1 /*
2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc/serial/defNewGeneration.inline.hpp"
27 #include "gc/shared/collectorCounters.hpp"
28 #include "gc/shared/gcHeapSummary.hpp"
29 #include "gc/shared/gcLocker.inline.hpp"
30 #include "gc/shared/gcPolicyCounters.hpp"
31 #include "gc/shared/gcTimer.hpp"
32 #include "gc/shared/gcTrace.hpp"
33 #include "gc/shared/gcTraceTime.hpp"
34 #include "gc/shared/genCollectedHeap.hpp"
35 #include "gc/shared/genOopClosures.inline.hpp"
36 #include "gc/shared/genRemSet.hpp"
37 #include "gc/shared/generationSpec.hpp"
38 #include "gc/shared/referencePolicy.hpp"
39 #include "gc/shared/space.inline.hpp"
40 #include "gc/shared/spaceDecorator.hpp"
41 #include "gc/shared/strongRootsScope.hpp"
42 #include "memory/iterator.hpp"
43 #include "oops/instanceRefKlass.hpp"
44 #include "oops/oop.inline.hpp"
45 #include "runtime/atomic.inline.hpp"
46 #include "runtime/java.hpp"
47 #include "runtime/prefetch.inline.hpp"
48 #include "runtime/thread.inline.hpp"
49 #include "utilities/copy.hpp"
50 #include "utilities/globalDefinitions.hpp"
51 #include "utilities/stack.inline.hpp"
52 #if INCLUDE_ALL_GCS
53 #include "gc/cms/parOopClosures.hpp"
54 #endif
55
56 //
57 // DefNewGeneration functions.
58
59 // Methods of protected closure types.
60
61 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
62 assert(_young_gen->kind() == Generation::ParNew ||
63 _young_gen->kind() == Generation::DefNew, "Expected the young generation here");
64 }
65
66 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
67 return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded();
68 }
69
70 DefNewGeneration::KeepAliveClosure::
71 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
72 GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
73 _rs = (CardTableRS*)rs;
74 }
75
76 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
77 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
78
79
80 DefNewGeneration::FastKeepAliveClosure::
81 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
82 DefNewGeneration::KeepAliveClosure(cl) {
83 _boundary = g->reserved().end();
84 }
85
86 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
87 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
88
89 DefNewGeneration::EvacuateFollowersClosure::
90 EvacuateFollowersClosure(GenCollectedHeap* gch,
91 ScanClosure* cur,
92 ScanClosure* older) :
93 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
94 {}
95
96 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
97 do {
98 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
99 } while (!_gch->no_allocs_since_save_marks());
100 }
101
102 DefNewGeneration::FastEvacuateFollowersClosure::
103 FastEvacuateFollowersClosure(GenCollectedHeap* gch,
104 FastScanClosure* cur,
105 FastScanClosure* older) :
106 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
107 {
108 assert(_gch->young_gen()->kind() == Generation::DefNew, "Generation should be DefNew");
109 _young_gen = (DefNewGeneration*)_gch->young_gen();
110 }
111
112 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
113 do {
114 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
115 } while (!_gch->no_allocs_since_save_marks());
116 guarantee(_young_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
117 }
118
119 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
120 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
121 {
122 _boundary = _g->reserved().end();
123 }
124
125 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
126 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
127
128 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
129 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
130 {
131 _boundary = _g->reserved().end();
132 }
133
134 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
135 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
136
137 void KlassScanClosure::do_klass(Klass* klass) {
138 #ifndef PRODUCT
139 if (TraceScavenge) {
140 ResourceMark rm;
141 gclog_or_tty->print_cr("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s",
142 p2i(klass),
143 klass->external_name(),
144 klass->has_modified_oops() ? "true" : "false");
145 }
146 #endif
147
148 // If the klass has not been dirtied we know that there's
149 // no references into the young gen and we can skip it.
150 if (klass->has_modified_oops()) {
151 if (_accumulate_modified_oops) {
152 klass->accumulate_modified_oops();
153 }
154
155 // Clear this state since we're going to scavenge all the metadata.
156 klass->clear_modified_oops();
157
158 // Tell the closure which Klass is being scanned so that it can be dirtied
159 // if oops are left pointing into the young gen.
