1 /*
2 * Copyright (c) 2001, 2012, 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/generationSpec.hpp"
38 #include "memory/iterator.hpp"
39 #include "memory/referencePolicy.hpp"
40 #include "memory/space.inline.hpp"
41 #include "oops/instanceRefKlass.hpp"
42 #include "oops/oop.inline.hpp"
43 #include "runtime/java.hpp"
44 #include "utilities/copy.hpp"
45 #include "utilities/stack.inline.hpp"
46 #ifdef TARGET_OS_FAMILY_linux
47 # include "thread_linux.inline.hpp"
48 #endif
49 #ifdef TARGET_OS_FAMILY_solaris
50 # include "thread_solaris.inline.hpp"
51 #endif
52 #ifdef TARGET_OS_FAMILY_windows
53 # include "thread_windows.inline.hpp"
54 #endif
55 #ifdef TARGET_OS_FAMILY_bsd
56 # include "thread_bsd.inline.hpp"
57 #endif
58
59 //
60 // DefNewGeneration functions.
61
62 // Methods of protected closure types.
63
64 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
65 assert(g->level() == 0, "Optimized for youngest gen.");
66 }
67 void DefNewGeneration::IsAliveClosure::do_object(oop p) {
68 assert(false, "Do not call.");
69 }
70 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
71 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
72 }
73
74 DefNewGeneration::KeepAliveClosure::
75 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
76 GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
77 assert(rs->rs_kind() == GenRemSet::CardTable, "Wrong rem set kind.");
78 _rs = (CardTableRS*)rs;
79 }
80
81 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
82 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
83
84
85 DefNewGeneration::FastKeepAliveClosure::
86 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
87 DefNewGeneration::KeepAliveClosure(cl) {
88 _boundary = g->reserved().end();
89 }
90
91 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
92 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
93
94 DefNewGeneration::EvacuateFollowersClosure::
95 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
96 ScanClosure* cur, ScanClosure* older) :
97 _gch(gch), _level(level),
98 _scan_cur_or_nonheap(cur), _scan_older(older)
99 {}
100
101 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
102 do {
103 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
104 _scan_older);
105 } while (!_gch->no_allocs_since_save_marks(_level));
106 }
107
108 DefNewGeneration::FastEvacuateFollowersClosure::
109 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
110 DefNewGeneration* gen,
111 FastScanClosure* cur, FastScanClosure* older) :
112 _gch(gch), _level(level), _gen(gen),
113 _scan_cur_or_nonheap(cur), _scan_older(older)
114 {}
115
116 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
117 do {
118 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
119 _scan_older);
120 } while (!_gch->no_allocs_since_save_marks(_level));
121 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
122 }
123
124 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
125 OopsInGenClosure(g), _g(g), _gc_barrier(gc_barrier)
126 {
127 assert(_g->level() == 0, "Optimized for youngest generation");
128 _boundary = _g->reserved().end();
129 }
130
131 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
132 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
133
134 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
135 OopsInGenClosure(g), _g(g), _gc_barrier(gc_barrier)
136 {
137 assert(_g->level() == 0, "Optimized for youngest generation");
138 _boundary = _g->reserved().end();
139 }
140
141 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
142 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
143
144 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
145 OopClosure(g->ref_processor()), _g(g)
146 {
147 assert(_g->level() == 0, "Optimized for youngest generation");
148 _boundary = _g->reserved().end();
149 }
150
151 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
152 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
153
154 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
155 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
156
157 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
158 size_t initial_size,
159 int level,
160 const char* policy)
161 : Generation(rs, initial_size, level),
162 _promo_failure_drain_in_progress(false),
163 _should_allocate_from_space(false)
164 {
165 MemRegion cmr((HeapWord*)_virtual_space.low(),
166 (HeapWord*)_virtual_space.high());
167 Universe::heap()->barrier_set()->resize_covered_region(cmr);
168
169 if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) {
170 _eden_space = new ConcEdenSpace(this);
171 } else {
172 _eden_space = new EdenSpace(this);
173 }
174 _from_space = new ContiguousSpace();
175 _to_space = new ContiguousSpace();
176
177 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
178 vm_exit_during_initialization("Could not allocate a new gen space");
179
180 // Compute the maximum eden and survivor space sizes. These sizes
181 // are computed assuming the entire reserved space is committed.
