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/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 const ReferenceProcessorStats& stats =
665 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
666 NULL, _gc_timer);
667 gc_tracer.report_gc_reference_stats(stats);
668 gc_tracer.report_tenuring_threshold(tenuring_threshold());
669
670 if (!_promotion_failed) {
671 // Swap the survivor spaces.
672 eden()->clear(SpaceDecorator::Mangle);
673 from()->clear(SpaceDecorator::Mangle);
674 if (ZapUnusedHeapArea) {
675 // This is now done here because of the piece-meal mangling which
676 // can check for valid mangling at intermediate points in the
677 // collection(s). When a young collection fails to collect
678 // sufficient space resizing of the young generation can occur
679 // an redistribute the spaces in the young generation. Mangle
680 // here so that unzapped regions don't get distributed to
681 // other spaces.
682 to()->mangle_unused_area();
683 }
684 swap_spaces();
685
686 assert(to()->is_empty(), "to space should be empty now");
687
688 adjust_desired_tenuring_threshold();
689
690 // A successful scavenge should restart the GC time limit count which is
691 // for full GC's.
692 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
693 size_policy->reset_gc_overhead_limit_count();
694 assert(!gch->incremental_collection_failed(), "Should be clear");
695 } else {
696 assert(_promo_failure_scan_stack.is_empty(), "post condition");
697 _promo_failure_scan_stack.clear(true); // Clear cached segments.
698
699 remove_forwarding_pointers();
700 log_info(gc, promotion)("Promotion failed");
701 // Add to-space to the list of space to compact
702 // when a promotion failure has occurred. In that
703 // case there can be live objects in to-space
704 // as a result of a partial evacuation of eden
705 // and from-space.
706 swap_spaces(); // For uniformity wrt ParNewGeneration.
707 from()->set_next_compaction_space(to());
708 gch->set_incremental_collection_failed();
709
710 // Inform the next generation that a promotion failure occurred.
711 _old_gen->promotion_failure_occurred();
712 gc_tracer.report_promotion_failed(_promotion_failed_info);
713
714 // Reset the PromotionFailureALot counters.
715 NOT_PRODUCT(gch->reset_promotion_should_fail();)
716 }
717 // We should have processed and cleared all the preserved marks.
718 _preserved_marks_set.reclaim();
719 // set new iteration safe limit for the survivor spaces
720 from()->set_concurrent_iteration_safe_limit(from()->top());
721 to()->set_concurrent_iteration_safe_limit(to()->top());
722
723 // We need to use a monotonically non-decreasing time in ms
724 // or we will see time-warp warnings and os::javaTimeMillis()
725 // does not guarantee monotonicity.
726 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
727 update_time_of_last_gc(now);
728
729 gch->trace_heap_after_gc(&gc_tracer);
730
731 _gc_timer->register_gc_end();
732
733 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
734 }
735
736 void DefNewGeneration::init_assuming_no_promotion_failure() {
737 _promotion_failed = false;
738 _promotion_failed_info.reset();
739 from()->set_next_compaction_space(NULL);
740 }
741
742 void DefNewGeneration::remove_forwarding_pointers() {
743 RemoveForwardedPointerClosure rspc;
744 eden()->object_iterate(&rspc);
745 from()->object_iterate(&rspc);
746
747 SharedRestorePreservedMarksTaskExecutor task_executor(GenCollectedHeap::heap()->workers());
748 _preserved_marks_set.restore(&task_executor);
749 }
750
751 void DefNewGeneration::handle_promotion_failure(oop old) {
752 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
753
754 _promotion_failed = true;
755 _promotion_failed_info.register_copy_failure(old->size());
756 _preserved_marks_set.get()->push_if_necessary(old, old->mark());
757 // forward to self
758 old->forward_to(old);
759
760 _promo_failure_scan_stack.push(old);
761
762 if (!_promo_failure_drain_in_progress) {
763 // prevent recursion in copy_to_survivor_space()
764 _promo_failure_drain_in_progress = true;
765 drain_promo_failure_scan_stack();
766 _promo_failure_drain_in_progress = false;
