1 /*
2 * Copyright (c) 2001, 2021, 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/serialGcRefProcProxyTask.hpp"
28 #include "gc/serial/serialHeap.inline.hpp"
29 #include "gc/serial/tenuredGeneration.hpp"
30 #include "gc/shared/adaptiveSizePolicy.hpp"
31 #include "gc/shared/ageTable.inline.hpp"
32 #include "gc/shared/cardTableRS.hpp"
33 #include "gc/shared/collectorCounters.hpp"
34 #include "gc/shared/gcArguments.hpp"
35 #include "gc/shared/gcHeapSummary.hpp"
36 #include "gc/shared/gcLocker.hpp"
37 #include "gc/shared/gcPolicyCounters.hpp"
38 #include "gc/shared/gcTimer.hpp"
39 #include "gc/shared/gcTrace.hpp"
40 #include "gc/shared/gcTraceTime.inline.hpp"
41 #include "gc/shared/generationSpec.hpp"
42 #include "gc/shared/genOopClosures.inline.hpp"
43 #include "gc/shared/preservedMarks.inline.hpp"
44 #include "gc/shared/referencePolicy.hpp"
45 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
46 #include "gc/shared/space.inline.hpp"
47 #include "gc/shared/spaceDecorator.inline.hpp"
48 #include "gc/shared/strongRootsScope.hpp"
49 #include "gc/shared/weakProcessor.hpp"
50 #include "logging/log.hpp"
51 #include "memory/iterator.inline.hpp"
52 #include "memory/resourceArea.hpp"
53 #include "oops/instanceRefKlass.hpp"
54 #include "oops/oop.inline.hpp"
55 #include "runtime/java.hpp"
56 #include "runtime/prefetch.inline.hpp"
57 #include "runtime/thread.inline.hpp"
58 #include "utilities/align.hpp"
59 #include "utilities/copy.hpp"
60 #include "utilities/globalDefinitions.hpp"
61 #include "utilities/stack.inline.hpp"
62
63 //
64 // DefNewGeneration functions.
65
66 // Methods of protected closure types.
67
68 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
69 assert(_young_gen->kind() == Generation::DefNew, "Expected the young generation here");
70 }
71
72 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
73 return cast_from_oop<HeapWord*>(p) >= _young_gen->reserved().end() || p->is_forwarded();
74 }
75
76 DefNewGeneration::KeepAliveClosure::
77 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
78 _rs = GenCollectedHeap::heap()->rem_set();
79 }
80
81 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
82 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
83
84
85 DefNewGeneration::FastKeepAliveClosure::
86 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
87 DefNewGeneration::KeepAliveClosure(cl) {
88 _boundary = g->reserved().end();
89 }
90
91 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
92 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
93
94 DefNewGeneration::FastEvacuateFollowersClosure::
95 FastEvacuateFollowersClosure(SerialHeap* heap,
96 DefNewScanClosure* cur,
97 DefNewYoungerGenClosure* older) :
98 _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older)
99 {
100 }
101
102 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
103 do {
104 _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older);
105 } while (!_heap->no_allocs_since_save_marks());
106 guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan");
107 }
108
109 void CLDScanClosure::do_cld(ClassLoaderData* cld) {
110 NOT_PRODUCT(ResourceMark rm);
111 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s",
112 p2i(cld),
113 cld->loader_name_and_id(),
114 cld->has_modified_oops() ? "true" : "false");
115
116 // If the cld has not been dirtied we know that there's
117 // no references into the young gen and we can skip it.
118 if (cld->has_modified_oops()) {
119
120 // Tell the closure which CLD is being scanned so that it can be dirtied
121 // if oops are left pointing into the young gen.
122 _scavenge_closure->set_scanned_cld(cld);
123
124 // Clean the cld since we're going to scavenge all the metadata.
125 cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);
126
127 _scavenge_closure->set_scanned_cld(NULL);
128 }
129 }
130
131 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
132 _g(g)
133 {
134 _boundary = _g->reserved().end();
135 }
136
137 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
138 size_t initial_size,
139 size_t min_size,
140 size_t max_size,
141 const char* policy)
142 : Generation(rs, initial_size),
143 _preserved_marks_set(false /* in_c_heap */),
144 _promo_failure_drain_in_progress(false),
145 _should_allocate_from_space(false)
146 {
147 MemRegion cmr((HeapWord*)_virtual_space.low(),
148 (HeapWord*)_virtual_space.high());
149 GenCollectedHeap* gch = GenCollectedHeap::heap();
150
151 gch->rem_set()->resize_covered_region(cmr);
152
153 _eden_space = new ContiguousSpace();
154 _from_space = new ContiguousSpace();
155 _to_space = new ContiguousSpace();
156
157 // Compute the maximum eden and survivor space sizes. These sizes
158 // are computed assuming the entire reserved space is committed.
