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/preservedMarks.inline.hpp"
43 #include "gc/shared/referencePolicy.hpp"
44 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
45 #include "gc/shared/space.hpp"
46 #include "gc/shared/spaceDecorator.hpp"
47 #include "gc/shared/strongRootsScope.hpp"
48 #include "gc/shared/weakProcessor.hpp"
49 #include "logging/log.hpp"
50 #include "memory/iterator.inline.hpp"
51 #include "memory/resourceArea.hpp"
52 #include "oops/instanceRefKlass.hpp"
53 #include "oops/oop.inline.hpp"
54 #include "runtime/java.hpp"
55 #include "runtime/javaThread.hpp"
56 #include "runtime/prefetch.inline.hpp"
57 #include "runtime/threads.hpp"
58 #include "utilities/align.hpp"
59 #include "utilities/copy.hpp"
60 #include "utilities/globalDefinitions.hpp"
61 #include "utilities/stack.inline.hpp"
62
63 class PromoteFailureClosure : public InHeapScanClosure {
64 template <typename T>
65 void do_oop_work(T* p) {
66 assert(is_in_young_gen(p), "promote-fail objs must be in young-gen");
67 assert(!SerialHeap::heap()->young_gen()->to()->is_in_reserved(p), "must not be in to-space");
68
69 try_scavenge(p, [] (auto) {});
70 }
71 public:
72 PromoteFailureClosure(DefNewGeneration* g) : InHeapScanClosure(g) {}
73
74 void do_oop(oop* p) { do_oop_work(p); }
75 void do_oop(narrowOop* p) { do_oop_work(p); }
76 };
77
78 class RootScanClosure : public OffHeapScanClosure {
79 template <typename T>
80 void do_oop_work(T* p) {
81 assert(!SerialHeap::heap()->is_in_reserved(p), "outside the heap");
82
83 try_scavenge(p, [] (auto) {});
84 }
85 public:
86 RootScanClosure(DefNewGeneration* g) : OffHeapScanClosure(g) {}
87
88 void do_oop(oop* p) { do_oop_work(p); }
89 void do_oop(narrowOop* p) { do_oop_work(p); }
90 };
91
92 class CLDScanClosure: public CLDClosure {
93
94 class CLDOopClosure : public OffHeapScanClosure {
95 ClassLoaderData* _scanned_cld;
96
97 template <typename T>
98 void do_oop_work(T* p) {
99 assert(!SerialHeap::heap()->is_in_reserved(p), "outside the heap");
100
101 try_scavenge(p, [&] (oop new_obj) {
102 assert(_scanned_cld != nullptr, "inv");
103 if (is_in_young_gen(new_obj) && !_scanned_cld->has_modified_oops()) {
104 _scanned_cld->record_modified_oops();
105 }
106 });
107 }
108
109 public:
110 CLDOopClosure(DefNewGeneration* g) : OffHeapScanClosure(g),
111 _scanned_cld(nullptr) {}
112
113 void set_scanned_cld(ClassLoaderData* cld) {
114 assert(cld == nullptr || _scanned_cld == nullptr, "Must be");
115 _scanned_cld = cld;
116 }
117
118 void do_oop(oop* p) { do_oop_work(p); }
119 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
120 };
121
122 CLDOopClosure _oop_closure;
123 public:
124 CLDScanClosure(DefNewGeneration* g) : _oop_closure(g) {}
125
126 void do_cld(ClassLoaderData* cld) {
127 // If the cld has not been dirtied we know that there's
128 // no references into the young gen and we can skip it.
129 if (cld->has_modified_oops()) {
130
131 // Tell the closure which CLD is being scanned so that it can be dirtied
132 // if oops are left pointing into the young gen.
133 _oop_closure.set_scanned_cld(cld);
134
135 // Clean the cld since we're going to scavenge all the metadata.
