1 /*
2 * Copyright (c) 2001, 2017, 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/preservedMarks.inline.hpp"
40 #include "gc/shared/referencePolicy.hpp"
41 #include "gc/shared/space.inline.hpp"
42 #include "gc/shared/spaceDecorator.hpp"
43 #include "gc/shared/strongRootsScope.hpp"
44 #include "logging/log.hpp"
45 #include "memory/iterator.hpp"
46 #include "memory/resourceArea.hpp"
47 #include "oops/instanceRefKlass.hpp"
48 #include "oops/oop.inline.hpp"
49 #include "runtime/atomic.hpp"
50 #include "runtime/java.hpp"
51 #include "runtime/prefetch.inline.hpp"
52 #include "runtime/thread.inline.hpp"
53 #include "utilities/align.hpp"
54 #include "utilities/copy.hpp"
55 #include "utilities/globalDefinitions.hpp"
56 #include "utilities/stack.inline.hpp"
57 #if INCLUDE_ALL_GCS
58 #include "gc/cms/parOopClosures.hpp"
59 #endif
60
61 //
62 // DefNewGeneration functions.
63
64 // Methods of protected closure types.
65
66 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
67 assert(_young_gen->kind() == Generation::ParNew ||
68 _young_gen->kind() == Generation::DefNew, "Expected the young generation here");
69 }
70
71 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
72 return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded();
73 }
74
75 DefNewGeneration::KeepAliveClosure::
76 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
77 _rs = GenCollectedHeap::heap()->rem_set();
78 }
79
80 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
81 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
82
83
84 DefNewGeneration::FastKeepAliveClosure::
85 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
86 DefNewGeneration::KeepAliveClosure(cl) {
87 _boundary = g->reserved().end();
88 }
89
90 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
91 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
92
93 DefNewGeneration::EvacuateFollowersClosure::
94 EvacuateFollowersClosure(GenCollectedHeap* gch,
95 ScanClosure* cur,
96 ScanClosure* older) :
97 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
98 {}
99
100 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
101 do {
102 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
103 } while (!_gch->no_allocs_since_save_marks());
104 }
105
106 DefNewGeneration::FastEvacuateFollowersClosure::
107 FastEvacuateFollowersClosure(GenCollectedHeap* gch,
108 FastScanClosure* cur,
109 FastScanClosure* older) :
110 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
111 {
112 assert(_gch->young_gen()->kind() == Generation::DefNew, "Generation should be DefNew");
113 _young_gen = (DefNewGeneration*)_gch->young_gen();
114 }
115
116 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
117 do {
118 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
119 } while (!_gch->no_allocs_since_save_marks());
120 guarantee(_young_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
121 }
122
123 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
124 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
125 {
126 _boundary = _g->reserved().end();
127 }
128
129 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
130 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
131
132 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
133 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
134 {
135 _boundary = _g->reserved().end();
136 }
137
138 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
139 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
140
141 void KlassScanClosure::do_klass(Klass* klass) {
142 NOT_PRODUCT(ResourceMark rm);
143 log_develop_trace(gc, scavenge)("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s",
144 p2i(klass),
145 klass->external_name(),
146 klass->has_modified_oops() ? "true" : "false");
147
148 // If the klass has not been dirtied we know that there's
149 // no references into the young gen and we can skip it.
150 if (klass->has_modified_oops()) {
151 if (_accumulate_modified_oops) {
152 klass->accumulate_modified_oops();
153 }
154
155 // Clear this state since we're going to scavenge all the metadata.
156 klass->clear_modified_oops();
157
158 // Tell the closure which Klass is being scanned so that it can be dirtied
159 // if oops are left pointing into the young gen.
