1 /*
2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc_implementation/shared/collectorCounters.hpp"
27 #include "gc_implementation/shared/gcPolicyCounters.hpp"
28 #include "gc_implementation/shared/gcHeapSummary.hpp"
29 #include "gc_implementation/shared/gcTimer.hpp"
30 #include "gc_implementation/shared/gcTraceTime.hpp"
31 #include "gc_implementation/shared/gcTrace.hpp"
32 #include "gc_implementation/shared/spaceDecorator.hpp"
33 #include "memory/defNewGeneration.inline.hpp"
34 #include "memory/gcLocker.inline.hpp"
35 #include "memory/genCollectedHeap.hpp"
36 #include "memory/genOopClosures.inline.hpp"
37 #include "memory/genRemSet.hpp"
38 #include "memory/generationSpec.hpp"
39 #include "memory/iterator.hpp"
40 #include "memory/referencePolicy.hpp"
41 #include "memory/space.inline.hpp"
42 #include "oops/instanceRefKlass.hpp"
43 #include "oops/oop.inline.hpp"
44 #include "runtime/atomic.inline.hpp"
45 #include "runtime/java.hpp"
46 #include "runtime/prefetch.inline.hpp"
47 #include "runtime/thread.inline.hpp"
48 #include "utilities/copy.hpp"
49 #include "utilities/globalDefinitions.hpp"
50 #include "utilities/stack.inline.hpp"
51
52 //
53 // DefNewGeneration functions.
54
55 // Methods of protected closure types.
56
57 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
58 assert(g->level() == 0, "Optimized for youngest gen.");
59 }
60 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
61 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
62 }
63
64 DefNewGeneration::KeepAliveClosure::
65 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
66 GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
67 _rs = (CardTableRS*)rs;
68 }
69
70 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
71 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
72
73
74 DefNewGeneration::FastKeepAliveClosure::
75 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
76 DefNewGeneration::KeepAliveClosure(cl) {
77 _boundary = g->reserved().end();
78 }
79
80 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
81 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
82
83 DefNewGeneration::EvacuateFollowersClosure::
84 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
85 ScanClosure* cur, ScanClosure* older) :
86 _gch(gch), _level(level),
87 _scan_cur_or_nonheap(cur), _scan_older(older)
88 {}
89
90 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
91 do {
92 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
93 _scan_older);
94 } while (!_gch->no_allocs_since_save_marks(_level));
95 }
96
97 DefNewGeneration::FastEvacuateFollowersClosure::
98 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
99 DefNewGeneration* gen,
100 FastScanClosure* cur, FastScanClosure* older) :
101 _gch(gch), _level(level), _gen(gen),
102 _scan_cur_or_nonheap(cur), _scan_older(older)
103 {}
104
105 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
106 do {
107 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
108 _scan_older);
109 } while (!_gch->no_allocs_since_save_marks(_level));
110 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
111 }
112
113 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
114 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
115 {
116 assert(_g->level() == 0, "Optimized for youngest generation");
117 _boundary = _g->reserved().end();
118 }
119
120 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
121 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
122
123 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
124 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
125 {
126 assert(_g->level() == 0, "Optimized for youngest generation");
127 _boundary = _g->reserved().end();
128 }
129
130 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
131 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
132
133 void KlassScanClosure::do_klass(Klass* klass) {
134 #ifndef PRODUCT
135 if (TraceScavenge) {
136 ResourceMark rm;
137 gclog_or_tty->print_cr("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s",
138 p2i(klass),
139 klass->external_name(),
140 klass->has_modified_oops() ? "true" : "false");
141 }
142 #endif
143
144 // If the klass has not been dirtied we know that there's
145 // no references into the young gen and we can skip it.
146 if (klass->has_modified_oops()) {
147 if (_accumulate_modified_oops) {
148 klass->accumulate_modified_oops();
149 }
150
151 // Clear this state since we're going to scavenge all the metadata.
152 klass->clear_modified_oops();
153
154 // Tell the closure which Klass is being scanned so that it can be dirtied
155 // if oops are left pointing into the young gen.
