1 /*
  2  * Copyright (c) 2001, 2021, 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/serial/defNewGeneration.inline.hpp"
 27 #include "gc/serial/serialGcRefProcProxyTask.hpp"
 28 #include "gc/serial/serialHeap.inline.hpp"
 29 #include "gc/serial/tenuredGeneration.hpp"
 30 #include "gc/shared/adaptiveSizePolicy.hpp"
 31 #include "gc/shared/ageTable.inline.hpp"
 32 #include "gc/shared/cardTableRS.hpp"
 33 #include "gc/shared/collectorCounters.hpp"
 34 #include "gc/shared/gcArguments.hpp"
 35 #include "gc/shared/gcHeapSummary.hpp"
 36 #include "gc/shared/gcLocker.hpp"
 37 #include "gc/shared/gcPolicyCounters.hpp"
 38 #include "gc/shared/gcTimer.hpp"
 39 #include "gc/shared/gcTrace.hpp"
 40 #include "gc/shared/gcTraceTime.inline.hpp"
 41 #include "gc/shared/generationSpec.hpp"
 42 #include "gc/shared/genOopClosures.inline.hpp"
 43 #include "gc/shared/preservedMarks.inline.hpp"
 44 #include "gc/shared/referencePolicy.hpp"
 45 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
 46 #include "gc/shared/space.inline.hpp"
 47 #include "gc/shared/spaceDecorator.inline.hpp"
 48 #include "gc/shared/strongRootsScope.hpp"
 49 #include "gc/shared/weakProcessor.hpp"
 50 #include "logging/log.hpp"
 51 #include "memory/iterator.inline.hpp"
 52 #include "memory/resourceArea.hpp"
 53 #include "oops/instanceRefKlass.hpp"
 54 #include "oops/oop.inline.hpp"
 55 #include "runtime/java.hpp"
 56 #include "runtime/prefetch.inline.hpp"
 57 #include "runtime/thread.inline.hpp"
 58 #include "utilities/align.hpp"
 59 #include "utilities/copy.hpp"
 60 #include "utilities/globalDefinitions.hpp"
 61 #include "utilities/stack.inline.hpp"
 62 
 63 //
 64 // DefNewGeneration functions.
 65 
 66 // Methods of protected closure types.
 67 
 68 DefNewGeneration::IsAliveClosure::IsAliveClosure(Generation* young_gen) : _young_gen(young_gen) {
 69   assert(_young_gen->kind() == Generation::DefNew, "Expected the young generation here");
 70 }
 71 
 72 bool DefNewGeneration::IsAliveClosure::do_object_b(oop p) {
 73   return cast_from_oop<HeapWord*>(p) >= _young_gen->reserved().end() || p->is_forwarded();
 74 }
 75 
 76 DefNewGeneration::KeepAliveClosure::
 77 KeepAliveClosure(ScanWeakRefClosure* cl) : _cl(cl) {
 78   _rs = GenCollectedHeap::heap()->rem_set();
 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::FastEvacuateFollowersClosure::
 95 FastEvacuateFollowersClosure(SerialHeap* heap,
 96                              DefNewScanClosure* cur,
 97                              DefNewYoungerGenClosure* older) :
 98   _heap(heap), _scan_cur_or_nonheap(cur), _scan_older(older)
 99 {
100 }
101 
102 void DefNewGeneration::FastEvacuateFollowersClosure::do_void() {
103   do {
104     _heap->oop_since_save_marks_iterate(_scan_cur_or_nonheap, _scan_older);
105   } while (!_heap->no_allocs_since_save_marks());
106   guarantee(_heap->young_gen()->promo_failure_scan_is_complete(), "Failed to finish scan");
107 }
108 
109 void CLDScanClosure::do_cld(ClassLoaderData* cld) {
110   NOT_PRODUCT(ResourceMark rm);
111   log_develop_trace(gc, scavenge)("CLDScanClosure::do_cld " PTR_FORMAT ", %s, dirty: %s",
112                                   p2i(cld),
113                                   cld->loader_name_and_id(),
114                                   cld->has_modified_oops() ? "true" : "false");
115 
116   // If the cld has not been dirtied we know that there's
117   // no references into  the young gen and we can skip it.
118   if (cld->has_modified_oops()) {
119 
120     // Tell the closure which CLD is being scanned so that it can be dirtied
121     // if oops are left pointing into the young gen.
122     _scavenge_closure->set_scanned_cld(cld);
123 
124     // Clean the cld since we're going to scavenge all the metadata.
