1 /*
2 * Copyright (c) 2001, 2013, 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/java.hpp"
45 #include "runtime/thread.inline.hpp"
46 #include "utilities/copy.hpp"
47 #include "utilities/stack.inline.hpp"
48
49 //
50 // DefNewGeneration functions.
51
52 // Methods of protected closure types.
53
54 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
55 assert(g->level() == 0, "Optimized for youngest gen.");
56 }
57 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
58 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
59 }
60
61 DefNewGeneration::KeepAliveClosure::
62 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
63 GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
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()->space_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 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
231 }
232
233 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
234 bool clear_space,
235 bool mangle_space) {
236 uintx alignment =
237 GenCollectedHeap::heap()->collector_policy()->space_alignment();
238
239 // If the spaces are being cleared (only done at heap initialization
240 // currently), the survivor spaces need not be empty.
241 // Otherwise, no care is taken for used areas in the survivor spaces
242 // so check.
243 assert(clear_space || (to()->is_empty() && from()->is_empty()),
244 "Initialization of the survivor spaces assumes these are empty");
245
246 // Compute sizes
247 uintx size = _virtual_space.committed_size();
248 uintx survivor_size = compute_survivor_size(size, alignment);
249 uintx eden_size = size - (2*survivor_size);
250 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
251
252 if (eden_size < minimum_eden_size) {
253 // May happen due to 64Kb rounding, if so adjust eden size back up
254 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
255 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
256 uintx unaligned_survivor_size =
257 align_size_down(maximum_survivor_size, alignment);
258 survivor_size = MAX2(unaligned_survivor_size, alignment);
259 eden_size = size - (2*survivor_size);
260 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
261 assert(eden_size >= minimum_eden_size, "just checking");
262 }
263
264 char *eden_start = _virtual_space.low();
265 char *from_start = eden_start + eden_size;
266 char *to_start = from_start + survivor_size;
267 char *to_end = to_start + survivor_size;
268
269 assert(to_end == _virtual_space.high(), "just checking");
270 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
271 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
272 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
273
274 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
275 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
276 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
277
278 // A minimum eden size implies that there is a part of eden that
279 // is being used and that affects the initialization of any
280 // newly formed eden.
281 bool live_in_eden = minimum_eden_size > 0;
282
283 // If not clearing the spaces, do some checking to verify that
284 // the space are already mangled.
285 if (!clear_space) {
286 // Must check mangling before the spaces are reshaped. Otherwise,
287 // the bottom or end of one space may have moved into another
288 // a failure of the check may not correctly indicate which space
289 // is not properly mangled.
290 if (ZapUnusedHeapArea) {
291 HeapWord* limit = (HeapWord*) _virtual_space.high();
292 eden()->check_mangled_unused_area(limit);
293 from()->check_mangled_unused_area(limit);
294 to()->check_mangled_unused_area(limit);
295 }
296 }
297
298 // Reset the spaces for their new regions.
299 eden()->initialize(edenMR,
300 clear_space && !live_in_eden,
301 SpaceDecorator::Mangle);
302 // If clear_space and live_in_eden, we will not have cleared any
303 // portion of eden above its top. This can cause newly
304 // expanded space not to be mangled if using ZapUnusedHeapArea.
305 // We explicitly do such mangling here.
306 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
307 eden()->mangle_unused_area();
308 }
309 from()->initialize(fromMR, clear_space, mangle_space);
310 to()->initialize(toMR, clear_space, mangle_space);
311
312 // Set next compaction spaces.
313 eden()->set_next_compaction_space(from());
314 // The to-space is normally empty before a compaction so need
315 // not be considered. The exception is during promotion
316 // failure handling when to-space can contain live objects.
317 from()->set_next_compaction_space(NULL);
318 }
319
320 void DefNewGeneration::swap_spaces() {
321 ContiguousSpace* s = from();
322 _from_space = to();
323 _to_space = s;
324 eden()->set_next_compaction_space(from());
325 // The to-space is normally empty before a compaction so need
326 // not be considered. The exception is during promotion
327 // failure handling when to-space can contain live objects.
