1 /*
2 * Copyright (c) 2001, 2022, 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/serialStringDedup.inline.hpp"
30 #include "gc/serial/tenuredGeneration.hpp"
31 #include "gc/shared/adaptiveSizePolicy.hpp"
32 #include "gc/shared/ageTable.inline.hpp"
33 #include "gc/shared/cardTableRS.hpp"
34 #include "gc/shared/collectorCounters.hpp"
35 #include "gc/shared/continuationGCSupport.inline.hpp"
36 #include "gc/shared/gcArguments.hpp"
37 #include "gc/shared/gcHeapSummary.hpp"
38 #include "gc/shared/gcLocker.hpp"
39 #include "gc/shared/gcPolicyCounters.hpp"
40 #include "gc/shared/gcTimer.hpp"
41 #include "gc/shared/gcTrace.hpp"
42 #include "gc/shared/gcTraceTime.inline.hpp"
43 #include "gc/shared/generationSpec.hpp"
44 #include "gc/shared/genOopClosures.inline.hpp"
45 #include "gc/shared/preservedMarks.inline.hpp"
46 #include "gc/shared/referencePolicy.hpp"
47 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
48 #include "gc/shared/space.inline.hpp"
49 #include "gc/shared/spaceDecorator.inline.hpp"
50 #include "gc/shared/strongRootsScope.hpp"
51 #include "gc/shared/weakProcessor.hpp"
52 #include "logging/log.hpp"
53 #include "memory/iterator.inline.hpp"
54 #include "memory/resourceArea.hpp"
55 #include "oops/instanceRefKlass.hpp"
56 #include "oops/oop.inline.hpp"
57 #include "runtime/java.hpp"
58 #include "runtime/javaThread.hpp"
59 #include "runtime/prefetch.inline.hpp"
60 #include "runtime/threads.hpp"
61 #include "utilities/align.hpp"
62 #include "utilities/copy.hpp"
63 #include "utilities/globalDefinitions.hpp"
64 #include "utilities/stack.inline.hpp"
65
66 //
67 // DefNewGeneration functions.
68
69 // Methods of protected closure types.
70
71 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
72 assert(_young_gen->kind() == Generation::DefNew, "Expected the young generation here");
73 }
74
75 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
76 return cast_from_oop<HeapWord*>(p) >= _young_gen->reserved().end() || p->is_forwarded();
77 }
78
79 DefNewGeneration::KeepAliveClosure::
80 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
81 _rs = GenCollectedHeap::heap()->rem_set();
82 }
83
84 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
85 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
86
87
88 DefNewGeneration::FastKeepAliveClosure::
89 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
90 DefNewGeneration::KeepAliveClosure(cl) {
91 _boundary = g->reserved().end();
92 }
93
94 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
95 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
96
97 DefNewGeneration::FastEvacuateFollowersClosure::
98 FastEvacuateFollowersClosure(SerialHeap* heap,
99 DefNewScanClosure* cur,
100 DefNewYoungerGenClosure* older) :
101 _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older)
102 {
103 }
104
105 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
106 do {
107 _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older);
108 } while (!_heap->no_allocs_since_save_marks());
109 guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan");
110 }
111
112 void CLDScanClosure::do_cld(ClassLoaderData* cld) {
113 NOT_PRODUCT(ResourceMark rm);
114 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s",
115 p2i(cld),
116 cld->loader_name_and_id(),
117 cld->has_modified_oops() ? "true" : "false");
118
119 // If the cld has not been dirtied we know that there's
120 // no references into the young gen and we can skip it.
121 if (cld->has_modified_oops()) {
122
123 // Tell the closure which CLD is being scanned so that it can be dirtied
124 // if oops are left pointing into the young gen.
125 _scavenge_closure->set_scanned_cld(cld);
126
127 // Clean the cld since we're going to scavenge all the metadata.
