1 /*
2 * Copyright (c) 2001, 2015, 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/cardTableRS.hpp"
28 #include "gc/shared/collectorCounters.hpp"
29 #include "gc/shared/gcHeapSummary.hpp"
30 #include "gc/shared/gcLocker.inline.hpp"
31 #include "gc/shared/gcPolicyCounters.hpp"
32 #include "gc/shared/gcTimer.hpp"
33 #include "gc/shared/gcTrace.hpp"
34 #include "gc/shared/gcTraceTime.inline.hpp"
35 #include "gc/shared/genCollectedHeap.hpp"
36 #include "gc/shared/genOopClosures.inline.hpp"
37 #include "gc/shared/generationSpec.hpp"
38 #include "gc/shared/referencePolicy.hpp"
39 #include "gc/shared/space.inline.hpp"
40 #include "gc/shared/spaceDecorator.hpp"
41 #include "gc/shared/strongRootsScope.hpp"
42 #include "logging/log.hpp"
43 #include "memory/iterator.hpp"
44 #include "oops/instanceRefKlass.hpp"
45 #include "oops/oop.inline.hpp"
46 #include "runtime/atomic.inline.hpp"
47 #include "runtime/java.hpp"
48 #include "runtime/prefetch.inline.hpp"
49 #include "runtime/thread.inline.hpp"
50 #include "utilities/copy.hpp"
51 #include "utilities/globalDefinitions.hpp"
52 #include "utilities/stack.inline.hpp"
53 #if INCLUDE_ALL_GCS
54 #include "gc/cms/parOopClosures.hpp"
55 #endif
56
57 //
58 // DefNewGeneration functions.
59
60 // Methods of protected closure types.
61
62 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
63 assert(_young_gen->kind() == Generation::ParNew ||
64 _young_gen->kind() == Generation::DefNew, "Expected the young generation here");
65 }
66
67 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
68 return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded();
69 }
70
71 DefNewGeneration::KeepAliveClosure::
72 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
73 _rs = GenCollectedHeap::heap()->rem_set();
74 }
75
76 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
77 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
78
79
80 DefNewGeneration::FastKeepAliveClosure::
81 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
82 DefNewGeneration::KeepAliveClosure(cl) {
83 _boundary = g->reserved().end();
84 }
85
86 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
87 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
88
89 DefNewGeneration::EvacuateFollowersClosure::
90 EvacuateFollowersClosure(GenCollectedHeap* gch,
91 ScanClosure* cur,
92 ScanClosure* older) :
93 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
94 {}
95
96 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
97 do {
98 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
99 } while (!_gch->no_allocs_since_save_marks());
100 }
101
102 DefNewGeneration::FastEvacuateFollowersClosure::
103 FastEvacuateFollowersClosure(GenCollectedHeap* gch,
104 FastScanClosure* cur,
105 FastScanClosure* older) :
106 _gch(gch), _scan_cur_or_nonheap(cur), _scan_older(older)
107 {
108 assert(_gch->young_gen()->kind() == Generation::DefNew, "Generation should be DefNew");
109 _young_gen = (DefNewGeneration*)_gch->young_gen();
110 }
111
112 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
113 do {
114 _gch->oop_since_save_marks_iterate(GenCollectedHeap::YoungGen, _scan_cur_or_nonheap, _scan_older);
115 } while (!_gch->no_allocs_since_save_marks());
116 guarantee(_young_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
117 }
118
119 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
120 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
121 {
122 _boundary = _g->reserved().end();
123 }
124
125 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
126 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
127
128 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
129 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
130 {
131 _boundary = _g->reserved().end();
132 }
133
134 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
135 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
136
137 void KlassScanClosure::do_klass(Klass* klass) {
138 NOT_PRODUCT(ResourceMark rm);
139 log_develop_trace(gc, scavenge)("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s",
140 p2i(klass),
141 klass->external_name(),
142 klass->has_modified_oops() ? "true" : "false");
143
144 // If the klass has not been dirtied we know that there's
145 // no references into the young gen and we can skip it.
146 if (klass->has_modified_oops()) {
147 if (_accumulate_modified_oops) {
148 klass->accumulate_modified_oops();
149 }
150
151 // Clear this state since we're going to scavenge all the metadata.
