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/collectorCounters.hpp"
28 #include "gc/shared/gcHeapSummary.hpp"
29 #include "gc/shared/gcLocker.inline.hpp"
30 #include "gc/shared/gcPolicyCounters.hpp"
31 #include "gc/shared/gcTimer.hpp"
32 #include "gc/shared/gcTrace.hpp"
33 #include "gc/shared/gcTraceTime.hpp"
34 #include "gc/shared/genCollectedHeap.hpp"
35 #include "gc/shared/genOopClosures.inline.hpp"
36 #include "gc/shared/genRemSet.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 "memory/iterator.hpp"
43 #include "oops/instanceRefKlass.hpp"
44 #include "oops/oop.inline.hpp"
45 #include "runtime/atomic.inline.hpp"
46 #include "runtime/java.hpp"
47 #include "runtime/prefetch.inline.hpp"
48 #include "runtime/thread.inline.hpp"
49 #include "utilities/copy.hpp"
50 #include "utilities/globalDefinitions.hpp"
51 #include "utilities/stack.inline.hpp"
52 #if INCLUDE_ALL_GCS
53 #include "gc/cms/parOopClosures.hpp"
54 #endif
55
56 //
57 // DefNewGeneration functions.
58
59 // Methods of protected closure types.
60
61 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
62 assert(g->level() == 0, "Optimized for youngest gen.");
63 }
64 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
65 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
66 }
67
68 DefNewGeneration::KeepAliveClosure::
69 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
70 GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
71 _rs = (CardTableRS*)rs;
72 }
73
74 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
75 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
76
77
78 DefNewGeneration::FastKeepAliveClosure::
79 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
80 DefNewGeneration::KeepAliveClosure(cl) {
81 _boundary = g->reserved().end();
82 }
83
84 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
85 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
86
87 DefNewGeneration::EvacuateFollowersClosure::
88 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
89 ScanClosure* cur, ScanClosure* older) :
90 _gch(gch), _level(level),
91 _scan_cur_or_nonheap(cur), _scan_older(older)
92 {}
93
94 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
95 do {
96 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
97 _scan_older);
98 } while (!_gch->no_allocs_since_save_marks(_level));
99 }
100
101 DefNewGeneration::FastEvacuateFollowersClosure::
102 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
103 DefNewGeneration* gen,
104 FastScanClosure* cur, FastScanClosure* older) :
105 _gch(gch), _level(level), _gen(gen),
106 _scan_cur_or_nonheap(cur), _scan_older(older)
107 {}
108
109 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
110 do {
111 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
112 _scan_older);
113 } while (!_gch->no_allocs_since_save_marks(_level));
114 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
115 }
116
117 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
118 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
119 {
120 assert(_g->level() == 0, "Optimized for youngest generation");
121 _boundary = _g->reserved().end();
122 }
123
124 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
125 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
126
127 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
128 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
129 {
130 assert(_g->level() == 0, "Optimized for youngest generation");
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 if (TraceScavenge) {
140 ResourceMark rm;
141 gclog_or_tty->print_cr("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s",
142 p2i(klass),
143 klass->external_name(),
144 klass->has_modified_oops() ? "true" : "false");
145 }
146 #endif
147
148 // If the klass has not been dirtied we know that there's
149 // no references into the young gen and we can skip it.
150 if (klass->has_modified_oops()) {
151 if (_accumulate_modified_oops) {
152 klass->accumulate_modified_oops();
153 }
154
155 // Clear this state since we're going to scavenge all the metadata.
156 klass->clear_modified_oops();
157
158 // Tell the closure which Klass is being scanned so that it can be dirtied
159 // if oops are left pointing into the young gen.
