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_implementation/shared/collectorCounters.hpp"
27 #include "gc_implementation/shared/gcPolicyCounters.hpp"
28 #include "gc_implementation/shared/gcHeapSummary.hpp"
29 #include "gc_implementation/shared/gcTimer.hpp"
30 #include "gc_implementation/shared/gcTraceTime.hpp"
31 #include "gc_implementation/shared/gcTrace.hpp"
32 #include "gc_implementation/shared/spaceDecorator.hpp"
33 #include "memory/defNewGeneration.inline.hpp"
34 #include "memory/gcLocker.inline.hpp"
35 #include "memory/genCollectedHeap.hpp"
36 #include "memory/genOopClosures.inline.hpp"
37 #include "memory/genRemSet.hpp"
38 #include "memory/generationSpec.hpp"
39 #include "memory/iterator.hpp"
40 #include "memory/referencePolicy.hpp"
41 #include "memory/space.inline.hpp"
42 #include "oops/instanceRefKlass.hpp"
43 #include "oops/oop.inline.hpp"
44 #include "runtime/atomic.inline.hpp"
45 #include "runtime/java.hpp"
46 #include "runtime/prefetch.inline.hpp"
47 #include "runtime/thread.inline.hpp"
48 #include "utilities/copy.hpp"
49 #include "utilities/globalDefinitions.hpp"
50 #include "utilities/stack.inline.hpp"
51 #if INCLUDE_ALL_GCS
52 #include "gc_implementation/parNew/parOopClosures.hpp"
53 #endif
54
55 //
56 // DefNewGeneration functions.
57
58 // Methods of protected closure types.
59
60 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
61 assert(g->level() == 0, "Optimized for youngest gen.");
62 }
63 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
64 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
65 }
66
67 DefNewGeneration::KeepAliveClosure::
68 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
69 GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
70 _rs = (CardTableRS*)rs;
71 }
72
73 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
74 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
75
76
77 DefNewGeneration::FastKeepAliveClosure::
78 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
79 DefNewGeneration::KeepAliveClosure(cl) {
80 _boundary = g->reserved().end();
81 }
82
83 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
84 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
85
86 DefNewGeneration::EvacuateFollowersClosure::
87 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
88 ScanClosure* cur, ScanClosure* older) :
89 _gch(gch), _level(level),
90 _scan_cur_or_nonheap(cur), _scan_older(older)
91 {}
92
93 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
94 do {
95 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
96 _scan_older);
97 } while (!_gch->no_allocs_since_save_marks(_level));
98 }
99
100 DefNewGeneration::FastEvacuateFollowersClosure::
101 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
102 DefNewGeneration* gen,
103 FastScanClosure* cur, FastScanClosure* older) :
104 _gch(gch), _level(level), _gen(gen),
105 _scan_cur_or_nonheap(cur), _scan_older(older)
106 {}
107
108 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
109 do {
110 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
111 _scan_older);
112 } while (!_gch->no_allocs_since_save_marks(_level));
113 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
114 }
115
116 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
117 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
118 {
119 assert(_g->level() == 0, "Optimized for youngest generation");
120 _boundary = _g->reserved().end();
121 }
122
123 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
124 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
125
126 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
127 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
128 {
129 assert(_g->level() == 0, "Optimized for youngest generation");
130 _boundary = _g->reserved().end();
131 }
132
133 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
134 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
135
136 void KlassScanClosure::do_klass(Klass* klass) {
137 #ifndef PRODUCT
138 if (TraceScavenge) {
139 ResourceMark rm;
140 gclog_or_tty->print_cr("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s",
141 p2i(klass),
142 klass->external_name(),
143 klass->has_modified_oops() ? "true" : "false");
144 }
145 #endif
146
147 // If the klass has not been dirtied we know that there's
148 // no references into the young gen and we can skip it.
