1 /*
2 * Copyright (c) 2001, 2012, 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/spaceDecorator.hpp"
29 #include "memory/defNewGeneration.inline.hpp"
30 #include "memory/gcLocker.inline.hpp"
31 #include "memory/genCollectedHeap.hpp"
32 #include "memory/genOopClosures.inline.hpp"
33 #include "memory/genRemSet.hpp"
34 #include "memory/generationSpec.hpp"
35 #include "memory/iterator.hpp"
36 #include "memory/referencePolicy.hpp"
37 #include "memory/space.inline.hpp"
38 #include "oops/instanceRefKlass.hpp"
39 #include "oops/oop.inline.hpp"
40 #include "runtime/java.hpp"
41 #include "runtime/thread.inline.hpp"
42 #include "utilities/copy.hpp"
43 #include "utilities/stack.inline.hpp"
44
45 //
46 // DefNewGeneration functions.
47
48 // Methods of protected closure types.
49
50 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
51 assert(g->level() == 0, "Optimized for youngest gen.");
52 }
53 void DefNewGeneration::IsAliveClosure::do_object(oop p) {
54 assert(false, "Do not call.");
55 }
56 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
57 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
58 }
59
60 DefNewGeneration::KeepAliveClosure::
61 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
62 GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
63 assert(rs->rs_kind() == GenRemSet::CardTable, "Wrong rem set kind.");
64 _rs = (CardTableRS*)rs;
65 }
66
67 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
68 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
69
70
71 DefNewGeneration::FastKeepAliveClosure::
72 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
73 DefNewGeneration::KeepAliveClosure(cl) {
74 _boundary = g->reserved().end();
75 }
76
77 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
78 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
79
80 DefNewGeneration::EvacuateFollowersClosure::
81 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
82 ScanClosure* cur, ScanClosure* older) :
83 _gch(gch), _level(level),
84 _scan_cur_or_nonheap(cur), _scan_older(older)
85 {}
86
87 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
88 do {
89 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
90 _scan_older);
91 } while (!_gch->no_allocs_since_save_marks(_level));
92 }
93
94 DefNewGeneration::FastEvacuateFollowersClosure::
95 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
96 DefNewGeneration* gen,
97 FastScanClosure* cur, FastScanClosure* older) :
98 _gch(gch), _level(level), _gen(gen),
99 _scan_cur_or_nonheap(cur), _scan_older(older)
100 {}
101
102 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
103 do {
104 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
105 _scan_older);
106 } while (!_gch->no_allocs_since_save_marks(_level));
107 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
108 }
109
110 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
111 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
112 {
113 assert(_g->level() == 0, "Optimized for youngest generation");
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 assert(_g->level() == 0, "Optimized for youngest generation");
124 _boundary = _g->reserved().end();
125 }
126
127 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
128 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
129
130 void KlassScanClosure::do_klass(Klass* klass) {
131 #ifndef PRODUCT
132 if (TraceScavenge) {
133 ResourceMark rm;
134 gclog_or_tty->print_cr("KlassScanClosure::do_klass %p, %s, dirty: %s",
135 klass,
136 klass->external_name(),
137 klass->has_modified_oops() ? "true" : "false");
138 }
139 #endif
140
141 // If the klass has not been dirtied we know that there's
142 // no references into the young gen and we can skip it.
143 if (klass->has_modified_oops()) {
144 if (_accumulate_modified_oops) {
145 klass->accumulate_modified_oops();
146 }
147
148 // Clear this state since we're going to scavenge all the metadata.
149 klass->clear_modified_oops();
150
151 // Tell the closure which Klass is being scanned so that it can be dirtied
152 // if oops are left pointing into the young gen.
