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/cardTableRS.hpp"
28 #include "gc/shared/collectorCounters.hpp"
29 #include "gc/shared/gcHeapSummary.hpp"
30 #include "gc/shared/gcLocker.inline.hpp"
31 #include "gc/shared/gcPolicyCounters.hpp"
32 #include "gc/shared/gcTimer.hpp"
33 #include "gc/shared/gcTrace.hpp"
34 #include "gc/shared/gcTraceTime.hpp"
35 #include "gc/shared/genCollectedHeap.hpp"
36 #include "gc/shared/genOopClosures.inline.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 _rs = GenCollectedHeap::heap()->rem_set();
73 }
74
75 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
76 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
77
78
79 DefNewGeneration::FastKeepAliveClosure::
80 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
81 DefNewGeneration::KeepAliveClosure(cl) {
82 _boundary = g->reserved().end();
83 }
84
85 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
86 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
87
88 DefNewGeneration::EvacuateFollowersClosure::
89 EvacuateFollowersClosure(GenCollectedHeap* gch,
90 ScanClosure* cur,
91 ScanClosure* older) :
92 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
93 {}
94
95 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
96 do {
97 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
98 } while (!_gch->no_allocs_since_save_marks());
99 }
100
101 DefNewGeneration::FastEvacuateFollowersClosure::
102 FastEvacuateFollowersClosure(GenCollectedHeap* gch,
103 FastScanClosure* cur,
104 FastScanClosure* older) :
105 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
106 {
107 assert(_gch->young_gen()->kind() == Generation::DefNew, "Generation should be DefNew");
108 _young_gen = (DefNewGeneration*)_gch->young_gen();
109 }
110
111 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
112 do {
113 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
114 } while (!_gch->no_allocs_since_save_marks());
115 guarantee(_young_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
116 }
117
118 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
119 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
120 {
121 _boundary = _g->reserved().end();
122 }
123
124 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
125 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
126
127 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
128 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
129 {
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 _boundary = _g->reserved().end();
171 }
172
173 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
174 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
175
176 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
177 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
178
179 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
180 KlassRemSet* klass_rem_set)
181 : _scavenge_closure(scavenge_closure),
182 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
183
184
185 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
186 size_t initial_size,
187 const char* policy)
188 : Generation(rs, initial_size),
189 _promo_failure_drain_in_progress(false),
190 _should_allocate_from_space(false)
191 {
192 MemRegion cmr((HeapWord*)_virtual_space.low(),
193 (HeapWord*)_virtual_space.high());
194 GenCollectedHeap* gch = GenCollectedHeap::heap();
195
196 gch->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
206 // Compute the maximum eden and survivor space sizes. These sizes
207 // are computed assuming the entire reserved space is committed.
208 // These values are exported as performance counters.
209 uintx alignment = gch->collector_policy()->space_alignment();
210 uintx size = _virtual_space.reserved_size();
211 _max_survivor_size = compute_survivor_size(size, alignment);
212 _max_eden_size = size - (2*_max_survivor_size);
213
214 // allocate the performance counters
215 GenCollectorPolicy* gcp = gch->gen_policy();
216
217 // Generation counters -- generation 0, 3 subspaces
218 _gen_counters = new GenerationCounters("new", 0, 3,
219 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
220 _gc_counters = new CollectorCounters(policy, 0);
221
222 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
223 _gen_counters);
224 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
225 _gen_counters);
226 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
227 _gen_counters);
228
229 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
230 update_counters();
231 _old_gen = NULL;
232 _tenuring_threshold = MaxTenuringThreshold;
233 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
234
235 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
236 }
237
238 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
239 bool clear_space,
240 bool mangle_space) {
241 uintx alignment =
242 GenCollectedHeap::heap()->collector_policy()->space_alignment();
243
244 // If the spaces are being cleared (only done at heap initialization
245 // currently), the survivor spaces need not be empty.