136 cld->oops_do(&_oop_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);
137
138 _oop_closure.set_scanned_cld(nullptr);
139 }
140 }
141 };
142
143 class IsAliveClosure: public BoolObjectClosure {
144 HeapWord* _young_gen_end;
145 public:
146 IsAliveClosure(DefNewGeneration* g): _young_gen_end(g->reserved().end()) {}
147
148 bool do_object_b(oop p) {
149 return cast_from_oop<HeapWord*>(p) >= _young_gen_end || p->is_forwarded();
150 }
151 };
152
153 class AdjustWeakRootClosure: public OffHeapScanClosure {
154 template <class T>
155 void do_oop_work(T* p) {
156 DEBUG_ONLY(SerialHeap* heap = SerialHeap::heap();)
157 assert(!heap->is_in_reserved(p), "outside the heap");
158
159 oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);
160 if (is_in_young_gen(obj)) {
161 assert(!heap->young_gen()->to()->is_in_reserved(obj), "inv");
162 assert(obj->is_forwarded(), "forwarded before weak-root-processing");
163 oop new_obj = obj->forwardee();
164 RawAccess<IS_NOT_NULL>::oop_store(p, new_obj);
165 }
166 }
167 public:
168 AdjustWeakRootClosure(DefNewGeneration* g): OffHeapScanClosure(g) {}
169
170 void do_oop(oop* p) { do_oop_work(p); }
171 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
172 };
173
174 class KeepAliveClosure: public OopClosure {
175 DefNewGeneration* _young_gen;
176 HeapWord* _young_gen_end;
177 CardTableRS* _rs;
178
179 bool is_in_young_gen(void* p) const {
180 return p < _young_gen_end;
181 }
182
183 template <class T>
184 void do_oop_work(T* p) {
185 oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);
186
187 if (is_in_young_gen(obj)) {
188 oop new_obj = obj->is_forwarded() ? obj->forwardee()
189 : _young_gen->copy_to_survivor_space(obj);
190 RawAccess<IS_NOT_NULL>::oop_store(p, new_obj);
191
192 if (is_in_young_gen(new_obj) && !is_in_young_gen(p)) {
193 _rs->inline_write_ref_field_gc(p);
194 }
195 }
196 }
197 public:
198 KeepAliveClosure(DefNewGeneration* g) :
199 _young_gen(g),
200 _young_gen_end(g->reserved().end()),
201 _rs(SerialHeap::heap()->rem_set()) {}
202
203 void do_oop(oop* p) { do_oop_work(p); }
204 void do_oop(narrowOop* p) { do_oop_work(p); }
205 };
206
207 class FastEvacuateFollowersClosure: public VoidClosure {
208 SerialHeap* _heap;
209 YoungGenScanClosure* _young_cl;
210 OldGenScanClosure* _old_cl;
211 public:
212 FastEvacuateFollowersClosure(SerialHeap* heap,
213 YoungGenScanClosure* young_cl,
214 OldGenScanClosure* old_cl) :
215 _heap(heap), _young_cl(young_cl), _old_cl(old_cl)
216 {}
217
218 void do_void() {
219 _heap->scan_evacuated_objs(_young_cl, _old_cl);
220 }
221 };
222
223 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
224 size_t initial_size,
225 size_t min_size,
226 size_t max_size,
227 const char* policy)
228 : Generation(rs, initial_size),
229 _promotion_failed(false),
230 _preserved_marks_set(false /* in_c_heap */),
231 _promo_failure_drain_in_progress(false),
232 _should_allocate_from_space(false),
233 _string_dedup_requests()
234 {
235 MemRegion cmr((HeapWord*)_virtual_space.low(),
236 (HeapWord*)_virtual_space.high());
237 SerialHeap* gch = SerialHeap::heap();
238
239 gch->rem_set()->resize_covered_region(cmr);
240
241 _eden_space = new ContiguousSpace();
242 _from_space = new ContiguousSpace();
243 _to_space = new ContiguousSpace();
244
245 // Compute the maximum eden and survivor space sizes. These sizes
246 // are computed assuming the entire reserved space is committed.
247 // These values are exported as performance counters.
