1 /*
2 * Copyright (c) 2001, 2022, 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/defNewGeneration.inline.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/cardTableRS.hpp"
34 #include "gc/shared/collectorCounters.hpp"
35 #include "gc/shared/continuationGCSupport.inline.hpp"
36 #include "gc/shared/gcArguments.hpp"
37 #include "gc/shared/gcHeapSummary.hpp"
38 #include "gc/shared/gcLocker.hpp"
39 #include "gc/shared/gcPolicyCounters.hpp"
40 #include "gc/shared/gcTimer.hpp"
41 #include "gc/shared/gcTrace.hpp"
42 #include "gc/shared/gcTraceTime.inline.hpp"
43 #include "gc/shared/generationSpec.hpp"
44 #include "gc/shared/genOopClosures.inline.hpp"
45 #include "gc/shared/preservedMarks.inline.hpp"
46 #include "gc/shared/referencePolicy.hpp"
47 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
48 #include "gc/shared/space.inline.hpp"
49 #include "gc/shared/spaceDecorator.inline.hpp"
50 #include "gc/shared/strongRootsScope.hpp"
51 #include "gc/shared/weakProcessor.hpp"
52 #include "logging/log.hpp"
53 #include "memory/iterator.inline.hpp"
54 #include "memory/resourceArea.hpp"
55 #include "oops/instanceRefKlass.hpp"
56 #include "oops/oop.inline.hpp"
57 #include "runtime/java.hpp"
58 #include "runtime/javaThread.hpp"
59 #include "runtime/prefetch.inline.hpp"
60 #include "runtime/threads.hpp"
61 #include "utilities/align.hpp"
62 #include "utilities/copy.hpp"
63 #include "utilities/globalDefinitions.hpp"
64 #include "utilities/stack.inline.hpp"
65
66 //
67 // DefNewGeneration functions.
68
69 // Methods of protected closure types.
70
71 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
72 assert(_young_gen->kind() == Generation::DefNew, "Expected the young generation here");
73 }
74
75 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
76 return cast_from_oop<HeapWord*>(p) >= _young_gen->reserved().end() || p->is_forwarded();
77 }
78
79 DefNewGeneration::KeepAliveClosure::
80 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
81 _rs = GenCollectedHeap::heap()->rem_set();
82 }
83
84 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
85 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
86
87
88 DefNewGeneration::FastKeepAliveClosure::
89 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
90 DefNewGeneration::KeepAliveClosure(cl) {
91 _boundary = g->reserved().end();
92 }
93
94 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
95 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
96
97 DefNewGeneration::FastEvacuateFollowersClosure::
98 FastEvacuateFollowersClosure(SerialHeap* heap,
99 DefNewScanClosure* cur,
100 DefNewYoungerGenClosure* older) :
101 _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older)
102 {
103 }
104
105 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
106 do {
107 _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older);
108 } while (!_heap->no_allocs_since_save_marks());
109 guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan");
110 }
111
112 void CLDScanClosure::do_cld(ClassLoaderData* cld) {
113 NOT_PRODUCT(ResourceMark rm);
114 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s",
115 p2i(cld),
116 cld->loader_name_and_id(),
117 cld->has_modified_oops() ? "true" : "false");
118
119 // If the cld has not been dirtied we know that there's
120 // no references into the young gen and we can skip it.
121 if (cld->has_modified_oops()) {
122
123 // Tell the closure which CLD is being scanned so that it can be dirtied
124 // if oops are left pointing into the young gen.
125 _scavenge_closure->set_scanned_cld(cld);
126
127 // Clean the cld since we're going to scavenge all the metadata.
