diff -r 000000000000 -r a61af66fc99e src/share/vm/memory/generation.hpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/memory/generation.hpp Sat Dec 01 00:00:00 2007 +0000 @@ -0,0 +1,710 @@ +/* + * Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. + * + * This code is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + */ + +// A Generation models a heap area for similarly-aged objects. +// It will contain one ore more spaces holding the actual objects. +// +// The Generation class hierarchy: +// +// Generation - abstract base class +// - DefNewGeneration - allocation area (copy collected) +// - ParNewGeneration - a DefNewGeneration that is collected by +// several threads +// - CardGeneration - abstract class adding offset array behavior +// - OneContigSpaceCardGeneration - abstract class holding a single +// contiguous space with card marking +// - TenuredGeneration - tenured (old object) space (markSweepCompact) +// - CompactingPermGenGen - reflective object area (klasses, methods, symbols, ...) +// - ConcurrentMarkSweepGeneration - Mostly Concurrent Mark Sweep Generation +// (Detlefs-Printezis refinement of +// Boehm-Demers-Schenker) +// +// The system configurations currently allowed are: +// +// DefNewGeneration + TenuredGeneration + PermGeneration +// DefNewGeneration + ConcurrentMarkSweepGeneration + ConcurrentMarkSweepPermGen +// +// ParNewGeneration + TenuredGeneration + PermGeneration +// ParNewGeneration + ConcurrentMarkSweepGeneration + ConcurrentMarkSweepPermGen +// + +class DefNewGeneration; +class GenerationSpec; +class CompactibleSpace; +class ContiguousSpace; +class CompactPoint; +class OopsInGenClosure; +class OopClosure; +class ScanClosure; +class FastScanClosure; +class GenCollectedHeap; +class GenRemSet; +class GCStats; + +// A "ScratchBlock" represents a block of memory in one generation usable by +// another. It represents "num_words" free words, starting at and including +// the address of "this". +struct ScratchBlock { + ScratchBlock* next; + size_t num_words; + HeapWord scratch_space[1]; // Actually, of size "num_words-2" (assuming + // first two fields are word-sized.) +}; + + +class Generation: public CHeapObj { + friend class VMStructs; + private: + jlong _time_of_last_gc; // time when last gc on this generation happened (ms) + MemRegion _prev_used_region; // for collectors that want to "remember" a value for + // used region at some specific point during collection. + + protected: + // Minimum and maximum addresses for memory reserved (not necessarily + // committed) for generation. + // Used by card marking code. Must not overlap with address ranges of + // other generations. + MemRegion _reserved; + + // Memory area reserved for generation + VirtualSpace _virtual_space; + + // Level in the generation hierarchy. + int _level; + + // ("Weak") Reference processing support + ReferenceProcessor* _ref_processor; + + // Performance Counters + CollectorCounters* _gc_counters; + + // Statistics for garbage collection + GCStats* _gc_stats; + + // Returns the next generation in the configuration, or else NULL if this + // is the highest generation. + Generation* next_gen() const; + + // Initialize the generation. + Generation(ReservedSpace rs, size_t initial_byte_size, int level); + + // Apply "cl->do_oop" to (the address of) (exactly) all the ref fields in + // "sp" that point into younger generations. + // The iteration is only over objects allocated at the start of the + // iterations; objects allocated as a result of applying the closure are + // not included. + void younger_refs_in_space_iterate(Space* sp, OopsInGenClosure* cl); + + public: + // The set of possible generation kinds. + enum Name { + ASParNew, + ASConcurrentMarkSweep, + DefNew, + ParNew, + MarkSweepCompact, + ConcurrentMarkSweep, + Other + }; + + enum SomePublicConstants { + // Generations are GenGrain-aligned and have size that are multiples of + // GenGrain. + LogOfGenGrain = 16, + GenGrain = 1 << LogOfGenGrain + }; + + // allocate and initialize ("weak") refs processing support + virtual void ref_processor_init(); + void set_ref_processor(ReferenceProcessor* rp) { + assert(_ref_processor == NULL, "clobbering existing _ref_processor"); + _ref_processor = rp; + } + + virtual Generation::Name kind() { return Generation::Other; } + GenerationSpec* spec(); + + // This properly belongs in the collector, but for now this + // will do. + virtual bool refs_discovery_is_atomic() const { return true; } + virtual bool refs_discovery_is_mt() const { return