/*
* Copyright 2000-2008 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.
*
*/
class SubTasksDone;
// A "GenCollectedHeap" is a SharedHeap that uses generational
// collection. It is represented with a sequence of Generation's.
class GenCollectedHeap : public SharedHeap {
friend class GenCollectorPolicy;
friend class Generation;
friend class DefNewGeneration;
friend class TenuredGeneration;
friend class ConcurrentMarkSweepGeneration;
friend class CMSCollector;
friend class GenMarkSweep;
friend class VM_GenCollectForAllocation;
friend class VM_GenCollectForPermanentAllocation;
friend class VM_GenCollectFull;
friend class VM_GenCollectFullConcurrent;
friend class VM_GC_HeapInspection;
friend class VM_HeapDumper;
friend class HeapInspection;
friend class GCCauseSetter;
friend class VMStructs;
public:
enum SomeConstants {
max_gens = 10
};
friend class VM_PopulateDumpSharedSpace;
protected:
// Fields:
static GenCollectedHeap* _gch;
private:
int _n_gens;
Generation* _gens[max_gens];
GenerationSpec** _gen_specs;
// The generational collector policy.
GenCollectorPolicy* _gen_policy;
// If a generation would bail out of an incremental collection,
// it sets this flag. If the flag is set, satisfy_failed_allocation
// will attempt allocating in all generations before doing a full GC.
bool _incremental_collection_will_fail;
bool _last_incremental_collection_failed;
// In support of ExplicitGCInvokesConcurrent functionality
unsigned int _full_collections_completed;
// Data structure for claiming the (potentially) parallel tasks in
// (gen-specific) strong roots processing.
SubTasksDone* _gen_process_strong_tasks;
// In block contents verification, the number of header words to skip
NOT_PRODUCT(static size_t _skip_header_HeapWords;)
// GC is not allowed during the dump of the shared classes. Keep track
// of this in order to provide an reasonable error message when terminating.
bool _preloading_shared_classes;
protected:
// Directs each generation up to and including "collectedGen" to recompute
// its desired size.
void compute_new_generation_sizes(int collectedGen);
// Helper functions for allocation
HeapWord* attempt_allocation(size_t size,
bool is_tlab,
bool first_only);
// Helper function for two callbacks below.
// Considers collection of the first max_level+1 generations.
void do_collection(bool full,
bool clear_all_soft_refs,
size_t size,
bool is_tlab,
int max_level);
// Callback from VM_GenCollectForAllocation operation.
// This function does everything necessary/possible to satisfy an
// allocation request that failed in the youngest generation that should
// have handled it (including collection, expansion, etc.)
HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
// Callback from VM_GenCollectFull operation.
// Perform a full collection of the first max_level+1 generations.
void do_full_collection(bool clear_all_soft_refs, int max_level);
// Does the "cause" of GC indicate that
// we absolutely __must__ clear soft refs?
bool must_clear_all_soft_refs();
public:
GenCollectedHeap(GenCollectorPolicy *policy);
GCStats* gc_stats(int level) const;
// Returns JNI_OK on success
virtual jint initialize();
char* allocate(size_t alignment, PermanentGenerationSpec* perm_gen_spec,
size_t* _total_reserved, int* _n_covered_regions,
ReservedSpace* heap_rs);
// Does operations required after initialization has been done.
void post_initialize();
// Initialize ("weak") refs processing support
virtual void ref_processing_init();
virtual CollectedHeap::Name kind() const {
return CollectedHeap::GenCollectedHeap;
}
// The generational collector policy.