128 cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);
129
130 _scavenge_closure->set_scanned_cld(NULL);
131 }
132 }
133
134 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
135 _g(g)
136 {
137 _boundary = _g->reserved().end();
138 }
139
140 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
141 size_t initial_size,
142 size_t min_size,
143 size_t max_size,
144 const char* policy)
145 : Generation(rs, initial_size),
146 _preserved_marks_set(false /* in_c_heap */),
147 _promo_failure_drain_in_progress(false),
148 _should_allocate_from_space(false),
149 _string_dedup_requests()
150 {
151 MemRegion cmr((HeapWord*)_virtual_space.low(),
152 (HeapWord*)_virtual_space.high());
153 GenCollectedHeap* gch = GenCollectedHeap::heap();
154
155 gch->rem_set()->resize_covered_region(cmr);
156
157 _eden_space = new ContiguousSpace();
158 _from_space = new ContiguousSpace();
159 _to_space = new ContiguousSpace();
160
161 // Compute the maximum eden and survivor space sizes. These sizes
162 // are computed assuming the entire reserved space is committed.
163 // These values are exported as performance counters.
164 uintx size = _virtual_space.reserved_size();
165 _max_survivor_size = compute_survivor_size(size, SpaceAlignment);
166 _max_eden_size = size - (2*_max_survivor_size);
167
168 // allocate the performance counters
169
170 // Generation counters -- generation 0, 3 subspaces
171 _gen_counters = new GenerationCounters("new", 0, 3,
172 min_size, max_size, &_virtual_space);
173 _gc_counters = new CollectorCounters(policy, 0);
174
175 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
176 _gen_counters);
177 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
178 _gen_counters);
179 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
180 _gen_counters);
181
182 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
183 update_counters();
184 _old_gen = NULL;
185 _tenuring_threshold = MaxTenuringThreshold;
186 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
187
188 _gc_timer = new STWGCTimer();
189
190 _gc_tracer = new DefNewTracer();
191 }
192
193 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
194 bool clear_space,
195 bool mangle_space) {
196 // If the spaces are being cleared (only done at heap initialization
197 // currently), the survivor spaces need not be empty.
198 // Otherwise, no care is taken for used areas in the survivor spaces
199 // so check.
200 assert(clear_space || (to()->is_empty() && from()->is_empty()),
201 "Initialization of the survivor spaces assumes these are empty");
202
203 // Compute sizes
204 uintx size = _virtual_space.committed_size();
205 uintx survivor_size = compute_survivor_size(size, SpaceAlignment);
206 uintx eden_size = size - (2*survivor_size);
207 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
208
209 if (eden_size < minimum_eden_size) {
210 // May happen due to 64Kb rounding, if so adjust eden size back up
211 minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment);
212 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
213 uintx unaligned_survivor_size =
214 align_down(maximum_survivor_size, SpaceAlignment);
215 survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment);
216 eden_size = size - (2*survivor_size);
217 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
218 assert(eden_size >= minimum_eden_size, "just checking");
219 }
220
221 char *eden_start = _virtual_space.low();
222 char *from_start = eden_start + eden_size;
223 char *to_start = from_start + survivor_size;
224 char *to_end = to_start + survivor_size;
225
226 assert(to_end == _virtual_space.high(), "just checking");
227 assert(Space::is_aligned(eden_start), "checking alignment");
228 assert(Space::is_aligned(from_start), "checking alignment");
229 assert(Space::is_aligned(to_start), "checking alignment");
230
231 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
232 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
233 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
234
235 // A minimum eden size implies that there is a part of eden that
236 // is being used and that affects the initialization of any
237 // newly formed eden.
238 bool live_in_eden = minimum_eden_size > 0;
239
240 // If not clearing the spaces, do some checking to verify that
241 // the space are already mangled.
242 if (!clear_space) {
243 // Must check mangling before the spaces are reshaped. Otherwise,
244 // the bottom or end of one space may have moved into another
245 // a failure of the check may not correctly indicate which space
246 // is not properly mangled.
247 if (ZapUnusedHeapArea) {
248 HeapWord* limit = (HeapWord*) _virtual_space.high();
249 eden()->check_mangled_unused_area(limit);
250 from()->check_mangled_unused_area(limit);
251 to()->check_mangled_unused_area(limit);
252 }
253 }
254
255 // Reset the spaces for their new regions.
