8065992: Change CMSCollector::_young_gen to be a ParNewGeneration*
Reviewed-by: mgerdin, kbarrett
/*
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#ifndef SHARE_VM_MEMORY_GENERATION_HPP
#define SHARE_VM_MEMORY_GENERATION_HPP
#include "gc_implementation/shared/collectorCounters.hpp"
#include "memory/allocation.hpp"
#include "memory/memRegion.hpp"
#include "memory/referenceProcessor.hpp"
#include "memory/universe.hpp"
#include "memory/watermark.hpp"
#include "runtime/mutex.hpp"
#include "runtime/perfData.hpp"
#include "runtime/virtualspace.hpp"
// 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)
// - ConcurrentMarkSweepGeneration - Mostly Concurrent Mark Sweep Generation
// (Detlefs-Printezis refinement of
// Boehm-Demers-Schenker)
//
// The system configurations currently allowed are:
//
// DefNewGeneration + TenuredGeneration
// DefNewGeneration + ConcurrentMarkSweepGeneration
//
// ParNewGeneration + TenuredGeneration
// ParNewGeneration + ConcurrentMarkSweepGeneration
//
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<mtGC> {
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 {
DefNew,
ParNew,
MarkSweepCompact,
ConcurrentMarkSweep,
Other
};
enum SomePublicConstants {
// Generations are GenGrain-aligned and have size that are multiples of
// GenGrain.
// Note: on ARM we add 1 bit for card_table_base to be properly aligned
// (we expect its low byte to be zero - see implementation of post_barrier)
LogOfGenGrain = 16 ARM_ONLY(+1),
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 are
// likely to succeed without a promotion failure.
// Promotion of the full amount is not guaranteed but
// might be attempted in the worst case.
virtual bool promotion_attempt_is_safe(size_t max_promotion_in_bytes) const;
// For a non-young generation, this interface can be used to inform a
// generation that a promotion attempt into that generation failed.
// Typically used to enable diagnostic output for post-mortem analysis,
// but other uses of the interface are not ruled out.
virtual void promotion_failure_occurred() { /* does nothing */ }
// 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 the committed areas 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);
}
// 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;
// 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
// physically 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 tlab_used() 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.
virtual oop promote(oop obj, size_t obj_size);
// 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);
// 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));
}
// Returns true if the collection is likely to be safely
// completed. Even if this method returns true, a collection
// may not be guaranteed to succeed, and the system should be
// able to safely unwind and recover from that failure, albeit
// at some additional cost.
virtual bool collection_attempt_is_safe() {
guarantee(false, "Are you sure you want to call this method?");
return true;
}
// 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) {};
// Save the high water marks for the used space in a generation.
virtual void record_spaces_top() {};
// 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) {
// Both _time_of_last_gc and now are set using a time source
// that guarantees monotonically non-decreasing values provided
// the underlying platform provides such a source. So we still
// have to guard against non-monotonicity.
NOT_PRODUCT(
if (now < _time_of_last_gc) {
warning("time warp: "INT64_FORMAT" to "INT64_FORMAT, (int64_t)_time_of_last_gc, (int64_t)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 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; }
virtual void sample_eden_chunk() {}
// 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
// implementation 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) {}
// Give each generation an opportunity to do clean up for any
// contributed scratch.
virtual void reset_scratch() {};
// 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; }
// 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(ExtendedOopClosure* cl);
// Iterate over all objects in the generation, calling "cl.do_object" on
// each.
virtual void object_iterate(ObjectClosure* cl);
// Iterate over all safe objects in the generation, calling "cl.do_object" on
// each. An object is safe if its references point to other objects in
// the heap. This defaults to object_iterate() unless overridden.
virtual void safe_object_iterate(ObjectClosure* cl);
// 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() = 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;
// current shrinking effect: this damps shrinking when the heap gets empty.
size_t _shrink_factor;
size_t _min_heap_delta_bytes; // Minimum amount to expand.
// Some statistics from before gc started.
// These are gathered in the gc_prologue (and should_collect)
// to control growing/shrinking policy in spite of promotions.
size_t _capacity_at_prologue;
size_t _used_at_prologue;
CardGeneration(ReservedSpace rs, size_t initial_byte_size, int level,
GenRemSet* remset);
public:
// Attempt to expand the generation by "bytes". Expand by at a
// minimum "expand_bytes". Return true if some amount (not
// necessarily the full "bytes") was done.
virtual bool expand(size_t bytes, size_t expand_bytes);
// Shrink generation with specified size (returns false if unable to shrink)
virtual void shrink(size_t bytes) = 0;
virtual void compute_new_size();
virtual void clear_remembered_set();
virtual void invalidate_remembered_set();
virtual void prepare_for_verify();
// Grow generation with specified size (returns false if unable to grow)
virtual bool grow_by(size_t bytes) = 0;
// Grow generation to reserved size.
virtual bool grow_to_reserved() = 0;
};
// 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 VM_PopulateDumpSharedSpace;
protected:
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)
virtual bool grow_by(size_t bytes);
// Grow generation to reserved size.
virtual bool grow_to_reserved();
// Shrink generation with specified size (returns false if unable to shrink)
void shrink_by(size_t bytes);
// Allocation failure
virtual bool 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,
int level, GenRemSet* remset,
ContiguousSpace* space) :
CardGeneration(rs, initial_byte_size, level, remset),
_the_space(space)
{}
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 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 record_spaces_top();
virtual void verify();
virtual void print_on(outputStream* st) const;
};
#endif // SHARE_VM_MEMORY_GENERATION_HPP