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 FastScanClosure* cur,
96 FastScanClosure* 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 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
109 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
110 {
111 _boundary = _g->reserved().end();
112 }
113
114 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
115 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
116 {
117 _boundary = _g->reserved().end();
118 }
119
120 void CLDScanClosure::do_cld(ClassLoaderData* cld) {
121 NOT_PRODUCT(ResourceMark rm);
122 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s",
123 p2i(cld),
124 cld->loader_name_and_id(),
125 cld->has_modified_oops() ? "true" : "false");
126
127 // If the cld has not been dirtied we know that there's
128 // no references into the young gen and we can skip it.
129 if (cld->has_modified_oops()) {
130 if (_accumulate_modified_oops) {
131 cld->accumulate_modified_oops();
132 }
133
134 // Tell the closure which CLD is being scanned so that it can be dirtied
135 // if oops are left pointing into the young gen.
136 _scavenge_closure->set_scanned_cld(cld);
137
138 // Clean the cld since we're going to scavenge all the metadata.
139 cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);
140
141 _scavenge_closure->set_scanned_cld(NULL);
142 }
143 }
144
145 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
146 _g(g)
147 {
148 _boundary = _g->reserved().end();
149 }
150
151 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
152 size_t initial_size,
153 size_t min_size,
154 size_t max_size,
155 const char* policy)
156 : Generation(rs, initial_size),
157 _preserved_marks_set(false /* in_c_heap */),
158 _promo_failure_drain_in_progress(false),
159 _should_allocate_from_space(false)
160 {
161 MemRegion cmr((HeapWord*)_virtual_space.low(),
162 (HeapWord*)_virtual_space.high());
163 GenCollectedHeap* gch = GenCollectedHeap::heap();
164
165 gch->rem_set()->resize_covered_region(cmr);
166
167 _eden_space = new ContiguousSpace();
168 _from_space = new ContiguousSpace();
169 _to_space = new ContiguousSpace();
170
171 // Compute the maximum eden and survivor space sizes. These sizes
172 // are computed assuming the entire reserved space is committed.
173 // These values are exported as performance counters.
174 uintx size = _virtual_space.reserved_size();
175 _max_survivor_size = compute_survivor_size(size, SpaceAlignment);
176 _max_eden_size = size - (2*_max_survivor_size);
177
178 // allocate the performance counters
179
180 // Generation counters -- generation 0, 3 subspaces
181 _gen_counters = new GenerationCounters("new", 0, 3,
182 min_size, max_size, &_virtual_space);
183 _gc_counters = new CollectorCounters(policy, 0);
184
185 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
186 _gen_counters);
187 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
188 _gen_counters);
189 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
190 _gen_counters);
191
192 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
193 update_counters();
194 _old_gen = NULL;
195 _tenuring_threshold = MaxTenuringThreshold;
196 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
197
198 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
199 }
200
201 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
202 bool clear_space,
203 bool mangle_space) {
204 // If the spaces are being cleared (only done at heap initialization
205 // currently), the survivor spaces need not be empty.
206 // Otherwise, no care is taken for used areas in the survivor spaces
207 // so check.
208 assert(clear_space || (to()->is_empty() && from()->is_empty()),
209 "Initialization of the survivor spaces assumes these are empty");
210
211 // Compute sizes
212 uintx size = _virtual_space.committed_size();
213 uintx survivor_size = compute_survivor_size(size, SpaceAlignment);
214 uintx eden_size = size - (2*survivor_size);
215 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
216
217 if (eden_size < minimum_eden_size) {
218 // May happen due to 64Kb rounding, if so adjust eden size back up
219 minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment);
220 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
221 uintx unaligned_survivor_size =
222 align_down(maximum_survivor_size, SpaceAlignment);
223 survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment);
224 eden_size = size - (2*survivor_size);
225 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
226 assert(eden_size >= minimum_eden_size, "just checking");
227 }
228
229 char *eden_start = _virtual_space.low();
230 char *from_start = eden_start + eden_size;
231 char *to_start = from_start + survivor_size;
232 char *to_end = to_start + survivor_size;
233
234 assert(to_end == _virtual_space.high(), "just checking");
235 assert(Space::is_aligned(eden_start), "checking alignment");
236 assert(Space::is_aligned(from_start), "checking alignment");
237 assert(Space::is_aligned(to_start), "checking alignment");
238
239 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
240 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
241 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
242
243 // A minimum eden size implies that there is a part of eden that
244 // is being used and that affects the initialization of any
245 // newly formed eden.