160 _scavenge_closure->set_scanned_klass(klass);
161
162 klass->oops_do(_scavenge_closure);
163
164 _scavenge_closure->set_scanned_klass(NULL);
165 }
166 }
167
168 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
169 _g(g)
170 {
171 _boundary = _g->reserved().end();
172 }
173
174 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
175 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
176
177 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
178 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
179
180 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
181 KlassRemSet* klass_rem_set)
182 : _scavenge_closure(scavenge_closure),
183 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
184
185
186 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
187 size_t initial_size,
188 const char* policy)
189 : Generation(rs, initial_size),
190 _promo_failure_drain_in_progress(false),
191 _should_allocate_from_space(false)
192 {
193 MemRegion cmr((HeapWord*)_virtual_space.low(),
194 (HeapWord*)_virtual_space.high());
195 GenCollectedHeap* gch = GenCollectedHeap::heap();
196
197 gch->barrier_set()->resize_covered_region(cmr);
198
199 _eden_space = new ContiguousSpace();
200 _from_space = new ContiguousSpace();
201 _to_space = new ContiguousSpace();
202
203 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
204 vm_exit_during_initialization("Could not allocate a new gen space");
205 }
206
207 // Compute the maximum eden and survivor space sizes. These sizes
208 // are computed assuming the entire reserved space is committed.
209 // These values are exported as performance counters.
210 uintx alignment = gch->collector_policy()->space_alignment();
211 uintx size = _virtual_space.reserved_size();
212 _max_survivor_size = compute_survivor_size(size, alignment);
213 _max_eden_size = size - (2*_max_survivor_size);
214
215 // allocate the performance counters
216 GenCollectorPolicy* gcp = (GenCollectorPolicy*)gch->collector_policy();
217
218 // Generation counters -- generation 0, 3 subspaces
219 _gen_counters = new GenerationCounters("new", 0, 3,
220 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
221 _gc_counters = new CollectorCounters(policy, 0);
222
223 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
224 _gen_counters);
225 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
226 _gen_counters);
227 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
228 _gen_counters);
229
230 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
231 update_counters();
232 _old_gen = NULL;
233 _tenuring_threshold = MaxTenuringThreshold;
234 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
235
236 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
237 }
238
239 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
240 bool clear_space,
241 bool mangle_space) {
242 uintx alignment =
243 GenCollectedHeap::heap()->collector_policy()->space_alignment();
244
245 // If the spaces are being cleared (only done at heap initialization
246 // currently), the survivor spaces need not be empty.
247 // Otherwise, no care is taken for used areas in the survivor spaces
248 // so check.
249 assert(clear_space || (to()->is_empty() && from()->is_empty()),
250 "Initialization of the survivor spaces assumes these are empty");
251
252 // Compute sizes
253 uintx size = _virtual_space.committed_size();
254 uintx survivor_size = compute_survivor_size(size, alignment);
255 uintx eden_size = size - (2*survivor_size);
256 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
257
258 if (eden_size < minimum_eden_size) {
259 // May happen due to 64Kb rounding, if so adjust eden size back up
260 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
261 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
262 uintx unaligned_survivor_size =
263 align_size_down(maximum_survivor_size, alignment);
264 survivor_size = MAX2(unaligned_survivor_size, alignment);
265 eden_size = size - (2*survivor_size);
266 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
267 assert(eden_size >= minimum_eden_size, "just checking");
268 }
269
270 char *eden_start = _virtual_space.low();
271 char *from_start = eden_start + eden_size;
272 char *to_start = from_start + survivor_size;
273 char *to_end = to_start + survivor_size;
274
275 assert(to_end == _virtual_space.high(), "just checking");
276 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
277 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
278 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
279
280 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
281 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
282 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
283
284 // A minimum eden size implies that there is a part of eden that
285 // is being used and that affects the initialization of any
286 // newly formed eden.
287 bool live_in_eden = minimum_eden_size > 0;
288
289 // If not clearing the spaces, do some checking to verify that
290 // the space are already mangled.
291 if (!clear_space) {
292 // Must check mangling before the spaces are reshaped. Otherwise,
293 // the bottom or end of one space may have moved into another
294 // a failure of the check may not correctly indicate which space
295 // is not properly mangled.
