Mon, 23 Jun 2008 16:49:37 -0700
6718086: CMS assert: _concurrent_iteration_safe_limit update missed
Summary: Initialize the field correctly in ContiguousSpace's constructor and initialize() methods, using the latter for the survivor spaces upon initial construction or a subsequent resizing of the young generation. Add some missing Space sub-class constructors.
Reviewed-by: apetrusenko
1 /*
2 * Copyright 2001-2007 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
25 # include "incls/_precompiled.incl"
26 # include "incls/_defNewGeneration.cpp.incl"
28 //
29 // DefNewGeneration functions.
31 // Methods of protected closure types.
33 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
34 assert(g->level() == 0, "Optimized for youngest gen.");
35 }
36 void DefNewGeneration::IsAliveClosure::do_object(oop p) {
37 assert(false, "Do not call.");
38 }
39 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
40 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
41 }
43 DefNewGeneration::KeepAliveClosure::
44 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
45 GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
46 assert(rs->rs_kind() == GenRemSet::CardTable, "Wrong rem set kind.");
47 _rs = (CardTableRS*)rs;
48 }
50 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
51 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
54 DefNewGeneration::FastKeepAliveClosure::
55 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
56 DefNewGeneration::KeepAliveClosure(cl) {
57 _boundary = g->reserved().end();
58 }
60 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
61 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
63 DefNewGeneration::EvacuateFollowersClosure::
64 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
65 ScanClosure* cur, ScanClosure* older) :
66 _gch(gch), _level(level),
67 _scan_cur_or_nonheap(cur), _scan_older(older)
68 {}
70 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
71 do {
72 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
73 _scan_older);
74 } while (!_gch->no_allocs_since_save_marks(_level));
75 }
77 DefNewGeneration::FastEvacuateFollowersClosure::
78 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
79 DefNewGeneration* gen,
80 FastScanClosure* cur, FastScanClosure* older) :
81 _gch(gch), _level(level), _gen(gen),
82 _scan_cur_or_nonheap(cur), _scan_older(older)
83 {}
85 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
86 do {
87 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
88 _scan_older);
89 } while (!_gch->no_allocs_since_save_marks(_level));
90 guarantee(_gen->promo_failure_scan_stack() == NULL
91 || _gen->promo_failure_scan_stack()->length() == 0,
92 "Failed to finish scan");
93 }
95 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
96 OopsInGenClosure(g), _g(g), _gc_barrier(gc_barrier)
97 {
98 assert(_g->level() == 0, "Optimized for youngest generation");
99 _boundary = _g->reserved().end();
100 }
102 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
103 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
105 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
106 OopsInGenClosure(g), _g(g), _gc_barrier(gc_barrier)
107 {
108 assert(_g->level() == 0, "Optimized for youngest generation");
109 _boundary = _g->reserved().end();
110 }
112 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
113 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
115 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
116 OopClosure(g->ref_processor()), _g(g)
117 {
118 assert(_g->level() == 0, "Optimized for youngest generation");
119 _boundary = _g->reserved().end();
120 }
122 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
123 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
125 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
126 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
128 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
129 size_t initial_size,
130 int level,
131 const char* policy)
132 : Generation(rs, initial_size, level),
133 _objs_with_preserved_marks(NULL),
134 _preserved_marks_of_objs(NULL),
135 _promo_failure_scan_stack(NULL),
136 _promo_failure_drain_in_progress(false),
137 _should_allocate_from_space(false)
138 {
139 MemRegion cmr((HeapWord*)_virtual_space.low(),
140 (HeapWord*)_virtual_space.high());
141 Universe::heap()->barrier_set()->resize_covered_region(cmr);
143 if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) {
144 _eden_space = new ConcEdenSpace(this);
145 } else {
146 _eden_space = new EdenSpace(this);
147 }
148 _from_space = new ContiguousSpace();
149 _to_space = new ContiguousSpace();
151 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
152 vm_exit_during_initialization("Could not allocate a new gen space");
154 // Compute the maximum eden and survivor space sizes. These sizes
155 // are computed assuming the entire reserved space is committed.
156 // These values are exported as performance counters.
