1 /*
2 * Copyright (c) 2001, 2016, 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/ageTable.inline.hpp"
28 #include "gc/shared/cardTableRS.hpp"
29 #include "gc/shared/collectorCounters.hpp"
30 #include "gc/shared/gcHeapSummary.hpp"
31 #include "gc/shared/gcLocker.inline.hpp"
32 #include "gc/shared/gcPolicyCounters.hpp"
33 #include "gc/shared/gcTimer.hpp"
34 #include "gc/shared/gcTrace.hpp"
35 #include "gc/shared/gcTraceTime.inline.hpp"
36 #include "gc/shared/genCollectedHeap.hpp"
37 #include "gc/shared/genOopClosures.inline.hpp"
38 #include "gc/shared/generationSpec.hpp"
39 #include "gc/shared/referencePolicy.hpp"
40 #include "gc/shared/space.inline.hpp"
41 #include "gc/shared/spaceDecorator.hpp"
42 #include "gc/shared/strongRootsScope.hpp"
43 #include "logging/log.hpp"
44 #include "memory/iterator.hpp"
45 #include "oops/instanceRefKlass.hpp"
46 #include "oops/oop.inline.hpp"
47 #include "runtime/atomic.inline.hpp"
48 #include "runtime/java.hpp"
49 #include "runtime/prefetch.inline.hpp"
50 #include "runtime/thread.inline.hpp"
51 #include "utilities/copy.hpp"
52 #include "utilities/globalDefinitions.hpp"
53 #include "utilities/stack.inline.hpp"
54 #if INCLUDE_ALL_GCS
55 #include "gc/cms/parOopClosures.hpp"
56 #endif
57
58 //
59 // DefNewGeneration functions.
60
61 // Methods of protected closure types.
62
63 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
64 assert(_young_gen->kind() == Generation::ParNew ||
65 _young_gen->kind() == Generation::DefNew, "Expected the young generation here");
66 }
67
68 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
69 return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded();
70 }
71
72 DefNewGeneration::KeepAliveClosure::
73 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
74 _rs = GenCollectedHeap::heap()->rem_set();
75 }
76
77 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
78 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
79
80
81 DefNewGeneration::FastKeepAliveClosure::
82 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
83 DefNewGeneration::KeepAliveClosure(cl) {
84 _boundary = g->reserved().end();
85 }
86
87 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
88 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
89
90 DefNewGeneration::EvacuateFollowersClosure::
91 EvacuateFollowersClosure(GenCollectedHeap* gch,
92 ScanClosure* cur,
93 ScanClosure* older) :
94 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
95 {}
96
97 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
98 do {
99 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
100 } while (!_gch->no_allocs_since_save_marks());
101 }
102
103 DefNewGeneration::FastEvacuateFollowersClosure::
104 FastEvacuateFollowersClosure(GenCollectedHeap* gch,
105 FastScanClosure* cur,
106 FastScanClosure* older) :
107 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
108 {
109 assert(_gch->young_gen()->kind() == Generation::DefNew, "Generation should be DefNew");
110 _young_gen = (DefNewGeneration*)_gch->young_gen();
111 }
112
113 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
114 do {
115 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
116 } while (!_gch->no_allocs_since_save_marks());
117 guarantee(_young_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
118 }
119
120 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
121 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
122 {
123 _boundary = _g->reserved().end();
124 }
125
126 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
127 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
128
129 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
130 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
131 {
132 _boundary = _g->reserved().end();
133 }
134
135 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
136 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
137
138 void KlassScanClosure::do_klass(Klass* klass) {
139 NOT_PRODUCT(ResourceMark rm);
140 log_develop_trace(gc, scavenge)("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s",
141 p2i(klass),
142 klass->external_name(),
143 klass->has_modified_oops() ? "true" : "false");
144
145 // If the klass has not been dirtied we know that there's
146 // no references into the young gen and we can skip it.
147 if (klass->has_modified_oops()) {
148 if (_accumulate_modified_oops) {
149 klass->accumulate_modified_oops();
150 }
151
152 // Clear this state since we're going to scavenge all the metadata.
153 klass->clear_modified_oops();
154
155 // Tell the closure which Klass is being scanned so that it can be dirtied
156 // if oops are left pointing into the young gen.
