1 /*
2 * Copyright (c) 2001, 2015, 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/shared/cardTableRS.hpp"
28 #include "gc/shared/collectorCounters.hpp"
29 #include "gc/shared/gcHeapSummary.hpp"
30 #include "gc/shared/gcLocker.inline.hpp"
31 #include "gc/shared/gcPolicyCounters.hpp"
32 #include "gc/shared/gcTimer.hpp"
33 #include "gc/shared/gcTrace.hpp"
34 #include "gc/shared/gcTraceTime.hpp"
35 #include "gc/shared/genCollectedHeap.hpp"
36 #include "gc/shared/genOopClosures.inline.hpp"
37 #include "gc/shared/generationSpec.hpp"
38 #include "gc/shared/referencePolicy.hpp"
39 #include "gc/shared/space.inline.hpp"
40 #include "gc/shared/spaceDecorator.hpp"
41 #include "gc/shared/strongRootsScope.hpp"
42 #include "logging/log.hpp"
43 #include "memory/iterator.hpp"
44 #include "oops/instanceRefKlass.hpp"
45 #include "oops/oop.inline.hpp"
46 #include "runtime/atomic.inline.hpp"
47 #include "runtime/java.hpp"
48 #include "runtime/prefetch.inline.hpp"
49 #include "runtime/thread.inline.hpp"
50 #include "utilities/copy.hpp"
51 #include "utilities/globalDefinitions.hpp"
52 #include "utilities/stack.inline.hpp"
53 #if INCLUDE_ALL_GCS
54 #include "gc/cms/parOopClosures.hpp"
55 #endif
56
57 //
58 // DefNewGeneration functions.
59
60 // Methods of protected closure types.
61
62 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
63 assert(_young_gen->kind() == Generation::ParNew ||
64 _young_gen->kind() == Generation::DefNew, "Expected the young generation here");
65 }
66
67 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
68 return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded();
69 }
70
71 DefNewGeneration::KeepAliveClosure::
72 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
73 _rs = GenCollectedHeap::heap()->rem_set();
74 }
75
76 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
77 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
78
79
80 DefNewGeneration::FastKeepAliveClosure::
81 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
82 DefNewGeneration::KeepAliveClosure(cl) {
83 _boundary = g->reserved().end();
84 }
85
86 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
87 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
88
89 DefNewGeneration::EvacuateFollowersClosure::
90 EvacuateFollowersClosure(GenCollectedHeap* gch,
91 ScanClosure* cur,
92 ScanClosure* older) :
93 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
94 {}
95
96 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
97 do {
98 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
99 } while (!_gch->no_allocs_since_save_marks());
100 }
101
102 DefNewGeneration::FastEvacuateFollowersClosure::
103 FastEvacuateFollowersClosure(GenCollectedHeap* gch,
104 FastScanClosure* cur,
105 FastScanClosure* older) :
106 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
107 {
108 assert(_gch->young_gen()->kind() == Generation::DefNew, "Generation should be DefNew");
109 _young_gen = (DefNewGeneration*)_gch->young_gen();
110 }
111
112 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
113 do {
114 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
115 } while (!_gch->no_allocs_since_save_marks());
116 guarantee(_young_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
117 }
118
119 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
120 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
121 {
122 _boundary = _g->reserved().end();
123 }
124
125 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
126 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
127
128 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
129 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
130 {
131 _boundary = _g->reserved().end();
132 }
133
134 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
135 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
136
137 void KlassScanClosure::do_klass(Klass* klass) {
138 #ifndef PRODUCT
139 ResourceMark rm;
140 log_develop(gc, scavenge)("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s",
141 p2i(klass),
142 klass->external_name(),
143 klass->has_modified_oops() ? "true" : "false");
144 #endif
145
146 // If the klass has not been dirtied we know that there's
147 // no references into the young gen and we can skip it.
148 if (klass->has_modified_oops()) {
149 if (_accumulate_modified_oops) {
150 klass->accumulate_modified_oops();
151 }
152
153 // Clear this state since we're going to scavenge all the metadata.
154 klass->clear_modified_oops();
155
156 // Tell the closure which Klass is being scanned so that it can be dirtied
157 // if oops are left pointing into the young gen.
