Thu, 07 Apr 2011 09:53:20 -0700
7009266: G1: assert(obj->is_oop_or_null(true )) failed: Error
Summary: A referent object that is only weakly reachable at the start of concurrent marking but is re-attached to the strongly reachable object graph during marking may not be marked as live. This can cause the reference object to be processed prematurely and leave dangling pointers to the referent object. Implement a read barrier for the java.lang.ref.Reference::referent field by intrinsifying the Reference.get() method, and intercepting accesses though JNI, reflection, and Unsafe, so that when a non-null referent object is read it is also logged in an SATB buffer.
Reviewed-by: kvn, iveresov, never, tonyp, dholmes
1 /*
2 * Copyright (c) 2001, 2011, 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
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23 */
25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
28 #include "gc_implementation/g1/concurrentMark.hpp"
29 #include "gc_implementation/g1/g1AllocRegion.hpp"
30 #include "gc_implementation/g1/g1RemSet.hpp"
31 #include "gc_implementation/g1/heapRegionSets.hpp"
32 #include "gc_implementation/parNew/parGCAllocBuffer.hpp"
33 #include "memory/barrierSet.hpp"
34 #include "memory/memRegion.hpp"
35 #include "memory/sharedHeap.hpp"
37 // A "G1CollectedHeap" is an implementation of a java heap for HotSpot.
38 // It uses the "Garbage First" heap organization and algorithm, which
39 // may combine concurrent marking with parallel, incremental compaction of
40 // heap subsets that will yield large amounts of garbage.
42 class HeapRegion;
43 class HeapRegionSeq;
44 class HRRSCleanupTask;
45 class PermanentGenerationSpec;
46 class GenerationSpec;
47 class OopsInHeapRegionClosure;
48 class G1ScanHeapEvacClosure;
49 class ObjectClosure;
50 class SpaceClosure;
51 class CompactibleSpaceClosure;
52 class Space;
53 class G1CollectorPolicy;
54 class GenRemSet;
55 class G1RemSet;
56 class HeapRegionRemSetIterator;
57 class ConcurrentMark;
58 class ConcurrentMarkThread;
59 class ConcurrentG1Refine;
61 typedef OverflowTaskQueue<StarTask> RefToScanQueue;
62 typedef GenericTaskQueueSet<RefToScanQueue> RefToScanQueueSet;
64 typedef int RegionIdx_t; // needs to hold [ 0..max_regions() )
65 typedef int CardIdx_t; // needs to hold [ 0..CardsPerRegion )
67 enum GCAllocPurpose {
68 GCAllocForTenured,
69 GCAllocForSurvived,
70 GCAllocPurposeCount
71 };
73 class YoungList : public CHeapObj {
74 private:
75 G1CollectedHeap* _g1h;
77 HeapRegion* _head;
79 HeapRegion* _survivor_head;
80 HeapRegion* _survivor_tail;
82 HeapRegion* _curr;
84 size_t _length;
85 size_t _survivor_length;
87 size_t _last_sampled_rs_lengths;
88 size_t _sampled_rs_lengths;
90 void empty_list(HeapRegion* list);
92 public:
93 YoungList(G1CollectedHeap* g1h);
95 void push_region(HeapRegion* hr);
96 void add_survivor_region(HeapRegion* hr);
98 void empty_list();
99 bool is_empty() { return _length == 0; }
100 size_t length() { return _length; }
101 size_t survivor_length() { return _survivor_length; }
103 void rs_length_sampling_init();
104 bool rs_length_sampling_more();
105 void rs_length_sampling_next();
107 void reset_sampled_info() {
108 _last_sampled_rs_lengths = 0;
109 }
110 size_t sampled_rs_lengths() { return _last_sampled_rs_lengths; }
112 // for development purposes
113 void reset_auxilary_lists();
114 void clear() { _head = NULL; _length = 0; }
116 void clear_survivors() {
117 _survivor_head = NULL;
118 _survivor_tail = NULL;
119 _survivor_length = 0;
120 }
122 HeapRegion* first_region() { return _head; }
123 HeapRegion* first_survivor_region() { return _survivor_head; }
124 HeapRegion* last_survivor_region() { return _survivor_tail; }
126 // debugging
127 bool check_list_well_formed();
128 bool check_list_empty(bool check_sample = true);
129 void print();
130 };
132 class MutatorAllocRegion : public G1AllocRegion {
133 protected:
134 virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
135 virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
136 public:
137 MutatorAllocRegion()
138 : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
139 };
141 class RefineCardTableEntryClosure;
142 class G1CollectedHeap : public SharedHeap {
143 friend class VM_G1CollectForAllocation;
144 friend class VM_GenCollectForPermanentAllocation;
145 friend class VM_G1CollectFull;
146 friend class VM_G1IncCollectionPause;
147 friend class VMStructs;
148 friend class MutatorAllocRegion;
150 // Closures used in implementation.
151 friend class G1ParCopyHelper;
152 friend class G1IsAliveClosure;
153 friend class G1EvacuateFollowersClosure;
154 friend class G1ParScanThreadState;
155 friend class G1ParScanClosureSuper;
156 friend class G1ParEvacuateFollowersClosure;
157 friend class G1ParTask;
158 friend class G1FreeGarbageRegionClosure;
159 friend class RefineCardTableEntryClosure;
160 friend class G1PrepareCompactClosure;
161 friend class RegionSorter;
162 friend class RegionResetter;
163 friend class CountRCClosure;
164 friend class EvacPopObjClosure;
165 friend class G1ParCleanupCTTask;
167 // Other related classes.
168 friend class G1MarkSweep;
170 private:
171 // The one and only G1CollectedHeap, so static functions can find it.
172 static G1CollectedHeap* _g1h;
174 static size_t _humongous_object_threshold_in_words;
176 // Storage for the G1 heap (excludes the permanent generation).
177 VirtualSpace _g1_storage;
178 MemRegion _g1_reserved;
180 // The part of _g1_storage that is currently committed.
181 MemRegion _g1_committed;
183 // The maximum part of _g1_storage that has ever been committed.
184 MemRegion _g1_max_committed;
186 // The master free list. It will satisfy all new region allocations.
187 MasterFreeRegionList _free_list;
189 // The secondary free list which contains regions that have been
190 // freed up during the cleanup process. This will be appended to the
191 // master free list when appropriate.
192 SecondaryFreeRegionList _secondary_free_list;
194 // It keeps track of the humongous regions.
195 MasterHumongousRegionSet _humongous_set;
197 // The number of regions we could create by expansion.
198 size_t _expansion_regions;
200 // The block offset table for the G1 heap.
201 G1BlockOffsetSharedArray* _bot_shared;
203 // Move all of the regions off the free lists, then rebuild those free
204 // lists, before and after full GC.
205 void tear_down_region_lists();
206 void rebuild_region_lists();
208 // The sequence of all heap regions in the heap.
209 HeapRegionSeq* _hrs;
211 // Alloc region used to satisfy mutator allocation requests.
212 MutatorAllocRegion _mutator_alloc_region;
214 // It resets the mutator alloc region before new allocations can take place.
215 void init_mutator_alloc_region();
217 // It releases the mutator alloc region.
218 void release_mutator_alloc_region();
220 void abandon_gc_alloc_regions();
222 // The to-space memory regions into which objects are being copied during
223 // a GC.
224 HeapRegion* _gc_alloc_regions[GCAllocPurposeCount];
225 size_t _gc_alloc_region_counts[GCAllocPurposeCount];
226 // These are the regions, one per GCAllocPurpose, that are half-full
227 // at the end of a collection and that we want to reuse during the
228 // next collection.
229 HeapRegion* _retained_gc_alloc_regions[GCAllocPurposeCount];
230 // This specifies whether we will keep the last half-full region at
231 // the end of a collection so that it can be reused during the next
232 // collection (this is specified per GCAllocPurpose)
233 bool _retain_gc_alloc_region[GCAllocPurposeCount];
235 // A list of the regions that have been set to be alloc regions in the
236 // current collection.
237 HeapRegion* _gc_alloc_region_list;
239 // Determines PLAB size for a particular allocation purpose.
240 static size_t desired_plab_sz(GCAllocPurpose purpose);
242 // When called by par thread, requires the FreeList_lock to be held.
243 void push_gc_alloc_region(HeapRegion* hr);
245 // This should only be called single-threaded. Undeclares all GC alloc
246 // regions.
247 void forget_alloc_region_list();
249 // Should be used to set an alloc region, because there's other
250 // associated bookkeeping.
251 void set_gc_alloc_region(int purpose, HeapRegion* r);
253 // Check well-formedness of alloc region list.
254 bool check_gc_alloc_regions();
256 // Outside of GC pauses, the number of bytes used in all regions other
257 // than the current allocation region.
258 size_t _summary_bytes_used;
260 // This is used for a quick test on whether a reference points into
261 // the collection set or not. Basically, we have an array, with one
262 // byte per region, and that byte denotes whether the corresponding
263 // region is in the collection set or not. The entry corresponding
264 // the bottom of the heap, i.e., region 0, is pointed to by
265 // _in_cset_fast_test_base. The _in_cset_fast_test field has been
266 // biased so that it actually points to address 0 of the address
267 // space, to make the test as fast as possible (we can simply shift
268 // the address to address into it, instead of having to subtract the
269 // bottom of the heap from the address before shifting it; basically
270 // it works in the same way the card table works).