246 // Otherwise, no care is taken for used areas in the survivor spaces
247 // so check.
248 assert(clear_space || (to()->is_empty() && from()->is_empty()),
249 "Initialization of the survivor spaces assumes these are empty");
250
251 // Compute sizes
252 uintx size = _virtual_space.committed_size();
253 uintx survivor_size = compute_survivor_size(size, alignment);
254 uintx eden_size = size - (2*survivor_size);
255 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
256
257 if (eden_size < minimum_eden_size) {
258 // May happen due to 64Kb rounding, if so adjust eden size back up
259 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
260 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
261 uintx unaligned_survivor_size =
262 align_size_down(maximum_survivor_size, alignment);
263 survivor_size = MAX2(unaligned_survivor_size, alignment);
264 eden_size = size - (2*survivor_size);
265 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
266 assert(eden_size >= minimum_eden_size, "just checking");
267 }
268
269 char *eden_start = _virtual_space.low();
270 char *from_start = eden_start + eden_size;
271 char *to_start = from_start + survivor_size;
272 char *to_end = to_start + survivor_size;
273
274 assert(to_end == _virtual_space.high(), "just checking");
275 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
276 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
277 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
278
279 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
280 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
281 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
282
283 // A minimum eden size implies that there is a part of eden that
284 // is being used and that affects the initialization of any
285 // newly formed eden.
286 bool live_in_eden = minimum_eden_size > 0;
287
288 // If not clearing the spaces, do some checking to verify that
289 // the space are already mangled.
290 if (!clear_space) {
291 // Must check mangling before the spaces are reshaped. Otherwise,
292 // the bottom or end of one space may have moved into another
293 // a failure of the check may not correctly indicate which space
294 // is not properly mangled.
295 if (ZapUnusedHeapArea) {
296 HeapWord* limit = (HeapWord*) _virtual_space.high();
297 eden()->check_mangled_unused_area(limit);
298 from()->check_mangled_unused_area(limit);
299 to()->check_mangled_unused_area(limit);
300 }
301 }
302
303 // Reset the spaces for their new regions.
304 eden()->initialize(edenMR,
305 clear_space && !live_in_eden,
306 SpaceDecorator::Mangle);
307 // If clear_space and live_in_eden, we will not have cleared any
308 // portion of eden above its top. This can cause newly
309 // expanded space not to be mangled if using ZapUnusedHeapArea.
310 // We explicitly do such mangling here.
311 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
312 eden()->mangle_unused_area();
313 }
314 from()->initialize(fromMR, clear_space, mangle_space);
315 to()->initialize(toMR, clear_space, mangle_space);
316
317 // Set next compaction spaces.
318 eden()->set_next_compaction_space(from());
319 // The to-space is normally empty before a compaction so need
320 // not be considered. The exception is during promotion
321 // failure handling when to-space can contain live objects.
322 from()->set_next_compaction_space(NULL);
323 }
324
325 void DefNewGeneration::swap_spaces() {
326 ContiguousSpace* s = from();
327 _from_space = to();
328 _to_space = s;
329 eden()->set_next_compaction_space(from());
330 // The to-space is normally empty before a compaction so need
331 // not be considered. The exception is during promotion
332 // failure handling when to-space can contain live objects.
333 from()->set_next_compaction_space(NULL);
334
335 if (UsePerfData) {
336 CSpaceCounters* c = _from_counters;
337 _from_counters = _to_counters;
338 _to_counters = c;
339 }
340 }
341
342 bool DefNewGeneration::expand(size_t bytes) {
343 MutexLocker x(ExpandHeap_lock);
344 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
345 bool success = _virtual_space.expand_by(bytes);
346 if (success && ZapUnusedHeapArea) {
347 // Mangle newly committed space immediately because it
348 // can be done here more simply that after the new
349 // spaces have been computed.
