1 /*
2 * Copyright (c) 2001, 2018, 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/serial/serialHeap.inline.hpp"
28 #include "gc/serial/tenuredGeneration.hpp"
29 #include "gc/shared/adaptiveSizePolicy.hpp"
30 #include "gc/shared/ageTable.inline.hpp"
31 #include "gc/shared/cardTableRS.hpp"
32 #include "gc/shared/collectorCounters.hpp"
33 #include "gc/shared/gcArguments.hpp"
34 #include "gc/shared/gcHeapSummary.hpp"
35 #include "gc/shared/gcLocker.hpp"
36 #include "gc/shared/gcPolicyCounters.hpp"
37 #include "gc/shared/gcTimer.hpp"
38 #include "gc/shared/gcTrace.hpp"
39 #include "gc/shared/gcTraceTime.inline.hpp"
40 #include "gc/shared/genOopClosures.inline.hpp"
41 #include "gc/shared/generationSpec.hpp"
42 #include "gc/shared/preservedMarks.inline.hpp"
43 #include "gc/shared/referencePolicy.hpp"
44 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
45 #include "gc/shared/space.inline.hpp"
46 #include "gc/shared/spaceDecorator.hpp"
47 #include "gc/shared/strongRootsScope.hpp"
48 #include "gc/shared/weakProcessor.hpp"
49 #include "logging/log.hpp"
50 #include "memory/iterator.inline.hpp"
51 #include "memory/resourceArea.hpp"
52 #include "oops/instanceRefKlass.hpp"
53 #include "oops/oop.inline.hpp"
54 #include "runtime/atomic.hpp"
55 #include "runtime/java.hpp"
56 #include "runtime/mutexLocker.inline.hpp"
57 #include "runtime/prefetch.inline.hpp"
58 #include "runtime/thread.inline.hpp"
59 #include "utilities/align.hpp"
60 #include "utilities/copy.hpp"
61 #include "utilities/globalDefinitions.hpp"
62 #include "utilities/stack.inline.hpp"
63
64 //
65 // DefNewGeneration functions.
66
67 // Methods of protected closure types.
68
69 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
70 assert(_young_gen->kind() == Generation::ParNew ||
71 _young_gen->kind() == Generation::DefNew, "Expected the young generation here");
72 }
73
74 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
75 return (HeapWord*)p >= _young_gen->reserved().end() || p->is_forwarded();
76 }
77
78 DefNewGeneration::KeepAliveClosure::
79 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
80 _rs = GenCollectedHeap::heap()->rem_set();
81 }
82
83 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
84 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
85
86
87 DefNewGeneration::FastKeepAliveClosure::
88 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
89 DefNewGeneration::KeepAliveClosure(cl) {
90 _boundary = g->reserved().end();
91 }
92
93 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
94 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
95
96 DefNewGeneration::FastEvacuateFollowersClosure::
97 FastEvacuateFollowersClosure(SerialHeap* heap,
98 FastScanClosure* cur,
99 FastScanClosure* older) :
100 _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older)
101 {
102 }
103
104 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
105 do {
106 _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older);
107 } while (!_heap->no_allocs_since_save_marks());
108 guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan");
109 }
110
111 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
112 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
113 {
114 _boundary = _g->reserved().end();
115 }
116
117 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
118 OopsInClassLoaderDataOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
119 {
120 _boundary = _g->reserved().end();
121 }
122
123 void CLDScanClosure::do_cld(ClassLoaderData* cld) {
124 NOT_PRODUCT(ResourceMark rm);
125 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s",
126 p2i(cld),
127 cld->loader_name_and_id(),
128 cld->has_modified_oops() ? "true" : "false");
129
130 // If the cld has not been dirtied we know that there's
131 // no references into the young gen and we can skip it.
132 if (cld->has_modified_oops()) {
133 if (_accumulate_modified_oops) {
134 cld->accumulate_modified_oops();
135 }
136
137 // Tell the closure which CLD is being scanned so that it can be dirtied
138 // if oops are left pointing into the young gen.
