1 /*
2 * Copyright (c) 2001, 2020, 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/serialHeap.inline.hpp"
28 #include "gc/serial/tenuredGeneration.hpp"
29 #include "gc/shared/adaptiveSizePolicy.hpp"
30 #include "gc/shared/ageTable.inline.hpp"
31 #include "gc/shared/cardTableRS.hpp"
32 #include "gc/shared/collectorCounters.hpp"
33 #include "gc/shared/gcArguments.hpp"
34 #include "gc/shared/gcHeapSummary.hpp"
35 #include "gc/shared/gcLocker.hpp"
36 #include "gc/shared/gcPolicyCounters.hpp"
37 #include "gc/shared/gcTimer.hpp"
38 #include "gc/shared/gcTrace.hpp"
39 #include "gc/shared/gcTraceTime.inline.hpp"
40 #include "gc/shared/genOopClosures.inline.hpp"
41 #include "gc/shared/generationSpec.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.inline.hpp"
46 #include "gc/shared/spaceDecorator.inline.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/prefetch.inline.hpp"
56 #include "runtime/thread.inline.hpp"
57 #include "utilities/align.hpp"
58 #include "utilities/copy.hpp"
59 #include "utilities/globalDefinitions.hpp"
60 #include "utilities/stack.inline.hpp"
61
62 //
63 // DefNewGeneration functions.
64
65 // Methods of protected closure types.
66
67 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
68 assert(_young_gen->kind() == Generation::DefNew, "Expected the young generation here");
69 }
70
71 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
72 return cast_from_oop<HeapWord*>(p) >= _young_gen->reserved().end() || p->is_forwarded();
73 }
74
75 DefNewGeneration::KeepAliveClosure::
76 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
77 _rs = GenCollectedHeap::heap()->rem_set();
78 }
79
80 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
81 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
82
83
84 DefNewGeneration::FastKeepAliveClosure::
85 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
86 DefNewGeneration::KeepAliveClosure(cl) {
87 _boundary = g->reserved().end();
88 }
89
90 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
91 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
92
93 DefNewGeneration::FastEvacuateFollowersClosure::
94 FastEvacuateFollowersClosure(SerialHeap* heap,
95 DefNewScanClosure* cur,
96 DefNewYoungerGenClosure* older) :
97 _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older)
98 {
99 }
100
101 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
102 do {
103 _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older);
104 } while (!_heap->no_allocs_since_save_marks());
105 guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan");
106 }
107
108 void CLDScanClosure::do_cld(ClassLoaderData* cld) {
109 NOT_PRODUCT(ResourceMark rm);
110 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s",
111 p2i(cld),
112 cld->loader_name_and_id(),
113 cld->has_modified_oops() ? "true" : "false");
114
115 // If the cld has not been dirtied we know that there's
116 // no references into the young gen and we can skip it.
117 if (cld->has_modified_oops()) {
118 if (_accumulate_modified_oops) {
119 cld->accumulate_modified_oops();
120 }
121
122 // Tell the closure which CLD is being scanned so that it can be dirtied
123 // if oops are left pointing into the young gen.
124 _scavenge_closure->set_scanned_cld(cld);
125
126 // Clean the cld since we're going to scavenge all the metadata.
127 cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);
128
129 _scavenge_closure->set_scanned_cld(NULL);
130 }
131 }
132
133 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
134 _g(g)
135 {
136 _boundary = _g->reserved().end();
137 }
138
139 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
140 size_t initial_size,
141 size_t min_size,
142 size_t max_size,
143 const char* policy)
144 : Generation(rs, initial_size),
145 _preserved_marks_set(false /* in_c_heap */),
146 _promo_failure_drain_in_progress(false),
147 _should_allocate_from_space(false)
148 {
149 MemRegion cmr((HeapWord*)_virtual_space.low(),
150 (HeapWord*)_virtual_space.high());
151 GenCollectedHeap* gch = GenCollectedHeap::heap();
152
153 gch->rem_set()->resize_covered_region(cmr);
154
155 _eden_space = new ContiguousSpace();
156 _from_space = new ContiguousSpace();
157 _to_space = new ContiguousSpace();
158
159 // Compute the maximum eden and survivor space sizes. These sizes
160 // are computed assuming the entire reserved space is committed.
161 // These values are exported as performance counters.