350 HeapWord* new_high = (HeapWord*) _virtual_space.high();
351 MemRegion mangle_region(prev_high, new_high);
352 SpaceMangler::mangle_region(mangle_region);
353 }
354
355 // Do not attempt an expand-to-the reserve size. The
356 // request should properly observe the maximum size of
357 // the generation so an expand-to-reserve should be
358 // unnecessary. Also a second call to expand-to-reserve
359 // value potentially can cause an undue expansion.
360 // For example if the first expand fail for unknown reasons,
361 // but the second succeeds and expands the heap to its maximum
362 // value.
363 if (GC_locker::is_active()) {
364 if (PrintGC && Verbose) {
365 gclog_or_tty->print_cr("Garbage collection disabled, "
366 "expanded heap instead");
367 }
368 }
369
370 return success;
371 }
372
373 void DefNewGeneration::compute_new_size() {
374 // This is called after a GC that includes the old generation, so from-space
375 // 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 GenCollectedHeap* gch = GenCollectedHeap::heap();
383
384 size_t old_size = gch->old_gen()->capacity();
385 size_t new_size_before = _virtual_space.committed_size();
386 size_t min_new_size = initial_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 gch->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, uint n_threads) {
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(" SIZE_FORMAT "):"
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 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->collector_policy()->counters();
553 _tenuring_threshold =
554 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize, gc_counters);
555 }
556
557 void DefNewGeneration::collect(bool full,
558 bool clear_all_soft_refs,
559 size_t size,
560 bool is_tlab) {
561 assert(full || size > 0, "otherwise we don't want to collect");
562
563 GenCollectedHeap* gch = GenCollectedHeap::heap();
564
565 _gc_timer->register_gc_start();
566 DefNewTracer gc_tracer;
567 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
568
569 _old_gen = gch->old_gen();
570
571 // If the next generation is too full to accommodate promotion
572 // from this generation, pass on collection; let the next generation
573 // do it.
574 if (!collection_attempt_is_safe()) {
575 if (Verbose && PrintGCDetails) {
576 gclog_or_tty->print(" :: Collection attempt not safe :: ");
577 }
578 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
579 return;
580 }
581 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
582
583 init_assuming_no_promotion_failure();
584
585 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL);
586 // Capture heap used before collection (for printing).
587 size_t gch_prev_used = gch->used();
588
589 gch->trace_heap_before_gc(&gc_tracer);
590
591 // These can be shared for all code paths
592 IsAliveClosure is_alive(this);
593 ScanWeakRefClosure scan_weak_ref(this);
594
595 age_table()->clear();
596 to()->clear(SpaceDecorator::Mangle);
597
598 gch->rem_set()->prepare_for_younger_refs_iterate(false);
599
600 assert(gch->no_allocs_since_save_marks(),
601 "save marks have not been newly set.");
602
603 // Not very pretty.
604 CollectorPolicy* cp = gch->collector_policy();
605
606 FastScanClosure fsc_with_no_gc_barrier(this, false);
607 FastScanClosure fsc_with_gc_barrier(this, true);
608
609 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
610 gch->rem_set()->klass_rem_set());
611 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
612 &fsc_with_no_gc_barrier,
613 false);
614
615 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
616 FastEvacuateFollowersClosure evacuate_followers(gch,
617 &fsc_with_no_gc_barrier,
618 &fsc_with_gc_barrier);
619
620 assert(gch->no_allocs_since_save_marks(),
621 "save marks have not been newly set.");
622
623 {
624 // DefNew needs to run with n_threads == 0, to make sure the serial
625 // version of the card table scanning code is used.
626 // See: CardTableModRefBSForCTRS::non_clean_card_iterate_possibly_parallel.
627 StrongRootsScope srs(0);
628
629 gch->gen_process_roots(&srs,
630 GenCollectedHeap::YoungGen,
631 true, // Process younger gens, if any,
632 // as strong roots.
