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 "gc_interface/collectedHeap.inline.hpp"
34 #include "memory/defNewGeneration.inline.hpp"
35 #include "memory/gcLocker.inline.hpp"
36 #include "memory/genCollectedHeap.inline.hpp"
37 #include "memory/genOopClosures.inline.hpp"
38 #include "memory/genRemSet.hpp"
39 #include "memory/generationSpec.hpp"
40 #include "memory/iterator.hpp"
41 #include "memory/referencePolicy.hpp"
42 #include "memory/space.inline.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
53 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
54
55 //
56 // DefNewGeneration functions.
57
58 // Methods of protected closure types.
59
60 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
61 assert(g->level() == 0, "Optimized for youngest gen.");
62 }
63 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
64 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
65 }
66
67 DefNewGeneration::KeepAliveClosure::
68 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
69 GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
70 _rs = (CardTableRS*)rs;
71 }
72
73 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
74 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
75
76
77 DefNewGeneration::FastKeepAliveClosure::
78 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
79 DefNewGeneration::KeepAliveClosure(cl) {
80 _boundary = g->reserved().end();
81 }
82
83 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
84 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
85
86 DefNewGeneration::EvacuateFollowersClosure::
87 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
88 ScanClosure* cur, ScanClosure* older) :
89 _gch(gch), _level(level),
90 _scan_cur_or_nonheap(cur), _scan_older(older)
91 {}
92
93 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
94 do {
95 _gch->gch_oop_since_save_marks_iterate<true>(_level, _scan_cur_or_nonheap,
96 _scan_older);
97 } while (!_gch->no_allocs_since_save_marks(_level));
98 }
99
100 DefNewGeneration::FastEvacuateFollowersClosure::
101 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
102 DefNewGeneration* gen,
103 FastScanClosure* cur, FastScanClosure* older) :
104 _gch(gch), _level(level), _gen(gen),
105 _scan_cur_or_nonheap(cur), _scan_older(older)
106 {}
107
108 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
109 do {
110 _gch->gch_oop_since_save_marks_iterate<true>(_level, _scan_cur_or_nonheap,
111 _scan_older);
112 } while (!_gch->no_allocs_since_save_marks(_level));
113 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
114 }
115
116 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
117 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
118 {
119 assert(_g->level() == 0, "Optimized for youngest generation");
120 _boundary = _g->reserved().end();
121 }
122
123 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
124 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
125
126 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
127 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
128 {
129 assert(_g->level() == 0, "Optimized for youngest generation");
130 _boundary = _g->reserved().end();
131 }
132
133 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
134 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
135
136 void KlassScanClosure::do_klass(Klass* klass) {
137 #ifndef PRODUCT
138 if (TraceScavenge) {
139 ResourceMark rm;
140 gclog_or_tty->print_cr("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s",
141 klass,
142 klass->external_name(),
143 klass->has_modified_oops() ? "true" : "false");
144 }
145 #endif
146
147 // If the klass has not been dirtied we know that there's
148 // no references into the young gen and we can skip it.
149 if (klass->has_modified_oops()) {
150 if (_accumulate_modified_oops) {
151 klass->accumulate_modified_oops();
152 }
153
154 // Clear this state since we're going to scavenge all the metadata.
155 klass->clear_modified_oops();
156
157 // Tell the closure which Klass is being scanned so that it can be dirtied
158 // if oops are left pointing into the young gen.
159 _scavenge_closure->set_scanned_klass(klass);
160
161 klass->oops_do(_scavenge_closure);
162
163 _scavenge_closure->set_scanned_klass(NULL);
164 }
165 }
166
167 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
168 _g(g)
169 {
170 assert(_g->level() == 0, "Optimized for youngest generation");
171 _boundary = _g->reserved().end();
172 }
173
174 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
175 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
176
177 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
178 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
179
180 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
181 KlassRemSet* klass_rem_set)
182 : _scavenge_closure(scavenge_closure),
183 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
184
185
186 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
187 size_t initial_size,
188 int level,
189 const char* policy)
190 : Generation(rs, initial_size, level, _dispatch_index_generation_def_new),
191 _promo_failure_drain_in_progress(false),
192 _should_allocate_from_space(false)
193 {
194 MemRegion cmr((HeapWord*)_virtual_space.low(),
195 (HeapWord*)_virtual_space.high());
196 Universe::heap()->barrier_set()->resize_covered_region(cmr);
197
198 if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) {
199 _eden_space = new ConcEdenSpace(this);
200 } else {
201 _eden_space = new EdenSpace(this);
202 }
203 _from_space = new ContiguousSpace();
204 _to_space = new ContiguousSpace();
205
206 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
207 vm_exit_during_initialization("Could not allocate a new gen space");
208
209 // Compute the maximum eden and survivor space sizes. These sizes
210 // are computed assuming the entire reserved space is committed.