182 // These values are exported as performance counters.
183 uintx alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();
184 uintx size = _virtual_space.reserved_size();
185 _max_survivor_size = compute_survivor_size(size, alignment);
186 _max_eden_size = size - (2*_max_survivor_size);
187
188 // allocate the performance counters
189
190 // Generation counters -- generation 0, 3 subspaces
191 _gen_counters = new GenerationCounters("new", 0, 3, &_virtual_space);
192 _gc_counters = new CollectorCounters(policy, 0);
193
194 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
195 _gen_counters);
196 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
197 _gen_counters);
198 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
199 _gen_counters);
200
201 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
202 update_counters();
203 _next_gen = NULL;
204 _tenuring_threshold = MaxTenuringThreshold;
205 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
206
207 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
208 }
209
210 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
211 bool clear_space,
212 bool mangle_space) {
213 uintx alignment =
214 GenCollectedHeap::heap()->collector_policy()->min_alignment();
215
216 // If the spaces are being cleared (only done at heap initialization
217 // currently), the survivor spaces need not be empty.
218 // Otherwise, no care is taken for used areas in the survivor spaces
219 // so check.
220 assert(clear_space || (to()->is_empty() && from()->is_empty()),
221 "Initialization of the survivor spaces assumes these are empty");
222
223 // Compute sizes
224 uintx size = _virtual_space.committed_size();
225 uintx survivor_size = compute_survivor_size(size, alignment);
226 uintx eden_size = size - (2*survivor_size);
227 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
228
229 if (eden_size < minimum_eden_size) {
230 // May happen due to 64Kb rounding, if so adjust eden size back up
231 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
232 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
233 uintx unaligned_survivor_size =
234 align_size_down(maximum_survivor_size, alignment);
235 survivor_size = MAX2(unaligned_survivor_size, alignment);
236 eden_size = size - (2*survivor_size);
237 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
238 assert(eden_size >= minimum_eden_size, "just checking");
239 }
240
241 char *eden_start = _virtual_space.low();
242 char *from_start = eden_start + eden_size;
243 char *to_start = from_start + survivor_size;
244 char *to_end = to_start + survivor_size;
245
246 assert(to_end == _virtual_space.high(), "just checking");
247 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
248 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
249 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
250
251 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
252 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
253 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
254
255 // A minimum eden size implies that there is a part of eden that
256 // is being used and that affects the initialization of any
257 // newly formed eden.
258 bool live_in_eden = minimum_eden_size > 0;
259
260 // If not clearing the spaces, do some checking to verify that
261 // the space are already mangled.
262 if (!clear_space) {
263 // Must check mangling before the spaces are reshaped. Otherwise,
264 // the bottom or end of one space may have moved into another
265 // a failure of the check may not correctly indicate which space
266 // is not properly mangled.
267 if (ZapUnusedHeapArea) {
268 HeapWord* limit = (HeapWord*) _virtual_space.high();
269 eden()->check_mangled_unused_area(limit);
270 from()->check_mangled_unused_area(limit);
271 to()->check_mangled_unused_area(limit);
272 }
273 }
274
275 // Reset the spaces for their new regions.
276 eden()->initialize(edenMR,
277 clear_space && !live_in_eden,
278 SpaceDecorator::Mangle);
279 // If clear_space and live_in_eden, we will not have cleared any
280 // portion of eden above its top. This can cause newly
281 // expanded space not to be mangled if using ZapUnusedHeapArea.
282 // We explicitly do such mangling here.
283 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
284 eden()->mangle_unused_area();
285 }
286 from()->initialize(fromMR, clear_space, mangle_space);
287 to()->initialize(toMR, clear_space, mangle_space);
288
289 // Set next compaction spaces.
290 eden()->set_next_compaction_space(from());
291 // The to-space is normally empty before a compaction so need
292 // not be considered. The exception is during promotion
293 // failure handling when to-space can contain live objects.