157 _scavenge_closure->set_scanned_klass(klass);
158
159 klass->oops_do(_scavenge_closure);
160
161 _scavenge_closure->set_scanned_klass(NULL);
162 }
163 }
164
165 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
166 _g(g)
167 {
168 _boundary = _g->reserved().end();
169 }
170
171 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
172 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
173
174 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
175 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
176
177 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
178 KlassRemSet* klass_rem_set)
179 : _scavenge_closure(scavenge_closure),
180 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
181
182
183 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
184 size_t initial_size,
185 const char* policy)
186 : Generation(rs, initial_size),
187 _promo_failure_drain_in_progress(false),
188 _should_allocate_from_space(false)
189 {
190 MemRegion cmr((HeapWord*)_virtual_space.low(),
191 (HeapWord*)_virtual_space.high());
192 GenCollectedHeap* gch = GenCollectedHeap::heap();
193
194 gch->barrier_set()->resize_covered_region(cmr);
195
196 _eden_space = new ContiguousSpace();
197 _from_space = new ContiguousSpace();
198 _to_space = new ContiguousSpace();
199
200 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
201 vm_exit_during_initialization("Could not allocate a new gen space");
202 }
203
204 // Compute the maximum eden and survivor space sizes. These sizes
205 // are computed assuming the entire reserved space is committed.
206 // These values are exported as performance counters.
207 uintx alignment = gch->collector_policy()->space_alignment();
208 uintx size = _virtual_space.reserved_size();
209 _max_survivor_size = compute_survivor_size(size, alignment);
210 _max_eden_size = size - (2*_max_survivor_size);
211
212 // allocate the performance counters
213 GenCollectorPolicy* gcp = gch->gen_policy();
214
215 // Generation counters -- generation 0, 3 subspaces
216 _gen_counters = new GenerationCounters("new", 0, 3,
217 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
218 _gc_counters = new CollectorCounters(policy, 0);
219
220 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
221 _gen_counters);
222 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
223 _gen_counters);
224 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
225 _gen_counters);
226
227 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
228 update_counters();
229 _old_gen = NULL;
230 _tenuring_threshold = MaxTenuringThreshold;
231 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
232
233 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
234 }
235
236 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
237 bool clear_space,
238 bool mangle_space) {
239 uintx alignment =
240 GenCollectedHeap::heap()->collector_policy()->space_alignment();
241
242 // If the spaces are being cleared (only done at heap initialization
243 // currently), the survivor spaces need not be empty.
244 // Otherwise, no care is taken for used areas in the survivor spaces
245 // so check.
246 assert(clear_space || (to()->is_empty() && from()->is_empty()),
247 "Initialization of the survivor spaces assumes these are empty");
248
249 // Compute sizes
250 uintx size = _virtual_space.committed_size();
251 uintx survivor_size = compute_survivor_size(size, alignment);
252 uintx eden_size = size - (2*survivor_size);
253 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
254
255 if (eden_size < minimum_eden_size) {
256 // May happen due to 64Kb rounding, if so adjust eden size back up
257 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
258 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
259 uintx unaligned_survivor_size =
260 align_size_down(maximum_survivor_size, alignment);
261 survivor_size = MAX2(unaligned_survivor_size, alignment);
262 eden_size = size - (2*survivor_size);
263 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
264 assert(eden_size >= minimum_eden_size, "just checking");
265 }
266
267 char *eden_start = _virtual_space.low();
268 char *from_start = eden_start + eden_size;
269 char *to_start = from_start + survivor_size;
270 char *to_end = to_start + survivor_size;
271
272 assert(to_end == _virtual_space.high(), "just checking");
273 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
274 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
275 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
276
277 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
278 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
279 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
280
281 // A minimum eden size implies that there is a part of eden that
282 // is being used and that affects the initialization of any
283 // newly formed eden.
284 bool live_in_eden = minimum_eden_size > 0;
285
286 // If not clearing the spaces, do some checking to verify that
287 // the space are already mangled.
288 if (!clear_space) {
289 // Must check mangling before the spaces are reshaped. Otherwise,
290 // the bottom or end of one space may have moved into another
291 // a failure of the check may not correctly indicate which space
292 // is not properly mangled.