160 _scavenge_closure->set_scanned_klass(klass);
161
162 klass->oops_do(_scavenge_closure);
163
164 _scavenge_closure->set_scanned_klass(NULL);
165 }
166 }
167
168 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
169 _g(g)
170 {
171 _boundary = _g->reserved().end();
172 }
173
174 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
175 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
176
177 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
178 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
179
180 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
181 KlassRemSet* klass_rem_set)
182 : _scavenge_closure(scavenge_closure),
183 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
184
185
186 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
187 size_t initial_size,
188 const char* policy)
189 : Generation(rs, initial_size),
190 _preserved_marks_set(false /* in_c_heap */),
191 _promo_failure_drain_in_progress(false),
192 _should_allocate_from_space(false)
193 {
194 MemRegion cmr((HeapWord*)_virtual_space.low(),
195 (HeapWord*)_virtual_space.high());
196 GenCollectedHeap* gch = GenCollectedHeap::heap();
197
198 gch->barrier_set()->resize_covered_region(cmr);
199
200 _eden_space = new ContiguousSpace();
201 _from_space = new ContiguousSpace();
202 _to_space = new ContiguousSpace();
203
204 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
205 vm_exit_during_initialization("Could not allocate a new gen space");
206 }
207
208 // Compute the maximum eden and survivor space sizes. These sizes
209 // are computed assuming the entire reserved space is committed.
210 // These values are exported as performance counters.
211 uintx alignment = gch->collector_policy()->space_alignment();
212 uintx size = _virtual_space.reserved_size();
213 _max_survivor_size = compute_survivor_size(size, alignment);
214 _max_eden_size = size - (2*_max_survivor_size);
215
216 // allocate the performance counters
217 GenCollectorPolicy* gcp = gch->gen_policy();
218
219 // Generation counters -- generation 0, 3 subspaces
220 _gen_counters = new GenerationCounters("new", 0, 3,
221 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
222 _gc_counters = new CollectorCounters(policy, 0);
223
224 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
225 _gen_counters);
226 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
227 _gen_counters);
228 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
229 _gen_counters);
230
231 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
232 update_counters();
233 _old_gen = NULL;
234 _tenuring_threshold = MaxTenuringThreshold;
235 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
236
237 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
238 }
239
240 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
241 bool clear_space,
242 bool mangle_space) {
243 uintx alignment =
244 GenCollectedHeap::heap()->collector_policy()->space_alignment();
245
246 // If the spaces are being cleared (only done at heap initialization
247 // currently), the survivor spaces need not be empty.
248 // Otherwise, no care is taken for used areas in the survivor spaces
249 // so check.
250 assert(clear_space || (to()->is_empty() && from()->is_empty()),
251 "Initialization of the survivor spaces assumes these are empty");
252
253 // Compute sizes
254 uintx size = _virtual_space.committed_size();
255 uintx survivor_size = compute_survivor_size(size, alignment);
256 uintx eden_size = size - (2*survivor_size);
257 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
258
259 if (eden_size < minimum_eden_size) {
260 // May happen due to 64Kb rounding, if so adjust eden size back up
261 minimum_eden_size = align_up(minimum_eden_size, alignment);
262 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
263 uintx unaligned_survivor_size =
264 align_down(maximum_survivor_size, alignment);
265 survivor_size = MAX2(unaligned_survivor_size, alignment);
266 eden_size = size - (2*survivor_size);
267 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
268 assert(eden_size >= minimum_eden_size, "just checking");
269 }
270
271 char *eden_start = _virtual_space.low();
272 char *from_start = eden_start + eden_size;
273 char *to_start = from_start + survivor_size;
274 char *to_end = to_start + survivor_size;
275
276 assert(to_end == _virtual_space.high(), "just checking");
277 assert(Space::is_aligned(eden_start), "checking alignment");
278 assert(Space::is_aligned(from_start), "checking alignment");
279 assert(Space::is_aligned(to_start), "checking alignment");
280
281 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
282 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
283 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
284
285 // A minimum eden size implies that there is a part of eden that
286 // is being used and that affects the initialization of any
287 // newly formed eden.
288 bool live_in_eden = minimum_eden_size > 0;
289
290 // If not clearing the spaces, do some checking to verify that
291 // the space are already mangled.
292 if (!clear_space) {
293 // Must check mangling before the spaces are reshaped. Otherwise,
294 // the bottom or end of one space may have moved into another
295 // a failure of the check may not correctly indicate which space
296 // is not properly mangled.