128 cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);
129
130 _scavenge_closure->set_scanned_cld(NULL);
131 }
132 }
133
134 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
135 _g(g)
136 {
137 _boundary = _g->reserved().end();
138 }
139
140 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
141 size_t initial_size,
142 size_t min_size,
143 size_t max_size,
144 const char* policy)
145 : Generation(rs, initial_size),
146 _preserved_marks_set(false /* in_c_heap */),
147 _promo_failure_drain_in_progress(false),
148 _should_allocate_from_space(false),
149 _string_dedup_requests()
150 {
151 MemRegion cmr((HeapWord*)_virtual_space.low(),
152 (HeapWord*)_virtual_space.high());
153 GenCollectedHeap* gch = GenCollectedHeap::heap();
154
155 gch->rem_set()->resize_covered_region(cmr);
156
157 _eden_space = new ContiguousSpace();
158 _from_space = new ContiguousSpace();
159 _to_space = new ContiguousSpace();
160
161 // Compute the maximum eden and survivor space sizes. These sizes
162 // are computed assuming the entire reserved space is committed.
163 // These values are exported as performance counters.
164 uintx size = _virtual_space.reserved_size();
165 _max_survivor_size = compute_survivor_size(size, SpaceAlignment);
166 _max_eden_size = size - (2*_max_survivor_size);
167
168 // allocate the performance counters
169
170 // Generation counters -- generation 0, 3 subspaces
171 _gen_counters = new GenerationCounters("new", 0, 3,
172 min_size, max_size, &_virtual_space);
173 _gc_counters = new CollectorCounters(policy, 0);
174
175 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
176 _gen_counters);
177 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
178 _gen_counters);
179 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
180 _gen_counters);
181
182 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
183 update_counters();
184 _old_gen = NULL;
185 _tenuring_threshold = MaxTenuringThreshold;
186 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
187
188 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
189 }
190
191 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
192 bool clear_space,
193 bool mangle_space) {
194 // If the spaces are being cleared (only done at heap initialization
195 // currently), the survivor spaces need not be empty.
196 // Otherwise, no care is taken for used areas in the survivor spaces
197 // so check.
198 assert(clear_space || (to()->is_empty() && from()->is_empty()),
199 "Initialization of the survivor spaces assumes these are empty");
200
201 // Compute sizes
202 uintx size = _virtual_space.committed_size();
203 uintx survivor_size = compute_survivor_size(size, SpaceAlignment);
204 uintx eden_size = size - (2*survivor_size);
205 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
206
207 if (eden_size < minimum_eden_size) {
208 // May happen due to 64Kb rounding, if so adjust eden size back up
209 minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment);
210 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
211 uintx unaligned_survivor_size =
212 align_down(maximum_survivor_size, SpaceAlignment);
213 survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment);
214 eden_size = size - (2*survivor_size);
215 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
216 assert(eden_size >= minimum_eden_size, "just checking");
217 }
218
219 char *eden_start = _virtual_space.low();
220 char *from_start = eden_start + eden_size;
221 char *to_start = from_start + survivor_size;
222 char *to_end = to_start + survivor_size;
223
224 assert(to_end == _virtual_space.high(), "just checking");
225 assert(Space::is_aligned(eden_start), "checking alignment");
226 assert(Space::is_aligned(from_start), "checking alignment");
227 assert(Space::is_aligned(to_start), "checking alignment");
228
229 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
230 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
231 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
232
233 // A minimum eden size implies that there is a part of eden that
234 // is being used and that affects the initialization of any
235 // newly formed eden.
236 bool live_in_eden = minimum_eden_size > 0;
237
238 // If not clearing the spaces, do some checking to verify that
239 // the space are already mangled.
240 if (!clear_space) {
241 // Must check mangling before the spaces are reshaped. Otherwise,
242 // the bottom or end of one space may have moved into another
243 // a failure of the check may not correctly indicate which space
244 // is not properly mangled.
245 if (ZapUnusedHeapArea) {
246 HeapWord* limit = (HeapWord*) _virtual_space.high();
247 eden()->check_mangled_unused_area(limit);
248 from()->check_mangled_unused_area(limit);
249 to()->check_mangled_unused_area(limit);
250 }
251 }
252
253 // Reset the spaces for their new regions.
254 eden()->initialize(edenMR,
255 clear_space && !live_in_eden,
256 SpaceDecorator::Mangle);
257 // If clear_space and live_in_eden, we will not have cleared any
258 // portion of eden above its top. This can cause newly
259 // expanded space not to be mangled if using ZapUnusedHeapArea.
