1 /*
2 * Copyright (c) 2001, 2023, 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 #include "gc/serial/cardTableRS.hpp"
27 #include "gc/serial/defNewGeneration.inline.hpp"
28 #include "gc/serial/serialGcRefProcProxyTask.hpp"
29 #include "gc/serial/serialHeap.inline.hpp"
30 #include "gc/serial/serialStringDedup.inline.hpp"
31 #include "gc/serial/tenuredGeneration.hpp"
32 #include "gc/shared/adaptiveSizePolicy.hpp"
33 #include "gc/shared/ageTable.inline.hpp"
34 #include "gc/shared/collectorCounters.hpp"
35 #include "gc/shared/continuationGCSupport.inline.hpp"
36 #include "gc/shared/gcArguments.hpp"
37 #include "gc/shared/gcHeapSummary.hpp"
38 #include "gc/shared/gcLocker.hpp"
39 #include "gc/shared/gcPolicyCounters.hpp"
40 #include "gc/shared/gcTimer.hpp"
41 #include "gc/shared/gcTrace.hpp"
42 #include "gc/shared/gcTraceTime.inline.hpp"
43 #include "gc/shared/preservedMarks.inline.hpp"
44 #include "gc/shared/referencePolicy.hpp"
45 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
46 #include "gc/shared/space.inline.hpp"
47 #include "gc/shared/spaceDecorator.inline.hpp"
48 #include "gc/shared/strongRootsScope.hpp"
49 #include "gc/shared/weakProcessor.hpp"
50 #include "logging/log.hpp"
51 #include "memory/iterator.inline.hpp"
52 #include "memory/resourceArea.hpp"
53 #include "oops/instanceRefKlass.hpp"
54 #include "oops/oop.inline.hpp"
55 #include "runtime/java.hpp"
56 #include "runtime/javaThread.hpp"
57 #include "runtime/prefetch.inline.hpp"
58 #include "runtime/threads.hpp"
59 #include "utilities/align.hpp"
60 #include "utilities/copy.hpp"
61 #include "utilities/globalDefinitions.hpp"
62 #include "utilities/stack.inline.hpp"
63
64 class PromoteFailureClosure : public InHeapScanClosure {
65 template <typename T>
66 void do_oop_work(T* p) {
67 assert(is_in_young_gen(p), "promote-fail objs must be in young-gen");
68 assert(!SerialHeap::heap()->young_gen()->to()->is_in_reserved(p), "must not be in to-space");
69
70 try_scavenge(p, [] (auto) {});
71 }
72 public:
73 PromoteFailureClosure(DefNewGeneration* g) : InHeapScanClosure(g) {}
74
75 void do_oop(oop* p) { do_oop_work(p); }
76 void do_oop(narrowOop* p) { do_oop_work(p); }
77 };
78
79 class YoungGenScanClosure : public InHeapScanClosure {
80 template <typename T>
81 void do_oop_work(T* p) {
82 assert(SerialHeap::heap()->young_gen()->to()->is_in_reserved(p), "precondition");
83
84 try_scavenge(p, [] (auto) {});
85 }
86 public:
87 YoungGenScanClosure(DefNewGeneration* g) : InHeapScanClosure(g) {}
88
89 void do_oop(oop* p) { do_oop_work(p); }
90 void do_oop(narrowOop* p) { do_oop_work(p); }
91 };
92
93 class RootScanClosure : public OffHeapScanClosure {
94 template <typename T>
95 void do_oop_work(T* p) {
96 assert(!SerialHeap::heap()->is_in_reserved(p), "outside the heap");
97
98 try_scavenge(p, [] (auto) {});
99 }
100 public:
101 RootScanClosure(DefNewGeneration* g) : OffHeapScanClosure(g) {}
102
103 void do_oop(oop* p) { do_oop_work(p); }
104 void do_oop(narrowOop* p) { do_oop_work(p); }
105 };
106
107 class CLDScanClosure: public CLDClosure {
108
109 class CLDOopClosure : public OffHeapScanClosure {
110 ClassLoaderData* _scanned_cld;
111
112 template <typename T>
113 void do_oop_work(T* p) {
114 assert(!SerialHeap::heap()->is_in_reserved(p), "outside the heap");
115
116 try_scavenge(p, [&] (oop new_obj) {
117 assert(_scanned_cld != nullptr, "inv");
118 if (is_in_young_gen(new_obj) && !_scanned_cld->has_modified_oops()) {
119 _scanned_cld->record_modified_oops();
120 }
121 });
122 }
123
124 public:
125 CLDOopClosure(DefNewGeneration* g) : OffHeapScanClosure(g),
126 _scanned_cld(nullptr) {}
127
128 void set_scanned_cld(ClassLoaderData* cld) {
129 assert(cld == nullptr || _scanned_cld == nullptr, "Must be");
130 _scanned_cld = cld;
131 }
132
133 void do_oop(oop* p) { do_oop_work(p); }
134 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
135 };
136
137 CLDOopClosure _oop_closure;
138 public:
139 CLDScanClosure(DefNewGeneration* g) : _oop_closure(g) {}
140
141 void do_cld(ClassLoaderData* cld) {
142 // If the cld has not been dirtied we know that there's
143 // no references into the young gen and we can skip it.
