Wed, 26 Jun 2013 16:58:37 +0200
8013590: NPG: Add a memory pool MXBean for Metaspace
Reviewed-by: jmasa, mgerdin
1 /*
2 * Copyright (c) 2001, 2013, 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.
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23 */
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/java.hpp"
45 #include "runtime/thread.inline.hpp"
46 #include "utilities/copy.hpp"
47 #include "utilities/stack.inline.hpp"
49 //
50 // DefNewGeneration functions.
52 // Methods of protected closure types.
54 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* g) : _g(g) {
55 assert(g->level() == 0, "Optimized for youngest gen.");
56 }
57 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
58 return (HeapWord*)p >= _g->reserved().end() || p->is_forwarded();
59 }
61 DefNewGeneration::KeepAliveClosure::
62 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
63 GenRemSet* rs = GenCollectedHeap::heap()->rem_set();
64 assert(rs->rs_kind() == GenRemSet::CardTable, "Wrong rem set kind.");
65 _rs = (CardTableRS*)rs;
66 }
68 void DefNewGeneration::KeepAliveClosure::do_oop(oop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
69 void DefNewGeneration::KeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::KeepAliveClosure::do_oop_work(p); }
72 DefNewGeneration::FastKeepAliveClosure::
73 FastKeepAliveClosure(DefNewGeneration* g, ScanWeakRefClosure* cl) :
74 DefNewGeneration::KeepAliveClosure(cl) {
75 _boundary = g->reserved().end();
76 }
78 void DefNewGeneration::FastKeepAliveClosure::do_oop(oop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
79 void DefNewGeneration::FastKeepAliveClosure::do_oop(narrowOop* p) { DefNewGeneration::FastKeepAliveClosure::do_oop_work(p); }
81 DefNewGeneration::EvacuateFollowersClosure::
82 EvacuateFollowersClosure(GenCollectedHeap* gch, int level,
83 ScanClosure* cur, ScanClosure* older) :
84 _gch(gch), _level(level),
85 _scan_cur_or_nonheap(cur), _scan_older(older)
86 {}
88 void DefNewGeneration::EvacuateFollowersClosure::do_void() {
89 do {
90 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
91 _scan_older);
92 } while (!_gch->no_allocs_since_save_marks(_level));
93 }
95 DefNewGeneration::FastEvacuateFollowersClosure::
96 FastEvacuateFollowersClosure(GenCollectedHeap* gch, int level,
97 DefNewGeneration* gen,
98 FastScanClosure* cur, FastScanClosure* older) :
99 _gch(gch), _level(level), _gen(gen),
100 _scan_cur_or_nonheap(cur), _scan_older(older)
101 {}
103 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
104 do {
105 _gch->oop_since_save_marks_iterate(_level, _scan_cur_or_nonheap,
106 _scan_older);
107 } while (!_gch->no_allocs_since_save_marks(_level));
108 guarantee(_gen->promo_failure_scan_is_complete(), "Failed to finish scan");
109 }
111 ScanClosure::ScanClosure(DefNewGeneration* g, bool gc_barrier) :
112 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
113 {
114 assert(_g->level() == 0, "Optimized for youngest generation");
115 _boundary = _g->reserved().end();
116 }
118 void ScanClosure::do_oop(oop* p) { ScanClosure::do_oop_work(p); }
119 void ScanClosure::do_oop(narrowOop* p) { ScanClosure::do_oop_work(p); }
121 FastScanClosure::FastScanClosure(DefNewGeneration* g, bool gc_barrier) :
122 OopsInKlassOrGenClosure(g), _g(g), _gc_barrier(gc_barrier)
123 {
124 assert(_g->level() == 0, "Optimized for youngest generation");
125 _boundary = _g->reserved().end();
126 }
128 void FastScanClosure::do_oop(oop* p) { FastScanClosure::do_oop_work(p); }
129 void FastScanClosure::do_oop(narrowOop* p) { FastScanClosure::do_oop_work(p); }
131 void KlassScanClosure::do_klass(Klass* klass) {
132 #ifndef PRODUCT
133 if (TraceScavenge) {
134 ResourceMark rm;
135 gclog_or_tty->print_cr("KlassScanClosure::do_klass %p, %s, dirty: %s",
136 klass,
137 klass->external_name(),
138 klass->has_modified_oops() ? "true" : "false");
139 }
140 #endif
142 // If the klass has not been dirtied we know that there's
143 // no references into the young gen and we can skip it.
144 if (klass->has_modified_oops()) {
145 if (_accumulate_modified_oops) {
146 klass->accumulate_modified_oops();
147 }
149 // Clear this state since we're going to scavenge all the metadata.
150 klass->clear_modified_oops();
152 // Tell the closure which Klass is being scanned so that it can be dirtied
153 // if oops are left pointing into the young gen.
