1 /*
2 * Copyright (c) 2001, 2024, 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/serialGcRefProcProxyTask.hpp"
28 #include "gc/serial/serialHeap.inline.hpp"
29 #include "gc/serial/serialStringDedup.inline.hpp"
30 #include "gc/serial/tenuredGeneration.hpp"
31 #include "gc/shared/adaptiveSizePolicy.hpp"
32 #include "gc/shared/ageTable.inline.hpp"
33 #include "gc/shared/collectorCounters.hpp"
34 #include "gc/shared/continuationGCSupport.inline.hpp"
35 #include "gc/shared/gcArguments.hpp"
36 #include "gc/shared/gcHeapSummary.hpp"
37 #include "gc/shared/gcLocker.hpp"
38 #include "gc/shared/gcPolicyCounters.hpp"
39 #include "gc/shared/gcTimer.hpp"
40 #include "gc/shared/gcTrace.hpp"
41 #include "gc/shared/gcTraceTime.inline.hpp"
42 #include "gc/shared/referencePolicy.hpp"
43 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
44 #include "gc/shared/space.hpp"
45 #include "gc/shared/spaceDecorator.hpp"
46 #include "gc/shared/strongRootsScope.hpp"
47 #include "gc/shared/weakProcessor.hpp"
48 #include "logging/log.hpp"
49 #include "memory/iterator.inline.hpp"
50 #include "memory/resourceArea.hpp"
51 #include "oops/instanceRefKlass.hpp"
52 #include "oops/oop.inline.hpp"
53 #include "runtime/java.hpp"
54 #include "runtime/javaThread.hpp"
55 #include "runtime/prefetch.inline.hpp"
56 #include "runtime/threads.hpp"
57 #include "utilities/align.hpp"
58 #include "utilities/copy.hpp"
59 #include "utilities/globalDefinitions.hpp"
60 #include "utilities/stack.inline.hpp"
61
62 class PromoteFailureClosure : public InHeapScanClosure {
63 template <typename T>
64 void do_oop_work(T* p) {
65 assert(is_in_young_gen(p), "promote-fail objs must be in young-gen");
66 assert(!SerialHeap::heap()->young_gen()->to()->is_in_reserved(p), "must not be in to-space");
67
68 try_scavenge(p, [] (auto) {});
69 }
70 public:
71 PromoteFailureClosure(DefNewGeneration* g) : InHeapScanClosure(g) {}
72
73 void do_oop(oop* p) { do_oop_work(p); }
74 void do_oop(narrowOop* p) { do_oop_work(p); }
75 };
76
77 class RootScanClosure : public OffHeapScanClosure {
78 template <typename T>
79 void do_oop_work(T* p) {
80 assert(!SerialHeap::heap()->is_in_reserved(p), "outside the heap");
81
82 try_scavenge(p, [] (auto) {});
83 }
84 public:
85 RootScanClosure(DefNewGeneration* g) : OffHeapScanClosure(g) {}
86
87 void do_oop(oop* p) { do_oop_work(p); }
88 void do_oop(narrowOop* p) { do_oop_work(p); }
89 };
90
91 class CLDScanClosure: public CLDClosure {
92
93 class CLDOopClosure : public OffHeapScanClosure {
94 ClassLoaderData* _scanned_cld;
95
96 template <typename T>
97 void do_oop_work(T* p) {
98 assert(!SerialHeap::heap()->is_in_reserved(p), "outside the heap");
99
100 try_scavenge(p, [&] (oop new_obj) {
101 assert(_scanned_cld != nullptr, "inv");
102 if (is_in_young_gen(new_obj) && !_scanned_cld->has_modified_oops()) {
103 _scanned_cld->record_modified_oops();
104 }
105 });
106 }
107
108 public:
109 CLDOopClosure(DefNewGeneration* g) : OffHeapScanClosure(g),
110 _scanned_cld(nullptr) {}
111
112 void set_scanned_cld(ClassLoaderData* cld) {
113 assert(cld == nullptr || _scanned_cld == nullptr, "Must be");
114 _scanned_cld = cld;
115 }
116
117 void do_oop(oop* p) { do_oop_work(p); }
118 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
119 };
120
121 CLDOopClosure _oop_closure;
122 public:
123 CLDScanClosure(DefNewGeneration* g) : _oop_closure(g) {}
124
125 void do_cld(ClassLoaderData* cld) {
126 // If the cld has not been dirtied we know that there's
127 // no references into the young gen and we can skip it.