271 bool* _in_cset_fast_test;
273 // The allocated array used for the fast test on whether a reference
274 // points into the collection set or not. This field is also used to
275 // free the array.
276 bool* _in_cset_fast_test_base;
278 // The length of the _in_cset_fast_test_base array.
279 size_t _in_cset_fast_test_length;
281 volatile unsigned _gc_time_stamp;
283 size_t* _surviving_young_words;
285 void setup_surviving_young_words();
286 void update_surviving_young_words(size_t* surv_young_words);
287 void cleanup_surviving_young_words();
289 // It decides whether an explicit GC should start a concurrent cycle
290 // instead of doing a STW GC. Currently, a concurrent cycle is
291 // explicitly started if:
292 // (a) cause == _gc_locker and +GCLockerInvokesConcurrent, or
293 // (b) cause == _java_lang_system_gc and +ExplicitGCInvokesConcurrent.
294 bool should_do_concurrent_full_gc(GCCause::Cause cause);
296 // Keeps track of how many "full collections" (i.e., Full GCs or
297 // concurrent cycles) we have completed. The number of them we have
298 // started is maintained in _total_full_collections in CollectedHeap.
299 volatile unsigned int _full_collections_completed;
301 // These are macros so that, if the assert fires, we get the correct
302 // line number, file, etc.
304 #define heap_locking_asserts_err_msg(_extra_message_) \
305 err_msg("%s : Heap_lock locked: %s, at safepoint: %s, is VM thread: %s", \
306 (_extra_message_), \
307 BOOL_TO_STR(Heap_lock->owned_by_self()), \
308 BOOL_TO_STR(SafepointSynchronize::is_at_safepoint()), \
309 BOOL_TO_STR(Thread::current()->is_VM_thread()))
311 #define assert_heap_locked() \
312 do { \
313 assert(Heap_lock->owned_by_self(), \
314 heap_locking_asserts_err_msg("should be holding the Heap_lock")); \
315 } while (0)
317 #define assert_heap_locked_or_at_safepoint(_should_be_vm_thread_) \
318 do { \
319 assert(Heap_lock->owned_by_self() || \
320 (SafepointSynchronize::is_at_safepoint() && \
321 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread())), \
322 heap_locking_asserts_err_msg("should be holding the Heap_lock or " \
323 "should be at a safepoint")); \
324 } while (0)
326 #define assert_heap_locked_and_not_at_safepoint() \
327 do { \
328 assert(Heap_lock->owned_by_self() && \
329 !SafepointSynchronize::is_at_safepoint(), \
330 heap_locking_asserts_err_msg("should be holding the Heap_lock and " \
331 "should not be at a safepoint")); \
332 } while (0)
334 #define assert_heap_not_locked() \
335 do { \
336 assert(!Heap_lock->owned_by_self(), \
337 heap_locking_asserts_err_msg("should not be holding the Heap_lock")); \
338 } while (0)
340 #define assert_heap_not_locked_and_not_at_safepoint() \
341 do { \
342 assert(!Heap_lock->owned_by_self() && \
343 !SafepointSynchronize::is_at_safepoint(), \
344 heap_locking_asserts_err_msg("should not be holding the Heap_lock and " \
345 "should not be at a safepoint")); \
346 } while (0)
348 #define assert_at_safepoint(_should_be_vm_thread_) \
349 do { \
350 assert(SafepointSynchronize::is_at_safepoint() && \
351 ((_should_be_vm_thread_) == Thread::current()->is_VM_thread()), \
352 heap_locking_asserts_err_msg("should be at a safepoint")); \
353 } while (0)
355 #define assert_not_at_safepoint() \
356 do { \
357 assert(!SafepointSynchronize::is_at_safepoint(), \
358 heap_locking_asserts_err_msg("should not be at a safepoint")); \
359 } while (0)
361 protected:
363 // Returns "true" iff none of the gc alloc regions have any allocations
364 // since the last call to "save_marks".
365 bool all_alloc_regions_no_allocs_since_save_marks();
366 // Perform finalization stuff on all allocation regions.
367 void retire_all_alloc_regions();
369 // The number of regions allocated to hold humongous objects.
370 int _num_humongous_regions;
371 YoungList* _young_list;
373 // The current policy object for the collector.
374 G1CollectorPolicy* _g1_policy;
376 // This is the second level of trying to allocate a new region. If
377 // new_region() didn't find a region on the free_list, this call will
378 // check whether there's anything available on the
379 // secondary_free_list and/or wait for more regions to appear on
380 // that list, if _free_regions_coming is set.
381 HeapRegion* new_region_try_secondary_free_list();
383 // Try to allocate a single non-humongous HeapRegion sufficient for
384 // an allocation of the given word_size. If do_expand is true,
385 // attempt to expand the heap if necessary to satisfy the allocation
386 // request.
387 HeapRegion* new_region(size_t word_size, bool do_expand);
389 // Try to allocate a new region to be used for allocation by
390 // a GC thread. It will try to expand the heap if no region is
391 // available.
392 HeapRegion* new_gc_alloc_region(int purpose, size_t word_size);
394 // Attempt to satisfy a humongous allocation request of the given
395 // size by finding a contiguous set of free regions of num_regions
396 // length and remove them from the master free list. Return the
397 // index of the first region or -1 if the search was unsuccessful.
398 int humongous_obj_allocate_find_first(size_t num_regions, size_t word_size);
400 // Initialize a contiguous set of free regions of length num_regions
401 // and starting at index first so that they appear as a single
402 // humongous region.
403 HeapWord* humongous_obj_allocate_initialize_regions(int first,
404 size_t num_regions,
405 size_t word_size);
407 // Attempt to allocate a humongous object of the given size. Return
408 // NULL if unsuccessful.
409 HeapWord* humongous_obj_allocate(size_t word_size);
411 // The following two methods, allocate_new_tlab() and
412 // mem_allocate(), are the two main entry points from the runtime
413 // into the G1's allocation routines. They have the following
414 // assumptions:
415 //
416 // * They should both be called outside safepoints.
417 //
418 // * They should both be called without holding the Heap_lock.
419 //
420 // * All allocation requests for new TLABs should go to
421 // allocate_new_tlab().
422 //
423 // * All non-TLAB allocation requests should go to mem_allocate()
424 // and mem_allocate() should never be called with is_tlab == true.
425 //
426 // * If either call cannot satisfy the allocation request using the
427 // current allocating region, they will try to get a new one. If
428 // this fails, they will attempt to do an evacuation pause and
429 // retry the allocation.
430 //
431 // * If all allocation attempts fail, even after trying to schedule
432 // an evacuation pause, allocate_new_tlab() will return NULL,
433 // whereas mem_allocate() will attempt a heap expansion and/or
434 // schedule a Full GC.
435 //
436 // * We do not allow humongous-sized TLABs. So, allocate_new_tlab
437 // should never be called with word_size being humongous. All
438 // humongous allocation requests should go to mem_allocate() which
439 // will satisfy them with a special path.
441 virtual HeapWord* allocate_new_tlab(size_t word_size);
443 virtual HeapWord* mem_allocate(size_t word_size,
444 bool is_noref,
445 bool is_tlab, /* expected to be false */
446 bool* gc_overhead_limit_was_exceeded);
448 // The following three methods take a gc_count_before_ret
449 // parameter which is used to return the GC count if the method
450 // returns NULL. Given that we are required to read the GC count
451 // while holding the Heap_lock, and these paths will take the
452 // Heap_lock at some point, it's easier to get them to read the GC
453 // count while holding the Heap_lock before they return NULL instead
454 // of the caller (namely: mem_allocate()) having to also take the
455 // Heap_lock just to read the GC count.
457 // First-level mutator allocation attempt: try to allocate out of
458 // the mutator alloc region without taking the Heap_lock. This
459 // should only be used for non-humongous allocations.
460 inline HeapWord* attempt_allocation(size_t word_size,
461 unsigned int* gc_count_before_ret);
463 // Second-level mutator allocation attempt: take the Heap_lock and
464 // retry the allocation attempt, potentially scheduling a GC
465 // pause. This should only be used for non-humongous allocations.
466 HeapWord* attempt_allocation_slow(size_t word_size,
467 unsigned int* gc_count_before_ret);
469 // Takes the Heap_lock and attempts a humongous allocation. It can
470 // potentially schedule a GC pause.
471 HeapWord* attempt_allocation_humongous(size_t word_size,
472 unsigned int* gc_count_before_ret);
474 // Allocation attempt that should be called during safepoints (e.g.,
475 // at the end of a successful GC). expect_null_mutator_alloc_region
476 // specifies whether the mutator alloc region is expected to be NULL
477 // or not.
478 HeapWord* attempt_allocation_at_safepoint(size_t word_size,
479 bool expect_null_mutator_alloc_region);
481 // It dirties the cards that cover the block so that so that the post
482 // write barrier never queues anything when updating objects on this
483 // block. It is assumed (and in fact we assert) that the block
484 // belongs to a young region.
485 inline void dirty_young_block(HeapWord* start, size_t word_size);
487 // Allocate blocks during garbage collection. Will ensure an
488 // allocation region, either by picking one or expanding the
489 // heap, and then allocate a block of the given size. The block
490 // may not be a humongous - it must fit into a single heap region.
491 HeapWord* par_allocate_during_gc(GCAllocPurpose purpose, size_t word_size);
493 HeapWord* allocate_during_gc_slow(GCAllocPurpose purpose,
494 HeapRegion* alloc_region,
495 bool par,
496 size_t word_size);
498 // Ensure that no further allocations can happen in "r", bearing in mind
499 // that parallel threads might be attempting allocations.