139 _scavenge_closure->set_scanned_cld(cld);
140
141 // Clean the cld since we're going to scavenge all the metadata.
142 cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);
143
144 _scavenge_closure->set_scanned_cld(NULL);
145 }
146 }
147
148 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
149 _g(g)
150 {
151 _boundary = _g->reserved().end();
152 }
153
154 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
155 size_t initial_size,
156 size_t min_size,
157 size_t max_size,
158 const char* policy)
159 : Generation(rs, initial_size),
160 _preserved_marks_set(false /* in_c_heap */),
161 _promo_failure_drain_in_progress(false),
162 _should_allocate_from_space(false)
163 {
164 MemRegion cmr((HeapWord*)_virtual_space.low(),
165 (HeapWord*)_virtual_space.high());
166 GenCollectedHeap* gch = GenCollectedHeap::heap();
167
168 gch->rem_set()->resize_covered_region(cmr);
169
170 _eden_space = new ContiguousSpace();
171 _from_space = new ContiguousSpace();
172 _to_space = new ContiguousSpace();
173
174 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
175 vm_exit_during_initialization("Could not allocate a new gen space");
176 }
177
178 // Compute the maximum eden and survivor space sizes. These sizes
179 // are computed assuming the entire reserved space is committed.
180 // These values are exported as performance counters.
181 uintx size = _virtual_space.reserved_size();
182 _max_survivor_size = compute_survivor_size(size, SpaceAlignment);
183 _max_eden_size = size - (2*_max_survivor_size);
184
185 // allocate the performance counters
186
187 // Generation counters -- generation 0, 3 subspaces
188 _gen_counters = new GenerationCounters("new", 0, 3,
189 min_size, max_size, &_virtual_space);
190 _gc_counters = new CollectorCounters(policy, 0);
191
192 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
193 _gen_counters);
194 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
195 _gen_counters);
196 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
197 _gen_counters);
198
199 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
200 update_counters();
201 _old_gen = NULL;
202 _tenuring_threshold = MaxTenuringThreshold;
203 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
204
205 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
206 }
207
208 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
209 bool clear_space,
210 bool mangle_space) {
211 // If the spaces are being cleared (only done at heap initialization
212 // currently), the survivor spaces need not be empty.
213 // Otherwise, no care is taken for used areas in the survivor spaces
214 // so check.
215 assert(clear_space || (to()->is_empty() && from()->is_empty()),
216 "Initialization of the survivor spaces assumes these are empty");
217
218 // Compute sizes
219 uintx size = _virtual_space.committed_size();
220 uintx survivor_size = compute_survivor_size(size, SpaceAlignment);
221 uintx eden_size = size - (2*survivor_size);
222 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
223
224 if (eden_size < minimum_eden_size) {
225 // May happen due to 64Kb rounding, if so adjust eden size back up
226 minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment);
227 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
228 uintx unaligned_survivor_size =
229 align_down(maximum_survivor_size, SpaceAlignment);
230 survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment);
231 eden_size = size - (2*survivor_size);
232 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
233 assert(eden_size >= minimum_eden_size, "just checking");
234 }
235
236 char *eden_start = _virtual_space.low();
237 char *from_start = eden_start + eden_size;
238 char *to_start = from_start + survivor_size;
239 char *to_end = to_start + survivor_size;
240
241 assert(to_end == _virtual_space.high(), "just checking");
242 assert(Space::is_aligned(eden_start), "checking alignment");
243 assert(Space::is_aligned(from_start), "checking alignment");
244 assert(Space::is_aligned(to_start), "checking alignment");
245
246 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
247 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
248 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
249
250 // A minimum eden size implies that there is a part of eden that
251 // is being used and that affects the initialization of any
252 // newly formed eden.
253 bool live_in_eden = minimum_eden_size > 0;
254
255 // If not clearing the spaces, do some checking to verify that
256 // the space are already mangled.