158 _scavenge_closure->set_scanned_klass(klass);
159
160 klass->oops_do(_scavenge_closure);
161
162 _scavenge_closure->set_scanned_klass(NULL);
163 }
164 }
165
166 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
167 _g(g)
168 {
169 _boundary = _g->reserved().end();
170 }
171
172 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
173 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
174
175 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
176 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
177
178 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
179 KlassRemSet* klass_rem_set)
180 : _scavenge_closure(scavenge_closure),
181 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
182
183
184 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
185 size_t initial_size,
186 const char* policy)
187 : Generation(rs, initial_size),
188 _promo_failure_drain_in_progress(false),
189 _should_allocate_from_space(false)
190 {
191 MemRegion cmr((HeapWord*)_virtual_space.low(),
192 (HeapWord*)_virtual_space.high());
193 GenCollectedHeap* gch = GenCollectedHeap::heap();
194
195 gch->barrier_set()->resize_covered_region(cmr);
196
197 _eden_space = new ContiguousSpace();
198 _from_space = new ContiguousSpace();
199 _to_space = new ContiguousSpace();
200
201 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
202 vm_exit_during_initialization("Could not allocate a new gen space");
203 }
204
205 // Compute the maximum eden and survivor space sizes. These sizes
206 // are computed assuming the entire reserved space is committed.
207 // These values are exported as performance counters.
208 uintx alignment = gch->collector_policy()->space_alignment();
209 uintx size = _virtual_space.reserved_size();
210 _max_survivor_size = compute_survivor_size(size, alignment);
211 _max_eden_size = size - (2*_max_survivor_size);
212
213 // allocate the performance counters
214 GenCollectorPolicy* gcp = gch->gen_policy();
215
216 // Generation counters -- generation 0, 3 subspaces
217 _gen_counters = new GenerationCounters("new", 0, 3,
218 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
219 _gc_counters = new CollectorCounters(policy, 0);
220
221 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
222 _gen_counters);
223 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
224 _gen_counters);
225 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
226 _gen_counters);
227
228 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
229 update_counters();
230 _old_gen = NULL;
231 _tenuring_threshold = MaxTenuringThreshold;
232 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
233
234 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
235 }
236
237 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
238 bool clear_space,
239 bool mangle_space) {
240 uintx alignment =
241 GenCollectedHeap::heap()->collector_policy()->space_alignment();
242
243 // If the spaces are being cleared (only done at heap initialization
244 // currently), the survivor spaces need not be empty.
245 // Otherwise, no care is taken for used areas in the survivor spaces
246 // so check.
247 assert(clear_space || (to()->is_empty() && from()->is_empty()),
248 "Initialization of the survivor spaces assumes these are empty");
249
250 // Compute sizes
251 uintx size = _virtual_space.committed_size();
252 uintx survivor_size = compute_survivor_size(size, alignment);
253 uintx eden_size = size - (2*survivor_size);
254 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
255
256 if (eden_size < minimum_eden_size) {
257 // May happen due to 64Kb rounding, if so adjust eden size back up
258 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
259 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
260 uintx unaligned_survivor_size =
261 align_size_down(maximum_survivor_size, alignment);
262 survivor_size = MAX2(unaligned_survivor_size, alignment);
263 eden_size = size - (2*survivor_size);
264 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
265 assert(eden_size >= minimum_eden_size, "just checking");
266 }
267
268 char *eden_start = _virtual_space.low();
269 char *from_start = eden_start + eden_size;
270 char *to_start = from_start + survivor_size;
271 char *to_end = to_start + survivor_size;
272
273 assert(to_end == _virtual_space.high(), "just checking");
274 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
275 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
276 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
277
278 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
279 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
280 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
281
282 // A minimum eden size implies that there is a part of eden that
283 // is being used and that affects the initialization of any
284 // newly formed eden.
285 bool live_in_eden = minimum_eden_size > 0;
286
287 // If not clearing the spaces, do some checking to verify that
288 // the space are already mangled.
289 if (!clear_space) {
290 // Must check mangling before the spaces are reshaped. Otherwise,
291 // the bottom or end of one space may have moved into another
292 // a failure of the check may not correctly indicate which space
293 // is not properly mangled.
294 if (ZapUnusedHeapArea) {
295 HeapWord* limit = (HeapWord*) _virtual_space.high();
296 eden()->check_mangled_unused_area(limit);
297 from()->check_mangled_unused_area(limit);
298 to()->check_mangled_unused_area(limit);
299 }
300 }
301
302 // Reset the spaces for their new regions.
