1 /*
2 * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26
27 #include "logging/log.hpp"
28 #include "logging/logStream.hpp"
29 #include "memory/metaspace/metachunk.hpp"
30 #include "memory/metaspace.hpp"
31 #include "memory/metaspace/chunkManager.hpp"
32 #include "memory/metaspace/metaDebug.hpp"
33 #include "memory/metaspace/metaspaceCommon.hpp"
34 #include "memory/metaspace/occupancyMap.hpp"
35 #include "memory/metaspace/virtualSpaceNode.hpp"
36 #include "memory/virtualspace.hpp"
37 #include "runtime/atomic.hpp"
38 #include "runtime/os.hpp"
39 #include "services/memTracker.hpp"
40 #include "utilities/copy.hpp"
41 #include "utilities/debug.hpp"
42 #include "utilities/globalDefinitions.hpp"
43
44 namespace metaspace {
45
46 // Decide if large pages should be committed when the memory is reserved.
47 static bool should_commit_large_pages_when_reserving(size_t bytes) {
48 if (UseLargePages && UseLargePagesInMetaspace && !os::can_commit_large_page_memory()) {
49 size_t words = bytes / BytesPerWord;
50 bool is_class = false; // We never reserve large pages for the class space.
51 if (MetaspaceGC::can_expand(words, is_class) &&
52 MetaspaceGC::allowed_expansion() >= words) {
53 return true;
54 }
55 }
56
57 return false;
58 }
59
60 // byte_size is the size of the associated virtualspace.
61 VirtualSpaceNode::VirtualSpaceNode(bool is_class, size_t bytes) :
62 _next(NULL), _is_class(is_class), _rs(), _top(NULL), _container_count(0), _occupancy_map(NULL) {
63 assert_is_aligned(bytes, Metaspace::reserve_alignment());
64 bool large_pages = should_commit_large_pages_when_reserving(bytes);
65 _rs = ReservedSpace(bytes, Metaspace::reserve_alignment(), large_pages);
66
67 if (_rs.is_reserved()) {
68 assert(_rs.base() != NULL, "Catch if we get a NULL address");
69 assert(_rs.size() != 0, "Catch if we get a 0 size");
70 assert_is_aligned(_rs.base(), Metaspace::reserve_alignment());
71 assert_is_aligned(_rs.size(), Metaspace::reserve_alignment());
72
73 MemTracker::record_virtual_memory_type((address)_rs.base(), mtClass);
74 }
75 }
76
77 void VirtualSpaceNode::purge(ChunkManager* chunk_manager) {
78 // When a node is purged, lets give it a thorough examination.
79 DEBUG_ONLY(verify(true);)
80 Metachunk* chunk = first_chunk();
81 Metachunk* invalid_chunk = (Metachunk*) top();
82 while (chunk < invalid_chunk ) {
83 assert(chunk->is_tagged_free(), "Should be tagged free");
84 MetaWord* next = ((MetaWord*)chunk) + chunk->word_size();
85 chunk_manager->remove_chunk(chunk);
86 chunk->remove_sentinel();
87 assert(chunk->next() == NULL &&
88 chunk->prev() == NULL,
89 "Was not removed from its list");
90 chunk = (Metachunk*) next;
91 }
92 }
93
94 void VirtualSpaceNode::print_map(outputStream* st, bool is_class) const {
95
96 if (bottom() == top()) {
97 return;
98 }
99
100 const size_t spec_chunk_size = is_class ? ClassSpecializedChunk : SpecializedChunk;
101 const size_t small_chunk_size = is_class ? ClassSmallChunk : SmallChunk;
102 const size_t med_chunk_size = is_class ? ClassMediumChunk : MediumChunk;
103
104 int line_len = 100;
105 const size_t section_len = align_up(spec_chunk_size * line_len, med_chunk_size);
106 line_len = (int)(section_len / spec_chunk_size);
107
108 static const int NUM_LINES = 4;
109
110 char* lines[NUM_LINES];
111 for (int i = 0; i < NUM_LINES; i ++) {
112 lines[i] = (char*)os::malloc(line_len, mtInternal);
113 }
114 int pos = 0;
115 const MetaWord* p = bottom();
116 const Metachunk* chunk = (const Metachunk*)p;
117 const MetaWord* chunk_end = p + chunk->word_size();
118 while (p < top()) {
119 if (pos == line_len) {
120 pos = 0;
121 for (int i = 0; i < NUM_LINES; i ++) {
122 st->fill_to(22);
123 st->print_raw(lines[i], line_len);
124 st->cr();
125 }
126 }
127 if (pos == 0) {
128 st->print(PTR_FORMAT ":", p2i(p));
129 }
130 if (p == chunk_end) {
131 chunk = (Metachunk*)p;
132 chunk_end = p + chunk->word_size();
133 }
134 // line 1: chunk starting points (a dot if that area is a chunk start).