293 if (ZapUnusedHeapArea) {
294 HeapWord* limit = (HeapWord*) _virtual_space.high();
295 eden()->check_mangled_unused_area(limit);
296 from()->check_mangled_unused_area(limit);
297 to()->check_mangled_unused_area(limit);
298 }
299 }
300
301 // Reset the spaces for their new regions.
302 eden()->initialize(edenMR,
303 clear_space && !live_in_eden,
304 SpaceDecorator::Mangle);
305 // If clear_space and live_in_eden, we will not have cleared any
306 // portion of eden above its top. This can cause newly
307 // expanded space not to be mangled if using ZapUnusedHeapArea.
308 // We explicitly do such mangling here.
309 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
310 eden()->mangle_unused_area();
311 }
312 from()->initialize(fromMR, clear_space, mangle_space);
313 to()->initialize(toMR, clear_space, mangle_space);
314
315 // Set next compaction spaces.
316 eden()->set_next_compaction_space(from());
317 // The to-space is normally empty before a compaction so need
318 // not be considered. The exception is during promotion
319 // failure handling when to-space can contain live objects.
320 from()->set_next_compaction_space(NULL);
321 }
322
323 void DefNewGeneration::swap_spaces() {
324 ContiguousSpace* s = from();
325 _from_space = to();
326 _to_space = s;
327 eden()->set_next_compaction_space(from());
328 // The to-space is normally empty before a compaction so need
329 // not be considered. The exception is during promotion
330 // failure handling when to-space can contain live objects.
331 from()->set_next_compaction_space(NULL);
332
333 if (UsePerfData) {
334 CSpaceCounters* c = _from_counters;
335 _from_counters = _to_counters;
336 _to_counters = c;
337 }
338 }
339
340 bool DefNewGeneration::expand(size_t bytes) {
341 MutexLocker x(ExpandHeap_lock);
342 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
343 bool success = _virtual_space.expand_by(bytes);
344 if (success && ZapUnusedHeapArea) {
345 // Mangle newly committed space immediately because it
346 // can be done here more simply that after the new
347 // spaces have been computed.
348 HeapWord* new_high = (HeapWord*) _virtual_space.high();
349 MemRegion mangle_region(prev_high, new_high);
350 SpaceMangler::mangle_region(mangle_region);
351 }
352
353 // Do not attempt an expand-to-the reserve size. The
354 // request should properly observe the maximum size of
355 // the generation so an expand-to-reserve should be
356 // unnecessary. Also a second call to expand-to-reserve
357 // value potentially can cause an undue expansion.
358 // For example if the first expand fail for unknown reasons,
359 // but the second succeeds and expands the heap to its maximum
360 // value.
361 if (GCLocker::is_active()) {
362 log_debug(gc)("Garbage collection disabled, expanded heap instead");
363 }
364
365 return success;
366 }
367
368 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
369 size_t new_size_before,
370 size_t alignment) const {
371 size_t desired_new_size = new_size_before;
372
373 if (NewSizeThreadIncrease > 0) {
374 int threads_count;
375 size_t thread_increase_size = 0;
376
377 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
378 threads_count = Threads::number_of_non_daemon_threads();
379 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
380 thread_increase_size = threads_count * NewSizeThreadIncrease;
381
382 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
383 if (new_size_candidate <= max_uintx - thread_increase_size) {
384 new_size_candidate += thread_increase_size;
385
386 // 3. Check an overflow at 'align_size_up'.
387 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
388 if (new_size_candidate <= aligned_max) {
389 desired_new_size = align_size_up(new_size_candidate, alignment);
390 }
391 }
392 }
393 }
394
395 return desired_new_size;
396 }
397
398 void DefNewGeneration::compute_new_size() {
399 // This is called after a GC that includes the old generation, so from-space
400 // will normally be empty.
401 // Note that we check both spaces, since if scavenge failed they revert roles.
402 // If not we bail out (otherwise we would have to relocate the objects).