159 // These values are exported as performance counters.
160 uintx size = _virtual_space.reserved_size();
161 _max_survivor_size = compute_survivor_size(size, SpaceAlignment);
162 _max_eden_size = size - (2*_max_survivor_size);
163
164 // allocate the performance counters
165
166 // Generation counters -- generation 0, 3 subspaces
167 _gen_counters = new GenerationCounters("new", 0, 3,
168 min_size, max_size, &_virtual_space);
169 _gc_counters = new CollectorCounters(policy, 0);
170
171 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
172 _gen_counters);
173 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
174 _gen_counters);
175 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
176 _gen_counters);
177
178 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
179 update_counters();
180 _old_gen = NULL;
181 _tenuring_threshold = MaxTenuringThreshold;
182 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
183
184 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
185 }
186
187 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
188 bool clear_space,
189 bool mangle_space) {
190 // If the spaces are being cleared (only done at heap initialization
191 // currently), the survivor spaces need not be empty.
192 // Otherwise, no care is taken for used areas in the survivor spaces
193 // so check.
194 assert(clear_space || (to()->is_empty() && from()->is_empty()),
195 "Initialization of the survivor spaces assumes these are empty");
196
197 // Compute sizes
198 uintx size = _virtual_space.committed_size();
199 uintx survivor_size = compute_survivor_size(size, SpaceAlignment);
200 uintx eden_size = size - (2*survivor_size);
201 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
202
203 if (eden_size < minimum_eden_size) {
204 // May happen due to 64Kb rounding, if so adjust eden size back up
205 minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment);
206 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
207 uintx unaligned_survivor_size =
208 align_down(maximum_survivor_size, SpaceAlignment);
209 survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment);
210 eden_size = size - (2*survivor_size);
211 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
212 assert(eden_size >= minimum_eden_size, "just checking");
213 }
214
215 char *eden_start = _virtual_space.low();
216 char *from_start = eden_start + eden_size;
217 char *to_start = from_start + survivor_size;
218 char *to_end = to_start + survivor_size;
219
220 assert(to_end == _virtual_space.high(), "just checking");
221 assert(Space::is_aligned(eden_start), "checking alignment");
222 assert(Space::is_aligned(from_start), "checking alignment");
223 assert(Space::is_aligned(to_start), "checking alignment");
224
225 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
226 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
227 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
228
229 // A minimum eden size implies that there is a part of eden that
230 // is being used and that affects the initialization of any
231 // newly formed eden.
232 bool live_in_eden = minimum_eden_size > 0;
233
234 // If not clearing the spaces, do some checking to verify that
235 // the space are already mangled.
236 if (!clear_space) {
237 // Must check mangling before the spaces are reshaped. Otherwise,
238 // the bottom or end of one space may have moved into another
239 // a failure of the check may not correctly indicate which space
240 // is not properly mangled.
241 if (ZapUnusedHeapArea) {
242 HeapWord* limit = (HeapWord*) _virtual_space.high();
243 eden()->check_mangled_unused_area(limit);
244 from()->check_mangled_unused_area(limit);
245 to()->check_mangled_unused_area(limit);
246 }
247 }
248
249 // Reset the spaces for their new regions.
250 eden()->initialize(edenMR,
251 clear_space && !live_in_eden,
252 SpaceDecorator::Mangle);
253 // If clear_space and live_in_eden, we will not have cleared any
254 // portion of eden above its top. This can cause newly
255 // expanded space not to be mangled if using ZapUnusedHeapArea.
256 // We explicitly do such mangling here.
257 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
258 eden()->mangle_unused_area();
259 }
260 from()->initialize(fromMR, clear_space, mangle_space);
261 to()->initialize(toMR, clear_space, mangle_space);
262
263 // Set next compaction spaces.
264 eden()->set_next_compaction_space(from());
265 // The to-space is normally empty before a compaction so need
266 // not be considered. The exception is during promotion
267 // failure handling when to-space can contain live objects.