GenCollectorPolicy* gen_policy() const { return _gen_policy; }
// Adaptive size policy
virtual AdaptiveSizePolicy* size_policy() {
return gen_policy()->size_policy();
}
size_t capacity() const;
size_t used() const;
// Save the "used_region" for generations level and lower,
// and, if perm is true, for perm gen.
void save_used_regions(int level, bool perm);
size_t max_capacity() const;
HeapWord* mem_allocate(size_t size,
bool is_large_noref,
bool is_tlab,
bool* gc_overhead_limit_was_exceeded);
// We may support a shared contiguous allocation area, if the youngest
// generation does.
bool supports_inline_contig_alloc() const;
HeapWord** top_addr() const;
HeapWord** end_addr() const;
// Return an estimate of the maximum allocation that could be performed
// without triggering any collection activity. In a generational
// collector, for example, this is probably the largest allocation that
// could be supported in the youngest generation. It is "unsafe" because
// no locks are taken; the result should be treated as an approximation,
// not a guarantee.
size_t unsafe_max_alloc();
// Does this heap support heap inspection? (+PrintClassHistogram)
virtual bool supports_heap_inspection() const { return true; }
// Perform a full collection of the heap; intended for use in implementing
// "System.gc". This implies as full a collection as the CollectedHeap
// supports. Caller does not hold the Heap_lock on entry.
void collect(GCCause::Cause cause);
// This interface assumes that it's being called by the
// vm thread. It collects the heap assuming that the
// heap lock is already held and that we are executing in
// the context of the vm thread.
void collect_as_vm_thread(GCCause::Cause cause);
// The same as above but assume that the caller holds the Heap_lock.
void collect_locked(GCCause::Cause cause);
// Perform a full collection of the first max_level+1 generations.
// Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
void collect(GCCause::Cause cause, int max_level);
// Returns "TRUE" iff "p" points into the allocated area of the heap.
// The methods is_in(), is_in_closed_subset() and is_in_youngest() may
// be expensive to compute in general, so, to prevent
// their inadvertent use in product jvm's, we restrict their use to
// assertion checking or verification only.
bool is_in(const void* p) const;
// override
bool is_in_closed_subset(const void* p) const {
if (UseConcMarkSweepGC) {
return is_in_reserved(p);
} else {
return is_in(p);
}
}
// Returns "TRUE" iff "p" points into the youngest generation.
bool is_in_youngest(void* p);
// Iteration functions.
void oop_iterate(OopClosure* cl);
void oop_iterate(MemRegion mr, OopClosure* cl);
void object_iterate(ObjectClosure* cl);
void safe_object_iterate(ObjectClosure* cl);
void object_iterate_since_last_GC(ObjectClosure* cl);
Space* space_containing(const void* addr) const;
// A CollectedHeap is divided into a dense sequence of "blocks"; that is,
// each address in the (reserved) heap is a member of exactly
// one block. The defining characteristic of a block is that it is
// possible to find its size, and thus to progress forward to the next
// block. (Blocks may be of different sizes.) Thus, blocks may
// represent Java objects, or they might be free blocks in a
// free-list-based heap (or subheap), as long as the two kinds are
// distinguishable and the size of each is determinable.
// 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. Assumes (and verifies in non-product
// builds) that addr is in the allocated part of the heap and is
// the start of a chunk.
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. Assumes (and verifies in non-product
// builds) that addr is in the allocated part of the heap and is
// the start of a chunk.
virtual bool block_is_obj(const HeapWord* addr) const;
// Section on TLAB's.
virtual bool supports_tlab_allocation() const;
virtual size_t tlab_capacity(Thread* thr) const;
virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
virtual HeapWord* allocate_new_tlab(size_t size);
// Can a compiler initialize a new object without store barriers?
// This permission only extends from the creation of a new object
// via a TLAB up to the first subsequent safepoint.
virtual bool can_elide_tlab_store_barriers() const {
return true;
}
// Can a compiler elide a store barrier when it writes
// a permanent oop into the heap? Applies when the compiler
// is storing x to the heap, where x->is_perm() is true.
virtual bool can_elide_permanent_oop_store_barriers() const {
// CMS needs to see all, even intra-generational, ref updates.
return !UseConcMarkSweepGC;
}
// The "requestor" generation is performing some garbage collection
// action for which it would be useful to have scratch space. The
// requestor promises to allocate no more than "max_alloc_words" in any
// older generation (via promotion say.) Any blocks of space that can
// be provided are returned as a list of ScratchBlocks, sorted by
// decreasing size.
ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
// Allow each generation to reset any scratch space that it has
// contributed as it needs.
void release_scratch();
size_t large_typearray_limit();
// Ensure parsability: override
virtual void ensure_parsability(bool retire_tlabs);
// Time in ms since the longest time a collector ran in
// in any generation.
virtual jlong millis_since_last_gc();
// Total number of full collections completed.
unsigned int total_full_collections_completed() {
assert(_full_collections_completed <= _total_full_collections,
"Can't complete more collections than were started");
return _full_collections_completed;
}
// Update above counter, as appropriate, at the end of a stop-world GC cycle
unsigned int update_full_collections_completed();
// Update above counter, as appropriate, at the end of a concurrent GC cycle
unsigned int update_full_collections_completed(unsigned int count);
// Update "time of last gc" for all constituent generations
// to "now".
void update_time_of_last_gc(jlong now) {
for (int i = 0; i < _n_gens; i++) {
_gens[i]->update_time_of_last_gc(now);
}
perm_gen()->update_time_of_last_gc(now);
}
// Update the gc statistics for each generation.
// "level" is the level of the lastest collection
void update_gc_stats(int current_level, bool full) {
for (int i = 0; i < _n_gens; i++) {
_gens[i]->update_gc_stats(current_level, full);
}
perm_gen()->update_gc_stats(current_level, full);
}
// Override.
bool no_gc_in_progress() { return !is_gc_active(); }
// Override.
void prepare_for_verify();
// Override.
void verify(bool allow_dirty, bool silent);
// Override.
void print() const;
void print_on(outputStream* st) const;
virtual void print_gc_threads_on(outputStream* st) const;
virtual void gc_threads_do(ThreadClosure* tc) const;
virtual void print_tracing_info() const;
// PrintGC, PrintGCDetails support
void print_heap_change(size_t prev_used) const;
void print_perm_heap_change(size_t perm_prev_used) const;
// The functions below are helper functions that a subclass of
// "CollectedHeap" can use in the implementation of its virtual
// functions.
class GenClosure : public StackObj {
public:
virtual void do_generation(Generation* gen) = 0;
};
// Apply "cl.do_generation" to all generations in the heap (not including
// the permanent generation). If "old_to_young" determines the order.
void generation_iterate(GenClosure* cl, bool old_to_young);
void space_iterate(SpaceClosure* cl);
// Return "true" if all generations (but perm) have reached the
// maximal committed limit that they can reach, without a garbage
// collection.
virtual bool is_maximal_no_gc() const;
// Return the generation before "gen", or else NULL.
Generation* prev_gen(Generation* gen) const {
int l = gen->level();
if (l == 0) return NULL;
else return _gens[l-1];
}
// Return the generation after "gen", or else NULL.
Generation* next_gen(Generation* gen) const {
int l = gen->level() + 1;
if (l == _n_gens) return NULL;
else return _gens[l];
}
Generation* get_gen(int i) const {
if (i >= 0 && i < _n_gens)
return _gens[i];
else
return NULL;
}
int n_gens() const {
assert(_n_gens == gen_policy()->number_of_generations(), "Sanity");
return _n_gens;
}
// Convenience function to be used in situations where the heap type can be
// asserted to be this type.
static GenCollectedHeap* heap();
void set_par_threads(int t);
// Invoke the "do_oop" method of one of the closures "not_older_gens"
// or "older_gens" on root locations for the generation at
// "level". (The "older_gens" closure is used for scanning references
// from older generations; "not_older_gens" is used everywhere else.)