297 if (ZapUnusedHeapArea) {
298 HeapWord* limit = (HeapWord*) _virtual_space.high();
299 eden()->check_mangled_unused_area(limit);
300 from()->check_mangled_unused_area(limit);
301 to()->check_mangled_unused_area(limit);
302 }
303 }
304
305 // Reset the spaces for their new regions.
306 eden()->initialize(edenMR,
307 clear_space && !live_in_eden,
308 SpaceDecorator::Mangle);
309 // If clear_space and live_in_eden, we will not have cleared any
310 // portion of eden above its top. This can cause newly
311 // expanded space not to be mangled if using ZapUnusedHeapArea.
312 // We explicitly do such mangling here.
313 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
314 eden()->mangle_unused_area();
315 }
316 from()->initialize(fromMR, clear_space, mangle_space);
317 to()->initialize(toMR, clear_space, mangle_space);
318
319 // Set next compaction spaces.
320 eden()->set_next_compaction_space(from());
321 // The to-space is normally empty before a compaction so need
322 // not be considered. The exception is during promotion
323 // failure handling when to-space can contain live objects.
324 from()->set_next_compaction_space(NULL);
325 }
326
327 void DefNewGeneration::swap_spaces() {
328 ContiguousSpace* s = from();
329 _from_space = to();
330 _to_space = s;
331 eden()->set_next_compaction_space(from());
332 // The to-space is normally empty before a compaction so need
333 // not be considered. The exception is during promotion
334 // failure handling when to-space can contain live objects.
335 from()->set_next_compaction_space(NULL);
336
337 if (UsePerfData) {
338 CSpaceCounters* c = _from_counters;
339 _from_counters = _to_counters;
340 _to_counters = c;
341 }
342 }
343
344 bool DefNewGeneration::expand(size_t bytes) {
345 MutexLocker x(ExpandHeap_lock);
346 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
347 bool success = _virtual_space.expand_by(bytes);
348 if (success && ZapUnusedHeapArea) {
349 // Mangle newly committed space immediately because it
350 // can be done here more simply that after the new
351 // spaces have been computed.
352 HeapWord* new_high = (HeapWord*) _virtual_space.high();
353 MemRegion mangle_region(prev_high, new_high);
354 SpaceMangler::mangle_region(mangle_region);
355 }
356
357 // Do not attempt an expand-to-the reserve size. The
358 // request should properly observe the maximum size of
359 // the generation so an expand-to-reserve should be
360 // unnecessary. Also a second call to expand-to-reserve
361 // value potentially can cause an undue expansion.
362 // For example if the first expand fail for unknown reasons,
363 // but the second succeeds and expands the heap to its maximum
364 // value.
365 if (GCLocker::is_active()) {
366 log_debug(gc)("Garbage collection disabled, expanded heap instead");
367 }
368
369 return success;
370 }
371
372 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
373 size_t new_size_before,
374 size_t alignment) const {
375 size_t desired_new_size = new_size_before;
376
377 if (NewSizeThreadIncrease > 0) {
378 int threads_count;
379 size_t thread_increase_size = 0;
380
381 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
382 threads_count = Threads::number_of_non_daemon_threads();
383 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
384 thread_increase_size = threads_count * NewSizeThreadIncrease;
385
386 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
387 if (new_size_candidate <= max_uintx - thread_increase_size) {
388 new_size_candidate += thread_increase_size;
389
390 // 3. Check an overflow at 'align_up'.
391 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
392 if (new_size_candidate <= aligned_max) {
393 desired_new_size = align_up(new_size_candidate, alignment);
394 }
395 }
396 }
397 }
398
399 return desired_new_size;
400 }
401
402 void DefNewGeneration::compute_new_size() {
403 // This is called after a GC that includes the old generation, so from-space
404 // will normally be empty.
405 // Note that we check both spaces, since if scavenge failed they revert roles.
406 // If not we bail out (otherwise we would have to relocate the objects).