128 if (cld->has_modified_oops()) {
129
130 // Tell the closure which CLD is being scanned so that it can be dirtied
131 // if oops are left pointing into the young gen.
132 _oop_closure.set_scanned_cld(cld);
133
134 // Clean the cld since we're going to scavenge all the metadata.
135 cld->oops_do(&_oop_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);
136
137 _oop_closure.set_scanned_cld(nullptr);
138 }
139 }
140 };
141
142 class IsAliveClosure: public BoolObjectClosure {
143 HeapWord* _young_gen_end;
144 public:
145 IsAliveClosure(DefNewGeneration* g): _young_gen_end(g->reserved().end()) {}
146
147 bool do_object_b(oop p) {
148 return cast_from_oop<HeapWord*>(p) >= _young_gen_end || p->is_forwarded();
149 }
150 };
151
152 class AdjustWeakRootClosure: public OffHeapScanClosure {
153 template <class T>
154 void do_oop_work(T* p) {
155 DEBUG_ONLY(SerialHeap* heap = SerialHeap::heap();)
156 assert(!heap->is_in_reserved(p), "outside the heap");
157
158 oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);
159 if (is_in_young_gen(obj)) {
160 assert(!heap->young_gen()->to()->is_in_reserved(obj), "inv");
161 assert(obj->is_forwarded(), "forwarded before weak-root-processing");
162 oop new_obj = obj->forwardee();
163 RawAccess<IS_NOT_NULL>::oop_store(p, new_obj);
164 }
165 }
166 public:
167 AdjustWeakRootClosure(DefNewGeneration* g): OffHeapScanClosure(g) {}
168
169 void do_oop(oop* p) { do_oop_work(p); }
170 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
171 };
172
173 class KeepAliveClosure: public OopClosure {
174 DefNewGeneration* _young_gen;
175 HeapWord* _young_gen_end;
176 CardTableRS* _rs;
177
178 bool is_in_young_gen(void* p) const {
179 return p < _young_gen_end;
180 }
181
182 template <class T>
183 void do_oop_work(T* p) {
184 oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);
185
186 if (is_in_young_gen(obj)) {
187 oop new_obj = obj->is_forwarded() ? obj->forwardee()
188 : _young_gen->copy_to_survivor_space(obj);
189 RawAccess<IS_NOT_NULL>::oop_store(p, new_obj);
190
191 if (is_in_young_gen(new_obj) && !is_in_young_gen(p)) {
192 _rs->inline_write_ref_field_gc(p);
193 }
194 }
195 }
196 public:
197 KeepAliveClosure(DefNewGeneration* g) :
198 _young_gen(g),
199 _young_gen_end(g->reserved().end()),
200 _rs(SerialHeap::heap()->rem_set()) {}
201
202 void do_oop(oop* p) { do_oop_work(p); }
203 void do_oop(narrowOop* p) { do_oop_work(p); }
204 };
205
206 class FastEvacuateFollowersClosure: public VoidClosure {
207 SerialHeap* _heap;
208 YoungGenScanClosure* _young_cl;
209 OldGenScanClosure* _old_cl;
210 public:
211 FastEvacuateFollowersClosure(SerialHeap* heap,
212 YoungGenScanClosure* young_cl,
213 OldGenScanClosure* old_cl) :
214 _heap(heap), _young_cl(young_cl), _old_cl(old_cl)
215 {}
216
217 void do_void() {
218 _heap->scan_evacuated_objs(_young_cl, _old_cl);
219 }
220 };
221
222 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
223 size_t initial_size,
224 size_t min_size,
225 size_t max_size,
226 const char* policy)
227 : Generation(rs, initial_size),
228 _promotion_failed(false),
229 _promo_failure_drain_in_progress(false),
230 _string_dedup_requests()
231 {
232 MemRegion cmr((HeapWord*)_virtual_space.low(),
233 (HeapWord*)_virtual_space.high());
234 SerialHeap* gch = SerialHeap::heap();
235
236 gch->rem_set()->resize_covered_region(cmr);
237
238 _eden_space = new ContiguousSpace();
239 _from_space = new ContiguousSpace();
240 _to_space = new ContiguousSpace();
241
242 // Compute the maximum eden and survivor space sizes. These sizes
243 // are computed assuming the entire reserved space is committed.