160 _scavenge_closure->set_scanned_klass(klass);
161
162 klass->oops_do(_scavenge_closure);
163
164 _scavenge_closure->set_scanned_klass(NULL);
165 }
166 }
167
168 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
169 _g(g)
170 {
171 assert(_g->level() == 0, "Optimized for youngest generation");
172 _boundary = _g->reserved().end();
173 }
174
175 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
176 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
177
178 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
179 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
180
181 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
182 KlassRemSet* klass_rem_set)
183 : _scavenge_closure(scavenge_closure),
184 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
185
186
187 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
188 size_t initial_size,
189 int level,
190 const char* policy)
191 : Generation(rs, initial_size, level),
192 _promo_failure_drain_in_progress(false),
193 _should_allocate_from_space(false)
194 {
195 MemRegion cmr((HeapWord*)_virtual_space.low(),
196 (HeapWord*)_virtual_space.high());
197 GenCollectedHeap* gch = GenCollectedHeap::heap();
198
199 gch->barrier_set()->resize_covered_region(cmr);
200
201 _eden_space = new ContiguousSpace();
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 = gch->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*)gch->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 == 1, "DefNewGeneration must be a young gen");
388
389 Generation* old_gen = gch->old_gen();
390 size_t old_size = old_gen->capacity();
391 size_t new_size_before = _virtual_space.committed_size();
392 size_t min_new_size = spec()->init_size();
393 size_t max_new_size = reserved().byte_size();
394 assert(min_new_size <= new_size_before &&
395 new_size_before <= max_new_size,
396 "just checking");
397 // All space sizes must be multiples of Generation::GenGrain.
398 size_t alignment = Generation::GenGrain;
399
400 // Compute desired new generation size based on NewRatio and
401 // NewSizeThreadIncrease
402 size_t desired_new_size = old_size/NewRatio;
403 int threads_count = Threads::number_of_non_daemon_threads();
404 size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
405 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
406
407 // Adjust new generation size
408 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
409 assert(desired_new_size <= max_new_size, "just checking");
410
411 bool changed = false;
412 if (desired_new_size > new_size_before) {
413 size_t change = desired_new_size - new_size_before;
414 assert(change % alignment == 0, "just checking");
415 if (expand(change)) {
416 changed = true;
417 }
418 // If the heap failed to expand to the desired size,
419 // "changed" will be false. If the expansion failed
420 // (and at this point it was expected to succeed),
421 // ignore the failure (leaving "changed" as false).
422 }
423 if (desired_new_size < new_size_before && eden()->is_empty()) {
424 // bail out of shrinking if objects in eden
425 size_t change = new_size_before - desired_new_size;
426 assert(change % alignment == 0, "just checking");
427 _virtual_space.shrink_by(change);
428 changed = true;
429 }
430 if (changed) {
431 // The spaces have already been mangled at this point but
432 // may not have been cleared (set top = bottom) and should be.
433 // Mangling was done when the heap was being expanded.
434 compute_space_boundaries(eden()->used(),
435 SpaceDecorator::Clear,
436 SpaceDecorator::DontMangle);
437 MemRegion cmr((HeapWord*)_virtual_space.low(),
438 (HeapWord*)_virtual_space.high());
439 gch->barrier_set()->resize_covered_region(cmr);
440 if (Verbose && PrintGC) {
441 size_t new_size_after = _virtual_space.committed_size();
442 size_t eden_size_after = eden()->capacity();
443 size_t survivor_size_after = from()->capacity();
444 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
445 SIZE_FORMAT "K [eden="
446 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
447 new_size_before/K, new_size_after/K,
448 eden_size_after/K, survivor_size_after/K);
449 if (WizardMode) {
450 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
451 thread_increase_size/K, threads_count);
452 }
453 gclog_or_tty->cr();
454 }
455 }
456 }
457
458 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
459 assert(false, "NYI -- are you sure you want to call this?");
460 }
461
462
463 size_t DefNewGeneration::capacity() const {
464 return eden()->capacity()
465 + from()->capacity(); // to() is only used during scavenge
466 }
467
468
469 size_t DefNewGeneration::used() const {
470 return eden()->used()
471 + from()->used(); // to() is only used during scavenge
472 }
473
474
475 size_t DefNewGeneration::free() const {
476 return eden()->free()
477 + from()->free(); // to() is only used during scavenge
478 }
479
480 size_t DefNewGeneration::max_capacity() const {
481 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
482 const size_t reserved_bytes = reserved().byte_size();
483 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
484 }
485
486 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
487 return eden()->free();
488 }
489
490 size_t DefNewGeneration::capacity_before_gc() const {
491 return eden()->capacity();
492 }
493
494 size_t DefNewGeneration::contiguous_available() const {
495 return eden()->free();
496 }
497
498
499 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
500 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
501
502 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
503 eden()->object_iterate(blk);
504 from()->object_iterate(blk);
505 }
506
507
508 void DefNewGeneration::space_iterate(SpaceClosure* blk,
509 bool usedOnly) {
510 blk->do_space(eden());
511 blk->do_space(from());
512 blk->do_space(to());
513 }
514
515 // The last collection bailed out, we are running out of heap space,
516 // so we try to allocate the from-space, too.