125     cld->oops_do(_scavenge_closure, ClassLoaderData::_claim_none, /*clear_modified_oops*/true);
126 
127     _scavenge_closure->set_scanned_cld(NULL);
128   }
129 }
130 
131 ScanWeakRefClosure::ScanWeakRefClosure(DefNewGeneration* g) :
132   _g(g)
133 {
134   _boundary = _g->reserved().end();
135 }
136 
137 DefNewGeneration::DefNewGeneration(ReservedSpace rs,
138                                    size_t initial_size,
139                                    size_t min_size,
140                                    size_t max_size,
141                                    const char* policy)
142   : Generation(rs, initial_size),
143     _preserved_marks_set(false /* in_c_heap */),
144     _promo_failure_drain_in_progress(false),
145     _should_allocate_from_space(false)
146 {
147   MemRegion cmr((HeapWord*)_virtual_space.low(),
148                 (HeapWord*)_virtual_space.high());
149   GenCollectedHeap* gch = GenCollectedHeap::heap();
150 
151   gch->rem_set()->resize_covered_region(cmr);
152 
153   _eden_space = new ContiguousSpace();
154   _from_space = new ContiguousSpace();
155   _to_space   = new ContiguousSpace();
156 
157   // Compute the maximum eden and survivor space sizes. These sizes
158   // are computed assuming the entire reserved space is committed.
159   // These values are exported as performance counters.
160   uintx size = _virtual_space.reserved_size();
161   _max_survivor_size = compute_survivor_size(size, SpaceAlignment);
162   _max_eden_size = size - (2*_max_survivor_size);
163 
164   // allocate the performance counters
165 
166   // Generation counters -- generation 0, 3 subspaces
167   _gen_counters = new GenerationCounters("new", 0, 3,
168       min_size, max_size, &_virtual_space);
169   _gc_counters = new CollectorCounters(policy, 0);
170 
171   _eden_counters = new CSpaceCounters("eden", 0, _max_eden_size, _eden_space,
172                                       _gen_counters);
173   _from_counters = new CSpaceCounters("s0", 1, _max_survivor_size, _from_space,
174                                       _gen_counters);
175   _to_counters = new CSpaceCounters("s1", 2, _max_survivor_size, _to_space,
176                                     _gen_counters);
177 
178   compute_space_boundaries(0, SpaceDecorator::Clear, SpaceDecorator::Mangle);
179   update_counters();
180   _old_gen = NULL;
181   _tenuring_threshold = MaxTenuringThreshold;
182   _pretenure_size_threshold_words = PretenureSizeThreshold >> LogHeapWordSize;
183 
184   _gc_timer = new (ResourceObj::C_HEAP, mtGC) STWGCTimer();
185 }
186 
187 void DefNewGeneration::compute_space_boundaries(uintx minimum_eden_size,
188                                                 bool clear_space,
189                                                 bool mangle_space) {
190   // If the spaces are being cleared (only done at heap initialization
191   // currently), the survivor spaces need not be empty.
192   // Otherwise, no care is taken for used areas in the survivor spaces
193   // so check.
194   assert(clear_space || (to()->is_empty() && from()->is_empty()),
195     "Initialization of the survivor spaces assumes these are empty");
196 
197   // Compute sizes
198   uintx size = _virtual_space.committed_size();
199   uintx survivor_size = compute_survivor_size(size, SpaceAlignment);
200   uintx eden_size = size - (2*survivor_size);
201   if (eden_size > max_eden_size()) {
202     eden_size = max_eden_size();
203     survivor_size = (size - eden_size)/2;
204   }
205   assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
206 
207   if (eden_size < minimum_eden_size) {
208     // May happen due to 64Kb rounding, if so adjust eden size back up
209     minimum_eden_size = align_up(minimum_eden_size, SpaceAlignment);
210     uintx maximum_survivor_size = (size - minimum_eden_size) / 2;
211     uintx unaligned_survivor_size =
212       align_down(maximum_survivor_size, SpaceAlignment);
213     survivor_size = MAX2(unaligned_survivor_size, SpaceAlignment);
214     eden_size = size - (2*survivor_size);
215     assert(eden_size > 0 && survivor_size <= eden_size, "just checking");
216     assert(eden_size >= minimum_eden_size, "just checking");
217   }
218 
219   char *eden_start = _virtual_space.low();
220   char *from_start = eden_start + eden_size;
221   char *to_start   = from_start + survivor_size;
222   char *to_end     = to_start   + survivor_size;
223 
224   assert(to_end == _virtual_space.high(), "just checking");
225   assert(Space::is_aligned(eden_start), "checking alignment");
226   assert(Space::is_aligned(from_start), "checking alignment");
227   assert(Space::is_aligned(to_start),   "checking alignment");
228 
229   MemRegion edenMR((HeapWord*)eden_start, (HeapWord*)from_start);
230   MemRegion fromMR((HeapWord*)from_start, (HeapWord*)to_start);
231   MemRegion toMR  ((HeapWord*)to_start, (HeapWord*)to_end);
232 
233   // A minimum eden size implies that there is a part of eden that
234   // is being used and that affects the initialization of any
235   // newly formed eden.