244 // These values are exported as performance counters.
245 uintx size = _virtual_space.reserved_size();
246 _max_survivor_size = compute_survivor_size(size, SpaceAlignment);
247 _max_eden_size = size - (2*_max_survivor_size);
248
249 // allocate the performance counters
250
251 // Generation counters -- generation 0, 3 subspaces
252 _gen_counters = new GenerationCounters("new", 0, 3,
253 min_size, max_size, &_virtual_space);
254 _gc_counters = new CollectorCounters(policy, 0);
255
256 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
257 _gen_counters);
258 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
259 _gen_counters);
260 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
261 _gen_counters);
262
263 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
264 update_counters();
265 _old_gen = nullptr;
266 _tenuring_threshold = MaxTenuringThreshold;
267 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
268
269 _ref_processor = nullptr;
270
271 _gc_timer = new STWGCTimer();
272
273 _gc_tracer = new DefNewTracer();
274 }
275
276 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
277 bool clear_space,
278 bool mangle_space) {
279 // If the spaces are being cleared (only done at heap initialization
280 // currently), the survivor spaces need not be empty.
281 // Otherwise, no care is taken for used areas in the survivor spaces
282 // so check.
283 assert(clear_space || (to()->is_empty() && from()->is_empty()),
284 "Initialization of the survivor spaces assumes these are empty");
285
286 // Compute sizes
287 uintx size = _virtual_space.committed_size();
288 uintx survivor_size = compute_survivor_size(size, SpaceAlignment);
289 uintx eden_size = size - (2*survivor_size);
290 if (eden_size > max_eden_size()) {
291 // Need to reduce eden_size to satisfy the max constraint. The delta needs
292 // to be 2*SpaceAlignment aligned so that both survivors are properly
293 // aligned.
294 uintx eden_delta = align_up(eden_size - max_eden_size(), 2*SpaceAlignment);
295 eden_size -= eden_delta;
296 survivor_size += eden_delta/2;
297 }
298 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
299
300 if (eden_size < minimum_eden_size) {
301 // May happen due to 64Kb rounding, if so adjust eden size back up
302 minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment);
303 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
304 uintx unaligned_survivor_size =
305 align_down(maximum_survivor_size, SpaceAlignment);
306 survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment);
307 eden_size = size - (2*survivor_size);
308 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
309 assert(eden_size >= minimum_eden_size, "just checking");
310 }
311
312 char *eden_start = _virtual_space.low();
313 char *from_start = eden_start + eden_size;
314 char *to_start = from_start + survivor_size;
315 char *to_end = to_start + survivor_size;
316
317 assert(to_end == _virtual_space.high(), "just checking");
318 assert(is_aligned(eden_start, SpaceAlignment), "checking alignment");
319 assert(is_aligned(from_start, SpaceAlignment), "checking alignment");
320 assert(is_aligned(to_start, SpaceAlignment), "checking alignment");
321
322 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
323 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
324 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
325
326 // A minimum eden size implies that there is a part of eden that
327 // is being used and that affects the initialization of any
328 // newly formed eden.
