1 /*
2 * Copyright (c) 2011, 2025, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2017, 2021 SAP SE. All rights reserved.
4 * Copyright (c) 2023, 2025, Red Hat, Inc. All rights reserved.
5 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
6 *
7 * This code is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License version 2 only, as
9 * published by the Free Software Foundation.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 *
25 */
26
27 #include "cds/cdsConfig.hpp"
28 #include "cds/metaspaceShared.hpp"
29 #include "classfile/classLoaderData.hpp"
30 #include "gc/shared/collectedHeap.hpp"
31 #include "logging/log.hpp"
32 #include "logging/logStream.hpp"
33 #include "memory/classLoaderMetaspace.hpp"
34 #include "memory/memoryReserver.hpp"
35 #include "memory/metaspace.hpp"
36 #include "memory/metaspace/chunkHeaderPool.hpp"
37 #include "memory/metaspace/chunkManager.hpp"
38 #include "memory/metaspace/commitLimiter.hpp"
39 #include "memory/metaspace/internalStats.hpp"
40 #include "memory/metaspace/metachunk.hpp"
41 #include "memory/metaspace/metaspaceCommon.hpp"
42 #include "memory/metaspace/metaspaceContext.hpp"
43 #include "memory/metaspace/metaspaceReporter.hpp"
44 #include "memory/metaspace/metaspaceSettings.hpp"
45 #include "memory/metaspace/runningCounters.hpp"
46 #include "memory/metaspace/virtualSpaceList.hpp"
47 #include "memory/metaspaceCriticalAllocation.hpp"
48 #include "memory/metaspaceStats.hpp"
49 #include "memory/metaspaceTracer.hpp"
50 #include "memory/metaspaceUtils.hpp"
51 #include "memory/resourceArea.hpp"
52 #include "memory/universe.hpp"
53 #include "nmt/memTracker.hpp"
54 #include "oops/compressedKlass.inline.hpp"
55 #include "oops/compressedOops.hpp"
56 #include "prims/jvmtiExport.hpp"
57 #include "runtime/atomic.hpp"
58 #include "runtime/globals_extension.hpp"
59 #include "runtime/init.hpp"
60 #include "runtime/java.hpp"
61 #include "runtime/mutexLocker.hpp"
62 #include "utilities/copy.hpp"
63 #include "utilities/debug.hpp"
64 #include "utilities/formatBuffer.hpp"
65 #include "utilities/globalDefinitions.hpp"
66
67 using metaspace::ChunkManager;
68 using metaspace::CommitLimiter;
69 using metaspace::MetaspaceContext;
70 using metaspace::MetaspaceReporter;
71 using metaspace::RunningCounters;
72 using metaspace::VirtualSpaceList;
73
74 size_t MetaspaceUtils::used_words() {
75 return RunningCounters::used_words();
76 }
77
78 size_t MetaspaceUtils::used_words(Metaspace::MetadataType mdtype) {
79 return mdtype == Metaspace::ClassType ? RunningCounters::used_words_class() : RunningCounters::used_words_nonclass();
80 }
81
82 size_t MetaspaceUtils::reserved_words() {
83 return RunningCounters::reserved_words();
84 }
85
86 size_t MetaspaceUtils::reserved_words(Metaspace::MetadataType mdtype) {
87 return mdtype == Metaspace::ClassType ? RunningCounters::reserved_words_class() : RunningCounters::reserved_words_nonclass();
88 }
89
90 size_t MetaspaceUtils::committed_words() {
91 return RunningCounters::committed_words();
92 }
93
94 size_t MetaspaceUtils::committed_words(Metaspace::MetadataType mdtype) {
95 return mdtype == Metaspace::ClassType ? RunningCounters::committed_words_class() : RunningCounters::committed_words_nonclass();
96 }
97
98 // Helper for get_statistics()
99 static void get_values_for(Metaspace::MetadataType mdtype, size_t* reserved, size_t* committed, size_t* used) {
100 #define w2b(x) (x * sizeof(MetaWord))
101 if (mdtype == Metaspace::ClassType) {
102 *reserved = w2b(RunningCounters::reserved_words_class());
103 *committed = w2b(RunningCounters::committed_words_class());
104 *used = w2b(RunningCounters::used_words_class());
105 } else {
106 *reserved = w2b(RunningCounters::reserved_words_nonclass());
107 *committed = w2b(RunningCounters::committed_words_nonclass());
108 *used = w2b(RunningCounters::used_words_nonclass());
109 }
110 #undef w2b
111 }
112
113 // Retrieve all statistics in one go; make sure the values are consistent.
114 MetaspaceStats MetaspaceUtils::get_statistics(Metaspace::MetadataType mdtype) {
115
116 // Consistency:
117 // This function reads three values (reserved, committed, used) from different counters. These counters
118 // may (very rarely) be out of sync. This has been a source for intermittent test errors in the past
119 // (see e.g. JDK-8237872, JDK-8151460).
120 // - reserved and committed counter are updated under protection of Metaspace_lock; an inconsistency
121 // between them can be the result of a dirty read.
122 // - used is an atomic counter updated outside any lock range; there is no way to guarantee
123 // a clean read wrt the other two values.
124 // Reading these values under lock protection would would only help for the first case. Therefore
125 // we don't bother and just re-read several times, then give up and correct the values.
126
127 size_t r = 0, c = 0, u = 0; // Note: byte values.
128 get_values_for(mdtype, &r, &c, &u);
129 int retries = 10;
130 // If the first retrieval resulted in inconsistent values, retry a bit...
131 while ((r < c || c < u) && --retries >= 0) {
132 get_values_for(mdtype, &r, &c, &u);
133 }
134 if (c < u || r < c) { // still inconsistent.
135 // ... but not endlessly. If we don't get consistent values, correct them on the fly.
136 // The logic here is that we trust the used counter - its an atomic counter and whatever we see
137 // must have been the truth once - and from that we reconstruct a likely set of committed/reserved
138 // values.