260 // We explicitly do such mangling here.
261 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
262 eden()->mangle_unused_area();
263 }
264 from()->initialize(fromMR, clear_space, mangle_space);
265 to()->initialize(toMR, clear_space, mangle_space);
266
267 // Set next compaction spaces.
268 eden()->set_next_compaction_space(from());
269 // The to-space is normally empty before a compaction so need
270 // not be considered. The exception is during promotion
271 // failure handling when to-space can contain live objects.
272 from()->set_next_compaction_space(NULL);
273 }
274
275 void DefNewGeneration::swap_spaces() {
276 ContiguousSpace* s = from();
277 _from_space = to();
278 _to_space = s;
279 eden()->set_next_compaction_space(from());
280 // The to-space is normally empty before a compaction so need
281 // not be considered. The exception is during promotion
282 // failure handling when to-space can contain live objects.
283 from()->set_next_compaction_space(NULL);
284
285 if (UsePerfData) {
286 CSpaceCounters* c = _from_counters;
287 _from_counters = _to_counters;
288 _to_counters = c;
289 }
290 }
291
292 bool DefNewGeneration::expand(size_t bytes) {
293 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
294 bool success = _virtual_space.expand_by(bytes);
295 if (success && ZapUnusedHeapArea) {
296 // Mangle newly committed space immediately because it
297 // can be done here more simply that after the new
298 // spaces have been computed.
299 HeapWord* new_high = (HeapWord*) _virtual_space.high();
300 MemRegion mangle_region(prev_high, new_high);
301 SpaceMangler::mangle_region(mangle_region);
302 }
303
304 // Do not attempt an expand-to-the reserve size. The
305 // request should properly observe the maximum size of
306 // the generation so an expand-to-reserve should be
307 // unnecessary. Also a second call to expand-to-reserve
308 // value potentially can cause an undue expansion.
309 // For example if the first expand fail for unknown reasons,
310 // but the second succeeds and expands the heap to its maximum
311 // value.
312 if (GCLocker::is_active()) {
313 log_debug(gc)("Garbage collection disabled, expanded heap instead");
314 }
315
316 return success;
317 }
318
319 size_t DefNewGeneration::calculate_thread_increase_size(int threads_count) const {
320 size_t thread_increase_size = 0;
321 // Check an overflow at 'threads_count * NewSizeThreadIncrease'.
322 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
323 thread_increase_size = threads_count * NewSizeThreadIncrease;
324 }
325 return thread_increase_size;
326 }
327
328 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
329 size_t new_size_before,
330 size_t alignment,
331 size_t thread_increase_size) const {
332 size_t desired_new_size = new_size_before;
333
334 if (NewSizeThreadIncrease > 0 && thread_increase_size > 0) {
335
336 // 1. Check an overflow at 'new_size_candidate + thread_increase_size'.
337 if (new_size_candidate <= max_uintx - thread_increase_size) {
338 new_size_candidate += thread_increase_size;
339
340 // 2. Check an overflow at 'align_up'.
341 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
342 if (new_size_candidate <= aligned_max) {
343 desired_new_size = align_up(new_size_candidate, alignment);
344 }
345 }
346 }
347
348 return desired_new_size;
349 }
350
351 void DefNewGeneration::compute_new_size() {
352 // This is called after a GC that includes the old generation, so from-space
353 // will normally be empty.
354 // Note that we check both spaces, since if scavenge failed they revert roles.
355 // If not we bail out (otherwise we would have to relocate the objects).
356 if (!from()->is_empty() || !to()->is_empty()) {
357 return;
358 }
359
360 GenCollectedHeap* gch = GenCollectedHeap::heap();
361
362 size_t old_size = gch->old_gen()->capacity();
363 size_t new_size_before = _virtual_space.committed_size();
364 size_t min_new_size = initial_size();
365 size_t max_new_size = reserved().byte_size();
366 assert(min_new_size <= new_size_before &&
367 new_size_before <= max_new_size,
368 "just checking");
369 // All space sizes must be multiples of Generation::GenGrain.