156 _scavenge_closure->set_scanned_klass(klass);
157
158 klass->oops_do(_scavenge_closure);
159
160 _scavenge_closure->set_scanned_klass(NULL);
161 }
162 }
163
164 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
165 _g(g)
166 {
167 assert(_g->level() == 0, "Optimized for youngest generation");
168 _boundary = _g->reserved().end();
169 }
170
171 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
172 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
173
174 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
175 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
176
177 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
178 KlassRemSet* klass_rem_set)
179 : _scavenge_closure(scavenge_closure),
180 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
181
182
183 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
184 size_t initial_size,
185 int level,
186 const char* policy)
187 : Generation(rs, initial_size, level),
188 _promo_failure_drain_in_progress(false),
189 _should_allocate_from_space(false)
190 {
191 MemRegion cmr((HeapWord*)_virtual_space.low(),
192 (HeapWord*)_virtual_space.high());
193 Universe::heap()->barrier_set()->resize_covered_region(cmr);
194
195 _eden_space = new ContiguousSpace();
196 _from_space = new ContiguousSpace();
197 _to_space = new ContiguousSpace();
198
199 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
200 vm_exit_during_initialization("Could not allocate a new gen space");
201
202 // Compute the maximum eden and survivor space sizes. These sizes
203 // are computed assuming the entire reserved space is committed.
204 // These values are exported as performance counters.
205 uintx alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
206 uintx size = _virtual_space.reserved_size();
207 _max_survivor_size = compute_survivor_size(size, alignment);
208 _max_eden_size = size - (2*_max_survivor_size);
209
210 // allocate the performance counters
211 GenCollectorPolicy* gcp = (GenCollectorPolicy*) GenCollectedHeap::heap()->collector_policy();
212
213 // Generation counters -- generation 0, 3 subspaces
214 _gen_counters = new GenerationCounters("new", 0, 3,
215 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
216 _gc_counters = new CollectorCounters(policy, 0);
217
218 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
219 _gen_counters);
220 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
221 _gen_counters);
222 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
223 _gen_counters);
224
225 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
226 update_counters();
227 _old_gen = NULL;
228 _tenuring_threshold = MaxTenuringThreshold;
229 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
230
231 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
232 }
233
234 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
235 bool clear_space,
236 bool mangle_space) {
237 uintx alignment =
238 GenCollectedHeap::heap()->collector_policy()->space_alignment();
239
240 // If the spaces are being cleared (only done at heap initialization
241 // currently), the survivor spaces need not be empty.
242 // Otherwise, no care is taken for used areas in the survivor spaces
243 // so check.
244 assert(clear_space || (to()->is_empty() && from()->is_empty()),
245 "Initialization of the survivor spaces assumes these are empty");
246
247 // Compute sizes
248 uintx size = _virtual_space.committed_size();
249 uintx survivor_size = compute_survivor_size(size, alignment);
250 uintx eden_size = size - (2*survivor_size);
251 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
252
253 if (eden_size < minimum_eden_size) {
254 // May happen due to 64Kb rounding, if so adjust eden size back up
255 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
256 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
257 uintx unaligned_survivor_size =
258 align_size_down(maximum_survivor_size, alignment);
259 survivor_size = MAX2(unaligned_survivor_size, alignment);
260 eden_size = size - (2*survivor_size);
261 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
262 assert(eden_size >= minimum_eden_size, "just checking");
263 }
264
265 char *eden_start = _virtual_space.low();
266 char *from_start = eden_start + eden_size;
267 char *to_start = from_start + survivor_size;
268 char *to_end = to_start + survivor_size;
269
270 assert(to_end == _virtual_space.high(), "just checking");
271 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
272 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
273 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
274
275 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
276 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
277 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
278
279 // A minimum eden size implies that there is a part of eden that
280 // is being used and that affects the initialization of any
281 // newly formed eden.
282 bool live_in_eden = minimum_eden_size > 0;
283
284 // If not clearing the spaces, do some checking to verify that
285 // the space are already mangled.
286 if (!clear_space) {
287 // Must check mangling before the spaces are reshaped. Otherwise,
288 // the bottom or end of one space may have moved into another
289 // a failure of the check may not correctly indicate which space
290 // is not properly mangled.