500 void par_allocate_remaining_space(HeapRegion* r);
502 // Retires an allocation region when it is full or at the end of a
503 // GC pause.
504 void retire_alloc_region(HeapRegion* alloc_region, bool par);
506 // These two methods are the "callbacks" from the G1AllocRegion class.
508 HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
509 void retire_mutator_alloc_region(HeapRegion* alloc_region,
510 size_t allocated_bytes);
512 // - if explicit_gc is true, the GC is for a System.gc() or a heap
513 // inspection request and should collect the entire heap
514 // - if clear_all_soft_refs is true, all soft references should be
515 // cleared during the GC
516 // - if explicit_gc is false, word_size describes the allocation that
517 // the GC should attempt (at least) to satisfy
518 // - it returns false if it is unable to do the collection due to the
519 // GC locker being active, true otherwise
520 bool do_collection(bool explicit_gc,
521 bool clear_all_soft_refs,
522 size_t word_size);
524 // Callback from VM_G1CollectFull operation.
525 // Perform a full collection.
526 void do_full_collection(bool clear_all_soft_refs);
528 // Resize the heap if necessary after a full collection. If this is
529 // after a collect-for allocation, "word_size" is the allocation size,
530 // and will be considered part of the used portion of the heap.
531 void resize_if_necessary_after_full_collection(size_t word_size);
533 // Callback from VM_G1CollectForAllocation operation.
534 // This function does everything necessary/possible to satisfy a
535 // failed allocation request (including collection, expansion, etc.)
536 HeapWord* satisfy_failed_allocation(size_t word_size, bool* succeeded);
538 // Attempting to expand the heap sufficiently
539 // to support an allocation of the given "word_size". If
540 // successful, perform the allocation and return the address of the
541 // allocated block, or else "NULL".
542 HeapWord* expand_and_allocate(size_t word_size);
544 public:
545 // Expand the garbage-first heap by at least the given size (in bytes!).
546 // Returns true if the heap was expanded by the requested amount;
547 // false otherwise.
548 // (Rounds up to a HeapRegion boundary.)
549 bool expand(size_t expand_bytes);
551 // Do anything common to GC's.
552 virtual void gc_prologue(bool full);
553 virtual void gc_epilogue(bool full);
555 // We register a region with the fast "in collection set" test. We
556 // simply set to true the array slot corresponding to this region.
557 void register_region_with_in_cset_fast_test(HeapRegion* r) {
558 assert(_in_cset_fast_test_base != NULL, "sanity");
559 assert(r->in_collection_set(), "invariant");
560 int index = r->hrs_index();
561 assert(0 <= index && (size_t) index < _in_cset_fast_test_length, "invariant");
562 assert(!_in_cset_fast_test_base[index], "invariant");
563 _in_cset_fast_test_base[index] = true;
564 }
566 // This is a fast test on whether a reference points into the
567 // collection set or not. It does not assume that the reference
568 // points into the heap; if it doesn't, it will return false.
569 bool in_cset_fast_test(oop obj) {
570 assert(_in_cset_fast_test != NULL, "sanity");
571 if (_g1_committed.contains((HeapWord*) obj)) {
572 // no need to subtract the bottom of the heap from obj,
573 // _in_cset_fast_test is biased
574 size_t index = ((size_t) obj) >> HeapRegion::LogOfHRGrainBytes;
575 bool ret = _in_cset_fast_test[index];
576 // let's make sure the result is consistent with what the slower
577 // test returns
578 assert( ret || !obj_in_cs(obj), "sanity");
579 assert(!ret || obj_in_cs(obj), "sanity");
580 return ret;
581 } else {
582 return false;
583 }
584 }
586 void clear_cset_fast_test() {
587 assert(_in_cset_fast_test_base != NULL, "sanity");
588 memset(_in_cset_fast_test_base, false,
589 _in_cset_fast_test_length * sizeof(bool));
590 }
592 // This is called at the end of either a concurrent cycle or a Full
593 // GC to update the number of full collections completed. Those two
594 // can happen in a nested fashion, i.e., we start a concurrent
595 // cycle, a Full GC happens half-way through it which ends first,
596 // and then the cycle notices that a Full GC happened and ends
597 // too. The concurrent parameter is a boolean to help us do a bit
598 // tighter consistency checking in the method. If concurrent is
599 // false, the caller is the inner caller in the nesting (i.e., the
600 // Full GC). If concurrent is true, the caller is the outer caller
601 // in this nesting (i.e., the concurrent cycle). Further nesting is
602 // not currently supported. The end of the this call also notifies
603 // the FullGCCount_lock in case a Java thread is waiting for a full
604 // GC to happen (e.g., it called System.gc() with
605 // +ExplicitGCInvokesConcurrent).
606 void increment_full_collections_completed(bool concurrent);
608 unsigned int full_collections_completed() {
609 return _full_collections_completed;
610 }
612 protected:
614 // Shrink the garbage-first heap by at most the given size (in bytes!).
615 // (Rounds down to a HeapRegion boundary.)
616 virtual void shrink(size_t expand_bytes);
617 void shrink_helper(size_t expand_bytes);
619 #if TASKQUEUE_STATS
620 static void print_taskqueue_stats_hdr(outputStream* const st = gclog_or_tty);
621 void print_taskqueue_stats(outputStream* const st = gclog_or_tty) const;
622 void reset_taskqueue_stats();
623 #endif // TASKQUEUE_STATS
625 // Schedule the VM operation that will do an evacuation pause to
626 // satisfy an allocation request of word_size. *succeeded will
627 // return whether the VM operation was successful (it did do an
628 // evacuation pause) or not (another thread beat us to it or the GC
629 // locker was active). Given that we should not be holding the
630 // Heap_lock when we enter this method, we will pass the
631 // gc_count_before (i.e., total_collections()) as a parameter since
632 // it has to be read while holding the Heap_lock. Currently, both
633 // methods that call do_collection_pause() release the Heap_lock
634 // before the call, so it's easy to read gc_count_before just before.
635 HeapWord* do_collection_pause(size_t word_size,
636 unsigned int gc_count_before,
637 bool* succeeded);
639 // The guts of the incremental collection pause, executed by the vm
640 // thread. It returns false if it is unable to do the collection due
641 // to the GC locker being active, true otherwise
642 bool do_collection_pause_at_safepoint(double target_pause_time_ms);
644 // Actually do the work of evacuating the collection set.
645 void evacuate_collection_set();
647 // The g1 remembered set of the heap.
648 G1RemSet* _g1_rem_set;
649 // And it's mod ref barrier set, used to track updates for the above.
650 ModRefBarrierSet* _mr_bs;
652 // A set of cards that cover the objects for which the Rsets should be updated
653 // concurrently after the collection.
654 DirtyCardQueueSet _dirty_card_queue_set;
656 // The Heap Region Rem Set Iterator.
657 HeapRegionRemSetIterator** _rem_set_iterator;
659 // The closure used to refine a single card.
660 RefineCardTableEntryClosure* _refine_cte_cl;
662 // A function to check the consistency of dirty card logs.
663 void check_ct_logs_at_safepoint();
665 // A DirtyCardQueueSet that is used to hold cards that contain
666 // references into the current collection set. This is used to
667 // update the remembered sets of the regions in the collection
668 // set in the event of an evacuation failure.
669 DirtyCardQueueSet _into_cset_dirty_card_queue_set;
671 // After a collection pause, make the regions in the CS into free
672 // regions.
673 void free_collection_set(HeapRegion* cs_head);
675 // Abandon the current collection set without recording policy
676 // statistics or updating free lists.
677 void abandon_collection_set(HeapRegion* cs_head);
679 // Applies "scan_non_heap_roots" to roots outside the heap,
680 // "scan_rs" to roots inside the heap (having done "set_region" to
681 // indicate the region in which the root resides), and does "scan_perm"
682 // (setting the generation to the perm generation.) If "scan_rs" is
683 // NULL, then this step is skipped. The "worker_i"
684 // param is for use with parallel roots processing, and should be
685 // the "i" of the calling parallel worker thread's work(i) function.
686 // In the sequential case this param will be ignored.
687 void g1_process_strong_roots(bool collecting_perm_gen,
688 SharedHeap::ScanningOption so,
689 OopClosure* scan_non_heap_roots,
690 OopsInHeapRegionClosure* scan_rs,
691 OopsInGenClosure* scan_perm,
692 int worker_i);
694 // Apply "blk" to all the weak roots of the system. These include
695 // JNI weak roots, the code cache, system dictionary, symbol table,
696 // string table, and referents of reachable weak refs.
697 void g1_process_weak_roots(OopClosure* root_closure,
698 OopClosure* non_root_closure);
700 // Invoke "save_marks" on all heap regions.
701 void save_marks();
703 // Frees a non-humongous region by initializing its contents and
704 // adding it to the free list that's passed as a parameter (this is
705 // usually a local list which will be appended to the master free
706 // list later). The used bytes of freed regions are accumulated in
707 // pre_used. If par is true, the region's RSet will not be freed
708 // up. The assumption is that this will be done later.