246 bool live_in_eden = minimum_eden_size > 0;
247
248 // If not clearing the spaces, do some checking to verify that
249 // the space are already mangled.
250 if (!clear_space) {
251 // Must check mangling before the spaces are reshaped. Otherwise,
252 // the bottom or end of one space may have moved into another
253 // a failure of the check may not correctly indicate which space
254 // is not properly mangled.
255 if (ZapUnusedHeapArea) {
256 HeapWord* limit = (HeapWord*) _virtual_space.high();
257 eden()->check_mangled_unused_area(limit);
258 from()->check_mangled_unused_area(limit);
259 to()->check_mangled_unused_area(limit);
260 }
261 }
262
263 // Reset the spaces for their new regions.
264 eden()->initialize(edenMR,
265 clear_space && !live_in_eden,
266 SpaceDecorator::Mangle);
267 // If clear_space and live_in_eden, we will not have cleared any
268 // portion of eden above its top. This can cause newly
269 // expanded space not to be mangled if using ZapUnusedHeapArea.
270 // We explicitly do such mangling here.
271 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
272 eden()->mangle_unused_area();
273 }
274 from()->initialize(fromMR, clear_space, mangle_space);
275 to()->initialize(toMR, clear_space, mangle_space);
276
277 // Set next compaction spaces.
278 eden()->set_next_compaction_space(from());
279 // The to-space is normally empty before a compaction so need
280 // not be considered. The exception is during promotion
281 // failure handling when to-space can contain live objects.
282 from()->set_next_compaction_space(NULL);
283 }
284
285 void DefNewGeneration::swap_spaces() {
286 ContiguousSpace* s = from();
287 _from_space = to();
288 _to_space = s;
289 eden()->set_next_compaction_space(from());
290 // The to-space is normally empty before a compaction so need
291 // not be considered. The exception is during promotion
292 // failure handling when to-space can contain live objects.
293 from()->set_next_compaction_space(NULL);
294
295 if (UsePerfData) {
296 CSpaceCounters* c = _from_counters;
297 _from_counters = _to_counters;
298 _to_counters = c;
299 }
300 }
301
302 bool DefNewGeneration::expand(size_t bytes) {
303 MutexLocker x(ExpandHeap_lock);
304 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
305 bool success = _virtual_space.expand_by(bytes);
306 if (success && ZapUnusedHeapArea) {
307 // Mangle newly committed space immediately because it
308 // can be done here more simply that after the new
309 // spaces have been computed.
310 HeapWord* new_high = (HeapWord*) _virtual_space.high();
311 MemRegion mangle_region(prev_high, new_high);
312 SpaceMangler::mangle_region(mangle_region);
313 }
314
315 // Do not attempt an expand-to-the reserve size. The
316 // request should properly observe the maximum size of
317 // the generation so an expand-to-reserve should be
318 // unnecessary. Also a second call to expand-to-reserve
319 // value potentially can cause an undue expansion.
320 // For example if the first expand fail for unknown reasons,
321 // but the second succeeds and expands the heap to its maximum
322 // value.
323 if (GCLocker::is_active()) {
324 log_debug(gc)("Garbage collection disabled, expanded heap instead");
325 }
326
327 return success;
328 }
329
330 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
331 size_t new_size_before,
332 size_t alignment) const {
333 size_t desired_new_size = new_size_before;
334
335 if (NewSizeThreadIncrease > 0) {
336 int threads_count;
337 size_t thread_increase_size = 0;
338
339 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
340 threads_count = Threads::number_of_non_daemon_threads();
341 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
342 thread_increase_size = threads_count * NewSizeThreadIncrease;
343
344 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
345 if (new_size_candidate <= max_uintx - thread_increase_size) {
346 new_size_candidate += thread_increase_size;
347
348 // 3. Check an overflow at 'align_up'.