370 size_t alignment = Generation::GenGrain;
371
372 int threads_count = Threads::number_of_non_daemon_threads();
373 size_t thread_increase_size = calculate_thread_increase_size(threads_count);
374
375 size_t new_size_candidate = old_size / NewRatio;
376 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
377 // and reverts to previous value if any overflow happens
378 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before,
379 alignment, thread_increase_size);
380
381 // Adjust new generation size
382 desired_new_size = clamp(desired_new_size, min_new_size, max_new_size);
383 assert(desired_new_size <= max_new_size, "just checking");
384
385 bool changed = false;
386 if (desired_new_size > new_size_before) {
387 size_t change = desired_new_size - new_size_before;
388 assert(change % alignment == 0, "just checking");
389 if (expand(change)) {
390 changed = true;
391 }
392 // If the heap failed to expand to the desired size,
393 // "changed" will be false. If the expansion failed
394 // (and at this point it was expected to succeed),
395 // ignore the failure (leaving "changed" as false).
396 }
397 if (desired_new_size < new_size_before && eden()->is_empty()) {
398 // bail out of shrinking if objects in eden
399 size_t change = new_size_before - desired_new_size;
400 assert(change % alignment == 0, "just checking");
401 _virtual_space.shrink_by(change);
402 changed = true;
403 }
404 if (changed) {
405 // The spaces have already been mangled at this point but
406 // may not have been cleared (set top = bottom) and should be.
407 // Mangling was done when the heap was being expanded.
408 compute_space_boundaries(eden()->used(),
409 SpaceDecorator::Clear,
410 SpaceDecorator::DontMangle);
411 MemRegion cmr((HeapWord*)_virtual_space.low(),
412 (HeapWord*)_virtual_space.high());
413 gch->rem_set()->resize_covered_region(cmr);
414
415 log_debug(gc, ergo, heap)(
416 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
417 new_size_before/K, _virtual_space.committed_size()/K,
418 eden()->capacity()/K, from()->capacity()/K);
419 log_trace(gc, ergo, heap)(
420 " [allowed " SIZE_FORMAT "K extra for %d threads]",
421 thread_increase_size/K, threads_count);
422 }
423 }
424
425
426 size_t DefNewGeneration::capacity() const {
427 return eden()->capacity()
428 + from()->capacity(); // to() is only used during scavenge
429 }
430
431
432 size_t DefNewGeneration::used() const {
433 return eden()->used()
434 + from()->used(); // to() is only used during scavenge
435 }
436
437
438 size_t DefNewGeneration::free() const {
439 return eden()->free()
440 + from()->free(); // to() is only used during scavenge
441 }
442
443 size_t DefNewGeneration::max_capacity() const {
444 const size_t reserved_bytes = reserved().byte_size();
445 return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment);
446 }
447
448 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
449 return eden()->free();
450 }
451
452 size_t DefNewGeneration::capacity_before_gc() const {
453 return eden()->capacity();
454 }
455
456 size_t DefNewGeneration::contiguous_available() const {
457 return eden()->free();
458 }
459
460
461 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
462 eden()->object_iterate(blk);
463 from()->object_iterate(blk);
464 }
465
466
467 void DefNewGeneration::space_iterate(SpaceClosure* blk,
468 bool usedOnly) {
469 blk->do_space(eden());
470 blk->do_space(from());
471 blk->do_space(to());
472 }
473
474 // The last collection bailed out, we are running out of heap space,
475 // so we try to allocate the from-space, too.
476 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
477 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
478
479 // If the Heap_lock is not locked by this thread, this will be called
480 // again later with the Heap_lock held.