403 if (!from()->is_empty() || !to()->is_empty()) {
404 return;
405 }
406
407 GenCollectedHeap* gch = GenCollectedHeap::heap();
408
409 size_t old_size = gch->old_gen()->capacity();
410 size_t new_size_before = _virtual_space.committed_size();
411 size_t min_new_size = initial_size();
412 size_t max_new_size = reserved().byte_size();
413 assert(min_new_size <= new_size_before &&
414 new_size_before <= max_new_size,
415 "just checking");
416 // All space sizes must be multiples of Generation::GenGrain.
417 size_t alignment = Generation::GenGrain;
418
419 int threads_count = 0;
420 size_t thread_increase_size = 0;
421
422 size_t new_size_candidate = old_size / NewRatio;
423 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
424 // and reverts to previous value if any overflow happens
425 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);
426
427 // Adjust new generation size
428 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
429 assert(desired_new_size <= max_new_size, "just checking");
430
431 bool changed = false;
432 if (desired_new_size > new_size_before) {
433 size_t change = desired_new_size - new_size_before;
434 assert(change % alignment == 0, "just checking");
435 if (expand(change)) {
436 changed = true;
437 }
438 // If the heap failed to expand to the desired size,
439 // "changed" will be false. If the expansion failed
440 // (and at this point it was expected to succeed),
441 // ignore the failure (leaving "changed" as false).
442 }
443 if (desired_new_size < new_size_before && eden()->is_empty()) {
444 // bail out of shrinking if objects in eden
445 size_t change = new_size_before - desired_new_size;
446 assert(change % alignment == 0, "just checking");
447 _virtual_space.shrink_by(change);
448 changed = true;
449 }
450 if (changed) {
451 // The spaces have already been mangled at this point but
452 // may not have been cleared (set top = bottom) and should be.
453 // Mangling was done when the heap was being expanded.
454 compute_space_boundaries(eden()->used(),
455 SpaceDecorator::Clear,
456 SpaceDecorator::DontMangle);
457 MemRegion cmr((HeapWord*)_virtual_space.low(),
458 (HeapWord*)_virtual_space.high());
459 gch->barrier_set()->resize_covered_region(cmr);
460
461 log_debug(gc, heap, ergo)(
462 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
463 new_size_before/K, _virtual_space.committed_size()/K,
464 eden()->capacity()/K, from()->capacity()/K);
465 log_trace(gc, heap, ergo)(
466 " [allowed " SIZE_FORMAT "K extra for %d threads]",
467 thread_increase_size/K, threads_count);
468 }
469 }
470
471 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
472 assert(false, "NYI -- are you sure you want to call this?");
473 }
474
475
476 size_t DefNewGeneration::capacity() const {
477 return eden()->capacity()
478 + from()->capacity(); // to() is only used during scavenge
479 }
480
481
482 size_t DefNewGeneration::used() const {
483 return eden()->used()
484 + from()->used(); // to() is only used during scavenge
485 }
486
487
488 size_t DefNewGeneration::free() const {
489 return eden()->free()
490 + from()->free(); // to() is only used during scavenge
491 }
492
493 size_t DefNewGeneration::max_capacity() const {
494 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
495 const size_t reserved_bytes = reserved().byte_size();
496 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
497 }
498
499 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
500 return eden()->free();
501 }
502
503 size_t DefNewGeneration::capacity_before_gc() const {
504 return eden()->capacity();
505 }
506
507 size_t DefNewGeneration::contiguous_available() const {
508 return eden()->free();
509 }
510
511
512 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
513 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
514
515 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
516 eden()->object_iterate(blk);
517 from()->object_iterate(blk);
518 }
519
520
521 void DefNewGeneration::space_iterate(SpaceClosure* blk,
522 bool usedOnly) {
523 blk->do_space(eden());
524 blk->do_space(from());
525 blk->do_space(to());
526 }
527
528 // The last collection bailed out, we are running out of heap space,
529 // so we try to allocate the from-space, too.
530 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
531 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
532
533 // If the Heap_lock is not locked by this thread, this will be called
534 // again later with the Heap_lock held.