303 eden()->initialize(edenMR,
304 clear_space && !live_in_eden,
305 SpaceDecorator::Mangle);
306 // If clear_space and live_in_eden, we will not have cleared any
307 // portion of eden above its top. This can cause newly
308 // expanded space not to be mangled if using ZapUnusedHeapArea.
309 // We explicitly do such mangling here.
310 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
311 eden()->mangle_unused_area();
312 }
313 from()->initialize(fromMR, clear_space, mangle_space);
314 to()->initialize(toMR, clear_space, mangle_space);
315
316 // Set next compaction spaces.
317 eden()->set_next_compaction_space(from());
318 // The to-space is normally empty before a compaction so need
319 // not be considered. The exception is during promotion
320 // failure handling when to-space can contain live objects.
321 from()->set_next_compaction_space(NULL);
322 }
323
324 void DefNewGeneration::swap_spaces() {
325 ContiguousSpace* s = from();
326 _from_space = to();
327 _to_space = s;
328 eden()->set_next_compaction_space(from());
329 // The to-space is normally empty before a compaction so need
330 // not be considered. The exception is during promotion
331 // failure handling when to-space can contain live objects.
332 from()->set_next_compaction_space(NULL);
333
334 if (UsePerfData) {
335 CSpaceCounters* c = _from_counters;
336 _from_counters = _to_counters;
337 _to_counters = c;
338 }
339 }
340
341 bool DefNewGeneration::expand(size_t bytes) {
342 MutexLocker x(ExpandHeap_lock);
343 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
344 bool success = _virtual_space.expand_by(bytes);
345 if (success && ZapUnusedHeapArea) {
346 // Mangle newly committed space immediately because it
347 // can be done here more simply that after the new
348 // spaces have been computed.
349 HeapWord* new_high = (HeapWord*) _virtual_space.high();
350 MemRegion mangle_region(prev_high, new_high);
351 SpaceMangler::mangle_region(mangle_region);
352 }
353
354 // Do not attempt an expand-to-the reserve size. The
355 // request should properly observe the maximum size of
356 // the generation so an expand-to-reserve should be
357 // unnecessary. Also a second call to expand-to-reserve
358 // value potentially can cause an undue expansion.
359 // For example if the first expand fail for unknown reasons,
360 // but the second succeeds and expands the heap to its maximum
361 // value.
362 if (GC_locker::is_active()) {
363 log_debug(gc)("Garbage collection disabled, expanded heap instead");
364 }
365
366 return success;
367 }
368
369 void DefNewGeneration::compute_new_size() {
370 // This is called after a GC that includes the old generation, so from-space
371 // will normally be empty.
372 // Note that we check both spaces, since if scavenge failed they revert roles.
373 // If not we bail out (otherwise we would have to relocate the objects).
374 if (!from()->is_empty() || !to()->is_empty()) {
375 return;
376 }
377
378 GenCollectedHeap* gch = GenCollectedHeap::heap();
379
380 size_t old_size = gch->old_gen()->capacity();
381 size_t new_size_before = _virtual_space.committed_size();
382 size_t min_new_size = initial_size();
383 size_t max_new_size = reserved().byte_size();
384 assert(min_new_size <= new_size_before &&
385 new_size_before <= max_new_size,
386 "just checking");
387 // All space sizes must be multiples of Generation::GenGrain.
388 size_t alignment = Generation::GenGrain;
389
390 // Compute desired new generation size based on NewRatio and
391 // NewSizeThreadIncrease
392 size_t desired_new_size = old_size/NewRatio;
393 int threads_count = Threads::number_of_non_daemon_threads();
394 size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
395 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
396
397 // Adjust new generation size
398 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
399 assert(desired_new_size <= max_new_size, "just checking");
400
401 bool changed = false;
402 if (desired_new_size > new_size_before) {
403 size_t change = desired_new_size - new_size_before;
404 assert(change % alignment == 0, "just checking");
405 if (expand(change)) {
406 changed = true;
407 }
408 // If the heap failed to expand to the desired size,
409 // "changed" will be false. If the expansion failed
410 // (and at this point it was expected to succeed),
411 // ignore the failure (leaving "changed" as false).