149 if (klass->has_modified_oops()) {
150 if (_accumulate_modified_oops) {
151 klass->accumulate_modified_oops();
152 }
153
154 // Clear this state since we're going to scavenge all the metadata.
155 klass->clear_modified_oops();
156
157 // Tell the closure which Klass is being scanned so that it can be dirtied
158 // if oops are left pointing into the young gen.
159 _scavenge_closure->set_scanned_klass(klass);
160
161 klass->oops_do(_scavenge_closure);
162
163 _scavenge_closure->set_scanned_klass(NULL);
164 }
165 }
166
167 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
168 _g(g)
169 {
170 assert(_g->level() == 0, "Optimized for youngest generation");
171 _boundary = _g->reserved().end();
172 }
173
174 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
175 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
176
177 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
178 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
179
180 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
181 KlassRemSet* klass_rem_set)
182 : _scavenge_closure(scavenge_closure),
183 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
184
185
186 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
187 size_t initial_size,
188 int level,
189 const char* policy)
190 : Generation(rs, initial_size, level),
191 _promo_failure_drain_in_progress(false),
192 _should_allocate_from_space(false)
193 {
194 MemRegion cmr((HeapWord*)_virtual_space.low(),
195 (HeapWord*)_virtual_space.high());
196 Universe::heap()->barrier_set()->resize_covered_region(cmr);
197
198 _eden_space = new ContiguousSpace();
199 _from_space = new ContiguousSpace();
200 _to_space = new ContiguousSpace();
201
202 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
203 vm_exit_during_initialization("Could not allocate a new gen space");
204
205 // Compute the maximum eden and survivor space sizes. These sizes
206 // are computed assuming the entire reserved space is committed.
207 // These values are exported as performance counters.
208 uintx alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
209 uintx size = _virtual_space.reserved_size();
210 _max_survivor_size = compute_survivor_size(size, alignment);
211 _max_eden_size = size - (2*_max_survivor_size);
212
213 // allocate the performance counters
214 GenCollectorPolicy* gcp = (GenCollectorPolicy*) GenCollectedHeap::heap()->collector_policy();
215
216 // Generation counters -- generation 0, 3 subspaces
217 _gen_counters = new GenerationCounters("new", 0, 3,
218 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
219 _gc_counters = new CollectorCounters(policy, 0);
220
221 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
222 _gen_counters);
223 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
224 _gen_counters);
225 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
226 _gen_counters);
227
228 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
229 update_counters();
230 _old_gen = NULL;
231 _tenuring_threshold = MaxTenuringThreshold;
232 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
233
234 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
235 }
236
237 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
238 bool clear_space,
239 bool mangle_space) {
240 uintx alignment =
241 GenCollectedHeap::heap()->collector_policy()->space_alignment();
242
243 // If the spaces are being cleared (only done at heap initialization
244 // currently), the survivor spaces need not be empty.
245 // Otherwise, no care is taken for used areas in the survivor spaces
246 // so check.
247 assert(clear_space || (to()->is_empty() && from()->is_empty()),
248 "Initialization of the survivor spaces assumes these are empty");
249
250 // Compute sizes
251 uintx size = _virtual_space.committed_size();
252 uintx survivor_size = compute_survivor_size(size, alignment);
253 uintx eden_size = size - (2*survivor_size);
254 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
255
256 if (eden_size < minimum_eden_size) {
257 // May happen due to 64Kb rounding, if so adjust eden size back up
258 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
259 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
260 uintx unaligned_survivor_size =
261 align_size_down(maximum_survivor_size, alignment);
262 survivor_size = MAX2(unaligned_survivor_size, alignment);
263 eden_size = size - (2*survivor_size);
264 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
265 assert(eden_size >= minimum_eden_size, "just checking");
266 }
267
268 char *eden_start = _virtual_space.low();
269 char *from_start = eden_start + eden_size;
270 char *to_start = from_start + survivor_size;
271 char *to_end = to_start + survivor_size;
272
273 assert(to_end == _virtual_space.high(), "just checking");
274 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
275 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
276 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
277
278 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
279 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
280 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
281
282 // A minimum eden size implies that there is a part of eden that
283 // is being used and that affects the initialization of any
284 // newly formed eden.
