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 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
53
54 //
55 // DefNewGeneration functions.
56
57 // Methods of protected closure types.
58
59 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
60 assert(g->level() == 0, "Optimized for youngest gen.");
61 }
62 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
63 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
64 }
65
66 DefNewGeneration::KeepAliveClosure::
67 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
68 GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
69 _rs = (CardTableRS*)rs;
70 }
71
72 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
73 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
74
75
76 DefNewGeneration::FastKeepAliveClosure::
77 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
78 DefNewGeneration::KeepAliveClosure(cl) {
79 _boundary = g->reserved().end();
80 }
81
82 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
83 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
84
85 DefNewGeneration::EvacuateFollowersClosure::
86 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
87 ScanClosure* cur, ScanClosure* older) :
88 _gch(gch), _level(level),
89 _scan_cur_or_nonheap(cur), _scan_older(older)
90 {}
91
92 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
93 do {
94 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
95 _scan_older);
96 } while (!_gch->no_allocs_since_save_marks(_level));
97 }
98
99 DefNewGeneration::FastEvacuateFollowersClosure::
100 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
101 DefNewGeneration* gen,
102 FastScanClosure* cur, FastScanClosure* older) :
103 _gch(gch), _level(level), _gen(gen),
104 _scan_cur_or_nonheap(cur), _scan_older(older)
105 {}
106
107 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
108 do {
109 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
110 _scan_older);
111 } while (!_gch->no_allocs_since_save_marks(_level));
112 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
113 }
114
115 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
116 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
117 {
118 assert(_g->level() == 0, "Optimized for youngest generation");
119 _boundary = _g->reserved().end();
120 }
121
122 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
123 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
124
125 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
126 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
127 {
128 assert(_g->level() == 0, "Optimized for youngest generation");
129 _boundary = _g->reserved().end();
130 }
131
132 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
133 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
134
135 void KlassScanClosure::do_klass(Klass* klass) {
136 #ifndef PRODUCT
137 if (TraceScavenge) {
138 ResourceMark rm;
139 gclog_or_tty->print_cr("KlassScanClosure::do_klass " PTR_FORMAT ", %s, dirty: %s",
140 klass,
141 klass->external_name(),
142 klass->has_modified_oops() ? "true" : "false");
143 }
144 #endif
145
146 // If the klass has not been dirtied we know that there's
147 // no references into the young gen and we can skip it.
148 if (klass->has_modified_oops()) {
149 if (_accumulate_modified_oops) {
150 klass->accumulate_modified_oops();
151 }
152
153 // Clear this state since we're going to scavenge all the metadata.
154 klass->clear_modified_oops();
155
156 // Tell the closure which Klass is being scanned so that it can be dirtied
157 // if oops are left pointing into the young gen.
158 _scavenge_closure->set_scanned_klass(klass);
159
160 klass->oops_do(_scavenge_closure);
161
162 _scavenge_closure->set_scanned_klass(NULL);
163 }
164 }
165
166 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
167 _g(g)
168 {
169 assert(_g->level() == 0, "Optimized for youngest generation");
170 _boundary = _g->reserved().end();
171 }
172
173 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
174 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
175
176 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
177 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
178
179 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
180 KlassRemSet* klass_rem_set)
181 : _scavenge_closure(scavenge_closure),
182 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
183
184
185 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
186 size_t initial_size,
187 int level,
188 const char* policy)
189 : Generation(rs, initial_size, level),
190 _promo_failure_drain_in_progress(false),
191 _should_allocate_from_space(false)
192 {
193 MemRegion cmr((HeapWord*)_virtual_space.low(),
194 (HeapWord*)_virtual_space.high());
195 Universe::heap()->barrier_set()->resize_covered_region(cmr);
196
197 _eden_space = new ContiguousSpace();
198 _from_space = new ContiguousSpace();
199 _to_space = new ContiguousSpace();
200
201 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
202 vm_exit_during_initialization("Could not allocate a new gen space");
203
204 // Compute the maximum eden and survivor space sizes. These sizes
205 // are computed assuming the entire reserved space is committed.
206 // These values are exported as performance counters.