139 metaspace::InternalStats::inc_num_inconsistent_stats();
140 if (c < u) {
141 c = align_up(u, Metaspace::commit_alignment());
142 }
143 if (r < c) {
144 r = align_up(c, Metaspace::reserve_alignment());
145 }
146 }
147 return MetaspaceStats(r, c, u);
148 }
149
150 MetaspaceCombinedStats MetaspaceUtils::get_combined_statistics() {
151 return MetaspaceCombinedStats(get_statistics(Metaspace::ClassType), get_statistics(Metaspace::NonClassType));
152 }
153
154 void MetaspaceUtils::print_metaspace_change(const MetaspaceCombinedStats& pre_meta_values) {
155 // Get values now:
156 const MetaspaceCombinedStats meta_values = get_combined_statistics();
157
158 // We print used and committed since these are the most useful at-a-glance vitals for Metaspace:
159 // - used tells you how much memory is actually used for metadata
160 // - committed tells you how much memory is committed for the purpose of metadata
161 // The difference between those two would be waste, which can have various forms (freelists,
162 // unused parts of committed chunks etc)
163 //
164 // Left out is reserved, since this is not as exciting as the first two values: for class space,
165 // it is a constant (to uninformed users, often confusingly large). For non-class space, it would
166 // be interesting since free chunks can be uncommitted, but for now it is left out.
167
168 if (Metaspace::using_class_space()) {
169 log_info(gc, metaspace)(HEAP_CHANGE_FORMAT" "
170 HEAP_CHANGE_FORMAT" "
171 HEAP_CHANGE_FORMAT,
172 HEAP_CHANGE_FORMAT_ARGS("Metaspace",
173 pre_meta_values.used(),
174 pre_meta_values.committed(),
175 meta_values.used(),
176 meta_values.committed()),
177 HEAP_CHANGE_FORMAT_ARGS("NonClass",
178 pre_meta_values.non_class_used(),
179 pre_meta_values.non_class_committed(),
180 meta_values.non_class_used(),
181 meta_values.non_class_committed()),
182 HEAP_CHANGE_FORMAT_ARGS("Class",
183 pre_meta_values.class_used(),
184 pre_meta_values.class_committed(),
185 meta_values.class_used(),
186 meta_values.class_committed()));
187 } else {
188 log_info(gc, metaspace)(HEAP_CHANGE_FORMAT,
189 HEAP_CHANGE_FORMAT_ARGS("Metaspace",
190 pre_meta_values.used(),
191 pre_meta_values.committed(),
192 meta_values.used(),
193 meta_values.committed()));
194 }
195 }
196
197 // This will print out a basic metaspace usage report but
198 // unlike print_report() is guaranteed not to lock or to walk the CLDG.
199 void MetaspaceUtils::print_basic_report(outputStream* out, size_t scale) {
200 MetaspaceReporter::print_basic_report(out, scale);
201 }
202
203 // Prints a report about the current metaspace state.
204 // Optional parts can be enabled via flags.
205 // Function will walk the CLDG and will lock the expand lock; if that is not
206 // convenient, use print_basic_report() instead.
207 void MetaspaceUtils::print_report(outputStream* out, size_t scale) {
208 const int flags =
209 (int)MetaspaceReporter::Option::ShowLoaders |
210 (int)MetaspaceReporter::Option::BreakDownByChunkType |
211 (int)MetaspaceReporter::Option::ShowClasses;
212 MetaspaceReporter::print_report(out, scale, flags);
213 }
214
215 void MetaspaceUtils::print_on(outputStream* out) {
216
217 // Used from all GCs. It first prints out totals, then, separately, the class space portion.
218 MetaspaceCombinedStats stats = get_combined_statistics();
219 out->print_cr(" Metaspace "
220 "used %zuK, "
221 "committed %zuK, "
222 "reserved %zuK",
223 stats.used()/K,
224 stats.committed()/K,
225 stats.reserved()/K);
226
227 if (Metaspace::using_class_space()) {
228 out->print_cr(" class space "
229 "used %zuK, "
230 "committed %zuK, "
231 "reserved %zuK",
232 stats.class_space_stats().used()/K,
233 stats.class_space_stats().committed()/K,
234 stats.class_space_stats().reserved()/K);
235 }
236 }
237
238 #ifdef ASSERT
239 void MetaspaceUtils::verify() {
240 if (Metaspace::initialized()) {
241
242 // Verify non-class chunkmanager...
243 ChunkManager* cm = ChunkManager::chunkmanager_nonclass();
244 cm->verify();
245
246 // ... and space list.
247 VirtualSpaceList* vsl = VirtualSpaceList::vslist_nonclass();
248 vsl->verify();
249
250 if (Metaspace::using_class_space()) {
251 // If we use compressed class pointers, verify class chunkmanager...
252 cm = ChunkManager::chunkmanager_class();
253 cm->verify();
254
255 // ... and class spacelist.
256 vsl = VirtualSpaceList::vslist_class();
257 vsl->verify();
258 }
259
260 }
261 }
262 #endif
263
264 ////////////////////////////////7
265 // MetaspaceGC methods
266
267 volatile size_t MetaspaceGC::_capacity_until_GC = 0;
268 uint MetaspaceGC::_shrink_factor = 0;
269
270 // VM_CollectForMetadataAllocation is the vm operation used to GC.
271 // Within the VM operation after the GC the attempt to allocate the metadata
272 // should succeed. If the GC did not free enough space for the metaspace
273 // allocation, the HWM is increased so that another virtualspace will be
274 // allocated for the metadata. With perm gen the increase in the perm
275 // gen had bounds, MinMetaspaceExpansion and MaxMetaspaceExpansion. The
276 // metaspace policy uses those as the small and large steps for the HWM.
