507 lines
19 KiB
C++
507 lines
19 KiB
C++
/*
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* Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#ifndef SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP
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#define SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP
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#include "gc/shared/adaptiveSizePolicy.hpp"
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#include "gc/shared/collectedHeap.hpp"
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#include "gc/shared/collectorPolicy.hpp"
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#include "gc/shared/generation.hpp"
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class StrongRootsScope;
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class SubTasksDone;
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class WorkGang;
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// A "GenCollectedHeap" is a CollectedHeap that uses generational
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// collection. It has two generations, young and old.
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class GenCollectedHeap : public CollectedHeap {
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friend class GenCollectorPolicy;
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friend class Generation;
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friend class DefNewGeneration;
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friend class TenuredGeneration;
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friend class ConcurrentMarkSweepGeneration;
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friend class CMSCollector;
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friend class GenMarkSweep;
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friend class VM_GenCollectForAllocation;
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friend class VM_GenCollectFull;
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friend class VM_GenCollectFullConcurrent;
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friend class VM_GC_HeapInspection;
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friend class VM_HeapDumper;
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friend class HeapInspection;
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friend class GCCauseSetter;
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friend class VMStructs;
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public:
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friend class VM_PopulateDumpSharedSpace;
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enum GenerationType {
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YoungGen,
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OldGen
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};
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private:
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Generation* _young_gen;
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Generation* _old_gen;
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// The singleton CardTable Remembered Set.
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CardTableRS* _rem_set;
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// The generational collector policy.
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GenCollectorPolicy* _gen_policy;
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// Indicates that the most recent previous incremental collection failed.
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// The flag is cleared when an action is taken that might clear the
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// condition that caused that incremental collection to fail.
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bool _incremental_collection_failed;
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// In support of ExplicitGCInvokesConcurrent functionality
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unsigned int _full_collections_completed;
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// Data structure for claiming the (potentially) parallel tasks in
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// (gen-specific) roots processing.
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SubTasksDone* _process_strong_tasks;
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// Collects the given generation.
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void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
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bool run_verification, bool clear_soft_refs,
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bool restore_marks_for_biased_locking);
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// In block contents verification, the number of header words to skip
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NOT_PRODUCT(static size_t _skip_header_HeapWords;)
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WorkGang* _workers;
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protected:
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// Helper functions for allocation
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HeapWord* attempt_allocation(size_t size,
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bool is_tlab,
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bool first_only);
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// Helper function for two callbacks below.
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// Considers collection of the first max_level+1 generations.
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void do_collection(bool full,
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bool clear_all_soft_refs,
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size_t size,
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bool is_tlab,
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GenerationType max_generation);
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// Callback from VM_GenCollectForAllocation operation.
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// This function does everything necessary/possible to satisfy an
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// allocation request that failed in the youngest generation that should
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// have handled it (including collection, expansion, etc.)
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HeapWord* satisfy_failed_allocation(size_t size, bool is_tlab);
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// Callback from VM_GenCollectFull operation.
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// Perform a full collection of the first max_level+1 generations.
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virtual void do_full_collection(bool clear_all_soft_refs);
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void do_full_collection(bool clear_all_soft_refs, GenerationType max_generation);
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// Does the "cause" of GC indicate that
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// we absolutely __must__ clear soft refs?
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bool must_clear_all_soft_refs();
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public:
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GenCollectedHeap(GenCollectorPolicy *policy);
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WorkGang* workers() const { return _workers; }
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GCStats* gc_stats(Generation* generation) const;
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// Returns JNI_OK on success
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virtual jint initialize();
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// Reserve aligned space for the heap as needed by the contained generations.
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char* allocate(size_t alignment, ReservedSpace* heap_rs);
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// Does operations required after initialization has been done.
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void post_initialize();
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// Initialize ("weak") refs processing support
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virtual void ref_processing_init();
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virtual Name kind() const {
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return CollectedHeap::GenCollectedHeap;
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}
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Generation* young_gen() const { return _young_gen; }
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Generation* old_gen() const { return _old_gen; }
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bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
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bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
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// The generational collector policy.