481 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
482
483 HeapWord* result = NULL;
484 if (do_alloc) {
485 result = from()->allocate(size);
486 }
487
488 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s",
489 size,
490 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
491 "true" : "false",
492 Heap_lock->is_locked() ? "locked" : "unlocked",
493 from()->free(),
494 should_try_alloc ? "" : " should_allocate_from_space: NOT",
495 do_alloc ? " Heap_lock is not owned by self" : "",
496 result == NULL ? "NULL" : "object");
497
498 return result;
499 }
500
501 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, bool is_tlab) {
502 // We don't attempt to expand the young generation (but perhaps we should.)
503 return allocate(size, is_tlab);
504 }
505
506 void DefNewGeneration::adjust_desired_tenuring_threshold() {
507 // Set the desired survivor size to half the real survivor space
508 size_t const survivor_capacity = to()->capacity() / HeapWordSize;
509 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
510
511 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
512
513 if (UsePerfData) {
514 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters();
515 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
516 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
517 }
518
519 age_table()->print_age_table(_tenuring_threshold);
520 }
521
522 void DefNewGeneration::collect(bool full,
523 bool clear_all_soft_refs,
524 size_t size,
525 bool is_tlab) {
526 assert(full || size > 0, "otherwise we don't want to collect");
527
528 SerialHeap* heap = SerialHeap::heap();
529
530 _gc_timer->register_gc_start();
531 DefNewTracer gc_tracer;
532 gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start());
533
534 _old_gen = heap->old_gen();
535
536 // If the next generation is too full to accommodate promotion
537 // from this generation, pass on collection; let the next generation
538 // do it.
539 if (!collection_attempt_is_safe()) {
540 log_trace(gc)(":: Collection attempt not safe ::");
541 heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
542 return;
543 }
544 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
545
546 init_assuming_no_promotion_failure();
547
548 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause());
549
550 heap->trace_heap_before_gc(&gc_tracer);
551
552 // These can be shared for all code paths
553 IsAliveClosure is_alive(this);
554 ScanWeakRefClosure scan_weak_ref(this);
555
556 age_table()->clear();
557 to()->clear(SpaceDecorator::Mangle);
558 // The preserved marks should be empty at the start of the GC.
559 _preserved_marks_set.init(1);
560
561 assert(heap->no_allocs_since_save_marks(),
562 "save marks have not been newly set.");
563
564 DefNewScanClosure scan_closure(this);
565 DefNewYoungerGenClosure younger_gen_closure(this, _old_gen);
566
567 CLDScanClosure cld_scan_closure(&scan_closure);
568
569 set_promo_failure_scan_stack_closure(&scan_closure);
570 FastEvacuateFollowersClosure evacuate_followers(heap,
571 &scan_closure,
572 &younger_gen_closure);
573
574 assert(heap->no_allocs_since_save_marks(),
575 "save marks have not been newly set.");
576
577 {
578 StrongRootsScope srs(0);
579
580 heap->young_process_roots(&scan_closure,
581 &younger_gen_closure,
582 &cld_scan_closure);
583 }
584
585 // "evacuate followers".
586 evacuate_followers.do_void();
587
588 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
589 ReferenceProcessor* rp = ref_processor();
590 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
591 SerialGCRefProcProxyTask task(is_alive, keep_alive, evacuate_followers);
592 const ReferenceProcessorStats& stats = rp->process_discovered_references(task, pt);
593 gc_tracer.report_gc_reference_stats(stats);
594 gc_tracer.report_tenuring_threshold(tenuring_threshold());
595 pt.print_all_references();
596
597 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
598
599 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
600
601 // Verify that the usage of keep_alive didn't copy any objects.
602 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
603
604 _string_dedup_requests.flush();
605
606 if (!_promotion_failed) {
607 // Swap the survivor spaces.
608 eden()->clear(SpaceDecorator::Mangle);
609 from()->clear(SpaceDecorator::Mangle);
610 if (ZapUnusedHeapArea) {
611 // This is now done here because of the piece-meal mangling which
612 // can check for valid mangling at intermediate points in the
613 // collection(s). When a young collection fails to collect
614 // sufficient space resizing of the young generation can occur
615 // an redistribute the spaces in the young generation. Mangle
616 // here so that unzapped regions don't get distributed to
617 // other spaces.