294 from()->set_next_compaction_space(NULL);
295 }
296
297 void DefNewGeneration::swap_spaces() {
298 ContiguousSpace* s = from();
299 _from_space = to();
300 _to_space = s;
301 eden()->set_next_compaction_space(from());
302 // The to-space is normally empty before a compaction so need
303 // not be considered. The exception is during promotion
304 // failure handling when to-space can contain live objects.
305 from()->set_next_compaction_space(NULL);
306
307 if (UsePerfData) {
308 CSpaceCounters* c = _from_counters;
309 _from_counters = _to_counters;
310 _to_counters = c;
311 }
312 }
313
314 bool DefNewGeneration::expand(size_t bytes) {
315 MutexLocker x(ExpandHeap_lock);
316 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
317 bool success = _virtual_space.expand_by(bytes);
318 if (success && ZapUnusedHeapArea) {
319 // Mangle newly committed space immediately because it
320 // can be done here more simply that after the new
321 // spaces have been computed.
322 HeapWord* new_high = (HeapWord*) _virtual_space.high();
323 MemRegion mangle_region(prev_high, new_high);
324 SpaceMangler::mangle_region(mangle_region);
325 }
326
327 // Do not attempt an expand-to-the reserve size. The
328 // request should properly observe the maximum size of
329 // the generation so an expand-to-reserve should be
330 // unnecessary. Also a second call to expand-to-reserve
331 // value potentially can cause an undue expansion.
332 // For example if the first expand fail for unknown reasons,
333 // but the second succeeds and expands the heap to its maximum
334 // value.
335 if (GC_locker::is_active()) {
336 if (PrintGC && Verbose) {
337 gclog_or_tty->print_cr("Garbage collection disabled, "
338 "expanded heap instead");
339 }
340 }
341
342 return success;
343 }
344
345
346 void DefNewGeneration::compute_new_size() {
347 // This is called after a gc that includes the following generation
348 // (which is required to exist.) So from-space will normally be empty.
349 // Note that we check both spaces, since if scavenge failed they revert roles.
350 // If not we bail out (otherwise we would have to relocate the objects)
351 if (!from()->is_empty() || !to()->is_empty()) {
352 return;
353 }
354
355 int next_level = level() + 1;
356 GenCollectedHeap* gch = GenCollectedHeap::heap();
357 assert(next_level < gch->_n_gens,
358 "DefNewGeneration cannot be an oldest gen");
359
360 Generation* next_gen = gch->_gens[next_level];
361 size_t old_size = next_gen->capacity();
362 size_t new_size_before = _virtual_space.committed_size();
363 size_t min_new_size = spec()->init_size();
364 size_t max_new_size = reserved().byte_size();
365 assert(min_new_size <= new_size_before &&
366 new_size_before <= max_new_size,
367 "just checking");
368 // All space sizes must be multiples of Generation::GenGrain.
369 size_t alignment = Generation::GenGrain;
370
371 // Compute desired new generation size based on NewRatio and
372 // NewSizeThreadIncrease
373 size_t desired_new_size = old_size/NewRatio;
374 int threads_count = Threads::number_of_non_daemon_threads();
375 size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
376 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
377
378 // Adjust new generation size
379 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
380 assert(desired_new_size <= max_new_size, "just checking");
381
382 bool changed = false;
383 if (desired_new_size > new_size_before) {
384 size_t change = desired_new_size - new_size_before;
385 assert(change % alignment == 0, "just checking");
386 if (expand(change)) {
387 changed = true;
388 }
389 // If the heap failed to expand to the desired size,
390 // "changed" will be false. If the expansion failed
391 // (and at this point it was expected to succeed),
392 // ignore the failure (leaving "changed" as false).
393 }
394 if (desired_new_size < new_size_before && eden()->is_empty()) {
395 // bail out of shrinking if objects in eden
396 size_t change = new_size_before - desired_new_size;
397 assert(change % alignment == 0, "just checking");
398 _virtual_space.shrink_by(change);
399 changed = true;
400 }
401 if (changed) {
402 // The spaces have already been mangled at this point but
403 // may not have been cleared (set top = bottom) and should be.
404 // Mangling was done when the heap was being expanded.