236   bool live_in_eden = minimum_eden_size > 0;
237 
238   // If not clearing the spaces, do some checking to verify that
239   // the space are already mangled.
240   if (!clear_space) {
241     // Must check mangling before the spaces are reshaped.  Otherwise,
242     // the bottom or end of one space may have moved into another
243     // a failure of the check may not correctly indicate which space
244     // is not properly mangled.
245     if (ZapUnusedHeapArea) {
246       HeapWord* limit = (HeapWord*) _virtual_space.high();
247       eden()->check_mangled_unused_area(limit);
248       from()->check_mangled_unused_area(limit);
249         to()->check_mangled_unused_area(limit);
250     }
251   }
252 
253   // Reset the spaces for their new regions.
254   eden()->initialize(edenMR,
255                      clear_space && !live_in_eden,
256                      SpaceDecorator::Mangle);
257   // If clear_space and live_in_eden, we will not have cleared any
258   // portion of eden above its top. This can cause newly
259   // expanded space not to be mangled if using ZapUnusedHeapArea.
260   // We explicitly do such mangling here.
261   if (ZapUnusedHeapArea && clear_space && live_in_eden && mangle_space) {
262     eden()->mangle_unused_area();
263   }
264   from()->initialize(fromMR, clear_space, mangle_space);
265   to()->initialize(toMR, clear_space, mangle_space);
266 
267   // Set next compaction spaces.
268   eden()->set_next_compaction_space(from());
269   // The to-space is normally empty before a compaction so need
270   // not be considered.  The exception is during promotion
271   // failure handling when to-space can contain live objects.
272   from()->set_next_compaction_space(NULL);
273 }
274 
275 void DefNewGeneration::swap_spaces() {
276   ContiguousSpace* s = from();
277   _from_space        = to();
278   _to_space          = s;
279   eden()->set_next_compaction_space(from());
280   // The to-space is normally empty before a compaction so need
281   // not be considered.  The exception is during promotion
282   // failure handling when to-space can contain live objects.
283   from()->set_next_compaction_space(NULL);
284 
285   if (UsePerfData) {
286     CSpaceCounters* c = _from_counters;
287     _from_counters = _to_counters;
288     _to_counters = c;
289   }
290 }
291 
292 bool DefNewGeneration::expand(size_t bytes) {
293   MutexLocker x(ExpandHeap_lock);
294   HeapWord* prev_high = (HeapWord*) _virtual_space.high();
295   bool success = _virtual_space.expand_by(bytes);
296   if (success && ZapUnusedHeapArea) {
297     // Mangle newly committed space immediately because it
298     // can be done here more simply that after the new
299     // spaces have been computed.
300     HeapWord* new_high = (HeapWord*) _virtual_space.high();
301     MemRegion mangle_region(prev_high, new_high);
302     SpaceMangler::mangle_region(mangle_region);
303   }
304 
305   // Do not attempt an expand-to-the reserve size.  The
306   // request should properly observe the maximum size of
307   // the generation so an expand-to-reserve should be
308   // unnecessary.  Also a second call to expand-to-reserve
309   // value potentially can cause an undue expansion.
310   // For example if the first expand fail for unknown reasons,
311   // but the second succeeds and expands the heap to its maximum
312   // value.
313   if (GCLocker::is_active()) {
314     log_debug(gc)("Garbage collection disabled, expanded heap instead");
315   }
316 
317   return success;
318 }
319 
320 size_t DefNewGeneration::adjust_for_thread_increase(size_t new_size_candidate,
321                                                     size_t new_size_before,
322                                                     size_t alignment) const {
323   size_t desired_new_size = new_size_before;
324 
325   if (NewSizeThreadIncrease > 0) {
326     int threads_count;
327     size_t thread_increase_size = 0;
328 
329     // 1. Check an overflow at 'threads_count * NewSizeThreadIncrease'.
330     threads_count = Threads::number_of_non_daemon_threads();
331     if (threads_count > 0 && NewSizeThreadIncrease <= max_uintx / threads_count) {
332       thread_increase_size = threads_count * NewSizeThreadIncrease;
333 
334       // 2. Check an overflow at 'new_size_candidate + thread_increase_size'.
335       if (new_size_candidate <= max_uintx - thread_increase_size) {
336         new_size_candidate += thread_increase_size;
337 
338         // 3. Check an overflow at 'align_up'.