328 from()->set_next_compaction_space(NULL);
329
330 if (UsePerfData) {
331 CSpaceCounters* c = _from_counters;
332 _from_counters = _to_counters;
333 _to_counters = c;
334 }
335 }
336
337 bool DefNewGeneration::expand(size_t bytes) {
338 MutexLocker x(ExpandHeap_lock);
339 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
340 bool success = _virtual_space.expand_by(bytes);
341 if (success && ZapUnusedHeapArea) {
342 // Mangle newly committed space immediately because it
343 // can be done here more simply that after the new
344 // spaces have been computed.
345 HeapWord* new_high = (HeapWord*) _virtual_space.high();
346 MemRegion mangle_region(prev_high, new_high);
347 SpaceMangler::mangle_region(mangle_region);
348 }
349
350 // Do not attempt an expand-to-the reserve size. The
351 // request should properly observe the maximum size of
352 // the generation so an expand-to-reserve should be
353 // unnecessary. Also a second call to expand-to-reserve
354 // value potentially can cause an undue expansion.
355 // For example if the first expand fail for unknown reasons,
356 // but the second succeeds and expands the heap to its maximum
357 // value.
358 if (GC_locker::is_active()) {
359 if (PrintGC && Verbose) {
360 gclog_or_tty->print_cr("Garbage collection disabled, "
361 "expanded heap instead");
362 }
363 }
364
365 return success;
366 }
367
368
369 void DefNewGeneration::compute_new_size() {
370 // This is called after a gc that includes the following generation
371 // (which is required to exist.) So from-space will normally be empty.
372 // Note that we check both spaces, since if scavenge failed they revert roles.
373 // If not we bail out (otherwise we would have to relocate the objects)
374 if (!from()->is_empty() || !to()->is_empty()) {
375 return;
376 }
377
378 int next_level = level() + 1;
379 GenCollectedHeap* gch = GenCollectedHeap::heap();
380 assert(next_level < gch->_n_gens,
381 "DefNewGeneration cannot be an oldest gen");
382
383 Generation* next_gen = gch->_gens[next_level];
384 size_t old_size = next_gen->capacity();
385 size_t new_size_before = _virtual_space.committed_size();
386 size_t min_new_size = spec()->init_size();
387 size_t max_new_size = reserved().byte_size();
388 assert(min_new_size <= new_size_before &&
389 new_size_before <= max_new_size,
390 "just checking");
391 // All space sizes must be multiples of Generation::GenGrain.
392 size_t alignment = Generation::GenGrain;
393
394 // Compute desired new generation size based on NewRatio and
395 // NewSizeThreadIncrease
396 size_t desired_new_size = old_size/NewRatio;
397 int threads_count = Threads::number_of_non_daemon_threads();
398 size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
399 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
400
401 // Adjust new generation size
402 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
403 assert(desired_new_size <= max_new_size, "just checking");
404
405 bool changed = false;
406 if (desired_new_size > new_size_before) {
407 size_t change = desired_new_size - new_size_before;
408 assert(change % alignment == 0, "just checking");
409 if (expand(change)) {
410 changed = true;
411 }
412 // If the heap failed to expand to the desired size,
413 // "changed" will be false. If the expansion failed
414 // (and at this point it was expected to succeed),
415 // ignore the failure (leaving "changed" as false).
416 }
417 if (desired_new_size < new_size_before && eden()->is_empty()) {
418 // bail out of shrinking if objects in eden
419 size_t change = new_size_before - desired_new_size;
420 assert(change % alignment == 0, "just checking");
421 _virtual_space.shrink_by(change);
422 changed = true;
423 }
424 if (changed) {
425 // The spaces have already been mangled at this point but
426 // may not have been cleared (set top = bottom) and should be.
427 // Mangling was done when the heap was being expanded.