false; } + + // Space enquiries (results in bytes) + virtual size_t capacity() const = 0; // The maximum number of object bytes the + // generation can currently hold. + virtual size_t used() const = 0; // The number of used bytes in the gen. + virtual size_t free() const = 0; // The number of free bytes in the gen. + + // Support for java.lang.Runtime.maxMemory(); see CollectedHeap. + // Returns the total number of bytes available in a generation + // for the allocation of objects. + virtual size_t max_capacity() const; + + // If this is a young generation, the maximum number of bytes that can be + // allocated in this generation before a GC is triggered. + virtual size_t capacity_before_gc() const { return 0; } + + // The largest number of contiguous free bytes in the generation, + // including expansion (Assumes called at a safepoint.) + virtual size_t contiguous_available() const = 0; + // The largest number of contiguous free bytes in this or any higher generation. + virtual size_t max_contiguous_available() const; + + // Returns true if promotions of the specified amount can + // be attempted safely (without a vm failure). + // Promotion of the full amount is not guaranteed but + // can be attempted. + // younger_handles_promotion_failure + // is true if the younger generation handles a promotion + // failure. + virtual bool promotion_attempt_is_safe(size_t promotion_in_bytes, + bool younger_handles_promotion_failure) const; + + // Return an estimate of the maximum allocation that could be performed + // in the generation without triggering any collection or expansion + // activity. It is "unsafe" because no locks are taken; the result + // should be treated as an approximation, not a guarantee, for use in + // heuristic resizing decisions. + virtual size_t unsafe_max_alloc_nogc() const = 0; + + // Returns true if this generation cannot be expanded further + // without a GC. Override as appropriate. + virtual bool is_maximal_no_gc() const { + return _virtual_space.uncommitted_size() == 0; + } + + MemRegion reserved() const { return _reserved; } + + // Returns a region guaranteed to contain all the objects in the + // generation. + virtual MemRegion used_region() const { return _reserved; } + + MemRegion prev_used_region() const { return _prev_used_region; } + virtual void save_used_region() { _prev_used_region = used_region(); } + + // Returns "TRUE" iff "p" points into an allocated object in the generation. + // For some kinds of generations, this may be an expensive operation. + // To avoid performance problems stemming from its inadvertent use in + // product jvm's, we restrict its use to assertion checking or + // verification only. + virtual bool is_in(const void* p) const; + + /* Returns "TRUE" iff "p" points into the reserved area of the generation. */ + bool is_in_reserved(const void* p) const { + return _reserved.contains(p); + } + + // Check that the generation kind is DefNewGeneration or a sub + // class of DefNewGeneration and return a DefNewGeneration* + DefNewGeneration* as_DefNewGeneration(); + + // If some space in the generation contains the given "addr", return a + // pointer to that space, else return "NULL". + virtual Space* space_containing(const void* addr) const; + + // Iteration - do not use for time critical operations + virtual void space_iterate(SpaceClosure* blk, bool usedOnly = false) = 0; + + // Returns the first space, if any, in the generation that can participate + // in compaction, or else "NULL". + virtual CompactibleSpace* first_compaction_space() const = 0; + + // Returns "true" iff this generation should be used to allocate an + // object of the given size. Young generations might + // wish to exclude very large objects, for example, since, if allocated + // often, they would greatly increase the frequency of young-gen + // collection. + virtual bool should_allocate(size_t word_size, bool is_tlab) { + bool result = false; + size_t overflow_limit = (size_t)1 << (BitsPerSize_t - LogHeapWordSize); + if (!is_tlab || supports_tlab_allocation()) { + result = (word_size > 0) && (word_size < overflow_limit); + } + return result; + } + + // Allocate and returns a block of the requested size, or returns "NULL". + // Assumes the caller has done any necessary locking. + virtual HeapWord* allocate(size_t word_size, bool is_tlab) = 0; + + // Like "allocate", but performs any necessary locking internally. + virtual HeapWord* par_allocate(size_t word_size, bool is_tlab) = 0; + + // A 'younger' gen has reached an allocation