339         size_t aligned_max = ((max_uintx - alignment) & ~(alignment-1));
340         if (new_size_candidate <= aligned_max) {
341           desired_new_size = align_up(new_size_candidate, alignment);
342         }
343       }
344     }
345   }
346 
347   return desired_new_size;
348 }
349 
350 void DefNewGeneration::compute_new_size() {
351   // This is called after a GC that includes the old generation, so from-space
352   // will normally be empty.
353   // Note that we check both spaces, since if scavenge failed they revert roles.
354   // If not we bail out (otherwise we would have to relocate the objects).
355   if (!from()->is_empty() || !to()->is_empty()) {
356     return;
357   }
358 
359   GenCollectedHeap* gch = GenCollectedHeap::heap();
360 
361   size_t old_size = gch->old_gen()->capacity();
362   size_t new_size_before = _virtual_space.committed_size();
363   size_t min_new_size = initial_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   int threads_count = 0;
372   size_t thread_increase_size = 0;
373 
374   size_t new_size_candidate = old_size / NewRatio;
375   // Compute desired new generation size based on NewRatio and NewSizeThreadIncrease
376   // and reverts to previous value if any overflow happens
377   size_t desired_new_size = adjust_for_thread_increase(new_size_candidate, new_size_before, alignment);
378 
379   // Adjust new generation size
380   desired_new_size = clamp(desired_new_size, min_new_size, max_new_size);
381   assert(desired_new_size <= max_new_size, "just checking");
382 
383   bool changed = false;
384   if (desired_new_size > new_size_before) {
385     size_t change = desired_new_size - new_size_before;
386     assert(change % alignment == 0, "just checking");
387     if (expand(change)) {
388        changed = true;
389     }
390     // If the heap failed to expand to the desired size,
391     // "changed" will be false.  If the expansion failed
392     // (and at this point it was expected to succeed),
393     // ignore the failure (leaving "changed" as false).
394   }
395   if (desired_new_size < new_size_before && eden()->is_empty()) {
396     // bail out of shrinking if objects in eden
397     size_t change = new_size_before - desired_new_size;
398     assert(change % alignment == 0, "just checking");
399     _virtual_space.shrink_by(change);
400     changed = true;
401   }
402   if (changed) {
403     // The spaces have already been mangled at this point but
404     // may not have been cleared (set top = bottom) and should be.
405     // Mangling was done when the heap was being expanded.
406     compute_space_boundaries(eden()->used(),
407                              SpaceDecorator::Clear,
408                              SpaceDecorator::DontMangle);
409     MemRegion cmr((HeapWord*)_virtual_space.low(),
410                   (HeapWord*)_virtual_space.high());
411     gch->rem_set()->resize_covered_region(cmr);
412 
413     log_debug(gc, ergo, heap)(
414         "New generation size " SIZE_FORMAT "K->" SIZE_FORMAT "K [eden=" SIZE_FORMAT "K,survivor=" SIZE_FORMAT "K]",
415         new_size_before/K, _virtual_space.committed_size()/K,
416         eden()->capacity()/K, from()->capacity()/K);
417     log_trace(gc, ergo, heap)(
418         "  [allowed " SIZE_FORMAT "K extra for %d threads]",
419           thread_increase_size/K, threads_count);
420       }
421 }
422 
423 
424 size_t DefNewGeneration::capacity() const {
425   return eden()->capacity()
426        + from()->capacity();  // to() is only used during scavenge
427 }
428 
429 
430 size_t DefNewGeneration::used() const {
431   return eden()->used()
432        + from()->used();      // to() is only used during scavenge
433 }
434 
435 
436 size_t DefNewGeneration::free() const {
437   return eden()->free()
438        + from()->free();      // to() is only used during scavenge
439 }
440 
441 size_t DefNewGeneration::max_capacity() const {
442   const size_t reserved_bytes = reserved().byte_size();
443   return reserved_bytes - compute_survivor_size(reserved_bytes, SpaceAlignment);
444 }
445 
446 size_t DefNewGeneration::unsafe_max_alloc_nogc() const {
447   return eden()->free();
448 }
449 
450 size_t DefNewGeneration::capacity_before_gc() const {
451   return eden()->capacity();
452 }
453 
454 size_t DefNewGeneration::contiguous_available() const {
455   return eden()->free();
456 }
457 
458 
459 HeapWord* volatile* DefNewGeneration::top_addr() const { return eden()->top_addr(); }
460 HeapWord** DefNewGeneration::end_addr() const { return eden()->end_addr(); }
461 
462 void DefNewGeneration::object_iterate(ObjectClosure* blk) {
463   eden()->object_iterate(blk);
464   from()->object_iterate(blk);
465 }
466 
467 
468 void DefNewGeneration::space_iterate(SpaceClosure* blk,
469                                      bool usedOnly) {
470   blk->do_space(eden());
471   blk->do_space(from());
472   blk->do_space(to());
473 }
474 
475 // The last collection bailed out, we are running out of heap space,
476 // so we try to allocate the from-space, too.
