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 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
61 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
62 }
63
64 DefNewGeneration::KeepAliveClosure::
65 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
66 GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
67 _rs = (CardTableRS*)rs;
68 }
69
70 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
71 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
72
73
74 DefNewGeneration::FastKeepAliveClosure::
75 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
76 DefNewGeneration::KeepAliveClosure(cl) {
77 _boundary = g->reserved().end();
78 }
79
80 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
81 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
82
83 DefNewGeneration::EvacuateFollowersClosure::
84 EvacuateFollowersClosure(GenCollectedHeap* gch,
85 ScanClosure* cur, ScanClosure* older) :
86 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
87 {}
88
89 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
90 do {
91 _gch->oop_since_save_marks_iterate(Generation::Young, _scan_cur_or_nonheap,
92 _scan_older);
93 } while (!_gch->no_allocs_since_save_marks(Generation::Young));
94 }
95
96 DefNewGeneration::FastEvacuateFollowersClosure::
97 FastEvacuateFollowersClosure(GenCollectedHeap* gch,
98 DefNewGeneration* gen,
99 FastScanClosure* cur, FastScanClosure* older) :
100 _gch(gch), _gen(gen), _scan_cur_or_nonheap(cur), _scan_older(older)
101 {}
102
103 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
104 do {
105 _gch->oop_since_save_marks_iterate(Generation::Young, _scan_cur_or_nonheap,
106 _scan_older);
107 } while (!_gch->no_allocs_since_save_marks(Generation::Young));
108 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
109 }
110
111 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
112 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
113 {
114 _boundary = _g->reserved().end();
115 }
116
117 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
118 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
119
120 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
121 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
122 {
123 _boundary = _g->reserved().end();
124 }
125
126 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
127 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
128
129 void KlassScanClosure::do_klass(Klass* klass) {
130 #ifndef PRODUCT
131 if (TraceScavenge) {
132 ResourceMark rm;
133 gclog_or_tty->print_cr("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s",
134 klass,
135 klass->external_name(),
136 klass->has_modified_oops() ? "true" : "false");
137 }
138 #endif
139
140 // If the klass has not been dirtied we know that there's
141 // no references into the young gen and we can skip it.
142 if (klass->has_modified_oops()) {
143 if (_accumulate_modified_oops) {
144 klass->accumulate_modified_oops();
145 }
146
147 // Clear this state since we're going to scavenge all the metadata.
148 klass->clear_modified_oops();
149
150 // Tell the closure which Klass is being scanned so that it can be dirtied
151 // if oops are left pointing into the young gen.
152 _scavenge_closure->set_scanned_klass(klass);
153
154 klass->oops_do(_scavenge_closure);
155
156 _scavenge_closure->set_scanned_klass(NULL);
157 }
158 }
159
160 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
161 _g(g)
162 {
163 _boundary = _g->reserved().end();
164 }
165
166 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
167 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
168
169 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
170 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
171
172 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
173 KlassRemSet* klass_rem_set)
174 : _scavenge_closure(scavenge_closure),
175 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
176
177
178 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
179 size_t initial_size,
180 const char* policy)
181 : Generation(rs, initial_size),
182 _promo_failure_drain_in_progress(false),
183 _should_allocate_from_space(false)
184 {
185 MemRegion cmr((HeapWord*)_virtual_space.low(),
186 (HeapWord*)_virtual_space.high());
187 Universe::heap()->barrier_set()->resize_covered_region(cmr);
188
189 if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) {
190 _eden_space = new ConcEdenSpace(this);
191 } else {
192 _eden_space = new EdenSpace(this);
193 }
194 _from_space = new ContiguousSpace();
195 _to_space = new ContiguousSpace();
196
197 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
198 vm_exit_during_initialization("Could not allocate a new gen space");
199
200 // Compute the maximum eden and survivor space sizes. These sizes
201 // are computed assuming the entire reserved space is committed.
202 // These values are exported as performance counters.