709 void free_region(HeapRegion* hr,
710 size_t* pre_used,
711 FreeRegionList* free_list,
712 bool par);
714 // Frees a humongous region by collapsing it into individual regions
715 // and calling free_region() for each of them. The freed regions
716 // will be added to the free list that's passed as a parameter (this
717 // is usually a local list which will be appended to the master free
718 // list later). The used bytes of freed regions are accumulated in
719 // pre_used. If par is true, the region's RSet will not be freed
720 // up. The assumption is that this will be done later.
721 void free_humongous_region(HeapRegion* hr,
722 size_t* pre_used,
723 FreeRegionList* free_list,
724 HumongousRegionSet* humongous_proxy_set,
725 bool par);
727 // The concurrent marker (and the thread it runs in.)
728 ConcurrentMark* _cm;
729 ConcurrentMarkThread* _cmThread;
730 bool _mark_in_progress;
732 // The concurrent refiner.
733 ConcurrentG1Refine* _cg1r;
735 // The parallel task queues
736 RefToScanQueueSet *_task_queues;
738 // True iff a evacuation has failed in the current collection.
739 bool _evacuation_failed;
741 // Set the attribute indicating whether evacuation has failed in the
742 // current collection.
743 void set_evacuation_failed(bool b) { _evacuation_failed = b; }
745 // Failed evacuations cause some logical from-space objects to have
746 // forwarding pointers to themselves. Reset them.
747 void remove_self_forwarding_pointers();
749 // When one is non-null, so is the other. Together, they each pair is
750 // an object with a preserved mark, and its mark value.
751 GrowableArray<oop>* _objs_with_preserved_marks;
752 GrowableArray<markOop>* _preserved_marks_of_objs;
754 // Preserve the mark of "obj", if necessary, in preparation for its mark
755 // word being overwritten with a self-forwarding-pointer.
756 void preserve_mark_if_necessary(oop obj, markOop m);
758 // The stack of evac-failure objects left to be scanned.
759 GrowableArray<oop>* _evac_failure_scan_stack;
760 // The closure to apply to evac-failure objects.
762 OopsInHeapRegionClosure* _evac_failure_closure;
763 // Set the field above.
764 void
765 set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_closure) {
766 _evac_failure_closure = evac_failure_closure;
767 }
769 // Push "obj" on the scan stack.
770 void push_on_evac_failure_scan_stack(oop obj);
771 // Process scan stack entries until the stack is empty.
772 void drain_evac_failure_scan_stack();
773 // True iff an invocation of "drain_scan_stack" is in progress; to
774 // prevent unnecessary recursion.
775 bool _drain_in_progress;
777 // Do any necessary initialization for evacuation-failure handling.
778 // "cl" is the closure that will be used to process evac-failure
779 // objects.
780 void init_for_evac_failure(OopsInHeapRegionClosure* cl);
781 // Do any necessary cleanup for evacuation-failure handling data
782 // structures.
783 void finalize_for_evac_failure();
785 // An attempt to evacuate "obj" has failed; take necessary steps.
786 oop handle_evacuation_failure_par(OopsInHeapRegionClosure* cl, oop obj);
787 void handle_evacuation_failure_common(oop obj, markOop m);
790 // Ensure that the relevant gc_alloc regions are set.
791 void get_gc_alloc_regions();
792 // We're done with GC alloc regions. We are going to tear down the
793 // gc alloc list and remove the gc alloc tag from all the regions on
794 // that list. However, we will also retain the last (i.e., the one
795 // that is half-full) GC alloc region, per GCAllocPurpose, for
796 // possible reuse during the next collection, provided
797 // _retain_gc_alloc_region[] indicates that it should be the
798 // case. Said regions are kept in the _retained_gc_alloc_regions[]
799 // array. If the parameter totally is set, we will not retain any
800 // regions, irrespective of what _retain_gc_alloc_region[]
801 // indicates.
802 void release_gc_alloc_regions(bool totally);
803 #ifndef PRODUCT
804 // Useful for debugging.
805 void print_gc_alloc_regions();
806 #endif // !PRODUCT
808 // Instance of the concurrent mark is_alive closure for embedding
809 // into the reference processor as the is_alive_non_header. This
810 // prevents unnecessary additions to the discovered lists during
811 // concurrent discovery.
812 G1CMIsAliveClosure _is_alive_closure;
814 // ("Weak") Reference processing support
815 ReferenceProcessor* _ref_processor;
817 enum G1H_process_strong_roots_tasks {
818 G1H_PS_mark_stack_oops_do,
819 G1H_PS_refProcessor_oops_do,
820 // Leave this one last.
821 G1H_PS_NumElements
822 };
824 SubTasksDone* _process_strong_tasks;
826 volatile bool _free_regions_coming;
828 public:
830 SubTasksDone* process_strong_tasks() { return _process_strong_tasks; }
832 void set_refine_cte_cl_concurrency(bool concurrent);
834 RefToScanQueue *task_queue(int i) const;
836 // A set of cards where updates happened during the GC
837 DirtyCardQueueSet& dirty_card_queue_set() { return _dirty_card_queue_set; }
839 // A DirtyCardQueueSet that is used to hold cards that contain
840 // references into the current collection set. This is used to
841 // update the remembered sets of the regions in the collection
842 // set in the event of an evacuation failure.
843 DirtyCardQueueSet& into_cset_dirty_card_queue_set()
844 { return _into_cset_dirty_card_queue_set; }
846 // Create a G1CollectedHeap with the specified policy.
847 // Must call the initialize method afterwards.
848 // May not return if something goes wrong.
849 G1CollectedHeap(G1CollectorPolicy* policy);
851 // Initialize the G1CollectedHeap to have the initial and
852 // maximum sizes, permanent generation, and remembered and barrier sets
853 // specified by the policy object.
854 jint initialize();
856 virtual void ref_processing_init();
858 void set_par_threads(int t) {
859 SharedHeap::set_par_threads(t);
860 _process_strong_tasks->set_n_threads(t);
861 }
863 virtual CollectedHeap::Name kind() const {
864 return CollectedHeap::G1CollectedHeap;
865 }
867 // The current policy object for the collector.
868 G1CollectorPolicy* g1_policy() const { return _g1_policy; }
870 // Adaptive size policy. No such thing for g1.
871 virtual AdaptiveSizePolicy* size_policy() { return NULL; }
873 // The rem set and barrier set.
874 G1RemSet* g1_rem_set() const { return _g1_rem_set; }
875 ModRefBarrierSet* mr_bs() const { return _mr_bs; }
877 // The rem set iterator.
878 HeapRegionRemSetIterator* rem_set_iterator(int i) {
879 return _rem_set_iterator[i];
880 }
882 HeapRegionRemSetIterator* rem_set_iterator() {
883 return _rem_set_iterator[0];
884 }
886 unsigned get_gc_time_stamp() {
887 return _gc_time_stamp;
888 }
890 void reset_gc_time_stamp() {
891 _gc_time_stamp = 0;
892 OrderAccess::fence();
893 }
895 void increment_gc_time_stamp() {
896 ++_gc_time_stamp;
897 OrderAccess::fence();
898 }
900 void iterate_dirty_card_closure(CardTableEntryClosure* cl,
901 DirtyCardQueue* into_cset_dcq,
902 bool concurrent, int worker_i);
904 // The shared block offset table array.
905 G1BlockOffsetSharedArray* bot_shared() const { return _bot_shared; }
907 // Reference Processing accessor
908 ReferenceProcessor* ref_processor() { return _ref_processor; }
910 virtual size_t capacity() const;
911 virtual size_t used() const;
912 // This should be called when we're not holding the heap lock. The
913 // result might be a bit inaccurate.
914 size_t used_unlocked() const;
915 size_t recalculate_used() const;
916 #ifndef PRODUCT
917 size_t recalculate_used_regions() const;
918 #endif // PRODUCT
920 // These virtual functions do the actual allocation.
921 // Some heaps may offer a contiguous region for shared non-blocking
922 // allocation, via inlined code (by exporting the address of the top and
923 // end fields defining the extent of the contiguous allocation region.)
924 // But G1CollectedHeap doesn't yet support this.
926 // Return an estimate of the maximum allocation that could be performed
927 // without triggering any collection or expansion activity. In a
928 // generational collector, for example, this is probably the largest
929 // allocation that could be supported (without expansion) in the youngest
930 // generation. It is "unsafe" because no locks are taken; the result
931 // should be treated as an approximation, not a guarantee, for use in
932 // heuristic resizing decisions.
933 virtual size_t unsafe_max_alloc();
935 virtual bool is_maximal_no_gc() const {
936 return _g1_storage.uncommitted_size() == 0;
937 }
939 // The total number of regions in the heap.
940 size_t n_regions();
942 // The number of regions that are completely free.
943 size_t max_regions();
945 // The number of regions that are completely free.
946 size_t free_regions() {
947 return _free_list.length();
948 }
950 // The number of regions that are not completely free.
951 size_t used_regions() { return n_regions() - free_regions(); }
953 // The number of regions available for "regular" expansion.
954 size_t expansion_regions() { return _expansion_regions; }
956 void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
957 void verify_dirty_young_regions() PRODUCT_RETURN;
959 // verify_region_sets() performs verification over the region
960 // lists. It will be compiled in the product code to be used when
961 // necessary (i.e., during heap verification).
962 void verify_region_sets();
964 // verify_region_sets_optional() is planted in the code for
965 // list verification in non-product builds (and it can be enabled in
966 // product builds by definning HEAP_REGION_SET_FORCE_VERIFY to be 1).