477 HeapWord* DefNewGeneration::allocate_from_space(size_t size) {
478   bool should_try_alloc = should_allocate_from_space() || GCLocker::is_active_and_needs_gc();
479 
480   // If the Heap_lock is not locked by this thread, this will be called
481   // again later with the Heap_lock held.
482   bool do_alloc = should_try_alloc && (Heap_lock->owned_by_self() || (SafepointSynchronize::is_at_safepoint() && Thread::current()->is_VM_thread()));
483 
484   HeapWord* result = NULL;
485   if (do_alloc) {
486     result = from()->allocate(size);
487   }
488 
489   log_trace(gc, alloc)("DefNewGeneration::allocate_from_space(" SIZE_FORMAT "):  will_fail: %s  heap_lock: %s  free: " SIZE_FORMAT "%s%s returns %s",
490                         size,
491                         GenCollectedHeap::heap()->incremental_collection_will_fail(false /* don't consult_young */) ?
492                           "true" : "false",
493                         Heap_lock->is_locked() ? "locked" : "unlocked",
494                         from()->free(),
495                         should_try_alloc ? "" : "  should_allocate_from_space: NOT",
496                         do_alloc ? "  Heap_lock is not owned by self" : "",
497                         result == NULL ? "NULL" : "object");
498 
499   return result;
500 }
501 
502 HeapWord* DefNewGeneration::expand_and_allocate(size_t size,
503                                                 bool   is_tlab,
504                                                 bool   parallel) {
505   // We don't attempt to expand the young generation (but perhaps we should.)
506   return allocate(size, is_tlab);
507 }
508 
509 void DefNewGeneration::adjust_desired_tenuring_threshold() {
510   // Set the desired survivor size to half the real survivor space
511   size_t const survivor_capacity = to()->capacity() / HeapWordSize;
512   size_t const desired_survivor_size = (size_t)((((double)survivor_capacity) * TargetSurvivorRatio) / 100);
513 
514   _tenuring_threshold = age_table()->compute_tenuring_threshold(desired_survivor_size);
515 
516   if (UsePerfData) {
517     GCPolicyCounters* gc_counters = GenCollectedHeap::heap()->counters();
518     gc_counters->tenuring_threshold()->set_value(_tenuring_threshold);
519     gc_counters->desired_survivor_size()->set_value(desired_survivor_size * oopSize);
520   }
521 
522   age_table()->print_age_table(_tenuring_threshold);
523 }
524 
525 void DefNewGeneration::collect(bool   full,
526                                bool   clear_all_soft_refs,
527                                size_t size,
528                                bool   is_tlab) {
529   assert(full || size > 0, "otherwise we don't want to collect");
530 
531   SerialHeap* heap = SerialHeap::heap();
532 
533   _gc_timer->register_gc_start();
534   DefNewTracer gc_tracer;
535   gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer->gc_start());
536 
537   _old_gen = heap->old_gen();
538 
539   // If the next generation is too full to accommodate promotion
540   // from this generation, pass on collection; let the next generation
541   // do it.
542   if (!collection_attempt_is_safe()) {
543     log_trace(gc)(":: Collection attempt not safe ::");
544     heap->set_incremental_collection_failed(); // Slight lie: we did not even attempt one
545     return;
546   }
547   assert(to()->is_empty(), "Else not collection_attempt_is_safe");
548 
549   init_assuming_no_promotion_failure();
550 
551   GCTraceTime(Trace, gc, phases) tm("DefNew", NULL, heap->gc_cause());
552 
553   heap->trace_heap_before_gc(&gc_tracer);
554 
555   // These can be shared for all code paths
556   IsAliveClosure is_alive(this);
557   ScanWeakRefClosure scan_weak_ref(this);
558 
559   age_table()->clear();
560   to()->clear(SpaceDecorator::Mangle);
561   // The preserved marks should be empty at the start of the GC.
562   _preserved_marks_set.init(1);
563 
564   assert(heap->no_allocs_since_save_marks(),
565          "save marks have not been newly set.");
566 
567   DefNewScanClosure       scan_closure(this);
568   DefNewYoungerGenClosure younger_gen_closure(this, _old_gen);
569 
570   CLDScanClosure cld_scan_closure(&scan_closure);
571 
572   set_promo_failure_scan_stack_closure(&scan_closure);
573   FastEvacuateFollowersClosure evacuate_followers(heap,
574                                                   &scan_closure,
575                                                   &younger_gen_closure);
576 
577   assert(heap->no_allocs_since_save_marks(),
578          "save marks have not been newly set.");
579 
580   {
581     StrongRootsScope srs(0);
582 
583     heap->young_process_roots(&scan_closure,
584                               &younger_gen_closure,
585                               &cld_scan_closure);
586   }
587 
588   // "evacuate followers".
