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/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/gcArguments.hpp"
36 #include "gc/shared/gcHeapSummary.hpp"
37 #include "gc/shared/gcLocker.hpp"
38 #include "gc/shared/gcPolicyCounters.hpp"
39 #include "gc/shared/gcTimer.hpp"
40 #include "gc/shared/gcTrace.hpp"
41 #include "gc/shared/gcTraceTime.inline.hpp"
42 #include "gc/shared/generationSpec.hpp"
43 #include "gc/shared/genOopClosures.inline.hpp"
44 #include "gc/shared/preservedMarks.inline.hpp"
45 #include "gc/shared/referencePolicy.hpp"
46 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
47 #include "gc/shared/space.inline.hpp"
48 #include "gc/shared/spaceDecorator.inline.hpp"
49 #include "gc/shared/strongRootsScope.hpp"
50 #include "gc/shared/weakProcessor.hpp"
51 #include "logging/log.hpp"
52 #include "memory/iterator.inline.hpp"
53 #include "memory/resourceArea.hpp"
54 #include "oops/instanceRefKlass.hpp"
55 #include "oops/oop.inline.hpp"
56 #include "runtime/java.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::DefNew, "Expected the young generation here");
71 }
72
73 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
74 return cast_from_oop<HeapWord*>(p) >= _young_gen->reserved().end() || p->is_forwarded();
75 }
76
77 DefNewGeneration::KeepAliveClosure::
78 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
79 _rs = GenCollectedHeap::heap()->rem_set();
80 }
81
82 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
83 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
84
85
86 DefNewGeneration::FastKeepAliveClosure::
87 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
88 DefNewGeneration::KeepAliveClosure(cl) {
89 _boundary = g->reserved().end();
90 }
91
92 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
93 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
94
95 DefNewGeneration::FastEvacuateFollowersClosure::
96 FastEvacuateFollowersClosure(SerialHeap* heap,
97 DefNewScanClosure* cur,
98 DefNewYoungerGenClosure* older) :
99 _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older)
100 {
101 }
102
103 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
104 do {
105 _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older);
106 } while (!_heap->no_allocs_since_save_marks());
107 guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan");
108 }
109
110 void CLDScanClosure::do_cld(ClassLoaderData* cld) {
111 NOT_PRODUCT(ResourceMark rm);
112 log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s",
113 p2i(cld),
114 cld->loader_name_and_id(),
115 cld->has_modified_oops() ? "true" : "false");
116
117 // If the cld has not been dirtied we know that there's
118 // no references into the young gen and we can skip it.
119 if (cld->has_modified_oops()) {
120
121 // Tell the closure which CLD is being scanned so that it can be dirtied
122 // if oops are left pointing into the young gen.
123 _scavenge_closure->set_scanned_cld(cld);
124
125 // Clean the cld since we're going to scavenge all the metadata.
126 cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);
127
128 _scavenge_closure->set_scanned_cld(NULL);
129 }
130 }
131
132 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
133 _g(g)
134 {
135 _boundary = _g->reserved().end();
136 }
137
138 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
139 size_t initial_size,
140 size_t min_size,
141 size_t max_size,
142 const char* policy)
143 : Generation(rs, initial_size),
144 _preserved_marks_set(false /* in_c_heap */),
145 _promo_failure_drain_in_progress(false),
146 _should_allocate_from_space(false),
147 _string_dedup_requests()
148 {
149 MemRegion cmr((HeapWord*)_virtual_space.low(),
150 (HeapWord*)_virtual_space.high());
151 GenCollectedHeap* gch = GenCollectedHeap::heap();
152
153 gch->rem_set()->resize_covered_region(cmr);
154
155 _eden_space = new ContiguousSpace();
156 _from_space = new ContiguousSpace();
157 _to_space = new ContiguousSpace();
158
159 // Compute the maximum eden and survivor space sizes. These sizes
160 // are computed assuming the entire reserved space is committed.
161 // These values are exported as performance counters.
