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