--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shared/genCollectedHeap.hpp Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,520 @@
+/*
+ * Copyright (c) 2000, 2016, 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_GC_SHARED_GENCOLLECTEDHEAP_HPP
+#define SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP
+
+#include "gc/shared/adaptiveSizePolicy.hpp"
+#include "gc/shared/collectedHeap.hpp"
+#include "gc/shared/collectorPolicy.hpp"
+#include "gc/shared/generation.hpp"
+
+class StrongRootsScope;
+class SubTasksDone;
+class WorkGang;
+
+// A "GenCollectedHeap" is a CollectedHeap that uses generational
+// collection. It has two generations, young and old.
+class GenCollectedHeap : public CollectedHeap {
+ 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:
+ friend class VM_PopulateDumpSharedSpace;
+
+ enum GenerationType {
+ YoungGen,
+ OldGen
+ };
+
+private:
+ Generation* _young_gen;
+ Generation* _old_gen;
+
+ // The singleton CardTable Remembered Set.
+ CardTableRS* _rem_set;
+
+ // 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;
+
+ // Collects the given generation.
+ void collect_generation(Generation* gen, bool full, size_t size, bool is_tlab,
+ bool run_verification, bool clear_soft_refs,
+ bool restore_marks_for_biased_locking);
+
+ // In block contents verification, the number of header words to skip
+ NOT_PRODUCT(static size_t _skip_header_HeapWords;)
+
+ WorkGang* _workers;
+
+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,
+ GenerationType max_generation);
+
+ // 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, GenerationType max_generation);
+
+ // Does the "cause" of GC indicate that
+ // we absolutely __must__ clear soft refs?
+ bool must_clear_all_soft_refs();
+
+public:
+ GenCollectedHeap(GenCollectorPolicy *policy);
+
+ WorkGang* workers() const { return _workers; }
+
+ // Returns JNI_OK on success
+ virtual jint initialize();
+
+ // Reserve aligned space for the heap as needed by the contained generations.
+ char* allocate(size_t alignment, 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 Name kind() const {
+ return CollectedHeap::GenCollectedHeap;
+ }
+
+ virtual const char* name() const {
+ if (UseConcMarkSweepGC) {
+ return "Concurrent Mark Sweep";
+ } else {
+ return "Serial";
+ }
+ }
+
+ Generation* young_gen() const { return _young_gen; }
+ Generation* old_gen() const { return _old_gen; }
+
+ bool is_young_gen(const Generation* gen) const { return gen == _young_gen; }
+ bool is_old_gen(const Generation* gen) const { return gen == _old_gen; }
+
+ // The generational collector policy.
+ GenCollectorPolicy* gen_policy() const { return _gen_policy; }
+
+ virtual CollectorPolicy* collector_policy() const { return 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 both generations.
+ void save_used_regions();
+
+ 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* volatile* top_addr() const;
+ HeapWord** end_addr() const;
+
+ // 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 generations up to and including max_generation.
+ // Mostly used for testing purposes. Caller does not hold the Heap_lock on entry.
+ void collect(GCCause::Cause cause, GenerationType max_generation);
+
+ // 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
+ 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_no_header(OopClosure* cl);
+ 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+Tenured and ParNew+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) {
+ 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 generations to "now".
+ void update_time_of_last_gc(jlong now) {
+ _young_gen->update_time_of_last_gc(now);
+ _old_gen->update_time_of_last_gc(now);
+ }
+
+ // Update the gc statistics for each generation.
+ void update_gc_stats(Generation* current_generation, bool full) {
+ _old_gen->update_gc_stats(current_generation, full);
+ }
+
+ bool no_gc_in_progress() { return !is_gc_active(); }
+
+ // Override.
+ void prepare_for_verify();
+
+ // Override.
+ void verify(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;
+
+ void print_heap_change(size_t young_prev_used, size_t old_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);
+
+ // 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;
+
+ // This function returns the CardTableRS object that allows us to scan
+ // generations in a fully generational heap.
+ CardTableRS* rem_set() { return _rem_set; }
+
+ // Convenience function to be used in situations where the heap type can be
+ // asserted to be this type.
+ static GenCollectedHeap* heap();
+
+ // The ScanningOption 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(StrongRootsScope* scope,
+ ScanningOption so,
+ OopClosure* strong_roots,
+ OopClosure* weak_roots,
+ CLDClosure* strong_cld_closure,
+ CLDClosure* weak_cld_closure,
+ CodeBlobToOopClosure* code_roots);
+
+ void process_string_table_roots(StrongRootsScope* scope,
+ OopClosure* root_closure);
+
+ public:
+ void young_process_roots(StrongRootsScope* scope,
+ OopsInGenClosure* root_closure,
+ OopsInGenClosure* old_gen_closure,
+ CLDClosure* cld_closure);
+
+ // If "young_gen_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.)
+ void cms_process_roots(StrongRootsScope* scope,
+ bool young_gen_as_roots,
+ ScanningOption so,
+ bool only_strong_roots,
+ OopsInGenClosure* root_closure,
+ CLDClosure* cld_closure);
+
+ void full_process_roots(StrongRootsScope* scope,
+ bool is_adjust_phase,
+ ScanningOption so,
+ bool only_strong_roots,
+ OopsInGenClosure* root_closure,
+ 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(GenerationType start_gen, \
+ 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 since the last
+ // call to "save_marks".
+ bool no_allocs_since_save_marks();
+
+ // 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) {
+ // The first disjunct remembers if an incremental collection failed, even
+ // when we thought (second disjunct) that it would not.
+ return incremental_collection_failed() ||
+ (consult_young && !_young_gen->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 generations up to and including max_generation.
+ // 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, GenerationType max_generation);
+
+ // 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:
+ void gc_prologue(bool full);
+ void gc_epilogue(bool full);
+
+public:
+ void stop();
+};
+
+#endif // SHARE_VM_GC_SHARED_GENCOLLECTEDHEAP_HPP