162 uintx size = _virtual_space.reserved_size();
163 _max_survivor_size = compute_survivor_size(size, SpaceAlignment);
164 _max_eden_size = size - (2*_max_survivor_size);
165
166 // allocate the performance counters
167
168 // Generation counters -- generation 0, 3 subspaces
169 _gen_counters = new GenerationCounters("new", 0, 3,
170 min_size, max_size, &_virtual_space);
171 _gc_counters = new CollectorCounters(policy, 0);
172
173 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
174 _gen_counters);
175 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
176 _gen_counters);
177 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
178 _gen_counters);
179
180 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
181 update_counters();
182 _old_gen = NULL;
183 _tenuring_threshold = MaxTenuringThreshold;
184 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
185
186 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
187 }
188
189 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
190 bool clear_space,
191 bool mangle_space) {
192 // If the spaces are being cleared (only done at heap initialization
193 // currently), the survivor spaces need not be empty.
194 // Otherwise, no care is taken for used areas in the survivor spaces
195 // so check.
196 assert(clear_space || (to()->is_empty() && from()->is_empty()),
197 "Initialization of the survivor spaces assumes these are empty");
198
199 // Compute sizes
200 uintx size = _virtual_space.committed_size();
201 uintx survivor_size = compute_survivor_size(size, SpaceAlignment);
202 uintx eden_size = size - (2*survivor_size);
203 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
204
205 if (eden_size < minimum_eden_size) {
206 // May happen due to 64Kb rounding, if so adjust eden size back up
207 minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment);
208 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
209 uintx unaligned_survivor_size =
210 align_down(maximum_survivor_size, SpaceAlignment);
211 survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment);
212 eden_size = size - (2*survivor_size);
213 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
214 assert(eden_size >= minimum_eden_size, "just checking");
215 }
216
217 char *eden_start = _virtual_space.low();
218 char *from_start = eden_start + eden_size;
219 char *to_start = from_start + survivor_size;
220 char *to_end = to_start + survivor_size;
221
222 assert(to_end == _virtual_space.high(), "just checking");
223 assert(Space::is_aligned(eden_start), "checking alignment");
224 assert(Space::is_aligned(from_start), "checking alignment");
225 assert(Space::is_aligned(to_start), "checking alignment");
226
227 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
228 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
229 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
230
231 // A minimum eden size implies that there is a part of eden that
232 // is being used and that affects the initialization of any
233 // newly formed eden.
234 bool live_in_eden = minimum_eden_size > 0;
235
236 // If not clearing the spaces, do some checking to verify that
237 // the space are already mangled.
238 if (!clear_space) {
239 // Must check mangling before the spaces are reshaped. Otherwise,
240 // the bottom or end of one space may have moved into another
241 // a failure of the check may not correctly indicate which space
242 // is not properly mangled.
243 if (ZapUnusedHeapArea) {
244 HeapWord* limit = (HeapWord*) _virtual_space.high();
245 eden()->check_mangled_unused_area(limit);
246 from()->check_mangled_unused_area(limit);
247 to()->check_mangled_unused_area(limit);
248 }
249 }
250
251 // Reset the spaces for their new regions.
252 eden()->initialize(edenMR,
253 clear_space && !live_in_eden,
254 SpaceDecorator::Mangle);
255 // If clear_space and live_in_eden, we will not have cleared any
256 // portion of eden above its top. This can cause newly
257 // expanded space not to be mangled if using ZapUnusedHeapArea.
258 // We explicitly do such mangling here.
259 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
260 eden()->mangle_unused_area();
261 }
262 from()->initialize(fromMR, clear_space, mangle_space);
263 to()->initialize(toMR, clear_space, mangle_space);
264
265 // Set next compaction spaces.
266 eden()->set_next_compaction_space(from());
267 // The to-space is normally empty before a compaction so need
268 // not be considered. The exception is during promotion
269 // failure handling when to-space can contain live objects.
270 from()->set_next_compaction_space(NULL);
271 }
272
273 void DefNewGeneration::swap_spaces() {
274 ContiguousSpace* s = from();
275 _from_space = to();
276 _to_space = s;
277 eden()->set_next_compaction_space(from());
278 // The to-space is normally empty before a compaction so need
279 // not be considered. The exception is during promotion
280 // failure handling when to-space can contain live objects.