291 if (ZapUnusedHeapArea) {
292 HeapWord* limit = (HeapWord*) _virtual_space.high();
293 eden()->check_mangled_unused_area(limit);
294 from()->check_mangled_unused_area(limit);
295 to()->check_mangled_unused_area(limit);
296 }
297 }
298
299 // Reset the spaces for their new regions.
300 eden()->initialize(edenMR,
301 clear_space && !live_in_eden,
302 SpaceDecorator::Mangle);
303 // If clear_space and live_in_eden, we will not have cleared any
304 // portion of eden above its top. This can cause newly
305 // expanded space not to be mangled if using ZapUnusedHeapArea.
306 // We explicitly do such mangling here.
307 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
308 eden()->mangle_unused_area();
309 }
310 from()->initialize(fromMR, clear_space, mangle_space);
311 to()->initialize(toMR, clear_space, mangle_space);
312
313 // Set next compaction spaces.
314 eden()->set_next_compaction_space(from());
315 // The to-space is normally empty before a compaction so need
316 // not be considered. The exception is during promotion
317 // failure handling when to-space can contain live objects.
318 from()->set_next_compaction_space(NULL);
319 }
320
321 void DefNewGeneration::swap_spaces() {
322 ContiguousSpace* s = from();
323 _from_space = to();
324 _to_space = s;
325 eden()->set_next_compaction_space(from());
326 // The to-space is normally empty before a compaction so need
327 // not be considered. The exception is during promotion
328 // failure handling when to-space can contain live objects.
329 from()->set_next_compaction_space(NULL);
330
331 if (UsePerfData) {
332 CSpaceCounters* c = _from_counters;
333 _from_counters = _to_counters;
334 _to_counters = c;
335 }
336 }
337
338 bool DefNewGeneration::expand(size_t bytes) {
339 MutexLocker x(ExpandHeap_lock);
340 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
341 bool success = _virtual_space.expand_by(bytes);
342 if (success && ZapUnusedHeapArea) {
343 // Mangle newly committed space immediately because it
344 // can be done here more simply that after the new
345 // spaces have been computed.
346 HeapWord* new_high = (HeapWord*) _virtual_space.high();
347 MemRegion mangle_region(prev_high, new_high);
348 SpaceMangler::mangle_region(mangle_region);
349 }
350
351 // Do not attempt an expand-to-the reserve size. The
352 // request should properly observe the maximum size of
353 // the generation so an expand-to-reserve should be
354 // unnecessary. Also a second call to expand-to-reserve
355 // value potentially can cause an undue expansion.
356 // For example if the first expand fail for unknown reasons,
357 // but the second succeeds and expands the heap to its maximum
358 // value.
359 if (GC_locker::is_active()) {
360 if (PrintGC && Verbose) {
361 gclog_or_tty->print_cr("Garbage collection disabled, "
362 "expanded heap instead");
363 }
364 }
365
366 return success;
367 }
368
369
370 void DefNewGeneration::compute_new_size() {
371 // This is called after a gc that includes the following generation
372 // (which is required to exist.) So from-space will normally be empty.
373 // Note that we check both spaces, since if scavenge failed they revert roles.
374 // If not we bail out (otherwise we would have to relocate the objects)
375 if (!from()->is_empty() || !to()->is_empty()) {
376 return;
377 }
378
379 int next_level = level() + 1;
380 GenCollectedHeap* gch = GenCollectedHeap::heap();
381 assert(next_level == 1, "DefNewGeneration cannot be an oldest gen");
382
383 Generation* old_gen = gch->old_gen();
384 size_t old_size = old_gen->capacity();
385 size_t new_size_before = _virtual_space.committed_size();
386 size_t min_new_size = spec()->init_size();
387 size_t max_new_size = reserved().byte_size();
388 assert(min_new_size <= new_size_before &&
389 new_size_before <= max_new_size,
390 "just checking");
391 // All space sizes must be multiples of Generation::GenGrain.
392 size_t alignment = Generation::GenGrain;
393
394 // Compute desired new generation size based on NewRatio and
395 // NewSizeThreadIncrease
396 size_t desired_new_size = old_size/NewRatio;
397 int threads_count = Threads::number_of_non_daemon_threads();
398 size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
399 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
400
401 // Adjust new generation size
402 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
403 assert(desired_new_size <= max_new_size, "just checking");
404
405 bool changed = false;
406 if (desired_new_size > new_size_before) {
407 size_t change = desired_new_size - new_size_before;
408 assert(change % alignment == 0, "just checking");
409 if (expand(change)) {
410 changed = true;
411 }
412 // If the heap failed to expand to the desired size,
413 // "changed" will be false. If the expansion failed
414 // (and at this point it was expected to succeed),
415 // ignore the failure (leaving "changed" as false).