154 _scavenge_closure->set_scanned_klass(klass);
156 klass->oops_do(_scavenge_closure);
158 _scavenge_closure->set_scanned_klass(NULL);
159 }
160 }
162 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
163 _g(g)
164 {
165 assert(_g->level() == 0, "Optimized for youngest generation");
166 _boundary = _g->reserved().end();
167 }
169 void ScanWeakRefClosure::do_oop(oop* p) { ScanWeakRefClosure::do_oop_work(p); }
170 void ScanWeakRefClosure::do_oop(narrowOop* p) { ScanWeakRefClosure::do_oop_work(p); }
172 void FilteringClosure::do_oop(oop* p) { FilteringClosure::do_oop_work(p); }
173 void FilteringClosure::do_oop(narrowOop* p) { FilteringClosure::do_oop_work(p); }
175 KlassScanClosure::KlassScanClosure(OopsInKlassOrGenClosure* scavenge_closure,
176 KlassRemSet* klass_rem_set)
177 : _scavenge_closure(scavenge_closure),
178 _accumulate_modified_oops(klass_rem_set->accumulate_modified_oops()) {}
181 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
182 size_t initial_size,
183 int level,
184 const char* policy)
185 : Generation(rs, initial_size, level),
186 _promo_failure_drain_in_progress(false),
187 _should_allocate_from_space(false)
188 {
189 MemRegion cmr((HeapWord*)_virtual_space.low(),
190 (HeapWord*)_virtual_space.high());
191 Universe::heap()->barrier_set()->resize_covered_region(cmr);
193 if (GenCollectedHeap::heap()->collector_policy()->has_soft_ended_eden()) {
194 _eden_space = new ConcEdenSpace(this);
195 } else {
196 _eden_space = new EdenSpace(this);
197 }
198 _from_space = new ContiguousSpace();
199 _to_space = new ContiguousSpace();
201 if (_eden_space == NULL || _from_space == NULL || _to_space == NULL)
202 vm_exit_during_initialization("Could not allocate a new gen space");
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()->min_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);
212 // allocate the performance counters
214 // Generation counters -- generation 0, 3 subspaces
215 _gen_counters = new GenerationCounters("new", 0, 3, &_virtual_space);
216 _gc_counters = new CollectorCounters(policy, 0);
218 _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
219 _gen_counters);
220 _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
221 _gen_counters);
222 _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
223 _gen_counters);
225 compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
226 update_counters();
227 _next_gen = NULL;
228 _tenuring_threshold = MaxTenuringThreshold;
229 _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
231 _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
232 }
234 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
235 bool clear_space,
236 bool mangle_space) {
237 uintx alignment =
238 GenCollectedHeap::heap()->collector_policy()->min_alignment();
240 // If the spaces are being cleared (only done at heap initialization
241 // currently), the survivor spaces need not be empty.
242 // Otherwise, no care is taken for used areas in the survivor spaces
243 // so check.
244 assert(clear_space || (to()->is_empty() && from()->is_empty()),
245 "Initialization of the survivor spaces assumes these are empty");
247 // Compute sizes
248 uintx size = _virtual_space.committed_size();
249 uintx survivor_size = compute_survivor_size(size, alignment);
250 uintx eden_size = size - (2*survivor_size);
251 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
253 if (eden_size < minimum_eden_size) {
254 // May happen due to 64Kb rounding, if so adjust eden size back up
255 minimum_eden_size = align_size_up(minimum_eden_size, alignment);
256 uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
257 uintx unaligned_survivor_size =
258 align_size_down(maximum_survivor_size, alignment);
259 survivor_size = MAX2(unaligned_survivor_size, alignment);
260 eden_size = size - (2*survivor_size);
261 assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
262 assert(eden_size >= minimum_eden_size, "just checking");
263 }
265 char *eden_start = _virtual_space.low();
266 char *from_start = eden_start + eden_size;
267 char *to_start = from_start + survivor_size;
268 char *to_end = to_start + survivor_size;
270 assert(to_end == _virtual_space.high(), "just checking");
271 assert(Space::is_aligned((HeapWord*)eden_start), "checking alignment");
272 assert(Space::is_aligned((HeapWord*)from_start), "checking alignment");
273 assert(Space::is_aligned((HeapWord*)to_start), "checking alignment");
275 MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
276 MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
277 MemRegion toMR ((HeapWord*)to_start, (HeapWord*)to_end);
279 // A minimum eden size implies that there is a part of eden that
280 // is being used and that affects the initialization of any
281 // newly formed eden.
282 bool live_in_eden = minimum_eden_size > 0;
284 // If not clearing the spaces, do some checking to verify that
285 // the space are already mangled.
286 if (!clear_space) {
287 // Must check mangling before the spaces are reshaped. Otherwise,
288 // the bottom or end of one space may have moved into another
289 // a failure of the check may not correctly indicate which space
290 // is not properly mangled.