211 // These values are exported as performance counters.
212 uintx alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
213 uintx size = _virtual_space.reserved_size();
214 _max_survivor_size = compute_survivor_size(size, alignment);
215 _max_eden_size = size - (2*_max_survivor_size);
216
217 // allocate the performance counters
218
219 // Generation counters -- generation 0, 3 subspaces
220 _gen_counters = new GenerationCounters("new", 0, 3, &_virtual_space);
221 _gc_counters = new CollectorCounters(policy, 0);
222
223 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
224 _gen_counters);
225 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
226 _gen_counters);
227 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
228 _gen_counters);
229
230 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
231 update_counters();
232 _next_gen = NULL;
233 _tenuring_threshold = MaxTenuringThreshold;
234 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
235
236 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
237 }
238
239 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
240 bool clear_space,
241 bool mangle_space) {
242 uintx alignment =
243 GenCollectedHeap::heap()->collector_policy()->space_alignment();
244
245 // If the spaces are being cleared (only done at heap initialization
246 // currently), the survivor spaces need not be empty.
247 // Otherwise, no care is taken for used areas in the survivor spaces
248 // so check.
249 assert(clear_space || (to()->is_empty() && from()->is_empty()),
250 "Initialization of the survivor spaces assumes these are empty");
251
252 // Compute sizes
253 uintx size = _virtual_space.committed_size();
254 uintx survivor_size = compute_survivor_size(size, alignment);
255 uintx eden_size = size - (2*survivor_size);
256 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
257
258 if (eden_size < minimum_eden_size) {
259 // May happen due to 64Kb rounding, if so adjust eden size back up
260 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
261 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
262 uintx unaligned_survivor_size =
263 align_size_down(maximum_survivor_size, alignment);
264 survivor_size = MAX2(unaligned_survivor_size, alignment);
265 eden_size = size - (2*survivor_size);
266 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
267 assert(eden_size >= minimum_eden_size, "just checking");
268 }
269
270 char *eden_start = _virtual_space.low();
271 char *from_start = eden_start + eden_size;
272 char *to_start = from_start + survivor_size;
273 char *to_end = to_start + survivor_size;
274
275 assert(to_end == _virtual_space.high(), "just checking");
276 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
277 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
278 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
279
280 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
281 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
282 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
283
284 // A minimum eden size implies that there is a part of eden that
285 // is being used and that affects the initialization of any
286 // newly formed eden.
287 bool live_in_eden = minimum_eden_size > 0;
288
289 // If not clearing the spaces, do some checking to verify that
290 // the space are already mangled.
291 if (!clear_space) {
292 // Must check mangling before the spaces are reshaped. Otherwise,
293 // the bottom or end of one space may have moved into another
294 // a failure of the check may not correctly indicate which space
295 // is not properly mangled.
296 if (ZapUnusedHeapArea) {
297 HeapWord* limit = (HeapWord*) _virtual_space.high();
298 eden()->check_mangled_unused_area(limit);
299 from()->check_mangled_unused_area(limit);
300 to()->check_mangled_unused_area(limit);
301 }
302 }
303
304 // Reset the spaces for their new regions.
305 eden()->initialize(edenMR,
306 clear_space && !live_in_eden,
307 SpaceDecorator::Mangle);
308 // If clear_space and live_in_eden, we will not have cleared any
309 // portion of eden above its top. This can cause newly
310 // expanded space not to be mangled if using ZapUnusedHeapArea.
311 // We explicitly do such mangling here.