limit, and uses this to notify + // the next older gen. The return value is a new limit, or NULL if none. The + // caller must do the necessary locking. + virtual HeapWord* allocation_limit_reached(Space* space, HeapWord* top, + size_t word_size) { + return NULL; + } + + // Some generation may offer a region for shared, contiguous allocation, + // via inlined code (by exporting the address of the top and end fields + // defining the extent of the contiguous allocation region.) + + // This function returns "true" iff the heap supports this kind of + // allocation. (More precisely, this means the style of allocation that + // increments *top_addr()" with a CAS.) (Default is "no".) + // A generation that supports this allocation style must use lock-free + // allocation for *all* allocation, since there are times when lock free + // allocation will be concurrent with plain "allocate" calls. + virtual bool supports_inline_contig_alloc() const { return false; } + + // These functions return the addresses of the fields that define the + // boundaries of the contiguous allocation area. (These fields should be + // physicall near to one another.) + virtual HeapWord** top_addr() const { return NULL; } + virtual HeapWord** end_addr() const { return NULL; } + + // Thread-local allocation buffers + virtual bool supports_tlab_allocation() const { return false; } + virtual size_t tlab_capacity() const { + guarantee(false, "Generation doesn't support thread local allocation buffers"); + return 0; + } + virtual size_t unsafe_max_tlab_alloc() const { + guarantee(false, "Generation doesn't support thread local allocation buffers"); + return 0; + } + + // "obj" is the address of an object in a younger generation. Allocate space + // for "obj" in the current (or some higher) generation, and copy "obj" into + // the newly allocated space, if possible, returning the result (or NULL if + // the allocation failed). + // + // The "obj_size" argument is just obj->size(), passed along so the caller can + // avoid repeating the virtual call to retrieve it. + // + // The "ref" argument, if non-NULL, is the address of some reference to "obj" + // (that is "*ref == obj"); some generations may use this information to, for + // example, influence placement decisions. + // + // The default implementation ignores "ref" and calls allocate(). + virtual oop promote(oop obj, size_t obj_size, oop* ref); + + // Thread "thread_num" (0 <= i < ParalleGCThreads) wants to promote + // object "obj", whose original mark word was "m", and whose size is + // "word_sz". If possible, allocate space for "obj", copy obj into it + // (taking care to copy "m" into the mark word when done, since the mark + // word of "obj" may have been overwritten with a forwarding pointer, and + // also taking care to copy the klass pointer *last*. Returns the new + // object if successful, or else NULL. + virtual oop par_promote(int thread_num, + oop obj, markOop m, size_t word_sz); + + // Undo, if possible, the most recent par_promote_alloc allocation by + // "thread_num" ("obj", of "word_sz"). + virtual void par_promote_alloc_undo(int thread_num, + HeapWord* obj, size_t word_sz); + + // Informs the current generation that all par_promote_alloc's in the + // collection have been completed; any supporting data structures can be + // reset. Default is to do nothing. + virtual void par_promote_alloc_done(int thread_num) {} + + // Informs the current generation that all oop_since_save_marks_iterates + // performed by "thread_num" in the current collection, if any, have been + // completed; any supporting data structures can be reset. Default is to + // do nothing. + virtual void par_oop_since_save_marks_iterate_done(int thread_num) {} + + // This generation will collect all younger generations + // during a full collection. + virtual bool full_collects_younger_generations() const { return false; } + + // This generation does in-place marking, meaning that mark words + // are mutated during the marking phase and presumably reinitialized + // to a canonical value after the GC. This is currently used by the + // biased locking implementation to determine whether additional + // work is required during the GC prologue and epilogue. + virtual bool performs_in_place_marking() const { return true; } + + // Returns "true" iff collect() should subsequently be called on this + // this generation. See comment below. + // This is a generic implementation which can be overridden. + // + // Note: in the current (1.4) implementation, when