152 klass->clear_modified_oops();
153
154 // Tell the closure which Klass is being scanned so that it can be dirtied
155 // if oops are left pointing into the young gen.
156 _scavenge_closure->set_scanned_klass(klass);
157
158 klass->oops_do(_scavenge_closure);
159
160 _scavenge_closure->set_scanned_klass(NULL);
161 }
162 }
163
164 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
165 _g(g)
166 {
167 _boundary = _g->reserved().end();
168 }
169
170 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
171 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
172
173 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
174 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
175
176 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
177 KlassRemSet* klass_rem_set)
178 : _scavenge_closure(scavenge_closure),
179 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
180
181
182 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
183 size_t initial_size,
184 const char* policy)
185 : Generation(rs, initial_size),
186 _promo_failure_drain_in_progress(false),
187 _should_allocate_from_space(false)
188 {
189 MemRegion cmr((HeapWord*)_virtual_space.low(),
190 (HeapWord*)_virtual_space.high());
191 GenCollectedHeap* gch = GenCollectedHeap::heap();
192
193 gch->barrier_set()->resize_covered_region(cmr);
194
195 _eden_space = new ContiguousSpace();
196 _from_space = new ContiguousSpace();
197 _to_space = new ContiguousSpace();
198
199 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
200 vm_exit_during_initialization("Could not allocate a new gen space");
201 }
202
203 // Compute the maximum eden and survivor space sizes. These sizes
204 // are computed assuming the entire reserved space is committed.
205 // These values are exported as performance counters.
206 uintx alignment = gch->collector_policy()->space_alignment();
207 uintx size = _virtual_space.reserved_size();
208 _max_survivor_size = compute_survivor_size(size, alignment);
209 _max_eden_size = size - (2*_max_survivor_size);
210
211 // allocate the performance counters
212 GenCollectorPolicy* gcp = gch->gen_policy();
213
214 // Generation counters -- generation 0, 3 subspaces
215 _gen_counters = new GenerationCounters("new", 0, 3,
216 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
217 _gc_counters = new CollectorCounters(policy, 0);
218
219 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
220 _gen_counters);
221 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
222 _gen_counters);
223 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
224 _gen_counters);
225
226 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
227 update_counters();
228 _old_gen = NULL;
229 _tenuring_threshold = MaxTenuringThreshold;
230 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
231
232 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
233 }
234
235 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
236 bool clear_space,
237 bool mangle_space) {
238 uintx alignment =
239 GenCollectedHeap::heap()->collector_policy()->space_alignment();
240
241 // If the spaces are being cleared (only done at heap initialization
242 // currently), the survivor spaces need not be empty.
243 // Otherwise, no care is taken for used areas in the survivor spaces
244 // so check.
245 assert(clear_space || (to()->is_empty() && from()->is_empty()),
246 "Initialization of the survivor spaces assumes these are empty");
247
248 // Compute sizes
249 uintx size = _virtual_space.committed_size();
250 uintx survivor_size = compute_survivor_size(size, alignment);
251 uintx eden_size = size - (2*survivor_size);
252 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
253
254 if (eden_size < minimum_eden_size) {
255 // May happen due to 64Kb rounding, if so adjust eden size back up
256 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
257 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
258 uintx unaligned_survivor_size =
259 align_size_down(maximum_survivor_size, alignment);
260 survivor_size = MAX2(unaligned_survivor_size, alignment);
261 eden_size = size - (2*survivor_size);
262 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
263 assert(eden_size >= minimum_eden_size, "just checking");
264 }
265
266 char *eden_start = _virtual_space.low();
267 char *from_start = eden_start + eden_size;
268 char *to_start = from_start + survivor_size;
269 char *to_end = to_start + survivor_size;
270
271 assert(to_end == _virtual_space.high(), "just checking");
272 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
273 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
274 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
275
276 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
277 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
278 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
279
280 // A minimum eden size implies that there is a part of eden that
281 // is being used and that affects the initialization of any
282 // newly formed eden.
283 bool live_in_eden = minimum_eden_size > 0;
284
285 // If not clearing the spaces, do some checking to verify that
286 // the space are already mangled.