312 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
313 eden()->mangle_unused_area();
314 }
315 from()->initialize(fromMR, clear_space, mangle_space);
316 to()->initialize(toMR, clear_space, mangle_space);
317
318 // Set next compaction spaces.
319 eden()->set_next_compaction_space(from());
320 // The to-space is normally empty before a compaction so need
321 // not be considered. The exception is during promotion
322 // failure handling when to-space can contain live objects.
323 from()->set_next_compaction_space(NULL);
324 }
325
326 void DefNewGeneration::swap_spaces() {
327 ContiguousSpace* s = from();
328 _from_space = to();
329 _to_space = s;
330 eden()->set_next_compaction_space(from());
331 // The to-space is normally empty before a compaction so need
332 // not be considered. The exception is during promotion
333 // failure handling when to-space can contain live objects.
334 from()->set_next_compaction_space(NULL);
335
336 if (UsePerfData) {
337 CSpaceCounters* c = _from_counters;
338 _from_counters = _to_counters;
339 _to_counters = c;
340 }
341 }
342
343 bool DefNewGeneration::expand(size_t bytes) {
344 MutexLocker x(ExpandHeap_lock);
345 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
346 bool success = _virtual_space.expand_by(bytes);
347 if (success && ZapUnusedHeapArea) {
348 // Mangle newly committed space immediately because it
349 // can be done here more simply that after the new
350 // spaces have been computed.
351 HeapWord* new_high = (HeapWord*) _virtual_space.high();
352 MemRegion mangle_region(prev_high, new_high);
353 SpaceMangler::mangle_region(mangle_region);
354 }
355
356 // Do not attempt an expand-to-the reserve size. The
357 // request should properly observe the maximum size of
358 // the generation so an expand-to-reserve should be
359 // unnecessary. Also a second call to expand-to-reserve
360 // value potentially can cause an undue expansion.
361 // For example if the first expand fail for unknown reasons,
362 // but the second succeeds and expands the heap to its maximum
363 // value.
364 if (GC_locker::is_active()) {
365 if (PrintGC && Verbose) {
366 gclog_or_tty->print_cr("Garbage collection disabled, "
367 "expanded heap instead");
368 }
369 }
370
371 return success;
372 }
373
374
375 void DefNewGeneration::compute_new_size() {
376 // This is called after a gc that includes the following generation
377 // (which is required to exist.) So from-space will normally be empty.
378 // Note that we check both spaces, since if scavenge failed they revert roles.
379 // If not we bail out (otherwise we would have to relocate the objects)
380 if (!from()->is_empty() || !to()->is_empty()) {
381 return;
382 }
383
384 int next_level = level() + 1;
385 GenCollectedHeap* gch = GenCollectedHeap::heap();
386 assert(next_level < gch->_n_gens,
387 "DefNewGeneration cannot be an oldest gen");
388
389 Generation* next_gen = gch->_gens[next_level];
390 size_t old_size = next_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 Universe::heap()->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) {
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 _tenuring_threshold =
559 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
560 }
561
562 void DefNewGeneration::collect(bool full,
563 bool clear_all_soft_refs,
564 size_t size,
565 bool is_tlab) {
566 assert(full || size > 0, "otherwise we don't want to collect");
567
568 GenCollectedHeap* gch = GenCollectedHeap::heap();
569
570 _gc_timer->register_gc_start();
571 DefNewTracer gc_tracer;
572 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
573
574 _next_gen = gch->next_gen(this);
575
576 // If the next generation is too full to accommodate promotion
577 // from this generation, pass on collection; let the next generation
578 // do it.
579 if (!collection_attempt_is_safe()) {
580 if (Verbose && PrintGCDetails) {
581 gclog_or_tty->print(" :: Collection attempt not safe :: ");
582 }
583 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
584 return;
585 }
586 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
587
588 init_assuming_no_promotion_failure();
589
590 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, gc_tracer.gc_id());
591 // Capture heap used before collection (for printing).