291 if (ZapUnusedHeapArea) {
292 HeapWord* limit = (HeapWord*) _virtual_space.high();
293 eden()->check_mangled_unused_area(limit);
294 from()->check_mangled_unused_area(limit);
295 to()->check_mangled_unused_area(limit);
296 }
297 }
299 // Reset the spaces for their new regions.
300 eden()->initialize(edenMR,
301 clear_space && !live_in_eden,
302 SpaceDecorator::Mangle);
303 // If clear_space and live_in_eden, we will not have cleared any
304 // portion of eden above its top. This can cause newly
305 // expanded space not to be mangled if using ZapUnusedHeapArea.
306 // We explicitly do such mangling here.
307 if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
308 eden()->mangle_unused_area();
309 }
310 from()->initialize(fromMR, clear_space, mangle_space);
311 to()->initialize(toMR, clear_space, mangle_space);
313 // Set next compaction spaces.
314 eden()->set_next_compaction_space(from());
315 // The to-space is normally empty before a compaction so need
316 // not be considered. The exception is during promotion
317 // failure handling when to-space can contain live objects.
318 from()->set_next_compaction_space(NULL);
319 }
321 void DefNewGeneration::swap_spaces() {
322 ContiguousSpace* s = from();
323 _from_space = to();
324 _to_space = s;
325 eden()->set_next_compaction_space(from());
326 // The to-space is normally empty before a compaction so need
327 // not be considered. The exception is during promotion
328 // failure handling when to-space can contain live objects.
329 from()->set_next_compaction_space(NULL);
331 if (UsePerfData) {
332 CSpaceCounters* c = _from_counters;
333 _from_counters = _to_counters;
334 _to_counters = c;
335 }
336 }
338 bool DefNewGeneration::expand(size_t bytes) {
339 MutexLocker x(ExpandHeap_lock);
340 HeapWord* prev_high = (HeapWord*) _virtual_space.high();
341 bool success = _virtual_space.expand_by(bytes);
342 if (success && ZapUnusedHeapArea) {
343 // Mangle newly committed space immediately because it
344 // can be done here more simply that after the new
345 // spaces have been computed.
346 HeapWord* new_high = (HeapWord*) _virtual_space.high();
347 MemRegion mangle_region(prev_high, new_high);
348 SpaceMangler::mangle_region(mangle_region);
349 }
351 // Do not attempt an expand-to-the reserve size. The
352 // request should properly observe the maximum size of
353 // the generation so an expand-to-reserve should be
354 // unnecessary. Also a second call to expand-to-reserve
355 // value potentially can cause an undue expansion.
356 // For example if the first expand fail for unknown reasons,
357 // but the second succeeds and expands the heap to its maximum
358 // value.
359 if (GC_locker::is_active()) {
360 if (PrintGC && Verbose) {
361 gclog_or_tty->print_cr("Garbage collection disabled, "
362 "expanded heap instead");
363 }
364 }
366 return success;
367 }
370 void DefNewGeneration::compute_new_size() {
371 // This is called after a gc that includes the following generation
372 // (which is required to exist.) So from-space will normally be empty.
373 // Note that we check both spaces, since if scavenge failed they revert roles.
374 // If not we bail out (otherwise we would have to relocate the objects)
375 if (!from()->is_empty() || !to()->is_empty()) {
376 return;
377 }
379 int next_level = level() + 1;
380 GenCollectedHeap* gch = GenCollectedHeap::heap();
381 assert(next_level < gch->_n_gens,
382 "DefNewGeneration cannot be an oldest gen");
384 Generation* next_gen = gch->_gens[next_level];
385 size_t old_size = next_gen->capacity();
386 size_t new_size_before = _virtual_space.committed_size();
387 size_t min_new_size = spec()->init_size();
388 size_t max_new_size = reserved().byte_size();
389 assert(min_new_size <= new_size_before &&
390 new_size_before <= max_new_size,
391 "just checking");
392 // All space sizes must be multiples of Generation::GenGrain.
393 size_t alignment = Generation::GenGrain;
395 // Compute desired new generation size based on NewRatio and
396 // NewSizeThreadIncrease
397 size_t desired_new_size = old_size/NewRatio;
398 int threads_count = Threads::number_of_non_daemon_threads();
399 size_t thread_increase_size = threads_count * NewSizeThreadIncrease;
400 desired_new_size = align_size_up(desired_new_size + thread_increase_size, alignment);
402 // Adjust new generation size
403 desired_new_size = MAX2(MIN2(desired_new_size, max_new_size), min_new_size);
404 assert(desired_new_size <= max_new_size, "just checking");
406 bool changed = false;
407 if (desired_new_size > new_size_before) {
408 size_t change = desired_new_size - new_size_before;
409 assert(change % alignment == 0, "just checking");
410 if (expand(change)) {
411 changed = true;
412 }
413 // If the heap failed to expand to the desired size,
414 // "changed" will be false. If the expansion failed
415 // (and at this point it was expected to succeed),
416 // ignore the failure (leaving "changed" as false).