967 #if HEAP_REGION_SET_FORCE_VERIFY
968 void verify_region_sets_optional() {
969 verify_region_sets();
970 }
971 #else // HEAP_REGION_SET_FORCE_VERIFY
972 void verify_region_sets_optional() { }
973 #endif // HEAP_REGION_SET_FORCE_VERIFY
975 #ifdef ASSERT
976 bool is_on_master_free_list(HeapRegion* hr) {
977 return hr->containing_set() == &_free_list;
978 }
980 bool is_in_humongous_set(HeapRegion* hr) {
981 return hr->containing_set() == &_humongous_set;
982 }
983 #endif // ASSERT
985 // Wrapper for the region list operations that can be called from
986 // methods outside this class.
988 void secondary_free_list_add_as_tail(FreeRegionList* list) {
989 _secondary_free_list.add_as_tail(list);
990 }
992 void append_secondary_free_list() {
993 _free_list.add_as_head(&_secondary_free_list);
994 }
996 void append_secondary_free_list_if_not_empty_with_lock() {
997 // If the secondary free list looks empty there's no reason to
998 // take the lock and then try to append it.
999 if (!_secondary_free_list.is_empty()) {
1000 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
1001 append_secondary_free_list();
1002 }
1003 }
1005 void set_free_regions_coming();
1006 void reset_free_regions_coming();
1007 bool free_regions_coming() { return _free_regions_coming; }
1008 void wait_while_free_regions_coming();
1010 // Perform a collection of the heap; intended for use in implementing
1011 // "System.gc". This probably implies as full a collection as the
1012 // "CollectedHeap" supports.
1013 virtual void collect(GCCause::Cause cause);
1015 // The same as above but assume that the caller holds the Heap_lock.
1016 void collect_locked(GCCause::Cause cause);
1018 // This interface assumes that it's being called by the
1019 // vm thread. It collects the heap assuming that the
1020 // heap lock is already held and that we are executing in
1021 // the context of the vm thread.
1022 virtual void collect_as_vm_thread(GCCause::Cause cause);
1024 // True iff a evacuation has failed in the most-recent collection.
1025 bool evacuation_failed() { return _evacuation_failed; }
1027 // It will free a region if it has allocated objects in it that are
1028 // all dead. It calls either free_region() or
1029 // free_humongous_region() depending on the type of the region that
1030 // is passed to it.
1031 void free_region_if_empty(HeapRegion* hr,
1032 size_t* pre_used,
1033 FreeRegionList* free_list,
1034 HumongousRegionSet* humongous_proxy_set,
1035 HRRSCleanupTask* hrrs_cleanup_task,
1036 bool par);
1038 // It appends the free list to the master free list and updates the
1039 // master humongous list according to the contents of the proxy
1040 // list. It also adjusts the total used bytes according to pre_used
1041 // (if par is true, it will do so by taking the ParGCRareEvent_lock).
1042 void update_sets_after_freeing_regions(size_t pre_used,
1043 FreeRegionList* free_list,
1044 HumongousRegionSet* humongous_proxy_set,
1045 bool par);
1047 // Returns "TRUE" iff "p" points into the allocated area of the heap.
1048 virtual bool is_in(const void* p) const;
1050 // Return "TRUE" iff the given object address is within the collection
1051 // set.
1052 inline bool obj_in_cs(oop obj);
1054 // Return "TRUE" iff the given object address is in the reserved
1055 // region of g1 (excluding the permanent generation).
1056 bool is_in_g1_reserved(const void* p) const {
1057 return _g1_reserved.contains(p);
1058 }
1060 // Returns a MemRegion that corresponds to the space that has been
1061 // reserved for the heap
1062 MemRegion g1_reserved() {
1063 return _g1_reserved;
1064 }
1066 // Returns a MemRegion that corresponds to the space that has been
1067 // committed in the heap
1068 MemRegion g1_committed() {
1069 return _g1_committed;
1070 }
1072 virtual bool is_in_closed_subset(const void* p) const;
1074 // Dirty card table entries covering a list of young regions.
1075 void dirtyCardsForYoungRegions(CardTableModRefBS* ct_bs, HeapRegion* list);
1077 // This resets the card table to all zeros. It is used after
1078 // a collection pause which used the card table to claim cards.
1079 void cleanUpCardTable();
1081 // Iteration functions.
1083 // Iterate over all the ref-containing fields of all objects, calling
1084 // "cl.do_oop" on each.
1085 virtual void oop_iterate(OopClosure* cl) {
1086 oop_iterate(cl, true);
1087 }
1088 void oop_iterate(OopClosure* cl, bool do_perm);
1090 // Same as above, restricted to a memory region.
1091 virtual void oop_iterate(MemRegion mr, OopClosure* cl) {
1092 oop_iterate(mr, cl, true);
1093 }
1094 void oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm);
1096 // Iterate over all objects, calling "cl.do_object" on each.
1097 virtual void object_iterate(ObjectClosure* cl) {
1098 object_iterate(cl, true);
1099 }
1100 virtual void safe_object_iterate(ObjectClosure* cl) {
1101 object_iterate(cl, true);
1102 }
1103 void object_iterate(ObjectClosure* cl, bool do_perm);
1105 // Iterate over all objects allocated since the last collection, calling
1106 // "cl.do_object" on each. The heap must have been initialized properly
1107 // to support this function, or else this call will fail.
1108 virtual void object_iterate_since_last_GC(ObjectClosure* cl);
1110 // Iterate over all spaces in use in the heap, in ascending address order.
1111 virtual void space_iterate(SpaceClosure* cl);
1113 // Iterate over heap regions, in address order, terminating the
1114 // iteration early if the "doHeapRegion" method returns "true".
1115 void heap_region_iterate(HeapRegionClosure* blk);
1117 // Iterate over heap regions starting with r (or the first region if "r"
1118 // is NULL), in address order, terminating early if the "doHeapRegion"
1119 // method returns "true".
1120 void heap_region_iterate_from(HeapRegion* r, HeapRegionClosure* blk);
1122 // As above but starting from the region at index idx.
1123 void heap_region_iterate_from(int idx, HeapRegionClosure* blk);
1125 HeapRegion* region_at(size_t idx);
1127 // Divide the heap region sequence into "chunks" of some size (the number
1128 // of regions divided by the number of parallel threads times some
1129 // overpartition factor, currently 4). Assumes that this will be called
1130 // in parallel by ParallelGCThreads worker threads with discinct worker
1131 // ids in the range [0..max(ParallelGCThreads-1, 1)], that all parallel
1132 // calls will use the same "claim_value", and that that claim value is
1133 // different from the claim_value of any heap region before the start of
1134 // the iteration. Applies "blk->doHeapRegion" to each of the regions, by
1135 // attempting to claim the first region in each chunk, and, if
1136 // successful, applying the closure to each region in the chunk (and
1137 // setting the claim value of the second and subsequent regions of the
1138 // chunk.) For now requires that "doHeapRegion" always returns "false",
1139 // i.e., that a closure never attempt to abort a traversal.
1140 void heap_region_par_iterate_chunked(HeapRegionClosure* blk,
1141 int worker,
1142 jint claim_value);
1144 // It resets all the region claim values to the default.
1145 void reset_heap_region_claim_values();
1147 #ifdef ASSERT
1148 bool check_heap_region_claim_values(jint claim_value);
1149 #endif // ASSERT
1151 // Iterate over the regions (if any) in the current collection set.
1152 void collection_set_iterate(HeapRegionClosure* blk);
1154 // As above but starting from region r
1155 void collection_set_iterate_from(HeapRegion* r, HeapRegionClosure *blk);
1157 // Returns the first (lowest address) compactible space in the heap.
1158 virtual CompactibleSpace* first_compactible_space();
1160 // A CollectedHeap will contain some number of spaces. This finds the
1161 // space containing a given address, or else returns NULL.
1162 virtual Space* space_containing(const void* addr) const;
1164 // A G1CollectedHeap will contain some number of heap regions. This
1165 // finds the region containing a given address, or else returns NULL.
1166 HeapRegion* heap_region_containing(const void* addr) const;
1168 // Like the above, but requires "addr" to be in the heap (to avoid a
1169 // null-check), and unlike the above, may return an continuing humongous
1170 // region.
1171 HeapRegion* heap_region_containing_raw(const void* addr) const;
1173 // A CollectedHeap is divided into a dense sequence of "blocks"; that is,
1174 // each address in the (reserved) heap is a member of exactly
1175 // one block. The defining characteristic of a block is that it is
1176 // possible to find its size, and thus to progress forward to the next
1177 // block. (Blocks may be of different sizes.) Thus, blocks may
1178 // represent Java objects, or they might be free blocks in a
1179 // free-list-based heap (or subheap), as long as the two kinds are
1180 // distinguishable and the size of each is determinable.
1182 // Returns the address of the start of the "block" that contains the
1183 // address "addr". We say "blocks" instead of "object" since some heaps
1184 // may not pack objects densely; a chunk may either be an object or a
1185 // non-object.
1186 virtual HeapWord* block_start(const void* addr) const;
1188 // Requires "addr" to be the start of a chunk, and returns its size.
1189 // "addr + size" is required to be the start of a new chunk, or the end
1190 // of the active area of the heap.
1191 virtual size_t block_size(const HeapWord* addr) const;
1193 // Requires "addr" to be the start of a block, and returns "TRUE" iff
1194 // the block is an object.
1195 virtual bool block_is_obj(const HeapWord* addr) const;
1197 // Does this heap support heap inspection? (+PrintClassHistogram)
1198 virtual bool supports_heap_inspection() const { return true; }
1200 // Section on thread-local allocation buffers (TLABs)
1201 // See CollectedHeap for semantics.