517 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
518 HeapWord* result = NULL;
519 if (Verbose && PrintGCDetails) {
520 gclog_or_tty->print("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):"
521 " will_fail: %s"
522 " heap_lock: %s"
523 " free: " SIZE_FORMAT,
524 size,
525 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
526 "true" : "false",
527 Heap_lock->is_locked() ? "locked" : "unlocked",
528 from()->free());
529 }
530 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
531 if (Heap_lock->owned_by_self() ||
532 (SafepointSynchronize::is_at_safepoint() &&
533 Thread::current()->is_VM_thread())) {
534 // If the Heap_lock is not locked by this thread, this will be called
535 // again later with the Heap_lock held.
536 result = from()->allocate(size);
537 } else if (PrintGC && Verbose) {
538 gclog_or_tty->print_cr(" Heap_lock is not owned by self");
539 }
540 } else if (PrintGC && Verbose) {
541 gclog_or_tty->print_cr(" should_allocate_from_space: NOT");
542 }
543 if (PrintGC && Verbose) {
544 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object");
545 }
546 return result;
547 }
548
549 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
550 bool is_tlab,
551 bool parallel) {
552 // We don't attempt to expand the young generation (but perhaps we should.)
553 return allocate(size, is_tlab);
554 }
555
556 void DefNewGeneration::adjust_desired_tenuring_threshold() {
557 // Set the desired survivor size to half the real survivor space
558 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->collector_policy()->counters();
559 _tenuring_threshold =
560 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize, gc_counters);
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 // These can be shared for all code paths
598 IsAliveClosure is_alive(this);
599 ScanWeakRefClosure scan_weak_ref(this);
600
601 age_table()->clear();
602 to()->clear(SpaceDecorator::Mangle);
603
604 gch->rem_set()->prepare_for_younger_refs_iterate(false);
605
606 assert(gch->no_allocs_since_save_marks(0),
607 "save marks have not been newly set.");
608
609 // Not very pretty.
610 CollectorPolicy* cp = gch->collector_policy();
611
612 FastScanClosure fsc_with_no_gc_barrier(this, false);
613 FastScanClosure fsc_with_gc_barrier(this, true);
614
615 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
616 gch->rem_set()->klass_rem_set());
617 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
618 &fsc_with_no_gc_barrier,
619 false);
620
621 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
622 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
623 &fsc_with_no_gc_barrier,
624 &fsc_with_gc_barrier);
625
626 assert(gch->no_allocs_since_save_marks(0),
627 "save marks have not been newly set.");
628
629 {
630 // DefNew needs to run with n_threads == 0, to make sure the serial
631 // version of the card table scanning code is used.
632 // See: CardTableModRefBS::non_clean_card_iterate_possibly_parallel.
633 StrongRootsScope srs(0);
634
635 gch->gen_process_roots(&srs,
636 _level,
637 true, // Process younger gens, if any,
638 // as strong roots.
639 GenCollectedHeap::SO_ScavengeCodeCache,
640 GenCollectedHeap::StrongAndWeakRoots,
641 &fsc_with_no_gc_barrier,
642 &fsc_with_gc_barrier,
643 &cld_scan_closure);
644 }
645
646 // "evacuate followers".
647 evacuate_followers.do_void();
648
649 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
650 ReferenceProcessor* rp = ref_processor();
651 rp->setup_policy(clear_all_soft_refs);
652 const ReferenceProcessorStats& stats =
653 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
654 NULL, _gc_timer, gc_tracer.gc_id());
655 gc_tracer.report_gc_reference_stats(stats);
656
657 if (!_promotion_failed) {
658 // Swap the survivor spaces.
659 eden()->clear(SpaceDecorator::Mangle);
660 from()->clear(SpaceDecorator::Mangle);
661 if (ZapUnusedHeapArea) {
662 // This is now done here because of the piece-meal mangling which
663 // can check for valid mangling at intermediate points in the
664 // collection(s). When a minor collection fails to collect
665 // sufficient space resizing of the young generation can occur
666 // an redistribute the spaces in the young generation. Mangle
667 // here so that unzapped regions don't get distributed to
668 // other spaces.