203 uintx alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
204 uintx size = _virtual_space.reserved_size();
205 _max_survivor_size = compute_survivor_size(size, alignment);
206 _max_eden_size = size - (2*_max_survivor_size);
207
208 // allocate the performance counters
209 GenCollectorPolicy* gcp = (GenCollectorPolicy*) GenCollectedHeap::heap()->collector_policy();
210
211 // Generation counters -- generation 0, 3 subspaces
212 _gen_counters = new GenerationCounters("new", 0, 3,
213 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
214 _gc_counters = new CollectorCounters(policy, 0);
215
216 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
217 _gen_counters);
218 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
219 _gen_counters);
220 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
221 _gen_counters);
222
223 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
224 update_counters();
225 _old_gen = NULL;
226 _tenuring_threshold = MaxTenuringThreshold;
227 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
228
229 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
230 }
231
232 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
233 bool clear_space,
234 bool mangle_space) {
235 uintx alignment =
236 GenCollectedHeap::heap()->collector_policy()->space_alignment();
237
238 // If the spaces are being cleared (only done at heap initialization
239 // currently), the survivor spaces need not be empty.
240 // Otherwise, no care is taken for used areas in the survivor spaces
241 // so check.
242 assert(clear_space || (to()->is_empty() && from()->is_empty()),
243 "Initialization of the survivor spaces assumes these are empty");
244
245 // Compute sizes
246 uintx size = _virtual_space.committed_size();
247 uintx survivor_size = compute_survivor_size(size, alignment);
248 uintx eden_size = size - (2*survivor_size);
249 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
250
251 if (eden_size < minimum_eden_size) {
252 // May happen due to 64Kb rounding, if so adjust eden size back up
253 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
254 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
255 uintx unaligned_survivor_size =
256 align_size_down(maximum_survivor_size, alignment);
257 survivor_size = MAX2(unaligned_survivor_size, alignment);
258 eden_size = size - (2*survivor_size);
259 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
260 assert(eden_size >= minimum_eden_size, "just checking");
261 }
262
263 char *eden_start = _virtual_space.low();
264 char *from_start = eden_start + eden_size;
265 char *to_start = from_start + survivor_size;
266 char *to_end = to_start + survivor_size;
267
268 assert(to_end == _virtual_space.high(), "just checking");
269 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
270 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
271 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
272
273 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
274 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
275 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
276
277 // A minimum eden size implies that there is a part of eden that
278 // is being used and that affects the initialization of any
279 // newly formed eden.
280 bool live_in_eden = minimum_eden_size > 0;
281
282 // If not clearing the spaces, do some checking to verify that
283 // the space are already mangled.
284 if (!clear_space) {
285 // Must check mangling before the spaces are reshaped. Otherwise,
286 // the bottom or end of one space may have moved into another
287 // a failure of the check may not correctly indicate which space
288 // is not properly mangled.
289 if (ZapUnusedHeapArea) {
290 HeapWord* limit = (HeapWord*) _virtual_space.high();
291 eden()->check_mangled_unused_area(limit);
292 from()->check_mangled_unused_area(limit);
293 to()->check_mangled_unused_area(limit);
294 }
295 }
296
297 // Reset the spaces for their new regions.
298 eden()->initialize(edenMR,
299 clear_space && !live_in_eden,
300 SpaceDecorator::Mangle);
301 // If clear_space and live_in_eden, we will not have cleared any
302 // portion of eden above its top. This can cause newly
303 // expanded space not to be mangled if using ZapUnusedHeapArea.
304 // We explicitly do such mangling here.
305 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
306 eden()->mangle_unused_area();
307 }
308 from()->initialize(fromMR, clear_space, mangle_space);
309 to()->initialize(toMR, clear_space, mangle_space);
310
311 // Set next compaction spaces.
312 eden()->set_next_compaction_space(from());
313 // The to-space is normally empty before a compaction so need
314 // not be considered. The exception is during promotion
315 // failure handling when to-space can contain live objects.
316 from()->set_next_compaction_space(NULL);
317 }
318
319 void DefNewGeneration::swap_spaces() {
320 ContiguousSpace* s = from();
321 _from_space = to();
322 _to_space = s;
323 eden()->set_next_compaction_space(from());
324 // The to-space is normally empty before a compaction so need
325 // not be considered. The exception is during promotion
326 // failure handling when to-space can contain live objects.