157 uintx alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();
158 uintx size = _virtual_space.reserved_size();
159 _max_survivor_size = compute_survivor_size(size, alignment);
160 _max_eden_size = size - (2*_max_survivor_size);
162 // allocate the performance counters
164 // Generation counters -- generation 0, 3 subspaces
165 _gen_counters = new GenerationCounters("new", 0, 3, &_virtual_space);
166 _gc_counters = new CollectorCounters(policy, 0);
168 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
169 _gen_counters);
170 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
171 _gen_counters);
172 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
173 _gen_counters);
175 compute_space_boundaries(0);
176 update_counters();
177 _next_gen = NULL;
178 _tenuring_threshold = MaxTenuringThreshold;
179 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
180 }
182 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size) {
183 uintx alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();
185 // Compute sizes
186 uintx size = _virtual_space.committed_size();
187 uintx survivor_size = compute_survivor_size(size, alignment);
188 uintx eden_size = size - (2*survivor_size);
189 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
191 if (eden_size < minimum_eden_size) {
192 // May happen due to 64Kb rounding, if so adjust eden size back up
193 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
194 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
195 uintx unaligned_survivor_size =
196 align_size_down(maximum_survivor_size, alignment);
197 survivor_size = MAX2(unaligned_survivor_size, alignment);
198 eden_size = size - (2*survivor_size);
199 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
200 assert(eden_size >= minimum_eden_size, "just checking");
201 }
203 char *eden_start = _virtual_space.low();
204 char *from_start = eden_start + eden_size;
205 char *to_start = from_start + survivor_size;
206 char *to_end = to_start + survivor_size;
208 assert(to_end == _virtual_space.high(), "just checking");
209 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
210 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
211 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
213 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
214 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
215 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
217 eden()->set_bounds(edenMR);
218 if (minimum_eden_size == 0) {
219 // The "minimum_eden_size" is really the amount of eden occupied by
220 // allocated objects -- if this is zero, then we can clear the space.
221 eden()->clear();
222 } else {
223 // Otherwise, we will not have cleared eden. This can cause newly
224 // expanded space not to be mangled if using ZapUnusedHeapArea.
225 // We explicitly do such mangling here.
226 if (ZapUnusedHeapArea) {
227 eden()->mangle_unused_area();
228 }
229 }
230 from()->initialize(fromMR, true /* clear */);
231 to()->initialize( toMR, true /* clear */);
232 // Make sure we compact eden, then from.
233 // The to-space is normally empty before a compaction so need
234 // not be considered. The exception is during promotion
235 // failure handling when to-space can contain live objects.
236 eden()->set_next_compaction_space(from());
237 from()->set_next_compaction_space(NULL);
238 }
240 void DefNewGeneration::swap_spaces() {
241 ContiguousSpace* s = from();
242 _from_space = to();
243 _to_space = s;
244 eden()->set_next_compaction_space(from());
245 // The to-space is normally empty before a compaction so need
246 // not be considered. The exception is during promotion
247 // failure handling when to-space can contain live objects.
248 from()->set_next_compaction_space(NULL);
250 if (UsePerfData) {
251 CSpaceCounters* c = _from_counters;
252 _from_counters = _to_counters;
253 _to_counters = c;
254 }
255 }
257 bool DefNewGeneration::expand(size_t bytes) {
258 MutexLocker x(ExpandHeap_lock);
259 bool success = _virtual_space.expand_by(bytes);
261 // Do not attempt an expand-to-the reserve size. The
262 // request should properly observe the maximum size of
263 // the generation so an expand-to-reserve should be
264 // unnecessary. Also a second call to expand-to-reserve
265 // value potentially can cause an undue expansion.
266 // For example if the first expand fail for unknown reasons,
267 // but the second succeeds and expands the heap to its maximum
268 // value.
269 if (GC_locker::is_active()) {
270 if (PrintGC && Verbose) {
271 gclog_or_tty->print_cr("Garbage collection disabled, expanded heap instead");
272 }
273 }
275 return success;
276 }
279 void DefNewGeneration::compute_new_size() {
280 // This is called after a gc that includes the following generation
281 // (which is required to exist.) So from-space will normally be empty.
282 // Note that we check both spaces, since if scavenge failed they revert roles.
