1 /*
2 * Copyright (c) 2001, 2018, 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/serial/serialHeap.inline.hpp"
28 #include "gc/serial/tenuredGeneration.hpp"
29 #include "gc/shared/adaptiveSizePolicy.hpp"
30 #include "gc/shared/ageTable.inline.hpp"
31 #include "gc/shared/cardTableRS.hpp"
32 #include "gc/shared/collectorCounters.hpp"
33 #include "gc/shared/gcArguments.hpp"
34 #include "gc/shared/gcHeapSummary.hpp"
35 #include "gc/shared/gcLocker.hpp"
36 #include "gc/shared/gcPolicyCounters.hpp"
37 #include "gc/shared/gcTimer.hpp"
38 #include "gc/shared/gcTrace.hpp"
39 #include "gc/shared/gcTraceTime.inline.hpp"
40 #include "gc/shared/genOopClosures.inline.hpp"
41 #include "gc/shared/generationSpec.hpp"
42 #include "gc/shared/preservedMarks.inline.hpp"
43 #include "gc/shared/referencePolicy.hpp"
44 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
45 #include "gc/shared/space.inline.hpp"
46 #include "gc/shared/spaceDecorator.inline.hpp"
47 #include "gc/shared/strongRootsScope.hpp"
48 #include "gc/shared/weakProcessor.hpp"
49 #include "logging/log.hpp"
50 #include "memory/iterator.inline.hpp"
51 #include "memory/resourceArea.hpp"
52 #include "oops/instanceRefKlass.hpp"
53 #include "oops/oop.inline.hpp"
54 #include "runtime/atomic.hpp"
55 #include "runtime/java.hpp"
56 #include "runtime/prefetch.inline.hpp"
57 #include "runtime/thread.inline.hpp"
58 #include "utilities/align.hpp"
59 #include "utilities/copy.hpp"
60 #include "utilities/globalDefinitions.hpp"
61 #include "utilities/stack.inline.hpp"
62
63 //
64 // DefNewGeneration functions.
65
66 // Methods of protected closure types.
67
68 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
69 assert(_young_gen->kind() == Generation::ParNew ||
70 _young_gen->kind() == Generation::DefNew, "Expected the young generation here");
71 }
72
73 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
74 return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded();
75 }
76
77 DefNewGeneration::KeepAliveClosure::
78 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
79 _rs = GenCollectedHeap::heap()->rem_set();
80 }
81
82 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
83 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
84
85
86 DefNewGeneration::FastKeepAliveClosure::
87 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
88 DefNewGeneration::KeepAliveClosure(cl) {
89 _boundary = g->reserved().end();
90 }
91
92 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
93 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
94
95 DefNewGeneration::FastEvacuateFollowersClosure::
96 FastEvacuateFollowersClosure(SerialHeap* heap,
97 FastScanClosure* cur,
98 FastScanClosure* older) :
99 _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older)
100 {
101 }
102
103 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
104 do {
105 _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older);
106 } while (!_heap->no_allocs_since_save_marks());
107 guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan");
108 }
109
110 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
111 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
112 {
113 _boundary = _g->reserved().end();
114 }
115
116 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
117 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
118 {
119 _boundary = _g->reserved().end();
120 }
121
122 void CLDScanClosure::do_cld(ClassLoaderData* cld) {
123 NOT_PRODUCT(ResourceMark rm);
124 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s",
125 p2i(cld),
126 cld->loader_name_and_id(),
127 cld->has_modified_oops() ? "true" : "false");
128
129 // If the cld has not been dirtied we know that there's
130 // no references into the young gen and we can skip it.
131 if (cld->has_modified_oops()) {
132 if (_accumulate_modified_oops) {
133 cld->accumulate_modified_oops();
134 }
135
136 // Tell the closure which CLD is being scanned so that it can be dirtied
137 // if oops are left pointing into the young gen.
138 _scavenge_closure->set_scanned_cld(cld);
139
140 // Clean the cld since we're going to scavenge all the metadata.