257 if (!clear_space) {
258 // Must check mangling before the spaces are reshaped. Otherwise,
259 // the bottom or end of one space may have moved into another
260 // a failure of the check may not correctly indicate which space
261 // is not properly mangled.
262 if (ZapUnusedHeapArea) {
263 HeapWord* limit = (HeapWord*) _virtual_space.high();
264 eden()->check_mangled_unused_area(limit);
265 from()->check_mangled_unused_area(limit);
266 to()->check_mangled_unused_area(limit);
267 }
268 }
269
270 // Reset the spaces for their new regions.
271 eden()->initialize(edenMR,
272 clear_space && !live_in_eden,
273 SpaceDecorator::Mangle);
274 // If clear_space and live_in_eden, we will not have cleared any
275 // portion of eden above its top. This can cause newly
276 // expanded space not to be mangled if using ZapUnusedHeapArea.
277 // We explicitly do such mangling here.
278 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
279 eden()->mangle_unused_area();
280 }
281 from()->initialize(fromMR, clear_space, mangle_space);
282 to()->initialize(toMR, clear_space, mangle_space);
283
284 // Set next compaction spaces.
285 eden()->set_next_compaction_space(from());
286 // The to-space is normally empty before a compaction so need
287 // not be considered. The exception is during promotion
288 // failure handling when to-space can contain live objects.
289 from()->set_next_compaction_space(NULL);
290 }
291
292 void DefNewGeneration::swap_spaces() {
293 ContiguousSpace* s = from();
294 _from_space = to();
295 _to_space = s;
296 eden()->set_next_compaction_space(from());
297 // The to-space is normally empty before a compaction so need
298 // not be considered. The exception is during promotion
299 // failure handling when to-space can contain live objects.
300 from()->set_next_compaction_space(NULL);
301
302 if (UsePerfData) {
303 CSpaceCounters* c = _from_counters;
304 _from_counters = _to_counters;
305 _to_counters = c;
306 }
307 }
308
309 bool DefNewGeneration::expand(size_t bytes) {
310 MutexLocker x(ExpandHeap_lock);
311 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
312 bool success = _virtual_space.expand_by(bytes);
313 if (success && ZapUnusedHeapArea) {
314 // Mangle newly committed space immediately because it
315 // can be done here more simply that after the new
316 // spaces have been computed.
317 HeapWord* new_high = (HeapWord*) _virtual_space.high();
318 MemRegion mangle_region(prev_high, new_high);
319 SpaceMangler::mangle_region(mangle_region);
320 }
321
322 // Do not attempt an expand-to-the reserve size. The
323 // request should properly observe the maximum size of
324 // the generation so an expand-to-reserve should be
325 // unnecessary. Also a second call to expand-to-reserve
326 // value potentially can cause an undue expansion.
327 // For example if the first expand fail for unknown reasons,
328 // but the second succeeds and expands the heap to its maximum
329 // value.
330 if (GCLocker::is_active()) {
331 log_debug(gc)("Garbage collection disabled, expanded heap instead");
332 }
333
334 return success;
335 }
336
337 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
338 size_t new_size_before,
339 size_t alignment) const {
340 size_t desired_new_size = new_size_before;
341
342 if (NewSizeThreadIncrease > 0) {
343 int threads_count;
344 size_t thread_increase_size = 0;
345
346 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
347 threads_count = Threads::number_of_non_daemon_threads();
348 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
349 thread_increase_size = threads_count * NewSizeThreadIncrease;
350
351 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
352 if (new_size_candidate <= max_uintx - thread_increase_size) {
353 new_size_candidate += thread_increase_size;
354
355 // 3. Check an overflow at 'align_up'.