592 size_t gch_prev_used = gch->used();
593
594 gch->trace_heap_before_gc(&gc_tracer);
595
596 SpecializationStats::clear();
597
598 // These can be shared for all code paths
599 IsAliveClosure is_alive(this);
600 ScanWeakRefClosure scan_weak_ref(this);
601
602 age_table()->clear();
603 to()->clear(SpaceDecorator::Mangle);
604
605 gch->rem_set()->prepare_for_younger_refs_iterate(false);
606
607 assert(gch->no_allocs_since_save_marks(0),
608 "save marks have not been newly set.");
609
610 // Not very pretty.
611 CollectorPolicy* cp = gch->collector_policy();
612
613 FastScanClosure fsc_with_no_gc_barrier(this, false);
614 FastScanClosure fsc_with_gc_barrier(this, true);
615
616 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
617 gch->rem_set()->klass_rem_set());
618 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
619 &fsc_with_no_gc_barrier,
620 false);
621
622 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
623 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
624 &fsc_with_no_gc_barrier,
625 &fsc_with_gc_barrier);
626
627 assert(gch->no_allocs_since_save_marks(0),
628 "save marks have not been newly set.");
629
630 gch->gen_process_roots(_level,
631 true, // Process younger gens, if any,
632 // as strong roots.
633 true, // activate StrongRootsScope
634 SharedHeap::SO_ScavengeCodeCache,
635 GenCollectedHeap::StrongAndWeakRoots,
636 &fsc_with_no_gc_barrier,
637 &fsc_with_gc_barrier,
638 &cld_scan_closure);
639
640 // "evacuate followers".
641 evacuate_followers.do_void();
642
643 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
644 ReferenceProcessor* rp = ref_processor();
645 rp->setup_policy(clear_all_soft_refs);
646 const ReferenceProcessorStats& stats =
647 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
648 NULL, _gc_timer, gc_tracer.gc_id());
649 gc_tracer.report_gc_reference_stats(stats);
650
651 if (!_promotion_failed) {
652 // Swap the survivor spaces.
653 eden()->clear(SpaceDecorator::Mangle);
654 from()->clear(SpaceDecorator::Mangle);
655 if (ZapUnusedHeapArea) {
656 // This is now done here because of the piece-meal mangling which
657 // can check for valid mangling at intermediate points in the
658 // collection(s). When a minor collection fails to collect
659 // sufficient space resizing of the young generation can occur
660 // an redistribute the spaces in the young generation. Mangle
661 // here so that unzapped regions don't get distributed to
662 // other spaces.
663 to()->mangle_unused_area();
664 }
665 swap_spaces();
666
667 assert(to()->is_empty(), "to space should be empty now");
668
669 adjust_desired_tenuring_threshold();
670
671 // A successful scavenge should restart the GC time limit count which is
672 // for full GC's.
673 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
674 size_policy->reset_gc_overhead_limit_count();
675 assert(!gch->incremental_collection_failed(), "Should be clear");
676 } else {
677 assert(_promo_failure_scan_stack.is_empty(), "post condition");
678 _promo_failure_scan_stack.clear(true); // Clear cached segments.
679
680 remove_forwarding_pointers();
681 if (PrintGCDetails) {
682 gclog_or_tty->print(" (promotion failed) ");
683 }
684 // Add to-space to the list of space to compact
685 // when a promotion failure has occurred. In that
686 // case there can be live objects in to-space
687 // as a result of a partial evacuation of eden
688 // and from-space.
689 swap_spaces(); // For uniformity wrt ParNewGeneration.
690 from()->set_next_compaction_space(to());
691 gch->set_incremental_collection_failed();
692
693 // Inform the next generation that a promotion failure occurred.
694 _next_gen->promotion_failure_occurred();
695 gc_tracer.report_promotion_failed(_promotion_failed_info);
696
697 // Reset the PromotionFailureALot counters.
698 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
699 }
700 if (PrintGC && !PrintGCDetails) {
701 gch->print_heap_change(gch_prev_used);
702 }
703 // set new iteration safe limit for the survivor spaces
704 from()->set_concurrent_iteration_safe_limit(from()->top());
705 to()->set_concurrent_iteration_safe_limit(to()->top());
706 SpecializationStats::print();
707
708 // We need to use a monotonically non-decreasing time in ms
709 // or we will see time-warp warnings and os::javaTimeMillis()
710 // does not guarantee monotonicity.