144 if (cld->has_modified_oops()) {
145
146 // Tell the closure which CLD is being scanned so that it can be dirtied
147 // if oops are left pointing into the young gen.
148 _oop_closure.set_scanned_cld(cld);
149
150 // Clean the cld since we're going to scavenge all the metadata.
151 cld->oops_do(&_oop_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);
152
153 _oop_closure.set_scanned_cld(nullptr);
154 }
155 }
156 };
157
158 class IsAliveClosure: public BoolObjectClosure {
159 HeapWord* _young_gen_end;
160 public:
161 IsAliveClosure(DefNewGeneration* g): _young_gen_end(g->reserved().end()) {}
162
163 bool do_object_b(oop p) {
164 return cast_from_oop<HeapWord*>(p) >= _young_gen_end || p->is_forwarded();
165 }
166 };
167
168 class AdjustWeakRootClosure: public OffHeapScanClosure {
169 template <class T>
170 void do_oop_work(T* p) {
171 DEBUG_ONLY(SerialHeap* heap = SerialHeap::heap();)
172 assert(!heap->is_in_reserved(p), "outside the heap");
173
174 oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);
175 if (is_in_young_gen(obj)) {
176 assert(!heap->young_gen()->to()->is_in_reserved(obj), "inv");
177 assert(obj->is_forwarded(), "forwarded before weak-root-processing");
178 oop new_obj = obj->forwardee();
179 RawAccess<IS_NOT_NULL>::oop_store(p, new_obj);
180 }
181 }
182 public:
183 AdjustWeakRootClosure(DefNewGeneration* g): OffHeapScanClosure(g) {}
184
185 void do_oop(oop* p) { do_oop_work(p); }
186 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
187 };
188
189 class KeepAliveClosure: public OopClosure {
190 DefNewGeneration* _young_gen;
191 HeapWord* _young_gen_end;
192 CardTableRS* _rs;
193
194 bool is_in_young_gen(void* p) const {
195 return p < _young_gen_end;
196 }
197
198 template <class T>
199 void do_oop_work(T* p) {
200 oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);
201
202 if (is_in_young_gen(obj)) {
203 oop new_obj = obj->is_forwarded() ? obj->forwardee()
204 : _young_gen->copy_to_survivor_space(obj);
205 RawAccess<IS_NOT_NULL>::oop_store(p, new_obj);
206
207 if (is_in_young_gen(new_obj) && !is_in_young_gen(p)) {
208 _rs->inline_write_ref_field_gc(p);
209 }
210 }
211 }
212 public:
213 KeepAliveClosure(DefNewGeneration* g) :
214 _young_gen(g),
215 _young_gen_end(g->reserved().end()),
216 _rs(SerialHeap::heap()->rem_set()) {}
217
218 void do_oop(oop* p) { do_oop_work(p); }
219 void do_oop(narrowOop* p) { do_oop_work(p); }
220 };
221
222 class FastEvacuateFollowersClosure: public VoidClosure {
223 SerialHeap* _heap;
224 YoungGenScanClosure* _young_cl;
225 OldGenScanClosure* _old_cl;
226 public:
227 FastEvacuateFollowersClosure(SerialHeap* heap,
228 YoungGenScanClosure* young_cl,
229 OldGenScanClosure* old_cl) :
230 _heap(heap), _young_cl(young_cl), _old_cl(old_cl)
231 {}
232
233 void do_void() {
234 do {
235 _heap->oop_since_save_marks_iterate(_young_cl, _old_cl);
236 } while (!_heap->no_allocs_since_save_marks());
237 guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan");
238 }
239 };
240
241 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
242 size_t initial_size,
243 size_t min_size,
244 size_t max_size,
245 const char* policy)
246 : Generation(rs, initial_size),
247 _preserved_marks_set(false /* in_c_heap */),
248 _promo_failure_drain_in_progress(false),
249 _should_allocate_from_space(false),
250 _string_dedup_requests()
251 {
252 MemRegion cmr((HeapWord*)_virtual_space.low(),
253 (HeapWord*)_virtual_space.high());
254 SerialHeap* gch = SerialHeap::heap();
255
256 gch->rem_set()->resize_covered_region(cmr);
257
258 _eden_space = new ContiguousSpace();
259 _from_space = new ContiguousSpace();
260 _to_space = new ContiguousSpace();
261
262 // Compute the maximum eden and survivor space sizes. These sizes
263 // are computed assuming the entire reserved space is committed.