162 uintx size = _virtual_space.reserved_size();
163 _max_survivor_size = compute_survivor_size(size, SpaceAlignment);
164 _max_eden_size = size - (2*_max_survivor_size);
165
166 // allocate the performance counters
167
168 // Generation counters -- generation 0, 3 subspaces
169 _gen_counters = new GenerationCounters("new", 0, 3,
170 min_size, max_size, &_virtual_space);
171 _gc_counters = new CollectorCounters(policy, 0);
172
173 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
174 _gen_counters);
175 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
176 _gen_counters);
177 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
178 _gen_counters);
179
180 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
181 update_counters();
182 _old_gen = NULL;
183 _tenuring_threshold = MaxTenuringThreshold;
184 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
185
186 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
187 }
188
189 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
190 bool clear_space,
191 bool mangle_space) {
192 // If the spaces are being cleared (only done at heap initialization
193 // currently), the survivor spaces need not be empty.
194 // Otherwise, no care is taken for used areas in the survivor spaces
195 // so check.
196 assert(clear_space || (to()->is_empty() && from()->is_empty()),
197 "Initialization of the survivor spaces assumes these are empty");
198
199 // Compute sizes
200 uintx size = _virtual_space.committed_size();
201 uintx survivor_size = compute_survivor_size(size, SpaceAlignment);
202 uintx eden_size = size - (2*survivor_size);
203 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
204
205 if (eden_size < minimum_eden_size) {
206 // May happen due to 64Kb rounding, if so adjust eden size back up
207 minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment);
208 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
209 uintx unaligned_survivor_size =
210 align_down(maximum_survivor_size, SpaceAlignment);
211 survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment);
212 eden_size = size - (2*survivor_size);
213 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
214 assert(eden_size >= minimum_eden_size, "just checking");
215 }
216
217 char *eden_start = _virtual_space.low();
218 char *from_start = eden_start + eden_size;
219 char *to_start = from_start + survivor_size;
220 char *to_end = to_start + survivor_size;
221
222 assert(to_end == _virtual_space.high(), "just checking");
223 assert(Space::is_aligned(eden_start), "checking alignment");
224 assert(Space::is_aligned(from_start), "checking alignment");
225 assert(Space::is_aligned(to_start), "checking alignment");
226
227 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
228 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
229 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
230
231 // A minimum eden size implies that there is a part of eden that
232 // is being used and that affects the initialization of any
233 // newly formed eden.
234 bool live_in_eden = minimum_eden_size > 0;
235
236 // If not clearing the spaces, do some checking to verify that
237 // the space are already mangled.
238 if (!clear_space) {
239 // Must check mangling before the spaces are reshaped. Otherwise,
240 // the bottom or end of one space may have moved into another
241 // a failure of the check may not correctly indicate which space
242 // is not properly mangled.
243 if (ZapUnusedHeapArea) {
244 HeapWord* limit = (HeapWord*) _virtual_space.high();
245 eden()->check_mangled_unused_area(limit);
246 from()->check_mangled_unused_area(limit);
247 to()->check_mangled_unused_area(limit);
248 }
249 }
250
251 // Reset the spaces for their new regions.
252 eden()->initialize(edenMR,
253 clear_space && !live_in_eden,
254 SpaceDecorator::Mangle);
255 // If clear_space and live_in_eden, we will not have cleared any
256 // portion of eden above its top. This can cause newly
257 // expanded space not to be mangled if using ZapUnusedHeapArea.
258 // We explicitly do such mangling here.
259 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
260 eden()->mangle_unused_area();
261 }
262 from()->initialize(fromMR, clear_space, mangle_space);
263 to()->initialize(toMR, clear_space, mangle_space);
264
265 // Set next compaction spaces.
266 eden()->set_next_compaction_space(from());
267 // The to-space is normally empty before a compaction so need
268 // not be considered. The exception is during promotion
269 // failure handling when to-space can contain live objects.
270 from()->set_next_compaction_space(NULL);
271 }
272
273 void DefNewGeneration::swap_spaces() {
274 ContiguousSpace* s = from();
275 _from_space = to();
276 _to_space = s;
277 eden()->set_next_compaction_space(from());
278 // The to-space is normally empty before a compaction so need
279 // not be considered. The exception is during promotion
280 // failure handling when to-space can contain live objects.