296 if (ZapUnusedHeapArea) {
297 HeapWord* limit = (HeapWord*) _virtual_space.high();
298 eden()->check_mangled_unused_area(limit);
299 from()->check_mangled_unused_area(limit);
300 to()->check_mangled_unused_area(limit);
301 }
302 }
303
304 // Reset the spaces for their new regions.
305 eden()->initialize(edenMR,
306 clear_space && !live_in_eden,
307 SpaceDecorator::Mangle);
308 // If clear_space and live_in_eden, we will not have cleared any
309 // portion of eden above its top. This can cause newly
310 // expanded space not to be mangled if using ZapUnusedHeapArea.
311 // We explicitly do such mangling here.
312 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
313 eden()->mangle_unused_area();
314 }
315 from()->initialize(fromMR, clear_space, mangle_space);
316 to()->initialize(toMR, clear_space, mangle_space);
317
318 // Set next compaction spaces.
319 eden()->set_next_compaction_space(from());
320 // The to-space is normally empty before a compaction so need
321 // not be considered. The exception is during promotion
322 // failure handling when to-space can contain live objects.
323 from()->set_next_compaction_space(NULL);
324 }
325
326 void DefNewGeneration::swap_spaces() {
327 ContiguousSpace* s = from();
328 _from_space = to();
329 _to_space = s;
330 eden()->set_next_compaction_space(from());
331 // The to-space is normally empty before a compaction so need
332 // not be considered. The exception is during promotion
333 // failure handling when to-space can contain live objects.
334 from()->set_next_compaction_space(NULL);
335
336 if (UsePerfData) {
337 CSpaceCounters* c = _from_counters;
338 _from_counters = _to_counters;
339 _to_counters = c;
340 }
341 }
342
343 bool DefNewGeneration::expand(size_t bytes) {
344 MutexLocker x(ExpandHeap_lock);
345 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
346 bool success = _virtual_space.expand_by(bytes);
347 if (success && ZapUnusedHeapArea) {
348 // Mangle newly committed space immediately because it
349 // can be done here more simply that after the new
350 // spaces have been computed.
351 HeapWord* new_high = (HeapWord*) _virtual_space.high();
352 MemRegion mangle_region(prev_high, new_high);
353 SpaceMangler::mangle_region(mangle_region);
354 }
355
356 // Do not attempt an expand-to-the reserve size. The
357 // request should properly observe the maximum size of
358 // the generation so an expand-to-reserve should be
359 // unnecessary. Also a second call to expand-to-reserve
360 // value potentially can cause an undue expansion.
361 // For example if the first expand fail for unknown reasons,
362 // but the second succeeds and expands the heap to its maximum
363 // value.
364 if (GC_locker::is_active()) {
365 if (PrintGC && Verbose) {
366 gclog_or_tty->print_cr("Garbage collection disabled, "
367 "expanded heap instead");
368 }
369 }
370
371 return success;
372 }
373
374 void DefNewGeneration::compute_new_size() {
375 // This is called after a GC that includes the old generation, so from-space
376 // will normally be empty.
377 // Note that we check both spaces, since if scavenge failed they revert roles.
378 // If not we bail out (otherwise we would have to relocate the objects).
379 if (!from()->is_empty() || !to()->is_empty()) {
380 return;
381 }
382
383 GenCollectedHeap* gch = GenCollectedHeap::heap();
384
385 size_t old_size = gch->old_gen()->capacity();
386 size_t new_size_before = _virtual_space.committed_size();
387 size_t min_new_size = spec()->init_size();
388 size_t max_new_size = reserved().byte_size();
389 assert(min_new_size <= new_size_before &&
390 new_size_before <= max_new_size,
391 "just checking");
392 // All space sizes must be multiples of Generation::GenGrain.