264 // These values are exported as performance counters.
265 uintx size = _virtual_space.reserved_size();
266 _max_survivor_size = compute_survivor_size(size, SpaceAlignment);
267 _max_eden_size = size - (2*_max_survivor_size);
268
269 // allocate the performance counters
270
271 // Generation counters -- generation 0, 3 subspaces
272 _gen_counters = new GenerationCounters("new", 0, 3,
273 min_size, max_size, &_virtual_space);
274 _gc_counters = new CollectorCounters(policy, 0);
275
276 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
277 _gen_counters);
278 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
279 _gen_counters);
280 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
281 _gen_counters);
282
283 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
284 update_counters();
285 _old_gen = nullptr;
286 _tenuring_threshold = MaxTenuringThreshold;
287 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
288
289 _ref_processor = nullptr;
290
291 _gc_timer = new STWGCTimer();
292
293 _gc_tracer = new DefNewTracer();
294 }
295
296 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
297 bool clear_space,
298 bool mangle_space) {
299 // If the spaces are being cleared (only done at heap initialization
300 // currently), the survivor spaces need not be empty.
301 // Otherwise, no care is taken for used areas in the survivor spaces
302 // so check.
303 assert(clear_space || (to()->is_empty() && from()->is_empty()),
304 "Initialization of the survivor spaces assumes these are empty");
305
306 // Compute sizes
307 uintx size = _virtual_space.committed_size();
308 uintx survivor_size = compute_survivor_size(size, SpaceAlignment);
309 uintx eden_size = size - (2*survivor_size);
310 if (eden_size > max_eden_size()) {
311 // Need to reduce eden_size to satisfy the max constraint. The delta needs
312 // to be 2*SpaceAlignment aligned so that both survivors are properly
313 // aligned.
314 uintx eden_delta = align_up(eden_size - max_eden_size(), 2*SpaceAlignment);
315 eden_size -= eden_delta;
316 survivor_size += eden_delta/2;
317 }
318 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
319
320 if (eden_size < minimum_eden_size) {
321 // May happen due to 64Kb rounding, if so adjust eden size back up
322 minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment);
323 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
324 uintx unaligned_survivor_size =
325 align_down(maximum_survivor_size, SpaceAlignment);
326 survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment);
327 eden_size = size - (2*survivor_size);
328 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
329 assert(eden_size >= minimum_eden_size, "just checking");
330 }
331
332 char *eden_start = _virtual_space.low();
333 char *from_start = eden_start + eden_size;
334 char *to_start = from_start + survivor_size;
335 char *to_end = to_start + survivor_size;
336
337 assert(to_end == _virtual_space.high(), "just checking");
338 assert(is_aligned(eden_start, SpaceAlignment), "checking alignment");
339 assert(is_aligned(from_start, SpaceAlignment), "checking alignment");
340 assert(is_aligned(to_start, SpaceAlignment), "checking alignment");
341
342 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
343 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
344 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
345
346 // A minimum eden size implies that there is a part of eden that
347 // is being used and that affects the initialization of any
348 // newly formed eden.
349 bool live_in_eden = minimum_eden_size > 0;
350
351 // If not clearing the spaces, do some checking to verify that
352 // the space are already mangled.
353 if (!clear_space) {
354 // Must check mangling before the spaces are reshaped. Otherwise,
355 // the bottom or end of one space may have moved into another
356 // a failure of the check may not correctly indicate which space
357 // is not properly mangled.
358 if (ZapUnusedHeapArea) {
359 HeapWord* limit = (HeapWord*) _virtual_space.high();
360 eden()->check_mangled_unused_area(limit);
361 from()->check_mangled_unused_area(limit);
362 to()->check_mangled_unused_area(limit);
363 }
364 }
365
366 // Reset the spaces for their new regions.
367 eden()->initialize(edenMR,
368 clear_space && !live_in_eden,
369 SpaceDecorator::Mangle);
370 // If clear_space and live_in_eden, we will not have cleared any
371 // portion of eden above its top. This can cause newly
372 // expanded space not to be mangled if using ZapUnusedHeapArea.
373 // We explicitly do such mangling here.
374 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
375 eden()->mangle_unused_area();
376 }
377 from()->initialize(fromMR, clear_space, mangle_space);
378 to()->initialize(toMR, clear_space, mangle_space);
379
380 // Set next compaction spaces.
381 eden()->set_next_compaction_space(from());
382 // The to-space is normally empty before a compaction so need
383 // not be considered. The exception is during promotion
384 // failure handling when to-space can contain live objects.