407 if (!from()->is_empty() || !to()->is_empty()) {
408 return;
409 }
410
411 GenCollectedHeap* gch = GenCollectedHeap::heap();
412
413 size_t old_size = gch->old_gen()->capacity();
414 size_t new_size_before = _virtual_space.committed_size();
415 size_t min_new_size = initial_size();
416 size_t max_new_size = reserved().byte_size();
417 assert(min_new_size <= new_size_before &&
418 new_size_before <= max_new_size,
419 "just checking");
420 // All space sizes must be multiples of Generation::GenGrain.
421 size_t alignment = Generation::GenGrain;
422
423 int threads_count = 0;
424 size_t thread_increase_size = 0;
425
426 size_t new_size_candidate = old_size / NewRatio;
427 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
428 // and reverts to previous value if any overflow happens
429 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);
430
431 // Adjust new generation size
432 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
433 assert(desired_new_size <= max_new_size, "just checking");
434
435 bool changed = false;
436 if (desired_new_size > new_size_before) {
437 size_t change = desired_new_size - new_size_before;
438 assert(change % alignment == 0, "just checking");
439 if (expand(change)) {
440 changed = true;
441 }
442 // If the heap failed to expand to the desired size,
443 // "changed" will be false. If the expansion failed
444 // (and at this point it was expected to succeed),
445 // ignore the failure (leaving "changed" as false).
446 }
447 if (desired_new_size < new_size_before && eden()->is_empty()) {
448 // bail out of shrinking if objects in eden
449 size_t change = new_size_before - desired_new_size;
450 assert(change % alignment == 0, "just checking");
451 _virtual_space.shrink_by(change);
452 changed = true;
453 }
454 if (changed) {
455 // The spaces have already been mangled at this point but
456 // may not have been cleared (set top = bottom) and should be.
457 // Mangling was done when the heap was being expanded.
458 compute_space_boundaries(eden()->used(),
459 SpaceDecorator::Clear,
460 SpaceDecorator::DontMangle);
461 MemRegion cmr((HeapWord*)_virtual_space.low(),
462 (HeapWord*)_virtual_space.high());
463 gch->barrier_set()->resize_covered_region(cmr);
464
465 log_debug(gc, ergo, heap)(
466 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
467 new_size_before/K, _virtual_space.committed_size()/K,
468 eden()->capacity()/K, from()->capacity()/K);
469 log_trace(gc, ergo, heap)(
470 " [allowed " SIZE_FORMAT "K extra for %d threads]",
471 thread_increase_size/K, threads_count);
472 }
473 }
474
475 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
476 assert(false, "NYI -- are you sure you want to call this?");
477 }
478
479
480 size_t DefNewGeneration::capacity() const {
481 return eden()->capacity()
482 + from()->capacity(); // to() is only used during scavenge
483 }
484
485
486 size_t DefNewGeneration::used() const {
487 return eden()->used()
488 + from()->used(); // to() is only used during scavenge
489 }
490
491
492 size_t DefNewGeneration::free() const {
493 return eden()->free()
494 + from()->free(); // to() is only used during scavenge
495 }
496
497 size_t DefNewGeneration::max_capacity() const {
498 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
499 const size_t reserved_bytes = reserved().byte_size();
500 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
501 }
502
503 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
504 return eden()->free();
505 }
506
507 size_t DefNewGeneration::capacity_before_gc() const {
508 return eden()->capacity();
509 }
510
511 size_t DefNewGeneration::contiguous_available() const {
512 return eden()->free();
513 }
514
515
516 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }
517 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
518
519 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
520 eden()->object_iterate(blk);
521 from()->object_iterate(blk);
522 }
523
524
525 void DefNewGeneration::space_iterate(SpaceClosure* blk,
526 bool usedOnly) {
527 blk->do_space(eden());
528 blk->do_space(from());
529 blk->do_space(to());
530 }
531
532 // The last collection bailed out, we are running out of heap space,
533 // so we try to allocate the from-space, too.
534 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
535 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
536
537 // If the Heap_lock is not locked by this thread, this will be called
538 // again later with the Heap_lock held.