1203 virtual bool supports_tlab_allocation() const;
1204 virtual size_t tlab_capacity(Thread* thr) const;
1205 virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
1207 // Can a compiler initialize a new object without store barriers?
1208 // This permission only extends from the creation of a new object
1209 // via a TLAB up to the first subsequent safepoint. If such permission
1210 // is granted for this heap type, the compiler promises to call
1211 // defer_store_barrier() below on any slow path allocation of
1212 // a new object for which such initializing store barriers will
1213 // have been elided. G1, like CMS, allows this, but should be
1214 // ready to provide a compensating write barrier as necessary
1215 // if that storage came out of a non-young region. The efficiency
1216 // of this implementation depends crucially on being able to
1217 // answer very efficiently in constant time whether a piece of
1218 // storage in the heap comes from a young region or not.
1219 // See ReduceInitialCardMarks.
1220 virtual bool can_elide_tlab_store_barriers() const {
1221 // 6920090: Temporarily disabled, because of lingering
1222 // instabilities related to RICM with G1. In the
1223 // interim, the option ReduceInitialCardMarksForG1
1224 // below is left solely as a debugging device at least
1225 // until 6920109 fixes the instabilities.
1226 return ReduceInitialCardMarksForG1;
1227 }
1229 virtual bool card_mark_must_follow_store() const {
1230 return true;
1231 }
1233 bool is_in_young(oop obj) {
1234 HeapRegion* hr = heap_region_containing(obj);
1235 return hr != NULL && hr->is_young();
1236 }
1238 // We don't need barriers for initializing stores to objects
1239 // in the young gen: for the SATB pre-barrier, there is no
1240 // pre-value that needs to be remembered; for the remembered-set
1241 // update logging post-barrier, we don't maintain remembered set
1242 // information for young gen objects. Note that non-generational
1243 // G1 does not have any "young" objects, should not elide
1244 // the rs logging barrier and so should always answer false below.
1245 // However, non-generational G1 (-XX:-G1Gen) appears to have
1246 // bit-rotted so was not tested below.
1247 virtual bool can_elide_initializing_store_barrier(oop new_obj) {
1248 // Re 6920090, 6920109 above.
1249 assert(ReduceInitialCardMarksForG1, "Else cannot be here");
1250 assert(G1Gen || !is_in_young(new_obj),
1251 "Non-generational G1 should never return true below");
1252 return is_in_young(new_obj);
1253 }
1255 // Can a compiler elide a store barrier when it writes
1256 // a permanent oop into the heap? Applies when the compiler
1257 // is storing x to the heap, where x->is_perm() is true.
1258 virtual bool can_elide_permanent_oop_store_barriers() const {
1259 // At least until perm gen collection is also G1-ified, at
1260 // which point this should return false.
1261 return true;
1262 }
1264 // The boundary between a "large" and "small" array of primitives, in
1265 // words.
1266 virtual size_t large_typearray_limit();
1268 // Returns "true" iff the given word_size is "very large".
1269 static bool isHumongous(size_t word_size) {
1270 // Note this has to be strictly greater-than as the TLABs
1271 // are capped at the humongous thresold and we want to
1272 // ensure that we don't try to allocate a TLAB as
1273 // humongous and that we don't allocate a humongous
1274 // object in a TLAB.
1275 return word_size > _humongous_object_threshold_in_words;
1276 }
1278 // Update mod union table with the set of dirty cards.
1279 void updateModUnion();
1281 // Set the mod union bits corresponding to the given memRegion. Note
1282 // that this is always a safe operation, since it doesn't clear any
1283 // bits.
1284 void markModUnionRange(MemRegion mr);
1286 // Records the fact that a marking phase is no longer in progress.
1287 void set_marking_complete() {
1288 _mark_in_progress = false;
1289 }
1290 void set_marking_started() {
1291 _mark_in_progress = true;
1292 }
1293 bool mark_in_progress() {
1294 return _mark_in_progress;
1295 }
1297 // Print the maximum heap capacity.
1298 virtual size_t max_capacity() const;
1300 virtual jlong millis_since_last_gc();
1302 // Perform any cleanup actions necessary before allowing a verification.
1303 virtual void prepare_for_verify();
1305 // Perform verification.
1307 // use_prev_marking == true -> use "prev" marking information,
1308 // use_prev_marking == false -> use "next" marking information
1309 // NOTE: Only the "prev" marking information is guaranteed to be
1310 // consistent most of the time, so most calls to this should use
1311 // use_prev_marking == true. Currently, there is only one case where
1312 // this is called with use_prev_marking == false, which is to verify
1313 // the "next" marking information at the end of remark.
1314 void verify(bool allow_dirty, bool silent, bool use_prev_marking);
1316 // Override; it uses the "prev" marking information
1317 virtual void verify(bool allow_dirty, bool silent);
1318 // Default behavior by calling print(tty);
1319 virtual void print() const;
1320 // This calls print_on(st, PrintHeapAtGCExtended).
1321 virtual void print_on(outputStream* st) const;
1322 // If extended is true, it will print out information for all
1323 // regions in the heap by calling print_on_extended(st).
1324 virtual void print_on(outputStream* st, bool extended) const;
1325 virtual void print_on_extended(outputStream* st) const;
1327 virtual void print_gc_threads_on(outputStream* st) const;
1328 virtual void gc_threads_do(ThreadClosure* tc) const;
1330 // Override
1331 void print_tracing_info() const;
1333 // If "addr" is a pointer into the (reserved?) heap, returns a positive
1334 // number indicating the "arena" within the heap in which "addr" falls.
1335 // Or else returns 0.
1336 virtual int addr_to_arena_id(void* addr) const;
1338 // Convenience function to be used in situations where the heap type can be
1339 // asserted to be this type.
1340 static G1CollectedHeap* heap();
1342 void empty_young_list();
1344 void set_region_short_lived_locked(HeapRegion* hr);
1345 // add appropriate methods for any other surv rate groups
1347 YoungList* young_list() { return _young_list; }
1349 // debugging
1350 bool check_young_list_well_formed() {
1351 return _young_list->check_list_well_formed();
1352 }
1354 bool check_young_list_empty(bool check_heap,
1355 bool check_sample = true);
1357 // *** Stuff related to concurrent marking. It's not clear to me that so
1358 // many of these need to be public.
1360 // The functions below are helper functions that a subclass of
1361 // "CollectedHeap" can use in the implementation of its virtual
1362 // functions.
1363 // This performs a concurrent marking of the live objects in a
1364 // bitmap off to the side.
1365 void doConcurrentMark();
1367 // This is called from the marksweep collector which then does
1368 // a concurrent mark and verifies that the results agree with
1369 // the stop the world marking.
1370 void checkConcurrentMark();
1371 void do_sync_mark();
1373 bool isMarkedPrev(oop obj) const;
1374 bool isMarkedNext(oop obj) const;
1376 // use_prev_marking == true -> use "prev" marking information,
1377 // use_prev_marking == false -> use "next" marking information
1378 bool is_obj_dead_cond(const oop obj,
1379 const HeapRegion* hr,
1380 const bool use_prev_marking) const {
1381 if (use_prev_marking) {
1382 return is_obj_dead(obj, hr);
1383 } else {
1384 return is_obj_ill(obj, hr);
1385 }
1386 }
1388 // Determine if an object is dead, given the object and also
1389 // the region to which the object belongs. An object is dead
1390 // iff a) it was not allocated since the last mark and b) it
1391 // is not marked.
1393 bool is_obj_dead(const oop obj, const HeapRegion* hr) const {
1394 return
1395 !hr->obj_allocated_since_prev_marking(obj) &&
1396 !isMarkedPrev(obj);
1397 }
1399 // This is used when copying an object to survivor space.
1400 // If the object is marked live, then we mark the copy live.
1401 // If the object is allocated since the start of this mark
1402 // cycle, then we mark the copy live.
1403 // If the object has been around since the previous mark
1404 // phase, and hasn't been marked yet during this phase,
1405 // then we don't mark it, we just wait for the
1406 // current marking cycle to get to it.
1408 // This function returns true when an object has been
1409 // around since the previous marking and hasn't yet
1410 // been marked during this marking.
1412 bool is_obj_ill(const oop obj, const HeapRegion* hr) const {
1413 return
1414 !hr->obj_allocated_since_next_marking(obj) &&
1415 !isMarkedNext(obj);
1416 }
1418 // Determine if an object is dead, given only the object itself.
1419 // This will find the region to which the object belongs and
1420 // then call the region version of the same function.
1422 // Added if it is in permanent gen it isn't dead.
1423 // Added if it is NULL it isn't dead.
1425 // use_prev_marking == true -> use "prev" marking information,
1426 // use_prev_marking == false -> use "next" marking information
1427 bool is_obj_dead_cond(const oop obj,
1428 const bool use_prev_marking) {
1429 if (use_prev_marking) {
1430 return is_obj_dead(obj);
1431 } else {
1432 return is_obj_ill(obj);
1433 }
1434 }
1436 bool is_obj_dead(const oop obj) {
1437 const HeapRegion* hr = heap_region_containing(obj);
1438 if (hr == NULL) {
1439 if (Universe::heap()->is_in_permanent(obj))
1440 return false;
1441 else if (obj == NULL) return false;
1442 else return true;
1443 }
1444 else return is_obj_dead(obj, hr);
1445 }
1447 bool is_obj_ill(const oop obj) {
1448 const HeapRegion* hr = heap_region_containing(obj);
1449 if (hr == NULL) {
1450 if (Universe::heap()->is_in_permanent(obj))
1451 return false;
1452 else if (obj == NULL) return false;
1453 else return true;
1454 }
1455 else return is_obj_ill(obj, hr);
1456 }
1458 // The following is just to alert the verification code
1459 // that a full collection has occurred and that the
1460 // remembered sets are no longer up to date.