669 to()->mangle_unused_area();
670 }
671 swap_spaces();
672
673 assert(to()->is_empty(), "to space should be empty now");
674
675 adjust_desired_tenuring_threshold();
676
677 // A successful scavenge should restart the GC time limit count which is
678 // for full GC's.
679 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
680 size_policy->reset_gc_overhead_limit_count();
681 assert(!gch->incremental_collection_failed(), "Should be clear");
682 } else {
683 assert(_promo_failure_scan_stack.is_empty(), "post condition");
684 _promo_failure_scan_stack.clear(true); // Clear cached segments.
685
686 remove_forwarding_pointers();
687 if (PrintGCDetails) {
688 gclog_or_tty->print(" (promotion failed) ");
689 }
690 // Add to-space to the list of space to compact
691 // when a promotion failure has occurred. In that
692 // case there can be live objects in to-space
693 // as a result of a partial evacuation of eden
694 // and from-space.
695 swap_spaces(); // For uniformity wrt ParNewGeneration.
696 from()->set_next_compaction_space(to());
697 gch->set_incremental_collection_failed();
698
699 // Inform the next generation that a promotion failure occurred.
700 _old_gen->promotion_failure_occurred();
701 gc_tracer.report_promotion_failed(_promotion_failed_info);
702
703 // Reset the PromotionFailureALot counters.
704 NOT_PRODUCT(gch->reset_promotion_should_fail();)
705 }
706 if (PrintGC && !PrintGCDetails) {
707 gch->print_heap_change(gch_prev_used);
708 }
709 // set new iteration safe limit for the survivor spaces
710 from()->set_concurrent_iteration_safe_limit(from()->top());
711 to()->set_concurrent_iteration_safe_limit(to()->top());
712
713 // We need to use a monotonically non-decreasing time in ms
714 // or we will see time-warp warnings and os::javaTimeMillis()
715 // does not guarantee monotonicity.
716 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
717 update_time_of_last_gc(now);
718
719 gch->trace_heap_after_gc(&gc_tracer);
720 gc_tracer.report_tenuring_threshold(tenuring_threshold());
721
722 _gc_timer->register_gc_end();
723
724 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
725 }
726
727 class RemoveForwardPointerClosure: public ObjectClosure {
728 public:
729 void do_object(oop obj) {
730 obj->init_mark();
731 }
732 };
733
734 void DefNewGeneration::init_assuming_no_promotion_failure() {
735 _promotion_failed = false;
736 _promotion_failed_info.reset();
737 from()->set_next_compaction_space(NULL);
738 }
739
740 void DefNewGeneration::remove_forwarding_pointers() {
741 RemoveForwardPointerClosure rspc;
742 eden()->object_iterate(&rspc);
743 from()->object_iterate(&rspc);
744
745 // Now restore saved marks, if any.
746 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
747 "should be the same");
748 while (!_objs_with_preserved_marks.is_empty()) {
749 oop obj = _objs_with_preserved_marks.pop();
750 markOop m = _preserved_marks_of_objs.pop();
751 obj->set_mark(m);
752 }
753 _objs_with_preserved_marks.clear(true);
754 _preserved_marks_of_objs.clear(true);
755 }
756
757 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
758 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
759 "Oversaving!");
760 _objs_with_preserved_marks.push(obj);
761 _preserved_marks_of_objs.push(m);
762 }
763
764 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
765 if (m->must_be_preserved_for_promotion_failure(obj)) {
766 preserve_mark(obj, m);
767 }
768 }
769
770 void DefNewGeneration::handle_promotion_failure(oop old) {
771 if (PrintPromotionFailure && !_promotion_failed) {
772 gclog_or_tty->print(" (promotion failure size = %d) ",
773 old->size());
774 }
775 _promotion_failed = true;
776 _promotion_failed_info.register_copy_failure(old->size());
777 preserve_mark_if_necessary(old, old->mark());
778 // forward to self
779 old->forward_to(old);
780
781 _promo_failure_scan_stack.push(old);
782
783 if (!_promo_failure_drain_in_progress) {
784 // prevent recursion in copy_to_survivor_space()
785 _promo_failure_drain_in_progress = true;
786 drain_promo_failure_scan_stack();
787 _promo_failure_drain_in_progress = false;
788 }
789 }
790