428 compute_space_boundaries(eden()->used(),
429 SpaceDecorator::Clear,
430 SpaceDecorator::DontMangle);
431 MemRegion cmr((HeapWord*)_virtual_space.low(),
432 (HeapWord*)_virtual_space.high());
433 Universe::heap()->barrier_set()->resize_covered_region(cmr);
434 if (Verbose && PrintGC) {
435 size_t new_size_after = _virtual_space.committed_size();
436 size_t eden_size_after = eden()->capacity();
437 size_t survivor_size_after = from()->capacity();
438 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
439 SIZE_FORMAT "K [eden="
440 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
441 new_size_before/K, new_size_after/K,
442 eden_size_after/K, survivor_size_after/K);
443 if (WizardMode) {
444 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
445 thread_increase_size/K, threads_count);
446 }
447 gclog_or_tty->cr();
448 }
449 }
450 }
451
452 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
453 assert(false, "NYI -- are you sure you want to call this?");
454 }
455
456
457 size_t DefNewGeneration::capacity() const {
458 return eden()->capacity()
459 + from()->capacity(); // to() is only used during scavenge
460 }
461
462
463 size_t DefNewGeneration::used() const {
464 return eden()->used()
465 + from()->used(); // to() is only used during scavenge
466 }
467
468
469 size_t DefNewGeneration::free() const {
470 return eden()->free()
471 + from()->free(); // to() is only used during scavenge
472 }
473
474 size_t DefNewGeneration::max_capacity() const {
475 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
476 const size_t reserved_bytes = reserved().byte_size();
477 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
478 }
479
480 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
481 return eden()->free();
482 }
483
484 size_t DefNewGeneration::capacity_before_gc() const {
485 return eden()->capacity();
486 }
487
488 size_t DefNewGeneration::contiguous_available() const {
489 return eden()->free();
490 }
491
492
493 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
494 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
495
496 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
497 eden()->object_iterate(blk);
498 from()->object_iterate(blk);
499 }
500
501
502 void DefNewGeneration::space_iterate(SpaceClosure* blk,
503 bool usedOnly) {
504 blk->do_space(eden());
505 blk->do_space(from());
506 blk->do_space(to());
507 }
508
509 // The last collection bailed out, we are running out of heap space,
510 // so we try to allocate the from-space, too.
511 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
512 HeapWord* result = NULL;
513 if (Verbose && PrintGCDetails) {
514 gclog_or_tty->print("DefNewGeneration::allocate_from_space(%u):"
515 " will_fail: %s"
516 " heap_lock: %s"
517 " free: " SIZE_FORMAT,
518 size,
519 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
520 "true" : "false",
521 Heap_lock->is_locked() ? "locked" : "unlocked",
522 from()->free());
523 }
524 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
525 if (Heap_lock->owned_by_self() ||
526 (SafepointSynchronize::is_at_safepoint() &&
527 Thread::current()->is_VM_thread())) {
528 // If the Heap_lock is not locked by this thread, this will be called
529 // again later with the Heap_lock held.
530 result = from()->allocate(size);
531 } else if (PrintGC && Verbose) {
532 gclog_or_tty->print_cr(" Heap_lock is not owned by self");
533 }
534 } else if (PrintGC && Verbose) {
535 gclog_or_tty->print_cr(" should_allocate_from_space: NOT");
536 }
537 if (PrintGC && Verbose) {
538 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object");
539 }
540 return result;
541 }
542
543 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
544 bool is_tlab,
545 bool parallel) {
546 // We don't attempt to expand the young generation (but perhaps we should.)
547 return allocate(size, is_tlab);
548 }
549
550 void DefNewGeneration::adjust_desired_tenuring_threshold() {
551 // Set the desired survivor size to half the real survivor space
552 _tenuring_threshold =
553 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
554 }
555
556 void DefNewGeneration::collect(bool full,
557 bool clear_all_soft_refs,
558 size_t size,
559 bool is_tlab) {
560 assert(full || size > 0, "otherwise we don't want to collect");
561
562 GenCollectedHeap* gch = GenCollectedHeap::heap();
563
564 _gc_timer->register_gc_start();
565 DefNewTracer gc_tracer;
566 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
567
568 _next_gen = gch->next_gen(this);
569
570 // If the next generation is too full to accommodate promotion
571 // from this generation, pass on collection; let the next generation
572 // do it.
573 if (!collection_attempt_is_safe()) {
574 if (Verbose && PrintGCDetails) {
575 gclog_or_tty->print(" :: Collection attempt not safe :: ");
576 }
577 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
578 return;
579 }
580 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
581
582 init_assuming_no_promotion_failure();
583
584 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL);
585 // Capture heap used before collection (for printing).