417 }
418 if (desired_new_size < new_size_before && eden()->is_empty()) {
419 // bail out of shrinking if objects in eden
420 size_t change = new_size_before - desired_new_size;
421 assert(change % alignment == 0, "just checking");
422 _virtual_space.shrink_by(change);
423 changed = true;
424 }
425 if (changed) {
426 // The spaces have already been mangled at this point but
427 // may not have been cleared (set top = bottom) and should be.
428 // Mangling was done when the heap was being expanded.
429 compute_space_boundaries(eden()->used(),
430 SpaceDecorator::Clear,
431 SpaceDecorator::DontMangle);
432 MemRegion cmr((HeapWord*)_virtual_space.low(),
433 (HeapWord*)_virtual_space.high());
434 Universe::heap()->barrier_set()->resize_covered_region(cmr);
435 if (Verbose && PrintGC) {
436 size_t new_size_after = _virtual_space.committed_size();
437 size_t eden_size_after = eden()->capacity();
438 size_t survivor_size_after = from()->capacity();
439 gclog_or_tty->print("New generation size " SIZE_FORMAT "K->"
440 SIZE_FORMAT "K [eden="
441 SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
442 new_size_before/K, new_size_after/K,
443 eden_size_after/K, survivor_size_after/K);
444 if (WizardMode) {
445 gclog_or_tty->print("[allowed " SIZE_FORMAT "K extra for %d threads]",
446 thread_increase_size/K, threads_count);
447 }
448 gclog_or_tty->cr();
449 }
450 }
451 }
453 void DefNewGeneration::object_iterate_since_last_GC(ObjectClosure* cl) {
454 // $$$ This may be wrong in case of "scavenge failure"?
455 eden()->object_iterate(cl);
456 }
458 void DefNewGeneration::younger_refs_iterate(OopsInGenClosure* cl) {
459 assert(false, "NYI -- are you sure you want to call this?");
460 }
463 size_t DefNewGeneration::capacity() const {
464 return eden()->capacity()
465 + from()->capacity(); // to() is only used during scavenge
466 }
469 size_t DefNewGeneration::used() const {
470 return eden()->used()
471 + from()->used(); // to() is only used during scavenge
472 }
475 size_t DefNewGeneration::free() const {
476 return eden()->free()
477 + from()->free(); // to() is only used during scavenge
478 }
480 size_t DefNewGeneration::max_capacity() const {
481 const size_t alignment = GenCollectedHeap::heap()->collector_policy()->min_alignment();
482 const size_t reserved_bytes = reserved().byte_size();
483 return reserved_bytes - compute_survivor_size(reserved_bytes, alignment);
484 }
486 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
487 return eden()->free();
488 }
490 size_t DefNewGeneration::capacity_before_gc() const {
491 return eden()->capacity();
492 }
494 size_t DefNewGeneration::contiguous_available() const {
495 return eden()->free();
496 }
499 HeapWord** DefNewGeneration::top_addr() const { return eden()->top_addr(); }
500 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
502 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
503 eden()->object_iterate(blk);
504 from()->object_iterate(blk);
505 }
508 void DefNewGeneration::space_iterate(SpaceClosure* blk,
509 bool usedOnly) {
510 blk->do_space(eden());
511 blk->do_space(from());
512 blk->do_space(to());
513 }
515 // The last collection bailed out, we are running out of heap space,
516 // so we try to allocate the from-space, too.
517 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
518 HeapWord* result = NULL;
519 if (Verbose && PrintGCDetails) {
520 gclog_or_tty->print("DefNewGeneration::allocate_from_space(%u):"
521 " will_fail: %s"
522 " heap_lock: %s"
523 " free: " SIZE_FORMAT,
524 size,
525 GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
526 "true" : "false",
527 Heap_lock->is_locked() ? "locked" : "unlocked",
528 from()->free());
529 }
530 if (should_allocate_from_space() || GC_locker::is_active_and_needs_gc()) {
531 if (Heap_lock->owned_by_self() ||
532 (SafepointSynchronize::is_at_safepoint() &&
533 Thread::current()->is_VM_thread())) {
534 // If the Heap_lock is not locked by this thread, this will be called
535 // again later with the Heap_lock held.
536 result = from()->allocate(size);
537 } else if (PrintGC && Verbose) {
538 gclog_or_tty->print_cr(" Heap_lock is not owned by self");
539 }
540 } else if (PrintGC && Verbose) {
541 gclog_or_tty->print_cr(" should_allocate_from_space: NOT");
542 }
543 if (PrintGC && Verbose) {
544 gclog_or_tty->print_cr(" returns %s", result == NULL ? "NULL" : "object");
545 }
546 return result;
547 }
549 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
550 bool is_tlab,
551 bool parallel) {
552 // We don't attempt to expand the young generation (but perhaps we should.)