405 compute_space_boundaries(eden()->used(),
406 SpaceDecorator::Clear,
407 SpaceDecorator::DontMangle);
408 MemRegion cmr((HeapWord*)_virtual_space.low(),
409 (HeapWord*)_virtual_space.high());
410 Universe::heap()->barrier_set()->resize_covered_region(cmr);
411 if (Verbose && PrintGC) {
412 size_t new_size_after = _virtual_space.committed_size();
413 size_t eden_size_after = eden()->capacity();
414 size_t survivor_size_after = from()->capacity();
415 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
416 SIZE_FORMAT "K [eden="
417 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
418 new_size_before/K, new_size_after/K,
419 eden_size_after/K, survivor_size_after/K);
420 if (WizardMode) {
421 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
422 thread_increase_size/K, threads_count);
423 }
424 gclog_or_tty->cr();
425 }
426 }
427 }
428
429 void DefNewGeneration::object_iterate_since_last_GC(ObjectClosure* cl) {
430 // $$$ This may be wrong in case of "scavenge failure"?
431 eden()->object_iterate(cl);
432 }
433
434 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
435 assert(false, "NYI -- are you sure you want to call this?");
436 }
437
438
439 size_t DefNewGeneration::capacity() const {
440 return eden()->capacity()
441 + from()->capacity(); // to() is only used during scavenge
442 }
443
444
445 size_t DefNewGeneration::used() const {
446 return eden()->used()
447 + from()->used(); // to() is only used during scavenge
448 }
449
450
451 size_t DefNewGeneration::free() const {
452 return eden()->free()
453 + from()->free(); // to() is only used during scavenge
454 }
455
456 size_t DefNewGeneration::max_capacity() const {
457 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();
458 const size_t reserved_bytes = reserved().byte_size();
459 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
460 }
461
462 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
463 return eden()->free();
464 }
465
466 size_t DefNewGeneration::capacity_before_gc() const {
467 return eden()->capacity();
468 }
469
470 size_t DefNewGeneration::contiguous_available() const {
471 return eden()->free();
472 }
473
474
475 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
476 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
477
478 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
479 eden()->object_iterate(blk);
480 from()->object_iterate(blk);
481 }
482
483
484 void DefNewGeneration::space_iterate(SpaceClosure* blk,
485 bool usedOnly) {
486 blk->do_space(eden());
487 blk->do_space(from());
488 blk->do_space(to());
489 }
490
491 // The last collection bailed out, we are running out of heap space,
492 // so we try to allocate the from-space, too.
493 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
494 HeapWord* result = NULL;
495 if (Verbose && PrintGCDetails) {
496 gclog_or_tty->print("DefNewGeneration::allocate_from_space(%u):"
497 " will_fail: %s"
498 " heap_lock: %s"
499 " free: " SIZE_FORMAT,
500 size,
501 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
502 "true" : "false",
503 Heap_lock->is_locked() ? "locked" : "unlocked",
504 from()->free());
505 }
506 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
507 if (Heap_lock->owned_by_self() ||
508 (SafepointSynchronize::is_at_safepoint() &&
509 Thread::current()->is_VM_thread())) {
510 // If the Heap_lock is not locked by this thread, this will be called
511 // again later with the Heap_lock held.
512 result = from()->allocate(size);
513 } else if (PrintGC && Verbose) {
514 gclog_or_tty->print_cr(" Heap_lock is not owned by self");
515 }
516 } else if (PrintGC && Verbose) {
517 gclog_or_tty->print_cr(" should_allocate_from_space: NOT");
518 }
519 if (PrintGC && Verbose) {
520 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object");
521 }
522 return result;
523 }
524
525 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
526 bool is_tlab,
527 bool parallel) {
528 // We don't attempt to expand the young generation (but perhaps we should.)
529 return allocate(size, is_tlab);
530 }
531
532
533 void DefNewGeneration::collect(bool full,
534 bool clear_all_soft_refs,
535 size_t size,
536 bool is_tlab) {
537 assert(full || size > 0, "otherwise we don't want to collect");
538
539 GenCollectedHeap* gch = GenCollectedHeap::heap();
540
541 _gc_timer->register_gc_start(os::elapsed_counter());
542 DefNewTracer gc_tracer;
543 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
544
545 _next_gen = gch->next_gen(this);
546 assert(_next_gen != NULL,
547 "This must be the youngest gen, and not the only gen");
548
549 // If the next generation is too full to accommodate promotion
550 // from this generation, pass on collection; let the next generation
551 // do it.