393 size_t alignment = Generation::GenGrain;
394
395 // Compute desired new generation size based on NewRatio and
396 // NewSizeThreadIncrease
397 size_t desired_new_size = old_size/NewRatio;
398 int threads_count = Threads::number_of_non_daemon_threads();
399 size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
400 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
401
402 // Adjust new generation size
403 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
404 assert(desired_new_size <= max_new_size, "just checking");
405
406 bool changed = false;
407 if (desired_new_size > new_size_before) {
408 size_t change = desired_new_size - new_size_before;
409 assert(change % alignment == 0, "just checking");
410 if (expand(change)) {
411 changed = true;
412 }
413 // If the heap failed to expand to the desired size,
414 // "changed" will be false. If the expansion failed
415 // (and at this point it was expected to succeed),
416 // ignore the failure (leaving "changed" as false).
417 }
418 if (desired_new_size < new_size_before && eden()->is_empty()) {
419 // bail out of shrinking if objects in eden
420 size_t change = new_size_before - desired_new_size;
421 assert(change % alignment == 0, "just checking");
422 _virtual_space.shrink_by(change);
423 changed = true;
424 }
425 if (changed) {
426 // The spaces have already been mangled at this point but
427 // may not have been cleared (set top = bottom) and should be.
428 // Mangling was done when the heap was being expanded.
429 compute_space_boundaries(eden()->used(),
430 SpaceDecorator::Clear,
431 SpaceDecorator::DontMangle);
432 MemRegion cmr((HeapWord*)_virtual_space.low(),
433 (HeapWord*)_virtual_space.high());
434 gch->barrier_set()->resize_covered_region(cmr);
435 if (Verbose && PrintGC) {
436 size_t new_size_after = _virtual_space.committed_size();
437 size_t eden_size_after = eden()->capacity();
438 size_t survivor_size_after = from()->capacity();
439 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
440 SIZE_FORMAT "K [eden="
441 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
442 new_size_before/K, new_size_after/K,
443 eden_size_after/K, survivor_size_after/K);
444 if (WizardMode) {
445 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
446 thread_increase_size/K, threads_count);
447 }
448 gclog_or_tty->cr();
449 }
450 }
451 }
452
453 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
454 assert(false, "NYI -- are you sure you want to call this?");
455 }
456
457
458 size_t DefNewGeneration::capacity() const {
459 return eden()->capacity()
460 + from()->capacity(); // to() is only used during scavenge
461 }
462
463
464 size_t DefNewGeneration::used() const {
465 return eden()->used()
466 + from()->used(); // to() is only used during scavenge
467 }
468
469
470 size_t DefNewGeneration::free() const {
471 return eden()->free()
472 + from()->free(); // to() is only used during scavenge
473 }
474
475 size_t DefNewGeneration::max_capacity() const {
476 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
477 const size_t reserved_bytes = reserved().byte_size();
478 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
479 }
480
481 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
482 return eden()->free();
483 }
484
485 size_t DefNewGeneration::capacity_before_gc() const {
486 return eden()->capacity();
487 }
488
489 size_t DefNewGeneration::contiguous_available() const {
490 return eden()->free();
491 }
492
493
494 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
495 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
496
497 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
498 eden()->object_iterate(blk);
499 from()->object_iterate(blk);
500 }
501
502
503 void DefNewGeneration::space_iterate(SpaceClosure* blk,
504 bool usedOnly) {
505 blk->do_space(eden());
506 blk->do_space(from());
507 blk->do_space(to());
508 }
509
510 // The last collection bailed out, we are running out of heap space,
511 // so we try to allocate the from-space, too.
512 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
513 HeapWord* result = NULL;
514 if (Verbose && PrintGCDetails) {
515 gclog_or_tty->print("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):"
516 " will_fail: %s"
517 " heap_lock: %s"
518 " free: " SIZE_FORMAT,
519 size,
520 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
521 "true" : "false",
522 Heap_lock->is_locked() ? "locked" : "unlocked",
523 from()->free());
524 }
525 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
526 if (Heap_lock->owned_by_self() ||
527 (SafepointSynchronize::is_at_safepoint() &&
528 Thread::current()->is_VM_thread())) {
529 // If the Heap_lock is not locked by this thread, this will be called
530 // again later with the Heap_lock held.