767 }
768 }
769
770 oop DefNewGeneration::copy_to_survivor_space(oop old) {
771 assert(is_in_reserved(old) && !old->is_forwarded(),
772 "shouldn't be scavenging this oop");
773 size_t s = old->size();
774 oop obj = NULL;
775
776 // Try allocating obj in to-space (unless too old)
777 if (old->age() < tenuring_threshold()) {
778 obj = (oop) to()->allocate_aligned(s);
779 }
780
781 // Otherwise try allocating obj tenured
782 if (obj == NULL) {
783 obj = _old_gen->promote(old, s);
784 if (obj == NULL) {
785 handle_promotion_failure(old);
786 return old;
787 }
788 } else {
789 // Prefetch beyond obj
790 const intx interval = PrefetchCopyIntervalInBytes;
791 Prefetch::write(obj, interval);
792
793 // Copy obj
794 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
795
796 // Increment age if obj still in new generation
797 obj->incr_age();
798 age_table()->add(obj, s);
799 }
800
801 // Done, insert forward pointer to obj in this header
802 old->forward_to(obj);
803
804 return obj;
805 }
806
807 void DefNewGeneration::drain_promo_failure_scan_stack() {
808 while (!_promo_failure_scan_stack.is_empty()) {
809 oop obj = _promo_failure_scan_stack.pop();
810 obj->oop_iterate(_promo_failure_scan_stack_closure);
811 }
812 }
813
814 void DefNewGeneration::save_marks() {
815 eden()->set_saved_mark();
816 to()->set_saved_mark();
817 from()->set_saved_mark();
818 }
819
820
821 void DefNewGeneration::reset_saved_marks() {
822 eden()->reset_saved_mark();
823 to()->reset_saved_mark();
824 from()->reset_saved_mark();
825 }
826
827
828 bool DefNewGeneration::no_allocs_since_save_marks() {
829 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
830 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
831 return to()->saved_mark_at_top();
832 }
833
834 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
835 \
836 void DefNewGeneration:: \
837 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
838 cl->set_generation(this); \
839 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
840 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
841 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
842 cl->reset_generation(); \
843 save_marks(); \
844 }
845
846 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
847
848 #undef DefNew_SINCE_SAVE_MARKS_DEFN
849
850 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
851 size_t max_alloc_words) {
852 if (requestor == this || _promotion_failed) {
853 return;
854 }
855 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
856
857 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
858 if (to_space->top() > to_space->bottom()) {
859 trace("to_space not empty when contribute_scratch called");
860 }
861 */
862
863 ContiguousSpace* to_space = to();
864 assert(to_space->end() >= to_space->top(), "pointers out of order");
865 size_t free_words = pointer_delta(to_space->end(), to_space->top());
866 if (free_words >= MinFreeScratchWords) {
867 ScratchBlock* sb = (ScratchBlock*)to_space->top();
868 sb->num_words = free_words;
869 sb->next = list;
870 list = sb;
871 }
872 }
873
874 void DefNewGeneration::reset_scratch() {
875 // If contributing scratch in to_space, mangle all of
876 // to_space if ZapUnusedHeapArea. This is needed because
877 // top is not maintained while using to-space as scratch.
878 if (ZapUnusedHeapArea) {
879 to()->mangle_unused_area_complete();
880 }
881 }
882
883 bool DefNewGeneration::collection_attempt_is_safe() {
884 if (!to()->is_empty()) {
885 log_trace(gc)(":: to is not empty ::");
886 return false;
887 }
888 if (_old_gen == NULL) {
889 GenCollectedHeap* gch = GenCollectedHeap::heap();
890 _old_gen = gch->old_gen();
891 }
892 return _old_gen->promotion_attempt_is_safe(used());
893 }
894
895 void DefNewGeneration::gc_epilogue(bool full) {
896 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
897
898 assert(!GCLocker::is_active(), "We should not be executing here");
899 // Check if the heap is approaching full after a collection has
900 // been done. Generally the young generation is empty at
901 // a minimum at the end of a collection. If it is not, then
902 // the heap is approaching full.