535 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
536
537 HeapWord* result = NULL;
538 if (do_alloc) {
539 result = from()->allocate(size);
540 }
541
542 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s",
543 size,
544 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
545 "true" : "false",
546 Heap_lock->is_locked() ? "locked" : "unlocked",
547 from()->free(),
548 should_try_alloc ? "" : " should_allocate_from_space: NOT",
549 do_alloc ? " Heap_lock is not owned by self" : "",
550 result == NULL ? "NULL" : "object");
551
552 return result;
553 }
554
555 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
556 bool is_tlab,
557 bool parallel) {
558 // We don't attempt to expand the young generation (but perhaps we should.)
559 return allocate(size, is_tlab);
560 }
561
562 void DefNewGeneration::adjust_desired_tenuring_threshold() {
563 // Set the desired survivor size to half the real survivor space
564 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->collector_policy()->counters();
565 _tenuring_threshold =
566 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize, gc_counters);
567 }
568
569 void DefNewGeneration::collect(bool full,
570 bool clear_all_soft_refs,
571 size_t size,
572 bool is_tlab) {
573 assert(full || size > 0, "otherwise we don't want to collect");
574
575 GenCollectedHeap* gch = GenCollectedHeap::heap();
576
577 _gc_timer->register_gc_start();
578 DefNewTracer gc_tracer;
579 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
580
581 _old_gen = gch->old_gen();
582
583 // If the next generation is too full to accommodate promotion
584 // from this generation, pass on collection; let the next generation
585 // do it.
586 if (!collection_attempt_is_safe()) {
587 log_trace(gc)(":: Collection attempt not safe ::");
588 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
589 return;
590 }
591 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
592
593 init_assuming_no_promotion_failure();
594
595 GCTraceTime(Trace, gc) tm("DefNew", NULL, gch->gc_cause());
596
597 gch->trace_heap_before_gc(&gc_tracer);
598
599 // These can be shared for all code paths
600 IsAliveClosure is_alive(this);
601 ScanWeakRefClosure scan_weak_ref(this);
602
603 age_table()->clear();
604 to()->clear(SpaceDecorator::Mangle);
605
606 gch->rem_set()->prepare_for_younger_refs_iterate(false);
607
608 assert(gch->no_allocs_since_save_marks(),
609 "save marks have not been newly set.");
610
611 // Not very pretty.
612 CollectorPolicy* cp = gch->collector_policy();
613
614 FastScanClosure fsc_with_no_gc_barrier(this, false);
615 FastScanClosure fsc_with_gc_barrier(this, true);
616
617 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
618 gch->rem_set()->klass_rem_set());
619 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
620 &fsc_with_no_gc_barrier,
621 false);
622
623 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
624 FastEvacuateFollowersClosure evacuate_followers(gch,
625 &fsc_with_no_gc_barrier,
626 &fsc_with_gc_barrier);
627
628 assert(gch->no_allocs_since_save_marks(),
629 "save marks have not been newly set.");
630
631 {
632 // DefNew needs to run with n_threads == 0, to make sure the serial
633 // version of the card table scanning code is used.
634 // See: CardTableModRefBSForCTRS::non_clean_card_iterate_possibly_parallel.
635 StrongRootsScope srs(0);
636
637 gch->gen_process_roots(&srs,
638 GenCollectedHeap::YoungGen,
639 true, // Process younger gens, if any,
640 // as strong roots.
641 GenCollectedHeap::SO_ScavengeCodeCache,
642 GenCollectedHeap::StrongAndWeakRoots,
643 &fsc_with_no_gc_barrier,
644 &fsc_with_gc_barrier,
645 &cld_scan_closure);
646 }
647
648 // "evacuate followers".
649 evacuate_followers.do_void();
650
651 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
652 ReferenceProcessor* rp = ref_processor();
653 rp->setup_policy(clear_all_soft_refs);
654 const ReferenceProcessorStats& stats =
655 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
656 NULL, _gc_timer);
657 gc_tracer.report_gc_reference_stats(stats);
658 gc_tracer.report_tenuring_threshold(tenuring_threshold());
659
660 if (!_promotion_failed) {
661 // Swap the survivor spaces.
662 eden()->clear(SpaceDecorator::Mangle);
663 from()->clear(SpaceDecorator::Mangle);
664 if (ZapUnusedHeapArea) {
665 // This is now done here because of the piece-meal mangling which
666 // can check for valid mangling at intermediate points in the
667 // collection(s). When a young collection fails to collect
668 // sufficient space resizing of the young generation can occur
669 // an redistribute the spaces in the young generation. Mangle
670 // here so that unzapped regions don't get distributed to
671 // other spaces.