141 cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);
142
143 _scavenge_closure->set_scanned_cld(NULL);
144 }
145 }
146
147 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
148 _g(g)
149 {
150 _boundary = _g->reserved().end();
151 }
152
153 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
154 size_t initial_size,
155 size_t min_size,
156 size_t max_size,
157 const char* policy)
158 : Generation(rs, initial_size),
159 _preserved_marks_set(false /* in_c_heap */),
160 _promo_failure_drain_in_progress(false),
161 _should_allocate_from_space(false)
162 {
163 MemRegion cmr((HeapWord*)_virtual_space.low(),
164 (HeapWord*)_virtual_space.high());
165 GenCollectedHeap* gch = GenCollectedHeap::heap();
166
167 gch->rem_set()->resize_covered_region(cmr);
168
169 _eden_space = new ContiguousSpace();
170 _from_space = new ContiguousSpace();
171 _to_space = new ContiguousSpace();
172
173 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
174 vm_exit_during_initialization("Could not allocate a new gen space");
175 }
176
177 // Compute the maximum eden and survivor space sizes. These sizes
178 // are computed assuming the entire reserved space is committed.
179 // These values are exported as performance counters.
180 uintx size = _virtual_space.reserved_size();
181 _max_survivor_size = compute_survivor_size(size, SpaceAlignment);
182 _max_eden_size = size - (2*_max_survivor_size);
183
184 // allocate the performance counters
185
186 // Generation counters -- generation 0, 3 subspaces
187 _gen_counters = new GenerationCounters("new", 0, 3,
188 min_size, max_size, &_virtual_space);
189 _gc_counters = new CollectorCounters(policy, 0);
190
191 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
192 _gen_counters);
193 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
194 _gen_counters);
195 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
196 _gen_counters);
197
198 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
199 update_counters();
200 _old_gen = NULL;
201 _tenuring_threshold = MaxTenuringThreshold;
202 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
203
204 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
205 }
206
207 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
208 bool clear_space,
209 bool mangle_space) {
210 // If the spaces are being cleared (only done at heap initialization
211 // currently), the survivor spaces need not be empty.
212 // Otherwise, no care is taken for used areas in the survivor spaces
213 // so check.
214 assert(clear_space || (to()->is_empty() && from()->is_empty()),
215 "Initialization of the survivor spaces assumes these are empty");
216
217 // Compute sizes
218 uintx size = _virtual_space.committed_size();
219 uintx survivor_size = compute_survivor_size(size, SpaceAlignment);
220 uintx eden_size = size - (2*survivor_size);
221 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
222
223 if (eden_size < minimum_eden_size) {
224 // May happen due to 64Kb rounding, if so adjust eden size back up
225 minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment);
226 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
227 uintx unaligned_survivor_size =
228 align_down(maximum_survivor_size, SpaceAlignment);
229 survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment);
230 eden_size = size - (2*survivor_size);
231 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
232 assert(eden_size >= minimum_eden_size, "just checking");
233 }
234
235 char *eden_start = _virtual_space.low();
236 char *from_start = eden_start + eden_size;
237 char *to_start = from_start + survivor_size;
238 char *to_end = to_start + survivor_size;
239
240 assert(to_end == _virtual_space.high(), "just checking");
241 assert(Space::is_aligned(eden_start), "checking alignment");
242 assert(Space::is_aligned(from_start), "checking alignment");
243 assert(Space::is_aligned(to_start), "checking alignment");
244
245 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
246 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
247 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
248
249 // A minimum eden size implies that there is a part of eden that
250 // is being used and that affects the initialization of any
251 // newly formed eden.
252 bool live_in_eden = minimum_eden_size > 0;
253
254 // If not clearing the spaces, do some checking to verify that
255 // the space are already mangled.
256 if (!clear_space) {
257 // Must check mangling before the spaces are reshaped. Otherwise,
258 // the bottom or end of one space may have moved into another
259 // a failure of the check may not correctly indicate which space
260 // is not properly mangled.