287 if (!clear_space) {
288 // Must check mangling before the spaces are reshaped. Otherwise,
289 // the bottom or end of one space may have moved into another
290 // a failure of the check may not correctly indicate which space
291 // is not properly mangled.
292 if (ZapUnusedHeapArea) {
293 HeapWord* limit = (HeapWord*) _virtual_space.high();
294 eden()->check_mangled_unused_area(limit);
295 from()->check_mangled_unused_area(limit);
296 to()->check_mangled_unused_area(limit);
297 }
298 }
299
300 // Reset the spaces for their new regions.
301 eden()->initialize(edenMR,
302 clear_space && !live_in_eden,
303 SpaceDecorator::Mangle);
304 // If clear_space and live_in_eden, we will not have cleared any
305 // portion of eden above its top. This can cause newly
306 // expanded space not to be mangled if using ZapUnusedHeapArea.
307 // We explicitly do such mangling here.
308 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
309 eden()->mangle_unused_area();
310 }
311 from()->initialize(fromMR, clear_space, mangle_space);
312 to()->initialize(toMR, clear_space, mangle_space);
313
314 // Set next compaction spaces.
315 eden()->set_next_compaction_space(from());
316 // The to-space is normally empty before a compaction so need
317 // not be considered. The exception is during promotion
318 // failure handling when to-space can contain live objects.
319 from()->set_next_compaction_space(NULL);
320 }
321
322 void DefNewGeneration::swap_spaces() {
323 ContiguousSpace* s = from();
324 _from_space = to();
325 _to_space = s;
326 eden()->set_next_compaction_space(from());
327 // The to-space is normally empty before a compaction so need
328 // not be considered. The exception is during promotion
329 // failure handling when to-space can contain live objects.
330 from()->set_next_compaction_space(NULL);
331
332 if (UsePerfData) {
333 CSpaceCounters* c = _from_counters;
334 _from_counters = _to_counters;
335 _to_counters = c;
336 }
337 }
338
339 bool DefNewGeneration::expand(size_t bytes) {
340 MutexLocker x(ExpandHeap_lock);
341 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
342 bool success = _virtual_space.expand_by(bytes);
343 if (success && ZapUnusedHeapArea) {
344 // Mangle newly committed space immediately because it
345 // can be done here more simply that after the new
346 // spaces have been computed.
347 HeapWord* new_high = (HeapWord*) _virtual_space.high();
348 MemRegion mangle_region(prev_high, new_high);
349 SpaceMangler::mangle_region(mangle_region);
350 }
351
352 // Do not attempt an expand-to-the reserve size. The
353 // request should properly observe the maximum size of
354 // the generation so an expand-to-reserve should be
355 // unnecessary. Also a second call to expand-to-reserve
356 // value potentially can cause an undue expansion.
357 // For example if the first expand fail for unknown reasons,
358 // but the second succeeds and expands the heap to its maximum
359 // value.
360 if (GC_locker::is_active()) {
361 log_debug(gc)("Garbage collection disabled, expanded heap instead");
362 }
363
364 return success;
365 }
366
367 void DefNewGeneration::compute_new_size() {
368 // This is called after a GC that includes the old generation, so from-space
369 // will normally be empty.
370 // Note that we check both spaces, since if scavenge failed they revert roles.
371 // If not we bail out (otherwise we would have to relocate the objects).
372 if (!from()->is_empty() || !to()->is_empty()) {
373 return;
374 }
375
376 GenCollectedHeap* gch = GenCollectedHeap::heap();
377
378 size_t old_size = gch->old_gen()->capacity();
379 size_t new_size_before = _virtual_space.committed_size();
380 size_t min_new_size = initial_size();
381 size_t max_new_size = reserved().byte_size();
382 assert(min_new_size <= new_size_before &&
383 new_size_before <= max_new_size,
384 "just checking");
385 // All space sizes must be multiples of Generation::GenGrain.
386 size_t alignment = Generation::GenGrain;
387
388 // To revert previous value when an overflow happens.