277 //
278 // After the GC the compute_new_size() for MetaspaceGC is called to
279 // resize the capacity of the metaspaces. The current implementation
280 // is based on the flags MinMetaspaceFreeRatio and MaxMetaspaceFreeRatio used
281 // to resize the Java heap by some GC's. New flags can be implemented
282 // if really needed. MinMetaspaceFreeRatio is used to calculate how much
283 // free space is desirable in the metaspace capacity to decide how much
284 // to increase the HWM. MaxMetaspaceFreeRatio is used to decide how much
285 // free space is desirable in the metaspace capacity before decreasing
286 // the HWM.
287
288 // Calculate the amount to increase the high water mark (HWM).
289 // Increase by a minimum amount (MinMetaspaceExpansion) so that
290 // another expansion is not requested too soon. If that is not
291 // enough to satisfy the allocation, increase by MaxMetaspaceExpansion.
292 // If that is still not enough, expand by the size of the allocation
293 // plus some.
294 size_t MetaspaceGC::delta_capacity_until_GC(size_t bytes) {
295 size_t min_delta = MinMetaspaceExpansion;
296 size_t max_delta = MaxMetaspaceExpansion;
297 size_t delta = align_up(bytes, Metaspace::commit_alignment());
298
299 if (delta <= min_delta) {
300 delta = min_delta;
301 } else if (delta <= max_delta) {
302 // Don't want to hit the high water mark on the next
303 // allocation so make the delta greater than just enough
304 // for this allocation.
305 delta = max_delta;
306 } else {
307 // This allocation is large but the next ones are probably not
308 // so increase by the minimum.
309 delta = delta + min_delta;
310 }
311
312 assert_is_aligned(delta, Metaspace::commit_alignment());
313
314 return delta;
315 }
316
317 size_t MetaspaceGC::capacity_until_GC() {
318 size_t value = Atomic::load_acquire(&_capacity_until_GC);
319 assert(value >= MetaspaceSize, "Not initialized properly?");
320 return value;
321 }
322
323 // Try to increase the _capacity_until_GC limit counter by v bytes.
324 // Returns true if it succeeded. It may fail if either another thread
325 // concurrently increased the limit or the new limit would be larger
326 // than MaxMetaspaceSize.
327 // On success, optionally returns new and old metaspace capacity in
328 // new_cap_until_GC and old_cap_until_GC respectively.
329 // On error, optionally sets can_retry to indicate whether if there is
330 // actually enough space remaining to satisfy the request.
331 bool MetaspaceGC::inc_capacity_until_GC(size_t v, size_t* new_cap_until_GC, size_t* old_cap_until_GC, bool* can_retry) {
332 assert_is_aligned(v, Metaspace::commit_alignment());
333
334 size_t old_capacity_until_GC = _capacity_until_GC;
335 size_t new_value = old_capacity_until_GC + v;
336
337 if (new_value < old_capacity_until_GC) {
338 // The addition wrapped around, set new_value to aligned max value.
339 new_value = align_down(max_uintx, Metaspace::reserve_alignment());
340 }
341
342 if (new_value > MaxMetaspaceSize) {
343 if (can_retry != nullptr) {
344 *can_retry = false;
345 }
346 return false;
347 }
348
349 if (can_retry != nullptr) {
350 *can_retry = true;
351 }
352 size_t prev_value = Atomic::cmpxchg(&_capacity_until_GC, old_capacity_until_GC, new_value);
353
354 if (old_capacity_until_GC != prev_value) {
355 return false;
356 }
357
358 if (new_cap_until_GC != nullptr) {
359 *new_cap_until_GC = new_value;
360 }
361 if (old_cap_until_GC != nullptr) {
362 *old_cap_until_GC = old_capacity_until_GC;
363 }
364 return true;
365 }
366
367 size_t MetaspaceGC::dec_capacity_until_GC(size_t v) {
368 assert_is_aligned(v, Metaspace::commit_alignment());
369
370 return Atomic::sub(&_capacity_until_GC, v);
371 }
372
373 void MetaspaceGC::initialize() {
374 // Set the high-water mark to MaxMetapaceSize during VM initializaton since
375 // we can't do a GC during initialization.
376 _capacity_until_GC = MaxMetaspaceSize;
377 }
378
379 void MetaspaceGC::post_initialize() {
380 // Reset the high-water mark once the VM initialization is done.
381 _capacity_until_GC = MAX2(MetaspaceUtils::committed_bytes(), MetaspaceSize);
382 }
383
384 bool MetaspaceGC::can_expand(size_t word_size, bool is_class) {
385 // Check if the compressed class space is full.
386 if (is_class && Metaspace::using_class_space()) {
387 size_t class_committed = MetaspaceUtils::committed_bytes(Metaspace::ClassType);
388 if (class_committed + word_size * BytesPerWord > CompressedClassSpaceSize) {
389 log_trace(gc, metaspace, freelist)("Cannot expand %s metaspace by %zu words (CompressedClassSpaceSize = %zu words)",
390 (is_class ? "class" : "non-class"), word_size, CompressedClassSpaceSize / sizeof(MetaWord));
391 return false;
392 }
393 }
394
395 // Check if the user has imposed a limit on the metaspace memory.
396 size_t committed_bytes = MetaspaceUtils::committed_bytes();
397 if (committed_bytes + word_size * BytesPerWord > MaxMetaspaceSize) {
398 log_trace(gc, metaspace, freelist)("Cannot expand %s metaspace by %zu words (MaxMetaspaceSize = %zu words)",
399 (is_class ? "class" : "non-class"), word_size, MaxMetaspaceSize / sizeof(MetaWord));
400 return false;
401 }
402
403 return true;
404 }
405
406 size_t MetaspaceGC::allowed_expansion() {
407 size_t committed_bytes = MetaspaceUtils::committed_bytes();
408 size_t capacity_until_gc = capacity_until_GC();
409
410 size_t left_until_max = MaxMetaspaceSize - committed_bytes;
411 // capacity_until_GC may have been decreased concurrently and may
412 // temporarily be lower than what metaspace has committed. Allow for that.
413 size_t left_until_GC = capacity_until_gc > committed_bytes ?