248 uintx size = _virtual_space.reserved_size();
249 _max_survivor_size = compute_survivor_size(size, SpaceAlignment);
250 _max_eden_size = size - (2*_max_survivor_size);
251
252 // allocate the performance counters
253
254 // Generation counters -- generation 0, 3 subspaces
255 _gen_counters = new GenerationCounters("new", 0, 3,
256 min_size, max_size, &_virtual_space);
257 _gc_counters = new CollectorCounters(policy, 0);
258
259 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
260 _gen_counters);
261 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
262 _gen_counters);
263 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
264 _gen_counters);
265
266 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
267 update_counters();
268 _old_gen = nullptr;
269 _tenuring_threshold = MaxTenuringThreshold;
270 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
271
272 _ref_processor = nullptr;
273
274 _gc_timer = new STWGCTimer();
275
276 _gc_tracer = new DefNewTracer();
277 }
278
279 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
280 bool clear_space,
281 bool mangle_space) {
282 // If the spaces are being cleared (only done at heap initialization
283 // currently), the survivor spaces need not be empty.
284 // Otherwise, no care is taken for used areas in the survivor spaces
285 // so check.
286 assert(clear_space || (to()->is_empty() && from()->is_empty()),
287 "Initialization of the survivor spaces assumes these are empty");
288
289 // Compute sizes
290 uintx size = _virtual_space.committed_size();
291 uintx survivor_size = compute_survivor_size(size, SpaceAlignment);
292 uintx eden_size = size - (2*survivor_size);
293 if (eden_size > max_eden_size()) {
294 // Need to reduce eden_size to satisfy the max constraint. The delta needs
295 // to be 2*SpaceAlignment aligned so that both survivors are properly
296 // aligned.
297 uintx eden_delta = align_up(eden_size - max_eden_size(), 2*SpaceAlignment);
298 eden_size -= eden_delta;
299 survivor_size += eden_delta/2;
300 }
301 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
302
303 if (eden_size < minimum_eden_size) {
304 // May happen due to 64Kb rounding, if so adjust eden size back up
305 minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment);
306 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
307 uintx unaligned_survivor_size =
308 align_down(maximum_survivor_size, SpaceAlignment);
309 survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment);
310 eden_size = size - (2*survivor_size);
311 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
312 assert(eden_size >= minimum_eden_size, "just checking");
313 }
314
315 char *eden_start = _virtual_space.low();
316 char *from_start = eden_start + eden_size;
317 char *to_start = from_start + survivor_size;
318 char *to_end = to_start + survivor_size;
319
320 assert(to_end == _virtual_space.high(), "just checking");
321 assert(is_aligned(eden_start, SpaceAlignment), "checking alignment");
322 assert(is_aligned(from_start, SpaceAlignment), "checking alignment");
323 assert(is_aligned(to_start, SpaceAlignment), "checking alignment");
324
325 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
326 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
327 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
328
329 // A minimum eden size implies that there is a part of eden that
330 // is being used and that affects the initialization of any
331 // newly formed eden.
332 bool live_in_eden = minimum_eden_size > 0;
333
334 // Reset the spaces for their new regions.
335 eden()->initialize(edenMR,
336 clear_space && !live_in_eden,
337 SpaceDecorator::Mangle);
338 // If clear_space and live_in_eden, we will not have cleared any
339 // portion of eden above its top. This can cause newly
340 // expanded space not to be mangled if using ZapUnusedHeapArea.
341 // We explicitly do such mangling here.
342 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
343 eden()->mangle_unused_area();
344 }
345 from()->initialize(fromMR, clear_space, mangle_space);
346 to()->initialize(toMR, clear_space, mangle_space);
347 }
348
349 void DefNewGeneration::swap_spaces() {
350 ContiguousSpace* s = from();
351 _from_space = to();
352 _to_space = s;
353
354 if (UsePerfData) {
355 CSpaceCounters* c = _from_counters;
356 _from_counters = _to_counters;
357 _to_counters = c;
358 }
359 }
360
361 bool DefNewGeneration::expand(size_t bytes) {
362 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
363 bool success = _virtual_space.expand_by(bytes);
364 if (success && ZapUnusedHeapArea) {
365 // Mangle newly committed space immediately because it
366 // can be done here more simply that after the new
367 // spaces have been computed.
368 HeapWord* new_high = (HeapWord*) _virtual_space.high();
369 MemRegion mangle_region(prev_high, new_high);
370 SpaceMangler::mangle_region(mangle_region);
371 }
372
373 // Do not attempt an expand-to-the reserve size. The
374 // request should properly observe the maximum size of
375 // the generation so an expand-to-reserve should be
376 // unnecessary. Also a second call to expand-to-reserve
377 // value potentially can cause an undue expansion.