586 size_t gch_prev_used = gch->used();
587
588 gch->trace_heap_before_gc(&gc_tracer);
589
590 SpecializationStats::clear();
591
592 // These can be shared for all code paths
593 IsAliveClosure is_alive(this);
594 ScanWeakRefClosure scan_weak_ref(this);
595
596 age_table()->clear();
597 to()->clear(SpaceDecorator::Mangle);
598
599 gch->rem_set()->prepare_for_younger_refs_iterate(false);
600
601 assert(gch->no_allocs_since_save_marks(0),
602 "save marks have not been newly set.");
603
604 // Not very pretty.
605 CollectorPolicy* cp = gch->collector_policy();
606
607 FastScanClosure fsc_with_no_gc_barrier(this, false);
608 FastScanClosure fsc_with_gc_barrier(this, true);
609
610 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
611 gch->rem_set()->klass_rem_set());
612
613 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
614 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
615 &fsc_with_no_gc_barrier,
616 &fsc_with_gc_barrier);
617
618 assert(gch->no_allocs_since_save_marks(0),
619 "save marks have not been newly set.");
620
621 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_ScavengeCodeCache;
622
623 gch->gen_process_strong_roots(_level,
624 true, // Process younger gens, if any,
625 // as strong roots.
626 true, // activate StrongRootsScope
627 SharedHeap::ScanningOption(so),
628 &fsc_with_no_gc_barrier,
629 &fsc_with_gc_barrier,
630 &klass_scan_closure);
631
632 // "evacuate followers".
633 evacuate_followers.do_void();
634
635 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
636 ReferenceProcessor* rp = ref_processor();
637 rp->setup_policy(clear_all_soft_refs);
638 const ReferenceProcessorStats& stats =
639 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
640 NULL, _gc_timer);
641 gc_tracer.report_gc_reference_stats(stats);
642
643 if (!_promotion_failed) {
644 // Swap the survivor spaces.
645 eden()->clear(SpaceDecorator::Mangle);
646 from()->clear(SpaceDecorator::Mangle);
647 if (ZapUnusedHeapArea) {
648 // This is now done here because of the piece-meal mangling which
649 // can check for valid mangling at intermediate points in the
650 // collection(s). When a minor collection fails to collect
651 // sufficient space resizing of the young generation can occur
652 // an redistribute the spaces in the young generation. Mangle
653 // here so that unzapped regions don't get distributed to
654 // other spaces.
655 to()->mangle_unused_area();
656 }
657 swap_spaces();
658
659 assert(to()->is_empty(), "to space should be empty now");
660
661 adjust_desired_tenuring_threshold();
662
663 // A successful scavenge should restart the GC time limit count which is
664 // for full GC's.
665 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
666 size_policy->reset_gc_overhead_limit_count();
667 assert(!gch->incremental_collection_failed(), "Should be clear");
668 } else {
669 assert(_promo_failure_scan_stack.is_empty(), "post condition");
670 _promo_failure_scan_stack.clear(true); // Clear cached segments.
671
672 remove_forwarding_pointers();
673 if (PrintGCDetails) {
674 gclog_or_tty->print(" (promotion failed) ");
675 }
676 // Add to-space to the list of space to compact
677 // when a promotion failure has occurred. In that
678 // case there can be live objects in to-space
679 // as a result of a partial evacuation of eden
680 // and from-space.
681 swap_spaces(); // For uniformity wrt ParNewGeneration.
682 from()->set_next_compaction_space(to());
683 gch->set_incremental_collection_failed();
684
685 // Inform the next generation that a promotion failure occurred.
686 _next_gen->promotion_failure_occurred();
687 gc_tracer.report_promotion_failed(_promotion_failed_info);
688
689 // Reset the PromotionFailureALot counters.
690 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
691 }
692 if (PrintGC && !PrintGCDetails) {
693 gch->print_heap_change(gch_prev_used);
694 }
695 // set new iteration safe limit for the survivor spaces
696 from()->set_concurrent_iteration_safe_limit(from()->top());
697 to()->set_concurrent_iteration_safe_limit(to()->top());
698 SpecializationStats::print();
699
700 // We need to use a monotonically non-decreasing time in ms
701 // or we will see time-warp warnings and os::javaTimeMillis()
702 // does not guarantee monotonicity.