281 from()->set_next_compaction_space(NULL);
282
283 if (UsePerfData) {
284 CSpaceCounters* c = _from_counters;
285 _from_counters = _to_counters;
286 _to_counters = c;
287 }
288 }
289
290 bool DefNewGeneration::expand(size_t bytes) {
291 MutexLocker x(ExpandHeap_lock);
292 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
293 bool success = _virtual_space.expand_by(bytes);
294 if (success && ZapUnusedHeapArea) {
295 // Mangle newly committed space immediately because it
296 // can be done here more simply that after the new
297 // spaces have been computed.
298 HeapWord* new_high = (HeapWord*) _virtual_space.high();
299 MemRegion mangle_region(prev_high, new_high);
300 SpaceMangler::mangle_region(mangle_region);
301 }
302
303 // Do not attempt an expand-to-the reserve size. The
304 // request should properly observe the maximum size of
305 // the generation so an expand-to-reserve should be
306 // unnecessary. Also a second call to expand-to-reserve
307 // value potentially can cause an undue expansion.
308 // For example if the first expand fail for unknown reasons,
309 // but the second succeeds and expands the heap to its maximum
310 // value.
311 if (GCLocker::is_active()) {
312 log_debug(gc)("Garbage collection disabled, expanded heap instead");
313 }
314
315 return success;
316 }
317
318 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
319 size_t new_size_before,
320 size_t alignment) const {
321 size_t desired_new_size = new_size_before;
322
323 if (NewSizeThreadIncrease > 0) {
324 int threads_count;
325 size_t thread_increase_size = 0;
326
327 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
328 threads_count = Threads::number_of_non_daemon_threads();
329 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
330 thread_increase_size = threads_count * NewSizeThreadIncrease;
331
332 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
333 if (new_size_candidate <= max_uintx - thread_increase_size) {
334 new_size_candidate += thread_increase_size;
335
336 // 3. Check an overflow at 'align_up'.
337 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
338 if (new_size_candidate <= aligned_max) {
339 desired_new_size = align_up(new_size_candidate, alignment);
340 }
341 }
342 }
343 }
344
345 return desired_new_size;
346 }
347
348 void DefNewGeneration::compute_new_size() {
349 // This is called after a GC that includes the old generation, so from-space
350 // will normally be empty.
351 // Note that we check both spaces, since if scavenge failed they revert roles.
352 // If not we bail out (otherwise we would have to relocate the objects).
353 if (!from()->is_empty() || !to()->is_empty()) {
354 return;
355 }
356
357 GenCollectedHeap* gch = GenCollectedHeap::heap();
358
359 size_t old_size = gch->old_gen()->capacity();
360 size_t new_size_before = _virtual_space.committed_size();
361 size_t min_new_size = initial_size();
362 size_t max_new_size = reserved().byte_size();
363 assert(min_new_size <= new_size_before &&
364 new_size_before <= max_new_size,
365 "just checking");
366 // All space sizes must be multiples of Generation::GenGrain.
367 size_t alignment = Generation::GenGrain;
368
369 int threads_count = 0;
370 size_t thread_increase_size = 0;
371
372 size_t new_size_candidate = old_size / NewRatio;
373 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
374 // and reverts to previous value if any overflow happens
375 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);
376
377 // Adjust new generation size
378 desired_new_size = clamp(desired_new_size, min_new_size, max_new_size);
379 assert(desired_new_size <= max_new_size, "just checking");
380
381 bool changed = false;
382 if (desired_new_size > new_size_before) {
383 size_t change = desired_new_size - new_size_before;
384 assert(change % alignment == 0, "just checking");
385 if (expand(change)) {
386 changed = true;
387 }
388 // If the heap failed to expand to the desired size,
389 // "changed" will be false. If the expansion failed
390 // (and at this point it was expected to succeed),
391 // ignore the failure (leaving "changed" as false).
392 }
393 if (desired_new_size < new_size_before && eden()->is_empty()) {
394 // bail out of shrinking if objects in eden
395 size_t change = new_size_before - desired_new_size;
396 assert(change % alignment == 0, "just checking");
397 _virtual_space.shrink_by(change);
398 changed = true;
399 }
400 if (changed) {
401 // The spaces have already been mangled at this point but
402 // may not have been cleared (set top = bottom) and should be.
403 // Mangling was done when the heap was being expanded.