711 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
712 update_time_of_last_gc(now);
713
714 gch->trace_heap_after_gc(&gc_tracer);
715 gc_tracer.report_tenuring_threshold(tenuring_threshold());
716
717 _gc_timer->register_gc_end();
718
719 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
720 }
721
722 class RemoveForwardPointerClosure: public ObjectClosure {
723 public:
724 void do_object(oop obj) {
725 obj->init_mark();
726 }
727 };
728
729 void DefNewGeneration::init_assuming_no_promotion_failure() {
730 _promotion_failed = false;
731 _promotion_failed_info.reset();
732 from()->set_next_compaction_space(NULL);
733 }
734
735 void DefNewGeneration::remove_forwarding_pointers() {
736 RemoveForwardPointerClosure rspc;
737 eden()->object_iterate(&rspc);
738 from()->object_iterate(&rspc);
739
740 // Now restore saved marks, if any.
741 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
742 "should be the same");
743 while (!_objs_with_preserved_marks.is_empty()) {
744 oop obj = _objs_with_preserved_marks.pop();
745 markOop m = _preserved_marks_of_objs.pop();
746 obj->set_mark(m);
747 }
748 _objs_with_preserved_marks.clear(true);
749 _preserved_marks_of_objs.clear(true);
750 }
751
752 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
753 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
754 "Oversaving!");
755 _objs_with_preserved_marks.push(obj);
756 _preserved_marks_of_objs.push(m);
757 }
758
759 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
760 if (m->must_be_preserved_for_promotion_failure(obj)) {
761 preserve_mark(obj, m);
762 }
763 }
764
765 void DefNewGeneration::handle_promotion_failure(oop old) {
766 if (PrintPromotionFailure && !_promotion_failed) {
767 gclog_or_tty->print(" (promotion failure size = %d) ",
768 old->size());
769 }
770 _promotion_failed = true;
771 _promotion_failed_info.register_copy_failure(old->size());
772 preserve_mark_if_necessary(old, old->mark());
773 // forward to self
774 old->forward_to(old);
775
776 _promo_failure_scan_stack.push(old);
777
778 if (!_promo_failure_drain_in_progress) {
779 // prevent recursion in copy_to_survivor_space()
780 _promo_failure_drain_in_progress = true;
781 drain_promo_failure_scan_stack();
782 _promo_failure_drain_in_progress = false;
783 }
784 }
785
786 oop DefNewGeneration::copy_to_survivor_space(oop old) {
787 assert(is_in_reserved(old) && !old->is_forwarded(),
788 "shouldn't be scavenging this oop");
789 size_t s = old->size();
790 oop obj = NULL;
791
792 // Try allocating obj in to-space (unless too old)
793 if (old->age() < tenuring_threshold()) {
794 obj = (oop) to()->allocate_aligned(s);
795 }
796
797 // Otherwise try allocating obj tenured
798 if (obj == NULL) {
799 obj = _next_gen->promote(old, s);
800 if (obj == NULL) {
801 handle_promotion_failure(old);
802 return old;
803 }
804 } else {
805 // Prefetch beyond obj
806 const intx interval = PrefetchCopyIntervalInBytes;
807 Prefetch::write(obj, interval);
808
809 // Copy obj
810 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
811
812 // Increment age if obj still in new generation
813 obj->incr_age();
814 age_table()->add(obj, s);
815 }
816
817 // Done, insert forward pointer to obj in this header
818 old->forward_to(obj);
819
820 return obj;
821 }
822
823 void DefNewGeneration::drain_promo_failure_scan_stack() {
824 while (!_promo_failure_scan_stack.is_empty()) {
825 oop obj = _promo_failure_scan_stack.pop();
826 obj->oop_iterate<false>(_promo_failure_scan_stack_closure);
827 }
828 }
829
830 void DefNewGeneration::save_marks() {
831 eden()->set_saved_mark();
832 to()->set_saved_mark();
833 from()->set_saved_mark();
834 }
835
836
837 void DefNewGeneration::reset_saved_marks() {
838 eden()->reset_saved_mark();
839 to()->reset_saved_mark();
840 from()->reset_saved_mark();
841 }
842
843
844 bool DefNewGeneration::no_allocs_since_save_marks() {
845 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
846 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
847 return to()->saved_mark_at_top();
848 }
849
850 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
851 size_t max_alloc_words) {
852 if (requestor == this || _promotion_failed) return;
853 assert(requestor->level() > level(), "DefNewGeneration must be youngest");
854
855 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
856 if (to_space->top() > to_space->bottom()) {
857 trace("to_space not empty when contribute_scratch called");
858 }
859 */
860
861 ContiguousSpace* to_space = to();
862 assert(to_space->end() >= to_space->top(), "pointers out of order");
863 size_t free_words = pointer_delta(to_space->end(), to_space->top());
864 if (free_words >= MinFreeScratchWords) {
865 ScratchBlock* sb = (ScratchBlock*)to_space->top();
866 sb->num_words = free_words;
867 sb->next = list;
868 list = sb;
869 }
870 }
871
872 void DefNewGeneration::reset_scratch() {
873 // If contributing scratch in to_space, mangle all of
874 // to_space if ZapUnusedHeapArea. This is needed because
875 // top is not maintained while using to-space as scratch.