412 }
413 if (desired_new_size < new_size_before && eden()->is_empty()) {
414 // bail out of shrinking if objects in eden
415 size_t change = new_size_before - desired_new_size;
416 assert(change % alignment == 0, "just checking");
417 _virtual_space.shrink_by(change);
418 changed = true;
419 }
420 if (changed) {
421 // The spaces have already been mangled at this point but
422 // may not have been cleared (set top = bottom) and should be.
423 // Mangling was done when the heap was being expanded.
424 compute_space_boundaries(eden()->used(),
425 SpaceDecorator::Clear,
426 SpaceDecorator::DontMangle);
427 MemRegion cmr((HeapWord*)_virtual_space.low(),
428 (HeapWord*)_virtual_space.high());
429 gch->barrier_set()->resize_covered_region(cmr);
430
431 log_debug(gc, heap, ergo)(
432 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
433 new_size_before/K, _virtual_space.committed_size()/K,
434 eden()->capacity()/K, from()->capacity()/K);
435 log_trace(gc, heap, ergo)(
436 " [allowed " SIZE_FORMAT "K extra for %d threads]",
437 thread_increase_size/K, threads_count);
438 }
439 }
440
441 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
442 assert(false, "NYI -- are you sure you want to call this?");
443 }
444
445
446 size_t DefNewGeneration::capacity() const {
447 return eden()->capacity()
448 + from()->capacity(); // to() is only used during scavenge
449 }
450
451
452 size_t DefNewGeneration::used() const {
453 return eden()->used()
454 + from()->used(); // to() is only used during scavenge
455 }
456
457
458 size_t DefNewGeneration::free() const {
459 return eden()->free()
460 + from()->free(); // to() is only used during scavenge
461 }
462
463 size_t DefNewGeneration::max_capacity() const {
464 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
465 const size_t reserved_bytes = reserved().byte_size();
466 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
467 }
468
469 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
470 return eden()->free();
471 }
472
473 size_t DefNewGeneration::capacity_before_gc() const {
474 return eden()->capacity();
475 }
476
477 size_t DefNewGeneration::contiguous_available() const {
478 return eden()->free();
479 }
480
481
482 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
483 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
484
485 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
486 eden()->object_iterate(blk);
487 from()->object_iterate(blk);
488 }
489
490
491 void DefNewGeneration::space_iterate(SpaceClosure* blk,
492 bool usedOnly) {
493 blk->do_space(eden());
494 blk->do_space(from());
495 blk->do_space(to());
496 }
497
498 // The last collection bailed out, we are running out of heap space,
499 // so we try to allocate the from-space, too.
500 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
501 bool should_try_alloc = should_allocate_from_space() || GC_locker::is_active_and_needs_gc();
502
503 // If the Heap_lock is not locked by this thread, this will be called
504 // again later with the Heap_lock held.
505 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
506
507 HeapWord* result = NULL;
508 if (do_alloc) {
509 result = from()->allocate(size);
510 }
511
512 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s",
513 size,
514 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
515 "true" : "false",
516 Heap_lock->is_locked() ? "locked" : "unlocked",
517 from()->free(),
518 should_try_alloc ? "" : " should_allocate_from_space: NOT",
519 do_alloc ? " Heap_lock is not owned by self" : "",
520 result == NULL ? "NULL" : "object");
521
522 return result;
523 }
524
525 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
526 bool is_tlab,
527 bool parallel) {
528 // We don't attempt to expand the young generation (but perhaps we should.)
529 return allocate(size, is_tlab);
530 }
531
532 void DefNewGeneration::adjust_desired_tenuring_threshold() {
533 // Set the desired survivor size to half the real survivor space
534 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->collector_policy()->counters();
535 _tenuring_threshold =
536 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize, gc_counters);
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 GenCollectedHeap* gch = GenCollectedHeap::heap();
546
547 _gc_timer->register_gc_start();
548 DefNewTracer gc_tracer;
549 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
550
551 _old_gen = gch->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 gch->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) tm("DefNew", NULL, gch->gc_cause());
566
567 gch->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
576 gch->rem_set()->prepare_for_younger_refs_iterate(false);
577
578 assert(gch->no_allocs_since_save_marks(),
579 "save marks have not been newly set.");
580
581 // Not very pretty.