207 uintx alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
208 uintx size = _virtual_space.reserved_size();
209 _max_survivor_size = compute_survivor_size(size, alignment);
210 _max_eden_size = size - (2*_max_survivor_size);
211
212 // allocate the performance counters
213 GenCollectorPolicy* gcp = (GenCollectorPolicy*) GenCollectedHeap::heap()->collector_policy();
214
215 // Generation counters -- generation 0, 3 subspaces
216 _gen_counters = new GenerationCounters("new", 0, 3,
217 gcp->min_young_size(), gcp->max_young_size(), &_virtual_space);
218 _gc_counters = new CollectorCounters(policy, 0);
219
220 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
221 _gen_counters);
222 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
223 _gen_counters);
224 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
225 _gen_counters);
226
227 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
228 update_counters();
229 _old_gen = NULL;
230 _tenuring_threshold = MaxTenuringThreshold;
231 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
232
233 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
234 }
235
236 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
237 bool clear_space,
238 bool mangle_space) {
239 uintx alignment =
240 GenCollectedHeap::heap()->collector_policy()->space_alignment();
241
242 // If the spaces are being cleared (only done at heap initialization
243 // currently), the survivor spaces need not be empty.
244 // Otherwise, no care is taken for used areas in the survivor spaces
245 // so check.
246 assert(clear_space || (to()->is_empty() && from()->is_empty()),
247 "Initialization of the survivor spaces assumes these are empty");
248
249 // Compute sizes
250 uintx size = _virtual_space.committed_size();
251 uintx survivor_size = compute_survivor_size(size, alignment);
252 uintx eden_size = size - (2*survivor_size);
253 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
254
255 if (eden_size < minimum_eden_size) {
256 // May happen due to 64Kb rounding, if so adjust eden size back up
257 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
258 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
259 uintx unaligned_survivor_size =
260 align_size_down(maximum_survivor_size, alignment);
261 survivor_size = MAX2(unaligned_survivor_size, alignment);
262 eden_size = size - (2*survivor_size);
263 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
264 assert(eden_size >= minimum_eden_size, "just checking");
265 }
266
267 char *eden_start = _virtual_space.low();
268 char *from_start = eden_start + eden_size;
269 char *to_start = from_start + survivor_size;
270 char *to_end = to_start + survivor_size;
271
272 assert(to_end == _virtual_space.high(), "just checking");
273 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
274 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
275 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
276
277 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
278 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
279 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
280
281 // A minimum eden size implies that there is a part of eden that
282 // is being used and that affects the initialization of any
283 // newly formed eden.
284 bool live_in_eden = minimum_eden_size > 0;
285
286 // If not clearing the spaces, do some checking to verify that
287 // the space are already mangled.
288 if (!clear_space) {
289 // Must check mangling before the spaces are reshaped. Otherwise,
290 // the bottom or end of one space may have moved into another
291 // a failure of the check may not correctly indicate which space
292 // is not properly mangled.
293 if (ZapUnusedHeapArea) {
294 HeapWord* limit = (HeapWord*) _virtual_space.high();
295 eden()->check_mangled_unused_area(limit);
296 from()->check_mangled_unused_area(limit);
297 to()->check_mangled_unused_area(limit);
298 }
299 }
300
301 // Reset the spaces for their new regions.
302 eden()->initialize(edenMR,
303 clear_space && !live_in_eden,
304 SpaceDecorator::Mangle);
305 // If clear_space and live_in_eden, we will not have cleared any
306 // portion of eden above its top. This can cause newly
307 // expanded space not to be mangled if using ZapUnusedHeapArea.
308 // We explicitly do such mangling here.
309 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
310 eden()->mangle_unused_area();
311 }
312 from()->initialize(fromMR, clear_space, mangle_space);
313 to()->initialize(toMR, clear_space, mangle_space);
314
315 // Set next compaction spaces.
316 eden()->set_next_compaction_space(from());
317 // The to-space is normally empty before a compaction so need
318 // not be considered. The exception is during promotion
319 // failure handling when to-space can contain live objects.