153 _scavenge_closure->set_scanned_klass(klass);
154
155 klass->oops_do(_scavenge_closure);
156
157 _scavenge_closure->set_scanned_klass(NULL);
158 }
159 }
160
161 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
162 _g(g)
163 {
164 assert(_g->level() == 0, "Optimized for youngest generation");
165 _boundary = _g->reserved().end();
166 }
167
168 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
169 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
170
171 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
172 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
173
174 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
175 KlassRemSet* klass_rem_set)
176 : _scavenge_closure(scavenge_closure),
177 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
178
179
180 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
181 size_t initial_size,
182 int level,
183 const char* policy)
184 : Generation(rs, initial_size, level),
185 _promo_failure_drain_in_progress(false),
186 _should_allocate_from_space(false)
187 {
188 MemRegion cmr((HeapWord*)_virtual_space.low(),
189 (HeapWord*)_virtual_space.high());
190 Universe::heap()->barrier_set()->resize_covered_region(cmr);
191
192 if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) {
193 _eden_space = new ConcEdenSpace(this);
194 } else {
195 _eden_space = new EdenSpace(this);
196 }
197 _from_space = new ContiguousSpace();
198 _to_space = new ContiguousSpace();
199
200 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
201 vm_exit_during_initialization("Could not allocate a new gen space");
202
203 // Compute the maximum eden and survivor space sizes. These sizes
204 // are computed assuming the entire reserved space is committed.
205 // These values are exported as performance counters.
206 uintx alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();
207 uintx size = _virtual_space.reserved_size();
208 _max_survivor_size = compute_survivor_size(size, alignment);
209 _max_eden_size = size - (2*_max_survivor_size);
210
211 // allocate the performance counters
212
213 // Generation counters -- generation 0, 3 subspaces
214 _gen_counters = new GenerationCounters("new", 0, 3, &_virtual_space);
215 _gc_counters = new CollectorCounters(policy, 0);
216
217 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
218 _gen_counters);
219 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
220 _gen_counters);
221 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
222 _gen_counters);
223
224 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
225 update_counters();
226 _next_gen = NULL;
227 _tenuring_threshold = MaxTenuringThreshold;
228 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
229 }
230
231 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
232 bool clear_space,
233 bool mangle_space) {
234 uintx alignment =
235 GenCollectedHeap::heap()->collector_policy()->min_alignment();
236
237 // If the spaces are being cleared (only done at heap initialization
238 // currently), the survivor spaces need not be empty.
239 // Otherwise, no care is taken for used areas in the survivor spaces
240 // so check.
241 assert(clear_space || (to()->is_empty() && from()->is_empty()),
242 "Initialization of the survivor spaces assumes these are empty");
243
244 // Compute sizes
245 uintx size = _virtual_space.committed_size();
246 uintx survivor_size = compute_survivor_size(size, alignment);
247 uintx eden_size = size - (2*survivor_size);
248 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
249
250 if (eden_size < minimum_eden_size) {
251 // May happen due to 64Kb rounding, if so adjust eden size back up
252 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
253 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
254 uintx unaligned_survivor_size =
255 align_size_down(maximum_survivor_size, alignment);
256 survivor_size = MAX2(unaligned_survivor_size, alignment);
257 eden_size = size - (2*survivor_size);
258 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
259 assert(eden_size >= minimum_eden_size, "just checking");
260 }
261
262 char *eden_start = _virtual_space.low();
263 char *from_start = eden_start + eden_size;
264 char *to_start = from_start + survivor_size;
265 char *to_end = to_start + survivor_size;
266
267 assert(to_end == _virtual_space.high(), "just checking");
268 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
269 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
270 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
271
272 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
273 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
274 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
275
276 // A minimum eden size implies that there is a part of eden that
277 // is being used and that affects the initialization of any
278 // newly formed eden.
279 bool live_in_eden = minimum_eden_size > 0;
280
281 // If not clearing the spaces, do some checking to verify that
282 // the space are already mangled.
283 if (!clear_space) {
284 // Must check mangling before the spaces are reshaped. Otherwise,
285 // the bottom or end of one space may have moved into another
286 // a failure of the check may not correctly indicate which space
287 // is not properly mangled.
288 if (ZapUnusedHeapArea) {
289 HeapWord* limit = (HeapWord*) _virtual_space.high();
290 eden()->check_mangled_unused_area(limit);
291 from()->check_mangled_unused_area(limit);
292 to()->check_mangled_unused_area(limit);
293 }
294 }
295
296 // Reset the spaces for their new regions.
297 eden()->initialize(edenMR,
298 clear_space && !live_in_eden,
299 SpaceDecorator::Mangle);
300 // If clear_space and live_in_eden, we will not have cleared any
301 // portion of eden above its top. This can cause newly
302 // expanded space not to be mangled if using ZapUnusedHeapArea.
303 // We explicitly do such mangling here.