589   evacuate_followers.do_void();
590 
591   FastKeepAliveClosure keep_alive(this, &scan_weak_ref);
592   ReferenceProcessor* rp = ref_processor();
593   rp->setup_policy(clear_all_soft_refs);
594   ReferenceProcessorPhaseTimes pt(_gc_timer, rp->max_num_queues());
595   SerialGCRefProcProxyTask task(is_alive, keep_alive, evacuate_followers);
596   const ReferenceProcessorStats& stats = rp->process_discovered_references(task, pt);
597   gc_tracer.report_gc_reference_stats(stats);
598   gc_tracer.report_tenuring_threshold(tenuring_threshold());
599   pt.print_all_references();
600 
601   assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
602 
603   WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
604 
605   // Verify that the usage of keep_alive didn't copy any objects.
606   assert(heap->no_allocs_since_save_marks(), "save marks have not been newly set.");
607 
608   if (!_promotion_failed) {
609     // Swap the survivor spaces.
610     eden()->clear(SpaceDecorator::Mangle);
611     from()->clear(SpaceDecorator::Mangle);
612     if (ZapUnusedHeapArea) {
613       // This is now done here because of the piece-meal mangling which
614       // can check for valid mangling at intermediate points in the
615       // collection(s).  When a young collection fails to collect
616       // sufficient space resizing of the young generation can occur
617       // an redistribute the spaces in the young generation.  Mangle
618       // here so that unzapped regions don't get distributed to
619       // other spaces.
620       to()->mangle_unused_area();
621     }
622     swap_spaces();
623 
624     assert(to()->is_empty(), "to space should be empty now");
625 
626     adjust_desired_tenuring_threshold();
627 
628     // A successful scavenge should restart the GC time limit count which is
629     // for full GC's.
630     AdaptiveSizePolicy* size_policy = heap->size_policy();
631     size_policy->reset_gc_overhead_limit_count();
632     assert(!heap->incremental_collection_failed(), "Should be clear");
633   } else {
634     assert(_promo_failure_scan_stack.is_empty(), "post condition");
635     _promo_failure_scan_stack.clear(true); // Clear cached segments.
636 
637     remove_forwarding_pointers();
638     log_info(gc, promotion)("Promotion failed");
639     // Add to-space to the list of space to compact
640     // when a promotion failure has occurred.  In that
641     // case there can be live objects in to-space
642     // as a result of a partial evacuation of eden
643     // and from-space.
644     swap_spaces();   // For uniformity wrt ParNewGeneration.
645     from()->set_next_compaction_space(to());
646     heap->set_incremental_collection_failed();
647 
648     // Inform the next generation that a promotion failure occurred.
649     _old_gen->promotion_failure_occurred();
650     gc_tracer.report_promotion_failed(_promotion_failed_info);
651 
652     // Reset the PromotionFailureALot counters.
653     NOT_PRODUCT(heap->reset_promotion_should_fail();)
654   }
655   // We should have processed and cleared all the preserved marks.
656   _preserved_marks_set.reclaim();
657 
658   heap->trace_heap_after_gc(&gc_tracer);
659 
660   _gc_timer->register_gc_end();
661 
662   gc_tracer.report_gc_end(_gc_timer->gc_end(), _gc_timer->time_partitions());
663 }
664 
665 void DefNewGeneration::init_assuming_no_promotion_failure() {
666   _promotion_failed = false;
667   _promotion_failed_info.reset();
668   from()->set_next_compaction_space(NULL);
669 }
670 
671 void DefNewGeneration::remove_forwarding_pointers() {
672   RemoveForwardedPointerClosure rspc;
673   eden()->object_iterate(&rspc);
674   from()->object_iterate(&rspc);
675   restore_preserved_marks();
676 }
677 
678 void DefNewGeneration::restore_preserved_marks() {
679   _preserved_marks_set.restore(NULL);
680 }
681 
682 void DefNewGeneration::handle_promotion_failure(oop old) {
683   log_debug(gc, promotion)("Promotion failure size = %d) ", old->size());
684 
685   _promotion_failed = true;
686   _promotion_failed_info.register_copy_failure(old->size());
687   _preserved_marks_set.get()->push_if_necessary(old, old->mark());
688   // forward to self
689   old->forward_to_self();
690 
691   _promo_failure_scan_stack.push(old);
692 
693   if (!_promo_failure_drain_in_progress) {