261 if (ZapUnusedHeapArea) {
262 HeapWord* limit = (HeapWord*) _virtual_space.high();
263 eden()->check_mangled_unused_area(limit);
264 from()->check_mangled_unused_area(limit);
265 to()->check_mangled_unused_area(limit);
266 }
267 }
268
269 // Reset the spaces for their new regions.
270 eden()->initialize(edenMR,
271 clear_space && !live_in_eden,
272 SpaceDecorator::Mangle);
273 // If clear_space and live_in_eden, we will not have cleared any
274 // portion of eden above its top. This can cause newly
275 // expanded space not to be mangled if using ZapUnusedHeapArea.
276 // We explicitly do such mangling here.
277 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
278 eden()->mangle_unused_area();
279 }
280 from()->initialize(fromMR, clear_space, mangle_space);
281 to()->initialize(toMR, clear_space, mangle_space);
282
283 // Set next compaction spaces.
284 eden()->set_next_compaction_space(from());
285 // The to-space is normally empty before a compaction so need
286 // not be considered. The exception is during promotion
287 // failure handling when to-space can contain live objects.
288 from()->set_next_compaction_space(NULL);
289 }
290
291 void DefNewGeneration::swap_spaces() {
292 ContiguousSpace* s = from();
293 _from_space = to();
294 _to_space = s;
295 eden()->set_next_compaction_space(from());
296 // The to-space is normally empty before a compaction so need
297 // not be considered. The exception is during promotion
298 // failure handling when to-space can contain live objects.
299 from()->set_next_compaction_space(NULL);
300
301 if (UsePerfData) {
302 CSpaceCounters* c = _from_counters;
303 _from_counters = _to_counters;
304 _to_counters = c;
305 }
306 }
307
308 bool DefNewGeneration::expand(size_t bytes) {
309 MutexLocker x(ExpandHeap_lock);
310 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
311 bool success = _virtual_space.expand_by(bytes);
312 if (success && ZapUnusedHeapArea) {
313 // Mangle newly committed space immediately because it
314 // can be done here more simply that after the new
315 // spaces have been computed.
316 HeapWord* new_high = (HeapWord*) _virtual_space.high();
317 MemRegion mangle_region(prev_high, new_high);
318 SpaceMangler::mangle_region(mangle_region);
319 }
320
321 // Do not attempt an expand-to-the reserve size. The
322 // request should properly observe the maximum size of
323 // the generation so an expand-to-reserve should be
324 // unnecessary. Also a second call to expand-to-reserve
325 // value potentially can cause an undue expansion.
326 // For example if the first expand fail for unknown reasons,
327 // but the second succeeds and expands the heap to its maximum
328 // value.
329 if (GCLocker::is_active()) {
330 log_debug(gc)("Garbage collection disabled, expanded heap instead");
331 }
332
333 return success;
334 }
335
336 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
337 size_t new_size_before,
338 size_t alignment) const {
339 size_t desired_new_size = new_size_before;
340
341 if (NewSizeThreadIncrease > 0) {
342 int threads_count;
343 size_t thread_increase_size = 0;
344
345 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
346 threads_count = Threads::number_of_non_daemon_threads();
347 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
348 thread_increase_size = threads_count * NewSizeThreadIncrease;
349
350 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
351 if (new_size_candidate <= max_uintx - thread_increase_size) {
352 new_size_candidate += thread_increase_size;
353
354 // 3. Check an overflow at 'align_up'.
355 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
356 if (new_size_candidate <= aligned_max) {
357 desired_new_size = align_up(new_size_candidate, alignment);
358 }
359 }
360 }
361 }
362
363 return desired_new_size;
364 }
365
366 void DefNewGeneration::compute_new_size() {
367 // This is called after a GC that includes the old generation, so from-space
368 // will normally be empty.
369 // Note that we check both spaces, since if scavenge failed they revert roles.
370 // If not we bail out (otherwise we would have to relocate the objects).