268 from()->set_next_compaction_space(NULL);
269 }
270
271 void DefNewGeneration::swap_spaces() {
272 ContiguousSpace* s = from();
273 _from_space = to();
274 _to_space = s;
275 eden()->set_next_compaction_space(from());
276 // The to-space is normally empty before a compaction so need
277 // not be considered. The exception is during promotion
278 // failure handling when to-space can contain live objects.
279 from()->set_next_compaction_space(NULL);
280
281 if (UsePerfData) {
282 CSpaceCounters* c = _from_counters;
283 _from_counters = _to_counters;
284 _to_counters = c;
285 }
286 }
287
288 bool DefNewGeneration::expand(size_t bytes) {
289 MutexLocker x(ExpandHeap_lock);
290 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
291 bool success = _virtual_space.expand_by(bytes);
292 if (success && ZapUnusedHeapArea) {
293 // Mangle newly committed space immediately because it
294 // can be done here more simply that after the new
295 // spaces have been computed.
296 HeapWord* new_high = (HeapWord*) _virtual_space.high();
297 MemRegion mangle_region(prev_high, new_high);
298 SpaceMangler::mangle_region(mangle_region);
299 }
300
301 // Do not attempt an expand-to-the reserve size. The
302 // request should properly observe the maximum size of
303 // the generation so an expand-to-reserve should be
304 // unnecessary. Also a second call to expand-to-reserve
305 // value potentially can cause an undue expansion.
306 // For example if the first expand fail for unknown reasons,
307 // but the second succeeds and expands the heap to its maximum
308 // value.
309 if (GCLocker::is_active()) {
310 log_debug(gc)("Garbage collection disabled, expanded heap instead");
311 }
312
313 return success;
314 }
315
316 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
317 size_t new_size_before,
318 size_t alignment) const {
319 size_t desired_new_size = new_size_before;
320
321 if (NewSizeThreadIncrease > 0) {
322 int threads_count;
323 size_t thread_increase_size = 0;
324
325 // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
326 threads_count = Threads::number_of_non_daemon_threads();
327 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
328 thread_increase_size = threads_count * NewSizeThreadIncrease;
329
330 // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
331 if (new_size_candidate <= max_uintx - thread_increase_size) {
332 new_size_candidate += thread_increase_size;
333
334 // 3. Check an overflow at 'align_up'.
335 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
336 if (new_size_candidate <= aligned_max) {
337 desired_new_size = align_up(new_size_candidate, alignment);
338 }
339 }
340 }
341 }
342
343 return desired_new_size;
344 }
345
346 void DefNewGeneration::compute_new_size() {
347 // This is called after a GC that includes the old generation, so from-space
348 // will normally be empty.
349 // Note that we check both spaces, since if scavenge failed they revert roles.
350 // If not we bail out (otherwise we would have to relocate the objects).
351 if (!from()->is_empty() || !to()->is_empty()) {
352 return;
353 }
354
355 GenCollectedHeap* gch = GenCollectedHeap::heap();
356
357 size_t old_size = gch->old_gen()->capacity();
358 size_t new_size_before = _virtual_space.committed_size();
359 size_t min_new_size = initial_size();
360 size_t max_new_size = reserved().byte_size();
361 assert(min_new_size <= new_size_before &&
362 new_size_before <= max_new_size,
363 "just checking");
364 // All space sizes must be multiples of Generation::GenGrain.
365 size_t alignment = Generation::GenGrain;
366
367 int threads_count = 0;
368 size_t thread_increase_size = 0;
369
370 size_t new_size_candidate = old_size / NewRatio;
371 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
372 // and reverts to previous value if any overflow happens
373 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);
374
375 // Adjust new generation size
376 desired_new_size = clamp(desired_new_size, min_new_size, max_new_size);
377 assert(desired_new_size <= max_new_size, "just checking");
378
379 bool changed = false;
380 if (desired_new_size > new_size_before) {
381 size_t change = desired_new_size - new_size_before;
382 assert(change % alignment == 0, "just checking");
383 if (expand(change)) {
384 changed = true;
385 }
386 // If the heap failed to expand to the desired size,
387 // "changed" will be false. If the expansion failed
388 // (and at this point it was expected to succeed),
389 // ignore the failure (leaving "changed" as false).
