1 /*
2 * Copyright (c) 2001, 2014, 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_implementation/shared/collectorCounters.hpp"
27 #include "gc_implementation/shared/gcPolicyCounters.hpp"
28 #include "gc_implementation/shared/gcHeapSummary.hpp"
29 #include "gc_implementation/shared/gcTimer.hpp"
30 #include "gc_implementation/shared/gcTraceTime.hpp"
31 #include "gc_implementation/shared/gcTrace.hpp"
32 #include "gc_implementation/shared/spaceDecorator.hpp"
33 #include "memory/defNewGeneration.inline.hpp"
34 #include "memory/gcLocker.inline.hpp"
35 #include "memory/genCollectedHeap.hpp"
36 #include "memory/genOopClosures.inline.hpp"
37 #include "memory/genRemSet.hpp"
38 #include "memory/generationSpec.hpp"
39 #include "memory/iterator.hpp"
40 #include "memory/referencePolicy.hpp"
41 #include "memory/space.inline.hpp"
42 #include "oops/instanceRefKlass.hpp"
43 #include "oops/oop.inline.hpp"
44 #include "runtime/atomic.inline.hpp"
45 #include "runtime/java.hpp"
46 #include "runtime/prefetch.inline.hpp"
47 #include "runtime/thread.inline.hpp"
48 #include "utilities/copy.hpp"
49 #include "utilities/globalDefinitions.hpp"
50 #include "utilities/stack.inline.hpp"
51
52 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
53
54 //
55 // DefNewGeneration functions.
56
57 // Methods of protected closure types.
58
59 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
60 assert(g->level() == 0, "Optimized for youngest gen.");
61 }
62 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
63 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
64 }
65
66 DefNewGeneration::KeepAliveClosure::
67 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
68 GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
69 _rs = (CardTableRS*)rs;
70 }
71
72 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
73 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
74
75
76 DefNewGeneration::FastKeepAliveClosure::
77 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
78 DefNewGeneration::KeepAliveClosure(cl) {
79 _boundary = g->reserved().end();
80 }
81
82 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
83 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
84
85 DefNewGeneration::EvacuateFollowersClosure::
86 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
87 ScanClosure* cur, ScanClosure* older) :
88 _gch(gch), _level(level),
89 _scan_cur_or_nonheap(cur), _scan_older(older)
90 {}
91
92 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
93 do {
94 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
95 _scan_older);
96 } while (!_gch->no_allocs_since_save_marks(_level));
97 }
98
99 DefNewGeneration::FastEvacuateFollowersClosure::
100 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
101 DefNewGeneration* gen,
102 FastScanClosure* cur, FastScanClosure* older) :
103 _gch(gch), _level(level), _gen(gen),
104 _scan_cur_or_nonheap(cur), _scan_older(older)
105 {}
106
107 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
108 do {
109 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
110 _scan_older);
111 } while (!_gch->no_allocs_since_save_marks(_level));
112 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
113 }
114
115 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
116 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
117 {
118 assert(_g->level() == 0, "Optimized for youngest generation");
119 _boundary = _g->reserved().end();
120 }
121
122 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
123 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
124
125 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
126 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
127 {
128 assert(_g->level() == 0, "Optimized for youngest generation");
129 _boundary = _g->reserved().end();
130 }
131
132 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
133 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
134
135 void KlassScanClosure::do_klass(Klass* klass) {
136 #ifndef PRODUCT
137 if (TraceScavenge) {
138 ResourceMark rm;
139 gclog_or_tty->print_cr("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s",
140 klass,
141 klass->external_name(),
142 klass->has_modified_oops() ? "true" : "false");
143 }
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 assert(_g->level() == 0, "Optimized for youngest generation");
170 _boundary = _g->reserved().end();
171 }
172
173 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
174 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
175
176 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
177 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
178
179 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
180 KlassRemSet* klass_rem_set)
181 : _scavenge_closure(scavenge_closure),
182 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
183
184
185 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
186 size_t initial_size,
187 int level,
188 const char* policy)
189 : Generation(rs, initial_size, level),
190 _promo_failure_drain_in_progress(false),
191 _should_allocate_from_space(false)
192 {
193 MemRegion cmr((HeapWord*)_virtual_space.low(),
194 (HeapWord*)_virtual_space.high());
195 Universe::heap()->barrier_set()->resize_covered_region(cmr);
196
197 if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) {
198 _eden_space = new ConcEdenSpace(this);
199 } else {
200 _eden_space = new EdenSpace(this);
201 }
202 _from_space = new ContiguousSpace();
203 _to_space = new ContiguousSpace();
204
205 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
206 vm_exit_during_initialization("Could not allocate a new gen space");
207
208 // Compute the maximum eden and survivor space sizes. These sizes
209 // are computed assuming the entire reserved space is committed.