703 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
704 update_time_of_last_gc(now);
705
706 gch->trace_heap_after_gc(&gc_tracer);
707 gc_tracer.report_tenuring_threshold(tenuring_threshold());
708
709 _gc_timer->register_gc_end();
710
711 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
712 }
713
714 class RemoveForwardPointerClosure: public ObjectClosure {
715 public:
716 void do_object(oop obj) {
717 obj->init_mark();
718 }
719 };
720
721 void DefNewGeneration::init_assuming_no_promotion_failure() {
722 _promotion_failed = false;
723 _promotion_failed_info.reset();
724 from()->set_next_compaction_space(NULL);
725 }
726
727 void DefNewGeneration::remove_forwarding_pointers() {
728 RemoveForwardPointerClosure rspc;
729 eden()->object_iterate(&rspc);
730 from()->object_iterate(&rspc);
731
732 // Now restore saved marks, if any.
733 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
734 "should be the same");
735 while (!_objs_with_preserved_marks.is_empty()) {
736 oop obj = _objs_with_preserved_marks.pop();
737 markOop m = _preserved_marks_of_objs.pop();
738 obj->set_mark(m);
739 }
740 _objs_with_preserved_marks.clear(true);
741 _preserved_marks_of_objs.clear(true);
742 }
743
744 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
745 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
746 "Oversaving!");
747 _objs_with_preserved_marks.push(obj);
748 _preserved_marks_of_objs.push(m);
749 }
750
751 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
752 if (m->must_be_preserved_for_promotion_failure(obj)) {
753 preserve_mark(obj, m);
754 }
755 }
756
757 void DefNewGeneration::handle_promotion_failure(oop old) {
758 if (PrintPromotionFailure && !_promotion_failed) {
759 gclog_or_tty->print(" (promotion failure size = " SIZE_FORMAT ") ",
760 old->size());
761 }
762 _promotion_failed = true;
763 _promotion_failed_info.register_copy_failure(old->size());
764 preserve_mark_if_necessary(old, old->mark());
765 // forward to self
766 old->forward_to(old);
767
768 _promo_failure_scan_stack.push(old);
769
770 if (!_promo_failure_drain_in_progress) {
771 // prevent recursion in copy_to_survivor_space()
772 _promo_failure_drain_in_progress = true;
773 drain_promo_failure_scan_stack();
774 _promo_failure_drain_in_progress = false;
775 }
776 }
777
778 oop DefNewGeneration::copy_to_survivor_space(oop old) {
779 assert(is_in_reserved(old) && !old->is_forwarded(),
780 "shouldn't be scavenging this oop");
781 size_t s = old->size();
782 oop obj = NULL;
783
784 // Try allocating obj in to-space (unless too old)
785 if (old->age() < tenuring_threshold()) {
786 obj = (oop) to()->allocate(s);
787 }
788
789 // Otherwise try allocating obj tenured
790 if (obj == NULL) {
791 obj = _next_gen->promote(old, s);
792 if (obj == NULL) {
793 handle_promotion_failure(old);
794 return old;
795 }
796 } else {
797 // Prefetch beyond obj
798 const intx interval = PrefetchCopyIntervalInBytes;
799 Prefetch::write(obj, interval);
800
801 // Copy obj
802 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
803
804 // Increment age if obj still in new generation
805 obj->incr_age();
806 age_table()->add(obj, s);
807 }
808
809 // Done, insert forward pointer to obj in this header
810 old->forward_to(obj);
811
812 return obj;
813 }
814
815 void DefNewGeneration::drain_promo_failure_scan_stack() {
816 while (!_promo_failure_scan_stack.is_empty()) {
817 oop obj = _promo_failure_scan_stack.pop();
818 obj->oop_iterate(_promo_failure_scan_stack_closure);
819 }
820 }
821
822 void DefNewGeneration::save_marks() {
823 eden()->set_saved_mark();
824 to()->set_saved_mark();
825 from()->set_saved_mark();
826 }
827
828
829 void DefNewGeneration::reset_saved_marks() {
830 eden()->reset_saved_mark();
831 to()->reset_saved_mark();
832 from()->reset_saved_mark();
833 }
834
835