378 // For example if the first expand fail for unknown reasons,
379 // but the second succeeds and expands the heap to its maximum
380 // value.
381 if (GCLocker::is_active()) {
382 log_debug(gc)("Garbage collection disabled, expanded heap instead");
383 }
384
385 return success;
386 }
387
388 size_t DefNewGeneration::calculate_thread_increase_size(int threads_count) const {
389 size_t thread_increase_size = 0;
390 // Check an overflow at 'threads_count * NewSizeThreadIncrease'.
391 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
392 thread_increase_size = threads_count * NewSizeThreadIncrease;
393 }
394 return thread_increase_size;
395 }
396
397 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
398 size_t new_size_before,
399 size_t alignment,
400 size_t thread_increase_size) const {
401 size_t desired_new_size = new_size_before;
402
403 if (NewSizeThreadIncrease > 0 && thread_increase_size > 0) {
404
405 // 1. Check an overflow at 'new_size_candidate + thread_increase_size'.
406 if (new_size_candidate <= max_uintx - thread_increase_size) {
407 new_size_candidate += thread_increase_size;
408
409 // 2. Check an overflow at 'align_up'.
410 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
411 if (new_size_candidate <= aligned_max) {
412 desired_new_size = align_up(new_size_candidate, alignment);
413 }
414 }
415 }
416
417 return desired_new_size;
418 }
419
420 void DefNewGeneration::compute_new_size() {
421 // This is called after a GC that includes the old generation, so from-space
422 // will normally be empty.
423 // Note that we check both spaces, since if scavenge failed they revert roles.
424 // If not we bail out (otherwise we would have to relocate the objects).
425 if (!from()->is_empty() || !to()->is_empty()) {
426 return;
427 }
428
429 SerialHeap* gch = SerialHeap::heap();
430
431 size_t old_size = gch->old_gen()->capacity();
432 size_t new_size_before = _virtual_space.committed_size();
433 size_t min_new_size = NewSize;
434 size_t max_new_size = reserved().byte_size();
435 assert(min_new_size <= new_size_before &&
436 new_size_before <= max_new_size,
437 "just checking");
438 // All space sizes must be multiples of Generation::GenGrain.
439 size_t alignment = Generation::GenGrain;
440
441 int threads_count = Threads::number_of_non_daemon_threads();
442 size_t thread_increase_size = calculate_thread_increase_size(threads_count);
443
444 size_t new_size_candidate = old_size / NewRatio;
445 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
446 // and reverts to previous value if any overflow happens
447 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before,
448 alignment, thread_increase_size);
449
450 // Adjust new generation size
451 desired_new_size = clamp(desired_new_size, min_new_size, max_new_size);
452 assert(desired_new_size <= max_new_size, "just checking");
453
454 bool changed = false;
455 if (desired_new_size > new_size_before) {
456 size_t change = desired_new_size - new_size_before;
457 assert(change % alignment == 0, "just checking");
458 if (expand(change)) {
459 changed = true;
460 }
461 // If the heap failed to expand to the desired size,
462 // "changed" will be false. If the expansion failed
463 // (and at this point it was expected to succeed),
464 // ignore the failure (leaving "changed" as false).
465 }
466 if (desired_new_size < new_size_before && eden()->is_empty()) {
467 // bail out of shrinking if objects in eden
468 size_t change = new_size_before - desired_new_size;
469 assert(change % alignment == 0, "just checking");
470 _virtual_space.shrink_by(change);
471 changed = true;
472 }
473 if (changed) {
474 // The spaces have already been mangled at this point but
475 // may not have been cleared (set top = bottom) and should be.
476 // Mangling was done when the heap was being expanded.