285 bool live_in_eden = minimum_eden_size > 0;
286
287 // If not clearing the spaces, do some checking to verify that
288 // the space are already mangled.
289 if (!clear_space) {
290 // Must check mangling before the spaces are reshaped. Otherwise,
291 // the bottom or end of one space may have moved into another
292 // a failure of the check may not correctly indicate which space
293 // is not properly mangled.
294 if (ZapUnusedHeapArea) {
295 HeapWord* limit = (HeapWord*) _virtual_space.high();
296 eden()->check_mangled_unused_area(limit);
297 from()->check_mangled_unused_area(limit);
298 to()->check_mangled_unused_area(limit);
299 }
300 }
301
302 // Reset the spaces for their new regions.
303 eden()->initialize(edenMR,
304 clear_space && !live_in_eden,
305 SpaceDecorator::Mangle);
306 // If clear_space and live_in_eden, we will not have cleared any
307 // portion of eden above its top. This can cause newly
308 // expanded space not to be mangled if using ZapUnusedHeapArea.
309 // We explicitly do such mangling here.
310 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
311 eden()->mangle_unused_area();
312 }
313 from()->initialize(fromMR, clear_space, mangle_space);
314 to()->initialize(toMR, clear_space, mangle_space);
315
316 // Set next compaction spaces.
317 eden()->set_next_compaction_space(from());
318 // The to-space is normally empty before a compaction so need
319 // not be considered. The exception is during promotion
320 // failure handling when to-space can contain live objects.
321 from()->set_next_compaction_space(NULL);
322 }
323
324 void DefNewGeneration::swap_spaces() {
325 ContiguousSpace* s = from();
326 _from_space = to();
327 _to_space = s;
328 eden()->set_next_compaction_space(from());
329 // The to-space is normally empty before a compaction so need
330 // not be considered. The exception is during promotion
331 // failure handling when to-space can contain live objects.
332 from()->set_next_compaction_space(NULL);
333
334 if (UsePerfData) {
335 CSpaceCounters* c = _from_counters;
336 _from_counters = _to_counters;
337 _to_counters = c;
338 }
339 }
340
341 bool DefNewGeneration::expand(size_t bytes) {
342 MutexLocker x(ExpandHeap_lock);
343 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
344 bool success = _virtual_space.expand_by(bytes);
345 if (success && ZapUnusedHeapArea) {
346 // Mangle newly committed space immediately because it
347 // can be done here more simply that after the new
348 // spaces have been computed.
349 HeapWord* new_high = (HeapWord*) _virtual_space.high();
350 MemRegion mangle_region(prev_high, new_high);
351 SpaceMangler::mangle_region(mangle_region);
352 }
353
354 // Do not attempt an expand-to-the reserve size. The
355 // request should properly observe the maximum size of
356 // the generation so an expand-to-reserve should be
357 // unnecessary. Also a second call to expand-to-reserve
358 // value potentially can cause an undue expansion.
359 // For example if the first expand fail for unknown reasons,
360 // but the second succeeds and expands the heap to its maximum
361 // value.
362 if (GC_locker::is_active()) {
363 if (PrintGC && Verbose) {
364 gclog_or_tty->print_cr("Garbage collection disabled, "
365 "expanded heap instead");
366 }
367 }
368
369 return success;
370 }
371
372
373 void DefNewGeneration::compute_new_size() {
374 // This is called after a gc that includes the following generation
375 // (which is required to exist.) So from-space will normally be empty.
376 // Note that we check both spaces, since if scavenge failed they revert roles.
