--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc/shared/collectedHeap.hpp Wed May 13 15:16:06 2015 +0200
@@ -0,0 +1,639 @@
+/*
+ * Copyright (c) 2001, 2015, 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_COLLECTEDHEAP_HPP
+#define SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP
+
+#include "gc/shared/gcCause.hpp"
+#include "gc/shared/gcWhen.hpp"
+#include "memory/allocation.hpp"
+#include "runtime/handles.hpp"
+#include "runtime/perfData.hpp"
+#include "runtime/safepoint.hpp"
+#include "utilities/events.hpp"
+
+// A "CollectedHeap" is an implementation of a java heap for HotSpot. This
+// is an abstract class: there may be many different kinds of heaps. This
+// class defines the functions that a heap must implement, and contains
+// infrastructure common to all heaps.
+
+class AdaptiveSizePolicy;
+class BarrierSet;
+class CollectorPolicy;
+class GCHeapSummary;
+class GCTimer;
+class GCTracer;
+class MetaspaceSummary;
+class Thread;
+class ThreadClosure;
+class VirtualSpaceSummary;
+class nmethod;
+
+class GCMessage : public FormatBuffer<1024> {
+ public:
+ bool is_before;
+
+ public:
+ GCMessage() {}
+};
+
+class GCHeapLog : public EventLogBase<GCMessage> {
+ private:
+ void log_heap(bool before);
+
+ public:
+ GCHeapLog() : EventLogBase<GCMessage>("GC Heap History") {}
+
+ void log_heap_before() {
+ log_heap(true);
+ }
+ void log_heap_after() {
+ log_heap(false);
+ }
+};
+
+//
+// CollectedHeap
+// GenCollectedHeap
+// G1CollectedHeap
+// ParallelScavengeHeap
+//
+class CollectedHeap : public CHeapObj<mtInternal> {
+ friend class VMStructs;
+ friend class IsGCActiveMark; // Block structured external access to _is_gc_active
+
+ private:
+#ifdef ASSERT
+ static int _fire_out_of_memory_count;
+#endif
+
+ // Used for filler objects (static, but initialized in ctor).
+ static size_t _filler_array_max_size;
+
+ GCHeapLog* _gc_heap_log;
+
+ // Used in support of ReduceInitialCardMarks; only consulted if COMPILER2 is being used
+ bool _defer_initial_card_mark;
+
+ MemRegion _reserved;
+
+ protected:
+ BarrierSet* _barrier_set;
+ bool _is_gc_active;
+ uint _n_par_threads;
+
+ unsigned int _total_collections; // ... started
+ unsigned int _total_full_collections; // ... started
+ NOT_PRODUCT(volatile size_t _promotion_failure_alot_count;)
+ NOT_PRODUCT(volatile size_t _promotion_failure_alot_gc_number;)
+
+ // Reason for current garbage collection. Should be set to
+ // a value reflecting no collection between collections.
+ GCCause::Cause _gc_cause;
+ GCCause::Cause _gc_lastcause;
+ PerfStringVariable* _perf_gc_cause;
+ PerfStringVariable* _perf_gc_lastcause;
+
+ // Constructor
+ CollectedHeap();
+
+ // Do common initializations that must follow instance construction,
+ // for example, those needing virtual calls.
+ // This code could perhaps be moved into initialize() but would
+ // be slightly more awkward because we want the latter to be a
+ // pure virtual.
+ void pre_initialize();
+
+ // Create a new tlab. All TLAB allocations must go through this.
+ virtual HeapWord* allocate_new_tlab(size_t size);
+
+ // Accumulate statistics on all tlabs.
+ virtual void accumulate_statistics_all_tlabs();
+
+ // Reinitialize tlabs before resuming mutators.
+ virtual void resize_all_tlabs();
+
+ // Allocate from the current thread's TLAB, with broken-out slow path.
+ inline static HeapWord* allocate_from_tlab(KlassHandle klass, Thread* thread, size_t size);
+ static HeapWord* allocate_from_tlab_slow(KlassHandle klass, Thread* thread, size_t size);
+
+ // Allocate an uninitialized block of the given size, or returns NULL if
+ // this is impossible.