356 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
357 if (new_size_candidate <= aligned_max) {
358 desired_new_size = align_up(new_size_candidate, alignment);
359 }
360 }
361 }
362 }
363
364 return desired_new_size;
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 int threads_count = 0;
389 size_t thread_increase_size = 0;
390
391 size_t new_size_candidate = old_size / NewRatio;
392 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
393 // and reverts to previous value if any overflow happens
394 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);
395
396 // Adjust new generation size
397 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
398 assert(desired_new_size <= max_new_size, "just checking");
399
400 bool changed = false;
401 if (desired_new_size > new_size_before) {
402 size_t change = desired_new_size - new_size_before;
403 assert(change % alignment == 0, "just checking");
404 if (expand(change)) {
405 changed = true;
406 }
407 // If the heap failed to expand to the desired size,
408 // "changed" will be false. If the expansion failed
409 // (and at this point it was expected to succeed),
410 // ignore the failure (leaving "changed" as false).
411 }
412 if (desired_new_size < new_size_before && eden()->is_empty()) {
413 // bail out of shrinking if objects in eden
414 size_t change = new_size_before - desired_new_size;
415 assert(change % alignment == 0, "just checking");
416 _virtual_space.shrink_by(change);
417 changed = true;
418 }
419 if (changed) {
420 // The spaces have already been mangled at this point but
421 // may not have been cleared (set top = bottom) and should be.
422 // Mangling was done when the heap was being expanded.
423 compute_space_boundaries(eden()->used(),
424 SpaceDecorator::Clear,
425 SpaceDecorator::DontMangle);
426 MemRegion cmr((HeapWord*)_virtual_space.low(),
427 (HeapWord*)_virtual_space.high());
428 gch->rem_set()->resize_covered_region(cmr);
429
430 log_debug(gc, ergo, heap)(
431 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
432 new_size_before/K, _virtual_space.committed_size()/K,
433 eden()->capacity()/K, from()->capacity()/K);
434 log_trace(gc, ergo, heap)(
435 " [allowed " SIZE_FORMAT "K extra for %d threads]",
436 thread_increase_size/K, threads_count);
437 }
438 }
439
440 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl, uint n_threads) {
441 assert(false, "NYI -- are you sure you want to call this?");
442 }
443
444
445 size_t DefNewGeneration::capacity() const {
446 return eden()->capacity()
447 + from()->capacity(); // to() is only used during scavenge
448 }
449
450
451 size_t DefNewGeneration::used() const {
452 return eden()->used()
453 + from()->used(); // to() is only used during scavenge
454 }
455
456
457 size_t DefNewGeneration::free() const {
458 return eden()->free()
459 + from()->free(); // to() is only used during scavenge
460 }
461
462 size_t DefNewGeneration::max_capacity() const {
463 const size_t reserved_bytes = reserved().byte_size();
464 return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment);
465 }
466
467 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
468 return eden()->free();
469 }
470
471 size_t DefNewGeneration::capacity_before_gc() const {
472 return eden()->capacity();
473 }
474
475 size_t DefNewGeneration::contiguous_available() const {
476 return eden()->free();
477 }
478
479
480 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }
481 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
482
483 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
484 eden()->object_iterate(blk);
485 from()->object_iterate(blk);
486 }
487
488
489 void DefNewGeneration::space_iterate(SpaceClosure* blk,
490 bool usedOnly) {
491 blk->do_space(eden());
492 blk->do_space(from());
493 blk->do_space(to());
494 }
495
496 // The last collection bailed out, we are running out of heap space,
497 // so we try to allocate the from-space, too.
498 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
499 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
500
501 // If the Heap_lock is not locked by this thread, this will be called
502 // again later with the Heap_lock held.
503 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
504
505 HeapWord* result = NULL;
506 if (do_alloc) {
507 result = from()->allocate(size);
508 }
509
510 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s",
511 size,
512 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
513 "true" : "false",
514 Heap_lock->is_locked() ? "locked" : "unlocked",
515 from()->free(),
516 should_try_alloc ? "" : " should_allocate_from_space: NOT",
517 do_alloc ? " Heap_lock is not owned by self" : "",
518 result == NULL ? "NULL" : "object");
519
520 return result;
521 }
522
523 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
524 bool is_tlab,
525 bool parallel) {
526 // We don't attempt to expand the young generation (but perhaps we should.)