281 from()->set_next_compaction_space(NULL);
282
283 if (UsePerfData) {
284 CSpaceCounters* c = _from_counters;
285 _from_counters = _to_counters;
286 _to_counters = c;
287 }
288 }
289
290 bool DefNewGeneration::expand(size_t bytes) {
291 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
292 bool success = _virtual_space.expand_by(bytes);
293 if (success && ZapUnusedHeapArea) {
294 // Mangle newly committed space immediately because it
295 // can be done here more simply that after the new
296 // spaces have been computed.
297 HeapWord* new_high = (HeapWord*) _virtual_space.high();
298 MemRegion mangle_region(prev_high, new_high);
299 SpaceMangler::mangle_region(mangle_region);
300 }
301
302 // Do not attempt an expand-to-the reserve size. The
303 // request should properly observe the maximum size of
304 // the generation so an expand-to-reserve should be
305 // unnecessary. Also a second call to expand-to-reserve
306 // value potentially can cause an undue expansion.
307 // For example if the first expand fail for unknown reasons,
308 // but the second succeeds and expands the heap to its maximum
309 // value.
310 if (GCLocker::is_active()) {
311 log_debug(gc)("Garbage collection disabled, expanded heap instead");
312 }
313
314 return success;
315 }
316
317 size_t DefNewGeneration::calculate_thread_increase_size(int threads_count) const {
318 size_t thread_increase_size = 0;
319 // Check an overflow at 'threads_count * NewSizeThreadIncrease'.
320 if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
321 thread_increase_size = threads_count * NewSizeThreadIncrease;
322 }
323 return thread_increase_size;
324 }
325
326 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
327 size_t new_size_before,
328 size_t alignment,
329 size_t thread_increase_size) const {
330 size_t desired_new_size = new_size_before;
331
332 if (NewSizeThreadIncrease > 0 && thread_increase_size > 0) {
333
334 // 1. Check an overflow at 'new_size_candidate + thread_increase_size'.
335 if (new_size_candidate <= max_uintx - thread_increase_size) {
336 new_size_candidate += thread_increase_size;
337
338 // 2. Check an overflow at 'align_up'.
339 size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
340 if (new_size_candidate <= aligned_max) {
341 desired_new_size = align_up(new_size_candidate, alignment);
342 }
343 }
344 }
345
346 return desired_new_size;
347 }
348
349 void DefNewGeneration::compute_new_size() {
350 // This is called after a GC that includes the old generation, so from-space
351 // will normally be empty.
352 // Note that we check both spaces, since if scavenge failed they revert roles.
353 // If not we bail out (otherwise we would have to relocate the objects).
354 if (!from()->is_empty() || !to()->is_empty()) {
355 return;
356 }
357
358 GenCollectedHeap* gch = GenCollectedHeap::heap();
359
360 size_t old_size = gch->old_gen()->capacity();
361 size_t new_size_before = _virtual_space.committed_size();
362 size_t min_new_size = initial_size();
363 size_t max_new_size = reserved().byte_size();
364 assert(min_new_size <= new_size_before &&
365 new_size_before <= max_new_size,
366 "just checking");
367 // All space sizes must be multiples of Generation::GenGrain.
368 size_t alignment = Generation::GenGrain;
369
370 int threads_count = Threads::number_of_non_daemon_threads();
371 size_t thread_increase_size = calculate_thread_increase_size(threads_count);
372
373 size_t new_size_candidate = old_size / NewRatio;
374 // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
375 // and reverts to previous value if any overflow happens
376 size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before,
377 alignment, thread_increase_size);
378
379 // Adjust new generation size
380 desired_new_size = clamp(desired_new_size, min_new_size, max_new_size);
381 assert(desired_new_size <= max_new_size, "just checking");
382
383 bool changed = false;
384 if (desired_new_size > new_size_before) {
385 size_t change = desired_new_size - new_size_before;
386 assert(change % alignment == 0, "just checking");
387 if (expand(change)) {
388 changed = true;
389 }
390 // If the heap failed to expand to the desired size,
391 // "changed" will be false. If the expansion failed
392 // (and at this point it was expected to succeed),
393 // ignore the failure (leaving "changed" as false).