414 capacity_until_gc - committed_bytes : 0;
415 size_t left_to_commit = MIN2(left_until_GC, left_until_max);
416 log_trace(gc, metaspace, freelist)("allowed expansion words: %zu"
417 " (left_until_max: %zu, left_until_GC: %zu.",
418 left_to_commit / BytesPerWord, left_until_max / BytesPerWord, left_until_GC / BytesPerWord);
419
420 return left_to_commit / BytesPerWord;
421 }
422
423 void MetaspaceGC::compute_new_size() {
424 assert(_shrink_factor <= 100, "invalid shrink factor");
425 uint current_shrink_factor = _shrink_factor;
426 _shrink_factor = 0;
427
428 // Using committed_bytes() for used_after_gc is an overestimation, since the
429 // chunk free lists are included in committed_bytes() and the memory in an
430 // un-fragmented chunk free list is available for future allocations.
431 // However, if the chunk free lists becomes fragmented, then the memory may
432 // not be available for future allocations and the memory is therefore "in use".
433 // Including the chunk free lists in the definition of "in use" is therefore
434 // necessary. Not including the chunk free lists can cause capacity_until_GC to
435 // shrink below committed_bytes() and this has caused serious bugs in the past.
436 const double used_after_gc = (double)MetaspaceUtils::committed_bytes();
437 const size_t capacity_until_GC = MetaspaceGC::capacity_until_GC();
438
439 const double minimum_free_percentage = MinMetaspaceFreeRatio / 100.0;
440 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
441
442 const double min_tmp = used_after_gc / maximum_used_percentage;
443 size_t minimum_desired_capacity =
444 (size_t)MIN2(min_tmp, double(MaxMetaspaceSize));
445 // Don't shrink less than the initial generation size
446 minimum_desired_capacity = MAX2(minimum_desired_capacity,
447 MetaspaceSize);
448
449 log_trace(gc, metaspace)("MetaspaceGC::compute_new_size: ");
450 log_trace(gc, metaspace)(" minimum_free_percentage: %6.2f maximum_used_percentage: %6.2f",
451 minimum_free_percentage, maximum_used_percentage);
452 log_trace(gc, metaspace)(" used_after_gc : %6.1fKB", used_after_gc / (double) K);
453
454 size_t shrink_bytes = 0;
455 if (capacity_until_GC < minimum_desired_capacity) {
456 // If we have less capacity below the metaspace HWM, then
457 // increment the HWM.
458 size_t expand_bytes = minimum_desired_capacity - capacity_until_GC;
459 expand_bytes = align_up(expand_bytes, Metaspace::commit_alignment());
460 // Don't expand unless it's significant
461 if (expand_bytes >= MinMetaspaceExpansion) {
462 size_t new_capacity_until_GC = 0;
463 bool succeeded = MetaspaceGC::inc_capacity_until_GC(expand_bytes, &new_capacity_until_GC);
464 assert(succeeded, "Should always successfully increment HWM when at safepoint");
465
466 Metaspace::tracer()->report_gc_threshold(capacity_until_GC,
467 new_capacity_until_GC,
468 MetaspaceGCThresholdUpdater::ComputeNewSize);
469 log_trace(gc, metaspace)(" expanding: minimum_desired_capacity: %6.1fKB expand_bytes: %6.1fKB MinMetaspaceExpansion: %6.1fKB new metaspace HWM: %6.1fKB",
470 (double) minimum_desired_capacity / (double) K,
471 (double) expand_bytes / (double) K,
472 (double) MinMetaspaceExpansion / (double) K,
473 (double) new_capacity_until_GC / (double) K);
474 }
475 return;
476 }
477
478 // No expansion, now see if we want to shrink
479 // We would never want to shrink more than this
480 assert(capacity_until_GC >= minimum_desired_capacity,
481 "%zu >= %zu",
482 capacity_until_GC, minimum_desired_capacity);
483 size_t max_shrink_bytes = capacity_until_GC - minimum_desired_capacity;
484
485 // Should shrinking be considered?
486 if (MaxMetaspaceFreeRatio < 100) {
487 const double maximum_free_percentage = MaxMetaspaceFreeRatio / 100.0;
488 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
489 const double max_tmp = used_after_gc / minimum_used_percentage;
490 size_t maximum_desired_capacity = (size_t)MIN2(max_tmp, double(MaxMetaspaceSize));
491 maximum_desired_capacity = MAX2(maximum_desired_capacity,
492 MetaspaceSize);
493 log_trace(gc, metaspace)(" maximum_free_percentage: %6.2f minimum_used_percentage: %6.2f",
494 maximum_free_percentage, minimum_used_percentage);
495 log_trace(gc, metaspace)(" minimum_desired_capacity: %6.1fKB maximum_desired_capacity: %6.1fKB",
496 (double) minimum_desired_capacity / (double) K, (double) maximum_desired_capacity / (double) K);
497
498 assert(minimum_desired_capacity <= maximum_desired_capacity,
499 "sanity check");
500
501 if (capacity_until_GC > maximum_desired_capacity) {
502 // Capacity too large, compute shrinking size
503 shrink_bytes = capacity_until_GC - maximum_desired_capacity;
504 // We don't want shrink all the way back to initSize if people call
505 // System.gc(), because some programs do that between "phases" and then
506 // we'd just have to grow the heap up again for the next phase. So we
507 // damp the shrinking: 0% on the first call, 10% on the second call, 40%
508 // on the third call, and 100% by the fourth call. But if we recompute
509 // size without shrinking, it goes back to 0%.