371 if (!from()->is_empty() || !to()->is_empty()) {
372 return;
373 }
374
375 GenCollectedHeap* gch = GenCollectedHeap::heap();
376
377 size_t old_size = gch->old_gen()->capacity();
378 size_t new_size_before = _virtual_space.committed_size();
379 size_t min_new_size = initial_size();
380 size_t max_new_size = reserved().byte_size();
381 assert(min_new_size <= new_size_before &&
382 new_size_before <= max_new_size,
383 "just checking");
384 // All space sizes must be multiples of Generation::GenGrain.
385 size_t alignment = Generation::GenGrain;
386
387 int threads_count = 0;
388 size_t thread_increase_size = 0;
389
390 size_t new_size_candidate = old_size / NewRatio;
391 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
392 // and reverts to previous value if any overflow happens
393 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);
394
395 // Adjust new generation size
396 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
397 assert(desired_new_size <= max_new_size, "just checking");
398
399 bool changed = false;
400 if (desired_new_size > new_size_before) {
401 size_t change = desired_new_size - new_size_before;
402 assert(change % alignment == 0, "just checking");
403 if (expand(change)) {
404 changed = true;
405 }
406 // If the heap failed to expand to the desired size,
407 // "changed" will be false. If the expansion failed
408 // (and at this point it was expected to succeed),
409 // ignore the failure (leaving "changed" as false).
410 }
411 if (desired_new_size < new_size_before && eden()->is_empty()) {
412 // bail out of shrinking if objects in eden
413 size_t change = new_size_before - desired_new_size;
414 assert(change % alignment == 0, "just checking");
415 _virtual_space.shrink_by(change);
416 changed = true;
417 }
418 if (changed) {
419 // The spaces have already been mangled at this point but
420 // may not have been cleared (set top = bottom) and should be.
421 // Mangling was done when the heap was being expanded.
422 compute_space_boundaries(eden()->used(),
423 SpaceDecorator::Clear,
424 SpaceDecorator::DontMangle);
425 MemRegion cmr((HeapWord*)_virtual_space.low(),
426 (HeapWord*)_virtual_space.high());
427 gch->rem_set()->resize_covered_region(cmr);
428
429 log_debug(gc, ergo, heap)(
430 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
431 new_size_before/K, _virtual_space.committed_size()/K,
432 eden()->capacity()/K, from()->capacity()/K);
433 log_trace(gc, ergo, heap)(
434 " [allowed " SIZE_FORMAT "K extra for %d threads]",
435 thread_increase_size/K, threads_count);
436 }
437 }
438
439 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
440 assert(false, "NYI -- are you sure you want to call this?");
441 }
442
443
444 size_t DefNewGeneration::capacity() const {
445 return eden()->capacity()
446 + from()->capacity(); // to() is only used during scavenge
447 }
448
449
450 size_t DefNewGeneration::used() const {
451 return eden()->used()
452 + from()->used(); // to() is only used during scavenge
453 }
454
455
456 size_t DefNewGeneration::free() const {
457 return eden()->free()
458 + from()->free(); // to() is only used during scavenge
459 }
460
461 size_t DefNewGeneration::max_capacity() const {
462 const size_t reserved_bytes = reserved().byte_size();
463 return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment);
464 }
465
466 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
467 return eden()->free();
468 }
469
470 size_t DefNewGeneration::capacity_before_gc() const {
471 return eden()->capacity();
472 }
473
474 size_t DefNewGeneration::contiguous_available() const {
475 return eden()->free();
476 }
477
478
479 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }
480 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
481
482 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
483 eden()->object_iterate(blk);
484 from()->object_iterate(blk);
485 }
486
487
488 void DefNewGeneration::space_iterate(SpaceClosure* blk,
489 bool usedOnly) {
490 blk->do_space(eden());
491 blk->do_space(from());
492 blk->do_space(to());
493 }
494
495 // The last collection bailed out, we are running out of heap space,
496 // so we try to allocate the from-space, too.
497 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
498 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
499
500 // If the Heap_lock is not locked by this thread, this will be called
501 // again later with the Heap_lock held.