633 GenCollectedHeap::SO_ScavengeCodeCache,
634 GenCollectedHeap::StrongAndWeakRoots,
635 &fsc_with_no_gc_barrier,
636 &fsc_with_gc_barrier,
637 &cld_scan_closure);
638 }
639
640 // "evacuate followers".
641 evacuate_followers.do_void();
642
643 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
644 ReferenceProcessor* rp = ref_processor();
645 rp->setup_policy(clear_all_soft_refs);
646 const ReferenceProcessorStats& stats =
647 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
648 NULL, _gc_timer);
649 gc_tracer.report_gc_reference_stats(stats);
650 gc_tracer.report_tenuring_threshold(tenuring_threshold());
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
716 _gc_timer->register_gc_end();
717
718 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
719 }
720
721 class RemoveForwardPointerClosure: public ObjectClosure {
722 public:
723 void do_object(oop obj) {
724 obj->init_mark();
725 }
726 };
727
728 void DefNewGeneration::init_assuming_no_promotion_failure() {
729 _promotion_failed = false;
730 _promotion_failed_info.reset();
731 from()->set_next_compaction_space(NULL);
732 }
733
734 void DefNewGeneration::remove_forwarding_pointers() {
735 RemoveForwardPointerClosure rspc;
736 eden()->object_iterate(&rspc);
737 from()->object_iterate(&rspc);
738
739 // Now restore saved marks, if any.
740 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
741 "should be the same");
742 while (!_objs_with_preserved_marks.is_empty()) {
743 oop obj = _objs_with_preserved_marks.pop();
744 markOop m = _preserved_marks_of_objs.pop();
745 obj->set_mark(m);
746 }
747 _objs_with_preserved_marks.clear(true);
748 _preserved_marks_of_objs.clear(true);
749 }
750
751 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
752 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
753 "Oversaving!");
754 _objs_with_preserved_marks.push(obj);
755 _preserved_marks_of_objs.push(m);
756 }
757
758 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
759 if (m->must_be_preserved_for_promotion_failure(obj)) {
760 preserve_mark(obj, m);
761 }
762 }
763
764 void DefNewGeneration::handle_promotion_failure(oop old) {
765 if (PrintPromotionFailure && !_promotion_failed) {
766 gclog_or_tty->print(" (promotion failure size = %d) ",
767 old->size());
768 }
769 _promotion_failed = true;
770 _promotion_failed_info.register_copy_failure(old->size());
771 preserve_mark_if_necessary(old, old->mark());
772 // forward to self
773 old->forward_to(old);
774
775 _promo_failure_scan_stack.push(old);
776
777 if (!_promo_failure_drain_in_progress) {
778 // prevent recursion in copy_to_survivor_space()
779 _promo_failure_drain_in_progress = true;
780 drain_promo_failure_scan_stack();
781 _promo_failure_drain_in_progress = false;
782 }
783 }
784
785 oop DefNewGeneration::copy_to_survivor_space(oop old) {
786 assert(is_in_reserved(old) && !old->is_forwarded(),
787 "shouldn't be scavenging this oop");
788 size_t s = old->size();
789 oop obj = NULL;
790
791 // Try allocating obj in to-space (unless too old)
792 if (old->age() < tenuring_threshold()) {
793 obj = (oop) to()->allocate_aligned(s);
794 }
795
796 // Otherwise try allocating obj tenured
797 if (obj == NULL) {
798 obj = _old_gen->promote(old, s);
799 if (obj == NULL) {
800 handle_promotion_failure(old);
801 return old;
802 }
803 } else {
804 // Prefetch beyond obj
805 const intx interval = PrefetchCopyIntervalInBytes;
806 Prefetch::write(obj, interval);
807
808 // Copy obj
809 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
810
811 // Increment age if obj still in new generation
812 obj->incr_age();
813 age_table()->add(obj, s);
814 }
815
816 // Done, insert forward pointer to obj in this header
817 old->forward_to(obj);
818
819 return obj;
820 }
821
822 void DefNewGeneration::drain_promo_failure_scan_stack() {
823 while (!_promo_failure_scan_stack.is_empty()) {
824 oop obj = _promo_failure_scan_stack.pop();
825 obj->oop_iterate(_promo_failure_scan_stack_closure);
826 }
827 }
828
829 void DefNewGeneration::save_marks() {
830 eden()->set_saved_mark();