416 }
417 if (desired_new_size < new_size_before && eden()->is_empty()) {
418 // bail out of shrinking if objects in eden
419 size_t change = new_size_before - desired_new_size;
420 assert(change % alignment == 0, "just checking");
421 _virtual_space.shrink_by(change);
422 changed = true;
423 }
424 if (changed) {
425 // The spaces have already been mangled at this point but
426 // may not have been cleared (set top = bottom) and should be.
427 // Mangling was done when the heap was being expanded.
428 compute_space_boundaries(eden()->used(),
429 SpaceDecorator::Clear,
430 SpaceDecorator::DontMangle);
431 MemRegion cmr((HeapWord*)_virtual_space.low(),
432 (HeapWord*)_virtual_space.high());
433 Universe::heap()->barrier_set()->resize_covered_region(cmr);
434 if (Verbose && PrintGC) {
435 size_t new_size_after = _virtual_space.committed_size();
436 size_t eden_size_after = eden()->capacity();
437 size_t survivor_size_after = from()->capacity();
438 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
439 SIZE_FORMAT "K [eden="
440 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
441 new_size_before/K, new_size_after/K,
442 eden_size_after/K, survivor_size_after/K);
443 if (WizardMode) {
444 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
445 thread_increase_size/K, threads_count);
446 }
447 gclog_or_tty->cr();
448 }
449 }
450 }
451
452 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
453 assert(false, "NYI -- are you sure you want to call this?");
454 }
455
456
457 size_t DefNewGeneration::capacity() const {
458 return eden()->capacity()
459 + from()->capacity(); // to() is only used during scavenge
460 }
461
462
463 size_t DefNewGeneration::used() const {
464 return eden()->used()
465 + from()->used(); // to() is only used during scavenge
466 }
467
468
469 size_t DefNewGeneration::free() const {
470 return eden()->free()
471 + from()->free(); // to() is only used during scavenge
472 }
473
474 size_t DefNewGeneration::max_capacity() const {
475 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
476 const size_t reserved_bytes = reserved().byte_size();
477 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
478 }
479
480 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
481 return eden()->free();
482 }
483
484 size_t DefNewGeneration::capacity_before_gc() const {
485 return eden()->capacity();
486 }
487
488 size_t DefNewGeneration::contiguous_available() const {
489 return eden()->free();
490 }
491
492
493 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
494 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
495
496 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
497 eden()->object_iterate(blk);
498 from()->object_iterate(blk);
499 }
500
501
502 void DefNewGeneration::space_iterate(SpaceClosure* blk,
503 bool usedOnly) {
504 blk->do_space(eden());
505 blk->do_space(from());
506 blk->do_space(to());
507 }
508
509 // The last collection bailed out, we are running out of heap space,
510 // so we try to allocate the from-space, too.
511 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
512 HeapWord* result = NULL;
513 if (Verbose && PrintGCDetails) {
514 gclog_or_tty->print("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):"
515 " will_fail: %s"
516 " heap_lock: %s"
517 " free: " SIZE_FORMAT,
518 size,
519 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
520 "true" : "false",
521 Heap_lock->is_locked() ? "locked" : "unlocked",
522 from()->free());
523 }
524 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
525 if (Heap_lock->owned_by_self() ||
526 (SafepointSynchronize::is_at_safepoint() &&
527 Thread::current()->is_VM_thread())) {
528 // If the Heap_lock is not locked by this thread, this will be called
529 // again later with the Heap_lock held.
530 result = from()->allocate(size);
531 } else if (PrintGC && Verbose) {
532 gclog_or_tty->print_cr(" Heap_lock is not owned by self");
533 }
534 } else if (PrintGC && Verbose) {
535 gclog_or_tty->print_cr(" should_allocate_from_space: NOT");
536 }
537 if (PrintGC && Verbose) {
538 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object");
539 }
540 return result;
541 }
542
543 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
544 bool is_tlab,
545 bool parallel) {
546 // We don't attempt to expand the young generation (but perhaps we should.)