377 // If not we bail out (otherwise we would have to relocate the objects)
378 if (!from()->is_empty() || !to()->is_empty()) {
379 return;
380 }
381
382 int next_level = level() + 1;
383 GenCollectedHeap* gch = GenCollectedHeap::heap();
384 assert(next_level == 1, "DefNewGeneration must be a young gen");
385
386 Generation* old_gen = gch->old_gen();
387 size_t old_size = old_gen->capacity();
388 size_t new_size_before = _virtual_space.committed_size();
389 size_t min_new_size = spec()->init_size();
390 size_t max_new_size = reserved().byte_size();
391 assert(min_new_size <= new_size_before &&
392 new_size_before <= max_new_size,
393 "just checking");
394 // All space sizes must be multiples of Generation::GenGrain.
395 size_t alignment = Generation::GenGrain;
396
397 // Compute desired new generation size based on NewRatio and
398 // NewSizeThreadIncrease
399 size_t desired_new_size = old_size/NewRatio;
400 int threads_count = Threads::number_of_non_daemon_threads();
401 size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
402 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
403
404 // Adjust new generation size
405 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
406 assert(desired_new_size <= max_new_size, "just checking");
407
408 bool changed = false;
409 if (desired_new_size > new_size_before) {
410 size_t change = desired_new_size - new_size_before;
411 assert(change % alignment == 0, "just checking");
412 if (expand(change)) {
413 changed = true;
414 }
415 // If the heap failed to expand to the desired size,
416 // "changed" will be false. If the expansion failed
417 // (and at this point it was expected to succeed),
418 // ignore the failure (leaving "changed" as false).
419 }
420 if (desired_new_size < new_size_before && eden()->is_empty()) {
421 // bail out of shrinking if objects in eden
422 size_t change = new_size_before - desired_new_size;
423 assert(change % alignment == 0, "just checking");
424 _virtual_space.shrink_by(change);
425 changed = true;
426 }
427 if (changed) {
428 // The spaces have already been mangled at this point but
429 // may not have been cleared (set top = bottom) and should be.
430 // Mangling was done when the heap was being expanded.
431 compute_space_boundaries(eden()->used(),
432 SpaceDecorator::Clear,
433 SpaceDecorator::DontMangle);
434 MemRegion cmr((HeapWord*)_virtual_space.low(),
435 (HeapWord*)_virtual_space.high());
436 Universe::heap()->barrier_set()->resize_covered_region(cmr);
437 if (Verbose && PrintGC) {
438 size_t new_size_after = _virtual_space.committed_size();
439 size_t eden_size_after = eden()->capacity();
440 size_t survivor_size_after = from()->capacity();
441 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
442 SIZE_FORMAT "K [eden="
443 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
444 new_size_before/K, new_size_after/K,
445 eden_size_after/K, survivor_size_after/K);
446 if (WizardMode) {
447 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
448 thread_increase_size/K, threads_count);
449 }
450 gclog_or_tty->cr();
451 }
452 }
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()->space_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(" SIZE_FORMAT "):"
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 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->collector_policy()->counters();
556 _tenuring_threshold =
557 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize, gc_counters);
558 }
559
560 void DefNewGeneration::collect(bool full,
561 bool clear_all_soft_refs,
562 size_t size,
563 bool is_tlab) {
564 assert(full || size > 0, "otherwise we don't want to collect");
565
566 GenCollectedHeap* gch = GenCollectedHeap::heap();
567
568 _gc_timer->register_gc_start();
569 DefNewTracer gc_tracer;
570 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
571
572 _old_gen = gch->old_gen();
573
574 // If the next generation is too full to accommodate promotion
575 // from this generation, pass on collection; let the next generation
576 // do it.
577 if (!collection_attempt_is_safe()) {
578 if (Verbose && PrintGCDetails) {
579 gclog_or_tty->print(" :: Collection attempt not safe :: ");
580 }
581 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
582 return;
583 }
584 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
585
586 init_assuming_no_promotion_failure();
587
588 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, gc_tracer.gc_id());
589 // Capture heap used before collection (for printing).