531 result = from()->allocate(size);
532 } else if (PrintGC && Verbose) {
533 gclog_or_tty->print_cr(" Heap_lock is not owned by self");
534 }
535 } else if (PrintGC && Verbose) {
536 gclog_or_tty->print_cr(" should_allocate_from_space: NOT");
537 }
538 if (PrintGC && Verbose) {
539 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object");
540 }
541 return result;
542 }
543
544 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
545 bool is_tlab,
546 bool parallel) {
547 // We don't attempt to expand the young generation (but perhaps we should.)
548 return allocate(size, is_tlab);
549 }
550
551 void DefNewGeneration::adjust_desired_tenuring_threshold() {
552 // Set the desired survivor size to half the real survivor space
553 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->collector_policy()->counters();
554 _tenuring_threshold =
555 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize, gc_counters);
556 }
557
558 void DefNewGeneration::collect(bool full,
559 bool clear_all_soft_refs,
560 size_t size,
561 bool is_tlab) {
562 assert(full || size > 0, "otherwise we don't want to collect");
563
564 GenCollectedHeap* gch = GenCollectedHeap::heap();
565
566 _gc_timer->register_gc_start();
567 DefNewTracer gc_tracer;
568 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
569
570 _old_gen = gch->old_gen();
571
572 // If the next generation is too full to accommodate promotion
573 // from this generation, pass on collection; let the next generation
574 // do it.
575 if (!collection_attempt_is_safe()) {
576 if (Verbose && PrintGCDetails) {
577 gclog_or_tty->print(" :: Collection attempt not safe :: ");
578 }
579 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
580 return;
581 }
582 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
583
584 init_assuming_no_promotion_failure();
585
586 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, gc_tracer.gc_id());
587 // Capture heap used before collection (for printing).
588 size_t gch_prev_used = gch->used();
589
590 gch->trace_heap_before_gc(&gc_tracer);
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(),
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 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
613 &fsc_with_no_gc_barrier,
614 false);
615
616 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
617 FastEvacuateFollowersClosure evacuate_followers(gch,
618 &fsc_with_no_gc_barrier,
619 &fsc_with_gc_barrier);
620
621 assert(gch->no_allocs_since_save_marks(),
622 "save marks have not been newly set.");
623
624 {
625 // DefNew needs to run with n_threads == 0, to make sure the serial
626 // version of the card table scanning code is used.
627 // See: CardTableModRefBSForCTRS::non_clean_card_iterate_possibly_parallel.
628 StrongRootsScope srs(0);
629
630 gch->gen_process_roots(&srs,
631 GenCollectedHeap::YoungGen,
632 true, // Process younger gens, if any,
633 // as strong roots.
634 GenCollectedHeap::SO_ScavengeCodeCache,
635 GenCollectedHeap::StrongAndWeakRoots,
636 &fsc_with_no_gc_barrier,
637 &fsc_with_gc_barrier,
638 &cld_scan_closure);
639 }
640
641 // "evacuate followers".
642 evacuate_followers.do_void();
643
644 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
645 ReferenceProcessor* rp = ref_processor();
646 rp->setup_policy(clear_all_soft_refs);
647 const ReferenceProcessorStats& stats =
648 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
649 NULL, _gc_timer, gc_tracer.gc_id());
650 gc_tracer.report_gc_reference_stats(stats);
651
652 if (!_promotion_failed) {
653 // Swap the survivor spaces.
654 eden()->clear(SpaceDecorator::Mangle);
655 from()->clear(SpaceDecorator::Mangle);
656 if (ZapUnusedHeapArea) {
657 // This is now done here because of the piece-meal mangling which
658 // can check for valid mangling at intermediate points in the
659 // collection(s). When a young collection fails to collect
660 // sufficient space resizing of the young generation can occur
661 // an redistribute the spaces in the young generation. Mangle
662 // here so that unzapped regions don't get distributed to
663 // other spaces.
664 to()->mangle_unused_area();
665 }
666 swap_spaces();
667
668 assert(to()->is_empty(), "to space should be empty now");
669
670 adjust_desired_tenuring_threshold();
671
672 // A successful scavenge should restart the GC time limit count which is
673 // for full GC's.
674 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
675 size_policy->reset_gc_overhead_limit_count();
676 assert(!gch->incremental_collection_failed(), "Should be clear");
677 } else {
678 assert(_promo_failure_scan_stack.is_empty(), "post condition");
679 _promo_failure_scan_stack.clear(true); // Clear cached segments.