547 return allocate(size, is_tlab);
548 }
549
550 void DefNewGeneration::adjust_desired_tenuring_threshold() {
551 // Set the desired survivor size to half the real survivor space
552 _tenuring_threshold =
553 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
554 }
555
556 void DefNewGeneration::collect(bool full,
557 bool clear_all_soft_refs,
558 size_t size,
559 bool is_tlab) {
560 assert(full || size > 0, "otherwise we don't want to collect");
561
562 GenCollectedHeap* gch = GenCollectedHeap::heap();
563
564 _gc_timer->register_gc_start();
565 DefNewTracer gc_tracer;
566 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
567
568 _old_gen = gch->old_gen();
569
570 // If the next generation is too full to accommodate promotion
571 // from this generation, pass on collection; let the next generation
572 // do it.
573 if (!collection_attempt_is_safe()) {
574 if (Verbose && PrintGCDetails) {
575 gclog_or_tty->print(" :: Collection attempt not safe :: ");
576 }
577 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
578 return;
579 }
580 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
581
582 init_assuming_no_promotion_failure();
583
584 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, gc_tracer.gc_id());
585 // Capture heap used before collection (for printing).
586 size_t gch_prev_used = gch->used();
587
588 gch->trace_heap_before_gc(&gc_tracer);
589
590 // These can be shared for all code paths
591 IsAliveClosure is_alive(this);
592 ScanWeakRefClosure scan_weak_ref(this);
593
594 age_table()->clear();
595 to()->clear(SpaceDecorator::Mangle);
596
597 gch->rem_set()->prepare_for_younger_refs_iterate(false);
598
599 assert(gch->no_allocs_since_save_marks(0),
600 "save marks have not been newly set.");
601
602 // Not very pretty.
603 CollectorPolicy* cp = gch->collector_policy();
604
605 FastScanClosure fsc_with_no_gc_barrier(this, false);
606 FastScanClosure fsc_with_gc_barrier(this, true);
607
608 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
609 gch->rem_set()->klass_rem_set());
610 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
611 &fsc_with_no_gc_barrier,
612 false);
613
614 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
615 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
616 &fsc_with_no_gc_barrier,
617 &fsc_with_gc_barrier);
618
619 assert(gch->no_allocs_since_save_marks(0),
620 "save marks have not been newly set.");
621
622 gch->gen_process_roots(_level,
623 true, // Process younger gens, if any,
624 // as strong roots.
625 true, // activate StrongRootsScope
626 GenCollectedHeap::SO_ScavengeCodeCache,
627 GenCollectedHeap::StrongAndWeakRoots,
628 &fsc_with_no_gc_barrier,
629 &fsc_with_gc_barrier,
630 &cld_scan_closure);
631
632 // "evacuate followers".
633 evacuate_followers.do_void();
634
635 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
636 ReferenceProcessor* rp = ref_processor();
637 rp->setup_policy(clear_all_soft_refs);
638 const ReferenceProcessorStats& stats =
639 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
640 NULL, _gc_timer, gc_tracer.gc_id());
641 gc_tracer.report_gc_reference_stats(stats);
642
643 if (!_promotion_failed) {
644 // Swap the survivor spaces.
645 eden()->clear(SpaceDecorator::Mangle);
646 from()->clear(SpaceDecorator::Mangle);
647 if (ZapUnusedHeapArea) {
648 // This is now done here because of the piece-meal mangling which
649 // can check for valid mangling at intermediate points in the
650 // collection(s). When a minor collection fails to collect
651 // sufficient space resizing of the young generation can occur
652 // an redistribute the spaces in the young generation. Mangle
653 // here so that unzapped regions don't get distributed to
654 // other spaces.
655 to()->mangle_unused_area();
656 }
657 swap_spaces();
658
659 assert(to()->is_empty(), "to space should be empty now");
660
661 adjust_desired_tenuring_threshold();
662
663 // A successful scavenge should restart the GC time limit count which is
664 // for full GC's.