477 compute_space_boundaries(eden()->used(),
478 SpaceDecorator::Clear,
479 SpaceDecorator::DontMangle);
480 MemRegion cmr((HeapWord*)_virtual_space.low(),
481 (HeapWord*)_virtual_space.high());
482 gch->rem_set()->resize_covered_region(cmr);
483
484 log_debug(gc, ergo, heap)(
485 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
486 new_size_before/K, _virtual_space.committed_size()/K,
487 eden()->capacity()/K, from()->capacity()/K);
488 log_trace(gc, ergo, heap)(
489 " [allowed " SIZE_FORMAT "K extra for %d threads]",
490 thread_increase_size/K, threads_count);
491 }
492 }
493
494 void DefNewGeneration::ref_processor_init() {
495 assert(_ref_processor == nullptr, "a reference processor already exists");
496 assert(!_reserved.is_empty(), "empty generation?");
497 _span_based_discoverer.set_span(_reserved);
498 _ref_processor = new ReferenceProcessor(&_span_based_discoverer); // a vanilla reference processor
499 }
500
501 size_t DefNewGeneration::capacity() const {
502 return eden()->capacity()
503 + from()->capacity(); // to() is only used during scavenge
504 }
505
506
507 size_t DefNewGeneration::used() const {
508 return eden()->used()
509 + from()->used(); // to() is only used during scavenge
510 }
511
512
513 size_t DefNewGeneration::free() const {
514 return eden()->free()
515 + from()->free(); // to() is only used during scavenge
516 }
517
518 size_t DefNewGeneration::max_capacity() const {
519 const size_t reserved_bytes = reserved().byte_size();
520 return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment);
521 }
522
523 bool DefNewGeneration::is_in(const void* p) const {
524 return eden()->is_in(p)
525 || from()->is_in(p)
526 || to() ->is_in(p);
527 }
528
529 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
530 return eden()->free();
531 }
532
533 size_t DefNewGeneration::capacity_before_gc() const {
534 return eden()->capacity();
535 }
536
537 size_t DefNewGeneration::contiguous_available() const {
538 return eden()->free();
539 }
540
541
542 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
543 eden()->object_iterate(blk);
544 from()->object_iterate(blk);
545 }
546
547 // If "p" is in the space, returns the address of the start of the
548 // "block" that contains "p". We say "block" instead of "object" since
549 // some heaps may not pack objects densely; a chunk may either be an
550 // object or a non-object. If "p" is not in the space, return null.
551 // Very general, slow implementation.
552 static HeapWord* block_start_const(const ContiguousSpace* cs, const void* p) {
553 assert(MemRegion(cs->bottom(), cs->end()).contains(p),
554 "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
555 p2i(p), p2i(cs->bottom()), p2i(cs->end()));
556 if (p >= cs->top()) {
557 return cs->top();
558 } else {
559 HeapWord* last = cs->bottom();
560 HeapWord* cur = last;
561 while (cur <= p) {
562 last = cur;
563 cur += cast_to_oop(cur)->size();
564 }
565 assert(oopDesc::is_oop(cast_to_oop(last)), PTR_FORMAT " should be an object start", p2i(last));
566 return last;
567 }
568 }
569
570 HeapWord* DefNewGeneration::block_start(const void* p) const {
571 if (eden()->is_in_reserved(p)) {
572 return block_start_const(eden(), p);
573 }
574 if (from()->is_in_reserved(p)) {
575 return block_start_const(from(), p);
576 }
577 assert(to()->is_in_reserved(p), "inv");
578 return block_start_const(to(), p);
579 }
580
581 // The last collection bailed out, we are running out of heap space,
582 // so we try to allocate the from-space, too.
583 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
584 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
585
586 // If the Heap_lock is not locked by this thread, this will be called
587 // again later with the Heap_lock held.
588 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
589
590 HeapWord* result = nullptr;
591 if (do_alloc) {
592 result = from()->allocate(size);
593 }
594
595 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s",
596 size,
597 SerialHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
598 "true" : "false",
599 Heap_lock->is_locked() ? "locked" : "unlocked",
600 from()->free(),
601 should_try_alloc ? "" : " should_allocate_from_space: NOT",
602 do_alloc ? " Heap_lock is not owned by self" : "",
603 result == nullptr ? "null" : "object");
604
605 return result;
606 }
607
608 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, bool is_tlab) {
609 // We don't attempt to expand the young generation (but perhaps we should.)