694     // prevent recursion in copy_to_survivor_space()
695     _promo_failure_drain_in_progress = true;
696     drain_promo_failure_scan_stack();
697     _promo_failure_drain_in_progress = false;
698   }
699 }
700 
701 oop DefNewGeneration::copy_to_survivor_space(oop old) {
702   assert(is_in_reserved(old) && !old->is_forwarded(),
703          "shouldn't be scavenging this oop");
704   size_t s = old->size();
705   oop obj = NULL;
706 
707   // Try allocating obj in to-space (unless too old)
708   if (old->age() < tenuring_threshold()) {
709     obj = cast_to_oop(to()->allocate(s));
710   }
711 
712   // Otherwise try allocating obj tenured
713   if (obj == NULL) {
714     obj = _old_gen->promote(old, s);
715     if (obj == NULL) {
716       handle_promotion_failure(old);
717       return old;
718     }
719   } else {
720     // Prefetch beyond obj
721     const intx interval = PrefetchCopyIntervalInBytes;
722     Prefetch::write(obj, interval);
723 
724     // Copy obj
725     Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(old), cast_from_oop<HeapWord*>(obj), s);
726 
727     // Increment age if obj still in new generation
728     obj->incr_age();
729     age_table()->add(obj, s);
730   }
731 
732   // Done, insert forward pointer to obj in this header
733   old->forward_to(obj);
734 
735   return obj;
736 }
737 
738 void DefNewGeneration::drain_promo_failure_scan_stack() {
739   while (!_promo_failure_scan_stack.is_empty()) {
740      oop obj = _promo_failure_scan_stack.pop();
741      obj->oop_iterate(_promo_failure_scan_stack_closure);
742   }
743 }
744 
745 void DefNewGeneration::save_marks() {
746   eden()->set_saved_mark();
747   to()->set_saved_mark();
748   from()->set_saved_mark();
749 }
750 
751 
752 void DefNewGeneration::reset_saved_marks() {
753   eden()->reset_saved_mark();
754   to()->reset_saved_mark();
755   from()->reset_saved_mark();
756 }
757 
758 
759 bool DefNewGeneration::no_allocs_since_save_marks() {
760   assert(eden()->saved_mark_at_top(), "Violated spec - alloc in eden");
761   assert(from()->saved_mark_at_top(), "Violated spec - alloc in from");
762   return to()->saved_mark_at_top();
763 }
764 
765 void DefNewGeneration::contribute_scratch(ScratchBlock*& list, Generation* requestor,
766                                          size_t max_alloc_words) {
767   if (requestor == this || _promotion_failed) {
768     return;
769   }
770   assert(GenCollectedHeap::heap()->is_old_gen(requestor), "We should not call our own generation");
771 
772   /* $$$ Assert this?  "trace" is a "MarkSweep" function so that's not appropriate.
773   if (to_space->top() > to_space->bottom()) {
774     trace("to_space not empty when contribute_scratch called");
775   }
776   */
777 
778   ContiguousSpace* to_space = to();
779   assert(to_space->end() >= to_space->top(), "pointers out of order");
780   size_t free_words = pointer_delta(to_space->end(), to_space->top());
781   if (free_words >= MinFreeScratchWords) {
782     ScratchBlock* sb = (ScratchBlock*)to_space->top();
783     sb->num_words = free_words;
784     sb->next = list;
785     list = sb;
786   }
787 }
788 
789 void DefNewGeneration::reset_scratch() {
790   // If contributing scratch in to_space, mangle all of
791   // to_space if ZapUnusedHeapArea.  This is needed because
792   // top is not maintained while using to-space as scratch.
793   if (ZapUnusedHeapArea) {
794     to()->mangle_unused_area_complete();
795   }
796 }
797 
798 bool DefNewGeneration::collection_attempt_is_safe() {
799   if (!to()->is_empty()) {
800     log_trace(gc)(":: to is not empty ::");
801     return false;
802   }
803   if (_old_gen == NULL) {
804     GenCollectedHeap* gch = GenCollectedHeap::heap();
805     _old_gen = gch->old_gen();
806   }
807   return _old_gen->promotion_attempt_is_safe(used());
808 }
809 
810 void DefNewGeneration::gc_epilogue(bool full) {
811   DEBUG_ONLY(static bool seen_incremental_collection_failed = false;)
812 
813   assert(!GCLocker::is_active(), "We should not be executing here");
814   // Check if the heap is approaching full after a collection has
815   // been done.  Generally the young generation is empty at
816   // a minimum at the end of a collection.  If it is not, then
817   // the heap is approaching full.