genCollectedHeap's + // incremental_collection_will_fail flag is set, all allocations are + // slow path (the only fast-path place to allocate is DefNew, which + // will be full if the flag is set). + // Thus, older generations which collect younger generations should + // test this flag and collect if it is set. + virtual bool should_collect(bool full, + size_t word_size, + bool is_tlab) { + return (full || should_allocate(word_size, is_tlab)); + } + + // Perform a garbage collection. + // If full is true attempt a full garbage collection of this generation. + // Otherwise, attempting to (at least) free enough space to support an + // allocation of the given "word_size". + virtual void collect(bool full, + bool clear_all_soft_refs, + size_t word_size, + bool is_tlab) = 0; + + // Perform a heap collection, attempting to create (at least) enough + // space to support an allocation of the given "word_size". If + // successful, perform the allocation and return the resulting + // "oop" (initializing the allocated block). If the allocation is + // still unsuccessful, return "NULL". + virtual HeapWord* expand_and_allocate(size_t word_size, + bool is_tlab, + bool parallel = false) = 0; + + // Some generations may require some cleanup or preparation actions before + // allowing a collection. The default is to do nothing. + virtual void gc_prologue(bool full) {}; + + // Some generations may require some cleanup actions after a collection. + // The default is to do nothing. + virtual void gc_epilogue(bool full) {}; + + // Some generations may need to be "fixed-up" after some allocation + // activity to make them parsable again. The default is to do nothing. + virtual void ensure_parsability() {}; + + // Time (in ms) when we were last collected or now if a collection is + // in progress. + virtual jlong time_of_last_gc(jlong now) { + // XXX See note in genCollectedHeap::millis_since_last_gc() + NOT_PRODUCT( + if (now < _time_of_last_gc) { + warning("time warp: %d to %d", _time_of_last_gc, now); + } + ) + return _time_of_last_gc; + } + + virtual void update_time_of_last_gc(jlong now) { + _time_of_last_gc = now; + } + + // Generations may keep statistics about collection. This + // method updates those statistics. current_level is + // the level of the collection that has most recently + // occurred. This allows the generation to decide what + // statistics are valid to collect. For example, the + // generation can decide to gather the amount of promoted data + // if the collection of the younger generations has completed. + GCStats* gc_stats() const { return _gc_stats; } + virtual void update_gc_stats(int current_level, bool full) {} + + // Mark sweep support phase2 + virtual void prepare_for_compaction(CompactPoint* cp); + // Mark sweep support phase3 + virtual void pre_adjust_pointers() {ShouldNotReachHere();} + virtual void adjust_pointers(); + // Mark sweep support phase4 + virtual void compact(); + virtual void post_compact() {ShouldNotReachHere();} + + // Support for CMS's rescan. In this general form we return a pointer + // to an abstract object that can be used, based on specific previously + // decided protocols, to exchange information between generations, + // information that may be useful for speeding up certain types of + // garbage collectors. A NULL value indicates to the client that + // no data recording is expected by the provider. The data-recorder is + // expected to be GC worker thread-local, with the worker index + // indicated by "thr_num". + virtual void* get_data_recorder(int thr_num) { return NULL; } + + // Some generations may require some cleanup actions before allowing + // a verification. + virtual void prepare_for_verify() {}; + + // Accessing "marks". + + // This function gives a generation a chance to note a point between + // collections. For example, a contiguous generation might note the + // beginning allocation point post-collection, which might allow some later + // operations to be optimized. + virtual void save_marks() {} + + // This function allows generations to initialize any "saved marks". That + // is, should only be called when the generation is empty. + virtual void reset_saved_marks() {} + + // This function is "true" iff any no allocations have occurred in the + // generation since the last call to "save_marks". + virtual bool no_allocs_since_save_marks() = 0; + + // Apply "cl->apply" to (the addresses of) all reference fields in objects + // allocated in the current generation since the last call to "save_marks". + // If more objects are allocated in this generation as a result of applying + // the closure, iterates over reference fields in those objects as well. + // Calls "save_marks" at the end of the iteration. + // General signature... + virtual void oop_since_save_marks_iterate_v(OopsInGenClosure* cl) = 0; + // ...and specializations for de-virtualization. (The general + // implemention of the _nv versions call the virtual version. + // Note that the _nv suffix is not really semantically necessary, + // but it avoids some not-so-useful warnings on Solaris.) +#define Generation_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ + virtual void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl) { \ + oop_since_save_marks_iterate_v((OopsInGenClosure*)cl); \ + } + SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(Generation_SINCE_SAVE_MARKS_DECL) + +#undef Generation_SINCE_SAVE_MARKS_DECL + + // The "requestor" generation is performing some garbage collection + // action for which it would be useful to have scratch space. If + // the target is not the requestor, no gc actions will be required + // of the target. The requestor promises to allocate no more than + // "max_alloc_words" in the target generation (via promotion say, + // if the requestor is a young generation and the target is older). + // If the target generation can provide any scratch space, it adds + // it to "list", leaving "list" pointing to the head of the + // augmented list. The default is to offer no space. + virtual void contribute_scratch(ScratchBlock*& list, Generation* requestor, + size_t max_alloc_words) {} + + // When an older generation has been collected, and perhaps resized, + // this method will be invoked on all younger generations (from older to + // younger), allowing them to resize themselves as appropriate. + virtual void compute_new_size() = 0; + + // Printing + virtual const char* name() const = 0; + virtual const char* short_name() const = 0; + + int level() const { return _level; } + + // Attributes + + // True iff the given generation may only be the youngest generation. + virtual bool must_be_youngest() const = 0; + // True iff the given generation may only be the oldest generation. + virtual bool must_be_oldest() const = 0; + + // Reference Processing accessor + ReferenceProcessor* const ref_processor() { return _ref_processor; } + + // Iteration. + + // Iterate over all the ref-containing fields of all objects in the + // generation, calling "cl.do_oop" on each. + virtual void oop_iterate(OopClosure* cl); + + // Same as above, restricted to the intersection of a memory region and + // the generation. + virtual void oop_iterate(MemRegion mr, OopClosure* cl); + + // Iterate over all objects in the generation, calling "cl.do_object" on + // each. + virtual void object_iterate(ObjectClosure* cl); + + // Iterate over all objects allocated in the generation since the last + // collection, calling "cl.do_object" on each. The generation must have + // been initialized properly to support this function, or else this call + // will fail. + virtual void object_iterate_since_last_GC(ObjectClosure* cl) = 0; + + // Apply "cl->do_oop" to (the address of) all and only all the ref fields + // in the current generation that contain pointers to objects in younger + // generations. Objects allocated since the last "save_marks" call are + // excluded. + virtual void younger_refs_iterate(OopsInGenClosure* cl) = 0; + + // Inform a generation that it longer contains references to objects + // in any younger generation. [e.g. Because younger gens are empty, + // clear the card table.] + virtual void clear_remembered_set() { } + + // Inform a generation that some of its objects have moved. [e.g. The + // generation's spaces were compacted, invalidating the card table.] + virtual void invalidate_remembered_set() { } + + // Block abstraction. + + // Returns the address of the start of the "block" that contains the + // address "addr". We say "blocks" instead of "object" since some heaps + // may not pack objects densely; a chunk may either be an object or a + // non-object. + virtual HeapWord* block_start(const void* addr) const; + + // Requires "addr" to be the start of a chunk, and returns its size. + // "addr + size" is required to be the start of a new chunk, or the end + // of the active area of the heap. + virtual size_t block_size(const HeapWord* addr) const ; + + // Requires "addr" to be the start of a block, and returns "TRUE" iff + // the block is an object. + virtual