672 to()->mangle_unused_area();
673 }
674 swap_spaces();
675
676 assert(to()->is_empty(), "to space should be empty now");
677
678 adjust_desired_tenuring_threshold();
679
680 // A successful scavenge should restart the GC time limit count which is
681 // for full GC's.
682 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
683 size_policy->reset_gc_overhead_limit_count();
684 assert(!gch->incremental_collection_failed(), "Should be clear");
685 } else {
686 assert(_promo_failure_scan_stack.is_empty(), "post condition");
687 _promo_failure_scan_stack.clear(true); // Clear cached segments.
688
689 remove_forwarding_pointers();
690 log_debug(gc)("Promotion failed");
691 // Add to-space to the list of space to compact
692 // when a promotion failure has occurred. In that
693 // case there can be live objects in to-space
694 // as a result of a partial evacuation of eden
695 // and from-space.
696 swap_spaces(); // For uniformity wrt ParNewGeneration.
697 from()->set_next_compaction_space(to());
698 gch->set_incremental_collection_failed();
699
700 // Inform the next generation that a promotion failure occurred.
701 _old_gen->promotion_failure_occurred();
702 gc_tracer.report_promotion_failed(_promotion_failed_info);
703
704 // Reset the PromotionFailureALot counters.
705 NOT_PRODUCT(gch->reset_promotion_should_fail();)
706 }
707 // set new iteration safe limit for the survivor spaces
708 from()->set_concurrent_iteration_safe_limit(from()->top());
709 to()->set_concurrent_iteration_safe_limit(to()->top());
710
711 // We need to use a monotonically non-decreasing time in ms
712 // or we will see time-warp warnings and os::javaTimeMillis()
713 // does not guarantee monotonicity.
714 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
715 update_time_of_last_gc(now);
716
717 gch->trace_heap_after_gc(&gc_tracer);
718
719 _gc_timer->register_gc_end();
720
721 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
722 }
723
724 class RemoveForwardPointerClosure: public ObjectClosure {
725 public:
726 void do_object(oop obj) {
727 obj->init_mark();
728 }
729 };
730
731 void DefNewGeneration::init_assuming_no_promotion_failure() {
732 _promotion_failed = false;
733 _promotion_failed_info.reset();
734 from()->set_next_compaction_space(NULL);
735 }
736
737 void DefNewGeneration::remove_forwarding_pointers() {
738 RemoveForwardPointerClosure rspc;
739 eden()->object_iterate(&rspc);
740 from()->object_iterate(&rspc);
741
742 // Now restore saved marks, if any.
743 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
744 "should be the same");
745 while (!_objs_with_preserved_marks.is_empty()) {
746 oop obj = _objs_with_preserved_marks.pop();
747 markOop m = _preserved_marks_of_objs.pop();
748 obj->set_mark(m);
749 }
750 _objs_with_preserved_marks.clear(true);
751 _preserved_marks_of_objs.clear(true);
752 }
753
754 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
755 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
756 "Oversaving!");
757 _objs_with_preserved_marks.push(obj);
758 _preserved_marks_of_objs.push(m);
759 }
760
761 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
762 if (m->must_be_preserved_for_promotion_failure(obj)) {
763 preserve_mark(obj, m);
764 }
765 }
766
767 void DefNewGeneration::handle_promotion_failure(oop old) {
768 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
769
770 _promotion_failed = true;
771 _promotion_failed_info.register_copy_failure(old->size());
772 preserve_mark_if_necessary(old, old->mark());
773 // forward to self
774 old->forward_to(old);
775
776 _promo_failure_scan_stack.push(old);
777
778 if (!_promo_failure_drain_in_progress) {
779 // prevent recursion in copy_to_survivor_space()
780 _promo_failure_drain_in_progress = true;
781 drain_promo_failure_scan_stack();
782 _promo_failure_drain_in_progress = false;
783 }
784 }
785
786 oop DefNewGeneration::copy_to_survivor_space(oop old) {
787 assert(is_in_reserved(old) && !old->is_forwarded(),