582 CollectorPolicy* cp = gch->collector_policy();
583
584 FastScanClosure fsc_with_no_gc_barrier(this, false);
585 FastScanClosure fsc_with_gc_barrier(this, true);
586
587 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
588 gch->rem_set()->klass_rem_set());
589 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
590 &fsc_with_no_gc_barrier,
591 false);
592
593 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
594 FastEvacuateFollowersClosure evacuate_followers(gch,
595 &fsc_with_no_gc_barrier,
596 &fsc_with_gc_barrier);
597
598 assert(gch->no_allocs_since_save_marks(),
599 "save marks have not been newly set.");
600
601 {
602 // DefNew needs to run with n_threads == 0, to make sure the serial
603 // version of the card table scanning code is used.
604 // See: CardTableModRefBSForCTRS::non_clean_card_iterate_possibly_parallel.
605 StrongRootsScope srs(0);
606
607 gch->gen_process_roots(&srs,
608 GenCollectedHeap::YoungGen,
609 true, // Process younger gens, if any,
610 // as strong roots.
611 GenCollectedHeap::SO_ScavengeCodeCache,
612 GenCollectedHeap::StrongAndWeakRoots,
613 &fsc_with_no_gc_barrier,
614 &fsc_with_gc_barrier,
615 &cld_scan_closure);
616 }
617
618 // "evacuate followers".
619 evacuate_followers.do_void();
620
621 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
622 ReferenceProcessor* rp = ref_processor();
623 rp->setup_policy(clear_all_soft_refs);
624 const ReferenceProcessorStats& stats =
625 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
626 NULL, _gc_timer);
627 gc_tracer.report_gc_reference_stats(stats);
628 gc_tracer.report_tenuring_threshold(tenuring_threshold());
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 = gch->gen_policy()->size_policy();
653 size_policy->reset_gc_overhead_limit_count();
654 assert(!gch->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_debug(gc)("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 gch->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(gch->reset_promotion_should_fail();)
676 }
677 // set new iteration safe limit for the survivor spaces
678 from()->set_concurrent_iteration_safe_limit(from()->top());
679 to()->set_concurrent_iteration_safe_limit(to()->top());
680
681 // We need to use a monotonically non-decreasing time in ms
682 // or we will see time-warp warnings and os::javaTimeMillis()
683 // does not guarantee monotonicity.
684 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
685 update_time_of_last_gc(now);
686
687 gch->trace_heap_after_gc(&gc_tracer);
688
689 _gc_timer->register_gc_end();
690
691 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
692 }
693
694 class RemoveForwardPointerClosure: public ObjectClosure {
695 public:
696 void do_object(oop obj) {
697 obj->init_mark();
698 }
699 };
700
701 void DefNewGeneration::init_assuming_no_promotion_failure() {
702 _promotion_failed = false;
703 _promotion_failed_info.reset();
704 from()->set_next_compaction_space(NULL);
705 }
706
707 void DefNewGeneration::remove_forwarding_pointers() {
708 RemoveForwardPointerClosure rspc;
709 eden()->object_iterate(&rspc);
710 from()->object_iterate(&rspc);
711
712 // Now restore saved marks, if any.