502 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
503
504 HeapWord* result = NULL;
505 if (do_alloc) {
506 result = from()->allocate(size);
507 }
508
509 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s",
510 size,
511 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
512 "true" : "false",
513 Heap_lock->is_locked() ? "locked" : "unlocked",
514 from()->free(),
515 should_try_alloc ? "" : " should_allocate_from_space: NOT",
516 do_alloc ? " Heap_lock is not owned by self" : "",
517 result == NULL ? "NULL" : "object");
518
519 return result;
520 }
521
522 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
523 bool is_tlab,
524 bool parallel) {
525 // We don't attempt to expand the young generation (but perhaps we should.)
526 return allocate(size, is_tlab);
527 }
528
529 void DefNewGeneration::adjust_desired_tenuring_threshold() {
530 // Set the desired survivor size to half the real survivor space
531 size_t const survivor_capacity = to()->capacity() / HeapWordSize;
532 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
533
534 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
535
536 if (UsePerfData) {
537 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters();
538 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
539 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
540 }
541
542 age_table()->print_age_table(_tenuring_threshold);
543 }
544
545 void DefNewGeneration::collect(bool full,
546 bool clear_all_soft_refs,
547 size_t size,
548 bool is_tlab) {
549 assert(full || size > 0, "otherwise we don't want to collect");
550
551 SerialHeap* heap = SerialHeap::heap();
552
553 _gc_timer->register_gc_start();
554 DefNewTracer gc_tracer;
555 gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start());
556
557 _old_gen = heap->old_gen();
558
559 // If the next generation is too full to accommodate promotion
560 // from this generation, pass on collection; let the next generation
561 // do it.
562 if (!collection_attempt_is_safe()) {
563 log_trace(gc)(":: Collection attempt not safe ::");
564 heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
565 return;
566 }
567 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
568
569 init_assuming_no_promotion_failure();
570
571 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause());
572
573 heap->trace_heap_before_gc(&gc_tracer);
574
575 // These can be shared for all code paths
576 IsAliveClosure is_alive(this);
577 ScanWeakRefClosure scan_weak_ref(this);
578
579 age_table()->clear();
580 to()->clear(SpaceDecorator::Mangle);
581 // The preserved marks should be empty at the start of the GC.
582 _preserved_marks_set.init(1);
583
584 heap->rem_set()->prepare_for_younger_refs_iterate(false);
585
586 assert(heap->no_allocs_since_save_marks(),
587 "save marks have not been newly set.");
588
589 FastScanClosure fsc_with_no_gc_barrier(this, false);
590 FastScanClosure fsc_with_gc_barrier(this, true);
591
592 CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier,
593 heap->rem_set()->cld_rem_set()->accumulate_modified_oops());
594
595 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
596 FastEvacuateFollowersClosure evacuate_followers(heap,
597 &fsc_with_no_gc_barrier,
598 &fsc_with_gc_barrier);
599
600 assert(heap->no_allocs_since_save_marks(),
601 "save marks have not been newly set.");
602
603 {
604 // DefNew needs to run with n_threads == 0, to make sure the serial
605 // version of the card table scanning code is used.
606 // See: CardTableRS::non_clean_card_iterate_possibly_parallel.
607 StrongRootsScope srs(0);
608
609 heap->young_process_roots(&srs,
610 &fsc_with_no_gc_barrier,
611 &fsc_with_gc_barrier,
612 &cld_scan_closure);
613 }
614
615 // "evacuate followers".
616 evacuate_followers.do_void();
617
618 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
619 ReferenceProcessor* rp = ref_processor();
620 rp->setup_policy(clear_all_soft_refs);
621 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
622 const ReferenceProcessorStats& stats =
623 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
624 NULL, &pt);
625 gc_tracer.report_gc_reference_stats(stats);
626 gc_tracer.report_tenuring_threshold(tenuring_threshold());
627 pt.print_all_references();
628
629 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
630
631 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
632
633 // Verify that the usage of keep_alive didn't copy any objects.
634 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
635
636 if (!_promotion_failed) {
637 // Swap the survivor spaces.