135 lines[0][pos] = p == (const MetaWord*)chunk ? '.' : ' ';
136
137 // Line 2: chunk type (x=spec, s=small, m=medium, h=humongous), uppercase if
138 // chunk is in use.
139 const bool chunk_is_free = ((Metachunk*)chunk)->is_tagged_free();
140 if (chunk->word_size() == spec_chunk_size) {
141 lines[1][pos] = chunk_is_free ? 'x' : 'X';
142 } else if (chunk->word_size() == small_chunk_size) {
143 lines[1][pos] = chunk_is_free ? 's' : 'S';
144 } else if (chunk->word_size() == med_chunk_size) {
145 lines[1][pos] = chunk_is_free ? 'm' : 'M';
146 } else if (chunk->word_size() > med_chunk_size) {
147 lines[1][pos] = chunk_is_free ? 'h' : 'H';
148 } else {
149 ShouldNotReachHere();
150 }
151
152 // Line 3: chunk origin
153 const ChunkOrigin origin = chunk->get_origin();
154 lines[2][pos] = origin == origin_normal ? ' ' : '0' + (int) origin;
155
156 // Line 4: Virgin chunk? Virgin chunks are chunks created as a byproduct of padding or splitting,
157 // but were never used.
158 lines[3][pos] = chunk->get_use_count() > 0 ? ' ' : 'v';
159
160 p += spec_chunk_size;
161 pos ++;
162 }
163 if (pos > 0) {
164 for (int i = 0; i < NUM_LINES; i ++) {
165 st->fill_to(22);
166 st->print_raw(lines[i], line_len);
167 st->cr();
168 }
169 }
170 for (int i = 0; i < NUM_LINES; i ++) {
171 os::free(lines[i]);
172 }
173 }
174
175
176 #ifdef ASSERT
177
178 // Verify counters, all chunks in this list node and the occupancy map.
179 void VirtualSpaceNode::verify(bool slow) {
180 log_trace(gc, metaspace, freelist)("verifying %s virtual space node (%s).",
181 (is_class() ? "class space" : "metaspace"), (slow ? "slow" : "quick"));
182 // Fast mode: just verify chunk counters and basic geometry
183 // Slow mode: verify chunks and occupancy map
184 uintx num_in_use_chunks = 0;
185 Metachunk* chunk = first_chunk();
186 Metachunk* invalid_chunk = (Metachunk*) top();
187
188 // Iterate the chunks in this node and verify each chunk.
189 while (chunk < invalid_chunk ) {
190 if (slow) {
191 do_verify_chunk(chunk);
192 }
193 if (!chunk->is_tagged_free()) {
194 num_in_use_chunks ++;
195 }
196 const size_t s = chunk->word_size();
197 // Prevent endless loop on invalid chunk size.
198 assert(is_valid_chunksize(is_class(), s), "Invalid chunk size: " SIZE_FORMAT ".", s);
199 MetaWord* next = ((MetaWord*)chunk) + s;
200 chunk = (Metachunk*) next;
201 }
202 assert(_container_count == num_in_use_chunks, "Container count mismatch (real: " UINTX_FORMAT
203 ", counter: " UINTX_FORMAT ".", num_in_use_chunks, _container_count);
204 // Also verify the occupancy map.
205 if (slow) {
206 occupancy_map()->verify(bottom(), top());
207 }
208 }
209
210 // Verify that all free chunks in this node are ideally merged
211 // (there not should be multiple small chunks where a large chunk could exist.)
212 void VirtualSpaceNode::verify_free_chunks_are_ideally_merged() {
213 Metachunk* chunk = first_chunk();
214 Metachunk* invalid_chunk = (Metachunk*) top();
215 // Shorthands.