680
681 remove_forwarding_pointers();
682 if (PrintGCDetails) {
683 gclog_or_tty->print(" (promotion failed) ");
684 }
685 // Add to-space to the list of space to compact
686 // when a promotion failure has occurred. In that
687 // case there can be live objects in to-space
688 // as a result of a partial evacuation of eden
689 // and from-space.
690 swap_spaces(); // For uniformity wrt ParNewGeneration.
691 from()->set_next_compaction_space(to());
692 gch->set_incremental_collection_failed();
693
694 // Inform the next generation that a promotion failure occurred.
695 _old_gen->promotion_failure_occurred();
696 gc_tracer.report_promotion_failed(_promotion_failed_info);
697
698 // Reset the PromotionFailureALot counters.
699 NOT_PRODUCT(gch->reset_promotion_should_fail();)
700 }
701 if (PrintGC && !PrintGCDetails) {
702 gch->print_heap_change(gch_prev_used);
703 }
704 // set new iteration safe limit for the survivor spaces
705 from()->set_concurrent_iteration_safe_limit(from()->top());
706 to()->set_concurrent_iteration_safe_limit(to()->top());
707
708 // We need to use a monotonically non-decreasing time in ms
709 // or we will see time-warp warnings and os::javaTimeMillis()
710 // does not guarantee monotonicity.
711 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
712 update_time_of_last_gc(now);
713
714 gch->trace_heap_after_gc(&gc_tracer);
715 gc_tracer.report_tenuring_threshold(tenuring_threshold());
716
717 _gc_timer->register_gc_end();
718
719 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
720 }
721
722 class RemoveForwardPointerClosure: public ObjectClosure {
723 public:
724 void do_object(oop obj) {
725 obj->init_mark();
726 }
727 };
728
729 void DefNewGeneration::init_assuming_no_promotion_failure() {
730 _promotion_failed = false;
731 _promotion_failed_info.reset();
732 from()->set_next_compaction_space(NULL);
733 }
734
735 void DefNewGeneration::remove_forwarding_pointers() {
736 RemoveForwardPointerClosure rspc;
737 eden()->object_iterate(&rspc);
738 from()->object_iterate(&rspc);
739
740 // Now restore saved marks, if any.
741 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
742 "should be the same");
743 while (!_objs_with_preserved_marks.is_empty()) {
744 oop obj = _objs_with_preserved_marks.pop();
745 markOop m = _preserved_marks_of_objs.pop();
746 obj->set_mark(m);
747 }
748 _objs_with_preserved_marks.clear(true);
749 _preserved_marks_of_objs.clear(true);
750 }
751
752 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
753 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
754 "Oversaving!");
755 _objs_with_preserved_marks.push(obj);
756 _preserved_marks_of_objs.push(m);
757 }
758
759 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
760 if (m->must_be_preserved_for_promotion_failure(obj)) {
761 preserve_mark(obj, m);
762 }
763 }
764
765 void DefNewGeneration::handle_promotion_failure(oop old) {
766 if (PrintPromotionFailure && !_promotion_failed) {
767 gclog_or_tty->print(" (promotion failure size = %d) ",
768 old->size());
769 }
770 _promotion_failed = true;
771 _promotion_failed_info.register_copy_failure(old->size());
772 preserve_mark_if_necessary(old, old->mark());
773 // forward to self
774 old->forward_to(old);
775
776 _promo_failure_scan_stack.push(old);
777
778 if (!_promo_failure_drain_in_progress) {
779 // prevent recursion in copy_to_survivor_space()
780 _promo_failure_drain_in_progress = true;
781 drain_promo_failure_scan_stack();
782 _promo_failure_drain_in_progress = false;
783 }
784 }
785
786 oop DefNewGeneration::copy_to_survivor_space(oop old) {
787 assert(is_in_reserved(old) && !old->is_forwarded(),
788 "shouldn't be scavenging this oop");
789 size_t s = old->size();
790 oop obj = NULL;
791
792 // Try allocating obj in to-space (unless too old)
793 if (old->age() < tenuring_threshold()) {
794 obj = (oop) to()->allocate_aligned(s);
795 }
796
797 // Otherwise try allocating obj tenured
798 if (obj == NULL) {
799 obj = _old_gen->promote(old, s);
800 if (obj == NULL) {
801 handle_promotion_failure(old);
802 return old;
803 }
804 } else {
805 // Prefetch beyond obj
806 const intx interval = PrefetchCopyIntervalInBytes;
807 Prefetch::write(obj, interval);
808
809 // Copy obj
810 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
811
812 // Increment age if obj still in new generation
813 obj->incr_age();
814 age_table()->add(obj, s);
815 }
816
817 // Done, insert forward pointer to obj in this header