552 if (!collection_attempt_is_safe()) {
553 if (Verbose && PrintGCDetails) {
554 gclog_or_tty->print(" :: Collection attempt not safe :: ");
555 }
556 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
557 return;
558 }
559 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
560
561 init_assuming_no_promotion_failure();
562
563 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL);
564 // Capture heap used before collection (for printing).
565 size_t gch_prev_used = gch->used();
566
567 gch->trace_heap_before_gc(&gc_tracer);
568
569 SpecializationStats::clear();
570
571 // These can be shared for all code paths
572 IsAliveClosure is_alive(this);
573 ScanWeakRefClosure scan_weak_ref(this);
574
575 age_table()->clear();
576 to()->clear(SpaceDecorator::Mangle);
577
578 gch->rem_set()->prepare_for_younger_refs_iterate(false);
579
580 assert(gch->no_allocs_since_save_marks(0),
581 "save marks have not been newly set.");
582
583 // Not very pretty.
584 CollectorPolicy* cp = gch->collector_policy();
585
586 FastScanClosure fsc_with_no_gc_barrier(this, false);
587 FastScanClosure fsc_with_gc_barrier(this, true);
588
589 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
590 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
591 &fsc_with_no_gc_barrier,
592 &fsc_with_gc_barrier);
593
594 assert(gch->no_allocs_since_save_marks(0),
595 "save marks have not been newly set.");
596
597 gch->gen_process_strong_roots(_level,
598 true, // Process younger gens, if any,
599 // as strong roots.
600 true, // activate StrongRootsScope
601 false, // not collecting perm generation.
602 SharedHeap::SO_AllClasses,
603 &fsc_with_no_gc_barrier,
604 true, // walk *all* scavengable nmethods
605 &fsc_with_gc_barrier);
606
607 // "evacuate followers".
608 evacuate_followers.do_void();
609
610 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
611 ReferenceProcessor* rp = ref_processor();
612 rp->setup_policy(clear_all_soft_refs);
613 const ReferenceProcessorStats& stats =
614 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
615 NULL, _gc_timer);
616 gc_tracer.report_gc_reference_stats(stats);
617 if (!_promotion_failed) {
618 // Swap the survivor spaces.
619 eden()->clear(SpaceDecorator::Mangle);
620 from()->clear(SpaceDecorator::Mangle);
621 if (ZapUnusedHeapArea) {
622 // This is now done here because of the piece-meal mangling which
623 // can check for valid mangling at intermediate points in the
624 // collection(s). When a minor collection fails to collect
625 // sufficient space resizing of the young generation can occur
626 // an redistribute the spaces in the young generation. Mangle
627 // here so that unzapped regions don't get distributed to
628 // other spaces.
629 to()->mangle_unused_area();
630 }
631 swap_spaces();
632
633 assert(to()->is_empty(), "to space should be empty now");
634
635 // Set the desired survivor size to half the real survivor space
636 _tenuring_threshold =
637 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
638
639 // A successful scavenge should restart the GC time limit count which is
640 // for full GC's.
641 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
642 size_policy->reset_gc_overhead_limit_count();
643 if (PrintGC && !PrintGCDetails) {
644 gch->print_heap_change(gch_prev_used);
645 }
646 assert(!gch->incremental_collection_failed(), "Should be clear");
647 } else {
648 assert(_promo_failure_scan_stack.is_empty(), "post condition");
649 _promo_failure_scan_stack.clear(true); // Clear cached segments.
650
651 remove_forwarding_pointers();
652 if (PrintGCDetails) {
653 gclog_or_tty->print(" (promotion failed) ");
654 }
655 // Add to-space to the list of space to compact
656 // when a promotion failure has occurred. In that
657 // case there can be live objects in to-space
658 // as a result of a partial evacuation of eden
659 // and from-space.
660 swap_spaces(); // For uniformity wrt ParNewGeneration.
661 from()->set_next_compaction_space(to());
662 gch->set_incremental_collection_failed();
663
664 // Inform the next generation that a promotion failure occurred.