320 from()->set_next_compaction_space(NULL);
321 }
322
323 void DefNewGeneration::swap_spaces() {
324 ContiguousSpace* s = from();
325 _from_space = to();
326 _to_space = s;
327 eden()->set_next_compaction_space(from());
328 // The to-space is normally empty before a compaction so need
329 // not be considered. The exception is during promotion
330 // failure handling when to-space can contain live objects.
331 from()->set_next_compaction_space(NULL);
332
333 if (UsePerfData) {
334 CSpaceCounters* c = _from_counters;
335 _from_counters = _to_counters;
336 _to_counters = c;
337 }
338 }
339
340 bool DefNewGeneration::expand(size_t bytes) {
341 MutexLocker x(ExpandHeap_lock);
342 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
343 bool success = _virtual_space.expand_by(bytes);
344 if (success && ZapUnusedHeapArea) {
345 // Mangle newly committed space immediately because it
346 // can be done here more simply that after the new
347 // spaces have been computed.
348 HeapWord* new_high = (HeapWord*) _virtual_space.high();
349 MemRegion mangle_region(prev_high, new_high);
350 SpaceMangler::mangle_region(mangle_region);
351 }
352
353 // Do not attempt an expand-to-the reserve size. The
354 // request should properly observe the maximum size of
355 // the generation so an expand-to-reserve should be
356 // unnecessary. Also a second call to expand-to-reserve
357 // value potentially can cause an undue expansion.
358 // For example if the first expand fail for unknown reasons,
359 // but the second succeeds and expands the heap to its maximum
360 // value.
361 if (GC_locker::is_active()) {
362 if (PrintGC && Verbose) {
363 gclog_or_tty->print_cr("Garbage collection disabled, "
364 "expanded heap instead");
365 }
366 }
367
368 return success;
369 }
370
371
372 void DefNewGeneration::compute_new_size() {
373 // This is called after a gc that includes the following generation
374 // (which is required to exist.) So from-space will normally be empty.
375 // Note that we check both spaces, since if scavenge failed they revert roles.
376 // If not we bail out (otherwise we would have to relocate the objects)
377 if (!from()->is_empty() || !to()->is_empty()) {
378 return;
379 }
380
381 int next_level = level() + 1;
382 GenCollectedHeap* gch = GenCollectedHeap::heap();
383 assert(next_level < gch->_n_gens,
384 "DefNewGeneration cannot be an oldest gen");
385
386 Generation* old_gen = gch->old_gen();
387 size_t old_size = old_gen->capacity();
388 size_t new_size_before = _virtual_space.committed_size();
389 size_t min_new_size = spec()->init_size();
390 size_t max_new_size = reserved().byte_size();
391 assert(min_new_size <= new_size_before &&
392 new_size_before <= max_new_size,
393 "just checking");
394 // All space sizes must be multiples of Generation::GenGrain.
395 size_t alignment = Generation::GenGrain;
396
397 // Compute desired new generation size based on NewRatio and
398 // NewSizeThreadIncrease
399 size_t desired_new_size = old_size/NewRatio;
400 int threads_count = Threads::number_of_non_daemon_threads();
401 size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
402 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
403
404 // Adjust new generation size
405 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
406 assert(desired_new_size <= max_new_size, "just checking");
407
408 bool changed = false;
409 if (desired_new_size > new_size_before) {
410 size_t change = desired_new_size - new_size_before;
411 assert(change % alignment == 0, "just checking");
412 if (expand(change)) {
413 changed = true;
414 }
415 // If the heap failed to expand to the desired size,
416 // "changed" will be false. If the expansion failed
417 // (and at this point it was expected to succeed),
418 // ignore the failure (leaving "changed" as false).
419 }
420 if (desired_new_size < new_size_before && eden()->is_empty()) {
421 // bail out of shrinking if objects in eden
422 size_t change = new_size_before - desired_new_size;
423 assert(change % alignment == 0, "just checking");
424 _virtual_space.shrink_by(change);
425 changed = true;
426 }
427 if (changed) {
428 // The spaces have already been mangled at this point but
429 // may not have been cleared (set top = bottom) and should be.