349 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
350 if (new_size_candidate <= aligned_max) {
351 desired_new_size = align_up(new_size_candidate, alignment);
352 }
353 }
354 }
355 }
356
357 return desired_new_size;
358 }
359
360 void DefNewGeneration::compute_new_size() {
361 // This is called after a GC that includes the old generation, so from-space
362 // will normally be empty.
363 // Note that we check both spaces, since if scavenge failed they revert roles.
364 // If not we bail out (otherwise we would have to relocate the objects).
365 if (!from()->is_empty() || !to()->is_empty()) {
366 return;
367 }
368
369 GenCollectedHeap* gch = GenCollectedHeap::heap();
370
371 size_t old_size = gch->old_gen()->capacity();
372 size_t new_size_before = _virtual_space.committed_size();
373 size_t min_new_size = initial_size();
374 size_t max_new_size = reserved().byte_size();
375 assert(min_new_size <= new_size_before &&
376 new_size_before <= max_new_size,
377 "just checking");
378 // All space sizes must be multiples of Generation::GenGrain.
379 size_t alignment = Generation::GenGrain;
380
381 int threads_count = 0;
382 size_t thread_increase_size = 0;
383
384 size_t new_size_candidate = old_size / NewRatio;
385 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
386 // and reverts to previous value if any overflow happens
387 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);
388
389 // Adjust new generation size
390 desired_new_size = clamp(desired_new_size, min_new_size, max_new_size);
391 assert(desired_new_size <= max_new_size, "just checking");
392
393 bool changed = false;
394 if (desired_new_size > new_size_before) {
395 size_t change = desired_new_size - new_size_before;
396 assert(change % alignment == 0, "just checking");
397 if (expand(change)) {
398 changed = true;
399 }
400 // If the heap failed to expand to the desired size,
401 // "changed" will be false. If the expansion failed
402 // (and at this point it was expected to succeed),
403 // ignore the failure (leaving "changed" as false).
404 }
405 if (desired_new_size < new_size_before && eden()->is_empty()) {
406 // bail out of shrinking if objects in eden
407 size_t change = new_size_before - desired_new_size;
408 assert(change % alignment == 0, "just checking");
409 _virtual_space.shrink_by(change);
410 changed = true;
411 }
412 if (changed) {
413 // The spaces have already been mangled at this point but
414 // may not have been cleared (set top = bottom) and should be.
415 // Mangling was done when the heap was being expanded.
416 compute_space_boundaries(eden()->used(),
417 SpaceDecorator::Clear,
418 SpaceDecorator::DontMangle);
419 MemRegion cmr((HeapWord*)_virtual_space.low(),
420 (HeapWord*)_virtual_space.high());
421 gch->rem_set()->resize_covered_region(cmr);
422
423 log_debug(gc, ergo, heap)(
424 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
425 new_size_before/K, _virtual_space.committed_size()/K,
426 eden()->capacity()/K, from()->capacity()/K);
427 log_trace(gc, ergo, heap)(
428 " [allowed " SIZE_FORMAT "K extra for %d threads]",
429 thread_increase_size/K, threads_count);
430 }
431 }
432
433 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
434 assert(false, "NYI -- are you sure you want to call this?");
435 }
436
437
438 size_t DefNewGeneration::capacity() const {
439 return eden()->capacity()
440 + from()->capacity(); // to() is only used during scavenge
441 }
442
443
444 size_t DefNewGeneration::used() const {
445 return eden()->used()
446 + from()->used(); // to() is only used during scavenge
447 }
448
449
450 size_t DefNewGeneration::free() const {
451 return eden()->free()
452 + from()->free(); // to() is only used during scavenge
453 }
454
455 size_t DefNewGeneration::max_capacity() const {
456 const size_t reserved_bytes = reserved().byte_size();
457 return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment);
458 }
459
460 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
461 return eden()->free();
462 }
463
464 size_t DefNewGeneration::capacity_before_gc() const {
465 return eden()->capacity();
466 }
467
468 size_t DefNewGeneration::contiguous_available() const {
469 return eden()->free();
470 }
471
472
473 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }
474 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
475
476 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
477 eden()->object_iterate(blk);
478 from()->object_iterate(blk);
479 }
480
481
482 void DefNewGeneration::space_iterate(SpaceClosure* blk,
483 bool usedOnly) {
484 blk->do_space(eden());
485 blk->do_space(from());
486 blk->do_space(to());
487 }
488
489 // The last collection bailed out, we are running out of heap space,
490 // so we try to allocate the from-space, too.