216 const size_t size_med = (is_class() ? ClassMediumChunk : MediumChunk) * BytesPerWord;
217 const size_t size_small = (is_class() ? ClassSmallChunk : SmallChunk) * BytesPerWord;
218 int num_free_chunks_since_last_med_boundary = -1;
219 int num_free_chunks_since_last_small_boundary = -1;
220 bool error = false;
221 char err[256];
222 while (!error && chunk < invalid_chunk ) {
223 // Test for missed chunk merge opportunities: count number of free chunks since last chunk boundary.
224 // Reset the counter when encountering a non-free chunk.
225 if (chunk->get_chunk_type() != HumongousIndex) {
226 if (chunk->is_tagged_free()) {
227 // Count successive free, non-humongous chunks.
228 if (is_aligned(chunk, size_small)) {
229 if (num_free_chunks_since_last_small_boundary > 0) {
230 error = true;
231 jio_snprintf(err, sizeof(err), "Missed chunk merge opportunity to merge a small chunk preceding " PTR_FORMAT ".", p2i(chunk));
232 } else {
233 num_free_chunks_since_last_small_boundary = 0;
234 }
235 } else if (num_free_chunks_since_last_small_boundary != -1) {
236 num_free_chunks_since_last_small_boundary ++;
237 }
238 if (is_aligned(chunk, size_med)) {
239 if (num_free_chunks_since_last_med_boundary > 0) {
240 error = true;
241 jio_snprintf(err, sizeof(err), "Missed chunk merge opportunity to merge a medium chunk preceding " PTR_FORMAT ".", p2i(chunk));
242 } else {
243 num_free_chunks_since_last_med_boundary = 0;
244 }
245 } else if (num_free_chunks_since_last_med_boundary != -1) {
246 num_free_chunks_since_last_med_boundary ++;
247 }
248 } else {
249 // Encountering a non-free chunk, reset counters.
250 num_free_chunks_since_last_med_boundary = -1;
251 num_free_chunks_since_last_small_boundary = -1;
252 }
253 } else {
254 // One cannot merge areas with a humongous chunk in the middle. Reset counters.
255 num_free_chunks_since_last_med_boundary = -1;
256 num_free_chunks_since_last_small_boundary = -1;
257 }
258
259 if (error) {
260 print_map(tty, is_class());
261 fatal("%s", err);
262 }
263
264 MetaWord* next = ((MetaWord*)chunk) + chunk->word_size();
265 chunk = (Metachunk*) next;
266 }
267 }
268 #endif // ASSERT
269
270 void VirtualSpaceNode::inc_container_count() {
271 assert_lock_strong(MetaspaceExpand_lock);
272 _container_count++;
273 }
274
275 void VirtualSpaceNode::dec_container_count() {
276 assert_lock_strong(MetaspaceExpand_lock);
277 _container_count--;
278 }
279
280 VirtualSpaceNode::~VirtualSpaceNode() {
281 _rs.release();
282 if (_occupancy_map != NULL) {
283 delete _occupancy_map;
284 }
285 #ifdef ASSERT
286 size_t word_size = sizeof(*this) / BytesPerWord;
287 Copy::fill_to_words((HeapWord*) this, word_size, 0xf1f1f1f1);
288 #endif
289 }
290
291 size_t VirtualSpaceNode::used_words_in_vs() const {
292 return pointer_delta(top(), bottom(), sizeof(MetaWord));
293 }
294
295 // Space committed in the VirtualSpace
296 size_t VirtualSpaceNode::capacity_words_in_vs() const {
297 return pointer_delta(end(), bottom(), sizeof(MetaWord));
298 }
299
300 size_t VirtualSpaceNode::free_words_in_vs() const {
301 return pointer_delta(end(), top(), sizeof(MetaWord));
302 }
303
304 // Given an address larger than top(), allocate padding chunks until top is at the given address.
305 void VirtualSpaceNode::allocate_padding_chunks_until_top_is_at(MetaWord* target_top) {
306
307 assert(target_top > top(), "Sanity");
308
309 // Padding chunks are added to the freelist.