430 // Mangling was done when the heap was being expanded.
431 compute_space_boundaries(eden()->used(),
432 SpaceDecorator::Clear,
433 SpaceDecorator::DontMangle);
434 MemRegion cmr((HeapWord*)_virtual_space.low(),
435 (HeapWord*)_virtual_space.high());
436 Universe::heap()->barrier_set()->resize_covered_region(cmr);
437 if (Verbose && PrintGC) {
438 size_t new_size_after = _virtual_space.committed_size();
439 size_t eden_size_after = eden()->capacity();
440 size_t survivor_size_after = from()->capacity();
441 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
442 SIZE_FORMAT "K [eden="
443 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
444 new_size_before/K, new_size_after/K,
445 eden_size_after/K, survivor_size_after/K);
446 if (WizardMode) {
447 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
448 thread_increase_size/K, threads_count);
449 }
450 gclog_or_tty->cr();
451 }
452 }
453 }
454
455 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
456 assert(false, "NYI -- are you sure you want to call this?");
457 }
458
459
460 size_t DefNewGeneration::capacity() const {
461 return eden()->capacity()
462 + from()->capacity(); // to() is only used during scavenge
463 }
464
465
466 size_t DefNewGeneration::used() const {
467 return eden()->used()
468 + from()->used(); // to() is only used during scavenge
469 }
470
471
472 size_t DefNewGeneration::free() const {
473 return eden()->free()
474 + from()->free(); // to() is only used during scavenge
475 }
476
477 size_t DefNewGeneration::max_capacity() const {
478 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->space_alignment();
479 const size_t reserved_bytes = reserved().byte_size();
480 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
481 }
482
483 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
484 return eden()->free();
485 }
486
487 size_t DefNewGeneration::capacity_before_gc() const {
488 return eden()->capacity();
489 }
490
491 size_t DefNewGeneration::contiguous_available() const {
492 return eden()->free();
493 }
494
495
496 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
497 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
498
499 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
500 eden()->object_iterate(blk);
501 from()->object_iterate(blk);
502 }
503
504
505 void DefNewGeneration::space_iterate(SpaceClosure* blk,
506 bool usedOnly) {
507 blk->do_space(eden());
508 blk->do_space(from());
509 blk->do_space(to());
510 }
511
512 // The last collection bailed out, we are running out of heap space,
513 // so we try to allocate the from-space, too.
514 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
515 HeapWord* result = NULL;
516 if (Verbose && PrintGCDetails) {
517 gclog_or_tty->print("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):"
518 " will_fail: %s"
519 " heap_lock: %s"
520 " free: " SIZE_FORMAT,
521 size,
522 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
523 "true" : "false",
524 Heap_lock->is_locked() ? "locked" : "unlocked",
525 from()->free());
526 }
527 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
528 if (Heap_lock->owned_by_self() ||
529 (SafepointSynchronize::is_at_safepoint() &&
530 Thread::current()->is_VM_thread())) {
531 // If the Heap_lock is not locked by this thread, this will be called
532 // again later with the Heap_lock held.
533 result = from()->allocate(size);
534 } else if (PrintGC && Verbose) {
535 gclog_or_tty->print_cr(" Heap_lock is not owned by self");
536 }
537 } else if (PrintGC && Verbose) {
538 gclog_or_tty->print_cr(" should_allocate_from_space: NOT");
539 }
540 if (PrintGC && Verbose) {
541 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object");
542 }
543 return result;
544 }
545
546 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
547 bool is_tlab,
548 bool parallel) {
549 // We don't attempt to expand the young generation (but perhaps we should.)
550 return allocate(size, is_tlab);
551 }
552
553 void DefNewGeneration::adjust_desired_tenuring_threshold() {
554 // Set the desired survivor size to half the real survivor space
555 _tenuring_threshold =
556 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
557 }
558
559 void DefNewGeneration::collect(bool full,
560 bool clear_all_soft_refs,
561 size_t size,
562 bool is_tlab) {
563 assert(full || size > 0, "otherwise we don't want to collect");
564
565 GenCollectedHeap* gch = GenCollectedHeap::heap();
566
567 _gc_timer->register_gc_start();
568 DefNewTracer gc_tracer;
569 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
570
571 _old_gen = gch->old_gen();
572
573 // If the next generation is too full to accommodate promotion
574 // from this generation, pass on collection; let the next generation
575 // do it.