256 eden()->initialize(edenMR,
257 clear_space && !live_in_eden,
258 SpaceDecorator::Mangle);
259 // If clear_space and live_in_eden, we will not have cleared any
260 // portion of eden above its top. This can cause newly
261 // expanded space not to be mangled if using ZapUnusedHeapArea.
262 // We explicitly do such mangling here.
263 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
264 eden()->mangle_unused_area();
265 }
266 from()->initialize(fromMR, clear_space, mangle_space);
267 to()->initialize(toMR, clear_space, mangle_space);
268
269 // Set next compaction spaces.
270 eden()->set_next_compaction_space(from());
271 // The to-space is normally empty before a compaction so need
272 // not be considered. The exception is during promotion
273 // failure handling when to-space can contain live objects.
274 from()->set_next_compaction_space(NULL);
275 }
276
277 void DefNewGeneration::swap_spaces() {
278 ContiguousSpace* s = from();
279 _from_space = to();
280 _to_space = s;
281 eden()->set_next_compaction_space(from());
282 // The to-space is normally empty before a compaction so need
283 // not be considered. The exception is during promotion
284 // failure handling when to-space can contain live objects.
285 from()->set_next_compaction_space(NULL);
286
287 if (UsePerfData) {
288 CSpaceCounters* c = _from_counters;
289 _from_counters = _to_counters;
290 _to_counters = c;
291 }
292 }
293
294 bool DefNewGeneration::expand(size_t bytes) {
295 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
296 bool success = _virtual_space.expand_by(bytes);
297 if (success && ZapUnusedHeapArea) {
298 // Mangle newly committed space immediately because it
299 // can be done here more simply that after the new
300 // spaces have been computed.
301 HeapWord* new_high = (HeapWord*) _virtual_space.high();
302 MemRegion mangle_region(prev_high, new_high);
303 SpaceMangler::mangle_region(mangle_region);
304 }
305
306 // Do not attempt an expand-to-the reserve size. The
307 // request should properly observe the maximum size of
308 // the generation so an expand-to-reserve should be
309 // unnecessary. Also a second call to expand-to-reserve
310 // value potentially can cause an undue expansion.
311 // For example if the first expand fail for unknown reasons,
312 // but the second succeeds and expands the heap to its maximum
313 // value.
314 if (GCLocker::is_active()) {
315 log_debug(gc)("Garbage collection disabled, expanded heap instead");
316 }
317
318 return success;
319 }
320
321 size_t DefNewGeneration::calculate_thread_increase_size(int threads_count) const {
322 size_t thread_increase_size = 0;
323 // Check an overflow at 'threads_count * NewSizeThreadIncrease'.
324 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
325 thread_increase_size = threads_count * NewSizeThreadIncrease;
326 }
327 return thread_increase_size;
328 }
329
330 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
331 size_t new_size_before,
332 size_t alignment,
333 size_t thread_increase_size) const {
334 size_t desired_new_size = new_size_before;
335
336 if (NewSizeThreadIncrease > 0 && thread_increase_size > 0) {
337
338 // 1. Check an overflow at 'new_size_candidate + thread_increase_size'.
339 if (new_size_candidate <= max_uintx - thread_increase_size) {
340 new_size_candidate += thread_increase_size;
341
342 // 2. Check an overflow at 'align_up'.
343 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
344 if (new_size_candidate <= aligned_max) {
345 desired_new_size = align_up(new_size_candidate, alignment);
346 }
347 }
348 }
349
350 return desired_new_size;
351 }
352
353 void DefNewGeneration::compute_new_size() {
354 // This is called after a GC that includes the old generation, so from-space
355 // will normally be empty.
356 // Note that we check both spaces, since if scavenge failed they revert roles.
357 // If not we bail out (otherwise we would have to relocate the objects).