310 ChunkManager* const chunk_manager = Metaspace::get_chunk_manager(is_class());
311
312 // shorthands
313 const size_t spec_word_size = chunk_manager->specialized_chunk_word_size();
314 const size_t small_word_size = chunk_manager->small_chunk_word_size();
315 const size_t med_word_size = chunk_manager->medium_chunk_word_size();
316
317 while (top() < target_top) {
318
319 // We could make this coding more generic, but right now we only deal with two possible chunk sizes
320 // for padding chunks, so it is not worth it.
321 size_t padding_chunk_word_size = small_word_size;
322 if (is_aligned(top(), small_word_size * sizeof(MetaWord)) == false) {
323 assert_is_aligned(top(), spec_word_size * sizeof(MetaWord)); // Should always hold true.
324 padding_chunk_word_size = spec_word_size;
325 }
326 MetaWord* here = top();
327 assert_is_aligned(here, padding_chunk_word_size * sizeof(MetaWord));
328 inc_top(padding_chunk_word_size);
329
330 // Create new padding chunk.
331 ChunkIndex padding_chunk_type = get_chunk_type_by_size(padding_chunk_word_size, is_class());
332 assert(padding_chunk_type == SpecializedIndex || padding_chunk_type == SmallIndex, "sanity");
333
334 Metachunk* const padding_chunk =
335 ::new (here) Metachunk(padding_chunk_type, is_class(), padding_chunk_word_size, this);
336 assert(padding_chunk == (Metachunk*)here, "Sanity");
337 DEBUG_ONLY(padding_chunk->set_origin(origin_pad);)
338 log_trace(gc, metaspace, freelist)("Created padding chunk in %s at "
339 PTR_FORMAT ", size " SIZE_FORMAT_HEX ".",
340 (is_class() ? "class space " : "metaspace"),
341 p2i(padding_chunk), padding_chunk->word_size() * sizeof(MetaWord));
342
343 // Mark chunk start in occupancy map.
344 occupancy_map()->set_chunk_starts_at_address((MetaWord*)padding_chunk, true);
345
346 // Chunks are born as in-use (see MetaChunk ctor). So, before returning
347 // the padding chunk to its chunk manager, mark it as in use (ChunkManager
348 // will assert that).
349 do_update_in_use_info_for_chunk(padding_chunk, true);
350
351 // Return Chunk to freelist.
352 inc_container_count();
353 chunk_manager->return_single_chunk(padding_chunk);
354 // Please note: at this point, ChunkManager::return_single_chunk()
355 // may already have merged the padding chunk with neighboring chunks, so
356 // it may have vanished at this point. Do not reference the padding
357 // chunk beyond this point.
358 }
359
360 assert(top() == target_top, "Sanity");
361
362 } // allocate_padding_chunks_until_top_is_at()
363
364 // Allocates the chunk from the virtual space only.
365 // This interface is also used internally for debugging. Not all
366 // chunks removed here are necessarily used for allocation.
367 Metachunk* VirtualSpaceNode::take_from_committed(size_t chunk_word_size) {
368 // Non-humongous chunks are to be allocated aligned to their chunk
369 // size. So, start addresses of medium chunks are aligned to medium
370 // chunk size, those of small chunks to small chunk size and so
371 // forth. This facilitates merging of free chunks and reduces
372 // fragmentation. Chunk sizes are spec < small < medium, with each
373 // larger chunk size being a multiple of the next smaller chunk
374 // size.
375 // Because of this alignment, me may need to create a number of padding
376 // chunks. These chunks are created and added to the freelist.
377
378 // The chunk manager to which we will give our padding chunks.
379 ChunkManager* const chunk_manager = Metaspace::get_chunk_manager(is_class());
380
381 // shorthands
382 const size_t spec_word_size = chunk_manager->specialized_chunk_word_size();
383 const size_t small_word_size = chunk_manager->small_chunk_word_size();
384 const size_t med_word_size = chunk_manager->medium_chunk_word_size();
385
386 assert(chunk_word_size == spec_word_size || chunk_word_size == small_word_size ||
387 chunk_word_size >= med_word_size, "Invalid chunk size requested.");
388
389 // Chunk alignment (in bytes) == chunk size unless humongous.
390 // Humongous chunks are aligned to the smallest chunk size (spec).
391 const size_t required_chunk_alignment = (chunk_word_size > med_word_size ?