283 // If not we bail out (otherwise we would have to relocate the objects)
284 if (!from()->is_empty() || !to()->is_empty()) {
285 return;
286 }
288 int next_level = level() + 1;
289 GenCollectedHeap* gch = GenCollectedHeap::heap();
290 assert(next_level < gch->_n_gens,
291 "DefNewGeneration cannot be an oldest gen");
293 Generation* next_gen = gch->_gens[next_level];
294 size_t old_size = next_gen->capacity();
295 size_t new_size_before = _virtual_space.committed_size();
296 size_t min_new_size = spec()->init_size();
297 size_t max_new_size = reserved().byte_size();
298 assert(min_new_size <= new_size_before &&
299 new_size_before <= max_new_size,
300 "just checking");
301 // All space sizes must be multiples of Generation::GenGrain.
302 size_t alignment = Generation::GenGrain;
304 // Compute desired new generation size based on NewRatio and
305 // NewSizeThreadIncrease
306 size_t desired_new_size = old_size/NewRatio;
307 int threads_count = Threads::number_of_non_daemon_threads();
308 size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
309 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
311 // Adjust new generation size
312 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
313 assert(desired_new_size <= max_new_size, "just checking");
315 bool changed = false;
316 if (desired_new_size > new_size_before) {
317 size_t change = desired_new_size - new_size_before;
318 assert(change % alignment == 0, "just checking");
319 if (expand(change)) {
320 changed = true;
321 }
322 // If the heap failed to expand to the desired size,
323 // "changed" will be false. If the expansion failed
324 // (and at this point it was expected to succeed),
325 // ignore the failure (leaving "changed" as false).
326 }
327 if (desired_new_size < new_size_before && eden()->is_empty()) {
328 // bail out of shrinking if objects in eden
329 size_t change = new_size_before - desired_new_size;
330 assert(change % alignment == 0, "just checking");
331 _virtual_space.shrink_by(change);
332 changed = true;
333 }
334 if (changed) {
335 compute_space_boundaries(eden()->used());
336 MemRegion cmr((HeapWord*)_virtual_space.low(), (HeapWord*)_virtual_space.high());
337 Universe::heap()->barrier_set()->resize_covered_region(cmr);
338 if (Verbose && PrintGC) {
339 size_t new_size_after = _virtual_space.committed_size();
340 size_t eden_size_after = eden()->capacity();
341 size_t survivor_size_after = from()->capacity();
342 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden="
343 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
344 new_size_before/K, new_size_after/K, eden_size_after/K, survivor_size_after/K);
345 if (WizardMode) {
346 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
347 thread_increase_size/K, threads_count);
348 }
349 gclog_or_tty->cr();
350 }
351 }
352 }
354 void DefNewGeneration::object_iterate_since_last_GC(ObjectClosure* cl) {
355 // $$$ This may be wrong in case of "scavenge failure"?
356 eden()->object_iterate(cl);
357 }
359 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
360 assert(false, "NYI -- are you sure you want to call this?");
361 }
364 size_t DefNewGeneration::capacity() const {
365 return eden()->capacity()
366 + from()->capacity(); // to() is only used during scavenge
367 }
370 size_t DefNewGeneration::used() const {
371 return eden()->used()
372 + from()->used(); // to() is only used during scavenge
373 }
376 size_t DefNewGeneration::free() const {
377 return eden()->free()
378 + from()->free(); // to() is only used during scavenge
379 }
381 size_t DefNewGeneration::max_capacity() const {
382 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();
383 const size_t reserved_bytes = reserved().byte_size();
384 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
385 }
387 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
388 return eden()->free();
389 }
391 size_t DefNewGeneration::capacity_before_gc() const {
392 return eden()->capacity();
393 }
395 size_t DefNewGeneration::contiguous_available() const {
396 return eden()->free();
397 }
400 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
401 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
403 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
404 eden()->object_iterate(blk);
405 from()->object_iterate(blk);
406 }
409 void DefNewGeneration::space_iterate(SpaceClosure* blk,
410 bool usedOnly) {
411 blk->do_space(eden());
412 blk->do_space(from());
413 blk->do_space(to());
414 }
416 // The last collection bailed out, we are running out of heap space,
417 // so we try to allocate the from-space, too.