210 // These values are exported as performance counters.
211 uintx alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
212 uintx size = _virtual_space.reserved_size();
213 _max_survivor_size = compute_survivor_size(size, alignment);
214 _max_eden_size = size - (2*_max_survivor_size);
215
216 // allocate the performance counters
217 GenCollectorPolicy* gcp = (GenCollectorPolicy*) GenCollectedHeap::heap()->collector_policy();
218
219 // Generation counters -- generation 0, 3 subspaces
220 _gen_counters = new GenerationCounters("new", 0, 3,
221 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
222 _gc_counters = new CollectorCounters(policy, 0);
223
224 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
225 _gen_counters);
226 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
227 _gen_counters);
228 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
229 _gen_counters);
230
231 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
232 update_counters();
233 _old_gen = NULL;
234 _tenuring_threshold = MaxTenuringThreshold;
235 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
236
237 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
238 }
239
240 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
241 bool clear_space,
242 bool mangle_space) {
243 uintx alignment =
244 GenCollectedHeap::heap()->collector_policy()->space_alignment();
245
246 // If the spaces are being cleared (only done at heap initialization
247 // currently), the survivor spaces need not be empty.
248 // Otherwise, no care is taken for used areas in the survivor spaces
249 // so check.
250 assert(clear_space || (to()->is_empty() && from()->is_empty()),
251 "Initialization of the survivor spaces assumes these are empty");
252
253 // Compute sizes
254 uintx size = _virtual_space.committed_size();
255 uintx survivor_size = compute_survivor_size(size, alignment);
256 uintx eden_size = size - (2*survivor_size);
257 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
258
259 if (eden_size < minimum_eden_size) {
260 // May happen due to 64Kb rounding, if so adjust eden size back up
261 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
262 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
263 uintx unaligned_survivor_size =
264 align_size_down(maximum_survivor_size, alignment);
265 survivor_size = MAX2(unaligned_survivor_size, alignment);
266 eden_size = size - (2*survivor_size);
267 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
268 assert(eden_size >= minimum_eden_size, "just checking");
269 }
270
271 char *eden_start = _virtual_space.low();
272 char *from_start = eden_start + eden_size;
273 char *to_start = from_start + survivor_size;
274 char *to_end = to_start + survivor_size;
275
276 assert(to_end == _virtual_space.high(), "just checking");
277 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
278 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
279 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
280
281 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
282 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
283 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
284
285 // A minimum eden size implies that there is a part of eden that
286 // is being used and that affects the initialization of any
287 // newly formed eden.
288 bool live_in_eden = minimum_eden_size > 0;
289
290 // If not clearing the spaces, do some checking to verify that
291 // the space are already mangled.
292 if (!clear_space) {
293 // Must check mangling before the spaces are reshaped. Otherwise,
294 // the bottom or end of one space may have moved into another
295 // a failure of the check may not correctly indicate which space
296 // is not properly mangled.
297 if (ZapUnusedHeapArea) {
298 HeapWord* limit = (HeapWord*) _virtual_space.high();
299 eden()->check_mangled_unused_area(limit);
300 from()->check_mangled_unused_area(limit);
301 to()->check_mangled_unused_area(limit);
302 }
303 }
304
305 // Reset the spaces for their new regions.
306 eden()->initialize(edenMR,
307 clear_space && !live_in_eden,
308 SpaceDecorator::Mangle);
309 // If clear_space and live_in_eden, we will not have cleared any
310 // portion of eden above its top. This can cause newly
311 // expanded space not to be mangled if using ZapUnusedHeapArea.
312 // We explicitly do such mangling here.
313 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
314 eden()->mangle_unused_area();
315 }
316 from()->initialize(fromMR, clear_space, mangle_space);
317 to()->initialize(toMR, clear_space, mangle_space);
318
319 // Set next compaction spaces.