1461 bool _full_collection;
1462 void set_full_collection() { _full_collection = true;}
1463 void clear_full_collection() {_full_collection = false;}
1464 bool full_collection() {return _full_collection;}
1466 ConcurrentMark* concurrent_mark() const { return _cm; }
1467 ConcurrentG1Refine* concurrent_g1_refine() const { return _cg1r; }
1469 // The dirty cards region list is used to record a subset of regions
1470 // whose cards need clearing. The list if populated during the
1471 // remembered set scanning and drained during the card table
1472 // cleanup. Although the methods are reentrant, population/draining
1473 // phases must not overlap. For synchronization purposes the last
1474 // element on the list points to itself.
1475 HeapRegion* _dirty_cards_region_list;
1476 void push_dirty_cards_region(HeapRegion* hr);
1477 HeapRegion* pop_dirty_cards_region();
1479 public:
1480 void stop_conc_gc_threads();
1482 // <NEW PREDICTION>
1484 double predict_region_elapsed_time_ms(HeapRegion* hr, bool young);
1485 void check_if_region_is_too_expensive(double predicted_time_ms);
1486 size_t pending_card_num();
1487 size_t max_pending_card_num();
1488 size_t cards_scanned();
1490 // </NEW PREDICTION>
1492 protected:
1493 size_t _max_heap_capacity;
1494 };
1496 #define use_local_bitmaps 1
1497 #define verify_local_bitmaps 0
1498 #define oop_buffer_length 256
1500 #ifndef PRODUCT
1501 class GCLabBitMap;
1502 class GCLabBitMapClosure: public BitMapClosure {
1503 private:
1504 ConcurrentMark* _cm;
1505 GCLabBitMap* _bitmap;
1507 public:
1508 GCLabBitMapClosure(ConcurrentMark* cm,
1509 GCLabBitMap* bitmap) {
1510 _cm = cm;
1511 _bitmap = bitmap;
1512 }
1514 virtual bool do_bit(size_t offset);
1515 };
1516 #endif // !PRODUCT
1518 class GCLabBitMap: public BitMap {
1519 private:
1520 ConcurrentMark* _cm;
1522 int _shifter;
1523 size_t _bitmap_word_covers_words;
1525 // beginning of the heap
1526 HeapWord* _heap_start;
1528 // this is the actual start of the GCLab
1529 HeapWord* _real_start_word;
1531 // this is the actual end of the GCLab
1532 HeapWord* _real_end_word;
1534 // this is the first word, possibly located before the actual start
1535 // of the GCLab, that corresponds to the first bit of the bitmap
1536 HeapWord* _start_word;
1538 // size of a GCLab in words
1539 size_t _gclab_word_size;
1541 static int shifter() {
1542 return MinObjAlignment - 1;
1543 }
1545 // how many heap words does a single bitmap word corresponds to?
1546 static size_t bitmap_word_covers_words() {
1547 return BitsPerWord << shifter();
1548 }
1550 size_t gclab_word_size() const {
1551 return _gclab_word_size;
1552 }
1554 // Calculates actual GCLab size in words
1555 size_t gclab_real_word_size() const {
1556 return bitmap_size_in_bits(pointer_delta(_real_end_word, _start_word))
1557 / BitsPerWord;
1558 }
1560 static size_t bitmap_size_in_bits(size_t gclab_word_size) {
1561 size_t bits_in_bitmap = gclab_word_size >> shifter();
1562 // We are going to ensure that the beginning of a word in this
1563 // bitmap also corresponds to the beginning of a word in the
1564 // global marking bitmap. To handle the case where a GCLab
1565 // starts from the middle of the bitmap, we need to add enough
1566 // space (i.e. up to a bitmap word) to ensure that we have
1567 // enough bits in the bitmap.
1568 return bits_in_bitmap + BitsPerWord - 1;
1569 }
1570 public:
1571 GCLabBitMap(HeapWord* heap_start, size_t gclab_word_size)
1572 : BitMap(bitmap_size_in_bits(gclab_word_size)),
1573 _cm(G1CollectedHeap::heap()->concurrent_mark()),
1574 _shifter(shifter()),
1575 _bitmap_word_covers_words(bitmap_word_covers_words()),
1576 _heap_start(heap_start),
1577 _gclab_word_size(gclab_word_size),
1578 _real_start_word(NULL),
1579 _real_end_word(NULL),
1580 _start_word(NULL)
1581 {
1582 guarantee( size_in_words() >= bitmap_size_in_words(),
1583 "just making sure");
1584 }
1586 inline unsigned heapWordToOffset(HeapWord* addr) {
1587 unsigned offset = (unsigned) pointer_delta(addr, _start_word) >> _shifter;
1588 assert(offset < size(), "offset should be within bounds");
1589 return offset;
1590 }
1592 inline HeapWord* offsetToHeapWord(size_t offset) {
1593 HeapWord* addr = _start_word + (offset << _shifter);
1594 assert(_real_start_word <= addr && addr < _real_end_word, "invariant");
1595 return addr;
1596 }
1598 bool fields_well_formed() {
1599 bool ret1 = (_real_start_word == NULL) &&
1600 (_real_end_word == NULL) &&
1601 (_start_word == NULL);
1602 if (ret1)
1603 return true;
1605 bool ret2 = _real_start_word >= _start_word &&
1606 _start_word < _real_end_word &&
1607 (_real_start_word + _gclab_word_size) == _real_end_word &&
1608 (_start_word + _gclab_word_size + _bitmap_word_covers_words)
1609 > _real_end_word;
1610 return ret2;
1611 }
1613 inline bool mark(HeapWord* addr) {
1614 guarantee(use_local_bitmaps, "invariant");
1615 assert(fields_well_formed(), "invariant");
1617 if (addr >= _real_start_word && addr < _real_end_word) {
1618 assert(!isMarked(addr), "should not have already been marked");
1620 // first mark it on the bitmap
1621 at_put(heapWordToOffset(addr), true);
1623 return true;
1624 } else {
1625 return false;
1626 }
1627 }
1629 inline bool isMarked(HeapWord* addr) {
1630 guarantee(use_local_bitmaps, "invariant");
1631 assert(fields_well_formed(), "invariant");
1633 return at(heapWordToOffset(addr));
1634 }
1636 void set_buffer(HeapWord* start) {
1637 guarantee(use_local_bitmaps, "invariant");
1638 clear();
1640 assert(start != NULL, "invariant");
1641 _real_start_word = start;
1642 _real_end_word = start + _gclab_word_size;
1644 size_t diff =
1645 pointer_delta(start, _heap_start) % _bitmap_word_covers_words;
1646 _start_word = start - diff;
1648 assert(fields_well_formed(), "invariant");
1649 }
1651 #ifndef PRODUCT
1652 void verify() {
1653 // verify that the marks have been propagated
1654 GCLabBitMapClosure cl(_cm, this);
1655 iterate(&cl);
1656 }
1657 #endif // PRODUCT
1659 void retire() {
1660 guarantee(use_local_bitmaps, "invariant");
1661 assert(fields_well_formed(), "invariant");
1663 if (_start_word != NULL) {
1664 CMBitMap* mark_bitmap = _cm->nextMarkBitMap();
1666 // this means that the bitmap was set up for the GCLab
1667 assert(_real_start_word != NULL && _real_end_word != NULL, "invariant");
1669 mark_bitmap->mostly_disjoint_range_union(this,
1670 0, // always start from the start of the bitmap
1671 _start_word,
1672 gclab_real_word_size());
1673 _cm->grayRegionIfNecessary(MemRegion(_real_start_word, _real_end_word));
1675 #ifndef PRODUCT
1676 if (use_local_bitmaps && verify_local_bitmaps)
1677 verify();
1678 #endif // PRODUCT
1679 } else {
1680 assert(_real_start_word == NULL && _real_end_word == NULL, "invariant");
1681 }
1682 }
1684 size_t bitmap_size_in_words() const {
1685 return (bitmap_size_in_bits(gclab_word_size()) + BitsPerWord - 1) / BitsPerWord;
1686 }
1688 };
1690 class G1ParGCAllocBuffer: public ParGCAllocBuffer {
1691 private:
1692 bool _retired;
1693 bool _during_marking;
1694 GCLabBitMap _bitmap;
1696 public:
1697 G1ParGCAllocBuffer(size_t gclab_word_size) :
1698 ParGCAllocBuffer(gclab_word_size),
1699 _during_marking(G1CollectedHeap::heap()->mark_in_progress()),
1700 _bitmap(G1CollectedHeap::heap()->reserved_region().start(), gclab_word_size),
1701 _retired(false)
1702 { }
1704 inline bool mark(HeapWord* addr) {
1705 guarantee(use_local_bitmaps, "invariant");
1706 assert(_during_marking, "invariant");
1707 return _bitmap.mark(addr);
1708 }
1710 inline void set_buf(HeapWord* buf) {
1711 if (use_local_bitmaps && _during_marking)
1712 _bitmap.set_buffer(buf);
1713 ParGCAllocBuffer::set_buf(buf);
1714 _retired = false;
1715 }
1717 inline void retire(bool end_of_gc, bool retain) {
1718 if (_retired)
1719 return;
1720 if (use_local_bitmaps && _during_marking) {
1721 _bitmap.retire();
1722 }
1723 ParGCAllocBuffer::retire(end_of_gc, retain);
1724 _retired = true;
1725 }
1726 };
1728 class G1ParScanThreadState : public StackObj {
1729 protected:
1730 G1CollectedHeap* _g1h;
1731 RefToScanQueue* _refs;
1732 DirtyCardQueue _dcq;
1733 CardTableModRefBS* _ct_bs;
1734 G1RemSet* _g1_rem;
1736 G1ParGCAllocBuffer _surviving_alloc_buffer;
1737 G1ParGCAllocBuffer _tenured_alloc_buffer;
1738 G1ParGCAllocBuffer* _alloc_buffers[GCAllocPurposeCount];
1739 ageTable _age_table;
1741 size_t _alloc_buffer_waste;
1742 size_t _undo_waste;
1744 OopsInHeapRegionClosure* _evac_failure_cl;
1745 G1ParScanHeapEvacClosure* _evac_cl;
1746 G1ParScanPartialArrayClosure* _partial_scan_cl;
1748 int _hash_seed;
1749 int _queue_num;
1751 size_t _term_attempts;
1753 double _start;
1754 double _start_strong_roots;
1755 double _strong_roots_time;
1756 double _start_term;
1757 double _term_time;
1759 // Map from young-age-index (0 == not young, 1 is youngest) to
1760 // surviving words. base is what we get back from the malloc call
1761 size_t* _surviving_young_words_base;
1762 // this points into the array, as we use the first few entries for padding
1763 size_t* _surviving_young_words;
1765 #define PADDING_ELEM_NUM (DEFAULT_CACHE_LINE_SIZE / sizeof(size_t))
1767 void add_to_alloc_buffer_waste(size_t waste) { _alloc_buffer_waste += waste; }
1769 void add_to_undo_waste(size_t waste) { _undo_waste += waste; }
1771 DirtyCardQueue& dirty_card_queue() { return _dcq; }
1772 CardTableModRefBS* ctbs() { return _ct_bs; }
1774 template <class T> void immediate_rs_update(HeapRegion* from, T* p, int tid) {
1775 if (!from->is_survivor()) {
1776 _g1_rem->par_write_ref(from, p, tid);
1777 }
1778 }
1780 template <class T> void deferred_rs_update(HeapRegion* from, T* p, int tid) {
1781 // If the new value of the field points to the same region or
1782 // is the to-space, we don't need to include it in the Rset updates.