836 bool DefNewGeneration::no_allocs_since_save_marks() {
837 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
838 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
839 return to()->saved_mark_at_top();
840 }
841
842 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
843 \
844 void DefNewGeneration:: \
845 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
846 cl->set_generation(this); \
847 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
848 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
849 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
850 cl->reset_generation(); \
851 save_marks(); \
852 }
853
854 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
855
856 #undef DefNew_SINCE_SAVE_MARKS_DEFN
857
858 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
859 size_t max_alloc_words) {
860 if (requestor == this || _promotion_failed) return;
861 assert(requestor->level() > level(), "DefNewGeneration must be youngest");
862
863 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
864 if (to_space->top() > to_space->bottom()) {
865 trace("to_space not empty when contribute_scratch called");
866 }
867 */
868
869 ContiguousSpace* to_space = to();
870 assert(to_space->end() >= to_space->top(), "pointers out of order");
871 size_t free_words = pointer_delta(to_space->end(), to_space->top());
872 if (free_words >= MinFreeScratchWords) {
873 ScratchBlock* sb = (ScratchBlock*)to_space->top();
874 sb->num_words = free_words;
875 sb->next = list;
876 list = sb;
877 }
878 }
879
880 void DefNewGeneration::reset_scratch() {
881 // If contributing scratch in to_space, mangle all of
882 // to_space if ZapUnusedHeapArea. This is needed because
883 // top is not maintained while using to-space as scratch.
884 if (ZapUnusedHeapArea) {
885 to()->mangle_unused_area_complete();
886 }
887 }
888
889 bool DefNewGeneration::collection_attempt_is_safe() {
890 if (!to()->is_empty()) {
891 if (Verbose && PrintGCDetails) {
892 gclog_or_tty->print(" :: to is not empty :: ");
893 }
894 return false;
895 }
896 if (_next_gen == NULL) {
897 GenCollectedHeap* gch = GenCollectedHeap::heap();
898 _next_gen = gch->next_gen(this);
899 }
900 return _next_gen->promotion_attempt_is_safe(used());
901 }
902
903 void DefNewGeneration::gc_epilogue(bool full) {
904 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
905
906 assert(!GC_locker::is_active(), "We should not be executing here");
907 // Check if the heap is approaching full after a collection has
908 // been done. Generally the young generation is empty at
909 // a minimum at the end of a collection. If it is not, then
910 // the heap is approaching full.
911 GenCollectedHeap* gch = GenCollectedHeap::heap();
912 if (full) {
913 DEBUG_ONLY(seen_incremental_collection_failed = false;)
914 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
915 if (Verbose && PrintGCDetails) {
916 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
917 GCCause::to_string(gch->gc_cause()));
918 }
919 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
920 set_should_allocate_from_space(); // we seem to be running out of space
921 } else {
922 if (Verbose && PrintGCDetails) {
923 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
924 GCCause::to_string(gch->gc_cause()));
925 }
926 gch->clear_incremental_collection_failed(); // We just did a full collection
927 clear_should_allocate_from_space(); // if set
928 }
929 } else {
930 #ifdef ASSERT
931 // It is possible that incremental_collection_failed() == true
932 // here, because an attempted scavenge did not succeed. The policy
933 // is normally expected to cause a full collection which should
934 // clear that condition, so we should not be here twice in a row
935 // with incremental_collection_failed() == true without having done
936 // a full collection in between.