590 size_t gch_prev_used = gch->used();
591
592 gch->trace_heap_before_gc(&gc_tracer);
593
594 // These can be shared for all code paths
595 IsAliveClosure is_alive(this);
596 ScanWeakRefClosure scan_weak_ref(this);
597
598 age_table()->clear();
599 to()->clear(SpaceDecorator::Mangle);
600
601 gch->rem_set()->prepare_for_younger_refs_iterate(false);
602
603 assert(gch->no_allocs_since_save_marks(0),
604 "save marks have not been newly set.");
605
606 // Not very pretty.
607 CollectorPolicy* cp = gch->collector_policy();
608
609 FastScanClosure fsc_with_no_gc_barrier(this, false);
610 FastScanClosure fsc_with_gc_barrier(this, true);
611
612 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
613 gch->rem_set()->klass_rem_set());
614 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
615 &fsc_with_no_gc_barrier,
616 false);
617
618 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
619 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
620 &fsc_with_no_gc_barrier,
621 &fsc_with_gc_barrier);
622
623 assert(gch->no_allocs_since_save_marks(0),
624 "save marks have not been newly set.");
625
626 gch->gen_process_roots(_level,
627 true, // Process younger gens, if any,
628 // as strong roots.
629 true, // activate StrongRootsScope
630 GenCollectedHeap::SO_ScavengeCodeCache,
631 GenCollectedHeap::StrongAndWeakRoots,
632 &fsc_with_no_gc_barrier,
633 &fsc_with_gc_barrier,
634 &cld_scan_closure);
635
636 // "evacuate followers".
637 evacuate_followers.do_void();
638
639 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
640 ReferenceProcessor* rp = ref_processor();
641 rp->setup_policy(clear_all_soft_refs);
642 const ReferenceProcessorStats& stats =
643 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
644 NULL, _gc_timer, gc_tracer.gc_id());
645 gc_tracer.report_gc_reference_stats(stats);
646
647 if (!_promotion_failed) {
648 // Swap the survivor spaces.
649 eden()->clear(SpaceDecorator::Mangle);
650 from()->clear(SpaceDecorator::Mangle);
651 if (ZapUnusedHeapArea) {
652 // This is now done here because of the piece-meal mangling which
653 // can check for valid mangling at intermediate points in the
654 // collection(s). When a minor collection fails to collect
655 // sufficient space resizing of the young generation can occur
656 // an redistribute the spaces in the young generation. Mangle
657 // here so that unzapped regions don't get distributed to
658 // other spaces.
659 to()->mangle_unused_area();
660 }
661 swap_spaces();
662
663 assert(to()->is_empty(), "to space should be empty now");
664
665 adjust_desired_tenuring_threshold();
666
667 // A successful scavenge should restart the GC time limit count which is
668 // for full GC's.
669 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
670 size_policy->reset_gc_overhead_limit_count();
671 assert(!gch->incremental_collection_failed(), "Should be clear");
672 } else {
673 assert(_promo_failure_scan_stack.is_empty(), "post condition");
674 _promo_failure_scan_stack.clear(true); // Clear cached segments.
675
676 remove_forwarding_pointers();
677 if (PrintGCDetails) {
678 gclog_or_tty->print(" (promotion failed) ");
679 }
680 // Add to-space to the list of space to compact
681 // when a promotion failure has occurred. In that
682 // case there can be live objects in to-space
683 // as a result of a partial evacuation of eden
684 // and from-space.
685 swap_spaces(); // For uniformity wrt ParNewGeneration.
686 from()->set_next_compaction_space(to());
687 gch->set_incremental_collection_failed();
688
689 // Inform the next generation that a promotion failure occurred.
690 _old_gen->promotion_failure_occurred();
691 gc_tracer.report_promotion_failed(_promotion_failed_info);
692
693 // Reset the PromotionFailureALot counters.