818 old->forward_to(obj);
819
820 return obj;
821 }
822
823 void DefNewGeneration::drain_promo_failure_scan_stack() {
824 while (!_promo_failure_scan_stack.is_empty()) {
825 oop obj = _promo_failure_scan_stack.pop();
826 obj->oop_iterate(_promo_failure_scan_stack_closure);
827 }
828 }
829
830 void DefNewGeneration::save_marks() {
831 eden()->set_saved_mark();
832 to()->set_saved_mark();
833 from()->set_saved_mark();
834 }
835
836
837 void DefNewGeneration::reset_saved_marks() {
838 eden()->reset_saved_mark();
839 to()->reset_saved_mark();
840 from()->reset_saved_mark();
841 }
842
843
844 bool DefNewGeneration::no_allocs_since_save_marks() {
845 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
846 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
847 return to()->saved_mark_at_top();
848 }
849
850 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
851 \
852 void DefNewGeneration:: \
853 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
854 cl->set_generation(this); \
855 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
856 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
857 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
858 cl->reset_generation(); \
859 save_marks(); \
860 }
861
862 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
863
864 #undef DefNew_SINCE_SAVE_MARKS_DEFN
865
866 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
867 size_t max_alloc_words) {
868 if (requestor == this || _promotion_failed) {
869 return;
870 }
871 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
872
873 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
874 if (to_space->top() > to_space->bottom()) {
875 trace("to_space not empty when contribute_scratch called");
876 }
877 */
878
879 ContiguousSpace* to_space = to();
880 assert(to_space->end() >= to_space->top(), "pointers out of order");
881 size_t free_words = pointer_delta(to_space->end(), to_space->top());
882 if (free_words >= MinFreeScratchWords) {
883 ScratchBlock* sb = (ScratchBlock*)to_space->top();
884 sb->num_words = free_words;
885 sb->next = list;
886 list = sb;
887 }
888 }
889
890 void DefNewGeneration::reset_scratch() {
891 // If contributing scratch in to_space, mangle all of
892 // to_space if ZapUnusedHeapArea. This is needed because
893 // top is not maintained while using to-space as scratch.
894 if (ZapUnusedHeapArea) {
895 to()->mangle_unused_area_complete();
896 }
897 }
898
899 bool DefNewGeneration::collection_attempt_is_safe() {
900 if (!to()->is_empty()) {
901 if (Verbose && PrintGCDetails) {
902 gclog_or_tty->print(" :: to is not empty :: ");
903 }
904 return false;
905 }
906 if (_old_gen == NULL) {
907 GenCollectedHeap* gch = GenCollectedHeap::heap();
908 _old_gen = gch->old_gen();
909 }
910 return _old_gen->promotion_attempt_is_safe(used());
911 }
912
913 void DefNewGeneration::gc_epilogue(bool full) {
914 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
915
916 assert(!GC_locker::is_active(), "We should not be executing here");
917 // Check if the heap is approaching full after a collection has
918 // been done. Generally the young generation is empty at
919 // a minimum at the end of a collection. If it is not, then
920 // the heap is approaching full.
921 GenCollectedHeap* gch = GenCollectedHeap::heap();
922 if (full) {
923 DEBUG_ONLY(seen_incremental_collection_failed = false;)
924 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
925 if (Verbose && PrintGCDetails) {
926 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
927 GCCause::to_string(gch->gc_cause()));
928 }
929 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
930 set_should_allocate_from_space(); // we seem to be running out of space
931 } else {
932 if (Verbose && PrintGCDetails) {
933 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
934 GCCause::to_string(gch->gc_cause()));
935 }
936 gch->clear_incremental_collection_failed(); // We just did a full collection
937 clear_should_allocate_from_space(); // if set
938 }
939 } else {
940 #ifdef ASSERT
941 // It is possible that incremental_collection_failed() == true
942 // here, because an attempted scavenge did not succeed. The policy
943 // is normally expected to cause a full collection which should
944 // clear that condition, so we should not be here twice in a row
945 // with incremental_collection_failed() == true without having done
946 // a full collection in between.