392 spec_word_size : chunk_word_size) * sizeof(MetaWord);
393
394 // Do we have enough space to create the requested chunk plus
395 // any padding chunks needed?
396 MetaWord* const next_aligned =
397 static_cast<MetaWord*>(align_up(top(), required_chunk_alignment));
398 if (!is_available((next_aligned - top()) + chunk_word_size)) {
399 return NULL;
400 }
401
402 // Before allocating the requested chunk, allocate padding chunks if necessary.
403 // We only need to do this for small or medium chunks: specialized chunks are the
404 // smallest size, hence always aligned. Homungous chunks are allocated unaligned
405 // (implicitly, also aligned to smallest chunk size).
406 if ((chunk_word_size == med_word_size || chunk_word_size == small_word_size) && next_aligned > top()) {
407 log_trace(gc, metaspace, freelist)("Creating padding chunks in %s between %p and %p...",
408 (is_class() ? "class space " : "metaspace"),
409 top(), next_aligned);
410 allocate_padding_chunks_until_top_is_at(next_aligned);
411 // Now, top should be aligned correctly.
412 assert_is_aligned(top(), required_chunk_alignment);
413 }
414
415 // Now, top should be aligned correctly.
416 assert_is_aligned(top(), required_chunk_alignment);
417
418 // Bottom of the new chunk
419 MetaWord* chunk_limit = top();
420 assert(chunk_limit != NULL, "Not safe to call this method");
421
422 // The virtual spaces are always expanded by the
423 // commit granularity to enforce the following condition.
424 // Without this the is_available check will not work correctly.
425 assert(_virtual_space.committed_size() == _virtual_space.actual_committed_size(),
426 "The committed memory doesn't match the expanded memory.");
427
428 if (!is_available(chunk_word_size)) {
429 LogTarget(Trace, gc, metaspace, freelist) lt;
430 if (lt.is_enabled()) {
431 LogStream ls(lt);
432 ls.print("VirtualSpaceNode::take_from_committed() not available " SIZE_FORMAT " words ", chunk_word_size);
433 // Dump some information about the virtual space that is nearly full
434 print_on(&ls);
435 }
436 return NULL;
437 }
438
439 // Take the space (bump top on the current virtual space).
440 inc_top(chunk_word_size);
441
442 // Initialize the chunk
443 ChunkIndex chunk_type = get_chunk_type_by_size(chunk_word_size, is_class());
444 Metachunk* result = ::new (chunk_limit) Metachunk(chunk_type, is_class(), chunk_word_size, this);
445 assert(result == (Metachunk*)chunk_limit, "Sanity");
446 occupancy_map()->set_chunk_starts_at_address((MetaWord*)result, true);
447 do_update_in_use_info_for_chunk(result, true);
448
449 inc_container_count();
450
451 #ifdef ASSERT
452 EVERY_NTH(VerifyMetaspaceInterval)
453 chunk_manager->locked_verify(true);
454 verify(true);
455 END_EVERY_NTH
456 do_verify_chunk(result);
457 #endif
458
459 result->inc_use_count();
460
461 return result;
462 }
463
464
465 // Expand the virtual space (commit more of the reserved space)
466 bool VirtualSpaceNode::expand_by(size_t min_words, size_t preferred_words) {
467 size_t min_bytes = min_words * BytesPerWord;
468 size_t preferred_bytes = preferred_words * BytesPerWord;
469
470 size_t uncommitted = virtual_space()->reserved_size() - virtual_space()->actual_committed_size();
471
472 if (uncommitted < min_bytes) {
473 return false;
474 }
475
476 size_t commit = MIN2(preferred_bytes, uncommitted);
477 bool result = virtual_space()->expand_by(commit, false);
478
479 if (result) {
480 log_trace(gc, metaspace, freelist)("Expanded %s virtual space list node by " SIZE_FORMAT " words.",
481 (is_class() ? "class" : "non-class"), commit);
482 DEBUG_ONLY(Atomic::inc(&g_internal_statistics.num_committed_space_expanded));
483 } else {
484 log_trace(gc, metaspace, freelist)("Failed to expand %s virtual space list node by " SIZE_FORMAT " words.",
485 (is_class() ? "class" : "non-class"), commit);
486 }
487
488 assert(result, "Failed to commit memory");
489
490 return result;
491 }
492
493 Metachunk* VirtualSpaceNode::get_chunk_vs(size_t chunk_word_size) {
494 assert_lock_strong(MetaspaceExpand_lock);
495 Metachunk* result = take_from_committed(chunk_word_size);
496 return result;
497 }
498
499 bool VirtualSpaceNode::initialize() {
500
501 if (!_rs.is_reserved()) {
502 return false;
503 }
504
505 // These are necessary restriction to make sure that the virtual space always
506 // grows in steps of Metaspace::commit_alignment(). If both base and size are
507 // aligned only the middle alignment of the VirtualSpace is used.