+ inline static HeapWord* common_mem_allocate_noinit(KlassHandle klass, size_t size, TRAPS);
+
+ // Like allocate_init, but the block returned by a successful allocation
+ // is guaranteed initialized to zeros.
+ inline static HeapWord* common_mem_allocate_init(KlassHandle klass, size_t size, TRAPS);
+
+ // Helper functions for (VM) allocation.
+ inline static void post_allocation_setup_common(KlassHandle klass, HeapWord* obj);
+ inline static void post_allocation_setup_no_klass_install(KlassHandle klass,
+ HeapWord* objPtr);
+
+ inline static void post_allocation_setup_obj(KlassHandle klass, HeapWord* obj, int size);
+
+ inline static void post_allocation_setup_array(KlassHandle klass,
+ HeapWord* obj, int length);
+
+ // Clears an allocated object.
+ inline static void init_obj(HeapWord* obj, size_t size);
+
+ // Filler object utilities.
+ static inline size_t filler_array_hdr_size();
+ static inline size_t filler_array_min_size();
+
+ DEBUG_ONLY(static void fill_args_check(HeapWord* start, size_t words);)
+ DEBUG_ONLY(static void zap_filler_array(HeapWord* start, size_t words, bool zap = true);)
+
+ // Fill with a single array; caller must ensure filler_array_min_size() <=
+ // words <= filler_array_max_size().
+ static inline void fill_with_array(HeapWord* start, size_t words, bool zap = true);
+
+ // Fill with a single object (either an int array or a java.lang.Object).
+ static inline void fill_with_object_impl(HeapWord* start, size_t words, bool zap = true);
+
+ virtual void trace_heap(GCWhen::Type when, const GCTracer* tracer);
+
+ // Verification functions
+ virtual void check_for_bad_heap_word_value(HeapWord* addr, size_t size)
+ PRODUCT_RETURN;
+ virtual void check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
+ PRODUCT_RETURN;
+ debug_only(static void check_for_valid_allocation_state();)
+
+ public:
+ enum Name {
+ GenCollectedHeap,
+ ParallelScavengeHeap,
+ G1CollectedHeap
+ };
+
+ static inline size_t filler_array_max_size() {
+ return _filler_array_max_size;
+ }
+
+ virtual Name kind() const = 0;
+
+ /**
+ * Returns JNI error code JNI_ENOMEM if memory could not be allocated,
+ * and JNI_OK on success.
+ */
+ virtual jint initialize() = 0;
+
+ // In many heaps, there will be a need to perform some initialization activities
+ // after the Universe is fully formed, but before general heap allocation is allowed.
+ // This is the correct place to place such initialization methods.
+ virtual void post_initialize();
+
+ // Stop any onging concurrent work and prepare for exit.
+ virtual void stop() {}
+
+ void initialize_reserved_region(HeapWord *start, HeapWord *end);
+ MemRegion reserved_region() const { return _reserved; }
+ address base() const { return (address)reserved_region().start(); }
+
+ virtual size_t capacity() const = 0;
+ virtual size_t used() const = 0;
+
+ // Return "true" if the part of the heap that allocates Java
+ // objects has reached the maximal committed limit that it can
+ // reach, without a garbage collection.
+ virtual bool is_maximal_no_gc() const = 0;
+
+ // Support for java.lang.Runtime.maxMemory(): return the maximum amount of
+ // memory that the vm could make available for storing 'normal' java objects.
+ // This is based on the reserved address space, but should not include space
+ // that the vm uses internally for bookkeeping or temporary storage
+ // (e.g., in the case of the young gen, one of the survivor
+ // spaces).
+ virtual size_t max_capacity() const = 0;
+
+ // Returns "TRUE" if "p" points into the reserved area of the heap.
