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