831 to()->set_saved_mark();
832 from()->set_saved_mark();
833 }
834
835
836 void DefNewGeneration::reset_saved_marks() {
837 eden()->reset_saved_mark();
838 to()->reset_saved_mark();
839 from()->reset_saved_mark();
840 }
841
842
843 bool DefNewGeneration::no_allocs_since_save_marks() {
844 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
845 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
846 return to()->saved_mark_at_top();
847 }
848
849 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
850 \
851 void DefNewGeneration:: \
852 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
853 cl->set_generation(this); \
854 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
855 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
856 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
857 cl->reset_generation(); \
858 save_marks(); \
859 }
860
861 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
862
863 #undef DefNew_SINCE_SAVE_MARKS_DEFN
864
865 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
866 size_t max_alloc_words) {
867 if (requestor == this || _promotion_failed) {
868 return;
869 }
870 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
871
872 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
873 if (to_space->top() > to_space->bottom()) {
874 trace("to_space not empty when contribute_scratch called");
875 }
876 */
877
878 ContiguousSpace* to_space = to();
879 assert(to_space->end() >= to_space->top(), "pointers out of order");
880 size_t free_words = pointer_delta(to_space->end(), to_space->top());
881 if (free_words >= MinFreeScratchWords) {
882 ScratchBlock* sb = (ScratchBlock*)to_space->top();
883 sb->num_words = free_words;
884 sb->next = list;
885 list = sb;
886 }
887 }
888
889 void DefNewGeneration::reset_scratch() {
890 // If contributing scratch in to_space, mangle all of
891 // to_space if ZapUnusedHeapArea. This is needed because
892 // top is not maintained while using to-space as scratch.
893 if (ZapUnusedHeapArea) {
894 to()->mangle_unused_area_complete();
895 }
896 }
897
898 bool DefNewGeneration::collection_attempt_is_safe() {
899 if (!to()->is_empty()) {
900 if (Verbose && PrintGCDetails) {
901 gclog_or_tty->print(" :: to is not empty :: ");
902 }
903 return false;
904 }
905 if (_old_gen == NULL) {
906 GenCollectedHeap* gch = GenCollectedHeap::heap();
907 _old_gen = gch->old_gen();
908 }
909 return _old_gen->promotion_attempt_is_safe(used());
910 }
911
912 void DefNewGeneration::gc_epilogue(bool full) {
913 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
914
915 assert(!GC_locker::is_active(), "We should not be executing here");
916 // Check if the heap is approaching full after a collection has
917 // been done. Generally the young generation is empty at
918 // a minimum at the end of a collection. If it is not, then
919 // the heap is approaching full.
920 GenCollectedHeap* gch = GenCollectedHeap::heap();
921 if (full) {
922 DEBUG_ONLY(seen_incremental_collection_failed = false;)
923 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
924 if (Verbose && PrintGCDetails) {
925 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
926 GCCause::to_string(gch->gc_cause()));
927 }
928 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
929 set_should_allocate_from_space(); // we seem to be running out of space
930 } else {
931 if (Verbose && PrintGCDetails) {
932 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
933 GCCause::to_string(gch->gc_cause()));
934 }
935 gch->clear_incremental_collection_failed(); // We just did a full collection
936 clear_should_allocate_from_space(); // if set
937 }
938 } else {
939 #ifdef ASSERT
940 // It is possible that incremental_collection_failed() == true
941 // here, because an attempted scavenge did not succeed. The policy
942 // is normally expected to cause a full collection which should
943 // clear that condition, so we should not be here twice in a row
944 // with incremental_collection_failed() == true without having done
945 // a full collection in between.