576 if (!collection_attempt_is_safe()) {
577 if (Verbose && PrintGCDetails) {
578 gclog_or_tty->print(" :: Collection attempt not safe :: ");
579 }
580 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
581 return;
582 }
583 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
584
585 init_assuming_no_promotion_failure();
586
587 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL, gc_tracer.gc_id());
588 // Capture heap used before collection (for printing).
589 size_t gch_prev_used = gch->used();
590
591 gch->trace_heap_before_gc(&gc_tracer);
592
593 // These can be shared for all code paths
594 IsAliveClosure is_alive(this);
595 ScanWeakRefClosure scan_weak_ref(this);
596
597 age_table()->clear();
598 to()->clear(SpaceDecorator::Mangle);
599
600 gch->rem_set()->prepare_for_younger_refs_iterate(false);
601
602 assert(gch->no_allocs_since_save_marks(0),
603 "save marks have not been newly set.");
604
605 // Not very pretty.
606 CollectorPolicy* cp = gch->collector_policy();
607
608 FastScanClosure fsc_with_no_gc_barrier(this, false);
609 FastScanClosure fsc_with_gc_barrier(this, true);
610
611 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
612 gch->rem_set()->klass_rem_set());
613 CLDToKlassAndOopClosure cld_scan_closure(&klass_scan_closure,
614 &fsc_with_no_gc_barrier,
615 false);
616
617 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
618 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
619 &fsc_with_no_gc_barrier,
620 &fsc_with_gc_barrier);
621
622 assert(gch->no_allocs_since_save_marks(0),
623 "save marks have not been newly set.");
624
625 gch->gen_process_roots(_level,
626 true, // Process younger gens, if any,
627 // as strong roots.
628 true, // activate StrongRootsScope
629 GenCollectedHeap::SO_ScavengeCodeCache,
630 GenCollectedHeap::StrongAndWeakRoots,
631 &fsc_with_no_gc_barrier,
632 &fsc_with_gc_barrier,
633 &cld_scan_closure);
634
635 // "evacuate followers".
636 evacuate_followers.do_void();
637
638 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
639 ReferenceProcessor* rp = ref_processor();
640 rp->setup_policy(clear_all_soft_refs);
641 const ReferenceProcessorStats& stats =
642 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
643 NULL, _gc_timer, gc_tracer.gc_id());
644 gc_tracer.report_gc_reference_stats(stats);
645
646 if (!_promotion_failed) {
647 // Swap the survivor spaces.
648 eden()->clear(SpaceDecorator::Mangle);
649 from()->clear(SpaceDecorator::Mangle);
650 if (ZapUnusedHeapArea) {
651 // This is now done here because of the piece-meal mangling which
652 // can check for valid mangling at intermediate points in the
653 // collection(s). When a minor collection fails to collect
654 // sufficient space resizing of the young generation can occur
655 // an redistribute the spaces in the young generation. Mangle
656 // here so that unzapped regions don't get distributed to
657 // other spaces.
658 to()->mangle_unused_area();
659 }
660 swap_spaces();
661
662 assert(to()->is_empty(), "to space should be empty now");
663
664 adjust_desired_tenuring_threshold();
665
666 // A successful scavenge should restart the GC time limit count which is
667 // for full GC's.
668 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
669 size_policy->reset_gc_overhead_limit_count();
670 assert(!gch->incremental_collection_failed(), "Should be clear");
671 } else {
672 assert(_promo_failure_scan_stack.is_empty(), "post condition");
673 _promo_failure_scan_stack.clear(true); // Clear cached segments.
674
675 remove_forwarding_pointers();
676 if (PrintGCDetails) {
677 gclog_or_tty->print(" (promotion failed) ");
678 }
679 // Add to-space to the list of space to compact
680 // when a promotion failure has occurred. In that
681 // case there can be live objects in to-space
682 // as a result of a partial evacuation of eden
683 // and from-space.