327 from()->set_next_compaction_space(NULL);
328
329 if (UsePerfData) {
330 CSpaceCounters* c = _from_counters;
331 _from_counters = _to_counters;
332 _to_counters = c;
333 }
334 }
335
336 bool DefNewGeneration::expand(size_t bytes) {
337 MutexLocker x(ExpandHeap_lock);
338 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
339 bool success = _virtual_space.expand_by(bytes);
340 if (success && ZapUnusedHeapArea) {
341 // Mangle newly committed space immediately because it
342 // can be done here more simply that after the new
343 // spaces have been computed.
344 HeapWord* new_high = (HeapWord*) _virtual_space.high();
345 MemRegion mangle_region(prev_high, new_high);
346 SpaceMangler::mangle_region(mangle_region);
347 }
348
349 // Do not attempt an expand-to-the reserve size. The
350 // request should properly observe the maximum size of
351 // the generation so an expand-to-reserve should be
352 // unnecessary. Also a second call to expand-to-reserve
353 // value potentially can cause an undue expansion.
354 // For example if the first expand fail for unknown reasons,
355 // but the second succeeds and expands the heap to its maximum
356 // value.
357 if (GC_locker::is_active()) {
358 if (PrintGC && Verbose) {
359 gclog_or_tty->print_cr("Garbage collection disabled, "
360 "expanded heap instead");
361 }
362 }
363
364 return success;
365 }
366
367
368 void DefNewGeneration::compute_new_size() {
369 // This is called after a gc that includes the following generation
370 // (which is required to exist.) So from-space will normally be empty.
371 // Note that we check both spaces, since if scavenge failed they revert roles.
372 // If not we bail out (otherwise we would have to relocate the objects)
373 if (!from()->is_empty() || !to()->is_empty()) {
374 return;
375 }
376
377 GenCollectedHeap* gch = GenCollectedHeap::heap();
378
379 size_t old_size = gch->old_gen()->capacity();
380 size_t new_size_before = _virtual_space.committed_size();
381 size_t min_new_size = spec()->init_size();
382 size_t max_new_size = reserved().byte_size();
383 assert(min_new_size <= new_size_before &&
384 new_size_before <= max_new_size,
385 "just checking");
386 // All space sizes must be multiples of Generation::GenGrain.
387 size_t alignment = Generation::GenGrain;
388
389 // Compute desired new generation size based on NewRatio and
390 // NewSizeThreadIncrease
391 size_t desired_new_size = old_size/NewRatio;
392 int threads_count = Threads::number_of_non_daemon_threads();
393 size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
394 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
395
396 // Adjust new generation size
397 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
398 assert(desired_new_size <= max_new_size, "just checking");
399
400 bool changed = false;
401 if (desired_new_size > new_size_before) {
402 size_t change = desired_new_size - new_size_before;
403 assert(change % alignment == 0, "just checking");
404 if (expand(change)) {
405 changed = true;
406 }
407 // If the heap failed to expand to the desired size,
408 // "changed" will be false. If the expansion failed
409 // (and at this point it was expected to succeed),
410 // ignore the failure (leaving "changed" as false).
411 }
412 if (desired_new_size < new_size_before && eden()->is_empty()) {
413 // bail out of shrinking if objects in eden
414 size_t change = new_size_before - desired_new_size;
415 assert(change % alignment == 0, "just checking");
416 _virtual_space.shrink_by(change);
417 changed = true;
418 }
419 if (changed) {
420 // The spaces have already been mangled at this point but
421 // may not have been cleared (set top = bottom) and should be.
422 // Mangling was done when the heap was being expanded.