389 size_t desired_new_size = new_size_before;
390
391 int threads_count = 0;
392 size_t thread_increase_size = 0;
393
394 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
395 if (NewSizeThreadIncrease > 0) {
396 size_t new_size_candidate = old_size / NewRatio;
397
398 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
399 threads_count = Threads::number_of_non_daemon_threads();
400 if (NewSizeThreadIncrease <= max_uintx / threads_count) {
401 thread_increase_size = threads_count * NewSizeThreadIncrease;
402
403 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
404 if (new_size_candidate <= max_uintx - thread_increase_size) {
405 new_size_candidate += thread_increase_size;
406
407 // 3. Check an overflow at 'align_size_up'.
408 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
409 if (new_size_candidate <= aligned_max) {
410 desired_new_size = align_size_up(new_size_candidate, alignment);
411 }
412 }
413 }
414 }
415
416 // Adjust new generation size
417 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
418 assert(desired_new_size <= max_new_size, "just checking");
419
420 bool changed = false;
421 if (desired_new_size > new_size_before) {
422 size_t change = desired_new_size - new_size_before;
423 assert(change % alignment == 0, "just checking");
424 if (expand(change)) {
425 changed = true;
426 }
427 // If the heap failed to expand to the desired size,
428 // "changed" will be false. If the expansion failed
429 // (and at this point it was expected to succeed),
430 // ignore the failure (leaving "changed" as false).
431 }
432 if (desired_new_size < new_size_before && eden()->is_empty()) {
433 // bail out of shrinking if objects in eden
434 size_t change = new_size_before - desired_new_size;
435 assert(change % alignment == 0, "just checking");
436 _virtual_space.shrink_by(change);
437 changed = true;
438 }
439 if (changed) {
440 // The spaces have already been mangled at this point but
441 // may not have been cleared (set top = bottom) and should be.
442 // Mangling was done when the heap was being expanded.
443 compute_space_boundaries(eden()->used(),
444 SpaceDecorator::Clear,
445 SpaceDecorator::DontMangle);
446 MemRegion cmr((HeapWord*)_virtual_space.low(),
447 (HeapWord*)_virtual_space.high());
448 gch->barrier_set()->resize_covered_region(cmr);
449
450 log_debug(gc, heap, ergo)(
451 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
452 new_size_before/K, _virtual_space.committed_size()/K,
453 eden()->capacity()/K, from()->capacity()/K);
454 log_trace(gc, heap, ergo)(
455 " [allowed " SIZE_FORMAT "K extra for %d threads]",
456 thread_increase_size/K, threads_count);
457 }
458 }
459
460 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
461 assert(false, "NYI -- are you sure you want to call this?");
462 }
463
464
465 size_t DefNewGeneration::capacity() const {
466 return eden()->capacity()
467 + from()->capacity(); // to() is only used during scavenge
468 }
469
470
471 size_t DefNewGeneration::used() const {
472 return eden()->used()
473 + from()->used(); // to() is only used during scavenge
474 }
475
476
477 size_t DefNewGeneration::free() const {
478 return eden()->free()
479 + from()->free(); // to() is only used during scavenge
480 }
481
482 size_t DefNewGeneration::max_capacity() const {
483 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
484 const size_t reserved_bytes = reserved().byte_size();
485 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
486 }
487
488 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
489 return eden()->free();
490 }
491
492 size_t DefNewGeneration::capacity_before_gc() const {
493 return eden()->capacity();
494 }
495
496 size_t DefNewGeneration::contiguous_available() const {
497 return eden()->free();
498 }
499
500
501 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
502 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
503
504 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
505 eden()->object_iterate(blk);
506 from()->object_iterate(blk);
507 }
508
509
510 void DefNewGeneration::space_iterate(SpaceClosure* blk,
511 bool usedOnly) {
512 blk->do_space(eden());
513 blk->do_space(from());
514 blk->do_space(to());
515 }
516
517 // The last collection bailed out, we are running out of heap space,
518 // so we try to allocate the from-space, too.
519 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
520 bool should_try_alloc = should_allocate_from_space() || GC_locker::is_active_and_needs_gc();
521
522 // If the Heap_lock is not locked by this thread, this will be called
523 // again later with the Heap_lock held.