394 }
395 if (desired_new_size < new_size_before && eden()->is_empty()) {
396 // bail out of shrinking if objects in eden
397 size_t change = new_size_before - desired_new_size;
398 assert(change % alignment == 0, "just checking");
399 _virtual_space.shrink_by(change);
400 changed = true;
401 }
402 if (changed) {
403 // The spaces have already been mangled at this point but
404 // may not have been cleared (set top = bottom) and should be.
405 // Mangling was done when the heap was being expanded.
406 compute_space_boundaries(eden()->used(),
407 SpaceDecorator::Clear,
408 SpaceDecorator::DontMangle);
409 MemRegion cmr((HeapWord*)_virtual_space.low(),
410 (HeapWord*)_virtual_space.high());
411 gch->rem_set()->resize_covered_region(cmr);
412
413 log_debug(gc, ergo, heap)(
414 "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
415 new_size_before/K, _virtual_space.committed_size()/K,
416 eden()->capacity()/K, from()->capacity()/K);
417 log_trace(gc, ergo, heap)(
418 " [allowed " SIZE_FORMAT "K extra for %d threads]",
419 thread_increase_size/K, threads_count);
420 }
421 }
422
423
424 size_t DefNewGeneration::capacity() const {
425 return eden()->capacity()
426 + from()->capacity(); // to() is only used during scavenge
427 }
428
429
430 size_t DefNewGeneration::used() const {
431 return eden()->used()
432 + from()->used(); // to() is only used during scavenge
433 }
434
435
436 size_t DefNewGeneration::free() const {
437 return eden()->free()
438 + from()->free(); // to() is only used during scavenge
439 }
440
441 size_t DefNewGeneration::max_capacity() const {
442 const size_t reserved_bytes = reserved().byte_size();
443 return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment);
444 }
445
446 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
447 return eden()->free();
448 }
449
450 size_t DefNewGeneration::capacity_before_gc() const {
451 return eden()->capacity();
452 }
453
454 size_t DefNewGeneration::contiguous_available() const {
455 return eden()->free();
456 }
457
458
459 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }
460 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
461
462 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
463 eden()->object_iterate(blk);
464 from()->object_iterate(blk);
465 }
466
467
468 void DefNewGeneration::space_iterate(SpaceClosure* blk,
469 bool usedOnly) {
470 blk->do_space(eden());
471 blk->do_space(from());
472 blk->do_space(to());
473 }
474
475 // The last collection bailed out, we are running out of heap space,
476 // so we try to allocate the from-space, too.
477 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
478 bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
479
480 // If the Heap_lock is not locked by this thread, this will be called
481 // again later with the Heap_lock held.
482 bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
483
484 HeapWord* result = NULL;
485 if (do_alloc) {
486 result = from()->allocate(size);
487 }
488
489 log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "): will_fail: %s heap_lock: %s free: " SIZE_FORMAT "%s%s returns %s",
490 size,
491 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
492 "true" : "false",
493 Heap_lock->is_locked() ? "locked" : "unlocked",
494 from()->free(),
495 should_try_alloc ? "" : " should_allocate_from_space: NOT",
496 do_alloc ? " Heap_lock is not owned by self" : "",
497 result == NULL ? "NULL" : "object");
498
499 return result;
500 }
501
502 HeapWord* DefNewGeneration::expand_and_allocate(size_t size, bool is_tlab) {
503 // We don't attempt to expand the young generation (but perhaps we should.)