713 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
714 "should be the same");
715 while (!_objs_with_preserved_marks.is_empty()) {
716 oop obj = _objs_with_preserved_marks.pop();
717 markOop m = _preserved_marks_of_objs.pop();
718 obj->set_mark(m);
719 }
720 _objs_with_preserved_marks.clear(true);
721 _preserved_marks_of_objs.clear(true);
722 }
723
724 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
725 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
726 "Oversaving!");
727 _objs_with_preserved_marks.push(obj);
728 _preserved_marks_of_objs.push(m);
729 }
730
731 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
732 if (m->must_be_preserved_for_promotion_failure(obj)) {
733 preserve_mark(obj, m);
734 }
735 }
736
737 void DefNewGeneration::handle_promotion_failure(oop old) {
738 log_debug(promotion)("Promotion failure size = %d) ", old->size());
739
740 _promotion_failed = true;
741 _promotion_failed_info.register_copy_failure(old->size());
742 preserve_mark_if_necessary(old, old->mark());
743 // forward to self
744 old->forward_to(old);
745
746 _promo_failure_scan_stack.push(old);
747
748 if (!_promo_failure_drain_in_progress) {
749 // prevent recursion in copy_to_survivor_space()
750 _promo_failure_drain_in_progress = true;
751 drain_promo_failure_scan_stack();
752 _promo_failure_drain_in_progress = false;
753 }
754 }
755
756 oop DefNewGeneration::copy_to_survivor_space(oop old) {
757 assert(is_in_reserved(old) && !old->is_forwarded(),
758 "shouldn't be scavenging this oop");
759 size_t s = old->size();
760 oop obj = NULL;
761
762 // Try allocating obj in to-space (unless too old)
763 if (old->age() < tenuring_threshold()) {
764 obj = (oop) to()->allocate_aligned(s);
765 }
766
767 // Otherwise try allocating obj tenured
768 if (obj == NULL) {
769 obj = _old_gen->promote(old, s);
770 if (obj == NULL) {
771 handle_promotion_failure(old);
772 return old;
773 }
774 } else {
775 // Prefetch beyond obj
776 const intx interval = PrefetchCopyIntervalInBytes;
777 Prefetch::write(obj, interval);
778
779 // Copy obj
780 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
781
782 // Increment age if obj still in new generation
783 obj->incr_age();
784 age_table()->add(obj, s);
785 }
786
787 // Done, insert forward pointer to obj in this header
788 old->forward_to(obj);
789
790 return obj;
791 }
792
793 void DefNewGeneration::drain_promo_failure_scan_stack() {
794 while (!_promo_failure_scan_stack.is_empty()) {
795 oop obj = _promo_failure_scan_stack.pop();
796 obj->oop_iterate(_promo_failure_scan_stack_closure);
797 }
798 }
799
800 void DefNewGeneration::save_marks() {
801 eden()->set_saved_mark();
802 to()->set_saved_mark();
803 from()->set_saved_mark();
804 }
805
806
807 void DefNewGeneration::reset_saved_marks() {
808 eden()->reset_saved_mark();
809 to()->reset_saved_mark();
810 from()->reset_saved_mark();
811 }
812
813
814 bool DefNewGeneration::no_allocs_since_save_marks() {
815 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
816 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
817 return to()->saved_mark_at_top();
818 }
819
820 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
821 \
822 void DefNewGeneration:: \
823 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
824 cl->set_generation(this); \
825 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
826 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
827 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
828 cl->reset_generation(); \
829 save_marks(); \
830 }
831
832 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
833
834 #undef DefNew_SINCE_SAVE_MARKS_DEFN
835
836 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
837 size_t max_alloc_words) {
838 if (requestor == this || _promotion_failed) {
839 return;
840 }
841 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
842
843 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
844 if (to_space->top() > to_space->bottom()) {
845 trace("to_space not empty when contribute_scratch called");
846 }
847 */
848
849 ContiguousSpace* to_space = to();
850 assert(to_space->end() >= to_space->top(), "pointers out of order");
851 size_t free_words = pointer_delta(to_space->end(), to_space->top());
852 if (free_words >= MinFreeScratchWords) {
853 ScratchBlock* sb = (ScratchBlock*)to_space->top();
854 sb->num_words = free_words;
855 sb->next = list;
856 list = sb;
857 }
858 }
859
860 void DefNewGeneration::reset_scratch() {
861 // If contributing scratch in to_space, mangle all of
862 // to_space if ZapUnusedHeapArea. This is needed because
863 // top is not maintained while using to-space as scratch.
864 if (ZapUnusedHeapArea) {
865 to()->mangle_unused_area_complete();
866 }
867 }
868
869 bool DefNewGeneration::collection_attempt_is_safe() {
870 if (!to()->is_empty()) {
871 log_trace(gc)(":: to is not empty ::");
872 return false;
873 }
874 if (_old_gen == NULL) {
875 GenCollectedHeap* gch = GenCollectedHeap::heap();
876 _old_gen = gch->old_gen();
877 }
878 return _old_gen->promotion_attempt_is_safe(used());
879 }
880
881 void DefNewGeneration::gc_epilogue(bool full) {
882 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
883
884 assert(!GC_locker::is_active(), "We should not be executing here");
885 // Check if the heap is approaching full after a collection has
886 // been done. Generally the young generation is empty at
887 // a minimum at the end of a collection. If it is not, then
888 // the heap is approaching full.