510 shrink_bytes = shrink_bytes / 100 * current_shrink_factor;
511
512 shrink_bytes = align_down(shrink_bytes, Metaspace::commit_alignment());
513
514 assert(shrink_bytes <= max_shrink_bytes,
515 "invalid shrink size %zu not <= %zu",
516 shrink_bytes, max_shrink_bytes);
517 if (current_shrink_factor == 0) {
518 _shrink_factor = 10;
519 } else {
520 _shrink_factor = MIN2(current_shrink_factor * 4, (uint) 100);
521 }
522 log_trace(gc, metaspace)(" shrinking: initThreshold: %.1fK maximum_desired_capacity: %.1fK",
523 (double) MetaspaceSize / (double) K, (double) maximum_desired_capacity / (double) K);
524 log_trace(gc, metaspace)(" shrink_bytes: %.1fK current_shrink_factor: %d new shrink factor: %d MinMetaspaceExpansion: %.1fK",
525 (double) shrink_bytes / (double) K, current_shrink_factor, _shrink_factor, (double) MinMetaspaceExpansion / (double) K);
526 }
527 }
528
529 // Don't shrink unless it's significant
530 if (shrink_bytes >= MinMetaspaceExpansion &&
531 ((capacity_until_GC - shrink_bytes) >= MetaspaceSize)) {
532 size_t new_capacity_until_GC = MetaspaceGC::dec_capacity_until_GC(shrink_bytes);
533 Metaspace::tracer()->report_gc_threshold(capacity_until_GC,
534 new_capacity_until_GC,
535 MetaspaceGCThresholdUpdater::ComputeNewSize);
536 }
537 }
538
539 ////// Metaspace methods /////
540
541 const MetaspaceTracer* Metaspace::_tracer = nullptr;
542 const void* Metaspace::_class_space_start = nullptr;
543 const void* Metaspace::_class_space_end = nullptr;
544
545 bool Metaspace::initialized() {
546 return metaspace::MetaspaceContext::context_nonclass() != nullptr
547 LP64_ONLY(&& (using_class_space() ? Metaspace::class_space_is_initialized() : true));
548 }
549
550 #ifdef _LP64
551
552 void Metaspace::print_compressed_class_space(outputStream* st) {
553 if (VirtualSpaceList::vslist_class() != nullptr) {
554 MetaWord* base = VirtualSpaceList::vslist_class()->base_of_first_node();
555 size_t size = VirtualSpaceList::vslist_class()->word_size_of_first_node();
556 MetaWord* top = base + size;
557 st->print("Compressed class space mapped at: " PTR_FORMAT "-" PTR_FORMAT ", reserved size: %zu",
558 p2i(base), p2i(top), (top - base) * BytesPerWord);
559 st->cr();
560 }
561 }
562
563 // Given a prereserved space, use that to set up the compressed class space list.
564 void Metaspace::initialize_class_space(ReservedSpace rs) {
565 assert(rs.size() >= CompressedClassSpaceSize,
566 "%zu != %zu", rs.size(), CompressedClassSpaceSize);
567 assert(using_class_space(), "Must be using class space");
568
569 assert(rs.size() == CompressedClassSpaceSize, "%zu != %zu",
570 rs.size(), CompressedClassSpaceSize);
571 assert(is_aligned(rs.base(), Metaspace::reserve_alignment()) &&
572 is_aligned(rs.size(), Metaspace::reserve_alignment()),
573 "wrong alignment");
574
575 MetaspaceContext::initialize_class_space_context(rs);
576 _class_space_start = rs.base();
577 _class_space_end = rs.end();
578 }
579
580 // Returns true if class space has been setup (initialize_class_space).
581 bool Metaspace::class_space_is_initialized() {
582 return MetaspaceContext::context_class() != nullptr;
583 }
584
585 // Reserve a range of memory that is to contain narrow Klass IDs. If "try_in_low_address_ranges"
586 // is true, we will attempt to reserve memory suitable for zero-based encoding.
587 ReservedSpace Metaspace::reserve_address_space_for_compressed_classes(size_t size, bool optimize_for_zero_base) {
588 char* result = nullptr;
589
590 NOT_ZERO(result =
591 (char*) CompressedKlassPointers::reserve_address_space_for_compressed_classes(size, RandomizeClassSpaceLocation,
592 optimize_for_zero_base));
593
594 if (result == nullptr) {
595 // Fallback: reserve anywhere
596 log_debug(metaspace, map)("Trying anywhere...");
597 result = os::reserve_memory_aligned(size, Metaspace::reserve_alignment(), false);
598 }
599
600 // Wrap resulting range in ReservedSpace
601 if (result != nullptr) {
602 log_debug(metaspace, map)("Mapped at " PTR_FORMAT, p2i(result));
603 assert(is_aligned(result, Metaspace::reserve_alignment()), "Alignment too small for metaspace");
604
605 return ReservedSpace(result,
606 size,
607 Metaspace::reserve_alignment(),
608 os::vm_page_size(),
609 !ExecMem,
610 false /* special */);
611 } else {
612 log_debug(metaspace, map)("Failed to map.");
613 return {};
614 }
615 }
616 #endif // _LP64
617
618 size_t Metaspace::reserve_alignment_words() {
619 return metaspace::Settings::virtual_space_node_reserve_alignment_words();
620 }
621
622 size_t Metaspace::commit_alignment_words() {
623 return metaspace::Settings::commit_granule_words();
624 }
625
626 void Metaspace::ergo_initialize() {
627
628 // Must happen before using any setting from Settings::---
629 metaspace::Settings::ergo_initialize();
630
631 // MaxMetaspaceSize and CompressedClassSpaceSize:
632 //
633 // MaxMetaspaceSize is the maximum size, in bytes, of memory we are allowed
634 // to commit for the Metaspace.
635 // It is just a number; a limit we compare against before committing. It
636 // does not have to be aligned to anything.
637 // It gets used as compare value before attempting to increase the metaspace
638 // commit charge. It defaults to max_uintx (unlimited).
639 //
640 // CompressedClassSpaceSize is the size, in bytes, of the address range we
641 // pre-reserve for the compressed class space (if we use class space).
642 // This size has to be aligned to the metaspace reserve alignment (to the
643 // size of a root chunk). It gets aligned up from whatever value the caller
644 // gave us to the next multiple of root chunk size.
645 //
646 // Note: Strictly speaking MaxMetaspaceSize and CompressedClassSpaceSize have
647 // very little to do with each other. The notion often encountered:
648 // MaxMetaspaceSize = CompressedClassSpaceSize + <non-class metadata size>
649 // is subtly wrong: MaxMetaspaceSize can besmaller than CompressedClassSpaceSize,
650 // in which case we just would not be able to fully commit the class space range.
651 //
652 // We still adjust CompressedClassSpaceSize to reasonable limits, mainly to
653 // save on reserved space, and to make ergnonomics less confusing.
654
655 MaxMetaspaceSize = MAX2(MaxMetaspaceSize, commit_alignment());
656
657 if (UseCompressedClassPointers) {
658 // Let Class Space not be larger than 80% of MaxMetaspaceSize. Note that is
659 // grossly over-dimensioned for most usage scenarios; typical ratio of
660 // class space : non class space usage is about 1:6. With many small classes,
661 // it can get as low as 1:2. It is not a big deal though since ccs is only
662 // reserved and will be committed on demand only.
663 const size_t max_ccs_size = 8 * (MaxMetaspaceSize / 10);
664
665 // Sanity check.
666 const size_t max_klass_range = CompressedKlassPointers::max_klass_range_size();
667 assert(max_klass_range >= reserve_alignment(),
668 "Klass range (%zu) must cover at least a full root chunk (%zu)",
669 max_klass_range, reserve_alignment());
670
671 size_t adjusted_ccs_size = MIN3(CompressedClassSpaceSize, max_ccs_size, max_klass_range);
672
673 // CCS must be aligned to root chunk size, and be at least the size of one
674 // root chunk.
675 adjusted_ccs_size = align_up(adjusted_ccs_size, reserve_alignment());
676 adjusted_ccs_size = MAX2(adjusted_ccs_size, reserve_alignment());
677
678 // Print a warning if the adjusted size differs from the users input
679 if (CompressedClassSpaceSize != adjusted_ccs_size) {
680 #define X "CompressedClassSpaceSize adjusted from user input " \
681 "%zu bytes to %zu bytes", CompressedClassSpaceSize, adjusted_ccs_size
682 if (FLAG_IS_CMDLINE(CompressedClassSpaceSize)) {
683 log_warning(metaspace)(X);
684 } else {
685 log_info(metaspace)(X);
686 }
687 #undef X
688 }
689
690 // Note: re-adjusting may have us left with a CompressedClassSpaceSize
691 // larger than MaxMetaspaceSize for very small values of MaxMetaspaceSize.
692 // Lets just live with that, its not a big deal.
693 if (adjusted_ccs_size != CompressedClassSpaceSize) {
694 FLAG_SET_ERGO(CompressedClassSpaceSize, adjusted_ccs_size);
695 log_info(metaspace)("Setting CompressedClassSpaceSize to %zu.",
696 CompressedClassSpaceSize);
697 }
698 }
699
700 // Set MetaspaceSize, MinMetaspaceExpansion and MaxMetaspaceExpansion
701 if (MetaspaceSize > MaxMetaspaceSize) {
702 MetaspaceSize = MaxMetaspaceSize;
703 }
704
705 MetaspaceSize = align_down_bounded(MetaspaceSize, commit_alignment());
706
707 assert(MetaspaceSize <= MaxMetaspaceSize, "MetaspaceSize should be limited by MaxMetaspaceSize");
708
709 MinMetaspaceExpansion = align_down_bounded(MinMetaspaceExpansion, commit_alignment());
710 MaxMetaspaceExpansion = align_down_bounded(MaxMetaspaceExpansion, commit_alignment());
711
712 }
713
714 void Metaspace::global_initialize() {
715 MetaspaceGC::initialize(); // <- since we do not prealloc init chunks anymore is this still needed?
716
717 metaspace::ChunkHeaderPool::initialize();
718
719 if (CDSConfig::is_dumping_static_archive()) {
720 MetaspaceShared::initialize_for_static_dump();
721 }
722
723 // If UseCompressedClassPointers=1, we have two cases:
724 // a) if CDS is active (runtime, Xshare=on), it will create the class space
725 // for us, initialize it and set up CompressedKlassPointers encoding.
726 // Class space will be reserved above the mapped archives.
727 // b) if CDS either deactivated (Xshare=off) or a static dump is to be done (Xshare:dump),
728 // we will create the class space on our own. It will be placed above the java heap,
729 // since we assume it has been placed in low
730 // address regions. We may rethink this (see JDK-8244943). Failing that,
731 // it will be placed anywhere.
732
733 #if INCLUDE_CDS
734 // case (a)
735 if (CDSConfig::is_using_archive()) {
736 if (!FLAG_IS_DEFAULT(CompressedClassSpaceBaseAddress)) {
737 log_warning(metaspace)("CDS active - ignoring CompressedClassSpaceBaseAddress.");
738 }
739 MetaspaceShared::initialize_runtime_shared_and_meta_spaces();
740 // If any of the archived space fails to map, UseSharedSpaces
741 // is reset to false.
742 }
743 #endif // INCLUDE_CDS
744
745 #ifdef _LP64
746
747 if (using_class_space() && !class_space_is_initialized()) {
748 assert(!CDSConfig::is_using_archive(), "CDS archive is not mapped at this point");
749
750 // case (b) (No CDS)
751 ReservedSpace rs;
752 const size_t size = align_up(CompressedClassSpaceSize, Metaspace::reserve_alignment());
753
754 // If CompressedClassSpaceBaseAddress is set, we attempt to force-map class space to
755 // the given address. This is a debug-only feature aiding tests. Due to the ASLR lottery
756 // this may fail, in which case the VM will exit after printing an appropriate message.
757 // Tests using this switch should cope with that.
758 if (CompressedClassSpaceBaseAddress != 0) {
759 const address base = (address)CompressedClassSpaceBaseAddress;
760 if (!is_aligned(base, Metaspace::reserve_alignment())) {
761 vm_exit_during_initialization(
762 err_msg("CompressedClassSpaceBaseAddress=" PTR_FORMAT " invalid "
763 "(must be aligned to 0x%zx).",
764 CompressedClassSpaceBaseAddress, Metaspace::reserve_alignment()));
765 }
766
767 rs = MemoryReserver::reserve((char*)base,
768 size,
769 Metaspace::reserve_alignment(),
770 os::vm_page_size());
771
772 if (rs.is_reserved()) {
773 log_info(metaspace)("Successfully forced class space address to " PTR_FORMAT, p2i(base));
774 } else {
775 LogTarget(Debug, metaspace) lt;
776 if (lt.is_enabled()) {
777 LogStream ls(lt);
778 os::print_memory_mappings((char*)base, size, &ls);
779 }
780 vm_exit_during_initialization(
781 err_msg("CompressedClassSpaceBaseAddress=" PTR_FORMAT " given, but reserving class space failed.",
782 CompressedClassSpaceBaseAddress));
783 }
784 }
785
786 // ...failing that, reserve anywhere, but let platform do optimized placement:
787 if (!rs.is_reserved()) {
788 log_info(metaspace)("Reserving compressed class space anywhere");
789 rs = Metaspace::reserve_address_space_for_compressed_classes(size, true);
790 }
791
792 // ...failing that, give up.
793 if (!rs.is_reserved()) {
794 vm_exit_during_initialization(
795 err_msg("Could not allocate compressed class space: %zu bytes",
796 CompressedClassSpaceSize));
797 }
798
799 // Mark class space as such
800 MemTracker::record_virtual_memory_tag(rs, mtClass);
801
802 // Initialize space
803 Metaspace::initialize_class_space(rs);
804
805 // Set up compressed class pointer encoding.
806 // In CDS=off mode, we give the JVM some leeway to choose a favorable base/shift combination.
807 CompressedKlassPointers::initialize((address)rs.base(), rs.size());
808
809 // After narrowKlass encoding scheme is decided: if the encoding base points to class space start,
810 // establish a protection zone. Accidentally decoding a zero nKlass ID and then using it will result
811 // in an immediate segmentation fault instead of a delayed error much later.
812 if (CompressedKlassPointers::base() == (address)rs.base()) {
813 // Let the protection zone be a whole commit granule. Otherwise, buddy allocator may later place neighboring
814 // chunks in the same granule, see that the granule is not yet committed, and commit it, which would replace
815 // the protection mapping and make the zone readable.
816 // Alternatively, we could commit the chunk right now, but that is a tiny bit more fiddly, since we are not
817 // fully set up yet at this point.
818 const size_t protzone_size = metaspace::Settings::commit_granule_bytes(); // granule size >= page size
819 const size_t protzone_wordsize = protzone_size / BytesPerWord;
820 const metaspace::chunklevel_t lvl = metaspace::chunklevel::level_fitting_word_size(protzone_wordsize);
821 metaspace::Metachunk* const chunk = MetaspaceContext::context_class()->cm()->get_chunk(lvl);
822 const address protzone = (address) chunk->base();
823 assert(protzone == (address)rs.base(), "The very first chunk should be located at the class space start?");
824 assert(chunk->word_size() == protzone_wordsize, "Weird chunk size");
825 CompressedKlassPointers::establish_protection_zone(protzone, protzone_size);
826 } else {
827 assert(CompressedKlassPointers::base() == nullptr, "Zero-based encoding expected");
828 }
829
830 }
831
832 #endif // _LP64
833
834 // Initialize non-class virtual space list, and its chunk manager:
835 MetaspaceContext::initialize_nonclass_space_context();
836
837 _tracer = new MetaspaceTracer();
838
839 #ifdef _LP64
840 if (UseCompressedClassPointers) {
841 // Note: "cds" would be a better fit but keep this for backward compatibility.
842 LogTarget(Info, gc, metaspace) lt;
843 if (lt.is_enabled()) {
844 LogStream ls(lt);
845 CDS_ONLY(MetaspaceShared::print_on(&ls);)
846 Metaspace::print_compressed_class_space(&ls);
847 CompressedKlassPointers::print_mode(&ls);
848 }
849 }
850 #endif
851
852 }
853
854 void Metaspace::post_initialize() {
855 MetaspaceGC::post_initialize();
856 }
857
858 size_t Metaspace::max_allocation_word_size() {
859 return metaspace::chunklevel::MAX_CHUNK_WORD_SIZE;
860 }
861
862 // This version of Metaspace::allocate does not throw OOM but simply returns null, and
863 // is suitable for calling from non-Java threads.
864 // Callers are responsible for checking null.
865 MetaWord* Metaspace::allocate(ClassLoaderData* loader_data, size_t word_size,
866 MetaspaceObj::Type type, bool use_class_space) {
867 assert(word_size <= Metaspace::max_allocation_word_size(),
868 "allocation size too large (%zu)", word_size);
869
870 assert(loader_data != nullptr, "Should never pass around a null loader_data. "
871 "ClassLoaderData::the_null_class_loader_data() should have been used.");
872
873 // Deal with concurrent unloading failed allocation starvation
874 MetaspaceCriticalAllocation::block_if_concurrent_purge();
875
876 MetadataType mdtype = use_class_space ? ClassType : NonClassType;
877
878 // Try to allocate metadata.
879 MetaWord* result = loader_data->metaspace_non_null()->allocate(word_size, mdtype);
880
881 if (result != nullptr) {
882 #ifdef ASSERT
883 if (using_class_space() && mdtype == ClassType) {
884 assert(is_in_class_space(result) &&
885 is_aligned(result, CompressedKlassPointers::klass_alignment_in_bytes()), "Sanity");
886 } else {
887 assert((is_in_class_space(result) || is_in_nonclass_metaspace(result)) &&
888 is_aligned(result, Metaspace::min_allocation_alignment_bytes), "Sanity");
889 }
890 #endif
891 // Zero initialize.
892 Copy::fill_to_words((HeapWord*)result, word_size, 0);
893 log_trace(metaspace)("Metaspace::allocate: type %d return " PTR_FORMAT ".", (int)type, p2i(result));
894 }
895
896 return result;
897 }
898
899 MetaWord* Metaspace::allocate(ClassLoaderData* loader_data, size_t word_size,
900 MetaspaceObj::Type type, bool use_class_space, TRAPS) {
901
902 if (HAS_PENDING_EXCEPTION) {
903 assert(false, "Should not allocate with exception pending");
904 return nullptr; // caller does a CHECK_NULL too
905 }
906 assert(!THREAD->owns_locks(), "allocating metaspace while holding mutex");
907
908 MetaWord* result = allocate(loader_data, word_size, type, use_class_space);
909
910 if (result == nullptr) {
911 MetadataType mdtype = use_class_space ? ClassType : NonClassType;
912 tracer()->report_metaspace_allocation_failure(loader_data, word_size, type, mdtype);
913
914 // Allocation failed.
915 if (is_init_completed()) {
916 // Only start a GC if the bootstrapping has completed.
917 // Try to clean out some heap memory and retry. This can prevent premature
918 // expansion of the metaspace.
919 result = Universe::heap()->satisfy_failed_metadata_allocation(loader_data, word_size, mdtype);
920 }
921
922 if (result == nullptr) {
923 report_metadata_oome(loader_data, word_size, type, mdtype, THREAD);
924 assert(HAS_PENDING_EXCEPTION, "sanity");
925 return nullptr;
926 }
927
928 // Zero initialize.
929 Copy::fill_to_words((HeapWord*)result, word_size, 0);
930
931 log_trace(metaspace)("Metaspace::allocate: type %d return " PTR_FORMAT ".", (int)type, p2i(result));
932 }
933
934 return result;
935 }
936
937 void Metaspace::report_metadata_oome(ClassLoaderData* loader_data, size_t word_size, MetaspaceObj::Type type, MetadataType mdtype, TRAPS) {
938 tracer()->report_metadata_oom(loader_data, word_size, type, mdtype);
939
940 // If result is still null, we are out of memory.
941 {
942 LogMessage(gc, metaspace, freelist, oom) log;
943 if (log.is_info()) {
944 log.info("Metaspace (%s) allocation failed for size %zu",
945 is_class_space_allocation(mdtype) ? "class" : "data", word_size);
946 ResourceMark rm;
947 if (log.is_debug()) {
948 if (loader_data->metaspace_or_null() != nullptr) {
949 NonInterleavingLogStream ls(LogLevelType::Debug, log);
950 loader_data->print_value_on(&ls);
951 }
952 }
953 NonInterleavingLogStream ls(LogLevelType::Info, log);
954 // In case of an OOM, log out a short but still useful report.
955 MetaspaceUtils::print_basic_report(&ls, 0);
956 }
957 }
958
959 bool out_of_compressed_class_space = false;
960 if (is_class_space_allocation(mdtype)) {
961 ClassLoaderMetaspace* metaspace = loader_data->metaspace_non_null();
962 out_of_compressed_class_space =
963 MetaspaceUtils::committed_bytes(Metaspace::ClassType) +
964 align_up(word_size * BytesPerWord, 4 * M) >
965 CompressedClassSpaceSize;
966 }
967
968 // -XX:+HeapDumpOnOutOfMemoryError and -XX:OnOutOfMemoryError support
969 const char* space_string = out_of_compressed_class_space ?
970 "Compressed class space" : "Metaspace";
971
972 report_java_out_of_memory(space_string);
973
974 if (JvmtiExport::should_post_resource_exhausted()) {
975 JvmtiExport::post_resource_exhausted(
976 JVMTI_RESOURCE_EXHAUSTED_OOM_ERROR,
977 space_string);
978 }
979
980 if (!is_init_completed()) {
981 vm_exit_during_initialization("OutOfMemoryError", space_string);
982 }
983
984 if (out_of_compressed_class_space) {
985 THROW_OOP(Universe::out_of_memory_error_class_metaspace());
986 } else {
987 THROW_OOP(Universe::out_of_memory_error_metaspace());
988 }
989 }
990
991 const char* Metaspace::metadata_type_name(Metaspace::MetadataType mdtype) {
992 switch (mdtype) {
993 case Metaspace::ClassType: return "Class";
994 case Metaspace::NonClassType: return "Metadata";
995 default:
996 assert(false, "Got bad mdtype: %d", (int) mdtype);
997 return nullptr;
998 }
999 }
1000
1001 void Metaspace::purge(bool classes_unloaded) {
1002 // The MetaspaceCritical_lock is used by a concurrent GC to block out concurrent metaspace
1003 // allocations, that would starve critical metaspace allocations, that are about to throw
1004 // OOM if they fail; they need precedence for correctness.
1005 MutexLocker ml(MetaspaceCritical_lock, Mutex::_no_safepoint_check_flag);
1006 if (classes_unloaded) {
1007 ChunkManager* cm = ChunkManager::chunkmanager_nonclass();
1008 if (cm != nullptr) {
1009 cm->purge();
1010 }
1011 if (using_class_space()) {
1012 cm = ChunkManager::chunkmanager_class();
1013 if (cm != nullptr) {
1014 cm->purge();
1015 }
1016 }
1017 }
1018
1019 // Try to satisfy queued metaspace allocation requests.
1020 //
1021 // It might seem unnecessary to try to process allocation requests if no
1022 // classes have been unloaded. However, this call is required for the code
1023 // in MetaspaceCriticalAllocation::try_allocate_critical to work.
1024 MetaspaceCriticalAllocation::process();
1025 }
1026
1027
1028 // Returns true if pointer points into one of the metaspace regions, or
1029 // into the class space.
1030 bool Metaspace::is_in_shared_metaspace(const void* ptr) {
1031 return MetaspaceShared::is_in_shared_metaspace(ptr);
1032 }
1033
1034 // Returns true if pointer points into one of the non-class-space metaspace regions.
1035 bool Metaspace::is_in_nonclass_metaspace(const void* ptr) {
1036 return VirtualSpaceList::vslist_nonclass()->contains((MetaWord*)ptr);
1037 }