665 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
666 size_policy->reset_gc_overhead_limit_count();
667 assert(!gch->incremental_collection_failed(), "Should be clear");
668 } else {
669 assert(_promo_failure_scan_stack.is_empty(), "post condition");
670 _promo_failure_scan_stack.clear(true); // Clear cached segments.
671
672 remove_forwarding_pointers();
673 if (PrintGCDetails) {
674 gclog_or_tty->print(" (promotion failed) ");
675 }
676 // Add to-space to the list of space to compact
677 // when a promotion failure has occurred. In that
678 // case there can be live objects in to-space
679 // as a result of a partial evacuation of eden
680 // and from-space.
681 swap_spaces(); // For uniformity wrt ParNewGeneration.
682 from()->set_next_compaction_space(to());
683 gch->set_incremental_collection_failed();
684
685 // Inform the next generation that a promotion failure occurred.
686 _old_gen->promotion_failure_occurred();
687 gc_tracer.report_promotion_failed(_promotion_failed_info);
688
689 // Reset the PromotionFailureALot counters.
690 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
691 }
692 if (PrintGC && !PrintGCDetails) {
693 gch->print_heap_change(gch_prev_used);
694 }
695 // set new iteration safe limit for the survivor spaces
696 from()->set_concurrent_iteration_safe_limit(from()->top());
697 to()->set_concurrent_iteration_safe_limit(to()->top());
698
699 // We need to use a monotonically non-decreasing time in ms
700 // or we will see time-warp warnings and os::javaTimeMillis()
701 // does not guarantee monotonicity.
702 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
703 update_time_of_last_gc(now);
704
705 gch->trace_heap_after_gc(&gc_tracer);
706 gc_tracer.report_tenuring_threshold(tenuring_threshold());
707
708 _gc_timer->register_gc_end();
709
710 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
711 }
712
713 class RemoveForwardPointerClosure: public ObjectClosure {
714 public:
715 void do_object(oop obj) {
716 obj->init_mark();
717 }
718 };
719
720 void DefNewGeneration::init_assuming_no_promotion_failure() {
721 _promotion_failed = false;
722 _promotion_failed_info.reset();
723 from()->set_next_compaction_space(NULL);
724 }
725
726 void DefNewGeneration::remove_forwarding_pointers() {
727 RemoveForwardPointerClosure rspc;
728 eden()->object_iterate(&rspc);
729 from()->object_iterate(&rspc);
730
731 // Now restore saved marks, if any.
732 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
733 "should be the same");
734 while (!_objs_with_preserved_marks.is_empty()) {
735 oop obj = _objs_with_preserved_marks.pop();
736 markOop m = _preserved_marks_of_objs.pop();
737 obj->set_mark(m);
738 }
739 _objs_with_preserved_marks.clear(true);
740 _preserved_marks_of_objs.clear(true);
741 }
742
743 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
744 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
745 "Oversaving!");
746 _objs_with_preserved_marks.push(obj);
747 _preserved_marks_of_objs.push(m);
748 }
749
750 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
751 if (m->must_be_preserved_for_promotion_failure(obj)) {
752 preserve_mark(obj, m);
753 }
754 }
755
756 void DefNewGeneration::handle_promotion_failure(oop old) {
757 if (PrintPromotionFailure && !_promotion_failed) {
758 gclog_or_tty->print(" (promotion failure size = %d) ",
759 old->size());
760 }
761 _promotion_failed = true;
762 _promotion_failed_info.register_copy_failure(old->size());
763 preserve_mark_if_necessary(old, old->mark());
764 // forward to self
765 old->forward_to(old);
766
767 _promo_failure_scan_stack.push(old);
768
769 if (!_promo_failure_drain_in_progress) {
770 // prevent recursion in copy_to_survivor_space()
771 _promo_failure_drain_in_progress = true;
772 drain_promo_failure_scan_stack();
773 _promo_failure_drain_in_progress = false;
774 }
775 }
776
777 oop DefNewGeneration::copy_to_survivor_space(oop old) {
778 assert(is_in_reserved(old) && !old->is_forwarded(),
779 "shouldn't be scavenging this oop");