504 return allocate(size, is_tlab);
505 }
506
507 void DefNewGeneration::adjust_desired_tenuring_threshold() {
508 // Set the desired survivor size to half the real survivor space
509 size_t const survivor_capacity = to()->capacity() / HeapWordSize;
510 size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
511
512 _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
513
514 if (UsePerfData) {
515 GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters();
516 gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
517 gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
518 }
519
520 age_table()->print_age_table(_tenuring_threshold);
521 }
522
523 void DefNewGeneration::collect(bool full,
524 bool clear_all_soft_refs,
525 size_t size,
526 bool is_tlab) {
527 assert(full || size > 0, "otherwise we don't want to collect");
528
529 SerialHeap* heap = SerialHeap::heap();
530
531 _gc_timer->register_gc_start();
532 DefNewTracer gc_tracer;
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 // forward to self
711 old->forward_to_self();
712
713 _promo_failure_scan_stack.push(old);
714
715 if (!_promo_failure_drain_in_progress) {
716 // prevent recursion in copy_to_survivor_space()
717 _promo_failure_drain_in_progress = true;
718 drain_promo_failure_scan_stack();
719 _promo_failure_drain_in_progress = false;
720 }
721 }
722
723 oop DefNewGeneration::copy_to_survivor_space(oop old) {
724 assert(is_in_reserved(old) && !old->is_forwarded(),
725 "shouldn't be scavenging this oop");
726 size_t s = old->size();
727 oop obj = NULL;
728
729 // Try allocating obj in to-space (unless too old)
730 if (old->age() < tenuring_threshold()) {
731 obj = cast_to_oop(to()->allocate(s));
732 }
733
734 bool new_obj_is_tenured = false;
735 // Otherwise try allocating obj tenured
736 if (obj == NULL) {
737 obj = _old_gen->promote(old, s);
738 if (obj == NULL) {
739 handle_promotion_failure(old);
740 return old;
741 }
742 new_obj_is_tenured = true;
743 } else {
744 // Prefetch beyond obj
745 const intx interval = PrefetchCopyIntervalInBytes;
746 Prefetch::write(obj, interval);
747
748 // Copy obj
749 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s);
750
751 // Increment age if obj still in new generation
752 obj->incr_age();
753 age_table()->add(obj, s);
754 }
755
756 // Done, insert forward pointer to obj in this header
757 old->forward_to(obj);
758
759 if (SerialStringDedup::is_candidate_from_evacuation(obj, new_obj_is_tenured)) {
760 // Record old; request adds a new weak reference, which reference
761 // processing expects to refer to a from-space object.
762 _string_dedup_requests.add(old);
763 }
764 return obj;
765 }
766
767 void DefNewGeneration::drain_promo_failure_scan_stack() {
768 while (!_promo_failure_scan_stack.is_empty()) {
769 oop obj = _promo_failure_scan_stack.pop();
770 obj->oop_iterate(_promo_failure_scan_stack_closure);
771 }
772 }
773
774 void DefNewGeneration::save_marks() {
775 eden()->set_saved_mark();
776 to()->set_saved_mark();
777 from()->set_saved_mark();
778 }
779
780
781 void DefNewGeneration::reset_saved_marks() {
782 eden()->reset_saved_mark();
783 to()->reset_saved_mark();
784 from()->reset_saved_mark();
785 }
786
787
788 bool DefNewGeneration::no_allocs_since_save_marks() {
789 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
790 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
791 return to()->saved_mark_at_top();
792 }
793
794 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
795 size_t max_alloc_words) {
796 if (requestor == this || _promotion_failed) {
797 return;
798 }
799 assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
800
801 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
802 if (to_space->top() > to_space->bottom()) {
803 trace("to_space not empty when contribute_scratch called");
804 }
805 */
806
807 ContiguousSpace* to_space = to();
808 assert(to_space->end() >= to_space->top(), "pointers out of order");
809 size_t free_words = pointer_delta(to_space->end(), to_space->top());
810 if (free_words >= MinFreeScratchWords) {
811 ScratchBlock* sb = (ScratchBlock*)to_space->top();
812 sb->num_words = free_words;
813 sb->next = list;
814 list = sb;
815 }
816 }
817
818 void DefNewGeneration::reset_scratch() {
819 // If contributing scratch in to_space, mangle all of
820 // to_space if ZapUnusedHeapArea. This is needed because
821 // top is not maintained while using to-space as scratch.
822 if (ZapUnusedHeapArea) {
823 to()->mangle_unused_area_complete();
824 }
825 }
826
827 bool DefNewGeneration::collection_attempt_is_safe() {
828 if (!to()->is_empty()) {
829 log_trace(gc)(":: to is not empty ::");
830 return false;
831 }
832 if (_old_gen == NULL) {
833 GenCollectedHeap* gch = GenCollectedHeap::heap();
834 _old_gen = gch->old_gen();
835 }
836 return _old_gen->promotion_attempt_is_safe(used());
837 }
838
839 void DefNewGeneration::gc_epilogue(bool full) {
840 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
841
842 assert(!GCLocker::is_active(), "We should not be executing here");
843 // Check if the heap is approaching full after a collection has
844 // been done. Generally the young generation is empty at
845 // a minimum at the end of a collection. If it is not, then
846 // the heap is approaching full.