527 return allocate(size, is_tlab);
528 }
529
530 void DefNewGeneration::adjust_desired_tenuring_threshold() {
531 // Set the desired survivor size to half the real survivor space
532 size_t const survivor_capacity = to()->capacity() / HeapWordSize;
533 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
534
535 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
536
537 if (UsePerfData) {
538 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters();
539 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
540 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
541 }
542
543 age_table()->print_age_table(_tenuring_threshold);
544 }
545
546 void DefNewGeneration::collect(bool full,
547 bool clear_all_soft_refs,
548 size_t size,
549 bool is_tlab) {
550 assert(full || size > 0, "otherwise we don't want to collect");
551
552 SerialHeap* heap = SerialHeap::heap();
553
554 _gc_timer->register_gc_start();
555 DefNewTracer gc_tracer;
556 gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start());
557
558 _old_gen = heap->old_gen();
559
560 // If the next generation is too full to accommodate promotion
561 // from this generation, pass on collection; let the next generation
562 // do it.
563 if (!collection_attempt_is_safe()) {
564 log_trace(gc)(":: Collection attempt not safe ::");
565 heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
566 return;
567 }
568 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
569
570 init_assuming_no_promotion_failure();
571
572 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause());
573
574 heap->trace_heap_before_gc(&gc_tracer);
575
576 // These can be shared for all code paths
577 IsAliveClosure is_alive(this);
578 ScanWeakRefClosure scan_weak_ref(this);
579
580 age_table()->clear();
581 to()->clear(SpaceDecorator::Mangle);
582 // The preserved marks should be empty at the start of the GC.
583 _preserved_marks_set.init(1);
584
585 heap->rem_set()->prepare_for_younger_refs_iterate(false);
586
587 assert(heap->no_allocs_since_save_marks(),
588 "save marks have not been newly set.");
589
590 FastScanClosure fsc_with_no_gc_barrier(this, false);
591 FastScanClosure fsc_with_gc_barrier(this, true);
592
593 CLDScanClosure cld_scan_closure(&fsc_with_no_gc_barrier,
594 heap->rem_set()->cld_rem_set()->accumulate_modified_oops());
595
596 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
597 FastEvacuateFollowersClosure evacuate_followers(heap,
598 &fsc_with_no_gc_barrier,
599 &fsc_with_gc_barrier);
600
601 assert(heap->no_allocs_since_save_marks(),
602 "save marks have not been newly set.");
603
604 {
605 // DefNew needs to run with n_threads == 0, to make sure the serial
606 // version of the card table scanning code is used.
607 // See: CardTableRS::non_clean_card_iterate_possibly_parallel.
608 StrongRootsScope srs(0);
609
610 heap->young_process_roots(&srs,
611 &fsc_with_no_gc_barrier,
612 &fsc_with_gc_barrier,
613 &cld_scan_closure);
614 }
615
616 // "evacuate followers".
617 evacuate_followers.do_void();
618
619 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
620 ReferenceProcessor* rp = ref_processor();
621 rp->setup_policy(clear_all_soft_refs);
622 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
623 const ReferenceProcessorStats& stats =
624 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
625 NULL, &pt);
626 gc_tracer.report_gc_reference_stats(stats);
627 gc_tracer.report_tenuring_threshold(tenuring_threshold());
628 pt.print_all_references();
629
630 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
631
632 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
633
634 // Verify that the usage of keep_alive didn't copy any objects.
635 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
636
637 if (!_promotion_failed) {
638 // Swap the survivor spaces.
639 eden()->clear(SpaceDecorator::Mangle);
640 from()->clear(SpaceDecorator::Mangle);
641 if (ZapUnusedHeapArea) {
642 // This is now done here because of the piece-meal mangling which
643 // can check for valid mangling at intermediate points in the
644 // collection(s). When a young collection fails to collect
645 // sufficient space resizing of the young generation can occur
646 // an redistribute the spaces in the young generation. Mangle
647 // here so that unzapped regions don't get distributed to
648 // other spaces.