694 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
695 }
696 if (PrintGC && !PrintGCDetails) {
697 gch->print_heap_change(gch_prev_used);
698 }
699 // set new iteration safe limit for the survivor spaces
700 from()->set_concurrent_iteration_safe_limit(from()->top());
701 to()->set_concurrent_iteration_safe_limit(to()->top());
702
703 // We need to use a monotonically non-decreasing time in ms
704 // or we will see time-warp warnings and os::javaTimeMillis()
705 // does not guarantee monotonicity.
706 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
707 update_time_of_last_gc(now);
708
709 gch->trace_heap_after_gc(&gc_tracer);
710 gc_tracer.report_tenuring_threshold(tenuring_threshold());
711
712 _gc_timer->register_gc_end();
713
714 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
715 }
716
717 class RemoveForwardPointerClosure: public ObjectClosure {
718 public:
719 void do_object(oop obj) {
720 obj->init_mark();
721 }
722 };
723
724 void DefNewGeneration::init_assuming_no_promotion_failure() {
725 _promotion_failed = false;
726 _promotion_failed_info.reset();
727 from()->set_next_compaction_space(NULL);
728 }
729
730 void DefNewGeneration::remove_forwarding_pointers() {
731 RemoveForwardPointerClosure rspc;
732 eden()->object_iterate(&rspc);
733 from()->object_iterate(&rspc);
734
735 // Now restore saved marks, if any.
736 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
737 "should be the same");
738 while (!_objs_with_preserved_marks.is_empty()) {
739 oop obj = _objs_with_preserved_marks.pop();
740 markOop m = _preserved_marks_of_objs.pop();
741 obj->set_mark(m);
742 }
743 _objs_with_preserved_marks.clear(true);
744 _preserved_marks_of_objs.clear(true);
745 }
746
747 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
748 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
749 "Oversaving!");
750 _objs_with_preserved_marks.push(obj);
751 _preserved_marks_of_objs.push(m);
752 }
753
754 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
755 if (m->must_be_preserved_for_promotion_failure(obj)) {
756 preserve_mark(obj, m);
757 }
758 }
759
760 void DefNewGeneration::handle_promotion_failure(oop old) {
761 if (PrintPromotionFailure && !_promotion_failed) {
762 gclog_or_tty->print(" (promotion failure size = %d) ",
763 old->size());
764 }
765 _promotion_failed = true;
766 _promotion_failed_info.register_copy_failure(old->size());
767 preserve_mark_if_necessary(old, old->mark());
768 // forward to self
769 old->forward_to(old);
770
771 _promo_failure_scan_stack.push(old);
772
773 if (!_promo_failure_drain_in_progress) {
774 // prevent recursion in copy_to_survivor_space()
775 _promo_failure_drain_in_progress = true;
776 drain_promo_failure_scan_stack();
777 _promo_failure_drain_in_progress = false;
778 }
779 }
780
781 oop DefNewGeneration::copy_to_survivor_space(oop old) {
782 assert(is_in_reserved(old) && !old->is_forwarded(),
783 "shouldn't be scavenging this oop");
784 size_t s = old->size();
785 oop obj = NULL;
786
787 // Try allocating obj in to-space (unless too old)
788 if (old->age() < tenuring_threshold()) {
789 obj = (oop) to()->allocate_aligned(s);
790 }
791
792 // Otherwise try allocating obj tenured
793 if (obj == NULL) {
794 obj = _old_gen->promote(old, s);
795 if (obj == NULL) {
796 handle_promotion_failure(old);
797 return old;
798 }
799 } else {
800 // Prefetch beyond obj
801 const intx interval = PrefetchCopyIntervalInBytes;
802 Prefetch::write(obj, interval);
803
804 // Copy obj
805 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
806
807 // Increment age if obj still in new generation
808 obj->incr_age();
809 age_table()->add(obj, s);
810 }
811
812 // Done, insert forward pointer to obj in this header
813 old->forward_to(obj);
814
815 return obj;
816 }
817
818 void DefNewGeneration::drain_promo_failure_scan_stack() {
819 while (!_promo_failure_scan_stack.is_empty()) {
820 oop obj = _promo_failure_scan_stack.pop();
821 obj->oop_iterate(_promo_failure_scan_stack_closure);
822 }
823 }
824
825 void DefNewGeneration::save_marks() {