847 GenCollectedHeap* gch = GenCollectedHeap::heap();
848 if (full) {
849 DEBUG_ONLY(seen_incremental_collection_failed = false;)
850 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
851 log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
852 GCCause::to_string(gch->gc_cause()));
853 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
854 set_should_allocate_from_space(); // we seem to be running out of space
855 } else {
856 log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
857 GCCause::to_string(gch->gc_cause()));
858 gch->clear_incremental_collection_failed(); // We just did a full collection
859 clear_should_allocate_from_space(); // if set
860 }
861 } else {
862 #ifdef ASSERT
863 // It is possible that incremental_collection_failed() == true
864 // here, because an attempted scavenge did not succeed. The policy
865 // is normally expected to cause a full collection which should
866 // clear that condition, so we should not be here twice in a row
867 // with incremental_collection_failed() == true without having done
868 // a full collection in between.
869 if (!seen_incremental_collection_failed &&
870 gch->incremental_collection_failed()) {
871 log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
872 GCCause::to_string(gch->gc_cause()));
873 seen_incremental_collection_failed = true;
874 } else if (seen_incremental_collection_failed) {
875 log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
876 GCCause::to_string(gch->gc_cause()));
877 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
878 !gch->incremental_collection_failed(),
879 "Twice in a row");
880 seen_incremental_collection_failed = false;
881 }
882 #endif // ASSERT
883 }
884
885 if (ZapUnusedHeapArea) {
886 eden()->check_mangled_unused_area_complete();
887 from()->check_mangled_unused_area_complete();
888 to()->check_mangled_unused_area_complete();
889 }
890
891 // update the generation and space performance counters
892 update_counters();
893 gch->counters()->update_counters();
894 }
895
896 void DefNewGeneration::record_spaces_top() {
897 assert(ZapUnusedHeapArea, "Not mangling unused space");
898 eden()->set_top_for_allocations();
899 to()->set_top_for_allocations();
900 from()->set_top_for_allocations();
901 }
902
903 void DefNewGeneration::update_counters() {
904 if (UsePerfData) {
905 _eden_counters->update_all();
906 _from_counters->update_all();
907 _to_counters->update_all();
908 _gen_counters->update_all();
909 }
910 }
911
912 void DefNewGeneration::verify() {
913 eden()->verify();
914 from()->verify();
915 to()->verify();
916 }
917
918 void DefNewGeneration::print_on(outputStream* st) const {
919 Generation::print_on(st);
920 st->print(" eden");
921 eden()->print_on(st);
922 st->print(" from");
923 from()->print_on(st);
924 st->print(" to ");
925 to()->print_on(st);
926 }
927
928
929 const char* DefNewGeneration::name() const {
930 return "def new generation";
931 }
932
933 // Moved from inline file as they are not called inline
934 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
935 return eden();
936 }
937
938 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
939 // This is the slow-path allocation for the DefNewGeneration.
940 // Most allocations are fast-path in compiled code.
941 // We try to allocate from the eden. If that works, we are happy.
942 // Note that since DefNewGeneration supports lock-free allocation, we
943 // have to use it here, as well.
944 HeapWord* result = eden()->par_allocate(word_size);
945 if (result == NULL) {
946 // If the eden is full and the last collection bailed out, we are running
947 // out of heap space, and we try to allocate the from-space, too.
948 // allocate_from_space can't be inlined because that would introduce a
949 // circular dependency at compile time.
950 result = allocate_from_space(word_size);
951 }
952 return result;
953 }
954
955 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
956 bool is_tlab) {
957 return eden()->par_allocate(word_size);
958 }
959
960 size_t DefNewGeneration::tlab_capacity() const {
961 return eden()->capacity();
962 }
963
964 size_t DefNewGeneration::tlab_used() const {
965 return eden()->used();
966 }
967
968 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
969 return unsafe_max_alloc_nogc();
970 }