649 to()->mangle_unused_area();
650 }
651 swap_spaces();
652
653 assert(to()->is_empty(), "to space should be empty now");
654
655 adjust_desired_tenuring_threshold();
656
657 // A successful scavenge should restart the GC time limit count which is
658 // for full GC's.
659 AdaptiveSizePolicy* size_policy = heap->size_policy();
660 size_policy->reset_gc_overhead_limit_count();
661 assert(!heap->incremental_collection_failed(), "Should be clear");
662 } else {
663 assert(_promo_failure_scan_stack.is_empty(), "post condition");
664 _promo_failure_scan_stack.clear(true); // Clear cached segments.
665
666 remove_forwarding_pointers();
667 log_info(gc, promotion)("Promotion failed");
668 // Add to-space to the list of space to compact
669 // when a promotion failure has occurred. In that
670 // case there can be live objects in to-space
671 // as a result of a partial evacuation of eden
672 // and from-space.
673 swap_spaces(); // For uniformity wrt ParNewGeneration.
674 from()->set_next_compaction_space(to());
675 heap->set_incremental_collection_failed();
676
677 // Inform the next generation that a promotion failure occurred.
678 _old_gen->promotion_failure_occurred();
679 gc_tracer.report_promotion_failed(_promotion_failed_info);
680
681 // Reset the PromotionFailureALot counters.
682 NOT_PRODUCT(heap->reset_promotion_should_fail();)
683 }
684 // We should have processed and cleared all the preserved marks.
685 _preserved_marks_set.reclaim();
686 // set new iteration safe limit for the survivor spaces
687 from()->set_concurrent_iteration_safe_limit(from()->top());
688 to()->set_concurrent_iteration_safe_limit(to()->top());
689
690 // We need to use a monotonically non-decreasing time in ms
691 // or we will see time-warp warnings and os::javaTimeMillis()
692 // does not guarantee monotonicity.
693 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
694 update_time_of_last_gc(now);
695
696 heap->trace_heap_after_gc(&gc_tracer);
697
698 _gc_timer->register_gc_end();
699
700 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
701 }
702
703 void DefNewGeneration::init_assuming_no_promotion_failure() {
704 _promotion_failed = false;
705 _promotion_failed_info.reset();
706 from()->set_next_compaction_space(NULL);
707 }
708
709 void DefNewGeneration::remove_forwarding_pointers() {
710 RemoveForwardedPointerClosure rspc;
711 eden()->object_iterate(&rspc);
712 from()->object_iterate(&rspc);
713 restore_preserved_marks();
714 }
715
716 void DefNewGeneration::restore_preserved_marks() {
717 SharedRestorePreservedMarksTaskExecutor task_executor(NULL);
718 _preserved_marks_set.restore(&task_executor);
719 }
720
721 void DefNewGeneration::handle_promotion_failure(oop old) {
722 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
723
724 _promotion_failed = true;
725 _promotion_failed_info.register_copy_failure(old->size());
726 _preserved_marks_set.get()->push_if_necessary(old, old->mark_raw());
727 // forward to self
728 old->forward_to(old);
729
730 _promo_failure_scan_stack.push(old);
731
732 if (!_promo_failure_drain_in_progress) {
733 // prevent recursion in copy_to_survivor_space()
734 _promo_failure_drain_in_progress = true;
735 drain_promo_failure_scan_stack();
736 _promo_failure_drain_in_progress = false;
737 }
738 }
739
740 oop DefNewGeneration::copy_to_survivor_space(oop old) {
741 assert(is_in_reserved(old) && !old->is_forwarded(),
742 "shouldn't be scavenging this oop");
743 size_t s = old->size();
744 oop obj = NULL;
745
746 // Try allocating obj in to-space (unless too old)
747 if (old->age() < tenuring_threshold()) {
748 obj = (oop) to()->allocate_aligned(s);
749 }
750
751 // Otherwise try allocating obj tenured
752 if (obj == NULL) {
753 obj = _old_gen->promote(old, s);
754 if (obj == NULL) {
755 handle_promotion_failure(old);
756 return old;
757 }
758 } else {
759 // Prefetch beyond obj
760 const intx interval = PrefetchCopyIntervalInBytes;
761 Prefetch::write(obj, interval);
762
763 // Copy obj