937 if (!seen_incremental_collection_failed &&
938 gch->incremental_collection_failed()) {
939 if (Verbose && PrintGCDetails) {
940 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
941 GCCause::to_string(gch->gc_cause()));
942 }
943 seen_incremental_collection_failed = true;
944 } else if (seen_incremental_collection_failed) {
945 if (Verbose && PrintGCDetails) {
946 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
947 GCCause::to_string(gch->gc_cause()));
948 }
949 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
950 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
951 !gch->incremental_collection_failed(),
952 "Twice in a row");
953 seen_incremental_collection_failed = false;
954 }
955 #endif // ASSERT
956 }
957
958 if (ZapUnusedHeapArea) {
959 eden()->check_mangled_unused_area_complete();
960 from()->check_mangled_unused_area_complete();
961 to()->check_mangled_unused_area_complete();
962 }
963
964 if (!CleanChunkPoolAsync) {
965 Chunk::clean_chunk_pool();
966 }
967
968 // update the generation and space performance counters
969 update_counters();
970 gch->collector_policy()->counters()->update_counters();
971 }
972
973 void DefNewGeneration::record_spaces_top() {
974 assert(ZapUnusedHeapArea, "Not mangling unused space");
975 eden()->set_top_for_allocations();
976 to()->set_top_for_allocations();
977 from()->set_top_for_allocations();
978 }
979
980 void DefNewGeneration::ref_processor_init() {
981 Generation::ref_processor_init();
982 }
983
984
985 void DefNewGeneration::update_counters() {
986 if (UsePerfData) {
987 _eden_counters->update_all();
988 _from_counters->update_all();
989 _to_counters->update_all();
990 _gen_counters->update_all();
991 }
992 }
993
994 void DefNewGeneration::verify() {
995 eden()->verify();
996 from()->verify();
997 to()->verify();
998 }
999
1000 void DefNewGeneration::print_on(outputStream* st) const {
1001 Generation::print_on(st);
1002 st->print(" eden");
1003 eden()->print_on(st);
1004 st->print(" from");
1005 from()->print_on(st);
1006 st->print(" to ");
1007 to()->print_on(st);
1008 }
1009
1010
1011 const char* DefNewGeneration::name() const {
1012 return "def new generation";
1013 }
1014
1015 // Moved from inline file as they are not called inline
1016 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1017 return eden();
1018 }
1019
1020 HeapWord* DefNewGeneration::allocate(size_t word_size,
1021 bool is_tlab) {
1022 // This is the slow-path allocation for the DefNewGeneration.
1023 // Most allocations are fast-path in compiled code.
1024 // We try to allocate from the eden. If that works, we are happy.
1025 // Note that since DefNewGeneration supports lock-free allocation, we
1026 // have to use it here, as well.
1027 HeapWord* result = eden()->par_allocate(word_size);
1028 if (result != NULL) {
1029 if (CMSEdenChunksRecordAlways && _next_gen != NULL) {
1030 _next_gen->sample_eden_chunk();
1031 }
1032 return result;
1033 }
1034 do {
1035 HeapWord* old_limit = eden()->soft_end();
1036 if (old_limit < eden()->end()) {
1037 // Tell the next generation we reached a limit.
1038 HeapWord* new_limit =
1039 next_gen()->allocation_limit_reached(eden(), eden()->top(), word_size);
1040 if (new_limit != NULL) {
1041 Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit);
1042 } else {
1043 assert(eden()->soft_end() == eden()->end(),
1044 "invalid state after allocation_limit_reached returned null");
1045 }
1046 } else {
1047 // The allocation failed and the soft limit is equal to the hard limit,
1048 // there are no reasons to do an attempt to allocate
1049 assert(old_limit == eden()->end(), "sanity check");
1050 break;
1051 }
1052 // Try to allocate until succeeded or the soft limit can't be adjusted
1053 result = eden()->par_allocate(word_size);
1054 } while (result == NULL);
1055
1056 // If the eden is full and the last collection bailed out, we are running
1057 // out of heap space, and we try to allocate the from-space, too.
1058 // allocate_from_space can't be inlined because that would introduce a
1059 // circular dependency at compile time.
1060 if (result == NULL) {
1061 result = allocate_from_space(word_size);
1062 } else if (CMSEdenChunksRecordAlways && _next_gen != NULL) {
1063 _next_gen->sample_eden_chunk();
1064 }
1065 return result;
1066 }
1067
1068 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1069 bool is_tlab) {
1070 HeapWord* res = eden()->par_allocate(word_size);
1071 if (CMSEdenChunksRecordAlways && _next_gen != NULL) {
1072 _next_gen->sample_eden_chunk();
1073 }
1074 return res;
1075 }
1076
1077 void DefNewGeneration::gc_prologue(bool full) {
1078 // Ensure that _end and _soft_end are the same in eden space.
1079 eden()->set_soft_end(eden()->end());
1080 }
1081
1082 size_t DefNewGeneration::tlab_capacity() const {
1083 return eden()->capacity();
1084 }
1085
1086 size_t DefNewGeneration::tlab_used() const {
1087 return eden()->used();
1088 }
1089
1090 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1091 return unsafe_max_alloc_nogc();
1092 }