418 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
419 HeapWord* result = NULL;
420 if (PrintGC && Verbose) {
421 gclog_or_tty->print("DefNewGeneration::allocate_from_space(%u):"
422 " will_fail: %s"
423 " heap_lock: %s"
424 " free: " SIZE_FORMAT,
425 size,
426 GenCollectedHeap::heap()->incremental_collection_will_fail() ? "true" : "false",
427 Heap_lock->is_locked() ? "locked" : "unlocked",
428 from()->free());
429 }
430 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
431 if (Heap_lock->owned_by_self() ||
432 (SafepointSynchronize::is_at_safepoint() &&
433 Thread::current()->is_VM_thread())) {
434 // If the Heap_lock is not locked by this thread, this will be called
435 // again later with the Heap_lock held.
436 result = from()->allocate(size);
437 } else if (PrintGC && Verbose) {
438 gclog_or_tty->print_cr(" Heap_lock is not owned by self");
439 }
440 } else if (PrintGC && Verbose) {
441 gclog_or_tty->print_cr(" should_allocate_from_space: NOT");
442 }
443 if (PrintGC && Verbose) {
444 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object");
445 }
446 return result;
447 }
449 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
450 bool is_tlab,
451 bool parallel) {
452 // We don't attempt to expand the young generation (but perhaps we should.)
453 return allocate(size, is_tlab);
454 }
457 void DefNewGeneration::collect(bool full,
458 bool clear_all_soft_refs,
459 size_t size,
460 bool is_tlab) {
461 assert(full || size > 0, "otherwise we don't want to collect");
462 GenCollectedHeap* gch = GenCollectedHeap::heap();
463 _next_gen = gch->next_gen(this);
464 assert(_next_gen != NULL,
465 "This must be the youngest gen, and not the only gen");
467 // If the next generation is too full to accomodate promotion
468 // from this generation, pass on collection; let the next generation
469 // do it.
470 if (!collection_attempt_is_safe()) {
471 gch->set_incremental_collection_will_fail();
472 return;
473 }
474 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
476 init_assuming_no_promotion_failure();
478 TraceTime t1("GC", PrintGC && !PrintGCDetails, true, gclog_or_tty);
479 // Capture heap used before collection (for printing).
480 size_t gch_prev_used = gch->used();
482 SpecializationStats::clear();
484 // These can be shared for all code paths
485 IsAliveClosure is_alive(this);
486 ScanWeakRefClosure scan_weak_ref(this);
488 age_table()->clear();
489 to()->clear();
491 gch->rem_set()->prepare_for_younger_refs_iterate(false);
493 assert(gch->no_allocs_since_save_marks(0),
494 "save marks have not been newly set.");
496 // Weak refs.
497 // FIXME: Are these storage leaks, or are they resource objects?
498 #ifdef COMPILER2
499 ReferencePolicy *soft_ref_policy = new LRUMaxHeapPolicy();
500 #else
501 ReferencePolicy *soft_ref_policy = new LRUCurrentHeapPolicy();
502 #endif // COMPILER2
504 // Not very pretty.
505 CollectorPolicy* cp = gch->collector_policy();
507 FastScanClosure fsc_with_no_gc_barrier(this, false);
508 FastScanClosure fsc_with_gc_barrier(this, true);
510 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
511 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
512 &fsc_with_no_gc_barrier,
513 &fsc_with_gc_barrier);
515 assert(gch->no_allocs_since_save_marks(0),
516 "save marks have not been newly set.");
518 gch->gen_process_strong_roots(_level,
519 true, // Process younger gens, if any, as
520 // strong roots.
521 false,// not collecting permanent generation.
522 SharedHeap::SO_AllClasses,
523 &fsc_with_gc_barrier,
524 &fsc_with_no_gc_barrier);
526 // "evacuate followers".
527 evacuate_followers.do_void();
529 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
530 ref_processor()->process_discovered_references(
531 soft_ref_policy, &is_alive, &keep_alive, &evacuate_followers, NULL);
532 if (!promotion_failed()) {
533 // Swap the survivor spaces.