876 if (ZapUnusedHeapArea) {
877 to()->mangle_unused_area_complete();
878 }
879 }
880
881 bool DefNewGeneration::collection_attempt_is_safe() {
882 if (!to()->is_empty()) {
883 if (Verbose && PrintGCDetails) {
884 gclog_or_tty->print(" :: to is not empty :: ");
885 }
886 return false;
887 }
888 if (_next_gen == NULL) {
889 GenCollectedHeap* gch = GenCollectedHeap::heap();
890 _next_gen = gch->next_gen(this);
891 }
892 return _next_gen->promotion_attempt_is_safe(used());
893 }
894
895 void DefNewGeneration::gc_epilogue(bool full) {
896 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
897
898 assert(!GC_locker::is_active(), "We should not be executing here");
899 // Check if the heap is approaching full after a collection has
900 // been done. Generally the young generation is empty at
901 // a minimum at the end of a collection. If it is not, then
902 // the heap is approaching full.
903 GenCollectedHeap* gch = GenCollectedHeap::heap();
904 if (full) {
905 DEBUG_ONLY(seen_incremental_collection_failed = false;)
906 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
907 if (Verbose && PrintGCDetails) {
908 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
909 GCCause::to_string(gch->gc_cause()));
910 }
911 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
912 set_should_allocate_from_space(); // we seem to be running out of space
913 } else {
914 if (Verbose && PrintGCDetails) {
915 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
916 GCCause::to_string(gch->gc_cause()));
917 }
918 gch->clear_incremental_collection_failed(); // We just did a full collection
919 clear_should_allocate_from_space(); // if set
920 }
921 } else {
922 #ifdef ASSERT
923 // It is possible that incremental_collection_failed() == true
924 // here, because an attempted scavenge did not succeed. The policy
925 // is normally expected to cause a full collection which should
926 // clear that condition, so we should not be here twice in a row
927 // with incremental_collection_failed() == true without having done
928 // a full collection in between.