889 GenCollectedHeap* gch = GenCollectedHeap::heap();
890 if (full) {
891 DEBUG_ONLY(seen_incremental_collection_failed = false;)
892 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
893 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
894 GCCause::to_string(gch->gc_cause()));
895 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
896 set_should_allocate_from_space(); // we seem to be running out of space
897 } else {
898 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
899 GCCause::to_string(gch->gc_cause()));
900 gch->clear_incremental_collection_failed(); // We just did a full collection
901 clear_should_allocate_from_space(); // if set
902 }
903 } else {
904 #ifdef ASSERT
905 // It is possible that incremental_collection_failed() == true
906 // here, because an attempted scavenge did not succeed. The policy
907 // is normally expected to cause a full collection which should
908 // clear that condition, so we should not be here twice in a row
909 // with incremental_collection_failed() == true without having done
910 // a full collection in between.
911 if (!seen_incremental_collection_failed &&
912 gch->incremental_collection_failed()) {
913 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
914 GCCause::to_string(gch->gc_cause()));
915 seen_incremental_collection_failed = true;
916 } else if (seen_incremental_collection_failed) {
917 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
918 GCCause::to_string(gch->gc_cause()));
919 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
920 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
921 !gch->incremental_collection_failed(),
922 "Twice in a row");
923 seen_incremental_collection_failed = false;
924 }
925 #endif // ASSERT
926 }
927
928 if (ZapUnusedHeapArea) {
929 eden()->check_mangled_unused_area_complete();
930 from()->check_mangled_unused_area_complete();
931 to()->check_mangled_unused_area_complete();
932 }
933
934 if (!CleanChunkPoolAsync) {
935 Chunk::clean_chunk_pool();
936 }
937
938 // update the generation and space performance counters
939 update_counters();
940 gch->collector_policy()->counters()->update_counters();
941 }
942
943 void DefNewGeneration::record_spaces_top() {
944 assert(ZapUnusedHeapArea, "Not mangling unused space");
945 eden()->set_top_for_allocations();
946 to()->set_top_for_allocations();
947 from()->set_top_for_allocations();
948 }
949
950 void DefNewGeneration::ref_processor_init() {
951 Generation::ref_processor_init();
952 }
953
954
955 void DefNewGeneration::update_counters() {
956 if (UsePerfData) {
957 _eden_counters->update_all();
958 _from_counters->update_all();
959 _to_counters->update_all();
960 _gen_counters->update_all();
961 }
962 }
963
964 void DefNewGeneration::verify() {
965 eden()->verify();
966 from()->verify();
967 to()->verify();
968 }
969
970 void DefNewGeneration::print_on(outputStream* st) const {
971 Generation::print_on(st);
972 st->print(" eden");
973 eden()->print_on(st);
974 st->print(" from");
975 from()->print_on(st);
976 st->print(" to ");
977 to()->print_on(st);
978 }
979
980
981 const char* DefNewGeneration::name() const {
982 return "def new generation";
983 }
984
985 // Moved from inline file as they are not called inline
986 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
987 return eden();
988 }
989
990 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
991 // This is the slow-path allocation for the DefNewGeneration.
992 // Most allocations are fast-path in compiled code.
993 // We try to allocate from the eden. If that works, we are happy.
994 // Note that since DefNewGeneration supports lock-free allocation, we
995 // have to use it here, as well.
996 HeapWord* result = eden()->par_allocate(word_size);
997 if (result != NULL) {
998 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
999 _old_gen->sample_eden_chunk();
1000 }
1001 } else {
1002 // If the eden is full and the last collection bailed out, we are running
1003 // out of heap space, and we try to allocate the from-space, too.
1004 // allocate_from_space can't be inlined because that would introduce a
1005 // circular dependency at compile time.
1006 result = allocate_from_space(word_size);
1007 }
1008 return result;
1009 }
1010
1011 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1012 bool is_tlab) {
1013 HeapWord* res = eden()->par_allocate(word_size);
1014 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1015 _old_gen->sample_eden_chunk();
1016 }
1017 return res;
1018 }
1019
1020 size_t DefNewGeneration::tlab_capacity() const {
1021 return eden()->capacity();
1022 }
1023
1024 size_t DefNewGeneration::tlab_used() const {
1025 return eden()->used();
1026 }
1027
1028 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1029 return unsafe_max_alloc_nogc();
1030 }