610 return allocate(size, is_tlab);
611 }
612
613 void DefNewGeneration::adjust_desired_tenuring_threshold() {
614 // Set the desired survivor size to half the real survivor space
615 size_t const survivor_capacity = to()->capacity() / HeapWordSize;
616 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
617
618 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
619
620 if (UsePerfData) {
621 GCPolicyCounters* gc_counters = SerialHeap::heap()->counters();
622 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
623 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
624 }
625
626 age_table()->print_age_table();
627 }
628
629 bool DefNewGeneration::collect(bool clear_all_soft_refs) {
630 SerialHeap* heap = SerialHeap::heap();
631
632 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
633 _gc_timer->register_gc_start();
634 _gc_tracer->report_gc_start(heap->gc_cause(), _gc_timer->gc_start());
635 _ref_processor->start_discovery(clear_all_soft_refs);
636
637 _old_gen = heap->old_gen();
638
639 init_assuming_no_promotion_failure();
640
641 GCTraceTime(Trace, gc, phases) tm("DefNew", nullptr, heap->gc_cause());
642
643 heap->trace_heap_before_gc(_gc_tracer);
644
645 // These can be shared for all code paths
646 IsAliveClosure is_alive(this);
647
648 age_table()->clear();
649 to()->clear(SpaceDecorator::Mangle);
650 // The preserved marks should be empty at the start of the GC.
651 _preserved_marks_set.init(1);
652
653 YoungGenScanClosure young_gen_cl(this);
654 OldGenScanClosure old_gen_cl(this);
655
656 FastEvacuateFollowersClosure evacuate_followers(heap,
657 &young_gen_cl,
658 &old_gen_cl);
659
660 {
661 StrongRootsScope srs(0);
662 RootScanClosure root_cl{this};
663 CLDScanClosure cld_cl{this};
664
665 MarkingNMethodClosure code_cl(&root_cl,
666 NMethodToOopClosure::FixRelocations,
667 false /* keepalive_nmethods */);
668
669 HeapWord* saved_top_in_old_gen = _old_gen->space()->top();
670 heap->process_roots(SerialHeap::SO_ScavengeCodeCache,
671 &root_cl,
672 &cld_cl,
673 &cld_cl,
674 &code_cl);
675
676 _old_gen->scan_old_to_young_refs(saved_top_in_old_gen);
677 }
678
679 // "evacuate followers".
680 evacuate_followers.do_void();
681
682 {
683 // Reference processing
684 KeepAliveClosure keep_alive(this);
685 ReferenceProcessor* rp = ref_processor();
686 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
687 SerialGCRefProcProxyTask task(is_alive, keep_alive, evacuate_followers);
688 const ReferenceProcessorStats& stats = rp->process_discovered_references(task, pt);
689 _gc_tracer->report_gc_reference_stats(stats);
690 _gc_tracer->report_tenuring_threshold(tenuring_threshold());
691 pt.print_all_references();
692 }
693
694 {
695 AdjustWeakRootClosure cl{this};
696 WeakProcessor::weak_oops_do(&is_alive, &cl);
697 }
698
699 _string_dedup_requests.flush();
700
701 if (!_promotion_failed) {
702 // Swap the survivor spaces.
703 eden()->clear(SpaceDecorator::Mangle);
704 from()->clear(SpaceDecorator::Mangle);
705 swap_spaces();
706
707 assert(to()->is_empty(), "to space should be empty now");
708
709 adjust_desired_tenuring_threshold();
710
711 assert(!heap->incremental_collection_failed(), "Should be clear");
712 } else {
713 assert(_promo_failure_scan_stack.is_empty(), "post condition");
714 _promo_failure_scan_stack.clear(true); // Clear cached segments.
715
716 remove_forwarding_pointers();
717 log_info(gc, promotion)("Promotion failed");
718 // Add to-space to the list of space to compact
719 // when a promotion failure has occurred. In that
720 // case there can be live objects in to-space
721 // as a result of a partial evacuation of eden
722 // and from-space.
723 swap_spaces(); // For uniformity wrt ParNewGeneration.
724 heap->set_incremental_collection_failed();
725
726 _gc_tracer->report_promotion_failed(_promotion_failed_info);
727
728 // Reset the PromotionFailureALot counters.
729 NOT_PRODUCT(heap->reset_promotion_should_fail();)
730 }
731 // We should have processed and cleared all the preserved marks.