818   GenCollectedHeap* gch = GenCollectedHeap::heap();
819   if (full) {
820     DEBUG_ONLY(seen_incremental_collection_failed = false;)
821     if (!collection_attempt_is_safe() && !_eden_space->is_empty()) {
822       log_trace(gc)("DefNewEpilogue: cause(%s), full, not safe, set_failed, set_alloc_from, clear_seen",
823                             GCCause::to_string(gch->gc_cause()));
824       gch->set_incremental_collection_failed(); // Slight lie: a full gc left us in that state
825       set_should_allocate_from_space(); // we seem to be running out of space
826     } else {
827       log_trace(gc)("DefNewEpilogue: cause(%s), full, safe, clear_failed, clear_alloc_from, clear_seen",
828                             GCCause::to_string(gch->gc_cause()));
829       gch->clear_incremental_collection_failed(); // We just did a full collection
830       clear_should_allocate_from_space(); // if set
831     }
832   } else {
833 #ifdef ASSERT
834     // It is possible that incremental_collection_failed() == true
835     // here, because an attempted scavenge did not succeed. The policy
836     // is normally expected to cause a full collection which should
837     // clear that condition, so we should not be here twice in a row
838     // with incremental_collection_failed() == true without having done
839     // a full collection in between.
840     if (!seen_incremental_collection_failed &&
841         gch->incremental_collection_failed()) {
842       log_trace(gc)("DefNewEpilogue: cause(%s), not full, not_seen_failed, failed, set_seen_failed",
843                             GCCause::to_string(gch->gc_cause()));
844       seen_incremental_collection_failed = true;
845     } else if (seen_incremental_collection_failed) {
846       log_trace(gc)("DefNewEpilogue: cause(%s), not full, seen_failed, will_clear_seen_failed",
847                             GCCause::to_string(gch->gc_cause()));
848       seen_incremental_collection_failed = false;
849     }
850 #endif // ASSERT
851   }
852 
853   if (ZapUnusedHeapArea) {
854     eden()->check_mangled_unused_area_complete();
855     from()->check_mangled_unused_area_complete();
856     to()->check_mangled_unused_area_complete();
857   }
858 
859   // update the generation and space performance counters
860   update_counters();
861   gch->counters()->update_counters();
862 }
863 
864 void DefNewGeneration::record_spaces_top() {
865   assert(ZapUnusedHeapArea, "Not mangling unused space");
866   eden()->set_top_for_allocations();
867   to()->set_top_for_allocations();
868   from()->set_top_for_allocations();
869 }
870 
871 void DefNewGeneration::ref_processor_init() {
872   Generation::ref_processor_init();
873 }
874 
875 
876 void DefNewGeneration::update_counters() {
877   if (UsePerfData) {
878     _eden_counters->update_all();
879     _from_counters->update_all();
880     _to_counters->update_all();
881     _gen_counters->update_all();
882   }
883 }
884 
885 void DefNewGeneration::verify() {
886   eden()->verify();
887   from()->verify();
888     to()->verify();
889 }
890 
891 void DefNewGeneration::print_on(outputStream* st) const {
892   Generation::print_on(st);
893   st->print("  eden");
894   eden()->print_on(st);
895   st->print("  from");
896   from()->print_on(st);
897   st->print("  to  ");
898   to()->print_on(st);
899 }
900 
901 
902 const char* DefNewGeneration::name() const {
903   return "def new generation";
904 }
905 
906 // Moved from inline file as they are not called inline
907 CompactibleSpace* DefNewGeneration::first_compaction_space() const {
908   return eden();
909 }
910 
911 HeapWord* DefNewGeneration::allocate(size_t word_size, bool is_tlab) {
912   // This is the slow-path allocation for the DefNewGeneration.
913   // Most allocations are fast-path in compiled code.
914   // We try to allocate from the eden.  If that works, we are happy.
915   // Note that since DefNewGeneration supports lock-free allocation, we
916   // have to use it here, as well.
917   HeapWord* result = eden()->par_allocate(word_size);
918   if (result == NULL) {
919     // If the eden is full and the last collection bailed out, we are running
920     // out of heap space, and we try to allocate the from-space, too.
921     // allocate_from_space can't be inlined because that would introduce a
922     // circular dependency at compile time.
923     result = allocate_from_space(word_size);
924   }
925   return result;
926 }
927 
928 HeapWord* DefNewGeneration::par_allocate(size_t word_size,
929                                          bool is_tlab) {
930   return eden()->par_allocate(word_size);
931 }
932 
933 size_t DefNewGeneration::tlab_capacity() const {
934   return eden()->capacity();
935 }
936 
937 size_t DefNewGeneration::tlab_used() const {
938   return eden()->used();
939 }
940 
941 size_t DefNewGeneration::unsafe_max_tlab_alloc() const {
942   return unsafe_max_alloc_nogc();
943 }