665 _next_gen->promotion_failure_occurred();
666 gc_tracer.report_promotion_failed(_promotion_failed_info);
667
668 // Reset the PromotionFailureALot counters.
669 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
670 }
671 // set new iteration safe limit for the survivor spaces
672 from()->set_concurrent_iteration_safe_limit(from()->top());
673 to()->set_concurrent_iteration_safe_limit(to()->top());
674 SpecializationStats::print();
675
676 // We need to use a monotonically non-decreasing time in ms
677 // or we will see time-warp warnings and os::javaTimeMillis()
678 // does not guarantee monotonicity.
679 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
680 update_time_of_last_gc(now);
681
682 gch->trace_heap_after_gc(&gc_tracer);
683
684 _gc_timer->register_gc_end(os::elapsed_counter());
685
686 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
687 }
688
689 class RemoveForwardPointerClosure: public ObjectClosure {
690 public:
691 void do_object(oop obj) {
692 obj->init_mark();
693 }
694 };
695
696 void DefNewGeneration::init_assuming_no_promotion_failure() {
697 _promotion_failed = false;
698 _promotion_failed_info.reset();
699 from()->set_next_compaction_space(NULL);
700 }
701
702 void DefNewGeneration::remove_forwarding_pointers() {
703 RemoveForwardPointerClosure rspc;
704 eden()->object_iterate(&rspc);
705 from()->object_iterate(&rspc);
706
707 // Now restore saved marks, if any.
708 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
709 "should be the same");
710 while (!_objs_with_preserved_marks.is_empty()) {
711 oop obj = _objs_with_preserved_marks.pop();
712 markOop m = _preserved_marks_of_objs.pop();
713 obj->set_mark(m);
714 }
715 _objs_with_preserved_marks.clear(true);
716 _preserved_marks_of_objs.clear(true);
717 }
718
719 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
720 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
721 "Oversaving!");
722 _objs_with_preserved_marks.push(obj);
723 _preserved_marks_of_objs.push(m);
724 }
725
726 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
727 if (m->must_be_preserved_for_promotion_failure(obj)) {
728 preserve_mark(obj, m);
729 }
730 }
731
732 void DefNewGeneration::handle_promotion_failure(oop old) {
733 if (PrintPromotionFailure && !_promotion_failed) {
734 gclog_or_tty->print(" (promotion failure size = " SIZE_FORMAT ") ",
735 old->size());
736 }
737 _promotion_failed = true;
738 _promotion_failed_info.register_copy_failure(old->size());
739 preserve_mark_if_necessary(old, old->mark());
740 // forward to self
741 old->forward_to(old);
742
743 _promo_failure_scan_stack.push(old);
744
745 if (!_promo_failure_drain_in_progress) {
746 // prevent recursion in copy_to_survivor_space()
747 _promo_failure_drain_in_progress = true;
748 drain_promo_failure_scan_stack();
749 _promo_failure_drain_in_progress = false;
750 }
751 }
752
753 oop DefNewGeneration::copy_to_survivor_space(oop old) {
754 assert(is_in_reserved(old) && !old->is_forwarded(),
755 "shouldn't be scavenging this oop");
756 size_t s = old->size();
757 oop obj = NULL;
758
759 // Try allocating obj in to-space (unless too old)
760 if (old->age() < tenuring_threshold()) {
761 obj = (oop) to()->allocate(s);
762 }
763
764 // Otherwise try allocating obj tenured
765 if (obj == NULL) {
766 obj = _next_gen->promote(old, s);
767 if (obj == NULL) {
768 handle_promotion_failure(old);
769 return old;
770 }
771 } else {
772 // Prefetch beyond obj
773 const intx interval = PrefetchCopyIntervalInBytes;
774 Prefetch::write(obj, interval);
775
776 // Copy obj
777 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
778
779 // Increment age if obj still in new generation
780 obj->incr_age();
781 age_table()->add(obj, s);
782 }
783
784 // Done, insert forward pointer to obj in this header
785 old->forward_to(obj);
786
787 return obj;
788 }
789
790 void DefNewGeneration::drain_promo_failure_scan_stack() {
791 while (!_promo_failure_scan_stack.is_empty()) {
792 oop obj = _promo_failure_scan_stack.pop();
793 obj->oop_iterate(_promo_failure_scan_stack_closure);
794 }
795 }
796
797 void DefNewGeneration::save_marks() {
798 eden()->set_saved_mark();