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GenCollectorPolicy* gen_policy() const { return _gen_policy; }
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virtual CollectorPolicy* collector_policy() const { return gen_policy(); }
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// Adaptive size policy
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virtual AdaptiveSizePolicy* size_policy() {
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return gen_policy()->size_policy();
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}
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// Return the (conservative) maximum heap alignment
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static size_t conservative_max_heap_alignment() {
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return Generation::GenGrain;
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}
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size_t capacity() const;
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size_t used() const;
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// Save the "used_region" for both generations.
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void save_used_regions();
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size_t max_capacity() const;
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HeapWord* mem_allocate(size_t size, bool* gc_overhead_limit_was_exceeded);
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// We may support a shared contiguous allocation area, if the youngest
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// generation does.
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bool supports_inline_contig_alloc() const;
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HeapWord** top_addr() const;
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HeapWord** end_addr() const;
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// Perform a full collection of the heap; intended for use in implementing
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// "System.gc". This implies as full a collection as the CollectedHeap
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// supports. Caller does not hold the Heap_lock on entry.
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void collect(GCCause::Cause cause);
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// The same as above but assume that the caller holds the Heap_lock.
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void collect_locked(GCCause::Cause cause);
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// Perform a full collection of generations up to and including max_generation.
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// Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
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void collect(GCCause::Cause cause, GenerationType max_generation);
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// Returns "TRUE" iff "p" points into the committed areas of the heap.
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// The methods is_in(), is_in_closed_subset() and is_in_youngest() may
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// be expensive to compute in general, so, to prevent
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// their inadvertent use in product jvm's, we restrict their use to
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// assertion checking or verification only.
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bool is_in(const void* p) const;
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// override
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bool is_in_closed_subset(const void* p) const {
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if (UseConcMarkSweepGC) {
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return is_in_reserved(p);
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} else {
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return is_in(p);
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}
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}
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// Returns true if the reference is to an object in the reserved space
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// for the young generation.
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// Assumes the the young gen address range is less than that of the old gen.
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bool is_in_young(oop p);
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#ifdef ASSERT
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bool is_in_partial_collection(const void* p);
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#endif
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virtual bool is_scavengable(const void* addr) {
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return is_in_young((oop)addr);
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}
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// Iteration functions.
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void oop_iterate_no_header(OopClosure* cl);
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void oop_iterate(ExtendedOopClosure* cl);
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void object_iterate(ObjectClosure* cl);
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void safe_object_iterate(ObjectClosure* cl);
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Space* space_containing(const void* addr) const;
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// A CollectedHeap is divided into a dense sequence of "blocks"; that is,
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// each address in the (reserved) heap is a member of exactly
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// one block. The defining characteristic of a block is that it is
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// possible to find its size, and thus to progress forward to the next
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// block. (Blocks may be of different sizes.) Thus, blocks may
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// represent Java objects, or they might be free blocks in a
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// free-list-based heap (or subheap), as long as the two kinds are
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// distinguishable and the size of each is determinable.
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// Returns the address of the start of the "block" that contains the
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// address "addr". We say "blocks" instead of "object" since some heaps
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// may not pack objects densely; a chunk may either be an object or a
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// non-object.
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virtual HeapWord* block_start(const void* addr) const;
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// Requires "addr" to be the start of a chunk, and returns its size.
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// "addr + size" is required to be the start of a new chunk, or the end
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// of the active area of the heap. Assumes (and verifies in non-product
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// builds) that addr is in the allocated part of the heap and is
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// the start of a chunk.
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virtual size_t block_size(const HeapWord* addr) const;
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// Requires "addr" to be the start of a block, and returns "TRUE" iff
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// the block is an object. Assumes (and verifies in non-product
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// builds) that addr is in the allocated part of the heap and is
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// the start of a chunk.
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virtual bool block_is_obj(const HeapWord* addr) const;
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// Section on TLAB's.
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virtual bool supports_tlab_allocation() const;
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virtual size_t tlab_capacity(Thread* thr) const;
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virtual size_t tlab_used(Thread* thr) const;
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virtual size_t unsafe_max_tlab_alloc(Thread* thr) const;
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virtual HeapWord* allocate_new_tlab(size_t size);
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// Can a compiler initialize a new object without store barriers?
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// This permission only extends from the creation of a new object
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// via a TLAB up to the first subsequent safepoint.