524 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
525
526 HeapWord* result = NULL;
527 if (do_alloc) {
528 result = from()->allocate(size);
529 }
530
531 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s",
532 size,
533 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
534 "true" : "false",
535 Heap_lock->is_locked() ? "locked" : "unlocked",
536 from()->free(),
537 should_try_alloc ? "" : " should_allocate_from_space: NOT",
538 do_alloc ? " Heap_lock is not owned by self" : "",
539 result == NULL ? "NULL" : "object");
540
541 return result;
542 }
543
544 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
545 bool is_tlab,
546 bool parallel) {
547 // We don't attempt to expand the young generation (but perhaps we should.)
548 return allocate(size, is_tlab);
549 }
550
551 void DefNewGeneration::adjust_desired_tenuring_threshold() {
552 // Set the desired survivor size to half the real survivor space
553 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->collector_policy()->counters();
554 _tenuring_threshold =
555 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize, gc_counters);
556 }
557
558 void DefNewGeneration::collect(bool full,
559 bool clear_all_soft_refs,
560 size_t size,
561 bool is_tlab) {
562 assert(full || size > 0, "otherwise we don't want to collect");
563
564 GenCollectedHeap* gch = GenCollectedHeap::heap();
565
566 _gc_timer->register_gc_start();
567 DefNewTracer gc_tracer;
568 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
569
570 _old_gen = gch->old_gen();
571
572 // If the next generation is too full to accommodate promotion
573 // from this generation, pass on collection; let the next generation
574 // do it.
575 if (!collection_attempt_is_safe()) {
576 log_trace(gc)(":: Collection attempt not safe ::");
577 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
578 return;
579 }
580 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
581
582 init_assuming_no_promotion_failure();
583
584 GCTraceTime(Trace, gc) tm("DefNew", NULL, gch->gc_cause());
585
586 gch->trace_heap_before_gc(&gc_tracer);
587
588 // These can be shared for all code paths
589 IsAliveClosure is_alive(this);
590 ScanWeakRefClosure scan_weak_ref(this);
591
592 age_table()->clear();
593 to()->clear(SpaceDecorator::Mangle);
594
595 gch->rem_set()->prepare_for_younger_refs_iterate(false);
596
597 assert(gch->no_allocs_since_save_marks(),
598 "save marks have not been newly set.");
599
600 // Not very pretty.
601 CollectorPolicy* cp = gch->collector_policy();
602
603 FastScanClosure fsc_with_no_gc_barrier(this, false);
604 FastScanClosure fsc_with_gc_barrier(this, true);
605
606 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
607 gch->rem_set()->klass_rem_set());
608 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
609 &fsc_with_no_gc_barrier,
610 false);
611
612 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
613 FastEvacuateFollowersClosure evacuate_followers(gch,
614 &fsc_with_no_gc_barrier,
615 &fsc_with_gc_barrier);
616
617 assert(gch->no_allocs_since_save_marks(),
618 "save marks have not been newly set.");
619
620 {
621 // DefNew needs to run with n_threads == 0, to make sure the serial
622 // version of the card table scanning code is used.
623 // See: CardTableModRefBSForCTRS::non_clean_card_iterate_possibly_parallel.
624 StrongRootsScope srs(0);
625
626 gch->gen_process_roots(&srs,
627 GenCollectedHeap::YoungGen,
628 true, // Process younger gens, if any,
629 // as strong roots.
630 GenCollectedHeap::SO_ScavengeCodeCache,
631 GenCollectedHeap::StrongAndWeakRoots,
632 &fsc_with_no_gc_barrier,
633 &fsc_with_gc_barrier,
634 &cld_scan_closure);
635 }
636
637 // "evacuate followers".
638 evacuate_followers.do_void();
639
640 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
641 ReferenceProcessor* rp = ref_processor();
642 rp->setup_policy(clear_all_soft_refs);
643 const ReferenceProcessorStats& stats =
644 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
645 NULL, _gc_timer);
646 gc_tracer.report_gc_reference_stats(stats);
647 gc_tracer.report_tenuring_threshold(tenuring_threshold());
648
649 if (!_promotion_failed) {
650 // Swap the survivor spaces.