bool block_is_obj(const HeapWord* addr) const; + + + // PrintGC, PrintGCDetails support + void print_heap_change(size_t prev_used) const; + + // PrintHeapAtGC support + virtual void print() const; + virtual void print_on(outputStream* st) const; + + virtual void verify(bool allow_dirty) = 0; + + struct StatRecord { + int invocations; + elapsedTimer accumulated_time; + StatRecord() : + invocations(0), + accumulated_time(elapsedTimer()) {} + }; +private: + StatRecord _stat_record; +public: + StatRecord* stat_record() { return &_stat_record; } + + virtual void print_summary_info(); + virtual void print_summary_info_on(outputStream* st); + + // Performance Counter support + virtual void update_counters() = 0; + virtual CollectorCounters* counters() { return _gc_counters; } +}; + +// Class CardGeneration is a generation that is covered by a card table, +// and uses a card-size block-offset array to implement block_start. + +// class BlockOffsetArray; +// class BlockOffsetArrayContigSpace; +class BlockOffsetSharedArray; + +class CardGeneration: public Generation { + friend class VMStructs; + protected: + // This is shared with other generations. + GenRemSet* _rs; + // This is local to this generation. + BlockOffsetSharedArray* _bts; + + CardGeneration(ReservedSpace rs, size_t initial_byte_size, int level, + GenRemSet* remset); + + public: + + virtual void clear_remembered_set(); + + virtual void invalidate_remembered_set(); + + virtual void prepare_for_verify(); +}; + +// OneContigSpaceCardGeneration models a heap of old objects contained in a single +// contiguous space. +// +// Garbage collection is performed using mark-compact. + +class OneContigSpaceCardGeneration: public CardGeneration { + friend class VMStructs; + // Abstractly, this is a subtype that gets access to protected fields. + friend class CompactingPermGen; + friend class VM_PopulateDumpSharedSpace; + + protected: + size_t _min_heap_delta_bytes; // Minimum amount to expand. + ContiguousSpace* _the_space; // actual space holding objects + WaterMark _last_gc; // watermark between objects allocated before + // and after last GC. + + // Grow generation with specified size (returns false if unable to grow) + bool grow_by(size_t bytes); + // Grow generation to reserved size. + bool grow_to_reserved(); + // Shrink generation with specified size (returns false if unable to shrink) + void shrink_by(size_t bytes); + + // Allocation failure + void expand(size_t bytes, size_t expand_bytes); + void shrink(size_t bytes); + + // Accessing spaces + ContiguousSpace* the_space() const { return _the_space; } + + public: + OneContigSpaceCardGeneration(ReservedSpace rs, size_t initial_byte_size, + size_t min_heap_delta_bytes, + int level, GenRemSet* remset, + ContiguousSpace* space) : + CardGeneration(rs, initial_byte_size, level, remset), + _the_space(space), _min_heap_delta_bytes(min_heap_delta_bytes) + {} + + inline bool is_in(const void* p) const; + + // Space enquiries + size_t capacity() const; + size_t used() const; + size_t free() const; + + MemRegion used_region() const; + + size_t unsafe_max_alloc_nogc() const; + size_t contiguous_available() const; + + // Iteration + void object_iterate(ObjectClosure* blk); + void space_iterate(SpaceClosure* blk, bool usedOnly = false); + void object_iterate_since_last_GC(ObjectClosure* cl); + + void younger_refs_iterate(OopsInGenClosure* blk); + + inline CompactibleSpace* first_compaction_space() const; + + virtual inline HeapWord* allocate(size_t word_size, bool is_tlab); + virtual inline HeapWord* par_allocate(size_t word_size, bool is_tlab); + + // Accessing marks + inline WaterMark top_mark(); + inline WaterMark bottom_mark(); + +#define OneContig_SINCE_SAVE_MARKS_DECL(OopClosureType, nv_suffix) \ + void oop_since_save_marks_iterate##nv_suffix(OopClosureType* cl); + OneContig_SINCE_SAVE_MARKS_DECL(OopsInGenClosure,_v) + SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES(OneContig_SINCE_SAVE_MARKS_DECL) + + void save_marks(); + void reset_saved_marks(); + bool no_allocs_since_save_marks(); + + inline size_t block_size(const HeapWord* addr) const; + + inline bool block_is_obj(const HeapWord* addr) const; + + virtual void collect(bool full, + bool clear_all_soft_refs, + size_t size, + bool is_tlab); + HeapWord* expand_and_allocate(size_t size, + bool is_tlab, + bool parallel = false); + + virtual void prepare_for_verify(); + + virtual void gc_epilogue(bool full); + + virtual void verify(bool allow_dirty); + virtual void print_on(outputStream* st) const; +};