491 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
492 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
493
494 // If the Heap_lock is not locked by this thread, this will be called
495 // again later with the Heap_lock held.
496 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
497
498 HeapWord* result = NULL;
499 if (do_alloc) {
500 result = from()->allocate(size);
501 }
502
503 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s",
504 size,
505 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
506 "true" : "false",
507 Heap_lock->is_locked() ? "locked" : "unlocked",
508 from()->free(),
509 should_try_alloc ? "" : " should_allocate_from_space: NOT",
510 do_alloc ? " Heap_lock is not owned by self" : "",
511 result == NULL ? "NULL" : "object");
512
513 return result;
514 }
515
516 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
517 bool is_tlab,
518 bool parallel) {
519 // We don't attempt to expand the young generation (but perhaps we should.)
520 return allocate(size, is_tlab);
521 }
522
523 void DefNewGeneration::adjust_desired_tenuring_threshold() {
524 // Set the desired survivor size to half the real survivor space
525 size_t const survivor_capacity = to()->capacity() / HeapWordSize;
526 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
527
528 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
529
530 if (UsePerfData) {
531 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters();
532 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
533 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
534 }
535
536 age_table()->print_age_table(_tenuring_threshold);
537 }
538
539 void DefNewGeneration::collect(bool full,
540 bool clear_all_soft_refs,
541 size_t size,
542 bool is_tlab) {
543 assert(full || size > 0, "otherwise we don't want to collect");
544
545 SerialHeap* heap = SerialHeap::heap();
546
547 _gc_timer->register_gc_start();
548 DefNewTracer gc_tracer;
549 gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start());
550
551 _old_gen = heap->old_gen();
552
553 // If the next generation is too full to accommodate promotion
554 // from this generation, pass on collection; let the next generation
555 // do it.
556 if (!collection_attempt_is_safe()) {
557 log_trace(gc)(":: Collection attempt not safe ::");
558 heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
559 return;
560 }
561 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
562
563 init_assuming_no_promotion_failure();
564
565 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause());
566
567 heap->trace_heap_before_gc(&gc_tracer);
568
569 // These can be shared for all code paths
570 IsAliveClosure is_alive(this);
571 ScanWeakRefClosure scan_weak_ref(this);
572
573 age_table()->clear();
574 to()->clear(SpaceDecorator::Mangle);
575 // The preserved marks should be empty at the start of the GC.
576 _preserved_marks_set.init(1);
577
578 heap->rem_set()->prepare_for_younger_refs_iterate(false);
579
580 assert(heap->no_allocs_since_save_marks(),
581 "save marks have not been newly set.");
582
583 FastScanClosure fsc_with_no_gc_barrier(this, false);
584 FastScanClosure fsc_with_gc_barrier(this, true);
585
586 CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier,
587 heap->rem_set()->cld_rem_set()->accumulate_modified_oops());
588
589 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
590 FastEvacuateFollowersClosure evacuate_followers(heap,
591 &fsc_with_no_gc_barrier,
592 &fsc_with_gc_barrier);
593
594 assert(heap->no_allocs_since_save_marks(),
595 "save marks have not been newly set.");
596
597 {
598 // DefNew needs to run with n_threads == 0, to make sure the serial
599 // version of the card table scanning code is used.
600 // See: CardTableRS::non_clean_card_iterate_possibly_parallel.