651 eden()->clear(SpaceDecorator::Mangle);
652 from()->clear(SpaceDecorator::Mangle);
653 if (ZapUnusedHeapArea) {
654 // This is now done here because of the piece-meal mangling which
655 // can check for valid mangling at intermediate points in the
656 // collection(s). When a young collection fails to collect
657 // sufficient space resizing of the young generation can occur
658 // an redistribute the spaces in the young generation. Mangle
659 // here so that unzapped regions don't get distributed to
660 // other spaces.
661 to()->mangle_unused_area();
662 }
663 swap_spaces();
664
665 assert(to()->is_empty(), "to space should be empty now");
666
667 adjust_desired_tenuring_threshold();
668
669 // A successful scavenge should restart the GC time limit count which is
670 // for full GC's.
671 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
672 size_policy->reset_gc_overhead_limit_count();
673 assert(!gch->incremental_collection_failed(), "Should be clear");
674 } else {
675 assert(_promo_failure_scan_stack.is_empty(), "post condition");
676 _promo_failure_scan_stack.clear(true); // Clear cached segments.
677
678 remove_forwarding_pointers();
679 log_debug(gc)("Promotion failed");
680 // Add to-space to the list of space to compact
681 // when a promotion failure has occurred. In that
682 // case there can be live objects in to-space
683 // as a result of a partial evacuation of eden
684 // and from-space.
685 swap_spaces(); // For uniformity wrt ParNewGeneration.
686 from()->set_next_compaction_space(to());
687 gch->set_incremental_collection_failed();
688
689 // Inform the next generation that a promotion failure occurred.
690 _old_gen->promotion_failure_occurred();
691 gc_tracer.report_promotion_failed(_promotion_failed_info);
692
693 // Reset the PromotionFailureALot counters.
694 NOT_PRODUCT(gch->reset_promotion_should_fail();)
695 }
696 // set new iteration safe limit for the survivor spaces
697 from()->set_concurrent_iteration_safe_limit(from()->top());
698 to()->set_concurrent_iteration_safe_limit(to()->top());
699
700 // We need to use a monotonically non-decreasing time in ms
701 // or we will see time-warp warnings and os::javaTimeMillis()
702 // does not guarantee monotonicity.
703 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
704 update_time_of_last_gc(now);
705
706 gch->trace_heap_after_gc(&gc_tracer);
707
708 _gc_timer->register_gc_end();
709
710 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
711 }
712
713 class RemoveForwardPointerClosure: public ObjectClosure {
714 public:
715 void do_object(oop obj) {
716 obj->init_mark();
717 }
718 };
719
720 void DefNewGeneration::init_assuming_no_promotion_failure() {
721 _promotion_failed = false;
722 _promotion_failed_info.reset();
723 from()->set_next_compaction_space(NULL);
724 }
725
726 void DefNewGeneration::remove_forwarding_pointers() {
727 RemoveForwardPointerClosure rspc;
728 eden()->object_iterate(&rspc);
729 from()->object_iterate(&rspc);
730
731 // Now restore saved marks, if any.
732 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
733 "should be the same");
734 while (!_objs_with_preserved_marks.is_empty()) {
735 oop obj = _objs_with_preserved_marks.pop();
736 markOop m = _preserved_marks_of_objs.pop();
737 obj->set_mark(m);
738 }
739 _objs_with_preserved_marks.clear(true);
740 _preserved_marks_of_objs.clear(true);
741 }
742
743 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
744 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
745 "Oversaving!");
746 _objs_with_preserved_marks.push(obj);
747 _preserved_marks_of_objs.push(m);
748 }
749
750 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
751 if (m->must_be_preserved_for_promotion_failure(obj)) {
752 preserve_mark(obj, m);
753 }
754 }
755
756 void DefNewGeneration::handle_promotion_failure(oop old) {
757 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
758
759 _promotion_failed = true;
760 _promotion_failed_info.register_copy_failure(old->size());
761 preserve_mark_if_necessary(old, old->mark());
762 // forward to self
763 old->forward_to(old);
764
765 _promo_failure_scan_stack.push(old);
766
767 if (!_promo_failure_drain_in_progress) {
768 // prevent recursion in copy_to_survivor_space()