385 from()->set_next_compaction_space(nullptr);
386 }
387
388 void DefNewGeneration::swap_spaces() {
389 ContiguousSpace* s = from();
390 _from_space = to();
391 _to_space = s;
392 eden()->set_next_compaction_space(from());
393 // The to-space is normally empty before a compaction so need
394 // not be considered. The exception is during promotion
395 // failure handling when to-space can contain live objects.
396 from()->set_next_compaction_space(nullptr);
397
398 if (UsePerfData) {
399 CSpaceCounters* c = _from_counters;
400 _from_counters = _to_counters;
401 _to_counters = c;
402 }
403 }
404
405 bool DefNewGeneration::expand(size_t bytes) {
406 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
407 bool success = _virtual_space.expand_by(bytes);
408 if (success && ZapUnusedHeapArea) {
409 // Mangle newly committed space immediately because it
410 // can be done here more simply that after the new
411 // spaces have been computed.
412 HeapWord* new_high = (HeapWord*) _virtual_space.high();
413 MemRegion mangle_region(prev_high, new_high);
414 SpaceMangler::mangle_region(mangle_region);
415 }
416
417 // Do not attempt an expand-to-the reserve size. The
418 // request should properly observe the maximum size of
419 // the generation so an expand-to-reserve should be
420 // unnecessary. Also a second call to expand-to-reserve
421 // value potentially can cause an undue expansion.
422 // For example if the first expand fail for unknown reasons,
423 // but the second succeeds and expands the heap to its maximum
424 // value.
425 if (GCLocker::is_active()) {
426 log_debug(gc)("Garbage collection disabled, expanded heap instead");
427 }
428
429 return success;
430 }
431
432 size_t DefNewGeneration::calculate_thread_increase_size(int threads_count) const {
433 size_t thread_increase_size = 0;
434 // Check an overflow at 'threads_count * NewSizeThreadIncrease'.
435 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
436 thread_increase_size = threads_count * NewSizeThreadIncrease;
437 }
438 return thread_increase_size;
439 }
440
441 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
442 size_t new_size_before,
443 size_t alignment,
444 size_t thread_increase_size) const {
445 size_t desired_new_size = new_size_before;
446
447 if (NewSizeThreadIncrease > 0 && thread_increase_size > 0) {
448
449 // 1. Check an overflow at 'new_size_candidate + thread_increase_size'.
450 if (new_size_candidate <= max_uintx - thread_increase_size) {
451 new_size_candidate += thread_increase_size;
452
453 // 2. Check an overflow at 'align_up'.
454 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
455 if (new_size_candidate <= aligned_max) {
456 desired_new_size = align_up(new_size_candidate, alignment);
457 }
458 }
459 }
460
461 return desired_new_size;
462 }
463
464 void DefNewGeneration::compute_new_size() {
465 // This is called after a GC that includes the old generation, so from-space
466 // will normally be empty.
467 // Note that we check both spaces, since if scavenge failed they revert roles.
468 // If not we bail out (otherwise we would have to relocate the objects).
469 if (!from()->is_empty() || !to()->is_empty()) {
470 return;
471 }
472
473 SerialHeap* gch = SerialHeap::heap();
474
475 size_t old_size = gch->old_gen()->capacity();
476 size_t new_size_before = _virtual_space.committed_size();
477 size_t min_new_size = NewSize;
478 size_t max_new_size = reserved().byte_size();
479 assert(min_new_size <= new_size_before &&
480 new_size_before <= max_new_size,
481 "just checking");
482 // All space sizes must be multiples of Generation::GenGrain.
483 size_t alignment = Generation::GenGrain;
484
485 int threads_count = Threads::number_of_non_daemon_threads();
486 size_t thread_increase_size = calculate_thread_increase_size(threads_count);
487
488 size_t new_size_candidate = old_size / NewRatio;
489 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
490 // and reverts to previous value if any overflow happens
491 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before,
492 alignment, thread_increase_size);
493
494 // Adjust new generation size
495 desired_new_size = clamp(desired_new_size, min_new_size, max_new_size);
496 assert(desired_new_size <= max_new_size, "just checking");
497
498 bool changed = false;
499 if (desired_new_size > new_size_before) {
500 size_t change = desired_new_size - new_size_before;
501 assert(change % alignment == 0, "just checking");
502 if (expand(change)) {
503 changed = true;
504 }
505 // If the heap failed to expand to the desired size,
506 // "changed" will be false. If the expansion failed
507 // (and at this point it was expected to succeed),
508 // ignore the failure (leaving "changed" as false).