601 StrongRootsScope srs(0);
602
603 heap->young_process_roots(&srs,
604 &fsc_with_no_gc_barrier,
605 &fsc_with_gc_barrier,
606 &cld_scan_closure);
607 }
608
609 // "evacuate followers".
610 evacuate_followers.do_void();
611
612 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
613 ReferenceProcessor* rp = ref_processor();
614 rp->setup_policy(clear_all_soft_refs);
615 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
616 const ReferenceProcessorStats& stats =
617 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
618 NULL, &pt);
619 gc_tracer.report_gc_reference_stats(stats);
620 gc_tracer.report_tenuring_threshold(tenuring_threshold());
621 pt.print_all_references();
622
623 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
624
625 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
626
627 // Verify that the usage of keep_alive didn't copy any objects.
628 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
629
630 if (!_promotion_failed) {
631 // Swap the survivor spaces.
632 eden()->clear(SpaceDecorator::Mangle);
633 from()->clear(SpaceDecorator::Mangle);
634 if (ZapUnusedHeapArea) {
635 // This is now done here because of the piece-meal mangling which
636 // can check for valid mangling at intermediate points in the
637 // collection(s). When a young collection fails to collect
638 // sufficient space resizing of the young generation can occur
639 // an redistribute the spaces in the young generation. Mangle
640 // here so that unzapped regions don't get distributed to
641 // other spaces.
642 to()->mangle_unused_area();
643 }
644 swap_spaces();
645
646 assert(to()->is_empty(), "to space should be empty now");
647
648 adjust_desired_tenuring_threshold();
649
650 // A successful scavenge should restart the GC time limit count which is
651 // for full GC's.
652 AdaptiveSizePolicy* size_policy = heap->size_policy();
653 size_policy->reset_gc_overhead_limit_count();
654 assert(!heap->incremental_collection_failed(), "Should be clear");
655 } else {
656 assert(_promo_failure_scan_stack.is_empty(), "post condition");
657 _promo_failure_scan_stack.clear(true); // Clear cached segments.
658
659 remove_forwarding_pointers();
660 log_info(gc, promotion)("Promotion failed");
661 // Add to-space to the list of space to compact
662 // when a promotion failure has occurred. In that
663 // case there can be live objects in to-space
664 // as a result of a partial evacuation of eden
665 // and from-space.
666 swap_spaces(); // For uniformity wrt ParNewGeneration.
667 from()->set_next_compaction_space(to());
668 heap->set_incremental_collection_failed();
669
670 // Inform the next generation that a promotion failure occurred.
671 _old_gen->promotion_failure_occurred();
672 gc_tracer.report_promotion_failed(_promotion_failed_info);
673
674 // Reset the PromotionFailureALot counters.
675 NOT_PRODUCT(heap->reset_promotion_should_fail();)
676 }
677 // We should have processed and cleared all the preserved marks.
678 _preserved_marks_set.reclaim();
679 // set new iteration safe limit for the survivor spaces
680 from()->set_concurrent_iteration_safe_limit(from()->top());
681 to()->set_concurrent_iteration_safe_limit(to()->top());
682
683 heap->trace_heap_after_gc(&gc_tracer);
684
685 _gc_timer->register_gc_end();
686
687 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
688 }
689
690 void DefNewGeneration::init_assuming_no_promotion_failure() {
691 _promotion_failed = false;
692 _promotion_failed_info.reset();
693 from()->set_next_compaction_space(NULL);
694 }
695
696 void DefNewGeneration::remove_forwarding_pointers() {
697 RemoveForwardedPointerClosure rspc;
698 eden()->object_iterate(&rspc);
699 from()->object_iterate(&rspc);
700 restore_preserved_marks();
701 }
702
703 void DefNewGeneration::restore_preserved_marks() {
704 _preserved_marks_set.restore(NULL);
705 }
706
707 void DefNewGeneration::handle_promotion_failure(oop old) {
708 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