946 if (!seen_incremental_collection_failed &&
947 gch->incremental_collection_failed()) {
948 if (Verbose && PrintGCDetails) {
949 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
950 GCCause::to_string(gch->gc_cause()));
951 }
952 seen_incremental_collection_failed = true;
953 } else if (seen_incremental_collection_failed) {
954 if (Verbose && PrintGCDetails) {
955 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
956 GCCause::to_string(gch->gc_cause()));
957 }
958 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
959 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
960 !gch->incremental_collection_failed(),
961 "Twice in a row");
962 seen_incremental_collection_failed = false;
963 }
964 #endif // ASSERT
965 }
966
967 if (ZapUnusedHeapArea) {
968 eden()->check_mangled_unused_area_complete();
969 from()->check_mangled_unused_area_complete();
970 to()->check_mangled_unused_area_complete();
971 }
972
973 if (!CleanChunkPoolAsync) {
974 Chunk::clean_chunk_pool();
975 }
976
977 // update the generation and space performance counters
978 update_counters();
979 gch->collector_policy()->counters()->update_counters();
980 }
981
982 void DefNewGeneration::record_spaces_top() {
983 assert(ZapUnusedHeapArea, "Not mangling unused space");
984 eden()->set_top_for_allocations();
985 to()->set_top_for_allocations();
986 from()->set_top_for_allocations();
987 }
988
989 void DefNewGeneration::ref_processor_init() {
990 Generation::ref_processor_init();
991 }
992
993
994 void DefNewGeneration::update_counters() {
995 if (UsePerfData) {
996 _eden_counters->update_all();
997 _from_counters->update_all();
998 _to_counters->update_all();
999 _gen_counters->update_all();
1000 }
1001 }
1002
1003 void DefNewGeneration::verify() {
1004 eden()->verify();
1005 from()->verify();
1006 to()->verify();
1007 }
1008
1009 void DefNewGeneration::print_on(outputStream* st) const {
1010 Generation::print_on(st);
1011 st->print(" eden");
1012 eden()->print_on(st);
1013 st->print(" from");
1014 from()->print_on(st);
1015 st->print(" to ");
1016 to()->print_on(st);
1017 }
1018
1019
1020 const char* DefNewGeneration::name() const {
1021 return "def new generation";
1022 }
1023
1024 // Moved from inline file as they are not called inline
1025 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1026 return eden();
1027 }
1028
1029 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1030 // This is the slow-path allocation for the DefNewGeneration.
1031 // Most allocations are fast-path in compiled code.
1032 // We try to allocate from the eden. If that works, we are happy.
1033 // Note that since DefNewGeneration supports lock-free allocation, we
1034 // have to use it here, as well.
1035 HeapWord* result = eden()->par_allocate(word_size);
1036 if (result != NULL) {
1037 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1038 _old_gen->sample_eden_chunk();
1039 }
1040 } else {
1041 // If the eden is full and the last collection bailed out, we are running
1042 // out of heap space, and we try to allocate the from-space, too.
1043 // allocate_from_space can't be inlined because that would introduce a
1044 // circular dependency at compile time.
1045 result = allocate_from_space(word_size);
1046 }
1047 return result;
1048 }
1049
1050 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1051 bool is_tlab) {
1052 HeapWord* res = eden()->par_allocate(word_size);
1053 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1054 _old_gen->sample_eden_chunk();
1055 }
1056 return res;
1057 }
1058
1059 size_t DefNewGeneration::tlab_capacity() const {
1060 return eden()->capacity();
1061 }
1062
1063 size_t DefNewGeneration::tlab_used() const {
1064 return eden()->used();
1065 }
1066
1067 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1068 return unsafe_max_alloc_nogc();
1069 }