509 }
510 if (desired_new_size < new_size_before && eden()->is_empty()) {
511 // bail out of shrinking if objects in eden
512 size_t change = new_size_before - desired_new_size;
513 assert(change % alignment == 0, "just checking");
514 _virtual_space.shrink_by(change);
515 changed = true;
516 }
517 if (changed) {
518 // The spaces have already been mangled at this point but
519 // may not have been cleared (set top = bottom) and should be.
520 // Mangling was done when the heap was being expanded.
521 compute_space_boundaries(eden()->used(),
522 SpaceDecorator::Clear,
523 SpaceDecorator::DontMangle);
524 MemRegion cmr((HeapWord*)_virtual_space.low(),
525 (HeapWord*)_virtual_space.high());
526 gch->rem_set()->resize_covered_region(cmr);
527
528 log_debug(gc, ergo, heap)(
529 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
530 new_size_before/K, _virtual_space.committed_size()/K,
531 eden()->capacity()/K, from()->capacity()/K);
532 log_trace(gc, ergo, heap)(
533 " [allowed " SIZE_FORMAT "K extra for %d threads]",
534 thread_increase_size/K, threads_count);
535 }
536 }
537
538 void DefNewGeneration::ref_processor_init() {
539 assert(_ref_processor == nullptr, "a reference processor already exists");
540 assert(!_reserved.is_empty(), "empty generation?");
541 _span_based_discoverer.set_span(_reserved);
542 _ref_processor = new ReferenceProcessor(&_span_based_discoverer); // a vanilla reference processor
543 }
544
545 size_t DefNewGeneration::capacity() const {
546 return eden()->capacity()
547 + from()->capacity(); // to() is only used during scavenge
548 }
549
550
551 size_t DefNewGeneration::used() const {
552 return eden()->used()
553 + from()->used(); // to() is only used during scavenge
554 }
555
556
557 size_t DefNewGeneration::free() const {
558 return eden()->free()
559 + from()->free(); // to() is only used during scavenge
560 }
561
562 size_t DefNewGeneration::max_capacity() const {
563 const size_t reserved_bytes = reserved().byte_size();
564 return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment);
565 }
566
567 bool DefNewGeneration::is_in(const void* p) const {
568 return eden()->is_in(p)
569 || from()->is_in(p)
570 || to() ->is_in(p);
571 }
572
573 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
574 return eden()->free();
575 }
576
577 size_t DefNewGeneration::capacity_before_gc() const {
578 return eden()->capacity();
579 }
580
581 size_t DefNewGeneration::contiguous_available() const {
582 return eden()->free();
583 }
584
585
586 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
587 eden()->object_iterate(blk);
588 from()->object_iterate(blk);
589 }
590
591 HeapWord* DefNewGeneration::block_start(const void* p) const {
592 if (eden()->is_in_reserved(p)) {
593 return eden()->block_start_const(p);
594 }
595 if (from()->is_in_reserved(p)) {
596 return from()->block_start_const(p);
597 }
598 assert(to()->is_in_reserved(p), "inv");
599 return to()->block_start_const(p);
600 }
601
602 // The last collection bailed out, we are running out of heap space,
603 // so we try to allocate the from-space, too.
604 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
605 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
606
607 // If the Heap_lock is not locked by this thread, this will be called
608 // again later with the Heap_lock held.
609 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
610
611 HeapWord* result = nullptr;
612 if (do_alloc) {
613 result = from()->allocate(size);
614 }
615
616 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s",
617 size,
618 SerialHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
619 "true" : "false",
620 Heap_lock->is_locked() ? "locked" : "unlocked",
621 from()->free(),
622 should_try_alloc ? "" : " should_allocate_from_space: NOT",
623 do_alloc ? " Heap_lock is not owned by self" : "",
624 result == nullptr ? "null" : "object");
625
626 return result;
627 }
628
629 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, bool is_tlab) {
630 // We don't attempt to expand the young generation (but perhaps we should.)
631 return allocate(size, is_tlab);
632 }
633
634 void DefNewGeneration::adjust_desired_tenuring_threshold() {
635 // Set the desired survivor size to half the real survivor space
636 size_t const survivor_capacity = to()->capacity() / HeapWordSize;
637 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
638
639 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
640
641 if (UsePerfData) {
642 GCPolicyCounters* gc_counters = SerialHeap::heap()->counters();
643 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
644 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
645 }
646
647 age_table()->print_age_table(_tenuring_threshold);
648 }
649
650 void DefNewGeneration::collect(bool full,
651 bool clear_all_soft_refs,
652 size_t size,
653 bool is_tlab) {
654 assert(full || size > 0, "otherwise we don't want to collect");
655
656 SerialHeap* heap = SerialHeap::heap();
657
658 // If the next generation is too full to accommodate promotion
659 // from this generation, pass on collection; let the next generation
660 // do it.
661 if (!collection_attempt_is_safe()) {
662 log_trace(gc)(":: Collection attempt not safe ::");
663 heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
664 return;
665 }
666 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
667 _gc_timer->register_gc_start();
668 _gc_tracer->report_gc_start(heap->gc_cause(), _gc_timer->gc_start());
669 _ref_processor->start_discovery(clear_all_soft_refs);
670
671 _old_gen = heap->old_gen();
672
673 init_assuming_no_promotion_failure();
674
675 GCTraceTime(Trace, gc, phases) tm("DefNew", nullptr, heap->gc_cause());
676
677 heap->trace_heap_before_gc(_gc_tracer);
678
679 // These can be shared for all code paths
680 IsAliveClosure is_alive(this);
681
682 age_table()->clear();
683 to()->clear(SpaceDecorator::Mangle);
684 // The preserved marks should be empty at the start of the GC.
685 _preserved_marks_set.init(1);
686
687 assert(heap->no_allocs_since_save_marks(),
688 "save marks have not been newly set.");
689
690 YoungGenScanClosure young_gen_cl(this);
691 OldGenScanClosure old_gen_cl(this);
692
693 FastEvacuateFollowersClosure evacuate_followers(heap,
694 &young_gen_cl,
695 &old_gen_cl);
696
697 assert(heap->no_allocs_since_save_marks(),
698 "save marks have not been newly set.");
699
700 {
701 StrongRootsScope srs(0);
702 RootScanClosure root_cl{this};
703 CLDScanClosure cld_cl{this};
704
705 MarkingCodeBlobClosure code_cl(&root_cl,
706 CodeBlobToOopClosure::FixRelocations,
707 false /* keepalive_nmethods */);
708
709 heap->process_roots(SerialHeap::SO_ScavengeCodeCache,
710 &root_cl,
711 &cld_cl,
712 &cld_cl,
713 &code_cl);
714
715 _old_gen->scan_old_to_young_refs();
716 }
717
718 // "evacuate followers".
719 evacuate_followers.do_void();
720
721 {
722 // Reference processing
723 KeepAliveClosure keep_alive(this);
724 ReferenceProcessor* rp = ref_processor();
725 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
726 SerialGCRefProcProxyTask task(is_alive, keep_alive, evacuate_followers);
727 const ReferenceProcessorStats& stats = rp->process_discovered_references(task, pt);
728 _gc_tracer->report_gc_reference_stats(stats);
729 _gc_tracer->report_tenuring_threshold(tenuring_threshold());
730 pt.print_all_references();
731 }
732 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
733
734 {
735 AdjustWeakRootClosure cl{this};
736 WeakProcessor::weak_oops_do(&is_alive, &cl);
737 }
738
739 // Verify that the usage of keep_alive didn't copy any objects.
740 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
741
742 _string_dedup_requests.flush();
743
744 if (!_promotion_failed) {
745 // Swap the survivor spaces.
746 eden()->clear(SpaceDecorator::Mangle);
747 from()->clear(SpaceDecorator::Mangle);
748 if (ZapUnusedHeapArea) {
749 // This is now done here because of the piece-meal mangling which
750 // can check for valid mangling at intermediate points in the
751 // collection(s). When a young collection fails to collect
752 // sufficient space resizing of the young generation can occur
753 // an redistribute the spaces in the young generation. Mangle
754 // here so that unzapped regions don't get distributed to
755 // other spaces.
756 to()->mangle_unused_area();
757 }
758 swap_spaces();
759
760 assert(to()->is_empty(), "to space should be empty now");
761
762 adjust_desired_tenuring_threshold();
763
764 assert(!heap->incremental_collection_failed(), "Should be clear");
765 } else {
766 assert(_promo_failure_scan_stack.is_empty(), "post condition");
767 _promo_failure_scan_stack.clear(true); // Clear cached segments.
768
769 remove_forwarding_pointers();
770 log_info(gc, promotion)("Promotion failed");
771 // Add to-space to the list of space to compact
772 // when a promotion failure has occurred. In that
773 // case there can be live objects in to-space
774 // as a result of a partial evacuation of eden
775 // and from-space.
776 swap_spaces(); // For uniformity wrt ParNewGeneration.
777 from()->set_next_compaction_space(to());
778 heap->set_incremental_collection_failed();
779
780 _gc_tracer->report_promotion_failed(_promotion_failed_info);
781
782 // Reset the PromotionFailureALot counters.
783 NOT_PRODUCT(heap->reset_promotion_should_fail();)
784 }
785 // We should have processed and cleared all the preserved marks.