799 to()->set_saved_mark();
800 from()->set_saved_mark();
801 }
802
803
804 void DefNewGeneration::reset_saved_marks() {
805 eden()->reset_saved_mark();
806 to()->reset_saved_mark();
807 from()->reset_saved_mark();
808 }
809
810
811 bool DefNewGeneration::no_allocs_since_save_marks() {
812 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
813 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
814 return to()->saved_mark_at_top();
815 }
816
817 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
818 \
819 void DefNewGeneration:: \
820 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
821 cl->set_generation(this); \
822 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
823 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
824 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
825 cl->reset_generation(); \
826 save_marks(); \
827 }
828
829 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
830
831 #undef DefNew_SINCE_SAVE_MARKS_DEFN
832
833 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
834 size_t max_alloc_words) {
835 if (requestor == this || _promotion_failed) return;
836 assert(requestor->level() > level(), "DefNewGeneration must be youngest");
837
838 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
839 if (to_space->top() > to_space->bottom()) {
840 trace("to_space not empty when contribute_scratch called");
841 }
842 */
843
844 ContiguousSpace* to_space = to();
845 assert(to_space->end() >= to_space->top(), "pointers out of order");
846 size_t free_words = pointer_delta(to_space->end(), to_space->top());
847 if (free_words >= MinFreeScratchWords) {
848 ScratchBlock* sb = (ScratchBlock*)to_space->top();
849 sb->num_words = free_words;
850 sb->next = list;
851 list = sb;
852 }
853 }
854
855 void DefNewGeneration::reset_scratch() {
856 // If contributing scratch in to_space, mangle all of
857 // to_space if ZapUnusedHeapArea. This is needed because
858 // top is not maintained while using to-space as scratch.
859 if (ZapUnusedHeapArea) {
860 to()->mangle_unused_area_complete();
861 }
862 }
863
864 bool DefNewGeneration::collection_attempt_is_safe() {
865 if (!to()->is_empty()) {
866 if (Verbose && PrintGCDetails) {
867 gclog_or_tty->print(" :: to is not empty :: ");
868 }
869 return false;
870 }
871 if (_next_gen == NULL) {
872 GenCollectedHeap* gch = GenCollectedHeap::heap();
873 _next_gen = gch->next_gen(this);
874 assert(_next_gen != NULL,
875 "This must be the youngest gen, and not the only gen");
876 }
877 return _next_gen->promotion_attempt_is_safe(used());
878 }
879
880 void DefNewGeneration::gc_epilogue(bool full) {
881 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
882
883 assert(!GC_locker::is_active(), "We should not be executing here");
884 // Check if the heap is approaching full after a collection has
885 // been done. Generally the young generation is empty at
886 // a minimum at the end of a collection. If it is not, then
887 // the heap is approaching full.
888 GenCollectedHeap* gch = GenCollectedHeap::heap();
889 if (full) {
890 DEBUG_ONLY(seen_incremental_collection_failed = false;)
891 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
892 if (Verbose && PrintGCDetails) {
893 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
894 GCCause::to_string(gch->gc_cause()));
895 }
896 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
897 set_should_allocate_from_space(); // we seem to be running out of space
898 } else {
899 if (Verbose && PrintGCDetails) {
900 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
901 GCCause::to_string(gch->gc_cause()));
902 }
903 gch->clear_incremental_collection_failed(); // We just did a full collection
904 clear_should_allocate_from_space(); // if set
905 }
906 } else {
907 #ifdef ASSERT
908 // It is possible that incremental_collection_failed() == true
909 // here, because an attempted scavenge did not succeed. The policy
910 // is normally expected to cause a full collection which should
911 // clear that condition, so we should not be here twice in a row
912 // with incremental_collection_failed() == true without having done
913 // a full collection in between.