553 return allocate(size, is_tlab);
554 }
556 void DefNewGeneration::adjust_desired_tenuring_threshold() {
557 // Set the desired survivor size to half the real survivor space
558 _tenuring_threshold =
559 age_table()->compute_tenuring_threshold(to()->capacity()/HeapWordSize);
560 }
562 void DefNewGeneration::collect(bool full,
563 bool clear_all_soft_refs,
564 size_t size,
565 bool is_tlab) {
566 assert(full || size > 0, "otherwise we don't want to collect");
568 GenCollectedHeap* gch = GenCollectedHeap::heap();
570 _gc_timer->register_gc_start(os::elapsed_counter());
571 DefNewTracer gc_tracer;
572 gc_tracer.report_gc_start(gch->gc_cause(), _gc_timer->gc_start());
574 _next_gen = gch->next_gen(this);
575 assert(_next_gen != NULL,
576 "This must be the youngest gen, and not the only gen");
578 // If the next generation is too full to accommodate promotion
579 // from this generation, pass on collection; let the next generation
580 // do it.
581 if (!collection_attempt_is_safe()) {
582 if (Verbose && PrintGCDetails) {
583 gclog_or_tty->print(" :: Collection attempt not safe :: ");
584 }
585 gch->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
586 return;
587 }
588 assert(to()->is_empty(), "Else not collection_attempt_is_safe");
590 init_assuming_no_promotion_failure();
592 GCTraceTime t1(GCCauseString("GC", gch->gc_cause()), PrintGC && !PrintGCDetails, true, NULL);
593 // Capture heap used before collection (for printing).
594 size_t gch_prev_used = gch->used();
596 gch->trace_heap_before_gc(&gc_tracer);
598 SpecializationStats::clear();
600 // These can be shared for all code paths
601 IsAliveClosure is_alive(this);
602 ScanWeakRefClosure scan_weak_ref(this);
604 age_table()->clear();
605 to()->clear(SpaceDecorator::Mangle);
607 gch->rem_set()->prepare_for_younger_refs_iterate(false);
609 assert(gch->no_allocs_since_save_marks(0),
610 "save marks have not been newly set.");
612 // Not very pretty.
613 CollectorPolicy* cp = gch->collector_policy();
615 FastScanClosure fsc_with_no_gc_barrier(this, false);
616 FastScanClosure fsc_with_gc_barrier(this, true);
618 KlassScanClosure klass_scan_closure(&fsc_with_no_gc_barrier,
619 gch->rem_set()->klass_rem_set());
621 set_promo_failure_scan_stack_closure(&fsc_with_no_gc_barrier);
622 FastEvacuateFollowersClosure evacuate_followers(gch, _level, this,
623 &fsc_with_no_gc_barrier,
624 &fsc_with_gc_barrier);
626 assert(gch->no_allocs_since_save_marks(0),
627 "save marks have not been newly set.");
629 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
631 gch->gen_process_strong_roots(_level,
632 true, // Process younger gens, if any,
633 // as strong roots.
634 true, // activate StrongRootsScope
635 true, // is scavenging
636 SharedHeap::ScanningOption(so),
637 &fsc_with_no_gc_barrier,
638 true, // walk *all* scavengable nmethods
639 &fsc_with_gc_barrier,
640 &klass_scan_closure);
642 // "evacuate followers".
643 evacuate_followers.do_void();
645 FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
646 ReferenceProcessor* rp = ref_processor();
647 rp->setup_policy(clear_all_soft_refs);
648 const ReferenceProcessorStats& stats =
649 rp->process_discovered_references(&is_alive, &keep_alive, &evacuate_followers,
650 NULL, _gc_timer);
651 gc_tracer.report_gc_reference_stats(stats);
653 if (!_promotion_failed) {
654 // Swap the survivor spaces.
655 eden()->clear(SpaceDecorator::Mangle);
656 from()->clear(SpaceDecorator::Mangle);
657 if (ZapUnusedHeapArea) {
658 // This is now done here because of the piece-meal mangling which
659 // can check for valid mangling at intermediate points in the
660 // collection(s). When a minor collection fails to collect
661 // sufficient space resizing of the young generation can occur
662 // an redistribute the spaces in the young generation. Mangle
663 // here so that unzapped regions don't get distributed to
664 // other spaces.
665 to()->mangle_unused_area();
666 }
667 swap_spaces();
669 assert(to()->is_empty(), "to space should be empty now");
671 adjust_desired_tenuring_threshold();
673 // A successful scavenge should restart the GC time limit count which is
674 // for full GC's.
675 AdaptiveSizePolicy* size_policy = gch->gen_policy()->size_policy();
676 size_policy->reset_gc_overhead_limit_count();
677 if (PrintGC && !PrintGCDetails) {
678 gch->print_heap_change(gch_prev_used);
679 }
680 assert(!gch->incremental_collection_failed(), "Should be clear");
681 } else {
682 assert(_promo_failure_scan_stack.is_empty(), "post condition");
683 _promo_failure_scan_stack.clear(true); // Clear cached segments.