+ bool is_in_reserved(const void* p) const {
+ return _reserved.contains(p);
+ }
+
+ bool is_in_reserved_or_null(const void* p) const {
+ return p == NULL || is_in_reserved(p);
+ }
+
+ // Returns "TRUE" iff "p" points into the committed areas of the heap.
+ // This method can be expensive so avoid using it in performance critical
+ // code.
+ virtual bool is_in(const void* p) const = 0;
+
+ DEBUG_ONLY(bool is_in_or_null(const void* p) const { return p == NULL || is_in(p); })
+
+ // Let's define some terms: a "closed" subset of a heap is one that
+ //
+ // 1) contains all currently-allocated objects, and
+ //
+ // 2) is closed under reference: no object in the closed subset
+ // references one outside the closed subset.
+ //
+ // Membership in a heap's closed subset is useful for assertions.
+ // Clearly, the entire heap is a closed subset, so the default
+ // implementation is to use "is_in_reserved". But this may not be too
+ // liberal to perform useful checking. Also, the "is_in" predicate
+ // defines a closed subset, but may be too expensive, since "is_in"
+ // verifies that its argument points to an object head. The
+ // "closed_subset" method allows a heap to define an intermediate
+ // predicate, allowing more precise checking than "is_in_reserved" at
+ // lower cost than "is_in."
+
+ // One important case is a heap composed of disjoint contiguous spaces,
+ // such as the Garbage-First collector. Such heaps have a convenient
+ // closed subset consisting of the allocated portions of those
+ // contiguous spaces.
+
+ // Return "TRUE" iff the given pointer points into the heap's defined
+ // closed subset (which defaults to the entire heap).
+ virtual bool is_in_closed_subset(const void* p) const {
+ return is_in_reserved(p);
+ }
+
+ bool is_in_closed_subset_or_null(const void* p) const {
+ return p == NULL || is_in_closed_subset(p);
+ }
+
+ // An object is scavengable if its location may move during a scavenge.
+ // (A scavenge is a GC which is not a full GC.)
+ virtual bool is_scavengable(const void *p) = 0;
+
+ void set_gc_cause(GCCause::Cause v) {
+ if (UsePerfData) {
+ _gc_lastcause = _gc_cause;
+ _perf_gc_lastcause->set_value(GCCause::to_string(_gc_lastcause));
+ _perf_gc_cause->set_value(GCCause::to_string(v));
+ }
+ _gc_cause = v;
+ }
+ GCCause::Cause gc_cause() { return _gc_cause; }
+
+ // Number of threads currently working on GC tasks.
+ uint n_par_threads() { return _n_par_threads; }
+
+ // May be overridden to set additional parallelism.
+ virtual void set_par_threads(uint t) { _n_par_threads = t; };
+
+ // General obj/array allocation facilities.
+ inline static oop obj_allocate(KlassHandle klass, int size, TRAPS);
+ inline static oop array_allocate(KlassHandle klass, int size, int length, TRAPS);
+ inline static oop array_allocate_nozero(KlassHandle klass, int size, int length, TRAPS);
+
+ inline static void post_allocation_install_obj_klass(KlassHandle klass,
+ oop obj);
+
+ // Raw memory allocation facilities
+ // The obj and array allocate methods are covers for these methods.
+ // mem_allocate() should never be
+ // called to allocate TLABs, only individual objects.
+ virtual HeapWord* mem_allocate(size_t size,
+ bool* gc_overhead_limit_was_exceeded) = 0;
+
+ // Utilities for turning raw memory into filler objects.
+ //
+ // min_fill_size() is the smallest region that can be filled.
+ // fill_with_objects() can fill arbitrary-sized regions of the heap using
+ // multiple objects. fill_with_object() is for regions known to be smaller
+ // than the largest array of integers; it uses a single object to fill the
+ // region and has slightly less overhead.