423 compute_space_boundaries(eden()->used(),
424 SpaceDecorator::Clear,
425 SpaceDecorator::DontMangle);
426 MemRegion cmr((HeapWord*)_virtual_space.low(),
427 (HeapWord*)_virtual_space.high());
428 Universe::heap()->barrier_set()->resize_covered_region(cmr);
429 if (Verbose && PrintGC) {
430 size_t new_size_after = _virtual_space.committed_size();
431 size_t eden_size_after = eden()->capacity();
432 size_t survivor_size_after = from()->capacity();
433 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
434 SIZE_FORMAT "K [eden="
435 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
436 new_size_before/K, new_size_after/K,
437 eden_size_after/K, survivor_size_after/K);
438 if (WizardMode) {
439 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
440 thread_increase_size/K, threads_count);
441 }
442 gclog_or_tty->cr();
443 }
444 }
445 }
446
447 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
448 assert(false, "NYI -- are you sure you want to call this?");
449 }
450
451
452 size_t DefNewGeneration::capacity() const {
453 return eden()->capacity()
454 + from()->capacity(); // to() is only used during scavenge
455 }
456
457
458 size_t DefNewGeneration::used() const {
459 return eden()->used()
460 + from()->used(); // to() is only used during scavenge
461 }
462
463
464 size_t DefNewGeneration::free() const {
465 return eden()->free()
466 + from()->free(); // to() is only used during scavenge
467 }
468
469 size_t DefNewGeneration::max_capacity() const {
470 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
471 const size_t reserved_bytes = reserved().byte_size();
472 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
473 }
474
475 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
476 return eden()->free();
477 }
478
479 size_t DefNewGeneration::capacity_before_gc() const {
480 return eden()->capacity();
481 }
482
483 size_t DefNewGeneration::contiguous_available() const {
484 return eden()->free();
485 }
486
487
488 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
489 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
490
491 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
492 eden()->object_iterate(blk);
493 from()->object_iterate(blk);
494 }
495
496
497 void DefNewGeneration::space_iterate(SpaceClosure* blk,
498 bool usedOnly) {
499 blk->do_space(eden());
500 blk->do_space(from());
501 blk->do_space(to());
502 }
503
504 // The last collection bailed out, we are running out of heap space,
505 // so we try to allocate the from-space, too.
506 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
507 HeapWord* result = NULL;
508 if (Verbose && PrintGCDetails) {
509 gclog_or_tty->print("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):"
510 " will_fail: %s"
511 " heap_lock: %s"
512 " free: " SIZE_FORMAT,
513 size,
514 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
515 "true" : "false",
516 Heap_lock->is_locked() ? "locked" : "unlocked",
517 from()->free());
518 }
519 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
520 if (Heap_lock->owned_by_self() ||
521 (SafepointSynchronize::is_at_safepoint() &&
522 Thread::current()->is_VM_thread())) {
523 // If the Heap_lock is not locked by this thread, this will be called
524 // again later with the Heap_lock held.
525 result = from()->allocate(size);
526 } else if (PrintGC && Verbose) {
527 gclog_or_tty->print_cr(" Heap_lock is not owned by self");
528 }
529 } else if (PrintGC && Verbose) {
530 gclog_or_tty->print_cr(" should_allocate_from_space: NOT");
531 }
532 if (PrintGC && Verbose) {
533 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object");
534 }
535 return result;
536 }
537
538 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
539 bool is_tlab,
540 bool parallel) {
541 // We don't attempt to expand the young generation (but perhaps we should.)
542 return allocate(size, is_tlab);
543 }
544
545 void DefNewGeneration::adjust_desired_tenuring_threshold() {
546 // Set the desired survivor size to half the real survivor space
547 _tenuring_threshold =
548 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
549 }
550
551 void DefNewGeneration::collect(bool full,
552 bool clear_all_soft_refs,
553 size_t size,
554 bool is_tlab) {
555 assert(full || size > 0, "otherwise we don't want to collect");
556
557 GenCollectedHeap* gch = GenCollectedHeap::heap();
558
559 _gc_timer->register_gc_start();
560 DefNewTracer gc_tracer;
561 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
562
563 _old_gen = gch->old_gen();
564
565 // If the next generation is too full to accommodate promotion
566 // from this generation, pass on collection; let the next generation
567 // do it.
568 if (!collection_attempt_is_safe()) {
569 if (Verbose && PrintGCDetails) {
570 gclog_or_tty->print(" :: Collection attempt not safe :: ");
571 }
572 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
573 return;
574 }
575 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
576
577 init_assuming_no_promotion_failure();
578
579 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, gc_tracer.gc_id());
580 // Capture heap used before collection (for printing).