534 eden()->clear();
535 from()->clear();
536 swap_spaces();
538 assert(to()->is_empty(), "to space should be empty now");
540 // Set the desired survivor size to half the real survivor space
541 _tenuring_threshold =
542 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
544 if (PrintGC && !PrintGCDetails) {
545 gch->print_heap_change(gch_prev_used);
546 }
547 } else {
548 assert(HandlePromotionFailure,
549 "Should not be here unless promotion failure handling is on");
550 assert(_promo_failure_scan_stack != NULL &&
551 _promo_failure_scan_stack->length() == 0, "post condition");
553 // deallocate stack and it's elements
554 delete _promo_failure_scan_stack;
555 _promo_failure_scan_stack = NULL;
557 remove_forwarding_pointers();
558 if (PrintGCDetails) {
559 gclog_or_tty->print(" (promotion failed)");
560 }
561 // Add to-space to the list of space to compact
562 // when a promotion failure has occurred. In that
563 // case there can be live objects in to-space
564 // as a result of a partial evacuation of eden
565 // and from-space.
566 swap_spaces(); // For the sake of uniformity wrt ParNewGeneration::collect().
567 from()->set_next_compaction_space(to());
568 gch->set_incremental_collection_will_fail();
570 // Reset the PromotionFailureALot counters.
571 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
572 }
573 // set new iteration safe limit for the survivor spaces
574 from()->set_concurrent_iteration_safe_limit(from()->top());
575 to()->set_concurrent_iteration_safe_limit(to()->top());
576 SpecializationStats::print();
577 update_time_of_last_gc(os::javaTimeMillis());
578 }
580 class RemoveForwardPointerClosure: public ObjectClosure {
581 public:
582 void do_object(oop obj) {
583 obj->init_mark();
584 }
585 };
587 void DefNewGeneration::init_assuming_no_promotion_failure() {
588 _promotion_failed = false;
589 from()->set_next_compaction_space(NULL);
590 }
592 void DefNewGeneration::remove_forwarding_pointers() {
593 RemoveForwardPointerClosure rspc;
594 eden()->object_iterate(&rspc);
595 from()->object_iterate(&rspc);
596 // Now restore saved marks, if any.
597 if (_objs_with_preserved_marks != NULL) {
598 assert(_preserved_marks_of_objs != NULL, "Both or none.");
599 assert(_objs_with_preserved_marks->length() ==
600 _preserved_marks_of_objs->length(), "Both or none.");
601 for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
602 oop obj = _objs_with_preserved_marks->at(i);
603 markOop m = _preserved_marks_of_objs->at(i);
604 obj->set_mark(m);
605 }
606 delete _objs_with_preserved_marks;
607 delete _preserved_marks_of_objs;
608 _objs_with_preserved_marks = NULL;
609 _preserved_marks_of_objs = NULL;
610 }
611 }
613 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
614 if (m->must_be_preserved_for_promotion_failure(obj)) {
615 if (_objs_with_preserved_marks == NULL) {
616 assert(_preserved_marks_of_objs == NULL, "Both or none.");
617 _objs_with_preserved_marks = new (ResourceObj::C_HEAP)
618 GrowableArray<oop>(PreserveMarkStackSize, true);
619 _preserved_marks_of_objs = new (ResourceObj::C_HEAP)
620 GrowableArray<markOop>(PreserveMarkStackSize, true);
621 }
622 _objs_with_preserved_marks->push(obj);
623 _preserved_marks_of_objs->push(m);
624 }
625 }
627 void DefNewGeneration::handle_promotion_failure(oop old) {
628 preserve_mark_if_necessary(old, old->mark());
629 // forward to self
630 old->forward_to(old);
631 _promotion_failed = true;
633 push_on_promo_failure_scan_stack(old);
635 if (!_promo_failure_drain_in_progress) {
636 // prevent recursion in copy_to_survivor_space()
637 _promo_failure_drain_in_progress = true;
638 drain_promo_failure_scan_stack();
639 _promo_failure_drain_in_progress = false;
640 }
641 }
643 oop DefNewGeneration::copy_to_survivor_space(oop old) {
644 assert(is_in_reserved(old) && !old->is_forwarded(),
645 "shouldn't be scavenging this oop");
646 size_t s = old->size();
647 oop obj = NULL;
649 // Try allocating obj in to-space (unless too old)
650 if (old->age() < tenuring_threshold()) {
651 obj = (oop) to()->allocate(s);
652 }
654 // Otherwise try allocating obj tenured
655 if (obj == NULL) {
656 obj = _next_gen->promote(old, s);
657 if (obj == NULL) {
658 if (!HandlePromotionFailure) {
659 // A failed promotion likely means the MaxLiveObjectEvacuationRatio flag
660 // is incorrectly set. In any case, its seriously wrong to be here!