786 _preserved_marks_set.reclaim();
787
788 heap->trace_heap_after_gc(_gc_tracer);
789
790 _gc_timer->register_gc_end();
791
792 _gc_tracer->report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
793 }
794
795 void DefNewGeneration::init_assuming_no_promotion_failure() {
796 _promotion_failed = false;
797 _promotion_failed_info.reset();
798 from()->set_next_compaction_space(nullptr);
799 }
800
801 void DefNewGeneration::remove_forwarding_pointers() {
802 assert(_promotion_failed, "precondition");
803
804 // Will enter Full GC soon due to failed promotion. Must reset the mark word
805 // of objs in young-gen so that no objs are marked (forwarded) when Full GC
806 // starts. (The mark word is overloaded: `is_marked()` == `is_forwarded()`.)
807 struct ResetForwardedMarkWord : ObjectClosure {
808 void do_object(oop obj) override {
809 if (obj->is_forwarded()) {
810 obj->forward_safe_init_mark();
811 }
812 }
813 } cl;
814 eden()->object_iterate(&cl);
815 from()->object_iterate(&cl);
816
817 restore_preserved_marks();
818 }
819
820 void DefNewGeneration::restore_preserved_marks() {
821 _preserved_marks_set.restore(nullptr);
822 }
823
824 void DefNewGeneration::handle_promotion_failure(oop old) {
825 log_debug(gc, promotion)("Promotion failure size = " SIZE_FORMAT ") ", old->size());
826
827 _promotion_failed = true;
828 _promotion_failed_info.register_copy_failure(old->size());
829 _preserved_marks_set.get()->push_if_necessary(old, old->mark());
830
831 ContinuationGCSupport::transform_stack_chunk(old);
832
833 // forward to self
834 old->forward_to_self();
835
836 _promo_failure_scan_stack.push(old);
837
838 if (!_promo_failure_drain_in_progress) {
839 // prevent recursion in copy_to_survivor_space()
840 _promo_failure_drain_in_progress = true;
841 drain_promo_failure_scan_stack();
842 _promo_failure_drain_in_progress = false;
843 }
844 }
845
846 oop DefNewGeneration::copy_to_survivor_space(oop old) {
847 assert(is_in_reserved(old) && !old->is_forwarded(),
848 "shouldn't be scavenging this oop");
849 size_t s = old->size();
850 oop obj = nullptr;
851
852 // Try allocating obj in to-space (unless too old)
853 if (old->age() < tenuring_threshold()) {
854 obj = cast_to_oop(to()->allocate(s));
855 }
856
857 bool new_obj_is_tenured = false;
858 // Otherwise try allocating obj tenured
859 if (obj == nullptr) {
860 obj = _old_gen->promote(old, s);
861 if (obj == nullptr) {
862 handle_promotion_failure(old);
863 return old;
864 }
865
866 ContinuationGCSupport::transform_stack_chunk(obj);
867
868 new_obj_is_tenured = true;
869 } else {
870 // Prefetch beyond obj
871 const intx interval = PrefetchCopyIntervalInBytes;
872 Prefetch::write(obj, interval);
873
874 // Copy obj
875 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s);
876
877 ContinuationGCSupport::transform_stack_chunk(obj);
878
879 // Increment age if obj still in new generation
880 obj->incr_age();
881 age_table()->add(obj, s);
882 }
883
884 // Done, insert forward pointer to obj in this header
885 old->forward_to(obj);
886
887 if (SerialStringDedup::is_candidate_from_evacuation(obj, new_obj_is_tenured)) {
888 // Record old; request adds a new weak reference, which reference
889 // processing expects to refer to a from-space object.
890 _string_dedup_requests.add(old);
891 }
892 return obj;
893 }
894
895 void DefNewGeneration::drain_promo_failure_scan_stack() {
896 PromoteFailureClosure cl{this};
897 while (!_promo_failure_scan_stack.is_empty()) {
898 oop obj = _promo_failure_scan_stack.pop();
899 obj->oop_iterate(&cl);
900 }
901 }
902
903 void DefNewGeneration::save_marks() {
904 eden()->set_saved_mark();
905 to()->set_saved_mark();
906 from()->set_saved_mark();
907 }
908
909
910 bool DefNewGeneration::no_allocs_since_save_marks() {
911 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
912 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
913 return to()->saved_mark_at_top();
914 }
915
916 void DefNewGeneration::contribute_scratch(void*& scratch, size_t& num_words) {
917 if (_promotion_failed) {
918 return;
919 }
920
921 const size_t MinFreeScratchWords = 100;
922
923 ContiguousSpace* to_space = to();
924 const size_t free_words = pointer_delta(to_space->end(), to_space->top());
925 if (free_words >= MinFreeScratchWords) {
926 scratch = to_space->top();
927 num_words = free_words;
928 }
929 }
930
931 void DefNewGeneration::reset_scratch() {
932 // If contributing scratch in to_space, mangle all of
933 // to_space if ZapUnusedHeapArea. This is needed because
934 // top is not maintained while using to-space as scratch.