769 _promo_failure_drain_in_progress = true;
770 drain_promo_failure_scan_stack();
771 _promo_failure_drain_in_progress = false;
772 }
773 }
774
775 oop DefNewGeneration::copy_to_survivor_space(oop old) {
776 assert(is_in_reserved(old) && !old->is_forwarded(),
777 "shouldn't be scavenging this oop");
778 size_t s = old->size();
779 oop obj = NULL;
780
781 // Try allocating obj in to-space (unless too old)
782 if (old->age() < tenuring_threshold()) {
783 obj = (oop) to()->allocate_aligned(s);
784 }
785
786 // Otherwise try allocating obj tenured
787 if (obj == NULL) {
788 obj = _old_gen->promote(old, s);
789 if (obj == NULL) {
790 handle_promotion_failure(old);
791 return old;
792 }
793 } else {
794 // Prefetch beyond obj
795 const intx interval = PrefetchCopyIntervalInBytes;
796 Prefetch::write(obj, interval);
797
798 // Copy obj
799 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
800
801 // Increment age if obj still in new generation
802 obj->incr_age();
803 age_table()->add(obj, s);
804 }
805
806 // Done, insert forward pointer to obj in this header
807 old->forward_to(obj);
808
809 return obj;
810 }
811
812 void DefNewGeneration::drain_promo_failure_scan_stack() {
813 while (!_promo_failure_scan_stack.is_empty()) {
814 oop obj = _promo_failure_scan_stack.pop();
815 obj->oop_iterate(_promo_failure_scan_stack_closure);
816 }
817 }
818
819 void DefNewGeneration::save_marks() {
820 eden()->set_saved_mark();
821 to()->set_saved_mark();
822 from()->set_saved_mark();
823 }
824
825
826 void DefNewGeneration::reset_saved_marks() {
827 eden()->reset_saved_mark();
828 to()->reset_saved_mark();
829 from()->reset_saved_mark();
830 }
831
832
833 bool DefNewGeneration::no_allocs_since_save_marks() {
834 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
835 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
836 return to()->saved_mark_at_top();
837 }
838
839 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
840 \
841 void DefNewGeneration:: \
842 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
843 cl->set_generation(this); \
844 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
845 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
846 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
847 cl->reset_generation(); \
848 save_marks(); \
849 }
850
851 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
852
853 #undef DefNew_SINCE_SAVE_MARKS_DEFN
854
855 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
856 size_t max_alloc_words) {
857 if (requestor == this || _promotion_failed) {
858 return;
859 }
860 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
861
862 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
863 if (to_space->top() > to_space->bottom()) {
864 trace("to_space not empty when contribute_scratch called");
865 }
866 */
867
868 ContiguousSpace* to_space = to();
869 assert(to_space->end() >= to_space->top(), "pointers out of order");
870 size_t free_words = pointer_delta(to_space->end(), to_space->top());
871 if (free_words >= MinFreeScratchWords) {
872 ScratchBlock* sb = (ScratchBlock*)to_space->top();
873 sb->num_words = free_words;
874 sb->next = list;
875 list = sb;
876 }
877 }
878
879 void DefNewGeneration::reset_scratch() {
880 // If contributing scratch in to_space, mangle all of
881 // to_space if ZapUnusedHeapArea. This is needed because
882 // top is not maintained while using to-space as scratch.
883 if (ZapUnusedHeapArea) {
884 to()->mangle_unused_area_complete();
885 }
886 }
887
888 bool DefNewGeneration::collection_attempt_is_safe() {
889 if (!to()->is_empty()) {
890 log_trace(gc)(":: to is not empty ::");
891 return false;
892 }
893 if (_old_gen == NULL) {
894 GenCollectedHeap* gch = GenCollectedHeap::heap();
895 _old_gen = gch->old_gen();
896 }
897 return _old_gen->promotion_attempt_is_safe(used());
898 }
899
900 void DefNewGeneration::gc_epilogue(bool full) {
901 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
902
903 assert(!GC_locker::is_active(), "We should not be executing here");
904 // Check if the heap is approaching full after a collection has
905 // been done. Generally the young generation is empty at
906 // a minimum at the end of a collection. If it is not, then
907 // the heap is approaching full.