581 size_t gch_prev_used = gch->used();
582
583 gch->trace_heap_before_gc(&gc_tracer);
584
585 SpecializationStats::clear();
586
587 // These can be shared for all code paths
588 IsAliveClosure is_alive(this);
589 ScanWeakRefClosure scan_weak_ref(this);
590
591 age_table()->clear();
592 to()->clear(SpaceDecorator::Mangle);
593
594 gch->rem_set()->prepare_for_younger_refs_iterate(false);
595
596 assert(gch->no_allocs_since_save_marks(Generation::Young),
597 "save marks have not been newly set.");
598
599 // Not very pretty.
600 CollectorPolicy* cp = gch->collector_policy();
601
602 FastScanClosure fsc_with_no_gc_barrier(this, false);
603 FastScanClosure fsc_with_gc_barrier(this, true);
604
605 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
606 gch->rem_set()->klass_rem_set());
607 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
608 &fsc_with_no_gc_barrier,
609 false);
610
611 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
612 FastEvacuateFollowersClosure evacuate_followers(gch, this,
613 &fsc_with_no_gc_barrier,
614 &fsc_with_gc_barrier);
615
616 assert(gch->no_allocs_since_save_marks(Generation::Young),
617 "save marks have not been newly set.");
618
619 gch->gen_process_roots(Generation::Young,
620 true, // Process younger gens, if any,
621 // as strong roots.
622 true, // activate StrongRootsScope
623 SharedHeap::SO_ScavengeCodeCache,
624 GenCollectedHeap::StrongAndWeakRoots,
625 &fsc_with_no_gc_barrier,
626 &fsc_with_gc_barrier,
627 &cld_scan_closure);
628
629 // "evacuate followers".
630 evacuate_followers.do_void();
631
632 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
633 ReferenceProcessor* rp = ref_processor();
634 rp->setup_policy(clear_all_soft_refs);
635 const ReferenceProcessorStats& stats =
636 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
637 NULL, _gc_timer, gc_tracer.gc_id());
638 gc_tracer.report_gc_reference_stats(stats);
639
640 if (!_promotion_failed) {
641 // Swap the survivor spaces.
642 eden()->clear(SpaceDecorator::Mangle);
643 from()->clear(SpaceDecorator::Mangle);
644 if (ZapUnusedHeapArea) {
645 // This is now done here because of the piece-meal mangling which
646 // can check for valid mangling at intermediate points in the
647 // collection(s). When a minor collection fails to collect
648 // sufficient space resizing of the young generation can occur
649 // an redistribute the spaces in the young generation. Mangle
650 // here so that unzapped regions don't get distributed to
651 // other spaces.
652 to()->mangle_unused_area();
653 }
654 swap_spaces();
655
656 assert(to()->is_empty(), "to space should be empty now");
657
658 adjust_desired_tenuring_threshold();
659
660 // A successful scavenge should restart the GC time limit count which is
661 // for full GC's.
662 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
663 size_policy->reset_gc_overhead_limit_count();
664 assert(!gch->incremental_collection_failed(), "Should be clear");
665 } else {
666 assert(_promo_failure_scan_stack.is_empty(), "post condition");
667 _promo_failure_scan_stack.clear(true); // Clear cached segments.
668
669 remove_forwarding_pointers();
670 if (PrintGCDetails) {
671 gclog_or_tty->print(" (promotion failed) ");
672 }
673 // Add to-space to the list of space to compact
674 // when a promotion failure has occurred. In that
675 // case there can be live objects in to-space
676 // as a result of a partial evacuation of eden
677 // and from-space.
678 swap_spaces(); // For uniformity wrt ParNewGeneration.
679 from()->set_next_compaction_space(to());
680 gch->set_incremental_collection_failed();
681
682 // Inform the next generation that a promotion failure occurred.
683 _old_gen->promotion_failure_occurred();
684 gc_tracer.report_promotion_failed(_promotion_failed_info);
685
686 // Reset the PromotionFailureALot counters.
687 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
688 }
689 if (PrintGC && !PrintGCDetails) {
690 gch->print_heap_change(gch_prev_used);
691 }
692 // set new iteration safe limit for the survivor spaces
693 from()->set_concurrent_iteration_safe_limit(from()->top());
694 to()->set_concurrent_iteration_safe_limit(to()->top());
695 SpecializationStats::print();
696
697 // We need to use a monotonically non-decreasing time in ms
698 // or we will see time-warp warnings and os::javaTimeMillis()
699 // does not guarantee monotonicity.