404 compute_space_boundaries(eden()->used(),
405 SpaceDecorator::Clear,
406 SpaceDecorator::DontMangle);
407 MemRegion cmr((HeapWord*)_virtual_space.low(),
408 (HeapWord*)_virtual_space.high());
409 gch->rem_set()->resize_covered_region(cmr);
410
411 log_debug(gc, ergo, heap)(
412 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
413 new_size_before/K, _virtual_space.committed_size()/K,
414 eden()->capacity()/K, from()->capacity()/K);
415 log_trace(gc, ergo, heap)(
416 " [allowed " SIZE_FORMAT "K extra for %d threads]",
417 thread_increase_size/K, threads_count);
418 }
419 }
420
421
422 size_t DefNewGeneration::capacity() const {
423 return eden()->capacity()
424 + from()->capacity(); // to() is only used during scavenge
425 }
426
427
428 size_t DefNewGeneration::used() const {
429 return eden()->used()
430 + from()->used(); // to() is only used during scavenge
431 }
432
433
434 size_t DefNewGeneration::free() const {
435 return eden()->free()
436 + from()->free(); // to() is only used during scavenge
437 }
438
439 size_t DefNewGeneration::max_capacity() const {
440 const size_t reserved_bytes = reserved().byte_size();
441 return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment);
442 }
443
444 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
445 return eden()->free();
446 }
447
448 size_t DefNewGeneration::capacity_before_gc() const {
449 return eden()->capacity();
450 }
451
452 size_t DefNewGeneration::contiguous_available() const {
453 return eden()->free();
454 }
455
456
457 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }
458 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
459
460 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
461 eden()->object_iterate(blk);
462 from()->object_iterate(blk);
463 }
464
465
466 void DefNewGeneration::space_iterate(SpaceClosure* blk,
467 bool usedOnly) {
468 blk->do_space(eden());
469 blk->do_space(from());
470 blk->do_space(to());
471 }
472
473 // The last collection bailed out, we are running out of heap space,
474 // so we try to allocate the from-space, too.
475 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
476 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
477
478 // If the Heap_lock is not locked by this thread, this will be called
479 // again later with the Heap_lock held.
480 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
481
482 HeapWord* result = NULL;
483 if (do_alloc) {
484 result = from()->allocate(size);
485 }
486
487 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s",
488 size,
489 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
490 "true" : "false",
491 Heap_lock->is_locked() ? "locked" : "unlocked",
492 from()->free(),
493 should_try_alloc ? "" : " should_allocate_from_space: NOT",
494 do_alloc ? " Heap_lock is not owned by self" : "",
495 result == NULL ? "NULL" : "object");
496
497 return result;
498 }
499
500 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
501 bool is_tlab,
502 bool parallel) {
503 // We don't attempt to expand the young generation (but perhaps we should.)
504 return allocate(size, is_tlab);
505 }
506
507 void DefNewGeneration::adjust_desired_tenuring_threshold() {
508 // Set the desired survivor size to half the real survivor space
509 size_t const survivor_capacity = to()->capacity() / HeapWordSize;
510 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
511
512 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
513
514 if (UsePerfData) {
515 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters();
516 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
517 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
518 }
519
520 age_table()->print_age_table(_tenuring_threshold);
521 }
522
523 void DefNewGeneration::collect(bool full,
524 bool clear_all_soft_refs,
525 size_t size,
526 bool is_tlab) {
527 assert(full || size > 0, "otherwise we don't want to collect");
528
529 SerialHeap* heap = SerialHeap::heap();
530
531 _gc_timer->register_gc_start();
532 DefNewTracer gc_tracer;
533 gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start());
534
535 _old_gen = heap->old_gen();
536
537 // If the next generation is too full to accommodate promotion
538 // from this generation, pass on collection; let the next generation
539 // do it.
540 if (!collection_attempt_is_safe()) {
541 log_trace(gc)(":: Collection attempt not safe ::");
542 heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
543 return;
544 }
545 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
546
547 init_assuming_no_promotion_failure();
548
549 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause());
550
551 heap->trace_heap_before_gc(&gc_tracer);
552
553 // These can be shared for all code paths
554 IsAliveClosure is_alive(this);
555 ScanWeakRefClosure scan_weak_ref(this);
556
557 age_table()->clear();
558 to()->clear(SpaceDecorator::Mangle);
559 // The preserved marks should be empty at the start of the GC.