914 if (!seen_incremental_collection_failed &&
915 gch->incremental_collection_failed()) {
916 if (Verbose && PrintGCDetails) {
917 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
918 GCCause::to_string(gch->gc_cause()));
919 }
920 seen_incremental_collection_failed = true;
921 } else if (seen_incremental_collection_failed) {
922 if (Verbose && PrintGCDetails) {
923 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
924 GCCause::to_string(gch->gc_cause()));
925 }
926 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
927 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
928 !gch->incremental_collection_failed(),
929 "Twice in a row");
930 seen_incremental_collection_failed = false;
931 }
932 #endif // ASSERT
933 }
934
935 if (ZapUnusedHeapArea) {
936 eden()->check_mangled_unused_area_complete();
937 from()->check_mangled_unused_area_complete();
938 to()->check_mangled_unused_area_complete();
939 }
940
941 if (!CleanChunkPoolAsync) {
942 Chunk::clean_chunk_pool();
943 }
944
945 // update the generation and space performance counters
946 update_counters();
947 gch->collector_policy()->counters()->update_counters();
948 }
949
950 void DefNewGeneration::record_spaces_top() {
951 assert(ZapUnusedHeapArea, "Not mangling unused space");
952 eden()->set_top_for_allocations();
953 to()->set_top_for_allocations();
954 from()->set_top_for_allocations();
955 }
956
957 void DefNewGeneration::ref_processor_init() {
958 Generation::ref_processor_init();
959 }
960
961
962 void DefNewGeneration::update_counters() {
963 if (UsePerfData) {
964 _eden_counters->update_all();
965 _from_counters->update_all();
966 _to_counters->update_all();
967 _gen_counters->update_all();
968 }
969 }
970
971 void DefNewGeneration::verify() {
972 eden()->verify();
973 from()->verify();
974 to()->verify();
975 }
976
977 void DefNewGeneration::print_on(outputStream* st) const {
978 Generation::print_on(st);
979 st->print(" eden");
980 eden()->print_on(st);
981 st->print(" from");
982 from()->print_on(st);
983 st->print(" to ");
984 to()->print_on(st);
985 }
986
987
988 const char* DefNewGeneration::name() const {
989 return "def new generation";
990 }
991
992 // Moved from inline file as they are not called inline
993 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
994 return eden();
995 }
996
997 HeapWord* DefNewGeneration::allocate(size_t word_size,
998 bool is_tlab) {
999 // This is the slow-path allocation for the DefNewGeneration.
1000 // Most allocations are fast-path in compiled code.
1001 // We try to allocate from the eden. If that works, we are happy.
1002 // Note that since DefNewGeneration supports lock-free allocation, we
1003 // have to use it here, as well.
1004 HeapWord* result = eden()->par_allocate(word_size);
1005 if (result != NULL) {
1006 return result;
1007 }
1008 do {
1009 HeapWord* old_limit = eden()->soft_end();
1010 if (old_limit < eden()->end()) {
1011 // Tell the next generation we reached a limit.
1012 HeapWord* new_limit =
1013 next_gen()->allocation_limit_reached(eden(), eden()->top(), word_size);
1014 if (new_limit != NULL) {
1015 Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit);
1016 } else {
1017 assert(eden()->soft_end() == eden()->end(),
1018 "invalid state after allocation_limit_reached returned null");
1019 }
1020 } else {
1021 // The allocation failed and the soft limit is equal to the hard limit,
1022 // there are no reasons to do an attempt to allocate
1023 assert(old_limit == eden()->end(), "sanity check");
1024 break;
1025 }
1026 // Try to allocate until succeeded or the soft limit can't be adjusted
1027 result = eden()->par_allocate(word_size);
1028 } while (result == NULL);
1029
1030 // If the eden is full and the last collection bailed out, we are running
1031 // out of heap space, and we try to allocate the from-space, too.
1032 // allocate_from_space can't be inlined because that would introduce a
1033 // circular dependency at compile time.
1034 if (result == NULL) {
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 return eden()->par_allocate(word_size);
1043 }
1044
1045 void DefNewGeneration::gc_prologue(bool full) {
1046 // Ensure that _end and _soft_end are the same in eden space.
1047 eden()->set_soft_end(eden()->end());
1048 }
1049
1050 size_t DefNewGeneration::tlab_capacity() const {
1051 return eden()->capacity();
1052 }
1053
1054 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1055 return unsafe_max_alloc_nogc();
1056 }