685 remove_forwarding_pointers();
686 if (PrintGCDetails) {
687 gclog_or_tty->print(" (promotion failed) ");
688 }
689 // Add to-space to the list of space to compact
690 // when a promotion failure has occurred. In that
691 // case there can be live objects in to-space
692 // as a result of a partial evacuation of eden
693 // and from-space.
694 swap_spaces(); // For uniformity wrt ParNewGeneration.
695 from()->set_next_compaction_space(to());
696 gch->set_incremental_collection_failed();
698 // Inform the next generation that a promotion failure occurred.
699 _next_gen->promotion_failure_occurred();
700 gc_tracer.report_promotion_failed(_promotion_failed_info);
702 // Reset the PromotionFailureALot counters.
703 NOT_PRODUCT(Universe::heap()->reset_promotion_should_fail();)
704 }
705 // set new iteration safe limit for the survivor spaces
706 from()->set_concurrent_iteration_safe_limit(from()->top());
707 to()->set_concurrent_iteration_safe_limit(to()->top());
708 SpecializationStats::print();
710 // We need to use a monotonically non-decreasing time in ms
711 // or we will see time-warp warnings and os::javaTimeMillis()
712 // does not guarantee monotonicity.
713 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
714 update_time_of_last_gc(now);
716 gch->trace_heap_after_gc(&gc_tracer);
717 gc_tracer.report_tenuring_threshold(tenuring_threshold());
719 _gc_timer->register_gc_end(os::elapsed_counter());
721 gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
722 }
724 class RemoveForwardPointerClosure: public ObjectClosure {
725 public:
726 void do_object(oop obj) {
727 obj->init_mark();
728 }
729 };
731 void DefNewGeneration::init_assuming_no_promotion_failure() {
732 _promotion_failed = false;
733 _promotion_failed_info.reset();
734 from()->set_next_compaction_space(NULL);
735 }
737 void DefNewGeneration::remove_forwarding_pointers() {
738 RemoveForwardPointerClosure rspc;
739 eden()->object_iterate(&rspc);
740 from()->object_iterate(&rspc);
742 // Now restore saved marks, if any.
743 assert(_objs_with_preserved_marks.size() == _preserved_marks_of_objs.size(),
744 "should be the same");
745 while (!_objs_with_preserved_marks.is_empty()) {
746 oop obj = _objs_with_preserved_marks.pop();
747 markOop m = _preserved_marks_of_objs.pop();
748 obj->set_mark(m);
749 }
750 _objs_with_preserved_marks.clear(true);
751 _preserved_marks_of_objs.clear(true);
752 }
754 void DefNewGeneration::preserve_mark(oop obj, markOop m) {
755 assert(_promotion_failed && m->must_be_preserved_for_promotion_failure(obj),
756 "Oversaving!");
757 _objs_with_preserved_marks.push(obj);
758 _preserved_marks_of_objs.push(m);
759 }
761 void DefNewGeneration::preserve_mark_if_necessary(oop obj, markOop m) {
762 if (m->must_be_preserved_for_promotion_failure(obj)) {
763 preserve_mark(obj, m);
764 }
765 }
767 void DefNewGeneration::handle_promotion_failure(oop old) {
768 if (PrintPromotionFailure && !_promotion_failed) {
769 gclog_or_tty->print(" (promotion failure size = " SIZE_FORMAT ") ",
770 old->size());
771 }
772 _promotion_failed = true;
773 _promotion_failed_info.register_copy_failure(old->size());
774 preserve_mark_if_necessary(old, old->mark());
775 // forward to self
776 old->forward_to(old);
778 _promo_failure_scan_stack.push(old);
780 if (!_promo_failure_drain_in_progress) {
781 // prevent recursion in copy_to_survivor_space()
782 _promo_failure_drain_in_progress = true;
783 drain_promo_failure_scan_stack();
784 _promo_failure_drain_in_progress = false;
785 }
786 }
788 oop DefNewGeneration::copy_to_survivor_space(oop old) {
789 assert(is_in_reserved(old) && !old->is_forwarded(),
790 "shouldn't be scavenging this oop");
791 size_t s = old->size();
792 oop obj = NULL;
794 // Try allocating obj in to-space (unless too old)
795 if (old->age() < tenuring_threshold()) {
796 obj = (oop) to()->allocate(s);
797 }
799 // Otherwise try allocating obj tenured
800 if (obj == NULL) {
801 obj = _next_gen->promote(old, s);
802 if (obj == NULL) {
803 handle_promotion_failure(old);
804 return old;
805 }
806 } else {
807 // Prefetch beyond obj
808 const intx interval = PrefetchCopyIntervalInBytes;
809 Prefetch::write(obj, interval);
811 // Copy obj
812 Copy::aligned_disjoint_words((HeapWord*)old, (HeapWord*)obj, s);
814 // Increment age if obj still in new generation
815 obj->incr_age();
816 age_table()->add(obj, s);
817 }
819 // Done, insert forward pointer to obj in this header
820 old->forward_to(obj);
822 return obj;
823 }