788 "shouldn't be scavenging this oop");
789 size_t s = old->size();
790 oop obj = NULL;
791
792 // Try allocating obj in to-space (unless too old)
793 if (old->age() < tenuring_threshold()) {
794 obj = (oop) to()->allocate_aligned(s);
795 }
796
797 // Otherwise try allocating obj tenured
798 if (obj == NULL) {
799 obj = _old_gen->promote(old, s);
800 if (obj == NULL) {
801 handle_promotion_failure(old);
802 return old;
803 }
804 } else {
805 // Prefetch beyond obj
806 const intx interval = PrefetchCopyIntervalInBytes;
807 Prefetch::write(obj, interval);
808
809 // Copy obj
810 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
811
812 // Increment age if obj still in new generation
813 obj->incr_age();
814 age_table()->add(obj, s);
815 }
816
817 // Done, insert forward pointer to obj in this header
818 old->forward_to(obj);
819
820 return obj;
821 }
822
823 void DefNewGeneration::drain_promo_failure_scan_stack() {
824 while (!_promo_failure_scan_stack.is_empty()) {
825 oop obj = _promo_failure_scan_stack.pop();
826 obj->oop_iterate(_promo_failure_scan_stack_closure);
827 }
828 }
829
830 void DefNewGeneration::save_marks() {
831 eden()->set_saved_mark();
832 to()->set_saved_mark();
833 from()->set_saved_mark();
834 }
835
836
837 void DefNewGeneration::reset_saved_marks() {
838 eden()->reset_saved_mark();
839 to()->reset_saved_mark();
840 from()->reset_saved_mark();
841 }
842
843
844 bool DefNewGeneration::no_allocs_since_save_marks() {
845 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
846 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
847 return to()->saved_mark_at_top();
848 }
849
850 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
851 \
852 void DefNewGeneration:: \
853 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
854 cl->set_generation(this); \
855 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
856 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
857 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
858 cl->reset_generation(); \
859 save_marks(); \
860 }
861
862 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
863
864 #undef DefNew_SINCE_SAVE_MARKS_DEFN
865
866 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
867 size_t max_alloc_words) {
868 if (requestor == this || _promotion_failed) {
869 return;
870 }
871 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
872
873 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
874 if (to_space->top() > to_space->bottom()) {
875 trace("to_space not empty when contribute_scratch called");
876 }
877 */
878
879 ContiguousSpace* to_space = to();
880 assert(to_space->end() >= to_space->top(), "pointers out of order");
881 size_t free_words = pointer_delta(to_space->end(), to_space->top());
882 if (free_words >= MinFreeScratchWords) {
883 ScratchBlock* sb = (ScratchBlock*)to_space->top();
884 sb->num_words = free_words;
885 sb->next = list;
886 list = sb;
887 }
888 }
889
890 void DefNewGeneration::reset_scratch() {
891 // If contributing scratch in to_space, mangle all of
892 // to_space if ZapUnusedHeapArea. This is needed because
893 // top is not maintained while using to-space as scratch.
894 if (ZapUnusedHeapArea) {
895 to()->mangle_unused_area_complete();
896 }
897 }
898
899 bool DefNewGeneration::collection_attempt_is_safe() {
900 if (!to()->is_empty()) {
901 log_trace(gc)(":: to is not empty ::");
902 return false;
903 }
904 if (_old_gen == NULL) {
905 GenCollectedHeap* gch = GenCollectedHeap::heap();
906 _old_gen = gch->old_gen();
907 }
908 return _old_gen->promotion_attempt_is_safe(used());
909 }
910
911 void DefNewGeneration::gc_epilogue(bool full) {
912 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
913
914 assert(!GCLocker::is_active(), "We should not be executing here");
915 // Check if the heap is approaching full after a collection has
916 // been done. Generally the young generation is empty at
917 // a minimum at the end of a collection. If it is not, then
918 // the heap is approaching full.