929 if (!seen_incremental_collection_failed &&
930 gch->incremental_collection_failed()) {
931 if (Verbose && PrintGCDetails) {
932 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
933 GCCause::to_string(gch->gc_cause()));
934 }
935 seen_incremental_collection_failed = true;
936 } else if (seen_incremental_collection_failed) {
937 if (Verbose && PrintGCDetails) {
938 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
939 GCCause::to_string(gch->gc_cause()));
940 }
941 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
942 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
943 !gch->incremental_collection_failed(),
944 "Twice in a row");
945 seen_incremental_collection_failed = false;
946 }
947 #endif // ASSERT
948 }
949
950 if (ZapUnusedHeapArea) {
951 eden()->check_mangled_unused_area_complete();
952 from()->check_mangled_unused_area_complete();
953 to()->check_mangled_unused_area_complete();
954 }
955
956 if (!CleanChunkPoolAsync) {
957 Chunk::clean_chunk_pool();
958 }
959
960 // update the generation and space performance counters
961 update_counters();
962 gch->collector_policy()->counters()->update_counters();
963 }
964
965 void DefNewGeneration::record_spaces_top() {
966 assert(ZapUnusedHeapArea, "Not mangling unused space");
967 eden()->set_top_for_allocations();
968 to()->set_top_for_allocations();
969 from()->set_top_for_allocations();
970 }
971
972 void DefNewGeneration::ref_processor_init() {
973 Generation::ref_processor_init();
974 }
975
976
977 void DefNewGeneration::update_counters() {
978 if (UsePerfData) {
979 _eden_counters->update_all();
980 _from_counters->update_all();
981 _to_counters->update_all();
982 _gen_counters->update_all();
983 }
984 }
985
986 void DefNewGeneration::verify() {
987 eden()->verify();
988 from()->verify();
989 to()->verify();
990 }
991
992 void DefNewGeneration::print_on(outputStream* st) const {
993 Generation::print_on(st);
994 st->print(" eden");
995 eden()->print_on(st);
996 st->print(" from");
997 from()->print_on(st);
998 st->print(" to ");
999 to()->print_on(st);
1000 }
1001
1002
1003 const char* DefNewGeneration::name() const {
1004 return "def new generation";
1005 }
1006
1007 // Moved from inline file as they are not called inline
1008 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1009 return eden();
1010 }
1011
1012 HeapWord* DefNewGeneration::allocate(size_t word_size,
1013 bool is_tlab) {
1014 // This is the slow-path allocation for the DefNewGeneration.
1015 // Most allocations are fast-path in compiled code.
1016 // We try to allocate from the eden. If that works, we are happy.
1017 // Note that since DefNewGeneration supports lock-free allocation, we
1018 // have to use it here, as well.
1019 HeapWord* result = eden()->par_allocate(word_size);
1020 if (result != NULL) {
1021 if (CMSEdenChunksRecordAlways && _next_gen != NULL) {
1022 _next_gen->sample_eden_chunk();
1023 }
1024 return result;
1025 }
1026 do {
1027 HeapWord* old_limit = eden()->soft_end();
1028 if (old_limit < eden()->end()) {
1029 // Tell the next generation we reached a limit.
1030 HeapWord* new_limit =
1031 next_gen()->allocation_limit_reached(eden(), eden()->top(), word_size);
1032 if (new_limit != NULL) {
1033 Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit);
1034 } else {
1035 assert(eden()->soft_end() == eden()->end(),
1036 "invalid state after allocation_limit_reached returned null");
1037 }
1038 } else {
1039 // The allocation failed and the soft limit is equal to the hard limit,
1040 // there are no reasons to do an attempt to allocate
1041 assert(old_limit == eden()->end(), "sanity check");
1042 break;
1043 }
1044 // Try to allocate until succeeded or the soft limit can't be adjusted
1045 result = eden()->par_allocate(word_size);
1046 } while (result == NULL);
1047
1048 // If the eden is full and the last collection bailed out, we are running
1049 // out of heap space, and we try to allocate the from-space, too.
1050 // allocate_from_space can't be inlined because that would introduce a
1051 // circular dependency at compile time.
1052 if (result == NULL) {
1053 result = allocate_from_space(word_size);
1054 } else if (CMSEdenChunksRecordAlways && _next_gen != NULL) {
1055 _next_gen->sample_eden_chunk();
1056 }
1057 return result;
1058 }
1059
1060 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1061 bool is_tlab) {
1062 HeapWord* res = eden()->par_allocate(word_size);
1063 if (CMSEdenChunksRecordAlways && _next_gen != NULL) {
1064 _next_gen->sample_eden_chunk();
1065 }
1066 return res;
1067 }
1068
1069 void DefNewGeneration::gc_prologue(bool full) {
1070 // Ensure that _end and _soft_end are the same in eden space.
1071 eden()->set_soft_end(eden()->end());
1072 }
1073
1074 size_t DefNewGeneration::tlab_capacity() const {
1075 return eden()->capacity();
1076 }
1077
1078 size_t DefNewGeneration::tlab_used() const {
1079 return eden()->used();
1080 }
1081
1082 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1083 return unsafe_max_alloc_nogc();
1084 }