329 bool live_in_eden = minimum_eden_size > 0;
330
331 // Reset the spaces for their new regions.
332 eden()->initialize(edenMR,
333 clear_space && !live_in_eden,
334 SpaceDecorator::Mangle);
335 // If clear_space and live_in_eden, we will not have cleared any
336 // portion of eden above its top. This can cause newly
337 // expanded space not to be mangled if using ZapUnusedHeapArea.
338 // We explicitly do such mangling here.
339 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
340 eden()->mangle_unused_area();
341 }
342 from()->initialize(fromMR, clear_space, mangle_space);
343 to()->initialize(toMR, clear_space, mangle_space);
344 }
345
346 void DefNewGeneration::swap_spaces() {
347 ContiguousSpace* s = from();
348 _from_space = to();
349 _to_space = s;
350
351 if (UsePerfData) {
352 CSpaceCounters* c = _from_counters;
353 _from_counters = _to_counters;
354 _to_counters = c;
355 }
356 }
357
358 bool DefNewGeneration::expand(size_t bytes) {
359 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
360 bool success = _virtual_space.expand_by(bytes);
361 if (success && ZapUnusedHeapArea) {
362 // Mangle newly committed space immediately because it
363 // can be done here more simply that after the new
364 // spaces have been computed.
365 HeapWord* new_high = (HeapWord*) _virtual_space.high();
366 MemRegion mangle_region(prev_high, new_high);
367 SpaceMangler::mangle_region(mangle_region);
368 }
369
370 // Do not attempt an expand-to-the reserve size. The
371 // request should properly observe the maximum size of
372 // the generation so an expand-to-reserve should be
373 // unnecessary. Also a second call to expand-to-reserve
374 // value potentially can cause an undue expansion.
375 // For example if the first expand fail for unknown reasons,
376 // but the second succeeds and expands the heap to its maximum
377 // value.
378 if (GCLocker::is_active()) {
379 log_debug(gc)("Garbage collection disabled, expanded heap instead");
380 }
381
382 return success;
383 }
384
385 size_t DefNewGeneration::calculate_thread_increase_size(int threads_count) const {
386 size_t thread_increase_size = 0;
387 // Check an overflow at 'threads_count * NewSizeThreadIncrease'.
388 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
389 thread_increase_size = threads_count * NewSizeThreadIncrease;
390 }
391 return thread_increase_size;
392 }
393
394 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
395 size_t new_size_before,
396 size_t alignment,
397 size_t thread_increase_size) const {
398 size_t desired_new_size = new_size_before;
399
400 if (NewSizeThreadIncrease > 0 && thread_increase_size > 0) {
401
402 // 1. Check an overflow at 'new_size_candidate + thread_increase_size'.
403 if (new_size_candidate <= max_uintx - thread_increase_size) {
404 new_size_candidate += thread_increase_size;
405
406 // 2. Check an overflow at 'align_up'.
407 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
408 if (new_size_candidate <= aligned_max) {
409 desired_new_size = align_up(new_size_candidate, alignment);
410 }
411 }
412 }
413
414 return desired_new_size;
415 }
416
417 void DefNewGeneration::compute_new_size() {
418 // This is called after a GC that includes the old generation, so from-space
419 // will normally be empty.
420 // Note that we check both spaces, since if scavenge failed they revert roles.
421 // If not we bail out (otherwise we would have to relocate the objects).
422 if (!from()->is_empty() || !to()->is_empty()) {
423 return;
424 }
425
426 SerialHeap* gch = SerialHeap::heap();
427
428 size_t old_size = gch->old_gen()->capacity();
429 size_t new_size_before = _virtual_space.committed_size();
430 size_t min_new_size = NewSize;
431 size_t max_new_size = reserved().byte_size();
432 assert(min_new_size <= new_size_before &&
433 new_size_before <= max_new_size,
434 "just checking");
435 // All space sizes must be multiples of Generation::GenGrain.