709
710 _promotion_failed = true;
711 _promotion_failed_info.register_copy_failure(old->size());
712 _preserved_marks_set.get()->push_if_necessary(old, old->mark_raw());
713 // forward to self
714 old->forward_to(old);
715
716 _promo_failure_scan_stack.push(old);
717
718 if (!_promo_failure_drain_in_progress) {
719 // prevent recursion in copy_to_survivor_space()
720 _promo_failure_drain_in_progress = true;
721 drain_promo_failure_scan_stack();
722 _promo_failure_drain_in_progress = false;
723 }
724 }
725
726 oop DefNewGeneration::copy_to_survivor_space(oop old) {
727 assert(is_in_reserved(old) && !old->is_forwarded(),
728 "shouldn't be scavenging this oop");
729 size_t s = old->size();
730 oop obj = NULL;
731
732 // Try allocating obj in to-space (unless too old)
733 if (old->age() < tenuring_threshold()) {
734 obj = (oop) to()->allocate_aligned(s);
735 }
736
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 } else {
745 // Prefetch beyond obj
746 const intx interval = PrefetchCopyIntervalInBytes;
747 Prefetch::write(obj, interval);
748
749 // Copy obj
750 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s);
751
752 // Increment age if obj still in new generation
753 obj->incr_age();
754 age_table()->add(obj, s);
755 }
756
757 // Done, insert forward pointer to obj in this header
758 old->forward_to(obj);
759
760 return obj;
761 }
762
763 void DefNewGeneration::drain_promo_failure_scan_stack() {
764 while (!_promo_failure_scan_stack.is_empty()) {
765 oop obj = _promo_failure_scan_stack.pop();
766 obj->oop_iterate(_promo_failure_scan_stack_closure);
767 }
768 }
769
770 void DefNewGeneration::save_marks() {
771 eden()->set_saved_mark();
772 to()->set_saved_mark();
773 from()->set_saved_mark();
774 }
775
776
777 void DefNewGeneration::reset_saved_marks() {
778 eden()->reset_saved_mark();
779 to()->reset_saved_mark();
780 from()->reset_saved_mark();
781 }
782
783
784 bool DefNewGeneration::no_allocs_since_save_marks() {
785 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
786 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
787 return to()->saved_mark_at_top();
788 }
789
790 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
791 size_t max_alloc_words) {
792 if (requestor == this || _promotion_failed) {
793 return;
794 }
795 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
796
797 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
798 if (to_space->top() > to_space->bottom()) {
799 trace("to_space not empty when contribute_scratch called");
800 }
801 */
802
803 ContiguousSpace* to_space = to();
804 assert(to_space->end() >= to_space->top(), "pointers out of order");
805 size_t free_words = pointer_delta(to_space->end(), to_space->top());
806 if (free_words >= MinFreeScratchWords) {
807 ScratchBlock* sb = (ScratchBlock*)to_space->top();
808 sb->num_words = free_words;
809 sb->next = list;
810 list = sb;
811 }
812 }
813
814 void DefNewGeneration::reset_scratch() {
815 // If contributing scratch in to_space, mangle all of
816 // to_space if ZapUnusedHeapArea. This is needed because
817 // top is not maintained while using to-space as scratch.
818 if (ZapUnusedHeapArea) {
819 to()->mangle_unused_area_complete();
820 }
821 }
822
823 bool DefNewGeneration::collection_attempt_is_safe() {
824 if (!to()->is_empty()) {
825 log_trace(gc)(":: to is not empty ::");
826 return false;
827 }
828 if (_old_gen == NULL) {
829 GenCollectedHeap* gch = GenCollectedHeap::heap();
830 _old_gen = gch->old_gen();
831 }
832 return _old_gen->promotion_attempt_is_safe(used());
833 }
834
835 void DefNewGeneration::gc_epilogue(bool full) {
836 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
837
838 assert(!GCLocker::is_active(), "We should not be executing here");
839 // Check if the heap is approaching full after a collection has
840 // been done. Generally the young generation is empty at
841 // a minimum at the end of a collection. If it is not, then
842 // the heap is approaching full.