+ static size_t min_fill_size() {
+ return size_t(align_object_size(oopDesc::header_size()));
+ }
+
+ static void fill_with_objects(HeapWord* start, size_t words, bool zap = true);
+
+ static void fill_with_object(HeapWord* start, size_t words, bool zap = true);
+ static void fill_with_object(MemRegion region, bool zap = true) {
+ fill_with_object(region.start(), region.word_size(), zap);
+ }
+ static void fill_with_object(HeapWord* start, HeapWord* end, bool zap = true) {
+ fill_with_object(start, pointer_delta(end, start), zap);
+ }
+
+ // Return the address "addr" aligned by "alignment_in_bytes" if such
+ // an address is below "end". Return NULL otherwise.
+ inline static HeapWord* align_allocation_or_fail(HeapWord* addr,
+ HeapWord* end,
+ unsigned short alignment_in_bytes);
+
+ // Some heaps may offer a contiguous region for shared non-blocking
+ // allocation, via inlined code (by exporting the address of the top and
+ // end fields defining the extent of the contiguous allocation region.)
+
+ // This function returns "true" iff the heap supports this kind of
+ // allocation. (Default is "no".)
+ virtual bool supports_inline_contig_alloc() const {
+ return false;
+ }
+ // These functions return the addresses of the fields that define the
+ // boundaries of the contiguous allocation area. (These fields should be
+ // physically near to one another.)
+ virtual HeapWord** top_addr() const {
+ guarantee(false, "inline contiguous allocation not supported");
+ return NULL;
+ }
+ virtual HeapWord** end_addr() const {
+ guarantee(false, "inline contiguous allocation not supported");
+ return NULL;
+ }
+
+ // Some heaps may be in an unparseable state at certain times between
+ // collections. This may be necessary for efficient implementation of
+ // certain allocation-related activities. Calling this function before
+ // attempting to parse a heap ensures that the heap is in a parsable
+ // state (provided other concurrent activity does not introduce
+ // unparsability). It is normally expected, therefore, that this
+ // method is invoked with the world stopped.
+ // NOTE: if you override this method, make sure you call
+ // super::ensure_parsability so that the non-generational
+ // part of the work gets done. See implementation of
+ // CollectedHeap::ensure_parsability and, for instance,
+ // that of GenCollectedHeap::ensure_parsability().
+ // The argument "retire_tlabs" controls whether existing TLABs
+ // are merely filled or also retired, thus preventing further
+ // allocation from them and necessitating allocation of new TLABs.
+ virtual void ensure_parsability(bool retire_tlabs);
+
+ // Section on thread-local allocation buffers (TLABs)
+ // If the heap supports thread-local allocation buffers, it should override
+ // the following methods:
+ // Returns "true" iff the heap supports thread-local allocation buffers.
+ // The default is "no".
+ virtual bool supports_tlab_allocation() const = 0;
+
+ // The amount of space available for thread-local allocation buffers.
+ virtual size_t tlab_capacity(Thread *thr) const = 0;
+
+ // The amount of used space for thread-local allocation buffers for the given thread.
+ virtual size_t tlab_used(Thread *thr) const = 0;
+
+ virtual size_t max_tlab_size() const;
+
+ // An estimate of the maximum allocation that could be performed
+ // for thread-local allocation buffers without triggering any
+ // collection or expansion activity.
+ virtual size_t unsafe_max_tlab_alloc(Thread *thr) const {
+ guarantee(false, "thread-local allocation buffers not supported");
+ return 0;
+ }
+
+ // 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. If such permission
+ // is granted for this heap type, the compiler promises to call
+ // defer_store_barrier() below on any slow path allocation of
+ // a new object for which such initializing store barriers will
+ // have been elided.
+ virtual bool can_elide_tlab_store_barriers() const = 0;
+
+ // If a compiler is eliding store barriers for TLAB-allocated objects,
+ // there is probably a corresponding slow path which can produce
+ // an object allocated anywhere. The compiler's runtime support
+ // promises to call this function on such a slow-path-allocated
+ // object before performing initializations that have elided
+ // store barriers. Returns new_obj, or maybe a safer copy thereof.
+ virtual oop new_store_pre_barrier(JavaThread* thread, oop new_obj);
+
+ // Answers whether an initializing store to a new object currently
+ // allocated at the given address doesn't need a store
+ // barrier. Returns "true" if it doesn't need an initializing
+ // store barrier; answers "false" if it does.