436 size_t alignment = Generation::GenGrain;
437
438 int threads_count = Threads::number_of_non_daemon_threads();
439 size_t thread_increase_size = calculate_thread_increase_size(threads_count);
440
441 size_t new_size_candidate = old_size / NewRatio;
442 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
443 // and reverts to previous value if any overflow happens
444 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before,
445 alignment, thread_increase_size);
446
447 // Adjust new generation size
448 desired_new_size = clamp(desired_new_size, min_new_size, max_new_size);
449 assert(desired_new_size <= max_new_size, "just checking");
450
451 bool changed = false;
452 if (desired_new_size > new_size_before) {
453 size_t change = desired_new_size - new_size_before;
454 assert(change % alignment == 0, "just checking");
455 if (expand(change)) {
456 changed = true;
457 }
458 // If the heap failed to expand to the desired size,
459 // "changed" will be false. If the expansion failed
460 // (and at this point it was expected to succeed),
461 // ignore the failure (leaving "changed" as false).
462 }
463 if (desired_new_size < new_size_before && eden()->is_empty()) {
464 // bail out of shrinking if objects in eden
465 size_t change = new_size_before - desired_new_size;
466 assert(change % alignment == 0, "just checking");
467 _virtual_space.shrink_by(change);
468 changed = true;
469 }
470 if (changed) {
471 // The spaces have already been mangled at this point but
472 // may not have been cleared (set top = bottom) and should be.
473 // Mangling was done when the heap was being expanded.
474 compute_space_boundaries(eden()->used(),
475 SpaceDecorator::Clear,
476 SpaceDecorator::DontMangle);
477 MemRegion cmr((HeapWord*)_virtual_space.low(),
478 (HeapWord*)_virtual_space.high());
479 gch->rem_set()->resize_covered_region(cmr);
480
481 log_debug(gc, ergo, heap)(
482 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
483 new_size_before/K, _virtual_space.committed_size()/K,
484 eden()->capacity()/K, from()->capacity()/K);
485 log_trace(gc, ergo, heap)(
486 " [allowed " SIZE_FORMAT "K extra for %d threads]",
487 thread_increase_size/K, threads_count);
488 }
489 }
490
491 void DefNewGeneration::ref_processor_init() {
492 assert(_ref_processor == nullptr, "a reference processor already exists");
493 assert(!_reserved.is_empty(), "empty generation?");
494 _span_based_discoverer.set_span(_reserved);
495 _ref_processor = new ReferenceProcessor(&_span_based_discoverer); // a vanilla reference processor
496 }
497
498 size_t DefNewGeneration::capacity() const {
499 return eden()->capacity()
500 + from()->capacity(); // to() is only used during scavenge
501 }
502
503
504 size_t DefNewGeneration::used() const {
505 return eden()->used()
506 + from()->used(); // to() is only used during scavenge
507 }
508
509
510 size_t DefNewGeneration::free() const {
511 return eden()->free()
512 + from()->free(); // to() is only used during scavenge
513 }
514
515 size_t DefNewGeneration::max_capacity() const {
516 const size_t reserved_bytes = reserved().byte_size();
517 return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment);
518 }
519
520 bool DefNewGeneration::is_in(const void* p) const {
521 return eden()->is_in(p)
522 || from()->is_in(p)
523 || to() ->is_in(p);
524 }
525
526 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
527 return eden()->free();
528 }
529
530 size_t DefNewGeneration::capacity_before_gc() const {
531 return eden()->capacity();
532 }
533
534 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
535 eden()->object_iterate(blk);
536 from()->object_iterate(blk);
537 }
538
539 // If "p" is in the space, returns the address of the start of the
540 // "block" that contains "p". We say "block" instead of "object" since
541 // some heaps may not pack objects densely; a chunk may either be an
542 // object or a non-object. If "p" is not in the space, return null.