791 oop DefNewGeneration::copy_to_survivor_space(oop old) {
792 assert(is_in_reserved(old) && !old->is_forwarded(),
793 "shouldn't be scavenging this oop");
794 size_t s = old->size();
795 oop obj = NULL;
796
797 // Try allocating obj in to-space (unless too old)
798 if (old->age() < tenuring_threshold()) {
799 obj = (oop) to()->allocate_aligned(s);
800 }
801
802 // Otherwise try allocating obj tenured
803 if (obj == NULL) {
804 obj = _old_gen->promote(old, s);
805 if (obj == NULL) {
806 handle_promotion_failure(old);
807 return old;
808 }
809 } else {
810 // Prefetch beyond obj
811 const intx interval = PrefetchCopyIntervalInBytes;
812 Prefetch::write(obj, interval);
813
814 // Copy obj
815 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
816
817 // Increment age if obj still in new generation
818 obj->incr_age();
819 age_table()->add(obj, s);
820 }
821
822 // Done, insert forward pointer to obj in this header
823 old->forward_to(obj);
824
825 return obj;
826 }
827
828 void DefNewGeneration::drain_promo_failure_scan_stack() {
829 while (!_promo_failure_scan_stack.is_empty()) {
830 oop obj = _promo_failure_scan_stack.pop();
831 obj->oop_iterate(_promo_failure_scan_stack_closure);
832 }
833 }
834
835 void DefNewGeneration::save_marks() {
836 eden()->set_saved_mark();
837 to()->set_saved_mark();
838 from()->set_saved_mark();
839 }
840
841
842 void DefNewGeneration::reset_saved_marks() {
843 eden()->reset_saved_mark();
844 to()->reset_saved_mark();
845 from()->reset_saved_mark();
846 }
847
848
849 bool DefNewGeneration::no_allocs_since_save_marks() {
850 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
851 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
852 return to()->saved_mark_at_top();
853 }
854
855 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
856 \
857 void DefNewGeneration:: \
858 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
859 cl->set_generation(this); \
860 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
861 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
862 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
863 cl->reset_generation(); \
864 save_marks(); \
865 }
866
867 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
868
869 #undef DefNew_SINCE_SAVE_MARKS_DEFN
870
871 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
872 size_t max_alloc_words) {
873 if (requestor == this || _promotion_failed) return;
874 assert(requestor->level() > level(), "DefNewGeneration must be youngest");
875
876 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
877 if (to_space->top() > to_space->bottom()) {
878 trace("to_space not empty when contribute_scratch called");
879 }
880 */
881
882 ContiguousSpace* to_space = to();
883 assert(to_space->end() >= to_space->top(), "pointers out of order");
884 size_t free_words = pointer_delta(to_space->end(), to_space->top());
885 if (free_words >= MinFreeScratchWords) {
886 ScratchBlock* sb = (ScratchBlock*)to_space->top();
887 sb->num_words = free_words;
888 sb->next = list;
889 list = sb;
890 }
891 }
892
893 void DefNewGeneration::reset_scratch() {
894 // If contributing scratch in to_space, mangle all of
895 // to_space if ZapUnusedHeapArea. This is needed because
896 // top is not maintained while using to-space as scratch.
897 if (ZapUnusedHeapArea) {
898 to()->mangle_unused_area_complete();
899 }
900 }
901
902 bool DefNewGeneration::collection_attempt_is_safe() {
903 if (!to()->is_empty()) {
904 if (Verbose && PrintGCDetails) {
905 gclog_or_tty->print(" :: to is not empty :: ");
906 }
907 return false;
908 }
909 if (_old_gen == NULL) {
910 GenCollectedHeap* gch = GenCollectedHeap::heap();
911 _old_gen = gch->old_gen();
912 }
913 return _old_gen->promotion_attempt_is_safe(used());
914 }
915
916 void DefNewGeneration::gc_epilogue(bool full) {
917 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
918
919 assert(!GC_locker::is_active(), "We should not be executing here");
920 // Check if the heap is approaching full after a collection has
921 // been done. Generally the young generation is empty at
922 // a minimum at the end of a collection. If it is not, then
923 // the heap is approaching full.