661 vm_exit_out_of_memory(s*wordSize, "promotion");
662 }
664 handle_promotion_failure(old);
665 return old;
666 }
667 } else {
668 // Prefetch beyond obj
669 const intx interval = PrefetchCopyIntervalInBytes;
670 Prefetch::write(obj, interval);
672 // Copy obj
673 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
675 // Increment age if obj still in new generation
676 obj->incr_age();
677 age_table()->add(obj, s);
678 }
680 // Done, insert forward pointer to obj in this header
681 old->forward_to(obj);
683 return obj;
684 }
686 void DefNewGeneration::push_on_promo_failure_scan_stack(oop obj) {
687 if (_promo_failure_scan_stack == NULL) {
688 _promo_failure_scan_stack = new (ResourceObj::C_HEAP)
689 GrowableArray<oop>(40, true);
690 }
692 _promo_failure_scan_stack->push(obj);
693 }
695 void DefNewGeneration::drain_promo_failure_scan_stack() {
696 assert(_promo_failure_scan_stack != NULL, "precondition");
698 while (_promo_failure_scan_stack->length() > 0) {
699 oop obj = _promo_failure_scan_stack->pop();
700 obj->oop_iterate(_promo_failure_scan_stack_closure);
701 }
702 }
704 void DefNewGeneration::save_marks() {
705 eden()->set_saved_mark();
706 to()->set_saved_mark();
707 from()->set_saved_mark();
708 }
711 void DefNewGeneration::reset_saved_marks() {
712 eden()->reset_saved_mark();
713 to()->reset_saved_mark();
714 from()->reset_saved_mark();
715 }
718 bool DefNewGeneration::no_allocs_since_save_marks() {
719 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
720 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
721 return to()->saved_mark_at_top();
722 }
724 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
725 \
726 void DefNewGeneration:: \
727 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
728 cl->set_generation(this); \
729 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
730 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
731 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
732 cl->reset_generation(); \
733 save_marks(); \
734 }
736 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
738 #undef DefNew_SINCE_SAVE_MARKS_DEFN
740 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
741 size_t max_alloc_words) {
742 if (requestor == this || _promotion_failed) return;
743 assert(requestor->level() > level(), "DefNewGeneration must be youngest");
745 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
746 if (to_space->top() > to_space->bottom()) {
747 trace("to_space not empty when contribute_scratch called");
748 }
749 */
751 ContiguousSpace* to_space = to();
752 assert(to_space->end() >= to_space->top(), "pointers out of order");
753 size_t free_words = pointer_delta(to_space->end(), to_space->top());
754 if (free_words >= MinFreeScratchWords) {
755 ScratchBlock* sb = (ScratchBlock*)to_space->top();
756 sb->num_words = free_words;
757 sb->next = list;
758 list = sb;
759 }
760 }
762 bool DefNewGeneration::collection_attempt_is_safe() {
763 if (!to()->is_empty()) {
764 return false;
765 }
766 if (_next_gen == NULL) {
767 GenCollectedHeap* gch = GenCollectedHeap::heap();
768 _next_gen = gch->next_gen(this);
769 assert(_next_gen != NULL,
770 "This must be the youngest gen, and not the only gen");
771 }
773 // Decide if there's enough room for a full promotion
774 // When using extremely large edens, we effectively lose a
775 // large amount of old space. Use the "MaxLiveObjectEvacuationRatio"
776 // flag to reduce the minimum evacuation space requirements. If
777 // there is not enough space to evacuate eden during a scavenge,
778 // the VM will immediately exit with an out of memory error.
779 // This flag has not been tested
780 // with collectors other than simple mark & sweep.
781 //
782 // Note that with the addition of promotion failure handling, the
783 // VM will not immediately exit but will undo the young generation
784 // collection. The parameter is left here for compatibility.
