/* * Copyright (c) 2000, 2013, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #ifndef SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP #define SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP #include "gc_implementation/shared/adaptiveSizePolicy.hpp" #include "memory/collectorPolicy.hpp" #include "memory/generation.hpp" #include "memory/sharedHeap.hpp" 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_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; // Indicates that the most recent previous incremental collection failed. // The flag is cleared when an action is taken that might clear the // condition that caused that incremental collection to fail. bool _incremental_collection_failed; // In support of ExplicitGCInvokesConcurrent functionality unsigned int _full_collections_completed; // Data structure for claiming the (potentially) parallel tasks in // (gen-specific) roots processing. SubTasksDone* _process_strong_tasks; // In block contents verification, the number of header words to skip NOT_PRODUCT(static size_t _skip_header_HeapWords;) protected: // 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. virtual void do_full_collection(bool clear_all_soft_refs); 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, 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; } virtual CollectorPolicy* collector_policy() const { return (CollectorPolicy*) gen_policy(); } // Adaptive size policy virtual AdaptiveSizePolicy* size_policy() { return gen_policy()->size_policy(); } // Return the (conservative) maximum heap alignment static size_t conservative_max_heap_alignment() { return Generation::GenGrain; } size_t capacity() const; size_t used() const; // Save the "used_region" for generations level and lower. void save_used_regions(int level); size_t max_capacity() const; HeapWord* mem_allocate(size_t size, 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; // 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); // 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 committed areas 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 if the reference is to an object in the reserved space // for the young generation. // Assumes the the young gen address range is less than that of the old gen. bool is_in_young(oop p); #ifdef ASSERT virtual bool is_in_partial_collection(const void* p); #endif virtual bool is_scavengable(const void* addr) { return is_in_young((oop)addr); } // Iteration functions. void oop_iterate(ExtendedOopClosure* cl); void object_iterate(ObjectClosure* cl); void safe_object_iterate(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 tlab_used(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; } virtual bool card_mark_must_follow_store() const { return UseConcMarkSweepGC; } // We don't need barriers for stores to objects in the // young gen and, a fortiori, for initializing stores to // objects therein. This applies to {DefNew,ParNew}+{Tenured,CMS} // only and may need to be re-examined in case other // kinds of collectors are implemented in the future. virtual bool can_elide_initializing_store_barrier(oop new_obj) { // We wanted to assert that:- // assert(UseParNewGC || UseSerialGC || UseConcMarkSweepGC, // "Check can_elide_initializing_store_barrier() for this collector"); // but unfortunately the flag UseSerialGC need not necessarily always // be set when DefNew+Tenured are being used. return is_in_young(new_obj); } // 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(); // 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); } } // 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); } } // Override. bool no_gc_in_progress() { return !is_gc_active(); } // Override. void prepare_for_verify(); // Override. void verify(bool silent, VerifyOption option); // Override. virtual 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; virtual void print_on_error(outputStream* st) const; // PrintGC, PrintGCDetails support void print_heap_change(size_t 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 // 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 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". Generation* prev_gen(Generation* gen) const { int l = gen->level(); guarantee(l > 0, "Out of bounds"); return _gens[l-1]; } // Return the generation after "gen". Generation* next_gen(Generation* gen) const { int l = gen->level() + 1; guarantee(l < _n_gens, "Out of bounds"); return _gens[l]; } Generation* get_gen(int i) const { guarantee(i >= 0 && i < _n_gens, "Out of bounds"); return _gens[i]; } 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(uint t); void set_n_termination(uint 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.) // The "so" argument determines which of the roots // the closure is applied to: // "SO_None" does none; enum ScanningOption { SO_None = 0x0, SO_AllCodeCache = 0x8, SO_ScavengeCodeCache = 0x10 }; private: void process_roots(bool activate_scope, ScanningOption so, OopClosure* strong_roots, OopClosure* weak_roots, CLDClosure* strong_cld_closure, CLDClosure* weak_cld_closure, CodeBlobClosure* code_roots); void gen_process_roots(int level, bool younger_gens_as_roots, bool activate_scope, ScanningOption so, OopsInGenClosure* not_older_gens, OopsInGenClosure* weak_roots, OopsInGenClosure* older_gens, CLDClosure* cld_closure, CLDClosure* weak_cld_closure, CodeBlobClosure* code_closure); public: static const bool StrongAndWeakRoots = false; static const bool StrongRootsOnly = true; void gen_process_roots(int level, bool younger_gens_as_roots, bool activate_scope, ScanningOption so, bool only_strong_roots, OopsInGenClosure* not_older_gens, OopsInGenClosure* older_gens, CLDClosure* cld_closure); // Apply "root_closure" to all the weak roots of the system. // These include JNI weak roots, string table, // and referents of reachable weak refs. void gen_process_weak_roots(OopClosure* 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". The "cur" closure is // applied to references in the generation at "level", and the "older" // closure to older 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 since the last // call to "save_marks". bool no_allocs_since_save_marks(int level); // Returns true if an incremental collection is likely to fail. // We optionally consult the young gen, if asked to do so; // otherwise we base our answer on whether the previous incremental // collection attempt failed with no corrective action as of yet. bool incremental_collection_will_fail(bool consult_young) { // Assumes a 2-generation system; the first disjunct remembers if an // incremental collection failed, even when we thought (second disjunct) // that it would not. assert(heap()->collector_policy()->is_two_generation_policy(), "the following definition may not be suitable for an n(>2)-generation system"); return incremental_collection_failed() || (consult_young && !get_gen(0)->collection_attempt_is_safe()); } // If a generation bails out of an incremental collection, // it sets this flag. bool incremental_collection_failed() const { return _incremental_collection_failed; } void set_incremental_collection_failed() { _incremental_collection_failed = true; } void clear_incremental_collection_failed() { _incremental_collection_failed = false; } // Promotion of obj into gen failed. Try to promote obj to higher // gens in ascending order; return the new location of obj if successful. // Otherwise, try expand-and-allocate for obj in both the young and old // generation; return the new location of obj if successful. Otherwise, return NULL. oop handle_failed_promotion(Generation* old_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); }; #endif // SHARE_VM_MEMORY_GENCOLLECTEDHEAP_HPP