700 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
701 update_time_of_last_gc(now);
702
703 gch->trace_heap_after_gc(&gc_tracer);
704 gc_tracer.report_tenuring_threshold(tenuring_threshold());
705
706 _gc_timer->register_gc_end();
707
708 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
709 }
710
711 class RemoveForwardPointerClosure: public ObjectClosure {
712 public:
713 void do_object(oop obj) {
714 obj->init_mark();
715 }
716 };
717
718 void DefNewGeneration::init_assuming_no_promotion_failure() {
719 _promotion_failed = false;
720 _promotion_failed_info.reset();
721 from()->set_next_compaction_space(NULL);
722 }
723
724 void DefNewGeneration::remove_forwarding_pointers() {
725 RemoveForwardPointerClosure rspc;
726 eden()->object_iterate(&rspc);
727 from()->object_iterate(&rspc);
728
729 // Now restore saved marks, if any.
730 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
731 "should be the same");
732 while (!_objs_with_preserved_marks.is_empty()) {
733 oop obj = _objs_with_preserved_marks.pop();
734 markOop m = _preserved_marks_of_objs.pop();
735 obj->set_mark(m);
736 }
737 _objs_with_preserved_marks.clear(true);
738 _preserved_marks_of_objs.clear(true);
739 }
740
741 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
742 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
743 "Oversaving!");
744 _objs_with_preserved_marks.push(obj);
745 _preserved_marks_of_objs.push(m);
746 }
747
748 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
749 if (m->must_be_preserved_for_promotion_failure(obj)) {
750 preserve_mark(obj, m);
751 }
752 }
753
754 void DefNewGeneration::handle_promotion_failure(oop old) {
755 if (PrintPromotionFailure && !_promotion_failed) {
756 gclog_or_tty->print(" (promotion failure size = %d) ",
757 old->size());
758 }
759 _promotion_failed = true;
760 _promotion_failed_info.register_copy_failure(old->size());
761 preserve_mark_if_necessary(old, old->mark());
762 // forward to self
763 old->forward_to(old);
764
765 _promo_failure_scan_stack.push(old);
766
767 if (!_promo_failure_drain_in_progress) {
768 // prevent recursion in copy_to_survivor_space()
769 _promo_failure_drain_in_progress = true;
770 drain_promo_failure_scan_stack();
771 _promo_failure_drain_in_progress = false;
772 }
773 }
774
775 oop DefNewGeneration::copy_to_survivor_space(oop old) {
776 assert(is_in_reserved(old) && !old->is_forwarded(),
777 "shouldn't be scavenging this oop");
778 size_t s = old->size();
779 oop obj = NULL;
780
781 // Try allocating obj in to-space (unless too old)
782 if (old->age() < tenuring_threshold()) {
783 obj = (oop) to()->allocate_aligned(s);
784 }
785
786 // Otherwise try allocating obj tenured
787 if (obj == NULL) {
788 obj = _old_gen->promote(old, s);
789 if (obj == NULL) {
790 handle_promotion_failure(old);
791 return old;
792 }
793 } else {
794 // Prefetch beyond obj
795 const intx interval = PrefetchCopyIntervalInBytes;
796 Prefetch::write(obj, interval);
797
798 // Copy obj
799 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
800
801 // Increment age if obj still in new generation
802 obj->incr_age();
803 age_table()->add(obj, s);
804 }
805
806 // Done, insert forward pointer to obj in this header
807 old->forward_to(obj);
808
809 return obj;
810 }
811
812 void DefNewGeneration::drain_promo_failure_scan_stack() {
813 while (!_promo_failure_scan_stack.is_empty()) {
814 oop obj = _promo_failure_scan_stack.pop();
815 obj->oop_iterate(_promo_failure_scan_stack_closure);
816 }
817 }
818
819 void DefNewGeneration::save_marks() {
820 eden()->set_saved_mark();
821 to()->set_saved_mark();
822 from()->set_saved_mark();
823 }
824
825
826 void DefNewGeneration::reset_saved_marks() {
827 eden()->reset_saved_mark();
828 to()->reset_saved_mark();
829 from()->reset_saved_mark();
830 }
831
832