764 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
765
766 // Increment age if obj still in new generation
767 obj->incr_age();
768 age_table()->add(obj, s);
769 }
770
771 // Done, insert forward pointer to obj in this header
772 old->forward_to(obj);
773
774 return obj;
775 }
776
777 void DefNewGeneration::drain_promo_failure_scan_stack() {
778 while (!_promo_failure_scan_stack.is_empty()) {
779 oop obj = _promo_failure_scan_stack.pop();
780 obj->oop_iterate(_promo_failure_scan_stack_closure);
781 }
782 }
783
784 void DefNewGeneration::save_marks() {
785 eden()->set_saved_mark();
786 to()->set_saved_mark();
787 from()->set_saved_mark();
788 }
789
790
791 void DefNewGeneration::reset_saved_marks() {
792 eden()->reset_saved_mark();
793 to()->reset_saved_mark();
794 from()->reset_saved_mark();
795 }
796
797
798 bool DefNewGeneration::no_allocs_since_save_marks() {
799 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
800 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
801 return to()->saved_mark_at_top();
802 }
803
804 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
805 size_t max_alloc_words) {
806 if (requestor == this || _promotion_failed) {
807 return;
808 }
809 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
810
811 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
812 if (to_space->top() > to_space->bottom()) {
813 trace("to_space not empty when contribute_scratch called");
814 }
815 */
816
817 ContiguousSpace* to_space = to();
818 assert(to_space->end() >= to_space->top(), "pointers out of order");
819 size_t free_words = pointer_delta(to_space->end(), to_space->top());
820 if (free_words >= MinFreeScratchWords) {
821 ScratchBlock* sb = (ScratchBlock*)to_space->top();
822 sb->num_words = free_words;
823 sb->next = list;
824 list = sb;
825 }
826 }
827
828 void DefNewGeneration::reset_scratch() {
829 // If contributing scratch in to_space, mangle all of
830 // to_space if ZapUnusedHeapArea. This is needed because
831 // top is not maintained while using to-space as scratch.
832 if (ZapUnusedHeapArea) {
833 to()->mangle_unused_area_complete();
834 }
835 }
836
837 bool DefNewGeneration::collection_attempt_is_safe() {
838 if (!to()->is_empty()) {
839 log_trace(gc)(":: to is not empty ::");
840 return false;
841 }
842 if (_old_gen == NULL) {
843 GenCollectedHeap* gch = GenCollectedHeap::heap();
844 _old_gen = gch->old_gen();
845 }
846 return _old_gen->promotion_attempt_is_safe(used());
847 }
848
849 void DefNewGeneration::gc_epilogue(bool full) {
850 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
851
852 assert(!GCLocker::is_active(), "We should not be executing here");
853 // Check if the heap is approaching full after a collection has
854 // been done. Generally the young generation is empty at
855 // a minimum at the end of a collection. If it is not, then
856 // the heap is approaching full.
857 GenCollectedHeap* gch = GenCollectedHeap::heap();
858 if (full) {
859 DEBUG_ONLY(seen_incremental_collection_failed = false;)
860 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
861 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
862 GCCause::to_string(gch->gc_cause()));
863 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
864 set_should_allocate_from_space(); // we seem to be running out of space
865 } else {
866 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
867 GCCause::to_string(gch->gc_cause()));
868 gch->clear_incremental_collection_failed(); // We just did a full collection
869 clear_should_allocate_from_space(); // if set
870 }
871 } else {
872 #ifdef ASSERT
873 // It is possible that incremental_collection_failed() == true
874 // here, because an attempted scavenge did not succeed. The policy
875 // is normally expected to cause a full collection which should
876 // clear that condition, so we should not be here twice in a row
877 // with incremental_collection_failed() == true without having done
878 // a full collection in between.