320 eden()->set_next_compaction_space(from());
321 // The to-space is normally empty before a compaction so need
322 // not be considered. The exception is during promotion
323 // failure handling when to-space can contain live objects.
324 from()->set_next_compaction_space(NULL);
325 }
326
327 void DefNewGeneration::swap_spaces() {
328 ContiguousSpace* s = from();
329 _from_space = to();
330 _to_space = s;
331 eden()->set_next_compaction_space(from());
332 // The to-space is normally empty before a compaction so need
333 // not be considered. The exception is during promotion
334 // failure handling when to-space can contain live objects.
335 from()->set_next_compaction_space(NULL);
336
337 if (UsePerfData) {
338 CSpaceCounters* c = _from_counters;
339 _from_counters = _to_counters;
340 _to_counters = c;
341 }
342 }
343
344 bool DefNewGeneration::expand(size_t bytes) {
345 MutexLocker x(ExpandHeap_lock);
346 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
347 bool success = _virtual_space.expand_by(bytes);
348 if (success && ZapUnusedHeapArea) {
349 // Mangle newly committed space immediately because it
350 // can be done here more simply that after the new
351 // spaces have been computed.
352 HeapWord* new_high = (HeapWord*) _virtual_space.high();
353 MemRegion mangle_region(prev_high, new_high);
354 SpaceMangler::mangle_region(mangle_region);
355 }
356
357 // Do not attempt an expand-to-the reserve size. The
358 // request should properly observe the maximum size of
359 // the generation so an expand-to-reserve should be
360 // unnecessary. Also a second call to expand-to-reserve
361 // value potentially can cause an undue expansion.
362 // For example if the first expand fail for unknown reasons,
363 // but the second succeeds and expands the heap to its maximum
364 // value.
365 if (GC_locker::is_active()) {
366 if (PrintGC && Verbose) {
367 gclog_or_tty->print_cr("Garbage collection disabled, "
368 "expanded heap instead");
369 }
370 }
371
372 return success;
373 }
374
375
376 void DefNewGeneration::compute_new_size() {
377 // This is called after a gc that includes the following generation
378 // (which is required to exist.) So from-space will normally be empty.
379 // Note that we check both spaces, since if scavenge failed they revert roles.
380 // If not we bail out (otherwise we would have to relocate the objects)
381 if (!from()->is_empty() || !to()->is_empty()) {
382 return;
383 }
384
385 int next_level = level() + 1;
386 GenCollectedHeap* gch = GenCollectedHeap::heap();
387 assert(next_level < gch->_n_gens,
388 "DefNewGeneration cannot be an oldest gen");
389
390 Generation* old_gen = gch->old_gen();
391 size_t old_size = old_gen->capacity();
392 size_t new_size_before = _virtual_space.committed_size();
393 size_t min_new_size = spec()->init_size();
394 size_t max_new_size = reserved().byte_size();
395 assert(min_new_size <= new_size_before &&
396 new_size_before <= max_new_size,
397 "just checking");
398 // All space sizes must be multiples of Generation::GenGrain.
399 size_t alignment = Generation::GenGrain;
400
401 // Compute desired new generation size based on NewRatio and
402 // NewSizeThreadIncrease
403 size_t desired_new_size = old_size/NewRatio;
404 int threads_count = Threads::number_of_non_daemon_threads();
405 size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
406 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
407
408 // Adjust new generation size
409 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
410 assert(desired_new_size <= max_new_size, "just checking");
411
412 bool changed = false;
413 if (desired_new_size > new_size_before) {
414 size_t change = desired_new_size - new_size_before;
415 assert(change % alignment == 0, "just checking");
416 if (expand(change)) {
417 changed = true;
418 }
419 // If the heap failed to expand to the desired size,
420 // "changed" will be false. If the expansion failed
421 // (and at this point it was expected to succeed),
422 // ignore the failure (leaving "changed" as false).
423 }
424 if (desired_new_size < new_size_before && eden()->is_empty()) {
425 // bail out of shrinking if objects in eden
426 size_t change = new_size_before - desired_new_size;
427 assert(change % alignment == 0, "just checking");
428 _virtual_space.shrink_by(change);
429 changed = true;
430 }
431 if (changed) {
432 // The spaces have already been mangled at this point but
433 // may not have been cleared (set top = bottom) and should be.