618 to()->mangle_unused_area();
619 }
620 swap_spaces();
621
622 assert(to()->is_empty(), "to space should be empty now");
623
624 adjust_desired_tenuring_threshold();
625
626 // A successful scavenge should restart the GC time limit count which is
627 // for full GC's.
628 AdaptiveSizePolicy* size_policy = heap->size_policy();
629 size_policy->reset_gc_overhead_limit_count();
630 assert(!heap->incremental_collection_failed(), "Should be clear");
631 } else {
632 assert(_promo_failure_scan_stack.is_empty(), "post condition");
633 _promo_failure_scan_stack.clear(true); // Clear cached segments.
634
635 remove_forwarding_pointers();
636 log_info(gc, promotion)("Promotion failed");
637 // Add to-space to the list of space to compact
638 // when a promotion failure has occurred. In that
639 // case there can be live objects in to-space
640 // as a result of a partial evacuation of eden
641 // and from-space.
642 swap_spaces(); // For uniformity wrt ParNewGeneration.
643 from()->set_next_compaction_space(to());
644 heap->set_incremental_collection_failed();
645
646 // Inform the next generation that a promotion failure occurred.
647 _old_gen->promotion_failure_occurred();
648 gc_tracer.report_promotion_failed(_promotion_failed_info);
649
650 // Reset the PromotionFailureALot counters.
651 NOT_PRODUCT(heap->reset_promotion_should_fail();)
652 }
653 // We should have processed and cleared all the preserved marks.
654 _preserved_marks_set.reclaim();
655
656 heap->trace_heap_after_gc(&gc_tracer);
657
658 _gc_timer->register_gc_end();
659
660 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
661 }
662
663 void DefNewGeneration::init_assuming_no_promotion_failure() {
664 _promotion_failed = false;
665 _promotion_failed_info.reset();
666 from()->set_next_compaction_space(NULL);
667 }
668
669 void DefNewGeneration::remove_forwarding_pointers() {
670 assert(_promotion_failed, "precondition");
671
672 // Will enter Full GC soon due to failed promotion. Must reset the mark word
673 // of objs in young-gen so that no objs are marked (forwarded) when Full GC
674 // starts. (The mark word is overloaded: `is_marked()` == `is_forwarded()`.)
675 struct ResetForwardedMarkWord : ObjectClosure {
676 void do_object(oop obj) override {
677 if (obj->is_forwarded()) {
678 #ifdef _LP64
679 oop forwardee = obj->forwardee();
680 markWord header = forwardee->mark();
681 if (header.has_displaced_mark_helper()) {
682 header = header.displaced_mark_helper();
683 }
684 assert(UseCompressedClassPointers, "assume +UseCompressedClassPointers");
685 narrowKlass nklass = header.narrow_klass();
686 obj->set_mark(markWord::prototype().set_narrow_klass(nklass));
687 #else
688 obj->init_mark();
689 #endif
690 }
691 }
692 } cl;
693 eden()->object_iterate(&cl);
694 from()->object_iterate(&cl);
695
696 restore_preserved_marks();
697 }
698
699 void DefNewGeneration::restore_preserved_marks() {
700 _preserved_marks_set.restore(NULL);
701 }
702
703 void DefNewGeneration::handle_promotion_failure(oop old) {
704 log_debug(gc, promotion)("Promotion failure size = " SIZE_FORMAT ") ", old->size());
705
706 _promotion_failed = true;
707 _promotion_failed_info.register_copy_failure(old->size());
708 _preserved_marks_set.get()->push_if_necessary(old, old->mark());
709
710 ContinuationGCSupport::transform_stack_chunk(old);
711
712 // forward to self
713 old->forward_to_self();
714
715 _promo_failure_scan_stack.push(old);
716
717 if (!_promo_failure_drain_in_progress) {
718 // prevent recursion in copy_to_survivor_space()
719 _promo_failure_drain_in_progress = true;
720 drain_promo_failure_scan_stack();
721 _promo_failure_drain_in_progress = false;
722 }
723 }
724
725 oop DefNewGeneration::copy_to_survivor_space(oop old) {
726 assert(is_in_reserved(old) && !old->is_forwarded(),
727 "shouldn't be scavenging this oop");