638 eden()->clear(SpaceDecorator::Mangle);
639 from()->clear(SpaceDecorator::Mangle);
640 if (ZapUnusedHeapArea) {
641 // This is now done here because of the piece-meal mangling which
642 // can check for valid mangling at intermediate points in the
643 // collection(s). When a young collection fails to collect
644 // sufficient space resizing of the young generation can occur
645 // an redistribute the spaces in the young generation. Mangle
646 // here so that unzapped regions don't get distributed to
647 // other spaces.
648 to()->mangle_unused_area();
649 }
650 swap_spaces();
651
652 assert(to()->is_empty(), "to space should be empty now");
653
654 adjust_desired_tenuring_threshold();
655
656 // A successful scavenge should restart the GC time limit count which is
657 // for full GC's.
658 AdaptiveSizePolicy* size_policy = heap->size_policy();
659 size_policy->reset_gc_overhead_limit_count();
660 assert(!heap->incremental_collection_failed(), "Should be clear");
661 } else {
662 assert(_promo_failure_scan_stack.is_empty(), "post condition");
663 _promo_failure_scan_stack.clear(true); // Clear cached segments.
664
665 remove_forwarding_pointers();
666 log_info(gc, promotion)("Promotion failed");
667 // Add to-space to the list of space to compact
668 // when a promotion failure has occurred. In that
669 // case there can be live objects in to-space
670 // as a result of a partial evacuation of eden
671 // and from-space.
672 swap_spaces(); // For uniformity wrt ParNewGeneration.
673 from()->set_next_compaction_space(to());
674 heap->set_incremental_collection_failed();
675
676 // Inform the next generation that a promotion failure occurred.
677 _old_gen->promotion_failure_occurred();
678 gc_tracer.report_promotion_failed(_promotion_failed_info);
679
680 // Reset the PromotionFailureALot counters.
681 NOT_PRODUCT(heap->reset_promotion_should_fail();)
682 }
683 // We should have processed and cleared all the preserved marks.
684 _preserved_marks_set.reclaim();
685 // set new iteration safe limit for the survivor spaces
686 from()->set_concurrent_iteration_safe_limit(from()->top());
687 to()->set_concurrent_iteration_safe_limit(to()->top());
688
689 // We need to use a monotonically non-decreasing time in ms
690 // or we will see time-warp warnings and os::javaTimeMillis()
691 // does not guarantee monotonicity.
692 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
693 update_time_of_last_gc(now);
694
695 heap->trace_heap_after_gc(&gc_tracer);
696
697 _gc_timer->register_gc_end();
698
699 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
700 }
701
702 void DefNewGeneration::init_assuming_no_promotion_failure() {
703 _promotion_failed = false;
704 _promotion_failed_info.reset();
705 from()->set_next_compaction_space(NULL);
706 }
707
708 void DefNewGeneration::remove_forwarding_pointers() {
709 RemoveForwardedPointerClosure rspc;
710 eden()->object_iterate(&rspc);
711 from()->object_iterate(&rspc);
712 restore_preserved_marks();
713 }
714
715 void DefNewGeneration::restore_preserved_marks() {
716 SharedRestorePreservedMarksTaskExecutor task_executor(NULL);
717 _preserved_marks_set.restore(&task_executor);
718 }
719
720 void DefNewGeneration::handle_promotion_failure(oop old) {
721 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
722
723 _promotion_failed = true;
724 _promotion_failed_info.register_copy_failure(old->size());
725 _preserved_marks_set.get()->push_if_necessary(old, old->mark_raw());
726 // forward to self
727 old->forward_to(old);
728
729 _promo_failure_scan_stack.push(old);
730
731 if (!_promo_failure_drain_in_progress) {
732 // prevent recursion in copy_to_survivor_space()
733 _promo_failure_drain_in_progress = true;