908 GenCollectedHeap* gch = GenCollectedHeap::heap();
909 if (full) {
910 DEBUG_ONLY(seen_incremental_collection_failed = false;)
911 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
912 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
913 GCCause::to_string(gch->gc_cause()));
914 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
915 set_should_allocate_from_space(); // we seem to be running out of space
916 } else {
917 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
918 GCCause::to_string(gch->gc_cause()));
919 gch->clear_incremental_collection_failed(); // We just did a full collection
920 clear_should_allocate_from_space(); // if set
921 }
922 } else {
923 #ifdef ASSERT
924 // It is possible that incremental_collection_failed() == true
925 // here, because an attempted scavenge did not succeed. The policy
926 // is normally expected to cause a full collection which should
927 // clear that condition, so we should not be here twice in a row
928 // with incremental_collection_failed() == true without having done
929 // a full collection in between.
930 if (!seen_incremental_collection_failed &&
931 gch->incremental_collection_failed()) {
932 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
933 GCCause::to_string(gch->gc_cause()));
934 seen_incremental_collection_failed = true;
935 } else if (seen_incremental_collection_failed) {
936 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
937 GCCause::to_string(gch->gc_cause()));
938 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
939 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
940 !gch->incremental_collection_failed(),
941 "Twice in a row");
942 seen_incremental_collection_failed = false;
943 }
944 #endif // ASSERT
945 }
946
947 if (ZapUnusedHeapArea) {
948 eden()->check_mangled_unused_area_complete();
949 from()->check_mangled_unused_area_complete();
950 to()->check_mangled_unused_area_complete();
951 }
952
953 if (!CleanChunkPoolAsync) {
954 Chunk::clean_chunk_pool();
955 }
956
957 // update the generation and space performance counters
958 update_counters();
959 gch->collector_policy()->counters()->update_counters();
960 }
961
962 void DefNewGeneration::record_spaces_top() {
963 assert(ZapUnusedHeapArea, "Not mangling unused space");
964 eden()->set_top_for_allocations();
965 to()->set_top_for_allocations();
966 from()->set_top_for_allocations();
967 }
968
969 void DefNewGeneration::ref_processor_init() {
970 Generation::ref_processor_init();
971 }
972
973
974 void DefNewGeneration::update_counters() {
975 if (UsePerfData) {
976 _eden_counters->update_all();
977 _from_counters->update_all();
978 _to_counters->update_all();
979 _gen_counters->update_all();
980 }
981 }
982
983 void DefNewGeneration::verify() {
984 eden()->verify();
985 from()->verify();
986 to()->verify();
987 }
988
989 void DefNewGeneration::print_on(outputStream* st) const {
990 Generation::print_on(st);
991 st->print(" eden");
992 eden()->print_on(st);
993 st->print(" from");
994 from()->print_on(st);
995 st->print(" to ");
996 to()->print_on(st);
997 }
998
999
1000 const char* DefNewGeneration::name() const {
1001 return "def new generation";
1002 }
1003
1004 // Moved from inline file as they are not called inline
1005 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1006 return eden();
1007 }
1008
1009 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1010 // This is the slow-path allocation for the DefNewGeneration.
1011 // Most allocations are fast-path in compiled code.
1012 // We try to allocate from the eden. If that works, we are happy.
1013 // Note that since DefNewGeneration supports lock-free allocation, we
1014 // have to use it here, as well.
1015 HeapWord* result = eden()->par_allocate(word_size);
1016 if (result != NULL) {
1017 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1018 _old_gen->sample_eden_chunk();
1019 }
1020 } else {
1021 // If the eden is full and the last collection bailed out, we are running
1022 // out of heap space, and we try to allocate the from-space, too.
1023 // allocate_from_space can't be inlined because that would introduce a
1024 // circular dependency at compile time.
1025 result = allocate_from_space(word_size);
1026 }
1027 return result;
1028 }
1029
1030 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1031 bool is_tlab) {
1032 HeapWord* res = eden()->par_allocate(word_size);
1033 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1034 _old_gen->sample_eden_chunk();
1035 }
1036 return res;
1037 }
1038
1039 size_t DefNewGeneration::tlab_capacity() const {
1040 return eden()->capacity();
1041 }
1042
1043 size_t DefNewGeneration::tlab_used() const {
1044 return eden()->used();
1045 }
1046
1047 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1048 return unsafe_max_alloc_nogc();
1049 }