935 if (ZapUnusedHeapArea) {
936 to()->mangle_unused_area_complete();
937 }
938 }
939
940 bool DefNewGeneration::collection_attempt_is_safe() {
941 if (!to()->is_empty()) {
942 log_trace(gc)(":: to is not empty ::");
943 return false;
944 }
945 if (_old_gen == nullptr) {
946 _old_gen = SerialHeap::heap()->old_gen();
947 }
948 return _old_gen->promotion_attempt_is_safe(used());
949 }
950
951 void DefNewGeneration::gc_epilogue(bool full) {
952 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
953
954 assert(!GCLocker::is_active(), "We should not be executing here");
955 // Check if the heap is approaching full after a collection has
956 // been done. Generally the young generation is empty at
957 // a minimum at the end of a collection. If it is not, then
958 // the heap is approaching full.
959 SerialHeap* gch = SerialHeap::heap();
960 if (full) {
961 DEBUG_ONLY(seen_incremental_collection_failed = false;)
962 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
963 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
964 GCCause::to_string(gch->gc_cause()));
965 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
966 set_should_allocate_from_space(); // we seem to be running out of space
967 } else {
968 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
969 GCCause::to_string(gch->gc_cause()));
970 gch->clear_incremental_collection_failed(); // We just did a full collection
971 clear_should_allocate_from_space(); // if set
972 }
973 } else {
974 #ifdef ASSERT
975 // It is possible that incremental_collection_failed() == true
976 // here, because an attempted scavenge did not succeed. The policy
977 // is normally expected to cause a full collection which should
978 // clear that condition, so we should not be here twice in a row
979 // with incremental_collection_failed() == true without having done
980 // a full collection in between.
981 if (!seen_incremental_collection_failed &&
982 gch->incremental_collection_failed()) {
983 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
984 GCCause::to_string(gch->gc_cause()));
985 seen_incremental_collection_failed = true;
986 } else if (seen_incremental_collection_failed) {
987 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
988 GCCause::to_string(gch->gc_cause()));
989 seen_incremental_collection_failed = false;
990 }
991 #endif // ASSERT
992 }
993
994 if (ZapUnusedHeapArea) {
995 eden()->check_mangled_unused_area_complete();
996 from()->check_mangled_unused_area_complete();
997 to()->check_mangled_unused_area_complete();
998 }
999
1000 // update the generation and space performance counters
1001 update_counters();
1002 gch->counters()->update_counters();
1003 }
1004
1005 void DefNewGeneration::record_spaces_top() {
1006 assert(ZapUnusedHeapArea, "Not mangling unused space");
1007 eden()->set_top_for_allocations();
1008 to()->set_top_for_allocations();
1009 from()->set_top_for_allocations();
1010 }
1011
1012 void DefNewGeneration::update_counters() {
1013 if (UsePerfData) {
1014 _eden_counters->update_all();
1015 _from_counters->update_all();
1016 _to_counters->update_all();
1017 _gen_counters->update_all();
1018 }
1019 }
1020
1021 void DefNewGeneration::verify() {
1022 eden()->verify();
1023 from()->verify();
1024 to()->verify();
1025 }
1026
1027 void DefNewGeneration::print_on(outputStream* st) const {
1028 Generation::print_on(st);
1029 st->print(" eden");
1030 eden()->print_on(st);
1031 st->print(" from");
1032 from()->print_on(st);
1033 st->print(" to ");
1034 to()->print_on(st);
1035 }
1036
1037
1038 const char* DefNewGeneration::name() const {
1039 return "def new generation";
1040 }
1041
1042 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1043 // This is the slow-path allocation for the DefNewGeneration.
1044 // Most allocations are fast-path in compiled code.
1045 // We try to allocate from the eden. If that works, we are happy.
1046 // Note that since DefNewGeneration supports lock-free allocation, we
1047 // have to use it here, as well.
1048 HeapWord* result = eden()->par_allocate(word_size);
1049 if (result == nullptr) {
1050 // If the eden is full and the last collection bailed out, we are running
1051 // out of heap space, and we try to allocate the from-space, too.
1052 // allocate_from_space can't be inlined because that would introduce a
1053 // circular dependency at compile time.
1054 result = allocate_from_space(word_size);
1055 }
1056 return result;
1057 }
1058
1059 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1060 bool is_tlab) {
1061 return eden()->par_allocate(word_size);
1062 }
1063
1064 size_t DefNewGeneration::tlab_capacity() const {
1065 return eden()->capacity();
1066 }
1067
1068 size_t DefNewGeneration::tlab_used() const {
1069 return eden()->used();
1070 }
1071
1072 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1073 return unsafe_max_alloc_nogc();
1074 }