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virtual bool can_elide_tlab_store_barriers() const {
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return true;
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}
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virtual bool card_mark_must_follow_store() const {
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return UseConcMarkSweepGC;
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}
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// We don't need barriers for stores to objects in the
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// young gen and, a fortiori, for initializing stores to
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// objects therein. This applies to DefNew+Tenured and ParNew+CMS
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// only and may need to be re-examined in case other
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// kinds of collectors are implemented in the future.
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virtual bool can_elide_initializing_store_barrier(oop new_obj) {
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return is_in_young(new_obj);
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}
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// The "requestor" generation is performing some garbage collection
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// action for which it would be useful to have scratch space. The
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// requestor promises to allocate no more than "max_alloc_words" in any
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// older generation (via promotion say.) Any blocks of space that can
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// be provided are returned as a list of ScratchBlocks, sorted by
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// decreasing size.
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ScratchBlock* gather_scratch(Generation* requestor, size_t max_alloc_words);
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// Allow each generation to reset any scratch space that it has
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// contributed as it needs.
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void release_scratch();
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// Ensure parsability: override
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virtual void ensure_parsability(bool retire_tlabs);
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// Time in ms since the longest time a collector ran in
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// in any generation.
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virtual jlong millis_since_last_gc();
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// Total number of full collections completed.
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unsigned int total_full_collections_completed() {
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assert(_full_collections_completed <= _total_full_collections,
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"Can't complete more collections than were started");
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return _full_collections_completed;
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}
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// Update above counter, as appropriate, at the end of a stop-world GC cycle
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unsigned int update_full_collections_completed();
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// Update above counter, as appropriate, at the end of a concurrent GC cycle
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unsigned int update_full_collections_completed(unsigned int count);
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// Update "time of last gc" for all generations to "now".
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void update_time_of_last_gc(jlong now) {
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_young_gen->update_time_of_last_gc(now);
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_old_gen->update_time_of_last_gc(now);
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}
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// Update the gc statistics for each generation.
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void update_gc_stats(Generation* current_generation, bool full) {
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_old_gen->update_gc_stats(current_generation, full);
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}
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bool no_gc_in_progress() { return !is_gc_active(); }
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// Override.
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void prepare_for_verify();
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// Override.
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void verify(bool silent, VerifyOption option);
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// Override.
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virtual void print_on(outputStream* st) const;
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virtual void print_gc_threads_on(outputStream* st) const;
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virtual void gc_threads_do(ThreadClosure* tc) const;
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virtual void print_tracing_info() const;
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virtual void print_on_error(outputStream* st) const;
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// PrintGC, PrintGCDetails support
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void print_heap_change(size_t prev_used) const;
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// The functions below are helper functions that a subclass of
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// "CollectedHeap" can use in the implementation of its virtual
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// functions.
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class GenClosure : public StackObj {
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public:
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virtual void do_generation(Generation* gen) = 0;
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};
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// Apply "cl.do_generation" to all generations in the heap
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// If "old_to_young" determines the order.
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void generation_iterate(GenClosure* cl, bool old_to_young);
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// Return "true" if all generations have reached the
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// maximal committed limit that they can reach, without a garbage
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// collection.
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virtual bool is_maximal_no_gc() const;
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// This function returns the CardTableRS object that allows us to scan
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// generations in a fully generational heap.
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CardTableRS* rem_set() { return _rem_set; }
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// Convenience function to be used in situations where the heap type can be
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// asserted to be this type.
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static GenCollectedHeap* heap();
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// Invoke the "do_oop" method of one of the closures "not_older_gens"
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// or "older_gens" on root locations for the generations depending on
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// the type. (The "older_gens" closure is used for scanning references
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// from older generations; "not_older_gens" is used everywhere else.)
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// If "younger_gens_as_roots" is false, younger generations are
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// not scanned as roots; in this case, the caller must be arranging to
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// scan the younger generations itself. (For example, a generation might
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// explicitly mark reachable objects in younger generations, to avoid
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// excess storage retention.)