833 bool DefNewGeneration::no_allocs_since_save_marks() {
834 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
835 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
836 return to()->saved_mark_at_top();
837 }
838
839 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
840 \
841 void DefNewGeneration:: \
842 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
843 cl->set_generation(this); \
844 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
845 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
846 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
847 cl->reset_generation(); \
848 save_marks(); \
849 }
850
851 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
852
853 #undef DefNew_SINCE_SAVE_MARKS_DEFN
854
855 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
856 size_t max_alloc_words) {
857 if (requestor == this || _promotion_failed) return;
858 assert(requestor == GenCollectedHeap::heap()->old_gen(), "We should not call our own generation");
859
860 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
861 if (to_space->top() > to_space->bottom()) {
862 trace("to_space not empty when contribute_scratch called");
863 }
864 */
865
866 ContiguousSpace* to_space = to();
867 assert(to_space->end() >= to_space->top(), "pointers out of order");
868 size_t free_words = pointer_delta(to_space->end(), to_space->top());
869 if (free_words >= MinFreeScratchWords) {
870 ScratchBlock* sb = (ScratchBlock*)to_space->top();
871 sb->num_words = free_words;
872 sb->next = list;
873 list = sb;
874 }
875 }
876
877 void DefNewGeneration::reset_scratch() {
878 // If contributing scratch in to_space, mangle all of
879 // to_space if ZapUnusedHeapArea. This is needed because
880 // top is not maintained while using to-space as scratch.
881 if (ZapUnusedHeapArea) {
882 to()->mangle_unused_area_complete();
883 }
884 }
885
886 bool DefNewGeneration::collection_attempt_is_safe() {
887 if (!to()->is_empty()) {
888 if (Verbose && PrintGCDetails) {
889 gclog_or_tty->print(" :: to is not empty :: ");
890 }
891 return false;
892 }
893 if (_old_gen == NULL) {
894 GenCollectedHeap* gch = GenCollectedHeap::heap();
895 _old_gen = gch->old_gen();
896 }
897 return _old_gen->promotion_attempt_is_safe(used());
898 }
899
900 void DefNewGeneration::gc_epilogue(bool full) {
901 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
902
903 assert(!GC_locker::is_active(), "We should not be executing here");
904 // Check if the heap is approaching full after a collection has
905 // been done. Generally the young generation is empty at
906 // a minimum at the end of a collection. If it is not, then
907 // the heap is approaching full.
908 GenCollectedHeap* gch = GenCollectedHeap::heap();
909 if (full) {
910 DEBUG_ONLY(seen_incremental_collection_failed = false;)
911 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
912 if (Verbose && PrintGCDetails) {
913 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
914 GCCause::to_string(gch->gc_cause()));
915 }
916 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
917 set_should_allocate_from_space(); // we seem to be running out of space
918 } else {
919 if (Verbose && PrintGCDetails) {
920 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
921 GCCause::to_string(gch->gc_cause()));
922 }
923 gch->clear_incremental_collection_failed(); // We just did a full collection
924 clear_should_allocate_from_space(); // if set
925 }
926 } else {
927 #ifdef ASSERT
928 // It is possible that incremental_collection_failed() == true
929 // here, because an attempted scavenge did not succeed. The policy
930 // is normally expected to cause a full collection which should
931 // clear that condition, so we should not be here twice in a row
932 // with incremental_collection_failed() == true without having done
933 // a full collection in between.