919 GenCollectedHeap* gch = GenCollectedHeap::heap();
920 if (full) {
921 DEBUG_ONLY(seen_incremental_collection_failed = false;)
922 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
923 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
924 GCCause::to_string(gch->gc_cause()));
925 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
926 set_should_allocate_from_space(); // we seem to be running out of space
927 } else {
928 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
929 GCCause::to_string(gch->gc_cause()));
930 gch->clear_incremental_collection_failed(); // We just did a full collection
931 clear_should_allocate_from_space(); // if set
932 }
933 } else {
934 #ifdef ASSERT
935 // It is possible that incremental_collection_failed() == true
936 // here, because an attempted scavenge did not succeed. The policy
937 // is normally expected to cause a full collection which should
938 // clear that condition, so we should not be here twice in a row
939 // with incremental_collection_failed() == true without having done
940 // a full collection in between.
941 if (!seen_incremental_collection_failed &&
942 gch->incremental_collection_failed()) {
943 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
944 GCCause::to_string(gch->gc_cause()));
945 seen_incremental_collection_failed = true;
946 } else if (seen_incremental_collection_failed) {
947 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
948 GCCause::to_string(gch->gc_cause()));
949 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
950 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
951 !gch->incremental_collection_failed(),
952 "Twice in a row");
953 seen_incremental_collection_failed = false;
954 }
955 #endif // ASSERT
956 }
957
958 if (ZapUnusedHeapArea) {
959 eden()->check_mangled_unused_area_complete();
960 from()->check_mangled_unused_area_complete();
961 to()->check_mangled_unused_area_complete();
962 }
963
964 if (!CleanChunkPoolAsync) {
965 Chunk::clean_chunk_pool();
966 }
967
968 // update the generation and space performance counters
969 update_counters();
970 gch->collector_policy()->counters()->update_counters();
971 }
972
973 void DefNewGeneration::record_spaces_top() {
974 assert(ZapUnusedHeapArea, "Not mangling unused space");
975 eden()->set_top_for_allocations();
976 to()->set_top_for_allocations();
977 from()->set_top_for_allocations();
978 }
979
980 void DefNewGeneration::ref_processor_init() {
981 Generation::ref_processor_init();
982 }
983
984
985 void DefNewGeneration::update_counters() {
986 if (UsePerfData) {
987 _eden_counters->update_all();
988 _from_counters->update_all();
989 _to_counters->update_all();
990 _gen_counters->update_all();
991 }
992 }
993
994 void DefNewGeneration::verify() {
995 eden()->verify();
996 from()->verify();
997 to()->verify();
998 }
999
1000 void DefNewGeneration::print_on(outputStream* st) const {
1001 Generation::print_on(st);
1002 st->print(" eden");
1003 eden()->print_on(st);
1004 st->print(" from");
1005 from()->print_on(st);
1006 st->print(" to ");
1007 to()->print_on(st);
1008 }
1009
1010
1011 const char* DefNewGeneration::name() const {
1012 return "def new generation";
1013 }
1014
1015 // Moved from inline file as they are not called inline
1016 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1017 return eden();
1018 }
1019
1020 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1021 // This is the slow-path allocation for the DefNewGeneration.
1022 // Most allocations are fast-path in compiled code.
1023 // We try to allocate from the eden. If that works, we are happy.
1024 // Note that since DefNewGeneration supports lock-free allocation, we
1025 // have to use it here, as well.
1026 HeapWord* result = eden()->par_allocate(word_size);
1027 if (result != NULL) {
1028 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1029 _old_gen->sample_eden_chunk();
1030 }
1031 } else {
1032 // If the eden is full and the last collection bailed out, we are running
1033 // out of heap space, and we try to allocate the from-space, too.
1034 // allocate_from_space can't be inlined because that would introduce a
1035 // circular dependency at compile time.
1036 result = allocate_from_space(word_size);
1037 }
1038 return result;
1039 }
1040
1041 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1042 bool is_tlab) {
1043 HeapWord* res = eden()->par_allocate(word_size);
1044 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1045 _old_gen->sample_eden_chunk();
1046 }
1047 return res;
1048 }
1049
1050 size_t DefNewGeneration::tlab_capacity() const {
1051 return eden()->capacity();
1052 }
1053
1054 size_t DefNewGeneration::tlab_used() const {
1055 return eden()->used();
1056 }
1057
1058 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1059 return unsafe_max_alloc_nogc();
1060 }