304 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
305 eden()->mangle_unused_area();
306 }
307 from()->initialize(fromMR, clear_space, mangle_space);
308 to()->initialize(toMR, clear_space, mangle_space);
309
310 // Set next compaction spaces.
311 eden()->set_next_compaction_space(from());
312 // The to-space is normally empty before a compaction so need
313 // not be considered. The exception is during promotion
314 // failure handling when to-space can contain live objects.
315 from()->set_next_compaction_space(NULL);
316 }
317
318 void DefNewGeneration::swap_spaces() {
319 ContiguousSpace* s = from();
320 _from_space = to();
321 _to_space = s;
322 eden()->set_next_compaction_space(from());
323 // The to-space is normally empty before a compaction so need
324 // not be considered. The exception is during promotion
325 // failure handling when to-space can contain live objects.
326 from()->set_next_compaction_space(NULL);
327
328 if (UsePerfData) {
329 CSpaceCounters* c = _from_counters;
330 _from_counters = _to_counters;
331 _to_counters = c;
332 }
333 }
334
335 bool DefNewGeneration::expand(size_t bytes) {
336 MutexLocker x(ExpandHeap_lock);
337 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
338 bool success = _virtual_space.expand_by(bytes);
339 if (success && ZapUnusedHeapArea) {
340 // Mangle newly committed space immediately because it
341 // can be done here more simply that after the new
342 // spaces have been computed.
343 HeapWord* new_high = (HeapWord*) _virtual_space.high();
344 MemRegion mangle_region(prev_high, new_high);
345 SpaceMangler::mangle_region(mangle_region);
346 }
347
348 // Do not attempt an expand-to-the reserve size. The
349 // request should properly observe the maximum size of
350 // the generation so an expand-to-reserve should be
351 // unnecessary. Also a second call to expand-to-reserve
352 // value potentially can cause an undue expansion.
353 // For example if the first expand fail for unknown reasons,
354 // but the second succeeds and expands the heap to its maximum
355 // value.
356 if (GC_locker::is_active()) {
357 if (PrintGC && Verbose) {
358 gclog_or_tty->print_cr("Garbage collection disabled, "
359 "expanded heap instead");
360 }
361 }
362
363 return success;
364 }
365
366
367 void DefNewGeneration::compute_new_size() {
368 // This is called after a gc that includes the following generation
369 // (which is required to exist.) So from-space will normally be empty.
370 // Note that we check both spaces, since if scavenge failed they revert roles.
371 // If not we bail out (otherwise we would have to relocate the objects)
372 if (!from()->is_empty() || !to()->is_empty()) {
373 return;
374 }
375
376 int next_level = level() + 1;
377 GenCollectedHeap* gch = GenCollectedHeap::heap();
378 assert(next_level < gch->_n_gens,
379 "DefNewGeneration cannot be an oldest gen");
380
381 Generation* next_gen = gch->_gens[next_level];
382 size_t old_size = next_gen->capacity();
383 size_t new_size_before = _virtual_space.committed_size();
384 size_t min_new_size = spec()->init_size();
385 size_t max_new_size = reserved().byte_size();
386 assert(min_new_size <= new_size_before &&
387 new_size_before <= max_new_size,
388 "just checking");
389 // All space sizes must be multiples of Generation::GenGrain.
390 size_t alignment = Generation::GenGrain;
391
392 // Compute desired new generation size based on NewRatio and
393 // NewSizeThreadIncrease
394 size_t desired_new_size = old_size/NewRatio;
395 int threads_count = Threads::number_of_non_daemon_threads();
396 size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
397 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
398
399 // Adjust new generation size
400 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
401 assert(desired_new_size <= max_new_size, "just checking");
402
403 bool changed = false;
404 if (desired_new_size > new_size_before) {
405 size_t change = desired_new_size - new_size_before;
406 assert(change % alignment == 0, "just checking");
407 if (expand(change)) {
408 changed = true;
409 }
410 // If the heap failed to expand to the desired size,
411 // "changed" will be false. If the expansion failed
412 // (and at this point it was expected to succeed),
413 // ignore the failure (leaving "changed" as false).
414 }
415 if (desired_new_size < new_size_before && eden()->is_empty()) {
416 // bail out of shrinking if objects in eden
417 size_t change = new_size_before - desired_new_size;
418 assert(change % alignment == 0, "just checking");
419 _virtual_space.shrink_by(change);
420 changed = true;
421 }
422 if (changed) {
423 // The spaces have already been mangled at this point but
424 // may not have been cleared (set top = bottom) and should be.