434 // Mangling was done when the heap was being expanded.
435 compute_space_boundaries(eden()->used(),
436 SpaceDecorator::Clear,
437 SpaceDecorator::DontMangle);
438 MemRegion cmr((HeapWord*)_virtual_space.low(),
439 (HeapWord*)_virtual_space.high());
440 Universe::heap()->barrier_set()->resize_covered_region(cmr);
441 if (Verbose && PrintGC) {
442 size_t new_size_after = _virtual_space.committed_size();
443 size_t eden_size_after = eden()->capacity();
444 size_t survivor_size_after = from()->capacity();
445 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
446 SIZE_FORMAT "K [eden="
447 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
448 new_size_before/K, new_size_after/K,
449 eden_size_after/K, survivor_size_after/K);
450 if (WizardMode) {
451 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
452 thread_increase_size/K, threads_count);
453 }
454 gclog_or_tty->cr();
455 }
456 }
457 }
458
459 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
460 assert(false, "NYI -- are you sure you want to call this?");
461 }
462
463
464 size_t DefNewGeneration::capacity() const {
465 return eden()->capacity()
466 + from()->capacity(); // to() is only used during scavenge
467 }
468
469
470 size_t DefNewGeneration::used() const {
471 return eden()->used()
472 + from()->used(); // to() is only used during scavenge
473 }
474
475
476 size_t DefNewGeneration::free() const {
477 return eden()->free()
478 + from()->free(); // to() is only used during scavenge
479 }
480
481 size_t DefNewGeneration::max_capacity() const {
482 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
483 const size_t reserved_bytes = reserved().byte_size();
484 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
485 }
486
487 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
488 return eden()->free();
489 }
490
491 size_t DefNewGeneration::capacity_before_gc() const {
492 return eden()->capacity();
493 }
494
495 size_t DefNewGeneration::contiguous_available() const {
496 return eden()->free();
497 }
498
499
500 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
501 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
502
503 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
504 eden()->object_iterate(blk);
505 from()->object_iterate(blk);
506 }
507
508
509 void DefNewGeneration::space_iterate(SpaceClosure* blk,
510 bool usedOnly) {
511 blk->do_space(eden());
512 blk->do_space(from());
513 blk->do_space(to());
514 }
515
516 // The last collection bailed out, we are running out of heap space,
517 // so we try to allocate the from-space, too.
518 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
519 HeapWord* result = NULL;
520 if (Verbose && PrintGCDetails) {
521 gclog_or_tty->print("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):"
522 " will_fail: %s"
523 " heap_lock: %s"
524 " free: " SIZE_FORMAT,
525 size,
526 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
527 "true" : "false",
528 Heap_lock->is_locked() ? "locked" : "unlocked",
529 from()->free());
530 }
531 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
532 if (Heap_lock->owned_by_self() ||
533 (SafepointSynchronize::is_at_safepoint() &&
534 Thread::current()->is_VM_thread())) {
535 // If the Heap_lock is not locked by this thread, this will be called
536 // again later with the Heap_lock held.
537 result = from()->allocate(size);
538 } else if (PrintGC && Verbose) {
539 gclog_or_tty->print_cr(" Heap_lock is not owned by self");
540 }
541 } else if (PrintGC && Verbose) {
542 gclog_or_tty->print_cr(" should_allocate_from_space: NOT");
543 }
544 if (PrintGC && Verbose) {
545 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object");
546 }
547 return result;
548 }
549
550 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
551 bool is_tlab,
552 bool parallel) {
553 // We don't attempt to expand the young generation (but perhaps we should.)
554 return allocate(size, is_tlab);
555 }
556
557 void DefNewGeneration::adjust_desired_tenuring_threshold() {
558 // Set the desired survivor size to half the real survivor space
559 _tenuring_threshold =
560 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
561 }
562
563 void DefNewGeneration::collect(bool full,
564 bool clear_all_soft_refs,
565 size_t size,
566 bool is_tlab) {
567 assert(full || size > 0, "otherwise we don't want to collect");
568
569 GenCollectedHeap* gch = GenCollectedHeap::heap();
570
571 _gc_timer->register_gc_start();
572 DefNewTracer gc_tracer;
573 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
574
575 _old_gen = gch->old_gen();
576
577 // If the next generation is too full to accommodate promotion
578 // from this generation, pass on collection; let the next generation
579 // do it.