// If "younger_gens_as_roots" is false, younger generations are
// not scanned as roots; in this case, the caller must be arranging to
// scan the younger generations itself. (For example, a generation might
// explicitly mark reachable objects in younger generations, to avoid
// excess storage retention.) If "collecting_perm_gen" is false, then
// roots that may only contain references to permGen objects are not
// scanned. The "so" argument determines which of the roots
// the closure is applied to:
// "SO_None" does none;
// "SO_AllClasses" applies the closure to all entries in the SystemDictionary;
// "SO_SystemClasses" to all the "system" classes and loaders;
// "SO_Symbols_and_Strings" applies the closure to all entries in
// SymbolsTable and StringTable.
void gen_process_strong_roots(int level, bool younger_gens_as_roots,
bool collecting_perm_gen,
SharedHeap::ScanningOption so,
OopsInGenClosure* older_gens,
OopsInGenClosure* not_older_gens);
// Apply "blk" to all the weak roots of the system. These include
// JNI weak roots, the code cache, system dictionary, symbol table,
// string table, and referents of reachable weak refs.
void gen_process_weak_roots(OopClosure* root_closure,
OopClosure* non_root_closure);
// Set the saved marks of generations, if that makes sense.
// In particular, if any generation might iterate over the oops
// in other generations, it should call this method.
void save_marks();
// Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
// allocated since the last call to save_marks in generations at or above
// "level" (including the permanent generation.) The "cur" closure is
// applied to references in the generation at "level", and the "older"
// closure to older (and permanent) generations.
#define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
void oop_since_save_marks_iterate(int level, \
OopClosureType* cur, \
OopClosureType* older);
ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
#undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
// Returns "true" iff no allocations have occurred in any generation at
// "level" or above (including the permanent generation) since the last
// call to "save_marks".
bool no_allocs_since_save_marks(int level);
// If a generation bails out of an incremental collection,
// it sets this flag.
bool incremental_collection_will_fail() {
return _incremental_collection_will_fail;
}
void set_incremental_collection_will_fail() {
_incremental_collection_will_fail = true;
}
void clear_incremental_collection_will_fail() {
_incremental_collection_will_fail = false;
}
bool last_incremental_collection_failed() const {
return _last_incremental_collection_failed;
}
void set_last_incremental_collection_failed() {
_last_incremental_collection_failed = true;
}
void clear_last_incremental_collection_failed() {
_last_incremental_collection_failed = false;
}
// Promotion of obj into gen failed. Try to promote obj to higher non-perm
// gens in ascending order; return the new location of obj if successful.
// Otherwise, try expand-and-allocate for obj in each generation starting at
// gen; return the new location of obj if successful. Otherwise, return NULL.
oop handle_failed_promotion(Generation* gen,
oop obj,
size_t obj_size);
private:
// Accessor for memory state verification support
NOT_PRODUCT(
static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
)
// Override
void check_for_non_bad_heap_word_value(HeapWord* addr,
size_t size) PRODUCT_RETURN;
// For use by mark-sweep. As implemented, mark-sweep-compact is global
// in an essential way: compaction is performed across generations, by
// iterating over spaces.
void prepare_for_compaction();
// Perform a full collection of the first max_level+1 generations.
// This is the low level interface used by the public versions of
// collect() and collect_locked(). Caller holds the Heap_lock on entry.
void collect_locked(GCCause::Cause cause, int max_level);
// Returns success or failure.
bool create_cms_collector();
// In support of ExplicitGCInvokesConcurrent functionality
bool should_do_concurrent_full_gc(GCCause::Cause cause);
void collect_mostly_concurrent(GCCause::Cause cause);
// Save the tops of the spaces in all generations
void record_gen_tops_before_GC() PRODUCT_RETURN;
protected:
virtual void gc_prologue(bool full);
virtual void gc_epilogue(bool full);
public:
virtual void preload_and_dump(TRAPS) KERNEL_RETURN;
};