903 GenCollectedHeap* gch = GenCollectedHeap::heap();
904 if (full) {
905 DEBUG_ONLY(seen_incremental_collection_failed = false;)
906 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
907 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
908 GCCause::to_string(gch->gc_cause()));
909 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
910 set_should_allocate_from_space(); // we seem to be running out of space
911 } else {
912 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
913 GCCause::to_string(gch->gc_cause()));
914 gch->clear_incremental_collection_failed(); // We just did a full collection
915 clear_should_allocate_from_space(); // if set
916 }
917 } else {
918 #ifdef ASSERT
919 // It is possible that incremental_collection_failed() == true
920 // here, because an attempted scavenge did not succeed. The policy
921 // is normally expected to cause a full collection which should
922 // clear that condition, so we should not be here twice in a row
923 // with incremental_collection_failed() == true without having done
924 // a full collection in between.
925 if (!seen_incremental_collection_failed &&
926 gch->incremental_collection_failed()) {
927 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
928 GCCause::to_string(gch->gc_cause()));
929 seen_incremental_collection_failed = true;
930 } else if (seen_incremental_collection_failed) {
931 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
932 GCCause::to_string(gch->gc_cause()));
933 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
934 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
935 !gch->incremental_collection_failed(),
936 "Twice in a row");
937 seen_incremental_collection_failed = false;
938 }
939 #endif // ASSERT
940 }
941
942 if (ZapUnusedHeapArea) {
943 eden()->check_mangled_unused_area_complete();
944 from()->check_mangled_unused_area_complete();
945 to()->check_mangled_unused_area_complete();
946 }
947
948 if (!CleanChunkPoolAsync) {
949 Chunk::clean_chunk_pool();
950 }
951
952 // update the generation and space performance counters
953 update_counters();
954 gch->gen_policy()->counters()->update_counters();
955 }
956
957 void DefNewGeneration::record_spaces_top() {
958 assert(ZapUnusedHeapArea, "Not mangling unused space");
959 eden()->set_top_for_allocations();
960 to()->set_top_for_allocations();
961 from()->set_top_for_allocations();
962 }
963
964 void DefNewGeneration::ref_processor_init() {
965 Generation::ref_processor_init();
966 }
967
968
969 void DefNewGeneration::update_counters() {
970 if (UsePerfData) {
971 _eden_counters->update_all();
972 _from_counters->update_all();
973 _to_counters->update_all();
974 _gen_counters->update_all();
975 }
976 }
977
978 void DefNewGeneration::verify() {
979 eden()->verify();
980 from()->verify();
981 to()->verify();
982 }
983
984 void DefNewGeneration::print_on(outputStream* st) const {
985 Generation::print_on(st);
986 st->print(" eden");
987 eden()->print_on(st);
988 st->print(" from");
989 from()->print_on(st);
990 st->print(" to ");
991 to()->print_on(st);
992 }
993
994
995 const char* DefNewGeneration::name() const {
996 return "def new generation";
997 }
998
999 // Moved from inline file as they are not called inline
1000 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1001 return eden();
1002 }
1003
1004 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1005 // This is the slow-path allocation for the DefNewGeneration.
1006 // Most allocations are fast-path in compiled code.
1007 // We try to allocate from the eden. If that works, we are happy.
1008 // Note that since DefNewGeneration supports lock-free allocation, we
1009 // have to use it here, as well.
1010 HeapWord* result = eden()->par_allocate(word_size);
1011 if (result != NULL) {
1012 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1013 _old_gen->sample_eden_chunk();
1014 }
1015 } else {
1016 // If the eden is full and the last collection bailed out, we are running
1017 // out of heap space, and we try to allocate the from-space, too.
1018 // allocate_from_space can't be inlined because that would introduce a
1019 // circular dependency at compile time.
1020 result = allocate_from_space(word_size);
1021 }
1022 return result;
1023 }
1024
1025 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1026 bool is_tlab) {
1027 HeapWord* res = eden()->par_allocate(word_size);
1028 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1029 _old_gen->sample_eden_chunk();
1030 }
1031 return res;
1032 }
1033
1034 size_t DefNewGeneration::tlab_capacity() const {
1035 return eden()->capacity();
1036 }
1037
1038 size_t DefNewGeneration::tlab_used() const {
1039 return eden()->used();
1040 }
1041
1042 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1043 return unsafe_max_alloc_nogc();
1044 }