539 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
540
541 HeapWord* result = NULL;
542 if (do_alloc) {
543 result = from()->allocate(size);
544 }
545
546 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s",
547 size,
548 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
549 "true" : "false",
550 Heap_lock->is_locked() ? "locked" : "unlocked",
551 from()->free(),
552 should_try_alloc ? "" : " should_allocate_from_space: NOT",
553 do_alloc ? " Heap_lock is not owned by self" : "",
554 result == NULL ? "NULL" : "object");
555
556 return result;
557 }
558
559 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
560 bool is_tlab,
561 bool parallel) {
562 // We don't attempt to expand the young generation (but perhaps we should.)
563 return allocate(size, is_tlab);
564 }
565
566 void DefNewGeneration::adjust_desired_tenuring_threshold() {
567 // Set the desired survivor size to half the real survivor space
568 size_t const survivor_capacity = to()->capacity() / HeapWordSize;
569 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
570
571 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
572
573 if (UsePerfData) {
574 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->gen_policy()->counters();
575 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
576 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
577 }
578
579 age_table()->print_age_table(_tenuring_threshold);
580 }
581
582 void DefNewGeneration::collect(bool full,
583 bool clear_all_soft_refs,
584 size_t size,
585 bool is_tlab) {
586 assert(full || size > 0, "otherwise we don't want to collect");
587
588 GenCollectedHeap* gch = GenCollectedHeap::heap();
589
590 _gc_timer->register_gc_start();
591 DefNewTracer gc_tracer;
592 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
593
594 _old_gen = gch->old_gen();
595
596 // If the next generation is too full to accommodate promotion
597 // from this generation, pass on collection; let the next generation
598 // do it.
599 if (!collection_attempt_is_safe()) {
600 log_trace(gc)(":: Collection attempt not safe ::");
601 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
602 return;
603 }
604 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
605
606 init_assuming_no_promotion_failure();
607
608 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, gch->gc_cause());
609
610 gch->trace_heap_before_gc(&gc_tracer);
611
612 // These can be shared for all code paths
613 IsAliveClosure is_alive(this);
614 ScanWeakRefClosure scan_weak_ref(this);
615
616 age_table()->clear();
617 to()->clear(SpaceDecorator::Mangle);
618 // The preserved marks should be empty at the start of the GC.
619 _preserved_marks_set.init(1);
620
621 gch->rem_set()->prepare_for_younger_refs_iterate(false);
622
623 assert(gch->no_allocs_since_save_marks(),
624 "save marks have not been newly set.");
625
626 // Not very pretty.
627 CollectorPolicy* cp = gch->collector_policy();
628
629 FastScanClosure fsc_with_no_gc_barrier(this, false);
630 FastScanClosure fsc_with_gc_barrier(this, true);
631
632 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
633 gch->rem_set()->klass_rem_set());
634 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
635 &fsc_with_no_gc_barrier,
636 false);
637
638 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
639 FastEvacuateFollowersClosure evacuate_followers(gch,
640 &fsc_with_no_gc_barrier,
641 &fsc_with_gc_barrier);
642
643 assert(gch->no_allocs_since_save_marks(),
644 "save marks have not been newly set.");
645
646 {
647 // DefNew needs to run with n_threads == 0, to make sure the serial
648 // version of the card table scanning code is used.
649 // See: CardTableModRefBSForCTRS::non_clean_card_iterate_possibly_parallel.
650 StrongRootsScope srs(0);
651
652 gch->young_process_roots(&srs,
653 &fsc_with_no_gc_barrier,
654 &fsc_with_gc_barrier,
655 &cld_scan_closure);
656 }
657
658 // "evacuate followers".
659 evacuate_followers.do_void();
660
661 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
662 ReferenceProcessor* rp = ref_processor();
663 rp->setup_policy(clear_all_soft_refs);
664 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->num_q());
665 const ReferenceProcessorStats& stats =
666 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
667 NULL, &pt);
668 gc_tracer.report_gc_reference_stats(stats);
669 gc_tracer.report_tenuring_threshold(tenuring_threshold());
670 pt.print_all_references();
671
672 if (!_promotion_failed) {
673 // Swap the survivor spaces.