+ virtual bool can_elide_initializing_store_barrier(oop new_obj) = 0;
+
+ // If a compiler is eliding store barriers for TLAB-allocated objects,
+ // we will be informed of a slow-path allocation by a call
+ // to new_store_pre_barrier() above. Such a call precedes the
+ // initialization of the object itself, and no post-store-barriers will
+ // be issued. Some heap types require that the barrier strictly follows
+ // the initializing stores. (This is currently implemented by deferring the
+ // barrier until the next slow-path allocation or gc-related safepoint.)
+ // This interface answers whether a particular heap type needs the card
+ // mark to be thus strictly sequenced after the stores.
+ virtual bool card_mark_must_follow_store() const = 0;
+
+ // If the CollectedHeap was asked to defer a store barrier above,
+ // this informs it to flush such a deferred store barrier to the
+ // remembered set.
+ virtual void flush_deferred_store_barrier(JavaThread* thread);
+
+ // Perform a collection of the heap; intended for use in implementing
+ // "System.gc". This probably implies as full a collection as the
+ // "CollectedHeap" supports.
+ virtual void collect(GCCause::Cause cause) = 0;
+
+ // Perform a full collection
+ virtual void do_full_collection(bool clear_all_soft_refs) = 0;
+
+ // 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.
+ virtual void collect_as_vm_thread(GCCause::Cause cause);
+
+ // Returns the barrier set for this heap
+ BarrierSet* barrier_set() { return _barrier_set; }
+ void set_barrier_set(BarrierSet* barrier_set);
+
+ // Returns "true" iff there is a stop-world GC in progress. (I assume
+ // that it should answer "false" for the concurrent part of a concurrent
+ // collector -- dld).
+ bool is_gc_active() const { return _is_gc_active; }
+
+ // Total number of GC collections (started)
+ unsigned int total_collections() const { return _total_collections; }
+ unsigned int total_full_collections() const { return _total_full_collections;}
+
+ // Increment total number of GC collections (started)
+ // Should be protected but used by PSMarkSweep - cleanup for 1.4.2
+ void increment_total_collections(bool full = false) {
+ _total_collections++;
+ if (full) {
+ increment_total_full_collections();
+ }
+ }
+
+ void increment_total_full_collections() { _total_full_collections++; }
+
+ // Return the AdaptiveSizePolicy for the heap.
+ virtual AdaptiveSizePolicy* size_policy() = 0;
+
+ // Return the CollectorPolicy for the heap
+ virtual CollectorPolicy* collector_policy() const = 0;
+
+ // Iterate over all objects, calling "cl.do_object" on each.
+ virtual void object_iterate(ObjectClosure* cl) = 0;
+
+ // Similar to object_iterate() except iterates only
+ // over live objects.
+ virtual void safe_object_iterate(ObjectClosure* cl) = 0;
+
+ // NOTE! There is no requirement that a collector implement these
+ // functions.
+ //
+ // 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 = 0;
+
+ // Requires "addr" to be the start of a chunk, and returns its size.
+ // "addr + size" is required to be the start of a new chunk, or the end
+ // of the active area of the heap.
+ virtual size_t block_size(const HeapWord* addr) const = 0;
+
+ // Requires "addr" to be the start of a block, and returns "TRUE" iff
+ // the block is an object.
+ virtual bool block_is_obj(const HeapWord* addr) const = 0;
+
+ // Returns the longest time (in ms) that has elapsed since the last
+ // time that any part of the heap was examined by a garbage collection.
+ virtual jlong millis_since_last_gc() = 0;
+
+ // Perform any cleanup actions necessary before allowing a verification.
+ virtual void prepare_for_verify() = 0;
+
+ // Generate any dumps preceding or following a full gc
+ void pre_full_gc_dump(GCTimer* timer);
+ void post_full_gc_dump(GCTimer* timer);
+
+ VirtualSpaceSummary create_heap_space_summary();
+ GCHeapSummary create_heap_summary();
+
+ MetaspaceSummary create_metaspace_summary();
+
+ // Print heap information on the given outputStream.