732 _preserved_marks_set.reclaim();
733
734 heap->trace_heap_after_gc(_gc_tracer);
735
736 _gc_timer->register_gc_end();
737
738 _gc_tracer->report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
739
740 return !_promotion_failed;
741 }
742
743 void DefNewGeneration::init_assuming_no_promotion_failure() {
744 _promotion_failed = false;
745 _promotion_failed_info.reset();
746 }
747
748 void DefNewGeneration::remove_forwarding_pointers() {
749 assert(_promotion_failed, "precondition");
750
751 // Will enter Full GC soon due to failed promotion. Must reset the mark word
752 // of objs in young-gen so that no objs are marked (forwarded) when Full GC
753 // starts. (The mark word is overloaded: `is_marked()` == `is_forwarded()`.)
754 struct ResetForwardedMarkWord : ObjectClosure {
755 void do_object(oop obj) override {
756 if (obj->is_forwarded()) {
757 obj->init_mark();
758 }
759 }
760 } cl;
761 eden()->object_iterate(&cl);
762 from()->object_iterate(&cl);
763
764 restore_preserved_marks();
765 }
766
767 void DefNewGeneration::restore_preserved_marks() {
768 _preserved_marks_set.restore(nullptr);
769 }
770
771 void DefNewGeneration::handle_promotion_failure(oop old) {
772 log_debug(gc, promotion)("Promotion failure size = " SIZE_FORMAT ") ", old->size());
773
774 _promotion_failed = true;
775 _promotion_failed_info.register_copy_failure(old->size());
776 _preserved_marks_set.get()->push_if_necessary(old, old->mark());
777
778 ContinuationGCSupport::transform_stack_chunk(old);
779
780 // forward to self
781 old->forward_to(old);
782
783 _promo_failure_scan_stack.push(old);
784
785 if (!_promo_failure_drain_in_progress) {
786 // prevent recursion in copy_to_survivor_space()
787 _promo_failure_drain_in_progress = true;
788 drain_promo_failure_scan_stack();
789 _promo_failure_drain_in_progress = false;
790 }
791 }
792
793 oop DefNewGeneration::copy_to_survivor_space(oop old) {
794 assert(is_in_reserved(old) && !old->is_forwarded(),
795 "shouldn't be scavenging this oop");
796 size_t s = old->size();
797 oop obj = nullptr;
798
799 // Try allocating obj in to-space (unless too old)
800 if (old->age() < tenuring_threshold()) {
801 obj = cast_to_oop(to()->allocate(s));
802 }
803
804 bool new_obj_is_tenured = false;
805 // Otherwise try allocating obj tenured
806 if (obj == nullptr) {
807 obj = _old_gen->promote(old, s);
808 if (obj == nullptr) {
809 handle_promotion_failure(old);
810 return old;
811 }
812
813 ContinuationGCSupport::transform_stack_chunk(obj);
814
815 new_obj_is_tenured = true;
816 } else {
817 // Prefetch beyond obj
818 const intx interval = PrefetchCopyIntervalInBytes;
819 Prefetch::write(obj, interval);
820
821 // Copy obj
822 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s);
823
824 ContinuationGCSupport::transform_stack_chunk(obj);
825
826 // Increment age if obj still in new generation
827 obj->incr_age();
828 age_table()->add(obj, s);
829 }
830
831 // Done, insert forward pointer to obj in this header
832 old->forward_to(obj);
833
834 if (SerialStringDedup::is_candidate_from_evacuation(obj, new_obj_is_tenured)) {
835 // Record old; request adds a new weak reference, which reference
836 // processing expects to refer to a from-space object.
837 _string_dedup_requests.add(old);
838 }
839 return obj;
840 }
841
842 void DefNewGeneration::drain_promo_failure_scan_stack() {
843 PromoteFailureClosure cl{this};
844 while (!_promo_failure_scan_stack.is_empty()) {
845 oop obj = _promo_failure_scan_stack.pop();
846 obj->oop_iterate(&cl);
847 }
848 }
849
850 void DefNewGeneration::contribute_scratch(void*& scratch, size_t& num_words) {
851 if (_promotion_failed) {
852 return;
853 }
854
855 const size_t MinFreeScratchWords = 100;
856
857 ContiguousSpace* to_space = to();
858 const size_t free_words = pointer_delta(to_space->end(), to_space->top());
859 if (free_words >= MinFreeScratchWords) {
860 scratch = to_space->top();
861 num_words = free_words;
862 }
863 }
864
865 void DefNewGeneration::reset_scratch() {
866 // If contributing scratch in to_space, mangle all of
867 // to_space if ZapUnusedHeapArea. This is needed because
868 // top is not maintained while using to-space as scratch.