1783 if (!from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) && !from->is_survivor()) {
1784 size_t card_index = ctbs()->index_for(p);
1785 // If the card hasn't been added to the buffer, do it.
1786 if (ctbs()->mark_card_deferred(card_index)) {
1787 dirty_card_queue().enqueue((jbyte*)ctbs()->byte_for_index(card_index));
1788 }
1789 }
1790 }
1792 public:
1793 G1ParScanThreadState(G1CollectedHeap* g1h, int queue_num);
1795 ~G1ParScanThreadState() {
1796 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words_base);
1797 }
1799 RefToScanQueue* refs() { return _refs; }
1800 ageTable* age_table() { return &_age_table; }
1802 G1ParGCAllocBuffer* alloc_buffer(GCAllocPurpose purpose) {
1803 return _alloc_buffers[purpose];
1804 }
1806 size_t alloc_buffer_waste() const { return _alloc_buffer_waste; }
1807 size_t undo_waste() const { return _undo_waste; }
1809 #ifdef ASSERT
1810 bool verify_ref(narrowOop* ref) const;
1811 bool verify_ref(oop* ref) const;
1812 bool verify_task(StarTask ref) const;
1813 #endif // ASSERT
1815 template <class T> void push_on_queue(T* ref) {
1816 assert(verify_ref(ref), "sanity");
1817 refs()->push(ref);
1818 }
1820 template <class T> void update_rs(HeapRegion* from, T* p, int tid) {
1821 if (G1DeferredRSUpdate) {
1822 deferred_rs_update(from, p, tid);
1823 } else {
1824 immediate_rs_update(from, p, tid);
1825 }
1826 }
1828 HeapWord* allocate_slow(GCAllocPurpose purpose, size_t word_sz) {
1830 HeapWord* obj = NULL;
1831 size_t gclab_word_size = _g1h->desired_plab_sz(purpose);
1832 if (word_sz * 100 < gclab_word_size * ParallelGCBufferWastePct) {
1833 G1ParGCAllocBuffer* alloc_buf = alloc_buffer(purpose);
1834 assert(gclab_word_size == alloc_buf->word_sz(),
1835 "dynamic resizing is not supported");
1836 add_to_alloc_buffer_waste(alloc_buf->words_remaining());
1837 alloc_buf->retire(false, false);
1839 HeapWord* buf = _g1h->par_allocate_during_gc(purpose, gclab_word_size);
1840 if (buf == NULL) return NULL; // Let caller handle allocation failure.
1841 // Otherwise.
1842 alloc_buf->set_buf(buf);
1844 obj = alloc_buf->allocate(word_sz);
1845 assert(obj != NULL, "buffer was definitely big enough...");
1846 } else {
1847 obj = _g1h->par_allocate_during_gc(purpose, word_sz);
1848 }
1849 return obj;
1850 }
1852 HeapWord* allocate(GCAllocPurpose purpose, size_t word_sz) {
1853 HeapWord* obj = alloc_buffer(purpose)->allocate(word_sz);
1854 if (obj != NULL) return obj;
1855 return allocate_slow(purpose, word_sz);
1856 }
1858 void undo_allocation(GCAllocPurpose purpose, HeapWord* obj, size_t word_sz) {
1859 if (alloc_buffer(purpose)->contains(obj)) {
1860 assert(alloc_buffer(purpose)->contains(obj + word_sz - 1),
1861 "should contain whole object");
1862 alloc_buffer(purpose)->undo_allocation(obj, word_sz);
1863 } else {
1864 CollectedHeap::fill_with_object(obj, word_sz);
1865 add_to_undo_waste(word_sz);
1866 }
1867 }
1869 void set_evac_failure_closure(OopsInHeapRegionClosure* evac_failure_cl) {
1870 _evac_failure_cl = evac_failure_cl;
1871 }
1872 OopsInHeapRegionClosure* evac_failure_closure() {
1873 return _evac_failure_cl;
1874 }
1876 void set_evac_closure(G1ParScanHeapEvacClosure* evac_cl) {
1877 _evac_cl = evac_cl;
1878 }
1880 void set_partial_scan_closure(G1ParScanPartialArrayClosure* partial_scan_cl) {
1881 _partial_scan_cl = partial_scan_cl;
1882 }
1884 int* hash_seed() { return &_hash_seed; }
1885 int queue_num() { return _queue_num; }
1887 size_t term_attempts() const { return _term_attempts; }
1888 void note_term_attempt() { _term_attempts++; }
1890 void start_strong_roots() {
1891 _start_strong_roots = os::elapsedTime();
1892 }
1893 void end_strong_roots() {
1894 _strong_roots_time += (os::elapsedTime() - _start_strong_roots);
1895 }
1896 double strong_roots_time() const { return _strong_roots_time; }
1898 void start_term_time() {
1899 note_term_attempt();
1900 _start_term = os::elapsedTime();
1901 }
1902 void end_term_time() {
1903 _term_time += (os::elapsedTime() - _start_term);
1904 }
1905 double term_time() const { return _term_time; }
1907 double elapsed_time() const {
1908 return os::elapsedTime() - _start;
1909 }
1911 static void
1912 print_termination_stats_hdr(outputStream* const st = gclog_or_tty);
1913 void
1914 print_termination_stats(int i, outputStream* const st = gclog_or_tty) const;
1916 size_t* surviving_young_words() {
1917 // We add on to hide entry 0 which accumulates surviving words for
1918 // age -1 regions (i.e. non-young ones)
1919 return _surviving_young_words;
1920 }
1922 void retire_alloc_buffers() {
1923 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
1924 size_t waste = _alloc_buffers[ap]->words_remaining();
1925 add_to_alloc_buffer_waste(waste);
1926 _alloc_buffers[ap]->retire(true, false);
1927 }
1928 }
1930 template <class T> void deal_with_reference(T* ref_to_scan) {
1931 if (has_partial_array_mask(ref_to_scan)) {
1932 _partial_scan_cl->do_oop_nv(ref_to_scan);
1933 } else {
1934 // Note: we can use "raw" versions of "region_containing" because
1935 // "obj_to_scan" is definitely in the heap, and is not in a
1936 // humongous region.
1937 HeapRegion* r = _g1h->heap_region_containing_raw(ref_to_scan);
1938 _evac_cl->set_region(r);
1939 _evac_cl->do_oop_nv(ref_to_scan);
1940 }
1941 }
1943 void deal_with_reference(StarTask ref) {
1944 assert(verify_task(ref), "sanity");
1945 if (ref.is_narrow()) {
1946 deal_with_reference((narrowOop*)ref);
1947 } else {
1948 deal_with_reference((oop*)ref);
1949 }
1950 }
1952 public:
1953 void trim_queue();
1954 };
1956 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP