1 /*
2 * Copyright (c) 2018, 2020, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2018, 2020 SAP SE. 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
28
29 #include "logging/log.hpp"
30 #include "logging/logStream.hpp"
31 #include "memory/metaspace/arenaGrowthPolicy.hpp"
32 #include "memory/metaspace/chunkLevel.hpp"
33 #include "memory/metaspace/chunkManager.hpp"
34 #include "memory/metaspace/internStat.hpp"
35 #include "memory/metaspace/metachunk.hpp"
36 #include "memory/metaspace/metaspaceCommon.hpp"
37 #include "memory/metaspace/metaspaceContext.hpp"
38 #include "memory/metaspace/metaspaceStatistics.hpp"
39 #include "memory/metaspace/settings.hpp"
40 #include "memory/metaspace/virtualSpaceNode.hpp"
41 #include "memory/metaspace/virtualSpaceList.hpp"
42 #include "runtime/mutexLocker.hpp"
43 #include "utilities/debug.hpp"
44 #include "utilities/globalDefinitions.hpp"
45
46 namespace metaspace {
47
48 #define LOGFMT "ChkMgr @" PTR_FORMAT " (%s)"
49 #define LOGFMT_ARGS p2i(this), this->_name
50
51 // Return a single chunk to the freelist and adjust accounting. No merge is attempted.
52 void ChunkManager::return_chunk_simple_locked(Metachunk* c) {
53
54 assert_lock_strong(MetaspaceExpand_lock);
55
56 DEBUG_ONLY(c->verify(false));
57
58 const chunklevel_t lvl = c->level();
59 _chunks.add(c);
60 c->reset_used_words();
61
62 // Tracing
63 log_debug(metaspace)("ChunkManager %s: returned chunk " METACHUNK_FORMAT ".",
64 _name, METACHUNK_FORMAT_ARGS(c));
65
66 }
67
68 // Creates a chunk manager with a given name (which is for debug purposes only)
69 // and an associated space list which will be used to request new chunks from
70 // (see get_chunk())
71 ChunkManager::ChunkManager(const char* name, VirtualSpaceList* space_list)
72 : _vslist(space_list),
73 _name(name),
74 _chunks()
75 {
76 }
77
78 // Given a chunk, split it into a target chunk of a smaller size (higher target level)
79 // and at least one, possible several splinter chunks.
80 // The original chunk must be outside of the freelist and its state must be free.
81 // The splinter chunks are added to the freelist.
82 // The resulting target chunk will be located at the same address as the original
83 // chunk, but it will of course be smaller (of a higher level).
84 // The committed areas within the original chunk carry over to the resulting
85 // chunks.
86 void ChunkManager::split_chunk_and_add_splinters(Metachunk* c, chunklevel_t target_level) {
87
88 assert_lock_strong(MetaspaceExpand_lock);
89
90 assert(c->is_free(), "chunk to be split must be free.");
91 assert(c->level() < target_level, "Target level must be higher than current level.");
92 assert(c->prev() == NULL && c->next() == NULL, "Chunk must be outside of any list.");
93
94 DEBUG_ONLY(chunklevel::check_valid_level(target_level);)
95 DEBUG_ONLY(c->verify(true);)
96
97 UL2(debug, "splitting chunk " METACHUNK_FORMAT " to " CHKLVL_FORMAT ".",
98 METACHUNK_FORMAT_ARGS(c), target_level);
99
100 DEBUG_ONLY(size_t committed_words_before = c->committed_words();)
101
102 const chunklevel_t orig_level = c->level();
103 c->vsnode()->split(target_level, c, &_chunks);
104
105 // Splitting should never fail.
106 assert(c->level() == target_level, "Sanity");
107
108 // The size of the committed portion should not change (subject to the reduced chunk size of course)
109 #ifdef ASSERT
110 if (committed_words_before > c->word_size()) {
111 assert(c->is_fully_committed(), "Sanity");
112 } else {
113 assert(c->committed_words() == committed_words_before, "Sanity");
114 }
115 #endif
116
117 DEBUG_ONLY(c->verify(false));
118
119 DEBUG_ONLY(verify_locked(true);)
120
121 SOMETIMES(c->vsnode()->verify_locked(true);)
122
123 InternalStats::inc_num_chunk_splits();
124
125 }
126
127 // On success, returns a chunk of level of <preferred_level>, but at most <max_level>.
128 // The first first <min_committed_words> of the chunk are guaranteed to be committed.
129 // On error, will return NULL.
130 //
131 // This function may fail for two reasons:
132 // - Either we are unable to reserve space for a new chunk (if the underlying VirtualSpaceList
133 // is non-expandable but needs expanding - aka out of compressed class space).
134 // - Or, if the necessary space cannot be committed because we hit a commit limit.
135 // This may be either the GC threshold or MaxMetaspaceSize.
136 Metachunk* ChunkManager::get_chunk(chunklevel_t preferred_level, chunklevel_t max_level, size_t min_committed_words) {
137
138 assert(preferred_level <= max_level, "Sanity");
139 assert(chunklevel::level_fitting_word_size(min_committed_words) >= max_level, "Sanity");
140
141 MutexLocker fcl(MetaspaceExpand_lock, Mutex::_no_safepoint_check_flag);
142
143 DEBUG_ONLY(verify_locked(false);)
144
145 DEBUG_ONLY(chunklevel::check_valid_level(max_level);)
146 DEBUG_ONLY(chunklevel::check_valid_level(preferred_level);)
147 assert(max_level >= preferred_level, "invalid level.");
148
149 UL2(debug, "requested chunk: pref_level: " CHKLVL_FORMAT
150 ", max_level: " CHKLVL_FORMAT ", min committed size: " SIZE_FORMAT ".",
151 preferred_level, max_level, min_committed_words);
152
153 // First, optimistically look for a chunk which is already committed far enough to hold min_word_size.
154
155 // 1) Search best or smaller committed chunks (first attempt):
156 // Start at the preferred chunk size and work your way down (level up).
157 // But for now, only consider chunks larger than a certain threshold -
158 // this is to prevent large loaders (eg boot) from unnecessarily gobbling up
159 // all the tiny splinter chunks lambdas leave around.
160 Metachunk* c = NULL;
161 c = _chunks.search_chunk_ascending(preferred_level, MIN2((chunklevel_t)(preferred_level + 2), max_level), min_committed_words);
162
163 // 2) Search larger committed chunks:
164 // If that did not yield anything, look at larger chunks, which may be committed. We would have to split
165 // them first, of course.
166 if (c == NULL) {
167 c = _chunks.search_chunk_descending(preferred_level, min_committed_words);
168 }
169
170 // 3) Search best or smaller committed chunks (second attempt):
171 // Repeat (1) but now consider even the tiniest chunks as long as they are large enough to hold the
172 // committed min size.
173 if (c == NULL) {
174 c = _chunks.search_chunk_ascending(preferred_level, max_level, min_committed_words);
175 }
176
177 // if we did not get anything yet, there are no free chunks commmitted enough. Repeat search but look for uncommitted chunks too:
178
179 // 4) Search best or smaller chunks, can be uncommitted:
180 if (c == NULL) {
181 c = _chunks.search_chunk_ascending(preferred_level, max_level, 0);
182 }
183
184 // 5) Search a larger uncommitted chunk:
185 if (c == NULL) {
186 c = _chunks.search_chunk_descending(preferred_level, 0);
187 }
188
189 if (c != NULL) {
190 UL(trace, "taken from freelist.");
191 }
192
193 // Failing all that, allocate a new root chunk from the connected virtual space.
194 // This may fail if the underlying vslist cannot be expanded (e.g. compressed class space)
195 if (c == NULL) {
196 c = _vslist->allocate_root_chunk();
197 if (c == NULL) {
198 UL(info, "failed to get new root chunk.");
199 } else {
200 assert(c->level() == chunklevel::ROOT_CHUNK_LEVEL, "root chunk expected");
201 UL(debug, "allocated new root chunk.");
202 }
203 }
204
205 if (c == NULL) {
206 // If we end up here, we found no match in the freelists and were unable to get a new
207 // root chunk (so we used up all address space, e.g. out of CompressedClassSpace).
208 UL2(info, "failed to get chunk (preferred level: " CHKLVL_FORMAT
209 ", max level " CHKLVL_FORMAT ".", preferred_level, max_level);
210 c = NULL;
211 }
212
213 if (c != NULL) {
214
215 // Now we have a chunk.
216 // It may be larger than what the caller wanted, so we may want to split it. This should
217 // always work.
218 if (c->level() < preferred_level) {
219 split_chunk_and_add_splinters(c, preferred_level);
220 assert(c->level() == preferred_level, "split failed?");
221 }
222
223 // Attempt to commit the chunk (depending on settings, we either fully commit it or just
224 // commit enough to get the caller going). That may fail if we hit a commit limit. In
225 // that case put the chunk back to the freelist (re-merging it with its neighbors if we
226 // did split it) and return NULL.
227 const size_t to_commit = Settings::new_chunks_are_fully_committed() ? c->word_size() : min_committed_words;
228 if (c->committed_words() < to_commit) {
229 if (c->ensure_committed_locked(to_commit) == false) {
230 UL2(info, "failed to commit " SIZE_FORMAT " words on chunk " METACHUNK_FORMAT ".",
231 to_commit, METACHUNK_FORMAT_ARGS(c));
232 c->set_in_use(); // gets asserted in return_chunk().
233 return_chunk_locked(c);
234 c = NULL;
235 }
236 }
237
238 if (c != NULL) {
239
240 // Still here? We have now a good chunk, all is well.
241 assert(c->committed_words() >= min_committed_words, "Sanity");
242
243 // Any chunk returned from ChunkManager shall be marked as in use.
244 c->set_in_use();
245
246 UL2(debug, "handing out chunk " METACHUNK_FORMAT ".", METACHUNK_FORMAT_ARGS(c));
247
248 InternalStats::inc_num_chunks_taken_from_freelist();
249
250 SOMETIMES(c->vsnode()->verify_locked(true);)
251
252 }
253
254 }
255
256 DEBUG_ONLY(verify_locked(false);)
257
258 return c;
259
260 }
261
262
263 // Return a single chunk to the ChunkManager and adjust accounting. May merge chunk
264 // with neighbors.
265 // As a side effect this removes the chunk from whatever list it has been in previously.
266 // Happens after a Classloader was unloaded and releases its metaspace chunks.
267 // !! Note: this may invalidate the chunk. Do not access the chunk after
268 // this function returns !!
269 void ChunkManager::return_chunk(Metachunk* c) {
270 MutexLocker fcl(MetaspaceExpand_lock, Mutex::_no_safepoint_check_flag);
271 return_chunk_locked(c);
272 }
273
274 // See return_chunk().
275 void ChunkManager::return_chunk_locked(Metachunk* c) {
276
277 assert_lock_strong(MetaspaceExpand_lock);
278
279 UL2(debug, ": returning chunk " METACHUNK_FORMAT ".", METACHUNK_FORMAT_ARGS(c));
280
281 DEBUG_ONLY(c->verify(true);)
282
283 assert(contains_chunk(c) == false, "A chunk to be added to the freelist must not be in the freelist already.");
284
285 assert(c->is_in_use(), "Unexpected chunk state");
286 assert(!c->in_list(), "Remove from list first");
287 c->set_free();
288 c->reset_used_words();
289
290 const chunklevel_t orig_lvl = c->level();
291
292 Metachunk* merged = NULL;
293 if (!c->is_root_chunk()) {
294 // Only attempt merging if we are not of the lowest level already.
295 merged = c->vsnode()->merge(c, &_chunks);
296 }
297
298 if (merged != NULL) {
299
300 InternalStats::inc_num_chunk_merges();
301
302 DEBUG_ONLY(merged->verify(false));
303
304 // We did merge our chunk into a different chunk.
305
306 // We did merge chunks and now have a bigger chunk.
307 assert(merged->level() < orig_lvl, "Sanity");
308
309 UL2(debug, "merged into chunk " METACHUNK_FORMAT ".", METACHUNK_FORMAT_ARGS(merged));
310
311 c = merged;
312
313 }
314
315 if (Settings::uncommit_free_chunks() &&
316 c->word_size() >= Settings::commit_granule_words())
317 {
318 UL2(debug, "uncommitting free chunk " METACHUNK_FORMAT ".", METACHUNK_FORMAT_ARGS(c));
319 c->uncommit_locked();
320 }
321
322 return_chunk_simple_locked(c);
323
324 DEBUG_ONLY(verify_locked(false);)
325 SOMETIMES(c->vsnode()->verify_locked(true);)
326
327 InternalStats::inc_num_chunks_returned_to_freelist();
328
329 }
330
331 // Given a chunk c, whose state must be "in-use" and must not be a root chunk, attempt to
332 // enlarge it in place by claiming its trailing buddy.
333 //
334 // This will only work if c is the leader of the buddy pair and the trailing buddy is free.
335 //
336 // If successful, the follower chunk will be removed from the freelists, the leader chunk c will
337 // double in size (level decreased by one).
338 //
339 // On success, true is returned, false otherwise.
340 bool ChunkManager::attempt_enlarge_chunk(Metachunk* c) {
341 MutexLocker fcl(MetaspaceExpand_lock, Mutex::_no_safepoint_check_flag);
342 return c->vsnode()->attempt_enlarge_chunk(c, &_chunks);
343 }
344
345 static void print_word_size_delta(outputStream* st, size_t word_size_1, size_t word_size_2) {
346 if (word_size_1 == word_size_2) {
347 print_scaled_words(st, word_size_1);
348 st->print (" (no change)");
349 } else {
350 print_scaled_words(st, word_size_1);
351 st->print("->");
352 print_scaled_words(st, word_size_2);
353 st->print(" (");
354 if (word_size_2 <= word_size_1) {
355 st->print("-");
356 print_scaled_words(st, word_size_1 - word_size_2);
357 } else {
358 st->print("+");
359 print_scaled_words(st, word_size_2 - word_size_1);
360 }
361 st->print(")");
362 }
363 }
364
365 void ChunkManager::purge() {
366
367 MutexLocker fcl(MetaspaceExpand_lock, Mutex::_no_safepoint_check_flag);
368
369 UL(info, ": reclaiming memory...");
370
371 const size_t reserved_before = _vslist->reserved_words();
372 const size_t committed_before = _vslist->committed_words();
373 int num_nodes_purged = 0;
374
375 // 1) purge virtual space list
376 num_nodes_purged = _vslist->purge(&_chunks);
377 InternalStats::inc_num_purges();
378
379 // 2) uncommit free chunks
380 if (Settings::uncommit_free_chunks()) {
381 const chunklevel_t max_level =
382 chunklevel::level_fitting_word_size(Settings::commit_granule_words());
383 for (chunklevel_t l = chunklevel::LOWEST_CHUNK_LEVEL;
384 l <= max_level;
385 l ++)
386 {
387 // Since we uncommit all chunks at this level, we do not break the "committed chunks are
388 // at the front of the list" condition.
389 for (Metachunk* c = _chunks.first_at_level(l); c != NULL; c = c->next()) {
390 c->uncommit_locked();
391 }
392 }
393 }
394
395 const size_t reserved_after = _vslist->reserved_words();
396 const size_t committed_after = _vslist->committed_words();
397
398 // Print a nice report.
399 if (reserved_after == reserved_before && committed_after == committed_before) {
400 UL(info, "nothing reclaimed.");
401 } else {
402 LogTarget(Info, metaspace) lt;
403 if (lt.is_enabled()) {
404 LogStream ls(lt);
405 ls.print_cr(LOGFMT ": finished reclaiming memory: ", LOGFMT_ARGS);
406
407 ls.print("reserved: ");
408 print_word_size_delta(&ls, reserved_before, reserved_after);
409 ls.cr();
410
411 ls.print("committed: ");
412 print_word_size_delta(&ls, committed_before, committed_after);
413 ls.cr();
414
415 ls.print_cr("full nodes purged: %d", num_nodes_purged);
416 }
417 }
418
419 DEBUG_ONLY(_vslist->verify_locked(true));
420 DEBUG_ONLY(verify_locked(true));
421
422 }
423
424 // Convenience methods to return the global class-space chunkmanager
425 // and non-class chunkmanager, respectively.
426 ChunkManager* ChunkManager::chunkmanager_class() {
427 return MetaspaceContext::context_class() == NULL ? NULL : MetaspaceContext::context_class()->cm();
428 }
429
430 ChunkManager* ChunkManager::chunkmanager_nonclass() {
431 return MetaspaceContext::context_nonclass() == NULL ? NULL : MetaspaceContext::context_nonclass()->cm();
432 }
433
434 // Update statistics.
435 void ChunkManager::add_to_statistics(cm_stats_t* out) const {
436
437 MutexLocker fcl(MetaspaceExpand_lock, Mutex::_no_safepoint_check_flag);
438
439 for (chunklevel_t l = chunklevel::ROOT_CHUNK_LEVEL; l <= chunklevel::HIGHEST_CHUNK_LEVEL; l ++) {
440 out->num_chunks[l] += _chunks.num_chunks_at_level(l);
441 out->committed_word_size[l] += _chunks.committed_word_size_at_level(l);
442 }
443
444 DEBUG_ONLY(out->verify();)
445
446 }
447
448 #ifdef ASSERT
449
450 void ChunkManager::verify(bool slow) const {
451 MutexLocker fcl(MetaspaceExpand_lock, Mutex::_no_safepoint_check_flag);
452 verify_locked(slow);
453 }
454
455 void ChunkManager::verify_locked(bool slow) const {
456 assert_lock_strong(MetaspaceExpand_lock);
457 assert(_vslist != NULL, "No vslist");
458 _chunks.verify();
459 }
460
461 bool ChunkManager::contains_chunk(Metachunk* c) const {
462 return _chunks.contains(c);
463 }
464
465 #endif // ASSERT
466
467 void ChunkManager::print_on(outputStream* st) const {
468 MutexLocker fcl(MetaspaceExpand_lock, Mutex::_no_safepoint_check_flag);
469 print_on_locked(st);
470 }
471
472 void ChunkManager::print_on_locked(outputStream* st) const {
473 assert_lock_strong(MetaspaceExpand_lock);
474 st->print_cr("cm %s: %d chunks, total word size: " SIZE_FORMAT ", committed word size: " SIZE_FORMAT, _name,
475 total_num_chunks(), total_word_size(), _chunks.committed_word_size());
476 _chunks.print_on(st);
477 }
478
479 } // namespace metaspace