674 eden()->clear(SpaceDecorator::Mangle);
675 from()->clear(SpaceDecorator::Mangle);
676 if (ZapUnusedHeapArea) {
677 // This is now done here because of the piece-meal mangling which
678 // can check for valid mangling at intermediate points in the
679 // collection(s). When a young collection fails to collect
680 // sufficient space resizing of the young generation can occur
681 // an redistribute the spaces in the young generation. Mangle
682 // here so that unzapped regions don't get distributed to
683 // other spaces.
684 to()->mangle_unused_area();
685 }
686 swap_spaces();
687
688 assert(to()->is_empty(), "to space should be empty now");
689
690 adjust_desired_tenuring_threshold();
691
692 // A successful scavenge should restart the GC time limit count which is
693 // for full GC's.
694 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
695 size_policy->reset_gc_overhead_limit_count();
696 assert(!gch->incremental_collection_failed(), "Should be clear");
697 } else {
698 assert(_promo_failure_scan_stack.is_empty(), "post condition");
699 _promo_failure_scan_stack.clear(true); // Clear cached segments.
700
701 remove_forwarding_pointers();
702 log_info(gc, promotion)("Promotion failed");
703 // Add to-space to the list of space to compact
704 // when a promotion failure has occurred. In that
705 // case there can be live objects in to-space
706 // as a result of a partial evacuation of eden
707 // and from-space.
708 swap_spaces(); // For uniformity wrt ParNewGeneration.
709 from()->set_next_compaction_space(to());
710 gch->set_incremental_collection_failed();
711
712 // Inform the next generation that a promotion failure occurred.
713 _old_gen->promotion_failure_occurred();
714 gc_tracer.report_promotion_failed(_promotion_failed_info);
715
716 // Reset the PromotionFailureALot counters.
717 NOT_PRODUCT(gch->reset_promotion_should_fail();)
718 }
719 // We should have processed and cleared all the preserved marks.
720 _preserved_marks_set.reclaim();
721 // set new iteration safe limit for the survivor spaces
722 from()->set_concurrent_iteration_safe_limit(from()->top());
723 to()->set_concurrent_iteration_safe_limit(to()->top());
724
725 // We need to use a monotonically non-decreasing time in ms
726 // or we will see time-warp warnings and os::javaTimeMillis()
727 // does not guarantee monotonicity.
728 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
729 update_time_of_last_gc(now);
730
731 gch->trace_heap_after_gc(&gc_tracer);
732
733 _gc_timer->register_gc_end();
734
735 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
736 }
737
738 void DefNewGeneration::init_assuming_no_promotion_failure() {
739 _promotion_failed = false;
740 _promotion_failed_info.reset();
741 from()->set_next_compaction_space(NULL);
742 }
743
744 void DefNewGeneration::remove_forwarding_pointers() {
745 RemoveForwardedPointerClosure rspc;
746 eden()->object_iterate(&rspc);
747 from()->object_iterate(&rspc);
748
749 SharedRestorePreservedMarksTaskExecutor task_executor(GenCollectedHeap::heap()->workers());
750 _preserved_marks_set.restore(&task_executor);
751 }
752
753 void DefNewGeneration::handle_promotion_failure(oop old) {
754 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
755
756 _promotion_failed = true;
757 _promotion_failed_info.register_copy_failure(old->size());
758 _preserved_marks_set.get()->push_if_necessary(old, old->mark());
759 // forward to self
760 old->forward_to(old);
761
762 _promo_failure_scan_stack.push(old);
763
764 if (!_promo_failure_drain_in_progress) {
765 // prevent recursion in copy_to_survivor_space()
766 _promo_failure_drain_in_progress = true;
767 drain_promo_failure_scan_stack();
768 _promo_failure_drain_in_progress = false;
769 }
770 }
771
772 oop DefNewGeneration::copy_to_survivor_space(oop old) {
773 assert(is_in_reserved(old) && !old->is_forwarded(),
774 "shouldn't be scavenging this oop");
775 size_t s = old->size();