780 size_t s = old->size();
781 oop obj = NULL;
782
783 // Try allocating obj in to-space (unless too old)
784 if (old->age() < tenuring_threshold()) {
785 obj = (oop) to()->allocate_aligned(s);
786 }
787
788 // Otherwise try allocating obj tenured
789 if (obj == NULL) {
790 obj = _old_gen->promote(old, s);
791 if (obj == NULL) {
792 handle_promotion_failure(old);
793 return old;
794 }
795 } else {
796 // Prefetch beyond obj
797 const intx interval = PrefetchCopyIntervalInBytes;
798 Prefetch::write(obj, interval);
799
800 // Copy obj
801 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
802
803 // Increment age if obj still in new generation
804 obj->incr_age();
805 age_table()->add(obj, s);
806 }
807
808 // Done, insert forward pointer to obj in this header
809 old->forward_to(obj);
810
811 return obj;
812 }
813
814 void DefNewGeneration::drain_promo_failure_scan_stack() {
815 while (!_promo_failure_scan_stack.is_empty()) {
816 oop obj = _promo_failure_scan_stack.pop();
817 obj->oop_iterate(_promo_failure_scan_stack_closure);
818 }
819 }
820
821 void DefNewGeneration::save_marks() {
822 eden()->set_saved_mark();
823 to()->set_saved_mark();
824 from()->set_saved_mark();
825 }
826
827
828 void DefNewGeneration::reset_saved_marks() {
829 eden()->reset_saved_mark();
830 to()->reset_saved_mark();
831 from()->reset_saved_mark();
832 }
833
834
835 bool DefNewGeneration::no_allocs_since_save_marks() {
836 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
837 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
838 return to()->saved_mark_at_top();
839 }
840
841 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
842 \
843 void DefNewGeneration:: \
844 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
845 cl->set_generation(this); \
846 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
847 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
848 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
849 cl->reset_generation(); \
850 save_marks(); \
851 }
852
853 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
854
855 #undef DefNew_SINCE_SAVE_MARKS_DEFN
856
857 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
858 size_t max_alloc_words) {
859 if (requestor == this || _promotion_failed) return;
860 assert(requestor->level() > level(), "DefNewGeneration must be youngest");
861
862 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
863 if (to_space->top() > to_space->bottom()) {
864 trace("to_space not empty when contribute_scratch called");
865 }
866 */
867
868 ContiguousSpace* to_space = to();
869 assert(to_space->end() >= to_space->top(), "pointers out of order");
870 size_t free_words = pointer_delta(to_space->end(), to_space->top());
871 if (free_words >= MinFreeScratchWords) {
872 ScratchBlock* sb = (ScratchBlock*)to_space->top();
873 sb->num_words = free_words;
874 sb->next = list;
875 list = sb;
876 }
877 }
878
879 void DefNewGeneration::reset_scratch() {
880 // If contributing scratch in to_space, mangle all of
881 // to_space if ZapUnusedHeapArea. This is needed because
882 // top is not maintained while using to-space as scratch.
883 if (ZapUnusedHeapArea) {
884 to()->mangle_unused_area_complete();
885 }
886 }
887
888 bool DefNewGeneration::collection_attempt_is_safe() {
889 if (!to()->is_empty()) {
890 if (Verbose && PrintGCDetails) {
891 gclog_or_tty->print(" :: to is not empty :: ");
892 }
893 return false;
894 }
895 if (_old_gen == NULL) {
896 GenCollectedHeap* gch = GenCollectedHeap::heap();
897 _old_gen = gch->old_gen();
898 }
899 return _old_gen->promotion_attempt_is_safe(used());
900 }
901
902 void DefNewGeneration::gc_epilogue(bool full) {
903 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
904
905 assert(!GC_locker::is_active(), "We should not be executing here");
906 // Check if the heap is approaching full after a collection has
907 // been done. Generally the young generation is empty at
908 // a minimum at the end of a collection. If it is not, then
909 // the heap is approaching full.