425 // Mangling was done when the heap was being expanded.
426 compute_space_boundaries(eden()->used(),
427 SpaceDecorator::Clear,
428 SpaceDecorator::DontMangle);
429 MemRegion cmr((HeapWord*)_virtual_space.low(),
430 (HeapWord*)_virtual_space.high());
431 Universe::heap()->barrier_set()->resize_covered_region(cmr);
432 if (Verbose && PrintGC) {
433 size_t new_size_after = _virtual_space.committed_size();
434 size_t eden_size_after = eden()->capacity();
435 size_t survivor_size_after = from()->capacity();
436 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
437 SIZE_FORMAT "K [eden="
438 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
439 new_size_before/K, new_size_after/K,
440 eden_size_after/K, survivor_size_after/K);
441 if (WizardMode) {
442 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
443 thread_increase_size/K, threads_count);
444 }
445 gclog_or_tty->cr();
446 }
447 }
448 }
449
450 void DefNewGeneration::object_iterate_since_last_GC(ObjectClosure* cl) {
451 // $$$ This may be wrong in case of "scavenge failure"?
452 eden()->object_iterate(cl);
453 }
454
455 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
456 assert(false, "NYI -- are you sure you want to call this?");
457 }
458
459
460 size_t DefNewGeneration::capacity() const {
461 return eden()->capacity()
462 + from()->capacity(); // to() is only used during scavenge
463 }
464
465
466 size_t DefNewGeneration::used() const {
467 return eden()->used()
468 + from()->used(); // to() is only used during scavenge
469 }
470
471
472 size_t DefNewGeneration::free() const {
473 return eden()->free()
474 + from()->free(); // to() is only used during scavenge
475 }
476
477 size_t DefNewGeneration::max_capacity() const {
478 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();
479 const size_t reserved_bytes = reserved().byte_size();
480 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
481 }
482
483 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
484 return eden()->free();
485 }
486
487 size_t DefNewGeneration::capacity_before_gc() const {
488 return eden()->capacity();
489 }
490
491 size_t DefNewGeneration::contiguous_available() const {
492 return eden()->free();
493 }
494
495
496 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
497 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
498
499 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
500 eden()->object_iterate(blk);
501 from()->object_iterate(blk);
502 }
503
504
505 void DefNewGeneration::space_iterate(SpaceClosure* blk,
506 bool usedOnly) {
507 blk->do_space(eden());
508 blk->do_space(from());
509 blk->do_space(to());
510 }
511
512 // The last collection bailed out, we are running out of heap space,
513 // so we try to allocate the from-space, too.
514 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
515 HeapWord* result = NULL;
516 if (Verbose && PrintGCDetails) {
517 gclog_or_tty->print("DefNewGeneration::allocate_from_space(%u):"
518 " will_fail: %s"
519 " heap_lock: %s"
520 " free: " SIZE_FORMAT,
521 size,
522 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
523 "true" : "false",
524 Heap_lock->is_locked() ? "locked" : "unlocked",
525 from()->free());
526 }
527 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
528 if (Heap_lock->owned_by_self() ||
529 (SafepointSynchronize::is_at_safepoint() &&
530 Thread::current()->is_VM_thread())) {
531 // If the Heap_lock is not locked by this thread, this will be called
532 // again later with the Heap_lock held.
533 result = from()->allocate(size);
534 } else if (PrintGC && Verbose) {
535 gclog_or_tty->print_cr(" Heap_lock is not owned by self");
536 }
537 } else if (PrintGC && Verbose) {
538 gclog_or_tty->print_cr(" should_allocate_from_space: NOT");
539 }
540 if (PrintGC && Verbose) {
541 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object");
542 }
543 return result;
544 }
545
546 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
547 bool is_tlab,
548 bool parallel) {
549 // We don't attempt to expand the young generation (but perhaps we should.)