358 if (!from()->is_empty() || !to()->is_empty()) {
359 return;
360 }
361
362 GenCollectedHeap* gch = GenCollectedHeap::heap();
363
364 size_t old_size = gch->old_gen()->capacity();
365 size_t new_size_before = _virtual_space.committed_size();
366 size_t min_new_size = initial_size();
367 size_t max_new_size = reserved().byte_size();
368 assert(min_new_size <= new_size_before &&
369 new_size_before <= max_new_size,
370 "just checking");
371 // All space sizes must be multiples of Generation::GenGrain.
372 size_t alignment = Generation::GenGrain;
373
374 int threads_count = Threads::number_of_non_daemon_threads();
375 size_t thread_increase_size = calculate_thread_increase_size(threads_count);
376
377 size_t new_size_candidate = old_size / NewRatio;
378 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
379 // and reverts to previous value if any overflow happens
380 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before,
381 alignment, thread_increase_size);
382
383 // Adjust new generation size
384 desired_new_size = clamp(desired_new_size, min_new_size, max_new_size);
385 assert(desired_new_size <= max_new_size, "just checking");
386
387 bool changed = false;
388 if (desired_new_size > new_size_before) {
389 size_t change = desired_new_size - new_size_before;
390 assert(change % alignment == 0, "just checking");
391 if (expand(change)) {
392 changed = true;
393 }
394 // If the heap failed to expand to the desired size,
395 // "changed" will be false. If the expansion failed
396 // (and at this point it was expected to succeed),
397 // ignore the failure (leaving "changed" as false).
398 }
399 if (desired_new_size < new_size_before && eden()->is_empty()) {
400 // bail out of shrinking if objects in eden
401 size_t change = new_size_before - desired_new_size;
402 assert(change % alignment == 0, "just checking");
403 _virtual_space.shrink_by(change);
404 changed = true;
405 }
406 if (changed) {
407 // The spaces have already been mangled at this point but
408 // may not have been cleared (set top = bottom) and should be.
409 // Mangling was done when the heap was being expanded.
410 compute_space_boundaries(eden()->used(),
411 SpaceDecorator::Clear,
412 SpaceDecorator::DontMangle);
413 MemRegion cmr((HeapWord*)_virtual_space.low(),
414 (HeapWord*)_virtual_space.high());
415 gch->rem_set()->resize_covered_region(cmr);
416
417 log_debug(gc, ergo, heap)(
418 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
419 new_size_before/K, _virtual_space.committed_size()/K,
420 eden()->capacity()/K, from()->capacity()/K);
421 log_trace(gc, ergo, heap)(
422 " [allowed " SIZE_FORMAT "K extra for %d threads]",
423 thread_increase_size/K, threads_count);
424 }
425 }
426
427
428 size_t DefNewGeneration::capacity() const {
429 return eden()->capacity()
430 + from()->capacity(); // to() is only used during scavenge
431 }
432
433
434 size_t DefNewGeneration::used() const {
435 return eden()->used()
436 + from()->used(); // to() is only used during scavenge
437 }
438
439
440 size_t DefNewGeneration::free() const {
441 return eden()->free()
442 + from()->free(); // to() is only used during scavenge
443 }
444
445 size_t DefNewGeneration::max_capacity() const {
446 const size_t reserved_bytes = reserved().byte_size();
447 return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment);
448 }
449
450 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
451 return eden()->free();
452 }
453
454 size_t DefNewGeneration::capacity_before_gc() const {
455 return eden()->capacity();
456 }
457
458 size_t DefNewGeneration::contiguous_available() const {
459 return eden()->free();
460 }
461
462
463 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
464 eden()->object_iterate(blk);
465 from()->object_iterate(blk);
466 }
467
468
469 void DefNewGeneration::space_iterate(SpaceClosure* blk,
470 bool usedOnly) {
471 blk->do_space(eden());
472 blk->do_space(from());
473 blk->do_space(to());
474 }
475
476 // The last collection bailed out, we are running out of heap space,
477 // so we try to allocate the from-space, too.
478 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
479 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
480
481 // If the Heap_lock is not locked by this thread, this will be called
482 // again later with the Heap_lock held.