543 // Very general, slow implementation.
544 static HeapWord* block_start_const(const ContiguousSpace* cs, const void* p) {
545 assert(MemRegion(cs->bottom(), cs->end()).contains(p),
546 "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
547 p2i(p), p2i(cs->bottom()), p2i(cs->end()));
548 if (p >= cs->top()) {
549 return cs->top();
550 } else {
551 HeapWord* last = cs->bottom();
552 HeapWord* cur = last;
553 while (cur <= p) {
554 last = cur;
555 cur += cast_to_oop(cur)->size();
556 }
557 assert(oopDesc::is_oop(cast_to_oop(last)), PTR_FORMAT " should be an object start", p2i(last));
558 return last;
559 }
560 }
561
562 HeapWord* DefNewGeneration::block_start(const void* p) const {
563 if (eden()->is_in_reserved(p)) {
564 return block_start_const(eden(), p);
565 }
566 if (from()->is_in_reserved(p)) {
567 return block_start_const(from(), p);
568 }
569 assert(to()->is_in_reserved(p), "inv");
570 return block_start_const(to(), p);
571 }
572
573 void DefNewGeneration::adjust_desired_tenuring_threshold() {
574 // Set the desired survivor size to half the real survivor space
575 size_t const survivor_capacity = to()->capacity() / HeapWordSize;
576 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
577
578 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
579
580 if (UsePerfData) {
581 GCPolicyCounters* gc_counters = SerialHeap::heap()->counters();
582 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
583 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
584 }
585
586 age_table()->print_age_table();
587 }
588
589 bool DefNewGeneration::collect(bool clear_all_soft_refs) {
590 SerialHeap* heap = SerialHeap::heap();
591
592 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
593 _gc_timer->register_gc_start();
594 _gc_tracer->report_gc_start(heap->gc_cause(), _gc_timer->gc_start());
595 _ref_processor->start_discovery(clear_all_soft_refs);
596
597 _old_gen = heap->old_gen();
598
599 init_assuming_no_promotion_failure();
600
601 GCTraceTime(Trace, gc, phases) tm("DefNew", nullptr, heap->gc_cause());
602
603 heap->trace_heap_before_gc(_gc_tracer);
604
605 // These can be shared for all code paths
606 IsAliveClosure is_alive(this);
607
608 age_table()->clear();
609 to()->clear(SpaceDecorator::Mangle);
610
611 YoungGenScanClosure young_gen_cl(this);
612 OldGenScanClosure old_gen_cl(this);
613
614 FastEvacuateFollowersClosure evacuate_followers(heap,
615 &young_gen_cl,
616 &old_gen_cl);
617
618 {
619 StrongRootsScope srs(0);
620 RootScanClosure root_cl{this};
621 CLDScanClosure cld_cl{this};
622
623 MarkingNMethodClosure code_cl(&root_cl,
624 NMethodToOopClosure::FixRelocations,
625 false /* keepalive_nmethods */);
626
627 HeapWord* saved_top_in_old_gen = _old_gen->space()->top();
628 heap->process_roots(SerialHeap::SO_ScavengeCodeCache,
629 &root_cl,
630 &cld_cl,
631 &cld_cl,
632 &code_cl);
633
634 _old_gen->scan_old_to_young_refs(saved_top_in_old_gen);
635 }
636
637 // "evacuate followers".
638 evacuate_followers.do_void();
639
640 {
641 // Reference processing
642 KeepAliveClosure keep_alive(this);
643 ReferenceProcessor* rp = ref_processor();
644 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
645 SerialGCRefProcProxyTask task(is_alive, keep_alive, evacuate_followers);
646 const ReferenceProcessorStats& stats = rp->process_discovered_references(task, pt);
647 _gc_tracer->report_gc_reference_stats(stats);
648 _gc_tracer->report_tenuring_threshold(tenuring_threshold());
649 pt.print_all_references();
650 }
651
652 {
653 AdjustWeakRootClosure cl{this};
654 WeakProcessor::weak_oops_do(&is_alive, &cl);
655 }
656
657 _string_dedup_requests.flush();
658
659 if (!_promotion_failed) {
660 // Swap the survivor spaces.