684 swap_spaces(); // For uniformity wrt ParNewGeneration.
685 from()->set_next_compaction_space(to());
686 gch->set_incremental_collection_failed();
687
688 // Inform the next generation that a promotion failure occurred.
689 _old_gen->promotion_failure_occurred();
690 gc_tracer.report_promotion_failed(_promotion_failed_info);
691
692 // Reset the PromotionFailureALot counters.
693 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
694 }
695 if (PrintGC && !PrintGCDetails) {
696 gch->print_heap_change(gch_prev_used);
697 }
698 // set new iteration safe limit for the survivor spaces
699 from()->set_concurrent_iteration_safe_limit(from()->top());
700 to()->set_concurrent_iteration_safe_limit(to()->top());
701
702 // We need to use a monotonically non-decreasing time in ms
703 // or we will see time-warp warnings and os::javaTimeMillis()
704 // does not guarantee monotonicity.
705 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
706 update_time_of_last_gc(now);
707
708 gch->trace_heap_after_gc(&gc_tracer);
709 gc_tracer.report_tenuring_threshold(tenuring_threshold());
710
711 _gc_timer->register_gc_end();
712
713 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
714 }
715
716 class RemoveForwardPointerClosure: public ObjectClosure {
717 public:
718 void do_object(oop obj) {
719 obj->init_mark();
720 }
721 };
722
723 void DefNewGeneration::init_assuming_no_promotion_failure() {
724 _promotion_failed = false;
725 _promotion_failed_info.reset();
726 from()->set_next_compaction_space(NULL);
727 }
728
729 void DefNewGeneration::remove_forwarding_pointers() {
730 RemoveForwardPointerClosure rspc;
731 eden()->object_iterate(&rspc);
732 from()->object_iterate(&rspc);
733
734 // Now restore saved marks, if any.
735 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
736 "should be the same");
737 while (!_objs_with_preserved_marks.is_empty()) {
738 oop obj = _objs_with_preserved_marks.pop();
739 markOop m = _preserved_marks_of_objs.pop();
740 obj->set_mark(m);
741 }
742 _objs_with_preserved_marks.clear(true);
743 _preserved_marks_of_objs.clear(true);
744 }
745
746 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
747 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
748 "Oversaving!");
749 _objs_with_preserved_marks.push(obj);
750 _preserved_marks_of_objs.push(m);
751 }
752
753 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
754 if (m->must_be_preserved_for_promotion_failure(obj)) {
755 preserve_mark(obj, m);
756 }
757 }
758
759 void DefNewGeneration::handle_promotion_failure(oop old) {
760 if (PrintPromotionFailure && !_promotion_failed) {
761 gclog_or_tty->print(" (promotion failure size = %d) ",
762 old->size());
763 }
764 _promotion_failed = true;
765 _promotion_failed_info.register_copy_failure(old->size());
766 preserve_mark_if_necessary(old, old->mark());
767 // forward to self
768 old->forward_to(old);
769
770 _promo_failure_scan_stack.push(old);
771
772 if (!_promo_failure_drain_in_progress) {
773 // prevent recursion in copy_to_survivor_space()
774 _promo_failure_drain_in_progress = true;
775 drain_promo_failure_scan_stack();
776 _promo_failure_drain_in_progress = false;
777 }
778 }
779
780 oop DefNewGeneration::copy_to_survivor_space(oop old) {
781 assert(is_in_reserved(old) && !old->is_forwarded(),
782 "shouldn't be scavenging this oop");
783 size_t s = old->size();
784 oop obj = NULL;
785
786 // Try allocating obj in to-space (unless too old)
787 if (old->age() < tenuring_threshold()) {
788 obj = (oop) to()->allocate_aligned(s);
789 }
790
791 // Otherwise try allocating obj tenured
792 if (obj == NULL) {
793 obj = _old_gen->promote(old, s);
794 if (obj == NULL) {
795 handle_promotion_failure(old);
796 return old;
797 }
798 } else {
799 // Prefetch beyond obj
800 const intx interval = PrefetchCopyIntervalInBytes;
801 Prefetch::write(obj, interval);
802
803 // Copy obj
804 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
805
806 // Increment age if obj still in new generation
807 obj->incr_age();
808 age_table()->add(obj, s);
809 }
810
811 // Done, insert forward pointer to obj in this header
812 old->forward_to(obj);
813
814 return obj;
815 }
816
817 void DefNewGeneration::drain_promo_failure_scan_stack() {
818 while (!_promo_failure_scan_stack.is_empty()) {