924 GenCollectedHeap* gch = GenCollectedHeap::heap();
925 if (full) {
926 DEBUG_ONLY(seen_incremental_collection_failed = false;)
927 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
928 if (Verbose && PrintGCDetails) {
929 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
930 GCCause::to_string(gch->gc_cause()));
931 }
932 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
933 set_should_allocate_from_space(); // we seem to be running out of space
934 } else {
935 if (Verbose && PrintGCDetails) {
936 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
937 GCCause::to_string(gch->gc_cause()));
938 }
939 gch->clear_incremental_collection_failed(); // We just did a full collection
940 clear_should_allocate_from_space(); // if set
941 }
942 } else {
943 #ifdef ASSERT
944 // It is possible that incremental_collection_failed() == true
945 // here, because an attempted scavenge did not succeed. The policy
946 // is normally expected to cause a full collection which should
947 // clear that condition, so we should not be here twice in a row
948 // with incremental_collection_failed() == true without having done
949 // a full collection in between.
950 if (!seen_incremental_collection_failed &&
951 gch->incremental_collection_failed()) {
952 if (Verbose && PrintGCDetails) {
953 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
954 GCCause::to_string(gch->gc_cause()));
955 }
956 seen_incremental_collection_failed = true;
957 } else if (seen_incremental_collection_failed) {
958 if (Verbose && PrintGCDetails) {
959 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
960 GCCause::to_string(gch->gc_cause()));
961 }
962 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
963 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
964 !gch->incremental_collection_failed(),
965 "Twice in a row");
966 seen_incremental_collection_failed = false;
967 }
968 #endif // ASSERT
969 }
970
971 if (ZapUnusedHeapArea) {
972 eden()->check_mangled_unused_area_complete();
973 from()->check_mangled_unused_area_complete();
974 to()->check_mangled_unused_area_complete();
975 }
976
977 if (!CleanChunkPoolAsync) {
978 Chunk::clean_chunk_pool();
979 }
980
981 // update the generation and space performance counters
982 update_counters();
983 gch->collector_policy()->counters()->update_counters();
984 }
985
986 void DefNewGeneration::record_spaces_top() {
987 assert(ZapUnusedHeapArea, "Not mangling unused space");
988 eden()->set_top_for_allocations();
989 to()->set_top_for_allocations();
990 from()->set_top_for_allocations();
991 }
992
993 void DefNewGeneration::ref_processor_init() {
994 Generation::ref_processor_init();
995 }
996
997
998 void DefNewGeneration::update_counters() {
999 if (UsePerfData) {
1000 _eden_counters->update_all();
1001 _from_counters->update_all();
1002 _to_counters->update_all();
1003 _gen_counters->update_all();
1004 }
1005 }
1006
1007 void DefNewGeneration::verify() {
1008 eden()->verify();
1009 from()->verify();
1010 to()->verify();
1011 }
1012
1013 void DefNewGeneration::print_on(outputStream* st) const {
1014 Generation::print_on(st);
1015 st->print(" eden");
1016 eden()->print_on(st);
1017 st->print(" from");
1018 from()->print_on(st);
1019 st->print(" to ");
1020 to()->print_on(st);
1021 }
1022
1023
1024 const char* DefNewGeneration::name() const {
1025 return "def new generation";
1026 }
1027
1028 // Moved from inline file as they are not called inline
1029 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1030 return eden();
1031 }
1032
1033 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1034 // This is the slow-path allocation for the DefNewGeneration.
1035 // Most allocations are fast-path in compiled code.
1036 // We try to allocate from the eden. If that works, we are happy.
1037 // Note that since DefNewGeneration supports lock-free allocation, we
1038 // have to use it here, as well.
1039 HeapWord* result = eden()->par_allocate(word_size);
1040 if (result != NULL) {
1041 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1042 _old_gen->sample_eden_chunk();
1043 }
1044 } else {
1045 // If the eden is full and the last collection bailed out, we are running
1046 // out of heap space, and we try to allocate the from-space, too.
1047 // allocate_from_space can't be inlined because that would introduce a
1048 // circular dependency at compile time.
1049 result = allocate_from_space(word_size);
1050 }
1051 return result;
1052 }
1053
1054 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1055 bool is_tlab) {
1056 HeapWord* res = eden()->par_allocate(word_size);
1057 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1058 _old_gen->sample_eden_chunk();
1059 }
1060 return res;
1061 }
1062
1063 size_t DefNewGeneration::tlab_capacity() const {
1064 return eden()->capacity();
1065 }
1066
1067 size_t DefNewGeneration::tlab_used() const {
1068 return eden()->used();
1069 }
1070
1071 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1072 return unsafe_max_alloc_nogc();
1073 }