728 size_t s = old->size();
729 oop obj = NULL;
730
731 // Try allocating obj in to-space (unless too old)
732 if (old->age() < tenuring_threshold()) {
733 obj = cast_to_oop(to()->allocate(s));
734 }
735
736 bool new_obj_is_tenured = false;
737 // Otherwise try allocating obj tenured
738 if (obj == NULL) {
739 obj = _old_gen->promote(old, s);
740 if (obj == NULL) {
741 handle_promotion_failure(old);
742 return old;
743 }
744 new_obj_is_tenured = true;
745 } else {
746 // Prefetch beyond obj
747 const intx interval = PrefetchCopyIntervalInBytes;
748 Prefetch::write(obj, interval);
749
750 // Copy obj
751 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s);
752
753 ContinuationGCSupport::transform_stack_chunk(obj);
754
755 // Increment age if obj still in new generation
756 obj->incr_age();
757 age_table()->add(obj, s);
758 }
759
760 // Done, insert forward pointer to obj in this header
761 old->forward_to(obj);
762
763 if (SerialStringDedup::is_candidate_from_evacuation(obj, new_obj_is_tenured)) {
764 // Record old; request adds a new weak reference, which reference
765 // processing expects to refer to a from-space object.
766 _string_dedup_requests.add(old);
767 }
768 return obj;
769 }
770
771 void DefNewGeneration::drain_promo_failure_scan_stack() {
772 while (!_promo_failure_scan_stack.is_empty()) {
773 oop obj = _promo_failure_scan_stack.pop();
774 obj->oop_iterate(_promo_failure_scan_stack_closure);
775 }
776 }
777
778 void DefNewGeneration::save_marks() {
779 eden()->set_saved_mark();
780 to()->set_saved_mark();
781 from()->set_saved_mark();
782 }
783
784
785 void DefNewGeneration::reset_saved_marks() {
786 eden()->reset_saved_mark();
787 to()->reset_saved_mark();
788 from()->reset_saved_mark();
789 }
790
791
792 bool DefNewGeneration::no_allocs_since_save_marks() {
793 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
794 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
795 return to()->saved_mark_at_top();
796 }
797
798 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
799 size_t max_alloc_words) {
800 if (requestor == this || _promotion_failed) {
801 return;
802 }
803 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
804
805 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
806 if (to_space->top() > to_space->bottom()) {
807 trace("to_space not empty when contribute_scratch called");
808 }
809 */
810
811 ContiguousSpace* to_space = to();
812 assert(to_space->end() >= to_space->top(), "pointers out of order");
813 size_t free_words = pointer_delta(to_space->end(), to_space->top());
814 if (free_words >= MinFreeScratchWords) {
815 ScratchBlock* sb = (ScratchBlock*)to_space->top();
816 sb->num_words = free_words;
817 sb->next = list;
818 list = sb;
819 }
820 }
821
822 void DefNewGeneration::reset_scratch() {
823 // If contributing scratch in to_space, mangle all of
824 // to_space if ZapUnusedHeapArea. This is needed because
825 // top is not maintained while using to-space as scratch.
826 if (ZapUnusedHeapArea) {
827 to()->mangle_unused_area_complete();
828 }
829 }
830
831 bool DefNewGeneration::collection_attempt_is_safe() {
832 if (!to()->is_empty()) {
833 log_trace(gc)(":: to is not empty ::");
834 return false;
835 }
836 if (_old_gen == NULL) {
837 GenCollectedHeap* gch = GenCollectedHeap::heap();
838 _old_gen = gch->old_gen();
839 }
840 return _old_gen->promotion_attempt_is_safe(used());
841 }
842
843 void DefNewGeneration::gc_epilogue(bool full) {
844 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
845
846 assert(!GCLocker::is_active(), "We should not be executing here");
847 // Check if the heap is approaching full after a collection has
848 // been done. Generally the young generation is empty at
849 // a minimum at the end of a collection. If it is not, then
850 // the heap is approaching full.