734 drain_promo_failure_scan_stack();
735 _promo_failure_drain_in_progress = false;
736 }
737 }
738
739 oop DefNewGeneration::copy_to_survivor_space(oop old) {
740 assert(is_in_reserved(old) && !old->is_forwarded(),
741 "shouldn't be scavenging this oop");
742 size_t s = old->size();
743 oop obj = NULL;
744
745 // Try allocating obj in to-space (unless too old)
746 if (old->age() < tenuring_threshold()) {
747 obj = (oop) to()->allocate_aligned(s);
748 }
749
750 // Otherwise try allocating obj tenured
751 if (obj == NULL) {
752 obj = _old_gen->promote(old, s);
753 if (obj == NULL) {
754 handle_promotion_failure(old);
755 return old;
756 }
757 } else {
758 // Prefetch beyond obj
759 const intx interval = PrefetchCopyIntervalInBytes;
760 Prefetch::write(obj, interval);
761
762 // Copy obj
763 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
764
765 // Increment age if obj still in new generation
766 obj->incr_age();
767 age_table()->add(obj, s);
768 }
769
770 // Done, insert forward pointer to obj in this header
771 old->forward_to(obj);
772
773 return obj;
774 }
775
776 void DefNewGeneration::drain_promo_failure_scan_stack() {
777 while (!_promo_failure_scan_stack.is_empty()) {
778 oop obj = _promo_failure_scan_stack.pop();
779 obj->oop_iterate(_promo_failure_scan_stack_closure);
780 }
781 }
782
783 void DefNewGeneration::save_marks() {
784 eden()->set_saved_mark();
785 to()->set_saved_mark();
786 from()->set_saved_mark();
787 }
788
789
790 void DefNewGeneration::reset_saved_marks() {
791 eden()->reset_saved_mark();
792 to()->reset_saved_mark();
793 from()->reset_saved_mark();
794 }
795
796
797 bool DefNewGeneration::no_allocs_since_save_marks() {
798 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
799 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
800 return to()->saved_mark_at_top();
801 }
802
803 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
804 size_t max_alloc_words) {
805 if (requestor == this || _promotion_failed) {
806 return;
807 }
808 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
809
810 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
811 if (to_space->top() > to_space->bottom()) {
812 trace("to_space not empty when contribute_scratch called");
813 }
814 */
815
816 ContiguousSpace* to_space = to();
817 assert(to_space->end() >= to_space->top(), "pointers out of order");
818 size_t free_words = pointer_delta(to_space->end(), to_space->top());
819 if (free_words >= MinFreeScratchWords) {
820 ScratchBlock* sb = (ScratchBlock*)to_space->top();
821 sb->num_words = free_words;
822 sb->next = list;
823 list = sb;
824 }
825 }
826
827 void DefNewGeneration::reset_scratch() {
828 // If contributing scratch in to_space, mangle all of
829 // to_space if ZapUnusedHeapArea. This is needed because
830 // top is not maintained while using to-space as scratch.
831 if (ZapUnusedHeapArea) {
832 to()->mangle_unused_area_complete();
833 }
834 }
835
836 bool DefNewGeneration::collection_attempt_is_safe() {
837 if (!to()->is_empty()) {
838 log_trace(gc)(":: to is not empty ::");
839 return false;
840 }
841 if (_old_gen == NULL) {
842 GenCollectedHeap* gch = GenCollectedHeap::heap();
843 _old_gen = gch->old_gen();
844 }
845 return _old_gen->promotion_attempt_is_safe(used());
846 }
847
848 void DefNewGeneration::gc_epilogue(bool full) {
849 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
850
851 assert(!GCLocker::is_active(), "We should not be executing here");
852 // Check if the heap is approaching full after a collection has
853 // been done. Generally the young generation is empty at
854 // a minimum at the end of a collection. If it is not, then
855 // the heap is approaching full.