+ virtual void print_on(outputStream* st) const = 0;
+ // The default behavior is to call print_on() on tty.
+ virtual void print() const {
+ print_on(tty);
+ }
+ // Print more detailed heap information on the given
+ // outputStream. The default behavior is to call print_on(). It is
+ // up to each subclass to override it and add any additional output
+ // it needs.
+ virtual void print_extended_on(outputStream* st) const {
+ print_on(st);
+ }
+
+ virtual void print_on_error(outputStream* st) const;
+
+ // Print all GC threads (other than the VM thread)
+ // used by this heap.
+ virtual void print_gc_threads_on(outputStream* st) const = 0;
+ // The default behavior is to call print_gc_threads_on() on tty.
+ void print_gc_threads() {
+ print_gc_threads_on(tty);
+ }
+ // Iterator for all GC threads (other than VM thread)
+ virtual void gc_threads_do(ThreadClosure* tc) const = 0;
+
+ // Print any relevant tracing info that flags imply.
+ // Default implementation does nothing.
+ virtual void print_tracing_info() const = 0;
+
+ void print_heap_before_gc();
+ void print_heap_after_gc();
+
+ // Registering and unregistering an nmethod (compiled code) with the heap.
+ // Override with specific mechanism for each specialized heap type.
+ virtual void register_nmethod(nmethod* nm);
+ virtual void unregister_nmethod(nmethod* nm);
+
+ void trace_heap_before_gc(const GCTracer* gc_tracer);
+ void trace_heap_after_gc(const GCTracer* gc_tracer);
+
+ // Heap verification
+ virtual void verify(bool silent, VerifyOption option) = 0;
+
+ // Non product verification and debugging.
+#ifndef PRODUCT
+ // Support for PromotionFailureALot. Return true if it's time to cause a
+ // promotion failure. The no-argument version uses
+ // this->_promotion_failure_alot_count as the counter.
+ inline bool promotion_should_fail(volatile size_t* count);
+ inline bool promotion_should_fail();
+
+ // Reset the PromotionFailureALot counters. Should be called at the end of a
+ // GC in which promotion failure occurred.
+ inline void reset_promotion_should_fail(volatile size_t* count);
+ inline void reset_promotion_should_fail();
+#endif // #ifndef PRODUCT
+
+#ifdef ASSERT
+ static int fired_fake_oom() {
+ return (CIFireOOMAt > 1 && _fire_out_of_memory_count >= CIFireOOMAt);
+ }
+#endif
+
+ public:
+ // Copy the current allocation context statistics for the specified contexts.
+ // For each context in contexts, set the corresponding entries in the totals
+ // and accuracy arrays to the current values held by the statistics. Each
+ // array should be of length len.
+ // Returns true if there are more stats available.
+ virtual bool copy_allocation_context_stats(const jint* contexts,
+ jlong* totals,
+ jbyte* accuracy,
+ jint len) {
+ return false;
+ }
+
+ /////////////// Unit tests ///////////////
+
+ NOT_PRODUCT(static void test_is_in();)
+};
+
+// Class to set and reset the GC cause for a CollectedHeap.
+
+class GCCauseSetter : StackObj {
+ CollectedHeap* _heap;
+ GCCause::Cause _previous_cause;
+ public:
+ GCCauseSetter(CollectedHeap* heap, GCCause::Cause cause) {
+ assert(SafepointSynchronize::is_at_safepoint(),
+ "This method manipulates heap state without locking");
+ _heap = heap;
+ _previous_cause = _heap->gc_cause();
+ _heap->set_gc_cause(cause);
+ }
+
+ ~GCCauseSetter() {
+ assert(SafepointSynchronize::is_at_safepoint(),
+ "This method manipulates heap state without locking");
+ _heap->set_gc_cause(_previous_cause);
+ }
+};
+
+#endif // SHARE_VM_GC_SHARED_COLLECTEDHEAP_HPP