826 eden()->set_saved_mark();
827 to()->set_saved_mark();
828 from()->set_saved_mark();
829 }
830
831
832 void DefNewGeneration::reset_saved_marks() {
833 eden()->reset_saved_mark();
834 to()->reset_saved_mark();
835 from()->reset_saved_mark();
836 }
837
838
839 bool DefNewGeneration::no_allocs_since_save_marks() {
840 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
841 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
842 return to()->saved_mark_at_top();
843 }
844
845 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
846 \
847 void DefNewGeneration:: \
848 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
849 cl->set_generation(this); \
850 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
851 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
852 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
853 cl->reset_generation(); \
854 save_marks(); \
855 }
856
857 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
858
859 #undef DefNew_SINCE_SAVE_MARKS_DEFN
860
861 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
862 size_t max_alloc_words) {
863 if (requestor == this || _promotion_failed) return;
864 assert(requestor->level() > level(), "DefNewGeneration must be youngest");
865
866 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
867 if (to_space->top() > to_space->bottom()) {
868 trace("to_space not empty when contribute_scratch called");
869 }
870 */
871
872 ContiguousSpace* to_space = to();
873 assert(to_space->end() >= to_space->top(), "pointers out of order");
874 size_t free_words = pointer_delta(to_space->end(), to_space->top());
875 if (free_words >= MinFreeScratchWords) {
876 ScratchBlock* sb = (ScratchBlock*)to_space->top();
877 sb->num_words = free_words;
878 sb->next = list;
879 list = sb;
880 }
881 }
882
883 void DefNewGeneration::reset_scratch() {
884 // If contributing scratch in to_space, mangle all of
885 // to_space if ZapUnusedHeapArea. This is needed because
886 // top is not maintained while using to-space as scratch.
887 if (ZapUnusedHeapArea) {
888 to()->mangle_unused_area_complete();
889 }
890 }
891
892 bool DefNewGeneration::collection_attempt_is_safe() {
893 if (!to()->is_empty()) {
894 if (Verbose && PrintGCDetails) {
895 gclog_or_tty->print(" :: to is not empty :: ");
896 }
897 return false;
898 }
899 if (_old_gen == NULL) {
900 GenCollectedHeap* gch = GenCollectedHeap::heap();
901 _old_gen = gch->old_gen();
902 }
903 return _old_gen->promotion_attempt_is_safe(used());
904 }
905
906 void DefNewGeneration::gc_epilogue(bool full) {
907 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
908
909 assert(!GC_locker::is_active(), "We should not be executing here");
910 // Check if the heap is approaching full after a collection has
911 // been done. Generally the young generation is empty at
912 // a minimum at the end of a collection. If it is not, then
913 // the heap is approaching full.
914 GenCollectedHeap* gch = GenCollectedHeap::heap();
915 if (full) {
916 DEBUG_ONLY(seen_incremental_collection_failed = false;)
917 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
918 if (Verbose && PrintGCDetails) {
919 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
920 GCCause::to_string(gch->gc_cause()));
921 }
922 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
923 set_should_allocate_from_space(); // we seem to be running out of space
924 } else {
925 if (Verbose && PrintGCDetails) {
926 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
927 GCCause::to_string(gch->gc_cause()));
928 }
929 gch->clear_incremental_collection_failed(); // We just did a full collection
930 clear_should_allocate_from_space(); // if set
931 }
932 } else {
933 #ifdef ASSERT
934 // It is possible that incremental_collection_failed() == true
935 // here, because an attempted scavenge did not succeed. The policy
936 // is normally expected to cause a full collection which should
937 // clear that condition, so we should not be here twice in a row
938 // with incremental_collection_failed() == true without having done
939 // a full collection in between.