825 void DefNewGeneration::drain_promo_failure_scan_stack() {
826 while (!_promo_failure_scan_stack.is_empty()) {
827 oop obj = _promo_failure_scan_stack.pop();
828 obj->oop_iterate(_promo_failure_scan_stack_closure);
829 }
830 }
832 void DefNewGeneration::save_marks() {
833 eden()->set_saved_mark();
834 to()->set_saved_mark();
835 from()->set_saved_mark();
836 }
839 void DefNewGeneration::reset_saved_marks() {
840 eden()->reset_saved_mark();
841 to()->reset_saved_mark();
842 from()->reset_saved_mark();
843 }
846 bool DefNewGeneration::no_allocs_since_save_marks() {
847 assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
848 assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
849 return to()->saved_mark_at_top();
850 }
852 #define DefNew_SINCE_SAVE_MARKS_DEFN(OopClosureType, nv_suffix) \
853 \
854 void DefNewGeneration:: \
855 oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \
856 cl->set_generation(this); \
857 eden()->oop_since_save_marks_iterate##nv_suffix(cl); \
858 to()->oop_since_save_marks_iterate##nv_suffix(cl); \
859 from()->oop_since_save_marks_iterate##nv_suffix(cl); \
860 cl->reset_generation(); \
861 save_marks(); \
862 }
864 ALL_SINCE_SAVE_MARKS_CLOSURES(DefNew_SINCE_SAVE_MARKS_DEFN)
866 #undef DefNew_SINCE_SAVE_MARKS_DEFN
868 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
869 size_t max_alloc_words) {
870 if (requestor == this || _promotion_failed) return;
871 assert(requestor->level() > level(), "DefNewGeneration must be youngest");
873 /* $$$ Assert this? "trace" is a "MarkSweep" function so that's not appropriate.
874 if (to_space->top() > to_space->bottom()) {
875 trace("to_space not empty when contribute_scratch called");
876 }
877 */
879 ContiguousSpace* to_space = to();
880 assert(to_space->end() >= to_space->top(), "pointers out of order");
881 size_t free_words = pointer_delta(to_space->end(), to_space->top());
882 if (free_words >= MinFreeScratchWords) {
883 ScratchBlock* sb = (ScratchBlock*)to_space->top();
884 sb->num_words = free_words;
885 sb->next = list;
886 list = sb;
887 }
888 }
890 void DefNewGeneration::reset_scratch() {
891 // If contributing scratch in to_space, mangle all of
892 // to_space if ZapUnusedHeapArea. This is needed because
893 // top is not maintained while using to-space as scratch.
894 if (ZapUnusedHeapArea) {
895 to()->mangle_unused_area_complete();
896 }
897 }
899 bool DefNewGeneration::collection_attempt_is_safe() {
900 if (!to()->is_empty()) {
901 if (Verbose && PrintGCDetails) {
902 gclog_or_tty->print(" :: to is not empty :: ");
903 }
904 return false;
905 }
906 if (_next_gen == NULL) {
907 GenCollectedHeap* gch = GenCollectedHeap::heap();
908 _next_gen = gch->next_gen(this);
909 assert(_next_gen != NULL,
910 "This must be the youngest gen, and not the only gen");
911 }
912 return _next_gen->promotion_attempt_is_safe(used());
913 }
915 void DefNewGeneration::gc_epilogue(bool full) {
916 DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
918 assert(!GC_locker::is_active(), "We should not be executing here");
919 // Check if the heap is approaching full after a collection has
920 // been done. Generally the young generation is empty at
921 // a minimum at the end of a collection. If it is not, then
922 // the heap is approaching full.
923 GenCollectedHeap* gch = GenCollectedHeap::heap();
924 if (full) {
925 DEBUG_ONLY(seen_incremental_collection_failed = false;)
926 if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
927 if (Verbose && PrintGCDetails) {
928 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
929 GCCause::to_string(gch->gc_cause()));
930 }
931 gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
932 set_should_allocate_from_space(); // we seem to be running out of space
933 } else {
934 if (Verbose && PrintGCDetails) {
935 gclog_or_tty->print("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
936 GCCause::to_string(gch->gc_cause()));
937 }
938 gch->clear_incremental_collection_failed(); // We just did a full collection
939 clear_should_allocate_from_space(); // if set
940 }
941 } else {
942 #ifdef ASSERT
943 // It is possible that incremental_collection_failed() == true
944 // here, because an attempted scavenge did not succeed. The policy
945 // is normally expected to cause a full collection which should
946 // clear that condition, so we should not be here twice in a row
947 // with incremental_collection_failed() == true without having done
948 // a full collection in between.