934 if (!seen_incremental_collection_failed &&
935 gch->incremental_collection_failed()) {
936 if (Verbose && PrintGCDetails) {
937 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
938 GCCause::to_string(gch->gc_cause()));
939 }
940 seen_incremental_collection_failed = true;
941 } else if (seen_incremental_collection_failed) {
942 if (Verbose && PrintGCDetails) {
943 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
944 GCCause::to_string(gch->gc_cause()));
945 }
946 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
947 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
948 !gch->incremental_collection_failed(),
949 "Twice in a row");
950 seen_incremental_collection_failed = false;
951 }
952 #endif // ASSERT
953 }
954
955 if (ZapUnusedHeapArea) {
956 eden()->check_mangled_unused_area_complete();
957 from()->check_mangled_unused_area_complete();
958 to()->check_mangled_unused_area_complete();
959 }
960
961 if (!CleanChunkPoolAsync) {
962 Chunk::clean_chunk_pool();
963 }
964
965 // update the generation and space performance counters
966 update_counters();
967 gch->collector_policy()->counters()->update_counters();
968 }
969
970 void DefNewGeneration::record_spaces_top() {
971 assert(ZapUnusedHeapArea, "Not mangling unused space");
972 eden()->set_top_for_allocations();
973 to()->set_top_for_allocations();
974 from()->set_top_for_allocations();
975 }
976
977 void DefNewGeneration::ref_processor_init() {
978 Generation::ref_processor_init();
979 }
980
981
982 void DefNewGeneration::update_counters() {
983 if (UsePerfData) {
984 _eden_counters->update_all();
985 _from_counters->update_all();
986 _to_counters->update_all();
987 _gen_counters->update_all();
988 }
989 }
990
991 void DefNewGeneration::verify() {
992 eden()->verify();
993 from()->verify();
994 to()->verify();
995 }
996
997 void DefNewGeneration::print_on(outputStream* st) const {
998 Generation::print_on(st);
999 st->print(" eden");
1000 eden()->print_on(st);
1001 st->print(" from");
1002 from()->print_on(st);
1003 st->print(" to ");
1004 to()->print_on(st);
1005 }
1006
1007
1008 const char* DefNewGeneration::name() const {
1009 return "def new generation";
1010 }
1011
1012 // Moved from inline file as they are not called inline
1013 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1014 return eden();
1015 }
1016
1017 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1018 // This is the slow-path allocation for the DefNewGeneration.
1019 // Most allocations are fast-path in compiled code.
1020 // We try to allocate from the eden. If that works, we are happy.
1021 // Note that since DefNewGeneration supports lock-free allocation, we
1022 // have to use it here, as well.
1023 HeapWord* result = eden()->par_allocate(word_size);
1024 if (result != NULL) {
1025 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1026 _old_gen->sample_eden_chunk();
1027 }
1028 return result;
1029 }
1030 do {
1031 HeapWord* old_limit = eden()->soft_end();
1032 if (old_limit < eden()->end()) {
1033 // Tell the old generation we reached a limit.
1034 HeapWord* new_limit =
1035 _old_gen->allocation_limit_reached(eden(), eden()->top(), word_size);
1036 if (new_limit != NULL) {
1037 Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit);
1038 } else {
1039 assert(eden()->soft_end() == eden()->end(),
1040 "invalid state after allocation_limit_reached returned null");
1041 }
1042 } else {
1043 // The allocation failed and the soft limit is equal to the hard limit,
1044 // there are no reasons to do an attempt to allocate
1045 assert(old_limit == eden()->end(), "sanity check");
1046 break;
1047 }
1048 // Try to allocate until succeeded or the soft limit can't be adjusted
1049 result = eden()->par_allocate(word_size);
1050 } while (result == NULL);
1051
1052 // If the eden is full and the last collection bailed out, we are running
1053 // out of heap space, and we try to allocate the from-space, too.
1054 // allocate_from_space can't be inlined because that would introduce a
1055 // circular dependency at compile time.
1056 if (result == NULL) {
1057 result = allocate_from_space(word_size);
1058 } else if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1059 _old_gen->sample_eden_chunk();
1060 }
1061 return result;
1062 }
1063
1064 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1065 bool is_tlab) {
1066 HeapWord* res = eden()->par_allocate(word_size);
1067 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1068 _old_gen->sample_eden_chunk();
1069 }
1070 return res;
1071 }
1072
1073 void DefNewGeneration::gc_prologue(bool full) {
1074 // Ensure that _end and _soft_end are the same in eden space.
1075 eden()->set_soft_end(eden()->end());
1076 }
1077
1078 size_t DefNewGeneration::tlab_capacity() const {
1079 return eden()->capacity();
1080 }
1081
1082 size_t DefNewGeneration::tlab_used() const {
1083 return eden()->used();
1084 }
1085
1086 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1087 return unsafe_max_alloc_nogc();
1088 }