390 }
391 if (desired_new_size < new_size_before && eden()->is_empty()) {
392 // bail out of shrinking if objects in eden
393 size_t change = new_size_before - desired_new_size;
394 assert(change % alignment == 0, "just checking");
395 _virtual_space.shrink_by(change);
396 changed = true;
397 }
398 if (changed) {
399 // The spaces have already been mangled at this point but
400 // may not have been cleared (set top = bottom) and should be.
401 // Mangling was done when the heap was being expanded.
402 compute_space_boundaries(eden()->used(),
403 SpaceDecorator::Clear,
404 SpaceDecorator::DontMangle);
405 MemRegion cmr((HeapWord*)_virtual_space.low(),
406 (HeapWord*)_virtual_space.high());
407 gch->rem_set()->resize_covered_region(cmr);
408
409 log_debug(gc, ergo, heap)(
410 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
411 new_size_before/K, _virtual_space.committed_size()/K,
412 eden()->capacity()/K, from()->capacity()/K);
413 log_trace(gc, ergo, heap)(
414 " [allowed " SIZE_FORMAT "K extra for %d threads]",
415 thread_increase_size/K, threads_count);
416 }
417 }
418
419
420 size_t DefNewGeneration::capacity() const {
421 return eden()->capacity()
422 + from()->capacity(); // to() is only used during scavenge
423 }
424
425
426 size_t DefNewGeneration::used() const {
427 return eden()->used()
428 + from()->used(); // to() is only used during scavenge
429 }
430
431
432 size_t DefNewGeneration::free() const {
433 return eden()->free()
434 + from()->free(); // to() is only used during scavenge
435 }
436
437 size_t DefNewGeneration::max_capacity() const {
438 const size_t reserved_bytes = reserved().byte_size();
439 return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment);
440 }
441
442 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
443 return eden()->free();
444 }
445
446 size_t DefNewGeneration::capacity_before_gc() const {
447 return eden()->capacity();
448 }
449
450 size_t DefNewGeneration::contiguous_available() const {
451 return eden()->free();
452 }
453
454
455 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }
456 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
457
458 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
459 eden()->object_iterate(blk);
460 from()->object_iterate(blk);
461 }
462
463
464 void DefNewGeneration::space_iterate(SpaceClosure* blk,
465 bool usedOnly) {
466 blk->do_space(eden());
467 blk->do_space(from());
468 blk->do_space(to());
469 }
470
471 // The last collection bailed out, we are running out of heap space,
472 // so we try to allocate the from-space, too.
473 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
474 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
475
476 // If the Heap_lock is not locked by this thread, this will be called
477 // again later with the Heap_lock held.
478 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
479
480 HeapWord* result = NULL;
481 if (do_alloc) {
482 result = from()->allocate(size);
483 }
484
485 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s",
486 size,
487 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
488 "true" : "false",
489 Heap_lock->is_locked() ? "locked" : "unlocked",
490 from()->free(),
491 should_try_alloc ? "" : " should_allocate_from_space: NOT",
492 do_alloc ? " Heap_lock is not owned by self" : "",
493 result == NULL ? "NULL" : "object");
494
495 return result;
496 }
497
498 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
499 bool is_tlab,
500 bool parallel) {
501 // We don't attempt to expand the young generation (but perhaps we should.)
502 return allocate(size, is_tlab);
503 }
504
505 void DefNewGeneration::adjust_desired_tenuring_threshold() {
506 // Set the desired survivor size to half the real survivor space
507 size_t const survivor_capacity = to()->capacity() / HeapWordSize;
508 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
509
510 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
511
512 if (UsePerfData) {
513 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters();
514 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
515 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
516 }
517
518 age_table()->print_age_table(_tenuring_threshold);
519 }
520
521 void DefNewGeneration::collect(bool full,
522 bool clear_all_soft_refs,
523 size_t size,
524 bool is_tlab) {
525 assert(full || size > 0, "otherwise we don't want to collect");
526
527 SerialHeap* heap = SerialHeap::heap();
528
529 _gc_timer->register_gc_start();
530 DefNewTracer gc_tracer;
531 gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start());
532
533 _old_gen = heap->old_gen();
534
535 // If the next generation is too full to accommodate promotion
536 // from this generation, pass on collection; let the next generation
537 // do it.