483 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
484
485 HeapWord* result = NULL;
486 if (do_alloc) {
487 result = from()->allocate(size);
488 }
489
490 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s",
491 size,
492 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
493 "true" : "false",
494 Heap_lock->is_locked() ? "locked" : "unlocked",
495 from()->free(),
496 should_try_alloc ? "" : " should_allocate_from_space: NOT",
497 do_alloc ? " Heap_lock is not owned by self" : "",
498 result == NULL ? "NULL" : "object");
499
500 return result;
501 }
502
503 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, bool is_tlab) {
504 // We don't attempt to expand the young generation (but perhaps we should.)
505 return allocate(size, is_tlab);
506 }
507
508 void DefNewGeneration::adjust_desired_tenuring_threshold() {
509 // Set the desired survivor size to half the real survivor space
510 size_t const survivor_capacity = to()->capacity() / HeapWordSize;
511 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
512
513 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
514
515 if (UsePerfData) {
516 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters();
517 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
518 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
519 }
520
521 age_table()->print_age_table(_tenuring_threshold);
522 }
523
524 void DefNewGeneration::collect(bool full,
525 bool clear_all_soft_refs,
526 size_t size,
527 bool is_tlab) {
528 assert(full || size > 0, "otherwise we don't want to collect");
529
530 SerialHeap* heap = SerialHeap::heap();
531
532 _gc_timer->register_gc_start();
533 _gc_tracer->report_gc_start(heap->gc_cause(), _gc_timer->gc_start());
534
535 _old_gen = heap->old_gen();
536
537 // If the next generation is too full to accommodate promotion
538 // from this generation, pass on collection; let the next generation
539 // do it.
540 if (!collection_attempt_is_safe()) {
541 log_trace(gc)(":: Collection attempt not safe ::");
542 heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
543 return;
544 }
545 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
546
547 init_assuming_no_promotion_failure();
548
549 GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause());
550
551 heap->trace_heap_before_gc(_gc_tracer);
552
553 // These can be shared for all code paths
554 IsAliveClosure is_alive(this);
555 ScanWeakRefClosure scan_weak_ref(this);
556
557 age_table()->clear();
558 to()->clear(SpaceDecorator::Mangle);
559 // The preserved marks should be empty at the start of the GC.
560 _preserved_marks_set.init(1);
561
562 assert(heap->no_allocs_since_save_marks(),
563 "save marks have not been newly set.");
564
565 DefNewScanClosure scan_closure(this);
566 DefNewYoungerGenClosure younger_gen_closure(this, _old_gen);
567
568 CLDScanClosure cld_scan_closure(&scan_closure);
569
570 set_promo_failure_scan_stack_closure(&scan_closure);
571 FastEvacuateFollowersClosure evacuate_followers(heap,
572 &scan_closure,
573 &younger_gen_closure);
574
575 assert(heap->no_allocs_since_save_marks(),
576 "save marks have not been newly set.");
577
578 {
579 StrongRootsScope srs(0);
580
581 heap->young_process_roots(&scan_closure,
582 &younger_gen_closure,
583 &cld_scan_closure);
584 }
585
586 // "evacuate followers".
587 evacuate_followers.do_void();
588
589 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
590 ReferenceProcessor* rp = ref_processor();
591 ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
592 SerialGCRefProcProxyTask task(is_alive, keep_alive, evacuate_followers);
593 const ReferenceProcessorStats& stats = rp->process_discovered_references(task, pt);
594 _gc_tracer->report_gc_reference_stats(stats);
595 _gc_tracer->report_tenuring_threshold(tenuring_threshold());
596 pt.print_all_references();
597
598 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
599
600 WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
601
602 // Verify that the usage of keep_alive didn't copy any objects.
603 assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
604
605 _string_dedup_requests.flush();
606
607 if (!_promotion_failed) {
608 // Swap the survivor spaces.
609 eden()->clear(SpaceDecorator::Mangle);
610 from()->clear(SpaceDecorator::Mangle);
611 if (ZapUnusedHeapArea) {
612 // This is now done here because of the piece-meal mangling which
613 // can check for valid mangling at intermediate points in the
614 // collection(s). When a young collection fails to collect
615 // sufficient space resizing of the young generation can occur
616 // an redistribute the spaces in the young generation. Mangle
617 // here so that unzapped regions don't get distributed to
618 // other spaces.