940 if (!seen_incremental_collection_failed &&
941 gch->incremental_collection_failed()) {
942 if (Verbose && PrintGCDetails) {
943 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
944 GCCause::to_string(gch->gc_cause()));
945 }
946 seen_incremental_collection_failed = true;
947 } else if (seen_incremental_collection_failed) {
948 if (Verbose && PrintGCDetails) {
949 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
950 GCCause::to_string(gch->gc_cause()));
951 }
952 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
953 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
954 !gch->incremental_collection_failed(),
955 "Twice in a row");
956 seen_incremental_collection_failed = false;
957 }
958 #endif // ASSERT
959 }
960
961 if (ZapUnusedHeapArea) {
962 eden()->check_mangled_unused_area_complete();
963 from()->check_mangled_unused_area_complete();
964 to()->check_mangled_unused_area_complete();
965 }
966
967 if (!CleanChunkPoolAsync) {
968 Chunk::clean_chunk_pool();
969 }
970
971 // update the generation and space performance counters
972 update_counters();
973 gch->collector_policy()->counters()->update_counters();
974 }
975
976 void DefNewGeneration::record_spaces_top() {
977 assert(ZapUnusedHeapArea, "Not mangling unused space");
978 eden()->set_top_for_allocations();
979 to()->set_top_for_allocations();
980 from()->set_top_for_allocations();
981 }
982
983 void DefNewGeneration::ref_processor_init() {
984 Generation::ref_processor_init();
985 }
986
987
988 void DefNewGeneration::update_counters() {
989 if (UsePerfData) {
990 _eden_counters->update_all();
991 _from_counters->update_all();
992 _to_counters->update_all();
993 _gen_counters->update_all();
994 }
995 }
996
997 void DefNewGeneration::verify() {
998 eden()->verify();
999 from()->verify();
1000 to()->verify();
1001 }
1002
1003 void DefNewGeneration::print_on(outputStream* st) const {
1004 Generation::print_on(st);
1005 st->print(" eden");
1006 eden()->print_on(st);
1007 st->print(" from");
1008 from()->print_on(st);
1009 st->print(" to ");
1010 to()->print_on(st);
1011 }
1012
1013
1014 const char* DefNewGeneration::name() const {
1015 return "def new generation";
1016 }
1017
1018 // Moved from inline file as they are not called inline
1019 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1020 return eden();
1021 }
1022
1023 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1024 // This is the slow-path allocation for the DefNewGeneration.
1025 // Most allocations are fast-path in compiled code.
1026 // We try to allocate from the eden. If that works, we are happy.
1027 // Note that since DefNewGeneration supports lock-free allocation, we
1028 // have to use it here, as well.
1029 HeapWord* result = eden()->par_allocate(word_size);
1030 if (result != NULL) {
1031 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1032 _old_gen->sample_eden_chunk();
1033 }
1034 } else {
1035 // If the eden is full and the last collection bailed out, we are running
1036 // out of heap space, and we try to allocate the from-space, too.
1037 // allocate_from_space can't be inlined because that would introduce a
1038 // circular dependency at compile time.
1039 result = allocate_from_space(word_size);
1040 }
1041 return result;
1042 }
1043
1044 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1045 bool is_tlab) {
1046 HeapWord* res = eden()->par_allocate(word_size);
1047 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1048 _old_gen->sample_eden_chunk();
1049 }
1050 return res;
1051 }
1052
1053 size_t DefNewGeneration::tlab_capacity() const {
1054 return eden()->capacity();
1055 }
1056
1057 size_t DefNewGeneration::tlab_used() const {
1058 return eden()->used();
1059 }
1060
1061 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1062 return unsafe_max_alloc_nogc();
1063 }