776 oop obj = NULL;
777
778 // Try allocating obj in to-space (unless too old)
779 if (old->age() < tenuring_threshold()) {
780 obj = (oop) to()->allocate_aligned(s);
781 }
782
783 // Otherwise try allocating obj tenured
784 if (obj == NULL) {
785 obj = _old_gen->promote(old, s);
786 if (obj == NULL) {
787 handle_promotion_failure(old);
788 return old;
789 }
790 } else {
791 // Prefetch beyond obj
792 const intx interval = PrefetchCopyIntervalInBytes;
793 Prefetch::write(obj, interval);
794
795 // Copy obj
796 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
797
798 // Increment age if obj still in new generation
799 obj->incr_age();
800 age_table()->add(obj, s);
801 }
802
803 // Done, insert forward pointer to obj in this header
804 old->forward_to(obj);
805
806 return obj;
807 }
808
809 void DefNewGeneration::drain_promo_failure_scan_stack() {
810 while (!_promo_failure_scan_stack.is_empty()) {
811 oop obj = _promo_failure_scan_stack.pop();
812 obj->oop_iterate(_promo_failure_scan_stack_closure);
813 }
814 }
815
816 void DefNewGeneration::save_marks() {
817 eden()->set_saved_mark();
818 to()->set_saved_mark();
819 from()->set_saved_mark();
820 }
821
822
823 void DefNewGeneration::reset_saved_marks() {
824 eden()->reset_saved_mark();
825 to()->reset_saved_mark();
826 from()->reset_saved_mark();
827 }
828
829
830 bool DefNewGeneration::no_allocs_since_save_marks() {
831 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
832 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
833 return to()->saved_mark_at_top();
834 }
835
836 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
837 \
838 void DefNewGeneration:: \
839 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
840 cl->set_generation(this); \
841 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
842 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
843 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
844 cl->reset_generation(); \
845 save_marks(); \
846 }
847
848 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
849
850 #undef DefNew_SINCE_SAVE_MARKS_DEFN
851
852 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
853 size_t max_alloc_words) {
854 if (requestor == this || _promotion_failed) {
855 return;
856 }
857 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
858
859 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
860 if (to_space->top() > to_space->bottom()) {
861 trace("to_space not empty when contribute_scratch called");
862 }
863 */
864
865 ContiguousSpace* to_space = to();
866 assert(to_space->end() >= to_space->top(), "pointers out of order");
867 size_t free_words = pointer_delta(to_space->end(), to_space->top());
868 if (free_words >= MinFreeScratchWords) {
869 ScratchBlock* sb = (ScratchBlock*)to_space->top();
870 sb->num_words = free_words;
871 sb->next = list;
872 list = sb;
873 }
874 }
875
876 void DefNewGeneration::reset_scratch() {
877 // If contributing scratch in to_space, mangle all of
878 // to_space if ZapUnusedHeapArea. This is needed because
879 // top is not maintained while using to-space as scratch.
880 if (ZapUnusedHeapArea) {
881 to()->mangle_unused_area_complete();
882 }
883 }
884
885 bool DefNewGeneration::collection_attempt_is_safe() {
886 if (!to()->is_empty()) {
887 log_trace(gc)(":: to is not empty ::");
888 return false;
889 }
890 if (_old_gen == NULL) {
891 GenCollectedHeap* gch = GenCollectedHeap::heap();
892 _old_gen = gch->old_gen();
893 }
894 return _old_gen->promotion_attempt_is_safe(used());
895 }
896
897 void DefNewGeneration::gc_epilogue(bool full) {
898 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
899
900 assert(!GCLocker::is_active(), "We should not be executing here");
901 // Check if the heap is approaching full after a collection has
902 // been done. Generally the young generation is empty at
903 // a minimum at the end of a collection. If it is not, then
904 // the heap is approaching full.