619 to()->mangle_unused_area();
620 }
621 swap_spaces();
622
623 assert(to()->is_empty(), "to space should be empty now");
624
625 adjust_desired_tenuring_threshold();
626
627 // A successful scavenge should restart the GC time limit count which is
628 // for full GC's.
629 AdaptiveSizePolicy* size_policy = heap->size_policy();
630 size_policy->reset_gc_overhead_limit_count();
631 assert(!heap->incremental_collection_failed(), "Should be clear");
632 } else {
633 assert(_promo_failure_scan_stack.is_empty(), "post condition");
634 _promo_failure_scan_stack.clear(true); // Clear cached segments.
635
636 remove_forwarding_pointers();
637 log_info(gc, promotion)("Promotion failed");
638 // Add to-space to the list of space to compact
639 // when a promotion failure has occurred. In that
640 // case there can be live objects in to-space
641 // as a result of a partial evacuation of eden
642 // and from-space.
643 swap_spaces(); // For uniformity wrt ParNewGeneration.
644 from()->set_next_compaction_space(to());
645 heap->set_incremental_collection_failed();
646
647 // Inform the next generation that a promotion failure occurred.
648 _old_gen->promotion_failure_occurred();
649 _gc_tracer->report_promotion_failed(_promotion_failed_info);
650
651 // Reset the PromotionFailureALot counters.
652 NOT_PRODUCT(heap->reset_promotion_should_fail();)
653 }
654 // We should have processed and cleared all the preserved marks.
655 _preserved_marks_set.reclaim();
656
657 heap->trace_heap_after_gc(_gc_tracer);
658
659 _gc_timer->register_gc_end();
660
661 _gc_tracer->report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
662 }
663
664 void DefNewGeneration::init_assuming_no_promotion_failure() {
665 _promotion_failed = false;
666 _promotion_failed_info.reset();
667 from()->set_next_compaction_space(NULL);
668 }
669
670 void DefNewGeneration::remove_forwarding_pointers() {
671 assert(_promotion_failed, "precondition");
672
673 // Will enter Full GC soon due to failed promotion. Must reset the mark word
674 // of objs in young-gen so that no objs are marked (forwarded) when Full GC
675 // starts. (The mark word is overloaded: `is_marked()` == `is_forwarded()`.)
676 struct ResetForwardedMarkWord : ObjectClosure {
677 void do_object(oop obj) override {
678 if (obj->is_forwarded()) {
679 #ifdef _LP64
680 oop forwardee = obj->forwardee();
681 markWord header = forwardee->mark();
682 if (header.has_displaced_mark_helper()) {
683 header = header.displaced_mark_helper();
684 }
685 assert(UseCompressedClassPointers, "assume +UseCompressedClassPointers");
686 narrowKlass nklass = header.narrow_klass();
687 obj->set_mark(markWord::prototype().set_narrow_klass(nklass));
688 #else
689 obj->init_mark();
690 #endif
691 }
692 }
693 } cl;
694 eden()->object_iterate(&cl);
695 from()->object_iterate(&cl);
696
697 restore_preserved_marks();
698 }
699
700 void DefNewGeneration::restore_preserved_marks() {
701 _preserved_marks_set.restore(NULL);
702 }
703
704 void DefNewGeneration::handle_promotion_failure(oop old) {
705 log_debug(gc, promotion)("Promotion failure size = " SIZE_FORMAT ") ", old->size());
706
707 _promotion_failed = true;
708 _promotion_failed_info.register_copy_failure(old->size());
709 _preserved_marks_set.get()->push_if_necessary(old, old->mark());
710
711 ContinuationGCSupport::transform_stack_chunk(old);
712
713 // forward to self
714 old->forward_to_self();
715
716 _promo_failure_scan_stack.push(old);
717
718 if (!_promo_failure_drain_in_progress) {
719 // prevent recursion in copy_to_survivor_space()
720 _promo_failure_drain_in_progress = true;
721 drain_promo_failure_scan_stack();
722 _promo_failure_drain_in_progress = false;
723 }
724 }
725
726 oop DefNewGeneration::copy_to_survivor_space(oop old) {
727 assert(is_in_reserved(old) && !old->is_forwarded(),