538 if (!collection_attempt_is_safe()) {
539 log_trace(gc)(":: Collection attempt not safe ::");
540 heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
541 return;
542 }
543 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
544
545 init_assuming_no_promotion_failure();
546
547 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause());
548
549 heap->trace_heap_before_gc(&gc_tracer);
550
551 // These can be shared for all code paths
552 IsAliveClosure is_alive(this);
553 ScanWeakRefClosure scan_weak_ref(this);
554
555 age_table()->clear();
556 to()->clear(SpaceDecorator::Mangle);
557 // The preserved marks should be empty at the start of the GC.
558 _preserved_marks_set.init(1);
559
560 assert(heap->no_allocs_since_save_marks(),
561 "save marks have not been newly set.");
562
563 DefNewScanClosure scan_closure(this);
564 DefNewYoungerGenClosure younger_gen_closure(this, _old_gen);
565
566 CLDScanClosure cld_scan_closure(&scan_closure);
567
568 set_promo_failure_scan_stack_closure(&scan_closure);
569 FastEvacuateFollowersClosure evacuate_followers(heap,
570 &scan_closure,
571 &younger_gen_closure);
572
573 assert(heap->no_allocs_since_save_marks(),
574 "save marks have not been newly set.");
575
576 {
577 StrongRootsScope srs(0);
578
579 heap->young_process_roots(&scan_closure,
580 &younger_gen_closure,
581 &cld_scan_closure);
582 }
583
584 // "evacuate followers".
585 evacuate_followers.do_void();
586
587 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
588 ReferenceProcessor* rp = ref_processor();
589 rp->setup_policy(clear_all_soft_refs);
590 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
591 SerialGCRefProcProxyTask task(is_alive, keep_alive, evacuate_followers);
592 const ReferenceProcessorStats& stats = rp->process_discovered_references(task, pt);
593 gc_tracer.report_gc_reference_stats(stats);
594 gc_tracer.report_tenuring_threshold(tenuring_threshold());
595 pt.print_all_references();
596
597 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
598
599 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
600
601 // Verify that the usage of keep_alive didn't copy any objects.
602 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
603
604 if (!_promotion_failed) {
605 // Swap the survivor spaces.
606 eden()->clear(SpaceDecorator::Mangle);
607 from()->clear(SpaceDecorator::Mangle);
608 if (ZapUnusedHeapArea) {
609 // This is now done here because of the piece-meal mangling which
610 // can check for valid mangling at intermediate points in the
611 // collection(s). When a young collection fails to collect
612 // sufficient space resizing of the young generation can occur
613 // an redistribute the spaces in the young generation. Mangle
614 // here so that unzapped regions don't get distributed to
615 // other spaces.
616 to()->mangle_unused_area();
617 }
618 swap_spaces();
619
620 assert(to()->is_empty(), "to space should be empty now");
621
622 adjust_desired_tenuring_threshold();
623
624 // A successful scavenge should restart the GC time limit count which is
625 // for full GC's.
626 AdaptiveSizePolicy* size_policy = heap->size_policy();
627 size_policy->reset_gc_overhead_limit_count();
628 assert(!heap->incremental_collection_failed(), "Should be clear");
629 } else {
630 assert(_promo_failure_scan_stack.is_empty(), "post condition");
631 _promo_failure_scan_stack.clear(true); // Clear cached segments.
632
633 remove_forwarding_pointers();
634 log_info(gc, promotion)("Promotion failed");
635 // Add to-space to the list of space to compact
636 // when a promotion failure has occurred. In that
637 // case there can be live objects in to-space
638 // as a result of a partial evacuation of eden
639 // and from-space.
640 swap_spaces(); // For uniformity wrt ParNewGeneration.
641 from()->set_next_compaction_space(to());
642 heap->set_incremental_collection_failed();
643
644 // Inform the next generation that a promotion failure occurred.
645 _old_gen->promotion_failure_occurred();
646 gc_tracer.report_promotion_failed(_promotion_failed_info);
647
648 // Reset the PromotionFailureALot counters.
649 NOT_PRODUCT(heap->reset_promotion_should_fail();)
650 }
651 // We should have processed and cleared all the preserved marks.