661 eden()->clear(SpaceDecorator::Mangle);
662 from()->clear(SpaceDecorator::Mangle);
663 swap_spaces();
664
665 assert(to()->is_empty(), "to space should be empty now");
666
667 adjust_desired_tenuring_threshold();
668 } else {
669 assert(_promo_failure_scan_stack.is_empty(), "post condition");
670 _promo_failure_scan_stack.clear(true); // Clear cached segments.
671
672 remove_forwarding_pointers();
673 log_info(gc, promotion)("Promotion failed");
674
675 _gc_tracer->report_promotion_failed(_promotion_failed_info);
676
677 // Reset the PromotionFailureALot counters.
678 NOT_PRODUCT(heap->reset_promotion_should_fail();)
679 }
680
681 heap->trace_heap_after_gc(_gc_tracer);
682
683 _gc_timer->register_gc_end();
684
685 _gc_tracer->report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
686
687 return !_promotion_failed;
688 }
689
690 void DefNewGeneration::init_assuming_no_promotion_failure() {
691 _promotion_failed = false;
692 _promotion_failed_info.reset();
693 }
694
695 void DefNewGeneration::remove_forwarding_pointers() {
696 assert(_promotion_failed, "precondition");
697
698 // Will enter Full GC soon due to failed promotion. Must reset the mark word
699 // of objs in young-gen so that no objs are marked (forwarded) when Full GC
700 // starts. (The mark word is overloaded: `is_marked()` == `is_forwarded()`.)
701 struct ResetForwardedMarkWord : ObjectClosure {
702 void do_object(oop obj) override {
703 if (obj->is_self_forwarded()) {
704 obj->unset_self_forwarded();
705 } else if (obj->is_forwarded()) {
706 // To restore the klass-bits in the header.
707 // Needed for object iteration to work properly.
708 obj->set_mark(obj->forwardee()->prototype_mark());
709 }
710 }
711 } cl;
712 eden()->object_iterate(&cl);
713 from()->object_iterate(&cl);
714 }
715
716 void DefNewGeneration::handle_promotion_failure(oop old) {
717 log_debug(gc, promotion)("Promotion failure size = " SIZE_FORMAT ") ", old->size());
718
719 _promotion_failed = true;
720 _promotion_failed_info.register_copy_failure(old->size());
721
722 ContinuationGCSupport::transform_stack_chunk(old);
723
724 // forward to self
725 old->forward_to_self();
726
727 _promo_failure_scan_stack.push(old);
728
729 if (!_promo_failure_drain_in_progress) {
730 // prevent recursion in copy_to_survivor_space()
731 _promo_failure_drain_in_progress = true;
732 drain_promo_failure_scan_stack();
733 _promo_failure_drain_in_progress = false;
734 }
735 }
736
737 oop DefNewGeneration::copy_to_survivor_space(oop old) {
738 assert(is_in_reserved(old) && !old->is_forwarded(),
739 "shouldn't be scavenging this oop");
740 size_t s = old->size();
741 oop obj = nullptr;
742
743 // Try allocating obj in to-space (unless too old)
744 if (old->age() < tenuring_threshold()) {
745 obj = cast_to_oop(to()->allocate(s));
746 }
747
748 bool new_obj_is_tenured = false;
749 // Otherwise try allocating obj tenured
750 if (obj == nullptr) {
751 obj = _old_gen->allocate_for_promotion(old, s);
752 if (obj == nullptr) {
753 handle_promotion_failure(old);
754 return old;
755 }
756
757 new_obj_is_tenured = true;
758 }
759
760 // Prefetch beyond obj
761 const intx interval = PrefetchCopyIntervalInBytes;
762 Prefetch::write(obj, interval);
763
764 // Copy obj
765 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s);
766
767 ContinuationGCSupport::transform_stack_chunk(obj);
768
769 if (!new_obj_is_tenured) {
770 // Increment age if obj still in new generation
771 obj->incr_age();
772 age_table()->add(obj, s);
773 }
774
775 // Done, insert forward pointer to obj in this header
776 old->forward_to(obj);
777
778 if (SerialStringDedup::is_candidate_from_evacuation(obj, new_obj_is_tenured)) {
779 // Record old; request adds a new weak reference, which reference
780 // processing expects to refer to a from-space object.