508 assert_is_aligned(_rs.base(), Metaspace::commit_alignment());
509 assert_is_aligned(_rs.size(), Metaspace::commit_alignment());
510
511 // ReservedSpaces marked as special will have the entire memory
512 // pre-committed. Setting a committed size will make sure that
513 // committed_size and actual_committed_size agrees.
514 size_t pre_committed_size = _rs.special() ? _rs.size() : 0;
515
516 bool result = virtual_space()->initialize_with_granularity(_rs, pre_committed_size,
517 Metaspace::commit_alignment());
518 if (result) {
519 assert(virtual_space()->committed_size() == virtual_space()->actual_committed_size(),
520 "Checking that the pre-committed memory was registered by the VirtualSpace");
521
522 set_top((MetaWord*)virtual_space()->low());
523 }
524
525 // Initialize Occupancy Map.
526 const size_t smallest_chunk_size = is_class() ? ClassSpecializedChunk : SpecializedChunk;
527 _occupancy_map = new OccupancyMap(bottom(), reserved_words(), smallest_chunk_size);
528
529 return result;
530 }
531
532 void VirtualSpaceNode::print_on(outputStream* st, size_t scale) const {
533 size_t used_words = used_words_in_vs();
534 size_t commit_words = committed_words();
535 size_t res_words = reserved_words();
536 VirtualSpace* vs = virtual_space();
537
538 st->print("node @" PTR_FORMAT ": ", p2i(this));
539 st->print("reserved=");
540 print_scaled_words(st, res_words, scale);
541 st->print(", committed=");
542 print_scaled_words_and_percentage(st, commit_words, res_words, scale);
543 st->print(", used=");
544 print_scaled_words_and_percentage(st, used_words, res_words, scale);
545 st->cr();
546 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", "
547 PTR_FORMAT ", " PTR_FORMAT ")",
548 p2i(bottom()), p2i(top()), p2i(end()),
549 p2i(vs->high_boundary()));
550 }
551
552 #ifdef ASSERT
553 void VirtualSpaceNode::mangle() {
554 size_t word_size = capacity_words_in_vs();
555 Copy::fill_to_words((HeapWord*) low(), word_size, 0xf1f1f1f1);
556 }
557 #endif // ASSERT
558
559 void VirtualSpaceNode::retire(ChunkManager* chunk_manager) {
560 assert(is_class() == chunk_manager->is_class(), "Wrong ChunkManager?");
561 #ifdef ASSERT
562 verify(false);
563 EVERY_NTH(VerifyMetaspaceInterval)
564 verify(true);
565 END_EVERY_NTH
566 #endif
567 for (int i = (int)MediumIndex; i >= (int)ZeroIndex; --i) {
568 ChunkIndex index = (ChunkIndex)i;
569 size_t chunk_size = chunk_manager->size_by_index(index);
570
571 while (free_words_in_vs() >= chunk_size) {
572 Metachunk* chunk = get_chunk_vs(chunk_size);
573 // Chunk will be allocated aligned, so allocation may require
574 // additional padding chunks. That may cause above allocation to
575 // fail. Just ignore the failed allocation and continue with the
576 // next smaller chunk size. As the VirtualSpaceNode comitted
577 // size should be a multiple of the smallest chunk size, we
578 // should always be able to fill the VirtualSpace completely.
579 if (chunk == NULL) {
580 break;
581 }
582 chunk_manager->return_single_chunk(chunk);
583 }
584 }
585 assert(free_words_in_vs() == 0, "should be empty now");
586 }
587
588 } // namespace metaspace