580 if (!collection_attempt_is_safe()) {
581 if (Verbose && PrintGCDetails) {
582 gclog_or_tty->print(" :: Collection attempt not safe :: ");
583 }
584 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
585 return;
586 }
587 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
588
589 init_assuming_no_promotion_failure();
590
591 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, gc_tracer.gc_id());
592 // Capture heap used before collection (for printing).
593 size_t gch_prev_used = gch->used();
594
595 gch->trace_heap_before_gc(&gc_tracer);
596
597 SpecializationStats::clear();
598
599 // These can be shared for all code paths
600 IsAliveClosure is_alive(this);
601 ScanWeakRefClosure scan_weak_ref(this);
602
603 age_table()->clear();
604 to()->clear(SpaceDecorator::Mangle);
605
606 gch->rem_set()->prepare_for_younger_refs_iterate(false);
607
608 assert(gch->no_allocs_since_save_marks(0),
609 "save marks have not been newly set.");
610
611 // Not very pretty.
612 CollectorPolicy* cp = gch->collector_policy();
613
614 FastScanClosure fsc_with_no_gc_barrier(this, false);
615 FastScanClosure fsc_with_gc_barrier(this, true);
616
617 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
618 gch->rem_set()->klass_rem_set());
619 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
620 &fsc_with_no_gc_barrier,
621 false);
622
623 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
624 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
625 &fsc_with_no_gc_barrier,
626 &fsc_with_gc_barrier);
627
628 assert(gch->no_allocs_since_save_marks(0),
629 "save marks have not been newly set.");
630
631 gch->gen_process_roots(_level,
632 true, // Process younger gens, if any,
633 // as strong roots.
634 true, // activate StrongRootsScope
635 SharedHeap::SO_ScavengeCodeCache,
636 GenCollectedHeap::StrongAndWeakRoots,
637 &fsc_with_no_gc_barrier,
638 &fsc_with_gc_barrier,
639 &cld_scan_closure);
640
641 // "evacuate followers".
642 evacuate_followers.do_void();
643
644 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
645 ReferenceProcessor* rp = ref_processor();
646 rp->setup_policy(clear_all_soft_refs);
647 const ReferenceProcessorStats& stats =
648 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
649 NULL, _gc_timer, gc_tracer.gc_id());
650 gc_tracer.report_gc_reference_stats(stats);
651
652 if (!_promotion_failed) {
653 // Swap the survivor spaces.
654 eden()->clear(SpaceDecorator::Mangle);
655 from()->clear(SpaceDecorator::Mangle);
656 if (ZapUnusedHeapArea) {
657 // This is now done here because of the piece-meal mangling which
658 // can check for valid mangling at intermediate points in the
659 // collection(s). When a minor collection fails to collect
660 // sufficient space resizing of the young generation can occur
661 // an redistribute the spaces in the young generation. Mangle
662 // here so that unzapped regions don't get distributed to
663 // other spaces.
664 to()->mangle_unused_area();
665 }
666 swap_spaces();
667
668 assert(to()->is_empty(), "to space should be empty now");
669
670 adjust_desired_tenuring_threshold();
671
672 // A successful scavenge should restart the GC time limit count which is
673 // for full GC's.
674 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
675 size_policy->reset_gc_overhead_limit_count();
676 assert(!gch->incremental_collection_failed(), "Should be clear");
677 } else {
678 assert(_promo_failure_scan_stack.is_empty(), "post condition");
679 _promo_failure_scan_stack.clear(true); // Clear cached segments.
680
681 remove_forwarding_pointers();
682 if (PrintGCDetails) {
683 gclog_or_tty->print(" (promotion failed) ");
684 }
685 // Add to-space to the list of space to compact
686 // when a promotion failure has occurred. In that
687 // case there can be live objects in to-space
688 // as a result of a partial evacuation of eden
689 // and from-space.
690 swap_spaces(); // For uniformity wrt ParNewGeneration.
691 from()->set_next_compaction_space(to());
692 gch->set_incremental_collection_failed();
693
694 // Inform the next generation that a promotion failure occurred.
695 _old_gen->promotion_failure_occurred();
696 gc_tracer.report_promotion_failed(_promotion_failed_info);
697
698 // Reset the PromotionFailureALot counters.