851 GenCollectedHeap* gch = GenCollectedHeap::heap();
852 if (full) {
853 DEBUG_ONLY(seen_incremental_collection_failed = false;)
854 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
855 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
856 GCCause::to_string(gch->gc_cause()));
857 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
858 set_should_allocate_from_space(); // we seem to be running out of space
859 } else {
860 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
861 GCCause::to_string(gch->gc_cause()));
862 gch->clear_incremental_collection_failed(); // We just did a full collection
863 clear_should_allocate_from_space(); // if set
864 }
865 } else {
866 #ifdef ASSERT
867 // It is possible that incremental_collection_failed() == true
868 // here, because an attempted scavenge did not succeed. The policy
869 // is normally expected to cause a full collection which should
870 // clear that condition, so we should not be here twice in a row
871 // with incremental_collection_failed() == true without having done
872 // a full collection in between.
873 if (!seen_incremental_collection_failed &&
874 gch->incremental_collection_failed()) {
875 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
876 GCCause::to_string(gch->gc_cause()));
877 seen_incremental_collection_failed = true;
878 } else if (seen_incremental_collection_failed) {
879 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
880 GCCause::to_string(gch->gc_cause()));
881 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
882 !gch->incremental_collection_failed(),
883 "Twice in a row");
884 seen_incremental_collection_failed = false;
885 }
886 #endif // ASSERT
887 }
888
889 if (ZapUnusedHeapArea) {
890 eden()->check_mangled_unused_area_complete();
891 from()->check_mangled_unused_area_complete();
892 to()->check_mangled_unused_area_complete();
893 }
894
895 // update the generation and space performance counters
896 update_counters();
897 gch->counters()->update_counters();
898 }
899
900 void DefNewGeneration::record_spaces_top() {
901 assert(ZapUnusedHeapArea, "Not mangling unused space");
902 eden()->set_top_for_allocations();
903 to()->set_top_for_allocations();
904 from()->set_top_for_allocations();
905 }
906
907 void DefNewGeneration::update_counters() {
908 if (UsePerfData) {
909 _eden_counters->update_all();
910 _from_counters->update_all();
911 _to_counters->update_all();
912 _gen_counters->update_all();
913 }
914 }
915
916 void DefNewGeneration::verify() {
917 eden()->verify();
918 from()->verify();
919 to()->verify();
920 }
921
922 void DefNewGeneration::print_on(outputStream* st) const {
923 Generation::print_on(st);
924 st->print(" eden");
925 eden()->print_on(st);
926 st->print(" from");
927 from()->print_on(st);
928 st->print(" to ");
929 to()->print_on(st);
930 }
931
932
933 const char* DefNewGeneration::name() const {
934 return "def new generation";
935 }
936
937 // Moved from inline file as they are not called inline
938 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
939 return eden();
940 }
941
942 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
943 // This is the slow-path allocation for the DefNewGeneration.
944 // Most allocations are fast-path in compiled code.
945 // We try to allocate from the eden. If that works, we are happy.
946 // Note that since DefNewGeneration supports lock-free allocation, we
947 // have to use it here, as well.
948 HeapWord* result = eden()->par_allocate(word_size);
949 if (result == NULL) {
950 // If the eden is full and the last collection bailed out, we are running
951 // out of heap space, and we try to allocate the from-space, too.
952 // allocate_from_space can't be inlined because that would introduce a
953 // circular dependency at compile time.
954 result = allocate_from_space(word_size);
955 }
956 return result;
957 }
958
959 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
960 bool is_tlab) {
961 return eden()->par_allocate(word_size);
962 }
963
964 size_t DefNewGeneration::tlab_capacity() const {
965 return eden()->capacity();
966 }
967
968 size_t DefNewGeneration::tlab_used() const {
969 return eden()->used();
970 }
971
972 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
973 return unsafe_max_alloc_nogc();
974 }