905 GenCollectedHeap* gch = GenCollectedHeap::heap();
906 if (full) {
907 DEBUG_ONLY(seen_incremental_collection_failed = false;)
908 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
909 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
910 GCCause::to_string(gch->gc_cause()));
911 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
912 set_should_allocate_from_space(); // we seem to be running out of space
913 } else {
914 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
915 GCCause::to_string(gch->gc_cause()));
916 gch->clear_incremental_collection_failed(); // We just did a full collection
917 clear_should_allocate_from_space(); // if set
918 }
919 } else {
920 #ifdef ASSERT
921 // It is possible that incremental_collection_failed() == true
922 // here, because an attempted scavenge did not succeed. The policy
923 // is normally expected to cause a full collection which should
924 // clear that condition, so we should not be here twice in a row
925 // with incremental_collection_failed() == true without having done
926 // a full collection in between.
927 if (!seen_incremental_collection_failed &&
928 gch->incremental_collection_failed()) {
929 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
930 GCCause::to_string(gch->gc_cause()));
931 seen_incremental_collection_failed = true;
932 } else if (seen_incremental_collection_failed) {
933 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
934 GCCause::to_string(gch->gc_cause()));
935 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
936 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
937 !gch->incremental_collection_failed(),
938 "Twice in a row");
939 seen_incremental_collection_failed = false;
940 }
941 #endif // ASSERT
942 }
943
944 if (ZapUnusedHeapArea) {
945 eden()->check_mangled_unused_area_complete();
946 from()->check_mangled_unused_area_complete();
947 to()->check_mangled_unused_area_complete();
948 }
949
950 if (!CleanChunkPoolAsync) {
951 Chunk::clean_chunk_pool();
952 }
953
954 // update the generation and space performance counters
955 update_counters();
956 gch->gen_policy()->counters()->update_counters();
957 }
958
959 void DefNewGeneration::record_spaces_top() {
960 assert(ZapUnusedHeapArea, "Not mangling unused space");
961 eden()->set_top_for_allocations();
962 to()->set_top_for_allocations();
963 from()->set_top_for_allocations();
964 }
965
966 void DefNewGeneration::ref_processor_init() {
967 Generation::ref_processor_init();
968 }
969
970
971 void DefNewGeneration::update_counters() {
972 if (UsePerfData) {
973 _eden_counters->update_all();
974 _from_counters->update_all();
975 _to_counters->update_all();
976 _gen_counters->update_all();
977 }
978 }
979
980 void DefNewGeneration::verify() {
981 eden()->verify();
982 from()->verify();
983 to()->verify();
984 }
985
986 void DefNewGeneration::print_on(outputStream* st) const {
987 Generation::print_on(st);
988 st->print(" eden");
989 eden()->print_on(st);
990 st->print(" from");
991 from()->print_on(st);
992 st->print(" to ");
993 to()->print_on(st);
994 }
995
996
997 const char* DefNewGeneration::name() const {
998 return "def new generation";
999 }
1000
1001 // Moved from inline file as they are not called inline
1002 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1003 return eden();
1004 }
1005
1006 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1007 // This is the slow-path allocation for the DefNewGeneration.
1008 // Most allocations are fast-path in compiled code.
1009 // We try to allocate from the eden. If that works, we are happy.
1010 // Note that since DefNewGeneration supports lock-free allocation, we
1011 // have to use it here, as well.
1012 HeapWord* result = eden()->par_allocate(word_size);
1013 if (result != NULL) {
1014 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1015 _old_gen->sample_eden_chunk();
1016 }
1017 } else {
1018 // If the eden is full and the last collection bailed out, we are running
1019 // out of heap space, and we try to allocate the from-space, too.
1020 // allocate_from_space can't be inlined because that would introduce a
1021 // circular dependency at compile time.
1022 result = allocate_from_space(word_size);
1023 }
1024 return result;
1025 }
1026
1027 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1028 bool is_tlab) {
1029 HeapWord* res = eden()->par_allocate(word_size);
1030 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1031 _old_gen->sample_eden_chunk();
1032 }
1033 return res;
1034 }
1035
1036 size_t DefNewGeneration::tlab_capacity() const {
1037 return eden()->capacity();
1038 }
1039
1040 size_t DefNewGeneration::tlab_used() const {
1041 return eden()->used();
1042 }
1043
1044 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1045 return unsafe_max_alloc_nogc();
1046 }