947 if (!seen_incremental_collection_failed &&
948 gch->incremental_collection_failed()) {
949 if (Verbose && PrintGCDetails) {
950 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
951 GCCause::to_string(gch->gc_cause()));
952 }
953 seen_incremental_collection_failed = true;
954 } else if (seen_incremental_collection_failed) {
955 if (Verbose && PrintGCDetails) {
956 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
957 GCCause::to_string(gch->gc_cause()));
958 }
959 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
960 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
961 !gch->incremental_collection_failed(),
962 "Twice in a row");
963 seen_incremental_collection_failed = false;
964 }
965 #endif // ASSERT
966 }
967
968 if (ZapUnusedHeapArea) {
969 eden()->check_mangled_unused_area_complete();
970 from()->check_mangled_unused_area_complete();
971 to()->check_mangled_unused_area_complete();
972 }
973
974 if (!CleanChunkPoolAsync) {
975 Chunk::clean_chunk_pool();
976 }
977
978 // update the generation and space performance counters
979 update_counters();
980 gch->collector_policy()->counters()->update_counters();
981 }
982
983 void DefNewGeneration::record_spaces_top() {
984 assert(ZapUnusedHeapArea, "Not mangling unused space");
985 eden()->set_top_for_allocations();
986 to()->set_top_for_allocations();
987 from()->set_top_for_allocations();
988 }
989
990 void DefNewGeneration::ref_processor_init() {
991 Generation::ref_processor_init();
992 }
993
994
995 void DefNewGeneration::update_counters() {
996 if (UsePerfData) {
997 _eden_counters->update_all();
998 _from_counters->update_all();
999 _to_counters->update_all();
1000 _gen_counters->update_all();
1001 }
1002 }
1003
1004 void DefNewGeneration::verify() {
1005 eden()->verify();
1006 from()->verify();
1007 to()->verify();
1008 }
1009
1010 void DefNewGeneration::print_on(outputStream* st) const {
1011 Generation::print_on(st);
1012 st->print(" eden");
1013 eden()->print_on(st);
1014 st->print(" from");
1015 from()->print_on(st);
1016 st->print(" to ");
1017 to()->print_on(st);
1018 }
1019
1020
1021 const char* DefNewGeneration::name() const {
1022 return "def new generation";
1023 }
1024
1025 // Moved from inline file as they are not called inline
1026 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1027 return eden();
1028 }
1029
1030 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1031 // This is the slow-path allocation for the DefNewGeneration.
1032 // Most allocations are fast-path in compiled code.
1033 // We try to allocate from the eden. If that works, we are happy.
1034 // Note that since DefNewGeneration supports lock-free allocation, we
1035 // have to use it here, as well.
1036 HeapWord* result = eden()->par_allocate(word_size);
1037 if (result != NULL) {
1038 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1039 _old_gen->sample_eden_chunk();
1040 }
1041 } else {
1042 // If the eden is full and the last collection bailed out, we are running
1043 // out of heap space, and we try to allocate the from-space, too.
1044 // allocate_from_space can't be inlined because that would introduce a
1045 // circular dependency at compile time.
1046 result = allocate_from_space(word_size);
1047 }
1048 return result;
1049 }
1050
1051 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1052 bool is_tlab) {
1053 HeapWord* res = eden()->par_allocate(word_size);
1054 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1055 _old_gen->sample_eden_chunk();
1056 }
1057 return res;
1058 }
1059
1060 size_t DefNewGeneration::tlab_capacity() const {
1061 return eden()->capacity();
1062 }
1063
1064 size_t DefNewGeneration::tlab_used() const {
1065 return eden()->used();
1066 }
1067
1068 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1069 return unsafe_max_alloc_nogc();
1070 }