869 if (ZapUnusedHeapArea) {
870 to()->mangle_unused_area();
871 }
872 }
873
874 bool DefNewGeneration::collection_attempt_is_safe() {
875 if (!to()->is_empty()) {
876 log_trace(gc)(":: to is not empty ::");
877 return false;
878 }
879 if (_old_gen == nullptr) {
880 _old_gen = SerialHeap::heap()->old_gen();
881 }
882 return _old_gen->promotion_attempt_is_safe(used());
883 }
884
885 void DefNewGeneration::gc_epilogue(bool full) {
886 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
887
888 assert(!GCLocker::is_active(), "We should not be executing here");
889 // Check if the heap is approaching full after a collection has
890 // been done. Generally the young generation is empty at
891 // a minimum at the end of a collection. If it is not, then
892 // the heap is approaching full.
893 SerialHeap* gch = SerialHeap::heap();
894 if (full) {
895 DEBUG_ONLY(seen_incremental_collection_failed = false;)
896 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
897 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
898 GCCause::to_string(gch->gc_cause()));
899 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
900 set_should_allocate_from_space(); // we seem to be running out of space
901 } else {
902 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
903 GCCause::to_string(gch->gc_cause()));
904 gch->clear_incremental_collection_failed(); // We just did a full collection
905 clear_should_allocate_from_space(); // if set
906 }
907 } else {
908 #ifdef ASSERT
909 // It is possible that incremental_collection_failed() == true
910 // here, because an attempted scavenge did not succeed. The policy
911 // is normally expected to cause a full collection which should
912 // clear that condition, so we should not be here twice in a row
913 // with incremental_collection_failed() == true without having done
914 // a full collection in between.
915 if (!seen_incremental_collection_failed &&
916 gch->incremental_collection_failed()) {
917 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
918 GCCause::to_string(gch->gc_cause()));
919 seen_incremental_collection_failed = true;
920 } else if (seen_incremental_collection_failed) {
921 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
922 GCCause::to_string(gch->gc_cause()));
923 seen_incremental_collection_failed = false;
924 }
925 #endif // ASSERT
926 }
927
928 // update the generation and space performance counters
929 update_counters();
930 gch->counters()->update_counters();
931 }
932
933 void DefNewGeneration::update_counters() {
934 if (UsePerfData) {
935 _eden_counters->update_all();
936 _from_counters->update_all();
937 _to_counters->update_all();
938 _gen_counters->update_all();
939 }
940 }
941
942 void DefNewGeneration::verify() {
943 eden()->verify();
944 from()->verify();
945 to()->verify();
946 }
947
948 void DefNewGeneration::print_on(outputStream* st) const {
949 Generation::print_on(st);
950 st->print(" eden");
951 eden()->print_on(st);
952 st->print(" from");
953 from()->print_on(st);
954 st->print(" to ");
955 to()->print_on(st);
956 }
957
958
959 const char* DefNewGeneration::name() const {
960 return "def new generation";
961 }
962
963 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
964 // This is the slow-path allocation for the DefNewGeneration.
965 // Most allocations are fast-path in compiled code.
966 // We try to allocate from the eden. If that works, we are happy.
967 // Note that since DefNewGeneration supports lock-free allocation, we
968 // have to use it here, as well.
969 HeapWord* result = eden()->par_allocate(word_size);
970 if (result == nullptr) {
971 // If the eden is full and the last collection bailed out, we are running
972 // out of heap space, and we try to allocate the from-space, too.
973 // allocate_from_space can't be inlined because that would introduce a
974 // circular dependency at compile time.
975 result = allocate_from_space(word_size);
976 }
977 return result;
978 }
979
980 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
981 bool is_tlab) {
982 return eden()->par_allocate(word_size);
983 }
984
985 size_t DefNewGeneration::tlab_capacity() const {
986 return eden()->capacity();
987 }
988
989 size_t DefNewGeneration::tlab_used() const {
990 return eden()->used();
991 }
992
993 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
994 return unsafe_max_alloc_nogc();
995 }