728 "shouldn't be scavenging this oop");
729 size_t s = old->size();
730 oop obj = NULL;
731
732 // Try allocating obj in to-space (unless too old)
733 if (old->age() < tenuring_threshold()) {
734 obj = cast_to_oop(to()->allocate(s));
735 }
736
737 bool new_obj_is_tenured = false;
738 // Otherwise try allocating obj tenured
739 if (obj == NULL) {
740 obj = _old_gen->promote(old, s);
741 if (obj == NULL) {
742 handle_promotion_failure(old);
743 return old;
744 }
745 new_obj_is_tenured = true;
746 } else {
747 // Prefetch beyond obj
748 const intx interval = PrefetchCopyIntervalInBytes;
749 Prefetch::write(obj, interval);
750
751 // Copy obj
752 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s);
753
754 ContinuationGCSupport::transform_stack_chunk(obj);
755
756 // Increment age if obj still in new generation
757 obj->incr_age();
758 age_table()->add(obj, s);
759 }
760
761 // Done, insert forward pointer to obj in this header
762 old->forward_to(obj);
763
764 if (SerialStringDedup::is_candidate_from_evacuation(obj, new_obj_is_tenured)) {
765 // Record old; request adds a new weak reference, which reference
766 // processing expects to refer to a from-space object.
767 _string_dedup_requests.add(old);
768 }
769 return obj;
770 }
771
772 void DefNewGeneration::drain_promo_failure_scan_stack() {
773 while (!_promo_failure_scan_stack.is_empty()) {
774 oop obj = _promo_failure_scan_stack.pop();
775 obj->oop_iterate(_promo_failure_scan_stack_closure);
776 }
777 }
778
779 void DefNewGeneration::save_marks() {
780 eden()->set_saved_mark();
781 to()->set_saved_mark();
782 from()->set_saved_mark();
783 }
784
785
786 void DefNewGeneration::reset_saved_marks() {
787 eden()->reset_saved_mark();
788 to()->reset_saved_mark();
789 from()->reset_saved_mark();
790 }
791
792
793 bool DefNewGeneration::no_allocs_since_save_marks() {
794 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
795 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
796 return to()->saved_mark_at_top();
797 }
798
799 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
800 size_t max_alloc_words) {
801 if (requestor == this || _promotion_failed) {
802 return;
803 }
804 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
805
806 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
807 if (to_space->top() > to_space->bottom()) {
808 trace("to_space not empty when contribute_scratch called");
809 }
810 */
811
812 ContiguousSpace* to_space = to();
813 assert(to_space->end() >= to_space->top(), "pointers out of order");
814 size_t free_words = pointer_delta(to_space->end(), to_space->top());
815 if (free_words >= MinFreeScratchWords) {
816 ScratchBlock* sb = (ScratchBlock*)to_space->top();
817 sb->num_words = free_words;
818 sb->next = list;
819 list = sb;
820 }
821 }
822
823 void DefNewGeneration::reset_scratch() {
824 // If contributing scratch in to_space, mangle all of
825 // to_space if ZapUnusedHeapArea. This is needed because
826 // top is not maintained while using to-space as scratch.
827 if (ZapUnusedHeapArea) {
828 to()->mangle_unused_area_complete();
829 }
830 }
831
832 bool DefNewGeneration::collection_attempt_is_safe() {
833 if (!to()->is_empty()) {
834 log_trace(gc)(":: to is not empty ::");
835 return false;
836 }
837 if (_old_gen == NULL) {
838 GenCollectedHeap* gch = GenCollectedHeap::heap();
839 _old_gen = gch->old_gen();
840 }
841 return _old_gen->promotion_attempt_is_safe(used());
842 }
843
844 void DefNewGeneration::gc_epilogue(bool full) {
845 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
846
847 assert(!GCLocker::is_active(), "We should not be executing here");
848 // Check if the heap is approaching full after a collection has
849 // been done. Generally the young generation is empty at
850 // a minimum at the end of a collection. If it is not, then
851 // the heap is approaching full.