785 const double evacuation_ratio = MaxLiveObjectEvacuationRatio / 100.0;
787 // worst_case_evacuation is based on "used()". For the case where this
788 // method is called after a collection, this is still appropriate because
789 // the case that needs to be detected is one in which a full collection
790 // has been done and has overflowed into the young generation. In that
791 // case a minor collection will fail (the overflow of the full collection
792 // means there is no space in the old generation for any promotion).
793 size_t worst_case_evacuation = (size_t)(used() * evacuation_ratio);
795 return _next_gen->promotion_attempt_is_safe(worst_case_evacuation,
796 HandlePromotionFailure);
797 }
799 void DefNewGeneration::gc_epilogue(bool full) {
800 // Check if the heap is approaching full after a collection has
801 // been done. Generally the young generation is empty at
802 // a minimum at the end of a collection. If it is not, then
803 // the heap is approaching full.
804 GenCollectedHeap* gch = GenCollectedHeap::heap();
805 clear_should_allocate_from_space();
806 if (collection_attempt_is_safe()) {
807 gch->clear_incremental_collection_will_fail();
808 } else {
809 gch->set_incremental_collection_will_fail();
810 if (full) { // we seem to be running out of space
811 set_should_allocate_from_space();
812 }
813 }
815 // update the generation and space performance counters
816 update_counters();
817 gch->collector_policy()->counters()->update_counters();
818 }
820 void DefNewGeneration::update_counters() {
821 if (UsePerfData) {
822 _eden_counters->update_all();
823 _from_counters->update_all();
824 _to_counters->update_all();
825 _gen_counters->update_all();
826 }
827 }
829 void DefNewGeneration::verify(bool allow_dirty) {
830 eden()->verify(allow_dirty);
831 from()->verify(allow_dirty);
832 to()->verify(allow_dirty);
833 }
835 void DefNewGeneration::print_on(outputStream* st) const {
836 Generation::print_on(st);
837 st->print(" eden");
838 eden()->print_on(st);
839 st->print(" from");
840 from()->print_on(st);
841 st->print(" to ");
842 to()->print_on(st);
843 }
846 const char* DefNewGeneration::name() const {
847 return "def new generation";
848 }
850 // Moved from inline file as they are not called inline
851 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
852 return eden();
853 }
855 HeapWord* DefNewGeneration::allocate(size_t word_size,
856 bool is_tlab) {
857 // This is the slow-path allocation for the DefNewGeneration.
858 // Most allocations are fast-path in compiled code.
859 // We try to allocate from the eden. If that works, we are happy.
860 // Note that since DefNewGeneration supports lock-free allocation, we
861 // have to use it here, as well.
862 HeapWord* result = eden()->par_allocate(word_size);
863 if (result != NULL) {
864 return result;
865 }
866 do {
867 HeapWord* old_limit = eden()->soft_end();
868 if (old_limit < eden()->end()) {
869 // Tell the next generation we reached a limit.
870 HeapWord* new_limit =
871 next_gen()->allocation_limit_reached(eden(), eden()->top(), word_size);
872 if (new_limit != NULL) {
873 Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit);
874 } else {
875 assert(eden()->soft_end() == eden()->end(),
876 "invalid state after allocation_limit_reached returned null");
877 }
878 } else {
879 // The allocation failed and the soft limit is equal to the hard limit,
880 // there are no reasons to do an attempt to allocate
881 assert(old_limit == eden()->end(), "sanity check");
882 break;
883 }
884 // Try to allocate until succeeded or the soft limit can't be adjusted
885 result = eden()->par_allocate(word_size);
886 } while (result == NULL);
888 // If the eden is full and the last collection bailed out, we are running
889 // out of heap space, and we try to allocate the from-space, too.
890 // allocate_from_space can't be inlined because that would introduce a
891 // circular dependency at compile time.
892 if (result == NULL) {
893 result = allocate_from_space(word_size);
894 }
895 return result;
896 }
898 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
899 bool is_tlab) {
900 return eden()->par_allocate(word_size);
901 }
903 void DefNewGeneration::gc_prologue(bool full) {
904 // Ensure that _end and _soft_end are the same in eden space.
905 eden()->set_soft_end(eden()->end());
906 }
908 size_t DefNewGeneration::tlab_capacity() const {
909 return eden()->capacity();
910 }
912 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
913 return unsafe_max_alloc_nogc();
914 }