781 _string_dedup_requests.add(old);
782 }
783 return obj;
784 }
785
786 void DefNewGeneration::drain_promo_failure_scan_stack() {
787 PromoteFailureClosure cl{this};
788 while (!_promo_failure_scan_stack.is_empty()) {
789 oop obj = _promo_failure_scan_stack.pop();
790 obj->oop_iterate(&cl);
791 }
792 }
793
794 void DefNewGeneration::contribute_scratch(void*& scratch, size_t& num_words) {
795 if (_promotion_failed) {
796 return;
797 }
798
799 const size_t MinFreeScratchWords = 100;
800
801 ContiguousSpace* to_space = to();
802 const size_t free_words = pointer_delta(to_space->end(), to_space->top());
803 if (free_words >= MinFreeScratchWords) {
804 scratch = to_space->top();
805 num_words = free_words;
806 }
807 }
808
809 void DefNewGeneration::reset_scratch() {
810 // If contributing scratch in to_space, mangle all of
811 // to_space if ZapUnusedHeapArea. This is needed because
812 // top is not maintained while using to-space as scratch.
813 if (ZapUnusedHeapArea) {
814 to()->mangle_unused_area();
815 }
816 }
817
818 void DefNewGeneration::gc_epilogue(bool full) {
819 assert(!GCLocker::is_active(), "We should not be executing here");
820 // update the generation and space performance counters
821 update_counters();
822 }
823
824 void DefNewGeneration::update_counters() {
825 if (UsePerfData) {
826 _eden_counters->update_all();
827 _from_counters->update_all();
828 _to_counters->update_all();
829 _gen_counters->update_all();
830 }
831 }
832
833 void DefNewGeneration::verify() {
834 eden()->verify();
835 from()->verify();
836 to()->verify();
837 }
838
839 void DefNewGeneration::print_on(outputStream* st) const {
840 st->print(" %-10s", name());
841
842 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
843 capacity()/K, used()/K);
844 st->print_cr(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
845 p2i(_virtual_space.low_boundary()),
846 p2i(_virtual_space.high()),
847 p2i(_virtual_space.high_boundary()));
848
849 st->print(" eden");
850 eden()->print_on(st);
851 st->print(" from");
852 from()->print_on(st);
853 st->print(" to ");
854 to()->print_on(st);
855 }
856
857 HeapWord* DefNewGeneration::allocate(size_t word_size) {
858 // This is the slow-path allocation for the DefNewGeneration.
859 // Most allocations are fast-path in compiled code.
860 // We try to allocate from the eden. If that works, we are happy.
861 // Note that since DefNewGeneration supports lock-free allocation, we
862 // have to use it here, as well.
863 HeapWord* result = eden()->par_allocate(word_size);
864 return result;
865 }
866
867 HeapWord* DefNewGeneration::par_allocate(size_t word_size) {
868 return eden()->par_allocate(word_size);
869 }
870
871 size_t DefNewGeneration::tlab_capacity() const {
872 return eden()->capacity();
873 }
874
875 size_t DefNewGeneration::tlab_used() const {
876 return eden()->used();
877 }
878
879 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
880 return unsafe_max_alloc_nogc();
881 }