699 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
700 }
701 if (PrintGC && !PrintGCDetails) {
702 gch->print_heap_change(gch_prev_used);
703 }
704 // set new iteration safe limit for the survivor spaces
705 from()->set_concurrent_iteration_safe_limit(from()->top());
706 to()->set_concurrent_iteration_safe_limit(to()->top());
707 SpecializationStats::print();
708
709 // We need to use a monotonically non-decreasing time in ms
710 // or we will see time-warp warnings and os::javaTimeMillis()
711 // does not guarantee monotonicity.
712 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
713 update_time_of_last_gc(now);
714
715 gch->trace_heap_after_gc(&gc_tracer);
716 gc_tracer.report_tenuring_threshold(tenuring_threshold());
717
718 _gc_timer->register_gc_end();
719
720 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
721 }
722
723 class RemoveForwardPointerClosure: public ObjectClosure {
724 public:
725 void do_object(oop obj) {
726 obj->init_mark();
727 }
728 };
729
730 void DefNewGeneration::init_assuming_no_promotion_failure() {
731 _promotion_failed = false;
732 _promotion_failed_info.reset();
733 from()->set_next_compaction_space(NULL);
734 }
735
736 void DefNewGeneration::remove_forwarding_pointers() {
737 RemoveForwardPointerClosure rspc;
738 eden()->object_iterate(&rspc);
739 from()->object_iterate(&rspc);
740
741 // Now restore saved marks, if any.
742 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
743 "should be the same");
744 while (!_objs_with_preserved_marks.is_empty()) {
745 oop obj = _objs_with_preserved_marks.pop();
746 markOop m = _preserved_marks_of_objs.pop();
747 obj->set_mark(m);
748 }
749 _objs_with_preserved_marks.clear(true);
750 _preserved_marks_of_objs.clear(true);
751 }
752
753 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
754 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
755 "Oversaving!");
756 _objs_with_preserved_marks.push(obj);
757 _preserved_marks_of_objs.push(m);
758 }
759
760 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
761 if (m->must_be_preserved_for_promotion_failure(obj)) {
762 preserve_mark(obj, m);
763 }
764 }
765
766 void DefNewGeneration::handle_promotion_failure(oop old) {
767 if (PrintPromotionFailure && !_promotion_failed) {
768 gclog_or_tty->print(" (promotion failure size = %d) ",
769 old->size());
770 }
771 _promotion_failed = true;
772 _promotion_failed_info.register_copy_failure(old->size());
773 preserve_mark_if_necessary(old, old->mark());
774 // forward to self
775 old->forward_to(old);
776
777 _promo_failure_scan_stack.push(old);
778
779 if (!_promo_failure_drain_in_progress) {
780 // prevent recursion in copy_to_survivor_space()
781 _promo_failure_drain_in_progress = true;
782 drain_promo_failure_scan_stack();
783 _promo_failure_drain_in_progress = false;
784 }
785 }
786
787 oop DefNewGeneration::copy_to_survivor_space(oop old) {
788 assert(is_in_reserved(old) && !old->is_forwarded(),
789 "shouldn't be scavenging this oop");
790 size_t s = old->size();
791 oop obj = NULL;
792
793 // Try allocating obj in to-space (unless too old)
794 if (old->age() < tenuring_threshold()) {
795 obj = (oop) to()->allocate_aligned(s);
796 }
797
798 // Otherwise try allocating obj tenured
799 if (obj == NULL) {
800 obj = _old_gen->promote(old, s);
801 if (obj == NULL) {
802 handle_promotion_failure(old);
803 return old;
804 }
805 } else {
806 // Prefetch beyond obj
807 const intx interval = PrefetchCopyIntervalInBytes;
808 Prefetch::write(obj, interval);
809
810 // Copy obj
811 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
812
813 // Increment age if obj still in new generation
814 obj->incr_age();
815 age_table()->add(obj, s);
816 }
817
818 // Done, insert forward pointer to obj in this header
819 old->forward_to(obj);
820
821 return obj;
822 }
823
824 void DefNewGeneration::drain_promo_failure_scan_stack() {
825 while (!_promo_failure_scan_stack.is_empty()) {
826 oop obj = _promo_failure_scan_stack.pop();
827 obj->oop_iterate(_promo_failure_scan_stack_closure);
828 }
829 }
830
831 void DefNewGeneration::save_marks() {