560 _preserved_marks_set.init(1);
561
562 heap->rem_set()->prepare_for_younger_refs_iterate(false);
563
564 assert(heap->no_allocs_since_save_marks(),
565 "save marks have not been newly set.");
566
567 DefNewScanClosure scan_closure(this);
568 DefNewYoungerGenClosure younger_gen_closure(this, _old_gen);
569
570 CLDScanClosure cld_scan_closure(&scan_closure,
571 heap->rem_set()->cld_rem_set()->accumulate_modified_oops());
572
573 set_promo_failure_scan_stack_closure(&scan_closure);
574 FastEvacuateFollowersClosure evacuate_followers(heap,
575 &scan_closure,
576 &younger_gen_closure);
577
578 assert(heap->no_allocs_since_save_marks(),
579 "save marks have not been newly set.");
580
581 {
582 // DefNew needs to run with n_threads == 0, to make sure the serial
583 // version of the card table scanning code is used.
584 // See: CardTableRS::non_clean_card_iterate_possibly_parallel.
585 StrongRootsScope srs(0);
586
587 heap->young_process_roots(&srs,
588 &scan_closure,
589 &younger_gen_closure,
590 &cld_scan_closure);
591 }
592
593 // "evacuate followers".
594 evacuate_followers.do_void();
595
596 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
597 ReferenceProcessor* rp = ref_processor();
598 rp->setup_policy(clear_all_soft_refs);
599 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
600 const ReferenceProcessorStats& stats =
601 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
602 NULL, &pt);
603 gc_tracer.report_gc_reference_stats(stats);
604 gc_tracer.report_tenuring_threshold(tenuring_threshold());
605 pt.print_all_references();
606
607 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
608
609 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
610
611 // Verify that the usage of keep_alive didn't copy any objects.
612 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
613
614 if (!_promotion_failed) {
615 // Swap the survivor spaces.
616 eden()->clear(SpaceDecorator::Mangle);
617 from()->clear(SpaceDecorator::Mangle);
618 if (ZapUnusedHeapArea) {
619 // This is now done here because of the piece-meal mangling which
620 // can check for valid mangling at intermediate points in the
621 // collection(s). When a young collection fails to collect
622 // sufficient space resizing of the young generation can occur
623 // an redistribute the spaces in the young generation. Mangle
624 // here so that unzapped regions don't get distributed to
625 // other spaces.
626 to()->mangle_unused_area();
627 }
628 swap_spaces();
629
630 assert(to()->is_empty(), "to space should be empty now");
631
632 adjust_desired_tenuring_threshold();
633
634 // A successful scavenge should restart the GC time limit count which is
635 // for full GC's.
636 AdaptiveSizePolicy* size_policy = heap->size_policy();
637 size_policy->reset_gc_overhead_limit_count();
638 assert(!heap->incremental_collection_failed(), "Should be clear");
639 } else {
640 assert(_promo_failure_scan_stack.is_empty(), "post condition");
641 _promo_failure_scan_stack.clear(true); // Clear cached segments.
642
643 remove_forwarding_pointers();
644 log_info(gc, promotion)("Promotion failed");
645 // Add to-space to the list of space to compact
646 // when a promotion failure has occurred. In that
647 // case there can be live objects in to-space
648 // as a result of a partial evacuation of eden
649 // and from-space.
650 swap_spaces(); // For uniformity wrt ParNewGeneration.
651 from()->set_next_compaction_space(to());
652 heap->set_incremental_collection_failed();
653
654 // Inform the next generation that a promotion failure occurred.
655 _old_gen->promotion_failure_occurred();
656 gc_tracer.report_promotion_failed(_promotion_failed_info);
657
658 // Reset the PromotionFailureALot counters.
659 NOT_PRODUCT(heap->reset_promotion_should_fail();)
660 }
661 // We should have processed and cleared all the preserved marks.