852 GenCollectedHeap* gch = GenCollectedHeap::heap();
853 if (full) {
854 DEBUG_ONLY(seen_incremental_collection_failed = false;)
855 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
856 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
857 GCCause::to_string(gch->gc_cause()));
858 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
859 set_should_allocate_from_space(); // we seem to be running out of space
860 } else {
861 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
862 GCCause::to_string(gch->gc_cause()));
863 gch->clear_incremental_collection_failed(); // We just did a full collection
864 clear_should_allocate_from_space(); // if set
865 }
866 } else {
867 #ifdef ASSERT
868 // It is possible that incremental_collection_failed() == true
869 // here, because an attempted scavenge did not succeed. The policy
870 // is normally expected to cause a full collection which should
871 // clear that condition, so we should not be here twice in a row
872 // with incremental_collection_failed() == true without having done
873 // a full collection in between.
874 if (!seen_incremental_collection_failed &&
875 gch->incremental_collection_failed()) {
876 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
877 GCCause::to_string(gch->gc_cause()));
878 seen_incremental_collection_failed = true;
879 } else if (seen_incremental_collection_failed) {
880 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
881 GCCause::to_string(gch->gc_cause()));
882 seen_incremental_collection_failed = false;
883 }
884 #endif // ASSERT
885 }
886
887 if (ZapUnusedHeapArea) {
888 eden()->check_mangled_unused_area_complete();
889 from()->check_mangled_unused_area_complete();
890 to()->check_mangled_unused_area_complete();
891 }
892
893 // update the generation and space performance counters
894 update_counters();
895 gch->counters()->update_counters();
896 }
897
898 void DefNewGeneration::record_spaces_top() {
899 assert(ZapUnusedHeapArea, "Not mangling unused space");
900 eden()->set_top_for_allocations();
901 to()->set_top_for_allocations();
902 from()->set_top_for_allocations();
903 }
904
905 void DefNewGeneration::update_counters() {
906 if (UsePerfData) {
907 _eden_counters->update_all();
908 _from_counters->update_all();
909 _to_counters->update_all();
910 _gen_counters->update_all();
911 }
912 }
913
914 void DefNewGeneration::verify() {
915 eden()->verify();
916 from()->verify();
917 to()->verify();
918 }
919
920 void DefNewGeneration::print_on(outputStream* st) const {
921 Generation::print_on(st);
922 st->print(" eden");
923 eden()->print_on(st);
924 st->print(" from");
925 from()->print_on(st);
926 st->print(" to ");
927 to()->print_on(st);
928 }
929
930
931 const char* DefNewGeneration::name() const {
932 return "def new generation";
933 }
934
935 // Moved from inline file as they are not called inline
936 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
937 return eden();
938 }
939
940 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
941 // This is the slow-path allocation for the DefNewGeneration.
942 // Most allocations are fast-path in compiled code.
943 // We try to allocate from the eden. If that works, we are happy.
944 // Note that since DefNewGeneration supports lock-free allocation, we
945 // have to use it here, as well.
946 HeapWord* result = eden()->par_allocate(word_size);
947 if (result == NULL) {
948 // If the eden is full and the last collection bailed out, we are running
949 // out of heap space, and we try to allocate the from-space, too.
950 // allocate_from_space can't be inlined because that would introduce a
951 // circular dependency at compile time.
952 result = allocate_from_space(word_size);
953 }
954 return result;
955 }
956
957 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
958 bool is_tlab) {
959 return eden()->par_allocate(word_size);
960 }
961
962 size_t DefNewGeneration::tlab_capacity() const {
963 return eden()->capacity();
964 }
965
966 size_t DefNewGeneration::tlab_used() const {
967 return eden()->used();
968 }
969
970 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
971 return unsafe_max_alloc_nogc();
972 }