832 eden()->set_saved_mark();
833 to()->set_saved_mark();
834 from()->set_saved_mark();
835 }
836
837
838 void DefNewGeneration::reset_saved_marks() {
839 eden()->reset_saved_mark();
840 to()->reset_saved_mark();
841 from()->reset_saved_mark();
842 }
843
844
845 bool DefNewGeneration::no_allocs_since_save_marks() {
846 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
847 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
848 return to()->saved_mark_at_top();
849 }
850
851 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
852 \
853 void DefNewGeneration:: \
854 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
855 cl->set_generation(this); \
856 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
857 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
858 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
859 cl->reset_generation(); \
860 save_marks(); \
861 }
862
863 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
864
865 #undef DefNew_SINCE_SAVE_MARKS_DEFN
866
867 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
868 size_t max_alloc_words) {
869 if (requestor == this || _promotion_failed) return;
870 assert(requestor->level() > level(), "DefNewGeneration must be youngest");
871
872 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
873 if (to_space->top() > to_space->bottom()) {
874 trace("to_space not empty when contribute_scratch called");
875 }
876 */
877
878 ContiguousSpace* to_space = to();
879 assert(to_space->end() >= to_space->top(), "pointers out of order");
880 size_t free_words = pointer_delta(to_space->end(), to_space->top());
881 if (free_words >= MinFreeScratchWords) {
882 ScratchBlock* sb = (ScratchBlock*)to_space->top();
883 sb->num_words = free_words;
884 sb->next = list;
885 list = sb;
886 }
887 }
888
889 void DefNewGeneration::reset_scratch() {
890 // If contributing scratch in to_space, mangle all of
891 // to_space if ZapUnusedHeapArea. This is needed because
892 // top is not maintained while using to-space as scratch.
893 if (ZapUnusedHeapArea) {
894 to()->mangle_unused_area_complete();
895 }
896 }
897
898 bool DefNewGeneration::collection_attempt_is_safe() {
899 if (!to()->is_empty()) {
900 if (Verbose && PrintGCDetails) {
901 gclog_or_tty->print(" :: to is not empty :: ");
902 }
903 return false;
904 }
905 if (_old_gen == NULL) {
906 GenCollectedHeap* gch = GenCollectedHeap::heap();
907 _old_gen = gch->old_gen();
908 }
909 return _old_gen->promotion_attempt_is_safe(used());
910 }
911
912 void DefNewGeneration::gc_epilogue(bool full) {
913 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
914
915 assert(!GC_locker::is_active(), "We should not be executing here");
916 // Check if the heap is approaching full after a collection has
917 // been done. Generally the young generation is empty at
918 // a minimum at the end of a collection. If it is not, then
919 // the heap is approaching full.
920 GenCollectedHeap* gch = GenCollectedHeap::heap();
921 if (full) {
922 DEBUG_ONLY(seen_incremental_collection_failed = false;)
923 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
924 if (Verbose && PrintGCDetails) {
925 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
926 GCCause::to_string(gch->gc_cause()));
927 }
928 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
929 set_should_allocate_from_space(); // we seem to be running out of space
930 } else {
931 if (Verbose && PrintGCDetails) {
932 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
933 GCCause::to_string(gch->gc_cause()));
934 }
935 gch->clear_incremental_collection_failed(); // We just did a full collection
936 clear_should_allocate_from_space(); // if set
937 }
938 } else {
939 #ifdef ASSERT
940 // It is possible that incremental_collection_failed() == true
941 // here, because an attempted scavenge did not succeed. The policy
942 // is normally expected to cause a full collection which should
943 // clear that condition, so we should not be here twice in a row
944 // with incremental_collection_failed() == true without having done
945 // a full collection in between.
