;
1934 }
1935 ls.print(SIZE_FORMAT "%% external, ", frag_ext);
1936
1937 size_t frag_int;
1938 if (_partitions.count(ShenandoahFreeSetPartitionId::Mutator) > 0) {
1939 frag_int = (100 * (total_used / _partitions.count(ShenandoahFreeSetPartitionId::Mutator))
1940 / ShenandoahHeapRegion::region_size_bytes());
1941 } else {
1942 frag_int = 0;
1943 }
1944 ls.print(SIZE_FORMAT "%% internal; ", frag_int);
1945 ls.print("Used: " SIZE_FORMAT "%s, Mutator Free: " SIZE_FORMAT,
1946 byte_size_in_proper_unit(total_used), proper_unit_for_byte_size(total_used),
1947 _partitions.count(ShenandoahFreeSetPartitionId::Mutator));
1948 }
1949
1950 {
1951 size_t max = 0;
1952 size_t total_free = 0;
1953 size_t total_used = 0;
1954
1955 for (idx_t idx = _partitions.leftmost(ShenandoahFreeSetPartitionId::Collector);
1956 idx <= _partitions.rightmost(ShenandoahFreeSetPartitionId::Collector); idx++) {
1957 if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::Collector, idx)) {
1958 ShenandoahHeapRegion *r = _heap->get_region(idx);
1959 size_t free = alloc_capacity(r);
1960 max = MAX2(max, free);
1961 total_free += free;
1962 total_used += r->used();
1963 }
1964 }
1965 ls.print(" Collector Reserve: " SIZE_FORMAT "%s, Max: " SIZE_FORMAT "%s; Used: " SIZE_FORMAT "%s",
1966 byte_size_in_proper_unit(total_free), proper_unit_for_byte_size(total_free),
1967 byte_size_in_proper_unit(max), proper_unit_for_byte_size(max),
1968 byte_size_in_proper_unit(total_used), proper_unit_for_byte_size(total_used));
1969 }
1970
1971 if (_heap->mode()->is_generational()) {
1972 size_t max = 0;
1973 size_t total_free = 0;
1974 size_t total_used = 0;
1975
1976 for (idx_t idx = _partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector);
1977 idx <= _partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector); idx++) {
1978 if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, idx)) {
1979 ShenandoahHeapRegion *r = _heap->get_region(idx);
1980 size_t free = alloc_capacity(r);
1981 max = MAX2(max, free);
1982 total_free += free;
1983 total_used += r->used();
1984 }
1985 }
1986 ls.print_cr(" Old Collector Reserve: " SIZE_FORMAT "%s, Max: " SIZE_FORMAT "%s; Used: " SIZE_FORMAT "%s",
1987 byte_size_in_proper_unit(total_free), proper_unit_for_byte_size(total_free),
1988 byte_size_in_proper_unit(max), proper_unit_for_byte_size(max),
1989 byte_size_in_proper_unit(total_used), proper_unit_for_byte_size(total_used));
1990 }
1991 }
1992 }
1993
1994 HeapWord* ShenandoahFreeSet::allocate(ShenandoahAllocRequest& req, bool& in_new_region) {
1995 shenandoah_assert_heaplocked();
1996 if (ShenandoahHeapRegion::requires_humongous(req.size())) {
1997 switch (req.type()) {
1998 case ShenandoahAllocRequest::_alloc_shared:
1999 case ShenandoahAllocRequest::_alloc_shared_gc:
2000 in_new_region = true;
2001 return allocate_contiguous(req);
2002 case ShenandoahAllocRequest::_alloc_plab:
2003 case ShenandoahAllocRequest::_alloc_gclab:
2004 case ShenandoahAllocRequest::_alloc_tlab:
2005 in_new_region = false;
2006 assert(false, "Trying to allocate TLAB in humongous region: " SIZE_FORMAT, req.size());
2007 return nullptr;
2008 default:
2009 ShouldNotReachHere();
2010 return nullptr;
2011 }
2012 } else {
2013 return allocate_single(req, in_new_region);
2014 }
2015 }
2016
2017 void ShenandoahFreeSet::print_on(outputStream* out) const {
2018 out->print_cr("Mutator Free Set: " SIZE_FORMAT "", _partitions.count(ShenandoahFreeSetPartitionId::Mutator));
2019 ShenandoahLeftRightIterator mutator(const_cast<ShenandoahRegionPartitions*>(&_partitions), ShenandoahFreeSetPartitionId::Mutator);
2020 for (idx_t index = mutator.current(); mutator.has_next(); index = mutator.next()) {
2021 _heap->get_region(index)->print_on(out);
2022 }
2023
2024 out->print_cr("Collector Free Set: " SIZE_FORMAT "", _partitions.count(ShenandoahFreeSetPartitionId::Collector));
2025 ShenandoahLeftRightIterator collector(const_cast<ShenandoahRegionPartitions*>(&_partitions), ShenandoahFreeSetPartitionId::Collector);
2026 for (idx_t index = collector.current(); collector.has_next(); index = collector.next()) {
2027 _heap->get_region(index)->print_on(out);
2028 }
2029
2030 if (_heap->mode()->is_generational()) {
2031 out->print_cr("Old Collector Free Set: " SIZE_FORMAT "", _partitions.count(ShenandoahFreeSetPartitionId::OldCollector));
2032 for (idx_t index = _partitions.leftmost(ShenandoahFreeSetPartitionId::OldCollector);
2033 index <= _partitions.rightmost(ShenandoahFreeSetPartitionId::OldCollector); index++) {
2034 if (_partitions.in_free_set(ShenandoahFreeSetPartitionId::OldCollector, index)) {
2035 _heap->get_region(index)->print_on(out);
2036 }
2037 }
2038 }
2039 }
2040
2041 double ShenandoahFreeSet::internal_fragmentation() {
2042 double squared = 0;
2043 double linear = 0;
2044
2045 ShenandoahLeftRightIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator);
2046 for (idx_t index = iterator.current(); iterator.has_next(); index = iterator.next()) {
2047 ShenandoahHeapRegion* r = _heap->get_region(index);
2048 size_t used = r->used();
2049 squared += used * used;
2050 linear += used;
2051 }
2052
2053 if (linear > 0) {
2054 double s = squared / (ShenandoahHeapRegion::region_size_bytes() * linear);
2055 return 1 - s;
2056 } else {
2057 return 0;
2058 }
2059 }
2060
2061 double ShenandoahFreeSet::external_fragmentation() {
2062 idx_t last_idx = 0;
2063 size_t max_contig = 0;
2064 size_t empty_contig = 0;
2065 size_t free = 0;
2066
2067 ShenandoahLeftRightIterator iterator(&_partitions, ShenandoahFreeSetPartitionId::Mutator);
2068 for (idx_t index = iterator.current(); iterator.has_next(); index = iterator.next()) {
2069 ShenandoahHeapRegion* r = _heap->get_region(index);
2070 if (r->is_empty()) {
2071 free += ShenandoahHeapRegion::region_size_bytes();
2072 if (last_idx + 1 == index) {
2073 empty_contig++;
2074 } else {
2075 empty_contig = 1;
2076 }
2077 } else {
2078 empty_contig = 0;
2079 }
2080 max_contig = MAX2(max_contig, empty_contig);
2081 last_idx = index;
2082 }
2083
2084 if (free > 0) {
2085 return 1 - (1.0 * max_contig * ShenandoahHeapRegion::region_size_bytes() / free);
2086 } else {
2087 return 0;
2088 }
2089 }
2090