662 _preserved_marks_set.reclaim();
663 // set new iteration safe limit for the survivor spaces
664 from()->set_concurrent_iteration_safe_limit(from()->top());
665 to()->set_concurrent_iteration_safe_limit(to()->top());
666
667 heap->trace_heap_after_gc(&gc_tracer);
668
669 _gc_timer->register_gc_end();
670
671 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
672 }
673
674 void DefNewGeneration::init_assuming_no_promotion_failure() {
675 _promotion_failed = false;
676 _promotion_failed_info.reset();
677 from()->set_next_compaction_space(NULL);
678 }
679
680 void DefNewGeneration::remove_forwarding_pointers() {
681 RemoveForwardedPointerClosure rspc;
682 eden()->object_iterate(&rspc);
683 from()->object_iterate(&rspc);
684 restore_preserved_marks();
685 }
686
687 void DefNewGeneration::restore_preserved_marks() {
688 _preserved_marks_set.restore(NULL);
689 }
690
691 void DefNewGeneration::handle_promotion_failure(oop old) {
692 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
693
694 _promotion_failed = true;
695 _promotion_failed_info.register_copy_failure(old->size());
696 _preserved_marks_set.get()->push_if_necessary(old, old->mark_raw());
697 // forward to self
698 old->forward_to(old);
699
700 _promo_failure_scan_stack.push(old);
701
702 if (!_promo_failure_drain_in_progress) {
703 // prevent recursion in copy_to_survivor_space()
704 _promo_failure_drain_in_progress = true;
705 drain_promo_failure_scan_stack();
706 _promo_failure_drain_in_progress = false;
707 }
708 }
709
710 oop DefNewGeneration::copy_to_survivor_space(oop old) {
711 assert(is_in_reserved(old) && !old->is_forwarded(),
712 "shouldn't be scavenging this oop");
713 size_t s = old->size();
714 oop obj = NULL;
715
716 // Try allocating obj in to-space (unless too old)
717 if (old->age() < tenuring_threshold()) {
718 obj = (oop) to()->allocate_aligned(s);
719 }
720
721 // Otherwise try allocating obj tenured
722 if (obj == NULL) {
723 obj = _old_gen->promote(old, s);
724 if (obj == NULL) {
725 handle_promotion_failure(old);
726 return old;
727 }
728 } else {
729 // Prefetch beyond obj
730 const intx interval = PrefetchCopyIntervalInBytes;
731 Prefetch::write(obj, interval);
732
733 // Copy obj
734 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s);
735
736 // Increment age if obj still in new generation
737 obj->incr_age();
738 age_table()->add(obj, s);
739 }
740
741 // Done, insert forward pointer to obj in this header
742 old->forward_to(obj);
743
744 return obj;
745 }
746
747 void DefNewGeneration::drain_promo_failure_scan_stack() {
748 while (!_promo_failure_scan_stack.is_empty()) {
749 oop obj = _promo_failure_scan_stack.pop();
750 obj->oop_iterate(_promo_failure_scan_stack_closure);
751 }
752 }
753
754 void DefNewGeneration::save_marks() {
755 eden()->set_saved_mark();
756 to()->set_saved_mark();
757 from()->set_saved_mark();
758 }
759
760
761 void DefNewGeneration::reset_saved_marks() {
762 eden()->reset_saved_mark();
763 to()->reset_saved_mark();
764 from()->reset_saved_mark();
765 }
766
767
768 bool DefNewGeneration::no_allocs_since_save_marks() {
769 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
770 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
771 return to()->saved_mark_at_top();
772 }
773
774 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
775 size_t max_alloc_words) {
776 if (requestor == this || _promotion_failed) {
777 return;
778 }
779 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
780
781 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
782 if (to_space->top() > to_space->bottom()) {
783 trace("to_space not empty when contribute_scratch called");
784 }
785 */
786
787 ContiguousSpace* to_space = to();
788 assert(to_space->end() >= to_space->top(), "pointers out of order");
789 size_t free_words = pointer_delta(to_space->end(), to_space->top());
790 if (free_words >= MinFreeScratchWords) {
791 ScratchBlock* sb = (ScratchBlock*)to_space->top();
792 sb->num_words = free_words;
793 sb->next = list;
794 list = sb;
795 }
796 }
797
798 void DefNewGeneration::reset_scratch() {
799 // If contributing scratch in to_space, mangle all of
800 // to_space if ZapUnusedHeapArea. This is needed because
801 // top is not maintained while using to-space as scratch.
802 if (ZapUnusedHeapArea) {
803 to()->mangle_unused_area_complete();
804 }
805 }
806
807 bool DefNewGeneration::collection_attempt_is_safe() {
808 if (!to()->is_empty()) {
809 log_trace(gc)(":: to is not empty ::");
810 return false;
811 }
812 if (_old_gen == NULL) {
813 GenCollectedHeap* gch = GenCollectedHeap::heap();
814 _old_gen = gch->old_gen();
815 }
816 return _old_gen->promotion_attempt_is_safe(used());
817 }
818
819 void DefNewGeneration::gc_epilogue(bool full) {
820 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
821
822 assert(!GCLocker::is_active(), "We should not be executing here");
823 // Check if the heap is approaching full after a collection has
824 // been done. Generally the young generation is empty at
825 // a minimum at the end of a collection. If it is not, then
826 // the heap is approaching full.