856 GenCollectedHeap* gch = GenCollectedHeap::heap();
857 if (full) {
858 DEBUG_ONLY(seen_incremental_collection_failed = false;)
859 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
860 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
861 GCCause::to_string(gch->gc_cause()));
862 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
863 set_should_allocate_from_space(); // we seem to be running out of space
864 } else {
865 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
866 GCCause::to_string(gch->gc_cause()));
867 gch->clear_incremental_collection_failed(); // We just did a full collection
868 clear_should_allocate_from_space(); // if set
869 }
870 } else {
871 #ifdef ASSERT
872 // It is possible that incremental_collection_failed() == true
873 // here, because an attempted scavenge did not succeed. The policy
874 // is normally expected to cause a full collection which should
875 // clear that condition, so we should not be here twice in a row
876 // with incremental_collection_failed() == true without having done
877 // a full collection in between.
878 if (!seen_incremental_collection_failed &&
879 gch->incremental_collection_failed()) {
880 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
881 GCCause::to_string(gch->gc_cause()));
882 seen_incremental_collection_failed = true;
883 } else if (seen_incremental_collection_failed) {
884 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
885 GCCause::to_string(gch->gc_cause()));
886 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
887 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
888 !gch->incremental_collection_failed(),
889 "Twice in a row");
890 seen_incremental_collection_failed = false;
891 }
892 #endif // ASSERT
893 }
894
895 if (ZapUnusedHeapArea) {
896 eden()->check_mangled_unused_area_complete();
897 from()->check_mangled_unused_area_complete();
898 to()->check_mangled_unused_area_complete();
899 }
900
901 if (!CleanChunkPoolAsync) {
902 Chunk::clean_chunk_pool();
903 }
904
905 // update the generation and space performance counters
906 update_counters();
907 gch->counters()->update_counters();
908 }
909
910 void DefNewGeneration::record_spaces_top() {
911 assert(ZapUnusedHeapArea, "Not mangling unused space");
912 eden()->set_top_for_allocations();
913 to()->set_top_for_allocations();
914 from()->set_top_for_allocations();
915 }
916
917 void DefNewGeneration::ref_processor_init() {
918 Generation::ref_processor_init();
919 }
920
921
922 void DefNewGeneration::update_counters() {
923 if (UsePerfData) {
924 _eden_counters->update_all();
925 _from_counters->update_all();
926 _to_counters->update_all();
927 _gen_counters->update_all();
928 }
929 }
930
931 void DefNewGeneration::verify() {
932 eden()->verify();
933 from()->verify();
934 to()->verify();
935 }
936
937 void DefNewGeneration::print_on(outputStream* st) const {
938 Generation::print_on(st);
939 st->print(" eden");
940 eden()->print_on(st);
941 st->print(" from");
942 from()->print_on(st);
943 st->print(" to ");
944 to()->print_on(st);
945 }
946
947
948 const char* DefNewGeneration::name() const {
949 return "def new generation";
950 }
951
952 // Moved from inline file as they are not called inline
953 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
954 return eden();
955 }
956
957 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
958 // This is the slow-path allocation for the DefNewGeneration.
959 // Most allocations are fast-path in compiled code.
960 // We try to allocate from the eden. If that works, we are happy.
961 // Note that since DefNewGeneration supports lock-free allocation, we
962 // have to use it here, as well.
963 HeapWord* result = eden()->par_allocate(word_size);
964 if (result != NULL) {
965 if (_old_gen != NULL) {
966 _old_gen->sample_eden_chunk();
967 }
968 } else {
969 // If the eden is full and the last collection bailed out, we are running
970 // out of heap space, and we try to allocate the from-space, too.
971 // allocate_from_space can't be inlined because that would introduce a
972 // circular dependency at compile time.
973 result = allocate_from_space(word_size);
974 }
975 return result;
976 }
977
978 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
979 bool is_tlab) {
980 HeapWord* res = eden()->par_allocate(word_size);
981 if (_old_gen != NULL) {
982 _old_gen->sample_eden_chunk();
983 }
984 return res;
985 }
986
987 size_t DefNewGeneration::tlab_capacity() const {
988 return eden()->capacity();
989 }
990
991 size_t DefNewGeneration::tlab_used() const {
992 return eden()->used();
993 }
994
995 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
996 return unsafe_max_alloc_nogc();
997 }