819 oop obj = _promo_failure_scan_stack.pop();
820 obj->oop_iterate(_promo_failure_scan_stack_closure);
821 }
822 }
823
824 void DefNewGeneration::save_marks() {
825 eden()->set_saved_mark();
826 to()->set_saved_mark();
827 from()->set_saved_mark();
828 }
829
830
831 void DefNewGeneration::reset_saved_marks() {
832 eden()->reset_saved_mark();
833 to()->reset_saved_mark();
834 from()->reset_saved_mark();
835 }
836
837
838 bool DefNewGeneration::no_allocs_since_save_marks() {
839 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
840 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
841 return to()->saved_mark_at_top();
842 }
843
844 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
845 \
846 void DefNewGeneration:: \
847 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
848 cl->set_generation(this); \
849 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
850 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
851 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
852 cl->reset_generation(); \
853 save_marks(); \
854 }
855
856 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
857
858 #undef DefNew_SINCE_SAVE_MARKS_DEFN
859
860 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
861 size_t max_alloc_words) {
862 if (requestor == this || _promotion_failed) return;
863 assert(requestor->level() > level(), "DefNewGeneration must be youngest");
864
865 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
866 if (to_space->top() > to_space->bottom()) {
867 trace("to_space not empty when contribute_scratch called");
868 }
869 */
870
871 ContiguousSpace* to_space = to();
872 assert(to_space->end() >= to_space->top(), "pointers out of order");
873 size_t free_words = pointer_delta(to_space->end(), to_space->top());
874 if (free_words >= MinFreeScratchWords) {
875 ScratchBlock* sb = (ScratchBlock*)to_space->top();
876 sb->num_words = free_words;
877 sb->next = list;
878 list = sb;
879 }
880 }
881
882 void DefNewGeneration::reset_scratch() {
883 // If contributing scratch in to_space, mangle all of
884 // to_space if ZapUnusedHeapArea. This is needed because
885 // top is not maintained while using to-space as scratch.
886 if (ZapUnusedHeapArea) {
887 to()->mangle_unused_area_complete();
888 }
889 }
890
891 bool DefNewGeneration::collection_attempt_is_safe() {
892 if (!to()->is_empty()) {
893 if (Verbose && PrintGCDetails) {
894 gclog_or_tty->print(" :: to is not empty :: ");
895 }
896 return false;
897 }
898 if (_old_gen == NULL) {
899 GenCollectedHeap* gch = GenCollectedHeap::heap();
900 _old_gen = gch->old_gen();
901 }
902 return _old_gen->promotion_attempt_is_safe(used());
903 }
904
905 void DefNewGeneration::gc_epilogue(bool full) {
906 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
907
908 assert(!GC_locker::is_active(), "We should not be executing here");
909 // Check if the heap is approaching full after a collection has
910 // been done. Generally the young generation is empty at
911 // a minimum at the end of a collection. If it is not, then
912 // the heap is approaching full.
913 GenCollectedHeap* gch = GenCollectedHeap::heap();
914 if (full) {
915 DEBUG_ONLY(seen_incremental_collection_failed = false;)
916 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
917 if (Verbose && PrintGCDetails) {
918 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
919 GCCause::to_string(gch->gc_cause()));
920 }
921 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
922 set_should_allocate_from_space(); // we seem to be running out of space
923 } else {
924 if (Verbose && PrintGCDetails) {
925 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
926 GCCause::to_string(gch->gc_cause()));
927 }
928 gch->clear_incremental_collection_failed(); // We just did a full collection
929 clear_should_allocate_from_space(); // if set
930 }
931 } else {
932 #ifdef ASSERT
933 // It is possible that incremental_collection_failed() == true
934 // here, because an attempted scavenge did not succeed. The policy
935 // is normally expected to cause a full collection which should
936 // clear that condition, so we should not be here twice in a row
937 // with incremental_collection_failed() == true without having done
938 // a full collection in between.