652 _preserved_marks_set.reclaim();
653
654 heap->trace_heap_after_gc(&gc_tracer);
655
656 _gc_timer->register_gc_end();
657
658 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
659 }
660
661 void DefNewGeneration::init_assuming_no_promotion_failure() {
662 _promotion_failed = false;
663 _promotion_failed_info.reset();
664 from()->set_next_compaction_space(NULL);
665 }
666
667 void DefNewGeneration::remove_forwarding_pointers() {
668 RemoveForwardedPointerClosure rspc;
669 eden()->object_iterate(&rspc);
670 from()->object_iterate(&rspc);
671 restore_preserved_marks();
672 }
673
674 void DefNewGeneration::restore_preserved_marks() {
675 _preserved_marks_set.restore(NULL);
676 }
677
678 void DefNewGeneration::handle_promotion_failure(oop old) {
679 log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
680
681 _promotion_failed = true;
682 _promotion_failed_info.register_copy_failure(old->size());
683 _preserved_marks_set.get()->push_if_necessary(old, old->mark());
684 // forward to self
685 old->forward_to_self();
686
687 _promo_failure_scan_stack.push(old);
688
689 if (!_promo_failure_drain_in_progress) {
690 // prevent recursion in copy_to_survivor_space()
691 _promo_failure_drain_in_progress = true;
692 drain_promo_failure_scan_stack();
693 _promo_failure_drain_in_progress = false;
694 }
695 }
696
697 oop DefNewGeneration::copy_to_survivor_space(oop old) {
698 assert(is_in_reserved(old) && !old->is_forwarded(),
699 "shouldn't be scavenging this oop");
700 size_t s = old->size();
701 oop obj = NULL;
702
703 // Try allocating obj in to-space (unless too old)
704 if (old->age() < tenuring_threshold()) {
705 obj = cast_to_oop(to()->allocate(s));
706 }
707
708 // Otherwise try allocating obj tenured
709 if (obj == NULL) {
710 obj = _old_gen->promote(old, s);
711 if (obj == NULL) {
712 handle_promotion_failure(old);
713 return old;
714 }
715 } else {
716 // Prefetch beyond obj
717 const intx interval = PrefetchCopyIntervalInBytes;
718 Prefetch::write(obj, interval);
719
720 // Copy obj
721 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s);
722
723 // Increment age if obj still in new generation
724 obj->incr_age();
725 age_table()->add(obj, s);
726 }
727
728 // Done, insert forward pointer to obj in this header
729 old->forward_to(obj);
730
731 return obj;
732 }
733
734 void DefNewGeneration::drain_promo_failure_scan_stack() {
735 while (!_promo_failure_scan_stack.is_empty()) {
736 oop obj = _promo_failure_scan_stack.pop();
737 obj->oop_iterate(_promo_failure_scan_stack_closure);
738 }
739 }
740
741 void DefNewGeneration::save_marks() {
742 eden()->set_saved_mark();
743 to()->set_saved_mark();
744 from()->set_saved_mark();
745 }
746
747
748 void DefNewGeneration::reset_saved_marks() {
749 eden()->reset_saved_mark();
750 to()->reset_saved_mark();
751 from()->reset_saved_mark();
752 }
753
754
755 bool DefNewGeneration::no_allocs_since_save_marks() {
756 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
757 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
758 return to()->saved_mark_at_top();
759 }
760
761 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
762 size_t max_alloc_words) {
763 if (requestor == this || _promotion_failed) {
764 return;
765 }
766 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
767
768 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
769 if (to_space->top() > to_space->bottom()) {
770 trace("to_space not empty when contribute_scratch called");
771 }
772 */
773
774 ContiguousSpace* to_space = to();
775 assert(to_space->end() >= to_space->top(), "pointers out of order");
776 size_t free_words = pointer_delta(to_space->end(), to_space->top());
777 if (free_words >= MinFreeScratchWords) {
778 ScratchBlock* sb = (ScratchBlock*)to_space->top();
779 sb->num_words = free_words;
780 sb->next = list;
781 list = sb;
782 }
783 }
784
785 void DefNewGeneration::reset_scratch() {
786 // If contributing scratch in to_space, mangle all of
787 // to_space if ZapUnusedHeapArea. This is needed because
788 // top is not maintained while using to-space as scratch.
789 if (ZapUnusedHeapArea) {
790 to()->mangle_unused_area_complete();
791 }
792 }
793
794 bool DefNewGeneration::collection_attempt_is_safe() {
795 if (!to()->is_empty()) {
796 log_trace(gc)(":: to is not empty ::");
797 return false;
798 }
799 if (_old_gen == NULL) {
800 GenCollectedHeap* gch = GenCollectedHeap::heap();
801 _old_gen = gch->old_gen();
802 }
803 return _old_gen->promotion_attempt_is_safe(used());
804 }
805
806 void DefNewGeneration::gc_epilogue(bool full) {
807 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
808
809 assert(!GCLocker::is_active(), "We should not be executing here");
810 // Check if the heap is approaching full after a collection has
811 // been done. Generally the young generation is empty at
812 // a minimum at the end of a collection. If it is not, then
813 // the heap is approaching full.