910 GenCollectedHeap* gch = GenCollectedHeap::heap();
911 if (full) {
912 DEBUG_ONLY(seen_incremental_collection_failed = false;)
913 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
914 if (Verbose && PrintGCDetails) {
915 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
916 GCCause::to_string(gch->gc_cause()));
917 }
918 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
919 set_should_allocate_from_space(); // we seem to be running out of space
920 } else {
921 if (Verbose && PrintGCDetails) {
922 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
923 GCCause::to_string(gch->gc_cause()));
924 }
925 gch->clear_incremental_collection_failed(); // We just did a full collection
926 clear_should_allocate_from_space(); // if set
927 }
928 } else {
929 #ifdef ASSERT
930 // It is possible that incremental_collection_failed() == true
931 // here, because an attempted scavenge did not succeed. The policy
932 // is normally expected to cause a full collection which should
933 // clear that condition, so we should not be here twice in a row
934 // with incremental_collection_failed() == true without having done
935 // a full collection in between.
936 if (!seen_incremental_collection_failed &&
937 gch->incremental_collection_failed()) {
938 if (Verbose && PrintGCDetails) {
939 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
940 GCCause::to_string(gch->gc_cause()));
941 }
942 seen_incremental_collection_failed = true;
943 } else if (seen_incremental_collection_failed) {
944 if (Verbose && PrintGCDetails) {
945 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
946 GCCause::to_string(gch->gc_cause()));
947 }
948 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
949 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
950 !gch->incremental_collection_failed(),
951 "Twice in a row");
952 seen_incremental_collection_failed = false;
953 }
954 #endif // ASSERT
955 }
956
957 if (ZapUnusedHeapArea) {
958 eden()->check_mangled_unused_area_complete();
959 from()->check_mangled_unused_area_complete();
960 to()->check_mangled_unused_area_complete();
961 }
962
963 if (!CleanChunkPoolAsync) {
964 Chunk::clean_chunk_pool();
965 }
966
967 // update the generation and space performance counters
968 update_counters();
969 gch->collector_policy()->counters()->update_counters();
970 }
971
972 void DefNewGeneration::record_spaces_top() {
973 assert(ZapUnusedHeapArea, "Not mangling unused space");
974 eden()->set_top_for_allocations();
975 to()->set_top_for_allocations();
976 from()->set_top_for_allocations();
977 }
978
979 void DefNewGeneration::ref_processor_init() {
980 Generation::ref_processor_init();
981 }
982
983
984 void DefNewGeneration::update_counters() {
985 if (UsePerfData) {
986 _eden_counters->update_all();
987 _from_counters->update_all();
988 _to_counters->update_all();
989 _gen_counters->update_all();
990 }
991 }
992
993 void DefNewGeneration::verify() {
994 eden()->verify();
995 from()->verify();
996 to()->verify();
997 }
998
999 void DefNewGeneration::print_on(outputStream* st) const {
1000 Generation::print_on(st);
1001 st->print(" eden");
1002 eden()->print_on(st);
1003 st->print(" from");
1004 from()->print_on(st);
1005 st->print(" to ");
1006 to()->print_on(st);
1007 }
1008
1009
1010 const char* DefNewGeneration::name() const {
1011 return "def new generation";
1012 }
1013
1014 // Moved from inline file as they are not called inline
1015 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1016 return eden();
1017 }
1018
1019 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1020 // This is the slow-path allocation for the DefNewGeneration.
1021 // Most allocations are fast-path in compiled code.
1022 // We try to allocate from the eden. If that works, we are happy.
1023 // Note that since DefNewGeneration supports lock-free allocation, we
1024 // have to use it here, as well.
1025 HeapWord* result = eden()->par_allocate(word_size);
1026 if (result != NULL) {
1027 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1028 _old_gen->sample_eden_chunk();
1029 }
1030 } else {
1031 // If the eden is full and the last collection bailed out, we are running
1032 // out of heap space, and we try to allocate the from-space, too.
1033 // allocate_from_space can't be inlined because that would introduce a
1034 // circular dependency at compile time.
1035 result = allocate_from_space(word_size);
1036 }
1037 return result;
1038 }
1039
1040 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1041 bool is_tlab) {
1042 HeapWord* res = eden()->par_allocate(word_size);
1043 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1044 _old_gen->sample_eden_chunk();
1045 }
1046 return res;
1047 }
1048
1049 size_t DefNewGeneration::tlab_capacity() const {
1050 return eden()->capacity();
1051 }
1052
1053 size_t DefNewGeneration::tlab_used() const {
1054 return eden()->used();
1055 }
1056
1057 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1058 return unsafe_max_alloc_nogc();
1059 }