879 if (!seen_incremental_collection_failed &&
880 gch->incremental_collection_failed()) {
881 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
882 GCCause::to_string(gch->gc_cause()));
883 seen_incremental_collection_failed = true;
884 } else if (seen_incremental_collection_failed) {
885 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
886 GCCause::to_string(gch->gc_cause()));
887 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
888 (GCCause::is_user_requested_gc(gch->gc_cause()) && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
889 !gch->incremental_collection_failed(),
890 "Twice in a row");
891 seen_incremental_collection_failed = false;
892 }
893 #endif // ASSERT
894 }
895
896 if (ZapUnusedHeapArea) {
897 eden()->check_mangled_unused_area_complete();
898 from()->check_mangled_unused_area_complete();
899 to()->check_mangled_unused_area_complete();
900 }
901
902 if (!CleanChunkPoolAsync) {
903 Chunk::clean_chunk_pool();
904 }
905
906 // update the generation and space performance counters
907 update_counters();
908 gch->counters()->update_counters();
909 }
910
911 void DefNewGeneration::record_spaces_top() {
912 assert(ZapUnusedHeapArea, "Not mangling unused space");
913 eden()->set_top_for_allocations();
914 to()->set_top_for_allocations();
915 from()->set_top_for_allocations();
916 }
917
918 void DefNewGeneration::ref_processor_init() {
919 Generation::ref_processor_init();
920 }
921
922
923 void DefNewGeneration::update_counters() {
924 if (UsePerfData) {
925 _eden_counters->update_all();
926 _from_counters->update_all();
927 _to_counters->update_all();
928 _gen_counters->update_all();
929 }
930 }
931
932 void DefNewGeneration::verify() {
933 eden()->verify();
934 from()->verify();
935 to()->verify();
936 }
937
938 void DefNewGeneration::print_on(outputStream* st) const {
939 Generation::print_on(st);
940 st->print(" eden");
941 eden()->print_on(st);
942 st->print(" from");
943 from()->print_on(st);
944 st->print(" to ");
945 to()->print_on(st);
946 }
947
948
949 const char* DefNewGeneration::name() const {
950 return "def new generation";
951 }
952
953 // Moved from inline file as they are not called inline
954 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
955 return eden();
956 }
957
958 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
959 // This is the slow-path allocation for the DefNewGeneration.
960 // Most allocations are fast-path in compiled code.
961 // We try to allocate from the eden. If that works, we are happy.
962 // Note that since DefNewGeneration supports lock-free allocation, we
963 // have to use it here, as well.
964 HeapWord* result = eden()->par_allocate(word_size);
965 if (result != NULL) {
966 if (_old_gen != NULL) {
967 _old_gen->sample_eden_chunk();
968 }
969 } else {
970 // If the eden is full and the last collection bailed out, we are running
971 // out of heap space, and we try to allocate the from-space, too.
972 // allocate_from_space can't be inlined because that would introduce a
973 // circular dependency at compile time.
974 result = allocate_from_space(word_size);
975 }
976 return result;
977 }
978
979 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
980 bool is_tlab) {
981 HeapWord* res = eden()->par_allocate(word_size);
982 if (_old_gen != NULL) {
983 _old_gen->sample_eden_chunk();
984 }
985 return res;
986 }
987
988 size_t DefNewGeneration::tlab_capacity() const {
989 return eden()->capacity();
990 }
991
992 size_t DefNewGeneration::tlab_used() const {
993 return eden()->used();
994 }
995
996 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
997 return unsafe_max_alloc_nogc();
998 }