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// The "so" argument determines which of the roots
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// the closure is applied to:
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// "SO_None" does none;
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enum ScanningOption {
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SO_None = 0x0,
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SO_AllCodeCache = 0x8,
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SO_ScavengeCodeCache = 0x10
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};
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private:
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void process_roots(StrongRootsScope* scope,
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ScanningOption so,
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OopClosure* strong_roots,
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OopClosure* weak_roots,
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CLDClosure* strong_cld_closure,
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CLDClosure* weak_cld_closure,
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CodeBlobClosure* code_roots);
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public:
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static const bool StrongAndWeakRoots = false;
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static const bool StrongRootsOnly = true;
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void gen_process_roots(StrongRootsScope* scope,
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GenerationType type,
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bool young_gen_as_roots,
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ScanningOption so,
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bool only_strong_roots,
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OopsInGenClosure* not_older_gens,
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OopsInGenClosure* older_gens,
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CLDClosure* cld_closure);
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// Apply "root_closure" to all the weak roots of the system.
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// These include JNI weak roots, string table,
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// and referents of reachable weak refs.
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void gen_process_weak_roots(OopClosure* root_closure);
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// Set the saved marks of generations, if that makes sense.
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// In particular, if any generation might iterate over the oops
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// in other generations, it should call this method.
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void save_marks();
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// Apply "cur->do_oop" or "older->do_oop" to all the oops in objects
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// allocated since the last call to save_marks in generations at or above
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// "level". The "cur" closure is
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// applied to references in the generation at "level", and the "older"
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// closure to older generations.
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#define GCH_SINCE_SAVE_MARKS_ITERATE_DECL(OopClosureType, nv_suffix) \
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void oop_since_save_marks_iterate(GenerationType start_gen, \
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OopClosureType* cur, \
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OopClosureType* older);
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ALL_SINCE_SAVE_MARKS_CLOSURES(GCH_SINCE_SAVE_MARKS_ITERATE_DECL)
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#undef GCH_SINCE_SAVE_MARKS_ITERATE_DECL
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// Returns "true" iff no allocations have occurred since the last
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// call to "save_marks".
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bool no_allocs_since_save_marks();
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// Returns true if an incremental collection is likely to fail.
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// We optionally consult the young gen, if asked to do so;
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// otherwise we base our answer on whether the previous incremental
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// collection attempt failed with no corrective action as of yet.
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bool incremental_collection_will_fail(bool consult_young) {
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// The first disjunct remembers if an incremental collection failed, even
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// when we thought (second disjunct) that it would not.
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return incremental_collection_failed() ||
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(consult_young && !_young_gen->collection_attempt_is_safe());
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}
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// If a generation bails out of an incremental collection,
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// it sets this flag.
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bool incremental_collection_failed() const {
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return _incremental_collection_failed;
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}
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void set_incremental_collection_failed() {
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_incremental_collection_failed = true;
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}
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void clear_incremental_collection_failed() {
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_incremental_collection_failed = false;
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}
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// Promotion of obj into gen failed. Try to promote obj to higher
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// gens in ascending order; return the new location of obj if successful.
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// Otherwise, try expand-and-allocate for obj in both the young and old
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// generation; return the new location of obj if successful. Otherwise, return NULL.
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oop handle_failed_promotion(Generation* old_gen,
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oop obj,
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size_t obj_size);
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private:
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// Accessor for memory state verification support
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NOT_PRODUCT(
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static size_t skip_header_HeapWords() { return _skip_header_HeapWords; }
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)
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// Override
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void check_for_non_bad_heap_word_value(HeapWord* addr,
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size_t size) PRODUCT_RETURN;
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// For use by mark-sweep. As implemented, mark-sweep-compact is global
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// in an essential way: compaction is performed across generations, by
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// iterating over spaces.
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void prepare_for_compaction();
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// Perform a full collection of the generations up to and including max_generation.
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// This is the low level interface used by the public versions of
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// collect() and collect_locked(). Caller holds the Heap_lock on entry.
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void collect_locked(GCCause::Cause cause, GenerationType max_generation);
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// Returns success or failure.
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bool create_cms_collector();
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// In support of ExplicitGCInvokesConcurrent functionality
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bool should_do_concurrent_full_gc(GCCause::Cause cause);
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void collect_mostly_concurrent(GCCause::Cause cause);
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// Save the tops of the spaces in all generations
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void record_gen_tops_before_GC() PRODUCT_RETURN;
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protected:
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void gc_prologue(bool full);
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void gc_epilogue(bool full);
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};
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#endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP
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