814 GenCollectedHeap* gch = GenCollectedHeap::heap();
815 if (full) {
816 DEBUG_ONLY(seen_incremental_collection_failed = false;)
817 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
818 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
819 GCCause::to_string(gch->gc_cause()));
820 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
821 set_should_allocate_from_space(); // we seem to be running out of space
822 } else {
823 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
824 GCCause::to_string(gch->gc_cause()));
825 gch->clear_incremental_collection_failed(); // We just did a full collection
826 clear_should_allocate_from_space(); // if set
827 }
828 } else {
829 #ifdef ASSERT
830 // It is possible that incremental_collection_failed() == true
831 // here, because an attempted scavenge did not succeed. The policy
832 // is normally expected to cause a full collection which should
833 // clear that condition, so we should not be here twice in a row
834 // with incremental_collection_failed() == true without having done
835 // a full collection in between.
836 if (!seen_incremental_collection_failed &&
837 gch->incremental_collection_failed()) {
838 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
839 GCCause::to_string(gch->gc_cause()));
840 seen_incremental_collection_failed = true;
841 } else if (seen_incremental_collection_failed) {
842 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
843 GCCause::to_string(gch->gc_cause()));
844 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
845 !gch->incremental_collection_failed(),
846 "Twice in a row");
847 seen_incremental_collection_failed = false;
848 }
849 #endif // ASSERT
850 }
851
852 if (ZapUnusedHeapArea) {
853 eden()->check_mangled_unused_area_complete();
854 from()->check_mangled_unused_area_complete();
855 to()->check_mangled_unused_area_complete();
856 }
857
858 // update the generation and space performance counters
859 update_counters();
860 gch->counters()->update_counters();
861 }
862
863 void DefNewGeneration::record_spaces_top() {
864 assert(ZapUnusedHeapArea, "Not mangling unused space");
865 eden()->set_top_for_allocations();
866 to()->set_top_for_allocations();
867 from()->set_top_for_allocations();
868 }
869
870 void DefNewGeneration::ref_processor_init() {
871 Generation::ref_processor_init();
872 }
873
874
875 void DefNewGeneration::update_counters() {
876 if (UsePerfData) {
877 _eden_counters->update_all();
878 _from_counters->update_all();
879 _to_counters->update_all();
880 _gen_counters->update_all();
881 }
882 }
883
884 void DefNewGeneration::verify() {
885 eden()->verify();
886 from()->verify();
887 to()->verify();
888 }
889
890 void DefNewGeneration::print_on(outputStream* st) const {
891 Generation::print_on(st);
892 st->print(" eden");
893 eden()->print_on(st);
894 st->print(" from");
895 from()->print_on(st);
896 st->print(" to ");
897 to()->print_on(st);
898 }
899
900
901 const char* DefNewGeneration::name() const {
902 return "def new generation";
903 }
904
905 // Moved from inline file as they are not called inline
906 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
907 return eden();
908 }
909
910 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
911 // This is the slow-path allocation for the DefNewGeneration.
912 // Most allocations are fast-path in compiled code.
913 // We try to allocate from the eden. If that works, we are happy.
914 // Note that since DefNewGeneration supports lock-free allocation, we
915 // have to use it here, as well.
916 HeapWord* result = eden()->par_allocate(word_size);
917 if (result == NULL) {
918 // If the eden is full and the last collection bailed out, we are running
919 // out of heap space, and we try to allocate the from-space, too.
920 // allocate_from_space can't be inlined because that would introduce a
921 // circular dependency at compile time.
922 result = allocate_from_space(word_size);
923 }
924 return result;
925 }
926
927 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
928 bool is_tlab) {
929 return eden()->par_allocate(word_size);
930 }
931
932 size_t DefNewGeneration::tlab_capacity() const {
933 return eden()->capacity();
934 }
935
936 size_t DefNewGeneration::tlab_used() const {
937 return eden()->used();
938 }
939
940 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
941 return unsafe_max_alloc_nogc();
942 }