946 if (!seen_incremental_collection_failed &&
947 gch->incremental_collection_failed()) {
948 if (Verbose && PrintGCDetails) {
949 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
950 GCCause::to_string(gch->gc_cause()));
951 }
952 seen_incremental_collection_failed = true;
953 } else if (seen_incremental_collection_failed) {
954 if (Verbose && PrintGCDetails) {
955 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
956 GCCause::to_string(gch->gc_cause()));
957 }
958 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
959 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
960 !gch->incremental_collection_failed(),
961 "Twice in a row");
962 seen_incremental_collection_failed = false;
963 }
964 #endif // ASSERT
965 }
966
967 if (ZapUnusedHeapArea) {
968 eden()->check_mangled_unused_area_complete();
969 from()->check_mangled_unused_area_complete();
970 to()->check_mangled_unused_area_complete();
971 }
972
973 if (!CleanChunkPoolAsync) {
974 Chunk::clean_chunk_pool();
975 }
976
977 // update the generation and space performance counters
978 update_counters();
979 gch->collector_policy()->counters()->update_counters();
980 }
981
982 void DefNewGeneration::record_spaces_top() {
983 assert(ZapUnusedHeapArea, "Not mangling unused space");
984 eden()->set_top_for_allocations();
985 to()->set_top_for_allocations();
986 from()->set_top_for_allocations();
987 }
988
989 void DefNewGeneration::ref_processor_init() {
990 Generation::ref_processor_init();
991 }
992
993
994 void DefNewGeneration::update_counters() {
995 if (UsePerfData) {
996 _eden_counters->update_all();
997 _from_counters->update_all();
998 _to_counters->update_all();
999 _gen_counters->update_all();
1000 }
1001 }
1002
1003 void DefNewGeneration::verify() {
1004 eden()->verify();
1005 from()->verify();
1006 to()->verify();
1007 }
1008
1009 void DefNewGeneration::print_on(outputStream* st) const {
1010 Generation::print_on(st);
1011 st->print(" eden");
1012 eden()->print_on(st);
1013 st->print(" from");
1014 from()->print_on(st);
1015 st->print(" to ");
1016 to()->print_on(st);
1017 }
1018
1019
1020 const char* DefNewGeneration::name() const {
1021 return "def new generation";
1022 }
1023
1024 // Moved from inline file as they are not called inline
1025 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1026 return eden();
1027 }
1028
1029 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1030 // This is the slow-path allocation for the DefNewGeneration.
1031 // Most allocations are fast-path in compiled code.
1032 // We try to allocate from the eden. If that works, we are happy.
1033 // Note that since DefNewGeneration supports lock-free allocation, we
1034 // have to use it here, as well.
1035 HeapWord* result = eden()->par_allocate(word_size);
1036 if (result != NULL) {
1037 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1038 _old_gen->sample_eden_chunk();
1039 }
1040 return result;
1041 }
1042 do {
1043 HeapWord* old_limit = eden()->soft_end();
1044 if (old_limit < eden()->end()) {
1045 // Tell the old generation we reached a limit.
1046 HeapWord* new_limit =
1047 _old_gen->allocation_limit_reached(eden(), eden()->top(), word_size);
1048 if (new_limit != NULL) {
1049 Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit);
1050 } else {
1051 assert(eden()->soft_end() == eden()->end(),
1052 "invalid state after allocation_limit_reached returned null");
1053 }
1054 } else {
1055 // The allocation failed and the soft limit is equal to the hard limit,
1056 // there are no reasons to do an attempt to allocate
1057 assert(old_limit == eden()->end(), "sanity check");
1058 break;
1059 }
1060 // Try to allocate until succeeded or the soft limit can't be adjusted
1061 result = eden()->par_allocate(word_size);
1062 } while (result == NULL);
1063
1064 // If the eden is full and the last collection bailed out, we are running
1065 // out of heap space, and we try to allocate the from-space, too.
1066 // allocate_from_space can't be inlined because that would introduce a
1067 // circular dependency at compile time.
1068 if (result == NULL) {
1069 result = allocate_from_space(word_size);
1070 } else if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1071 _old_gen->sample_eden_chunk();
1072 }
1073 return result;
1074 }
1075
1076 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1077 bool is_tlab) {
1078 HeapWord* res = eden()->par_allocate(word_size);
1079 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1080 _old_gen->sample_eden_chunk();
1081 }
1082 return res;
1083 }
1084
1085 void DefNewGeneration::gc_prologue(bool full) {
1086 // Ensure that _end and _soft_end are the same in eden space.
1087 eden()->set_soft_end(eden()->end());
1088 }
1089
1090 size_t DefNewGeneration::tlab_capacity() const {
1091 return eden()->capacity();
1092 }
1093
1094 size_t DefNewGeneration::tlab_used() const {
1095 return eden()->used();
1096 }
1097
1098 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1099 return unsafe_max_alloc_nogc();
1100 }