843 GenCollectedHeap* gch = GenCollectedHeap::heap();
844 if (full) {
845 DEBUG_ONLY(seen_incremental_collection_failed = false;)
846 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
847 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
848 GCCause::to_string(gch->gc_cause()));
849 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
850 set_should_allocate_from_space(); // we seem to be running out of space
851 } else {
852 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
853 GCCause::to_string(gch->gc_cause()));
854 gch->clear_incremental_collection_failed(); // We just did a full collection
855 clear_should_allocate_from_space(); // if set
856 }
857 } else {
858 #ifdef ASSERT
859 // It is possible that incremental_collection_failed() == true
860 // here, because an attempted scavenge did not succeed. The policy
861 // is normally expected to cause a full collection which should
862 // clear that condition, so we should not be here twice in a row
863 // with incremental_collection_failed() == true without having done
864 // a full collection in between.
865 if (!seen_incremental_collection_failed &&
866 gch->incremental_collection_failed()) {
867 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
868 GCCause::to_string(gch->gc_cause()));
869 seen_incremental_collection_failed = true;
870 } else if (seen_incremental_collection_failed) {
871 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
872 GCCause::to_string(gch->gc_cause()));
873 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
874 !gch->incremental_collection_failed(),
875 "Twice in a row");
876 seen_incremental_collection_failed = false;
877 }
878 #endif // ASSERT
879 }
880
881 if (ZapUnusedHeapArea) {
882 eden()->check_mangled_unused_area_complete();
883 from()->check_mangled_unused_area_complete();
884 to()->check_mangled_unused_area_complete();
885 }
886
887 if (!CleanChunkPoolAsync) {
888 Chunk::clean_chunk_pool();
889 }
890
891 // update the generation and space performance counters
892 update_counters();
893 gch->counters()->update_counters();
894 }
895
896 void DefNewGeneration::record_spaces_top() {
897 assert(ZapUnusedHeapArea, "Not mangling unused space");
898 eden()->set_top_for_allocations();
899 to()->set_top_for_allocations();
900 from()->set_top_for_allocations();
901 }
902
903 void DefNewGeneration::ref_processor_init() {
904 Generation::ref_processor_init();
905 }
906
907
908 void DefNewGeneration::update_counters() {
909 if (UsePerfData) {
910 _eden_counters->update_all();
911 _from_counters->update_all();
912 _to_counters->update_all();
913 _gen_counters->update_all();
914 }
915 }
916
917 void DefNewGeneration::verify() {
918 eden()->verify();
919 from()->verify();
920 to()->verify();
921 }
922
923 void DefNewGeneration::print_on(outputStream* st) const {
924 Generation::print_on(st);
925 st->print(" eden");
926 eden()->print_on(st);
927 st->print(" from");
928 from()->print_on(st);
929 st->print(" to ");
930 to()->print_on(st);
931 }
932
933
934 const char* DefNewGeneration::name() const {
935 return "def new generation";
936 }
937
938 // Moved from inline file as they are not called inline
939 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
940 return eden();
941 }
942
943 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
944 // This is the slow-path allocation for the DefNewGeneration.
945 // Most allocations are fast-path in compiled code.
946 // We try to allocate from the eden. If that works, we are happy.
947 // Note that since DefNewGeneration supports lock-free allocation, we
948 // have to use it here, as well.
949 HeapWord* result = eden()->par_allocate(word_size);
950 if (result != NULL) {
951 if (_old_gen != NULL) {
952 _old_gen->sample_eden_chunk();
953 }
954 } else {
955 // If the eden is full and the last collection bailed out, we are running
956 // out of heap space, and we try to allocate the from-space, too.
957 // allocate_from_space can't be inlined because that would introduce a
958 // circular dependency at compile time.
959 result = allocate_from_space(word_size);
960 }
961 return result;
962 }
963
964 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
965 bool is_tlab) {
966 HeapWord* res = eden()->par_allocate(word_size);
967 if (_old_gen != NULL) {
968 _old_gen->sample_eden_chunk();
969 }
970 return res;
971 }
972
973 size_t DefNewGeneration::tlab_capacity() const {
974 return eden()->capacity();
975 }
976
977 size_t DefNewGeneration::tlab_used() const {
978 return eden()->used();
979 }
980
981 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
982 return unsafe_max_alloc_nogc();
983 }