550 return allocate(size, is_tlab);
551 }
552
553 void DefNewGeneration::adjust_desired_tenuring_threshold() {
554 // Set the desired survivor size to half the real survivor space
555 _tenuring_threshold =
556 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
557 }
558
559 void DefNewGeneration::collect(bool full,
560 bool clear_all_soft_refs,
561 size_t size,
562 bool is_tlab) {
563 assert(full || size > 0, "otherwise we don't want to collect");
564 GenCollectedHeap* gch = GenCollectedHeap::heap();
565 _next_gen = gch->next_gen(this);
566 assert(_next_gen != NULL,
567 "This must be the youngest gen, and not the only gen");
568
569 // If the next generation is too full to accomodate promotion
570 // from this generation, pass on collection; let the next generation
571 // do it.
572 if (!collection_attempt_is_safe()) {
573 if (Verbose && PrintGCDetails) {
574 gclog_or_tty->print(" :: Collection attempt not safe :: ");
575 }
576 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
577 return;
578 }
579 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
580
581 init_assuming_no_promotion_failure();
582
583 TraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, gclog_or_tty);
584 // Capture heap used before collection (for printing).
585 size_t gch_prev_used = gch->used();
586
587 SpecializationStats::clear();
588
589 // These can be shared for all code paths
590 IsAliveClosure is_alive(this);
591 ScanWeakRefClosure scan_weak_ref(this);
592
593 age_table()->clear();
594 to()->clear(SpaceDecorator::Mangle);
595
596 gch->rem_set()->prepare_for_younger_refs_iterate(false);
597
598 assert(gch->no_allocs_since_save_marks(0),
599 "save marks have not been newly set.");
600
601 // Not very pretty.
602 CollectorPolicy* cp = gch->collector_policy();
603
604 FastScanClosure fsc_with_no_gc_barrier(this, false);
605 FastScanClosure fsc_with_gc_barrier(this, true);
606
607 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
608 gch->rem_set()->klass_rem_set());
609
610 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
611 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
612 &fsc_with_no_gc_barrier,
613 &fsc_with_gc_barrier);
614
615 assert(gch->no_allocs_since_save_marks(0),
616 "save marks have not been newly set.");
617
618 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
619
620 gch->gen_process_strong_roots(_level,
621 true, // Process younger gens, if any,
622 // as strong roots.
623 true, // activate StrongRootsScope
624 true, // is scavenging
625 SharedHeap::ScanningOption(so),
626 &fsc_with_no_gc_barrier,
627 true, // walk *all* scavengable nmethods
628 &fsc_with_gc_barrier,
629 &klass_scan_closure);
630
631 // "evacuate followers".
632 evacuate_followers.do_void();
633
634 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
635 ReferenceProcessor* rp = ref_processor();
636 rp->setup_policy(clear_all_soft_refs);
637 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
638 NULL);
639 if (!promotion_failed()) {
640 // Swap the survivor spaces.
641 eden()->clear(SpaceDecorator::Mangle);
642 from()->clear(SpaceDecorator::Mangle);
643 if (ZapUnusedHeapArea) {
644 // This is now done here because of the piece-meal mangling which
645 // can check for valid mangling at intermediate points in the
646 // collection(s). When a minor collection fails to collect
647 // sufficient space resizing of the young generation can occur
648 // an redistribute the spaces in the young generation. Mangle
649 // here so that unzapped regions don't get distributed to
650 // other spaces.
651 to()->mangle_unused_area();
652 }
653 swap_spaces();
654
655 assert(to()->is_empty(), "to space should be empty now");
656
657 adjust_desired_tenuring_threshold();
658
659 // A successful scavenge should restart the GC time limit count which is
660 // for full GC's.
661 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
662 size_policy->reset_gc_overhead_limit_count();
663 if (PrintGC && !PrintGCDetails) {
664 gch->print_heap_change(gch_prev_used);
665 }
666 assert(!gch->incremental_collection_failed(), "Should be clear");
667 } else {
668 assert(_promo_failure_scan_stack.is_empty(), "post condition");
669 _promo_failure_scan_stack.clear(true); // Clear cached segments.
670
671 remove_forwarding_pointers();
672 if (PrintGCDetails) {
673 gclog_or_tty->print(" (promotion failed) ");
674 }
675 // Add to-space to the list of space to compact
676 // when a promotion failure has occurred. In that
677 // case there can be live objects in to-space
678 // as a result of a partial evacuation of eden
679 // and from-space.
680 swap_spaces(); // For uniformity wrt ParNewGeneration.
681 from()->set_next_compaction_space(to());
682 gch->set_incremental_collection_failed();
683
684 // Inform the next generation that a promotion failure occurred.