949 if (!seen_incremental_collection_failed &&
950 gch->incremental_collection_failed()) {
951 if (Verbose && PrintGCDetails) {
952 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
953 GCCause::to_string(gch->gc_cause()));
954 }
955 seen_incremental_collection_failed = true;
956 } else if (seen_incremental_collection_failed) {
957 if (Verbose && PrintGCDetails) {
958 gclog_or_tty->print("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
959 GCCause::to_string(gch->gc_cause()));
960 }
961 assert(gch->gc_cause() == GCCause::_scavenge_alot ||
962 (gch->gc_cause() == GCCause::_java_lang_system_gc && UseConcMarkSweepGC && ExplicitGCInvokesConcurrent) ||
963 !gch->incremental_collection_failed(),
964 "Twice in a row");
965 seen_incremental_collection_failed = false;
966 }
967 #endif // ASSERT
968 }
970 if (ZapUnusedHeapArea) {
971 eden()->check_mangled_unused_area_complete();
972 from()->check_mangled_unused_area_complete();
973 to()->check_mangled_unused_area_complete();
974 }
976 if (!CleanChunkPoolAsync) {
977 Chunk::clean_chunk_pool();
978 }
980 // update the generation and space performance counters
981 update_counters();
982 gch->collector_policy()->counters()->update_counters();
983 }
985 void DefNewGeneration::record_spaces_top() {
986 assert(ZapUnusedHeapArea, "Not mangling unused space");
987 eden()->set_top_for_allocations();
988 to()->set_top_for_allocations();
989 from()->set_top_for_allocations();
990 }
992 void DefNewGeneration::ref_processor_init() {
993 Generation::ref_processor_init();
994 }
997 void DefNewGeneration::update_counters() {
998 if (UsePerfData) {
999 _eden_counters->update_all();
1000 _from_counters->update_all();
1001 _to_counters->update_all();
1002 _gen_counters->update_all();
1003 }
1004 }
1006 void DefNewGeneration::verify() {
1007 eden()->verify();
1008 from()->verify();
1009 to()->verify();
1010 }
1012 void DefNewGeneration::print_on(outputStream* st) const {
1013 Generation::print_on(st);
1014 st->print(" eden");
1015 eden()->print_on(st);
1016 st->print(" from");
1017 from()->print_on(st);
1018 st->print(" to ");
1019 to()->print_on(st);
1020 }
1023 const char* DefNewGeneration::name() const {
1024 return "def new generation";
1025 }
1027 // Moved from inline file as they are not called inline
1028 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
1029 return eden();
1030 }
1032 HeapWord* DefNewGeneration::allocate(size_t word_size,
1033 bool is_tlab) {
1034 // This is the slow-path allocation for the DefNewGeneration.
1035 // Most allocations are fast-path in compiled code.
1036 // We try to allocate from the eden. If that works, we are happy.
1037 // Note that since DefNewGeneration supports lock-free allocation, we
1038 // have to use it here, as well.
1039 HeapWord* result = eden()->par_allocate(word_size);
1040 if (result != NULL) {
1041 return result;
1042 }
1043 do {
1044 HeapWord* old_limit = eden()->soft_end();
1045 if (old_limit < eden()->end()) {
1046 // Tell the next generation we reached a limit.
1047 HeapWord* new_limit =
1048 next_gen()->allocation_limit_reached(eden(), eden()->top(), word_size);
1049 if (new_limit != NULL) {
1050 Atomic::cmpxchg_ptr(new_limit, eden()->soft_end_addr(), old_limit);
1051 } else {
1052 assert(eden()->soft_end() == eden()->end(),
1053 "invalid state after allocation_limit_reached returned null");
1054 }
1055 } else {
1056 // The allocation failed and the soft limit is equal to the hard limit,
1057 // there are no reasons to do an attempt to allocate
1058 assert(old_limit == eden()->end(), "sanity check");
1059 break;
1060 }
1061 // Try to allocate until succeeded or the soft limit can't be adjusted
1062 result = eden()->par_allocate(word_size);
1063 } while (result == NULL);
1065 // If the eden is full and the last collection bailed out, we are running
1066 // out of heap space, and we try to allocate the from-space, too.
1067 // allocate_from_space can't be inlined because that would introduce a
1068 // circular dependency at compile time.
1069 if (result == NULL) {
1070 result = allocate_from_space(word_size);
1071 }
1072 return result;
1073 }
1075 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
1076 bool is_tlab) {
1077 return eden()->par_allocate(word_size);
1078 }
1080 void DefNewGeneration::gc_prologue(bool full) {
1081 // Ensure that _end and _soft_end are the same in eden space.
1082 eden()->set_soft_end(eden()->end());
1083 }
1085 size_t DefNewGeneration::tlab_capacity() const {
1086 return eden()->capacity();
1087 }
1089 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
1090 return unsafe_max_alloc_nogc();
1091 }