827 GenCollectedHeap* gch = GenCollectedHeap::heap();
828 if (full) {
829 DEBUG_ONLY(seen_incremental_collection_failed = false;)
830 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
831 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
832 GCCause::to_string(gch->gc_cause()));
833 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
834 set_should_allocate_from_space(); // we seem to be running out of space
835 } else {
836 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
837 GCCause::to_string(gch->gc_cause()));
838 gch->clear_incremental_collection_failed(); // We just did a full collection
839 clear_should_allocate_from_space(); // if set
840 }
841 } else {
842 #ifdef ASSERT
843 // It is possible that incremental_collection_failed() == true
844 // here, because an attempted scavenge did not succeed. The policy
845 // is normally expected to cause a full collection which should
846 // clear that condition, so we should not be here twice in a row
847 // with incremental_collection_failed() == true without having done
848 // a full collection in between.
849 if (!seen_incremental_collection_failed &&
850 gch->incremental_collection_failed()) {
851 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
852 GCCause::to_string(gch->gc_cause()));
853 seen_incremental_collection_failed = true;
854 } else if (seen_incremental_collection_failed) {
855 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
856 GCCause::to_string(gch->gc_cause()));
857 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
858 !gch->incremental_collection_failed(),
859 "Twice in a row");
860 seen_incremental_collection_failed = false;
861 }
862 #endif // ASSERT
863 }
864
865 if (ZapUnusedHeapArea) {
866 eden()->check_mangled_unused_area_complete();
867 from()->check_mangled_unused_area_complete();
868 to()->check_mangled_unused_area_complete();
869 }
870
871 if (!CleanChunkPoolAsync) {
872 Chunk::clean_chunk_pool();
873 }
874
875 // update the generation and space performance counters
876 update_counters();
877 gch->counters()->update_counters();
878 }
879
880 void DefNewGeneration::record_spaces_top() {
881 assert(ZapUnusedHeapArea, "Not mangling unused space");
882 eden()->set_top_for_allocations();
883 to()->set_top_for_allocations();
884 from()->set_top_for_allocations();
885 }
886
887 void DefNewGeneration::ref_processor_init() {
888 Generation::ref_processor_init();
889 }
890
891
892 void DefNewGeneration::update_counters() {
893 if (UsePerfData) {
894 _eden_counters->update_all();
895 _from_counters->update_all();
896 _to_counters->update_all();
897 _gen_counters->update_all();
898 }
899 }
900
901 void DefNewGeneration::verify() {
902 eden()->verify();
903 from()->verify();
904 to()->verify();
905 }
906
907 void DefNewGeneration::print_on(outputStream* st) const {
908 Generation::print_on(st);
909 st->print(" eden");
910 eden()->print_on(st);
911 st->print(" from");
912 from()->print_on(st);
913 st->print(" to ");
914 to()->print_on(st);
915 }
916
917
918 const char* DefNewGeneration::name() const {
919 return "def new generation";
920 }
921
922 // Moved from inline file as they are not called inline
923 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
924 return eden();
925 }
926
927 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
928 // This is the slow-path allocation for the DefNewGeneration.
929 // Most allocations are fast-path in compiled code.
930 // We try to allocate from the eden. If that works, we are happy.
931 // Note that since DefNewGeneration supports lock-free allocation, we
932 // have to use it here, as well.
933 HeapWord* result = eden()->par_allocate(word_size);
934 if (result != NULL) {
935 if (_old_gen != NULL) {
936 _old_gen->sample_eden_chunk();
937 }
938 } else {
939 // If the eden is full and the last collection bailed out, we are running
940 // out of heap space, and we try to allocate the from-space, too.
941 // allocate_from_space can't be inlined because that would introduce a
942 // circular dependency at compile time.
943 result = allocate_from_space(word_size);
944 }
945 return result;
946 }
947
948 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
949 bool is_tlab) {
950 HeapWord* res = eden()->par_allocate(word_size);
951 if (_old_gen != NULL) {
952 _old_gen->sample_eden_chunk();
953 }
954 return res;
955 }
956
957 size_t DefNewGeneration::tlab_capacity() const {
958 return eden()->capacity();
959 }
960
961 size_t DefNewGeneration::tlab_used() const {
962 return eden()->used();
963 }
964
965 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
966 return unsafe_max_alloc_nogc();
967 }