685 _next_gen->promotion_failure_occurred();
686
687 // Reset the PromotionFailureALot counters.
688 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
689 }
690 // set new iteration safe limit for the survivor spaces
691 from()->set_concurrent_iteration_safe_limit(from()->top());
692 to()->set_concurrent_iteration_safe_limit(to()->top());
693 SpecializationStats::print();
694
695 // We need to use a monotonically non-deccreasing time in ms
696 // or we will see time-warp warnings and os::javaTimeMillis()
697 // does not guarantee monotonicity.
698 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
699 update_time_of_last_gc(now);
700 }
701
702 class RemoveForwardPointerClosure: public ObjectClosure {
703 public:
704 void do_object(oop obj) {
705 obj->init_mark();
706 }
707 };
708
709 void DefNewGeneration::init_assuming_no_promotion_failure() {
710 _promotion_failed = false;
711 from()->set_next_compaction_space(NULL);
712 }
713
714 void DefNewGeneration::remove_forwarding_pointers() {
715 RemoveForwardPointerClosure rspc;
716 eden()->object_iterate(&rspc);
717 from()->object_iterate(&rspc);
718
719 // Now restore saved marks, if any.
720 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
721 "should be the same");
722 while (!_objs_with_preserved_marks.is_empty()) {
723 oop obj = _objs_with_preserved_marks.pop();
724 markOop m = _preserved_marks_of_objs.pop();
725 obj->set_mark(m);
726 }
727 _objs_with_preserved_marks.clear(true);
728 _preserved_marks_of_objs.clear(true);
729 }
730
731 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
732 assert(promotion_failed() && m->must_be_preserved_for_promotion_failure(obj),
733 "Oversaving!");
734 _objs_with_preserved_marks.push(obj);
735 _preserved_marks_of_objs.push(m);
736 }
737
738 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
739 if (m->must_be_preserved_for_promotion_failure(obj)) {
740 preserve_mark(obj, m);
741 }
742 }
743
744 void DefNewGeneration::handle_promotion_failure(oop old) {
745 if (PrintPromotionFailure && !_promotion_failed) {
746 gclog_or_tty->print(" (promotion failure size = " SIZE_FORMAT ") ",
747 old->size());
748 }
749 _promotion_failed = true;
750 preserve_mark_if_necessary(old, old->mark());
751 // forward to self
752 old->forward_to(old);
753
754 _promo_failure_scan_stack.push(old);
755
756 if (!_promo_failure_drain_in_progress) {
757 // prevent recursion in copy_to_survivor_space()
758 _promo_failure_drain_in_progress = true;
759 drain_promo_failure_scan_stack();
760 _promo_failure_drain_in_progress = false;
761 }
762 }
763
764 oop DefNewGeneration::copy_to_survivor_space(oop old) {
765 assert(is_in_reserved(old) && !old->is_forwarded(),
766 "shouldn't be scavenging this oop");
767 size_t s = old->size();
768 oop obj = NULL;
769
770 // Try allocating obj in to-space (unless too old)
771 if (old->age() < tenuring_threshold()) {
772 obj = (oop) to()->allocate(s);
773 }
774
775 // Otherwise try allocating obj tenured
776 if (obj == NULL) {
777 obj = _next_gen->promote(old, s);
778 if (obj == NULL) {
779 handle_promotion_failure(old);
780 return old;
781 }
782 } else {
783 // Prefetch beyond obj
784 const intx interval = PrefetchCopyIntervalInBytes;
785 Prefetch::write(obj, interval);
786
787 // Copy obj
788 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
789
790 // Increment age if obj still in new generation
791 obj->incr_age();
792 age_table()->add(obj, s);
793 }
794
795 // Done, insert forward pointer to obj in this header
796 old->forward_to(obj);
797
798 return obj;
799 }
800
801 void DefNewGeneration::drain_promo_failure_scan_stack() {
802 while (!_promo_failure_scan_stack.is_empty()) {
803 oop obj = _promo_failure_scan_stack.pop();
804 obj->oop_iterate(_promo_failure_scan_stack_closure);
805 }
806 }
807
808 void DefNewGeneration::save_marks() {
809 eden()->set_saved_mark();
810 to()->set_saved_mark();
811 from()->set_saved_mark();
812 }
813
814
815 void DefNewGeneration::reset_saved_marks() {
816 eden()->reset_saved_mark();