939 if (!seen_incremental_collection_failed &&
940 gch->incremental_collection_failed()) {
941 if (Verbose && PrintGCDetails) {
942 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
943 GCCause::to_string(gch->gc_cause()));
944 }
945 seen_incremental_collection_failed = true;
946 } else if (seen_incremental_collection_failed) {
947 if (Verbose && PrintGCDetails) {
948 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
949 GCCause::to_string(gch->gc_cause()));
950 }
951 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
952 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
953 !gch->incremental_collection_failed(),
954 "Twice in a row");
955 seen_incremental_collection_failed = false;
956 }
957 #endif // ASSERT
958 }
959
960 if (ZapUnusedHeapArea) {
961 eden()->check_mangled_unused_area_complete();
962 from()->check_mangled_unused_area_complete();
963 to()->check_mangled_unused_area_complete();
964 }
965
966 if (!CleanChunkPoolAsync) {
967 Chunk::clean_chunk_pool();
968 }
969
970 // update the generation and space performance counters
971 update_counters();
972 gch->collector_policy()->counters()->update_counters();
973 }
974
975 void DefNewGeneration::record_spaces_top() {
976 assert(ZapUnusedHeapArea, "Not mangling unused space");
977 eden()->set_top_for_allocations();
978 to()->set_top_for_allocations();
979 from()->set_top_for_allocations();
980 }
981
982 void DefNewGeneration::ref_processor_init() {
983 Generation::ref_processor_init();
984 }
985
986
987 void DefNewGeneration::update_counters() {
988 if (UsePerfData) {
989 _eden_counters->update_all();
990 _from_counters->update_all();
991 _to_counters->update_all();
992 _gen_counters->update_all();
993 }
994 }
995
996 void DefNewGeneration::verify() {
997 eden()->verify();
998 from()->verify();
999 to()->verify();
1000 }
1001
1002 void DefNewGeneration::print_on(outputStream* st) const {
1003 Generation::print_on(st);
1004 st->print(" eden");
1005 eden()->print_on(st);
1006 st->print(" from");
1007 from()->print_on(st);
1008 st->print(" to ");
1009 to()->print_on(st);
1010 }
1011
1012
1013 const char* DefNewGeneration::name() const {
1014 return "def new generation";
1015 }
1016
1017 // Moved from inline file as they are not called inline
1018 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1019 return eden();
1020 }
1021
1022 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
1023 // This is the slow-path allocation for the DefNewGeneration.
1024 // Most allocations are fast-path in compiled code.
1025 // We try to allocate from the eden. If that works, we are happy.
1026 // Note that since DefNewGeneration supports lock-free allocation, we
1027 // have to use it here, as well.
1028 HeapWord* result = eden()->par_allocate(word_size);
1029 if (result != NULL) {
1030 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1031 _old_gen->sample_eden_chunk();
1032 }
1033 } else {
1034 // If the eden is full and the last collection bailed out, we are running
1035 // out of heap space, and we try to allocate the from-space, too.
1036 // allocate_from_space can't be inlined because that would introduce a
1037 // circular dependency at compile time.
1038 result = allocate_from_space(word_size);
1039 }
1040 return result;
1041 }
1042
1043 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1044 bool is_tlab) {
1045 HeapWord* res = eden()->par_allocate(word_size);
1046 if (CMSEdenChunksRecordAlways && _old_gen != NULL) {
1047 _old_gen->sample_eden_chunk();
1048 }
1049 return res;
1050 }
1051
1052 size_t DefNewGeneration::tlab_capacity() const {
1053 return eden()->capacity();
1054 }
1055
1056 size_t DefNewGeneration::tlab_used() const {
1057 return eden()->used();
1058 }
1059
1060 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1061 return unsafe_max_alloc_nogc();
1062 }