817 to()->reset_saved_mark();
818 from()->reset_saved_mark();
819 }
820
821
822 bool DefNewGeneration::no_allocs_since_save_marks() {
823 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
824 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
825 return to()->saved_mark_at_top();
826 }
827
828 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
829 \
830 void DefNewGeneration:: \
831 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
832 cl->set_generation(this); \
833 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
834 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
835 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
836 cl->reset_generation(); \
837 save_marks(); \
838 }
839
840 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
841
842 #undef DefNew_SINCE_SAVE_MARKS_DEFN
843
844 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
845 size_t max_alloc_words) {
846 if (requestor == this || _promotion_failed) return;
847 assert(requestor->level() > level(), "DefNewGeneration must be youngest");
848
849 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
850 if (to_space->top() > to_space->bottom()) {
851 trace("to_space not empty when contribute_scratch called");
852 }
853 */
854
855 ContiguousSpace* to_space = to();
856 assert(to_space->end() >= to_space->top(), "pointers out of order");
857 size_t free_words = pointer_delta(to_space->end(), to_space->top());
858 if (free_words >= MinFreeScratchWords) {
859 ScratchBlock* sb = (ScratchBlock*)to_space->top();
860 sb->num_words = free_words;
861 sb->next = list;
862 list = sb;
863 }
864 }
865
866 void DefNewGeneration::reset_scratch() {
867 // If contributing scratch in to_space, mangle all of
868 // to_space if ZapUnusedHeapArea. This is needed because
869 // top is not maintained while using to-space as scratch.
870 if (ZapUnusedHeapArea) {
871 to()->mangle_unused_area_complete();
872 }
873 }
874
875 bool DefNewGeneration::collection_attempt_is_safe() {
876 if (!to()->is_empty()) {
877 if (Verbose && PrintGCDetails) {
878 gclog_or_tty->print(" :: to is not empty :: ");
879 }
880 return false;
881 }
882 if (_next_gen == NULL) {
883 GenCollectedHeap* gch = GenCollectedHeap::heap();
884 _next_gen = gch->next_gen(this);
885 assert(_next_gen != NULL,
886 "This must be the youngest gen, and not the only gen");
887 }
888 return _next_gen->promotion_attempt_is_safe(used());
889 }
890
891 void DefNewGeneration::gc_epilogue(bool full) {
892 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
893
894 assert(!GC_locker::is_active(), "We should not be executing here");
895 // Check if the heap is approaching full after a collection has
896 // been done. Generally the young generation is empty at
897 // a minimum at the end of a collection. If it is not, then
898 // the heap is approaching full.
899 GenCollectedHeap* gch = GenCollectedHeap::heap();
900 if (full) {
901 DEBUG_ONLY(seen_incremental_collection_failed = false;)
902 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
903 if (Verbose && PrintGCDetails) {
904 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
905 GCCause::to_string(gch->gc_cause()));
906 }
907 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
908 set_should_allocate_from_space(); // we seem to be running out of space
909 } else {
910 if (Verbose && PrintGCDetails) {
911 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
912 GCCause::to_string(gch->gc_cause()));
913 }
914 gch->clear_incremental_collection_failed(); // We just did a full collection
915 clear_should_allocate_from_space(); // if set
916 }
917 } else {
918 #ifdef ASSERT
919 // It is possible that incremental_collection_failed() == true
920 // here, because an attempted scavenge did not succeed. The policy
921 // is normally expected to cause a full collection which should
922 // clear that condition, so we should not be here twice in a row
923 // with incremental_collection_failed() == true without having done
924 // a full collection in between.
925 if (!seen_incremental_collection_failed &&
926 gch->incremental_collection_failed()) {
927 if (Verbose && PrintGCDetails) {
928 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
929 GCCause::to_string(gch->gc_cause()));
930 }
931 seen_incremental_collection_failed = true;
932 } else if (seen_incremental_collection_failed) {
933 if (Verbose && PrintGCDetails) {
934 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
935 GCCause::to_string(gch->gc_cause()));
936 }
937 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
938 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
939 !gch->incremental_collection_failed(),
940 "Twice in a row");
941 seen_incremental_collection_failed = false;
942 }
943 #endif // ASSERT
944 }
945
946 if (ZapUnusedHeapArea) {
947 eden()->check_mangled_unused_area_complete();
948 from()->check_mangled_unused_area_complete();
949 to()->check_mangled_unused_area_complete();
950 }
951
952 if (!CleanChunkPoolAsync) {
953 Chunk::clean_chunk_pool();
954 }
955
956 // update the generation and space performance counters
957 update_counters();
958 gch->collector_policy()->counters()->update_counters();
959 }
960
961 void DefNewGeneration::record_spaces_top() {
962 assert(ZapUnusedHeapArea, "Not mangling unused space");
963 eden()->set_top_for_allocations();
964 to()->set_top_for_allocations();
965 from()->set_top_for_allocations();
966 }
967
968
969 void DefNewGeneration::update_counters() {
970 if (UsePerfData) {
971 _eden_counters->update_all();
972 _from_counters->update_all();
973 _to_counters->update_all();
974 _gen_counters->update_all();
975 }
976 }
977
978 void DefNewGeneration::verify() {
979 eden()->verify();
980 from()->verify();
981 to()->verify();
982 }
983
984 void DefNewGeneration::print_on(outputStream* st) const {
985 Generation::print_on(st);
986 st->print(" eden");
987 eden()->print_on(st);
988 st->print(" from");
989 from()->print_on(st);
990 st->print(" to ");
991 to()->print_on(st);
992 }
993
994
995 const char* DefNewGeneration::name() const {
996 return "def new generation";
997 }
998
999 // Moved from inline file as they are not called inline
1000 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1001 return eden();
1002 }
1003
1004 HeapWord* DefNewGeneration::allocate(size_t word_size,
1005 bool is_tlab) {
1006 // This is the slow-path allocation for the DefNewGeneration.
1007 // Most allocations are fast-path in compiled code.
1008 // We try to allocate from the eden. If that works, we are happy.
1009 // Note that since DefNewGeneration supports lock-free allocation, we
1010 // have to use it here, as well.
1011 HeapWord* result = eden()->par_allocate(word_size);
1012 if (result != NULL) {
1013 if (CMSEdenChunksRecordAlways && _next_gen) {
1014 _next_gen->sample_eden_chunk();
1015 }
1016 return result;
1017 }
1018 do {
1019 HeapWord* old_limit = eden()->soft_end();
1020 if (old_limit < eden()->end()) {
1021 // Tell the next generation we reached a limit.
1022 HeapWord* new_limit =
1023 next_gen()->allocation_limit_reached(eden(), eden()->top(), word_size);
1024 if (new_limit != NULL) {
1025 Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit);
1026 } else {
1027 assert(eden()->soft_end() == eden()->end(),
1028 "invalid state after allocation_limit_reached returned null");
1029 }
1030 } else {
1031 // The allocation failed and the soft limit is equal to the hard limit,
1032 // there are no reasons to do an attempt to allocate
1033 assert(old_limit == eden()->end(), "sanity check");
1034 break;
1035 }
1036 // Try to allocate until succeeded or the soft limit can't be adjusted
1037 result = eden()->par_allocate(word_size);
1038 } while (result == NULL);
1039
1040 // If the eden is full and the last collection bailed out, we are running
1041 // out of heap space, and we try to allocate the from-space, too.
1042 // allocate_from_space can't be inlined because that would introduce a
1043 // circular dependency at compile time.
1044 if (result == NULL) {
1045 result = allocate_from_space(word_size);
1046 } else if (CMSEdenChunksRecordAlways && _next_gen) {
1047 _next_gen->sample_eden_chunk();
1048 }
1049 return result;
1050 }
1051
1052 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1053 bool is_tlab) {
1054 HeapWord* res = eden()->par_allocate(word_size);
1055 if (CMSEdenChunksRecordAlways && _next_gen) {
1056 _next_gen->sample_eden_chunk();
1057 }
1058 return res;
1059 }
1060
1061 void DefNewGeneration::gc_prologue(bool full) {
1062 // Ensure that _end and _soft_end are the same in eden space.
1063 eden()->set_soft_end(eden()->end());
1064 }
1065
1066 size_t DefNewGeneration::tlab_capacity() const {
1067 return eden()->capacity();
1068 }
1069
1070 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1071 return unsafe_max_alloc_nogc();
1072 }